GB287557A - Improvements in and relating to regulating systems for thermionic devices - Google Patents

Abstract

287,557. British Thomson-Houston Co., Ltd., (Assignees of Kearsley, W. K.). March 24, 1927, [Convention date]. Regulation, automatic.-The space current in a R÷ntgen-ray or other thermionic tube 1 is maintained constant, on variations of the supply voltage or of the residual gas in the tube, by means of a thermionic control tube 21 with means such as a grid 24 for controlling the current from its cathode 22 to its anode 23, the potential of the grid 24 being controlled in accordance with the space current in the tube 1 and the current through the tube 21 controlling the heating current to the cathode 2 of the tube 1. The space current of the tube 1 is supplied from the mains 10 through a transformer 12 with secondary windings 16, 17 in series with a non-inductive resistance 18 shunted by a condenser 19. The grid 24 is connected to the cathode 22 through a biassing battery 35 and a part of the resistance 18, the current through the resistance 18 producing a potential on the grid 24 opposing the battery 35. When the space current in the tube 1 rises above a certain value in any half-wave impulse, the grid 24 becomes positive and a current then passes from the mains 10 through a non- inductive resistance 31 and through the tube 21. The increased potential drop in the resistance 31 due to increasing current through the tube 21 reduces the current supplied to the cathode 2 through a transformer 7, the electron emission from the cathode 2 decreasing to maintain the space current in the tube 1 constant. In a modification, the resistance 18 is replaced by an inductance and the battery 35 by a transformer connected to the mains 10. The tube 1 is operated at saturation current and may be of the kind described in Specification 14892/13, [Class 39 (1), Electric lamps, Arc &c.]. Specifications 210,743, and 223,921, [Class 39 (i), Electric lamps, Arc &c.], also are referred to. Vacuum tubes; low pressure metallic-vapour apparatus.-The thermionic control tube 21 operates with gas-ionization and, after being exhausted and freed from moisture, is filled with a vapour such as that of mercury or a gas such as argon at a pressure of 5.5 cms. The grid 24 may surround the anode 23. Reference has been directed by the Comptroller to Specifications 275,784 and 292,001.