What is a linear actuator, and where can I use it?

A servomotor is a packaged combination of several components: a motor (usually electric, although fluid power motors may also be used), a gear train to reduce the many rotations of the motor to a higher torque rotation, a position encoder that identifies the position of the output shaft and an inbuilt control system. Just as it is in pneumatic rotary actuator, the vane configuration type of the hydraulic actuator makes use of pressurized fluid to make the rotation of the vane possible, thereby leading to the rotational motion of the central shaft. High torque rotary actuators have the efficiency and capability of transforming hydraulic power/pressure, electric energy, or pneumatic energy into mechanical rotation. Our vane style actuators use hydraulic pressure applied to the shaft mounted vane to produce higher torque than pneumatic applications.

2 Fluid power actuators are of two common forms: those where a linear piston and cylinder mechanism is geared to produce rotation (illustrated), and those where a rotating asymmetrical vane swings through a cylinder of two different radii. Common design configurations for hydraulic rotary actuators include piston type, vane type, or gear type. This rotary actuator provides torque to load the system while the drive motor provides the rotational speed and is sized only to overcome the friction in the system, resulting in an energy efficient test stand.

The concepts for efficient high – torque rotary actuators will be valuable in numerous electric drive applications, including industrial motors, material handling, and robotics. The Type 3-EF and Type 5-EF Rotary Incremental Actuators are designed based on a recently developed extra fine step angle permanent magnet stepper motor; which in combination with the standard harmonic drive gear reducers produces extra fine output step resolution. Pneumatic and hydraulic rack-and-pinion rotary actuators are available in a variety of styles and sizes, from compact series to larger series for applications requiring up to 31,000 in/lb of torque.

Vane actuators are a good fit for applications requiring extremely high endurance, high rotational speeds, and a need for constant control of movement without the need to maintain the load in a particular position. The motion produced by an actuator may be either continuous rotation, as for an electric motor , or movement to a fixed angular position as for servomotors and stepper motors A further form, the torque motor , does not necessarily produce any rotation but merely generates a precise torque which then either causes rotation, or is balanced by some opposing torque. All the rotary actuators described so far have been pneumatic or hydraulic equivalents of electric motors.

They can be of radial design similar to the pump of Figures 2.12 and, or in-line (axial) design similar to those of Figures 2.14 and Radial piston motors tend to be most common in pneumatic applications, with in-line piston motors most common in hydraulics. The principles of hydraulic and pneumatic devices are very similar, but the much higher hydraulic pressures give larger available torques and powers despite lower rotational speeds. There are three basic designs of rotary or pump compressor: the gear pump, vane pump and various designs of piston pump or compressor described earlier in Chapter 2. These can also be used as the basis of rotary actuators.

Rotary actuators are the hydraulic or pneumatic equivalents of electric motors. Key advantages of hydraulic rotary actuators include simplicity of design and the ability to generate high torques and low speeds. In piston-type actuators, pressurized hydraulic fluid is used to displace a piston and generate rotational motion.

Intellidrives engineers have developed what they say is a simpler, quieter, and economical alternative: The RA40 rotary actuator consists of a 24V dc permanent magnet motor that turns a series of gear stages to produce a working torque output of 184 ft-lbs (350 Nm) via a rotating arm. A comparison of the response characteristics to the change of an inertia load using a 130mm frame size DGII Series hollow rotary actuator and a direct drive motor that produce equivalent torque was performed. Since direct drive motors can receive a load directly, generate high torque without a gearhead, and utilize the hollow structure for wiring and piping, they are being used in the industrial equipment field as a positioning system.  For more information, visit www.intellidrives.com

The ESBE ARC/ ARD series of high torque rotary low voltage motorized actuators provide a 90° operating range of rotation. Fail-safe actuators are spring-loaded to ensure the return of the shaft to a safe position – they are available with torque outputs to over 5,000 lb-in.