GB444737A - Improvements in and relating to thermionic electron emissive electrodes for gas or vapour electric discharge devices - Google Patents

Abstract

444,737. Thermionic cathodes. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwvch, London. Aug. 7, 1935, No. 22338. Convention date, Aug. 10, 1934. [Class 39 (i)] A thermionic electron - emissive electrode, suitable for use in gas or vapour electric discharge devices such as lamps, comprises a base 5 of metal such as nickel and of tubular formation for accommodation of a heater 10, upon the surface of which is wound a coiled filamentary wire 15 of tungsten or molybdenum, electron-emissive material being adherent both to the base and to the coiled wire and in the interstices between the convolutions, yet leaving open the intervals between the outer convolutions. The base 5 may also be of konel metal. Leads 8, 9 to the heater 10 pass through shouldered lava insulators 7, the base 5 being connected to one lead by a nickel strip 11. A lamp may contain two such electrodes with their heaters connected in series by a refractory molybdenum lead, the filling comprising sodium (1-2 microns), mercury (1-2 mms.) or cadmium, together with a starting gas such as neon or argon (1-7 mms.). The Specification as open to inspection under Sect. 91 comprises a thermionic electronemissive electrode having a metal base and a roughened overlay of tungsten or molybdenum carrying the emissive material, and describes an overlay of coarse tungsten powder (50-60 mesh per inch) which is applied with a binder of nickel or tungsten oxide in amyl acetate and nitrocellulose to a nickel base, the whole being baked in hydrogen at 1200‹ C. Molybdenum may replace the tungsten, and the binding oxides may be omitted. The nickel base mav be similar in construction to base 5 described above or, as shown in Fig. 3 (Cancelled), may be open at one end with the roughened overlay 12 on the inside of the tube. This subject-matter does not appear in the Specification as accepted.