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| Illustration 1 | g03385044 |
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Boom drift reduction valve (BOOM RAISE) (1) Boom drift reduction valve (2) Drain port (3) Passage (4) Port (5) Valve (6) Passage (7) Spring (8) Spring chamber (9) Spool (10) Drain passage (11) Port (12) Port (13) Passage (14) Port | |
During a BOOM RAISE operation, pilot oil is not sent from the pilot control valve to port (12) of boom drift reduction valve (1). Spool (9) does not shift.
The oil flow from the boom I and boom II control valves combines in the main control valve. The combined oil flow enters port (4) of boom drift reduction valve (1). The combined oil flow flows into passage (3). As the oil pressure in passage (3) increases, valve (5) shifts against the force of spring (7). The oil in spring chamber (8) flows through passages (13) and (6) to port (14). The oil delivery in passage (3) now flows through port (14) to the head end of the boom cylinders.
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| Illustration 2 | g03385054 |
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Boom drift reduction valve (BOOM LOWER) (1) Boom drift reduction valve (2) Drain port (3) Passage (4) Port (5) Valve (6) Passage (7) Spring (8) Spring chamber (9) Spool (10) Drain passage (11) Port (12) Port (13) Passage (14) Port (15) Spring chamber (16) Cover | |
During a BOOM LOWER operation, pilot oil is sent from the pilot control valve to port (12) of boom drift reduction valve (1). Spool (9) shifts to the right until the spool contacts cover (16). The oil in spring chamber (8) flows through passage (13), the orifice in spool (9), and spring chamber (15). The oil in spring chamber (8) also flows through drain line (10) to the hydraulic tank.
The return oil from the boom cylinder head end enters port (14). Since the pressure in spring chamber (8) is low, the oil in port (14) shifts valve (5) against the force of spring (7). The oil from the head end of the boom cylinders flows through port (14), passage (3) and port (4) to the boom I control valve.