Camera having a shutter mechanism controlled to remain closed as a failure warning

Claim 1

In a single lens reflex camera having an actuating member, a mirror for reflecting light passing through the single lens to enable composition and focusing when the mirror is in a picturecomposing position, the mirror being pivoted for rotation from its picture-composing position to a picture-taking position whereat it does not reflect the light, a shutter mechanism of the type which includes simultaneously chargeable and separately releasable leading and following shutter screens, and electromechanical means which when operable is operative upon movement of the actuating member to release the leading shutter screen and thereafter temporarily to hold and then release the following shutter screen so as to define an exposure slit as the released leading shutter screen moves ahead of the following shutter screen, said electromechanical means including an electromagnet and an armature magnetically attracted thereto when the electromagnet is operated in connection with the operation of holding the following shutter screen, the improvement for providing a warning that said electromechanical means is not operable, which comprises: means for moving the mirror from its picture-composing position to its picture-taking position so that until said electromechanical means has completed its operation light passing through the single lens is not blocked from passing through the exposure slit; a movable member for supporting the armature; biasing means for urging the movable member in a direction away from a first position; means, including said actuating member, for temporarily overcoming the urging of the biasing means so as to place the movable member in the first position during a first time interval in which the shutter screens are charged; the movable member having a first mode of operation when the electromagnet is operating, in which first mode the movable member is held in the first position owing to magnetic attraction between the armature and the electromagnet, and having a second mode of operation if not so held during a second time interval immediately following the first time interval, in which second mode the movable member moves to reach a second position before the leading shutter screen is released; and stop means responsive to the movable member operating in the second mode for preventing movement of the leading shutter screen while the mirror remains in its picture-composing position.