Patent GB-717910-A (GB)
Title: Photographic roll film cameras
IPC: G03B17/42
Filed: 1951-02-13
Abstract: 717,910. Photographic roll-film cameras. FRYE, J. Feb. 13, 1951 [March 8, 1950], No. 3501/51. Class 98(1) A roll-film camera comprises a hinged cover extending over the exposure gate between the supply magazine and tak-up storage compartments and bearing film transporting means extending into the camera body, a locking means for said cover a manual release for said locking means, a film rewinding mechanism tensioned by actuation of the film transporting means, and an interlock between said locking means and the rewind mechanism for holding said locking means while the rewind mechanism is in the tensioned position and for releasing the said locking means in the rewound position of the rewind mechanism. As shown, the camera back 16, which is hinged to the body at 35 and closed by a latch 36 on the body engaging a catch 22 on the body, carries a pair of claws 25 mounted by leaf springs 72 on a bar 68 having a boss 67 guided in a slot extending longitudinally of the back and engaged in a forked member 66 secured to a film winding lever 26, the claws protruding through longitudinal slots in a film presser plate 19 to engage the marginal film feed perforations whereby the film is fed from a light tight supply casette in a chamber 18<SP>1</SP> across the exposure gate 17 to a receiving chamber having a film-coiling leaf spring upon each anti-clockwise (as seen in Fig. 4) rotation of the lever 26. At the end of each such movement, a lug 77 on the fork 66 rotates clockwise one tooth a one way ratchet wheel 74 and with it an exposure counter 27 co-operating with a fixed index on the back, the claws trailing across the film as the lever 26 returns clockwise to rest. Each film feeding movement of the lever 26 tensions a helical spring 51 fixed to the body at 52 and to a rotatable shell 54 having a key 90 engaging in a key slot in the supply cassette spool, rewinding of the film into the cassette being prevented by a spring brake 60 gripping the shell 54 and opposing its anticlockwise rotation, spring 60 being more powerful than spring 51. Prior to feeding the film, a slide bar 43 may be moved freely against its spring 46, but once the first film frame is fed, an eccentric 55 on the spring 51 allows an anti-clockwise urged lever 57 to move a bolt 58 behind a lug 59 on the slide to restrict its movement to the right. Moving the slide to the right then only releases the brake 60 which is connected at one end to a bar 61 carried by the slide, whereupon the spring 51 rewinds the film into the supply cassette, the speed of rewinding being controlled by a centrifugal governor comprising pivoted pawls 83 on the shell 54 engaging the inside of a fixed drum 82. Simultaneously with the release of the brake, the slide rotates pivoted levers 49 which move the presser plate clear of the film. When the film has been rewound, the spring 51 returns to the position shown so that its eccentric 55 rotates the lever 57 to withdraw the bolt 58, allowing the slide to be moved fully to the right to open the camera by cam 41 depressing the extension 40 on the latch 36. The total movement of the film and the tensioning and unwinding of spring 51 are limited by a disc 86 movable as a nut along a stationary threaded pin 79 between two fixed discs 89 and having two notches engaged by keys 88 on the inside of the shell 54. To permit manual rewinding if the spring motor fails and to ensure proper engagement of the key 90 and cassette spool slot, a spindle 93 having an external knob extends through the pin 79 and has a key 92 engageable in a recess 91 in the shell 54, the key 92 normally being held clear of the recess by a spring 95 between the body 15 and the knob 94. The spool cassette may carry numerals corresponding to the total number of exposures possible and erasable to indicate the number remaining if the film is rewound before the whole of it is exposed. A disc 27<SP>1</SP> for indicating the kind of film in use may be provided.