GB562497A - Improvements in and relating to radiographic apparatus - Google Patents

Abstract

562,497. Radiographic apparatus. SCHALL & SON, Ltd., and HARDING, B. W. Feb. 4, 1943, No. 1881. [Class 98 (i)] The apparatus comprises a carrier for a film or plate large enough to record more than one image, or several juxtaposed smaller films or plates, the carrier being movable between successive exposures away from its operative position, and means for automatically locating the carrier on its return to operative position comprising rotatable stops automatically set by the movements of the carrier into the path of blocks on the carrier so that different areas of film or plate are presented successively in the exposure position. The apparatus may include a fluorescent screen or support therefor to permit radioscopic inspection between successive exposures. As shown, the film or plate cassette is mounted in a frame 1 having a cassette-locking catch 19 and a spring 18 to facilitate removal of the cassette when unlocked. The frame 1 is guided on runners 2 in a protective casing 3 having an exposure aperture 17 in line with the X-ray beam and may be displaced in relation to the aperture by a hand-operable crank pivoted at 7 to the casing 3 and connected by a link 4 to a lug 6 on the frame 1. The automatic locating mechanism comprises a shaft 9 mounted in the casing 3 and carrying a ratchet wheel 10 prevented from reverse rotation by a spring pawl 14 and wheels 11, 12 having stop-teeth adapted respectively to engage stop-blocks 15, 16 spaced along the frame 1. In the position shown,.the left-hand third of the film or plate is in position for exposure, with a tooth of wheel 11 engaging block 15. After exposure, the linkage 4, 5 is operated to move frame 1 to the right, leaving the window 17 free for radioscopic examination; and during this movement a spring pawl 13 on frame 1 turns the ratchet wheel 10 so as to lift said tooth of wheel 11 out of the path of block 15 and bring a tooth of wheel 12 into the path of block 16. Thus, when the linkage 4, 5 is operated to return frame 1 to operative position, the frame is arrested b block 16 with the middle third of the film or plate opposite the window 17 for the second exposure. Thereafter, repetition of this procedure causes further rotation of the ratchet wheel 10 to raise the tooth of wheel 12 also out of arresting position, so that on the final return movement frame 1 is arrested by the left-hand end of casing 3 in position to expose the right-hand third of the film or plate at the window 17. More than three images may be successively recorded by multiplying the number of toothed wheels and stop-blocks. If desired, a spring detent device may be located between the frame 1 and casing 3 to hold the frame more securely in each of the positions in which it is arrested.