GB394304A - Improvements in and relating to incandescent cathode rectifier - Google Patents

Abstract

394,304. Electron-discharge tubes. INTERNATIONAL GENERAL ELECTRIC CO., Inc., 120, Broadway, New York, U.S.A. -(Assignees of Allgemeine Elektricitats- Ges.; 2, Friedrich Karl-Ufer, Berlin.) Sept. 16, 1931, No. 25959. Convention date, Sept. 16, 1930. Void [Published under Sect. 91 of the Acts]. [Class 39 (i).] In a thermionic rectifier the heated cathode is brought .very close to the anode and the latter is coated with a material which absorbs or combines chemically with electronemitting material vaporized from the cathode with the formation of a non- emitting product. Preferably the coating material comprises one or more acidic oxides, e.g. zinc oxide, alumina, stannic oxide, silica, or oxides of lead, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, uranium, manganese or iron. Such oxides may be applied to the anode as pastes with or without a binding medium and made firm by a heat treatment or, when the anode is made of one of the metals referred to or of such metals alloyed together, the surface may be oxidized chemically or electrochemically. Alternatively a foundation metal, e.g. iron, may be coated with a second metal, e.g. chromium, and the latter subjected to oxidation. Salts such as zinc chromite, iron chromite, &c. may be applied as pastes to the anode or produced thereon, e.g. by immersing a sheet-iron or sheet-zinc foundation in chromic acid solution and heating. In the construction shown the anode a is of tungsten coated with an oxide layer b by a heat treatment in oxygen, and the cathode c coated with emitting oxide is arranged at ¢-1 mm. or less from the coating b with the aid of insulating spacing members d.