GB941226A - Automatic overload safety device - Google Patents

Abstract

941,226. Hydraulically operated devices for preventing overloading in cranes. INSTITUT FUR FORDERTECHNIK LEIPZIG. March 22, 1962, No. 11104/63. Heading B8B. An overload device 5 controls lowering of the jib of an hydraulically operated crane, overloading being prevented by valves 7, 11, which are closed by the hydraulic fluid when its pressure reaches dangerous limits, to prevent further movement of fluid and thereby arrest the jib. Fluid returning to a reservoir from a luffing ram 3 passes through a control valve 2 and a conduit 6 to the overload device 5. In the device 5 the fluid passes through a spring- loaded throttle valve 7, a chamber 8 restricted by an adjusting screw 9 and a discharge valve 11, held open by a spring 14, to a conduit 12. If pressure in the discharge conduits rises to too high a value, fluid in a conduit 15 closes the valve 11 by urging it upwards and the valve 7 is pushed downwards into a closed position by pressure fluid in a conduit 16. The tension of springs 13, 14 is adjustable. A further conduit 17 is connected to winch overflow valves, which are closed when the pressure in the system is too high, thereby stopping the winches. The valve 11 may be housed in a separate block which may be either attached to or separate from the block 5. When the overload limit is reached during raising of the jib an overload valve 4 opens and no further upward movement is possible.