Valve Section
Neutral position
- 1. To right-hand side of piston
- 2. To left-hand side of piston
- 3. Supply
- 4. Return oil
- 5. Servo oil, free flow
The valve is open when the car engine is running and there is no steering input. In the open position none of the ducts to the operating cylinders are blocked. The servo oil circulates through the valve freely.
Steering left
- 6. Servo oil, low pressure
- 7. Servo oil, high pressure
When the steering wheel is turned to the left and the wheel resistance is so great that the torsion bar inertia is overcome, the steering gear input shaft moves to the left in relation to the worm screw, within the play between the lugs.
With this movement the input shaft stops the free flow through the valve and sends the fluid through the upper feed pipe to the right-hand side of the piston.
As long as the torsion bar is affected by steering input the oil pressure continues to push the steering rack to the left. If the steering input diminishes the torsion bar springs back. The valve section returns to the centre position so that the oil can circulate freely within the valve housing.
Steering right
- 6. Servo oil, low pressure
- 7. Servo oil, high pressure
The function when turning right is, in principle, the same as to the left. The only difference is that the steering gear input shaft stops the flow of high pressure oil through the return and down through the groove on the inside of the valve spool and out through the low pressure pipe (return oil) to the left-hand side of the piston.