Komatsu ecot3 PC300LC-8 Shop Manual page 180

SEN01994-01
2-stage safety-suction valve
[Installed to port (B) on the boom cylinder head side and port (B) of the service valve]
1. Spring
2. Piston
3. Spring
4. Holder
Function
q Enables to provide the safety valve set pres-
sure in two stages, and make the low-pressure
setting smaller.
Enables to relieve a load without lever opera-
q
tion if high load is applied to the cylinder.
q Improves work efficiency and reduces machine
body vibration.
54
10 Structure, function and maintenance standard
Operation
q The safety set pressure is determined by
spring (1) installed load.
1. If pilot pressure is OFF (high-pressure set-
ting)
q Since pilot pressure (P) is OFF, piston (2) is
pressed to the left by spring (3). [Spring (1)
installed load < spring (3) installed load]
q Spring (1) installed load becomes maximum
and the set pressure rises.
Passage (B) is interconnected to the drain cir-
q
cuit via passage (C) and chamber (D).
PC300, 350-8