| 摘要 |
A d.c. motor drives an output wheel, only partly provided with teeth, through a multistage spur gear reduction train. The electric motor can be reversed in rotation and the output wheel has a cam-shaped portion and a stop device. The output wheel operates a swinging lever or bell crank, fixed to the same axis, activated at one end by the cam which presses against a projecting bar (extending outwards for manual use) and at the other end by the stop which is a crank moving in a slot of a certain length in the face of the output wheel. During switching on, the output wheel moves so that the cam or the cam rise moves against the bar, turning the lever. This action forces a plate to swivel about its pivot, tripping the switch with its other end. This also disconnects the supply to the electric motor.
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