Patent GB-869548-A (GB)
Title: Improvements in or relating to apparatus for use in serial radiography
Inventor: BRYER ROBERT FRANK
IPC: G03B42/02
Filed: 1958-05-28
Abstract: 869,548. Radiography apparatus. GENERAL ELECTRIC CO. Ltd. May 28, 1959 [May 28, 1958], No. 17011/58. Addition to 783,851. Class 98(1) In apparatus for serial radiography in which a cassette holder is mounted in a carriage for rectilinear movement between loading and exposure positions, and in which the carriage is located in a series of exposure positions by selectable stops, as in the parent Specification, the disposition of the stops is governed by rotary cam means, said means being actuated by a rectilinearly moving member dependent on the movement of the cassette carriage. The apparatus has the form of a cast metal framework 1 having two square openings 2, 3. Through opening 2 the cassettes are loaded into a holder 12 in a carriage 4 which can move across to the other opening 3 where photographic exposures may be made. Movement of the carriage 4 is controlled by a pneumatically operated piston and cylinder assembly 16, the carriage moving one way or the other as pressurised air is admitted to one side or the other of the piston. A buffering device 13 acts as a shock-absorber. The carriage moves until it is arrested by one of two retractable stops 19, 20, or a further fixed stop (not shown) beyond 19. Stop 19 arrests the carriage in such a position that the film in the cassette lies symmetrically about the vertical plane through the centre of the X-ray beam passing through the fluorescent screen 5; stop 20 and the fixed stop arrest the carriage in such a position that one half or the other half of the film (that is, divided vertically) lies symmetrically about said vertical plane. The stops 19, 20 are normally spring-loaded into a retracted position, but are pushed into a forward (operative) position by the engagement of studs 29 with similar studs 30 on a rotatable shaft 23. The position of the shaft can be set initially by a spindle 33 operated by knob 34. At the end of shaft 23 is a star wheel 25 having six arms, which can be engaged by rollers, so that the shaft can be retained in six different positions. This end of the shaft 23 is coupled to shaft 39 (Fig. 4) which is connected to a barrel cam 38. On this cam are six longitudinally running slots; four of these are inclined, traversing a 60 degrees arc from one end to the other, and the remaining two slots are axial. The barrel cam, and consequently the shaft 23, is indexed round by a pneumatic cylinder 42, within which moves a piston rod 43, to which is secured a housing within which a projecting finger engages in one of the cam slots. Thus on the indexing stroke of piston 43, the cam, and thus shaft 23, is rotated by 60 degrees. On the return stroke, the finger is lifted out of engagement with the cam slot by a spring strip 48, until the end of the return stroke, when it re-engages with the next slot. The operations are controlled by pressing a button 10 on a handle 11. For a four-exposure sequence, the setting knob 34 is set accordingly, and button 10 is pressed. This admits air to cylinder 16, and the cassette is moved into engagement with stop 20, and the top left-hand quarter of the film lies ready for exposure, which is effected by further pressure on knob 10. When knob 10 is released, the cassette is retracted to its original position, and rod 23 indexed round 60 degrees, as described above. When knob 10 is pressed again, the cassette now moves into engagement with the fixed stop, so that the top right-hand quarter of the film lies ready for exposure. After retraction from this position, the cassette holder 12 is automatically sprung from its lower position in carriage 4, as shown in Fig. 1, to its upper position, and the previous sequences repeated, so that the bottom left-hand quarter and then the bottom right-hand quarter are exposed. If only a single exposure, or two exposures one vertically above the other, is required, stop 19 is used, and the finger is arranged to engage with an axial slot in the cam barrel, so that no rotation of shaft 23 occurs. Specification 744,793 also is referred to in the visional Specification.