US2932880A - Method of making electrical switching devices - Google Patents

Description

April 1960 J. s. GELLATLY ETAL 2,932,880

METHOD OF MAKING ELECTRICAL SWITCHING DEVICES Filed Feb. 24, 1955 United States Patent METHOD F MAKING ELECTRICAL SWITCHING DEVICES John S. Geliatly, Westiield, N.J., and Charies F. Triteline, Downers Grove, 15]., assignors to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Application February 24, 1955, Serial No. 490,219

2 Claims. (Cl. 29-45555) This invention relates to the method of making electrical switching devices, and more particularly to the method of making step-by-step switch wipers.

An object of the invention is to provide new and improved methods of making switch wipers.

Another object of the invention is to provide new and improved methods of making step-by-step switch wipers.

A further object of the invention is to provide methods of making contact springs or wipers having convex precious metal contacts backed by convex base metal tips.

A method illustrating certain features of the invention may include cutting out portions of a strip of spring metal to form only tip ends of elongated contact springs, welding precious metal tips to the tip ends, and then forming the tip ends and blanking and forming the remaining portions of the contact springs.

A complete understanding of the invention may be obtained from the following detailed description of a switching device and method of making the same forming specific embodiments thereof, when read in conjunction with the appended drawings, in which Fig. 1 is a top plan view of a strip of stock having contact wiper springs in progressive stages of completion fonned therefrom by a method forming one embodiment of the invention;

Fig. 2 is an enlarged top plan view of a finished contact wiper spring;

Fig. 3 is an enlarged side elevation of the wiper spring shown in Fig. 2;

Fig. 4 is an enlarged fragmentary partially sectional view of the wiper spring shown in Fig. 2, and

Fig. 5 is an enlarged fragmentary perspective view of the spring shown in Fig. 2.

Referring now in detail to the drawings, there is shown therein a strip composed of electroconductive spring metal stock, such as, for example, nickel silver or solder coated nickel silver from which a step-by-step wiper spring 11 is to be fabricated, cut and formed. Pilot holes 12 are first formed in the strip to index the strip, and notches 13 are formed in the strip to form tips 14 and necks 15. Then rectangular plates 16 of precious metal, such as, for example, an alloy of gold, silver and palladium, larger than the tips 14 are welded to one face of the tips. The plates 16 have welding beads or bars 24 thereon which fuse with the tips 14 at the portions thereof in contact with the tips 14. The uncontacted portions of the beads form extra wear material on the portions of the plates beyond the tips 14, which portions of the plates are those subjected to wear during use of the springs 11. Then end portions 17 of the plates 16 are trimmed to form rounded end portions 18, and each tip and plate 16 is formed to present a convex contacting edge or tip corner 19 (Fig. 3) and cutouts 20 are formed to leave terminals 21. In the latter step, pilot holes 22 also are formed, after which the terminals 21 are corrugated and the notches 13 are'extended by punching to form notches 23 and shanks 25. In the next step, bends 26, 27 and 28 are formed, and then holes 29 and arcuate slots 30 are punched. Embossings 31 are formed in the next step, and then the entire spring contact or wiper 11 is punched out of the strip.

The notches 13 are preferably formed by a punch press and then welding of the plates can be effected by a separate welding machine, the strip 10 being uncoiled from a roll and then recoiled for each of these steps, after which the remaining steps may be done by a progressive punch and die. Thus, the strip has no portions except the thin fiat plates 16 out of the plane thereof to interfere with reeling and unreeling operations thereof. The tips 14 of the wipers 11 are strongly bonded to the plates 16 and provide rigidity and mechanical strength for the resulting tip assemblies. Also, the plates 16 extend beyond the front and sides of the tips 14 so that the ends 17 of the plates may be cut olf or trimmed without also cutting the tips 14. Hence, the precious metal plates 16 are not contaminated by the base metal of the tips 14 as: would occur if the tips 14 were trimmed with the plates 16. Thus, the scrapping of the plates 16 is avoided, and the precious metal scrap is uncontaminated. Also, the plate extends substantially beyond the tip 14 so that a large quantity of precious metal is available before the edge 19 wears down to the tips 14. The material available for wear is that to the right of a broken-line 31, as viewed in Fig. 4. This wear material is increased at the critical point by the bead. Also, the tips 14 provide high mechanical strength to the combined tip assemblies, and, since the tips 14 are full thickness throughout, this strength is present near the wear portions of the plates 16.

It is to be understood that the above-described arrangements are simply illustrative of the application of the principles of the invention. Numerous other arrangements may be readily devised by those skilled in the art which will embody the principles of the invention and fall within the spirit and scope thereof.

What is claimed is:

1. The method of making wiper springs each having a body portion, a terminal, a bent shank, a bent neck, a convex tab and a convex face plate of precious metal connected to the tab, which comprises forming notches along one edge of a strip of fiat spring metal to form the neck and a laterally extending tab having rounded ends, welding a fiat rectangular face plate substantially longer and wider than the tab to one face of the tab whereby the plate extends beyond the front and the sides of the tab, trimming only the portions of the rectangular plate extending beyond the front and sides of the tab to conform to the shape of the tab, then forming the tab and the plate to convex shapes, cutting the terminal outlines in the strip, then cutting the notches longer to form the shank, then bending the neck and the shank to final bent form, then forming the body portion in the strip, and then cutting the finished spring from the strip.

2. A method of fabricating electrical contact wipers having precious metal contact surfaces, which comprises punching out spaced acute angular sections along an edge of a strip of flat base metal to form spaced contact shanks having two tips laterally extending from the ends thereof, welding individual fiat precious metal contact elements to the flat tips of the shanks so that the elements overlay and extend laterally and forwardly beyond the edges of the tips, trimming the edges of the precious metal that extend beyond the edges of the tips without Patented Apr. 19,.196 0 Q 7 trimmingathe tips, then formingboth the tabs and precious metal contact elements into a convex shape,- and then punching out body portions attached to the shanks from the strip.

References Cited in the file of this patent UNITED STATES PATENTS 2,116,269 Kobzy May 3', 1938 4 1 Mehlhouse Aug. 23, 1938 Larson Oct; 10, 1944 Keitel July 3, 1945 Blattner Jan. 11, 1949 Iuvinall et a1. Oct. 9, 1951 Arms Jan. 18, 1955 Elliott May 22, 1956

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