Rotation control system

1,026,052. Winches; self-sustaining gear. DOWTY HYDRAULIC UNITS Ltd. March 14, 1963 [Jan. 18, 1962], No. 1929/62. Heading B8B. [Also in Division F2] Rotation of a driving shaft 11 or winding drum of a winch is prevented, except when driven by power means, by a brake 21 which is engaged by mechanical, electric or hydraulic means responsive to rotation of the shaft 11 or drum. As shown on rotation of the shaft 11, other than by a variable speed hydraulic transmission 1, 4, an arm 13 in light frictional engagement with the shaft 11 rotates to open a valve 14 or 15 which vents a brake release servo 23, whereupon a spring 22 engages the brake 21. Rotation of the arm 13 is limited by pegs 32, 33 on a ring 31 freely rotatable on the shaft 11 and integral with an arm 28 linked at 27 to the transmission control lever 24. The control lever 24 is arranged so that clockwise movement thereof produces anticlockwise rotation of the shaft 11 and vice versa. To raise the load the lever 24 and interconnected ring 31 are moved anticlockwise, whereupon the transmission rotates the shaft 11 clockwise. Initial movement of the shaft 11 permitted by lost motion in the brake rotates the arm 13 into the position shown against the stop 33. The values 14, 15 are thus closed and pressure liquid is supplied from a pump 5 through a restrictor 19 to the servo 23 which disengages the brake 21 and permits further rotation of the shaft 11 to raise the load. On stopping the transmission, the load tends to rotate anticlockwise the shaft 11 and arm 13 which opens the valve 14 and applies the brake 21. To lower the load the lever 24 is moved clockwise, whereupon the stop 32 on the ring 31 moves the arm 13 into the position shown, wherein the valves 14, 15 are closed and the brake 21 is thus disengaged to permit anticlockwise rotation of the shaft 11.