GB438653A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

438,653. Discharge apparatus.. BRITISH THOMSON - HOUSTON CO., Ltd., Crown House, Aldwych, London. July 19, 1935, No. 20598. Convention date, July 21, 1934. [Class 39 (i)] A circuit arrangement for operating a device having a heated cathode from a constant - current circuit comprises means for dividing the supply between the discharge path and the cathode heater, and a circuit connected in shunt across the discharge path is arranged to carry the normal discharge current until the cathode has been heated to its operating temper. ature. In one form, a transformer 2 supplied from a constantcurrent circuit has a secondary 5 supplying the discharge current and secondaries 4, 6 supplying the cathode heaters 10, 11 of the lamp 7. A time-delay switch 17 comprises a heater 21 supplied from the secondary 6 and contacts 18, 19 which are opened by a bimetallic strip 20 and when closed provide, with the resistance 22, a shunt circuit across the discharge path. When the cathodes have reached operating temperature, the strip 20 opens the contacts 18, 19 and the full voltage is impressed on the lamp. If the lamp does not start within a short period a film contact short-circuit device 43 breaks down. In a modification for continuous-current, the cathode heater is connected in shunt with the discharge path and in series with the heater for the time-delay switch.