THEORY OF OPERATION - CONTINUED
HYDRAULIC SYSTEM - CONTINUED
When less flow is required, piston pump destrokes. Piston pump destrokes when force at right of flow
compensator spool becomes greater than force at left.
Flow compensator spool moves left, which allows more oil flow to actuator piston. Pressure on actuator
piston is now increased.
Increased pressure overcomes force of bias spring, which moves swashplate to a reduced angle. When
pressure from pump outlet matches force at left of flow compensator spool, spool returns to a metering
position. Piston pump will return to a constant flow.
These conditions result in destroking piston pump:
(a) Hand metering unit is turned at a slower rate of speed.
(b) Engine speed increases.
N OT E
Load sensing signal pressure does not need to decrease in order to destroke piston pump.
When piston pump destrokes, supply oil pressure from pump outlet decreases on right side of flow com-
pensator spool. Pressure on left side of flow compensator spool is sum of load sensing signal and margin
spring pressures. Flow compensator spool will meter force on both ends of spool. Once forces become
equal on each end of spool, system will stabilize.