Patent GB-765558-A (GB)
Title: Photographic shutter
IPC: G03B9/22
Filed: 1953-05-11
Abstract: 765,558. Photographic pivoted blade shutters. BURGER, E. May 11, 1953 [June 5, 1952], No. 13131/53. Addition to 747,814. Class 98(1) In a setting type shutter having a recipe rocable rotary blade ring capable of effecting to and fro opening and closing movements of pivoted shutter blades, a shutter master member is adapted to drive the blade ring in the opening direction by a tensioned spring, while closing is effected by a resilient stop which intercepts and reverses the movement of the blade ring or a part of the shutter mechanism adapted to drive the blade ring in the closing direction and which during the first part of its intercepting before the full opening of the shutter relieves the opening spring and releases a second spring which assists closing of the shutter, whereby the full opening of the shutter is retarded and the closing is accelerated by comparison with a shutter not having resilient driving elements, the resilient stopping means being adjustable so as to alter the speed of the shutter and also to limit the blade ring travel so that the exposure aperture is only just completely uncovered. As shown, the shutter driving members comprise two concentrically pivoted parts 3, 6 which are mounted on a plate 10 pivoted about the same point and urged clockwise by a spring 14 and which are connected by a spring 5 located between pins 3c, 6<SP>1</SP> and held in the set position by latch levers 1 and 7 respectively. Clockwise movement of the trigger 2 trips the latch lever 1 so that the spring 5 drives the parts 3 clockwise and by a pin-and-slot connection 4a, 3b rotates the blade ring 4 anticlockwise to open the shutter. When the pin 3c strikes the resilient latch lever 7 for the part 6, this is driven anticlockwise by the spring 9 so that by engagement of the projection 6a and the pin 3c the part 3 is first decelerated and then moved in the opposite direction to cause the blade ring to close the shutter, the spring 5 assisting the spring 9 during the closing movement which ceases when the part 3 engages the fixed pin 16, the lever 1 re-engaging the part 3. The shutter must then be set by rotating the part 6 clockwise tensioning the springs 9, 5 and moving the projection 6a past the nose of the latch 7. To vary the time between the opening and closing movements, the resilient lever 7 is angularly adjustable by means of the pivoted plate 10 having a pin 10a following a movable cam surface 11. For high speeds, the tension of the spring 9 is increased by means of a link 17 pin-and-slot connecting the plate 10 to the pivoted lever 18 to which one end of the spring 9 is attached and the shutter blades overlap considerably so that they attain a high speed before the shutter opens. To obtain slow speeds, the part 3 is braked by a shoulder 3e engaging a slide on a lever 19 and moved inwardly by said engagement against a spring 20, application of this braking being determined by the position of the cam 11 against which the lever 19 is spring urged. Different slow speeds may be produced by means of the usual adjustable gear retard train controlling a pivoted lever 12 engaged by the lug 3e. When the retard device is used, the spring 9 may be relieved completely of tension during closing of the shutter which is effected by the spring 20. In an alternative construction, (Fig. 4 not shown), the blade ring pin 4a is driven anticlockwise by a lug on the part 3 to open the shutter and is reversed and driven clockwise to close the shutter by a resilent projcetion on the part 6, the part 3 being returned to its initial position, where it is brought to rest against a resilient stop and is latched by a manually operable lever, by engagement of the pin 3c by the projection 6a. Slow exposures are obtained by means of a lever delay system for the tripping of the latch for the part 6 operated by a pin on the blade ring. This pin engages one limb of a bell-crank lever which is adjustable by an adjustable eccentric and against which is' spring-urged a slide acting as a brake for the blade ring and held in engagement with the cam 11 by a spring, the cam and the eccentric being adjustable simultaneously. Different slow speeds are obtained by a pivoted lever 12 engaging the other limb of the bell crank lever and controlled by an adjustable gear retard train. In a different embodiment, (Figs. 2, 3 not shown), a lug on the blade ring is engaged to open the shunter by a spring-urged slide released by operation of the trigger. When a pin on the lug engages a cam edge of a pivoted link pin-and-slot connected to the slide and moves both the link and slide out of the path of the lug, thereby disengaging the drive for the blade ring so that the shutter is closed by a return spring for the blade ring, part of the link acting as a resilient stop. The time at which the shutter is closed is determined by the initial position of the pivoted link which is pivoted to the shutter setting lever which after setting is spring returned to a rest position against an adjustable eccentric stop, the slide being moved to the set position by the pin-and-slot connection between it and the link. Different slow exposures are produced by a lever engaging a pin on the link and controlled by an adjustable gear retard train.