Komatsu PC500LC-10R Shop Manual page 256

COMPONENT PARTS OF HYDRAULIC SYSTEM 10 STRUCTURE AND FUNCTION
OPERATION OF ARM REGENERATION CIRCUIT OF CONTROL VALVE
When cylinder head pressure is higher than bottom pressure
When the cylinder head pressure is higher than the bottom pressure, part of pressurized oil (A) from the cylinder
head flows to drain circuit (B) through the notch of arm spool (2).
The remaining oil flows to the regeneration circuit (C), opens check valve (6), and flows to the cylinder bottom
through circuit (D).
The flows from regeneration circuit (C) and main pump (1) merge in circuit (E).
10-162 PC500LC-10R