| 摘要 |
A manually operated on-off switch comprising a frame with a magnetizable core surrounded by windings, and a spring loaded armature moveable between open and closed positions relative to the frame, the armature carrying a plurality of moving contacts which interact with stationary, normally open and normally closed contacts, and a manual rocker or toggle operator or the like attached to or acting upon the armature and serving to either close it against the spring action until it is held closed by electromagnetic force, or break it open against said holding force; a second embodiment of the switch described above comprising in addition a separate winding consisting of relatively few turns of heavy wire connected in series with the load and arranged to produce a field counteracting the field of the holding coil, the objective being to release the armature and open the working contacts when the load reaches a predetermined maximum value; and a third embodiment comprising in addition motor braking means in the form of a circuit serving to inject a brief pulse of direct current into the motor windings through the normally closed contacts mentioned as soon as the switch is either manually opened or magnetically reset.
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