R3000H Load Haul Dump Steering System Caterpillar

Pilot Valve (STIC Steering)

Usage:

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Illustration 1	g06005140
Pilot valve (STIC steering) (1) Handle (2) Link (3) Link (4) Plunger (5) Plunger (6) Spring (7) Spring (8) Cap (9) Cap (10) Spring seat (11) Spring seat (12) Spring (13) Spring (14) Outlet port to tank (15) Spring (16) Spring (17) Passage (18) Passage (19) Spool (20) Spool (21) Port to the steering neutralizer valve for a left turn (22) Inlet port (23) Port to the steering neutralizer valve for a right turn

When pilot oil pressure is available, pilot oil flows from the implement and steering solenoid valve to the STIC steering pilot valve. The STIC steering pilot valve modulates the pilot oil supply to the spool in the steering control valve. Pilot oil enters the STIC steering pilot valve through 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 spools (19) and (20). In this position, the spools block the flow of oil to the steering neutralizer valves and the steering control valve. With the spools in this position, the oil returns through outlet port (14) to the hydraulic tank. Ports (21) and (23) are also open to the hydraulic tank.

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 spring (6) causing 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 link (3) and plunger (5) move upwards through cap (9). Spring seat (11), spring (13), spring (16) and spool (20) remain stationary.

When spool (19) moves downward, passage (17) opens. Pilot oil can now flow from inlet port (22) into passage (17). The pilot oil then flows through passage (17), past spool (19) and out port (21).

The pilot oil flows from port (21) to the steering neutralizer valve for a left turn. The pilot oil then flows to the end of the spool in the steering control valve.

Pilot oil at the other end of the spool returns through the steering neutralizer valve for a right turn to port (23). Port (23) is open to the hydraulic tank.

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, spring (7) moves downward. As the plunger moves downward through cap (9), the plunger causes spring seat (11), spring (13), spring (16), and spool (20) to move downward.

At the same time link (2) and plunger (4) move upwards through cap (8). Spring seat (10), spring (12), spring (15) and spool (19) remain stationary.

When spool (20) moves downward, passage (18) opens. Pilot oil can now flow from inlet port (22) into passage (18). The pilot oil then flows through passage (18), past spool (20), and out port (23). Spool valve (19) remains stationary.

The pilot oil flows from port (23) to the steering neutralizer valve for a right turn. The pilot oil then flows to the end of the spool in the steering control valve.

Pilot oil at the other end of the spool returns through the steering neutralizer valve for a left turn to port (21). Port (21) is open to the hydraulic tank.

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