US2786191A - Electrical connector - Google Patents

Description

March 19, 1957 w. F. BROSKE ,1 1

ELECTRICAL CONNECTOR Filed May 14. 1948 I 2 Sheets-Sheet 1 III/Ill! ail aw ATTORN Y5 March 19, 1957 w, BRQSKE 2,786,191

ELECTRICAL CONNECTOR 2 Sheets-Shae: 2

Filed May 14, 1948 INVENT R fiA/AM E Pas/E.

52 w w wd ATTORN United States Patent ELECTRICAL CONNECTOR William F. Broske, Mechanicsbul'g, Pa, assignor to AMP Incorporated, a corporation of New Jersey Application May 14, 1948, Serial No. 27,087

14 Claims. (Cl. 339-276) This invention relates to electrical connectors and particularly to electrical connectors of malleable metal adapted for pressure-formed engagement with wires or other electrical conductors, and which are provided with external insulation adapted to protect the metal of the connector against accidental contact with other parts external to the connection, such insulation being a part of the connector before application to the conductor and adapted to avoid interference with the pressure application of the connector and to avoid destruction of its insulating value during the pressure-forming of the connector onto the conductor.

In a prior Patent No. 2,410,321 issued to Willam S. Watts on October 29, 1946, there 'has been disclosed a connector having a seamless sleeve of insulating plastic applied over a ferrule portion of an electrical connector I and disclosing broadly the idea of applying a plastic of the character there set forth onto a malleable metal so as to provide a connector with the insulation secured in place before pressure forming, and which will provide an effectively insulated pressure-formed connection without any separate application of insulation after the connection is made. The present invention is an improve ment thereon.

According to this invention the sheet metal of which the electrical connector is to be made is first laminated with a tough insulating plastic which, under the conditions of crimping or pressure-forming the connector onto the wire, is not subject to cold plastic flow much-greater than that of the metal, whereby a crimping pressure may be transmitted through the plastic and effective metal flow and consequent pressure-forming ofthe metal can be produced without puncturing or dangerously weaken.

ing the plastic coat. A number of plastics are known having the quality of toughness, resistance to fracture on bending and cold forming and a resistance to cold plastic flow comparable to that of the softer metals such as annealed copper and soft brass and soft steel. Particularly suitable among these plastics above mentioned are the superpolymers and copolymers, especially the polyamides known under the general term nylon, the vinyl-chloride plastics and the vinyl-chloride vinyl-ace tate copolymers, in which the amount of the vinyl acetate is less than 5% and advantageously about 3%, and the vinylidene chloride polymers, particularly vinylidenechloride vinyl-chloride copolymers, as commonly known under the name Saran.

Advantageously, these resins when applied to the metal are unplasticized or only slightly plasticized, but they may be formed into sheets or strips either as solutions or as plasticized compositions by ordinary methods and subsequently baked or leached; and the plasticized composition may even be applied in that condition to the metal by plastic coating or laminating methods and the solvent and/or plasticizing agent subsequently baked or leached out of the plastic. If the plasticizer is removed after laminating there is a tendency to shrinkage, which should advantageously be relieved by heating to the soft- A 2,786,191 Patented Mar. 19, 1957 'ice ening point of the plastic at which its elastic memory is erased and internal stresses relieved.

In another co-pending application of Robert C. Swengel Serial No. 523,004, filed February 19, 1944, there is disclosed the advantage of cementing an insulating ferrule onto a metal ferrule which is to be bent or pressureformed onto a wire or like conductor. I have now found that a sheet of tough insulating material can be advantageously cemented to a sheet of malleable metal and the electrical connectors formed of the resulting composite of laminated sheet by ordinary manufacturing methods, particularly stamping, drawing, bending, etc.

