Patent GB-587578-A (GB)
Title: Improvements in or relating to x-ray cassettes
IPC: G03B42/02
Filed: 1944-05-26
Abstract: 587,578. R÷ntgen-ray cassettes. POWERS, F. T. May 26, 1944, No. 10239. Convention date, April 9, 1943. [Classes 98 (i) and 98 (ii)] A cassette for use with X-ray apparatus has an air-tight casing with a suction port, vacuum means connected with the port, a flexible X-ray permeable window, means for moving a long strip of X-ray sensitized material for the exposure of successive lengths thereof to X- rays through the window, means for holding a length of the strip stationed in the exposed position against the window, the holding means being movable into and out of the exposed position, and valve means responsive to movement of the holding means to open and close the suction port. As shown in Fig. 1, the casing 1 of the cassette is mounted on a platform 2 from which depend legs 3 into a housing 4 of the carriage movable on casters 39. A rotatable shaft having an external operating handle is carried in the housing 4 and carries reels connected by metal ribbons to bracing plates connected to the legs 3. Operation of the handle effects the vertical movement of the casing 1. Counterbalancing means are provided in the housing 4. The housing 4 contains an electrically-driven suction fan drawing air through a telescopic duct from a port, normally closed by a valve, in the bottom of the casing 1. The casing 1, Fig. 7, is opaque to light, is airtight, and is lead-lined except over the exposure area formed by the X-ray permeable window 42. Adjustable steadying wheels 40, Fig. 1, are provided to engage the wall against which the cassette is positioned in use. A presser plate 46 movable in brackets 47 comprises a rigid plywood backing 50, stiffened with metal straps 54, 56, a lead sheet 51, and an intensifying screen 53. A shaft 60 rotatable by an external crank 62 movable between stops 63 carries arms 64 joined by a bar 65 lodged in a socket 66 attached to the plate 46. The supply reel .72 carrying the X-ray-sensitized strip 73, either of transparent film or paper, is carried in bearings 70. The strip 73, which is divided into equal successive lengths separated by weakened severance lines and notched at both edges at each severance line, passes from the reel 72 over a large diameter flanged guide roller 77, over the exposure area between guide rollers 79 and 80, and on to the take-up reel 85 carried in bearings 82 and driven by an external crank 91<1>. The winding means is locked when each successive length of strip is stationed in exposure position by the engagement of a pawl with a ratchet on the shaft driving the reel 85. The pawl is controlled by a feeler running along the edge of the strip and moving to permit the pawl to engage the ratchet when a notch is encountered. The locking means is releasable by operation of an external handle 112, which may be returned by a spring or manually or by an extension stud on the handle 91<1>. The valve flap at the bottom of the casing 1 is connected by a wire 126 to a lever 127 on the shaft 60, so that operation of the handle 62 to move forward the presser plate 46 opens the valve to establish a vacuum in the casing 1 and to cause the flexible window 42 to press the sensitized strip against the intensifying screen. Operation of the handle 62 also actuates a dial 140 to indicate the number of exposures. A zeroizing knob 141 is provided.