MXPA00007213A - Dual level gas generator - Google Patents

Abstract

In order to allow for at least two different rates of air bag inflation a gas generator is provided with a single pyrotechnic charge which is disposed in a chamber in which argon or a similar type of non-toxic inert gas is stored under pressure. The chamber is closed off by two or more burst discs, only one of which is not exposed to a selectively ignitable squib. The non-exposed burst disc is arranged to breach when the pyrotechnic charge is ignited and increases the gas pressure in the chamber to a predetermined pressure. Each other disc is arranged to withstand the predetermined pressure and requires weakening by exposure to the heat from an associated squib before breaching will occur. The hybrid compressed gas/pyrotechnic pressure generation is such that the rate of air bag inflation varies essentially in proportion to the area of the exit port or ports which are opened by the breach of the burst disc or discs. By limiting the number of burst discs which are breached, the exit port area and the rate of air bag inflation/deployment can be controlled for slow speed collisions. Breaching more or all of the discs maximizes port area and increases the rate of pressurization to a level suitable for high speed collisions.

Description

DOUBLE LEVEL GAS GENERATOR BACKGROUND OF THE INVENTION Field of the Invention The present invention relates generally to a gas generating device and more specifically to a gas generating device which can selectively release gas at different rates and thereby allow a bag of air or similar device of an inflatable safety device, is deployed at different speeds, according to the different speeds of a vehicle.

Description of Related Art Recently, there has been a demand to control the inflation rate of safety devices such as airbag restriction systems, according to variables such as the size of the passenger and the speed of the vehicle at the time of a collision. In the case of a low speed accident, the passenger? passengers will tend to move within the vehicle (for example, forward) with much less force than in the case where a collision occurs at a relatively high speed. Consequently, since an airbag requires a given amount of gas to achieve its full deployment (inflation) and proper pressurization, if a passenger is moving within a vehicle under the influence of relatively small forces, then more time is available to fully deploy the restriction air bag in the event of a high-speed crash. Therefore, the rate of inflation may be lower than that which is necessary under high-speed conditions. To achieve the two inflation rates, it has been proposed in U.S. Pat. No. 3,773,353 to Trowbridge et al. to provide two separate charges and burn one in the case that slow inflation is required and burn both in the case of a high-speed collision, thus achieving inflation and very rapid deployment of the airbag that is necessary under such circumstances. In this device the charges are arranged inside a housing which is filled with a non-toxic gas under pressure. This housing is sealed by a rupture layer that is punctured by a piston and connecting rod type arrangement when a first of the two charges detonates. This arrangement, however, does not suffer from the disadvantage of being relatively complex and therefore relatively expensive. For example, not less than three break plate arrangements and two loads are required together with a housing arrangement that allows the two different loads to be stored separately and separately exposed to ignition devices such as detonators. US Patent No. 3,905,515 to Allemann discloses another two-stage inflator assembly which uses two separate charges and which deposits the charge in a chamber which is used to store a non-toxic gas under pressure. However, this arrangement is even more complex than that of Patent No. 3,773,353. In this arrangement a portion of the rupture disc forms the head of a slidable double-acting valve member which can project into an exhaust passage to partially reduce outflow after the detonation of one or both of the two charges.