As one example of my invention a sheet of the copolymer of vinyl-chloride and vinyl-acetate having the acetate in proportion about 7% vinyl acetate to 93% vinyl-chloride and an average molecular weight in excess of about 20,000, such as is commercially available under the name Vinylite VYNW in a sheet of a few hundredths of an inch in thickness, e. g., about .03 inch. One surface of this sheet may be coated with adhesive and then pressed onto a sheet of electrical copper, one surface of which has been cleaned and coated with a compatible adhesive. A vinyl polymer type adhesive is desirable for these coatings, e. g., vinyl chloride polymer in methyl ethyl ketone. Such adhesives are obtainable from Stoner-Mudge Co., among others under the name Keglined or under the name Pliobond from the U. S. Plywood Co., and others described in the publication of Bakelite Corporation, Vinylite Resins for Surface Coatings, Technical Data, Copyright 1942.

The resin sheet is pressed onto the resin coated metal between the platens of a flat bed press or by passing between press rolls. This may be effected at room temperature if adhesive coatings are used which are somewhat tacky, or are made so by moistening with a solvent, e. g., methyl ethyl ketone; but I prefer to do this pressing at elevated temperature below the fusion point of the resin sheet, e. g., -200 F. and with sufiicient pressure at the given temperature to eflect preliminary adhesion of the sheet to the metal. The laminated sheet is then transferred from the press to an oven where it is raised to a temperature between 350 to 375 F. and held at such temperature for a period between one and two hours, the temperature conditions being maintained as uniform as possible by forced circulation of hot gases through the oven. During this oven treatment the coating softens to give maximum adhesion to the metal and both plasticizer and residual solvent which may be contained in the laquer are driven OE and to a greater or less extent curing of the plastic with increase in average polymer length is carried on, thus leaving a tough and only slightly plasticized layer of insulating plastic on the metal. Other methods of lamination are known to the art and may be used for purposes of this invention. See for example the Brous Patent 2,234,621. Baking can be done after the connectors are formed, but before application to the wire, or with very tough plastic, the baking step can sometimes be omitted.

The resulting laminated material is then stamped in the usual way for blanking and forming electrical connectors. Advantageously the metal side during these operations faces the male punching and stamping dies.

For crimping with pressure concentrated in a narrow area, as with indenting dies, a tougher plastic may be more desirable. Thus one may use with advantage a copolymer having 3% or less of vinyl acetate and 97% or more of vinyl chloride. Or one may use the vinylidene chloride polymer known as Saran.

In the accompanying drawings I have shown several embodiments of my invention which will be described in detail below. It is to be understood that these are not intended to be exhaustive not limiting of the invention, but

on the contrary are selected and set forth herein for the purpose of illustrating the invention and instructing others in its use and in the principles of its use and its modification, 50 that those skilled in the art will be enabled to apply it in numerous forms and with numerous modifications, each as may be best suited to the conditions of a particular use.

In these drawings:

Figure 1 is an isometric fragmentary view, with the end in section, of a laminated sheet adapted for use in the invention;

Figure 2 is an isometric View of an electrical terminal made in accordance with the present invention from the sheet of Figure 1;

Figure 3 is a view similar to Figure 1 showing a modified type of laminated strip made in accordance with the present invention;

Figure 4 is a view similar to Figure 2, showing a terminal made from the strip of Figure 3;

Figure 5 is a view in cross section showing an in-turned crimp or pressure-formed connection made in a confined die set by compressing the ferrule of a terminal such as that of Figure 2 or Figure 4 onto a stranded connector;

Figure 6 is a sectional view similar to that of Figure 5, but showing a different type crimp;

Figure 7 is a view similar to Figure 1, but showing still another modified form of composite strip embodying the present invention;

Figure 8 is a view in longitudinal section of an electrical connector made from the strip of Figure 7;

Figure 9 is a view similar to Figure 1 showing another modified type of strip in accordance with the present invention and with the outline of a terminal blank indicated thereon in broken lines;

Figure 10 is a view similar to Figure 1, showing still another modified form of strip with the outline of a connector blank indicated by broken lines;

Figures 11 and 12 are sectional views similar to Figure 5 taken through a crimped connection made by use of the strip shown in Figure 10;

Figure 13 shows in plan View a series of connector blanks stamped from ordinary sheet metal;

Figure 14 shows the connectors of Figure 13 bonded to a strip of plastic;

Figure 15 shows in vertical section the same in the trimming die by which the excess plastic is cut away;

Figure 16 shows in vertical section the trimmed composite blank;

Figure 17 shows the same blank after forming the plastic around the opening for the binding post or connector screw, etc.;

Figure 18 is a View similar to Figure 1 showing another composite strip embodying the invention; and,

Figure 19 is a view similar to Figure 5 but showing the connector made from the strip of Figure 18.

