| 摘要 |
PURPOSE: To eliminate jarring actuating noise when a locking pawl overrides teeth of a ratchet during a return to its original position after completion of operation, and to reduce a load upon a motor so as to prolong the use life of a battery. CONSTITUTION: After completion of exposure operation, a step motor 2 is reversed so as to turn a ratchet wheel 7 meshed with a distance measuring ring 4, in a clockwise direction as view in the figure. Accordingly, when a locking pawl 8a overrides teeth 7 of the ratchet wheel, an iron piece 19 approaches an electromagnet 9 which therefore attracts the iron piece 19 so as to turn a locking lever 8 counterclockwise and hold the same at a position where it does not engage with the ratchet wheel 7, and accordingly, the distance measuring ring 4 is returned to its original position. |