BRIEF DESCRIPTION OF THE INVENTION An object of the present invention is to provide a simple and inexpensive gas generator for an airbag or similar type of flammable restriction device, which allows the device to be inflated at least at two different speeds and thus allows deployment according to a detected vehicle speed. A further object of the present invention is to provide a gas generator for an automotive safety restriction system such as an air bag that requires only a single charge which ignites in response to a collision and which controls the rate of inflation using a multi-disk bursting arrangement where all but one of the disks are opened in response to the application of a detonator or similar type of disk-debilitating device. In the case where solid propellants are used to generate inflation gases from the stock market, the solid fuel is burned in an obstructed or strangulated combustion chamber, where the area of the exit door is fixed. With pyrotechnic generators the flow velocity of the gas is inversely proportional to the area of the door. Consequently, increasing the area of the door results in a decrease in the flow velocity and retards the inflation of the bag. Consequently, a large door is required for low speed collisions while a smaller one is required in the case of an accident at higher speed. On the other hand, in hybrid arrangements where pyrotechnic gas generation is used in combination with a source of compressed gas, and where the products of propellant combustion are mixed with compressed gas (eg argon) in the gas storage bottle in a form that raises the temperature and presses the container, the mixing ratio of the compressed gas and combustion products, which determines the orifice coefficient, varies in a complex way with respect to time. The numerical solutions to the flow equation show that the flow velocity is proportional to the area of the gate. The invention is based on the concept of using an arrangement of pyrotechnic gas / hybrid tablet and varying the area of the door in a way that allows the flow rate to be controlled to at least two different levels and thus allow the Inflation velocity of an airbag is controlled at least at a fast speed and a slow speed. That is, using a hybrid arrangement where a gas under pressure is provided in combination with a pyrotechnic charge, which establishes a situation where the flow velocity is proportional to the area of the door through which the gases are discharged, it is possible selectively opening only one of a plurality of doors in the event that slow inflation is required, and increasing the number of doors that open at the same time in case an inflation rate and faster deployment is necessary. In brief, the above objects are achieved by an arrangement where a gas generator is provided with a single charge which is deposited in a chamber in which it is stored under argon pressure or a similar type of non-toxic inert gas. The chamber is closed by two or more rupture discs, only one of which is not exposed to a selectively flammable detonator. The unexposed rupture disc is arranged to break when the pyrotechnic charge ignites and brings the gas pressure in the chamber above a predetermined tolerance limit. The other disc or discs are arranged to resist this pressure and require weakening by exposure to the heat of an associated detonator before the break occurs. The hybrid generation of compressed gas / pyrotechnic pressure is such that the rate of inflation of the bag varies essentially in proportion to the area of the door or doors that are opened by the broken rupture disk. By limiting the number of rupture discs that break, the door area and inflation / deployment velocity of the airbag can be controlled for low speed collisions. The rupture of all the discs maximizes the area of the door and maximizes the pressurization speed to a level suitable for high speed collisions. On the other hand, the breaking of a selected number of disks may allow the inflation rate to be controlled so that it is more suited to an intermediate speed collision. More specifically, a first aspect of the present invention resides in an inflation device for a vehicle security restriction comprising: a container, a partition that divides the interior of the container into a first chamber and a second chamber, the first one chamber is hermetically sealed, the second chamber is ventilated by means of a multiple outlet opening; a pyrotechnic charge placed in the first chamber; means for selectively igniting the pyrotechnic charge; a predetermined amount of a predetermined gas stored in the first chamber under a first predetermined pressure; first rupture disc means closing a first door which communicates with the first and second chambers, the first rupture disc is adapted to fail when the pressure in the first chamber reaches a second predetermined pressure; second means of rupture discs closing a second door the sual communicates with the first and second chambers; and means for selectively introducing the failure of the second rupture disc under a pressure which is approximately at the first predetermined pressure. A second aspect of the invention resides in an inflation device for use in a vehicle restraint system having an inflatable restriction member, comprising: a first rupture disc operatively positioned between a source of gas under pressure and an aperture of discharge, the first rupture disc is adapted to fail under a predetermined pressure to open a first door and allow communication between the source of gas under pressure and the discharge opening; a second rupture disc operatively positioned between the source of gas under pressure and the discharge opening, the second rupture disc is adapted to fail under an excess pressure of the predetermined pressure and to open a second door; and means for reducing the structural strength of the second rupture disc to a degree where it will fail under the predetermined pressure and open the second door. A third aspect of the invention resides in a method for controlling the inflation of an inflatable safety restriction device comprising the steps of: producing gas under pressure by igniting the pyrotechnic charge in a volume of pressurized gas; breaking a first rupture disc and opening a first door exposing the first rupture disc to the gas under pressure; allowing the gas to be released at a velocity which is essentially proportional to the area of the first door; reducing the structural strength of a second rupture disc in response to the detection of a vehicle valve exceeding a predetermined first speed to induce the rupture of the second rupture disc and opening a second door under the application of gas under pressure; and allowing the gas to be released through the first and second doors and at a velocity which is essentially proportional to the combined areas of the first and second doors.

