2) WHEN THE RCV LEVER IS IN THE LOWER POSITION Steering unit P port 3 Steering unit LS port SX P Pst T Regeneration check valve b1 b3 b2 4 B.D/F B.U CRAWD DUMP 1 3 4 2 P T 1.1 2.1 7 A1 P1 T Cut off valve P1 port Return line 24 X1 PS 1 18 Return line B1 E/G 17 L L1 S1 74096WE04 В When the RCV lever (4) is pushed forward, the boom spool is moved to lower position by pilot pressure. The oil from main pump (1) flows into main control valve (3) and then goes to small chamber of boom cylinder (8) by pushing the load check valve of the boom spool. The oil returned from large chamber of boom cylinder (8) returns to hydraulic tank (17) 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 6-6 9 8 LH a1 a2 A1 B1 A2 ( ) ( ) mp Floating )( ) ( Du Rollback Down Up