Pneumatic Rotary Actuator

A pneumatic rotary actuator, also known as a rotary cylinder, is a device that converts linear motion—either single-acting or double-acting—into rotary motion using pressurized air. 

They are commonly used in applications such as the repeated opening and closing of valves (e.g., butterfly valves or ball valves), which typically require a quarter-turn (90°) to operate. Thus, most rotary actuators are designed for motion limited to 0–90 degrees.

Pneumatic rotary actuators may also be referred to as:

1. Pneumatic rotary cylinders
2. Air rotary cylinders
3. Air rotary actuators

All these terms describe the same air-powered motion control device.

Types and Mechanisms

Based on their internal structure and operating principles, pneumatic rotary actuators can be categorized into four main types:

1. Vane Type

2. Rack and Pinion Type

3. Screw Type

4. Crank Type

All types—except the vane actuator—consist of a cylinder and a motion-converting mechanism.

Vane Actuator

The vane-type actuator features a compact design and high efficiency, making it suitable for lightweight automation tasks such as flipping, sorting, and clamping. It is commonly used as a manipulator wrist joint in robotic systems.

Vane actuators are further divided into:

• Single vane

• Double vane

• Multi-vane

Performance characteristics:

• Single vane: swing angle < 360°

• Double vane: swing angle < 180°

• Three-vane: swing angle < 120°

• More vanes result in greater torque but smaller swing angles.