US2281446A - Electrical contact - Google Patents

Description

April 1.942- c. A. LAISE v 2,281,446

ELECTRICAL CONTACT Filed Jan. 7, 1937 4 a 2 4 1 AV INVENTQR. Clemens ,1 .Zma

ATTORNEY.

Patented Apr. 28,1942

-' Emcrmciu. CONTACT Clemens A. Laise, Tenafly, N. J.; Fidelity Union'- Trust Company, executor of said Clemens A. Laise, deceased, assignor to Callite Tungsten Corporation, Union City, N. J., a corporation of Delaware Application January 7, 1937, Serial No. 119,378

13 Claims. (01. 200-166) This invention relates to the art of composite metal bodies and is particularly concerned with such bodies in the form of sheets or plates, composed ofthree metals or metal alloys, adapted -to be cut, punched, stamped, extruded or drawn out into a shape suitable for use as face plates for electrical contacts.

The invention contemplates the construction of electrical contacts in which the metal which serves actually to make the contact which completes an electrical circuit, is composed of silver or silver alloy.

The invention is applicable to electrical contacts of various types and to vibratory circuit making and -breaking devices of the type adapted for use as sparking or igniting contacts for internal combustion engines, circuit controllers,

regulators, therapeutic apparatus, automatic recording machines, sign flashers, etc.

Heretofore, silver contacts have been made in 1 the form of a face plate welded to a base of brass or cuprous metal in the form of a tack (so called) or an arm. It has, however, been dificult to efiect'a satisfactory union between them and a base of iron or iron-containing meta1.

often causes the silver face plates to become pitted and rendered unfit for the purpose for which -they are designed.

It is anobject of the present invention to provide an electric contact of composite metal having a face plate of silver or silver alloy and a base plate of iron or iron-containing alloy that will be adapted to unite firmly with a tack or arm of iron or iron-containing metal.

It is a further object of the present invention to provide an electrical contact having a face plate of silver or silver alloy, which is easy to make and which stands up under long continued use;

Another object is to p'rovide an argentic face plate for electrical contacts that is peculiarly adapted .to be Welded or otherwise firmly united to an arm or screw of ferric material.

Other objects of the present invention include the production of acomposite sheet, bar or plate having a face plate of silver or silver alloy, an intermediate member of a metal or alloy of high conductivity, and a base layer of ferric metal, or alloy containing iron or nickel, each of the three metals or alloys being firmly and uniformly united to its adjacent layers.

The proportion and composition of the metals Moreover, such contacts have been subject to an excessive rate of wear and short life due to the, heat produced at the point of contact which I efficient conduction of heat away from the or alloys -of which the various members of my novel sheet are composed are so regulated and adjusted that the same is softer and easier to work than is the ordinary steel silver material and causes less wear on the tools used to form the ultimate contact member which are formed from it. The composite body of the present in .vention is so constructed that the silver and iron components thereof are very intimately Joined together by a metal which has a strong affinity for argentic soldering or brazing material and for iron and silver as well. Consequently, the components of my-novel electrical contacts are less apt to come apart thanare ordinary contacts composed ,only of silver and steel, and in addition they last much longer by reason of the surface at which the heat is generated.

This conduction ofheat is obtained through the use of the intermediate layer of a metal of high heat conductivity which is so proportioned with relation to the other layers that it comprises between 15% to by weight of the total composite body. The intermediate layer may be as much as? of the total thickness of the composite body.

In general, the three metals or alloys are so adjusted that none of them exceeds'50% of the; total weight of the' entire composition. Satisfactory material for the purpose may be constructed so that the various components fall with-- v in the following ranges by weight:

I r I I Percent Silver or silver alloy 25to50 1 Copper or copper alloy 15 to 35 Iron or iron alloy '50to 15 The silver component of the composite body 7 which represents the contacting surface proper may be either pure silver or sterling silver which i is about 92.5% silverand 7.5% copper, or may be coinage silver which consists of 90% silver and a 10% copper, or it may be a different type of silveralloy. However, if the silver component is an alloy, the silver should exceed thereof.

