Patent GB-890689-A (GB)
Title: Improvements in or relating to x-ray apparatus
IPC: G03B42/02
Filed: 1958-08-13
Abstract: 890,689. X - ray spot film apparatus. SIEMENS-REINIGER-WERKE A.G. Aug. 13, 1958 [Aug. 21, 1957], No. 26031/58. Class 98(1). An X-ray spot film device arranged to arrest a cassette fitted thereto in different positions for exposure comprises a cassette carrier, electromagnetic means for limiting the path of movement of the cassette carrier and holding a cassette carried thereby in the desired position for exposure, a circuit for energizing said electromagnetic means, switchin contacts connected in parallel in said energizing circuit, operating elements for said switch-in contacts projecting into the path of the cassette carrier in different positions corresponding to the desired exposure positions, and a mechanism for selecting from the parallel-connected switch-in contacts that switch-in contact which is to become effective for a chosen exposure position. As shown the cassette carriage 8 is slidably mounted on rails 9, 10 in a frame for movement between a ready position shown in dotted lines and an exposure position between the patient and a fluorescent screen, the frame itself being movable relative to a support for the patient. The carriage 8 carries an armature bar 12 co-operating with an electromagnet 11 and a trip cam 13 for engaging switch-in contact operating plungers A, B, C. For single exposures, switch bar 14 is closed on to contact 15. Thereupon on moving the carriage 8 from the ready position, movement of plunger A has no effect so that the carriage moves on for cam 13 to push up plunger B as shown, closing contacts b 1 , b 2  and so energizing magnet 11 which arrests the carriage and simultaneously energizing relay D to close a contact d 1  in the X-ray exposure circuit. On operation of the exposure button (Fig. 1 not 'shown) relay E is energized and in turn energizes relay F whereby the magnet circuit is maintained over contact e 1  before that through b 1 , f 2  is broken and a signal lamp 19 is lit via contact f 3 . At the end of the exposure contacts e 1 , e 2  open, de-energizing magnet 11 and freeing the carriage 8, but relay F remains energized through hold-on contact f 1  to prevent plunger B energizing the magnet again and so, by virtue of contact d, being open, preventing a double exposure. Due to contact 16 being open accidental operation of plunger C has no effect. On returning the carriage 8 to the ready position and removing the cassette 7, switch 18 is opened, de-energizing relay F. For serial radiography, e.g. in which two separate sideby-side exposures are made within the area of a single cassette, the switch bar 14 is moved on to contact 16 rendering plunger B ineffective. The carriage 8 is then first arrested by operation of plunger A and after an exposure has been made, as indicated by lamp 19, the cassette carriage is moved further to the left and is again arrested by operation of plunger C. When the second exposure is 'made relay G is energized through contact C 2  in the same way as relay F was via contact a 2  and so lights lamp 20 over contact g 3  and prevents further exposure. If separate pairs of exposures are to be made on the upper and lower halves of the cassette film, the cassette is arranged to be movable vertically in the carriage, such movement momentarily opening a switch 21 to de-energize relay G to permit a second series of exposures. By the provision of further plunger-controlled contacts of three or more side-by-side radiographs may be obtained. If cassettes of two different sizes are employed, a movable lateral framing bar (Fig. 3 not shown) is provided having a nut engaging in a spiral guide on a sleeve fixed axially on the cassette carriage and slidable on a square shaft along the bottom of the carriage guiding frame, movement of the framing bar rotating the shaft. Two sets of plungers, one for each cassette size and each with its own operating circuit as in Fig. 2, are provided and the rotation of the shaft operates a selector switch in accordance with the size of cassette inserted in the carriage. A doublepole double-throw with one pole connected to each operating circuit (cp switch bar 14 and contacts 15, 16) permits selection of either single or serial radiograph operation. By providing further sets of plungers and operating circuits and arranging for the square shaft operated switch to have more contacts, three or more cassette sizes may be accommodated. In order that the arresting of the cassette carrier may be effected smoothly, the carrier 41 is moved by being attached to one run of an endless cord 45 trained over pulleys 46, 47 and driven through a slip clutch 48 from an electric motor 49 energized by press button 50 while the carriage 56 for the magnet 43 co-operating with the armature 42 on the carriage is mounted for sliding movement against a return spring 58 until engaged by an abutment 63. Movement of the magnet which is carried along by the cassette carrier operates via rack 59 and pinion 60 a variable resistor 62 in parallel with the armature of the motor 49 so that by suitable design of the resistor a sinusoidal braking effect is applied to the holder 41. When the magnet carriage presses against the abulment 63 contacts 64 are closed to initiate the exposure. On release of the button 50 the motor 49 is reversed to return the cassette carrier to the rest position in which it opens contacts 65 to stop the motor.