US1799645A - Electron-emission element - Google Patents

Description

April 7, 1931. s. RUBEN 1,799,645

ELECTRON EMISSION ELEMENT Filed Nov. 27, 1926 mnwunm WP MAM NAME) INVENT OR SAMUEL RUBEN A TTORNEY Patented Apr. 7, 1931 UNITED STATES PATENT OFFICE SAMUEL RUBENfOF NEW YORK, N. Y., ASSIGNOR TO RUBEN PATENTS COMPANY, OF

NEW YORK, N. Y., A CORPORATION OF DELAWARE ELECTRON-EMISSION ELEMENT Application filed November 27, 1926. Serial No. 151,237.

This invention relates to improvements in electron emission elements for use in devices which function through the use of electron emission or ionic discharges in low pressure spaces, such as the vacuum tubes of the radio art and gaseous discharge tubes, both devices employing electron emission for their operation.

The object of my invention is to provide an electrode that is low in cost of production, durable, and adapted to withstand the eifects of high potential discharge.

In carrying out my invention, I provide an electron emission element composed of a conductive mixture of metallic oxides, brought into close molecular contact by heating to a sintering temperature, where high specific resistance is desired and by fusin and casting in any desired form of rods or bars, under pressure if still greater density is desired, when highly compressed state, or that of very close molecular contact is obtained by so heating the mixture of oxides. For certain uses an alkaline earth oxide is added.

. I have found that a rod cast from a fused mixture of ferrosoferric oxide (F0 0 and chromic oxide (C150 has a low specific rcsistance and a high degree of efficiency in electronic and ionic discharges, with a relatively low applied potential due to the low cathode d op of potential and to the high emission constant of the materials, and that the specific resistance of the electrode in creases directly with the chromic oxide content. Electrodes composed ofthis mixture show very low gas occlusion and electrode sputtering, which latter does not occur under certain conditions.

In preparing these cathodes, the materials are first mixed, preferably in powdered form, and heated to the fusion point in a non-reducing atmosphere, preferably in a high frequency induction furnace, andpoured into suitable moulds under pressure. So treated, the material forms a dense, crystalline con ductive mass. For electrodes of higher specific resistance the powdered material is compressed and then heated to a sintering temerature. As the fused oxide is highly conductive no auxiliary heating means is required, and the dissipation of the current discharging through the conductive oxide body directly heats the body..

For use in devices dependent more upon primary electron emission than upon secondary bombardment effects, it is of advantage to add to the mixture before heating a small percentage of alkaline earth oxides, such as those of barium or strontium, which are particularly desirable for their exceptionally low cathode drop of potential; also for devices operating through high vacuum by primary electron conduction, as in vacuum tubes or in rectifiers, of the radio art. At normal temperatures these alkaline earth oxides are non-conducting, but when heated they become highly conductive.

The invention may be better understood by reference to the accompanying drawing which represents one form of device employing an electrode embodying this invention.

The drawing shows diagrammatically a gaseous ionic discharge device employing fused and cast electrodes as described, in which, due to low electrode contact losses a high percentage of the applied energy is directly dissipated through the gas content.

A gaseous discharge glass vessel 1, contains neon gas 2, at low pressure and the described fused and cast electrodes 3, suitablv mounted in seals 4, the electrodes being electrically connected with generator 6, through step-up transformer 5 having primary 5,,, and secondary 5 windings.

As high potential current is discharged between the electrodes 3 through the low pressure neon gas 2, the electronic and ionic bombardment of the gas causes it to give off a luminous glow, there being high emission from the cathode elements with negligible disintegration.

Such devices should be exhausted to a degree of pressure at which practically no positive ionization can occur, when the desired gas is admitted to the vessel until the connected ammeter indicates that the conductivity of sion and gas absorption by the evacuated parts.

What I claim is:

1. In a low pressure electrical device which functions through an electrical discharge, a cathode element containing a mixture of ferrosoferric oxide and chromic oxide fused and cast into suitable form.

2. In a low pressure electrical device which functions through an electrical discharge, a cathode element containing a mixture of ferrosoferric oxide, chromic oxide and an alkaline earth oxide fused and cast into suitable form.

3. In a low pressure electrical device which functions through an electrical discharge, a cathode element containing a mixture of ferrosoferric oxide, chromic oxide and strontium oxide fused and cast into suitable form.

In testimony whereof, SAMUEL RUBEN has signed his name to this specification, this 23rd day of November, 1926.

SAMUEL RUBEN.

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