US1860793A - Electrical contacting element - Google Patents

Description

-May 31, 1932. A WE|GER 1,860,793

ELECTRICAL CONTACTING ELEMENT Filed July 9, 1927 INVENTOR.

v M ATTORNEYS.

atented a? 9 E93 JOSEPH A. WEIGER, O15 UNION 0, NEW JERSEY,

nurses, are r. a coaronarroar or mna a moan comm ASSIGNOR, BY MESNE- ASSIGN- LORY 62 GO, INCORPORATED, 015 INDIANAPOLIS, INDIANA, A

i G mmmm Application filed July 9, 1927. Serial No. 2%,475.

This invention relates to electrical contact ing elements, and particularly to contacting elements having a durable contacting facing.

The invention has for its object generally to provide an improved contacting element, which is efiicient, economical and possesses great durability in electrical contacting service.

More specifically, an object of the invention is to provide a contacting element for makeand-break contacting devices, or for devices employing wiping contacting elements, with an improved contact facing which is non-fusing and enables it to be both mechanically and electrically durable and not readily liable to pit when arcing.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the features of construction, combinations of elements, and arrangement of parts, which will be exemplified in the constructions hereinafter set forth and the scope of the applica-.

tion of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings, in which:

Fig. 1 is a side elevation showing an electromagnetic make-and-break contacting device provided with contacting elements constructed in accordance with the present invention;

Fig. 2 is an enlarged perspective View showing the details of the contacting element employed in Fig. l; and

Fig. 3 is an elevational view showing a contacting element adapted for making a wiping electrical contact.

Referring now to Fig. 1, 1O denotes a slab of insulation forming a base on which the members of the electromagnetic make-andbreak contacting device are mounted. As shown, this base has an electromagnet 11 mounted thereon and adapted to actuate a movable arm 12 of the device, this arm having at its upper end a contacting element 13 provided in accordance with the present invention. The element 13 is arranged to engage with a similar contacting element 14 secured on a stationary arm 15 of the device. The contacting device here shown is also provided with a-magnetic blow-out coil 16, operatively disposed with respect to the contacting elements 13 and 14 so asto function in the usual manner.

In Fig. 2 a contacting element, such as shown at 13 and 14, is shown on enlarged scale. The element, here depicted, has a backing portion 20 provided with an arm 21 in order that the element may be convenientl attached to an arm of the make-and-breali device. The backing portion 20 is given any convenient shape, that shown bein a curved or somewhat arcuate shape in or er that it may dissipate quickly any are that may form betweeen the contacting elements when separating. The backing has a facing portion 22 fitted over its arcuate surface which is intimately joined to the backing by a bra-zing medium that has relatively high electrical and heat conductivities.

' The backing portion 20 serves as a frame for carrying the facing portion 22. In consequence the backing portion is designed to carry substantially all the mechanical stresses incident to the contacting service, and in order to have requisite strength may be more bulky than is required for the maximum current densities involved in the contacting service. The backing portion is of a material having relatively high electrical conductivity and may be of copper, brass, bronze, and also of iron or its alloys. The latter materials are of course emplioyed in a contacting service where the mechanical stresses are particularly severe and where relatively small currents pass through the contacting element.

In the practice of the present invention the facing portion is a metal of composite character, and is arranged to make direct contact with a corresponding facing portion of the cooperating contacting element. This portion is formed to overlie substantially the whole of the surface of the contacting element that is designed to be opposed in any manner to the contacting surface of the cooperating con- 'tively low vapor tension, so that an are,

tacting element, and also to overlie in addiconstituting the tion those portions of the contacting element that may be exposed to an arc. By this arrangement it has a relatively large area disposed as a contacting surface in comparison to its thickness. As a consequence contacting devices employing the present invention have a cuttent-carrying capacity of many amperes. The composite metal, which is here used in the facing portion, has a porous body of hardened refractory material, such as, for example, molybdenum or tungsten which is impregnated with another metal, imparting to it relatively high electrical conductivity and other desired properties. The base of refractory material is preferably treated with carbon to produce a hardening effect, an amount of not more than 1.5 per cent carbon being used such that the particles of the porous base are only surface hardened. The impregnating metal is a relatively light, low melting-point metal, which is compounded with the hardened tungsten body substantially in the manner as set forth in the application filed on August 26, 1925, by G. N. Sieger and myself, Serial No. 52,690. This impregnating metal is selected not only to have a relatively low melting-point with respect to tungsten, but also to have a relai 1 formed, is not sustained by metallic ionization during the process of arcing. Metallic material here employed as having the desired characteristics may be one or more of the following metals Aluminum, copper, nickel, silver, tin and zinc. The tungsten for the composite metal is to be taken in substantially from 25 to 90 parts by weight to from 75 to 10 parts by weight of the lighter metal or metals employed. The facing portion in consequence has both relatively high electrical and heat conductivities. It is to be understood that wherever the term tungsten is used, it is intended to cover any recognized equivalents in the art to which the invention relates, such as, for example, molybdenum.

