GROUP 4 SINGLE OPERATION 1.
BOOM UP OPERATION TRAVEL MOTOR-LH TRAVEL MOTOR-RH SWING MOTOR PP L/H R E D R E D R/H R E D DR PP PP A(FW) B(BW) DR2 DR1 DR1 DR2 A(FW) B(BW) ARM CYL EXTENSION CYL DOZER CYL STOP VALVE B(CW) A(CCW) T BOOM HOLDING VALVE SOLENOID SELECTOR 3WAY VALVE BUCKET CYL BOOM CYL D B C A G H F E T P TURNING JOINT C2 C3 C1 C4 P2 P1 B/SWING CYL B10 A10 B7 A9 B8 Pa10 Pb8' DR2 Pa8 Pa6 Pa7 Pa4 Pa5 AC Pa3 Pa1 Pa2 BUCKET BOOM DOZER MAIN CONTROL VALVE Pb10 T2 Pb6 Pb7 Pb4 Pb8 Dr1 BU Pp1 T1 Pb3 Pb1 Pb2 TRAVEL L/H 2 1 Pb7 Pa7 SAFETY 2-SPEED ACC A1 A2 7 B/SWING 2WAY OPT K1 K2 LH 1 2 RH LH 1 2 RH P4 P2 P1 K3 TR T Pb2 Pa2 Pb4 Pa4 SOLENOID VALVE K4 MAIN PUMP 189AK3HC10 When the right control lever is pulled back, the boom spool 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 cylinder. At the same time, the oil from the small chamber of boom cylinder 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.
3-11 P1 P2 A7 A6 B6 A5 B5 PTO A4 B4 P3 B3 A3 B2 ARM SWING CROWD A2 B1 A1 ARM TRAVEL(RH) TRAVEL(LH) BS MRV-P2 MRV-P1 MRV-P3 DOZER /H 3 4 DOWN UP 1 2 Pa6 Pb6 Pb1 Pa1 SWING ARM BUCKET BOOM LH RH OUT IN IN OUT UP DOWN 1 3 2 4 3 1 2 4 Pb3 Pa3 Pb5 Pb10 Pa10 Pb8 Pa5 Pa8