CA1154049A - Method of and apparatus for gas generation - Google Patents
Method of and apparatus for gas generationInfo
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- CA1154049A CA1154049A CA000340555A CA340555A CA1154049A CA 1154049 A CA1154049 A CA 1154049A CA 000340555 A CA000340555 A CA 000340555A CA 340555 A CA340555 A CA 340555A CA 1154049 A CA1154049 A CA 1154049A
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- combustion
- gas
- combustion chamber
- filter means
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Abstract
TITLE: METHOD OF AND APPARATUS FOR GAS GENERATION
ABSTRACT OF THE DISCLOSURE: A solid fuel gas generator generates extremely clean odorless nitrogen gas by a combustion process that involves the burning in an annular combustion chamber having gas discharge orifices of a gas generant composition having combustion product residues including alkali metal oxides and hydroxides and which may also include iron particulates, and features the provision between the composition and the gas discharge orifices of an annular primary cooling and filtering pack in the com-bustion product residues, the cooling and filtering pack including a fine mesh screen surrounding the gas generant composition and one or more layers of fiberglass woven fabric around the screen, the fabric being selected for its characteristic property at the combustion chamber temperature of reacting with the caustic soda in the combustion products to form innocuous sodium silicate and of becoming tacky to enhance particle entrapment, and further features in surrounding relation to the combustion chamber an annular secondary cooling and filtering pack including an aluminum silicate blanket that reacts with caustic soda residue to form innocuous sodium silicate.
ABSTRACT OF THE DISCLOSURE: A solid fuel gas generator generates extremely clean odorless nitrogen gas by a combustion process that involves the burning in an annular combustion chamber having gas discharge orifices of a gas generant composition having combustion product residues including alkali metal oxides and hydroxides and which may also include iron particulates, and features the provision between the composition and the gas discharge orifices of an annular primary cooling and filtering pack in the com-bustion product residues, the cooling and filtering pack including a fine mesh screen surrounding the gas generant composition and one or more layers of fiberglass woven fabric around the screen, the fabric being selected for its characteristic property at the combustion chamber temperature of reacting with the caustic soda in the combustion products to form innocuous sodium silicate and of becoming tacky to enhance particle entrapment, and further features in surrounding relation to the combustion chamber an annular secondary cooling and filtering pack including an aluminum silicate blanket that reacts with caustic soda residue to form innocuous sodium silicate.
Description
S40 ~9 TrTLE: METHOD OF AND APPARATUS FOR G~S GENERATION
BACKG~WND OF THE INVENTION
Field of the Invention .
This invention relates to a gas generator that utilizes 5 the combustion of a solid gas yenerant composition for the rapid generation of an extremely clean gas in which most of the ccm-bustion particle residue and noxious and offensive gases have been removed. The generator is particularly useful for rapidly filling vehicle inflatable cushion restraint systems for the 10 pr~tection of the occupants fron severe impact and possible injury during a collision.
Description of the Prior Art Gas generators that utilize ccmbustible solid gas generant compositions are known in the prior art. Common features of such 15 generators that are used for the inflation of cushion restraint svstems are the inclusion in a housing of a gas generant composition containing a pelletized aIkali metal azide and means to filter and to cool the gas positioned between the composition and gas discharge orifices, as defined by the housing. Such compositiolls 20 are considered advantageous for use in such applications because the product of combustion is mainly nitrogen, an inert gas, and the speed of reaction or burning thereof, upon ignition, may be selected to be such as to effect the generation of gas at a very rapid rate but without detonation. Such constituents that burn 25 rapidly, however, usually burn with a ten~erature of about 1000C, and develop a pressure in the housing in excess of 2000 psia.
Further, the gas that is generated contains ccmbustion residue incïuding molten particles of metal and/or reactant oxides and also noxious and offensive gases. The high pressure that builds '' : , ' ' - , `` -` 1~54~14~
up in the hous~ng tends to produce an explosive discharge of residue frc~t the housing.
Accordingly, among the problems associated with such prior art gas generators has been the containment of the high pressure 5 reaction within a housing of acceptable weight and bt~ , and adequate filtering and cooling of the generated gas. Various chemical and mechanical cooling means that hav~ been provid~
have been found to be either unreliable after extended periods, unacceptably buLky, and/or incapable of reducing the generated 10 gas temperature to a desirably low level. The filtering means that have been provided have also been incapable of reducing the carnbustion residue entrained in the gas to a desirably low level.
In each case the result is discomfort to the vehicle occupants who have been spared severe impact during a collision.
lS A proposal made in the prior art for reducing the tempera-ture of the generated gas, as disclosed in U. S. Patent 3,985,076, granted October 12, 1976, is to prc~note both the cooling and speed of the reaction by a mechanical arrangement of a pelletized gas generant composition, ignition means therefor, and means for 20 filtering and the cooling, thereby allowing the use of a cooler burrL~ng gas generant. That is to say, the gas generant canposition is disposed to surround the ignition means so that a greater proportion of the gas generant material is directly exposed to the hot gases and flame therefrom. Cooling and the speed of 25 reaction are enhanced by the fact that the gases generated expand rapidly in all directions rather than linearly, as in a cylindrical arrangement. While an improvement in these respects, there still exists a need for further improv~r~nts in respect of providing a gas that is generated at even lower telr~eratures 30 and lower pressures, also, and with less entrained canbustible residue and noxious and offensive gases.
Gas generating compositions have been proposed that comprise mixtures of metal azides, o~idant metal compounds and silicon dioxide. The stated purpose of the silicon dioxide is to react 35 with and thereby transform the toxic solid cc~bt~tstion residue - ~
~ . . . .
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1~54(:~ ~9 to a non-toxic or physiologically harr~ess residue, specifically a glass-like aLkali silica-te I~own U. S. patents that disclose such compositions are 3,883,373, granted May 13, 1975, 3,912,561, granted October 14, 1975, 3,947,300, granted March 30, 1976, and 5 4,021,275, granted ~lay 3, 1977. Such compositions leave so~ething to be desired because of difficulty in uniforr~y mixing silicon dioxide with the rnetal azide and oxidant cc~l~pound c~s r~c~lir~l to react the silicon dioxide ~ith the residues and or ob~ ly satisfactory cornbustibility.
Mechanical filtering systems are also kncwn that include filter packs in the gas-flc~w path, such filter packs including multiple layers of screen of various mesh sizes, s~ne made of rnetal and including one or more layers of high temperature glass fibers in which the filtering action is determlned solely by the 15 mesh sizes of the various filter layers. U. S. patents disclos mg such filter packs are 4,017,100, granted April 12, 1977, and 4,0i2,211 granted March 15, 1977.
There is also described in the prior art gas generant cc~mposi-tions that are said to burn with the production o or~y the~
20 desired gaseous product and a solid product i~ the forrn of a sinter or clinker that does not escape frorn the generator housing.
Such compositions are described in U. S. Patent Nos. 3,895/098, grant-ed July 15, 1975, 3,931,040, yranted January 6, 1976, 3,996,079, granted December 7, 1976 and 4,062,708, granted Decenlber 13, 1977.
25 mey are described as comprising mixtures of metal oxides such as nickel oxide or iron axide, and an alkali metal azide. A prin~ry partiele size for the reactant oxide in the rc~nye oE a sn~lll fraction of a mie~n to a Ecw mierons i~ irlclicated as cssential for effeeting a burniny rate fast enough for inflating an inflat-30 able occupant restraint system.
Efforts to make an operative gas generator utilizing a gasgenerant cc~mposition as described in the aforemention0d patents have been unsuccessful. Among the problems encountered were difficulty in compacting the mixture to forrn a stable pellet, and difficul-ty 35 in igniting the mixture.
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Pelletizing the gas generating comFosition h~s been found to be essential for the composition to remain reliable over ex-tended periods, and for providing a uniform surface area for uni-form burning upon ignition of the composition. Otherwise the 5 burning rate is not predictable. Without pelletizing there is a tendency for packing and separation of the finely divided particles ; after the gas generator has been su~jccted to vibration over ~l extended period of time, as occurs during ordinary use, particu-larly when applied to a vehicle.
U.S. Patent 4r203,~87~f Fred E. Schneiter and George F. Kirchoff, Jr.
~ there is described a gas generant com-;~ position consisting of a mLxture of 60-80% of sodium azide (NaN3)
BACKG~WND OF THE INVENTION
Field of the Invention .
This invention relates to a gas generator that utilizes 5 the combustion of a solid gas yenerant composition for the rapid generation of an extremely clean gas in which most of the ccm-bustion particle residue and noxious and offensive gases have been removed. The generator is particularly useful for rapidly filling vehicle inflatable cushion restraint systems for the 10 pr~tection of the occupants fron severe impact and possible injury during a collision.
Description of the Prior Art Gas generators that utilize ccmbustible solid gas generant compositions are known in the prior art. Common features of such 15 generators that are used for the inflation of cushion restraint svstems are the inclusion in a housing of a gas generant composition containing a pelletized aIkali metal azide and means to filter and to cool the gas positioned between the composition and gas discharge orifices, as defined by the housing. Such compositiolls 20 are considered advantageous for use in such applications because the product of combustion is mainly nitrogen, an inert gas, and the speed of reaction or burning thereof, upon ignition, may be selected to be such as to effect the generation of gas at a very rapid rate but without detonation. Such constituents that burn 25 rapidly, however, usually burn with a ten~erature of about 1000C, and develop a pressure in the housing in excess of 2000 psia.
Further, the gas that is generated contains ccmbustion residue incïuding molten particles of metal and/or reactant oxides and also noxious and offensive gases. The high pressure that builds '' : , ' ' - , `` -` 1~54~14~
up in the hous~ng tends to produce an explosive discharge of residue frc~t the housing.
Accordingly, among the problems associated with such prior art gas generators has been the containment of the high pressure 5 reaction within a housing of acceptable weight and bt~ , and adequate filtering and cooling of the generated gas. Various chemical and mechanical cooling means that hav~ been provid~
have been found to be either unreliable after extended periods, unacceptably buLky, and/or incapable of reducing the generated 10 gas temperature to a desirably low level. The filtering means that have been provided have also been incapable of reducing the carnbustion residue entrained in the gas to a desirably low level.
In each case the result is discomfort to the vehicle occupants who have been spared severe impact during a collision.
lS A proposal made in the prior art for reducing the tempera-ture of the generated gas, as disclosed in U. S. Patent 3,985,076, granted October 12, 1976, is to prc~note both the cooling and speed of the reaction by a mechanical arrangement of a pelletized gas generant composition, ignition means therefor, and means for 20 filtering and the cooling, thereby allowing the use of a cooler burrL~ng gas generant. That is to say, the gas generant canposition is disposed to surround the ignition means so that a greater proportion of the gas generant material is directly exposed to the hot gases and flame therefrom. Cooling and the speed of 25 reaction are enhanced by the fact that the gases generated expand rapidly in all directions rather than linearly, as in a cylindrical arrangement. While an improvement in these respects, there still exists a need for further improv~r~nts in respect of providing a gas that is generated at even lower telr~eratures 30 and lower pressures, also, and with less entrained canbustible residue and noxious and offensive gases.
Gas generating compositions have been proposed that comprise mixtures of metal azides, o~idant metal compounds and silicon dioxide. The stated purpose of the silicon dioxide is to react 35 with and thereby transform the toxic solid cc~bt~tstion residue - ~
~ . . . .
- ' , . :~
:
1~54(:~ ~9 to a non-toxic or physiologically harr~ess residue, specifically a glass-like aLkali silica-te I~own U. S. patents that disclose such compositions are 3,883,373, granted May 13, 1975, 3,912,561, granted October 14, 1975, 3,947,300, granted March 30, 1976, and 5 4,021,275, granted ~lay 3, 1977. Such compositions leave so~ething to be desired because of difficulty in uniforr~y mixing silicon dioxide with the rnetal azide and oxidant cc~l~pound c~s r~c~lir~l to react the silicon dioxide ~ith the residues and or ob~ ly satisfactory cornbustibility.
