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Publication numberUS3622946 A
Publication typeGrant
Publication dateNov 23, 1971
Filing dateMar 2, 1970
Priority dateMar 2, 1970
Publication numberUS 3622946 A, US 3622946A, US-A-3622946, US3622946 A, US3622946A
InventorsEugene T Rogers
Original AssigneePermali Inc
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Electrical connector with breakaway stud
US 3622946 A
Abstract  available in
Previous page
Next page
Claims  available in
Description  (OCR text may contain errors)

United States Patent [72] Inventor Eugene T. Rogers Mount Pleasant, Pa. [21] App]. No. 15,507 [22] Filed Mar. 2, 1970 [45] Patented Nov. 23, 1971 [73] Assignee Permali Incorporated Mt. Pleasant, Pa.


[52] U.S. Cl 339/126 RS, 339/263 R [51] Int. Cl H0lr 9/10 [50] Field of Search 339/126, 214, 263, 31, 213, 218, 277; 174/152, 153

[56] References Cited UNITED STATES PATENTS 1,266,480 5/1918 Johannesen 339/263, X

Primary Examiner-Richard E. Moore Attorney-Brown, Murray, Flick & Peckham ABSTRACT: An internally threaded metal sleeve is rigidly mounted in a passage through an insulating bushing and extends outwardly to an end of the passage or beyond it. The bushing is intended to be mounted in the wall of electrical apparatus, with the outer end of the sleeve outside. Screwed into the sleeve and projecting from its outer end is a threaded stud that carries a nut which presses tightly against the outer end of the sleeve. Outwardly of the nut the stud is provided with a groove that weakens it, and a pair of nuts mounted on the stud outwardly of the groove are for holding an electric cable terminal which, if enough tension is applied to it, will cause the stud to break at its weakening groove without damaging the sleeve or bushing.

ELECTRICAL CONNECTOR WITH BREAKAWAY STUD Electrical transformers are often mounted at ground level on concrete pads, or underground in concrete vaults. In either case the electric cables that extend away from the transformers are generally buried in the ground. The usual practice is to connect the cable terminals to threaded studs mounted in insulating bushings that in turn are rigidly mounted in the wall so the transformers. The studs are wired into the transformers. It has been found that, not infrequently, one of these buried cables is snagged by a digging machine or. the like, with the result that the cable is pulled hard enough for it to break off the stud in the bushing at the transformer. This damages the bushing, so that the entire connector must be replaced. When this happens it becomes necessary to disconnect the transformer and take it to a shop where the damaged electrical connector is removed and new one put in its place. Of course, this is a rather expensive operation. The same misfortune can happen to other electrical apparatus where similar electrical connectors are used.

It is an object of this invention to provide an electrical connector for a transformer or other electrical apparatus, which can be repaired without moving the apparatus if tension on a cable breaks the connector stud.

The preferred embodiment of the invention is illustrated in the accompanying drawings, in which FIG. 1 is a fragmentary section through a transformer housing and electrical connector; and

FIG. 2 is a fragmentary side view of the connector with the stud shown breaking off.

Referring to FIG. 1 of the drawings, the wall 1 of electrical apparatus, such as a pad-mounted or underground mounted transformer, is provided with an opening 2 in which an electrical connector is mounted. The connector includes a rigid insulating bushings 3 made of a suitable insulating plastic that is encircled by a metal flange 4. The inner edge of the flange is embedded in the bushing. This flange is welded to the transformer wall around the opening. The bushing is provided with a central passage 5 extending through it from the inside of the transformer to the outside.

Molded into this passage is an internally threaded metal sleeve 7. The sleeve could extend the full length of the passage, but it is preferred that it be mounted in only about the outer half of the passage. A rod 8, with a threaded end screwed into the inner end of the sleeve, is molded into the bushing between its inner end and the sleeve. This rod projects from the bushing into the transformer and may be threaded for an electrical connection to it.

Screwed into the other end of the metal sleeve is a threaded stud that projects from the sleeve, which extends at least to the outer end of the bushing. It is a feature of this invention that is short distance away from the sleeve the stud is provided with a circumferential groove 11 that reduces the cross section of the stud at that point and thereby makes it weaker there than at any other location along the exposed portion of the stud. A nut 12 is mounted on the stud outwardly beyond the groove, and a spade terminal 13 or the like of an electric cable 14 is clamped tightly against the nut by another nut 15 screwed onto the outer end of the stud. The cable is generally buried in the ground, but regardless of its location, if it is put under enough tension, such as being caught by a mechanical the point where it is weakened by the circumferential groove 11, as shown in FIG. 2. Because the stud breaks instead of merely bending and breaking the plastic bushing or tearing out of the bushing, the bushing should not be damaged.

