Patent GB-175991-A (GB)
Title: Improvements in and relating to photographic shutters
IPC: G03B9/22
Filed: 1922-02-23
Abstract: 175,991. Wollensak, A., and Pirwitz, F. A. G. Feb. 24, 1921, [Convention date]. Shutters with pivoting or rotating blades.- Relates to shutters of the pivoted-blade type in which the exposure is timed by a retarding- mechanism of variable resistance operating on the blade-actuating member, and comprises mechanism in which the operating-lever of the shutter actuates a rotary member co-pivotal with a swing- ing lever geared to an escapement, the initial angular position of the swinging lever being adjustable so that it is engaged and rotated by a projection on the rotary member earlier or later during the rotation of this member. The escapement retarding device comprises an anchor escapement having in the escape-wheel a slot in which is engaged a projection on the aforementioned swinging lever, and a balance wheel driven from the anchor. In the form shown, the shutter is of the automatic type, operated by a trigger 16, a projection 19 on which first rotates a master lever 12 clockwise on its pivot 13, and then releases it. During the clockwise rotation, a down-turned ear 23 on the springy lever 12 rides up an incline 25 and drops behind a shoulder 26 on a pivoted member 9 having a downturned end 8 engaging a forked member 6 which actuates the pivoted shutter-blades 1 in any well-known manner; and a down-turned ear 45 on the lever 12 rides over and engages the arm 46 of a lever 43<a> co-pivotal at 27 with a swinging lever 28 having an ear 32 slidable in a slot in an escape-wheel 34 engaged by an anchor 36, which is fast with a counterweighted lever 38 having an ear 39 slidable in a slot in a balance-wheel 41. The lever 28 may be set to any initial angular position, as by a rotary cam on the outside of the shutter casing, and it is held in this position by a spring 29; but the lever 43<a> is always held in a fixed initial position by a spring 47. When the trigger 16 releases the lever 12, a spring rotates the lever counterclockwise; the ear 23 thereon rotates the member 9 counterclockwise, and opens the shutter blades; and the ear 45 rotates the lever 43<a> clockwise, so that, after an angular movement depending on the initial setting of the lever 28, an ear 44 on the lever 43<a> engages the lever 28 and causes this to rotate with the lever 43<a>, the combined movement being retarded by the escapement to which the lever 28 is coupled. After the lever 12 has rotated through a certain angle, the ear 23 slips off the shoulder 26 and releases the member 9, which is returned to its initial position by a spring 11, thereby closing the blades; and the ear 45 slips off the end of the lever 43<a>, permitting the springs 29, 47 to return the levers 28, 43<a> to their initial positions. The ear 19 on the trigger 16 is bevelled, so that when the trigger is returned by its spring 20, the ear rides over the end of the springy lever 12 and re-arms the shutter. Any or all of the elements 34, 36, 38, 41 may be dispensed with; they may be removed from their studs when a plate bearing on the ends of the studs, and carrying a pin 51 fitting into a socket 52, has been removed.