US1924300A - Copper oxide rectifier - Google Patents

Description

Aug. 29, 1933, A. L. ATHER'roN COPPER OXIDE RECTIFIER Filed Dec. s1, 1927 INVENToR Y y k AT'ToRNEY Patented Aug. 29, 1933 UNITED STATES PATEN'I'I OFFICE.

1,924,300 corran oxma asoma Alfred L.

Atherton, Verona, Pa., assigner to Westinghouse Electric & Manufacturing Oompany, a Corporation of Pennsylvania Application December 3l,l 1921 Serial No. 243,904 l 15 Claims. (CL175-368) 4 surfaces placed in contact with terminal plates of i a different metal. n

yOne object of my invention is to produce rectifiers or other devices likely to be heated, and which Vcomprise a metal and a compound thereof with a conducting contact material therefor, 1 which shall lundergo no gradual change during their life.

A further object of my invention is to produce oxidized copper rectiflers which shall not -deteriorate or otherwise change their electrical 5 characteristics during use. Other objects of my invention will be apparent upon reading `the following specification, taken in connectionwith the appended drawing in which is shown an oxidized copper rectiiier provided with contacts in accordance with my invention.

In the present art, rectiiiers comprising discsl of copper or other metal having formed on one surface a layer of some chemical compound, such as an oxide, are well known.- It appears that the junction between the oxidized layer and the mother metal possesses the property of unilateral conductivity. In consequence of this, if an alternating electromotive force of proper magnitude o is impressed in series with this junction, a uni directional current is caused to flow in the cir--A cuit. A problem, however, is presented of making contact between the external surface of the oxidized layer and the remaining conductors of the electric circuit.

One solution of this problem has been found through the use of washers of lead or other impressible metal which readily conform to the L0 oxidized surface and make lfair electrical contact therewith. However, it has been found that, when contacts are made in this manner, the electrical resistivity of the combined unit gradually i rises in thecourse of its operative life'. For many l purposes, the resistance rise just mentioned is undesirable and the present invention provides a method of making contact which avoids it'.

While my invention is not, in any way, defpendent upon the correctness of the following` theory, it appears probable thatthe rise in resistance is the result of the oxidation of the impressible lead washer under the influence of heat generated within the body of the rectifier unit when in use. It further appears probable that a part, at least, of the oxidation necessary to the foregoing reaction comes from the/layer of oxidized metal. In accordance with my invention, I prevent the gradual oxidation of the. metallic washer by forming its surface of a material .which is chemically inert to oxidation at the operatingv temperatures of the rectifier. .i0 As specific methods of giving effect to this i fundamental idea, I may form the washer of some soft metal, such as nickel, which is chemically inert to oxidation at ordinary temperatures. Alternatively, I may employ a washer of somesoft .55 metal not thus chemically inert but having its surface coated by electroplating or otherwise with a thin film of metal inert to oxidation. In a still further modification, I may coat the surface of the metal with a compound of the very element 79 which combines with the rectifier metal to form the active surface compound thereof. For example, in the case of an oxidized copper rectifier, I may use a lead washer, the surface of which has been subjected to a preliminary oxidation. E In the drawing, Figure iis a sectional view of a rectifier embodying my invention and Figs. 2 and 3 are sectional views of modified single recti- A'iler elements. In Figure 1 is shown a rectiner so. l

comprising three component elements, each of which consists of a metallic base 1, which may be of copper, and which has a layer 2 of some compound formed on one surface. When copper is used, this compound may be the oxide. United BtatesfPatent 1,640,335 discloses waysl of making` auch" oxidized copper rectifier units. `In contact with vthe oxidelayer 2 is a washer 3 consisting of lead, the contacting surface of which has previously been provided with an oxidized layer 4.

Any desired number of component units such as that just described may be combined to form a circuit element possessing unilateral conductivity.

