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| Illustration 1 | g06015308 |
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Partial hydraulic schematic (Boom DOWN) (1) Boom cylinder (2) Main control valve (3) Relief valve (Inner pump) (4) Boom control valve (5) Hydraulic pump (6) Hydraulic tank (13) HPU changeover valve | |
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| Illustration 2 | g02458724 |
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Control valve (Boom DOWN) (7) Cylinder port A (8) Cylinder port B (9) Return passage (10) Spool (11) Center bypass passage (12) Parallel feeder passage | |
Spool (10) has a mechanical linkage which actuates the valve. When the linkage is pulled, spool (10) shifts upward. The pump oil then flows to cylinder port A (7). The oil flows through lines to the head end of the boom cylinder to extend the cylinder rod. Return oil in cylinder port B (8) flows through the spool to return passage (9). The oil then returns to the tank.
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| Illustration 3 | g02458721 |
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Boom control valve (Boom UP) (7) Cylinder port A (8) Cylinder port B (9) Return passage (10) Spool (11) Center bypass passage (12) Parallel feeder passage | |
Spool (10) has a mechanical linkage which actuates the valve. When the linkage is pushed, spool (10) shifts downward. The pump oil then flows to cylinder port B (8). The oil flows through lines to the rod end of the boom cylinder to retract the cylinder rod. Return oil in cylinder port A (7) flows through the spool to return passage (9). The oil then returns to the tank.
Refer to the Systems Operation, "Main Control Valve" for more information on the main control valve and the boom control valve.