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| Illustration 1 | g01207252 |
(1) Steering cylinder (2) Line relief and makeup valve for the head end of the steering cylinder (3) Line relief and makeup valve for the rod end of the steering cylinder (4) Steering neutralizer valve for a left turn (5) Steering neutralizer valve for a right turn (6) Implement and steering solenoid valve (7) Parking brake control valve (8) Spool (9) Load sensing shuttle valve (10) Secondary steering pump (11) Spool (12) STIC steering pilot valve (13) Line to parking brake circuit (14) Primary steering flow switch (15) Spool (16) Steering system relief valve (17) Steering control valve (18) Steering system pressure tap (19) Check valve (20) Check valve (21) Line from lift circuit (22) Secondary steering diverter valve (23) Hydraulic oil cooler (24) Pressure tap for the pilot system (25) Check valve (26) Pilot oil pressure reducing valve (27) Check valve (28) Pilot and braking pump (29) Steering pump (30) Implement pump (31) Breaker relief valve (32) Portable hydraulic quick connect coupler (33) Selector and pressure control valve (34) Line to the brake accumulator charging valve (35) Hydraulic filters (36) Hydraulic tank (37) Portable hydraulic quick connect coupler | |
The steering pilot circuit controls the movement of spool (8) in steering control valve (17) .
With the engine running, oil is drawn from hydraulic tank (36) by pilot and braking pump (28). Pilot and braking pump (28) supplies oil through check valve (27) to pilot oil pressure reducing valve (26) .
Pilot oil pressure reducing valve (26) reduces the pilot and braking pump oil to a reduced pressure.
The pilot oil, now at a reduced pressure flows through check valve (25) to selector and pressure control valve (33), and implement and steering solenoid valve (6) .
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 system.
If the pilot and braking pump fails, or pilot oil is not available, then selector and pressure control valve (33) will allow alternate pilot 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 (33) will allow alternate pilot oil to flow into the pilot system from steering control valve (17) .
Also oil from check valve (25) flows to implement and steering solenoid valve (6). The implement and steering solenoid valve prevents pilot oil from flowing to STIC steering pilot valve (13) and the implement pilot circuit when implement and steering solenoid valve (6) is de-energized.
When implement and steering solenoid valve (6) is energized, pilot oil from the implement and steering solenoid valve flows to STIC steering pilot valve (12). When the STIC steering control lever is moved to either position, STIC steering pilot valve (12) directs the pilot oil through steering neutralizer valve (4) for a left turn or steering neutralizer valve (5) for a right turn.
Pilot oil flows from the steering neutralizer valve to spool (8) in steering control valve (17). The pilot oil pressure causes spool (8) to move, when spool (8) moves, steering system oil pressure from steering pump (29) can flow to steering cylinder (1) .
Return pilot oil from spool (8) returns through neutralizer valve (5) or neutralizer valve (4) and STIC steering pilot valve (12) to hydraulic tank (36).