US1990783A - Electrical make-and-break contactor and method of mounting points thereof - Google Patents

Description

C. B' GWYN. JR ELECTRICAL MAKE AND-BREAK CONTACTORS AND Feb. 12, 1935.

METHOD'OF MOUNTING POINTS THEREOF Filed July 2, 1932 INVENTOR ATTORNEYS Patented Feb. 12, 1935 UNITED STATES PATENT OFFICE ELECTRICAL MAKE-AND-BREAK CONTACT- OR AND METHOD OF MOUNTING POINTS THEREOF Application July 2, 1932, Serial No. 620,569

7 Claims. (01. 200-166) This invention relates to a method of preparing and mounting electrical contact points on supports and contactors produced thereby and, more particularly, to such a method of preparing and mounting electrical make-and-break contact points of refractory metallic material on metallic supports and the improved contactors produced thereby.

A general object of the invention is the provision of such a method and articles produced thereby which insure efficiency in practice and operation heretofore unattainable, improve the service life of such contactors, and provide a mini-.

mum cost in production.

provisions of a method whereby an electrical make-and-break contact point of a refractory material oxidizable at brazing temperatures is readily provided with a bead of bonding material in a non-oxidizing atmosphere making efficient physical and electrical connections therewith, the bead then being locally fused to a metallic support, all of which can be simply and readily carried out; and contactors resulting from the practice of such method each including a contact point of the above mentioned material, such as tungsten, molybdenum, and compositions thereof, provided with a bead of lower melting point metallic material fused thereto and re-fused to a metallic support to form an efficient bond between the contact point and the support with the latter unaltered in its physical properties except in the immediate vicinity of the contact point.

Other objects of the invention will in part be 35 obvious and will in part appear hereinafter.

The invention accordingly comprises the several steps and the relation of one or more of such steps with respect to each of the others, and the article possessing the features, properties, and the relation of elements, which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated the claims. I

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 drawing, in which:

Fig. 1 is a sectional elevational view of a 50 furnace boat provided with recesses adapted to receive discs of bonding metallic material and contact points adjacent thereto in accordance with one feature of the present invention;

Fig. 2 is avertical section of a contact body consisting of a contact point provided with a. head of More specific objects of the invention are thebonding material fused thereto as a result of a heat treatment of these elements in the boat shown in Fig. 1;

Fig. 3 is a side view with parts broken away of the apparatus used to re-fuse the'bead of bonding 5 material to link the contact point to the support in accordance with another feature of this invention;

Fig. 4 is a side view with parts in section of a modification of the apparatus shown in Fig. 3; 10 and Fig. 5 is a side view with parts in section of a still further modification of the apparatus shown in Fig. 3.

Prior to the present invention electrical make- 15 and-break contact points of tungsten or the like have usually been secured to the heads of rivets and the rivets then secured to suitable supports, wherever the supports would be deleteriously affected by the heat of the brazing operation. 20 Such a method of mounting contact points was necessary since many metallic materials used for contact points, such as tungsten, molybdenum and compositions thereof, are not sufliciently malleable to be riveted directly to the supports. 25 Various brazing materials have been used to secure such contact points to the rivet heads, the brazing being usually carried out in a hydrogen furnace to prevent oxidization of the contact points which deleteriously affects the wetting, but it has been found to be undesirable to secure such contact elements directly to supports by such a method since the entire support would be subjected to the furnace heat, thus altering its physical properties and giving rise to various undesirable characteristics. Although the use of rivets avoids such difficulties, they have frequently been found to be loose or to work loose under conditions of operation attended by rapidly recurring impacts, to be a source of frequent inaccuracies in alignment and positioning, and to provide unreliable electrical connections between the supports and the rivets; furthermore the riveting operation has frequently been found to result in cracking of the contact points mounted on the rivets. In addition such brazed joints have been found to be frequently faulty, physically weak and inferior as electrical connections between contact elements and rivets and/or supports. All of these and various other undesirable characteristics of the prior art are substantially eliminated by the present invention.

In accordance with the present invention an electrical make-and-break contact point formed from refractory metallic material such as tungsten or the like is provided on its back surface with a bead of metallic bonding material having a lower melting point than that of the material from which the contact point is formed, by disposing adjacent the back surface of the contact point a body of a bonding material and subjecting the point and bonding material in a nonoxidlzing atmosphere to heat suflicient to fuse the bonding material and cause it to adhere to the contact point. 7

The resulting contact body consisting of a contact point provided with a bead of bonding material is then secured on any desired metallic support by a heat fusion of the head of bonding material which causes the latter to adhere to the material of the support, the bonding material serving as a linking layer between the con-'-' tact point and the support. This mounting may be readily obtained by interposing between suitable welding electrodes the support and the beaded contact point with the bead'adjacent the support and causing an electric current to flow between the welding electrodes through the support, the bead and the contact point, to raise the temperature of the bead sufliciently to cause it to fuse.

