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| Illustration 1 | g03557336 |
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Schematic for the steering pilot system (1) Steering control valve (2) Pilot oil pressure reducing valve (3) Left neutralizer valve (4) Right neutralizer valve (5) To braking system (6) Pilot oil filter (7) Manifold (8) To electric brake release pump (9) Manifold (10) Check valve (11) Hydraulic tank breather (12) From hoist system (13) Hydraulic tank (14) Steering metering pump (15) Brake and pilot section of the gear pump (16) Screen (AA) Steering system pressure tap (BB) Pilot system pressure tap | |
The pilot circuit controls the movement of the spool in steering control valve (1). The main components of the pilot circuit are hydraulic tank (13), brake and pilot pump (15), pilot oil pressure reducing valve (2), pilot oil filter (6), steering metering pump (14), left and right neutralizer valves (3) and (4) and steering control valve (1).
With the engine running, oil flows from hydraulic tank (13) to brake and pilot pump (15). The pump is a gear type pump. Pressure oil then flows from the pump, through check valve (10) to pilot oil pressure reducing valve (2). Part of the oil also flows from the pump and check valve to the braking system.
From pilot oil pressure reducing valve (2), oil flows through pilot oil filter (6) to manifold (7). Manifold (7) distributes pilot oil to various components of the hydraulic system, the braking system, the steering system, and the optional automatic lubrication system.
From manifold (7), part of the oil branches off and passes on to steering metering pump (14). The steering metering pump is a small hydraulic pump that is used as a metering directional control valve. The steering metering pump sends pilot oil through one of the neutralizer valves when the steering wheel is turned.
Neutralizer valves (3) and (4) stop the flow of pilot oil when the machine is turned completely to the left or to the right. When the machine turns, the pilot oil flows through the neutralizer valve to the respective end of the valve spool in steering control valve (1). The oil then flows across the metering orifices in the valve spool. The flow across the orifices causes the spool to move. When the spool moves, high-pressure oil flows from the steering pump to the steering cylinders.
Return oil from steering metering pump (14) and neutralizer valves (3) and (4) flows through manifold (9). The oil then flows through screen (16) into hydraulic tank (13).