Theory of Operation
NOTE: The cross section of flow regulator valve spool
spool into the bottom spring chamber and through the
shown in the illustration is in the arm out pilot
orifice plate (K) to the pilot cap (D). As the pressure
increases the spool is push up letting pilot oil flow
unrestricted to the pilot cap to move the control valve
spool. The unrestricted pilot oil flow past the spool is
The flow regulator valve (Q) is an manifold containing
represented by the check valve (I) in the schematic.
a flow regulator valve spool (G) in the arm out pilot
Return oil from the opposite end of control valve spool
circuit and check valves (E). The check valves (E) are
flows from the pilot cap and through the manifold to
used in the warm-up oil passage (L) for arm in, arm
the pilot controller.
out, boom down, and boom up pilot circuits. No check
valves are used in the bucket and swing pilot circuits.
When the arm in (N) function is actuated, pilot oil flows
The valve spool contains an orifice plate (K) and
from the pilot controller through the manifold to the
springs (J) and also operates as a check valve (I).
pilot cap shifting the control valve spool. Return oil
from the opposite end of control valve spool flows from
The pilot lines for boom, arm, bucket, and swing
the pilot cap to the manifold and through the orifice
functions are connected through the flow regulator
plate (K) in the valve spool (G). As the return pressure
valve manifold to the pilot caps on the control valve.
increases, the spool is pushed down in proportion to
The arm out pilot line (D) is also connected to the PL
the pressure increase regulating the return oil flow to
port at the arm head end reduced leakage valve. The
provide precise movement of the arm in function. From
pilot lines for propel function are connected directly to
here, oil flows to the pilot controller.
the pilot caps.
When the arm out (M) function is actuated, pilot oil
flows from the pilot controller (A), through the valve