Patent GB-553949-A (GB)
Title: Improvements in or relating to photographic cameras
IPC: G03B27/58
Filed: 1941-09-09
Abstract: 553,949. Photographic cameras. WATSON & SONS, Ltd., W., PERKINS, S., and FRY, C. H. Sept 9, 1941, No. 11500. [Class 98 (i)] A photographic camera comprises a shutter the opening and closing of which are controlled in succession by two electromagnets arranged to operate at an interval determined automatically (for example by an electric timing device) or at will, a shaft driven by an electric motor which is energized by the switch operated on the closing of the shutter and de-energized after a predetermined rotation of the shaft, and film feeding and shutter-setting means operable by the motor-driven shaft. The camera shown comprises a two-plate shutter, a movable mask for reducing the area of the film exposed, and means for automatically adjusting the feed of film to the exposure area similar to those described in Specification 528,851. A detachable film magazine 12 is secured to the top of a lever housing 10 by clamps 16, the film passing from a spool 18 to a driven sprocket 20, against which it is held by grooved spindles 26 carried by a spring blade 27, then below a pressure plate 21 to a second driven sprocket 22, and finally to a take-up spool 23 driven through a slipping clutch. The sprockets and take-up spool are driven from a pinion 33 which projects through the base of the magazine and engages a gear 38 in the lower housing. The driving motor (not shown) rotates through reduction gearing a mutilated pinion 42, Fig. 8, which engages a segment wheel 43 carried on a shaft 44 and urged in a counterclockwise direction by a coiled spring. Prior to the filmfeeding operation the pinion 42 engages the tooth 48, the adjacent tooth being removed to ensure that the pinion tooth bears correctly on the tooth 48 when the motor is switched on. The motor rotates the segment wheel clockwise to the position shown, during which movement the film is fed, and the segment which is then released by the mutilation of the pinion and is returned by the spring until a land 46 formed on it engages a spring buffer 47. Subsequently a cam 50 carried by the pinion 42 engages a contact spring 51 and completes the circuit of a solenoid which opens a switch controlling the motor circuit, the parts then being in readiness for a further film-feeding operation. The film is fed, during the rotation of the shaft 44 by the motor, by a ratchet and pawl drive 52, 53 to a gear 54 which rotates the gear 38 through a variable ratio-mechanism. This mechanism comprises two idler gears 94, 95 engaging the gear 54 and carried on a frame 96 pivoted on the shaft 44. When the mechanism is adjusted for taking full-size exposures, as shown in Fig. 2, the gear 94 engages the smaller gear 98 of a compound gear 98, 38. To adjust the camera for exposure of smaller size an external knob on a shaft 116 is rotated to cause a cam 115 operating in an opening in a link 111 pivoted to the frame 96 to lower the link, swinging the frame 96 anticlockwise so that the gear 94 disengages the gear 98 and the gear 95 engages the larger gear 38, thus diminishing the length of film fed. At the same time a sliding mask 100 is moved by links 104, 106, 107, the last of which has a pin and slot connection to the frame 96, so that an opening 101 in the mask is substituted for the full-size exposure opening 41. The frame 96 is latched in each of its alternative positions by a lever 118 operated by a cam 117 on the shaft 116 and having a tooth 120 engaging either of a pair of notches in the edge of the frame. The shutter shown in its set position in Fig. 4, comprises two sliding plates 60, 65 carrying pins 61, 66 engaging holes in the turned-over ends of arms 62, 67 which are urged to the left by springs 64, 69. During the film-feeding operation a pin 70 on a disc carried by the motor-driven shaft 44, and engaging in a slot in a link 73 pivoted to the arm 62, moves the arm to the right, together with the plate 60, which drives the plate 65 before it. In the set position the plate 60 is latched by a pivoted arm 76 which engages a lug 82 on it, and is connected to the pivoted armature 79 of an electromagnet 80. The plate 65 is latched by the armature 84 of an electromagnet 85, which engages the pin 66. On completion of a starting circuit by a remotely-situated finger button the coil 80 is energized and operates the arm 76 to release the plate 60, which is then moved by the arm 62 to initiate the exposure. At the same time an arm 132 on the armature 79 closes contacts which complete the circuit of an electric timing device which, after a set interval, closes a circuit including the magnet coil 85, which then unlatches the shutter blade 65 to terminate the exposure. The " on " coil of an electromagnetic switch controlling the circuit of the film-winding and shutter-setting motor is simultaneously energized, the motor then operating until the "off" coil is energized by the contacts 50, 51, Fig. 8, at the termination of the operation. A bank of lamps for illuminating the copy is fed through a dimming resistance except during the exposure, when the resistance is shorted by a mercury switch the operating coil of which is energized and de-energized on completion respectively of the circuits for initiating and terminating the exposure. The electrical timing device may be of any known kind, or a clockwork device started by the completion of the circuit for initiating the exposure may be used. In either case the timer may be put out of action and the closing circuit completed by hand. An exposure-counter 87 is actuated by a crank 88 on the shaft 44, which moves a slide 89 coupled by wires and a bellcrank lever to the counter.