Patent GB-654233-A (GB)
Title: Improvements in electrically-operated photographic roll film cameras
IPC: G03B9/08
Filed: 1945-01-26
Abstract: 654,233. Photographic roll film cameras. WILLIAMSON, S. Jan. 26, 1945, No. 2134. [Class 98 (i)] A camera suitable for aerial surveying has film-winding means provided with its own positively-coupled electrical drive and separately electrically-controlled means for holding the film in the exposure position and for controlling the shutter, the said drive and controlling means being electrically interconnected so that during each cycle of operations the positioning means releases the film before winding commences, repositions it when winding is completed and the film is not released during an exposure, while the winding means is in operation during a period determined by measuring means actuated by passage of the film. As shown, the camera comprises a body 1 containing an objective 2, a shutter 6, a shutter-operating electric motor 12, instrument board photographing means consisting of instrument 10, lamps 11 and objective 9, and film guide means 8; and a magazine 3 which is attachable to the back of the camera containing film spools 4, 5, an electric motor 20 driving the spool 5 through a clutch mechanism 21 and worm gear 22, a cam drum 29 which is gear-driven from a film measuring roller 19 and controls the length of film wound, and a pressure-plate 7 which holds the film against the guide 8 in the camera back. The movable relay arm 30, one lead of the electric motor 20 through a switch 39, the movable member of the switch 14a, and one lead of the electric motor 12 are connected to the positive lead of the electrical supply; and one end of each of the solenoids 13, 14, one side of one of the lamps 11, the other leads of motors 12, 20 and one end of the solenoid 37 through a switch 37b are connected to the negative supply lead. Starting with the circuits electrically dead and the film positioned ready for exposure as in Fig. 1, the mode of operation is as follows. On actuating an externally-situated pushbutton 43 current flows via contact arm 30, contact 31, plug-and-socket connection 41 (joining the circuits in the camera body and magazine), and the push-button switch 43 to emergize the solenoid 13 operating the shutter 6 by causing a member coupled to the shutteractuating member to clutch for one revolution with a fly-wheel constantly rotated by the motor 12, and closing a hold-on contact 13a which short-circuits the push-button. Simultaneously solenoid 14, connected in parallel with solenoid 13, is energized, closes contact 14a, lighting the lamps 11, and operates through a delay mechanism (not shown) a bellcrank lever 16 arranged to trip the movable arm of the relay at the end of the delay period, breaking the lamp circuit at 14c and closing contacts 14b, thus causing the solenoid 37 to be energized. The energization of the solenoid 37 breaks the contacts 37b, reducing the hold-on current by including further turns 37a and rotates spindle 34 anti-clockwise, which rotation first raises the pressure-plate 7 and then closes the motor-operating switch 39 and lets in the clutch 21, causing the film to be wound over. In doing this, the cam drum 29 is rotated, raising the arm 30 which breaks the contacts 31, rendering dead all the circuits (except motor 12) in the body 1, and closes contacts 32, thus maintaining the solenoid 37 energized. After one complete revolution of the drum 29 during which one picture length of film is wound, the arm 30 falls back into the cam groove, breaking the contacts 32 and thus de-energizing the solenoid 37, whereupon the clutch 21 is disengaged, stopping the film feed and shaft 34 turns clockwise, lowering the pressure-plate 7 and opening the switch 39 controlling the motor, which idles to rest. The cycle of operations is then complete. The motor 20 may be either series-wound with a dropping load-speed characteristic, thus winding the film at approximately constant rate throughout, or may have a variable resistor in the field coils controlled by a roller pressing against the film on the spool 5. In modifications the shutteractuating member may be operated directly by a solenoid and the intermittent illumination of meter 10 for recording purposes may be replaced by constant illumination of meter in association with a solenoid-operated shutter in front of the objective 9. Specification 654,232 is referred to. Reference has been directed by the Comptroller to Specification 599,077.