US3916364A

US3916364A - Enclosed, non-vented fuse suitable for use with universal fuse links

Info

Publication number: US3916364A
Application number: US436815A
Authority: US
Inventors: Robert Lynn Cooper
Original assignee: Deutsche ITT Industries GmbH
Current assignee: Thomas and Betts Holdings Inc
Priority date: 1974-01-25
Filing date: 1974-01-25
Publication date: 1975-10-28
Anticipated expiration: 1992-10-28
Also published as: JPS50104352A; GB1490655A; JPS5436727B2; CA1034994A

Abstract

An enclosed, non-vented expulsion fuse comprises a hermetically sealed tank, having a universal load-side bushing well and a line-side fuse module mounted thereon. The fuse module includes a stationary element fixedly mounted to the tank, and a fuse cartridge removably mounted in the stationary element. The fuse cartridge includes a universal bushing well which provides a line terminal connection at a bushing well cap thereof. This fuse bushing well includes a feedthrough connection to a removable fuse holder assembly which, in turn, is mounted within a torque tube portion of the fuse cartridge. The torque tube engages the fuse bushing well and is removably secured at a lower end of the fuse holder assembly by way of a spring clip. The lower end of the fuse holder assembly includes a conductive latch which removably secures the fuse holder assembly to a lower conductive pressure container portion of the stationary element, upon rotation of the fuse bushing well. The fuse bushing well is rotated by a safety interlocking handle which latches the fuse bushing well cap in its sealed position with respect to the stationary element. The removable fuse holder assembly includes an insulated fuse tube having an arc-responsive liner which receives a universal fuse link therein. A conductive strap couples the conductive container to the load-side bushing well to complete a fuse circuit. The container includes a thermal quenching medium which acts to rapidly remove thermal energy from the expanding gases which result from the arc drawn in the fuse holder once the fuse element melts.

Description

United States Patent [1 1 Cooper Oct. 28, 1975 1 ENCLOSED, NON-VENTED FUSE SUITABLE FOR USE WITH UNIVERSAL FUSE LINKS [75] Inventor: Robert Lynn Cooper, Creve Coeur,

[73] Assignee: International Telephone &

Telegraph Corporation, New York, NY.

[22] Filed: Jan. 25, 1974 [21] App]. No.: 436,815

[52] US. Cl. 337/217; 337/237; 337/249 [51] Int. Cl. l-IOIH 85/02 [58] Field of Search 337/186, 190, 202, 217,

[56] References Cited UNITED STATES PATENTS 2,247,702 7/1941 Ramsey 337/279 2,937,253 5/1960 Smith 337/219 X 3,719,912 3/1973 Harner et al.... 337/282 X 3,827,011 7/1974 Braunstein 337/279 X Primary Examiner-G. Harris Attorney, Agent, or Firm-James B. Raden; William J. Michals [57] ABSTRACT An enclosed, non-vented expulsion fuse comprises a hermetically sealed tank, having a universal load-side bushing well and a line-side fuse module mounted thereon. The fuse module includes a stationary element fixedly mounted to the tank, and a fuse cartridge removably mounted in the stationary element. The fuse cartridge includes a universal bushing well which provides a line terminal connection at a bushing well cap thereof. This fuse bushing well includes a feedthrough connection to a removable fuse holder assembly which, in turn, is mounted within a torque tube portion of the fuse cartridge. The torque tube engages the fuse bushing well and is removably secured at a lower end of the fuse holder assembly by way of a spring clip. The lower end of the fuse holder assembly includes a conductive latch which removably secures the fuse holder assembly to a lower conductive pressure container portion of the stationary element, upon rotation of the fuse bushing well. The fuse bushing well is rotated by a safety interlocking handle which latches the fuse bushing well cap in its sealed position with respect to the stationary element. The removable fuse holder assembly includes an insulated fuse tube having an arc-responsive liner which receives a universal fuse link therein. A conductive strap couples the conductive container to the load-side bushing well to complete a fuse circuit. The container includes a thermal quenching medium which acts to rapidly remove thermal energy from the expanding gases which result from the are drawn in the fuse holder once the fuse element melts.

