US3381263A - Forked contact and method of manufacture - Google Patents

Description

A ril 30, 1968 E. E. GEHRT ETAL 3,381,253

FQRKED CONTACT AND METHOD OF MANUFACTURE Original Filed March 20, 1961 ATTORNEYS United States Patent 1 Claim. or. 339-477 ABSTRACT OF THE DISCLOSURE A bifurcated electrical contact of the type adapted to mate with an identical contact to establish positive electrical connection between two components is formed of sheet metal stock of uniform thickness and the legs of the bifurcation are swaged to provide opposed contact surfaces which conform substantially to the section of a cylinder of uniform diameter to facilitate mating and unmating while maintaining positive electric contact in the mated position.

This application is a division of our earlier application Serial vNo. 381,285 filed June 25, 1964, now U.S-. Patent No. 3,299,493 and the latter is a continuation of our earlier application Serial No. 96,947, filed March 20, 1961, now abandoned.

This invention is concerned with contacts for use in forming electrical connectors. The contact is of the bifurcated or forked type where two contacts of identical construction are engaged with their prongs in contact with each other to form a connector. The prongs of each contact function both as a socket and as a prong for the opposing contact.

Contacts of this type are useful for many purposes, one example being use on printed circuit boards as shown in US. patent to Blain 2,946,976 where a set of forked contacts are mounted on the board and another set of contacts are carried by a suitable base or support and oriented to engage the first set. If the inner edge faces of the prongs are formed of flat areas joined along sharp corners, such corners are likely to prevent smooth sliding engagement of two contact pieces, especially if the two pieces are not mounted with their planes exactly at right angles to each other, or if one contact piece is cocked with respect to the other.

An object of the invention is to devise a forked contact of novel structure which will provide for smoother mating of the prongs of a pair of contacts when placed into mating relation.

A specific object is to devise a forked contact in which the surfaces of the inner edges of the prongs of the contact are rounded to conform substantially with a cylindrical surface. In the preferred embodiment the inner edge portions of the prongs are formed as rounded bead portions extending along the active length of each prong.

A further object of the invention is to devise a novel method of forming the improved contact, involving the use of swaging dies to form the beaded edges on the contact prongs.

The invention is illustrated in the accompanying drawing in which:

FIGURE 1 shows a plan view of the novel contact;

FIGURE 2 is a view of a section of FIGURE 1 taken along the transverse plane 2-2 of FIGURE 1;

FIGURE 3 is a plan view on a smaller scale than FIG- URE 1 showing a strip of metal from which the contact is formed and showing various stages in the formation of the contact;

FIGURE 4 is a sectional view on a greatly enlarged scale showing a section of FIGURE 3 taken along the cutting plane 4-4 of FIGURE 3 and showing the swaging dies forming the beaded edge portions; and

FIGURE 5 is a transverse sectional view on a greatly enlarged scale showing portions of two contacts arranged in mating relation.

Referring to the drawing, FIGURE 1 shows a plan view of the contact formed from a flat strip of metal. The scale of FIGURES 1 and 2 is considerably enlarged for contacts which would be used on printed circuit panels. The contact is provided with a shank portion 1 having suitable mounting ears 2 and 3 extending from one edge thereof. In the drawing these cars extend rearwardly from the rear end of the shank portion, but they might extend from one of the side edges of the shank portion. At the forward end of the shank portion two prongs 4- and 5 extend forwardly in parallel relation and are separated by a slot or gap 6 which terminates at its rear end in an enlarged opening 7 which, for convenience in producing the necessary die parts, is of circular outline but could be triangular or of other shape.

As shown in FIGURE 2, the inner or facing edge portions 4a and 5a of the prongs 4 and 5 on opposite sides of the slot 6 have a rounded surface conforming substantially to a cylindrical surface extending over a circular arc of more than that is, more than 45 on each side of the common plane of the two prongs. In the particular construction shown the cylindrical surface of the inner edge portions 4a and 5a of the prong extend over a circular arc of substantially 270.

