Mirror-shutter device in single-lens reflex camera

In a single-lens reflex camera having a photographic optical system, a finder optical system, a film magazine, and a mirror which is movable between a first position for reflecting light rays passing through the photographic optical system to the finder optical system and a second position for permitting light rays to pass to the film magazine, the combination therewith of a mirror-shutter device comprising:

• a leading shutter supporting the mirror and hinged about a hinge axis to swing between third and fourth positions thereof to move the mirror between the first and second positions, respectively;
• a trailing shutter hinged about the same hinge axis to swing between fifth and sixth positions thereof at which the trailing shutter is in close contact with the leading shutter at the third and fourth positions, respectively;
• spring means for continually urging the leading and trailing shutters to swing mutually together into said close contact;
• driving means activated by a shutter release device of the camera to drive the leading shutter from the third position to the fourth position and thereafter to return the leading shutter from the fourth position to the third position;
• and
• locking means for releasably locking the trailing shutter in the fifth position, said locking means comprising a stud member fixed to the trailing shutter, latch means having a catch edge against which the stud member is normally caught and locked, resilient means urging the latch means to the stud member, intercoupling means for operating the latch means so as to cause the same to release the stud member, when the leading shutter has driven from the third position substantially to the fourth position during a specific interval, thereby to release the trailing shutter to permit the same to swing after, and closely contact the leadng shutter under the force of the spring means, and stationary buttressing means for buttressing the stud member, when the trailing shutter is at the fifth position, to place the stud member at a constant position relative to the latch means thereby to assure regular release timing thereof.