Patent GB-661893-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/14
Filed: 1949-01-03
Abstract: 661,893. Photographic shutters. KODAK, Ltd. Jan. 3, 1949 [Jan. 7, 1948], No. 84/49. Class 98 (i). A shutter comprises an apertured casing containing a pair of pivotally mounted apertured shutter blades interconnected so as to move in opposite directions across an exposure aperture, a pivotally mounted release trigger directly carrying a cover blade which in the rest position covers the exposure aperture so that the shutter blades may uncover the aperture while they are moved by a setting lever against a spring to a set position in which they are retained by the engagement between a surface on one shutter blade and a surface on the release trigger until the latter is actuated, the coacting surfaces remaining engaged during the first part of the releasing movement of the trigger when the cover blade is moved clear of the aperture, and being disengaged in the second part of the trigger movement to allow the spring to move the blades across the aperture to effect an exposure, and a spring for returning the cover blade to its position covering the exposure aperture. The shutter may also include a speed-setting arm movable in the casing for controlling instantaneous or bulb exposures, and coacting parts on said arm and the trigger for moving the latter to an inoperative position when the arm is set for a bulb exposure, so that the shutter blades are operated by the setting lever to effect a bulb exposure. As shown, shutter blades 16, 17 having apertures 18, 19 are pivoted on the casing 3 at 23, 24 and are pin-and-slot connected at 25, 26.so that on moving clockwise the setting lever 27 integral with the blade 17 the blade driving spring 20 attached between lugs on the two blades is tensioned and the shutter is held set by a bevelled lug 28 on the blade 17 passing beneath and engaging behind a flange 29 arranged concentrically with the pivot 31 on the pivoted release trigger 7 which is formed integrally with a cover blade 30 covering the exposure aperture 4. The shutter is released by moving the trigger and the cover blade 30 anticlockwise either manually or by a flexible cable release engaging a flange 34 when the lug 28 rides off the flange 29. A pallet wheel 48 pivoted on a clockwise-urged lever 45 is adapted to engage with the toothed edge 50 of the blade 17 to produce slower exposures. With the speed setting lever 40 pivoted at 38 in the position shown, an arm 43 on the lever holds the pallet out of action but as the arm is moved clockwise from that setting an increasing delay is introduced until the lever reaches the bulb exposure setting. After a slow instantaneous exposure has been made the return movement of the trigger! moves the pallet away from the teeth 50 by the flange 29 engaging the lug 49 on the lever 45 thereby permitting unhampered cocking of the shutter. The shutter being unset, when the lever 40 is turned clockwise to the righthand end of the slot 11, the nose 44 on the lever 40 engages the tail 56 of the lever 45 moving the pallet away from the blade 17 and a lug 41 on the lever 40 engages a pin 55 on the trigger which is moved to and held in an inoperative position with the cover blade clear of the aperture. A bulb exposure may then be made by depression of the setting lever 27 either manually or by means of a cable release, the apertures in the blades, being located in register over the exposure aperture 4 by one edge of the blade 17 engaging a lug 57 depending from the lever 40. A second embodiment is described which is identical with that forming the subject-matter of Specification 658,632, to which reference is made, this Specification claiming a bulb exposure mechanism operated by the shutter trigger.