GB360419A - Improvements in and relating to electric discharge tubes - Google Patents

Abstract

360,419. Discharge apparatus. EDISON SWAN ELECTRIC CO., Ltd., 123, Victoria Street, London.-(Assignees of Spanner, H. J. ; 117, Chausseestrasse, Berlin.) May 5, 1930, No. 13828. Convention date, May 4, 1929. [Class 39 (i).] An electric discharge tube adapted particularly for use as a rectifier is provided with a cathode comprising a core of a neutral metal such as nickel coated with an activating substance composed of an electropositive metal, such as barium, mixed with a metal compound such as strontium-zirconiate, magnesium cuprate, barium zincate, or caesium tungstate, which have a low heat conductivity, the tube being filled with a rare gas at a pressure of from one to five millimeters of mercury, preferably with the addition of a small proportion of metallic vapour such as that of caesium or mercury. The anode or anodes may consist of graphite, or of quartz heated and mixed with a metal powder and silicon oxide. The cathode may be either larger or smaller than the anode, and may be in the form of a spiral, and the anodes may be formed as hollow chambers containing fixed shields to control the path of the discharge. The cathode core may be composite, for example of tantalum covered with thin copper wire. Starting may be facilitated by an auxiliary anode at a short distance from the cathode.