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The oil from the A1 and A2 pump flows through the neutral oil passage, bypass oil passage and
confluence oil passage in the main control valve. Then the oil goes to each actuator and operates
them. Check valves and orifices are located on these oil passage in the main control valve. These
control the oil from the main pumps so as to correspond to the operation of each actuator and
smooth the combined operation.
STRAIGHT TRAVEL SPOOL
This straight travel spool is provided in the main control valve.
If any actuator is operated when traveling, the straight travel spool is pushed to the right by the pilot
oil pressure from the pilot pump.
Consequently, the left and right travel oil supply passage are connected, and equivalent amount of
oil flows into the left and right travel motors. This keeps the straight travel.
1. OUTLINE
PS
(P4)
(P3)
N2
Pca
Dr3
P2c2
Ba
Aa
PAa
PBa
Bo
Ao
PAo
PBo
(Ck2)
Drb
PBb2
PSp
Dra
Bs
As
PAs
PBs
Dr4
Pns
Br
Ar
PAr
PBr
TRAVEL(RH)
SWING
BOOM 2
T1
Pa
P2
P1 P1g
P2g
R4
(PTb)
PS
PL1
Py
PBL
PAL
BL
AL
Px
P
PBb
PAb
Ab
Bb
P2c1
Dr3'
PBc
PAc
PAcs
Bc
Ac
PBa2
PAa2
Pcb
N1
OPTION
ARM 1
ARM 2
BUCKET
BOOM 1
TRAVEL(LH)
SH
HYDRAULIC TANK
STRAIGHT
TRAVEL
SPOOL
TRAVEL MOTOR
SWING MOTOR
ARM
CYLINDER
BUCKET
CYLINDER
BOOM
CYLINDER
PILOT
PUMP
R3
PUMP
A1
PUMP
A2
GROUP 5 COMBINED OPERATION
380L3HC20