GB459163A - Improvements in and relating to electric discharge tubes - Google Patents

Abstract

459,163. Discharge tubes. SCHALLREUTER, W. L. W., 89, Scrubs Lane, Willesden, London. July 3, 1935, Nos. 18971 and 18972. [Class 39 (i)] The cathode 13 of a gas-and /or vapour-filled discharge tube is surrounded by a perforated metal cylinder 12 which at starting of the discharge acts both as cathode and anode and after the cathode 13 has been heated and becomes emissive as the anode ; an independent heater coil 15 may also surround the cathode and be connected at one end to the cylinder or to the cathode. The cathode is formed by pressing and heating at about 1300‹ C. a powdered mixture consisting of electron emitting ingredient 40-50 per cent, a compound of a refractory metal 20 per cent, a reducing agent 5 to 10 per cent and an ingredient chemically inert with respect to the others but of high specific heat 25-30 per cent. One example consists of barium oxide 40 per cent, tungsten carbide 20 per cent, zirconium metal 10 per cent and zirconium oxide 30 per cent. Another example consists of barium hydroxide 50 per cent, tungsten oxide 20 per cent, graphite 5 per cent and thorium oxide 25 per cent. According to the first Provisional Specification, the proportions are barium oxide 10 per cent, silicon oxide 50 per cent, tungsten 20 per cent, graphite 20 per cent.