Patent GB-697434-A (GB)
Title: Improvements in or relating to x-ray apparatus
IPC: H05G1/62
Filed: 1951-11-20
Abstract: 697,434. X-ray apparatus. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Nov. 20, 1951 [Dec. 4, 1950], No. 27198/51. Class 98 (i). [Also in Group XL (c)] X-ray apparatus comprises a multivibrator, a relay responsive to the output current of the multivibrator, the relay including a switch, connections for. connecting a voltage source to one side of the switch, connections for connecting the other side of the switch to the control circuit of an X-ray tube which is thus energized by operation of the switch, and connections for connecting the other side of the switch also to a camera control circuit so that the camera is operated by operation of the switch. The connections between the switch and the X-ray tube may comprise contactor apparatus independent of the multivibrator for periodically opening and closing the circuit. The apparatus may be used in angiocardiography, for taking a series of X-ray photographs when an X-ray opaque substance is passing through each auricle of the patient's heart. As shown, a contactor 8 is connected in the power supply circuit of an X-ray tube 2 so as to energize the tube 2 when operated by a series of pulses. These pulses may be provided by an electrocardiograph 13, a camera control circuit 14, or a multivibrator 16, the required source of pulses being selected by a switch 10. A switch 11 ganged with switch 10 and a switch 200 connects the pulse source to the camera control circuit when the electro-cardiograph or the multivibrator is selected, so that at each energization of the X-ray tube 2 an X-ray photograph is made. The operation of the contactor by the pulses is controlled by five thyratrons 28, 38, 46, 38, 50, which normally have negative bias applied to their control electrodes to render them non-conductive. To start the apparatus, at the moment when the opaque substance is injected into the patient's blood-stream, a switch 30 is closed, earthing the grid of thyratron 28 which start to conduct, energizing relay 32. This relay opens switch 34, disconnecting the bias voltage from the control electrode of thyratron 38, which conducts, as soon as the charge on condenser 153 leaks off through resistor 163, operating a relay which closes a switch 12, completing a circuit by which pulses are applied to contactor 8. The relay also opens switch 42, disconnecting the bias from thyratron 38. The thyratrons all come into operation in turn after delay periods controlled by adjusting resistors 163, 165, 167, 169 and energize switching relays so that the pulse circuit is closed for two separate periods. The timing is so adjusted that these periods coincide with the periods during which the X-ray opaque substance is passing through the auricles of the heart. The apparatus is reset by means of a manually-operated switch 62 in the common anode circuit of the thyratrons. The multivibrator circuit 16 consists of two double-triode valves and a thyratron 83, and periodically energizes a relay 95 operating a switch 97 to provide pulses for the contactor 8. A variable resistance 93 enables the duration of the pulses to be adjusted. The frequency of the pulses is controlled by a variable resistor 70, having two sliders connected to switches 72, 74 operated when thyratron 46 conducts so that, one opens and the other closes. The pulse frequency therefore may have different values in the two periods of operation. The multivibrator is so connected to the thyratrons as to impress a negative bias on their second control electrodes when the relay 95 is energized, thus preventing any thyratron from starting to conduct while a pulse is in progress. A thermal delay switch 82 prevents operation until the apparatus has warmed up, and when operated lights a signal lamp 99. This lamp is in series with a switch 84 operated by the last thyratron 50, so that when this thyratron conducts at the end of a sequence lamp 99 goes out, and lights again when the re-setting switch 62 has been operated. To test the apparatus, switch 88 is operated, so that the pulses, instead of actuating contactor 8, cause a lamp 86 to flash.