2) WHEN THE RCV LEVER IS IN THE LOWER POSITION WHEN THE RCV LEVER IS IN THE LOWER POSITION S1 40 S2 760F6WE04 В When the RCV lever (4, boom) is pushed forward, the boom spool is moved to lower position by pilot pressure from EH control block (40). The oil from main pump (1) flows into main control valve (3) and then goes to small chamber of boom cylinder (12). The oil returned from large chamber of boom cylinder (12) returns to hydraulic tank (21) through the boom spool at the same time.
When the lowering speed of boom is faster, the return oil from the large chamber of boom cylinder combines with the oil from the pump through the regeneration check valve, and flows into the small chamber of the cylinder. This prevents cylinder cavitation by the negative pressure when the pump flow cannot match the boom down speed. В В В 6-5 13 12 28 PS RH 28 PS a2 a3 LS 3 T P a1 A1 B1 A2 B2 pst A3 B3 Floating Aux Bucket Boom Down 4 Joystick Dump 5 9 Control unit Bucket Boom Aux back (Electro-Hydraulic & Joysick steering) Roll Up EH18 EH17 EH20 EH19 EH22 EH21 T P 4 1 6(4) 3(2) 5(3) 2(1) ( ) :
2 Spool b1 Regeneration A2 B2 check valve To MCV b2 LH b3 12 a3 b3 a1 b1 a2 b2 41 A1 Steering valve 27 27 10 (EHPS) EF port Steering valve (EHPS) LS port S1 X1 X2 P1 T 11 X3 Return line 28PS1 X1 X2 22 Return line ring system 23 B1 B2 24 25 21 S1 L2 L1 S2 L4L3 Fan & brake pump 3 12 28 PS RH 28 PS a3 LS A3 B3 a2 1 B1 A2 B2 pst Dump Down Floating Bucket back Roll Up Boom Aux