GB201741A - Improvements in and relating to x-ray apparatus - Google Patents

Abstract

201,741. British Thomson-Houston Co., Ltd., (General Electric Co.). July 14, 1922. R÷ntgen-ray and like apparatus.-The heating current for the cathode filament of a R÷ntgenray tube is controlled by means responsive to variations in the supply voltage and in the current through the tube in such a manner that the rays produced are of substantially constant radiographic intensity. As shown, the cathode filament is supplied with current from the low-tension secondary of a transformer 5, the primary of which is connected across the alternating-current mains 6, 7 in series with a fixed contact 11 and a contact 10 carried by the armature 12 of an electromagnet 13, forming a make-and-break switch. The current through the tube is supplied by the high-tension secondary windings 19, 20 of a transformer 2, in series with which is one winding 15 of the electromagnet 13. A second winding 14 is connected, in series with an inductance 16, across the mains 6, 7 and therefore causes the period of break of the switch 12 to lengthen with increasing voltage and thereby reduce the filament current, the winding 15 being responsive to the current through the tube. These windings are so proportioned that the current through the tube varies inversely as the square of the line voltage. The reactance 16 is operated at a point on the saturation curve where the current increases rapidly with increase of voltage. The movement of the armature 12 may insert and cut out resistance in the cathodeheating circuit. Specifications 121,278, [Class 39 (i), Electric lamps, Arc &c.], 166,097, and 170,546 are referred to.