In accordance with the preferred method of forming composite metal about parts by weight of tungsten and about .5 parts by weight of lamp black are mixed together, preferably in powdered form, and the ingot is formed therefrom by subjecting the mixture to pressure, forexample ten pounds to the square inch. The latter is fired in a hydrogen furnace at about 1000 C., and continued for a few minutes. In the ingot the voids will amount to about between 40 per cent and 50 per cent so that theoretically and practically the limit of additional material will be approximately equal. The metal is then placed in a refractory receptacle, and the low melting point metal or metals is or are placed preferably in solid form about'it. The whole is then further heated in a reducing atmosphere, and the low melting point metal or metals remainder of the composite metal will penetrate the base throughout. Thus with metal, which melts at about 1080 (1., the temperature of the ingot is raised to approximately 1300 C., and maintained at this temperature for approximately one hour, after which it is allowed to cool.

The joint by which the facing material is joined to the backing material is made by employin a brazing medium which has both high e ectrical and heat conductivities and may also be made by autogenous welding. A suitable brazing) medium for making this joint, when the acking portion is of co per or an alloy thereof, is silver solder. en

thereof, the brazing medium is preferably a.

fused film of copper.

A contacting element thus constructed is adapted for contacting service under severe operating conditions where the currents to be broken are irregular and of large magnitude and the breaks of frequent occurrence. By reason of the non-fusing character of the facing material, the arcs do not readily form and are easily extinguished. The contacting surface in consequence is resistant to fusion so that the original contour of the contacting surface is substantially continuously maintained, and pitting is avoided. A long an uniform contacting service without annoyance from arcing or pitting in consequence results.

A contacting element provided in accordance with the present invention is not limited to service in make-and-break contacting devices, but may be used as a contactin element where a wiping contact is desire A wiping contact device is illustrated in Fi 3 in the.form of a contacting shoe 30, whic is shown as making wiping contact with a conducting bus or -so-called third-rail 31. The contacting shoe 30 is sustained in contacting relation with the bus by means of the pantograph suspension means shown at 32. This contacting shoe has a backing portion 33 which is faced with. a facing portion 34, which is a relatively thin layer of metal that imparts to the s oe the mechanical and electrical durability provided in accordance with the present invention. This facing portion, as indicated above, is a composite metal having a body of tungsten impregnated with a relatively light, nonarcing, low melting-point metal of the character indicated above.

The contacting shoe in consequence has relatively high electrical and heat conductivities and is not readilvdeleteriously affected by the drawing 0 arcs, which is of frequent occurrence where the shoe asses over a discontinuity in the bus or th'rd rail.

Since certain changes may be made in the above construction and different embodiments of the invention could be made without de- .the backing portion is of iron or an alloy partin from the scope thereof, it is intended that all matter contained in the above descrip- I tion or shown in the accompanying drawings shall be interpreted as illustrative and not in a limitin sense.

Having escribed my invention, what I claim as new and desire to secure by Letters Patent is:

1. A contacting element for electrical contact devices adapted for making and breaking relatively large currents under severe arcing conditions comprising a composite metallic facing having a porous body of hardened tungsten including about .5 per cent carbon and an auxiliarly metallic constituent of one or more of the metals silver and copper impregnating said porous body throughout.

2. A contacting element for electrical contact devices adapted for making and breaking relativel large currents under severe arcing con itions comprising a metallic backing and a composite-metallic facing including tungsten in preponderatin amount, carbon about .5 per cent and the fialance of one or more of the metals silver and copper.

In testimony whereof I aflix my slgnature.

JOSEPH A. WEIGER.

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