4.
ARM ROLL OUT OPERATION TRAVEL MOTOR-LH TRAVEL MOTOR-RH L/H R E D R E D R/H SWING MOTOR R E D PP DR PP PP ARM CYL EXTENSION CYL DOZER CYL A(FW) B(BW) DR2 DR1 DR1 DR2 A(FW) B(BW) STOP VALVE B(CW) A(CCW) T D B C A G H F E T P TURNING JOINT SOLENOID SELECTOR 3WAY VALVE BUCKET CYL BOOM CYL C2 C3 C1 C4 P2 P1 B/SWING CYL DR2 Pa8 B10 A10 B7 A9 B8 Pa10 Pb8' Pa8 Pa6 Pa7 Pa4 Pa5 AC Pa3 Pa1 Pa2 DOZER BUCKET BOOM Pb10 T2 Pb1 MAIN CONTROL VALVE Pb8 TRAVEL DOZER R/H L/H 2 4 3 1 DOWN UP 1 2 Pb6 Pa6 Pb7 Pa7 Pb1 Pa1 A B C D SAFETY 2-SPEED ACC A1 A2 7 B/SWING 2WAY OPT BOOM SWING BUCKET ARM E K1 K2 LH 1 2 RH LH 1 2 RH LH 1 2 3 2 RH IN OUT UP DOWN OUT IN 4 4 1 3 P1 P2 P3 P4 P2 P1 K3 TR T Pa3 Pb2 Pb3 Pa2 Pb4 Pa4 Pb5 Pb10 Pa10 Pb8 E SOLENOID VALVE K4 Pa5 Pa8 S1 MAIN PUMP HYD TANK 189AK3HC13 When the left control lever is pushed forward, the arm spool in the main control valve are moved to the roll out position by the pilot oil pressure from the remote control valve.
The oil from the P2 and P3 pump flows into the main control valve and then goes to the small chamber of arm cylinder. At the same time, the oil from the large chamber of arm cylinder returns to the hydraulic oil tank through the arm spool in the main control valve. When this happens, the arm rolls out. The cavitation and excessive pressure in the rod of the arm cylinder is also prevented by the make- up valve and relief valve in the main control valve. 3-14 P1 P2 7 A6 B6 A5 B5 A4 B4 TRAVEL(LH) TRAVEL(RH) ARM PTO P3 B3 A3 B2 ARM SWING CROWD A2 B1 A1 BS MRV-P1 MRV-P2 Relief valve Make up valve MRV-P3 Pb7 Dr1 Pb6 Pb4 BU Pb5