US2680235A - Electrical connector - Google Patents

Description

June 1, 1954 F. L. PIERCE 2,680,235 ELECTRICAL CONNECTOR Filed Sept. 16, 1949 2 Sheets-Sheet l ATTORNE June 1, 1954 P|ERE 2,680,235

ELECTRICAL CONNECTOR Filed Sept. 16, 1949- 2 Sheets-Sheet 2 4242;, wm wz ATTORNEYS.

Patented June 1, 1954 UNITED STATES TNT OFFICE ELECTRICAL CONNECTOR Frank L. Pierce, Camp Hill, Pa., assignor to Aircraft-Marine Products Inc., Harrisburg, Pa.

Claims.

This invention relates to electrical connectors for use on insulated wire, and to the methods of making and applying such connectors. The invention relates particularly to insulation-piercing solderless type connectors.

Prior to this invention, it has been proposed to secure connectors to insulated wire by crimping the connector around the outside of the insulation and. driving a sharpened conductive barb through the insulating sheath to the central conductor to complete the electrical circuit between the terminal and the conductor. For example, connectors have been proposed having sharp barbs or prongs extending upwardly from the bottom of a trough-like wire-engaging ferrule portion. The insulated conductor was intended to be pressed down upon these barbs so that the barbs would pierce the insulation sheath to make contact with the conductive core of the wire, the ferrule then being pressed around the outside of the insulation of the wire.

Such connectors can be attached to the insulated wire easier and more rapidly than the more usual type of connectors wherein the insulation must be stripped from the wire and the connector then crimpcd or soldered to the wire core. However, the solderless insulation-piercing connectors proposed prior to the present invention have not replaced other connectors for most applications because, in practice, the electrical connections produced by such connectors have not been satisfactory. This is in part because low contact resistance of the connector requires not only that the connector make contact with the conductive core of the wire, but that the two contacting members be maintained continuously under sufiicient pressure that enough actual points of contact are established and maintained to carry the required current. Thus, with some suggested constructions the normal fatigue of the metal of the connector with aging causes enough decrease in contact pressure to interfere with the performance of the connector. Another difiiculty has been that the area of the connector making contact with the conductive wire core has been small as compared with the cross-sectional area of the wire with the result that the connectors did not have sufficient current-carrying capacity for many applications.

Still another disadvantage of earlier connectors is that, subsequent to their being pressed onto an insulated conductor, the plastic or semifiuid nature of the insulating sheath would allow the centrally located conducting core to move away from the contacting barbs thereby decreasing the efiectiveness of the electrical con- 2 nection. This drifting of the center conductor under the influence of the applied forces has been most troublesome with non-braided insulation sheaths such as rubber and the like. Moreover, the mechanical strength, particularly the tensile strength, in insulation piercing connectors, has generally been poor, especially when the conductor is insulated with such soft, semi-fluid, or rubber-like insulation.

It is an object of the present invention to provide a solderless insulation-piercing connector that makes a good electrical connection and that is simple and economical in use and which, in a large measure, overcomes the disadvantages of earlier solderless type connectors. In one embodiment of the invention a wire-engaging ferrule portion is provided with an inwardly extending sharpened barb positioned between two oppositely-disposed ear portions which are adapted to be circled and driven inwardly on or into the conductive core of the wire so as to clamp the conducting core of the insulated wire firmly in compression between the ear portions and the barb thus holding the wire in excellent contacting relationship with the connector irrespective of concurrent or subsequent flow, or distortion in the shape of the insulating material.

In addition to providing for the transverse gripping of the conducting core, as mentioned above, the invention also provides for anchoring the conductor against axial movement with respect to the connector by providing an additional pair of oppositely disposed ears, displaced axially a substantial distance from the first pair, which also grip the insulating material and extrude it under pressure into the space between the two sets or ears, thereby increasing the mechanical strength, particularly in tension, of the assembly and maintaining continued clamping force on the conductive core, thus insuring mechanical and electrical stability under normal conditions of use for a long period of time.

