Hydraulic valve to maintain control in fluid-loss condition

摘要

A hydraulic fluid-loss control valve for preventing uncontrolled load movement in the event of a fluid loss such as from the bursting of a hose and further for allowing an operator to move the load in a controlled way despite the fluid loss. The control valve is situated between a conventional main spool valve and a piston/cylinder hydraulic actuator which powers the load. The control valve has a spool sliding reciprocally in a bore. Grooves and lands on the spool combine with passages in the control valve body to provide alternate fluid paths between a pump and the actuator and between the actuator and a reservoir. Fluid can flow from a controlled chamber of the actuator only when the spool is in a position which provides a fluid path. A passage within the spool provides fluid communication between an input fluid flow and a chamber at one end of the spool. A second passage within the spool provides fluid communication between an actuator chamber and a chamber at the other end of the spool. The position of the spool is determined by the balancing of the opposing end-chamber pressures, which is under the control of the operator.