3-10
When the right control lever is pulled back, the boom spools in the main control valve are moved to
the up position by the pilot oil pressure from the remote control valve.
The oil from the P1 and P3 pump flows into the main control valve and then goes to the large
chamber of boom cylinders. At the same time, the oil from the small chamber of boom cylinders
returns to the hydraulic oil tank through the boom spool in the main control valve. When this
happens, the boom goes up. The excessive pressure in the boom cylinder bottom end circuit is
prevented by relief valve. When the boom is up and the control lever is returned to neutral position,
the circuit for the holding pressure at the bottom end of the boom cylinder is closed by the boom
holding valve. This prevents the hydraulic drift of boom cylinder.
1. BOOM UP OPERATION
A1
A2
A4
A3
S1
S1
BOOM
SWING
Pb5
4
4
1
3
LH
BUCKET
ARM
A2
1
2
3
2
Pa5
Pb10
Pa10
T
A1
A2
RH
IN
OUT
UP
DOWN
OUT
IN
P
Pa3
Pb2
Pb3
Pa2
Pa8
Pb8
Pa10
Dr2
Pb8'
P2
P1
Pa6
Pa7
Pa4
Pa5
Pa3
Pa1
Pa2
Pb10
Pb8
T2
Pb6
Pb7
Pb4
T1
Pb3
Pp1
Pb1
Pb2
LH
1
2
RH
B/SWING
1
2
Pa4
Pb4
2WAY OPTION
ACC
P3
A6
B6
A3
B3
A4
B4
A2
B2
B1
A1
B5
A5
B10
A10
B7
A7
A9
B8
Dr1
Pa8
BU
2
4
3
1
L/H
R/H
Pb6
Pa6 Pb7
Pa7
TRAVEL
DOZER
DOWN
1
2
UP
Pb1
Pa1
PILOT PUMP
LINE FILTER
MAIN CONTROL VALVE
BUCKET CYL
BOOM CYL
DOZER CYL
TURNING JOINT
STOP VALVES
B/SWING CYL
BUCKET
ARM CYL
Pb5
Dr1
R1
MAIN PUMP
TRAVEL MOTOR-LH
SWING MOTOR
TRAVEL MOTOR-RH
a1
a2
Ps
T1
T2
R/G
R/H
L/H
T2
a2
a1
T1
Ps
R/G
GB
GA
"R1"
"R2"
DB
P2(BW)
P1(FW)
P2(FW)
P1(BW)
B(CCW)
A(CW)
Mu
PB
BOOM
HOLDING
VALVE
BOOM
TRAVEL-RH
TRAVEL-LH
ARM
PTO
DOZER
SWING
BOOM
SWING
GROUP 4 SINGLE OPERATION
R35Z73HC10
