Rotary actuators are used to pivot a joint when a conventional cylinder mounting proves impractical due to space, weight, or motion requirements. Rotary actuators can mount right at the equipment joint without taking up the long stroke lengths required of cylinders.
Rotary actuators also are not limited to the 90° pivot arc typical of cylinders; they can achieve arc lengths of 180°, 360°, or even 720° or more, depending on the configuration.
There are four main types of rotary actuator: helical-spline actuator, enclosed piston crank actuator, scotch-yoke actuator & rack-and-pinion actuator.
