Patent GB-932901-A (GB)
Title: A diaphragm and a photographic or cinematographic camera including the same
IPC: G03B7/12
Filed: 1962-03-12
Abstract: 932,901. Photographic camera diaphragms. AGFA A.G. March 12, 1962 [March 14, 1961], No. 9480/62. Class 98 (1). A diaphragm for a photographic camera comprises a plurality of leaves and three slotted, independently rotatable leaf bearing rings in parallel planes, each leaf having two pins engaging a slot in one ring and the superimposed slots of the other two rings respectively. In the embodiment shown in Fig. 1, rings 2, 3, 4 are provided with slots 5, 11, 12 respectively which are engaged by pins 9, 10 of diaphragm blades 6. Rings 2, 3 are provided with scales 7, 13 respectively which co-operate with indices 8a, 8b, 8c. Spring 14 urges a projection on ring 4 into contact with a stop 16 on the camera. For automatic setting of the diaphragm, rod 18 is released by depressing button 27 on rod 25 whereby rod 18 is urged downwards by spring 24 until jaw 20 abuts the galvanometer pointer 21 and simultaneously rotates ring 4 by means of pin 4 and causes pin 10 to move along cam 11 and pin 9 along part 56 of slot 5, the blades 6 being adjusted by a corresponding amount. If a filter is to be used, ring 3 is rotated manually until the filter factor required, on scale 13, is set against index 8a, thus causing pin 10 to slide in slot 12 and adjust blades 6. For unusual exposure conditions such as photographing into the sun or if a small bright important part of a subject appears before a dark ground, scale 13 is set against one of indices 8b, 8c (if no filter is used reference " 1 " on scale 13 is set). For setting the diaphragm by hand ring 2 is rotated until the required diaphragm value on scale 7 is in register with mark 8a, pin 9 moving in part 5a of slot 56 adjust the blades 6. Before making an automatic exposure setting, ring 2 is turned until mark " A " on scale 7 is adjacent mark 8a. In the embodiment in Fig. 3, rings 31, 32, 33 are provided with slots 35, 36, 37 respectively for adjusting diaphragm blades 34 by means of pins 57, 58. Spring 42 urges pin 43 on ring 32 against projection 44 of ring 31 and spring 47 urges pin 48 of ring 31 against projection 50 of ring 33, neither spring being as strong as a friction holding spring 40 on ring 31 which engages toothed part 41. For automatic exposure setting, ring 31 is set with its index mark 38 adjacent mark 39a on scale 39 and pin 55 on ring 33 lies in the path of rod 56 (similar to rod 18 of Fig. 1) which is moved down to engage pin 55 and rotate ring 33 (rings 31, 32 are stationary due to friction device 40, 41) and pin 57 moves in slot 36 to set blades 34. For flash light exposure, ring 31 is rotate; until its mark 38 is set along flash guide number scale 39b, during which movement, projection 50 on ring 33 meets impact surface 51 on a ring 52 after which further rotation of ring 31 causes pin 57 to be moved along slot 37 and adjust the blades. The position of surface 51 can be varied by rotating ring 52, which is provided with scale 53 to allow for different focusing distance settings. To set a particular diaphragm value, ring 31 is rotated until mark 28 is set along scale 39c during which movement projection 45 meets fixed stop 46 and subsequent rotation of ring 31 causes pin 57 to slide along slot 36 and adjust blades 34.