The symbol is representative of the mechanics. We find 4 holes:
- P : Pressure.
- T : Tank.
- A & B: Directional valve Outlets.
The spool has 3 positions (item 7):
- A central position: P closed, A & B open to T.
- A straight arrows position: P to A & B to T.
- A crossed arrows position: P to B & A to T.
The spool is pulled back by 2 springs (items 11 and 10).
The control is electric, the coils are represented (item 5 and item 6).
To note : A pusher (item 8) makes it possible to force the spool manually by means of a peg. This additional command is very useful during troubleshooting. It allows to force the control of the directional valve and to quickly know if the problem is electric or hydraulic.
The pump (item1) driven by a heat engine (item 2) delivers 30l / min. The spool (item 7) of the directional valve isolates the orifice P from the other outlets. The oil from the pump accumulates and returns to the tank by raising the pressure relief valve to 200 bars observed in M1.
It can be seen that the two chambers of the jack (item 9) are decompressed in the tank by the spool (item 7) of the directional valve. The cylinder can enter or leave depending on the mechanical stresses it may suffer. It is says "floating".