9 Claims, 16 Drawing Figures iii U.S. Patent Oct.28, 1975 Sheet 1 of6 3,916 364 US. Patent Oct. 28, 1975 Sheet 2 of6 3,916,364

FEE, 3

L mum! U.S. Patent Oct.

ill-HF Sheet 3 of 6 US. Patent Oct.28, 1975 Sheet40f6 3,916,364

3 0 .FIG. I

l I V780 32 U.S. Patfint Oct. 28, 1975 Sheet 5 of6 3,916,364

as FIG. 11

FIG. 10

FIG. 13

U.S. Patent Oct.28,1975 Sheet6of6 3,916,364

FIG. 15

ENCLOSED, NON-VENTED FUSE SUITABLE FOR USE WITH UNIVERSAL FUSE LINKS BACKGROUND OF THE INVENTION This invention relates to an enclosed, non-vented expulsion fuse structure and, more particularly, to a fuse structure suitable for use with universal fuse links.

In the prior art, expulsion fuses such as overhead fuse cutouts are well known. In its simplest form, the overhead fuse cutout can be considered as a meltable, weak-link fuse installed in a relatively long tube lined with an organic material such as horn fiber. Upon sensing an abnormal condition in current, such as an overload of high-current fault, the link melts or blows, and an are forms in the resulting gap. The normal energy loss from the arc is sufficient to decompose a portion of the organic liner into a high-pressure, highly turbulent gas which acts on the core of the arc to sufficiently cool and de-ionize the arc gas, and, thusly, effect circuit interruption at a current zero. The resulting highenergy, high-pressure gas is expulsed into the atmosphere in a loud, explosive and luminous cloud.

The violent operating characteristics of expulsiontype distribution fuses and cutouts are not only environmentally objectionable for many overhead applications, but also effectively preclude the use of an expulsion-type fuse in underground power distribution sytems. That is, for underground distribution applications, the fuse must generally be insulated during operation for safety considerations as well as hermetically sealed to protect it from its environment. However, presently known underground fuses-such as, for example, current-limiting fuses and oil-filled fuses-fail to provide the standardized time-current characteristics afforded by overhead cutout fuses. Accordingly, the present practice in the art of underground distribution systems is to provide pole-mounted overhead cutout fuses at periodic locations along the underground distribution system. This practice obviously does not provide a completely underground distribution system.

The present invention overcomes the problems and disadvantages of prior art fuses by providing an enclosed, non-vented expulsion fuse suitable for use with universal fuse links having, for example, standard NEMA K and T time-current characteristics. Accordingly, the expulsion fuse, in accordance with the present invention, is suitable for use-in underground distribution systems, sub-surface and submersed applications, and those applications where a non-violent operating fuse is required.

SUMMARY OF THE INVENTION Briefly,an enclosed,nonvented expulsion fuse structure for use with universal fuse links is provided. the fuse structure includes a housing having a bushing and a fuse module mounted thereon and projecting therein. The fuse module comprises a stationary element fixedly mounted to the housing and a fuse cartridge removably mounted within the stationary element. A thermal quenching medium is disposed in a lower portion of the stationary element. The fuse cartridge includes a removably mounted fuse holder therein for receiving a fuse link. The fuse holder includes a liner of arcresponsive material of the type wherein energy loss from an arc drawn within the fuse holder decomposes a portion of the liner into a turbulent, high-pressure, high-temperature gas. The lower end of the fuse holder opens into a pressure container portion of the stationary element wherein the thermal quenching medium is disposed. Means are provided for directing the gases discharged from the fuse holder into the pressure container. Means are also provided for coupling the bushing to the fuse module to complete a fuse circuit within the housing.

BRIEF DESCRIPTION OF THE DRAWING The advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description when taken in conjunction with the accompanying drawing wherein:

FIG. 1 is a top view of an outdoor tank which serves as a housing for the fuse structure in accordance with the present invention;

FIG. 2 is a side view of the tank of FIG. 1;

FIG. 3 is a side view of the tank cover showing the relative mounting position of the stationary element and load-side universal bushing well;

FIG. 4 is a side view of the load-side universal bushing well of FIG. 3;

FIG. 5 is a side view of a preferred fuse module in accordance with the present invention;

FIG. 6 is a partial cross-section of the fuse module of FIG. 5;

FIG. 7 illustrates a partial cross-section of the removable fuse cartridge and fuse holder assembly of the fuse structure in accordance with the present invention;

FIG. 8 is a partial cross-sectional view of the portion of the stationary element of the fuse module which is mounted to the tank cover;

FIG. 9 is a cross-sectional view taken along the line 9-9 of FIG. 7 and illustrating the means by which the torque tube of FIG. 7 is removably mounted to the fuse holder assembly of FIG. 7;