BRIEF DESCRIPTION OF THE DRAWINGS The various features and claimed advantages of the present invention will be more clearly appreciated as a description of the preferred embodiment given in conjunction with the accompanying drawings in which: Figure 1 is a cross-sectional view of one embodiment of the present invention; invention; Figure 2 is a schematic view from one end of a plate in which the rupture discs, which form a vital part of the embodiment shown in Figure 1, are formed, and showing the disposition of the rupture discs in the manner in which an additional disk could be provided; Figure 3 is a block diagram showing the arrangement of a circuit which is used to control the number of rupture discs that break and therefore control the inflation rate of the air bag restriction device; and Figure 4 is a schematic description of a modified detonator, which includes an autoignition pill (AIP) which is used to ignite the second detonator with predetermined delay after the first detonator is fired.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figure 1 shows an embodiment of the invention where a gas generating device 100, which includes a pyrotechnic charge 101, is supported by a steel cylindrical housing or pressure vessel 102 which, as shown , is basically comprised of a length of cylindrical tube 104 which is closed by two cap-shaped end members, 106, 108 which are in a fixed position (eg, soldiers). A detonator or similar type of the ignition device 110 and an ignition disk 112 are placed in the first end member 106 very close to the pyrotechnic charge 101. A partition plate 114 is placed in the tube 104 near the second end member 108 of so that it is relatively distal of the detonator 110. The partition plate 114 is fixed in a position such that it defines a load 116 within the tube 104 which is filled with a suitable non-toxic gas, such as an argon or helium, under pressure, and hermetically sealed. A filling port 117 is provided in the first end member 106 to facilitate loading of the chamber 116 with the non-toxic gas selected after the device is mounted and the different components are secured together. As shown in Figures 1 and 2, the partition plate 114 is formed with two separate rupture discs 118, 120. The first disc 118 is adapted to fail and break under the application of a predetermined pressure, while the second disc 118 120 is designed to require a higher pressure or some form of weakening before the fault occurs. A second detonator 122 is mounted on the second end member 108 of the housing very close to the second rupture disc 120. The second detonator 122 is arranged to heat and weaken the second rupture disc 120 in a way that will allow a pressure that will break the first disk 118, also breaks the second disk 120. A plurality of multiple outputs 124 are formed through the wall of the tube 104 to allow the gases, which are released into a sub-chamber 126 defined between the partition plate 114 and the second end member 108, through the doors that open when one or both of the rupture discs 118, 120 are induced to fail, flow outward toward a conduit or conduit arrangements (not shown) which directs the gas flow to an air bag or similar type of inflatable restriction device (not shown). Since the construction and arrangement of the pyrotechnic charge is not directly related to the invention, and can be of any known suitable type, a detailed description thereof was omitted for brevity. However, as an additional reference in relation to this aspect of the device, reference has been made, by way of example, to U.S. Patent No. 5,482,579 issued January 9, 1996 in the name of Ochi et al., Patent No. 5,439,251 issued in August 1995 in the name of Onishi et al., United States Patent No. 5,431,103 issued July 11, 1995 in the name of Hoc et al., US Patent No. 4,948,439 issued August 14, 1990 in the name of Poole. et al., and U.S. Patent No. 3,613,579 issued October 19, 1971 in the name of Warren. As shown in Figure 3, the two detonators 110 and 122 are operatively connected to a circuit 200 which is sensitive to the output of a G 201 sensor which detects vehicle acceleration, for example, and a vehicle speed sensor. 202, and is arranged to determine whether both detonators 110, 122 need to be fired simultaneously or if only the 110 needs to be fired initially. It will be noted that with this embodiment, it is preferred that both detonators 110, 122 be fired. In the case of a high-speed collision it is necessary to simultaneously fire both to blow (break) both rupture discs 118, 120 and to open both doors in a way that allows rapid inflation of the air bag restriction system. However, in the case of a low speed collision, the first detonator 110 is initially triggered and is followed by a delayed ignition of the second 122. This delay is set to approximately 100 ms, which allows a very substantial portion of the pressure that develops in chamber 116 is substantially ventilated. With this delay, the firing of the second detonator 122 has no essential effect on the inflation rate of the air bag and may not in fact result in the second break disk 120 breaking. That is, heating of the rupture disk 120 by the second detonator 122 is designed to weaken the second disk 120 to the extent that the high pressure developing in the chamber 116 as a result of detonation of the pyrotechnic charge 101 is Break However, if the heating of the second disk 120 is delayed, the pressure that remains in the chamber 116 at the moment in which the second detonator is fired may in fact not be sufficient to actually break the second rupture disk 120 and open the second door. It will be understood that interested in safety, both detonators 110, 120 are preferably fired within a very short period of time to ensure that very briefly after a collision and deployment of the airbag retention system, the unit is fully inert and unable to detonate additionally, which could induce undesirable side effects. In the case of a severe accident, for example, it would be extremely undesirable that an inadvertently very delayed detonation (for example of more than 20 seconds) of the second detonator will ignite combustible vapors. Unexpected detonations when the airbag is replaced after a collision are also eliminated by this delayed firing of the detonator 122. Either as an alternative or as a supplement to the firing signal, it is within the scope of the present invention provide the second detonator 122 'with an autoignition pill (AIP) 301 in the manner illustrated in Figure 4. This pill 301 is, as shown schematically in Figure 4, protected by a suitable layer 302, so that the heat of the hot effluent escaping via the sub-chamber 126, is transmitted to the pill 301 with a sufficient delay to ensure that ignition and subsequent detonation of the second detonator 122 ', occurs after a delay of approximately lOOms and has no effect on the number of sets that they open and that they control the inflation rate of the airbag. The provision of the AIP 301 is to ensure that the second detonator 122 is fired and becomes harmless regardless of whether the control circuit 200 is damaged by the collision so that it is unable to send a second ignition signal.