Mechanical filtering systems are also kncwn that include filter packs in the gas-flc~w path, such filter packs including multiple layers of screen of various mesh sizes, s~ne made of rnetal and including one or more layers of high temperature glass fibers in which the filtering action is determlned solely by the 15 mesh sizes of the various filter layers. U. S. patents disclos mg such filter packs are 4,017,100, granted April 12, 1977, and 4,0i2,211 granted March 15, 1977.
There is also described in the prior art gas generant cc~mposi-tions that are said to burn with the production o or~y the~
20 desired gaseous product and a solid product i~ the forrn of a sinter or clinker that does not escape frorn the generator housing.
Such compositions are described in U. S. Patent Nos. 3,895/098, grant-ed July 15, 1975, 3,931,040, yranted January 6, 1976, 3,996,079, granted December 7, 1976 and 4,062,708, granted Decenlber 13, 1977.
25 mey are described as comprising mixtures of metal oxides such as nickel oxide or iron axide, and an alkali metal azide. A prin~ry partiele size for the reactant oxide in the rc~nye oE a sn~lll fraction of a mie~n to a Ecw mierons i~ irlclicated as cssential for effeeting a burniny rate fast enough for inflating an inflat-30 able occupant restraint system.
Efforts to make an operative gas generator utilizing a gasgenerant cc~mposition as described in the aforemention0d patents have been unsuccessful. Among the problems encountered were difficulty in compacting the mixture to forrn a stable pellet, and difficul-ty 35 in igniting the mixture.
~:15404~
Pelletizing the gas generating comFosition h~s been found to be essential for the composition to remain reliable over ex-tended periods, and for providing a uniform surface area for uni-form burning upon ignition of the composition. Otherwise the 5 burning rate is not predictable. Without pelletizing there is a tendency for packing and separation of the finely divided particles ; after the gas generator has been su~jccted to vibration over ~l extended period of time, as occurs during ordinary use, particu-larly when applied to a vehicle.
U.S. Patent 4r203,~87~f Fred E. Schneiter and George F. Kirchoff, Jr.
~ there is described a gas generant com-;~ position consisting of a mLxture of 60-80% of sodium azide (NaN3)
2-2~% or iron oxide (Fe2O3), 0-6% of sulfur (S2) and 2-26~ of 15 molybdenum disulfide (MoS2), a preferred mixture comprising 66%
sodium aæide, 30% iron oxide, 2~ sulfur and 2% moly~denum disulfide.
It has been found that this mixture is readily compacted to form a stable pellet and provides a burning rate at a combustion tempera-ture of 1025C, that is fast enough to effect inflation of a 20 vehicle cushion restraint system within 45 to 60 millisecounds.
; Important features of the combustible composition are its subt stantially lower operative burning temperature at a high burning rate and at a substantially lower pressure, providing a gas, as generated, that is cooler by at least 200~C than that available 25 fram prior art generators. The sodium azide produces a high percentage of nitrogen generating efficiency. The molybdenum disulfide and sulfur provide excellent ccn~lstion stability.
m e iron oxide is reduced durmg combustion, and the iron, Fe, that is thereby produced, forms a shcwer of molten particulate.
30 This particulate tends to be blown out of the combustion chamber, being carried along with the generated gas. There remains, additionally, combustible residue in the form of offensive gases that also tend to be carried out of the generator with the gener-ated gas.
'9 35 Thus, there still exists a need for further improvements .. . .
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1154045~
in solid fuel yas generators, particularly in respect of the filter structure and its ccoperative relation with the gas generant composition and the combustion chamber, at the high temperature environment therein, ~or enabling the trapping within the com-5 bustion chamber of larger amounts of the particulate matter andfor rendering mnocuous the noxious and offensive gases that are produced, thereby to make the gas g~lerator more at'~ractivc to both the user and the manufacturer, to the user from the standpoint of comfort as well as safety, and to the manufacturer 10 from the standpoint of simplifying and reducing the weight and size of the structure, and hence, reducing the manufacturing cost, and further, enhancing reliability.
SU~RY OF THE INVENTION
Among the objects of the invention is to provide a method 15 of and apparatus for producing an extremely clean odorless inert gas.
Another object of the invention is to provide for use in a solid fuel gas generator an improved method of and ap~aratus for filtering combustion particulate residues and gases.
~ 20 Another object of the invention is to provide an improved ; filter structure for use in a solid fuel gas generator.
A further object of the invention is to provide an improved solid fuel gas generator that produces a gas having a pH of 7 to 8 without the use of a chemical neutralizer.
Still another object of the invention is to provide an improved solid fuel gas generator in which the ccmbustion chamber operating pressure is under 1500 psi thereby allowing the use of light weight cc~ponents .for the housiny and combustion ch~lmber structure.
Another object o the invention is to provide such a : generator that functi.ons with good ballistic ,cerformance.
In accGmplishing the foregoing objects and other objec-tives of the invention, there is provided a gas generator that is generally similar in its mechanical arranyement to the generator 35 disclosed in the aforementioned patent 3,985,076. The generator .:-' .
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of the present invention, however, features improvements in respect of simplifying the generator, in the ignition and gas generant conpositions employed, in the construction and arrange-ment of the primary or combustion chamber filter, and of the sec-5 ondary or fine particulate final cha~ber filter. In an operativeembodlment of the invention, the improved primary and secondary filters provide a capability of filt~ring out 9~.6~ of tl~e ~r-ticulate solids from the generator effluent, such filtering oc-curring during a 45 millisecond functiOn time with an operating 10 pressure in the combustion chamber in the 1500 psi-2000 psi range.
Specifically, in accordance with one aspect of the invention, the primary or combustion chanber filter includes one or more layers of a woven fabric or cloth that is selected for its compatibility with the combustion chamber temperature during 15 burning of the gas generant ccmposition to the end that the fabric, at that temperature, provides a tacky surface that facilitates the entrapment of particulate solid residues but does not melt or erode away under the effects of the high temperature environ-ment. The effectiveness of the filter is enhanced by its immedi-20 ate proximity to the gas generant ccmposition, in close surround-ing relation thereto. mus the filter is in a position to be effective while the acceleration and velocity of the generated gases are still at a relatively low level. It is believed that as a result of the formation of the tacky surface, the porosity 25 of the woven fabric is reduced for a short interval of one or two milliseconds of the function ~ime at an early stage of the function time. During this short interval solid particulate combustion residue is prevented from being blcwn out of the combustion chamber thus allowing the solid particulate residue to condense 30 and become trapped in the filter.
In one specific form of the invention the combustion chamber filter includes one to three layers of coaîse screen immediately adjacent the combustion chamber wall. Inboard of the coarse screen are one or more layers of the fiberglass woven fabric or 35 cloth. M~ltiple layers of fine mesh screen, preferably of carbon .
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steel, are provided inboard of the multiple layers of fiberylass cloth for providing a relatively large cool surface for the condensation of particulate combustion residue prior to encounter-ing the multiple layers of fiberglass fabric. An added benefit 5 of the use of the fiberglass woven fabric in the primary filter is that under the high temperature environment, the glass reacts with caustic sodium oxide, Na20, an effluent of the cal~ustion process, to form innocuous sodium silicate.
me secondary or fine particulate final filter is located 10 outside the combustion chamber, in a diffuser space of the gas generator. miS filter is comprised of nLIltiple wraps of wire mesh which serves to cool the gas and also to provide a surface for condensation of solid particles. Surrounding the wire mesh are one or mDre wraps of an aluminum silicate blanket. Thls blan-15 ket serves as a particle trap for solid particulate ccmbustion residue that still is entrained in the gas stream, and also reacts with particles of sodium oxide which come into intimate contact with the secondary filter to form sodium silicate.
DESCRIPTION OF THE DRAWINGS
Figure 1 of the drawing is a sectional view of a gas generator having particular utility in a vehicle cushion restraint system for protecting the driver of the vehicle;
Figure 2 is a sectional view of a gas generator having particular utility in a vehicle cushion restraint system for 25 protecting the passengers in the vehicle.DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in Figure 1 of the drawings, the gas generator 1 includes a diffuser housing 10 co~prising a lcwer concave half shell or base 12 and an upper convex half shell or cover 14 30 having an annular unting flange 16 suitably welded thereto for mounting the generator l,typically, centrally of the steering wheel of a vehicle. The half shells 12 and 14 have internal screw threads 18 and 20 for engagement of and locking of the half shells together. Enclosed within the half shells 12 and 14 are 35 a cylindrical member 22 having a plurality of circumferentially llS4049 spaced ports or orifices 24. The opposite ends of nu~ber 22 engage the respective concave and convex surfaces of the half shells in sealing relation to form an outer annular chambex 26 and an inner cylindrical chamber 28. A xupturable hermetically 5 sealed cylindrical cartridge ox container 30 is positioned in chamber 28, being disposed coaxially therewith and held firmly in position. The lower and upper surfaces of~cartridge 30 conform to -~ the lower and upper inner s~rfaoe s of half shells 12 and 41, respectively.
10 The cylindrical side wall of cartridge 30 engages the inner surface of cylindrical member 22, completely around its periphery.
The upper end of cartridge 30 comprises an end disc 34 that is sealed by a sealant 32 to the cylindrical side wall with a ,; double-crimp seal and suitable sealant, typically as provided 'l~ 15 in metal containers used for preserving food and beverages.
' ~ Positioned in cartridge 30 in coaxial relationship there-with is a perforated cylindrical initiator tube 36 having a ~,~ rupturable metal foil or diaphragm 38 sealed to the outer wall thereof. A closure cap 40 is provided for the tube 36 at th,e ,~ 20 upper end. Tube 36 is supported at the lower end thereof on a shoulder 44 of a generally cylindrical hollow initiator mounting adbp*er 42 having a flange 46, a thin upper tubular initiator barrier portion 48, and a thick lower tubular portion 50, said ~I tubular portions 48 and 50 being concentrically arranged with b~l~ 25 respect to tube 36. A ring-like projection 52 on the lower side ~,, of flange 46 extends through and is retained by a circular opening ~` 54 that is provided in the bottom of cartridge 30. The tubular portion S0 of adapter 40 also extends throucJh and is retained ; in a circular opening 56 that is provided in the bottom of the , J~ 30 half shell 12. Desirably, tubular portion 50 is press fit in `~ opening 56.
A sealing O-ring 58 is provided between the flange 46 and t the half shell 12.
A conventional electric squib 60 having a pair of energizing 35 lead wires or terminals 62 is positioned in the upper portion 48 ,i ~ , .. ~, . ..
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1~:54049 of adapter 42, with lead wires extending through ferrite beads indicated at 64. The ferrite beads are provided to render the squib 60 substantially insensitive to extraneous radio frequency energy that may pervade the environment surrounding the gas 5 generator.
. 10 As shown in the drawing, the tubular portion 48 and the electric squib 60 are centrally located in perforated tube 36 and are surrounded therein by pyrotechnic material comprising igniter granules 66. Although various pyrotechnic materials may be 15 employed, a preferred material is a granular mixture of 15%
by weight of boron and 85% of potassium nitrate plus or minus 10% of lead azide. This mixture, as described in the above mentioned United States Patent 4,203,787 has been found to burn with a very hot flame.
As noted, the rupturable metal foil 38 surrounds the Fer~
, forated tube 36. The metal foil 38 and tube 36 are surrounded by uniformly distributed pellets 68 of a gas generant ccmFosition.
