Komatsu PC500LC-10R Shop Manual page 251

10 STRUCTURE AND FUNCTION
C: Arm IN PPC pressure
D: Arm OUT PPC pressure
1: Boom cylinder
2: Arm cylinder
3: Arm Hi-spool
1.
When the boom is raised, boom RAISE PPC pressure (E) enters small chamber "d" and pushes boom Hi-
spool (5) to the left, then the pump pressure flows through the passage to the bottom of boom cylinder (1).
2.
When the arm IN operation is performed, arm IN PPC pressure (C) enters chamber "a" and pushes arm Hi-
spool (3) to the left, then the pump pressure flows through the passage to the bottom of arm cylinder (2).
3.
When the arm OUT operation is performed, arm OUT PPC pressure (D) enters chamber "b" and pushes
boom Hi spool (3) to the right, then flows to the drain passage. At the same time, the pressure flows into the
L.H. spring chamber through passage "c" in the boom Hi-spool, and presses and fixes the boom Hi-spool to
the right.
BOOM REGENERATION CIRCUIT OF CONTROL VALVE
FUNCTION OF BOOM REGENERATION CIRCUIT OF CONTROL VALVE
When the cylinder head pressure is lower than the bottom pressure (when hy-
draulic drift, etc.)
1: Main pump
2: Boom valve spool
PC500LC-10R
COMPONENT PARTS OF HYDRAULIC SYSTEM
E: Boom RAISE PPC pressure
4: Pump
5: Boom Hi-spool
3: Pressure compensation valve
4: Suction safety valve
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