Note: The pilot valve in illustration 1 is for machines with an auxiliary function (logging fork, side dump bucket, multipurpose bucket, etc). Machines without an auxiliary function will not have auxiliary valve (3).
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| Illustration 1 | g00485883 |
Side View of the Pilot Valve (1) Tilt valve. (2) Lift valve. (3) Auxiliary valve (attachment coupler). (4) Return port to the hydraulic oil tank. (5) Supply port from the pilot valve (oil manifold). | |
When the engine is running, oil flows from the pilot/brake pump to the pilot valve (oil manifold). The pilot valve reduces the pressure at port (5) to 2600 ± 200 kPa (375 ± 30 psi).
The lift arms can be lowered if the engine is stopped or the implement oil pressure fails. The pilot valve supplies pilot oil to the pilot valve at reduced pressure. The reduced pressure at port (5) is 2070 ± 200 kPa (300 ± 30 psi).
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| Illustration 2 | g00837652 |
Implement Lockout Control Lever (6) Ball valve. (A) Implement lockout control lever in the UNLOCKED position. (B) Implement lockout control lever in the LOCKED position | |
When the implement lockout control lever is in the UNLOCKED position (A), the oil flows through ball valve (6) to port (5). When the implement lockout control lever is in the LOCKED position (B), the flow of oil to port (5) is blocked.
Tilt valve (1) has a detent in the TILT BACK position. Lift valve (2) has detents in both the LOWER position and the RAISE position. Auxiliary valve (3) does not have a DETENT position.
Note: The operation of tilt valve (1), lift valve (2), and auxiliary valve (3) are similar. Only the operation of the tilt valve is described.
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| Illustration 3 | g00485943 |
Tilt Valve in the Hold Position (7) Plunger (8) Lever assembly (9) Washer (10) Upper plunger (11) Upper plunger (12) Centering spring (13) Centering spring (14) Ball (15) Ball (16) Coil assembly (17) Retainer (18) Retainer (19) Spool (20) Spool (21) Pressure control valve spring (22) Pressure control valve spring (23) Return port to the hydraulic oil tank (24) Controlled pressure chamber (25) Controlled pressure chamber (26) Bias spring (27) Bias spring (28) Pilot oil supply passage (29) Pilot oil supply passage (30) Pilot oil supply port | |
HOLD Position
When the tilt valve is in the HOLD position, centering springs (12) and (13), pressure control valve springs (21) and (22), and bias springs (26) and (27) keep lever assembly (1) in the CENTERED HOLD position. Pilot pressure oil flows from port (30) to pilot oil supply passages (28) and (29).
The position of spools (19) and (20) prevent oil from flowing into controlled pressure chambers (24) and (25). The controlled pressure chambers are open to return port (23). This also provides a passage for the pilot lines from the main control valve to return port (23). Return port (23) provides a path back to the hydraulic oil tank.
DUMP Position
When the tilt control lever is moved to the DUMP position, lever assembly (8) causes upper plunger (11) to move downward. As upper plunger (11) moves downward, the force on retainer (18) overcomes spring (22) .
As pressure control valve spring (22) compresses, spool (20) shifts against bias spring (27). This moves spool (20) which closes the passage to the hydraulic oil tank. At the same time, pilot oil supply passage (28) opens. The oil pressure at controlled pressure chamber (24) also increases.
As upper plunger (11) continues to move down, pressure in controlled pressure chamber (24) increases. This shifts the main control valve into the DUMP position.
At approximately 85 percent lever travel, ball (15) contacts both upper plunger (11) and spool (20). This causes the oil pressure inside controlled pressure chamber (24) to increase. The oil pressure increases to a pressure that is equal to the oil pressure at pilot oil supply port (30) .
When the tilt control lever is moved back to the HOLD position, centering spring (13), pressure control valve spring (22), and bias spring (27), force spool (20) and upper plunger (11) back into the HOLD position. The HOLD position is shown in Illustration 3. This prevents any oil flow into controlled pressure chamber (24). This also opens a passage to return port (23) .
TILT BACK Position
When the tilt control lever is moved to the TILT BACK position, lever assembly (8) causes upper plunger (10) to move downward. As upper plunger (10) moves downward, the force on retainer (17) overcomes pressure control valve spring (21).
This causes pressure control valve spring (21) to shift spool (19), which increases the control pressure in passage (25). Before ball (14) makes contact with spool (19), plunger (7) contacts the bracket at approximately 75 percent of lever travel.
At approximately 92 percent of lever travel, washer (9) contacts coil assembly (16). When the coil is energized, the coil assembly holds washer (9) so that the implement valve remains in the TILT BACK position.
Coil assembly (16) can be deactivated by the bucket positioner or by movement of the tilt control lever. Approximately 10 percent lever travel is required to deactivate the detent.
When the tilt control lever is moved back to the HOLD position, centering spring (12), pressure control valve spring (21), and bias spring (26), force spool (19) and upper plunger (10) back into the HOLD position. The HOLD position is shown in Illustration 3. This prevents any oil flow into controlled pressure chamber (25). This also opens a passage to return port (23) .