GB303369A - - Google Patents

Abstract

303,369. Soc. Anon. des Etablissements Industriels de E. C. Grammont et de A. Grammont. Dec. 31, 1927, [Convention date]. Vacuum tubes.-The cathode of an electron discharge device is provided with highly emissive material by first rendering it porous by heating in a gas, coating it with the emissive substance, such as barium, thorium, caesium or salts thereof, and then restoring it to its original condition, metals suitable for this purpose being those capable of occluding large quantities of gas, such as platinum or palladium. In the case of these metals, the porous condition is induced by the occlusion of hydrogen which occurs when a wire is heated, for example electrically, in an atmosphere of this gas, the filament being then coated by electrolysis, immersion &c. with an active material and afterwards heated in vacuo to a dull red heat. The cathode need not consist entirely of platinum or palladium but may be constituted by a tungsten base coated with either of these metals by electrolysis or wire drawing. After the deposition of the emissive material, expulsion of the occluded gas may be effected by laminating or wire drawing; this procedure may be repeated. As emissive materials, barium, thorium or caesium, their salts or a mixture of these may be employed. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the removal of the occluded gas by heating the metal in a gas capable of combining with that occluded. This subject-matter does not appear in the Specification as accepted.