This valve assembly will, when connected to a pneumatic cylinder, cause the cylinder will go in and out indefinitely until the air supply is removed.
The speed of both the in and out strokes can be controlled and can be different from each other.
It is made from standard components and works by detecting the pressure in the exhaust side of the cylinder. When there is no pressure the cylinder is at the end of its stroke (or has got stuck in mid position) and can therefore be sent in the other direction. It continues in this manner until the air supply is removed.
The oscillating valve shown here is 1/4″ BSP but the principle can be applied to larger or smaller valves which are available on request (using standard components which are normally available from stock).