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| Illustration 1 | g01148156 |
(1) Selector and pressure control valve. | |
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| Illustration 2 | g00324605 |
Selector and Pressure Control Valve (2) Spacers. (3) Spring. (4) Holes (four). (5) Inlet passage from head end of lift cylinders. (6) Valve spool. (7) Outlet passage to pilot control valve. (8) Holes (two). (9) Inlet passage from pilot pump section. (10) Drain passage. | |
Selector and pressure control valve (1) reduces high pressure oil from the lift cylinders. This oil is used in the pilot system when the engine is stopped and when the bucket is raised. The selector and pressure control valve routes the oil to the pilot control valve. This enables a raised bucket to be lowered when the engine is stopped. This also allows a loaded bucket to be dumped.
During normal operation, inlet passage (9) is blocked. There is a load check valve in outlet passage (7) which prevents primary pilot supply flow from entering the dead engine lower system.
When the engine is stopped and the lift arms are raised, the combined weight of the bucket and of the lift arm causes oil pressure from the head end of the lift cylinders in inlet passage (5). If the lift pilot valve stem and the tilt pilot valve stem are in the HOLD position, then the oil will be stopped in the lines.
When the pilot control valve is moved to the LOWER position or to the DUMP position, the pressure oil from the head end of the lift cylinders can now flow through holes (8) in valve spool (6). The oil then flows through outlet passage (7) and to the pilot control valve. The pilot control valve uses this oil to move the spools in the main control valve. A raised bucket can then be lowered or a loaded bucket can be dumped.
When the engine is stopped, valve spool (6) also maintains the maximum oil pressure from inlet passage (5) to the pilot valve at approximately 1350 kPa (195 psi). When the pressure through outlet passage (7) increases too much, the pressure will cause valve spool (6) to move left against the force of spring (3). This will block hole (8) and this will prevent an increase in the outlet pressure through passage (7). As the outlet pressure in outlet passage (7) decreases, valve spool (6) will move to the right. This action will reveal inlet passage (5) to outlet passage (7) through hole (8).