GROUP 4 SINGLE OPERATION 1. BOOM UP OPERATION ARM CYLINDER BUCKET CYLINDER BOOM CYLINDER TRAVEL MOTOR P5 P4 Pi2 Rs MU Pi1 Pn1 Pn2 SWING MOTOR PBa PAb1 P02 P04 PDb2 A1 PUMP PILOT PUMP A2 PUMP HYDRAULIC TANK 330S3HC09 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 A1 and A2 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 1 spool in the main control valve. When this happens, the boom goes up.
The excessive pressure in the boom cylinder head side 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.
3-14 BC1 NRV2 Cck DR9 Co P05 Do PCo PDo OPTION Ca Da BC2 NRV1 Cco CoR AkR LCk1 LCk2 DoR 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 LCs AbR LCb Relief valve Holding valve CRb BOOM1 P03 DR3 Ctl Dtl PCtl PDtl SH Patt ( TR RIG AVH ET L) PS DR1 P01 PtrPS TS P03 DR3 Ctl Dtl PCtl PDtl Patt (RIGHT) TRAVEL DR1 BtR AtR (RIGHT) TRAVEL (LEFT) TRAVEL MRV