US3248684A - Electrical connector clamp - Google Patents

Description

April 1966 D. c. HUBBARD ETAL 3,248,684

ELECTRICAL CONNECTOR CLAMP Original Filed Nov. 13, 1962 2 Sheets-Sheet 1 INVENTORS. Dav/d C. Hubbard BY Vernon Hellsfer'n April 6, 1966 D. c. HUBBARD ETAL 3,248,684

ELECTRICAL CONNECTOR CLAMP Original Filed NOV. 15, 1962 2 Sheets-Sheet 2 1 1 :9 INVENTORS. Dav/d C. Hubbard Vernon fiells'ferfi WMMTM United States Patent 3,248,684 ELECTRICAL CONNECTOR CLAMP David C. Hubbard, Centralia, and Vernon Hellstern,

Webster Groves, Mo., assignors to A. B. Chance Company, Centralia, Mo., a corporation of Missouri Original application Nov. 13, 1962, Ser. No. 237,204. Divided and this application May 4, 1964, Ser. No.

1 Claim. (Cl. 339-95 ducting surface coatings, such as oxides, are adequately pierced or sufiiciently removed from the conductors before attempt is made to establish the electrical connection therewith. Scraping, brushing and other techniques can, of course, be used successfully but they are time consuming and care must be taken to assure proper and adequate removal or break through.

Where dependence is made on the grounding of an electrical circuit for protection of workmen, or for the joining of two electrical conductors for the transmission of electric power, it is absolutely necessary that there be a good, low resistance electrical path established at the point of connection. Every effort should be made to remove or penetrate nonconducting oxides between the conductors and the connector to avoid the insulating or undesirable high resistance effects of these surface coatings.

carelessness or forgetfulness on the part-of workmen in removing the oxides present a condition of potential hazard; hence, it is the most important object of the instant invention to provide a connector that will assist in establishing a low resistance electrical contact with the conductor as the connector is manipulated during its installation such that its serrations may scrape away oxides without need for auxiliary tools or brushes for this purpose.

Another object of this invention is to provide a clamp or connector having teeth capable of piercing the thin but resistance-inducing oxides of lightly oxidized conductors workmen may misconstrue as like new and hence not requiring scrubbing action, such teeth being nondamaging to the conductor.

Still another object is to provide for means to assure full and firm contact by all the conductor-engaging teeth when the connector is clamped tightly to the conductor following scrubbing actions.

A further object-of the instant invention is the provision of a connector that causes the teeth to scrub away the oxides as the result of a rotative action on the conductor and as a function of drawing the connector tight.

Another important feature of the instant invention is the provision of replaceable inserts for jaws of clamps wherein the inserts are provided with teeth of the aforeextended parallel groove clamp made pursuant to one form of the present invention;

FIG. 2 is an elevational view showing the opposite sidethereof;

FIG. 3 is an inside view of one of the elements of the clamp;

FIG. 4 is a transverse cross-sectional view showing the clamp prior to drawing it tightly against the conductors;

FIG. 5 is a view similar to FIG. 4 showing the clamp tightly against the conductors;

FIG. 6 is a fragmentary, side elevational view of a multiple angle grounding clamp having replaceable inserts made according to a modified form of the present invention;

FIG. 7 is an end view of the clamp shown in FIG. 6;

FIG. 8 is a fragmentary cross sectional view taken on line 8-8- of FIG. 6; and

FIG. 9 is a fragmentary cross sectional view taken on line 99 of FIG. 6.

The present invention provides a clamp for interconnecting a pair of electrical conductors and includes a pair of elements interconencted by a stud bolt. Each element is extruded or otherwise formed from a resilient, metallic or other conductive material and provided with two pairs of spaced, serrated, conductor-engaging faces disposed on opposite sides of the bolt. The inner, curved faces of the elements are such that when the bolt draws on the elements, their faces move into positions concentric to and in full engagement with the conductors, which is accomplished by the elements deflecting under the force required to draw the members tightly against the conductors. The serrated faces present conductor-engaging teeth which bite through and, by rotative action, scrub away the oxides and thereby electrically connect with the conductors.

One of the elements is provided with the projections engageable with the bolt for movement toward the latter so as to providebolt locking means as the elements deflect under the force required to draw the members against the conductors.

The clamp shown in FIGS. 1-5 of the drawings is broadly denoted by the numeral 10 and includes a pair of clamping elements 12 and 14, and fastening means in the nature of a bolt 16 interconnecting the elements 12 and 14. The clamp 10 is adapted to be utilized for interconnecting a pair of electrical conductors 18 and 19 therebetween, although, as will hereinafter become apparent, the principles of the instant invention are also applicable in situations where connection is to be made with but a single conductor.

