The 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.
In version 4WREEM..., the valve is equipped with a symmetric spool overlap and features an operating direction and spool central position monitoring function.
In addition, version 4WREEM...J... has a step function to compensate for this overlap. This means that the spool overlap is passed quickly.
The valve is mainly used in machines with high safety requirements, e. g. in hydraulic press controls.
Set-up:
The valve basically consists of:
- Housing (1) with connection surface
- Control spool (2) with compression springs (3 and 4)
- Solenoids (5 and 6) with central thread
- Integrated electronics (8)
Function:
- With de-energized solenoids (5 and 6), central position of the control spool (2) due to compression springs (3 and 4)
- Direct actuation of the control spool (2) by energization of one proportional solenoid, e. g. solenoid "b" (6)
- 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 flow
- Switching off of solenoid “b” (6)
- Control spool (2) is returned to the central position by the compression spring (3)
If no enable signal is available, the output stage is locked and the valve is not functional. The readiness for operation of the output stages can be queried via pin 8. If the supply voltage fails or if no command value is available, the valve control spool is maintained in the central position by centering springs. In this spool position, A, B, P are blocked with spool E and A and B are connected to T with spool W.
Monitoring function:
- Monitoring of the control spool position via an inductive position transducer
- Output signals of the integrated electronics can be evaluated by an external safety control in order to detect any malfunction of the valve
- The power output stages are blocked by switching off the voltage for enable (pin 3). Notice: Not released for switching off according to EN13849!
- The output stages are enabled via the enable input (pin 3). The status message is sent via pin 8
- The signals to the signal outputs pin 9, pin 10 and pin 11 of the connector are led out. The signals are enabled by the logic switching statuses if the threshold values (+ Xw and – Xw) are exceeded
- The switching signals are used in a superior control system for monitoring functions
Precondition for the use as a safety-relevant component in hydraulic circuits:
- The entire control must meet the requirements of the standards that are relevant for the application, such as e. g. EN693, EN12622 or EN13849
- If safety requires or if the control system detects an error, switching off the supply voltage (pin 1 and pin 2) and enable (pin 3) must cause the valve to be switched off
- The valve must not be operated vertically with the spool position sensor hanging upside down
Important notice:
The PG fitting (9) must not be opened. Mechanical adjustment of the adjustment nut located below is prohibited and damages the valve!
Notice:
Due to the design principle, internal leakage which may increase over the life cycle is inherent to the valves.
Notice:
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.
