Hydraulics for Motors

The overcenter valves are employed to control the stop and the motion of one direction of an actuator (single overcenter valves) or both the directions (dual overcenter valves).Functions:- load lowering control: the lowering of the load is possible only if there is a pilot pressure from the other line; this operation ensures the oil supply of the cylinder preventing cavitation problems;- containing of the pressure at the setting value, pressure relief for any pressure peaks caused by shocks or overloads; - arrest of the flow (and of the load) when the pump is not working or the directional valve is in neutral position;- free flow for load lifting, with reduced pressure drops;They consist of a body where are placed:- check valve: it allows the flow in only one direction;- pilot piston: it permits to control the gradual opening of the relief valve;- relief valve: it permits to limit the maximum pressure in the actuator, it withholds the load and controls its lowering during the opening of the valve by the pilot signal.