Patent GB-275462-A (GB)
Title: Improvements in or relating to photographic shutters
IPC: G03B9/22
Filed: 1926-11-24
Abstract: 275,462. Deckel, F., and Geiger, M. Nov. 24, 1926. Shutters with pivoting blade.-A photographic shutter for attachment to a camera comprises, in a single housing, a device for varying the duration of exposure, and a device for retarding the beginning of the exposure so that the operator, after releasing the shutter, may move into position to be himself photographed. A single master member may be provided to operate either both devices, or only the device for retarding the duration of exposure. In the form shown, the shutter mechanism and an iris diaphragm are enclosed in casing surrounding the lens elements. The master member comprises a ring 5, Fig. 6, which is fast with an operating handle 6 projecting through a slot 7 in the casing, and is turned clockwise against the action of a spring 8 to set the shutter. A stop in the slot 7 arrests the ring when a catch 94 on a locking-lever 95 enters a notch 78 on the ring, and in this setting the device for retarding the duration of exposure. will alone operate when the shutter is released. This stop may be displaced to permit further rotation of the ring until the catch 94 engages a second notch 79 on the ring, and in this setting both retarding devices will operate. The shutter is released by operating a trigger 101 having toothed engagement with the tail of the locking- lever 95, or by the usual cable release connected at 104 and actuating the trigger 101 through a lever 103. Varying duration of exposure. As the ring 5, after release of the lever 95 from the notch 78, turns clockwise under the action of the spring 8, a spring-urged lever 22, Fig. 12, pivoted on the ring is caused, by the engagement of a pin 26 on the lever with the straight part of a fixed cam groove 25, to displace by its nose 30 the arm 19 of a bell crank-lever, the arm 18 of which embraces a pin 17 adapted to operate the blade actuating-mechanism in known manner, so that the blades are rapidly opened. When the pin 26 slips from the end of the straight part of the groove 25 into the semi-circular part, a spring 23 reverses the rotation of the bell-crank, and the shutter blades are rapidly closed, this movement being accelerated by a projection 31 on the lever 22 striking the pin 17. In the period between the opening and closing of the blades, a brake shoe 56, Figs. 6 and 8, mounted on spring-urged lever 54 turning on a fixed pivot, is pressed by a spring 55 against the ring 5. On this lever is pivoted an anchor 53 engaging an escapement wheel 52 connected by a gear train with a sector 44 carrying a pin 46 engaging a cam slot in a setting disc which is mounted concentrically with the ring 5 and is operable from the exterior of the casing. By rotating the disc over an external scale, the sector may be swung towards or away from the ring 5 according to the degree of retardation desired. As the shutter blades open, a. nose 59, Fig. 6, on the ring 5 engages the edge 60 of the sector 44 so that the rotation of the ring is retarded by the escapement device until the nose 59 moves past the sector. At the commencement of the retardation the brake shoe 56 enters a depression 66 in the ring 5, causing the lever 54 to move the anchor into full engagement with the escapement wheel 52 and thereby to provide maximum resistance to cushion the blow of the nose 59 upon the sector 44. Thereafter the shoe passes to a raised part 67 of the ring 5, and the depth of the engagement of the anchor is diminished for the remainder of the retarding period. For very rapid exposures, the returnspring 8 of the ring 5 is reinforced by a spring 68, one end 71 of which bears against a pin 9 on the ring 5, and the other end 70 of which is engaged by a projection on the setting-disc when this is set for such exposures. On resetting the ring 5 for a further exposure the pin on the lever 22 traverses the semi-circular part of the cam groove 25 and the shutter blades are not actuated. Retarding the beginning of the exposure. When the ring 5 is set so that the lever 95 engages the notch 79, a spring-urged clutch lever 90, Figs 6 and 10, pivoted on the ring 5 engages a triple-toothed clutch member 89 fast with a gear wheel 82 connected through a gear train with an escapement wheel 86 engaged by a weighted anchor 87. On releasing the shutter, the motion of the ring 5 is retarded by the escapement 86, 87, until the lever 90 slips off the member 89, whereafter the shutter opens and the exposure is regulated by the brake mechanism previously described. To prevent the locking- lever 95 from engaging the notch 78 as this passes the end of the lever, the notch 79 stands out further radially than the notch 78, so that a greater rotation of the trigger 101 is necessary for releasing the lever 95 from the notch 79, and provision is made for preventing the return of the trigger 101, and therefore of the locking-lever 95, until the ring 5 has completed its return movement. Time and bulb exposures. A spring-urged lever 105, Fig. 14, linked to the trigger 101 has a notch 106 adapted to operate directly a projection 107 on the blade actuating-ring for making time or bulb exposures. Auxiliary levers, having projections co-operating with the setting disc and with the lever 105, serve to throw this lever into or out of action, and also to control the closing of the shutter blades for the two settings.