Komatsu ecot3 PC300LC-8 Shop Manual page 169

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