4. ARM ROLL OUT OPERATION R/G R/G Ps Ps Pm1 Pm2 T1,T2 Pm2 T1,T2 Pm1 P2 P1 P2 P1 Rs CK1 Pn2 Pn1 D B A C DR P BC COMP.
NRV2 NRV1 S/Motor DB Pk C5 A5 B5 Pc5 Pd5 D5 OPTION-B BUCKET CK2 Pb5 Pa5 SRG ARG SH C4 D4 B4 (RG) SGo Dr PG Pd4 DR3 Pc4 1 REGENERATIION CUT BREAKER Pa4 Pb4 Au Dr(R7) 0 Pc4 0 ARM1 OPTION-A Pc4 2 Pb3 GB GA DR2 Pc3 Pa2 1 BOOM2 ARM2 Pd4 1 B(CW) Mu A(CCW) C2 D2 V3 Pb2 1 B2 A2 DR1 Pd2 Pc2 SWING BOOM1 P02 Pa2 Pb2 0 0 Pc1 D1 C1 Patt B1 A1 Pb1 Pa1 P01 DR0 Pd1 TRAVEL (LEFT) TRAVEL (RIGHT) Ptr STRAIGHT TRAVEL T1 P2 P1 Pu MRV SWING ARM BUCKET BOOM TRAVEL Psv (2) (4) (3) (1) SH (3) (1) (2) (4) Pd1 Pc1 Pb1 Pa1 (1) (2) (3) (4) A1 A2 a4 A B D E G F H J Pd2 Pc2 Pc4 0 Pa2 0 Pb2 0 T P Pd4 0 Pa5 Pb5 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 T P2 P1 Dr B1 B3 A3 a3 T(dr2) D21073HS12 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 front and rear 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 which will happen to the rod of the arm cylinder is also prevented by the make-up valve in the main control valve. 3-15