Komatsu ecot3 PC300LC-8 Shop Manual page 161

10 Structure, function and maintenance standard
LS select valve
Function
Prevents high LS pressure from the swinging
q
from entering the LS circuit of work valves
while the swinging and work equipment are in
combined operation.
Prevents high pressure generated during
q
swing drive and improves operability of work
equipment.
a The illustration shows the state of simulta-
neous operation of swinging and R.H. travel.
[(BP) pressure ON]
1. Valve
2. Spring
3. Piston
4. Piston
5. Swing spool
6. L.H. travel spool
7. Arm spool
8. LS shuttle valve
9. LS circuit
PC300, 350-8
Operation
1. If pilot pressure (BP) is OFF
q Since pilot pressure (BP) is OFF, piston (3) is
pressed to the left by spring (2).
q When swing-operated, swing LS pressure (P1)
enters port (A) after passing swing spool (5).
q Valve (1) is pressed to the left and ports (A)
and (B) are interconnected.
Swing LS pressure (P1) flows to LS shuttle
q
valve (8).
2. If pilot pressure (BP) is ON
q If pilot pressure (BP) is ON, BP pressure con-
tracts spring (2), and piston (3) shifts to the
right.
q Valve (1) is pressed to the right and intercon-
nection between ports (A) and (B) is closed.
q Swing LS pressure (P1) stops flowing to LS
shuttle valve (8).
q If swing LS pressure (P1) rises, other LS cir-
cuits are not affected.
SEN01994-01
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