Patent GB-1501992-A (GB)
Title: Mirror mounting assembly for single lens reflex cameras
IPC: G03B19/12
Filed: 1975-04-10
Abstract: 1501992 Mirror movement in reflex cameras ASAHI KOGAKU KOGYO KK 10 April 1975 [13 April 1974] 14847/75 Heading G2A In a single lens reflex camera the shaft on which the mirror rotates can move from a first (viewing) position to a second (exposure) position, the camera having manual means for raising the mirror partially from the first to the second position, and further means, operated by pressing the release button, for completing the raising movement towards the second position. A charge or cocking lever 1 and an operating lever 5 are both pivoted on a shaft A, and are biased together by a spring 6 attached to both levers. Lever 5 is prevented from pivoting anti-clockwise, in the "viewing" position of Fig. 1, by an engaging lever 7. Lever 5 is connected by a spring 9 to a diaphragm-operating rod 8 which determines the position of an automatic diaphragm pin 10, normally spring-urged upwards. Lever 5 is also linked to a shutter disengaging lever 11 by a connecting rod 12. The mirror 20 pivots on a shaft E (and a corresponding shaft part E' not seen in Fig. 1), which shaft parts form part of a lever 14. The shaft parts engage in angles 21 fixed to the mirror, which is normally spring-biased clockwise into the "down" or "viewing" position. When the film wind/cocking is actuated, a charge member 24 moves to position 24', moving charge lever 1 to position 1', where it is held by engaging member 25. Member 5 remains latched against movement by lever 7a, so that springs 6 and 4 are tensioned. When the shutter release is pressed, a member 26 moves downwards to engage and pivot lever 7 anti-clockwise, thus disengaging it from lever 5, which pivots anti-clockwise. Lever 5 pivots rod 8 clockwise to the Fig. 3 position, so that pin 10 is spring-urged into position 10', and the diaphragm is stopped down to its predetermined value. Also as lever 5 pivots anti-clockwise it engages and pivots lever 13 clockwise. End 13b of lever 13 engages angle 21 and causes mirror 20 to pivot anti-clockwise towards the "up" position. However, lever 14, and hence shaft E, does not move because it is retained by an end 11b of lever 11 abutting against a pin 14c on lever 14. After the mirror has executed part of its movement, lever 11 is pivoted anti-clockwise, so that it disengages from pin 14c, which is then engaged from the other side by lever 13. Levers 13 and 14 then pivot together until the mirror reaches its fully raised position (Fig. 3), the shaft E moving from the lower end of its guiding slot 19a, Fig. 2, (not shown) and Fig. 1, to the upper end, Fig. 3. As it pivots clockwise, lever 11 engages and pushes to the left a member 27, which releases the shutter. When the mirror is to be raised manually, a member 29 is moved upwards, which engages a pin 13d and so pivots lever 13 clockwise. This pivots mirror 20 towards the "up" position as before, and pressing of the release button enables the mirror to reach the fully raised position, shaft E moving along slot 19a as before. Since the shaft E, on which the mirror pivots, itself moves during the latter part of the mirror movement, this acts as a shock absorber.