4WRZ Hydraulic Proportional Directional Valves

– When the solenoids (5 and 6) are in the de-energised condition, the control spool (2) is held by compression springs (8) in the central position
– Direct operation of the control spool (2) by energising a proportional solenoid, e.g. energisation of solenoid "a" (5)
→ Pressure measuring spool (3) and control spool (2) are shifted to the left in proportion to the electrical input signal
→ Connection from P to B and A to T via orifice-like crosssections with progressive flow characteristics – De-energisation of the solenoid (5) → Control spool (2) is returned to the central position by the compression spring (8) In the central position, ports A and B are open to T, i.e. the hydraulic fluid can flow to the tank without any restrictions.