GB716176A - Improvements in or relating to electric discharge lamps - Google Patents

Abstract

716,176. Discharge lamps. ATELIERS DE CONSTRUCTIONS ELECTRIQUES DE CHARLEROI. May 19, 1950 [May 21, 1949], No. 12581/50. Class 39(1) [Also in Group XXXV] A circuit includes an electric discharge lamp, preferably fluorescent, having auxiliary electrodes made of a metal of low ionizing potential, the dimensions of the auxiliary electrodes and the circuit characteristics being such that the current density of the auxiliary electrodes is of the order of 0.0005 to 0.001 amperes per square centimetre. The auxiliary electrodes can be made of aluminium, magnesium, an alloy of these metals or an alkali metal. The auxiliary electrode 5 may comprise a plurality of superposed annular discs spaced from one another but electrically connected as shown in Fig. 1, a corrugated cylinder as shown in Fig. 4, or a cylinder having internal fins as shown in Fig. 6. In the construction shown in Fig. 7 an annular metallic screen 8, which is connected to a source of potential through the lead 9, prevents metallic particles sputtered from the auxiliary electrode 5 reaching the main electrode 3. In the construction shown in Fig. 8 the metallic screen is replaced by a screen 10 of insulating material such as mica or steatite. In the construction shown in Fig. 9 the main electrode is formed of two coaxial helicoidal windings 12 and 13, the internal winding 12, which may be covered with emissive materials, forming the electrode proper and the external winding 13 forming a protective screen between the winding 12 and the auxiliary electrode 5.