Pneumatic cylinders are used in numerous applications. One example is the air cylinder for a bottom (belly) dump trailer that we manufacture (see home page). Because pneumatic cylinders are so versatile in the types of forces and motion they can produce, they are very popular.
In general, pneumatic cylinders are classified in three categories: light duty, medium duty and heavy duty. They can be designed as single-acting where the air pressure forces the piston to move in one direction only and the piston is returned by gravity or an external spring. Or, they can be designed as double-acting where the air pressure moves the piston in both directions.