Electro-hydraulic directional valves type WEH use solenoids as pilot control. It is for sub-plate
mounting, and its porting patten accords with DIN 24 340 and ISO 4401.
There are many different features and additional device for selection.
Solenoids of pilot valve are wet-pin DC or AC.
The main valve uses spring or hydraulic centered and spring or hydraulic offset. With or without
shifting time adjustment; With or without stroke adjustment ; Pre-load valve or throttle insert can
be installed in the main valve. Pressure reducing valve can be installed when operating pressure
exceeds 25 MPa.
Valves of type WEH are directional spool valves with electrohydraulic operation, using the directional
valve as pilot control. They control the start, stop and direction of a fluid flow.
The directional valves basically consist of the main valve with housing (1), main control spool (2), one
or two return springs, and the pilot valve (4) with one or two solenoids.
The main control spool (2) is held in the neutral or in the initial position either by the springs or by
means of pressure. Pilot valve has wet DC or AC solenoids (5), optional. The main control spool is
shifted by pilot valve (4).
The pilot valve has 4 versions (see symbols).
Hereinafter it is illustration for various valves.
4/3-way directional valve with spring centred of the main valve.
The main control spool (2) is held in the neutral position by two return springs (3), and the two spring
chambers (6) are connected to the tank via the pilot valve (4). The pilot oil is supplied via the pilot line
(7). When the pilot valve (4) switches direction(one solenoid of the pilot valve energizes), the pilot
fluid acts on the one end of the main spool (2) and pushes it (2) to move and the required port is
connected, thus the flow direction of the fluid is changed.
When the solenoid is de-energized, the pilot spool returns to its initial position (exception: impulse
valve). The spring chambers (6) are connected to tank by pilot valve (4). Under the force of spring, the
spool returns to its neutral position. The oil in the spring chamber (6) flows to return line from external
port Y or internal line T via the pilot valve (4).
4/3-way directional valve with hydraulic centred of the main control spool.
The main control spool (2) is held in the neutral position by pressure oil acting on the two end faces,
and is located in the neutral position by a locating sleeve(9).
By removing the pressure from one of the spool(2) ends, the main control spool(2) is moved to the
shifted position. The fluid in unload chamber flows into Y channel via the pilot valve(4) , and the internal
drain fluid direct return to tank via port L.