GB818309A - Improvements relating to overspeed protection devices - Google Patents

Abstract

818,309. Winch overspeed devices. METROPOLITAN-VICKERS ELECTRICAL CO. Ltd. Dec. 19, 1957 [Jan. 11, 1957], No. 1161/57. Class 78 (5). [Also in Group XXXVII] A winch overspeed device which applies the brakes to stop the winch drum when a predetermined, speed is exceeded, includes a cage 37 which is rotatable in bearings 38, 39 mounted on fixed frame 42 and is driven by the winch drum through gear 45. The cage mounts weights 8 positioned on wheels 4, 4<SP>1</SP> and 5, 51 secured respectively to shafts 1 and 2 mounted rotatably on and in the sides of the cage. The rotation of the cage, and therefore of the weights, causes centrifugal forces to act on said weights, and these forces cause a torque to act upon shaft 1, which is transmitted as an axial thrust along slidable shaft 7 via cam 9 secured to shaft 1, cam 10 secured to rotatable shaft 3, and cam 11 fixed to the end of shaft 7. Shaft 7 is connected to push-rod 16 of magnetic snap-switch 17, the connection being such that displacement but not rotation of shaft 7 is transmitted to switch 17. The displacement of push-rod 16 is resisted by the snap-switch. When the winch drum exceeds the predetermined speed, the torque of shaft 1 increases to cause the resultant axial thrust along shaft 7 to be transmitted by push-rod 16 to operate the snap switch to apply the brakes. The value of the predetermined speed is adjusted by rotation of cam 21, the said rotation causing an upward displacement of shaft 7, and a consequential rotation of wheels 4, 41, 5, 5<SP>1</SP> and therefore of weights 8, so as to vary the said thrust for a given speed. Wheels 5, 5<SP>1</SP> serve to double the torque by driving the wheels 4, 4<SP>1</SP> and, in conjunction with wheels 12, 13, to balance the cage dynamically. Cam 21 may be driven by the winch drum.