Patent GB-541492-A (GB)
Title: Improvements in or relating to a photographic shutter
IPC: G03B9/14
Filed: 1940-05-28
Abstract: 541,492. Photographic shutters. STRASSENBURG, E. May 28, 1940, No. 9353. [Class 98 (i)] In a photographic shutter, a spring-pressed main lever is released to operate the blades by a release trigger which dunng its return movement under the action of a spring engages the main lever and returns it to its set position in readiness for the next operation. As shown, a pair of oppositely-moving shutter blades 32, 34 pivoted respectively on pins 24, 26 are moved by a member 28, shown separately in Fig. 16, pivoted on the pin 26 and carrying a stud 30 which engages in slots in the blades. The member 28 is rocked to open the blades, and against a spring 44, by a main lever 52, pivoted on a screw 56 and having a nose 58 which, when the lever is moved anti-clockwise by its operating spring 60, engages an inclined abutment wall 48 on the, member 28, as shown in Fig. 4. The main lever 52 is held in the set position, Fig. 1, by the release trigger 80 which is pivoted at 82 and provided with a hook 96 which engages over the lever. On depressing the trigger the hook 96 releases the lever 52 which is, however, at first held by the engagement of a lug 74 on it with a spring catch 76. Towards the end of the trigger movement an extension 94 moves the spring 76, releasing the lever 52, which is then moved anticlockwise by the spring 60 so that its nose 58 engages the abutment 48 on the member 28 and rocks it to open the blades, Fig. 4. The movemertt of the lever 52 is limited by a pin 112, adjustable along an arcuate slot 114 by rotation of an exposure-timing ring to which it is secured. Fig. 4 shows the adjustment for "bulb" exposures, the pin 112 engaging a projection 122 on the edge, of the lever 52 when the latter arrives at the position shown. The trigger on release is returned by the spring 88, the hook 96 moving the lever 52 back to the set position, and the member 28 moving under the action of the spring 44 to close the blades. When set for " time " exposures, the pin 112 is opposite a recess 124 in the edge of the lever 52, which on release thus moves somewhat beyond the position shown in Fig. 4, so that the lug 74 moves below and to the other side of a stop 104, Fig. 5, on the underside of a member 90. When the trigger is released, a vertical edge cam on it below the hook 96 tilts the lever 52, so that the extension 94 engages behind the stop 104, Fig. 7, so preventing the return of the lever 52 and maintaining the blades open. The tilting of the lever also raises it above the top of the pin 112, so that on depressing the trigger for the second time the lever moves over the pin and carries the lug 74 beyond the catch member 90, Fig. 9, and also releases the member 28, allowing the blades to close. On the return of the trigger and lever the latter is still maintained in the tilted position, so that the lug 74 passes above the catch member 90 and the nose 58 passes through the space 49 above the abutment 48 of the member 28. When set for "instantaneous" exposures the pin 112 is opposite a recessed portion 126 or 128 of the arm 52, which thus on release is allowed to move out substantially to the position shown in Fig. 9, the nose 58 brushing past the abutment 48 and momentarily opening the blades for a period dependent on the speed of movement of the arm, the return movement of the arm being effected on release of the trigger as described for time exposures. For exposures of 1-25th of a second the movement of the arm is opposed by a spring 116 secured to it at one end and engaging the pin 112. As the pin is moved to decrease the exposure it engages a pivoted arm 70 which it moves to put increasing tension on the spring 60 operating the lever 52. When the pin comes opposite to the recess 128 in the lever 52 the latter is allowed an increased movement which permits the lug 74 on it to strike an inclined abutment 50 on the member 28, which is thus moved more rapidly to close the blades than by the spring 44 acting alone.