Four-way Flapper-nozzle Control Valve

The four-way flapper-nozzle valve has two identical hydraulic circuits, one supplies flow and pressure to one side of an actuator, the other circuit supplies the hydraulic fluid to the other side of the actuator. In other words l the valve provides proportional push-pull control to the actuator. The common point of the two circuits is at the flapper (see Fig. 1.27) which controls the orifice areas of both nozzles. As the flapper is moved in one direction, one orifice area is decreased and the other orifice area is increased, thereby causing the pressure to increase on one side of the actuator and decrease on the other side. When the flapper is centered between the two nozzle faces, equal pressures are supplied to both sides of the actuator.

In general, the relationships of the fixed-area orifices and the variable area orifices are designed so that when the flapper is in its null or centered position, the control pressures to the actuator are about one-half of the supply pressure to the valve. With this design, the valve has a wider range of linear operation.

Four-way Flapper-nozzle

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