GB601200A - Improvements in or relating to incandescent cathode for use in gas or vapour filled discharged tubes - Google Patents

Abstract

601,200. Thermionic valves. PHILIPS LAMPS, Ltd. Aug. 1, 1946, No. 22917. Convention date, March 27, 1940. [Class 39 (i)] An incandescent cathode for gas- or vapour-filled discharge tubes comprises a number of identical wire elements connected in parallel and interconnected at intermediate equipotential points so as to form an openwork structure having apertures not less than 5 mms. wide, through which the discharge can penetrate into the interior of the structure. The connections may be made with sintered iron or nickel or similar metal, or by binding with thin refractory wire. The individual filaments may be worked into a braided body, preferably symmetrical. In one form, zig-zag filaments 1, Fig. 1b, are formed into a hollow star-shaped prism and alternate bends 2, 3 are connected to corresponding bends of adjacent filaments. The end connections 4 are ring-shaped. For smaller currents, zig-zag filaments 1, Fig. 3b, are arranged in star fashion in radial planes about a common axis and inner bends are all connected at points 6. Zig-zag filaments may be replaced by filaments formed by compressing a helix in a direction perpendicular to its axis, so that the successive loops of approximately trochoid form lie in a single plane. The filaments may be tungsten wire wound with nickel wire and a further coating of nickel may provide the base for an emissive coating. Dimensions and working currents of an example are given. The filling may be mercury at a pressure exceeding 1 mm. The subject-matter is identical with that of Specification 549,992. Specification 427,609 and U.S.A. Specification, 1,890,339 also are referred to.