US2070271A - Electrical contact - Google Patents

Description

vPatented Feb. 9, 1937 PATENT OFFICE ELECTRICAL CONTACT Childress B. Gwyn, Jr., Indianapolis, Ind assignor, by mesne assignments, to P. R. Mallory & 00., Inc.-, Indianapolis, Ind., a corporation 01 Delaware No Drawing. Application January 31, 1935,

Serial No. 4,305

6 Claims.

This invention relates to electrical make-andbreak contacts.

An object of the invention is to provide an electrical make-and-break contact which is suitable for use in connection with magnetos, relays and similar devices.

Another object is to provide an electrical makeand-break contact which may be substituted for contacts of the platinum-iridium, and similar types.

'A further object is the provision of an electrical make-and-break contact of high hardness, superior electrical characteristics, and which, compared to contacts commonly used in the various fields mentioned, is relatively free from carburizing.

Further objects will be apparent from the following disclosure.

For many purposes, such as for magneto contacts, relay contacts, etc. it has heretofore been customary to use electrical make-and-break contacts coniposed of platinum-ruthenium or iridium-platinum alloys. While such contacts are fairly satisfactory, due to their hardness, non-corrosiveness in normal and most industrial atmospheres and low transfer (carry-over) under the electrical arcing inherent to magneto and most relay operations, they also possess the disadvantages of high initial cost and difflculty of fabrication and have usually required a fairly high percentage of iridium or ruthenium to reach the desired degree of hardness. Moreover, the'alloys of platinum and iridium have shown a marked aifinity for hydrocarbon vapours under electrical arcing conditions and this characteristicseems to increase with the increased percentages of iridium necessary to produce suflicient mechanical strength and hardness for magneto and similar uses.

My invention includes the use of an alloy of palladium, nickel and silver, and particularly an alloy of such metals suitable as a substitute for platinum-ruthenium and platinum-iridium alloys, in the fabrication of electrical make-andbreak contacts.

In some instances, I may substitute copper for the silver, and cobalt or iron for the nickel and in special cases where low cost is not of essential importance. Platinum for the palladium. Where iron is substituted for the nickel, I find it desirable to keep the percentage at not more than 2% by weight. r

The alloy from which the contacts in my invention are preferably formed contains a preponderance of palladium. :1 smaller amount of silver, which may be pure or commercial silver, and a much smaller amount of nickel. For general purposes, I prefer to keep the limits as follows: I

Percent Palladium -75 Silver 10 -35 Nickel 0.5- 5

Where the contacts are to be used for magnetos and relays, however, I prefer to keep the limits down as follows:

Percent Palladium -80 Silver 20-30 Nickel 1- 3 A contact element formed from an alloy of 72% palladium, 26% silver and 2% nickel has a Rockwell B hardness comparable with that of a 25% iridium platinum alloy contact, and has a density of approximately 11.66 grams per 0. c. as compared to a minimum of 21.4 grams per 0. c. for the iridium-platinum. In addition to this volumetric advantage of or 184%, my alloy has, of course, considerable advantage in lower cost.

The contact of this invention compares favorably in electrical characteristics with iridiumplatinum contacts, particularly on relay and magneto service and is superior to such contacts from a carburizing standpoint when exposed to hydrocarbon vapours.

As compared with platinum-ruthenium contacts generally formed from about 92% platinum .and 8% ruthenium, there is, in addition to other my alloy on the negative (battery) side of the contact circuit withthe refractory contact on the positive (battery) side. This prevents or ameliorates transfer.

I have also found that the alloys which I have described herein may, to advantage, be used as a substitute for gold and gold alloys generally used for jewelry, dental and other purposes, the alloy of this invention being both cheaper and harder than the standard gold or white gold metals.

Since I may desire to vary the elements of my alloy somewhat to overcome peculiar arcing characteristics or to secure various desirable degrees of hardness, I do not limit myself to the percentages set forth in my alloy but use them as illustrative of the proportions only and not as liTiiting proportions.

What is claimed is:

1. An electrical contact element composed of one of the metals palladium and platinum-% to 85%; one of the metals silver and copper- 10% to 35%; and one of the metals nickel, cobalt and iron-0.5% to 5%.

2. An electrical contact element composed of one of the metals palladium and platinum-% to I an alloy containing about 2% one of the metals silver and copperan alloy containing about 0.5 to 5% nickel, about 10 to 35% silver and the remainder substantially all palladium characterized by such hardness and other electrical and mechanical characteristics as to admit of substitution for electrical contact elements of platinum-ruthenium or platinum-iridium.

6. An electrical contact element composed of nickel, about 26% silver and the remainder substantially all palladium, characterized by a hardness comparable with that of a 25% iridium-platinum alloy con-, tact.

CHILDRESS B. GWYN, JR.

silver and about 2% nickel.-