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| Illustration 1 | g00951259 |
The Leveling Valve with the Axle Suspension Turned Off. (1) Solenoid valve (2) Manifold (3) Drain to hydraulic tank (4) Leveling stem (5) Drain passage for the accumulator (6) Passage for pilot oil supply (7) Directional spool (8) Passage to accumulator (9) Passage to head end of the load cylinders (10) Outlet passage to the hydraulic tank (11) Inlet passage from the axle suspension pump (12) Passage to rod end of the load cylinders (13) Detent ball (14) Check valve for the pump supply (15) Drain passage to the hydraulic tank (16) Springs for the directional spool (17) Cover | |
The leveling valve is activated by oil flow from the axle suspension pump. Movement of leveling stem (4) is controlled by a leaf spring. The leaf spring is connected to the right side of the lower link assembly and to the bottom of the leveling stem. Directional spool (7) is controlled by pilot oil from solenoid valve (1). The solenoid valve is controlled by the axle suspension switch. The switch is located in the operator compartment.
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| Illustration 2 | g00951262 |
View A-A (3) Drain to the hydraulic tank (5) Drain passage for the accumulator (6) Passage for the pilot oil supply (15) Drain passage to the hydraulic tank (20) Passage for pilot oil (21) Passage for pilot oil | |
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| Illustration 3 | g00951263 |
Section Views of Manifold (2) (18) Spring (19) Passage (20) Passage for pilot oil (21) Passage (22) Accumulator valve stem (23) Orifice plug | |
Leveling Stem
Leveling stem (4) has three positions:
- Lockdown (no axle suspension)
- Axle suspension
- Lower (relief from shock load)
There are detents in the positions for the lockdown and for the axle suspension. When the engine is first started, leveling stem (4) is positioned in order to keep the axle suspension off. The leveling stem is against manifold (2). At this time, pump oil flows through inlet passage (11) and into passage (6) for the pilot oil supply and passage (8) for the accumulator. Pilot oil from passage (6) flows into passage (21) and passage (19). Valve stem (22) shifts to the left. This blocks the oil flow to the hydraulic tank. The accumulator for the axle suspension system fills with oil from passage (8). Oil also flows to directional spool (7) .
When leveling stem (4) is in the position for axle suspension, pump oil in inlet passage (11) is blocked from passage (8).
No detent holds the leveling stem in the lower position in order to relieve shock loads. When leveling stem (4) is in the lower position because of a very large shock, detent ball (13) moves upward on the bevel of the leveling stem. Pump oil in inlet passage (11) is still blocked. Oil in passage (8) is free to flow through the notches in the upper end of the leveling stem into outlet passage (10). Oil is also free to flow through outlet passage (10) to the hydraulic tank.
Directional Spool
Directional spool (7) has two positions:
- Lockdown
- Axle suspension
When the engine is first started, there is no oil pressure in passage (20). Also, when the axle suspension is turned off, there is no oil pressure in passage (20). Springs (16) keep directional spool (7) against manifold (2). This is the position for the directional spool when the axle suspension is turned off. When the axle suspension is turned off, notches in the lower end of the directional spool allow oil from passage (8) to flow through passage (12) and into the rod end of the load cylinders.
When the axle suspension switch is moved to the position for axle suspension, pilot oil from solenoid valve (1) flows into passage (20) through orifice plug (23) to the upper end of directional spool (7). The directional spool moves downward against cover (17). This is the position for axle suspension for the directional spool. Oil from passage (8) is now free to flow through passage (9) to the head end of the load cylinders.
Whenever the pressure in passage (20) becomes less than the force of springs (16), the springs will move directional spool (7) upward in order to turn off the axle suspension.
Solenoid Valve
Solenoid valve (1) is activated with the axle suspension switch. The switch is located in the operator compartment. When the axle suspension is turned off, oil flows through manifold (2) and drains back to the hydraulic tank. When the switch is in the position for axle suspension, a stem shifts in the solenoid valve. This allows oil to flow into passage (20). This pilot oil pressure moves directional spool (7) downward against cover (17) .
Valve Group
Before the engine is started, the leveling stem is positioned in order to keep the axle suspension off. When the engine is started, oil flows into manifold (2) through passage (6) for the pilot oil supply. The oil flows into passage (21) and passage (19). Stem (22) is shifted to the left and the oil flow to the hydraulic tank is shut off. The accumulator for the axle suspension system fills with oil.
When solenoid valve (1) is activated by the axle suspension switch, oil from passage (6) can flow into passage (20) and downward through plug (23). This is the oil that shifts the directional spool (7) into the position for axle suspension.
When the axle suspension is turned off, the valve stem in solenoid valve (1) blocks oil flow to passage (20). The oil that is pushing directional spool (7) downward can now flow back through passage (20) and through stem (22). The oil then flows into passage (10) and drains back to the hydraulic tank. Springs (16) move the directional spool upward against manifold (2). Oil is then allowed to flow through the notches in the lower end of the directional spool into passage (12) and to the rod end of the load cylinders.
Accumulator Valve Stem
When oil flows into passage (19), stem (22) is shifted to the left. Passage (5) is now closed and the oil flow to the hydraulic tank is blocked. The accumulator for the axle suspension will now fill with oil. When the engine is stopped, or the oil flow in passage (6) is stopped, stem (22) shifts back to the right from the force of spring (18). This allows pressure oil from the accumulator to flow through drain passage (5) through drain (3) and into the hydraulic tank.