The element 12 is provided with an opening 20 for loosely receiving the bolt 16, head 22 of the latter being engageable with outer, convex surface 23 of the element 12. The element 12 is further provided with a pair of spaced, elongated, transversely arcuate, fine serrated, inner faces disposed on opposite sides of the opening 20 and presenting sharp, conductor-engaging teeth 25.

The element 14 is -provided with a pair of similar conductor-receiving surfaces disposed on opposite sides of the bolt 16 when the latter is threaded into the tapped bore 28 extending through the element 14 and normally aligned with the opening 20 of the element 12. These surfaces are serrated for presenting a number of sharp teeth 32 similar to the teeth 25, such teeth 25 and 32 being formed and disposed for biting through oxides of the conductors 18 and 19 to effect positive electrical interconnections.

The element 14 is further provided with a pair of pro jections 34 on its outer surface 30 embracing the bolt 28. Projections 34 are disposed for engaging bolt 16 and to this end they are partially threaded in alignment with the bore 28.

The elements 12 and 14 are preferably formed by an extrusion process from a material capable of deflecting,

. 3 such as an aluminum alloy, since such a material has efficient electrical current-carrying capabilities, is relatively inexpensive, rugged in construction, resistant to corrosion, and of a nature rendering it capable of being easily extruded.

In use, the conductors 18 and 19 are placed between elements 12 and 14 as shown in FIG. 4, and the bolt 16 is manipulated to draw on the elements 12 and 14, thereby moving the teeth 25 and 32 into engagement with the convex outermost surfaces of the conductors 18 and 19. The elements 12 deflect under the pressure and take the shapes illustrated in FIG. 5 when elements 12 and 14 are drawn tightly in place.

The projections 34 move toward each other and at the same time grip the threaded portion of the bolt 16 therebetween to provide locking means therefor. Thus, a considerably greater torque is required to loosen the bolt 16 than would be required in the absence of projections 34.

Since the conductors 18 and 19 are generally exposed to the atmosphere during normal use, a film or coating of non-conductive oxidation forms on their surfaces. Teeth 25 and 32 bite through but scrub away such films or coatings to provide an electrical path of minimum resistance capable of efficiently transmitting electrical currents and effectively resisting the damaging and injurious efiects of short circuits and surge currents.

In order to understand the principles involved for accomplishing such results, it must first be recognized that if the recesses or arcuate grooves containing the teeth 25 and 32 were initially concentric with the conductors 18 and 19 (i.e., when in the condition of FIG. 4) the forces of the bolt 16 would produce an eccentric relationship. This has been one of the faults of conventional connectors. When fully clamped, the only zones which actually engage the conductors tightly are those next adjacent the bolt 16. Such results are caused by the inward flexing of the material at the bolt andbetween the conductors. This in turn causes the outer wings of both elements to flex or spring apart resulting in a tight grip only along a small portion of the concave faces 'of the connector.

In the instant invention, on the other hand, as seen in FIG. 4, the elements 12 and 14 are initially arched outwardly. Also, the concave faces are not initially concentric with the conductors 18 and 19. Instead, when the bolt 16 first brings the elements into engagement with the conductors 18 and 19, only. the outermost of the teeth 25 and 32, i.e., those remote from the bolt 16 are in contact with the conductors 18 and 19.

Then, as the bolt 16 is gradually tightened, the median zones of the elements 12 and 14 adjacent and around the bolt 16 begin to bend inwardly, pulling the four wings or jaws of the elements 12 and 14 inwardly around the conductors 18 and 19 in a rotative manner. This not only gradually forms the jaws into conformity with the shapes of the conductors 18 and 19, but pulls the teeth 25 and 32 inwardly across the conductors 18 and 19.

The inwardly rotative shifting of the teeth 25 and 32 across the conductors 18 and 19 produces a scraping or scrubing action which wipes away the oxide crust and causes the teeth 25 and 32 to come into contact with the conductive material of the conductors 18 and 19 beneath the encrustations.

The results are somewhat dependent also on the nature of the teeth 25 and 32 themselves. The V-shape configuration, as shown, has been found satisfactory, but most important is that the serrations be very fine and that the long 'edges of the teeth 25 and 32 be rather sharp. Also, they must extend lengthwise of the conductors 18 and 19 rather than transversely thereof.

When such care is taken in producing the teeth 25 and 32., the proper scrubbing action, above explained, is accomplished and the sharp edges actually cut through the n-oncondutive coatings without damage to the conductors themselves.

The additional function of the teeth 25 and 32 in cutting through the oxides must take place in a manner to avoid weakening of the conductors as would be true if the teeth gouged into the conductive body of the conductors beyond the surface coatings. It has been found that the use of a large number of closely-spaced, fine serrations that are rather shallow will accomplish the described results when they are formed longitudinally of the conductors as shown. Then, when the coatings have been scrubbed away and cut through by the teeth, there is a full and safe engagement by all of the teeth with the conductive material of the conductors 18 and 19 as depicted in FIG. 5. And it must be remembered that such firm and positive electrical connection is also caused in part by the form of the jaws and the inward bending 'of the elements 12 and 14, as above explained.