The intermediate layer of high heat conductivity may consist of pure copper or of copper alloy such as a copper-beryllium alloy or a copper-nickel alloy. If this layer is alloy, the amount of copper should exceed 50% of the to tal weight thereof.'

The base layer may be pure iron such as Swedish iron or Armco iron or it may be an ironnickel alloy. If it is an alloy, the iron should comprise more than 50% of the total. In its simplest form the composite body of the 'gether by a thin film of silver solder.

' the nature described, I may join the respective.

isfactory to provide a starting material composed of a layer of silver metal having a. thickness of .30 inch, an intervening layer of copper metal .20 inch and a third layer of Swedish iron of a thickness of,.08 inch. Between each of the layers is inserted a thin layer of silver solder ranging from .002 inch to .004 inch in thickness.

The composite sheet of the presentinvention is produced by clamping the three metallic layers, together'with the intervening strips of silver solder, with platers clamps and'placing the assembly into a suitable furnace, which is heated to a temperature sufliciently high to form a firm union between the metals with the silver solder. As will be hereinafter described, the assembly is subsequently worked down toa sheet of the desired thickness from which the ultimate contact members are formed.

As an example of a silver solder suitable for use in accordance with the present invention, the following'is illustrative:

Percent Silver 60 Copper 30 Zinc 8.2 Tin 1.8

acts as a brazing material but should not be raised to a temperature at which the constituents of the bar or sheet-are caused to melt or alloy with each other. The time of heating should not' be prolonged so that the soldering or brazing metal is caused to seep out and run off from the seam between the constituent materials.

It should be understood that the union between the various constituents may be accomplished in an electric furnace, a gas furnace, or it may be electrically done by well known methods. It is preferable to carry out this operation in the presence of a reducing gas such as hydrogen.

layers of my composite sheet together directly by welding, as by electric welding or by welding in a furnace, with or without the application of pressure. The welding operations are preferably carried out in an atmosphere of hydrogen at a temperature regulated to cause a welding or alloying of the respective surfaces without causing any appreciable melting of the constituentparts. The process of the invention contemplates the combination of pressure with a temperature sufficiently high to make the metals plasticenough to cause them to flow and dissolve into one another. This is facilitated by working the metals in the manner previously described, except that they are rolled, swaged, etc'., particularly during the first working operations, while they are relatively hot. This heat treatment during working may sometimes be found desirable in cases'where the metals are brazed together as previously described, although it is not necessary in such cases.

When electrically welding the constituent metals, they may be placed between electrodes and sumcient pressure applied to theelectrodes, as the current passes through them, sothat the combined heat and pressure efiects a perfect, union of the nature described. It should be noted, however, that the current applied should plates of various shapes and sizes.

beregulated so that the heat produced is not sufiicient to bring the metals to their melting points.-

The sheet may be processed into contact face It may be punched out into discs which may be circular, square, or of any convenient shape, adapted to be welded or brazed to suitable members such as metal arms, bimetallic members, metalplates, screws or rivets. Forginstance, if the disc is to be used for spot welding, itmay be extruded through rivet headers or other suitable machines to form small projections M on the steel 'or iron end of the composite member. These projections aid in permitting the contact to be more readily spot welded onto an iron or iron-containing arm or other suitable body to which it is to be attached. It may also be attached by its fer- After the composite sheet has been formed into a unitary mass, the same is'removed from the furnace and allowed to cool, after which it is mechanically worked down by hammering, rolling, swaging', etc., until the desired thickness is obtained.

In the drawing, Fig. 1 illustrates in section a sheet or bar in which the above described metals 1 with a projection I4 on the steel end B; Fig;

3 shows a steel or bimetallic strip l5 to' which one of such contacts has'been welded; and Fig. 4

shows a contact associated with a steel screw.

Instead of employing a fbrazing material of rous backing to a ferrous arm or tack by spot welding.

