US2200854A - Electrical contact - Google Patents

Description

Patented ay 14, 1940 No Drawing. Application May 2,1989, Serial No. 271,346

Claims.

This invention relates to electrical contacts, specifically to copper or silver base contacts.

The art discloses silver contacts containing a relatively high melting point oxide, such as lead oxide or thallium oxide, added to reduce arcing and tendency to stick. Such oxides after sintering of the contact have usually remained in the contact as localized particles, the distribution depending upon initial grain size and extent of intermixing prior to pressing.

The present invention comprises generally a copper or silver contact employing an electrically conductive oxide fusible at a temperature below the sintering or melting point of the metal to which it is added. The preferred oxide is vanadium pentoxide, which unlike lead oxide or thallium oxide previously suggested in the art, is conductive. This quality avoids the possibility of insulating local areas in the contact. The vanadium pentoxide is preferably added to the silver or copper in powdered form, the mixed materials being reduced to fine mesh size and ball milled for a sufficient length of time to insure uniform distribution. The mixed powders are then preferably pressed into contacts which can be heated to the melting point of the vanadium pentoxide, which at 690 C. will flow between the granules of silver or copper and afford a uniform distribution and bonding action.

The vanadium pentoxide is preferably present in the proportions of about .1% to The preferred range is between 1% and 5%. An example of a silver base contact especially useful for a number of applications is one containing 98% silver and 2% vanadium pentoxide.

In addition to its bonding action and its quality of being electrically conductive, the sintered silver vanadium pentoxide contacts are harder than the sintered silver contacts. I attribute this to crystal structure and efiect at the grain boundaries of the silver of the vanadium pentoxide film which forms on the silver particles when the contact is heated up to the melting point of the vanadium pentoxide.

The percent of vanadium pentoxide added to the silver or copper will vary with the size of the powdered metal grains, the service to which 5 the contacts are to be applied, etc.

The vanadium pentoxide is the only oxide of vanadium which is suitable for the purposes of this invention, the addition of other oxides of vanadium to silver or copper contacts not producing similar or desirable results.

While the invention is specifically directed to contacts of silver or copper containing a relatively small proportion of vanadium pentoxide it is recognized that other elements may be added 35 to the silver or copper, or that the silver and copper may be alloyed, in order to reduce the cost of the contact, and that the term silver base" or copper base" contact when used herein will cover compositions of silver and copper with other metals.

The vanadium pentoxide will also act as a conductive binder for graphite or other conductive forms of carbon and contacts made therefrom will be found useful in a number of applications. Carbon-vanadium pentoxide contacts are much harder than carbon contacts and are also much stronger and more durable.

What is claimed is:

1. An electric contact composed of a contact material characterized by the addition of a relatively small amount of vanadium pentoxide.

2. An electrical contact of the group consisting of silver and opper base contacts containing from .1 to 10% vanadium pentoxide.

3. A silver base electrical contact containing from .1% to 10% vanadium pentoxide.

4. A copper base electrical contact containing from .1 to 10% vanadium pentoxide- 5. A silver base electrical contact containing from about 1% to about 5% vanadium pentoxide.

SAMUEL RUBEN.