Thus, in one aspect, this invention is directed to a simple connector structure and method of its application to insulated wire which provides a connection of excellent electrical stability and high tensile strength. In another aspect, this invention is directed to an electrical connector of the insulation-piercing type which is electrically and mechanically secure and which has substantially highencurrent carrying capacity than is known in such connectors in the prior art. Another aspect relates to an electrical connector and method of application which will make and maintain secure electrical connection of high current capacity with an electrical conductor even through a relatively large thickness of a pliable insulation sheath. These and other aspects, objects, and advantages of the invention will in part be pointed out in, and will in part become apparent from the following description when considered in conjunction with the accompanying drawings, in which:

Figure 1 is a perspective view of a strip of electrical connectors embodying the invention, for use in automatic connector-assembling machinery;

Figure 2 is an enlarged plan View of the connector shown in Figure 1;

Figure 3 is an elevational view of the connector shown in Figures 1 and 2;

Figure 4 is a sectional view of the connector shown in Figure 1, taken along line s-c of Figure 3, and an insulated conductor in a die structure for assembling the connector and conductor;

Figure 5 is a perspective view of the connector of Figure 1 after being assembled with an insulated conductor;

Figure 6 is a cross-sectional view taken along line 56 of Figure 5;

Figure 7 is a perspective view of a connector showing another embodiment of the invention.

Figure 8 is an isometric vi w of the connector shown in Figure 7 after being assembled with an insulated conductor;

Figure 9 is a cross-sectional view taken along line 99 of Figure 8;

Figure 10 is a sectional view similar to Figure 9 showing another embodiment of the invention;

Figure 11 is an isometric view of a plug type connector representing still another embodiment of the invention;

Figure 12 is an isometric view of the connector shown in Figure 11 assembled with an insulated conductor; and,

Figure 13 is a cross-sectional view taken along line l3--l3 of Figure 12.

Components serving similar functions in difierent embodiments of the invention have been designated by adding one hundred to the indicating numerals of such similar components in each succeeding embodiment Figure 1 shows a group of electrical connectors which have been fabricated in a continuous strip to facilitate handling and their use in automatic machinery, which cuts apart the individual connectors, generally indicated at 2, and assembles them with the insulated conductors. Each connector 2 includes a wire-engaging ferruleforming portion, generally indicated at 4, shown here as a trough-like channel, and a secondary connecting portion, generally indicated at d, shown representationally as a forked or spadetongue connector, such as is used for making a connection to a screw-type binding post or the like, which is formed integrally with the ferruleforming portion 4 to which it is joined by a neck portion 1.

The ferrule-forming portion 4 (see also Figures 2 and 3) includes a base portion 8 having two pairs of upwardly extending, oppositely-disposed, lateral ears l2 and I l which are spaced from each other axially, that is, longitudinally along the axis of the connector. The base 8 is provided with two upwardly extending, spaced, barbs or prongs i6 and i8 which are positioned near the longitudinal center line of the connector and, respectively, between each pair of opposed ears l2 and It. By placing at least a portion of each of the barbs i6 and 18 between an adjacent pair of the ears in the same transverse plane,

that is, in a plane extending at right angles to the longitudinal axis of the connector and through a pair of opposed cars, a clamping or gripping action on the conductor core is obtained, as will be described later. The connector advantageously is formed of corrosion proofed steel, but other materials such as copper or brass can be used if desired.

Figures 5 and 6 show a connector 2 assembled with a conventional insulated conductor, generally indicated at 22, having a centrally located metallic conductive core 24, formed in this example of twisted wire strands, surrounded by a sheath 2% of insulating material. The forward ears M have been curled sharply inwardly and driven end-wise down through the insulating sheath 26 and between the strands of the conductive core 24, thus making intimate contact with these strands over a substantial area. Such piercing of the strands is not always used; a scraping contact which clamps the entire conductor between the ear portions H3 is sometimes preferred, and will be illustrated subsequently.

In order to assemble the connector 2 with the insulated conductor 22, the conductor 22 is placed in the trough of the ferrule-forming portion 1 of the connector, which is positioned in a die structure, generally indicated at 28 in Figure 4. The upper die 32 includes spaced parallel wall portions it, which extend, respectively, into sharply curved portions 36, which at their juncture form a sharp ridge 38, which if desired can be somewhat blunted to reduce wear on the die. The lower die 42 drives the connector 2 and the upper die 32 together curling the ears Hl, as they follow along the inwardly curved die surfaces 35, and driving them downwardly end-wise into the insulated conductor 22. Dies such as this can be used in automatic machines which sever the connector 2 from its strip during the cycle in which the connector is crimped onto the conductor 22. This method of curling laterallyopposed ear portions, is disclosed more fully in the copending application of James C. Macy, Serial No. 717,842, filed December 23, 1946.

The ear portions l2, in this embodiment, are curled around the periphery of the insulation sheath 2G, by a portion of the die structure 28 or other suitable means (not shown) and compressed and cold-worked thereagainst so that the ears l2, exerting pressure through the insulation 26, clamp the conductor core 24 firmly down upon the barb H5 thereunder. These ears i2 and the ears hi exert a compressive force on the deformable insulation sheath 26 resulting in an outwardly extending bulge 36 of insulation between the ears l2 and the ears M.