FIG. 10 is a partial cross-section view of the fuse holder of the removable fuse bushing well of the present invention;

FIGS. 11 and 12 provide top and cross-section views of the fuse tube cap of the fuse holder of FIG. 10;

FIG. 13 is a partial cross-sectional view of a universal fuse link adapted with a link extension assembly;

FIG. 14 is a partial cross-sectional view of the latch assembly of the fuse holder assembly of FIG. 10 and illustrating particularly the flexible lead connection and extractor spring features of the present invention;

FIG. 15 provides a bottom view of the latch of FIG. 14; and, 4

FIG. 16 is a cross-sectional view of the pressure container portion of the stationary element of the fuse module as taken along the line 16-16 of FIG. 6.

DETAILED DESCRIPTION Referring now to FIGS. 1 and 2, there is shown generally at 10 a hermetically sealed tank having a drum l2 and a top cover 14. Tank 10 provides a housing for the enclosed, non-vented expulsion fuse structure in accordance with the present invention. Mounted on cover 14 and projecting within drum 12 are a load-side universal bushing well 16 and a fuse module shown generally at 18. The portion of fuse module 18 which projects externally of tank 10 provides a universal bushing well having a recess essentially identical to that of the universal bushing well recess of bushing well 16. Bushing well 16 is provided with a threaded projecting stud 16a, and fuse module 18 is similarly provided with a threaded projecting stud 18a. Threaded studs 16a and 18a provide means for attaching external bushing terminals for use with terrninators such as an elbow as is well-known in the art. Top cover 14 is provided with conventional lifting eyes 20, threaded grounding pads 22, and parking stand brackets 24. Pads 22 provide connectors for securing the concentric ground leads of the associated power distribution lines, and brackets 24 provide means for conveniently storing the associated elbow connectors, etc., when the fuse structure is being serviced. Top cover 14 is provided with a name plate 26, and drum 12 is provided with mounting handles 28.

The upper bushing well portion of fuse module 18 includes a bushing well cap 30 having an interlocking handle 32 pivotally mounted thereon about

pins

34a and 34b; As discussed more fully hereinafter, handle 32 serves to latch cap 30 into its sealed position with respect to tank and the cooperating structure of fuse module 18. Handle 32 also serves as a safety interlock feature in that the associated line terminal connections must be removed from

bushing wells

16 and 18 before handle 32 may be raised in such a position so as to permit withdrawal of fuse module 18 from tank 10.

Referring now to FIG. 3, there is shown a side view of tank cover 14 showing the relative mounting position of load-side bushing well 16 and fuse module 18. FIG. 3 also illustrates the construction of a stationary element 34. of fuse module 18. The upper portion 36 of stationary element 34 is suitably mounted and hermetically sealed to top cover 14 at a flatened portion thereon. Upper portion 36 preferably takes the form of filament wound fiberglass or any other suitable insulating material having adequate strength to support the internal assembly of fuse module 18. The lower portion of stationary element 34 comprises a pressure container 38. pressure container 38 is preferably formed or cast from asuitable material such as aluminum. As will be discussed more fully hereinafter, pressure container 38 conductively engages the lower terminal of the associated fuse link and thereby provides means for completingthe fuse circuit within drum 12 of tank 10 as by wayof strap 40. Strap 40 is coupled to pressure container 38 by way of a suitable fastening means 42, and coupled to the lower projection of bushing well 16 as by way of asuitable fastening means shown generally at 44. Bushing well 16 also includes a cylinder shield 46 which is suitably bonded or secured to top cover 14 and encloses the insulator portion ,of bushing well 16. Shield 46 comprises rubber or any other suitable insulating material and serves to increase the dielectric or withstand voltage strength between top cover 14 and strap 40. v

Referring now to FIG. 4, there is shown a side view of bushing well 16 and illustrating particularly the conductive feed-through member 16a and recessed well 16b. It can be seen thatbushing well 16 provides a conductive path from the outer surface of tank 10 to strap 40 by way of stud 16a and member 16a.

Turning now to FIG. 5, there is shown a side view of fuse module 18 illustrating particularly the structural features'of interlocking handle 32 and stationary element 34. Handle 32 further includes roller shafts 48a and 48b upon which

rollers

50a and 50b are disposed.

