GB517349A - Improvements in or relating to control arrangements for x-ray apparatus - Google Patents

Abstract

517.349. Controlling X-ray apparatus. GENERAL ELECTRIC CO., Ltd., and CALDWELL, J. T. July 25, 1938, No. 22053. [Class 38 (iv)] In a control for X-ray apparatus of the kind comprising separate means for controlling the value of the high-tension current through the tube and for adjusting the time of exposure, the two controls are independently adjustable but are interlocked so that the time of exposure cannot exceed the safe maximum corresponding to the value of the high tension current. In the form shown, high-tension current is supplied to the tube from a transformer 2 the primary of which is fed from an auto-transformer 4 by way of a contactor 5 with an operating winding 6. The filament heating transformer 7 is also supplied from the transformer 4 by way of a tapped choke or resistance 9, by which the filament current, and hence the high-tension current, is controlled. The duration of the exposure is determined by a rotary time switch 10, which is driven by a synchronous motor 19 through a magnetic clutch 20 and operates contacts 11 in the circuit of the operating coil 6 of the contactor 5. During the exposure, the wiper 13 rotates anticlockwise and completes the circuit of the coil 6 by bridging a segment 14 and one of a number of segments 15. The latter are connected to corresponding contact segments 18, any number of which may be connected in parallel according to the position of a wiper 17 which rotates with the switch 16 which determines the current through the tube. In the position shown the minimum current of 100 milliamperes is employed, 'all the segments 18 are in parallel, hence all the segments 15 are in circuit, and the maximum exposure of 10 seconds may be given. As the switch 10 is set successively to each higher current value the wiper 17 passes off one of the segments 18 and the corresponding segment 15 becomes dead, so that should the time switch have been set for too long an exposure the exposure actually given will not commence until the wiper 13 has moved on to the first live sector 15, corresponding to the maximum safe time. The choke 9 may be omitted, the switch 16 selecting tappings on the transformer 7.