GB400806A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

400,806. Discharge tubes. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, and GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, both in London. Jan. 16, 1933, No. 1456. Convention date, Jan. 15, 1932. [Class 39 (i).] The starting of a discharge tube having a filling of metallic vapour and a self-heated cathode, such as is described in Specifications 356,234 and 364,578, is facilitated by the provision of an interrupted ignition coating 3 which is, by contraction of the electrode chambers, brought to a distance' of about 2 mm. from the electrode. The tube may be made of Thuringian or coloured glass or of quartz and is provided with spiral or trayshaped electrodes 2. The coating consists of silver which forms a reflector and covers from one third to one half of the tube surface, or of a conductive network which encloses the tube, the gap being defined by a metallic coating. The lamp may be adapted to produce a mixed light and may contain argon at 8 mm. Ignition is facilitated by means of a choke and a condenser in the circuit of which a switch may be connected. The Specification as open to inspection under Sect. 91 states also that a nickel electrode is coated with a compound which is heated to form barium coating, separated from the electrode by a layer of barium nickelate. This subject-matter does not appear in the Specification as accepted.