GB223246A - Improvements in and relating to regulating mechanism for electrical apparatus - Google Patents

Abstract

223,246. British Thomson-Houston Co., Ltd., (Assignees of Thomson, E.). Oct. 11, 1923, [Convention date]. R÷ntgen-ray and like apparatus.-The heating circuit of the incandescent cathode of an X-ray tube enclosed in a sealed chamber is controllec by a member within the chamber coupled inductively with a member which is situated outside the chamber and may be adjusted to vary the inductance between the two members. In the form shown, an X-ray tube 3, Fig. 1, and trans former 2 are enclosed in an oil-filled tank 1 of non-magnetic material. The cathode 7 of the tube is rendered incandescent by an auxiliary transformer 8, Fig. 4, and in the heating-circuit is included an inductance coil 13 mounted inside the tank round a tube of non-magnetic materia sealed into the wall of the tank. Through the open outer end of this tube a core 15 is inserted which is adjustable by a screw 16 in order t'o vary the reactance of the heating-circuit and hence the temperature of the cathode. The core 15 may have a bi-polar or bone-shoe shape. A magnetic shunt 19 consisting of radially split thin iron plates prevents eddy currents in the tube surrounding the core. In a modification, the secondary of the heating transformer is excited from the primary of the main transformer 2, and the heating circuit includes an inductance coil 21, Fig. 7, inside the tank inductively coupled to a coil 22 outside the tank, from which tappings are taken to a commutator 23, co-operating with fixed brushes which are either short-circuited or are connected to the secondary of an auxiliary transformer. The coil 22 and commutator are rotatable by means of a hand-wheel 31 so as to vary the epective number of turns of the coil 22, and hence through the coil 21 to vary the reactance in the heating circuit as before. Specification 14892/13, [Class 39 (i), Electric lamps, Arc &c.], is referred to.