5. BUCKET IN OPERATION ARM CYLINDER BUCKET CYLINDER BOOM CYLINDER P5 P4 Pi2 MU Pi1 TRAVEL MOTOR Rs Pn1 Pn2 SWING MOTOR PBa P02 PAb1 PDb2 P04 A2 PUMP A1 PUMP PILOT PUMP HYDRAULIC TANK 330S3HC13 When the right control lever is pulled left, the bucket spool in the main control valve is moved to the roll in position by the pilot oil pressure from the remote control valve. The oil from the A2 pump flows into the main control valve and then goes to the large chamber of bucket cylinder. The oil form the A1 pump flows into the large chamber of bucket cylinder through confluence oil passage in the main control valve by bypass cut pilot pressure (PCbc).
At the same time, the oil from the small chamber of bucket cylinder returns to the hydraulic oil tank through the bucket spool in the main control valve. When this happens, the bucket rolls in. The excessive pressure in the bucket cylinder head side is prevented by relief valve. The cavitation which will happen to the head side of the bucket cylinder is also prevented by the make-up valve in the main control valve.
3-18 BC1 NRV2 Cck Relief valve DR9 Co P05 Do PCo PDo OPTION Ca Da BC2 NRV1 Relief valve Cco CoR AkR LCk1 LCk2 DoR Make up valve OPTION LCo CaR DaR BUCKET BbkR DR7 CRa PaL ARM1 LCa LCa2 ARM2 PAa2 DR6 Csp Db2 BOOM2 Ccb SWING P/R LCar LCbk BbR ARM REGEN P02 Abk PBrc PAbk DR4 Cs Ds PCs PDs DR5 SWING P03 DR3 Ctl Dtl PCtl PDtl SH Patt ( TR RIG AVH ET L) PS DR1 P01 PtrPS TS Cs Ds PCs PDs DR5 SWING LCs AbR LCb CRb BOOM1 P03 DR3 Ctl Dtl PCtl PDtl Patt (RIGHT) TRAVEL DR1 BtR AtR (RIGHT) TRAVEL (LEFT) TRAVEL MRV