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| Illustration 1 | g00816759 |
(1) Pilot operated hydraulic control ( work tool) (2) Ball valve ( manual work tool lowering) (3) Control valve ( work tool) (4) Lift cylinders (5) Tilt cylinders (6) Auxiliary couplings (7) Return manifold (8) Gear pump (9) Hydraulic tank | |
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| Illustration 2 | g00816783 |
(3) Control valve ( work tool) (8) Gear pump (9) Hydraulic tank | |
The work tool hydraulic system is open center. The rear section of the gear pump (8) supplies the work tool hydraulic system with oil. The gear pump continuously pumps oil through the control valve ( work tool) (3). The gear pump is splined to the drive shaft of the engine. When the engine speed increases, the speed of the gear pump increases. This causes the gear pump to pump more oil to the control valve.
Pilot oil flows from the pilot operated hydraulic control ( work tool) to the pilot ports on the control valve. The pilot oil shifts the spools. This allows oil to flow to the lift cylinders (4), the tilt cylinders (5), and the auxiliary couplings (6). Refer to the Systems Operation, "Pilot Hydraulic System" for more information on the pilot system.
Hydraulic System for the Lift Arms Without the Diverter Valve (If Equipped)
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| Illustration 3 | g00816759 |
(1) Pilot operated hydraulic control ( work tool) (2) Ball valve ( manual work tool lowering) (3) Control valve ( work tool) (4) Lift cylinders (5) Tilt cylinders (6) Auxiliary couplings (7) Return manifold (8) Gear pump (9) Hydraulic tank | |
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| Illustration 4 | g00816788 |
(2) Ball valve ( manual work tool lowering) (3) Control valve ( work tool) (4) Lift cylinder | |
When the pilot operated hydraulic control ( work tool) (1) is moved to the RAISE position, the lift spool in the control valve ( work tool) is shifted to the RAISE position by pilot oil. Hydraulic oil flows from the gear pump (8) through the lift spool and into the line for the head end of the lift cylinders (4). Near the lift cylinders, the single line splits into two branches. The two lines deliver hydraulic oil to the head end of both lift cylinders.
As the rods extend, oil is forced out of the rod end of the cylinders. The oil flows to the lift spool. Then, the oil flows to the tilt spool.
When the pilot operated hydraulic control is moved to the LOWER position, the lift spool is shifted to the LOWER position by pilot oil. Hydraulic oil flows from the gear pump through the spool and into the line for the rod end of the lift cylinders. Near the hydraulic cylinders, the single line splits into two branches. The two lines deliver hydraulic oil to the rod end of both lift cylinders.
As the rods retract, oil is forced out of the head end of the cylinders. The oil flows to the lift spool. Then, the oil flows to the tilt spool.
When the pilot operated hydraulic control is moved to the FLOAT position, the lift spool is shifted to the FLOAT position by pilot oil. This position opens the rod ends of the lift cylinders and the head ends of the lift cylinders to the tank. The weight of the work tool will cause the work tool to lower to the ground. The work tool will then follow the contour of the ground. Supply oil from the gear pump can continue to flow to the tilt spool when the lift spool is in the FLOAT position.
The ball valve ( manual work tool lowering) (2) is used for manual lowering of the lift arms. The ball valve allows oil to drain out of the head end of the cylinder. The hydraulic oil flow is directed to the return manifold (7). The ball valve should be used to lower the lift arms when the engine fails.
Hydraulic System for the Lift Arms with the Diverter Valve (If Equipped)
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| Illustration 5 | g00816762 |
(1) Pilot operated hydraulic control ( work tool) (2) Ball valve ( manual work tool lowering) (3) Control valve ( work tool) (4) Lift cylinders (5) Tilt cylinders (6) Auxiliary couplings (7) Return manifold (8) Gear pump (9) Hydraulic tank (10) Diverter valve | |
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| Illustration 6 | g00816792 |
(2) Ball valve ( manual work tool lowering) (3) Control valve ( work tool) (4) Lift cylinder (10) Diverter valve | |
When the pilot operated hydraulic control ( work tool) (1) is moved to the RAISE position, the lift spool in the control valve ( work tool) (3) is shifted to the RAISE position by pilot oil. Hydraulic oil flows from the gear pump (8) through the lift spool and into the line for the head end of the lift cylinders (4). The oil from the rod end of the lift cylinders flows to the diverter valve (10). The pressure from the rod end of the lift cylinders is balanced with the pressure from the head end of the tilt cylinders. This causes the work tool to remain level while the lift arms are raised. From the diverter valve, the oil flows to the lift spool. The oil then flows to the tilt spool.
The diverter valve only affects the RAISE function. The LOWER function is not affected by the diverter valve.
In the LOWER position, oil flows from the spool to the diverter valve. From the diverter valve, the oil flows to the rod end of the cylinders. The oil pushes on the piston. The cylinders retract. Oil from the head end of the cylinders flows to the lift spool. Then, the oil flows to the tilt spool.
For information on the operation of the diverter valve, refer to the Systems Operation, "Diverter Valve".
The ball valve ( manual work tool lowering) (2) is used for manual lowering of the lift arms. The ball valve allows oil to drain out of the head end of the lift cylinders. The hydraulic oil flow is directed to the return manifold (7). The ball valve should be used to lower the lift arms when the engine fails.
Tilt and Auxiliary Hydraulic System
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| Illustration 7 | g00816759 |
(1) Pilot operated hydraulic control ( work tool) (2) Ball valve ( manual work tool lowering) (3) Control valve ( work tool) (4) Lift cylinders (5) Tilt cylinders (6) Auxiliary couplings (7) Return manifold (8) Gear pump (9) Hydraulic tank | |
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| Illustration 8 | g00816795 |
(3) Control valve ( work tool) (5) Tilt cylinders (6) Auxiliary couplings | |
Hydraulic oil can be routed to the tilt cylinders (5) or hydraulic oil can be routed to the auxiliary circuit (6) .
The hydraulic oil is directed to the tilt spool in the control valve ( work tool) (3) by the pilot operated hydraulic control ( work tool) (1). The end of the spool that receives the pilot oil depends on the position of the pilot operated hydraulic control.
As the spool is shifted, hydraulic oil flows through the appropriate passages and into the appropriate line. Near the tilt cylinders (5), the single line splits into two branches. The two lines deliver hydraulic oil to both of the tilt cylinders.
If the machine is equipped with a diverter valve, the tilt cylinders will also be connected to the diverter valve. The diverter valve acts as a load leveler. The diverter valve is used only when the lift cylinders are being raised.
Pilot oil is directed to the auxiliary circuit spool that is located in the control valve ( work tool) by the auxiliary circuit switch. The auxiliary circuit switch is located on the pilot operated hydraulic control ( work tool).
The pilot oil for the auxiliary circuit does not flow through the pilot operated hydraulic control. When the auxiliary circuit switch is pressed, one of the modulating valves in the control valve ( work tool) (3) will shift. This causes the auxiliary circuit spool to shift. Oil can then flow from the gear pump (8) to auxiliary couplings (6) .
For more information on the operation of the tilt and auxiliary hydraulic system, refer to the Systems Operation, "Control Valve (Work Tool)".