US2983801A - High current disconnect device - Google Patents

Description

May 9, 1961 H. VAN BILLIARD HIGH CURRENT DISCONNECT DEVICE Filed Feb. 20, 1959 INVENTOR. LEWIS H. VAN BILLIARD ATTORNEY United States Patent Ofirice HIGH CURRENT DISCONNECT DEVICE Lewis H. Van Billiard, Pittsfielzl, Mass., assignor to General Electric Company, a corporation of New York Filed Feb. 20, 1959, Ser. No. 794,671

4 Claims. (Cl. 200-81) This invention relates to electrical circuit opening, or disconnect, devices, and more particularly to improved electrical current disconnect devices for quickly and completely breaking large electric currents.

Wherever large electric currents are used, it is often necessary to interrupt such currents in order to prevent damage to the source of the current, to prevent damage to the devices using the current, or to prevent fires. In many applications for circuit interrupting, or breaking, devices such as in aircraft, torpedoes, etc. it is desirable that the weight of, and the volume occupied by circuit disconnect devices be minimized. The size and weight of prior art electromechanical circuit breakers have made their use unsatisfactory in systems, such as torpedoes, where the weight and volume of each item of the system are of critical importance.

It is, therefore, an object of this invention to provide an improved device for breaking large electric currents.

It is a further object of this invention to provide an improved disconnect device for breaking large electric currents in which the weight and volume of the device are minimized.

It is a still further object of this invention to provide an electric current disconnect device which is economical to manufacture.

. It is still another object of this invention to provide an electric circuit disconnect device, which, when energized, quickly and completely opens up an electric circuit through it.

It is still another object of this device to provide an electric current disconnect device whose operation is not adversely affected by large accelerations and vibrations.

Other objects and many of the attendant advantages of this invention will be readily appreciated after the same become better understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Fig. 1 is a side elevation, partly in section, of a circuit interrupting device in its closed condition, and an electrical circuit through the device exists;

. Fig. 2 is a side elevation, partly in section, of the circuit interrupting device in its open condition, and no electrical circuit through the device exists; and

Fig. 3 is a greatly enlarged and exaggerated fragmentary section showing the area of contact between the two principal portions of the circuit disconnect device.

Referring to Figs. 1 and 2, the two main elements of electric current disconnect device are socket member 12 and plug member 14. Both socket member 12 and plug member 14 are made of a soft malleable electrical conductive material, such as aluminum; soft navy brass," an alloy comprised approximately of 68% copper and 32% zinc; copper, etc. Side wall 16 and the base, or bottom wall, 18 of socket member 12 form a cylindrical plug chamber 20, which is more clearly seen in Fig. 2. A plurality of saw cuts 22, preferably uniformly spaced around the circumference of the cylindrical plug chamber 20, make the side walls 16 of the plug chamber 20 slightly resilient. It should be noted that saw cuts 22, as illustrated, do not extend to the base, or bottom wall,

Patented May 9, 1961 18 of socket member 12, for a reason that will be pointed out later. Socket member 12 is also provided with an integral and internally threaded boss 24. This permits socket member 12 to be mounted on the threaded end of electrical conductor 26 which in turn may be rigidly mounted in, or secured to, wall, or support, 28. If conductor 26 is ever at a potential other than ground, then conductor 26 will be insulated from wall 28, or wall 28 will be made from a suitable electrically non-conductive material.

There is also formed in the socket member 12 a plurality of bores 32. Bores 32 communicate with plug chamber 20 through its bottom wall 18, as can be seen in Figs. 1 and 2. The ends of each of the bores 32 nearest to plug chamber 20 are counterbored to form squib recesses 34. Each of the recesses 34 is of the size to receive a squib 36 of the type described and illustrated in US. Patent No. 2,801,585, dated August 6, 1957. The number of squib chambers 34 formed in socket member 12 is in part a function of the size of socket member 12 and plug 14, and a safety factor based on the number of squibs 36 that can be permitted to misfire and still have electrical current disconnect device 10 operate as intended. In a preferred example, three bores 32 are made parallel with the longitudinal axis 38 of socket member 12, they are equiangularly disposed with respect to axis 38, and they are equidistant from axis 38. Their distance from axis 38 is such that they clear boss 24 as can be seen in Figs. 1 and 2.

Plug 14 consists of a pilot piston 40, a piston 42, a conically shaped connector 44, and a stem 46. Pilot piston 40 has a diameter chosen so that it will have a slip fit within walls 16 of socket member 12, and thus can be easily placed in plug chamber 20- of member 12. Piston 42 has a slightly greater diameter than that of pilot piston 40, its diameter being such that piston 42 has a drive fit within walls 16 of socket member 12. To the flattened end portion 48 of stem 46 there is secured a flexible electrical conductor 50. Conductor 50 is illustrated as being bolted to stem 46. Obviously other conventional means for securing the normally insulated electrical conductor 50 to stem 46 may be used.

