GB539465A - Improved circuit arrangements for operating electric discharge lamps - Google Patents

Abstract

539,465. Discharge lamps. BRITISH THOMSONHOUSTON, CO., Ltd., and SCOTT, W. J. March 19, 1940, No. 5066. [Class 39 (i)] [Also in Groups XXXV and XXXVII] In a circuit for operating lowpressure discharge lamps of the type comprising thermionic filamentary cathodes which are preheated to 'initiate the discharge, the heating current being discontinued during the normal operation of the lamp, a switching arrangement is provided for putting the filamentary cathodes in circuit with the source of heating current and subsequently connecting the ends of the filaments together so that all parts thereof are at the same potential. The switch may be electromagnetically operated, or of the thermal responsive type such as described in Specification 532,490, [Group XXXVII]. The arrangement described is a glow discharge device comprising two fixed contacts 5, 6 and two bimetallic elements 3, 4 carrying contact member 7, 8. The contacts 6, 8 and 5, 7 are connected to the ends of the filamentary cathodes of a discharge lamp operating on A.C. When the operating current is first supplied, the glow discharge between the elements 3, 4 causes these elements to deflect until the contacts 7, 8 short circuit the glow discharge causing a relatively heavy heating current to pass through the filaments, and allowing the elements to cool, whereby they return to their normal position closing the contacts 6, 8 and 5, 7.