Patent GB-1370736-A (GB)
Title: Winch apparatus
IPC: F15B11/04
Filed: 1972-01-26
Abstract: 1370736 Winch brakes HAGGLUND & SONER AG 26 Jan 1972 [28 Jan 1971] 3736/72 Heading B8B [Also in Division F2] A device for controlling a brake 11, of a winch driven by an hydraulic motor 6, wherein the brake, which is normally engaged due to spring force, is released by the supply of pressurized fluid to an hydraulic cylinder 12 connected to the brake 11, and a brake controlling unit is connected to the load raising input 8 of the motor 6 to regulate the supply of pressurized fluid to the cylinder 12 depending on the size of load on the motor, so that during lifting, the brake releases only after the pressure on the motor's load raising input substantially corresponds to the pressure required to balance the load, the arrangement allowing release of the brake, during lowering of the load, at a pressure independent of the load size. In operation, when a load is to be lifted off the ground, a hand valve 3 is moved to the left (Fig. 2) into a lifting position and fluid is fed from a pump 1 through a line 7 and a back pressure valve 9 to the load raising input 8 of the motor 6, and simultaneously over lines 18; 19. through a pilot controlled valve 16 to the brake cylinder 12, the valve 16 being held in the position shown by a spring 17, and the brake 11 being released at a low pressure to take up slack in the lifting cable. As the load is lifted, the pressure at the load raising input 8 of the motor increases, charging an hydraulic accumulator 14 of the brake controlling unit, the valve 16 being held in its open position by the balanced pressures in line 18 and from the accumulator 14. By selecting the neutral position (as shown) of valve 3, the pressure in line 18 drops but the accumulator pressure is d eue dhlto a non-return valve 15, whereby the pilot valve 16 is moved into a position to drain the brake cylinder 12 to apply the brake. To further lift the load, the valve 3 is again moved into the lift position, but the pilot valve 16 will not be moved into the brake releasing position until the pressure of the load raising input 8 of the motor and hence line 18, has equalled the pressure of the accumulator which is sufficient to support the load on the motor. When the left hand (in Fig.) lowering position of the valve 3 is selected, the pump 1 is connected to the brake cylinder 12 through line 22 and valve 21 which is operable because the line 20 is connected to tank 2, the valve 16 moving to this condition as lines 18, 19 are connected to tank 2 with movement of the valve 3. The brake 11 is therefore released irrespective of the load on the motor. The rate of load lowering is controlled by a back pressure valve 9 in the motor line 7 the extent of opening of the valve 9 being controlled in proportion to the pressure in the line 4. A valve 23 to short circuit the one way valve 15 to exhaust the accumulator 14 is also controlled by the pressure in the line 4, such that if the lowering operation is stopped before the load reaches the ground and the load to be raised again, the accumulator is still pressurized to control the pilot valve 16 to prevent premature release of the brake 11.