Referring first to Figure l, the composite sheet there shown is composed of a sheet 20 of malleable metal, advantageously annealed electrical copper, and adhesively bonded thereto a sheet 22 of insulating resin which may, as indicated above, be any of the tough flexible high strength insulating materials capable of being adhesively bonded with metal, but in this case most advantageously nylon or Saran or vinyl-chloride vinyl-acetate copolymer having about 3% acetate to 95 to 97% chloride of high molecular weight and slightly plasticized, as set forth above. From the sheet, as shown in Figure 1, a blank is stamped out, as indicated in the broken lines of Figure 1, and the ear portions 24 are rolled up to form a substantially cylindrical ferrule 26, the tongue portion 28 being left flat as shown, but having a hole punched at 30 for reception of a binding post or connection screw or the like.

In this connector as shown in Figure 2, it will be observed that the exterior of the ferrule portion 26 is composed entirely of insulating plastic, and also the lower Cit part of the tongue portion, whereas the inside of the ferrule and the upper part of the tongue are composed of copper or other connector metal.

In the use of this connector a wire or other conductor is inserted into the hollow ferrule 26 and the ferrule is then crimped by means of any broad area crimping dies, for example, one of those described in the patent of S. N. Buchanan No. 2,379,567, or the patents of Carlson Nos. 2,359,083 and 2,359,084, or in the application of James C. Macy Serial No. 580,841, filed March 3, 1945, or Serial No. 679,630, filed June 27, 1946, Patent No. 2,557,126, or Serial No. 717,842, filed December 23, 1946, Patent No. 2,600,012. The forming pressure of the dies is transmitted by the tough plastic to the metal and the latter is formed and flows into the tight intimate and secure connecion with the wire or other conductor. During this operation the plastic on the exterior withstands the pressure transmitting it to the metal and avoiding puncture, so that when the pressure-formed connection is completed, it is insulated and requires no further covering.

in this crimping operation the plastic exterior on the ears 24a is of advantage because of its greater frictional engagement with the die surfaces and a better connection is formed when the ears slip easily over the die only until they encounter resistance and then engage the die so as to resist further slippage and thus drive the edge down into the Wire with flow of the metal during the final movement of the die. It is desirable, however, that the plastic in this operation should be extruded longitudinally to a somewhat greater extent than the metal and this ordinarily results from the fact that whereas the metal tends to flow inwardly in the interstices of the stranded wire and fill the space around the wire, such flow as occurs in the plastic tends to be longitudinally from under the die. The result of this, particularly if the crimp is made near the end of the ferrule, is to extrude the insulation over the end of the metal and against the insulation on the end of the wire and thereby to that extent to insulate the end of the metal ferrule when in use.

The character of the crimping dies used in this operation is related to the character of plastic required. The greater the area of the ferrule which is engaged by the dies throughout the pressure-forming operation, and the more closely the form of the dies approaches the form of the ferrule at the beginning of plastic flow phase of the pressure-forming, the more one may relax the requirement for toughness in the insulating plastic.

The plastic of the tongue 28 is not ordinarily necessary to prevent contact, but it may serve a useful insulating purpose particularly where the diameter of the tongue is greater than the diameter of the connecting screw or nut, and it may also serve an advantageous purpose in holding the connecting screw or nut by virtue of its e1asticity and frictional qualities. In the case where a screw is used through the hole, if the plastic around the hole is designed to give a tight fit, this plastic may give resili ent gripping of the screw similar to that used in the familiar lock nuts. Such a terminal is illustrated in Figure 17 and further described below.