Referring to the drawing, in Fig. 1 is depicted a boat 10 of any suitable material such as graphite, carbon,-alundum, or other suitable refractory material, provided with a plurality of recesses 11 adapted to receive discs or bodies 12 of bonding metallic material and contact points 13 and 13', the latter having a specially treated face, as for example, a radius ground face. The boat is placed in a furnace provided with a suitable non-oxidizing atmosphere, such as hydrogen, for a sufflcient length of time and at a sufiicient temperature to fuse the bodies of bonding material which have a melting point lower than that of the material of the contact points, and then removed from this heating zone to a cooling zone in which the contact bodies are allowed to cool while still in a suitable non-oxidizing atmosphere. A section of one of the resulting bodies is shown in Fig. 2, 14 indicating the bead and 15 indicating the wetting or impregnation of the surface of the back of the contact point by the bondingmetallic material.

In assembling each contact body upon a support, an apparatus similar to that shown in Fig. 3 may be used wherein one electrode 16 of copper or a composition of copper and tungsten or molybdenum is fitted with a suitable insert 17, preferably formed from tungsten or molybdenum and provided with a recess 18 adapted to receive a contact body with the bead thereof exposed. electrode die i6 is preferably provided with any suitable member or members such as 19 to serve as a mount for a support 20 and also as a guide to insure the proper positioning of the support. The other electrode 21 adapted to eontact with the support 20 may consist of a single ization or zoning of the brazing For example where the material of the support has a high electrical resistance an electrode of relatively low electrical resistance is used and when the material of the support has a low electrical resistance an electrode of relatively high resistance is used.

A contact body, such as 13', is positioned in the electrode die with the headed back exposed. A suitable support 20 is then mounted on the member or members 19 and the electrode 21 is brought down into engagement with the support so that the latter is pressed against the bead 14 of the contact body. In mounting contact points of tungsten or molybdenum upon phosphor bronze supports, a contact body is preferably wetted with water before placement in the die hole 18 and the portion of the support to which the contact point is to be welded is likewise preferably wetted. A'relatively large electric 'current is then passed between the electrodes for a suflicient length of time to fuse the bead of prising about per cent by weight of silver and 40 per cent by weight of copper, to link the a contact point to the support. In mounting such contact points of sizes up to about .187 in diameter upon phosphor bronze supports an alternating current of approximately 500 amperes at about 1 /2 volts is passed between the electrodes for not more than about a second.

Since the time of current flow is a function of the resistances of the support and the contact element it will vary somewhat in accordance with the variations'in thematerial and thickness of the support and variations in the size and materials of the contact element. Such time variations, however, will be found to be of the order of fractions of a second. 0

In many cases it is desirable to provide a support with a locating portion such as an elevated table 22 or a depression '23 as depicted in Figs. 4 and 5 respectively. In either case the electrode 21 may be shaped to fit the deformation of the support but in the case of a depression in the support an inversion of the assembly is desirable as depicted in Fig. 5 wherein the lower electrode 24 is shown provided with a depression 25 adapted to receive the deformed portion of the support 20 provided by the depression 23 therein and the upper electrode 26 is provided with an insert 27 similar to the insert 17 of the die 16. The support is then positioned below the contact body 13' during the welding process.

The electrical heating operation by which the prepared contact body is secured to the support .except in the vicinity of the contact point, and

materially aids in the production of stronger and more eiilcient brazes or welds. The use of water also tends to prevent sticking of the contact points to the welding electrodes and adherence to the contact points of foreign material deleterious to operation which may be present on the electrodes. These features may be obtained by the use of water cooled electrodes or by performing the brazing or welding operation under water.

It is to be understood that the apparatus shown in the drawing is set forth only by way of example since any suitable apparatus may be used in practicing the method which will result in the formation of a bead of bonding metallic material on a contact point of tungsten, or the like, and the rapid local application of heat to the beaded contact point and an adjacent support sufficient to fuse the head of bonding material to secure the contact point to the support. Likewise, the relative positions of the contact point and body of bonding material in the furnace boat and that of the support and contact body may obviously be interchanged so long as such alterations allow the bead of bonding material to be formed on the back of the contact point and the formed bead to make contact with the desired portion of the support during the welding or brazing operation.

In practicing the present invention the contact points are formed from any refractory metallic material oxidizable at brazing temperatures, such as, tungsten, molybdenum, tungsten compositions, molybdenum compositions, etc., the terms tungsten compositions and molybdenum compositions being intended to include the compositions consisting of a major portion of highly refractory material such as tungsten or molybdenum.

