| 摘要 |
981,091. Control of D.C. motors; electromagnetic switches. S. SMITH & SONS (ENGLAND) Ltd. May 5, 1961 [May 5, 1960], No. l5899/60 Headings H2B and H2J. When switch 3 is closed to energize radio set 1, relay coil 4 is energized to close contacts 21, 22, so that motor 25 operates to extend aerial 27. When the aerial is fully extended, stops 33, 34 engage to stall the motor, the increased current causing bimetal 24 to open contacts 23. Coil 13 is then energized to disengage plate 18 and leaf 11, whereby contacts 21, 22, open to de-energize both the motor and the coil 13. Plate 18 is returned to its normal position by spring 17, the leaf 11 being engaged within slot 19. When the coil 4 is de-energized by opening switch 3, contacts 20, 21 engage and the motor is energized in a sense to retract the aerial. The motor is stalled in the fully - retracted position, the contact 23 again opening to displace plate 18 and open contacts 20, 21. The motor and the coil 13 are now de-energized and the parts are returned to their original positions in readiness for a new cycle of operations. |
