GB802754A - Improvements relating to x-ray apparatus - Google Patents

Abstract

802,754. X-ray apparatus. PICKER XRAY CORPORATION WAITE MANUFACTURING DIVISION, Inc. May 2, 1956, No. 13549/56. Class 98(1) In X-ray apparatus having a grid mounted for movement with respect to an X- ray tube, an electric synchronous motor is connected to the source of A.C. supply for the X-ray tube, and mechanism driven by the motor for reciprocating the grid during X-ray exposure includes a gridengaging cam co-acting with the grid to provide a grid speed that is non-synchronous with respect to the frequency of the supply throughout the grid movement. As shown in Fig. 3, a frame 20 is slidable along rails 16, 17 mounted longitudinally below an X-ray table. The side walls 14, 18 of the frame have bottom flanges 23 slidably supporting a plate 30 carrying an X-ray cassette 35 in clips 36. The table has a slot along its side, through which the plate 30 may be pulled out to change the cassette. A Bucky grid 40 is supported above the plate 30 in a frame 41, Fig. 5, which is supported at one side by rollers 42 engaging flanges on the wall 18 of frame 20, and at the other side by brackets 43 sliding on rods 45, 46 mounted in brackets on the wall 14 of frame 20. The grid is movable to and fro by means of a heartshaped cam 52, Fig. 6, driven through gearing from an electric synchronous motor 60 and engaging rollers 51 on a bar 50 connected to one of the brackets 43. The grid - reciprocating mechanism is mounted on wall 14 of frame 20 and enclosed by a removable housing 70. If the exposures are long enough to include several strokes of the grid, the phase of grid movement at which the exposure is initiated does not matter and all that is needed is a switch for the motor 60 and an exposure-controlling switch, or a common switch for both. When the apparatus is to be used for shorter exposures, a pair of cams are mounted on the shaft of cam 52, and these cams operate switches connected in an electric circuit in such a way that an exposure cannot be made at the time when the grid is reversing. The X- ray tube is connected to the same source of alternating current as the motor, and the gearing between the motor and the cam is preferably so designed that the grid moves through a distance covering ten of its slats during thirteen cycles of the alternating current, though other relationships which avoid grid shadow are permissible. Any change in the alternating current frequency affects the motor speed, so that the relation of the grid speed to the current cycle remains constant.