Pellets 68 in turn, are surrounded by an annul æ primary or com-bustion chamber filter indicated at 70. The metal foil 38 serves 25 the dual purpose of retaining the granular pyrotechnic material 66 in the perforated tube 36 and of insuring that the high temperature gases produced by the pyrotechnic material 66, upon firing of the squlb 60, have sufficient pressure to permeate the gas generant composition 68 thoroughl~ for efficient and sustained ignition 30 before they are released by rupture of the metal foil 38.
Although in the broader aspects of the present invention, the gas generant composition may be any one of a numb~r of con~
positions meeting the requirements for burning rate, nontoxicity, and flame temperature, a preferred material is that described in 35 the aforementioned U~S. Patent 4,203,787 :, .` ,:
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, -, , llS4049 --10-- . -of Fr~d E. Schneiter and C~orge ~. Kirchoff. ~lso : preferred are the azide, sulfur, molybdenum sulfide gas generant c~n-positions descriked in U. S. Patent 3,741,585. of these latter com-positions, particularly preferred are compositions comprising fram 5 akout 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur and from a~out 27 weight percent and about 33 weight percent molybdenum disulfide, especially a ca position comprisir.g about 68 weight percent sodium azide, akout 2 weight percent sulfur and about 30 weight percent molykdenum disulfide.
me combustion chamber filter 70 is preferably made in three parts, specifically one to three layers of coarse screen 72 adjacent to the inner or chamber wall of cartridge 30, one or more layers of filter cloth 74, specifically of fiberglass woven fabric or cloth, and multiple layers of fine mesh screen 76.
;l 15 A secondary filter 78 is located outside of the inner or c~n-bustion chamber 28, in the diffuser area. Filter 78 is a screen pack comprised of three parts, specifically, multiple wraps of coarse wire mesh 80, one or more wraps of aluminum silicate blanket 82 that ~ surround the wire mesh 80, and several wraps of fine mesh screen 84, '''!' 20 preferably 100 x 100 mesh, adjacent to the inner wall of the upper halfshell 14 and that surround and provide structural suppo~t for the alumlnum silicate blanket 82 and also cover exit ports or orifices 86 that are circumferentially disposed in the upper portion of the ; sidewall of the half shell 14. Orifices 86 desirably are angularly 25 offset from the orifices 24 in the cylindrical mim~er 22 and provide exit openings for the gas that is generated by the generator 1 . upon ccmbustion of the gas generant composition 68.
`` The screen pack co~prising filter 78 is formed around the cylin-drical nember 22, a suitable seal strip 88 being placed around the .30 outer wraps of fine mesh screen 84 for contacting the inner surface of the upper half shell 14 when the latter is brought into cooperative ; locking engagement with the lower half shell 12. The arrangement is such that the screen pack 78 is then brought under a suitable compressive load., with the upper edges curved. inwardly, in the ~`; 35 annular space between the ports 24 in t~.le cylindrical member 22 and. the exit ports 86 in the upper half shell 14.
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1~L5~049 By way of illustration and not limitation it is notcd that in an operative embodirent of Figure 1 of the invention, the external diameter of the generator 10 is 10.998 cm. (4.330") and its height is 6.353 cm. (2.501"), and the materials of which several components 5 are made and the dimensions thereof where relevant are as indicated belcw:
Components Materials Din~nsions half shell 12 carbon steel half shell 14 carbon steel 10 cartridge 30 aluminum primary filter coarse screen carbon steel 18 x 18 mesh filter cloth 74 fiberglass, 42 x 32 plain Style 1528 mfd. by Hexcel mesh Trevarno, Dublin, California 15 fine mesh screen 74 carbon steel 40 x 40 mesh secondary filter coarse screen 80 0.635 cm.(.25") blanket 82 A binder of content of 5% and thick a chemical analysis of fibers of 46% by weight, binder free and 54% of Alumina (A12O ) silica (SiO2) crabfiber paper, Johns-; Manvllle, Denver, Colo.
fine mesh screen 84 100 x 100 mesh ; Figure 2 is a sectional view of a gas generator 90 according 25 to the present invention that is particularly applicable for use in a vehicle cushion restraint system for protecting the p~ssengers, being mounted in an appropriate manner in or on the dash board oE the vehicle.
As shcJwn, the generator 90, similarly to the generator 1 of Figure 1, is annular in general construction, and essentially 30 differs in principle and operation from the generator 1 only in being elongated, typically having a length of 52.54 cm. (21") - and having the capability of a greater output of generated gas.
Thus, the generator 90 includes an elongated cylindrical housing 92 preferably made of carbon steel that for most of its length has 35 thin walls but at the left en~, as seen in Figure 2, includes a `
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heavier diffuser flange section 94 that provides a shouldcr indi-cated at 96. Section 94 flares outt~lrdly to receive a second elongated thin cylindrical m~mber 98 made of carbon steel that is concentrically positioned with respect to housing 92. The wall 5 of the right end of cylindrical housing 92 is rolled inwardly as indicated at 93 and is provided with a stud end flange 100 having a centrally disposed opening 102 therein. ~le rigllt end of cylindrical n~Yl~cr 98 i~ provid~d Wi~ U~ S-s~
curl as indicated at 99. Cooperating with the right ends of housing 10 92 and cylindrical member 98 for firmly locking those ends together are a stud end cap 104, a weld screw 106, a nut 108 and a lockwasher 110. The stud end cap 104 fits within the right end of cylindri-cal member 98 and has a peripheral surface that matches the S-shaped curllOOin the end of member 98. Weld screw 106 extends 15 through stud end cap 104 and outwardly of the stud end flange 100 to engage the nut 108 which extends partially through stud end cap lOA, the lockwasher 110 being provided to firmly retain ~le mcmbers together for long periods notwithstanding the presence of vibration.
When the weld screw 106 and nut 108 are pulled together in locking 20 relationship, the right end of cylindrical m~mker 98 is brought `l into tight engagement with the inner wall of stud end flange 100.
It will be noted that the interior of the cylindrical member 98 forms a combustion chamber 112 and that the annular space 114 between the member 98 and the inner surface of housing 92 provides 25 a diffuser space that extends to the left, however, only as far as the inner shoulder 96 on housing 92.
The left ends of the housing 92 and cylindrical member 98 are closed by a ring-shaped closure m~nber 116 that has a first peripheral portion 118 that fits inside a flared left end 120 30 of cylindrical mem~er 98, and a second peripheral externally threaded portion 122 that fits inside the flared internally threaded section 94 of housing 92, in threaded engagement therewith ; retaining and sealing O-r.ing 124 may also be provided, as shown.
An elongated rupturable hermetically sealed cylindrical 35 cartridge 126, preferably made of aluminum, is positioned in L
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11540~9 cl~Imber 112, being disposed coaxially therewith, completely filling the chamber and being held firmly against either radial or length-wise movement. The left end of cartridge 126 comprises an end disc 128 that is sealed by a suitable sealant to the cylindrical sidewall 5 with a double crimp seal.
Positioned in cartridge 126 in coaxial relationship thcl-c-with is an elongated perforatcd cylindrical initia~or or i~oitcr tube 130 having a rupturable metal foil or igniter barrier 132 sealed to the outer wall thereof. An igniter plug 134 is provided 10 adjacent the left end of igniter tube 130 and a separate igniter plug 136 is provided at the right end of tube 130, adjacent the right end wall of cartridge 126. As sht~n, the inner right end wall of cartridge 126 include.s an inwardly projecting short cylindrical portion 138 for retaining the right end of igniter 15 tube 130 in position. The left end of igniter tube is supported on the end of an initiator mounting member 140 that, in turn, is retained by a circular opening 142 in the cartridge 126 and includes a portion 144 that is press fit in a central opening 146 provided in ring shaped closure member 116. A O-ring 148 is provided to 20 retain mounting mem~er 140 in position. !:
Aconventional electric squib 150 having suitable energizing terminals is provided in the right end portion of initiator unting member 140, ferrite beads 152 being provided to render the squib 150 inse~sitive to extraneous radio frequency energy.
25 Between the igniter plugs 134 and 136 in the igniter tube 130 is pyrotechnic material comprising igniter granules 15~. Sur- i rounding the ignitex tub~ 130 are ~ ormly tListributed pellets 156 of gas generant composition, which composition, in turn, is surrounded by an elongated annular primary or combustion chamber 30 filter 158 which, generally, is similar to the filter 70 of the Figure 1 gas genexator.
The primary filter 158 comprises a filter pack of three screens including one to three layers of coarse screen 160 that are adjacent the inner wall of cartridge 126, one or m~re layers of 35 fiberglass woven fabric or cloth 162, and multiple layers of ~S4V49 fine mesh screen 164, preferably 40 x 40 mesh carbon steel.
A secondary filter 166 which, generally, is similar to the filter 78 of Figure 1, is located in the annular chamber 114 c~nprising the diffuser region and ccmprises a coarse, 18 mesh, stand-5 off screen 168 that surrounds the cartridge 126 in contact therewith,multiple wraps of coarse screen 170, one or more ~raps of al~un~n silicate blanket 172 that surround the cck~rse screen 170, .~ d æveral wraps of fine 100 m.esh screen 174 that are provided adjacent the inner wall of housing 92. me 18 ~esh standoff screen 168 10 is provided to allow the aluminum foil of cartridge 126 to blow out of the way.
me secondary filter 166 is arranged to cover a plurality of exit ports or orifices 176 that are provided in the cylindrical housing 92 and a plurality of exit ports or orifices (not shcwn) 15 that are provided in the housing 98. Preferably, four angularly spaced rows of exit ports are provided circumferentially of each of members 92 and 98, with 12 ports in each row, the exit ports in member 98 being offset both linearly and radially frcm the exit ports 176 in housing 92. ' The mechanical arrangement of the gas generator component of the present invention inherently promotes speed of reaction, cooling and filtering. Accordingly, with the structures of each of Figures 1 and 2 a slower burning, and hence, cooler burning gas 25 generant may be used. m e speed of reaction is increased notwith-standing the inherent characteristic of slower burning gas generants to be hard to ignite. mis is the result of several factors including the use of a composition for the igniter granules in the combustion initiator that provides a higher flame temperature 30 than in the prior art generators, and by arranging the gas generant composition pellets in uniformly distributed annular surrounding contact with the initiator whereby the entire peripheral area of the gas generant composition is immediately and simultaneously exposed to the hot gases and high te~perature flame fron the 35 initiator.
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The speed of reaction in the gcneration of the dcsircd gas, that desired for inflation of a vehicle cushion restraint, for example, is enhanced because the burning gases frcm the initiator and from the gas generant composition are made to expand rapidly 5 in all directions, without detonating, however, thus permeating and diffusing rapidly throughout the gas generant composition.
Featured, also, are thc arrallgal~lt. al-d construction oÇ ti)c llrin~
or c2mbustion chlmber filtèr and ~le secondary or fine particulate final filter that have the capability of filtering out 99.6% of 10 the solids from the gas generator effluent during a 45 milli-second function time with a low operating pressure of less than 1500 psi. The porosity of the fiberglass woven fabric or cloth of the primary or combustion chamber filter is so lcw in this pressure range as to retain the products of combustion or particu-15 late residues in the combustion chamber for a short interval, aninterval of one or tw~ milliseconds only in the 45-60 millisecond function time of the generator. This prevents most of such combustion products or particulate resi.dues from being explosively blown out ; of the combustion chamber and allows them to be cooled and con-20 densed on the carbon steel fine mesh screen that is located inboard of the fiberglass woven fabric element of the filter.
