Apparatus for disabling an obstructed lift mechanism

摘要

An apparatus for disabling an obstructed lift mechanism having at least two hydraulic cylinders for controllably lifting and lowering a load includes a pair of valves, each arranged for sensing the differential pressure between a first sensing line and a second sensing line. The first valve is movable to a position for preventing the flow of hydraulic fluid from a first cylinder when the pressure in the second sensing line exceeds that in the first sensing line by a first predetermined value. The second value is movable to a position for preventing the flow of hydraulic fluid from the first cylinder when the pressure in the first sensing line exceeds that in the second sensing line by a second predetermined value. If the flow of hydraulic fluid from the first cylinder is prevented by the movement of either the first valve or the second valve, the operator is required to lift the load slightly to remove the obstruction.