Patent GB-747615-A (GB)
Title: Improvements relating to film winding mechanism for photographic cameras
Inventor: RUSSELL LIONEL VIVIAN FRANK
IPC: G03B19/04
Filed: 1953-03-18
Abstract: 747,615. Photographic roll film cameras. AERONAUTICAL & GENERAL INSTRUMENTS, Ltd. March 17, 1954 [March 18, 1953], No. 7515/53. Class 98(1). A film-winding mechanism for a camera comprises, for driving a film-winding spool, a driving member connected through a clutch to a hand-operated winding member; a cammember and a follower which are moved relatively to each other upon operation of the handoperated member and which co-operate to maintain the clutch in a disengaged condition for a portion of the movement of the handoperated member; and indexing mechanism which acts at each operation of the handoperated member to adjust the relationship between the cam-member and the follower so that, at each successive operation, the clutch is disengaged for a longer portion of the movement of the hand-operated member. As shown, a hand-operated lever 16 is secured to a plate 17 carrying a ring 23 having a semicircular flange 23A and fixed to a rotatable housing 25 bearing planet gears 26 (Fig. 4, not shown), meshing with a fixed internal gear ring 28 and a sun gear 29 connected to a clutch comprising a pivoted pawl 32 which is mounted on a plate 31 fixed to the sun gear and is in driving engagement with a ratchet wheel 35 on the film take-up spool driving shaft 5 which can be driven only clockwise due to a friction ratchet 7. Due to the epicyclic drive the plate 31 overtakes the inverted cup 22 so that the tail 37 of the pawl 32 rides up on to the cam 38, disengaging the drive to the shaft 5 and so stopping further film winding. A spring-urged pawl 18 pivoted at 19 on the plate 17 engages a sector gear 21 secured to an inverted cup 22 which is rotatably mounted in the ring 23 and has teeth 39 masked by the upstanding rim 40 of the ring except for a window 43 of length equal to two of the teeth 39. Just prior to the end of the movement of the lever 16 which is limited by the engagement of an arm 47 driven by a boss 50 on the rotatable housing 25 with stops 48, 49 (Fig. 5, not shown), on the fixed bearing 4 for the shaft 5, the window 43 comes opposite a pawl 41 in a fixed housing 15 so that the inverted cup 22 is arrested and the coupling 18, 21 slips so that the ring 23 moves on a distance equal to one tooth 39, thereby advancing the pawl tail 37 relatively to the cam 38 for the next operation, whereafter clockwise movement of the lever 16 is arrested. On return of the lever 16, under the action of a return spring (not shown), the mechanism 17, 22, 23, 25, 26, 29, 31, i.e. all except the ratchet wheel 35 and the shaft 5, freewheels back to its rest position. Thus, at each succeeding clockwise movement of the lever 16 the spool is rotated a slightly less amount to compensate for the increasing size of the roll. When the inverted cup 22 is arrested, the pawl 18 moves over one tooth of the sector 21 and the window 51 in the plate 17 moves over one unit on the exposure counting scale 52 on the inverted cup. When a new film is inserted in the camera the scale is reset by means of the fingerpiece 54. The arm 47 which limits. the clockwise movement of the lever 16 serves also to return to the viewing position the mirror in a reflex camera while a cable 45 attached to the housing 25 simultaneously sets the camera shutter.