Rollers

50a and 50b slidably engage

tongues

52a and 52b respectively. As handle 32 is pushed downwardly into the position shown in FIG. 5, bushing well cap is forced downwardly onto the uppermost portion of stationary element 34. An Oring (not shown in FIG. 5) provides a gas-tight seal between stationary element 34 and bushing well cap 30 when handle 32 is in its position as depicted in FIG. 5.

Referring now to FIG. 6, there is shown a partial cross-section view of fuse module 18 and illustrating particularly the removable fuse cartridge 60 mounted therein. The removable fuse cartridge 60 is independently illustrated in FIG. 7. As illustrated in FIG. 7, fuse cartridge 60 comprises handle 32, bushing well cap 30, a torque tube 62, a latch 64, and a strainer assembly 66. Fuse cartridge 60 further includes a conductive garter spring 68 and a rubber O-ring 70. Torquetube 62 is fixedly secured to bushing well cap 30, and removably secured to latch 64 by way of a spring clip 72. That is, the upper portion of torque tube 62 is positioned via four equally spaced grooves 74 which engage corresponding tongues of bushing well cap 30 and is suitably bonded thereat; and, the inwardly projecting portions of spring clip 72 engage the lower portion of torque tube 62 and a corresponding opening in the upper portion of latch 64. As described more fully hereinafter, latch 64 includes latch lugs 64a and 64b (not shown in FIG. 7).

One function of torque tube 62 is to transfer the torque or torsion provided by handle 32 to latch 64. Referring to FIG. 9, there is shown across-section view of fuse cartridge 60 as taken along the line 9-9 of FIG. 7. It can be seen than spring clip 72 is provided with two inwardly projecting end portions which function to removably secure torque tube- 62 to latch 64. Once spring clip 72 is removed from torque tube 62, latch 64 is free to be removed from fuse cartridge 60.

As illustrated in FIG. 10, latch 64 forms part of a fus holder assembly 80. It can be seen that latch 64 is provided with a central bore having threads which engage and are suitably bonded to one end of a fuse tube 82. The other end of fuse tube 82 threadedly engages and is similarly bonded to end fitting 84, which in turn, threadedly engages fuse tube cap 86. A fuse tube cap 86 is provided with a conductive garter spring 88. The uppermost portion of fuse tube cap is provided with torque means such as a hexagonal nut head 86'.

Fuse holder further includes a fuse link extender 90 having a threaded portion which engages extension link top 92. The lower portion of link extender 90 includes a threaded bore which engages a corresponding threaded member of a universal fuse link as described more fully hereinafter.

Fuse tube 82 preferably takes the form of filament wound fiberglass or any other suitable insulating material having sufficient strength to support the associated members of fuse holder 80. Fuse tube 82 includes a tube liner 94 of arc-responsive material such as vulcanized fiber or hom fiber. Tube liner 94 is arcresponsive in that energy loss from an associated are drawn within fuse tube 82 decomposes a portinn of tube liner 94 into a turbulent, high-pressure, high-- temperature gas.

Still referring to FIG. 10, it can be seen that the lower portion of latch 64 is provided with a suitable threaded portion which engages corresponding threads on the inner portion of strainer assembly 66. Latch 64 also includes an Allen setscrew 64' disposed in a suitable bore of latch 64 as best shown in FIG. 15. This bore communicates with a second longitudinal bore 65 provided in latch 64 which receives the flexible lead of the associated fuse link. Setscrew 64' is provided with a suitable surface such as a half-dog point to thereby secure the flexible lead of the associated fuse link in bore 65 of latch 64, and to provide good electrical contacts between the flexible lead and latch 64.

Referring to FIGS. 11 and 12, there are shown top and cross-sectional side views of fuse tube cap 86, of FIG.- 10. It can be seen by reference to FIG. 12 that fuse tube cap 86 is provided with a threaded portion 86a and an unthreaded portion 86b. In FIG. 13 there is shown a universal fuse link '100 assembled with fuse link extender 90 and extension link top 92. In currently preferred practice, link top 92 is securedly fastened to link extender 90 as by staking the male threads of link extender 90 as shown in FIG. 13. The outer threads of link top 92 correspond to the inner threads 86a of fuse tube cap 86. The assembly comprising link top 92 and link extender 90 is advanced into fuse tube cap by rotating the assembly in the usual manner. Once link top 92 clears thread 86a, the assembly is free to swivel within fuse tube cap 86. This swivel feature permits fuse tube cap 86 to be tightened onto fuse tube 82 without imposing shear stresses or torsional forces on fuse link 100. In currently preferred practice, the threads of link top 92 are deformed, such as by staking, after link top 92 has been advanced into pontion 86b of fuse tube cap 86. This provision serves to prevent removal of fuse link extender 90. Hence, the possibility of installing a fuse link without extender 90 is avoided. The function of a fuse link extender is known to the art as exemplitied in US. Pat. No. 2,816,979.

