GB441000A - Improvements in and relating to vapour electric discharge devices - Google Patents

Abstract

441,000. Discharge apparatus. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. Aug. 17, 1935, No. 23187. Convention date, Aug. 18, 1934. [Class 39 (i)] A vapour electric discharge device comprises an envelope containing a substance vaporizable during the operation of the device and provided with a relatively cool region adapted to condense the substance, said cool region having therein a part subject to attack by the hot vapour and a portion of the condensed substance covering the part for protecting the latter from the vapour. The part may be a recess, preferably of capillary dimensions, through which a current lead passes, or a non-resistant stem or other portion over which a resistant glaze has been destroyed during fusion. Discharge lamps are described containing sodium or other alkali metal and 1-7 mms. of neon, argon, &c. In one form, Fig. 1, the leading-in wire 12 to the electrode 11 passes through a tubular recess 15 to the seal 16, and the condensed alkali metal fills the recess 15 and protects the seal from attack. To reduce heat conduction from the electrode, a coil 17 of one or two turns is introduced in the lead 12. In modifications, the tube 15 is bent at right angles or, as shown in Fig. 3, is sealed into the side of the tube and bent so as to lie parallel to the lamp axis. In another form, the lamp is provided with a neck 15c, Fig. 4, within which is a stem 20, the neck 15c being filled with condensed metal. The lead 12c, proceeding to the electrode at the other end of the lamp, is protected and insulated by a sheath 23 of glass or alumina sealed to the pinch 21. In another form, a tubular recess of the kind shown in Fig. 1 is provided at one end of the lamp, and a neck and stem of the kind shown in Fig. 4 at the other. Heat-insulating asbestos gaskets 30 may be employed to support the lamp within a vacuum jacket, and also assist in cooling the protected parts. A similar asbestos gasket 30b may be provided at the position shown in Fig. 3, for cooling only. The electrodes may be either discharge-heated, as shown, or indirectly heated with series-connected heaters in parallel with the discharge, Fig. 5 (not shown).