GB406413A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

406,413. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Buttolph, L. J. ; 1, Columbia Avenue, Grantwood, New Jersey, U.S.A.) Oct. 24, 1932, No. 29717. Convention date, Oct. 24, 1931. [Class 39 (i).] A discharge device, such as a lamp or a rectifier, the operating potential of which is insufficient to initiate the discharge, is started by the application of a high potential, which is obtained by interrupting the passage through an inductance of a current fed from a unidirectional source, the potential of which is lower than that used for maintaining the discharge. The potential, preferably, is less than the ionizing potential of mercury in order to avoid arcing in the mercury switch connected in the inductance circuit. The source of low potential may be obtained from an alternating-current supply through a double or a half-wave oxide rectifier, from a battery, or from a potentiometer connected across a direct-current supply. A double-wave rectifier 10, Fig. 1, is connected to tappings on the supply autotransformer 5, and a mercury switch 9 is adapted to break the current through an inductance 7 to impose a high potential upon an external electrode 4. The rectifier may be connected to the supply transformer through an autotransformer 11, Fig. 3. Two separate half-wave rectifiers 10<1>, Fig. 4, may be connected to a switch 9<1>, Fig. 4, provided with three contacts as shown. In a modification, one inductance 7<1>, Fig. 7, is connected in series with the device for normal operation and another inductance 7<11> is used in the ignition circuit. The magnitude of the condenser 13 is such that it will pass the high potential current but will not pass the normal discharge current. The inductances may consist of two or of tapped windings on the same core or of windings on separate cores, in which case the switch is adapted to be operated by either inductance through separate armatures. In a lamp 21, Fig. 8, having an indirectly-heated cathode 22, starting is delayed by a thermostat 28 which is heated by a resistance 27 connected in the inductance circuit to short-circuit the said resistance. The low-potential source may be obtained from a potentiometer 17, Fig. 12. A switch 9 in series with the inductance and a hydrogen-filled switch 16, which is adapted to disconnect the potentiometer from the mains upon ignition, are actuated by the inductance through one armature.