- If an alternating electromotive force is impressed between the terminal discs 5 and 6. current will/'be 95 transmitted freely in that direction in which the :L y copper is negative in potential to its oxidized layer and scarcely at all in the reverse direction. Any desired number of the above described discs may be mounted on a through bolt '1 having an insu- 100 lated covering '8, as indicated. 4 9;.

In another `modification shown in Fig. 2, the contacting washers consists entirely of an impressible metal which is chemically inert to oxidation below 200 C., for example, gold or nickel.

In a third modification shown in Fig. 3, the contact washers 10 may consist of lead or other soft metal having a coating such as nickel oi'tgold which is chemically inert to oxidation at temperatures below 200 C..

Accordingly, by means of my invention, I proments of my invention, the broad principles of such character as to' undergo no change in electrical characteristics during the operative life of the rectifier.

Where in the following claims the expression common metal occurs, it is used .to designate metals which are readily obtainable and, therefore, inexpensive as distinguished from the rare metals such as gold, platinum and the like.

While I have here described particular embodithereof are otherwise applicable in ways which will be apparent to those skilled in the art. I desire, therefore, that the terms of the following claims shall be given the broadest interpretation of which they are .susceptible in View of the limitations of the prior art. i

I claim as my invention:

1. In a rectifier of the type comprising a metal and an oxide of said metal thereon, a contact element cooperating with said compound and having a surface of a composition of common metal, said composition being devoid of chemical'afl'inty Vfor said oxide.

Y 2. In a rectifier of the type comprising a metal and a compound thereof With another substance formed thereon, a contact element cooperating with said compound and comprising a common metal chemically inert to said compound at all temperatures at which the rectifier operates.

3. In a rectifier of the type comprising a metal and a compound thereof with another substance formed thereon. a contact element cooperating with said compound and comprising an impressible common metal chemically inert to said compound at all temperatures at which the rectifier operates.

4. In a rectifier of the type comprising a surface of metal having oxygen in combination therewith, a contact element cooperating with said surface and comprising a composition of common metal,

and a compound thereof with a non-metallic element, a contact element cooperating with said ff; compound and comprising an impressible comvidean oxidizedmetal rectifier with contact plates '7. VIn a rectifier of the type comprising ametal and an oxide thereof, a contact element cooperating with said oxide and comprising a surface layer of a composition of common metal, said composition having no tendency to reduce said oxide.

. 8. In a rectifier ofthe type comprising a metal and an oxide thereof, a contact element cooperating with said oxide and comprising a common metal chemically inert to said oxide at all temperatures at which the rectifier operates.

9. In a rectifier of the type comprising a metal and an oxide thereof, a contact element cooperating with said oxide and comprising an impressible common metal chemically inert to oxidation at all temperatures at which the rectifier operates.

10. In a rectifier of the type comprising copper and an oxidized layer thereof formed thereon, a contact element cooperating with said layer and' comprising a composition of common metal, said composition being devoid of tendency to take up oxygen from said layer. I

11. In a rectifier of the type comprising copper and an oxidized layer formed thereon, a contact element cooperating with said layer and compris-- ing a common metal chemically inert to said layer at all temperatures at which the rectifier operates.

12. In a rectier of the type comprising copper and an oxidized layer formed thereon, a contact element cooperating with said layer and comprising an impressible common metal chemically inert to said layer at all temperatures at which the rectifier operates.

13. In combination with a metal and an oxide of said metal thereon and subject to heat, a contact element cooperating with said oxide and having a surface layer of a composition of common metal, said composition having less chemical aflinity for said oxide than said metal has.

14. In combination with a metal and a compound thereof with another-substance' formed thereon and subject to heat, a contact element cooperating with said compound and comprisingA a common metal chemically inert to said compound at all temperatures to which said substances are subjected.

15. In combination with a metal and a-compound thereof .with anotller substance formed thereon and subject to heat, a contact element cooperating with said compound and comprising an impressible common metal chemically inert to said compound at all temperatures to which said substances. are subjected.

\ ALFRED L. ATHER'IION.

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