As stated above, it is not ordinarily necessary to have the tongue portion 23 of such a terminal connector in sulated; and the cost of the extra plastic required may be prohibitive for some uses; and the additional thickness under the screw or nut is often objectionable. I have now discovered that this can be avoided by laminating with the plastic only that part of the metal sheet which is to form the projecting part or parts requiring insulation in the finished connection. This is illustrated in Figures 3 and 4,

As shown in Figures 3, the plastic lamination 22a is made of width equal to the length of the ferrule, whereas the metal sheet 20 is of width sufiicient to make the full blank. In cutting the blanks from this sheet the connector is oriented cross-wise of the strip, with the ferrule-forming portion extending along the plastic lamination, with the ear portions 24a of adjacent blanks arranged side by side in the sheet. The tongue portions 28a then extend beyond the insulation so that they are stamped from the bare metal. This blank can then be formed to bring the ferrule-forming portion to a closed tubular form as in the case of Figure 2 or to the U-form as shown in Figure 4.

Figure 5 shows in cross-section a connector of the type as shown in either Figure 2 or Figure 4 which has been crimped onto a wire in dies with faces of the form corresponding to the exterior of the crimped connection as shown. This crimped connection and the method of making it and the dies used therefor are the subject of a copending application of James C. Macy Serial No. 717,842, filed December 23, 1946, Patent No. 2,600,012, and as there shown the ferrule-forming portion is confined laterally while it is compressed between concave die faces on the top'and bottom (as shown in Figure 7 of said patent) which afford support and distribute the pressure over a broad area, advantageously almost the entire area of the ferrule. When so crimped, the lateral edges of the ferrule-forming portion of the connector shown in Figure 5 of this application, are turned inward against the wire, bringing the plastic edges together face to face. The metal is driven against and compacted with the wire, while the plastic is pressed together at the edges and extruded to some extent over the end of the ferrule as described above.

In Figure 6 is shown another type of crimped connection made with a closed ferrule, e. g. as shown in Figure 2. The dies and method of making such connection are shown and described in a Buchanan patent No. 2,379,567 and a copending application of Stephen N. Buchanan Serial No. 559,604, filed October 20, 1944, Patent No. 2,554,813. In this case the die surfaces do not conform so closely to the overall form of the ferrule but are tangent thereto with a longer radius of curvature such that the ferrule is first bent to elliptical form to take up some or all of the clearance between the interior of the ferrule and the wire, and after the flattened ferrule conforms approximately to the broad areas of the die so as to have the pressure thereon well distributed over the surface of the plastic it is subjected to the final pressureforming whereby the ferrule and wire are compacted into a solid mass with some plastic flow of both metal and plastic. In this crimping operation the ferrule is unsupported in a narrow area at each side, so that lateral extrusion of plastic and metal does occur, but this is in an area subjected to greatest edgewise compression so that puncture of the plastic due to such extrusion can be avoided.

In Figures 7 and 8 is shown a'modified embodiment of the invention wherein the insulation layer 2212 is extended on one side beyond the metal and on the other side the metal extends beyond the insulation. This provides for an insulation support for insulated wires and also a long leakage path from the metal parts of the connector. If the insulation on the wire is of larger diameter than the exterior of the metal liner in the ferrule, the extended insulation can be expanded to a larger diameter by a hot punch or in a hot spinning die followed by chilling to secure the expanded form, e. g. as described and claimed in a copending application of John R. Vicke'ry Serial No. 22,630 filed April 22, 1948.

In Figure 9 is shown a strip .of width such that the blanks are in longitudinal orientation as indicated by the broken line outline in .this figure. in this case the plastic lamination 220 extends beyond and over the lateral edges of the metal thus providing insulation covered longitudinal edges for the U-shaped ferrule-forming portion of the connector prior to crimping. This may be used, particularly with a crimp of the type shown in Figure 6, to insure a meeting of the plastic edges at the beginning of the pressure-forming or crimping and thus to facilitate the making of an effective and practical butt joint.

Figure 10 represents a modification in which the metal layer 20d of the opposite blank extends laterally beyond the sides of the plastic 22d. This is designed for terminals, for example, with prongs 24d as shown in outline in Figure 10 and, in cross section after crimping onto a wire, in Figure 12. In this case the lateral borders 32 of the ferrule-forming portion and therefore the ends of the prongs 24d which drive into the wire are left bare.

