| 摘要 |
379,334. Thermionic cathodes. LOEWE, S., 10, Wiesenweg, Steglitz, and WIENECKE, B., 73, Honowerstrasse, Mahlsdorf, both in Berlin. May 26, 1931, No. 15325. Convention date, May 28, 1930. [Class 39 (i).] Indirectly heated cathodes comprise a highly emissive layer 5 on a helically wound wire or band 4 resting on a firm metallic base 3 surrounding the insulator tube 1 and heating filament 2. The base 3 may be of greater coefficient of expansion than the wire 4 to improve the contact when the cathode is hot, a nickel base being used with a tungsten wire 4. The layer 5 is of barium sprayed on as by a reaction on the anode, the barium also improving the vacuum. The base 3 may be a tube slipped over the tube 1 hot or a sheet bent around the tube, the edges overlapping or the gap being away from the place at which the barium is developed. In modifications, the nickel base 3 is sprayed on or applied electrolytically after treatment of the tube 1 with graphite or silver or is applied by heating the tube 1 in nickel tetracarbonyl. In another modification, the base 3 is a helix of closely wound wire. The tube 1 is of porcelain, zircon oxide, magnesia, silicates, &c., and is thin compared with its diameter, a spiral heater 2 being used. The Specification as open to inspection under Sect. 91 (3) (a) comprises also cathodes in which the helix 4 is replaced by a coating of tungsten produced by heating in tungsten hexachloride or by atomizing or spraying tungsten dust or a compound. This subjectmatter does not appear in the Specification as accepted. |
