GB366473A - Improvements in and relating to x-ray apparatus - Google Patents

Abstract

366,473. R÷ntgen -ray tubes &c. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Coolidge, W. D. ; 36, Bedford Road, Schenectady, New York, U.S.A.) Oct. 29, 1930, No. 32540. Convention date, Nov. 4, 1929. [Class 39 (i).] In X-ray tubes with several cathodes which give focal spots of different area and which are selectively energized according to whether the load is large or small, the heating current to a cathode is automatically controlled by a regulator the setting of which is interlocked with, and varied by, the means for selecting a cathode so that the current is maintained at the correct value for each cathode. The regulator described in Specification 170,546, [Class 39 (i), Electric lamps, Arc &c.], may be provided with two coils 25, 26, Fig. 1, controlled by a switch 27 interlocked with a switch 17 for energizing either of two cathodes 8, 9, Fig. 3, in the same focusing device 7. According to which cathode is energized, one or both of the coils 25, 26 are in the discharge circuit 24 and the periods during which the resistance 19 is shorted are thus varied. In a modification in which the X-ray tube and the transformer supplying the heating and discharge currents are in an oilfilled tank, the resistance 19 is in the primary circuits of two filament-heating transformers and the coils of the regulator are in series between two secondaries of the dischargecurrent transformer. Rheostats across the primaries of the filament-heating transformers may provide hand control of the heating currents. The Specification as open to inspection under Sect. 91 (3) (a), comprises also references to applying the regulator to thermionic devices generally and refers to Specification 239,511, [Class 39 (i), Electric lamps, Arc &c.]. This subject-matter does not appear in the Specification as accepted.