What is a Pneumatic Actuator?

A pneumatic actuator is a mechanism that uses air pressure to move, position, or control the operation of a device. “Pneumatic” means air-based, while “an actuator” is any device that causes something to move.

Depending on the type, a pneumatic force actuator may push a load, pull it along a straight line, or cause it to rotate. Its design also varies greatly, ranging from the simple to the complex. The most used mechanisms are:

• A piston that moves inside a cylinder

• A rotating vane in an enclosure

• A flexible diaphragm inside a casing

• A rack and pinion gear system

In the real world, air actuators have many applications. They can be the on/off mechanisms of flow-regulating valves or control the operation of automotive systems.

In factories, they form part of process control equipment such as material handling and packaging machines; the list is endless.

The operation of a pneumatic air actuator illustrated

How Does a Pneumatic Actuator Work?

Pneumatic or air actuators turn the force of a compressed gas into linear or rotary motion. The motion then performs a valuable function, such as controlling the operation of a device or part of a system. Let’s see how that happens.

• Compressed air or other gas enters the actuator housing through the supply port

• Inside the housing, the air pushes against a piston, diaphragm, or vane, creating motion

• Depending on the actuator design, the motion is along a straight line or a rotation

• The compressed air moves out of the exhaust or other port

• Air pressure reduces, and the moving component returns to its former position

A single-acting pneumatic actuator includes a return spring in its actuating assembly. The spring pulls back the moving part when air pressure is no longer acting on it. Double-acting types use compressed air for the return action.

Pneumatic actuator assembly components

Pneumatic Actuator Parts

Different parts make up a pneumatic or air-operated actuator assembly. The main ones and their specific function include the following:

• A flow control valve

• Cylinder/housing

• Rod or shaft, piston, or diaphragm

• A return spring and several other smaller components.

Valve – the pneumatic actuator valve controls the flow of compressed gas as it goes into the cylinder or housing, allowing for variable actuator speed, torque, and other options.

Cylinder/Housing – the pneumatic actuator cylinder is the air-tight chamber that receives compressed gas. It contains a piston that moves under the action of air pressure.

Piston/Diaphragm/Vane – depending on the type of this device, a piston, diaphragm, or vane is pushed by pressurized air to cause motion.

Rod/Shaft – this part connects the moving piston, diaphragm, or vane to the load, transferring the air-generated motion.

Return spring – some types of air actuators, called single-acting actuators, use a return spring to retract the moving part when air vents out and pressure reduces.

Pneumatic actuator types