GB597681A - Improvements relating to indirectly heated thermionic cathodes - Google Patents

Abstract

597,681. Thermionic valves: BRITISH THOMSON-HOUSTON CO., Ltd., and RUSHFORTH, L. Sept. 25, 1945, No. 24788. [Class 39 (i)] An indirectly heated cathode, particularly for magnetrons, comprises a metal cylinder 1 with an electron emissive outer surface, the ends of which are closed by metal plates 3, 4 to which is attached, preferably under tension, a heating element 2. Both end plates are insulated from the cylinder by flanged ceramic discs 8 which fit into the ends of the cylinder and are carried in flanged metal cups 9 which are spot welded to the discs 3, 4. Metal strips 12 are welded to the cylinder and are bent over to engage the outer surface of the discs, clearance holes being provided in the end plates 3, 4 and the cups 9. Alternatively, where the end plates are to provide the cathode lead as well as the heater leads, one of the plates may be secured and electrically connected to the cylinder by straps 13. The heater element may be connected to the end plates between strips, Fig. 2 (not shown), or by metal tongues, Fig. 3 (not shown).