GB401828A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

401,828. Discharge devices. INTERNATIONAL GENERAL ELECTRIC CO., Inc., 120, Broadway, New York, U.S.A.- (Assignees of Allgemeine Elektricitats-Ges. ; 2, Friedrich Karl-Ufer, Berlin.) Aug. 2, 1932, No. 21689. Convention date, Aug. 1, 1931. [Classes 39 (i) and 40 (v).] In a discharge device having a hot cathode and an internal control electrode to which is applied an alternating potential adjustable in magnitude and phase to ensure initiation and maintenance of the discharge, means responsive to thermal radiation from the cathode are provided to influence the voltage condition of the control electrode whereby the discharge is prevented from occurring until the temperature of the cathode has reached a predetermined value. A load 10, Fig. 1, is supplied through a valve 1 from a transformer 6. An alternating potential for the electrode 4 is obtained from a secondary winding 7 and the phase relationship with respect to the anode potential is obtained by means of the condenser 8 and the resistance 9. A bimetallic strip 13 is adapted at a certain temperature of the indirectly-heated cathode 2 to be disconnected from a contact 11 to open a circuit comprising a battery 14 and a resistance 15 and thus to remove a negative potential on the grid. In a modification, a condenser 8, Fig. 2, and resistances 16, 17 are connected across the winding 7, the grid being connected to a point between the condenser 8 and resistance 16. The thermal switch 18 is closed at a certain temperature of the cathode to shortcircuit the resistance 17 to shift the phase of the control grid potential by 180 degrees. In a further modification, the voltages of thermal elements 2a, 2b are applied through an amplifier 24 to a relay winding 25 which is adapted to open relay contacts 27, 28 to shift the phase of the control grid potential by 180 degrees. The thermal responsive means may consist of a photo-electric cell.