GB304604A - Improvements in and relating to methods of exhausting electric discharge devices - Google Patents

Abstract

304,604. British Thomson-Houston Co., Ltd., (Assignees of Pike, O. W.). Jan. 21, 1928, [Convention date]. Vacuum tubes.-The removal of occluded gases from the electrodes, leads, &c. of a discharge device during evacuation is effected by connecting the electrodes in a circuit resonant at a predetermined high frequency and supplying current of that frequency to the circuit, the current being independent of that in the device due to filament emission, but dependent on the capacity between the grid and the anode. In the form shown in Fig. 1, a pump 5 is connected to a discharge tube 1 through a liquid-air trap 7 and a tube 6, and the high-frequency oscillating circuit for use therewith, of 60,000 kilocycles, includes a grid 3, an anode 2, inductances 8, 9, and a condenser 11. Chokes 12, 13, 14, 15 are inserted in the electrode leads, while a grid leak 17 is connected between the grid lead and the secondary of the transformer 16. A potential of 500 volts between the anode lead and earth generates in the oscillatory circuit currents of low power factor and having a magnitude of from 5 to 30 amperes. Current is supplied to the cathode 4 through a transformer 16. In a modification, Fig. 2, current from a discharge tube 18 flows in a resonant circuit comprising an anode 2, a grid 3, inductances 8, 9, and the anode and grid of the discharge tube 18. After the grid has been sufficiently heated, the wire 20 is disconnected therefrom and connected to the cathode 4. Specification 284,623 is referred to.