Patent GB-914235-A (GB)
Title: Improvements in or relating to photographic reflex cameras
IPC: G03B9/07
Filed: 1961-03-02
Abstract: 914,235. Photographic reflex cameras. LEITZ G.m.b.H., ERNST. March 2, 1961 [March 3, 1960], No. 7656/61. Class 98 (1). In a single lens reflex camera with an objective and a presettable diaphragm, in which camera two separately rotatably actuating rings are provided for actuation of the diaphragm lamellµ, one of the actuating rings is rotatable through the range of stop values to a position determined by a diaphragm aperture preselecting ring by spring-loaded actuating means provided in the camera body, and the other actuating ring is rotatable through the range of stop values independently of the first actuating ring by a setting element operable from the outside of the camera. As shown (Fig. 1) a presetting diaphragm contained in an objective mount 2 and connected to the camera front 1 by a bayonet connection 3 comprises blades 6 and two rotatably mounted blade rings 4 and 5, ring 5 of which is urged by a strong spring 9 so as always to be in an end position corresponding to maximum diaphragm aperture at least immediately prior to each exposure. Ring 4 is coupled for rotation with a ring 11a through an arm 4b and a coupling element 11c, said ring 11a being itself coupled through a weak spring 11e to a further ring 1 la which is connected to one end of a strong driving-spring 11d The arrangement is such that when ring 11a is releasedprior to each exposure-from its tensioned position in a manner to be described later, this ring is driven into an end position by spring 11d and at the same time the coupled rings 4 and 11b are driven from a position corresponding to maximum diaphragm aperture into a position in which a projection 4a (cf. also Fig. 4) engages a lug 7b of a pre-setting ring 7, the difference in angles of rotation between rings 11b and 11a being accommodated by flexing of the weak spring 11e. The pre-setting ring 7 is coupled to a ring 7a (cf. also Fig. 6) which bears an index mark for co-operation with a stop value scale on the objective mount 2 and is manually adjustable against the resistance of a spring detent device comprising detent notches 8 in the ring 7 and a spring-urged projection 12a of a setting member 12. The setting member 12 provides an alternative means for positioning the lug 7b of the pre-setting ring 7 and also enables the effect on depth of focus of the chosen aperture to be observed-on the usual matt focusing screen (not shown)-prior to exposure. For this purpose, the member 12 is depressed against loading of the spring 13a whereby projection 12a is disengaged from detent notches 8 on ring 7 and a further spring-urged member 12b is disengaged from a single locking notch provided therefor in the mount 2. The member 12 may now be moved in the slot 14 (cf. Fig. 6) to adjust the diaphragm aperture by way of the ring 5 which has a lug 5a urged by the spring 9 into constant engagement with projection 12a. After the desired aperture has been selected the member 12 may be released whereupon the following movements takes place : (a) under loading of spring 13a the projection 12a reengages with one of notches 8, (b) ring 5 and members 12 and 12b are driven by spring 9 into their end positions, and (c) member 12b in its end position re-engages with its locking notch. Due, however, to the re-making of the coupling between members 12a and 7, the lug 7b is now in a position corresponding to the chosen aperture value. In a modification (Fig. 1a-not shown) in which the effect of different apertures on the depth of focus can still be observed on the matt-focusing screen but in which the alternative method of positioning the pre-setting ring 7 is not possible, the elaborate setting member 12 is replaced by a simple member rigid with the spring-urged ring 5 and the ring 7 is permanently engaged by a spring-detent latching device. The camera operates as follows, starting from the ready-for-exposure condition shown in Figs. 5, 6 and 8. On depressing a spring-urged release knob 58a arranged coaxially with a film-winding knob 16, a slide 59 is moved axially forwards by the action of a cam 58b, and, by way of a lever 60 and a spring-urged slidable member 61 having a fork 61a engaging an annular groove in a pinion 51 which is slidable on its shaft 50a but which is keyed for rotation therewith, the pinion 51 is moved axially out of engagement with a toothed portion of ring 11a, whereupon this ring is freed to adjust the diaphragm under loading of its spring 11d to a pre-selected value, as described above. During this rotation, by way of cam 62 on ring 11a an angled slide member 63, a cam 64 and a spring-urged pivoted latch member 57, the pivoted viewing mirror 55 is freed to move under loading of its spring 56 out of the path of the exposure beam. Near the end of this movement, by means of a lug 67a on a disc 67 connected for rotation with the mirror, a spring- urged pivoted lever 58 is moved out of engagement with a lug 71 whereby the tensioning shaft 23 of a conventional focal-plane shutter (not described in detail) is released for rotation. So as to uncouple the shaft 23 from the film-winding and shutter-tensioning mechanism during running-down of the shutter, a dog-clutch 29 between gears 22 and 22a is disengaged by a member 28 connected with the release rod 58. At the end of the running-down movement of the shaft 23, a lug 25a (cf. Figs. 5 and 7a) disengages a spring-urged filmfeed-limiting lever 24 from a recess 17a in a metering-roller shaft 17. The film may then be advanced one frame and the shutter retensioned by rotation of the knob 16. The take-up spool is coupled to the shaft 17 by gears 18, 20 and a friction clutch 21. The shutter is re-tensioned by drive transmitted through gears 19, 22, 22a and 26. The ring 11a of the pre-setting diaphragm mechanism is re-tensioned by drive transmitted through gears 19, 22, 46, 47, 48, bevel gears 49, 50, shaft 50a and pinion 51. The mirror 55 is returned to its operative position by drive transmitted through gears 19, 22, 46, 47, 48, bevel gears 52, 53 and an eccentrically mounted pin 54.