| 摘要 |
PURPOSE:To stop a stop ring at a position corresponding exactly to an aperture value by disengaging a planetary gear and a cam gear from each other immediately after an aperture value determination signal is sent out. CONSTITUTION:When a TTL light measuring circuit operates to determine a proper aperture value, current supply to an electromagnet 9 is stopped. Then, an armature 9a is freed from the electromagnet 9, a ratchet lever 5 is rotated counterclockwise with the counterclockwise tensile force of a coil spring 52, and the lock claw 5a of the ratchet lever 5 engages a ratchet wheel part 7a to stop the rotation of the cam gear 7 and also holds the stop ring 13 at its rotational position as it is. Further, the planetary gear 3 engaging a sun gear 2 rotating counterclockwise engages the claw part 5a and ratchet wheel part 7a to rotate the ratchet lever 5 slightly clockwise, so it is disengaged from the cam gear 7. Namely, even if a motor 1 keeps on rotating clockwise, the planetary gear 3 and cam gear 7 are disengaged from each other, so this cam gear 7 is never rotated.
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