| 摘要 |
PURPOSE:To prevent breaks of parts such as disconnection of wires, burning of a motor, or the like and detect disconnection of wires by providing a lock detecting mechanism to prevent lock of a driving system. CONSTITUTION:Though a driving pulley 46 is rotated counterclockwise and a stopper 12 and a stop pin 36 are brought into contact with each other in case of setting of magnifications, a high tension is applied to the tense side of a wire 45 because a motor 58 is not stopped, and therefore, a worm 53 and a worm wheel 51 are locked. Then, when the tension of the wire is applied to a pulley 22, a lever 23 is rotated counterclockwise to turn off a detecting switch 26, and a force exceeding a certain value is not applied to the wire 45 to prevent lock. If the wire 45 is disconnected, the lever 23 is rotated clockwise to turn off the detecting switch 26. Since the motor 58 is stopped by the detecting switch 26 in this manner, lock of the driving system is prevented, and disconnection of the wire and burning of the motor are prevented, and disconnection of the wire is detected. |
