Patent GB-681050-A (GB)
Title: Improvements in x-ray apparatus
IPC: G03B42/02
Filed: 1950-08-17
Abstract: 681,050. X - ray apparatus. NEWTON VICTOR, Ltd. Aug. 17, 1950 [Nov. 3, 19491, No. 20463/50. Class 98 (i). In X-ray apparatus comprising a carriage arranged in a frame for longitudinal movement between a projected position in which an X-ray image of an object under examination can be recorded on photographic material supported on the carriage and a position in which the carriage is retracted to allow the X-ray image to be received on a fluorescent screen mounted on the frame in alignment with the projected position of the carriage in the direction of the X-rays, there are provided a number of tracks for guiding the longitudinal movement of the carriage which guide tracks are spaced apart transversely of the direction of the longitudinal movement and are selectively engaged to guide the carriage into a desired transverse setting in its projected position together with a number of selectively operated stops for stopping the carriage in desired longitudinal settings in the projected position. The carriage may have a follower engaging the tracks and selecting means to guide the follower into a selected track. Preferably the tracks, at their ends remote from the projected position, converge towards a point, and a transfer section of the guide track is pivoted about that point. As shown, Fig. 3, a table comprising a frame 26 and top panel 24 is supported at one side only by a pedestal 25 for tilting in the manner described in Specification 657,166. A support 27 for a Bucky grid and a cassette runs on tracks just below panel 24. A carriage 34 also runs on tracks along the table frame 26, and itself has tracks in which a member 36 runs, laterally with respect to the table. Preferably, an X-ray tube 37 is carried by member 36. A member 45 runs on vertical guides 42 carried by member 36, and carries horizontal guides 46 for a member 47 in which the fluorescent screen and the photographic material are mounted. Member 47 is movable between two positions, one over the table and the other clear of the table. The screen and cassette holder 47, Fig. 5, comprises a rectangular frame with a bay 5, formed at one end, and formed with a lip around the top. The rear part of the top is covered by a panel 55 with an opening 58 for insertion of a cassette, while the fluorescent screen 60 is mounted in the front part. The bottom of the holder is closed by a laminated panel having inner and outer sheets of steel and aluminium respectively and an intermediate sheet of lead, the steel and lead sheets having apertures registering with the screen 60. Grooves 50 in the sides of the frame, and a groove 68 in the top thereof, engage pins on guides 46. The holder 47 is held in its two positions by a latch released by pressing a button 69. The movable cassette holder, Fig. 9, comprises a carriage 74 for holding the cassette, which rolls on rails 84 of a sub-carriage 83 movable on rollers 86 on rails 87 fixed to the base-plate of the holder 47. Sub-carriage 83 is drawn to the left by a cord 88 passing over a pulley system and tightened by a spring 89. It also has a bracket 94 with a pin 95 extending through a slot 96 in the top of the holder (Fig. 5) having a handle 97, whereby the sub-carriage can be moved to the right, clear of the screen, in which position it is held by a nose 98 on bracket 94 which engages a catch 99. On release of this catch by depression of a button, the subcarriage moves to the left, its speed being limited by a dashpot comprising a piston-rod 107, fixed to the sub-carriage, and a cylinder 108. During movement, carriage 74 is guided into one of three positions on rails 84 by means of a roller 82 on a bracket 81 fixed to the frame of the carriage, which roller travels in one of three guide grooves 112, 113, 114 formed in a plate mounted on the base of holder 47. In the left-hand position of sub-carriage 83, roller 82 engages a groove 116 in a plate 115 which is pivoted at 117 so that groove 116 may be brought into register with any of grooves 112, 113, 114. Sub-carriage 83 may be stopped in three positions. For this purpose, levers 124, 127, 156 are pivoted to the bottom of holder 47. Lever 124 carries a pin 121 to one end, and is forked at the other end to engage a pin 122 on lever 127. A pin on the other end of lever 127 is engaged by a fork on the end of lever 156. As shown, pin 122 is in the path of a bracket 120 on the sub-carriage 83 to stop it on release of catch 99. The levers may be rocked to bring them into a straight line with both pins 121, 122 out of the path of bracket 120; in this case the sub-carriage is not stopped until pin 95 reaches the end of slot 96. By rocking the levers further, pin 121 is brought into the path of bracket 120. When groove 113 and stop pin 121 are in action, the cassette, at the