GB877165A - Improvements relating to hydraulic control of brakes - Google Patents

Abstract

877,165. Hoist drum brakes. KEELAVITE CO. Ltd. March 12, 1958 [March 12, 1957], No. 8117/57. Class 103 (1). A power transmission system incor-. porates a motor, a brake arranged to act on a member driven by the motor, control means operable to cause movement of the motor in either direction and capable of controlling power (the driving power) delivered through power delivery means to drive the motor, at least one anchoring member movable in two directions from a neutral position, each of which directions corresponds respectively with a direction of movement of the motor, into contact with an appropriate fixed part to transmit to that part the reaction upon the brake during braking, and brake control means arranged to receive from the power delivery means operating power to release the brake and automatically effective to allow release of the brake upon movement of the anchoring member from its neutral position only in that direction corresponding to the direction in which the motor is urged by the driving power applied to it. In the apparatus shown, a hoisting drum 1 around which is wound the normal hoisting cable 2 supporting a load 4, the drum 1 is arranged to be driven in either direction through transmission mechanism indicated at 5 by a reversible hydraulic motor 6 having fluid inlet and outlet passages 7 and 8 either of which can be connected by a piston-type control valve indicated at 9, to a source of fluid under pressure at 10. Freely mounted upon the shaft 18 of the drum 1 is a movable anchorage member 19, to which are pivoted at 20 a pair of brake shoes 21, 22, arranged to act upon a brake drum 23, rigid with the drum 1. The lower end of the member 19 is connected through rods 43 to a further piston-type slide valve having chambers in communication with passages 7 and 8 connected to the reversible hydraulic motor 6. A conduit 51 leads from the latter piston-type slide valve to an hydraulic cylinder 35, wherein fluid pressure may act upon a piston 36 to release the brake shoes against the pressure of spring 27. If the lifting torque exceeds any load applied to the drum 1, through cable 2, the drum and hence the movable anchorage member 19 will rock, so that the projection 37 engages the adjustable stop 39, as shown in Fig. 3. The valve 44 is therefore moved to admit fluid to the cylinder 35 to release the brake. This arrangement avoids the condition wherein, if a light load is being handled, it is necessary to use an hydraulic pressure much greater than that necessary to lift the load so that the hoisting operation starts with a jolt.