Vehicle System System Operation 23
Working Principle of Lifting Valve Section
1. Neutral Position
Oil from the pump returns to the tank through
unload path.
2. Lifting up of spools
Close the unloading path, oil from the pump opens a
load check through parallel path and flow out from
port A. Spool returns to neutral position by the
neutral spring.
3. Lifting down of spool
When lifting down the spool, unload path is not
closed, oil from the pump returns to the tank.
Meanwhile, oil from Port Are turns to tank through
the back flow path open by the spool. And the spool
comes back to the neutral position by reset spring.
Working principle of tilting valve
1. Neutral Position
Oil from the pump returns to the tank through unload
path.
2. Tilting up of spool
While unload path is closed, oil from pump opens a
load check through parallel path and flow out from
Port B. Flow back oil at port Are turn to the tank
through tank path. When the cylinder load is in
excess of the rated pressure of relief valve, the relief
valve works with oil flows into tank path and the
spool return to the neutral position by the spring.
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