A pneumatic linear actuator is a device that is powered by compressed gas and moves in a straight line. The operation of this type of actuator is different from a rotary actuator, which moves in a circle. Pneumatic actuators are sometimes called pneumatic cylinders. These devices are most often driven by pressurized air, although other compressible gases can also be used.
Compressed gases have been used to perform work for many centuries. Some ancient cultures made use of simple bellow systems to pressurize air by hand, and focused this air to help form heated metal into shapes. It was not until the 1800s that the invention of electric air compressors allowed the pneumatic linear actuator to be used extensively in industry.
Modern linear actuators operate in a similar way as hydraulic cylinders. A piston is housed within a round cylinder. The piston is large enough to create an airtight seal against the interior of the cylinder. When compressed gas is introduced into the base of the housing, the pressure forces the piston to rise. Pistons are typically attached to a straight rod, which can be used to move an object.
The amount of force that a pneumatic linear actuator is able to produce is related to the size of the piston and the pressure of the compressed gas. This means that by either increasing the compression of the incoming air or the width of the piston, the effective strength of the actuator will grow. Pressure can often be adjusted while in use, allowing the proper amount of linear force to be created.
Generally, a pneumatic linear actuator is simple and clean. It is often able to move very quickly, which can be useful in some industrial applications. A pneumatic linear actuator does have some disadvantages, however. Unlike similar hydraulic systems, they can be difficult to control with high precision and are not able to lift extremely heavy loads. These limitations are caused by the fact that air in a cylinder will compress under load, while hydraulic fluid will not.
Common uses for a pneumatic linear actuator include die casting and precision machining in manufacturing facilities. They are also often used in safety devices and fail-safe locks, thanks to their quick reaction time. Due to their reliance on compressed air instead of electric motors, pneumatic actuators can be used in applications that are sensitive to magnetic interference, such as microchip manufacturing.