GB498654A - Improvements in or relating to photographic focal plane shutters - Google Patents

Abstract

498,654. Roller-blind shutters. ZEISS IKON AKT.-GES. March 29, 1938, Nos. 9624 and 9625. Convention dates, June 10, 1937 and July 23, 1937. [Class 98 (i)] In a roller-blind shutter, the blind 1 is wound on a shaft 3 by a spring 2 and the bands 4 which draw it into the wound-up position are wound on rollers 5 on a shaft 8 coaxial with the shaft 6 of the blind 7. The bands attached to the blind 7 are wound on rollers 9 under the action of springs 10. One roller 5 and the shaft 6 are provided with crown wheel teeth 11, 12 engaging a differential pinion 13 on a carrier 14 mounted on a hollow shaft 16 and carrying a bevel-wheel 17 connected with the winding mechanism. The roller 5 is provided with a lug 18, which in the end position of the woimd-up blind abuts against a fixed lug 19. On rotating the wheel 17 carrying the pinion. 13, the two superimposed blinds 1, 7 are drawn up. When the lugs 18, 19 are in contact, the blind 1 remains stationary, the pinion 13 rotates, and the shaft 6 with blind 7 move on to the end position. When the shutter is released, the blinds move without variation of the slit, under the action of the springs 2, 10 which have similar tensions. When the blind 1 has reached its end position, the pinion 13 rotates together with the shaft 16 until the blind 7 reaches the position shown. In a modification, the lower blind is first released and the slit width is determined during running-down by the time lag of the shutter in releasing the upper blind, the differential pinion meanwhile rotating. Both blinds then move together till the lower blind is fully unwound, and the upper blind follows, with movement of the differential pinion, to close the slit. Both blinds are wound up together. The differential gear in both modifications is so arranged that its frictional resistance is greater than the force tending to vary the relative positions of the curtains during winding or running down.