Directional Control Valves

Directional Control Valves

To change the direction of airflow to and from the cylinder, we use a directional
control valve. The moving part in a directional control valve will connect and
disconnect internal flow passages within the valve body. This action results in a
control of airflow direction.
The typical directional control valve consists of a valve body with
four internal flow passages within the valve body and a sliding spool.

Shifting the spool alternately connects a cylinder port to supply pressure or the
exhaust port. With the spool in the position where the supply pressure is connected
to port A and port B is connected to the exhaust port, the cylinder will extend. Then,
with the spool in the other extreme position, supply pressure is connected to port B
and port A is connected to the exhaust port, now the cylinder retracts. With a
directional control valve in a circuit, the cylinder's piston rod can be extended or
retracted and work performed.