In the case illustrated by Figure 11 the ferrule part of the soft metal connecting piece is first formed U-shaped in cross section and with substantially straight parallel longitudinal edges as in Figure 4, except for the plastic layer terminating below or short of the longitudinal edges of the U; and the bare longitudinal edges 320 of said piece are then driven over concave semi-cylindrical die surfaces of radius approximately one-quarter the width of the U, so that said edges are brought together face to face and then driven down onto the wire in the interior of the ferrule, after which the whole is compressed and compacted.

Figure 12 shows a connector produced from a terminal having a pronged ferrule of the type outlined in broken lines on Figure 10. The bare prongs 24d are each curled over and driven back by dies such as those shown in Macy 2,557,126, for example, into the interior of the ferrule to make contact with the wire, but each is curled on a radius greater than one-quarter of the width of the U and therefore in the crirnped embodiment these prongs are in staggered relationship.

In Figure 13 is shown a strip of sheet metal connector blanks still connected by slugs 34. These metal blanks are laminated with sheet plastic after the blanks are stamped out. Figure 14 shows this stage with the plastic 22F still in sheet form. Subsequently, the plastic is stamped out or otherwise trimmed to leave an extension beyond the metal, as in the case illustrated in Figures 7 and 8, but in this case the extended portion is made wider so that it can be formed to an insulation supporting sleeve of larger internal diameter than the exterior diameter of the metal ferrule. By stamping the plastic with female dies 35 larger than the metal blank and using the male die 37 against the metal blank with the female die 35 and a presser foot 38 on the plastic side, the plastic is drawn to some extent over the edges of the blank. This is facilitated if the female die is heated so that the plastic is softened along the edges. Figure 15 shows such dies in vertical section with the metal blank and plastic sheet in place between them. Figure 16 shows the laminated blank produced by operation of the die set shown in Figure 15. It will be noted that in this the plastic overlaps the metal on all edges including the central opening in the tongue, so that the opening is smaller in the plastic than in the metal. Figure 17 shows the same connector after a hot punch has been forced back through the central opening, thus producing a rib 39 of plastic around it. Such a terminal when used under a screw acts as its own lock washer. The plastic because of its frictional characteristics against the head of the screw, or against a nut on a binding post, gives in any case considerable holding power against accidental loosening due to vibration; but when the rib 39 is provided of size to give a close fit tothe screw, the clamping pressure tends to press the plastic against and into the threadsof the screw and to give a locking action substantially like that of the familiar stop not with plastic insert.

Figures 18 and 19 show another embodiment of the invention wherein the metal strip is insulated on all exterior surfaces and edges, e. g. in manner which is commonly used for insulating enameled and plastic coated wire. When a blank is stamped from such strip oriented as shown in broken lines on Figure 18, the end of the ferrule remains fully insulated, whereas at the edges of the ears 24g the metal is exposed. When such a connector is crimped as already described for the connections of Figures 5, l1 and 12, the exposed edge is driven against the wire and a good electrical contact is made, while the exterior of the ferrule is insulated. The tongue 28g in this case has all its edges turned up so that the cut surfaces can contact a binding post or screw head, etc. This form of the invention embodies and has the advantages of the invention of Quentin Berg described and claimed in his application Serial No. 11,082 filed February 26, 1948.

Although I have shown in each case the ring tongue type of connector, since that is the most commonly used, the invention is generally applicable to electrical connectors of other forms as well.

I claim:

1. An electrical connector of the type which includes a ferrule-forming portion of malleable metal open on one side for reception of an electrical conductor and adapted to be forged together with the electrical conductor to form a permanent electrical and mechanical connection therewith, in combination with a layer of tough, flexible electrical insulation material secured on the outside of said ferrule-forming portion, whereby it can, without fracture, be bent and formed with'the metal of said portion for closing the ferrule and its compression onto the conductor.

2. The connector combination as defined in claim 1 in which a sheet of plastic material which serves as said insulating layer is adhesively secured to the metal of said ferrule-forming portion substantially throughout their common area.

3. The connector combination as defined in claim 2 in which the insulating sheet material extends laterally beyond the lateral edges of said ferrule-forming portion whereby they are clamped between them when the ferrule is crimped.