Specifically, the pyrotechnic material of the initiator, the gas generant ccmposition and the primary filter are all contained in the hermetically sealed aluminum cartridge. This 25 insures reliability of the generator over long periods. me aluminum cartridge is positioned in the ccmbustion chamber of the generator. Upon initiation of combustion by the firiny of the squib, the rising gas pressure ruptures the sidewall areas of ~le cartridge adjacent the orifices of ~le combustion chamb~r. This 30 allows gas to flow through the primary filter and out of the ccmr bustion chamber through the several orifices. The combustion chamber filter in each of Figures 1 and 2, consists of one to three layers of a coarse screen adjacent to the wall of the chamber. This serves as a collecting area for gas to flcw along 35 the chamcer wall to the chaTber orifices ar~ penmits gas to flow : ;
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~ lS4049 through the prirnary filter and out of tlle ccmbustion ch~mber through the several orifices. The combustion chamber filter in each of Figures 1 and 2, consists of one to three layers of a coarse screen adjacent to the wall of the chamber. This serves as a 5 collecting area for gas to flGw along the chan~er wall to the chamber orifices and permits gas to flow evenly through the prir~ary filter regardless of the proximity of a cc~ustion ch~lmber orifices. Inboard of the coarse screen are one or more layers ; of the fiberglass woven fabric. The fiberglass fabric is selected10 for compatability with the t~nperature in the combustion cham~er during burning of the seleeted gas generant ec~çosition thereby to provide a tacky surface for particle entraprnent that does not - melt or erode away under the effeets of the high temperature gas.
An effect accompanying the production of the tacky surface appears 15 to be a swelling of the fibers of the fiberglass fabric that reduces the porosity of the primary filter, and hence, causes the primary filter to restrict the flow of gas and combustion residue out of the eombustion ehamber. This effeet continues for only a short interval, as described, but long enough to allow cool~ing ; 20 and condensation of hot and molten particulate residue within the voids of the filter. Inside the rnultiple layers of the fiber-glass cloth are multiple layers of fine mesh carbon steel screen. .
The layers of the fine mesh earbon steel provide a large rela-tively eool surfaee for condensation of combustion solids prior 25 to encountering the multiple layers of fiberglass woven fabric.
Approximately 95 percent of all solid products of cGmbustion are trapped in the eombustion ehamber filter. It is noted that outside of the eombustion ehamber the aeeeleration of ~le gases that are generated bec~nes so high that trapping of the products of can-- 30 bustion in that region beeomes exceedingly difficult.
An addecl benefit of the fiberglass cloth is that uncler the high temperature environment, the glass reacts with caustic soclium oxide, Na2O, an effluent of the combustion process, to forrn innoeuous socliurn silicate.
The seeondary filter in each of Figures 1 and 2, is located 1~540'1~
outside of the ccmbustion chamber in the diff~scr arca of the annular chamber 26. This fllter is ccmprised of multiple wraps of wire mesh which serves to cool the gas and provide surface for condensation of solid particles. Surrounding the wire mesh filter 5 pack are one or more wraps of the aluminum silicate blanket. The aluminum silicate blanket serves two distinct functions. One of these functions is to react with particles of sodi~n oxide ~lic11 c~ne into intimate contact~with the secolld filter to ~O~lll soli~n silicate.
Surroundiny the aluminum silicate blanket are several wraps of fine mesh screen which provide structural support for the aluminum silicate blanket. It is noted that aluminum silicate blanket is porous, has very little strength, and tends to dis-integrate under the effects of the high velocity gas stre~m. The 15 filter elements, however, retain the solids entrapped. The fine mesh outer screen is used to trap these aluminum silicate filter particles and prevent them from being carried out of the exit orifices of the housing with the clean combustion gases.
The present invention is not dependent upon the specific 20 chemical composition of the combustible gas generant, the selection of the fiberglass woven fabric or cloth for compatibility with the combustion temperature of the selected gas generant composi-tion being the prime requirement. The use of the disc]oscd primary filter within the combustion chamber provided by the 25 cartridge in a gas generator utilizing a yas generating ccmposition as disclosed in the aforementioned copending application provides distinct advantages.These advantages are derived frcm the lcw~r temperature and pressure at which combuskion oE th~at cc~osition takes place in the combustion chamber. T~s makes possible a gas 30 generator of lighter weight since the structural components are subjected to lower combustion chamber temperature and pressure, and the production of an extremely clean gas and odor free gas.
In the aforementioned operative embodlment of this form of the invention, the amount of solid or particulate matter in the effluent 35 gas was reduced from 3 to 5 grams, as obtained in the prior art .~ I
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115404g generator of Patent 2,985,076, to 250 milliyr~ns. ~breover, the generator of the invention produced a substantially chemically neutral gas with a pH of 7 to 8 without the use of a chemical neutralizer.
; 5 Thus, there has been provided, according to the invention, an Lmprovement in the generation of gas by a solid fuel generator that results in the generation of extr~nely clean odorless ~as having a substantially reduced temperature. Such gas generation is accomplished by a generator of smaller size, having lighter 10 weight ccmponents, that operates at a pressure under lS00 psi.
m e improved generator includes a gas generant composition character-ized by sustained combustion at a lcwer temperature of a~out ¦ 1025C but nevertheless at a burning rate high enough to inflate a vehicle cushion restraint system within 45 millisecounds. I.
15 The pyrotechnic material for initiating combustion provides a desirably strong burning initiative thereby rapidly to effect sustained vigorous combustion of the gas generant composition. I
A combustion chamber cooling filter for maxLmum solids retention li with low pressure drop, that is, the primary filter, includes 20 a fiberglass woven fabric or cloth that provides a restriction to ~j~ retard for a short interval the flow of combustion products out ;~ of the oombustion chamber, and reacts with the caustic soda : r effluent resulting frn the combustion process, to provide a tacky surface for trapping solid particulate products and for ~` 25 converting the caustic soda to form innocuous sodium silicate.
The action of the filter is facilitated because of its location in the combustion chamber where it is operative to condense and ~`j trap solid particulate residue and to react wlth the caustic soda j ~ effluent during the short intervaL that the generated gases are 30 still undergoing relatively low rates of acceleration and velocity.
~ The invention further features a secondary filter that serves toj ~ cool the gas, provides a surface for further condensation of particles, and additionally, reacts with caustic soda particles to form sodium silicate. The secondary filter constitutes a final ~ 35 cooling filter for fine particle entrapment with lcw pressure drop.
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1~4~49 It will be un~erstood that where the a~-~li metal azide forming the gas generant composition is a metal other than sodium, and is for example, potassium or lithium, the reaction of the glass of the fiberglass or cloth of the primary filter and the 5 reaction of the aluminum silicate blanket of the secondary fil-ter with the metallic oxide effluent of the combustion process would, in each case, be to form an innocuous alkali metal silicate, that is, potassium silicatè or lithium silicate.
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sodium aæide, 30% iron oxide, 2~ sulfur and 2% moly~denum disulfide.
It has been found that this mixture is readily compacted to form a stable pellet and provides a burning rate at a combustion tempera-ture of 1025C, that is fast enough to effect inflation of a 20 vehicle cushion restraint system within 45 to 60 millisecounds.
; Important features of the combustible composition are its subt stantially lower operative burning temperature at a high burning rate and at a substantially lower pressure, providing a gas, as generated, that is cooler by at least 200~C than that available 25 fram prior art generators. The sodium azide produces a high percentage of nitrogen generating efficiency. The molybdenum disulfide and sulfur provide excellent ccn~lstion stability.
m e iron oxide is reduced durmg combustion, and the iron, Fe, that is thereby produced, forms a shcwer of molten particulate.
30 This particulate tends to be blown out of the combustion chamber, being carried along with the generated gas. There remains, additionally, combustible residue in the form of offensive gases that also tend to be carried out of the generator with the gener-ated gas.
'9 35 Thus, there still exists a need for further improvements .. . .
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1154045~
in solid fuel yas generators, particularly in respect of the filter structure and its ccoperative relation with the gas generant composition and the combustion chamber, at the high temperature environment therein, ~or enabling the trapping within the com-5 bustion chamber of larger amounts of the particulate matter andfor rendering mnocuous the noxious and offensive gases that are produced, thereby to make the gas g~lerator more at'~ractivc to both the user and the manufacturer, to the user from the standpoint of comfort as well as safety, and to the manufacturer 10 from the standpoint of simplifying and reducing the weight and size of the structure, and hence, reducing the manufacturing cost, and further, enhancing reliability.
SU~RY OF THE INVENTION
Among the objects of the invention is to provide a method 15 of and apparatus for producing an extremely clean odorless inert gas.
Another object of the invention is to provide for use in a solid fuel gas generator an improved method of and ap~aratus for filtering combustion particulate residues and gases.
~ 20 Another object of the invention is to provide an improved ; filter structure for use in a solid fuel gas generator.
A further object of the invention is to provide an improved solid fuel gas generator that produces a gas having a pH of 7 to 8 without the use of a chemical neutralizer.
Still another object of the invention is to provide an improved solid fuel gas generator in which the ccmbustion chamber operating pressure is under 1500 psi thereby allowing the use of light weight cc~ponents .for the housiny and combustion ch~lmber structure.
Another object o the invention is to provide such a : generator that functi.ons with good ballistic ,cerformance.
In accGmplishing the foregoing objects and other objec-tives of the invention, there is provided a gas generator that is generally similar in its mechanical arranyement to the generator 35 disclosed in the aforementioned patent 3,985,076. The generator .:-' .
~5404S~
of the present invention, however, features improvements in respect of simplifying the generator, in the ignition and gas generant conpositions employed, in the construction and arrange-ment of the primary or combustion chamber filter, and of the sec-5 ondary or fine particulate final cha~ber filter. In an operativeembodlment of the invention, the improved primary and secondary filters provide a capability of filt~ring out 9~.6~ of tl~e ~r-ticulate solids from the generator effluent, such filtering oc-curring during a 45 millisecond functiOn time with an operating 10 pressure in the combustion chamber in the 1500 psi-2000 psi range.
Specifically, in accordance with one aspect of the invention, the primary or combustion chanber filter includes one or more layers of a woven fabric or cloth that is selected for its compatibility with the combustion chamber temperature during 15 burning of the gas generant ccmposition to the end that the fabric, at that temperature, provides a tacky surface that facilitates the entrapment of particulate solid residues but does not melt or erode away under the effects of the high temperature environ-ment. The effectiveness of the filter is enhanced by its immedi-20 ate proximity to the gas generant ccmposition, in close surround-ing relation thereto. mus the filter is in a position to be effective while the acceleration and velocity of the generated gases are still at a relatively low level. It is believed that as a result of the formation of the tacky surface, the porosity 25 of the woven fabric is reduced for a short interval of one or two milliseconds of the function ~ime at an early stage of the function time. During this short interval solid particulate combustion residue is prevented from being blcwn out of the combustion chamber thus allowing the solid particulate residue to condense 30 and become trapped in the filter.
In one specific form of the invention the combustion chamber filter includes one to three layers of coaîse screen immediately adjacent the combustion chamber wall. Inboard of the coarse screen are one or more layers of the fiberglass woven fabric or 35 cloth. M~ltiple layers of fine mesh screen, preferably of carbon .
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steel, are provided inboard of the multiple layers of fiberylass cloth for providing a relatively large cool surface for the condensation of particulate combustion residue prior to encounter-ing the multiple layers of fiberglass fabric. An added benefit 5 of the use of the fiberglass woven fabric in the primary filter is that under the high temperature environment, the glass reacts with caustic sodium oxide, Na20, an effluent of the cal~ustion process, to form innocuous sodium silicate.
me secondary or fine particulate final filter is located 10 outside the combustion chamber, in a diffuser space of the gas generator. miS filter is comprised of nLIltiple wraps of wire mesh which serves to cool the gas and also to provide a surface for condensation of solid particles. Surrounding the wire mesh are one or mDre wraps of an aluminum silicate blanket. Thls blan-15 ket serves as a particle trap for solid particulate ccmbustion residue that still is entrained in the gas stream, and also reacts with particles of sodium oxide which come into intimate contact with the secondary filter to form sodium silicate.
