3. ARM ROLL IN OPERATION R/G R/G Ps Ps Pm1 Pm2 Pm2 Pm1 P2 P1 T1,T2 T1,T2 P2 P1 P Rs CK1 Pn2 Pn1 D B A C DR BC COMP.
NRV2 NRV1 S/Motor DB Pk D5 C5 A5 B5 Pc5 Pd5 OPTION-B BUCKET CK2 Pb5 Pa5 (RG) SGo Dr SRG ARG SH DR3 C4 D4 B4 Au PG Pd4 0 Pc4 Pc4 1 ARM1 REGENERATIION CUT OPTION-A BREAKER Pc4 2 Pa4 Pb4 Dr(R7) 0 DR2 Pc3 Pb3 GB GA Pa2 1 V3 BOOM2 ARM2 Pd4 B2 1 B(CW) Mu A(CCW) Pd2 Pc2 C2 D2 Pb2 1 A2 DR1 Pa2 Pb2 0 C1 SWING BOOM1 P02 Patt B1 0 Pc1 D1 Pd1 TRAVEL (LEFT) TRAVEL (RIGHT) A1 Pb1 Pa1 P01 DR0 Ptr STRAIGHT TRAVEL T1 P2 P1 Pu MRV SWING ARM BUCKET BOOM TRAVEL (2) (4) (3) (1) SH (3) (1) (2) (4) (1) (2) A1 A2 Psv a4 A B D E G F H J Pd2 Pc2 Pc4 0 Pa2 0 Pb2 0 T P Pa5 Pb5 Pd1 Pc1 Pb1 Pa1 (3) (4) Dr#,dr#,R# a2 a1 Pm1 (Pump) Pm2 (Pump) Pd4 0 Pk (T/Joint) Pm1 Pm2 A1 A2 A1 A2 ACC P4 PG(S/Motor) Pi1 (Fl,MCV) Pi2 (Fr,MCV) M T P2 P3 P1 Po1(MCV) Dr B1 B3 A3 a3 T(dr2) T D21073HS11 When the left control lever is pulled back, the arm spools in the main control valve are moved the to roll in 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 arm cylinder. At the same time, the oil from small 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 in. The cavitation which will happen to the bottom of the arm cylinder is also prevented by the make-up valve in the main control valve. 3-14