In certain applications, it is desirable to make certain that neither of the two main elements of disconnect device 10 be permitted to contact other elements of the system of which device 10 is one item, and also to make certain that plug 14 and socket 12 do not accidentally contact one another after disconnect device 10 has hen energized to place it in its open condition. A preferred manner of accomplishing this is to provide a protective housing 54 which may be made from a suitable tough electrical insulating material such as Textolite, nylon, etc. Housing 54 is illustrated as being mounted on socket member 1'2 by machine screws 56, for example. Housing 54 has a relatively long cylindrical chamber 58 formed in it which has a sufficient diameter so that the plug member 14 may move freely in it. End wall 60 of housing 54 has a central opening 62 formed in it through which stem 46 of plug member 14 may move freely. Since opening 62 in the end wall 60 of protective housing 54 is only slightly greater in diameter than that of stem 46, the other elements of plug member 14 are prevented from passing out of protective housing 54. Formed through the side walls 64 of housing 54 are a plurality of openings 66 which have the function of permitting gases produced by squibs 36, when they are fired, to escape from chamber 58. Openings 66 also permit spring fingers 68 to be mounted on the outer surface of housing 54 by machine screws 70, for example, and yet project into chamber '58 as can be seen in Figs. 1 and 2. Thus, when plug member 14 moves into the position illustrated in Fig. 2, spring fingers 68 project into chamber 58 and prevent plug member 14 from inadvertently contactingv socket member 12.

When current disconnect device is to be assembled, asquib 36 is placed in each. of the squib recesses 34 formed in socket member 12. The. pair of insulated wires 72, with which each squib 36 is provided, extend through the bore 32. Socket member 12 may then be threaded onto the threaded end of. conductor 26; The Wires 72 of each squib are'then connected to a firing, or ignition circuit,- of conventional design, which is not illustrated, so that all of thesquibs: are connected in parallel with the firing circuit. Pilot piston 40 of plug member 14 is then slipped into plug chamber 20. The leading edge 74 of pilot piston 40 may be chamfered remake it easier to insert pilot piston dtl into chamber 26. The length of pilot piston 44) measured in the direction of its longitudinal axis 76 of plug member 14 is slightly less than the. length of plug chamber Ztlmeasuredin the direction ofaxis 38. As a result, when pilot piston 40 of plug. member 14 isin plug chamber 20, the respective longitudinal axes 38 and 76 of socket member 12 and plug. member 14 substantially coincide. Thus, plug member 14 will not be canted, or at an angle, with respect to socket member 12. The diameter of piston '42 of plug member 14 is greater than that of pilot piston 40 by' a sufiicient amount so that it must be driven, by being tapped with a hammer, for example, into plug chamber 20, Plug member 14 is driven into socket member 12 until pilot piston 40 substantially contacts bottom wall 18 of socket member 12. After plug member 14 and socket member 12 have been assembled, protective housing 54 may then he slipped over plug member 14'- and secured to socket member 12. Flexible conductor 50 may then be secured to stem- 46.

Figure 3 is a greatly enlarged fragmentary section of the area of contact 78 between walls 16 of socket member 12 and piston 42 of plug member 14. While plug member 14 is being driven into plug chamber to a point where pilot piston 40 engages the bottom wall 18 of plug chamber 29, some of the metal behind the leading edge of St of piston 42 is removed, or displaced, to form the area of very close contact 78 between piston 42 and side walls 16. The force acting on the surface of piston 42 also acts to remove or displace some of the metal of the inner surface of wall 16 to help increase the width of area 78. It is, therefore, not necessary to clean either side walls 16 of socket member 12, or the surface of piston 42 before driving plug member 14 into socket member 12. The drive fit between plug member 14 and socket member 12 firmly secures plug and socket'mem bers 14, 12 together so that most accelerations or vibrations to which device 19 will be subject will not cause them to separate.

7 If at some time the current through disconnect device 10 exceeds a certain maximum value, or if a time is reached when the system of which device 10 is an item is to be de-energized, then device 10 can be caused to open the circuit through it, by firing squibs '36. A firing circuit which can consist of a dry cell battery and a switch will cause, when the switch is closed, a current of sufficient magnitude to flow through squibs 36 to ignite them, or to fire them. One of the characteristics of squibs 36, such as are described in the aforesaid US; Patent 2,801,585, are that the gases and flame produced by the squibs do not produce a shattering effect, or that the squibs have substantially no brisance: As a result, the gases produced by squibs 36 produce a relatively gradual increase in pressure in chamber 29 between bottom wall 18 and pilot piston 40.

