A pneumatic cylinder works by forcing air or gas into a cylinder, which moves a piston after a certain pressure is achieved. The piston is attached to another mechanism that performs the desired function of the machine.
A common example of a pneumatic cylinder is the engine of a car. The engine cylinder functions by forcing a piston to the top of its cylinder, compressing a mixture of fuel and air. The piston is forced downward when the air and fuel mixture is ignited. The reciprocating motion of the piston is converted to rotary motion through the crankshaft, and this motion eventually makes the wheels turn. Other types of pneumatic cylinders allow doors to open and close, as well as many industrial machines to function in the workplace.
There are two basic types of pneumatic cylinders. A single acting cylinder has one valve for air to enter the cylinder, pushing the piston in one direction. The piston is returned by either a spring device or a load on the piston when air pressure is removed. A double acting pneumatic cylinder consists of multiple air valves. Once air is forced into the cylinder, pushing the piston one direction, air can be removed through a different valve, creating a vacuum that pulls the piston in the opposite direction.