DESCRIPTION OF THE DRAWINGS
Figure 1 of the drawing is a sectional view of a gas generator having particular utility in a vehicle cushion restraint system for protecting the driver of the vehicle;
Figure 2 is a sectional view of a gas generator having particular utility in a vehicle cushion restraint system for 25 protecting the passengers in the vehicle.DESCRIPTION OF THE PREFERRED EMBODIMENTS
As shown in Figure 1 of the drawings, the gas generator 1 includes a diffuser housing 10 co~prising a lcwer concave half shell or base 12 and an upper convex half shell or cover 14 30 having an annular unting flange 16 suitably welded thereto for mounting the generator l,typically, centrally of the steering wheel of a vehicle. The half shells 12 and 14 have internal screw threads 18 and 20 for engagement of and locking of the half shells together. Enclosed within the half shells 12 and 14 are 35 a cylindrical member 22 having a plurality of circumferentially llS4049 spaced ports or orifices 24. The opposite ends of nu~ber 22 engage the respective concave and convex surfaces of the half shells in sealing relation to form an outer annular chambex 26 and an inner cylindrical chamber 28. A xupturable hermetically 5 sealed cylindrical cartridge ox container 30 is positioned in chamber 28, being disposed coaxially therewith and held firmly in position. The lower and upper surfaces of~cartridge 30 conform to -~ the lower and upper inner s~rfaoe s of half shells 12 and 41, respectively.
10 The cylindrical side wall of cartridge 30 engages the inner surface of cylindrical member 22, completely around its periphery.
The upper end of cartridge 30 comprises an end disc 34 that is sealed by a sealant 32 to the cylindrical side wall with a ,; double-crimp seal and suitable sealant, typically as provided 'l~ 15 in metal containers used for preserving food and beverages.
' ~ Positioned in cartridge 30 in coaxial relationship there-with is a perforated cylindrical initiator tube 36 having a ~,~ rupturable metal foil or diaphragm 38 sealed to the outer wall thereof. A closure cap 40 is provided for the tube 36 at th,e ,~ 20 upper end. Tube 36 is supported at the lower end thereof on a shoulder 44 of a generally cylindrical hollow initiator mounting adbp*er 42 having a flange 46, a thin upper tubular initiator barrier portion 48, and a thick lower tubular portion 50, said ~I tubular portions 48 and 50 being concentrically arranged with b~l~ 25 respect to tube 36. A ring-like projection 52 on the lower side ~,, of flange 46 extends through and is retained by a circular opening ~` 54 that is provided in the bottom of cartridge 30. The tubular portion S0 of adapter 40 also extends throucJh and is retained ; in a circular opening 56 that is provided in the bottom of the , J~ 30 half shell 12. Desirably, tubular portion 50 is press fit in `~ opening 56.
A sealing O-ring 58 is provided between the flange 46 and t the half shell 12.
A conventional electric squib 60 having a pair of energizing 35 lead wires or terminals 62 is positioned in the upper portion 48 ,i ~ , .. ~, . ..
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1~:54049 of adapter 42, with lead wires extending through ferrite beads indicated at 64. The ferrite beads are provided to render the squib 60 substantially insensitive to extraneous radio frequency energy that may pervade the environment surrounding the gas 5 generator.
. 10 As shown in the drawing, the tubular portion 48 and the electric squib 60 are centrally located in perforated tube 36 and are surrounded therein by pyrotechnic material comprising igniter granules 66. Although various pyrotechnic materials may be 15 employed, a preferred material is a granular mixture of 15%
by weight of boron and 85% of potassium nitrate plus or minus 10% of lead azide. This mixture, as described in the above mentioned United States Patent 4,203,787 has been found to burn with a very hot flame.
As noted, the rupturable metal foil 38 surrounds the Fer~
, forated tube 36. The metal foil 38 and tube 36 are surrounded by uniformly distributed pellets 68 of a gas generant ccmFosition.
Pellets 68 in turn, are surrounded by an annul æ primary or com-bustion chamber filter indicated at 70. The metal foil 38 serves 25 the dual purpose of retaining the granular pyrotechnic material 66 in the perforated tube 36 and of insuring that the high temperature gases produced by the pyrotechnic material 66, upon firing of the squlb 60, have sufficient pressure to permeate the gas generant composition 68 thoroughl~ for efficient and sustained ignition 30 before they are released by rupture of the metal foil 38.
Although in the broader aspects of the present invention, the gas generant composition may be any one of a numb~r of con~
positions meeting the requirements for burning rate, nontoxicity, and flame temperature, a preferred material is that described in 35 the aforementioned U~S. Patent 4,203,787 :, .` ,:
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, -, , llS4049 --10-- . -of Fr~d E. Schneiter and C~orge ~. Kirchoff. ~lso : preferred are the azide, sulfur, molybdenum sulfide gas generant c~n-positions descriked in U. S. Patent 3,741,585. of these latter com-positions, particularly preferred are compositions comprising fram 5 akout 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur and from a~out 27 weight percent and about 33 weight percent molybdenum disulfide, especially a ca position comprisir.g about 68 weight percent sodium azide, akout 2 weight percent sulfur and about 30 weight percent molykdenum disulfide.
me combustion chamber filter 70 is preferably made in three parts, specifically one to three layers of coarse screen 72 adjacent to the inner or chamber wall of cartridge 30, one or more layers of filter cloth 74, specifically of fiberglass woven fabric or cloth, and multiple layers of fine mesh screen 76.
;l 15 A secondary filter 78 is located outside of the inner or c~n-bustion chamber 28, in the diffuser area. Filter 78 is a screen pack comprised of three parts, specifically, multiple wraps of coarse wire mesh 80, one or more wraps of aluminum silicate blanket 82 that ~ surround the wire mesh 80, and several wraps of fine mesh screen 84, '''!' 20 preferably 100 x 100 mesh, adjacent to the inner wall of the upper halfshell 14 and that surround and provide structural suppo~t for the alumlnum silicate blanket 82 and also cover exit ports or orifices 86 that are circumferentially disposed in the upper portion of the ; sidewall of the half shell 14. Orifices 86 desirably are angularly 25 offset from the orifices 24 in the cylindrical mim~er 22 and provide exit openings for the gas that is generated by the generator 1 . upon ccmbustion of the gas generant composition 68.
`` The screen pack co~prising filter 78 is formed around the cylin-drical nember 22, a suitable seal strip 88 being placed around the .30 outer wraps of fine mesh screen 84 for contacting the inner surface of the upper half shell 14 when the latter is brought into cooperative ; locking engagement with the lower half shell 12. The arrangement is such that the screen pack 78 is then brought under a suitable compressive load., with the upper edges curved. inwardly, in the ~`; 35 annular space between the ports 24 in t~.le cylindrical member 22 and. the exit ports 86 in the upper half shell 14.
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1~L5~049 By way of illustration and not limitation it is notcd that in an operative embodirent of Figure 1 of the invention, the external diameter of the generator 10 is 10.998 cm. (4.330") and its height is 6.353 cm. (2.501"), and the materials of which several components 5 are made and the dimensions thereof where relevant are as indicated belcw:
Components Materials Din~nsions half shell 12 carbon steel half shell 14 carbon steel 10 cartridge 30 aluminum primary filter coarse screen carbon steel 18 x 18 mesh filter cloth 74 fiberglass, 42 x 32 plain Style 1528 mfd. by Hexcel mesh Trevarno, Dublin, California 15 fine mesh screen 74 carbon steel 40 x 40 mesh secondary filter coarse screen 80 0.635 cm.(.25") blanket 82 A binder of content of 5% and thick a chemical analysis of fibers of 46% by weight, binder free and 54% of Alumina (A12O ) silica (SiO2) crabfiber paper, Johns-; Manvllle, Denver, Colo.
fine mesh screen 84 100 x 100 mesh ; Figure 2 is a sectional view of a gas generator 90 according 25 to the present invention that is particularly applicable for use in a vehicle cushion restraint system for protecting the p~ssengers, being mounted in an appropriate manner in or on the dash board oE the vehicle.
As shcJwn, the generator 90, similarly to the generator 1 of Figure 1, is annular in general construction, and essentially 30 differs in principle and operation from the generator 1 only in being elongated, typically having a length of 52.54 cm. (21") - and having the capability of a greater output of generated gas.
Thus, the generator 90 includes an elongated cylindrical housing 92 preferably made of carbon steel that for most of its length has 35 thin walls but at the left en~, as seen in Figure 2, includes a `
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heavier diffuser flange section 94 that provides a shouldcr indi-cated at 96. Section 94 flares outt~lrdly to receive a second elongated thin cylindrical m~mber 98 made of carbon steel that is concentrically positioned with respect to housing 92. The wall 5 of the right end of cylindrical housing 92 is rolled inwardly as indicated at 93 and is provided with a stud end flange 100 having a centrally disposed opening 102 therein. ~le rigllt end of cylindrical n~Yl~cr 98 i~ provid~d Wi~ U~ S-s~
curl as indicated at 99. Cooperating with the right ends of housing 10 92 and cylindrical member 98 for firmly locking those ends together are a stud end cap 104, a weld screw 106, a nut 108 and a lockwasher 110. The stud end cap 104 fits within the right end of cylindri-cal member 98 and has a peripheral surface that matches the S-shaped curllOOin the end of member 98. Weld screw 106 extends 15 through stud end cap 104 and outwardly of the stud end flange 100 to engage the nut 108 which extends partially through stud end cap lOA, the lockwasher 110 being provided to firmly retain ~le mcmbers together for long periods notwithstanding the presence of vibration.
When the weld screw 106 and nut 108 are pulled together in locking 20 relationship, the right end of cylindrical m~mker 98 is brought `l into tight engagement with the inner wall of stud end flange 100.
It will be noted that the interior of the cylindrical member 98 forms a combustion chamber 112 and that the annular space 114 between the member 98 and the inner surface of housing 92 provides 25 a diffuser space that extends to the left, however, only as far as the inner shoulder 96 on housing 92.
The left ends of the housing 92 and cylindrical member 98 are closed by a ring-shaped closure m~nber 116 that has a first peripheral portion 118 that fits inside a flared left end 120 30 of cylindrical mem~er 98, and a second peripheral externally threaded portion 122 that fits inside the flared internally threaded section 94 of housing 92, in threaded engagement therewith ; retaining and sealing O-r.ing 124 may also be provided, as shown.
An elongated rupturable hermetically sealed cylindrical 35 cartridge 126, preferably made of aluminum, is positioned in L
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11540~9 cl~Imber 112, being disposed coaxially therewith, completely filling the chamber and being held firmly against either radial or length-wise movement. The left end of cartridge 126 comprises an end disc 128 that is sealed by a suitable sealant to the cylindrical sidewall 5 with a double crimp seal.
Positioned in cartridge 126 in coaxial relationship thcl-c-with is an elongated perforatcd cylindrical initia~or or i~oitcr tube 130 having a rupturable metal foil or igniter barrier 132 sealed to the outer wall thereof. An igniter plug 134 is provided 10 adjacent the left end of igniter tube 130 and a separate igniter plug 136 is provided at the right end of tube 130, adjacent the right end wall of cartridge 126. As sht~n, the inner right end wall of cartridge 126 include.s an inwardly projecting short cylindrical portion 138 for retaining the right end of igniter 15 tube 130 in position. The left end of igniter tube is supported on the end of an initiator mounting member 140 that, in turn, is retained by a circular opening 142 in the cartridge 126 and includes a portion 144 that is press fit in a central opening 146 provided in ring shaped closure member 116. A O-ring 148 is provided to 20 retain mounting mem~er 140 in position. !:
Aconventional electric squib 150 having suitable energizing terminals is provided in the right end portion of initiator unting member 140, ferrite beads 152 being provided to render the squib 150 inse~sitive to extraneous radio frequency energy.
