SECTION 3. FUNCTION

1.Open Center Non Load Reaction

1.Neutral Position

When the steering control valve is in the neutral position,inlet flow(P) from the priority valve moves the flow selector spool against its spring.This flow is blocked at the control valve control spool.The signal port is connected to the reservoir(T) through orifices in the control spool.The priority valve will only supply enough oil to the control valve to compensate for internal leakage and maintain low stand-by pressure.The oil at each side of the steering cylinder is connected to each side of the metering pump,this allows a degree of self centering when turning out of a bend.

2)Right Turn

When the steering control valve shaft is rotated to the right,the control valve moves off center.This connects the inlet port (P) to one port of each metering pump section and also connects the other port of each metering pump section to the cylinder.The amount that the spool moves off center depends on how fast the steering wheel is rotated and also how much effort is required to turn the wheel.

3)Left turn

When the steering control valve shaft is rotated to the left,the control valve spool moves off center.This connects the inlet port(P) to the one port of each metering pump section and also connects the other port of each metering pump section to the cylinder.The amount that the spool shifts off center depends on how fast the steering wheel is turned and how much effort is required to turn the wheel.

4) Manual steering

When there is no piston pump supply pressure the flow selector is moved to the left by its spring.This connects together the inlet and outlet ports of the lower gyrotor pump and disconnects this pump from the system.When the steering is operated manually,only the upper gyrotor pump section is used to direct flow to the steering cylinder. This reduces operator effort to an acceptable level,however the number of turns from lock to lock is increased. TP