GB457378A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

457,378. Discharge lamps. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. May 19, 1936, No. 14204. Convention date, May 20, 1935. [Class 39 (i)] Two electrodes are so arranged that a positive column discharge can occur between them and their fronts are covered with glowresisting material such as finelydivided aluminium whilst their backs are coated with an alkaline earth substance so that a positive column occupies the entire interelectrode path. In one form, Fig. 2, electrodes 5, 8 are provided with aluminium and barium oxide coatings and are apertured, auxiliary starting cathodes 13, 15 being placed opposite the apertures. Each main electrode may be hollow so as to enclose the negative glow, and a mantle of glass, itself fluorescent or coated with a fluorescent material may be arranged between the electrodes, the discharge then passing through this mantle. The filling may consist of À01 to 1 per cent, preferably 1 per cent, mercury and the remainder argon, or at room temperature, of argon at a pressure of 1À5 mm. and mercury at À0013 mm. Neon at 28À5 mm. or 30 mm. may be added. The neon and argon may be wholly or partly replaced by helium and krypton respectively, and the mercury by cadmium, zinc or alkali metals. A mica washer may be arranged around the leads, opaque to resonance radiations and preventing a discharge near the pinch. With a mercuryneon-argon filling a fluorescent coating on the mantle of calcium tungstate may be used. Other fluorescent materials which mav be used are willemite, zinc orthosilicate, calcite, and uranium glass. The envelope itself may have a fluorescent coating or be of a fluorescent glass.