As rnentio'ned above, cuts 22. made in wall 1.6 do not extend to bottom wall 18 of socket member 12. The reason for this is to prevent the gases released initially by squibs 36, from having a paththroughcuts 22 around plug 14 and thus partially reduce the pressure acting on plug member 14. The length of cuts 22 is not a critieal limitation,v since current disconnect device 10 will work reliably if cuts 22 are made down to wall 18.

The gases produced by squibs 36 develop more than enough pressure to quickly drive plug member 14 toward the end of protective housing 54 until connector 44 engages the inner surface-of endwall 60 of housing 54 as illustrated-in Fig. 2. As.- plug member 14 is. forced away from socket member 12, it pushes spring fingers 68 out of. its way; After plug member 14 has passed openings 66, spring fingers 68 return to their'initial position and project into chamber 58 a sufficient distance, as seen in Fig. 2, to make certain that plug member 14 cannot accidentally contact socket memb'er'12'. Once plug member 14 has passed openings 66 in housing 54, the gases produced by squibs 36 have an escape route from cham ber 58. V

The speed of movement of plug'member 14 away from socket member 12 is reduced, or some of the kinetic energy of plug member 14' is absorbed, by air compressed between piston 42 and end wall 60 of housing 54- since only a' restricted passage exists between stem 46 and opening 62 of end wall 60 for such compressed This, of course, reduces the force of impact of plug member 14 against housing 54'.

One of the unforeseen advantages of highcurrent disconnect device 10 is that the gases produced bysquibs 36 have a higher dielectric constant than that of' the ambient atmosphere. Another advantage results from the fact that the gases in the space between pilot piston 40 and socket member 12 are turbulent. The combina tion of the higher dielectric constant of the gases' produced by squibs 36 and their turbulence quickly extinguishes any arcs between plug member 14 and" socket member 12 as'they separate.

The electrical current carrying capacity per unit area of contact between electrodes made of a given metal is a constant and well known by persons working inthis art. The current carrying capacity per square mil of contact of electrodes made of soft navybrass is .005 ampere per square mil. The area of contact between plug'member 14 and socket member 12 is, of course, equal tothe width. of the area of contact 78 as seen in Fig. 3 multi plied by the circumference of piston 42. The width of area 78 ranges from .015 inch in the smaller disconnect device to .030 inch in the larger, It is thus possible to design acircuit disconnect device to handle a given maximum value of current by making certain that the product of the circumference of piston 42, the width of the area contact, and the amount of current that the material can carry per unit area at least equals, or preferably exceeds, that designed maximum current value. By increasing the diameter of piston 42 and plug chamber '20, it is possible to scale up disconnect device 10 to handle very large electrical currents. V

It is possible to rigidly mount protective housing 54 on plug member 14 and have socket member 12 move relative to the plug member 14. Under certain circumstances it ispossible to dispense with the protective housing 54, particularly where there is practically no possibility of plug member 14, for example, accidentally contacting socket member 12', or in contacting other items in the system.

In one embodiment of the invention, the length of pilot piston 40 was .437 inch and'its diameterwas 1.248 inches. The diameter of piston 42 was 1.256 inches. The length of plug chamber 20 was .500 inch andits diameter was 1.250 inches, Wall 16 ofsocket member 12 was .125 inch thick. Both of the members 12, 14 were made of soft navy brass. The width of the area of contact 78 was .020 inch. The maximum current that the disconnect device wasdesigned to carry was 600 amperes at 250 volts. The dimensions, characteristics, and'performance characteristics are included by ways of example as being suitable for the device. illus trated. It should be understood that devices in accord-,

ance with the invention may vary with the design for any particular application.

The invention lends itself to very economical production since piston 42, pilot piston 40, and stem 46 have the same longitudinal axis 76, and thus can be easily turned out on a lathe. Similarly plug chamber 20 is cylindrical and concentric with respect to the longitudinal axis 38 of socket member 12. Bores 32 through which leads 72 of the squibs 36 are connected to a firing circuit, are also parallel to longitudinal axis 38 of socket member 12, and therefore, may easily be machined, Squib chambers 34 can be readily made by counterboring bores 32. Thus, it is possible to economically manufacture current disconnect devices of the type described and claimed.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described and illustrated.

