New Holland WorkMaster 50 Service Manual page 462

Hydraulic systems - Main control valve
Main control valve - Overview
The distributor is pre-set to perform three phases.
A. Neutral phase
B. Lifting phase
C. Lowering phase
A. Neutral phase
In this phase the control valve keeps pressure on the oil contained in the cylinder thus allowing the oil coming from
the pump to flow freely to the tank.
In this phase the control spool (1) is in such a position to connect the chamber (5) of the differential valve (2) directly
to the discharge through hole (6).
The oil coming from the pump enters the annular duct (8) and moves the differential valve (2) upwards which then
opens the discharge hole (7) and enables the oil to go to the tank.
The oil contained in the cylinder (9) is kept under pressure by the check valve (3), by the discharge valve (4) and safety
valve (10) connected to the cylinder (9) by the annular duct (11) thus holding the load applied to the lifting arms.
The safety valve (10) secures protection from any possible over-pressure during the implement movement.
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