Komatsu ecot3 PC300LC-8 Shop Manual page 172

SEN01994-01
Arm drift prevention valve
(if equipped)
1. When arm OUT
Function
q This valve prevents the oil in the arm head
from leaking through spool (1) and the boom
from lowering under its weight while the arm
lever is not operated.
Operation
q When the arm OUT is operated, pressurized
oil from the control valve works on the ring-
shaped area (S)[=
caused by the difference between the outside
diameter (d1) of poppet (5) and the seat diam-
eter (d2) to move it to the left.
q Contracts spring (4) and poppet (5) moves to
the left.
As a result, pressurized oil from the control
q
valve passes through the opening of poppet
(5) and flows to the arm cylinder head.
46
φ φ
(d1) area – (d2) area]
10 Structure, function and maintenance standard
PC300, 350-8