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| Illustration 1 | g01276251 |
Hydraulic schematic for the steering system (1) Steering cylinder (2) Steering cylinder (3) Steering cylinder crossover relief valve (4) Steering cylinder crossover relief valve (5) Brake release cylinder (6) Brake release cylinder pressure tap (7) Steering control valve (8) Steering release diverter valve (9) STIC steering pilot valve (10) Check valve (11) Line to parking brakes (12) Secondary steering diverter valve (13) Secondary steering pump (14) Brake release sequence valve (15) Steering system pressure tap (16) Spool (17) Implement and steering solenoid valve (18) Selector and pressure control valve (19) Parking brake control valve (20) Line from implement lift circuit (21) Check valve (22) Hydraulic oil cooler (23) Primary steering flow switch (24) Steering neutralizer valve for a right turn (25) Check valve (26) Pilot oil pressure tap (27) Check valve (28) Steering neutralizer valve for a left turn (29) Check valve (30) Line to parking brakes (31) Steering pump (32) Steering dual pilot check valve (33) Breaker relief valve (34) Pilot oil pressure reducing valve (35) Portable hydraulic pump quick connect coupler (36) Hydraulic tank (37) Pilot and Braking pump (38) Hydraulic filters (39) Portable hydraulic pump quick connect coupler (40) Line to brake accumulator charging valve | |
Note: Illustration 1 shows a machine with the secondary steering system. Machines without the secondary steering system will not have secondary steering pump (13), secondary steering diverter valve (12) and primary steering flow switch (23) .
The steering pilot circuit controls the movement of spool (16) in steering control valve (7) .
With the engine running, oil is drawn from hydraulic tank (36) by pilot and braking pump (37). Pilot and braking pump (37) supplies pilot oil through check valve (27) to pilot oil pressure reducing valve (34) .
Pilot oil pressure reducing valve (34) maintains the pilot system at a constant pressure. Pilot oil pressure reducing valve (34) relieves excess pilot system pressure through a line to the hydraulic tank.
The pilot oil flows to selector and pressure control valve (18). While the pilot and braking pump is supplying pilot oil to the pilot system, the selector and pressure control valve will block the flow of alternate oil into the pilot oil system.
If pilot and braking pump (37) fails, or pilot oil is not available, then selector and pressure control valve (18) will allow alternate oil to flow into the pilot system from the lift cylinders. If oil is not available from the lift cylinders, then selector and pressure control valve (18) will allow alternate oil to flow into the pilot system from steering control valve (7).
Oil from the pilot system also flows to implement and steering solenoid valve (17). Implement and steering solenoid valve (17) prevents pilot oil from flowing to STIC steering pilot valve (9) and the implement pilot circuit when implement and steering solenoid valve (17) is de-energized.
When implement and steering solenoid valve (17) is energized, pilot oil from implement and steering solenoid valve (17) flows to STIC steering pilot valve (9). When the STIC steering control lever is moved to either turn position, STIC steering pilot valve (9) directs the pilot oil through steering dual pilot check valve (32) to steering neutralizer valve (28) for a left turn or steering neutralizer valve (24) for a right turn. Pilot oil from the steering neutralizer valve flows to spool (16) in steering control valve (7). The pilot oil pressure causes spool (16) to move. When spool (16) moves, high pressure oil from steering pump (31) can flow through spool (16) to steering cylinder (1) and steering cylinder (2) .
Pilot oil from spool (16) returns through neutralizer valve (24) or neutralizer valve (28), steering dual pilot check valve (32) and STIC steering pilot valve (9) to hydraulic tank (36).