US1889105A - Thermionic tube - Google Patents

Description

Nov. 29, 1932. w, PARK-ER I 1,889,105

THERMIONIC TUBE Filed Feb. 15. 1930 NICKEL. COPPER COPPER /OXIDE INVENTOR HEIllH W Parker I ATTORNEY Patented Nov. 29, 1932 UNITED STATES Arsr oFFicE HENRY W. PARKER, OF TORONTO, ONTARIO, CANADA, ASSIGNOR TO ROGERS RADIO TUBES LIMITED, 015 TORONTO, ONTARIO, CANADA, A CORPORATION OF ONTARIO,

CANADA THERMIONIG TUBE Application filed. February 13, 1930. Serial No. 428,102.

My invention relates to electron discharge devices or thermionic tubes and pertains particularly to that class of such devices which employ an oxide coated emitter as a cathode and find their chief use in carrier current communication systems as detectors, amplifiers or oscillators.

An object of my invention comprises producing a tube in which the useful life of the cathode or emitter is increased over that now common to such tubes.

Another object of my invention is to produce a tube of such novel construction that the free water vapor therein is, during the process of exhausting the tube, reduced to a minimum.

A further object of my invention resides in increasing the thermal emissivity of the anode.

A still further object of my invention comprises producing a tube in which the cathode may be operated at a higher temperature than ordinarily used to produce a gain in anode conductance.

The theoretical useful life of an oxide coated emitter or cathode, whether of the indirect sleeve or filament type, when operated at a temperature of approximately 1135 K., is about 30,000 hours. This life is only theoretical, of course, and is never achieved in practice, due to the action of the water vapor within the tube envelope activated by thermal dissociation'and catalysis in carrying active barium away from the surfaces of the hot cathode. It has been repeatedly experimentally proved that water vapor carries away hundreds of times as much barium by this carrier-ion process than is evaporated from the surface of the bariumstrontium oxide surfaces of the emitter.

Many methods have been tried and are being used at present to reduce the amount of free Water vapor in thermionic tubes to a minimum. One method which has been used comprises introducing into the tube a small piece of oxidized copper attached to a standard or wire supporting one of the electrodes of the tube. This method, however, employs the limitation that at no time during the processing of the tube can the temperature be raised to the melting point of the copper oxide or copper. As the out-gassing temperature normally used is quite closeto the melting point of both copper oxide and copper, the method is difficult to control.

In my invention I propose to construct the anode, of tubes employing oxide coated emittors, of solid nickel which has been given a substantial coating of copper and then oxidized, thus leaving on the surface of the entire anode an extensive surface of copper oxide for the absorption of the water vapor Within the tube.

In the drawing accompanying and forming a part of this specification, I have illustrated an enlarged partially sectioned per spective view of a preferred form of my improved anode in position in the stem of a thermionic tube with the thickness of the anode material greatly exaggeratedto clearly show the composition thereof.

A tube provided within an anode as above described and illustrated in the drawing may be exhausted and processed at the usual temperature of 1300 K. without fear of melting the anode, as nickel does not melt until a temperature of 1725 K. is reached. Further, the copper oxide or copper will not melt because of the relatively large radiating area of the nickel anode, which serves as a refractory metal base for the copper at the outgassing temperature. A tube provided with such an anode can readily be processed in the usual manner on an automatic exhaust machine and the large surface of copper oxide exposed will absorb water vapor to a degree not hitherto achieved. The blackened surface of the anode also increases the amount of thermal emissivity to about the same delonger life than those known at present. This gain in life factor can, if desired, be utilized to permit the operation of the cathode at a higher temperature and thereby gain in anode conductance thus increasing the satisfaction of the user in the operation of the tube.

Another advantage gained by the use of copper oxide coated nickel anode when the same is employed in a tube used as a rectifier resides in the fact that sputtered barium will not base upon copper oxide in the same-manner that it does on nickel and a rectifier can thus be produced which is free from the effects of inverse currents, an advantage which is very notable.

It will be readily realized that in carrying out my invention I may vary the details as described herein without departing from the spirit or narrowing the scope of the invention. For example, I may construct the anode of solid nickel and thereafter copper plate the anode and subsequently oxidize the copper thereon, or I may construct the anode of nickel which has previously been copper plated and thereafter oxidize the copper plating without departing from the spirit or scope of the invention.

Having thus described my invention, What I claim and desire to secure by United States Letters Patent is as follows:

1. An anode for an electron discharge device composed of nickel bearing a coating of copper thereon, said copper coating having an oxidized surface capable of absorbing water vapor.

2. An eletcrode for an electron discharge device composed of a metal having a melting point above 17 00 K. bearing thereon a coating of a metal having a melting point between 1300 K. and 17 00 K., said metal of lower melting point having an oxidized surface capable of absorbing water vapor.

3. An electrode for an electron discharge device composed of a metal having a melting point higher than that of copper, a coating of copper thereon, said copper coating having an oxidized surface capable of absorbing water vapor.

- HENRY W. PARKER.

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