GB803729A - Improved time limit overload switch device - Google Patents

Abstract

803,729. Controllers. MAVOR & COULSON, Ltd. Feb. 12, 1955, No. 4232/55. Class 38 (3). Heavy overload conditions during the starting operation of electric motor-driven apparatus cause shafts 15, 16 to be turned until arm 18 engages stop 19B. A cam 21 moves with the shaft 16 to open a switch 12 in the control circuit of the motor, but the control circuit is maintained by a similar switch 11 which is connected in parallel with the switch 12. Rotation of the shaft 16 also allows a pin 25 to move clear of a slot in a sleeve 23 which is loosely mounted on the shaft 16, so that a spring 33 is free to raise a rod 29. This causes an arm 32 on the sleeve 23 to move and actuate a striker 20 for operating the switch 11. The upward movement of the rod 29 is controlled by a time delay device fixed to a bracket 28 and comprising a clockwork mechanism incorporating an escapement. Assuming that the starting conditions are normal, the switch 12 is re-closed before the switch 11 opens, whereby the motor circuit is maintained. When running conditions are reached, any overload is dealt with by the switch 12, the time-lag switch 11 remaining open. If, during the starting operation, the heavy overload conditions continue for an extended period, the switch 12 remains open, so that the motor is disconnected when the time-delay switch 11 opens. Specification. 803,730, [Group XXX], is referred to.