Single acting cylinder (SAC)

Single-acting cylinder.

In a single-acting cylinder compressed air is used to push a piston down, and a spring to push it up 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).

In the picture a Single Acting Cylinder (SAC) is shown, when the air goes into the cylinder it extends and a spring retracts it back again.

The movement of a single-acting cylinder is normally controlled by a Three Port Valve (3PV) – a type of simple switch which governs the flow of air.