US1948687A - Electric contact - Google Patents

Description

Feb. 27, 1934. R. swlNN ELECTRIC CONTACTv Filed JulyV 21, 1932 INVENTOR /P/araSa//lfz/Ye.

ATToR EY Patented Feb. 21, 1934 PATENT OFFICE ELECTRIC CONTACT` Richard Swinne, Berlin-Siemensstadt, Germany,

assignor to Westinghouse Electric & Manufacturing Company, Pittsburgh, Pa., a corporation of Pennsylvania.

Application July 21, 1932, Serial No. 623,825 In qermany July 29, 1931 9 Claims.

My invention relates to electrical contacts and to contacts arranged to interrupt current flow in an electric circuit.

I have discovered that contacts at least one of 5 which consists of the element gallium are remarkable for extremely low contact resistance.

One object of my invention is accordingly, to produce a contact between different parts of an electrical circuit by providing separable contacts between two masses of gallium (or gallium alloy), or between a gallium (or gallium alloys) contact and a contact of copper, mercury, tungsten, nickel or other metal.

Another object of my invention is to provide an electrical switch in which one or both separable contacts are of gallium or gallium alloys.

An important advantage is obtained in both uses, because of the low vapor pressure of gallium. When using a solid cooperating contact, where the iluid Contact material is open to the air, we obtain the advantage that gallium does not vaporize at all at ordinary room temperatures, so that dangers as to bodily health will be avoided. The contact resistance between gallium and a solid contact member may be reduced to a very small value and this is even true when the contact is covered with a layer of grease, which may easily happen because of handling.

With regard to the second object of this invention, and particularly where both conta/ct members are uid, gallium has the great advantage that great amounts of energy can be interrupted because of the very low vapor pressure, so there is a minimized danger that an arc will be started and will continue when large amounts of energy are interrupted.

The fact that gallium changes from the solid to the iiuid form only when it reaches a temperature of 30 C. causes no substantial drawback because it is easy to provide an auxiliary heating means to maintain the gallium at a temperature above its solidiiication point. As a source of electric energy is always available when gallium is used for circuit breaker contacts, it is desirable to `utilize electric heaters, as they are commercially eilicient and may also be easily adapted to the device.

An illustration of the principles of my invention will be found in the drawing in which Fig. 1 shows a separable contact or terminal Fig. 2 shows a switch in which the separable contacts are both of gallium and Fig. 3 shows a switch in which one separable contact is of gallium and the other of a solid conductor.

(Cl. 20o-152) Referring in detail to Fig. 1 a terminal post 1 is adapted to be supported in an insulating panel 2 or the like by means of a threadedy stud 3, to which a cable terminal 4 may be bolted, welded or otherwise connected. At the top of post 1 is a 60 cup 5 containing some metallic gallium or gallium alloy 6. A cooporating terminal 7 to which a second cable 8 is soldered, welded or otherwise conected is pressed firmly down intol contact with the gallium 6 by a threaded bolt and nut 9 65 or other well known pressure exerting means. The post 1 may be heated above the melting point of the gallium if desired veither when the contact 7 is iirst bolted home, or alternatively may be maintained at such temperature by auxiliary heating means such as an electric heater 11.

Referring to Fig. 2 a container 21 preferably, Vacuum tight, of insulating material has two inleading conductors 22, 23 each of which dips into a quantity of gallium or gallium alloy, the conductor 23 dipping well down into a well 25 in the container wall. An electric heater 26 and heat insulation 27 may be provided if desired. The container 21 may be maintained at high vacuum, say a ten millionth of atmospheric pressure, or 50 may contain a gaseous atmosphere such as neon. An auxiliary chamber 27 formed with a well or depression 28 which may contain materials well known as getters such as alkali metals which y absorb undesired gases may also be provided when desired. The electrical Contact is broken, when this arrangement is tilted counterclockwise by part of the gallium running into the end of container 21 adjacent conductor 22 and parting contact with a remnant of the gallium retained in 90 well 25.

The arrangement of Fig. 3 differs in principle from that of Fig. 2 only in that the electrical contact is broken between the gallium and a solid conductor 31 and it needs no separate detailed deg5 scription. It may be provided with a heater and auxiliary chamber similar to 27 of Fig. 2 if desired.

When using a gallium circuit breaker of the kind in which the gallium is separated to `interrupt the circuit, any insulating material may be used for the tank or casing, which will not be affected by the gallium under the operating conditions existing in the breaker, e. g. borosilicate,

glass or quartz glass. These casings may either be evacuated in the usual manner and maintained at a high vacuum, or they may be i'llled with one or more suitable gases which are neutral, such as a pure noble gas, argon, helium, or a mixture such as neon and helium. no

As the character of the contact with or by gallium is deleteriously aiected by coatings of oxide thereon, materials are introduced, preferably into an auxiliary container communicating with the main casing containing the gallium, which are capable of combining with hydrogen, oxygen and other substances which might affect the contact resistance and increase the same, such materials including the alkali or alkali earth metals. It is also desirable to use the present highvacuum methods of removing the water coating from the container in which the contacts are located; and it is further advisable to degasify the gallium or the gallium alloy in a high vacuum. The heating of the gallium contact material can also be dispensed with if an alloy is used whose melting point is lower than that of pure gallium. Such an alloy can be made by the use of aluminum for the alloying means.

For the solid cooperating contact member, high melting point metals which do not react with gallium, such as tungsten, molybdenum, tantalum, iron, nickel or alloys of these metals with each other lor with other substances, may be employed, and in order to maintain the desired high quality of the contact it is desirable to degasify these metals or alloys as completely as possible in a high vacuum, even in cases to melt them in a vacuum and to permit them to solidify therein.

I claim as my invention:

1. In an electric circuit, a pair of separable contact members at least one of which consists of gallium.

2. In an electric circuit, a pair of separable contact members at least one of which contains gallium in the form of a gallium alloy.

3. Contact device according to claim 1, characterized in that one contact member consists oi gallium and the other contact member consists of a solid conducting material, preferably o! a high melting point metal which does not react with gallium, such as tungsten, molybdenum, tantalum, iron, nickel, or of their alloys with each other or with other substances.

4. Contact device according to claim 1 characterized in that said contacts are contained in borosilicate or quartz affect the character of the contact, e. g. alkali orI earth alkali metals, located in an auxiliary container communicating with the main container.

7. Contact device according to claim 1, characterized by the use of metallic contacts including gallium or gallium alloys which have been degasied or reduced in high vacuum.

8. Contacts according to claim l, characterized by the use of proper electric heating means providing such an amount of heat for the gallium contact member that the temperature of the contact will be maintained above 30 centigrade even under the lowest temperatures occurring in operation.

9. Contact device according to claim 1, characterized by the use of a gallium alloy Whose melting point is lower than that of pure gallium.

RICHARD SWINNE.

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