The above-described arrangement results in several advantageous features which may not be entirely apparent from the structural description. For example, the barb i8 is disposed in a transverse plane (perpendicular to the longitudinal axis of the connector) through the ears l4, so that the conductor core is driven down upon the barb l8 and held compressively thereagainst by the faces of the tips 44 of the ears id. The contact pressure between the ears and barb l8 and the conductor core 24 is made and maintained at a high value without depending upon transmission of these forces through the insulating material, and the conductor core is firmly locked in position so that it cannot drift or work away from the areas of contact, thus assuring good conductivity even at low voltages. This arrangement is of particular importance when relatively thick or pliable insulating material is used.

In addition, the barbs It and i8 can be fabricated economically by cutting two oppositely directed V-shape notches in the base 8 of ferruleforming portion 4 and bending the severed portions of the base upwardly to form the barbs. The resulting openings in the base 8 must be sumciently small that the ferrule is not weakened excessively, but the barbs must be long enough to insure adequate contact with the core 24 of the insulated conductor 22. Moreover, the strength and orientation of the barbs must be such as to prevent the barbs from bending downwardly instead of piercing the insulation when the connector is assembled. Accordingly, after the initial formation of the barbs, by stamping or other means, the barbs are swaged, or otherwise shaped, to form a pointed and sharpened projection, which process results in lengthening of the barbs and at the same time making it easier for the barbs to penetrate the insulated conductor 22. The final length of the barbs advantageously is at least equal to one-half the transverse width of the channel of the ferruleforming portion 4, so that the barbs are at least equal to the radius of any circular conductor placed in the ferrule-forming portion i. In order to prevent the barbs from bending toward the openings which resulted from their formation, the barbs are bent slightly beyond the vertical position, so that the point of each barb is directly above the solid portion of the ferrule channel at the junction of the base 8 and the barb.

In order to provide maximum contact area between the cars It and the conductor core 26, the ears i i are generally quadrilateral in shape and the upper ends of these ears are rectilinear in the direction of the longitudinal axis of the core 25, so that substantially greater contact area is achieved than if the ears were formed in a generally triangular configuration, and larger surface areas are effective in clamping the conductor core 2% between the ears Hi and the barb I8.

In order that the ears M can readily penetrate the insulation, and extend between the strands of the core 24 where that is desired, the upper end of these ears are reduced in thickas by swaging. such as those shown at M for use in curling dies of the type shown in Figure such knifeedge-like configuration has been found, helpful in preventing buckling of the ears during crimping and in obtaining early conformation of the ear portion [5 with the die surface during the crimping operation, which assures that the ear portions M assume the proper curvature for making contact with the conductor core 2 3 in the desired precise manner, as well as in enhancing the ability of such ear portions to pierce the insulation sheath 26 of the conductor 22.

Such swaging of the ear tips is advantageous also for the ears l2 as it enables the ears to be simply wrapped around and compressed down upon the insulation sheath with the curled set of the ears extending to their tips, thus giving the compacted ears a smoothly curved surface where they meet.

It is to be noted also that the forward edges d3 of the ear portions i2, which are compressed around the insulation sheath and co-operate with the ear portions id to extrude, by virtue of their compression upon the sheath 2%, the previouslymentioned bulge 48 of insulation, are substan- In adapting ear portions 6*. tially rectilinear and at least partially abut the adjacent edges of bulge d6 of insulation. The firm grip thus obtained on the insulation by the ears l2 and it also increases and helps to maintain the compression of the insulation in the area of contact and increases the support of the con ductor core. Further advantages derive from the fact that the bulge as of insulation maintains a continued. pressure between the insulation sheath 2B and the ear portions !2 and it; this has been found to retard the entrance of corrosive fluids into the area of contact between conductor core 2%, the ear tips 4%, and the barbs it and 58.

It is to be understood that the rearward ear portions 42 also can be driven into contact with the conductor core 24, as are the cars it, to provide even greater area of contact. Such an arrangement is advantageous where maximum current-carrying capacity is desired.

In the above embodiment, the ear portions it are so constructed, and the upper die 32 is so designed, that the car tips M are curled away from each other in the connection, thus clamping the conductor core 2:; between the faces of tips it and the barb it. The ears are shown tapered in thickness from each side to form the km'feedges on their upper surfaces, which aid in enabling the ear tips 4-5 to curl readily in the die 23, as previously discussed. Note also the lateral separation, as at 5d, of the ears Hi at their points of entrance into the insulation sheath 2E, leavin a portion of the insulation sheath 26 compressed in the space 54 between the cars it, thus giving the contact area added protection against the entrance of corrosive fluids.

