Patent GB-1420349-A (GB)
Title: Photographic exposure control apparatus
IPC: G03B9/58
Filed: 1973-11-12
Abstract: 1420349 Exposure control apparatus EASTMAN KODAK CO 12 Nov 1973 [11 Nov 1972] 52320/73 Heading G2A A camera has a variable diaphragm whose setting is adjusted by the intensity of the received light, the termination of the exposure being related to the time required to form the diaphragm aperture. As shown, the exposure aperture is formed by the overlapping of openings 14a and 16a in respective diaphragm blades 14 and 16, both blades being slidably mounted on a support plate 12. Blade 14 is biased in direction A by a spring 28, and the two blades are linked by a lever 32, so that they move together but in opposite directions: The blades have two further openings 14b, 16b, which overlap to form an aperture 42 behind which is located a photo-cell. The shutter blade is a plate 80, also slidably mounted on plate 12, and biased in direction A by a spring 84. Fig. 1 (not shown) represents the mechanism in the tensioned position, blades 14 and 16 being retained in this position by a control member 46 which is engaged with a post 49 on a flange 26 of blade 14, the member 46 itself being retained against the action of a spring 48 by a detent 134 forming part of a camera release member 30. The shutter blade 80 has an exposure opening 86, and is retained in the tensioned "shutter closed" position by a latch 88 engaging a notch 90 in the upper edge of the blade. When the release member 130 is depressed, the control member 46 is released to move in direction A, which also releases diaphragm blade 14 to move in the same direction. Aperture 42 thus increases from the minimum size of Fig. 1 (not shown) until an aperture of predetermined value (e.g. f/16) is reached, when the light admitted to the photo-cell activates a circuit which energizes an electromagnet 74. This attracts an armature 72, and a pawl 70 at the end thereof engages in a serrated edge 76 at the lower edge of diaphragm blade 14 to arrest its further movement, at an aperture setting formed by overlapping openings 14a and 16a, corresponding to f/16. At the same time, a flange 94 on member 46 engages a cam surface 92 on latch 88 and pivots it out of engagement with shutter blade 80, so releasing the latter for movement in direction A. When the opening 86 in shutter 80 is aligned with the aperture opening 14a, 16a, the shutter is arrested in this position by a detent 98 of a spring-loaded latch 96 which engages in a notch 99 in the lower edge of the shutter. Exposure is now initiated. At the same time as armature 72 is actuated to arrest the movement of the diaphragm blades, an extension 120 of the armature, previously in latching engagement with a spring-loaded shutter release member 102, disengages from this release member, which then also moves in direction A. A striker 124, forming part of member 102, engages latch 96 and pivots it out of engagement with shutter 80, so permitting it to continue in direction A and so to terminate the exposure period. Both control member 46 and release member 102 are inhibited in this movement by repective interia flywheels 60 and 118. These members are inter-connected to be released for movement in a predetermined relation, which is also related to the opening of the diaphragm blades and to the movement of the shutter blade.