GB1030146A - Improvements in grab cranes - Google Patents

Abstract

1,030,146. Controlling winding apparatus on grab-cranes. PRIESTMAN BROS. Ltd. March 1, 1965 [April 23, 1964], No. 16889/64. Heading B8B. A grab crane in which the grab is controlled by a hoist rope and a hold rope which are wound on separate drums driven through separate fluid-operated clutches under the control of separate manually operated valves comprises a further valve controlling fluid pressure supplied through a further conduit to the hold rope drum clutch and mechanically connected with the hoist rope control valve to a single handpiece so that the latter is movable to supply fluid pressure to both clutches simultaneously, thereby holding the hold rope taut during hoisting of the grab. As described, two pneumatic control valve assemblies 1, 2, Fig. 1, are provided for controlling the hold and hoist ropes and slewing of the jib, the assembly 1 consisting of two valves with a single joystick control and the assembly 2 being similar but with three valves. One valve in the assembly 1 controls the air supply through a line 3 to the joist rope drum clutch, the valve being opened by movement of the joystick in the direction of the arrow 5. The second valve in the assembly 1 forms the further valve which is operable by movement 7 of the joystick in the direction of the arrow 8 to supply air through the further conduit 6 and a double check valve 7 to the hold rope drum clutch sufficient to hold that rope taut during hoisting. The assembly 1 is provided with an adjustable plate 9, Fig. 4 (not shown), having a guide edge 10 along which the joystick 4 is moved in the direction of the arrow 11 to ensure that both valves are opened. The joystick is spring-loaded to its neutral position and is held in its fully moved position by a pivoted, spring-loaded hook catch 12, the latter being connected by a Bowden cable 17 to a brake pedal for the hoist rope drum so that when the brake is applied the joystick reverts to its neutral position. The three valves of the assembly 2 are arranged at 90 degrees to each other and are operated by a central joystick, one pair of opposite valves being connected by conduits 22, 23 to pneumatic control means for slewing the jib in one direction or the other and the third valve being connected by a conduit 26 to the check valve 7 for supplying air to the hold rope drum clutch at a pressure higher than that supplied to the check valve 7 by the further valve of the assembly 1 so that by operation of the third valve the hold rope can take the full weight of the grab when the hoist rope is to be released to open the grab. An additional valve may be provided in each of the assemblies 1 and 2, these valves being opened by movement of the joysticks in the direction of arrows 27, 28 to supply air to clutches for driving the hoist rope drum and the hold rope drum in a direction for lowering the grab.