TM 5-3805-280-24-1
Theory of Operation
BOOM AND ARM REDUCED LEAKAGE VALVES OPERATION
9025
05
52
shifts the pilot valve (F). The oil pressure from the
Reduced leakage valves (G) are used in the boom
cylinder is blocked by the pilot valve. The oil pressure
head end circuit and arm rod end circuit. The function
at the top (spring end) of check valve poppet can now
of a reduced leakage valve is to reduce cylinder drift
flow through the pilot valve to the warm-up passage in
by stopping leakage from the cylinder back through the
the pilot caps and then to the hydraulic oil tank. The oil
control valve.
pressure from the cylinder pushes the poppet off its
seat opening the passage for oil to flow into the control
When the control valve is in neutral, the oil pressure
valve return passage. The poppet is pushed off its seat
generated in the boom cylinder head end or arm
because the OD of upper land at the head end of
cylinder rod end by the load on the cylinders is applied
poppet is slightly larger than the lower land.
to the top (spring end) of check valve poppet (E)
through the pilot valve (F). The poppet is held closed
The boom manual lower screw (H) is used to lower the
against the seat in housing trapping the oil from the
boom if the engine should stop with the boom in the
cylinder at the work port.
raised position. (See Lower Boom With Engine
Stopped in Group 9025-25.)
When boom down or arm in function is actuated, the
pilot pressure signal (C) from the pilot controller also
TX,05,GG2186 1920MAY981/1
6-49
