GB596360A - Improvements in and relating to the starting control for electric discharge devices - Google Patents

Abstract

596,360. Discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 16, 1943, No. 21136. Convention date, Dec. 17, 1942. [Class 39 (i)] [Also in Group XXXV] The starting of a discharge device having a thermionic cathode is controlled by electron emission. Fig. 1 shows a lamp L having an internal fluorescent coating and containing low-pressure gas, e.g. argon, together with a working substance such as mercury. A starting and heating circuit H may be connected across the power supply P through the activated filamentary cathodes 11, 11 and have included therein a starting relay s having an operating coil 19 connected in a control circuit 20. This circuit 20 connects a variable tap 28 on a starting and ballast inductance 14 through the winding 19 to a spring contact 26 engaging a metal band 25 on the lamp base, the band being in turn connected to an auxiliary anode 22 consisting of a straight length of wire, e.g. nickel. The auxiliary anode, which may be of T-shape, 22a, Fig. 2, is sealed through the cathode mount 23. Said anodes are placed at both ends of the lamp to ensure operation of the starting circuit regardless of which way the lamp is placed in its holder. When starting, current flows through the circuit H until the cathodes 11, 11 have preheated to a temperature sufficient to cause adequate emission between the electrodes 11, 22 to permit a discharge current to flow in the circuit 20 which will operate the switch S and initiate the main discharge. In a modification, Fig. 7 (not shown), an auxiliary cathode, the exact counterpart with regard to heating and time, characteristics of the cathodes 11, 11, is placed together with an auxiliary anode of base refractory metal wire in a separate envelope so that uneven wear of the cathodes 11, 11 is avoided.