end of its travel, is centred on the fluorescent screen. When parts of the photographic material, e.g. halves (divided in either direction) or quarters, are separately exposed, the part to be exposed can be centred on the fluorescent screen by bringing the appropriate groove and stop into action. A square-leaf diaphragm 39 (Fig. 3) is provided to limit the beam of X-rays to the area of the photographic material to be exposed, and is controlled by concentric knobs 130, 131 (Fig. 5). Knob 130 actuates a lever 136 (Fig. 9) linked to a lever 140 on a hollow shaft 142, in which a rod (not shown) is splined to allow for movement of holder 47 in the guides 46. By means of further rods and levers, including a splined connection to allow for vertical movement of the supporting member 45, movement of knob 130 is connected to the diaphragm and causes one pair of plates to open and close. By similar means knob 131 causes the other pair of plates to open and close. Sequential selection of cassette position is effected by means of mechanism controlled by a concentrically-mounted knob 149 and lever 150, Fig. 9. Lever 156 is normally urged by a spring into the position shown, but when lever 150 is rocked, a cam 154 thereon engages a roller on lever 156, rocking the levers 156, 127, 124 to bring pin 121 into operation to stop subcarriage 83 in a position centred on the fluorescent screen. When the lever 150 is returned, the lever system is controlled by mechanism on the shaft of knob 149, comprising a cam disc 161, Fig. 21, an index wheel 162, and a toothed wheel 163. A lever 180 pivoted at 181 is spring-urged to engage at one end depressions 162<SP>11</SP> formed in the index wheel 162, and to bear at the other end on a lever 172 pivoted at 173. A pawl 170, pivoted at 171 to lever 172, is urged by spring 174 to engage the depressions in the index wheel 162. When sub-carriage 83 is moved to the right, a stop 179 thereon (Fig. 9) engages a pin 175 on lever 172 and turns it about its pivot. This raises lever 180 from wheel 162, freeing it for movement by pawl 170. When the sub-carriage is released, levers 172, 180 return; during this movement a pin 187 on pawl 170 rides over a leaf-spring 188, lifting the pawl from the index-wheel. A pawl 184<SP>1</SP> prevents reverse rotation of the wheel. At each movement of pawl 170 cam 161, index wheel 162, and wheel 163 turn through one-eighth of a revolution, and a wheel 190 in mesh with wheel 163 turns through half a revolution. A disc 192 fast with wheel 190 is linked by a rod 194 to the plate 115 (Fig. 9). According to the initial position of wheel 163, which is adjustable by knob 149, the plate 115 will be swung at each operation, either from and back to a central position, or between to extreme positions. In the first case groove 116 is always brought in line with groove 113, and carriage 74 is always brought to a central position on sub-carriage 83. In the second case groove 116 is brought in line with grooves 112, 114 alternately, and the carriage 74 is brought alternately to one of its extreme positions on the sub-carriage. When lever 156 is released by cam 154, the roller 155 on its end is urged against cam 161, which is so shaped that the lever system moves between a straight-line position in which sub-carriage 83 is free to move to the end of its travel, and a position in which the sub-carriage is stopped by engagement of bracket 120 with pin 122. As cam 161 has sixteen points which roller 155 may engage, and the cam moves through one-eighth of a revolution at a time, two sequences of operation are possible; one in which pin 122 is brought into and out of the path of bracket 120 alternately, and one in which pin 122 is in said path for two successive movements of the cam and out of said path for the next two movements, and so on. Also by operation of lever 150 pin 121 may be brought into said path. By proper adjustment of knob 149 and lever 150, radiographs may be made sequentially (1) on the whole of the cassette area, (2) on halves of the cassette area, the area being divided either longitudinally or laterally, or (3) on quarters of the cassette area. A dial 165, Fig. 9, fast with cam 161, bears graduations visible through a selected aperture 211 on a plate fast with cam 154 and a window 166 (Figs. 5 and 9) to facilitate the initial setting. An electrical circuit is provided for controlling the tube voltage and lights during radioscopy and radiography. A switch 216, Fig. 9, mounted in the holder 47 is operated by roller 82 on carriage 74 to increase the voltage for the X-ray tube for radioscopy, whenever the carriage is in its right-hand position, and to reduce the voltage for radiography when the carriage moves away. The tube may be energized as by a foot switch. A switch 213 (Fig..5) ensures that external lights are switched off when the tube is switched on, and vice versa.