25 Between the igniter plugs 134 and 136 in the igniter tube 130 is pyrotechnic material comprising igniter granules 15~. Sur- i rounding the ignitex tub~ 130 are ~ ormly tListributed pellets 156 of gas generant composition, which composition, in turn, is surrounded by an elongated annular primary or combustion chamber 30 filter 158 which, generally, is similar to the filter 70 of the Figure 1 gas genexator.
The primary filter 158 comprises a filter pack of three screens including one to three layers of coarse screen 160 that are adjacent the inner wall of cartridge 126, one or m~re layers of 35 fiberglass woven fabric or cloth 162, and multiple layers of ~S4V49 fine mesh screen 164, preferably 40 x 40 mesh carbon steel.
A secondary filter 166 which, generally, is similar to the filter 78 of Figure 1, is located in the annular chamber 114 c~nprising the diffuser region and ccmprises a coarse, 18 mesh, stand-5 off screen 168 that surrounds the cartridge 126 in contact therewith,multiple wraps of coarse screen 170, one or more ~raps of al~un~n silicate blanket 172 that surround the cck~rse screen 170, .~ d æveral wraps of fine 100 m.esh screen 174 that are provided adjacent the inner wall of housing 92. me 18 ~esh standoff screen 168 10 is provided to allow the aluminum foil of cartridge 126 to blow out of the way.
me secondary filter 166 is arranged to cover a plurality of exit ports or orifices 176 that are provided in the cylindrical housing 92 and a plurality of exit ports or orifices (not shcwn) 15 that are provided in the housing 98. Preferably, four angularly spaced rows of exit ports are provided circumferentially of each of members 92 and 98, with 12 ports in each row, the exit ports in member 98 being offset both linearly and radially frcm the exit ports 176 in housing 92. ' The mechanical arrangement of the gas generator component of the present invention inherently promotes speed of reaction, cooling and filtering. Accordingly, with the structures of each of Figures 1 and 2 a slower burning, and hence, cooler burning gas 25 generant may be used. m e speed of reaction is increased notwith-standing the inherent characteristic of slower burning gas generants to be hard to ignite. mis is the result of several factors including the use of a composition for the igniter granules in the combustion initiator that provides a higher flame temperature 30 than in the prior art generators, and by arranging the gas generant composition pellets in uniformly distributed annular surrounding contact with the initiator whereby the entire peripheral area of the gas generant composition is immediately and simultaneously exposed to the hot gases and high te~perature flame fron the 35 initiator.
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llS4(~9 . .
The speed of reaction in the gcneration of the dcsircd gas, that desired for inflation of a vehicle cushion restraint, for example, is enhanced because the burning gases frcm the initiator and from the gas generant composition are made to expand rapidly 5 in all directions, without detonating, however, thus permeating and diffusing rapidly throughout the gas generant composition.
Featured, also, are thc arrallgal~lt. al-d construction oÇ ti)c llrin~
or c2mbustion chlmber filtèr and ~le secondary or fine particulate final filter that have the capability of filtering out 99.6% of 10 the solids from the gas generator effluent during a 45 milli-second function time with a low operating pressure of less than 1500 psi. The porosity of the fiberglass woven fabric or cloth of the primary or combustion chamber filter is so lcw in this pressure range as to retain the products of combustion or particu-15 late residues in the combustion chamber for a short interval, aninterval of one or tw~ milliseconds only in the 45-60 millisecond function time of the generator. This prevents most of such combustion products or particulate resi.dues from being explosively blown out ; of the combustion chamber and allows them to be cooled and con-20 densed on the carbon steel fine mesh screen that is located inboard of the fiberglass woven fabric element of the filter.
Specifically, the pyrotechnic material of the initiator, the gas generant ccmposition and the primary filter are all contained in the hermetically sealed aluminum cartridge. This 25 insures reliability of the generator over long periods. me aluminum cartridge is positioned in the ccmbustion chamber of the generator. Upon initiation of combustion by the firiny of the squib, the rising gas pressure ruptures the sidewall areas of ~le cartridge adjacent the orifices of ~le combustion chamb~r. This 30 allows gas to flow through the primary filter and out of the ccmr bustion chamber through the several orifices. The combustion chamber filter in each of Figures 1 and 2, consists of one to three layers of a coarse screen adjacent to the wall of the chamber. This serves as a collecting area for gas to flcw along 35 the chamcer wall to the chaTber orifices ar~ penmits gas to flow : ;
, .
.
~ lS4049 through the prirnary filter and out of tlle ccmbustion ch~mber through the several orifices. The combustion chamber filter in each of Figures 1 and 2, consists of one to three layers of a coarse screen adjacent to the wall of the chamber. This serves as a 5 collecting area for gas to flGw along the chan~er wall to the chamber orifices and permits gas to flow evenly through the prir~ary filter regardless of the proximity of a cc~ustion ch~lmber orifices. Inboard of the coarse screen are one or more layers ; of the fiberglass woven fabric. The fiberglass fabric is selected10 for compatability with the t~nperature in the combustion cham~er during burning of the seleeted gas generant ec~çosition thereby to provide a tacky surface for particle entraprnent that does not - melt or erode away under the effeets of the high temperature gas.
An effect accompanying the production of the tacky surface appears 15 to be a swelling of the fibers of the fiberglass fabric that reduces the porosity of the primary filter, and hence, causes the primary filter to restrict the flow of gas and combustion residue out of the eombustion ehamber. This effeet continues for only a short interval, as described, but long enough to allow cool~ing ; 20 and condensation of hot and molten particulate residue within the voids of the filter. Inside the rnultiple layers of the fiber-glass cloth are multiple layers of fine mesh carbon steel screen. .
The layers of the fine mesh earbon steel provide a large rela-tively eool surfaee for condensation of combustion solids prior 25 to encountering the multiple layers of fiberglass woven fabric.
Approximately 95 percent of all solid products of cGmbustion are trapped in the eombustion ehamber filter. It is noted that outside of the eombustion ehamber the aeeeleration of ~le gases that are generated bec~nes so high that trapping of the products of can-- 30 bustion in that region beeomes exceedingly difficult.
An addecl benefit of the fiberglass cloth is that uncler the high temperature environment, the glass reacts with caustic soclium oxide, Na2O, an effluent of the combustion process, to forrn innoeuous socliurn silicate.
The seeondary filter in each of Figures 1 and 2, is located 1~540'1~
outside of the ccmbustion chamber in the diff~scr arca of the annular chamber 26. This fllter is ccmprised of multiple wraps of wire mesh which serves to cool the gas and provide surface for condensation of solid particles. Surrounding the wire mesh filter 5 pack are one or more wraps of the aluminum silicate blanket. The aluminum silicate blanket serves two distinct functions. One of these functions is to react with particles of sodi~n oxide ~lic11 c~ne into intimate contact~with the secolld filter to ~O~lll soli~n silicate.
Surroundiny the aluminum silicate blanket are several wraps of fine mesh screen which provide structural support for the aluminum silicate blanket. It is noted that aluminum silicate blanket is porous, has very little strength, and tends to dis-integrate under the effects of the high velocity gas stre~m. The 15 filter elements, however, retain the solids entrapped. The fine mesh outer screen is used to trap these aluminum silicate filter particles and prevent them from being carried out of the exit orifices of the housing with the clean combustion gases.
The present invention is not dependent upon the specific 20 chemical composition of the combustible gas generant, the selection of the fiberglass woven fabric or cloth for compatibility with the combustion temperature of the selected gas generant composi-tion being the prime requirement. The use of the disc]oscd primary filter within the combustion chamber provided by the 25 cartridge in a gas generator utilizing a yas generating ccmposition as disclosed in the aforementioned copending application provides distinct advantages.These advantages are derived frcm the lcw~r temperature and pressure at which combuskion oE th~at cc~osition takes place in the combustion chamber. T~s makes possible a gas 30 generator of lighter weight since the structural components are subjected to lower combustion chamber temperature and pressure, and the production of an extremely clean gas and odor free gas.
In the aforementioned operative embodlment of this form of the invention, the amount of solid or particulate matter in the effluent 35 gas was reduced from 3 to 5 grams, as obtained in the prior art .~ I
., .
115404g generator of Patent 2,985,076, to 250 milliyr~ns. ~breover, the generator of the invention produced a substantially chemically neutral gas with a pH of 7 to 8 without the use of a chemical neutralizer.
; 5 Thus, there has been provided, according to the invention, an Lmprovement in the generation of gas by a solid fuel generator that results in the generation of extr~nely clean odorless ~as having a substantially reduced temperature. Such gas generation is accomplished by a generator of smaller size, having lighter 10 weight ccmponents, that operates at a pressure under lS00 psi.
m e improved generator includes a gas generant composition character-ized by sustained combustion at a lcwer temperature of a~out ¦ 1025C but nevertheless at a burning rate high enough to inflate a vehicle cushion restraint system within 45 millisecounds. I.
15 The pyrotechnic material for initiating combustion provides a desirably strong burning initiative thereby rapidly to effect sustained vigorous combustion of the gas generant composition. I
A combustion chamber cooling filter for maxLmum solids retention li with low pressure drop, that is, the primary filter, includes 20 a fiberglass woven fabric or cloth that provides a restriction to ~j~ retard for a short interval the flow of combustion products out ;~ of the oombustion chamber, and reacts with the caustic soda : r effluent resulting frn the combustion process, to provide a tacky surface for trapping solid particulate products and for ~` 25 converting the caustic soda to form innocuous sodium silicate.
The action of the filter is facilitated because of its location in the combustion chamber where it is operative to condense and ~`j trap solid particulate residue and to react wlth the caustic soda j ~ effluent during the short intervaL that the generated gases are 30 still undergoing relatively low rates of acceleration and velocity.
~ The invention further features a secondary filter that serves toj ~ cool the gas, provides a surface for further condensation of particles, and additionally, reacts with caustic soda particles to form sodium silicate. The secondary filter constitutes a final ~ 35 cooling filter for fine particle entrapment with lcw pressure drop.
;- !
I
.-:
.. : . , : ~ ,: : : .
- - :.- :, - , :~ :
1~4~49 It will be un~erstood that where the a~-~li metal azide forming the gas generant composition is a metal other than sodium, and is for example, potassium or lithium, the reaction of the glass of the fiberglass or cloth of the primary filter and the 5 reaction of the aluminum silicate blanket of the secondary fil-ter with the metallic oxide effluent of the combustion process would, in each case, be to form an innocuous alkali metal silicate, that is, potassium silicatè or lithium silicate.
