Shear-action wire-connector

Dec. 20, 1960 e. w. bollmeier 2,965,699

SHEAR-ACTION WIRE-CONNECTOR

Filed Feb. 13, 1957

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2,965,699

Patented Dec. 20, I960

United States Patent Office

2,965,699

SHEAR-ACTION WIRE-CONNECTOR

Emil Wayne Bollmeier, Mendota Heights, Mini!., assignor to Minnesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware

Filed Feb. 13,1957, Ser. No. 640,001

Claims. (CL 174—84)

This invention is concerned with wire-connectors, such as may be used for splicing or connecting together bare or insulated copper or aluminum wire conductors in telephone and other electrical circuits. One application for which the connectors of the invention are particularly well adapted is the splicing of plastic-covered copper wires in telephone cable junctions.

Wire-connectors made in accordance with the principles of this invention are capable of forming low-resistance connections between wire conductors. The connection is permanent and is not loosened or increased in electrical resistance by repeated mechanical stresses, temperature or pressure changes, or exposure to moisture. Insulation-covered wire conductors need not be preliminarily stripped of insulation. Heating and soldering are dispensed with. Connections are therefore completed in much less time than was formerly required; yet the connectors, and the tools or apparatus needed for their installation, are extremely simple both to manufacture and to use.

The invention is illustrated in the accompanying drawings, in which:

Figure 1 is a view in perspective of one form of shearaction connector element;

Figure 2 is a plan view of the element of Figure 1 in flat extended position;

Figure 3 is a sectional view of the element of Figures 1 and 2 as applied to a wire conductor;

Figure 4 is a cross-section of a completed connector assembly in position for splicing together three insulated wire conductors;

Figure 5 is a plan view of another form of connector element;

Figure 6 is an end elevation of the element of Figure 5;

Figure 7 is a plan view, partly in section, of a connector assembly including the connector element of Figures 5 and 6, applied to a pair of insulated wire conductors and in readiness for final sealing by means of a reducing die, and Figure Ία is a .partial plan view of one jaw member of the reducing die;

Figure 8 is a plan view, partly in section, of an insulated connector assembly applied to and sealed about a connected pair of insulated wire conductors;

Figure 9 is an end elevation of another form of connector element in position for compression;

Figure 10 is a plan view of the connector element of Figure 9, and Figure 10α is a view in perspective of one of the shear segments thereof;

Figure 11 is an end elevation of the connector of Figures 9 and 10 in compressed form; and

Figure 12 is an exploded view illustrating in perspective a still further modification of my wire-connector.

Figure 3 will serve to illustrate the principles on which each of these wire connectors operate. The insulated wire conductor 10 is here shown pressed between the two sides of the connector element 11 of-Figure 1, the upper side consisting of bars 12, 13, 14 and 15, and the lower side correspondingly consisting of bars 16, 17 and 18. Bars 12 and 16 are spaced apart a distance substantially greater than the diameter of the insulated conductor 10, whereas bars 15 and 18 come into sliding contact. The spaces between the intervening pairs of bars gradually decrease in the direction from bar 12 to bar 15, providing for a series of shearing actions of gradually increasing severity. As the two sets of bars, i.e. the two sides of the connector 11, are forceably pressed together and against the conductor previously inserted therebetween, the latter deforms into an increasingly serpentine shape. Where the wire passes between a pair of bars spaced the full diameter of the insulated covering, the action is primarily that of bending. Where the bars are more and more closely spaced, the plastic covering is first deformed and forced from the metallic conductor 19, the latter is next drawn out Or reduced in cross-section and is eventually either completely severed or reduced to a thickness permitting easy removal of the extending segment 20 by hand pulling.

The required control of the spacings between the several bars of this connector element is insured by the presence of the widened tips 21, 22 and 23 of the bars 16, 17 and 18 respectively. The tip 21, for example, fits snugly between the bars 12 and 13 when the connector is formed into the shape shown in Figure 1.

The spacings between the several bars, and the distance between the two sets of bars, i.e. between the two sides of the connector element of Figure 1, are based on the particular size of wire which is to be connected. Thus, the largest space between bars of the shear-action connector in fully closed condition should be at least as large as the maximum wire diameter, and the interior opening of the connector should be of a size sufficient to accept the number and size of wires for which connection is desired.

The connector element 11 is shown in Figure 4 surrounding three insulated wire conductors 10α, 106, and 10c, and is itself surrounded by a metal sheath 24 and an insulating covering 25. Typical sheath and cover structures are shown in greater detail in Figures 7, 8 and 12. Jaws 26 and 27 are shown in position for exerting pressure against the two opposing sides of the connector assembly in forming the desired connection. Pressure is applied as indicated by arrows, by means not shown, but which may be either mechanical or hand-operated, as for example with suitable pliers or other lever arrangement. During such operation, the bars of the connector element 11 form the connection with the several conductors, the metal sheath 24 is flattened around the connector 11, fitting snugly against both ends of the connector and preventing it from expanding axially along the wires and thereby becoming loosened, and the insulating covering 25 conforms to the compressed assembly and provides electrical insulation and physical isolation.

