GROUP 4 SINGLE OPERATION 1. BOOM UP OPERATION R/G R/G Ps Ps Pm1 T1,T2 Pm2 Pm2 T1,T2 Pm1 P2 P1 P P2 P1 Rs CK1 Pn2 Pn1 D B A C DR BC COMP.
NRV2 NRV1 S/Motor DB Pk Pc5 C5 D5 A5 B5 Pb5 Pd5 OPTION-B BUCKET CK2 Pa5 (RG) SGo Dr SRG ARG SH DR3 Pc4 C4 D4 1 REGENERATIION CUT Pb4 B4 Au Dr(R7) PG Pd4 0 Pc4 0 ARM1 OPTION-A BREAKER Pc4 2 Pa4 DR2 Pc3 Pa2 1 ARM2 Pd4 Pb3 1 GB GA B(CW) Mu A(CCW) C2 D2 V3 BOOM2 Pb2 1 B2 A2 Pd2 Pc2 SWING BOOM1 P02 DR1 Pa2 Pb2 0 0 Pc1 D1 Pd1 C1 Patt A1 Pb1 B1 Pa1 P01 DR0 TRAVEL (LEFT) TRAVEL (RIGHT) Ptr STRAIGHT TRAVEL T1 P2 P1 Pu MRV SWING ARM BUCKET BOOM TRAVEL (2) (4) (3) (1) SH (3) (1) (2) (4) (1) (2) (3) (4) A1 A2 Psv a4 A B D E G F H J Pd2 Pc2 Pc4 0 Pa2 0 Pb2 0 T P Pd4 0 Pa5 Pb5 Pd1 Pc1 Pb1 Pa1 Dr#,dr#,R# a2 a1 Pm1 (Pump) Pm2 (Pump) Pk (T/Joint) Pi1 (Fl,MCV) Pi2 (Fr,MCV) Pm1 Pm2 A1 A2 A1 A2 ACC P3 P4 PG(S/Motor) Po1(MCV) M T(dr2) T T P2 P1 Dr B1 B3 A3 a3 D21073HS09 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 front and rear 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. 3-12