The supports may be formed from any suitable metallic material, such as, for example, phos phor bronze, beryllium-bronze, bronze, spring steel, soft silicon steel, heat treated or normalized steel, Invar metal, brass, aluminum, duralumin, etc.

The bonding material may consist of any .suitable metallic material, having a desirable high electrical conductivity and a melting point lower than that of the material from which the contact points are formed, such as, for example, silver, copper, and alloys thereof, but preferably is an alloy of silver and copper, or an alloy of silver, zinc, copper and nickel. Other suitable bonding materials are alloys of copper and nickel and alloys of nickel and iron.

It will thus be seen that the present invention efficiently attains the objects set forth above and provides a method for the production of contactors with linking welds which have excellent mechanical and electrical characteristics and can be made at much lower temperatures than is possible in making direct welds or welds with bodies of bonding material interposed between contact points and supports.

Since certain changes in carrying out the above process, and certain modifications in the article which embody the invention may be made without departing from its scope, it is intended that all matter contained in the above description or shown in the accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

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

1. The method of mounting on metallic supports refractory metallic contact points oxidizable at normal brazing temperatures which comprises, fusing to the back of the contact point in a. nonoxidizing atmosphere a bead of metallic bonding material of a lower melting point, positioning the beaded contact point on the metallic support, and passing electric current through the contact point, bead and support under ordinary atmospheric conditions to re -fuse the bead and bond the contact and support together.

2. The method of mounting on metallic supports refractory metallic contacts oxidizable at normal brazing temperatures which comprises, fusing to the back of the contact point in a nonoxidizing atmosphere a head of metallic bonding material of a lower melting point, positioning and passing electric current through the contact point, bead and support in the presence of water to re-fuse the bead and bond the contact and support together.

3. The method of mounting on metallic supports refractory metallic electrical make-andbreak contact points oxidizable at normal brazing temperatures which comprises, fusing in a nonoxidizing atmosphere to the back of the contact point formed from any of the materials tungsten, molybdenum, tungsten compositions and molybdenum compositions, a bead of a metallic bonding material of any of silver, copper, nickel, silver alloys, copper alloys and nickel alloys, having a melting point lower than that of the contact point, positioning the beaded contact point on a metallic support, and passing electric current through the contact point, bead and support to re-fuse the bead and bond the contact and support together. I

4. The method of mounting on metallic supports refractory metallic contact points oxidizable at normal brazing temperatures which comprises, placing the contact point formed from any of the materials tungsten, molybdenum, tungsten compositions and molybdenum compositions with a'body of metallic bonding material of a lower melting point adjacent the back thereof in a furnace having a non-oxidizing atmosphere for a suflicient length of time at a suificient temperature to fuse the body of bonding material to cause the latter to adhere to the back of said contact point and form a bead thereon, removing the beaded contact point from the furnace and positioning it adjacent an electrode with the bead exposed, placing a metallic support adjacent to the bead, positioning another electrode adjacent the support opposite the contact point, and passing electric current between the electrodes under ordinary atmospheric conditions to re-fuse the bead and bond the contact point and support together.

5. The method of mounting on metallic supports refractory metallic electrical make-andbreak contact points oxidizable at normal brazing temperatures which comprises, placing a contact point formed from any of the metallic materials tungsten, molybdenum, tungsten compositions and molybdenum compositions with a body of silver alloy having a melting point lower than that of the contact point adjacent the back thereof in a hydrogen furnace for a sufiicient length of time at a temperature sufiicient to fuse the bonding material to cause the latter to adhere to the back of the contact point and form a bead thereon, removing from the furnace and wetting the beaded contact point, positioning the wetted contact adjacent an electrode with the bead exposed, placing a metallic support adjacent another electrode with a wetted portion thereof adjacent to the bead, bringing the electrodes together to cause the bead to firmly contact with the support and passing between the electrodes electric current of about 500 amperes at about 1 volts for not more than about one second to re-fuse the bead and bond the contact and support together. r g

6. An electrical make-and-break contactor comprising a contact point of refractory metallic material, a support of a different metallic material and a layer of metallic bonding material fused to said contact point and re-fused to said support, the latter being altered in its physical properties: by heatlng'only 1n the immediate v1- cinity of the contact point.

'7. An electrical make-and-break contactor comprising a contact point of any of the metallic 6 materials tungsten, molybdenum, tungsten compositions and molybdenum compositions, a support of a different metallic material and a layer of metallic bonding material 01' a silver alloy fused to said contact point and re-fused to said support, the latter being altered in its physical properties by heating only in theimmedlate v1- cinity of the contact point.

cmmnmss B. GWYN. Jl.

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