Patent GB-978486-A (GB)
Title: Improvements in or relating to monocular reflex cameras
Inventor: WIESSNER MANFRED
IPC: G03B19/12
Filed: 1961-01-24
Abstract: 978,486. Reflex photographic cameras. PENTACON DRESDEN KAMERA-UND KINOWERKE VEB. Jan. 24,1961, No. 2766/61. Heading G2A. A single lens mirror reflex camera having a focal plane or a between-the-lens shutter comprises a common shutter cocking and film winding gearing, a rotatable radially-or axially-acting cam element for driving the mirror into the viewfinding position by means of a cam follower connected thereto, spring means connected to said cam element for driving the latter and capable of being tensioned by said gearing, a pivoted blocking lever or latch for holding the mirror in its viewfinding position against the action of a spring which tends to move the mirror out of this position, said blocking lever being operable to release the mirror by means of the camera release mechanism or the shutter, and a detent co-operable with a projection connected to said cam element, which detent is operable by said shutter after actuation thereof for exposure so as to effect release of said cam element whereby the mirror is driven in to the viewfinding position. As shown in Fig. 1, the mirror 3 is latched in the viewfinding position by a latch 79 and the roller blind shutter has been set by rotation of a shutter cocking wheel 26 clockwise as seen from above by a gear train operated by a oneway quick wind lever 31 for feeding the film (Fig. 2 not shown). In this position reached after one complete revolution of the wheel 26 a pin 35 on the wheel 26 engages a leaf spring 17 attached to the gear 18 meshing with a gear 19 driving the leading blind roller and a pin-and-slot connected at 36 to the gear 23 meshing with the gear 24 driving the trailing blind roller, the wheel 26 which is freely mounted on a fixed shaft 21 being held against back rotation by a one-way drive of the lever. On pressing the camera release 9, lever 10 causes a bell crank pawl 78 to release the latch 79 so that the mirror is moved upwardly by its spring to cover the focusing screen, a projection 3a on the mirror striking an arm 14 to move it and its supporting pin 15 against a compression spring and the mirror being cushioned to rest by a pin 8 on the mirror arm 7 riding along an inclined surface 52 of an axial cam 39 (see also Fig. 3) which rotates against spring action sufficiently to allow the mirror pin to enter a recess 51 which holds the mirror raised. As the arm 14 moves upwardly a flange 16 on it raises the leaf spring 17 to free the roller blind shutter to make an exposure. When this is completed a pin 46 on the gear 23 connected to the trailing blind engages an arm 45 secured to a pivot 44 carrying also a detent arm 43 to free a bush 38 (Figs. 3, 4) freely mounted on the shaft 21. The bush is then rotated clockwise (see also Fig. 4) by a spring 41 tensioned by a peg 42 on the drive wheel 26 during cocking of the shutter so that the helical cam 39, which is freely rotatable on the bush and engages it through a projection 49 under loading of a spring 47, returns the mirror into the viewfinding position where it is again held by the latch 79 irrespective of whether or,not the operator has freed the camera release 9, and the cam finally moves into the Fig. 1 position clear of the mirror pin 8. In a modification (Figs. 5 to 7, not shown), the axial cam is replaced by a radial cam and a horizontal slidably mounted cam follower which is pin-and-slot connected under spring control to the driving disc 38 engages an arm extending from the mirror on the opposite side of the mirror pivot to drive the mirror back to the viewfinding position. In another embodiment (Figs. 8 and 10), a between-lens shutter is cocked on operation of the lever 31 by a wheel 126 driving a gear 29 which via shaft 62 and pinion 63 moves a rack 64 so that a pin 66 engages and drives anticlockwise (as seen in Fig. 10) a control ring 59 to cock the shutter mechanism and open the blades for focusing. When the cocking is completed a gap in the gear 63 allows the rack to return to its initial position while the ring 59 is held set by the lever 10. On pressing the camera release, the lever 10 first frees the ring 59 for a limited rotation so that the shutter, which has been opened for focusing is closed, the ring then being held by an arm 70, and then trips the latch 79 for the mirror which, as it reaches the position covering the focusing screen, moves an arm 73 secured to the arm 70 to free the ring 59 for exposure operation of the shutter and subsequently to trip via projection 45 the detent arm for the cam 38. In a further modification (Fig. 12 not shown), the lever 10 only releases the ring 59 and this in turn trips the latch 79 for the mirror.