In the embodiment of our invention illustrated by FIGS. 6 to 9 inclusive, there is depicted a clamp broadly designated by the numeral 100 that includes a pair of clamping elements or jaws 112 and 114 provided with inserts 112a and 114a, respectively. I

The jaws 112 and 114 are carried by a support 116, shown only fr agmentarily in FIG. 6 for swinging movement toward and away from each other by virtue of pivot bolts 117 and 121. The jaws 112 and 114 are moved toward each other by a spreader device (not shown) that moves between their inner ends 112b and 114b, respectively. They are yieldably held apart by a compression spring (not shown) interposed therebetween immediately above the pivots 117 and 121 within the support or base structure 116.

Inasmuch as the jaw 112 includes a pair of fingers or sections 112a disposed to receive the jaw 114 there/between when the jaws are moved toward each other, there are in fact two inserts 1120, one for each finger 112C, respectively, as seen in FIGS. 7 and 9, whereas the jaw 114 has but one insert 114a as seen in FIG. 8. Suitable fasteners 123 are provided for holding the inserts on their corresponding jaws rendering the same replaceable.

The inserts 112a are each provided with an elongated, transversely V-shaped, finely serrated inner face, presenting sharp, conductor-engaging teeth 125. The insert 114a is provided with a similar conductor-receiving surface, serrated for presenting a number of sharp teeth 132 similar to the teeth 125, such teeth 125 and 132 being formed and disposed for biting through oxides of a conductor that is gripped between the inserts 112a and 114a so as to effect positive electrical interconnection.

In all essential respects the serrations or teeth 125 and 132 perform the same function of establishing the electrical interconnection and in substantially the same manner as above described with respect to the teeth of the clamp shown in FIGS. 1 to 5 inclusive. Although the jaws 112 and 114 and their inserts 112a and 114a will perhaps not have the degree of resilience as the jaws of the modification first hereinabove described, nonetheless, much the same scrubbing action on the oxide takes place when the jaws 112 and 114 are swung relatively toward each other to move the inserts 112a and 114a into engagement with the conductor. Additionally, in the case of the clamp shown in FIGS. 6 to 9 inclusive, it is possible to swing or rotate the clamp about the cable or conductor, thereby utilizing the teeth and 132 as a scrubbing medium so as to remove the oxides and assure proper electrical contact between the teeth 125-132 and the conductor.

It can now be seen that there has been provided a reliable, low resistance electrical contact with reference both to system reliability in the transmission and distribution power and to the added security of carefully applied gr-ounding equipment. The heavy currents that may produce a hazardous condition where any connector is inadequately applied in a grounding situation is also damaging to electrical circuits inadequately joined. The contacts hereinabove described materially reduce the pos sibility of human error.

Having thus described the invention, what is claimed as said axes and extending in generally tangential relanew and desired to be secured by letters Patent is: tionship to said conductor when the latter is clamped A clamp comprising: between the jaws, first and second opposed, generally C-shaped jaws said structure mounting said sections in disposition to adapted to receive an electrical conductor there- 5 receive said second jaw therebetween as said jaws are between, said jaws having replaceable inserts each moved toward each other, whereby to adapt the having an inner V-s-haped surface provided with a clamp for a wide range of conductor diameters. series of relatively fine serrations presenting a large number of teeth having parallel, elongated cutting References Cited by the Examiner edges 10 UNITED STATES PATENTS structure mountlng said aws for swinging movement toward and away from each other about respective 1,786,369 12/1930 Terrell et 339 95 spaced, substantially parallel axes with said edges 1,844,011 2/1932 H extending in substantial parallelism to said axes and 1,981,796 11/1934 Blsseu 339 266 X spaced .circumferentially of said conductor when the 15 2,078,846 4/1937 Gouldlng et X latter is received by the jaws; and 2,221,923 11/1940 Passauermeans connected with said jaws for shifting the same 2,270,807 1/1942 Johnson 339 246 toward and away from each other, whereby to grip 215521924 5/1951 Athy et said conductor when the latter is received by the jaws 2,679,032 5/1954 Thomas et a1 and, by virtue of said swinging movement, assist 3,002,173 9/1961 Allen 39114X in scrubbing away nonconductive coatings on said FOREIGN PATENTS conductor to establish a low resistance contact as said edges bite through the coatings, 1,154,750 11/1957 Francesaid first jaw including a pair of elongated, substantially parallel clamping sections spaced longitudinally of JOSEPH SEERS, Examlmlfi

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