Referring again to FIG. 7, it can be seen that the assembled fuse holder, as depicted in FIG. 10, is united with bushing well cap 30 by way of torque tube 62 and fastened therewith by way of spring clip 72. Further, the assembly depicted in FIG. 7 is united with stationary element 34 of FIGS. 3, 5, and 6 by inserting fuse cartridge 60 through the upper opening of stationary element 34 and sealingly engaging it therewith by rotating safety interlock handle 32 until latch 64 locks into place with pressure container 38.

It can be seen by reference to FIG. 8 that the upper portion of stationary element 34 is provided with an outer annular groove 102 which carries an O-ring 104. Accordingly, when bushing well cap 30 of fuse cartridge 60 engages stationary element 34, a relatively gas-tight seal is provided between stationary element 34 and bushing well cap 30 at the annular groove provided in the uppermost portion of stationary element 34. FIG. 8 also illustrates an electrical stress relief surface 106 provided on that portion of stationary element 34 which engages the surface of tank cover 14. Stress relief surface 106 increases the dielectric or withstand voltage rating of the fuse structure in accordance with the present invention.

Referring again to FIG. 6, it can be seen that when fuse module 18 is completely assembled, garter spring 88 of fuse holder 80 engages a bushing contact insert 108 of bushing well cap 301. Projection stud 18a and bushing contact insert 108 are preferably provided as an integral unit. Accordingly, a conductive path is provided between threaded projection stud 18a and fuse tube cap 86. Since fuse tube cap 86 conductively engages the upper terminal of fuse link 100 by way of link extender top 92 and link extender 90, a first line terminal connection to fuse link 100 is thusly provided. It

can also be seen that latch 64 conductively engages pressure container 38 by way of garter spring 68. Since the flexible lead of fuse link 100 is fastened to latch 64 by way of Allen screw 64, it can be seen that a second line terminal connection to fuse link 100 is provided by way of fastener means 42, strap 40, and bushing 16.

Still referring to FIG. 6, it can be seen that O-ring provides a seal between the lower portion of fuse holder and pressure container 38. Accordingly, fuse holder 80 is substantially enclosed except at a lower opening thereof, and the lower opening is closed into a substantially enclosed chamber defined by pressure container 38. As discussed more fully hereinafter, pressure container 38 is provided with a pressure relief fitting 110 having an aperture 112 which communicates with the enclosed volume of pressure container 38.

Disposed within pressure container 38 is a thermal quenching medium 114 which rests upon vertical members 116. As discussed more fully in the co-pending application of G. L. Schurter, Ser. No. 436,644 filed Jan. 25, 1974, quenching medium 114 may comprise any one of a number of suitable media or materials. For example, quenching medium 114 may comprise copper, steel or other suitable metal, screen rolled in cylindrical form, without a plating or with a nickel or paladium plating thereon. I Members 116 function to raise quenching medium 114 from the lower-most portion of pressure container 38. That is, in the operation of the fuse structure in accordance with the present invention, it has been found that the greatest heat is experienced in the lower-most portion. Accordingly, to avoid the possibility of unnecessary damage or melting of quenching medium 114, members 116 effectively raise medium 114 from the concentrated heat portion of pressure container 38.

Referring now to FIG. 14, there is shown a partial cross-sectional view of latch 64 of fuse holder 80, and illustrating particularly the flexible lead connection and extractor spring features of the present invention. In FIG. 14, strainer assembly 66 has been removed in order to expose extractor spring assembly 120. Spring assembly 120 includes a spring extension rod 122 and a constant force spring 124 which is secured at one end to rod 122 by way of a suitable fastening means 126 such as a rivet. The other end of constant force spring 124 is confined to spring drum 128 as by winding spring 124 about a recessed groove of spring drum 128. Spring extension rod 122 slidably engages latch 64 at one of two bores A and B, provided therein. Bores A and B are illustrated more fully in FIG. 15.

