Patent GB-939137-A (GB)
Title: Improvements in or relating to single lens reflex cameras
IPC: G03B19/12
Filed: 1962-01-03
Abstract: 939,137. Reflex cameras. ERNST LEITZ G.m.b.H. Jan. 3, 1962 [Jan. 11, 1961], No. 253/62. Class 98 (1). In a single lens reflex camera the mirror is swung into and out of the light path (" viewing " and " exposure " positions) by a lever system dependent on actuation of the camera shutter, the lever system comprising a crank slide mechanism having a crank member engaging a guide formed on or secured to the mirror or a carrier therefor, the arrangement being such that in the " viewing " and " exposure " positions, which correspond to end positions of the mirror movement, the crank is in a " dead point " position in the guide, i.e. for a slight further movement of the crank, no movement is imparted to the guide. In the form shown, the camera comprises a housing 10 having a focal plane roller blind shutter 20, the shutter being tensioned by a winding lever 22 which also operates the film transport. The mirror 40 is arranged on a carrier 40a having a guide slot 41; in the slot engages the stud 42a of a crank 42 pivoted on the housing at 43. The mirror and its associated mechanism is shown in the " viewing " position in Fig. 4, and raised into the " exposure " position in Fig. 6 (not shown). The mirror is moved by a main lever 50, which is in driving connection with crank 42 through an offset arm 51 and a link 44, the lever 50 being controlled by a driving spring 65. Main lever 50 is pivoted on a shaft 45, which also carries an auxiliary multi-armed lever 60. This has an arm 61 having locking projections 61a, 61b arranged arrow-head fashion, an abutment arm 63a which can engage against lever 50, a tensioning arm 62, and a coupling arm 64 which co-operates with part 53b on a coupling lever 53. Lever 53 is pivoted at 52b on to lever 50, a stud 53a at its other end being abutted by an arm of the driving spring 65. Above and below shaft 45 are blocking levers 70, 71, 72 which serve to control and limit the movements of the lever system. A slide 80 is displaceably mounted on the housing 11e, and can be moved up and down to occupy three different positions by an eccentric 81 adjustable from outside the camera. In the lowest position, blocking lever 70 is uninfluenced and lever 72 is held out of range of the arrow-head (Fig. 4a, not shown). This corresponds to normal operation, when the mirror is swung from the viewfinding position to the exposure position after the shutter release, and then automatically back again after the shutter run-down. In the central position of slide 80, lever 70 is still uninfluenced, but lever 72 is brought into the range of action of the arrow-head (Fig. 8). In this position, the mirror is not returned to the viewfinding position after exposure, thus enabling a rapid series of exposures to be made. In the upper position of slide 80, the lever 70 is lifted out of engagement with arm 52 of lever 50 (dash-dotted lines in Fig. 8), so that the mirror is moved into the exposure position under the action of spring 65, and remains there. This allows the use of a short focal length objective which extends far into the interior space, and would prevent the use of the mirror. Such an objective may have a projection such that, on attaching the objective, it effects the necessary displacement of slide 80 into the upper position. Lever 70 is lifted out of engagement with lever 50, to allow the mirror to be swung up to the exposure position, on pressing the camera release 34, by a lever 36 (Fig. 3) which engages under arm 70b of lever 70 and lifts it. Release of the shutter blinds is prevented until the mirror is completely retracted by a blocking pawl 33 engaging a projection 32a on a disc 32 (Fig. 3). As the mirror moves upwards, it strikes arm 36a of a lever 36, whose other arm 36b frees the blocking pawl 33, so releasing disc 32 to cause successive release of the shutter blinds. As seen from Figs. 3 and 5, the arm 54 of main lever 50 extends into the range of a projection 91a of a diaphragm-setting ring 91 for the diaphragm 19a. Ring 91 is also coupled by a fork 91b to the blade-setting ring 92. An aperture pre-selecting ring 93 is coaxially mounted with ring 91, and can be adjusted by a tab 93a to a selected value on the scale ring 95 by means of an integral pointer 93c. By rotorably adjusting ring 93, various closure paths can be set between a stud 93b on the ring and the abutment 91a. The blade-setting ring 92 is under the action of a spring 97 which displaces it to the smallest diaphragm opening. Scale ring 95 is under the action of a spring 98 which tends to maintain an open position of the diaphragm. When the camera is ready for exposure, spring 97 has been tensioned, diaphragm 19a is fully open, and stud 93b and abutment 91a are a distance apart corresponding to the pre-selected aperture value. On pressing the camera release, arm 54 of lever 50 moves upwards from its position in Fig. 4. Abutment 91a follows, until it is held by stud 93b. Thus the pre-selected aperture is set, ready for when the shutter release takes place.