6.
COMBINED BOOM AND TRAVEL OPERATION ARM CYLINDER BUCKET CYLINDER BOOM CYLINDER TRAVEL MOTOR P5 P4 Pi2 Rs MU Pi1 Pn1 Pn2 SWING MOTOR PCa PDa PBa PAb1 P02 P04 PDb2 SH A2 PUMP A1 PUMP PILOT PUMP HYDRAULIC TANK 330S3HC22 BC1 NRV2 Cck BC2 NRV1 Cco CoR AkR LCk1 LCk2 DoR LCo CaR DaR BUCKET BbkR BaDR7 CRa PaL ARM1 LCa LCa2 ARM2 PAa2 DR6 a2 PCsp PDb2 BOOM2 Ccb SWING P/R LCar LCbk ARM REGEN P02 Abk PBrc PAbk DR4 Cs Ds PCs PDs DR5 SWING P03 LCs BbR AbR LCb CRb BOOM1 DR3 Ctl Dtl PCtl PDtl Patt (RIGHT) TRAVEL S DR1 BtR AtR (LEFT) TRAVEL P01 PtrPS TS STRAIGHT TRAVEL SPOOL MRV When the boom and travel functions are operated, simultaneously the boom spools and travel spools in the main control valve are moved to the functional position by the pilot oil pressure from the remote control valve and the straight travel spool is pushed to the right by the oil pressure from pilot pump.
The oil from the A1 pump flows into the travel motors through the RH travel spool of the left control valve and the LH travel spool of the right control valve via the straight travel spool. The oil from the A2 pump flows into the boom cylinders through the boom 2 spool and boom 1 spool via the parallel and confluence oil passage in case boom up operation. When the pressure of the travel motors is lower than the pressure of the boom cylinders, some oil from the A2 pump flows into the travel motors through the check valve and orifice in the straight travel spool. This prevents the rapid slowdown of the travel. The boom is operated and the machine travels straight. 3-29