Once the combination of fuse link 100, link extender and link extender 92, as illustrated in FIG. 13, is installed in the uppermost portion of fuse holder 80 at fuse tube cap 86, the flexible lead 101 of fuse link projects from the lower most portion of fuse tube 82. At this point the operator or installer cuts the flexible lead 101 to the desired length and feeds the shortened flexible lead 101 through spring drum 128 and fastens same under screw 64. The length of the shortened flexible lead 101 is selected so as to extend constant spring force 124 to its full length as illustrated in FIG. 14. In currently preferred practice, the spring constant of constant force spring 124 is selected so as to provide approximately 8 lbs. of downward pressure on flexible lead 101. It will be appreciated by those skilled in the art that 8 lbs. of pressure thusly provided is less than the maximum allowable stress on a typical universal fuse link.

The alternate bores provided in latch 64 permit the operator to select alternate mounting positions for extension rod 122. Accordingly, regardless of which position extractor spring assembly 120 is installed in with respect to latch 64 and flexible lead 101, the operator is permitted to install spring extension rod 122 at the nearest or most convenient bore in latch 64. Thus, spring drum 128 of extractor spring assembly 120, when installed either as depicted in FIG. 14 or in a reversed position, is effectively always conveniently located in relative axial alignment with the central axis of fuse holder 80.

is provided with

projections

140 and 142 along its inside diameter.

Projections

140 and 142 cooperate with

latch pads

64a and 64b to secure fuse cartridge 60 into stationary element 34. That is, once fuse cartridge 60 is inserted into stationary element 34, fuse cartridge 60 is rotated approximately 90 until latch lugs 64a and 64b are aligned beneath

projections

140 and 142. This feature provides a mechanically secure but removable means of fastening fuse cartridge 60 into stationary element 34. Whereas, however, the hermetic sealing function is accomplished by way of O-ring 102 at the uppermost portion of stationary element 34.

The operation of the fuse structure in accordance with the present invention is described as follows. It is assumed that the fuse structure is suitably connected between the line and load sides of a power distribution system (not shown) by way of the universal bushing well connections at the surface of tank 10. Upon sensing an abnormal condition in current, such as an overload or high current fault, the fusible member of fuse link 100 melts or is vaporized and an arc forms in the resulting gap. The thermal energy loss from the arc decomposes a portion of fuse tube liner 94 into a highpressure, high-temperature turbulent gas which, in turn, acts on the core of the arc to sufficiently cool and de-ionize the gap and thus effect circuit interruption at a current zero. At this time, flexible lead 101 of fuse link 100 drops out from fuse holder 80 either due to the resulting gas pressure, or as assisted by extractor spring assembly 120.

The expulsion of the gases from fuse holder 80 continues and, in accordance with the present invention, impinges upon quenching medium 1 14 in pressure container 38. As is explained in greater detail in the copending application of G. L. Schurter, Ser. No. 436,644 filed Jan. 25, I974 quenching medium 114 functions to extract thermal energy from the discharging gases at a rate sufficient to stop the thermal reaction. Once the reaction has been stopped and'the circuit is totally cleared, a resulting residual pressure is present in pressure container 38.

In order to relieve this residual gas pressure and thereby avoid endangering an operator or installer in those cases where it is desired to replace the fuse almost immediately after a fault occurs, pressure relief assembly 110 is provided on a suitable surface of pressure container 38. Accordingly, the residual gas pressure is gradually relieved until the gas pressure within the total enclosed volume of tank is reduced to a FIGS. 3 and 5. Pinhole 150'also functions as a pressure relief opening so as to equalize any residual pressure in the upper portion of stationary element 34. Thus, within minutes after a fuse clears, an operator or installer can safely remove fuse cartridge 60 from stationary assembly 34. At this time, the pressure within tank 10 in accordance with currently preferred practice, will be typically equal to or less than 5 psig which is a manageable pressure level.

It should be noted, however, that when the resulting residual pressure in pressure container 38 is of the order of 30 psig, or greater, latch lugs 64a and 64b will be so tightly engaged with

projections

140 and 142 of pressure container 38, that rotation of fuse cartridge 60 is effectively prevented. Accordingly, this feature affords operator-safety as the other-dangerous pressure must be relieved before fuse cartridge 60 can be readily removed.