What is claimed is:

1. An electrical current disconnect device comprising a socket member having a base and side walls, the base and side walls forming a plug receiving chamber; a squib recess formed in said socket member, said squib recess communicating with the plug chamber and being adapted to receive a squib having lead Wires; a passage through the socket member communicating with the squib recess, said passage providing means through which the lead wires of the squib may be connected to a squib firing circuit; a plug member having a pilot piston, and a piston, said pilot piston having a slip fit within the side walls of the socket member, said piston having a drive fit with the side walls of the socket member, said plug member adapted to be driven into the plug receiving chamber of the socket member so that a portion of the piston of the plug member is within the chamber; and means for connecting electrical conductors respectively to the plug member and the socket member.

2. An electrical current disconnect device comprising a socket member made of a soft malleable electrical conductor having a base and resilient side walls, said base and side walls forming a plug chamber; a squib recess in said base communicating with the plug chamber; a passage through the base communicating with the squib recess; a squib having lead wires, said squib being mounted in the squib recess with its lead wires extending through the passage for connecting the squib to a squib firing circuit; means for connecting an electrical conductor to the socket member; a plug member made of a soft malleable electrical conductor and having a stem, a piston, and a pilot piston, the pilot piston having a slip fit with the walls of the socket member, and the piston having a drive fit with the side walls of the socket member, the pilot piston and the piston of the plug member adapted to be placed within the plug chamber of the socket member so that the pilot piston is within the plug chamber and substantially engages the base of the socket member, and at least a portion of the piston of the plug member is Within said chamber; and means for connecting an electrical conductor to the stem of a plug member; whereby the plug member will be forced from the plug chamber of the socket member when the squib is fired.

3. An electrical current disconnect device comprising a socket member made of a malleable electrical conductor and having a base and side walls, a plurality of cuts in said walls, said base and side walls forming a cylindrical plug chamber, a passage through the base communicating with the plug chamber, the end of said passage nearest the plug chamber being enlarged to form a squib recess; a squib having a pair of lead wires, said squib being mounted in the squib recess with the lead wires extending through the passage for connecting the squib to means for igniting said squib; means for connecting an electrical conductor to the socket member; a plug member having a stem, a cylindrical piston and a cylindrical pi-lot piston, the pilot piston having a slip fit within the walls of the socket member forming the plug chamber, the piston having a drive fit with the side walls of the socket member forming the plug chamber, the pilot piston and piston of the plug member being placed within the plug chamber of the socket member so that the pilot piston is Within the plug chamber and substantially engages to the base of the socket member, and at least a portion of the piston of the plug member is within said chamber; means for connecting a flexible electrical conductor to the stem of the plug member; a protective housing made of an electrical insulating material; means for rigidly attaching the housing to the socket member, said housing being so designed as to limit the distance that the plug member may move away from the socket member when the squib in the squib recess is fired, and means mounted on the protective housing for maintaining the plug member separated from the socket member.

4. An electrical current disconnect device comprising a socket member and a plug member; said members being made from the same malleable electrical conductive material; said socket member having a base and side walls, a plurality of cuts in said walls, said base and side Walls forming a cylindrical plug chamber, a plurality of bores through the base communicating with the plug chamber, and the ends of said bores nearest the plug chamber being enlarged to form a squib recess; a plurality of squibs, each squib having a pair of lead wires and each being mounted in one of said squib recesses with the lead wires extending through the bores for connecting the squibs to means for igniting said squibs; a boss on said socket member for threadably connecting the socket member to a threaded electrical conductor; said plug member having a stem, a cylindrical piston and a cylindrical pilot piston, the pilot piston having a slip fit within the walls of the socket member, the piston having a drive fit with the side walls of the socket member, the pilot piston and piston adapted to be placed within the plug chamber so that the pilot piston substantially engages the base of the socket member and so that at least a portion of the piston of the plug member is within said chamber; means for connecting a flexible electrical conductor to the stem of the plug chamber; a housing made of an electrical insulating material and having an end wall and side walls; means for rigidly attaching the housing to the socket member; an opening in the end wall through which the stem of the plug member is adapted to extend, said housing limiting the distance that the plug member may move away from the socket member when the squibs are fired; a plurality of openings in the side Walls of the protective housing; a plurality of catch means mounted on the housing and extending into said housing through the openings in the side walls of the protective housing, said catch means maintaining the plug member separated from the socket member when said squibs have been fired and have forced the plug member away from the socket member until the plug member is stopped by the protective housing.

References Cited in the file of this patent UNITED STATES PATENTS 2,458,464 Busacker et al. Ian. 4, 1949 2,559,024 McFarlin July 3, 1951 2,712,791 Bleakney et al. July 12, 1955 2,816,196 Daudelin Dec. 10, 1957 2,835,758 Atkins May 20, 1958 2,860,210 Stoelting et al. Nov. 11, 1958 2,883,492 Landers Apr. 21, 1959 2,892,062 Bruckner et al. June 23, 1959 2,931,874 Leaman Apr. 5, 1960

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