US2294783A

US2294783A - Contact member

Info

Publication number: US2294783A
Application number: US329459A
Authority: US
Inventors: James K Ely
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1940-04-13
Filing date: 1940-04-13
Publication date: 1942-09-01
Anticipated expiration: 1959-09-01

Description

p 1, 1942- J. K. ELY 2,294,783

- CONTACT MEMBER Filed April 13, 1940 WITNESSES: Z3 INVENTOR Patented Sept. 1, 1942 UNITED STATES PATENT- OFFICE CONTACT MEMBER James K. Ely, Wiikinsburg, Pa., assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, l'a., a. corporation of Pennsyl- Vania.

Application April 13, 1940, Serial No. 329,459

3 Claims. (01. 200-166) This invention relates to electrical conductors, and more particularly electrical contact members and process for making the same.

Contact members for electrical circuit making and breaking devices should have low electrical resistance, low contact drop, resistance to sticking and wear resistance. Good conductingmetals such, for example, as copper and silverhave relatively low melting points and poor wear resistance, and are not entirely satisfactory as con- The object of this invention is to provide for combining refractory metals with good conducting metals to form contact members.

Other objects of the invention will, in part be 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 other and the article possessing the features, roperties and the relation of elements which are exemplified in the following detailed disclosure and the scope of the application of which will be indicated in the claims.

v 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:

Figure 1 is a top plan view of a mold;

Fig. 2 is a side elevational view, partly in section, of a mold and an element formed therein, in accordance with the teachings of this invention: 1

Fig. 3 is a view in perspective of a pair of contact members;

Fig. 4 is a cross-sectional view entially reinforced contact;

- Fig. 5 is a cross-sectional view of a contact; Fig. 6 is a top planview of a split mold, and Fig. 7 is an enlarged end view of a modified form of refractory metal spacing.

of a circumfer- It is the purpose of the invention to embed refractory metals having good wear resistance and good resistance to sticking within a main base member of a good electrical conducting metal. It is a purpose of. the invention to so locatethe refractory metal within the contact member so as not to interrupt the continuity of the electrical path through the good conducting metal.

The refractory metals whichhave been found to provide excellent wear resistance and resistance to sticking are the metals tungsten and molybdenum, particularly in wire or rod form.

The members are preferably of an elongated shape with any general cross section. A further characteristic which will be desirable in the refractory members is the property of being wetted by molten good conducting metal and with a good bond being formed on solidification. Accordingly, other refractory metals having these general properties may be employed as the equivalents of the refractory metals specifically set forth.

The main body of the contact members is composed of a good conducting metal such, for

example, as copper and silver. The properties which are desirable for the main body metals are good electrical conductivity and low contact drop. Copper. and silver base alloys, while they may not have as goodconducting characteristics as pure silver or copper, may -.be suitable for application in contact members, and it is contemplated to make use of them in this invention.

The copper and silver will not form a good allay with tungsten and molybdenum since these metals do not form solid solutions. Thus, it is not possible to alloy the-good conducting metal with a refractory metal to secure a combination of their desirable properties. It is accordingly necessary to mechanically intermingle selected shapes of each of these groups of metals and by proper casting or other uniting treatment, form a unitary contact member body. I,

In order to secure the combined advantages of the good conducting metals, copper or silver,

and the refractory metals, tungsten or molybdenum, it is proposed to make electrical contact members embodyingelements of the rethrough the good conducting metal is'not interrupted by'the refractory metal.

For one method of manufacturing the contact member according to the invention, reference is made to Figs. 1 and 2 of the drawing. In Fig. 2 a circular shell l constituting a mold in which to cast the good conducting metal is closed at its bottom by a circular blank cap l2 fitting tightly therein. The blank cap l2 has arranged therein aseries of indentations ll for properly spacing the refractory metal wires or rods 22.

In order to use the blank cap I2 more than once, it may be advisable to coat it with a thin layer of graphite, aluminum oxide, or other refractory mineral which will prevent adherence thereto of the cast metal. The shell Ill may likewisebe treated with a graphite or aluminum,

oxide to permit of easy withdrawal of the cast contact body.

At the top of the mold IQ is placed a second cap l6, preferably of a size smaller than the mold 10, having a series of perforations l1 corresponding to the indentations I in the lower cap l2. Preferably the upper cap I 6 is elevated somewhat above the shell ill by means of rods or spacing members IS. The gap effected by the use of members l8 provides for escape of gases and for casting of the copper.

In Fig. l a casting lip or trough 20 in the shell I0 is shown. However other means may be provided for introducing the molten metal into mold l0.

It may be desirable to assemble the refractory rods and the caps l2 and I6 together before inby means of an abrasive wheel into contact members of predetermined length. The cutting is intended to be in ,a direction perpendicular to the refractory members 22. v

Fig. 5 is a top plan view of one of the contact members "after being cut off from a casting.

The contact member 30 comprises a main body member 24 of a substantially unitary structure having embedded therein a plurality of refractory metal rods 22 extending substantially entirely therethrough. The face visible in Fig. 5 is the face which will be subjected to impact with another similar contact member during the making and breaking of electrical circuits.

Referring to Fig. .3, there is illustrated a. pair of opposed contact members 30 similar to the Fig. 5constructionmounted by means of silver brazing or other suitable welding technique upon a pair of contact arms 32 and 34. Suitable circuit breaker, mechanism may be arranged to provide for the separation and contact of the opposed contact members 30 by actuating one or the other of arms 32, 34.

