Komatsu Galeo PC138US-8 Shop Manual page 175

10 Structure, function and maintenance standard
3. When boom is lowered
Operation
If the boom is lowered, pilot pressure (P1) from
q
the PPC valve pushes pilot spool (3) and the
pressurized oil in chamber (b) in the poppet is
drained.
The pressurized oil in port (Ab) is raised by the
q
pressurized oil from the boom cylinder bottom,
but the pressurized oil in chamber (b) is low-
ered by orifice (a).
If the pressure in chamber (b) is lowered below
q
the pressure in port (Aa), poppet (5) opens and
the pressurized oil from port (Ab) flows through
port (Aa) into the control valve.
PC138US, USLC-8
SEN02549-02
41