The type 4WREE valve is a direct operated proportional directional valve with electrical position feedback and integrated electronics (OBE).
Set-up
The valve basically consists of:
- Housing (1) with connection surface
- Control spool (2) with compression springs (3 and 4) and spring plate (5 and 6)
- Solenoids (7 and 8) with central thread
- Integrated electronics (13)
- Electric zero point adjustment (12) accessible via the rubber plug
Function
- With de-energized solenoids (7 and 8), central position of the control spool (2) by compression springs (3 and 4) between spring plates (5 and 6)
- Direct operation of the control spool (2) by controlling a proportional solenoid, e.g. solenoid "b" (8)
- Displacement of the control spool (2) to the left proportional to the electric input signal
- This opens the connection from P to A and B to T via orifice-type cross-sections with progressive flow characteristic
In the de-energized condition, 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.
Valve with 2 spool positions (version "4WREE…A…")
The function of this valve version basically corresponds to the valve with three spool positions. The 2 spool position valves are, however, only equipped with solenoid "a" (7). Instead of the 2nd proportional solenoid, there is a plug screw (10).
Pressure compensation element in the OBE "-967"
To prevent condensate formation in the housing of the integrated electronics (OBE), an electronics protection membrane (11) can be used.
Recommended for use outside industry-standard conditions with high ambient air humidity and significant cyclic temperature changes (e. g. outdoors).
Notes:
- Due to the design principle, internal leakage is inherent to the valves, which may increase over the life cycle.
- 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.
- The PG fitting (14) must not be opened.
