The 4/2 and 4/3 proportional directional valves are designed as direct operated devices in plate design. Operation by means of proportional solenoids with central thread and detachable coil. The solenoids are controlled via integrated electronics.
The valve basically consists of:
Housing (1) with connection surface
Control spool (2) with compression springs (3 and 4) and spring plates (5 and 6)
Solenoids (7 and 8) with central thread
Position transducer (9)
Integrated electronics (13)
Electrical zero point adjustment (12), accessible via Pg7
With de-energized solenoids (7 and 8), central position of the control spool (2) due to compression springs (3 and 4) between the spring plates (5 and 6)
Direct actuation of the control spool (2) by the control of one proportional solenoid, e. g. solenoid "b" (8)
→ Control spool (2) is moved to the left in proportion to the electrical input signal
→ Connection from P to A and B to T via orifice-type cross-sections with progressive
Switching off of the solenoid (8)
→ Control spool (2) is returned to the central position by the compression spring (3)
In the de-energized state, the control spool (2) is held in a mechanical central position by the return springs of the solenoids. With control spool symbol "V", this position does not correspond to the hydraulic central position! When the electric valve control loop is closed, the control spool is positioned in the hydraulic central position.
The PG fitting (11) must not be opened. Mechanical adjustment of the adjustment nut located below is prohibited and damages the valve!
Valve with two spool positions: (Type 4WREE...A...)
The function of this valve version basically corresponds to the valve with three spool positions. The 2 spool position valve is, however, only equipped with solenoid “a” (7). Instead of the 2nd proportional solenoid, a plug screw (10) is installed.
Due to the design principle, internal leakage which may increase over the life cycle is inherent to the valves.
The tank line must not be allowed to run empty. With corresponding installation conditions, a preload valve (preload pressure approx. 2 bar) must be installed.