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| Illustration 1 | g03741655 |
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Top of the main control valve (1) Drain port (2) Pilot port | |
The boom drift reduction valve is placed in the boom circuit between the main control valve and the boom cylinders. When the joystick for the boom is in the NEUTRAL position, the boom drift reduction valve stops oil leakage. The boom drift reduction valve stops oil leakage from the head end of the boom cylinders. Stopping oil leakage prevents boom drift.
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| Illustration 2 | g03741663 |
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Boom drift reduction valve (BOOM RAISE) (1) Drain port (2) Pilot port (3) Boom cylinders (4) Passage (5) Boom drift reduction valve (6) Spring chamber (7) Spring (8) Port (9) Valve (10) Passage (11) Spool (12) Drain passage (13) Passage (14) Boom control valve (15) Pilot control valve (16) Hydraulic tank | |
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| Illustration 3 | g03741966 |
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Boom drift reduction valve (BOOM RAISE) (1) Drain port (2) Pilot port (5) Boom drift reduction valve (6) Spring chamber (7) Spring (8) Port (9) Valve (10) Passage (11) Spool (12) Spool (17) Spring chamber (18) Plug | |
During a BOOM RAISE operation, pilot oil is not sent from pilot control valve (15) to port (2) of boom drift reduction valve (5). Spool (11) does not shift.
The oil flow from the boom control valve (14) enters through passage (4). As the oil pressure in passage (4) increases, valve (9) shifts against the force of spring (7). The oil in spring chamber (6) flows through passages (10) and (13) to port (8). The oil delivery in passage (4) now flows through valve (9) and port (8) to the head end of the boom cylinders (3).
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| Illustration 4 | g03741703 |
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Boom drift reduction valve (BOOM LOWER without regeneration) (1) Drain port (2) Pilot port (3) Boom cylinders (4) Passage (5) Boom drift reduction valve (6) Spring chamber (7) Spring (8) Port (9) Valve (10) Passage (11) Spool (12) Drain passage (13) Passage (14) Boom control valve (15) Pilot control valve (16) Hydraulic tank | |
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| Illustration 5 | g03742009 |
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Boom drift reduction valve (BOOM RAISE) (1) Drain port (2) Pilot port (5) Boom drift reduction valve (6) Spring chamber (7) Spring (8) Port (9) Valve (10) Passage (11) Spool (12) Spool (17) Spring chamber (18) Plug | |
During a BOOM LOWER operation, pilot oil is sent from the pilot control valve (15) to port (2) of boom drift reduction valve (5). Spool (11) shifts until the spool contacts plug (18). The oil in spring chamber (6) flows through passage (10), the orifice in spool (11), and spring chamber (17). The oil in spring chamber (6) now flows through drain passage (12) to the hydraulic tank (16).
The return oil from boom cylinder (3) head end enters port (8). Since the pressure in spring chamber (6) is low, the oil in port (8) shifts valve (9) against the force of spring (7). The oil from the head end of boom cylinders (3) flows through port (8), valve (9), and passage (4) to the boom control valve (14).