Patent GB-961969-A (GB)
Title: Film counting mechanism for photographic cameras
IPC: G03B1/66
Filed: 1960-07-04
Abstract: 961,969. Photographic cameras; exposure counters. VOIGTLANDER A. G. July 4, 1960 [July 2, 1959], No. 23351/60. Heading G2A. In a photographic camera having a counter indicating the supply of film available, the scale carrier of which is moved against spring action in the counting direction, the spring always bringing it back to the same starting position when the rear wall of the camera is opened, a scale carrier carries a single scale readable against an index mark at at least two reading positions and arranged to be readable at only one of the said reading positions at any one time. As shown (Fig. 3)the counter comprises a counter disc 37 which together with a saw-toothed wheel 24 is mounted on a hub 35 freely rotatable on a bush 36 secured to a wall 14 in the lower part of a camera. The bush 36 also provides a bearing for the spindle 5 of a quick-feed lever 4 which is coupled to a sprocketed film-feed roller 10 by way of a gear wheel 6 rigid with said spindle 5, a one-way ratchet device comprising a spring-urged pawl 7 on a freely rotatable gear wheel 8, and also by way of gear wheels 9. The take-up spool 12 is freely rotatable on the spindle 5. The wheel 24 of the counter is constantly urged towards the starting position by a spring 26, is normally prevented from returning thereto by means of a spring-urged pawl 27 (Fig. 2) and is advanced by one tooth at each operation of the lever 4 by means of mechanism comprising a spring-urged pawl 19 which is pivoted with the aid of a slot 20 about a fixed pin 21 and has a tooth 23 for engagement with the teeth of wheel 24, and a gear wheel 17 which is coupled by way of gears 15 and 16 to the shaft 13 of the roller 10, is made to rotate through half a revolution for each operation of the lever 4, and carries two projections 18 which engage and displace the pawl 19 to bring the tooth 23 into driving engagement with the teeth of wheel 24. The disc 37 is numbered so as to indicate the supply of film still available, and in order that the camera may be used with films of different lengths two spaced index marks 38 and 39 are provided together with two co-operating reading windows 40 and 41 (Fig. 1, not shown) in the cap portion of the lever 4. A cover disc 42 in the cap portion of the lever 4 is arranged so as to allow only one of said windows to be open at a time, has a projection 43 for adjustment thereof, and may be arranged to display in that window which is closed a number indicating the length of the film in the camera. The pawl 27 is carried by a spring-urged lever 29 which, when the back 3 of the camera is opened and the projection 33 is removed therefrom, removes the pawl 27 from engagement with the teeth of the wheel 24 and allows the counter to return to its starting position. In modifications, the gear wheel 17 may be arranged to rotate through a whole revolution for each operation of the lever 4 and more than two index marks and reading windows may be provided. In an alternative embodiment (Fig. 4 not shown) the counter disc is arranged under a cap other than that of the winding lever 4, a single reading window is provided in this cap, and a single index mark is provided on a ring which is adjustable to either of two positions according to the length of the film loaded into the camera.