The electrical connector combination as defined in claim 2 wherein said insulating layer extends laterally over the surface portions or" said ferrule forming portion tothe edges thereof and projects longitudinally beyond the end of said ferrule forming portion to form a wire supporting member.

5. The electrical connector combination as defined in claim 2 wherein said connector with its ferrule forming portion is formed from a high conductivity sheet metal and said insulating layer is formed from a sheet of plastic laminated on said metal and having edge portions covering and engaging the lateral edges of said metal.

6. The electrical connector combination as defined in claim. 1 further characterized by a plurality of insulation piercing prongs disposed on the lateral edges of said ferrule-forming portion and said insulating layer terminating short of the tips of said prongs.

7. Method of making an insulated electrical connection wherein a metal connector having a. ferrule-forming portion and an insulating cover thereon are forged about an electrical conductor, which method includes forming a metal connector with a ferrule-forming portion having a pair of side walls and a. side opening, covering the exterior surface of said ferrule-forming portion with a layer of tough, flexible insulation, moving a portion of a conductor through said side opening into the channel in said ferrule-forming portion, curling the free edge portions of said walls inwardly toward each other and against said conductor wire, and pressing said edge portions of said insulating cover into close contact to form in effect a continuous insulating cover extending across and en closing the inwardly curled portions of said walls and forging the ferrule forming portion onto the conductor, while peripherally confining said ferrule'forrning portion said insulating cover against lateral extrusion.

8. The method of claim 7 wherein the connector and the insulating cover are laminated prior to bending the ferrule-forming portion of said connector piece into a U-shaped channel.

9. The method of claim 7 wherein the cover is a flat piece of rigid plastic applied to said connector piece with opposed edge portions overlapping and engaging the opposed free edge portions of said channel.

10. The method of claim 7 and wherein the cover is laminated to oneentire surface of said connector piece.

11. The method of claim 7 and wherein the cover is laminated to the ferrule-forming portion only of said connector piece and extends longitudinally therebeyond to form an insulation supporting portion.

12. The method of claim 7 further characterized by forming a plurality of insulation piercing prongs along the opposed free edges of the ferrule-forming portion, applying the cover layerto the central portion only of said ferrule-forming portion, and curling the free edge portions of said walls inwardly toward each other to force said prongs into intimate contact with the conductor Wire therein.

13. The method of making an insulated electrical connector which comprises the steps of, laminating a plurality of sheet metal connector blanks to a sheet of tough flexible insulating material, severing said connector blanks from said insulating material by stamping out areas of insulation slightly larger than the areas or" said connector blanks, forcing said insulation over and about the edges of said blanks, and bending said ferrule-forming portions to provide channel shaped cross-section with spaced walls, opposed free edges, and a longitudinally disposed side opening therein.

14. The method of insulating an electrical connection which comprises assembly on open side connector with a strip of plastic insulation and a conductor Wire, pressing portions of said connector together to close said open side thereof and to embrace said wire, pressing edge portions of the plastic strip together to form a cover enclosing the wire embracing portions of said connector, and compressing said insulation cover onto the connector by applying thereto peripherally a substantially uniform pressure while confining said insulation and said wire enclosing portion of the connector against lateral escape from the compression zone.

References Cited in the file of this patent UNITED STATES PATENTS 1,018,138 Stanley Feb. 20, 1912 2,017,071 Minor Oct. 15, 1935 2,058,246 McCortney Oct. 20, 1936 2,137,617 lmes et al Nov. 22, 1938 2,148,392 Ransone Feb. 21, 1939 2,149,732 Grotf Mar. 7, 1939 2,173,668 Smith Sept. 19, 1939 2,206,662 Conradi et a1 July 2, 1940 2,379,567 Buchanan July 3, 1945 2,385,792 Carlson Oct. 2, 1945 2,410,321 Watts Oct. 29, 1946 2,417,175 Rallies- Mar. 11, 1947 2,429,585 Rogoff Oct. 21, 1947 2,438,075 Smith Mar. 16, 1948 2,549,838 Miller Apr. 24, 1951 2,557,126 Macy June 19, 1951 2,567,155 Macy Sept. 4, 1951 2,600,012 Macy a- June 10, 1952

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