Patent GB-576223-A (GB)
Title: Improvements in photographic hand cameras
IPC: G03B17/56
Filed: 1943-03-25
Abstract: 576,223. Photographic roll - film cameras. WOODCOCK, E. C., and WILLIAMSON, S. March 25,1943, No. 4850. [Class 98(i)] A hand camera, particularly for use on aircraft, having on each side a hand-grip one of which when twisted actuates the shutter-setting and film-feeding mechanisms, and having also film-feed and shutter release mechanisms interlocked so that they can only be operated alternately, has (1) a trigger lock pawl which after depression of the shutter trigger, prevents a second depression until the twist-grip has been operated ; (2) an additional interlock to prevent operation of either the twist-grip or the shutter trigger while the other is being operated ; and (3) a pressure plate operated by the twist-grip to press the film against the focal window during exposure and to release it when winding the film. The camera shown has a rear compartment 1, Fig. 2, enclosing a film cassette and take-up spool, a focal plane window 29 against which the film is pressed during exposure by a spring-biassed plate 26, and a removable rollerblind shutter mechanism 5, all these parts being accessible on removal of a side plate 4. A' second removable side plate 6 carries the film-feed and shutter-operating mechanisms, with the exception of the shutter-tension adjusting mechanism (not shown) which is carried by the plate 4. The camera has a fixed grip 7, and a twist grip 8 for feeding the film and winding the shutter, the grip 8 being carried by a disc 9 which is pivoted in the plate 6 and eccentrically supports a rotatable shutter trigger 18 so that this is carried round when the grip is twisted ; fixed to the hub 11 of this disc is a gear wheel 15 meshing with a pinion 44, Fig. 3, serving to wind the shutter 5, and also with a pinion 43 which turns on the spindle of the take-up spool and is fast with a disc carrying a feed pawl 35 adapted to rotate the spool through a snail cam 34 on the end of a sleeve intermediate between the spool and its spindle, there being provided also a spring- biassed spool-holding pawl 36. Provision is made on the wheel 15 for raising and releasing the pressure plate 26 by means of its supporting spring-biassed bell-crank lever 27 at the beginning and end respectively of the film feed movement. The wound shutter is held by a detent 39, Fig. 11, adapted to be released to make the exposure by a lever 41 on the shutter casing actuated by an adjustable screw 49 on a lever 48 mounted on the spindle of the shutter trigger 18, Fig. 2 before releasing the detent 39, the lever 41 through links 42 opens self-capping flaps in front of the focal window. In order to prevent actuation either of the grip 8 or of the trigger 18 while the other is being actuated, the plate 6 carries an arcuate rib 52 centred on the pivot of the. grip 8, and the shutter lever 48 carries a pin 53. When the camera is ready for exposure, the pin 53 lies as shown in Fig. 3, so that the rib 53 does not obstruct the pin when the trigger 18 is pressed ; pressure on the trigger causes the pin 53 to abut the end of the rib 52 so that the wheel 15 and grip disc 9 are thereby locked and the grip 8 cannot be actuated. On releasing the trigger, the pin 53 moves back clear of the end of the rib 52, and when the grip 8 is thereafter twisted, the pin 53 rides along the edge of the rib 52 so that depression of the trigger 18 during the movement is prevented. In order to ensure that the film feed and shutter release mechanisms shall only be operable alternately, there is provided a spring-biassed film-winding lock-pawl 55, Fig. 3, turning on the spindle of the trigger 18 and adapted to cooperate with a stop pin 54 on the plate 6 ; pawl 55 carries a pin 56 adapted to co-operate on the one hand with a wide notch in a spring-biassed shutter-trigger lock-pawl 57 pivoted on a plate 14 fast with the wheel 15, and on the other hand with a wide notch in the shutter release lever 48. In the position of the parts shown in Fig. 3, prior to exposure, the stop 54 locks the pawl 55 so that the grip 8 cannot be turned, but the pin 53 being free from the rib 52, the trigger 18 can be pressed to make the exposure. During the release of the shutter, rotation of the lever 48 causes a shoulder of the notch therein to displace the pin 56 and move the pawl 55 clear of the stop 54; and the pin 56 is held so displaced by the hooked end of the pawl 57 dropping over it. Thus when the trigger 12 is released and returns to normal position, pawl 57 maintains pawl 55 clear of the stop 54 ; and further, a tooth 61 on the shutter lever 48 moves into a position in which it is held by the notch in the pawl 57, so that the trigger cannot be depressed again. The grip 8 may now be twisted; its forward stroke, through gear wheels 15, 44, winds the shutter, but gear wheels 15, 43 merely cause the filmfeed pawl 35 to ride idly over the cam 34; the pressure plate 26 is, however raised by cam means and held by a catch ; at the end of the stroke a pin 64 on the wheel 15 displaces temporarily the film-spool holding pawl 36 from the cam 34 so that if desired the film may be wound back into its cassette for removal, and also the trigger lock-pawl 57 is turned by a pin 58 to cause it to release the pin 56 and set free the winding lock-pawl 55, and also to release the tooth 61 and set free the shutter lever 48. On its return stroke, the grip 8, through gear wheels 15, 43 and pawl 35 rotates the take-up spool to feed the film ; at the end of the stroke a pin on the wheel 15 disengages the catch - holding up the pressure plate 26 so that this descends upon the film, and also the pin 54 reengages the pawl 55 to prevent further actuation of the grip 8 until the shutter has been released. The camera has a sighting tube attached to one side.