Patent GB-557664-A (GB)
Title: Improvements in or relating to roll film cameras particularly stereo cameras with film feed locking mechanism
IPC: G03B35/10
Filed: 1942-10-28
Abstract: 557,664. Roll-film cameras. KODAK, Ltd. Oct. 28, 1942, No. 15108. Convention date, Oct. 28, 1941. [Classes 98 (i) and 98 (ii)] A roll-film camera of the kind in which film-measuring means engaging and operated by the film are operatively connected with a control member which permits operation of a film feed locking device when a pre-determined length of film has been wound, is provided with rotatable means capable of being manually pre-set to disconnect the control member from the film-measuring means to render it inoperative during winding of a leader strip of the film, the control member being rotated relatively to the rotatable means during winding of the leader strip and thereafter rotating with it to permit the operation of the filmfeed locking means. The invention is described as applied to a twin-lens stereoscopic camera having a pair of spaced exposure apertures and so arranged that the frames forming each pair on the film are separated by one frame of the preceding or succeeding exposure. Thus, after the first exposure the film must be fed through a distance corresponding to one frame, and after the second exposure through a distance of three frames, and so on alternately. The film-winding, shuttersetting and shutter-releasing means are interlocked so that they can be operated only in correct sequence, provision for intentional double exposures being made. The means for locking the film-winding device comprises a locking-bar 20 slidably mounted on a pair of studs 21, and provided at the left-hand end with a pawl 27 to engage a ratchet 28 on the film-winding shaft. The bar is held, against the action of a spring 29, in the now locking position shown by a lug 49 which bears on the edge of a disc 33. As the film is wound the disc is rotated through a gear train from a shaft 46, which is rotated by a sprocket 47 engaging the film perforations, until the lug 49 falls into the next one of two slots 35, 36 in the disc, when the bar 20 moves to the left and locks the winding-spindle. The slots 35, 36 are spaced 90 degrees apart, so that the length of film fed corresponds alternately to one frame and three frames. As the bar 20 moves to the left a tooth 125 formd on a bell-crank lever 65 pivoted at 66 on the bar engages a lug 121 on a blocking member 117, which is thus rotated anticlockwise from the position shown to withdraw a portion 122 from the path of a shutter-setting lever 108, so that the shutters may now be set. The bar 20 is latched in locking position by a lug 69 on the lever 65 engaging the left-hand side of a fixed stop 71. Operation of the shutter release arm 75 imparts a small clockwise movement to a trip plate 79, which releases the shutter and also carries a lug 82 which engages a lug 83 depending from the lever 65, so rocking this lever in an anti-clockwise direction. This movement releases the blocking-member 117 from the tooth 125, the member being then returned by a spring to the position shown, in which it prevents a second operation of the shutter-setting lever, and also in which the lug 121 lies under the tooth 125 and holds the lever 65 with the lug 69 out of engagement with the stop 71. The bar 20 may now be moved to the right to the position shown, to allow. the film to be fed, by pressure on a button 85, which rocks a bell-crank lever 87 one arm of which carries a pin 89 which engages an offset extension 91 of the bar. To prevent re-entry of the lug 49 on the bar into the slot in the locking disc 33 when the button 85 is released, the slot in the bar engaged by the left-hand stud 21 is widened at the left-hand end, so that the spring 29 causes the bar at the end of its travel to the right to swing slightly about the right-hand stud 21, bringing the lug 49 out of register with the slot. The film may now be wound until the lug engages the next slot and causes the operation of the locking-bar 20. To prevent operation of the shutter-release until the shutter has been set a catch 135 on a lever 133 engages in a notch on the end of the trip plate 79 and restrains it from movement except when the shutter is set, the lever being then rocked to unlatch it by a cam on the shuttersetting shaft 100, which engages the other end of the lever. The shutter is set by depressing a crank arm 106, which raises the lever 108 together with a rod 110 pivoted to it, a pin on this rod engaging a cam 114 on the setting shaft and rocking it counterclockwise. A similar second shutter (not shown) for the second lens is connected to the first so as to be simultaneously set and released. A second exposure may be made without winding on the film by operating an external lever (not shown) which rotates the blocking member to its inoperative position, the member automatically returning to the operative position after the second exposure. To prevent locking of the filmfeeding mechanism while the leader-strip of the film is being wound, a cam 52 is rotated by an external knob to the position shown in Fig. 11, in which it masks the slots 35, 36 in the locking disc 33, which is also turned to the correct starting position by the engagement of the edge of the cam with a pin 58 on it. When the film is wound the lug 49 engages the edge of the cam and holds it still until the disc 33 has rotated sufficiently to unmask the slots. The pin 58 then engages a shoulder 59 on the cam, which then rotates with the disc during the winding up of the final portion of the leader strip. An exposure counter is operated by a ratchet 95 engaged at each operation of the locking bar by a pawl 92 on the latter.