4) WHEN THE RCV LEVER IS IN THE DUMP POSITION 14 13 4 Aux Bucket 5 Control unit 6 EH18 EH17 EH20 EH19 4 1 6(4) 3(2) a3 b3 a1 b1 a2 b2 Steering valve (EHPS) EF port Steering valve (EHPS) LS port Return line Steering system 757F6WE06 В If the RCV lever (4, bucket) is pushed right, the bucket spool is moved to dump position by pilot oil pressure from EH control block (6). The oil from main pump (1) flows into main control valve (3) and then goes to the small chamber of bucket cylinder (14) by pushing the load check valve of the bucket spool. The oil at the large chamber of bucket cylinder (14) returns to hydraulic tank (22). When this happens, the bucket is dumped.
When the dumping speed of bucket is faster, the oil returned from the large chamber of bucket cylinder combines with the oil from the pump, and flows into the small chamber of the cylinder. This prevents cylinder cavitation by the negative pressure when the pump flow cannot match the bucket dump speed. В В В В 6-8 LH RH 29 PS PS 29 40 a1 a2 a3 P A1 B1 A2 B2 A3 B3 3 Floating Dump LS Boom Bucket Boom Aux Down Joystick 4' Pst back Up Roll ick steering) T H22 EH21 T P 5(3) 2(1) ( ) :
2 Spool Regeneration check valve To MCV b1 b2 b3 A1 28 28 11 12 S1 X1 X2 P1 T X3 9PS1 X1 X2 23 Return line B1 B2 24 25 26 22 S1 L2 L1 S2 L4L3 Fan & brake pump LH 40 a1 a2 A1 B1 A2 LH RH 29 PS PS 29 a3 B2 A3 B3 Dump Bucket Floating Down Boom Aux Roll back Up Up