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Claims (26)
1. A gas generator comprising:
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon ignition to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby the porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby prevent-ing combustion products from being blown out of the combustion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means comprises a plurality of layers of a fiberglass woven fabric, wherein said primary filter means includes a plurality of filter portions of which said fiberglass woven fabric layers comprise an interior portion, wherein the portion of said primary filter means adjacent to said gas discharge orifice means comprises at least one layer of a coarse screen and the portion of said primary filter means adjacent the gas generating means comprises a plurality of layers of fine mesh screen, wherein the composition of said gas generating means is such that one of the products of combustion is an alkali metal oxide, said fiberglass woven fabric reacting chemically with said alkali metal oxide to produce an alkali metal silicate and to cause the fibers of said fiberglass woven fabric to swell and to be effective, as the pressure in said combustion chamber rises to a predetermined level, to restrict the flow of gas through said filter means thereby allowing molten products of combustion to cool and condense on said fine mesh screen, wherein said one of the products of combustion is caustic soda and the product of the reaction of said caustic soda with said fiberglass woven fabric is sodium silicate, wherein said generating means and said primary filter means are contained in a hermetically sealed cartridge, wherein said cartridge and said combustion chamber are both cylindrical in shape, said cartridge being concentrically arranged with respect to and substantially completely filling said combustion chamber, and wherein said housing means further includes wall means defining an annular space external of said combustion chamber, said wall means having second gas discharge orifice means, and further including secondary filter means in said annular space between said first and second orifice means further to cool said gas and trap combustion products, wherein said secondary filter means includes a plurality of filter portions, an intermediate portion of said secondary filter means comprising a blanket of aluminum silicate which reacts chemically with caustic soda to form sodium silicate, wherein said secondary filter means includes a standoff screen and a coarse screen between said first gas discharge orifice means and said blanket of aluminum silicate, and a fine screen between said blanket of aluminum silicate and said second gas discharge orifice means, wherein said combustible gas generating means includes ignition means, said ignition means being disposed along the common cylindrical axis of said cartridge and combustion chamber, and wherein said gas generating means includes a plurality of pellets that are uniformly distributed in said cartridge in surrounding relation to said ignition means and that are comprised of a compacted mixture of 66% sodium azide, 30% ferric oxide, 2% sulfur and 2%
molybdenum disulfide.
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon ignition to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby the porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby prevent-ing combustion products from being blown out of the combustion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means comprises a plurality of layers of a fiberglass woven fabric, wherein said primary filter means includes a plurality of filter portions of which said fiberglass woven fabric layers comprise an interior portion, wherein the portion of said primary filter means adjacent to said gas discharge orifice means comprises at least one layer of a coarse screen and the portion of said primary filter means adjacent the gas generating means comprises a plurality of layers of fine mesh screen, wherein the composition of said gas generating means is such that one of the products of combustion is an alkali metal oxide, said fiberglass woven fabric reacting chemically with said alkali metal oxide to produce an alkali metal silicate and to cause the fibers of said fiberglass woven fabric to swell and to be effective, as the pressure in said combustion chamber rises to a predetermined level, to restrict the flow of gas through said filter means thereby allowing molten products of combustion to cool and condense on said fine mesh screen, wherein said one of the products of combustion is caustic soda and the product of the reaction of said caustic soda with said fiberglass woven fabric is sodium silicate, wherein said generating means and said primary filter means are contained in a hermetically sealed cartridge, wherein said cartridge and said combustion chamber are both cylindrical in shape, said cartridge being concentrically arranged with respect to and substantially completely filling said combustion chamber, and wherein said housing means further includes wall means defining an annular space external of said combustion chamber, said wall means having second gas discharge orifice means, and further including secondary filter means in said annular space between said first and second orifice means further to cool said gas and trap combustion products, wherein said secondary filter means includes a plurality of filter portions, an intermediate portion of said secondary filter means comprising a blanket of aluminum silicate which reacts chemically with caustic soda to form sodium silicate, wherein said secondary filter means includes a standoff screen and a coarse screen between said first gas discharge orifice means and said blanket of aluminum silicate, and a fine screen between said blanket of aluminum silicate and said second gas discharge orifice means, wherein said combustible gas generating means includes ignition means, said ignition means being disposed along the common cylindrical axis of said cartridge and combustion chamber, and wherein said gas generating means includes a plurality of pellets that are uniformly distributed in said cartridge in surrounding relation to said ignition means and that are comprised of a compacted mixture of 66% sodium azide, 30% ferric oxide, 2% sulfur and 2%
molybdenum disulfide.
2. A gas generator comprising:
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon ignition to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby he porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby prevent-ing combustion products from being blown out of the combustion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means is a woven fabric the fibers of which swell as they become tacky to increase the restrictive effect of said filter means to the flow of combus-tion products therethrough, such increased flow restrictive effect existing for a short interval only during the combustion process function period to retard the flow out of said combus-tion chamber of combustion products to increase the period for cooling thereof and thereby condensation and trapping of molten solid products of combustion by said filter means to minimize the quantity of such solid products of combustion that are blown out of said combustion chamber through said orifice means, and wherein said combustible gas generating means includes a plurality of pellets that are uniformly disposed in said combustion chamber and that are comprised of a compacted mixture of 66% sodium axide, 30% ferric oxide, 2% sulfur and 2%
molybdenum disulfide.
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon ignition to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby he porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby prevent-ing combustion products from being blown out of the combustion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means is a woven fabric the fibers of which swell as they become tacky to increase the restrictive effect of said filter means to the flow of combus-tion products therethrough, such increased flow restrictive effect existing for a short interval only during the combustion process function period to retard the flow out of said combus-tion chamber of combustion products to increase the period for cooling thereof and thereby condensation and trapping of molten solid products of combustion by said filter means to minimize the quantity of such solid products of combustion that are blown out of said combustion chamber through said orifice means, and wherein said combustible gas generating means includes a plurality of pellets that are uniformly disposed in said combustion chamber and that are comprised of a compacted mixture of 66% sodium axide, 30% ferric oxide, 2% sulfur and 2%
molybdenum disulfide.
3. A gas generator as specified in claim 2 wherein said substance of said primary filter means comprises a plurality of layers of a fiberglass woven fabric.
4. A gas generator as specified in claim 3 wherein said primary filter means includes a plurality of filter portions of which said fiberglass woven fabric comprises in interior portion, and wherein the portion of said primary filter means adjacent to said first gas discharge orifice means comprises at least one layer of a coarse screen and the portion of said filter means adjacent the gas generating means comprises a plurality of layers of fine mesh screen.
5. A gas generator as specified in claim 4 wherein said gas generating means and said primary filter means are contained in a rupturable hermetically sealed cartridge, and wherein said cartridge and said combustion chamber are both cylindrical in shape, said cartridge being concentrically arranged with respect to and substantially filling said combustion chamber.
6. A gas generator as specified in claim 5 wherein said housing means further includes wall means defining an annular space external of said combustion chamber, said wall means having second gas discharge orifices and further including secondary filter means in said annular space between said first and second orifice means further to cool said gas and trap combustion products, said second filter means including a plurality of filter portions of which an interior portion comprises aluminum silicate which reacts with caustic soda in the products of combustion to form sodium silicate.
7. A gas generator as specified in claim 6 wherein said gas generating means includes ignition means comprising a granular mixture of 15% by weight of boron and 85% of potassium nitrate plus or minus 10% for each component with the further addition of 3-10% of lead azide, said gas generating pellets surrounding said ignition means in contact therewith.
8. A gas generator as specified in claim 7 wherein said ignition means further includes an electric squib, a perforated tube and a rupturable metal foil sealed to the outer wall of said tube, said electric squib being centrally of said tube with said granular mixture in surrounding relation and in contact therewith.
9. A method of generating clean nitrogen gas in which most of the combustion residue product has been removed comprising a. providing a combustible composition essentially 60-80% sodium azide, 2-26% ferric oxide, 2-26% molybdenum disulfide and 0-6% sulfur, b. placing said combustible composition in a com-bustion chamber having gas discharge orifices, c. raising the temperature of said combustible com-30 position sufficiently to ignite it, and d. providing filtering means and cooling means between said combustible composition and said gas discharge orifices, said filtering means being selected for its compatibility with the combustion process and for its characteristic property at the combustion temperature of said composition of becoming less porous for a short interval during the combustion function time thereby, during such interval, to increase the restrictive effect thereof and to retard the flow of combustion products out of said gas discharge orifices to allow such combustion products to be cooled by and condensed on said cooling means.
10. A method as specified in claim 9 wherein said filtering means comprises at least one layer of a woven fabric, and said cooling means comprises a fine mesh screen provided between said fabric and said combustible composition.
11. A method as specified in claim 9 wherein said combustible composition is in pellitized form, the pellets being so placed in said combustion chamber as to be uniformly distributed therein, and wherein said woven fabric comprises a fiberglass woven fabric that reacts with a product of the combustion process, an alkali metal oxide, to form an innocuous alkali metal silicate.
12. A method as specified in claim 10 wherein said product of the combustion process is caustic soda and said fiberglass woven fabric reacts with said caustic soda to form innocuous sodium silicate, and further comprising providing a diffuser chamber in surrounding relation to said combustion chamber, said diffuser chamber having gas discharge orifices, and providing filtering means and cooling means in said diffuser chamber between the gas discharge orifice of said combustion chamber and diffuser chamber, said diffuser chamber filtering means including a blanket of aluminum silicate to react with caustic soda particulate residue to form innocuous sodium silicate.
13. A gas generator comprising:
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon ignition to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby the porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby prevent-ing combustion products from being blown out of the combustion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means comprises a plurality of layers of a fiberglass woven fabric, wherein said primary filter means includes a plurality of filter portions of which said fiberglass woven fabric layers comprise an interior portion, wherein the portion of said primary filter means adjacent to said gas discharge orifice means comprises at least one layer of a coarse screen and the portion of said primary filter means adjacent the gas generating means comprises a plurality of layers of fine mesh screen, wherein the composition of said gas generating means is such that one of the products of combustion is an alkali metal oxide, said fiberglass woven fabric reacting chemically with said alkali metal oxide to produce an alkali metal silicate and to cause the fibers of said fiberglass woven fabric to swell and to be effective, as the pressure in said combustion chamber rises to a predetermined level, to restrict the flow of gas through said filter means thereby allowing molten products of combustion to cool and condense on said fine mesh screen, wherein said one of the products of combustion is caustic soda and the product of the reaction of said caustic soda with said fiberglass woven fabric is sodium silicate, wherein said generating means and said primary filter means are contained in a hermetically sealed cartridge, wherein said cartridge and said combustion chamber are both cylindrical in shape, said cartridge being concentrically arranged with respect to and substantially completely filling said combustion chamber, and wherein said housing means further includes wall means defining an annular space external of said combustion chamber, said wall means having second gas discharge orifice means, and further including secondary filter means in said annular space between said first and second orifice means further to cool said gas and trap combustion products, wherein said secondary filter means includes a plurality of filter portions, an intermediate portion of said secondary filter means comprising a blanket of aluminum silicate which reacts chemically with caustic soda to form sodium silicate, wherein said secondary filter means includes a standoff screen and a coarse screen between said first gas discharge orifice means and said blanket of aluminum silicate, and a fine screen between said blanket of aluminum silicate and said second gas discharge orifice means, and wherein said combustible gas generating means includes ignition means, said ignition means being disposed along the common cylindrical axis of said cartridge and combustion chamber, and wherein said gas generating means includes a plurality of pellets that are uniformly distributed in said cartridge in surrounding relation to said ignition means and that are comprised of a compacted mixture of about 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur and from about 27 weight percent to about 33 weight percent molybdenum disulfide.