In experiments which were carried out during the development of the present invention, a gas generator was charged with argon at 3112 psi (218.8 gf / cm2) and fired in a 60 liter tank. The rupture disc arrangement was such that the sum of the areas of the doors was 75% greater than that of the primary door. In a simulated high-speed collision both doors opened simultaneously. The primary door was opened by the pressure rise of the bottle while the secondary door was opened by a combination of the pressure rise and the heat of the second detonator 122. The result was a rapid deflation, with the pressure of the Argon bottle with a maximum of 5821 psi (409.27 kgf / cm2) in only lOms, and tank pressure of 60 liters with a maximum pressure of 88.34 psi (6.21 kgf / cm2) in 76ms. In a simulated low-speed collision, only the primary gate was opened when the pressure of the argon bottle. The secondary door remained unopened due to the delayed activation of the second detonator 122. Due to the reduced flow area, the deflation took place more slowly with the tank pressure without reaching 88.34 (6.21 kgf / cm2) in up to lOOms. The inflation velocity of the airbag was correspondingly slower although the driving force "(ie the pressure of the argon bottle) was much higher than 12.518 psi (91.23 kgf / cm2), although it developed more slowly in a maximum of 23ms compared to the lOms observed in the simulated high-speed collision, Table 1 shows more specific data, which is explained below.

TABLE 1 MEASURED EFFECT OF THE REDUCED AREA OF THE DOOR ON THE PRESSURE AND TIME: SHOOTING THE GAS GENERATOR OF AN AIR BAG, HYBRID, IN A TANK OF 60 LITERS SPEED OF PRESSURE DIAMETER PRESSURE OF THE INCREASE OF THE THE XIMA DOOR OF THE TANK AT THE PRESSURE OF THE IN INCHES BOTTLE IN TIME 97% IN PSI TIME TANK TO 97% EBN (CM) PSI (KGF / CM2) IN MS JKGF / CM-) IN MS PSI (KGF / CM2) 0. 171 9270 (651.7) 21.1 55.8 (3.9) 61.4 9.909 (0.696) (0 .43) 0. 197 7843 (551.4) 16.0 58.4 (4.1) 58.0 1.007 (0.071) (0 .50) As will be appreciated from the above data, a 33% increase in the door area resulted in a 4.6% increase in tank pressure, a 5.5% decrease in the rise time, and consequently a 11% increase in the rate of increase in tank pressure, although the driving force (ie, bottle pressure) was reduced by 15%. Although the present invention has been discussed with reference to a main embodiment, it will be appreciated that the inventors are not limited and that various changes and modifications can be made without departing from the scope of the present invention. For example, the generator can be provided with three or more rupture discs all of which except one are provided with a detonator to selectively weaken and allow the pressure to blow first, to also break one or more of the others. This of course means that instead of changing two stages in the door area, a variation of three or four stages is possible to increase the speed levels that can be accommodated. Additional modifications may include the arrangement of the rupture discs in different members / partition positions.

Claims (16)

CHAPTER CLAIMING Having described the invention, it is considered as a novelty and, therefore, what is claimed is contained in the following CLAIMS:

1. The inflation device for a vehicle security restriction, characterized in that it comprises: a housing; a partition dividing the interior of the housing in a first chamber and a second chamber, the first chamber is hermetically sealed, the second chamber is ventilated by means of a multiple outlet opening; a pyrotechnic charge placed in the first chamber; means for selectively igniting the pyrotechnic charge; a predetermined amount of predetermined gas stored in the first chamber under a first predetermined pressure; first rupture disc means closing a first door which connects the first and second chambers, the first rupture disc is adapted to fail when the pressure in the first chamber reaches a second predetermined pressure that is greater than the first predetermined pressure; second rupture disc means closing a second door which connects the first and second chambers; and means for selectively inducing failure of the second rupture disc means substantially simultaneously with the first disc means, or subsequently under a pressure that is less than the second predetermined pressure.

