Patent GB-537914-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/42
Filed: 1940-08-26
Abstract: 537,914. Photographic shutters. KODAK, Ltd. Aug. 26, 1940, No. 13472. Convention date, Jan. 4. [Class 98 (i)] A photographic shutter comprises a pair of slidable plates 17, 18 held in set position against the tension of a spring 20 and means for releasing them one after the other including a slidable mount 67 carrying a retard gear train and means to move it to position a toothed wheel 65a of the train so as to be engaged by a toothed member carried by the following plate 18 when a slow automatic exposure is required. The camera shown is of the type described in Specification 534,063, in which the sliding shutter plates 17, 18 move in rails 16 carried by a plate 15 at the front of the camera, and have rearward extensions 17a, 19 the rear edges of which are spaced apart during the exposure to form a slot adjacent to and travelling across, the exposure opening 7. The spring 20 is held by a lug on an adjustable washer 27, so that by adjusting the washer, or by engaging the lug between different convolutions of the spring, the shutter plates may be moved at the same speed. The shutter is set by a lever 30 which is rocked in a clockwise direction by mechanism operated from the film-winding means and which engages the top of a lever 31 the lower end of which is thus caused to engage a pin 34 on the plate 17, which it moves to the left, pushing the plate 18 in front of it. The plate 17 is latched by a lever 37 engaging a lug 35 on it and the plate 18 by the hooked end 42 of a telescopic arm 43, 44, which engages a lug 41. In making a fast automatic exposure, operation of the release 39 swings the lever 37 to unlatch the leading plate 17, which then moves alone until the lug 35 engages a lug 45 on the arm 44, so rocking the arm about its pivot 46 and unlatching the following plate 18. Rotation of a speed-adjusting dial causes a gear 54 through intermediate gears to rotate a gear 51 concentric with the pivot 46 of the telescopic arm 43, 44, this gear engaging a rack on the upper edge of a slot of the part 44. The part 44 is thus adjusted longitudinally, sliding within the part 43, so varying the position of the lug 45 and hence the extent of movement of the plate 17 before release of the plate 18. When the dial is adjusted for a slow automatic exposure the part 44 is fully extended, as shown, so that the plate 17 fully uncovers the aperture before release of the plate 18. A mutilated portion of the gear 54 prevents further movement of the part 44 in the slow speed range of adjustment, during which a stepped cam 76 swings a lever 74, 72 having a forked end engaging a pin on the retard gear mount 67, which is thus adjusted in a horizontal direction in order to bring the ratchet wheel 65a of the train into engagement with a selected point of a rack on an arm 78 pivoted on the blade 18, The initial movement of the blade is therefore retarded before it moves sufficiently to commence the closure of the exposure opening 7. As above explained, the shutter is set by a rocking movement of the lever 30. This is produced by a link 95 pivoted to it and to a gear 94 driven from a gear 97 turned by the filmwinding knob. The film passes over a measuring sprocket 8, a pin 85 on which engages a.lug 86 on an arm 90 to arrest further movement when a new length has been wound. At the same time a mutilated portion of the gear 94 comes opposite the gear 97. Operation of the shutter release depresses the arm 90, which frees the sprocket 8 and also the gear 94, previously held by a lug 91 on the arm engaging a shoulder 92 on a washer 93 secured to the gear. The link 95, under the action of a spring 96 then partially rotates the gear 94 until the toothed portion again engages the gear 97 in readiness for the film to be again wound.