Lift control spool valve with Rexroth auxiliary spool valves


The lift control spool valve is fixed to a manifold provided with three drilled channels. It is mounted on the centre housing, in front of the lift control shaft. The role of the spool valve is to regulate the oil flow, the feed to and return from the lift rams, in relation to signals transmitted by the electronic linkage control (ELC) calculator. It has a LS port for the Load Sensing system. This control port allows the spool valve to transmit pressure information to the variable displacement pump, via the priority block(s).
- The number of hydraulic ports on the lift control spool valve varies depending on whether it is assembled with a manifold (21) and Rexroth auxiliary spool valves

Lift control spool valve with Rexroth auxiliary spool valves
- The lift control spool valve is fixed on a manifold that has three ports.
- It is assembled on the centre housing in front of the lift control shaft.

Designation of the ports

- On the manifold (21)


with Rexroth auxiliary spool valves
(15) Return to housing
(30) HP feed from variable displacement pump via the priority block(s)
(31) LS signal

- On the lift control spool valve (17)


with Rexroth auxiliary spool valves
(15) Return to housing
(16) HP feed to rams
(30) HP feed from variable displacement pump via the priority block(s)
(31) LS signal


To distinguish a hydraulic problem from an electrical problem, operate the push buttons on the end of the solenoid valves (13) (14), thus eliminating the effect of the electrical circuit on lift control.

Special points
- The return oil from the lift control spool valve is directed to the centre housing at the manifold (21)
outlet by a large section pipe the end of which is beneath the oil level.
- This pipe is also used for the return from the auxiliary spool valves.

Diagrams


Layout with Rexroth auxiliary spool valves
(1) Priority block(s)
(17) Lift control spool valve
(20) Auxiliary spool valves
(21) Manifold
(31) LS signal to pump regulator via the priority block(s)
P : High pressure
R : Return beneath the oil level
V : Lift rams

Removing and refitting the spool Valve

On the manifold with Rexroth auxiliary spool valves
- Access to the lift control spool valve is limited given the presence of the neighbouring components. Before removing it, disassemble the Rexroth auxiliary spool valves.
- The seals (1) are maintained in the spot faced ports of manifold (21) by washer "R" and rings "B" (depending on the channels), in order to provide the correct oil tightness of the mating face when the lift control function is activated.


Removal
Disassemble the auxiliary spool valves. Locate the colour of the connector and disconnect the Move Up solenoid valves (13) and the Move Down solenoid valves (14). Using a locally manufactured tool, disassemble the feed pipes to the rams, connected to union (16)Take out bolts (1). Remove the cover (2) and spool valve (17). Take off the seals, washer "R" and rings "B".


Refitting
Clean the mating faces of the cover and the spool valve.
Position new seals (1) with washer "R" and rings "B" on the channels concerned of the manifold (21). Replace the seals (1) between the spool valve (17) and the cover (2). Fit and tighten bolts (1) to a torque of 25 - 35 Nm.
Definitively tighten union (16) on the ram feed pipes.
Reconnect the solenoid valves (according to their markings) and refit the auxiliary spool valves. Start the engine.
Check the operation of the lift control system and the auxiliary spool valves, the oil tightness of all seals and hydraulic unions.