The'component members of the present invention are very firmly and uniformly united to gether into .a composite sheet which does not rapidly to conduct the heat away from the silver "or alloys have been firmly united. The layer In contact but it also serves to act: as a cushion during processing, to give a strong bond between the silver and the steel, and to produce a superior contact. 5 I

It is a further advantage of the contact of this invention thatby reason of the fact that the composite material of which it iscomposed provides a face plate .of silver or silver alloy; an intermediate layer of copper or cuprous metal, and a backing of iron or ferrous metal, it is easily joined in a firm manner to iron-containing arms, rivets or the like. The contact of this invention may, indeed, be easily spot welded to an arm of thermostatic bimetal where the side of the bimetal to which it is to be so welded consists of a of argentic material, an intermediateelayer of A cupric material and a base layer of ferric material, the said intermediate layer comprising from to 35% by weight of the composite member, and metallic means integrally uniting the same to the adjacent layers.

2. A composite member consisting of a layer of argentic material, an intermediate layer of cupric material and a base layer of ferric material, the said intermediate layer comprising from. 15% to 35% by weight of the composite member and a substantial proportion of the total thickness thereof, and metallic means integrally uniting the same to the adjacent layers.

3. A composite member which consists of separate layers consisting, by weight, of 25% to 50% argentic material, 15% to 35% cupric material, and 50% to 15%-ferric material, the said cupric layer being intermediate the other two and integrally uniting the adjacent layers together.

4. A composite member which consists ofseparate layers consisting, by weight, or 25% to 50% argentic'material, 15% to 35% cupric material, and 50% to 15% ferric material, the said cupric layer being intermediate the other two layers and being intimately brazed thereto.

5. A tri-metallic member consisting of separate layers of argentic material and ferric maposite memberand a substantial proportion of the total thickness thereof. and a silver solder disposed between said respective layers whereby the same are integrally united -to each other.

9. A composite material in the form of a sheet consisting of a layer of silver or silver alloy, a layer of iron or iron alloy, and an intermediate layer between the two said layers of copper or copper alloy comprising a relatively large proportion by weight of the thickness of the composite sheet, each of said three layers being integrally united to the next adjacent layer.

10. A composite metalmember consisting of a layer of silver, an intermediate layer of copper, and a base layer of iron, the said intermediate layer comprising from 15% to 35% by weight of the composite member and comprising a substantial proportion of the total thickness thereof, and metallic means integrally uniting the same to the adjacent layers.

11. A composite metal member consisting of a layer of argentic material containing at least 50% silver, an intermediate layerof cupric material containing at least 50% copper, and a base layer of ferric material containing at least 50% iron, the said intermediate layer comprising from 15% to 35% by weight of the composite member and comprising a substantial proportion of the total thickness thereof, each of said layers 'beingsintegrally united with the layer adjacent thereto. 1

12. A composite metal member consisting of a layer of argentic material containing at least 50% silver, an intermediate layer of cupric maer-Jf cupric material, the said intermediate layer a comprising 15% to 35% by weight of the composite whole.

6. A tri-metallic electrical contact consisting of separate layers of argentic material and ferterial containing at least copper, and a base layer of ferric material containing at least 50% iron,the said intermediate layer comprising from 15% to 35% by weight of the composite member and comprising a substantial proportion of ric material intimately joined to an intermediate layer of cupric material, the said intermediate layer comprising 15% to 35 composite whole. l

'7. A composite metal member consisting of a layer of argentic material, an intermediate layer byweight of the of cupric material, and a base layer of ferric material, the said intermediate layer comprising from 15% to 35% by weightof the composite member, and metallic means integrally uniting the same to the adjacent layers, said means comprising a silver solder.

8. A composite metal memberconsisting of a layer of argentic material, an intermediate layer of cupric material, and a base layer of ferric material, the said intermediate layer comprising from 15% to 35% by weight of the comthe total thickness thereof, each of said layers being united with the layer adjacent thereto by a thin metallic film having a lower melting point than any of said layers. I

13. An electrical contact member comprising a layer of argentic material containing at least 50% silver, an intermediate layer of cupric material containing at least 50% copper, and a base layer of ferric material containing at least 50% iron, the said intermediate-layer comprising 'from 15% to 35% by weight of :the contact memher and comprising a substantial proportion of the total thickness thereof, each of said layers being united with the layer adjacent thereto by a thin metallic film in a bond affording a good electrically conductive path throughout said con tact member.

' CLEMENS A. LA ISE.

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