GENERAL AR 2808672 - Caterpillar

Bucket Close
Illustration 1 g03730717
Hydraulic schematic for BUCKET CLOSE (1) Flow combiner PHMV (2) Bucket cylinder (3) Line (oil flow to bucket cylinder head end) (4) Line (oil flow from bucket cylinder rod end) (5) Main control valve (6) Flow combiner spool (7) Passage (8) Bucket independent metering valve (IMV) (9) Passage (12) Flow compensator (15) Drive pump bypass PHMV (16) Idler pump bypass PHMV (19) Return passage (23) Bucket pump-to-cylinder head end spool (24) Bucket cylinder-to-tank rod end spool (27) Load check valve (29) Drive pump (30) Pilot pump (31) Idler pump (61) Port (bucket OPEN) (62) Bucket rod end cylinder-to-tank PHMV (63) Bucket rod end pump-to-cylinder PHMV (64) Bucket head end pump-to-cylinder PHMV (65) Bucket head end cylinder-to-tank PHMV (66) Port (bucket CLOSE)A BUCKET CLOSE operation is accomplished when the oil delivery from only idler pump (31) is supplied to the head end of bucket cylinder (2). Flow combiner PHMV (1) is activated by the machine ECM. Flow combiner spool (6) then shifts to the center position blocking idler pump oil from the drive pump oil in passage (7). The oil from the idler pump then flows to bucket IMV section (8).
Illustration 2 g03124739
Main control valve (61) Port (bucket OPEN) (62) Bucket head end cylinder-to-tank PHMV (63) Bucket head end pump-to-cylinder PHMV (64) Bucket rod end pump-to-cylinder PHMV (65) Bucket rod end cylinder-to-tank PHMV (66) Port (bucket CLOSE)When the joystick for the bucket is moved to the full BUCKET CLOSE position, the ACS valve ECM activates pump-to-cylinder PHMV (64) and cylinder-to-tank PHMV (62). Pilot oil then shifts spool (23) and spool (24) upward. Simultaneously, the machine ECM activates idler pump bypass PHMV (16). Bypass PHMV (16) is modulated according to the joystick position. Pump oil is then supplied to passage (9) in main control valve (5) and supplied to bucket IMV section (8) .Drive pump bypass PHMV (15) is not activated by the machine ECM. The oil delivery from drive pump (29) flows through the bypass spool and returns to the hydraulic tank.
Illustration 3 g03009657
Bucket IMV section (bucket CLOSE) (2) Bucket cylinder (3) Line (oil flow from bucket cylinder rod end) (4) Line (oil flow to bucket cylinder head end) (9) Passage (12) Flow compensator (21) Pressure sensor (bucket cylinder rod end) (22) Pressure sensor (bucket cylinder head end) (23) Bucket pump-to-cylinder head end spool (24) Bucket cylinder-to-tank rod end spool (27) Load check valve (60) Bucket drift reduction solenoid valve (61) Port (bucket OUT) (62) Bucket head end cylinder-to-tank PHMV (63) Bucket head end pump-to-cylinder PHMV (64) Bucket rod end pump-to-cylinder PHMV (65) Bucket rod end cylinder-to-tank PHMV (66) Port (bucket IN)Pump delivery oil in passage (9) flows through flow compensator (12). Load check valve (27) opens and allows the pump oil to flow to bucket pump-to-cylinder spool (23). The pump oil then flows through valve port (66), and line (4) to the head end of bucket cylinder (2) .Return oil from the rod end of bucket cylinder (2) flows through line (3) to port (61). Return oil flows