Due to the high flow forces pilot-controlled directional valves for high flow rates are not returned with springs but with hydraulic pressure to the centre positionand centred there. This action is achieved by the interaction of the pressurised area of the control spool on one side and the sum of the areas of the piston and sleeve on the other side (Figure D 85). The springs here only have an auxiliary function for centring in the unpressurised state. Opposite: Centring by springs
Figure D 85: Pressure-centred directional valve