The inflation device according to claim 1, characterized in that the means inducing selective failure comprise a detonator which ignites to heat and weaken the second rupture disc.

The inflation device according to claim 1, characterized in that the predetermined gas is a non-toxic gas selected from the group comprising argon and helium.

4. The inflation device according to claim 1, characterized in that the first predetermined pressure is about 3000 psi (20841 kPa).

5. The inflation device for use in a vehicle restraint system having an inflatable restriction member, characterized in that it comprises: a first rupture disc operatively positioned between a source of gas under pressure and a discharge opening, the first disc Rupture is adapted to fail under a predetermined pressure to open the first door and connect the gas source under pressure and the discharge opening; a second rupture disc operatively positioned between a source of gas under pressure and the discharge opening, the second rupture disc is adapted to fail under a pressure exceeding the predetermined pressure to open the second door that connects the gas source under pressure and the discharge opening; and means for reducing the structural strength of the second rupture disc so that it fails under the predetermined pressure and opens the second door.

The inflation device according to claim 5, characterized in that the source of gas under pressure comprises a container which is filled with a predetermined gas under a pressure which is lower than the predetermined pressure, and a selectively flammable pyrotechnic charge. , which upon ignition produces hot gaseous products which mix with the predetermined gas and produce a gas pressure at least as high as the predetermined pressure.

The inflation device according to claim 6, characterized in that it further comprises means for controlling the ignition time of the flammable pyrotechnic charge selectively and controlling the means that reduce the structural force to weaken the second rupture disk.

The inflation device according to claim 7, characterized in that the control means are sensitive to the acceleration of the vehicle and to the speed of the vehicle, and where the control means ignite the pyrotechnic charge and control the means that reduce the resistance structural to reduce the strength of the second rupture disc, so that it fails under the predetermined pressure when it is detected that the vehicle speed is higher than a predetermined limit.

The inflation device according to claim 8, characterized in that the control means ignite the pyrotechnic charge and control the means that reduce the structural resistance to reduce the resistance of the second rupture disk with a predetermined time delay after the ignition of the pyrotechnic charge when it is detected that the speed of the vehicle is below the predetermined limit.

The inflation device according to claim 5, characterized in that the means reducing the resistance comprise a detonator which ignites to heat and weaken the second rupture disc.

The inflation device according to claim 10, characterized in that the detonator includes igniter pill means which are sensitive to the heat of the gases that are released through the first gate to cause the detonator to ignite with a Default delay time after the ignition of the pyrotechnic charge.

12. The inflation device according to claim 5, characterized in that the source of gas under pressure includes a pyrotechnic charge and a predetermined amount of gas under a pressure, which is less than the predetermined pressure, the pyrotechnic charge is combustible, selectively to produce hot gaseous combustion products which mix with and heat the predetermined amount of gas at a pressure at least as high as the predetermined pressure at which the first rupture disc will fail and at which the second rupture disc will remain intact .

The inflation device according to claim 6, characterized in that the predetermined gas is a non-toxic gas selected from the group comprising argon and helium.

14. A method for controlling inflation of an inflatable safety restriction device, characterized in that it comprises the steps of: producing gas under pressure by igniting a pyrotechnic charge in a volume of pressurized gas; breaking a first rupture disc and opening a first exit door exposing the first rupture disc to gas under pressure; allowing the gas to be released at a velocity which is essentially proportional to the area of the first exit door; reducing the structural strength of a second rupture disc in response to detection of the vehicle speed exceeds a predetermined first speed to induce the breaking of the second rupture disc and opening a second exit port under the application of gas under pressure; and allowing the gas to be released through the first and second exit doors at a velocity which is essentially proportional to the combined areas of the first and second exit doors when the vehicle speed exceeds the predetermined speed.

The method according to claim 14, characterized in that the step of reducing the structural resistance includes using a flammable detonator to heat and weaken the second rupture disk.

16. The method according to claim 15, characterized in that the flammable detonator ignites with a predetermined delay time after the pyrotechnic charge ignites when the speed of the vehicle is lower than the predetermined speed of the vehicle.