Patent GB-655013-A (GB)
Abstract: 655,013. Control of A.C. motors: actuation of switches. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Nov. 10, 1948, No. 29245. Convention date, Dec. 11, 1947. [Classes 38(iii) and 38(v)] [Also in Group XX] Apparatus for photographing X- ray stereoscopic images on a fluorescent screen comprises chain means connecting an X-ray tube and photographic equipment in such relationship that both may be moved up and. down together, and apparatus for automatically changing the relative vertical position of the X-ray tube and photographic equipment, comprising a crank carrying a pulley over which the connecting chain passes, a cam mounted on the crankshaft, and a motor driving the crankshaft for moving the X-ray tube. Timer mechanism may be included which sequentially energizes the X-ray tube for an exposure period, moves the photographic film one frame, causes the motor to turn through 180 degrees to move the X-ray tube to another stereo position, energizes the tube and shifts the film again, and causes the motor to turn through a further 180 degrees to return the tube to its initial position. As shown, Fig. 1, the apparatus is similar to that described in Specification 650,179, but is modified by the addition of apparatus in a housing 36 for moving the X-ray tube 22 between two positions, without moving the assembly 15 comprising the fluorescent screen and photographic camera, and for causing an X-ray image to be photographed in each position, to provide stereoscopic X- ray photographs. The chain 34 connecting the carriages of the tube 22 and assembly 15, permitting them to move up and down together for preliminary adjustment, passes over a pulley 35. The shaft 48 of the pulley is eccentrically disposed with respect to a shaft 44, Fig. 3, rotatable by an induction motor and carrying a cam 45 operating switches 46, 47. Pulley 35 is rotated round shaft 44 when the latter is driven, and causes tube 22 to move between its upper and lower positions. The weight of the tube is at least partly counterbalanced by a weight 49 connected to chain 34. The control circuit, Fig. 10, comprises a control stand from which power for operating the various parts is supplied by power lines 69, 76 and a toggle switch 55 to a motor 58 driving a camshaft 50, a motor 43 for raising and lowering the X-ray tube, means 124, 133 for controlling the duration of the X-ray exposures and effecting film change, relays 109, 111, and control switches or press buttons 56, 57. By depressing button 56, . power is supplied to motor 43 causing it to turn through half a revolution to move the X-ray tube to its lower position. The apparatus is then ready for taking a pair of stereoscopic photographs. Switch 57 is depressed, starting motor 58, which thereupon turns through one revolution, driving the cams 64, 62, 59, 66 to operate switches 65, 63, 61, 67 in the required sequence. The X-ray tube is energized for a time determined by the elements 124, 133, and the film is changed in the camera. Motor 43 is energized to turn through half a revolution, raising the X-ray tube to its second position, another exposure is made, the film is changed, and motor 43 again energized to return the X-ray tube to its former position. All parts return to their previous positions ready for another operation. If desired, by operation of switch 55, the X-ray tube may be raised to its upper position for taking single X-ray photographs. The shaft 44 of motor 43 carries, in addition to cam 45 and pulley 35, an arm 53 frictionally engaged therewith by means of a sliding shoe member 20 pressed against the shaft by a spring 30. When the motor runs, arm 53 is pressed against a switch 54 which is thereby closed. When the motor completes half a revolution, a solenoid 68 is energized to operate switches 77, 79, which place a phase-splitting condenser 60, originally in series with winding 51 of motor 43, in series with winding 52 thereof, causing reversal of the motor. Current to the motor is then supplied through switch 54, which opens as soon as arm 53 is moved away from it. Over-running of the motor is thereby prevented.