The connector element 50 of Figures 5 and 6 is, like that of Figures 1-4, conveniently stamped and formed from a single flat strip of metal. The bar segments 51, 52 and 53 are displaced from the plane of the metal strip in one direction, and segments 54, 55 and 56 are displaced in the opposite direction, as shown in Figure 6, to provide an open channel through which the wire conductors may be threaded. Pressure applied against the opposing extended surfaces of the connector, as previously indicated in connection with the device of Figure 4, then forces the bars into contact with the conductors and provides the desired shearing action between those pairs of bars having the proper spacing for the particular conductor. Accurate spacing of the bars is maintained, since both ends of each bar are permanently attached to the side portions 57, 58,. which however necessarily

8,985,699 increase the over-all width of the connector element over that of the structure of Figure 1.

In Figure 7 the connector element 50 of Figures 5 and 6 is assembled within a metal shell 70 and a section of plastic insulating tubing 71 having constricted end portions 72, 73, surrounded by metal tube elements 74, 75 respectively. Since this form of connector element is self-restraining and does not require exterior longitudinal restraint as does the connector of Figure 1, the metal shell 70 may be omitted if desired, but is here included for added mechanical protection. The insulated wires 76 and 77 pass entirely through the assembly, thus assuring that they are adequately encompassed by the connector element. After compression of the connector 50 within its retaining shell 70 and insulating covering 71, as described in connection with Figure 4, the segments 78 and 79 of the conductors are easily removed at the shear plane location between the contacting bars 56 and 53 of the compressed connector, by slight hand bending and pulling if necessary; or they may alternatively be left in place. In either case, both of the constricted end portions are next tightly closed and sealed by means of intermeshing reducing die elements 80 partially indicated in cross-section, and 81 partially indicated in elevation, forming a moisture proof seal at both ends of the connector assembly. The working portion of die 81 is shown in plan view in Figure Ία, wherein is indicated at section s-s the sectional view shown in Figure 7. The dies are forced against the tube segment 74 (and 75) by pressure applied as indicated by the arrows.

A somewhat different sealing assembly is illustrated in Figure 8. In this case, the conductors are first cut to the desired length for insertion in the connector assembly, which in this instance is open only at the upper end. The connector element 83, metal sheath 84, and insulating covering 85 are next compressed to form the connection, and the metal tube 82 is separately compressed, by means of reducing dies as in Figure 7, to form the moisture proof seal. The metal sheath 84 is here shown to be constricted at both ends, as required for preventing longitudinal displacement of the shear bars of connector 83 which, like the bars of connector element 11 of Figure 1, are disconnected along one side of the connector.

The insulating covering provided in these connector assemblies is relatively tough and rigid, and does not of itself adequately conform to the shape of the conductors so as to provide a fully moisture resistant seal. For this latter purpose, it has been found effective to coat the inner surface of at least the constricted portion or portions of the insulating covering with a soft plastic tacky hydrophobic substance such as a silicone grease, soft hydrocarbon polymer, or fluorocarbon wax. A suitable material adheres well to all surfaces contacted, will flow around all of the components of the seal, and will thereafter remain in place as an effective permanent moisture barrier. Surprisingly small amounts of such plastic sealing materials are required, particularly with plastic-insulated wires. The high pressures used in compressing the seals serve to distribute the hydrophobic sealant in extremely thin adherent and highly shear-resistant films over all insulation interfaces within the sealed area, and also tend to deform the plastic insulation, to provide a fully moisture-resistant barrier which effectively resists displacement and penetration under repeated variations in external fluid pressure.

A further modification of my novel connector element is illustrated in Figures 9, 10, 10α and 11. The connector element 90 consists of a flat multi-slotted segment 91 and a plurality of raised shear bars 92, 93 and 94 passing through the slots. The shear bars are maintained in accurate, position by widened end portions frictionally fitting against the slot edges, and are prevented from being pulled through the slots by extended corner segments, all as illustrated in Figure 10α. The same shearing action is obtained with this connector element as with those previously described, and permanent electrical connections may be obtained, particularly where effective transverse restraining means, such as an exterior conformable steel shell, are additionally provided.

The connector element 90 is applied to the conductors by passing the conductor ends between the plate 91 and the shear bars 92, 93 and 94, and then compressing the assembly between flat pressure plate 95 and shaped die 96 as indicated by arrows in connection with Figure 9. The ends of the shear bars are thereby deformed into substantial parallelism with the edges of the plate 91, as indicated in Figure 11.

The several slots in the segment 91 of the connector element 90 are identical in width, whereas the slot openings formed in the connector element 11 of Figure 1 are each of a different width. Either system may be applied to either style of connector element.

The steel shell 110 of Figure 12 is similar to the shell 24 of Figure 4 in being completely closed at one end. In the connector of Figure 12, however, the shell serves an additional function of holding the several independent deformable segments of shear bars of the connector in operative position both before and after compression about the wire or wires. The segments, of which two are shown as bars 111 and 112, are forced snugly into the shell 110 and the open end of the latter is then crimped over the outer edge of the outermost segment so that fully effective Shearing action is obtained between opposing bars on compression of the connector. The assembly may be further protected with an insulating covering and a moisture resisting seal as heretofore described. In this connector, as in other connectors with a metal shell having only a single opening, moisture resistance may alternatively be effected by introducing into the bottom of the shell a small amount of a hydrophobic sealing compound or composition as hereinbefore identified. When the connector is applied to conductors and compressed to form the connection, the plastic composition is forced around the several parts to form a highly effective moisture barrier.

