Patent GB-542303-A (GB)
Title: Improvements in or relating to roll film photographic cameras
IPC: G03B17/42
Filed: 1941-04-04
Abstract: 542,303. Roll-film photographic cameras. KODAK, Ltd. April 4, 1941, No. 4526. Convention date, May 3, 1940. [Class 98 (i)] In a roll-film camera in which the film is automatically wound by a motor drive unit after each exposure, a locking member for the motor drive is held in the inoperative position by means actuated through mechanical connections by the film winding mechanism, so that the locking member is released to engage the drive unit and stop rotation of the film winding mechanism after a pre-determined length of film has been wound. In the camera shown, a motor drive unit of the general construction described in Specification 513,768, and comprising a housing 23 'for the mechanism carried by a plate 24 the ends of which are curved to form the walls of the spool chambers, is detachably hinged to the camera body as described in that Specification. The spring motor 42 drives a crown gear 43 geared to the film-winding mechanism, and also drives a governor shaft on the end of which is a disc 40 carrying lugs 39. When the motor drive unit is attached, it is latched by sliding an external button 29 which moves a slidable latch bar 36 to the position shown in Fig. 8 ; when detaching the unit the bar 36 is first slid to the unlatched position shown in Fig. 3, in which a hook 37 on a depending arm of the bar engages one of the lugs 39 and so locks the motor mechanism. When the film is being wound by the motor a shaft 52, Figs. 5 and 13, which carries the film sprockets (not shown) makes a single revolution, carrying with it a disc 57 which is latched to the shaft by means of a pawl 58 pivoted at 59 and engaging a single tooth ratchet 56 on the shaft. A stub shaft carrying the disc 57 is geared to the shutter-tensioning shaft in the manner described for example in Specification 539,136, the shutter thus being wound. When the film is fully wound, the stud 59 on the disc 57 engages an ear 69 on a bar 70, Figs. 5, 7, which it moves to the right as seen in Fig. 7. An extension 106 of this bar then rocks a bellcrank lever 109 from the position shown in Fig. 8 to that shown in Fig. 3, raising a plunger 114 to release a second plunger 120 which bears on a slidable bar 97 upwardly urged by a spring 101. The bar 97 then rises, so that an offset portion 100 on it engages one of the lugs 59 and stops the motor. A second latch for the motor is formed by a lever 123, Fig. 5, which engages a notch in the bar 70 so that when the latter is moved to the right a lug 128 on the lever engages the shoulder 129 on the film sprocket shaft. The lug 69 is carried by a spring-pressed plate 89 pivoted to the rod 70 in order to cushion the blow when the stud 59 strikes it. On operation of the shutter release, a lever 84, Fig. 13, is swung by a link 82 so that a lug 86 on it engages the tail of the ratchet 58, so unlatching the disc 57 and allowing the shutter to operate. At the same time the stud 59 moves away from the ear 69, allowing springs 88 and 122 to return the bar 70, so depressing the plungers 114, 120 and the bar 97 to release the motor governor shaft, and also causing the lever 123, Fig. 5, to unlatch the film sprocket shaft. To prevent operation of the motor before completion of the exposure, a lug 86 on the lever 84 engages a lug 127 on the bar 70 and prevents the return of the latter until the release of the trigger. The motor then winds on the film until stopped as before. Before sliding the button 29 to unlatch the motor unit, it must be rotated until an arcuate portion of a cam groove 34 has slid over a fixed pin, and the latter is opposite a radial part of the groove. This causes a cam 130 to engage an inclined shoulder 131 on the bar 97, and the sliding movement of the button causes the cam to depress the bar to the inoperative position at the same time as the nose 37 on the bar 36 locks the governor shaft. An exposure-indicator dial 76 is rotated step-by-step by a pawl 74 carried by an upturned part 72 of the bar 70.