In a typical high-current fault operation, the gases discharged from fuse tube 82 generally melt or destroy extraction spring assembly 120 as well as flexible lead 101. Accordingly, strainer assembly 66, as depicted in FIG. 7, is provided to collect the resulting debris. Any residual debris which does escape the screen material of strainer assembly 66 is prevented from blasting up into the upper portion of stationary element 34 by way of rubber O-ring 70.

It should now be appreciated that once fuse link does clear, it can be conveniently replaced with a new fuse link by removing and disassembling fuse cartridge 60. Once fuse cartridge 60 is removed from stationary element 34, fuse holder 80 is removed from fuse cartridge 60 by simply removing spring clip 72 at which time fuse holder 80 is free to be removed from fuse bushing well cap 30. Once fuse holder 80 is removed, strainer assembly 66 and fuse tube cap 86 are respectively removed from their threaded engagement with fuse holder 80. At this time, a new fuse link is installed onto link extension 90. In currently preferred practice, the button head cap of the universal fuse link is removed and discarded, and the remaining threaded member is advanced into link extender 90. The extended fuse link assembly is then reassembled onto the upper portion of fuse holder 80. At this time, a new extractor spring assembly is also installed at the lower portion of fuse holder 80 as described hereinbefore. The strainer assembly 66 is then advanced onto the lower portion of latch 64, and fuse holder 80 is now ready to be reassembled with the corresponding parts of fuse cartridge 60. The assembled fuse cartridge 60 is then inserted into stationary element 34 and secured therein with a 90 rotation of handle 32 as described hereinbefore.

It will be appreciated by those skilled in the art that fuse cartridge 60, in accordance with the present invention, serves a plurality of functions. For example, the assembly provided by fuse cartridge 60 functions to transfer torque or torsion from handle 32 to the latch mechanism comprising latch 64 of fuse holder 80, and projections and 142 of pressure container 38. Fuse cartridge 60 also functions to provide, at the bushing well cap 30, a hermetic seal between the outside environment of the fuse structure and the fuse structure itself. Additionally, fuse cartridge 60 provides a current transfer terminal or connection for the line-side of the fuse as at the recess in bushing well cap 30.

Although the preferred embodiment of the invention as illustrated herein incorporates a generally cylindrical fuse cartridge, it will be appreciated by those skilled in the art that other geometric forms and variations may be indulged in within the scope of the appended claims. What has been taught, then, is a totally enclosed, nonvented expulsion fuse particularly suitable for use with universal fuse links and providing non-violent expulsion fuse operation.

What is claimed is:

1. An enclosed, non-vented expulsion fuse structure comprising, in combination:

a housing;

a bushing mounted on said housing and projecting therein;

a fuse module mounted on said housing and projecting therein, said fuse module comprising a stationary element fixedly mounted to said housing for receiving and substantially enclosing a fuse cartridge removably mounted within said stationary element, said fuse cartridge including a first portion thereof projecting externally of said housing and further including a removably mounted fuse holder therein for receiving a fuse link internally of said stationary element and said housing, said fuse holder having a liner of arc-responsive material of the type wherein energy loss from an are drawn Within said fuse holder decomposesa portion of said liner into a turbulent, high-pressure, high-temperature gas;

a thermal quenching medium disposed in said stationary element to receive the gas discharged from said fuse holder; and,

means for coupling said bushing to said fuse module internally of said housing to complete a fuse circuit.

2. The fuse structure according to claim 1, wherein said stationary element includes a pressure container receptive of said discharged gas and said thermal quenching medium being disposed in said pressure container.

3. The fuse structure according to claim 2, wherein said fuse holder and said pressure container form a substantially enclosed volume within said stationary element and said housing.

4. The fuse structure according to claim 3, wherein said housing is hermetically sealed.

5. The fuse structure according to claim 4, wherein said fuse cartridge and said pressure container include latch means for removably securing said fuse cartridge to said stationary element in response to a given translation of said fuse cartridge.

6. The fuse structure according to claim 5, wherein said fuse cartridge includes means for coupling said fuse link to an external line terminal.

7. The fuse structure according to claim 6, wherein said fuse module includes an interlocking handle pivotally mounted about one end of said fuse cartridge and wherein said handle includes an extension which encircles at least a portion of the bushing mounted on said housing when said handle is in a first given position.

