A pneumatic cylinder or air cylinder is a mechanical device which employ compressed gas as the medium to deliver force and often in combination with movement similar to an actuator.
The delivery of force and movement is basically converting the potential energy of compressed gas into kinetic energy. Once a pneumatic cylinder is actuated, compressed air enters into the cylinder and imparts force on the piston on the other end. Consequently, the piston is pushed by the expansion of previously compressed air in an attempt to reach atmospheric pressure of the surroundings.
Common types of pneumatic cylinders include Single acting cylinders, Double acting cylinders, Rotary air cylinders, and Rod-less cylinders. They come with various sizes ranging from 2.5 mm to 400 mm or even as large as 1,000 mm in diameter.