Three port valve (3PV)

Single-acting cylinder with three-port valve

In a single-acting cylinder compressed air is used to push a piston out, and a spring to push it in again. When compressed air is supplied to the cylinder, the piston rod extends (called the outstroke). When the air supply is switched off, the internal spring returns the piston rod to its retracted position (the instroke). The movement of a single-acting cylinder is normally controlled by a three-port valve – a type of simple switch which governs the flow of air. In the diagram below, a unidirectional-flow control valve is used to slow the speed of the piston on the outstroke. The instroke will be full speed.

Press play to see how this works.