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| Illustration 1 | g00118123 |
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Pilot Valve (STIC Steering) (1) Handle (2) Link (3) Link (4) Plunger (5) Plunger (6) Centering spring (7) Centering spring (8) Cap (9) Cap (10) Spring seat (11) Spring seat (12) Centering spring (13) Centering spring (14) Port (to hydraulic tank) (15) Spring (16) Spring (17) Passage (18) Passage (19) Metering spool (20) Metering spool (21) Port (to neutralizer valve for left turns) (22) Inlet (from selector valve and pressure control valve) (23) Port (to neutralizer valve for Right turns) | |
With the engine in operation, pilot oil flows from the selector and pressure control valve to the pilot valve (STIC Steering). Oil enters the valve at inlet port (22).
The STIC steering control lever is attached to handle (1). When the STIC steering control lever is in the STRAIGHT AHEAD position, centering springs (6), (7), (12), (13), (15) and (16) keep the pivot plate in the CENTERED position.
Pilot oil flows through inlet (22) to metering spools (19) and (20). In this position, the spools block the flow of oil to the steering control valve. This causes the oil to flow back to the hydraulic tank for the steering and brake systems.
When the STIC steering control lever is moved to the LEFT TURN position, the pivot plate causes link (2) to move plunger (4) downward.
As the plunger moves downward, the plunger overcomes the force of centering spring (6). This causes the spring to move downward. As the plunger moves downward through cap (8), the plunger also causes spring seat (10), spring (12), spring (15), and spool (19) to move downward.
At the same time, the pivot plate causes link (3) to move plunger (5) upward. As the plunger moves upward, spring (7) moves upward. As the plunger moves upward through cap (9), spring (13) and spring seat (11) moves upward. Spring (16) moves spool (20) upward.
When metering spool (19) moves downward, passage (17) opens. Oil can now flow from inlet port (22) into passage (17). The oil then flows through passage (17) and past metering spool (19). The oil then flows out of port (21).
The oil flows from port (21) to the neutralizer valve for left turns. Next, the oil flows to the steering control valve.
Some of the oil that flows from the steering control valve flows through the neutralizer valve for right turns. The oil then flows from the neutralizer valve for right turns and to port (23).
Because metering spool (20) is up, the oil can flow past the spool into the return oil passage . The oil flows through the passage and out port (14) back to the hydraulic tank for the steering and brake systems.
When the STIC steering control lever is moved to the RIGHT TURN position, the pivot plate causes link (3) to move plunger (5) downward.
As the plunger moves downward, centering spring (7) moves downward. As the plunger moves downward through cap (9), the plunger causes spring seat (11), spring (13), spring (16), and metering spool (20) to move downward.
At the same time, the pivot plate causes link (2) to move plunger (4) upward. As the plunger moves up, centering spring (6) moves up. As the plunger moves up through cap (8), the plunger also causes spring (12) and spring seat (10) to move upward. Spring (15) moves spool (19) upward.
When centering spool (20) moves down, passage (18) opens. Oil can now flow from inlet port (22) into passage (18). The oil then flows through passage (18), past spool (20), and out port (23).
The oil flows from port (23) to the neutralizer valve for right turns. The oil then flows to the steering control valve.
Some of the oil from the steering control valve flows through the neutralizer valve for left turns. The oil then flows from the neutralizer valve into port (21).
Because spool (19) is up, the oil can flow past the spool into the return oil passage. The oil then flows out of port (14) to the hydraulic tank for the steering and brake systems.