US 2298999 A
Description (OCR text may contain errors)
Oct, 13, 1942. w. T. ALLEN 2,298,999
ELECTRICAL CONTACT Filed Aug. 3 1940 lNVENTO/f A TTORNE Y at... Oct. 13, 1942 azoaaos amc'rmcu. com'sc'r Wallace '1. Allen, Royal Oak, Mich auignor to Square D Company, Detroit, Mich a corporation of Michigan Application August 3, 1940, Serial No. 350,859
3 Claims. (Cl. 209-186) This invention relates to electrical contacts and more. particularly to electrical contacts having non-welding characteristics.
The object of the invention is to provide a relatively non-welding electrical contact having an improved construction for readily securing it to a conducting support.
Other objects and features of the invention will be readily apparent to those skilled in the art from the specification and appended drawing 11- lustrating certain preferred embodiments in which:
Figure 1 is a side elevational view of a cooperating pair of contacts embodying the present invention.
Figure 2' is a perspective view or a contact according to the present invention.
Figure 3 is a sectional view of the contact taken on the line IIIIII of Figure 2.
Figure is a sectional view of the contact similar to Figure 3, but showing the soldering material as disposed over th entire back surface or the contact.
Referring to Figure l, a pair of cooperating contact elements I and 2 for making and breakin an electrical circuit are shown secured respectively to contact supporting arms 3 and t. The contact elements I and 2 are of similar construction and according to the present invention comprise a body portion 5 having a corrugated back surface, the corrugations being formed of a series of transverse and. longitudinally aligned truncated pyramidal formations 5 for a purpose to be hereinafter described.
To avoid a welding together of the cooperating contacts which would force a discontinuation of operation of the electrical instrumentality at which the contacts ar to form a part, the contacts are composed oi a mixture of silver and a relatively highly refractory material such as molybdenum, tungsten or the like. t has been found that a mixture comprising thirty-five to fifty-five percent by weight of silver with the balance of molybdenum or tungsten, with or without a minor percentage of carbon, provides a satisfactory contact element having relatively non-welding characteristics.
The contact element may be molded into the desired shape from a powdered metai mixture, r the refractory metal, in porous forgo, may b im pregnated with the silver. Applicant makes no claim herein to the process of making the contact as this forms no part of this invention. Nor is any particular manner of forming the element material oi essential to the present invention, as it is contemplated that it may be formed by any of the common and well known methods now in existence. I
The contact element is secured to its arm by brazing by means of resistance welding similar to spot welding. Applicant's invention lies in producing a contact element so constructed as to facilitate the brazing of the element to its supporting arm. The back surface of the contact element, as above described, comprises a series oi. transversely and longitudinally aligned truncated pyramidal elevations. This construction provides a multitude of hot points or areas at which the welding current is concentrated to produce a relatively high heat to insure the proper bonding of v the contact to its support.
The bonding material used in brazing the con tact to its supporting arm may be either free silver or one of the well-known silver solders such as Gil-Foe" which has an approximate composition or 89% silver, 15% copper and 5% phosphorous. This bonding material may be disposed upon the back contact surface in the recesses, as at l in Figure 3, or it may also be disposed to overlap th truncated pyramidal formations, as shown at e in Figure 4.
While certain preferred embodiments of this invention have been specifically disclosed, it is understood that the invention is not limited thereto, as many variations will be readily apparent to those skilled in the art and the invention is to be given its broadest possible interpre tation within the terms of the following claims.
What is claimed is:
i. An electrical contact adapted to be brazed a conducting support, comprising a body portion, or a refractory material having a surface of thaving a plurality of localized heating areas raised from the main. body portion, surface having a bonded coating oi a fusible bonding material, at least the said points or areas, said coating born applied to said contact before the brazing operation to form therewith a unitary article adapted to be subse quentiy applied to said support and brazed there to with the coating forming the bonding medium.
2. An electrical contact adapted to be brazed. to a conducting support, comprising body per tion. formed or silver 35% to 55% refractory the group tmzgsten-molybdenwn 45% to the surface of said contact adapted for attachment to the support having a plurality of localized heating points or area-s raised from arts between with a fusible bonding material of the group silver-silver, solder, said bonding material being applied to said contact before the brazing operation to form therewith a unitary article adapted to be subsequently applied to said support ando denum 45% to 65%, the suriace oi said contact adapted for attachment to the support, having a plurality of localized heating points or areas raised from the main body portion, said surface being flooded over its entire area including said heating points or areas, with a fusible bonding coating of free silver, said coating being applied to said contact before the brazing operation to form therewith a unitary article adapted to be subsequently applied to said support and brazed l0 thereto with the coating forming the bonding medium.
. WALLACE T. ALLEN.