US1971053A

US1971053A - Resistance device

Info

Publication number: US1971053A
Application number: US651278A
Authority: US
Inventors: Ruben Samuel
Original assignee: Individual
Current assignee: Individual
Priority date: 1933-01-12
Filing date: 1933-01-12
Publication date: 1934-08-21
Anticipated expiration: 1951-08-21

Description

Aug. 21, 1934. s. RUBEN 1,971,053

RESISTANCE DEVICE Filed Jan. 12, 1935 INVENTOR- JAMUEL RUBEN ATTORNEY- Patented Aug. 21, 1934 RESISTANCE DEVICE Samuel Ruben, New Rochelle, N. Y. Application January 12, 1933, Serial No. 651,278

9 Claims.

ticularly in respect to the material used and to the manufacture thereof. In my co-pending application the resistance base is composed of a sintered mass of crystals of cuprous oxide having a surface layer of specified compounds. I have found that if a compound of cadmium and an element of the sulphur group, except oxygen, such so as cadmium sulphide or cadmium selenide crystals, with a non-conductive filler and a binder are pressed into a hard mass and heated sufficiently in an oxidizing atmosphere, the surface is converted from a relatively non-conductive ma-=- terial into a good electrical conductor because of the conversion of cadmium sulphide or cadmium selenide into cadmium oxide over the surface of the element. Cadmium telluride also may be so oxidized, but its use is not as satisfactory. By

varying the time of heating, and the concentration of the oxidizing atmosphere, resistances of various ranges are obtainable. Cadmium oxide is a good electrical conductor having the desirable characteristic of a negligible temperature resistance coeflicient. This is quite different from other.

electronically conductive crystals which have a high negative temperature resistance co-efiicient.

The preferred method for making this resistance element is to mix cadmium sulphide or .40 selenide with a suitable binder, such as 2% sodium silicate or lead borate, compress the mixture under high pressure into the desired form and heat the mass until it is completely sintered in a non-oxidizing atmosphere such as nitrogen.

For a variable resistance having an exponential relation of resistances along its length, various portions of the surface of the cadmium sulphide or cadmium selenide elements are exposed to an oxidizing heat which converts the con- 5 tacting portion into cadmium oxide, the time of exposure, the temperature and the concentration of oxygen determining the ultimate electrical resistance value for each area so treated, the resistance decreasingv with the temperature, the concentration and time of application. Terminals with a suitable movable contact member are provided.

For a uniform resistance value along the length, the compressed and sintered cadmium compound element is placed in an oxidizing furnace and by continuous measurement, its resistance value can be fixed at any point, when the element. is removed from further exposure. Likewise a definite resistance may be fixed over any section. For high resistances I have found that by the addition of a filler of zircite, a hard mass having much higher resistance values is yielded.

Reference is made to the accompanying drawing in which Fig. 1 represents a plan' view of a rheostat and Fig. 2 a section view thereof embodying the invention.

Referring more particularly to the drawing, at 1 is a compressed and sintered arcuate resistance plate composed of cadmium sulphide crystals with a binder and having a surface layer of varying thicknesses of cadmium oxide. The plate rests upon an insulating base 2, attached thereto by terminals 3 and 4. A rotatable conductive arm 5, having a contact electrode 6, is mounted upon shaft 7 and connected in a circuit by conduc- 80 tive plate 8 on shaft 7. At 9 is'a knob for rotating arm 5 and nut 10, 11 being a compression spring to insure uniform pressure between the resistance element and contact electrode 6.

What I claim is:

1. A resistancev element having a base com posed of a compound of cadmium with one of the elements sulphur, selenium and telluriurn, and having a surface layer composed of cadmium oxide reduced in situ from the said base compound.

2. A resistance element as in claim 1 in which different sectors of the resistance element surface have different resistance values.

3. A resistance element as in claim 1 in which the cadmium oxide varies in depth along the length thereof.

4.. A resistance element having a base composed of cadmium sulphide and having a surface layer composed of cadmium oxide reduced in 100 situ from said cadmium sulphide base.

5. A resistance element having a base composed of cadmium selenide and having a surface layer composed of cadmium oxide reduced in situ from said cadmium selenide base.

6. A resistance element having a base composed of cadmium telluride and having a surface layer composed of cadmium oxide reduced in situ from said cadmium telluride base.

7. A variable resistance device comprising a 110 and a contact member adapted to make selective electrical connection with said cadmium 0xide surface along its length.

9. The method of making a resistance element which consists in heating a base compound composed of cadmium and one of the elements sulphur, selenium and tellurium, in an oxidizing atmosphere until said base compound surface is reduced to cadmium oxide.

SAMUEL RUBEN.