Komatsu Galeo PC138US-8 Shop Manual page 232

SEN02550-01
3. When returning pressurized oil to the main
valve from the work equipment cylinder
When the piping is free of burst
Holding pressure of the work equipment cylin-
q
der is led to chamber (b) and check valve (5)
closes.
Pilot pressure from the PPC valve is led to port
q
(PI) and reaches [Pilot Pressure > Force of
Spring (3)] (area of d).
Spool (1) moves to the right to the standby
q
position.(1st stage stroke)
At this point, chambers (a) and (b) are not
q
interconnected.
Pilot pressure further rises, and reaches [Pilot
q
pressure > Force of spring (2)] (area of d).
Spool (1) moves further to the right, and cham-
q
bers (a) and (b) are interconnected. (2nd stage
stroke)
Pressurized oil returns to the control valve
q
from the work equipment cylinder.
50
10 Structure, function and maintenance standard
If the piping is bursted
If piping (A) bursts between the control valve
q
and the work equipment cylinder.
Pressurized oil in chamber (a) flows out to the
q
bursted portion but resupplied from chamber
(b).
Since pressurized oil flows via opening (c) of
q
spool (1), a sudden drop of the cylinder is pre-
vented.
PC138US, USLC-8