In some instances it may be desirable to reinforce the contact member of Fig. 5 to restrain possible mushrooming of the contact under heavy and repeated circuit making contact. In Fig. 4 theexternal shell 40 of the contact member 28 is made of some metal having considerable tensile strength such, for example, as beryllium copper, with moderate conducting properties.

Other metals, depending on the requirements,

the refractory mineral employed in Fig. 2 on the interior of the shell member ill will be dispensed a position where rods l8 may be introduced to prevent its falling down. The cap I: may be then forced tightly into the bottom portion of shell [0 to provide a leak-tight joint.

In some instances it may be advisable to preheat the assembly l0, I2, 22 and IS in order to effect the best casting of the good conducting metal therein. Since the member l0 may be several feet in length, preheating the mold will aid in forming a uniform casting.

Preheating to a temperature somewhat below the melting temperature of the copper or silver I will be sufficient to ensure a uniform and homogeneous casting about the refractory rods 22.

A ladle of molten copper or silver or their good conducting alloys may be conveyed to the mold l0 and the molten metal poured by lip means 20 into the preheated assembly. The molten metal 24 will flow to the bottom of the mold above blank cap I2 and the level of the molten metal will rise until the top of shell l0 has been reached. Gradual cooling, preferably from the bottom of the mold adjacent the cap l2, will ensure'a sound casting in the mold Ill.

After; the entire casting has been solidified, the upper cap l6 may be withdrawn from the upper ends of the rods '22, the bars l8 removed and the lower cap l2 may be forced off. If the shell I! has had its' interior surface coatedwith some refractory mineral such as graphite or aluminum oxide, it will be relatively easy to withdraw the casting therefrom. The cast body may be cut with in order that the cast metal may integrally bond, asshown at 26, throughout the entire length and with the inner surface of the shell 40.

Thus a unitary, well-bonded contact member resistant to mushrooming will be provided.

The molten good conducting metal bonds well with the refractory metals, tungsten and molybdenum, and in the separate contact members formed from the cast body of Fig. 2 or having the reinforced structure described hereinbefore, will exhibit a solid well-bonded contact unit. Under impact it is found that with the'refractory metal members disposed as .described and extending through the contact member to the backing member or contact arm that the resulting stress will be well distributed in the entire contact member. It is believed that such contact members will exhibit well matched faces whereby the current will be' uniformly spread over the entire face of the contact and will not be concentrated in small areas. Moreover the small current in refractory rods 22 will easily enter the good con ductor main body in which they are bonded.

The shell mold of Fig. 2 may be constructed according to the arrangement of Fig. 6 for ease in separating the cast body from the mold where the contact members are to be formed without the circumferential reinforcing ring or shell.

The mold illustrated in Fig. 6 comprises two flcatlon of Fig. 7 may be resorted to in some instances. In Fig. '7 the refractory members 22 are woven into a sort of fabric by means of spaced apart woof wires 23, 25. For example, the wires 23 and 25 may be spaced an inch or more from each other along the length of the refractory metal members 22. The refractory metal fabric made in this way may be rolled up on itself as shown on the lower part of Fig. 7 until a column of refractory material sumcient for use in the mold Ill of Fig. 2 has been obtained. The wires 23 and 25 will provide adequate spacing between refractory rods so that molten copper or silver may penetrate and bond the mass as a whole. Obviously the wires 23 and 25 are selected for size according to the spacing desired between the consecutive refractory wires 22. In any event the refractory members constitute a minor proportion of the whole cross section of a contac member.

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. Therefore, I desire that my invention be interpreted as broadly as possible and that it be limited only by what is expressly set forth in the following claims.

I claim as my invention:

1. An electrical contact member having a contact surface, comprising in combination, a unitary conducting base member comprising the major cross-section of material in a plane parallel to the contact surface, the conducting base member being of a metal selected from the group of copper, silver and their alloys, heat and impact resisting refractory metal members selected'from the group of tungsten and molybdenum embedded in and bondedto the conducting base member, th refractory metal members being separated from each other and extending substantially entirely through the conducting base member in a direction perpendicular to the contact surface, and an external shell extending about and bonded to the base member substantially perpendicularly to the contact surface to restrain mushrooming of the contact.

2. An electrical contact member having a contact surface, comprising in combination, a unitary conducting base member comprising the major cross-section of material in a plane parallel to the contact surface, the conducting base member being of a metal selected from the group of copper, silver and their alloys, heat and impact resisting refractory metal wires selected from the group of tungsten and molybdenum embedded in and bonded to the conducting base member, the refractory metal wires being separated rfrom each other and extending substantially entirely through the conducting base member in a direction perpendicular to the contact surface, and an external shell extending about and bonded to the base member substantially perpendicularly to the contact surface to restrain mushrooming of the contact.

3. An electrical contact member having a contact face, comprising, in combination, a unitary base of good conducting metal forming the major cross-section of material in a plane parallel to the contact face, and substantially parallel heat and impact resisting refractory metal members embedded in and bonded to the good conducting base metal, the parallel refractory metal members being substantially uniformly separated from one another by woof wires, the separated, parallel refractory metal members extending lengthwise entirely through the conducting base metal perpendicular to the contact surface, and an external shell extending around and bonded to the arse metal to restrain mushrooming of the con- JAMES K. ELY.