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon ignition to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby the porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby prevent-ing combustion products from being blown out of the combustion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means comprises a plurality of layers of a fiberglass woven fabric, wherein said primary filter means includes a plurality of filter portions of which said fiberglass woven fabric layers comprise an interior portion, wherein the portion of said primary filter means adjacent to said gas discharge orifice means comprises at least one layer of a coarse screen and the portion of said primary filter means adjacent the gas generating means comprises a plurality of layers of fine mesh screen, wherein the composition of said gas generating means is such that one of the products of combustion is an alkali metal oxide, said fiberglass woven fabric reacting chemically with said alkali metal oxide to produce an alkali metal silicate and to cause the fibers of said fiberglass woven fabric to swell and to be effective, as the pressure in said combustion chamber rises to a predetermined level, to restrict the flow of gas through said filter means thereby allowing molten products of combustion to cool and condense on said fine mesh screen, wherein said one of the products of combustion is caustic soda and the product of the reaction of said caustic soda with said fiberglass woven fabric is sodium silicate, wherein said generating means and said primary filter means are contained in a hermetically sealed cartridge, wherein said cartridge and said combustion chamber are both cylindrical in shape, said cartridge being concentrically arranged with respect to and substantially completely filling said combustion chamber, and wherein said housing means further includes wall means defining an annular space external of said combustion chamber, said wall means having second gas discharge orifice means, and further including secondary filter means in said annular space between said first and second orifice means further to cool said gas and trap combustion products, wherein said secondary filter means includes a plurality of filter portions, an intermediate portion of said secondary filter means comprising a blanket of aluminum silicate which reacts chemically with caustic soda to form sodium silicate, wherein said secondary filter means includes a standoff screen and a coarse screen between said first gas discharge orifice means and said blanket of aluminum silicate, and a fine screen between said blanket of aluminum silicate and said second gas discharge orifice means, and wherein said combustible gas generating means includes ignition means, said ignition means being disposed along the common cylindrical axis of said cartridge and combustion chamber, and wherein said gas generating means includes a plurality of pellets that are uniformly distributed in said cartridge in surrounding relation to said ignition means and that are comprised of a compacted mixture of about 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur and from about 27 weight percent to about 33 weight percent molybdenum disulfide.
14. A gas generator as specified in claim 13 wherein said pellets are comprised of a compacted mixture of about 68 weight percent sodium azide, about 2 weight percent sulfur and about 30 weight percent molybdenum disulfide.
15. A gas generator comprising:
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon igniton to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby the porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby pre-venting combustion products from being blown out of the combus-tion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means is a woven fabric the fibers of which swell as they become tacky to increase the restrictive effect of said filter means to the flow of combustion products therethrough, such increased flow restrictive effect existing for a short interval only during the combustion process function period to retard the flow out of said combustion chamber of combustion products to increase the period for cooling thereof and thereby condensation and trapping of molten solid products of combustion by said filter means to minimize the quantity of such solid products of combustion that are blown out of said combustion chamber through said orifice means, and wherein said combustible gas generating means includes a plurality of pellets that are uniformly disposed in said combustion chamber and that are comprised of a compacted mixture of about 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur, and from about 27 weight percent to about 33 weight percent molybdenum disulfide.
housing means defining a combustion chamber having first gas discharge orifice means;
combustible gas generating means disposed in said combustion chamber, said generating means being operable upon igniton to produce gas and combustion products; and primary filter means disposed in said combus-tion chamber adjacent said orifice means to cool said gas and to trap said combustion products, said filter means including a substance proximate to said gas generating means, in close surrounding relation thereto, said substance being selected for its compatibility with the combustion process and having a surface which at the temperature and environment of the combus-tion process, begins to melt and becomes tacky at an early stage of the combustion process whereby the porosity of said filter means is reduced for a short interval of the combustion process function time while the acceleration and velocity of the generated gases are at a relatively low level, thereby pre-venting combustion products from being blown out of the combus-tion chamber through said orifice means and allowing such products to condense and become entrapped in said filter means, wherein said substance of said primary filter means is a woven fabric the fibers of which swell as they become tacky to increase the restrictive effect of said filter means to the flow of combustion products therethrough, such increased flow restrictive effect existing for a short interval only during the combustion process function period to retard the flow out of said combustion chamber of combustion products to increase the period for cooling thereof and thereby condensation and trapping of molten solid products of combustion by said filter means to minimize the quantity of such solid products of combustion that are blown out of said combustion chamber through said orifice means, and wherein said combustible gas generating means includes a plurality of pellets that are uniformly disposed in said combustion chamber and that are comprised of a compacted mixture of about 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur, and from about 27 weight percent to about 33 weight percent molybdenum disulfide.
16. A gas generator as specified in claim 15 wherein said pellets are comprised of a compacted mixture of about 68 weight percent sodium azide, about 2 weight percent sulfur and about 30 weight percent molybdenum disulfide.
17. A gas generator as specified in claim 15 wherein said substance of said primary filter means comprises a plurality of layers of a fiberglass woven fabric.
18. A gas generator as specified in claim 17 wherein said primary filter means includes a plurality of filter portions of which said fiberglass woven fabric comprises an interior portion and wherein the portion of said primary filter means adjacent to said first gas discharge orifice means comprises at least one layer of coarse screen and the portion of said filter means adjacent the gas generating means comprises a plurality of layers of fine mesh screen.
19. A gas generator as specified in claim 18 wherein said gas generating means and said primary filter means are contained in rupturable hermetically sealed cartridge, and wherein said cartridge and said combustion chamber are both cylindrical in shape, said cartridge being concentrically arranged with respect to and substan-tially filling said combustion chamber.
20. A gas generator means as specified in claim 19 wherein said housing means further includes wall means defining an annular space external of said combustion chamber, said wall means having filter means in said annular space between said first and second orifice means further to cool said gas and trap combustion products, said second filter means including a plurality of filter portions of which an interior portion comprises aluminum silicate which reacts with caustic soda in the combustion products to form sodium silicate.
21. A gas generator as specified in claim 20 wherein said gas generating means includes ignition means comprising a granular mixture of 15% by weight of boron and 85% of potassium nitrate plus or minus 10% for each component with the further addition of 3 to 10% load azide said gas generating pellets surrounding said ignition means in contact therewith.
22 . A gas generator as defined in claim 21 wherein said ignition means further includes an electric squib, a perforated tube and a rupturable metal foil sealed to the outer wall of said tube, said electric squib being centrally of said tube with said granular mixture in surrounding relation and in contact therewith.
23 . A method of generating clean nitrogen gas in which most of the combustion residue product has been removed comprising:
a) providing a combustible composition essentially about 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur and from about 27 weight percent to about 33 weight percent molybdenum disulfide;
b) placing said combustible composition in a combustion chamber having gas discharge orifices;
c) raising the temperature of said combustible composition sufficiently to ignite it; and d) providing filtering means and cooling means between said combustible composition and said gas discharge orifices, said filtering means being selected for its compatibility with the com-bustion process and for its characteristic property at the combustion temperature of said composition of becoming less porous for a short interval during the combustion function time thereby, during such interval, to increase the restrictive effect thereof and to retard the flow of combustion products out of said gas discharge orifices to allow such combustion products to be cooled by and condensed on said cooling means.
a) providing a combustible composition essentially about 65 weight percent to about 70 weight percent alkali metal azide, up to about 4 weight percent sulfur and from about 27 weight percent to about 33 weight percent molybdenum disulfide;
b) placing said combustible composition in a combustion chamber having gas discharge orifices;
c) raising the temperature of said combustible composition sufficiently to ignite it; and d) providing filtering means and cooling means between said combustible composition and said gas discharge orifices, said filtering means being selected for its compatibility with the com-bustion process and for its characteristic property at the combustion temperature of said composition of becoming less porous for a short interval during the combustion function time thereby, during such interval, to increase the restrictive effect thereof and to retard the flow of combustion products out of said gas discharge orifices to allow such combustion products to be cooled by and condensed on said cooling means.
24 A method as specified in claim 23 wherein said filtering means comprises at least one layer of a woven fabric and said cooling means comprises a fine mesh screen provided between said fabric and said combustible composition.
25. A method as specified in claim 24 wherein said combustible composition is in pelletized form, the pellets being so placed in said combustion chamber as to be uniformly distributed therein, and wherein said woven fabric comprises a fiberglass woven fabric that reacts with a product of the combustion process, an alkali metal oxide, to form an innocuous alkali metal silicate.
26. A method as specified in claim 24 wherein said product of the combustion process is caustic soda and said fiberglass woven fabric reacts with said caustic soda to form innocuous sodium silicate, and further comprising providing a diffuser chamber in surrounding relation to said combustion chamber, said diffuser chamber having gas discharge orifices, and providing filtering means and cooling means in said diffuser chamber between the gas discharge orifice of said combustion including a blanket of aluminum silicate to react with caustic soda particulate residue to form innocuous sodium silicate.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US97068778A | 1978-12-18 | 1978-12-18 | |
| US970,687 | 1978-12-18 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1154049A true CA1154049A (en) | 1983-09-20 |
Family
ID=25517327
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000340555A Expired CA1154049A (en) | 1978-12-18 | 1979-11-23 | Method of and apparatus for gas generation |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPS55110642A (en) |
| CA (1) | CA1154049A (en) |
Families Citing this family (17)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4923212A (en) * | 1988-08-17 | 1990-05-08 | Talley Automotive Products, Inc. | Lightweight non-welded inflator unit for automobile airbags |
| US4907819A (en) * | 1988-09-16 | 1990-03-13 | Talley Automotive Products, Inc. | Lightweight non-welded gas generator with rolled spun lip |
| JP2598814B2 (en) * | 1988-12-05 | 1997-04-09 | 日本工機株式会社 | Combustion gas filtration device for gas generator for airbag deployment |
| JP2598815B2 (en) * | 1988-12-05 | 1997-04-09 | 日本工機株式会社 | Gas generating agent pack of gas generator for air bag deployment |
| US4943086A (en) * | 1989-06-30 | 1990-07-24 | Morton Thiokol, Inc. | Gas bag inflator with a two welded joint housing |
| DE69105179T2 (en) * | 1990-09-06 | 1995-06-22 | Nippon Oils & Fats Co Ltd | Gas generator device. |
| JPH0559418U (en) * | 1992-01-17 | 1993-08-06 | コパル電子株式会社 | Light deflector |
| US5503079A (en) * | 1992-02-10 | 1996-04-02 | Daicel Chemical Industries, Ltd. | Linear gas generant and filter structure for gas generator |
| JPH0769164A (en) * | 1993-09-01 | 1995-03-14 | Takata Kk | Inflator for air bag device |
| JPH07215162A (en) * | 1994-01-27 | 1995-08-15 | Daicel Chem Ind Ltd | Gas generator for air bag |
| JP4627581B2 (en) * | 2000-06-23 | 2011-02-09 | ダイセル化学工業株式会社 | Housing for gas generator for airbag and gas generator for airbag using the same |
| JPWO2001074632A1 (en) * | 2000-04-03 | 2004-01-08 | 日本化薬株式会社 | Gas generator |
| JP5021447B2 (en) * | 2007-12-21 | 2012-09-05 | 株式会社ダイセル | Gas generator |
| JP5016620B2 (en) * | 2009-01-15 | 2012-09-05 | 株式会社ダイセル | Gas generator for vehicle restraint system |
| JP5324930B2 (en) * | 2009-01-15 | 2013-10-23 | 株式会社ダイセル | Gas generator for vehicle restraint system |
| JP5016619B2 (en) * | 2009-01-15 | 2012-09-05 | 株式会社ダイセル | Gas generator for vehicle restraint system |
| JP6801164B2 (en) * | 2017-03-23 | 2020-12-16 | 株式会社ダイセル | Fixing structure of igniter and fixing method of igniter |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5713485B2 (en) * | 1973-07-23 | 1982-03-17 | ||
| JPS5313411A (en) * | 1976-07-23 | 1978-02-07 | Mitsubishi Paper Mills Ltd | Photographic material improved in coating property |
| JPS589505B2 (en) * | 1976-08-16 | 1983-02-21 | 松下電器産業株式会社 | Index printing control method for dictation recorder |
-
1979
- 1979-11-23 CA CA000340555A patent/CA1154049A/en not_active Expired
- 1979-12-14 JP JP16266779A patent/JPS55110642A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0219020B2 (en) | 1990-04-27 |
| JPS55110642A (en) | 1980-08-26 |
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| MKEX | Expiry |