8. A fuse cartridge for use with a universal fuse link, said fuse cartridge comprising, in combination:

a fuse holder having a fuse tube for receiving said fuse link and having fuse terminals at its ends for connection to an external circuit;

a generally cylindrically-shaped bushing well cap for receiving and engaging said fuse holder at one end thereof, said bushing well cap comprising an insulating material having a recess with a threaded metallic member therein for receiving and attaching an external bushing terminal thereby to provide a current transfer connection to one of said fuse terminals of said fuse holder; and,

a torque tube surrounding said fuse holder, said torque tube removably engaging said bushing well cap at one end thereof and said torque tube including removable fastening means at its other end, wherein said fastening means removably secures said torque tube to the other end of said fuse holder.

9. An enclosed, non-vented expulsion-type fuse comprising, in combination:

a housing;

at least one bushing projecting into said housing;

at least one removably mounted fuse module projecting into said housing, said fuse module including a removable fuse cartridge having a portion extending externally of said housing to facilitate removal of said fuse cartridge from said housing and said fuse cartridge including a universal fuse link fixedly mounted within said fuse cartridge by a fuse holder;

said universal fuse link normally including a button head fastener at one end thereof and having a flexible lead extending from the other end thereof;

a thermal quenching medium fixedly positioned within said housing to receive gas discharged when said fuse link separates; and,

means for coupling said one bushing to said flexible lead within said fuse module to complete a fuse circult.

UNTTTJD STATES PATENT oTFz-clz QTRTTTTQATT oT CORRECTEGN Patent 3,916,364 Dated October 28, 1975 lnventol-(s') Robert Lynn Cooper It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 3, line 37 change "pressure" to -Pressure-.

Column 4, line 30 change "than" to -that-. Column 5, line 60 change "301" to 30-. Column 10, line 26 delete "removably".

Signed and Sealed this twentieth D of January 976 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner ojlatents and Trademarks Patent No.

UNETED STATES T 1 YT QEJRTAL ATENT I-[CAZE ()F CGRRECTEGN October 28, 1975 Inventor(s) Robert Lynn Cooper Dated It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

7 Column Column Column Column [SEAL] line line line line A nest:

change change change delete RUTH C. MASON Atlesting Officer Signed and Scaled this twentieth D of January 9 C. MARSHALL DANN Commissioner oj'latents and Trademarks

Claims

1. An enclosed, non-vented expulsion fuse structure comprising, in combination: a housing; a bushing mounted on said housing and projecting therein; a fuse module mounted on said housing and projecting therein, said fuse module comprising a stationary element fixedly mounted to said housing for receiving and substantially enclosing a fuse cartridge removably mounted within said stationary element, said fuse cartridge including a first portion thereof projecting externally of said housing and further including a removably mounted fuse holder therein for receiving a fuse link internally of said stationary element and said housing, said fuse holder having a liner of arc-responsive material of the type wherein energy loss from an arc drawn within said fuse holder decomposes a portion of said liner into a turbulent, high-pressure, high-temperature gas; a thermal quenching medium disposed in said stationary element to receive the gas discharged from said fuse holder; and, means for coupling said bushing to said fuse module internally of said housing to complete a fuse circuit.

8. A fuse cartridge for use with a universal fuse link, said fuse cartridge comprising, in combination: a fuse holder having a fuse tube for receiving said fuse link and having fuse terminals at its ends for connection to an external circuit; a generally cylindrically-shaped bushing well cap for receiving and engaging said fuse holder at one end thereof, said bushing well cap comprising an insulating material having a recess with a threaded metallic member therein for receiving and attaching an external bushing terminal thereby to provide a current transfer connection to one of said fuse terminals of said fuse holder; and, a torque tube surrounding said fuse holder, said torque tube removably engaging said bushing well cap at one end thereof and said torque tube including removable fastening means at its other end, wherein said fastening means removably secures said torque tube to the other end of said fuse holder.

9. An enclosed, non-vented expulsion-type fuse comprising, in combination: a housing; at least one bushing projecting into said housing; at least one removably mounted fuse module projecting into said housing, said fuse module including a removable fuse cartridge having a portion extending externally of said housing to facilitate removal of said fuse cartridge from said housing and said fuse cartridge including a universal fuse link fixedly mounted within said fuse cartridge by a fuse holder; said universal fuse link normally including a button head fastener at one end thereof and having a flexible lead extending from the other end thereof; a thermal quenching medium fixedly positioned within said housing to receive gas discharged when said fuse link separates; and, means for coupling said one bushing to said flexible lead within said fuse module to complete a fuse circuit.