These connectors have been applied to aluminum as well as copper wires, both bare and insulated, and in a wide variety of wire diameters. The wire may be insulated with plastic, paper, or other insulating covering; in all cases, the shearing action has been found sufficient to displace the insulation and to provide good electrical contact between connector element and metal conductor. The effect is particularly good with wires coated with polyethylene or similar plastic material, since the shearing and stretching action appears to cause orientation of the polymer and reduction in its subsequent flow characteristics. The formation of completely moisture-proof seals with this type of wire is of particular importance, since the polyethylene wire covering itself is also substantially completely impervious to moisture. The requirement is much less important in the case of paper covered conductors, where other means must be provided for insuring the absence of moisture throughout the entire circuit.

It has been pointed out that the effectiveness of these connectors depends in great measure on the shearing action provided by the adjoining opposed shear blades or pressure bars. Surprisingly, it is found that the shearing edges themselves need not be harder than the material of the conductors, but may in fact be substantially softer. For example, the connector unit 11 of Figure 1 may be made of half-hard copper plate or of aluminum plate having a hardness of S-2 or S-3. The wire deforms the shearing edges of the connector even as it is itself deformed and cold drawn, thereby apparently providing much better electrical contact than would otherwise be obtained.

Additional cutting action may be provided where desired, for example by hardening or burring the cutting edges at the juncture between bars 15 and 18 of the coh2,960, hector of Figtires 1-3 so as to facilitate removal of the wire-ends; but such alteration is ordinarily hot needed, as noted in connection with the description of Figure 7. Plated steel may also be used. Where differences in cutting action at the several shearing zones are desired, 5 the connectors of Figures 10 and 12 are particularly useful, since the separate shear bars of these connectors may be made of different materials having different degrees of hardness. The metal of the connector element should be as free of springiness as possible. 10

While the numbers and dimensions of the shearing bars of the connector elements are not critical, it has been found that 5 to 7 bars, properly spaced, are adequate in a connector designed, for example, to accept wires from number 19 gauge to number 26 gauge inclusive. 15 Larger numbers of bars may be used; fewer bars may be found effective where wires of a single diameter are to be connected. The spaces between bars along the connector will preferably be uniformly progressively altered as shown; but two or more such spaces may be 20 made equal in width provided the bars are sufficiently rigid.

It is desirable in most cases to hold the over-all dimensions of the connector assembly to a minimum. The present connector may be made extremely small and com- 25 pact while remaining highly effective. The individual bar elements must of course be of sufficient width and thickness to withstand the pressures involved in bending and shearing the conductors without themselves being unduly deformed. It has further been noted that some- 30 what improved connections are obtained where the width of these bars is increased even beyond the minimum thus established. The additional length of conductor provided between areas of shear appears in these cases to permit additional cold drawing of the metallic conductor and to 35 avoid any possibility of decreased cross-section and weakening of the conductor at such areas.

An exemplary connector assembly for use on telephone cable connections may include a connector element as illustrated in Figure 1 and made of aluminum plate of a ⁴⁰thickness approximately twice the diameter of the largest copper conductor to be used. It may be protected by, and contained within, a cold-drawn open-ended steel shell such as that of Figure 11, made of steel plate having an initial thickness of 0.012 inch. The assembly may be 45 contained within an insulating jacket closed at one end and constricted at the other, as illustrated in Figure 8, the jacket being formed of a thin film of hard and tough copolymer of vinyl chloride and vinyl acetate and having a thickness approximately the same as that of the metal go connector element. The constricted neck portion may be interiorly coated with a thin layer of soft sticky isobutylene polymer, and externally surrounded with a close fitting thin copper or aluminum tube. Such a connector assembly has been applied to test pairs of polyethylene 55 insulated copper wires, one wire being number 26 gauge and the other number 19 gauge, and subjected to prolonged testing including 50 cycles alternating from 10 Ibs./sq. in. pressure to a vacuum of 20 inches of mercury while suspended in an aqueous electrolyte at a tempera- 50 ture of 130° F., and repeated at a temperature of 0° F., without any failures whatever and with no significant decrease in conductivity across the connection.

Further modifications and combinations of the connectors herein described and illustrated, such as double- 65 ended connectors, connectors in which the final servering stage is omitted, connectors designed for mounting on binding-posts, heavy-duty connectors for use with large diameter wires or cables, connectors in which shear elements are mounted directly on or formed from a compression shell member, and various others in which the principles of this invention are incorporated, are contemplated as coming within the scope of this invention as defined in the appended claims. One such combination involves a double-ended connector having one or more

699 narrow slot areas at the center portion and one or more wide slot areas at each end portion, and hence being equally well adapted for application to wire-ends at either end portion.