In some instances, such separation of the ears it, or even the curling apart of their tips 84 can be advantageously replaced by maintaining the abutting face-to-face relationship of the ear tips at, which occurs early in their curling and crimping cycle, in the completed connection. Thus the ears it remain in actual contact with their tips canted outwardly so as to produce a lateral clamping effect analogous to that shown in Figure 6, though of lesser degree, which tends to restrain the conductor core 25 from moving laterally.

In the above embodiment wherein three metal portions are driven adjacently into the conductor 22, the final stages of compression of the wireconnector assembly is opposed by the reaction of the compressed wire, and, particularly with small wires or those having insulation sheaths which are relatively thin, tough, or lacking in pliability, the compression of the insulation sheath should be relieved by holes in the connector walls, either in the base or ear portions, into which the insulation can extrude and allow proper setting of the ear portions. With suihciently thick and pliable insulation sheaths, extrusion into the hole in the base portion 8 left by the upturned barbs is E8, plus the longitudinal axial extrusion, is usually sufficient to permit such proper setting.

Figures 7, 8 and 9 show another embodiment of the invention wherein a connector, generally indicated at 182, includes a secondary connector in the form of a tip E and a ferrule-forming portion, generally indicated at Hi4, having two upwai'dlyextending, opposed, generally quadrilaterally-shaped ears H4. These ears extend axially along the connector blank for a suflicient distance to encompass two upwardly-extending barbs H8, similar to the barb it of Figure 1.

Figure 9 shows a vertical section through the connector I02 after assembly with an insulated conductor 122, having an inner conductive core 5%, either solid or stranded, and an outer sheath 526 of insulating material. The: ears H 1 curve upwardly around the outside of the insulation I26 and thence downwardly into the insulation. The ends of the ears H4 are advantageously sharpened or swaged to form a knife-like edge and the tips Md of the ears are oppositely curved, as by a die structure, such as is shown at 28 in Figure 4, with their surfaces in pressure contact with the outer surface of the conductor core 12 The pointed barbs I18 extend upwardly from the bottom of the ferrule-forming portion I94 and make contact with the core i2 3.

Thus, the connector Hi2, at the position of each of the barbs H8, makes intimate contact with the conductor core I24 at three points spaced approximately equidistant around its periphery, anchoring the core {2d firmly in position and providing other advantages pointed out above.

With larger size conductors, or where the insulation is thin or relatively rigid, it is not necessary to curl the ears Hi to obtain this three point clamping effect. Figure 10 shows an embodiment wherein the ears He are curved upwardly, around the insulation 26, as above, but in which they extend downwardly through the insulation sheath I26 so that their rectilinear ends abut the upper surface of the conductor core I2 i. Because of the relatively long axial length of the ears H4 and because contact between the ears H4 and the core I24 is maintained substantially throughout the axial length of the ears, a relatively low resistance connection is provided.

When conductors having thin or rigid insulation sheath are to be used in circuits that do not demand connections with high current ca pacity, the connector can be made smaller and simplified, by using two sets of laterally-opposed ears in a manner similar to that described in connection with Figures 1 to 6, but in which the ears do not pierce the insulation, but are wrapped around the insulation sheath and coldworked to remove their elastic memory. If the ears are adjacent the upturned barb, the great compression thus acquired in the area of contact compacts the insulation thereunder and reduces the likelihood that the conductor core will work 7 away from the barb.

Figures ll, 12 and 13 show such an embodiment of the invention wherein a connector, generally indicated at 292, includes a ferrule-forming portion 294 and a secondary connector in the form i of a plug 256. The ferrule-forming portion 205 includes a channel-like base portion 288 having two pairs of opposed, axially spaced, generally quadrilaterally-shaped, ears 2I2 extending upwardly therefrom.

The connector is provided also with two barbs 2 IE each positioned between one of the two pairs of ears 2&2, the arrangement and construction being generally similar to the embodiment described in connection with Figure 1.

Figure 12 shows the connector 282 after assembly with an insulated conductor 222. In this embodiment, the ears 2G2 extend around the insulation sheath 226, but do not pierce it. The compressive force achieved by the spaced quadrilateral ears 2I2, which produces a bulge 2 15 of insulation between the ears, being relied upon to maintain the contact between the conductor core 224 and the connector 202. This arrangement results in a simple and easily-assembled 8 connector which is satisfactory for many purposes, but which can not be expected to have so much current carrying capacity as the connector shown in Figure 1.

