Patent GB-685451-A (GB)
Title: Improvements in apparatus for producing radiographs
Inventor: ORMEROD ERIC DOUGLAS
IPC: G03B42/02
Filed: 1949-06-16
Abstract: 685,451. X-ray apparatus. NEWTON VICTOR, Ltd. June 15, 1950 [June 16, 1949], No. 16069/49. Class 98 (i). Apparatus for producing a sequence of radiographs comprises a carrier supporting a stack of superposed cassettes containing X-ray film and means for moving the carrier and the stack substantially at right angles to the planes of the cassettes to bring the outermost cassette into position for exposure and for removing the outermost cassette from the stack laterally in its own plane after exposure, the said means being arranged for automatically recurring operation so as to bring the cassettes successively into the exposure position at preselected time intervals. As shown, Figs. 1, 2, the cassettes are held each in a tray 20, the trays being stacked on a carrier 3 mounted to be raised or lowered in a frame 4. This frame is accommodated in a main frame 4a supporting a table top 5 on which the patient rests, having a window 6 transparent to X- rays. A cam 7 is driven by an electric motor, and at each revolution rocks a lever system which turns a shaft 14 stepby step through a ratchet-and-pawl. Shaft 14 carries drums 15 to each of which two chains 17 are attached, and the chains pass over pulleys 18 and are connected to the carrier 3 through springs 19 to lift the carrier by the thickness of one tray at each revolution of cam 7. The shaft 8 of cam 7 is connected by a spring coupling to a shaft 25 geared to upright shafts 22 carrying arms 21 which, at each revolution, push the top tray 20 into a frame 30 whence it drops on to a carrier 31. This carrier is connected to carrier 3 by a chain 33 and moves so that the trays are piled upon it. Carriers 3 and 31 are counterbalanced by springs so that the force required to move them remains constant throughout the operation. Carrier 31 is pivoted and is supported by a stay 35, but may be folded down into an inoperative position, and frame 30 may be raised while trays are being loaded on to carrier 3. An electric motor 47 drives shaft 8 through a gearbox 48 and a clutch 49, 50 which is electrically operated to transmit drive to shaft 8 when engaged and to brake shaft 8 when disengaged. The speed of operation may be varied by use of a variable ratio gear-box. A timer 59 has a sleeve 63 driven from the main shaft by a band 60 through an electrically-operated clutch, and carries projections actuating switches 70, 71, 72 at different times after the actuation of the clutch. A spring returns the sleeve to its original position as soon as the clutch is disengaged. The timer is connected to an electrical circuit in a control box 54, including a sequence switch 78 operated by shaft 14. The arrangement is such that for a given number of exposures, shaft 25 rotates continuously. Thereafter, at each revolution shaft 25 is stopped by operating clutch 49, 50 (which also brakes the shaft whenever the clutch is released) and the timer clutch is engaged. As soon as switch 70 is operated, the timer clutch is disengaged and clutch 49, 50 is engaged, and rotation of shaft 25 continues. After a further given number of exposures, switch 70 is short-circuited. The time during which shaft 25 is stationary is now the time required to operate switch 71. When the required number of exposures is completed, switch 71 is short-circuited, and operation of switch 72 switches the apparatus off. Thus a number of exposures are made with a minimum interval, then a number with a greater interval, then a number with a still greater interval, the number of exposures at each interval being determined by the setting of control knobs 56, 57, 58.