TM 5-3805-280-24-1
Theory of Operation
NOTE: The cross section of flow regulator valve
When the boom down or arm in (N) function is
shown in the illustration is in the boom up pilot
actuated, the pilot oil to move the control valve spool
circuit.
flows from the pilot controller through the manifold to
the pilot cap. Return oil from the opposite end of
control valve spool flows from the pilot cap to the
The pilot lines for boom, arm, bucket, and swing
manifold and through the orifice plate (K) in the spool
functions are connected through the flow regulator to
(J). As the return pressure increases, the spool is
the pilot caps on the control valve. The pilot lines for
pushed down in proportion to the pressure increase
propel function are connected directly to the pilot caps.
regulating the return oil flow to provide precise
movement of a function. From here, oil flows to the
The flow regulator valve (R) is a manifold containing
pilot controller.
similar flow regulator valve spools (J) in the arm out
and boom up pilot circuits. Check valves (E) are also
WARM-UP CIRCUIT OPERATION:
included in the warm-up oil passage (O) for arm in,
arm out, boom down, and boom up pilot circuits; no
When the pilot shut-off valve is in the OFF position
check valves are used in the bucket and swing pilot
and the engine is running, pilot oil flows from the pilot
circuits. Each valve spool contains an orifice plate (K)
shut-off valve (F) to the flow regulator valve manifold.
and springs. The size of the orifice is 2.5 mm (0.098
The oil is heated as it flows through a restriction at the
in.).
inlet to manifold. The warm-up oil from pilot shut-off
valve (L) flows through the warm-up oil passage (O)
When the boom up or arm out (M) function is actuated,
past the check valves (E) and out to the left and right
pilot oil from the pilot controller (A) flows through the
pilot controllers and top pilot caps to warm the pilot
spool into the bottom spring chamber and through the
circuit. At the pilot controllers, the warm-up oil flows
orifice plate (K) to the pilot cap (D). As the pressure
through the pilot controllers, out the return port,
increases the spool pushes upward allowing pilot oil to
through the pilot shut-off valve to the solenoid valve
flow unrestricted to the pilot cap to move the control
manifold, and then to the hydraulic oil tank. At the pilot
valve spool. The spool acts as a check valve (I).
caps, warm-up oil flows through orifices into a return
Return oil from the opposite end of control valve spool
9025
passage in the pilot caps and then to the hydraulic oil
flows from the pilot cap and through the manifold to
05
tank.
the pilot controller.
13
TX,9025,GG2290 1929MAY982/2
6-12