It is to be understood that the word connector is used herein in its generic sense, including end terminals, terminals for connecting insulated wires to binding posts, jacks, or the like, as well as connectors for joining two or more lengths of wires.

From the foregoing it will be observed that the connectors embodying my invention are well adapted for the attainment of the ends and objects herein set forth and to be manufactured economically, since the separate features are Well suited to common production methods and are subject to a variety of modifications as may be desirable in adapting the invention to different applications. It is to be understood that many other embodiments of my invention may be made and, accordingly, all matter hereinbefore set forth or shown in the drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. An electrical connection comprising an electrical conductor having a central core of electrically conductive material and a surrounding cylindrical sheath of pliable insulating material, and a connector for making electrical contact with said core including a ferrule portion substantially surrounding said sheath in compressive gripping relationship and having three inwardly projecting portions, a first one of which has a sharp point that penetrates the said core and the other two of which abut said core at two points generally opposite said first portion thereby anchoring said central core firmly in position in said connection and making permanent electrical contact therewith.

2. An electrical connection comprising an electrical conductor having a central wire core and a surrounding sheath of pliable insulating material, and a connector having a base portion, a barb extending upwardly from said base and into said core, and two laterally-opposed ear portions extending from opposite sides of the base adjacent said barb and around and in compressive engagement with said sheath, said ears being curled inwardly into said insulating sheath in opposed iace-to-face relationship with the face of each of said ear portions making pressure contact near its tip with said central core, said ears entering said insulation at spaced points on the surface of said sheath and a portion of the sheath being held in compressive engagement between the adjacent surfaces of said ears.

3. An electrical connection including an electrical conductor having a centrally-positioned wire core and a surrounding sheath of pliable insulation, and a connector having a ferrule portion including a base portion extending along and in intimate pressure engagement with the outer surface of said insulation, a barb extending inwardly from said base and penetrating said central core, and a pair of laterally-opposed ear portions extending from the said base around said sheath and inwardly into it outside said central core, said ears being in opposed face-to-face relationship at the point of entrance into said sheath and each being in pressure engagement with the outer surface of said central core, said ears engaging said core at spaced points generally opposite said barb, said conductor being anchored in position between said barb and the surfaces of said ears.

4. A connection comprising an electrical conductor having a centrally-positioned wire core and a surrounding sheath of pliable insulation, and a conductor having a ferrule portion including a base portion extending along and in intimate pressure engagement with the outer surface of said insulation, a sharpened barb extending inwardly from said base and penetrating said core, and a pair of laterally-opposed quadrilaterally-shaped ears having rectilinear ends extending substantially parallel with the longitudinal axis of said conductor, said ears extending from opposite sides of said base around the outer sur" face of said sheath and therein'to, the ears being in face-to-face relationship at the point of entrance into said sheath and saidrectilinear end surfaces of said ears abutting said central core substantially opposite said barb.

5. An electrical connection including an electrical conductor having a centrally-positioned wire core and a surrounding sheath of pliable insulation, and a connector having a ferrule portion including a base portion extending along and in intimate pressure engagement with the outer surface of said insulation, a pair of laterally-opposed quadrilaterally-shaped ear portions having rectilinear ends extending substantially parallel with the longitudinal axis of said central wire core, said ears extending from opposite sides of said base around the outer surface of said sheath with their ends in substantially abutting relationship, the end portions of said ears exerting substantial compressive force radially inwardly on said insulation, and a sharpened barb extending inwardly of said base between said ears, the end portion of said barb engaging said central core, substantial compressive pressure being maintained between said core and said barb by radial force exerted by the oppositely-disposed end portions of said ears, said base portion having an opening therein adjacent said barb permitting extrusion thereinto of the insulation sheath to assure good mechanical and electrical contact between said barb and the central core.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 379,688 Dennis Mar. 20, 1838 1,160,534 Schmidt Nov. 16, 1915 1,706,005 Thompson Mar. 19, 1929 1,816,674 Fortner July 28, 1931 2,197,578 Darnell Apr. 16, 1940 2,226,849 Douglas Dec. 31, 1940 2,302,767 Hackbarth Nov. 24, 1942 2,379,567 Buchanan July 3, 1945 2,476,429 Paules July 19, 1949 2,494,137 Martines Jan. 10, 1950 2,511,806 Macy June 13, 1950 2,600,012 Macy June 10, 1952 FOREIGN PATENTS Number Country Date 617,955 France Mar. 1, 1927

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