Patent GB-648284-A (GB)
Title: Improvements in or relating to x-ray apparatus
IPC: G21K1/02
Filed: 1947-10-30
Abstract: 648,284. Control systems for X-ray apparatus. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. Oct. 30, 1947, No. 28990. Convention date, Oct. 30, 1946. [Class 38 (iv)] [Also in Groups XX and XL (c)] A control arrangement for X-ray apparatus of the type in which a Bucky grid is moved through the field of exposure of an X-ray sensitive film comprises means operable after an inherent time delay for energizing the X-ray tube for a preselected period of time, a control circuit for controlling the release of the Bucky grid and switch means for initiating an X-ray exposure, and a second part operated by the first part when the exposure initiating switch is operated, the second part when operated being effective to release the Bucky grid after a predetermined time interval such that the Bucky grid is permitted to attain a constant rate of movement in the field during the entire time of an X-ray exposure. As shown, the supply circuit of a rotary anode X-ray tube 5 is energized from mains L1, L2 through a main switch 13, a switch control 15, and (normally open) contacts of a relay 14. A timer 16 contains a continuously-operated motor and a magnetic clutch; the clutch, when actuated, connects the motor to mechanism in switch control 15 to close a circuit allowing current to energize the supply circuit of tube 5 for a predetermined time, as described in Specification 640,026. An auto-transformer (not shown) supplies A.C. to terminals 20, 21, 24, 38, 26, 23. The heater of an indirectly-heated rectifier valve V1 is heated at a temperature insufficient for full emission by 4 v. A.C. from terminals 28, 23. When the main switch 13 is closed, a relay 33 operates to connect terminal 21 (200 v.) to the anode of V1, thereby charging a condenser C1 which is connected through the winding of a relay 32 to a gas discharge tube V2 shunted by a condenser and a resistance. The potential across C1 rises until V2 conducts, when the current passing through its winding actuates relay 32, closing contacts 36 and connecting the heater of V to terminal 38. The heater voltage of V1 is now sufficient for full emission so that relay 32 remains energized. A switch-bar 39 may now be depressed, and first meets a contact 40, connecting terminal 24 (110 v.) to relay 14 and the anode motor of tube 5. Just afterwards, switch-bar 39 meets contact 44, supplying 110 v. A.C. to a 3-branched conductor 45, with the following results: (1) The magnetic clutch, connected across terminals a, b of timer 16, is operated, so that the motor (connected to terminals e, f operates the switch control 15 so that the supply circuit of tube 5 is energized for a period selected by adjustment of timer 16. Initiation of the X-ray exposure follows the energization of the magnetic clutch after a time delay inherent in the apparatus. At the end of the timing cycle a switch connected across terminals c, d of the timer closes momentarily, energizing a relay 17. This opens contacts 18 in the circuit to the magnetic clutch, and closes contacts 19 to form a hold-on circuit. (2) Relay 48 is energized and closes contacts 52, 49, applying the potential across C1 to a condenser C2 through a variable resistance 53. The trigger electrode of a gas discharge tube V3 is connected through a resistance to condenser C2. After a time depending on the value of resistance 53, the potential across C2 rises until V3 conducts, energizing a relay 47 to close contacts 46. (3) The closing of contacts 46 connects conductor 45 through a switch 56 to a relay 57, which releases a vertical Bucky grid 27, which moves under spring action. The time delays are so arranged that the grid has attained a constant speed when the tube 5 begins to emit X-rays. When the exposure as determined by the timer is complete, switch 39 is released, de-energizing relays 14, 17, 47, 48, switch 13 is opened, de-energizing relays 33, 32, and the apparatus is restored to its initial condition. A second exposure may be made using a horizontal Bucky grid, by first operating gauged switches 59, 56, which respectively replace resistance 53 by a resistance 60 in the circuit, and connect contact 46 to a relay 58 which releases the horizontal Bucky grid.