The weakening groove just described does not completely solve the problem, however, because lateral stress on the projecting portion of the stud before it breaks could cause it to mash the threads in one side of the metal sleeve. This would make it difficult or impossible to remove the broken stud, and even if it is removed a new stud could not be screwed into the damaged sleeve, so the transformer would have to be taken into the sho for repair.

It IS a fea ore of this invention that IS difficulty is overcome by applying a third nut 17 to the projecting portion of the stud. This nut is applied before the others and is located between groove 11 and the adjacent end of the sleeve, against which it is tightened as much as possible. With this construction, lateral stress on the stud, caused by tension on the cable connected to it, will be distributed through nut 17 more or less uniformly around the sleeve, at least to such an extent that the sideways pull on the stud will not damage the sleeve threads. Consequently, if the outer end of the stud is broken off, it is a simple matter to unscrew the rest of the stud from the sleeve and to insert a new stud. This operation takes the transformer out of service for only a short time and the expense of taking it to a shop, removing the entire connector and replacing it with a new one is avoided. It will be realized that the metal sleeve makes it possible to remove the broken stud and replace it with a new one, which could not be done if the stud were molded in the bushing as has been the practice heretofore.

To make sure that lateral pressure on the stud will not cause nut 17 to press against the end of the bushing at one side of the stud, it is desirable to extend the sleeve a short distance out wardly beyond the bushing. The nut then can never tough the plastic bushing.

I claim:

1. An electrical connector comprising an insulating bushing provided with a passage therethrough, an internally threaded metal sleeve rigidly mounted in said passage and extending outwardly at least to an end of it, means for rigidly mounting the bushing in the wall of electrical apparatus with said end of the passage outside, a threaded stud screwed into said sleeve and projecting from its outer end, a nut on the stud pressing tightly against the outer end of the sleeve, the stud outwardly of the nut being provided with a circumferential groove reducing the cross-sectional area of the stud to weaken it, a second nut on the stud outwardly of said groove, the outer end of the stud being adapted to receive a nut for holding an electric cable terminal on the stud against said second nut, and means for making an electrical connection to the opposite end of the stud.

2. An electrical connector according to claim 1, in which said last mentioned means is a second stud screwed into the

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1266480 *Dec 11, 1915May 14, 1918Gen ElectricTransformer.
US2085074 *May 13, 1935Jun 29, 1937Waterous CoHydrant and deformable or breakable valve stem therefor
US3448337 *Dec 21, 1967Jun 3, 1969Joslyn Mfg & Supply CoGaseous discharge device with keep-alive fifctrodes
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3721942 *Dec 3, 1971Mar 20, 1973Gen ElectricLock plate for high voltage bushings with removable connectors
US3977750 *Jan 15, 1976Aug 31, 1976Amp IncorporatedRuggedized high voltage connector
US4353611 *Mar 6, 1980Oct 12, 1982Amerace CorporationBushing well stud construction
US4611093 *Jan 20, 1984Sep 9, 1986Colt Industries Operating CorpElectrical bushing having a replaceable stud
US4782197 *Mar 21, 1988Nov 1, 1988Westinghouse Electric Corp.Electrical bushing having a replaceable stud
US5286211 *Jan 29, 1993Feb 15, 1994The Whitaker CorporationGround connector
US5494462 *May 3, 1994Feb 27, 1996Electric Motion Company, Inc.Ground rod clamp
US9054478 *Feb 27, 2013Jun 9, 2015Apple Inc.Electrical connector having a designed breaking strength
US9172167 *Apr 29, 2013Oct 27, 2015Al Cop LlcJunction failure inhibiting connector
US20120306444 *Jun 3, 2011Dec 6, 2012Leviton Manufacturing Co., Inc.Breakaway device for electric vehicle supply equipment
US20140242848 *Feb 27, 2013Aug 28, 2014Apple Inc.Electrical connector having a designed breaking strength
US20140322994 *Apr 29, 2013Oct 30, 2014James C. KeevenJunction failure inhibiting connector
U.S. Classification439/475, 439/921, 439/559
International ClassificationH01R9/16
Cooperative ClassificationH01R9/16, Y10S439/921
European ClassificationH01R9/16