Patent GB-671238-A (GB)
Title: Improvements in or relating to a bucky grid actuating mechanism and a method of making x-ray photographs employing said mechanism
IPC: G21K1/02
Filed: 1950-01-13
Abstract: 671,238. X-ray apparatus. LIEBELFLARSHEIM CO. Jan. 13, 1950 [Jan. 15, 1949], No. 965/50. Class 98 (i). Mechanism for reciprocating a Bucky grid during an X-ray exposure comprises a holder for the grid, means for moving the holder in opposite directions at different given speeds, including electrical power means operable to shift the grid in one direction, mechanical power means biasing the electrical power means and operable to shift the grid in the opposite direc- 'tion, and means operable intermittently to energize and de-energize the electrical power means to cause,sustained reciprocation of the grid. The movement of the grid and the X:ray exposure may be started together, and may also be terminated together by a photo-electric cell device. A movable disc of X-ray opaque material may have openings of different sizes through which X-rays pass to energize the photo-electric cell, and an electric circuit may be provided to bring any required aperture into position by operation of a switch. As shown, Fig. 1, the Bucky grid 21 and associated apparatus is mounted in a shallow casing 20, and -is supported on one side by lugs 40 sliding on rods 35 mounted on a partition 37, and on the other side by lugs 42 sliding on rails 43 fixed to the casing wall, so that it may reciprocate through a distance of about 2 inches. The grid frame is fixed to a bracket 48 (see also Fig. 12) carried by the plunger 47 of a solenoid 46, so that when the solenoid is energized by pressing a push-button, the grid moves to the right. At the end of this movement a switch 24 with a snap action is operated by a cam 25 on the grid to de-energize the solenoid, and the grid returns to its starting-point under action of a spring 23, which has been tensioned by the forward movement. On reaching its starting-point, cam 25 again operates switch 24 to energize the solenoid and the cycle of movement continues. Bracket 48 is connected to the rod 56 of a piston 55 movable in an oil-filled cylinder 27; the oil moves through a by-pass tube 66 and a valve 67, whereby the rate of movement of the grid is adjusted in manufacture. Piston 55, however, has a valve through which. oil passes during movement of the grid to the right, so that this movement is faster than movement in the opposite direction. An expansible metal bellows 70 is connected to the cylinder to allow for the displacement of oil by the piston-rod 56 and for changes of the volume of oil with temperature. When the movement of the grid begins, a nose 162 thereon operates a switch 30 to switch on the X-ray tube, which remains energized until switched off by a timing-mechanism, which is preferably of the kind wherein the X-rays, after passing through the object of the examination and through the photographic plate or film, fall on a fluorescent screen; the light from the screen falls on a photo-electric cell which charges a condenser; and an electric circuit switches off the X-ray tube when the condenser has been charged to a predetermined voltage. An X-ray opaque screen is placed between the photographic material and the fluorescent screen, and has an aperture therein the size of which depends on the size of the object being examined. A tray for supporting an X-ray cassette is mounted below the Bucky grid 21, and has an aperture through which X-rays may pass. A disc 28 of X-ray opaque material, Fig. 11, is pivoted at 124 below the tray, and is rotatable to bring three groups of apertures 105, 106, 107 selectively into register with the aperture in the tray, according to the size of the object being examined. The X-rays can then pass through an aperture in the bottom of casing 20 to the fluorescent screen. The disc is driven by an electric motor 109 (Fig. 1) geared to a pulley 114 which drives disc 28 by means of a belt 115. A three-pole selector switch (not shown) is turned to the position corresponding to the aperture to be used, connecting one side of an A.C. supply to one of three single-pole double-throw switches 140, mounted on a supporting plate adjacent to the disc 28. A circuit is completed through the switch 140 to energize the motor 109 and a solenoid 134 connected to the other side of the mains supply, withdrawing a plunger 128 from the disc. The motor drives the disc, and just before the required aperture comes into position, a cam 141 on the disc operates the switch 140 in circuit, disconnecting the motor 109 and the solenoid 134. The disc continues to move by inertia until stopped by one of three pins 130 coming into contact with the plunger. At the same time another connection is made from the supply mains through the selector switch and the switch 140 which has been operated, to one side of the push-button switch which initiates the grid movement. Current still passes through motor 109 and solenoid 134 through an indicator lamp which indicates to the operator which aperture is in position, but the current is too small to operate the motor or solenoid. When the indicator lamp glows, the operator presses the push-button completing the circuit through switch 24 and a rectifier supplying D.C. to solenoid 46, starting the movement of the grid. This movement, as stated above, energizes the X-ray tube and the timing- mechanism, which has a lamp which glows while the tube is energized. When the exposure is complete, the operator releases the pushbutton, permitting the grid to return to its position of rest.