SUPPORT AS 4682120 - Caterpillar

Control Valve Section
The control valve section (2) of the steering gear has spool (7) that is operated mechanically. The spool is held in its center position by torsion bar (8). The valve is an open center type.The purpose of the control valve section is to send oil to and from metering section (1), and to and from the steering cylinder. The control valve section will also control the pressure supplied to the cylinder.Metering Section
The main parts of the metering section (1) are commutator (4), manifold (5) and rotor group (3). The commutator and rotor turn with the steering wheel, and can operate in either direction.The metering section sends a controlled amount of oil (meters the oil) to the steering cylinder. It will keep the relation the same between the steering wheel and the wheels. The metering section is also used as a manually operated pump to give manual steering if there is a pump failure.Rotor Group Operation
ROTOR GROUP OPERATION
1. Rotor. 2. Stator. 3. Rotor lobes. 4. Oil cavity. A. Direction of rotor rotation.The rotor group and commutator are the parts of the metering section that control (meter) the oil that flows to the steering cylinder. Oil from the steering pump is sent by the control valve spool to the commutator. The commutator then sends the oil to the rotor group.Rotor (1) and stator (2) are the parts of the rotor group. The rotor is turned by the torsion bar and drive link as the steering wheel is turned. The rotor and stator are made so that when one lobe (3) is in a cavity (4), the opposite lobe is on the part of the stator with the curve. As the rotor is turned, each lobe in sequence is moved out of its cavity to the top of the stator's curve. This will push each opposite lobe, in sequence, into a cavity. As this action goes on, oil from the pump will always flow into three of the cavities, while oil flows out through three other cavities back to the control valve section. The other cavity will be closed.Oil Flow In Neutral
METERING VALVE (NEUTRAL POSITION) 1. Pressure oil (from steering pump).2. Cylinder oil (no flow in NEUTRAL).3. Cylinder oil (no flow in NEUTRAL).4. Return oil.5. Commutator.6. Drive link.7. Rotor group.8. Torsion bar.9. Valve spool.10. Ball.When the steering wheel is in its center position or when it is stopped during a turn, the metering valve is in NEUTRAL position. The hydraulic oil from the steering pump comes into the metering valve and flows to the opposite end of the valve. The oil flows past a land on spool (9) and then back to the hydraulic tank.With the spool in this position, the oil flow is stopped (blocked) to or from the steering cylinder. This holds the wheels and keeps them in position.Right Turn Operation
METERING VALVE (RIGHT TURN) 1. Pressure oil (from steering pump).2. Cylinder oil (return).3. Cylinder oil (pressure).4. Return oil.5. Commutator.6. Drive link.7. Rotor group.8. Torsion bar.9. Valve spool.10.