GB375851A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

375,851. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Found, C. G. ; 148, Plymouth Avenue, Schenectady, New York, U.S.A.) March 30, 1931. No. 9652. Convention date, April 5, 1930. [Class 39 (i).] A thermionic cathode for electric discharge devices, for example glow discharge lamps, comprises a funnel-shaped shell open at the end of greater diameter and provided with means for heating the shell to an operating temperature. In one form the cathode comprises a coniform shell 1, Figs. 1 and 3, consisting of a base metal such as nickel or iron coated on its inner surface 2 with an electron-emitting material such as barium oxide, the exterior surface preferably being shiny. The heater consists of a wire 3 of tungsten, tantalum or other refractory metal wound on a support 4 of refractory insulating material such as beryllia, thoria, alumina or magnesia through which passes a molybdenum or tungsten conductor 5 connected to the inner end 6 of the resistance heater, the other end of the heater being connected to the shell 1 at 7. An end closure 8 is secured by welding or otherwise to the narrow portion of the shell, and a closure 9, apertured at 10 for the passage of the electrons, may be secured at the other end. An outer shell spaced at a short distance from the cathode may be provided to conserve the heat. The cathode is supported on conducting-wires 13, 14 respectively connected to the conductor 5 and the shell 1, and may have either its smaller or larger end directed towards the anode or anodes, the latter arrangement being shown in Fig. 2. The envelope 12 is charged with a gas or vapour such as neon, helium or mercury vapour, or a mixture of gases. Specification 356,745 is referred to.