| 摘要 |
<p>892,336. Centrifugal switches. ENGLISH ELECTRIC CO. Ltd. June 2, 1959 [June 3, 1958], No. 17687/58. Class 38 (5). A speed-responsive switch for an electric motor comprises a bush 14 secured to the rotor shaft 15 and carrying a spring-steel frame 11 provided with four resilient lugs 12 having notches 13 to receive lugs 16 of a thin spring- plate 10 which is held in a bowed condition as shown, when the motor is stationary. The spring-plate 10 has an elongated central clearance hole and is loosely attached to an annular slider 19 by means of grooves 21 in lugs 20. The slider 19 engages a rubbing plate 22 to hold a contact 24 on an insulated spring-strip 23 mounted on the motor end-plate (not shown) against a fixed contact 25, the plate 23 being biased to the contacts-open position. Weights 18 are attached to the ends 17 of spring-plate 10 and when the shaft 15 rotates centrifugal force causes the weights 18 to exert a bending moment about notches 13 until at a predetermined speed the centre part of spring- plate 10 snaps over to allow contacts 24, 25 to open (Fig. 2, not shown). The initial movement of the spring-plate 10 is followed up by the springiness of strip 23 such that contacts 24, 25 do not open until the snap-over occurs. The slider 19 abuts bush 14 to stop the plate 10 attaining a stable reversed position and when the speed falls below another predetermined value the plate automatically snaps back to the position shown in Fig. 1.</p> |