The inner edges of prongs 4 and 5 at the ends thereof are tapered or flared outwardly as shown at 4b and 5b to provide converging surfaces at the entrance to slot 6 to facilitate proper mating when two forked contacts are being moved into mating relation.

The manner of forming the contact from a strip of sheet metal, preferably spring tempered Phosphor bronze, is as .follows:

It will be understood that the metal strip 8 is fed stepby-step into a suitable punch-press which is provided with suitable punch and die tools at different stations or locations, the strip 8 traveling from right to left as shown in FIGURE 3. The strip is properly indexed or piloted in the different stations by a series of pilot holes 9 formed by a punch at one location. At the first station, a suitable punch and die forms the triangular perforation 10 having its broad side parallel with one edge of the strip 8 and the apex directed towards the opposite edge. The apex sides of perforation 10 form the tapered edges 4b and 5b for prongs 4 and 5 which are punched out at a later station. It is preferred that the edges 4b and 5b be at right angles to each other. At the second station a punch forms the enlarged hole 7. At the third station a narrow punch cuts a narrow slot 6 through the strip and connecting the holes 7 and 10. At this point slot 6 has a Width less than the thickness of the strip 8 and is slightly wider than in its final form, to allow for a certain narrowing of the slot by the swaging operation.

At the fourth station a pair of swaging dies of the forms shown at 11 and 12 in FIGURE 4 engage the edge portions of the slot walls, both above and below the strip, to form the bead portions 4a and 5a extending along the inner edges of prongs 4 and 5, respectively. This swaging operation causes cold flow of the edge portions of strip 8 and shapes these portions into bead strips of round section as shown in FIGURES 2 and 4. The forming surfaces of dies 11 and 12 conform substantially with cylindrical surfaces having axes located in the mid-plane of strip 8 and having a radius equal to or somewhat less than half the thickness of the strip. The metal flow during swaging also effects some closing of the slot 6 to its proper width. The dotted lines in FIG- UR-E 4 show the shape of the edge portions of the prongs before the swaging or coining operation. The pointed rib- portions 11a, 11b and 12a and 12b bite into strip 8 and cause a certain fiow of metal towards the center of the die without imposing substantial spreading action on the two prongs. These rib portions of die members 11 and 12 serve to hold the prongs against outward displacement laterally of the slot 6 while the rounded portions of die members 11 and 12 are squeezing or coining the inner edge portions of the two prongs into rounded bead form.

At the fifth station a 'blanking die having the shape of the outline of the contact piece blanks the completed contact piece from the strip 8 and leaves the perforation 13.

FIGURE shows the rounded edge portions of the prongs engage each other when two contact pieces are placed into mating relation, prongs 4 and 5 being on one piece and prongs 4 and 5 on the other piece.

It is desirable that each contact piece be formed so that the gap between the prongs at the end portions is of a width slightly less than near the shank, so that the prongs of each piece will exert a gripping action on the prongs of the other piece when two pieces are in mating engagement.

We claim:

1. A bifurcated contact formed of sheet metal of uniform thickness comprising a shank portion and two prong portions formed integrally with said shank portion and extending in parallel relation from said shank portion, said prongs being separated by a narrow gap of a width less than the thickness of the prongs, each of said prongs having longitudinal grooves formed in opposite faces thereof and adjacent said gap to define an edge portion adjacent said gap of a width substantially less than the width of the remaining or outer longitudinal portion of the prong, and the edge portions of said prongs defining opposite sides of said gap being of a rounded sectional form presenting outer surfaces conforming substantially to cylindrical surfaces extending on opposite sides of the common central plane of said prongs to an arcuate extent of more than on each side of said plane.

References Cited UNITED STATES PATENTS 2,377,558 6/1945 Johnson 78-60 2,828,474 3/1958 Fox 339-47 3,070,769 12/ 1962 Murphy 339-49 FOREIGN PATENTS 20,685 1898 Great Britain. 4,974 1905 Great Britain.

MARVIN A. CHAMPION, Primary Examiner.

P. TEITELBAUM, Assistant Examiner.

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