3-32
When the boom up and bucket functions are operated simultaneously, each spool in the main control
valve is moved to the functional position by the pilot oil pressure from the remote control valve.
The oil from the A1 pump flows into the boom cylinders through the boom 2 spool in the left control
valve. The oil from the A2 pump flows into the boom cylinders and bucket cylinder through the boom
1 spool, bucket spool and the parallel and confluence oil passage in the right control valve.
Also, when the boom up and bucket in functions are operated simultaneously, the boom up operation
preference function is operated by the pilot pressure PAcs and then the bucket spool transfers in the
half stroke not full stroke (Refer to page 2-33). Therefore, the most of pressurized oil flows into boom
1 spool than the bucket spool to make the boom up operation more preferential.
The boom and bucket are operated.
9. COMBINED BOOM UP AND BUCKET OPERATION
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
Bucket in strock
limiter spool
TRAVEL MOTOR
SWING MOTOR
ARM
CYLINDER
BUCKET
CYLINDER
BOOM
CYLINDER
PILOT
PUMP
R3
PUMP
A1
PUMP
A2
380L3HC28