A rack-and-pinion type pneumatic rotary actuator is a rotary actuator used for turning, opening, closing, mixing, oscillating, positioning, and many more mechanical functions involving restricted rotation. It is also often used for automation of quarter-turn or half-turn motion mechanisms. The actuator works in conjunction with a cylindrical piston which is connected to a gear called a rack. From the moment the actuator starts working, the output shaft, piston and rack gear start working together in a linear motion. Rack-and-pinion pneumatic rotary actuators are available in a variety of styles and sizes providing double output torque. They are durable and offer simple installation and high force for their size. SMC offers rack-and-pinion actuators with both shaft and table connections, with rotational arc lengths of 90°, 180°, 190°, or even 270°, depending on the configuration.