Patent GB-747814-A (GB)
Title: Photographic shutter
IPC: G03B9/08
Filed: 1951-07-18
Abstract: 747,814. Photographic iris diaphragm-type shutters. BURGER, E. July 18, 1951 [July 21, 1950], No. 17085/61. Class 98 (1). A setting type shutter comprising a master member driving to-and-fro a rotary blade ring which controls blades arranged to pivot in one direction to open and in the opposite direction to close includes in its blade-driving mechanism means adapted to be resiliently deformed by the application of the shutter-opening impulse by the master member and to undergo during the running down of the shutter a resilience oscillation whereby the full opening of the blades is retarded and the closing of the blades is retarded by comparison with a comparable shutter consisting of only rigid members in its blade-driving mechanism, the blade-operating mechanism also including variable means for adjusting the extent of travel of the blade ring in the shutter-opening operation so that the blades only just completely open the shutter aperture. As shown, the shutter blade operating ring 4 carries a pin 6 engaging in a forked lever 5 pivoted at 5a on a plate 1 and connected by a resilient link 7 to a master member 2 pivoted on a pin 3 on the plate 1 which itself rotatable about the pin 3 and is adjustable by the engagement of a pin 1a with a cam 17a on the shutter speed selecting ring. On depressing the setting lever secured to the master member, its driving spring 12 overcomes a weaker spring 13 holding the plate in the position shown and so first moves the plate anti-clockwise until it is arrested by a stop 14, thereby disengaging the forked lever from the pin 6 so that setting of the master member does not move the blade ring which is held against accidental movement by a leaf spring 16. Alternatively if the stop 14 does not permit sufficient movement to disengage the lever 5 and pin 6, the shutter is provided with a cover blade which is moved clear of the exposure aperture during the initial movement of the shutter trigger. Further pressure on the setting lever then rotates the master member anti-clockwise from against its stop 8 until a latch 11 on the plate 1 engages the nose 21 to hold the master member set with its spring 12 tensioned, the spring 13 returning the plate to the position shown and so re-engaging the lever 5 and pin 6 on letting go the setting lever. On depressing the trigger (Fig. 5, not shown), which is profiled so that it always engages the latch 11 in the same way irrespective of the position of the plate due to the cam 17a, the master member is released and is driven clockwise by its spring so that the link 7 oscillates the forked lever through a fixed angle # to cause the blade ring to open and close the shutter. The extent of the driven movement of the blade ring and hence the overall speed of the blades depends on the adjustment of the plate by the cam 17a, the applied impulse being least and the power-driven blade movement being greatest when the exposure is longest with the plate in the position shown. In all settings, the travel of the blades is only just sufficient to open the shutter fully. To permit further adjustment of short exposure times, one end of an auxiliary spring 20 may be connected to the master member and the other end of the spring may be attached to a pivoted lever 21 angularly adjustable by a cam 17b controlled by the shutter speed selecting ring. In a modification, the pin 9 of the link 7 engages in a slot 10 (Fig. 2, not shown) in the plate 1. By adjusting the plate, the slot makes different angles with the fork of a projection on the blade ring. Thus although the pin 9 always has the same stroke, the blade ring is rotated through different angles thereby altering the exposure time. Instead of making the link 7 resilient it may be rigid but connected to the master member at one end of a nearly circular leaf spring or to a springy forked lever 5, or the pin 3 may be carried on the inner free end of a springy G- shaped support or a carrier on which the blade pivot pins are fixed and the blade ring rotates may be mounted for resilient movement about the centre line of the shutter aperture.