In its simplest form, a rotary actuator is a device that uses hydraulic fluid to generate rotary motion without a linkage. These devices come in handy when applications call for any form of transporting, securing, or positioning of parts. 

How Do Rotary Actuators Work?

In terms of  design, rotary actuators are most often configured as vane type, rack-and-pinon type, or helical spline actuators.

Our rotary actuators are the helical spline design. This means, a piston and a helix, or sliding spline, work together to convert the linear motion of the piston into rotational motion. Helical spline actuators function when the piston is axially displaced using hydraulic pressure causing simultaneous rotation of the piston.

Hydraulic rotary actuators are typically designed to operate at low speeds and produce high torque through arc lengths ranging between 90°, 180°, 270°, and 360°. They also can be configured up to 720° or more by making the spline gears longer while maintaining the same diameter.

Common Applications of Rotary Actuators

From manipulating the angle of a boom in construction applications to opening or closing flaps in the aircraft and aerospace industries, rotary actuators are dependable and durable devices used for a wide range of uses.

One common application is using a rotary actuator for tipping devices. A helical rotary actuator, for example, would be a suitable option for bin tippers in waste management applications due to its high torque in a compact package. 

Additionally, rotary actuators can function as simple tool changers. One example of this is using a rotary-linear actuator for a pallet changer that weighs 1,000 kg. This device is a combination of a rotary actuator and a dual-action linear cylinder, allowing for full flexibility in a minimal amount of space. Since the rotary actuator and the linear cylinder are hydraulically driven separately, any movement sequences can be selected: for example, rotating to the left and right, extending linearly, and retracting.

A rotary actuator could also be used for gate valve control too. While a hydraulic rotary actuator may be more expensive than pneumatic actuators, these devices have a higher level of precision, require less space, and can achieve high torque outputs. 

Other uses for rotary actuators include linear actuation, bending machines, work piece positioning, rotational devices, and transport applications.

Hydraulic Rotary Actuator Benefits

Hydraulic rotary actuators are known for their strong ability to produce power quickly. In comparison to pneumatic and electric rotary actuators, hydraulic actuators are the most powerful and have the capacity to achieve a torque output up to 2,200,000 Ibs-in (250,000 Nm) as a helical spine actuator and even higher as a rack and pinion actuator.

Rotary actuators also require a minimal amount of space while delivering high performance and flexibility due to its compact design. They also have high-efficient end cushioning and wear-resistant sliding surfaces.  

How to Choose the Right Rotary Actuator for your Application

Different actuator models typically depend on the system’s operating pressure. This is why it’s important to know the pressure required, along with other key factors including load capacity, rotation angle, rotation speed, and more.

Dynamic Movement

First, determine if the rotary actuator will be used in highly dynamic applications, such as torque/torsion testing of axial loads and other drive line components. If so, end-cushioning is important to have, along with a servo valve that can be mounted to the actuator to offer more control to the device.

End-cushioning

End-cushioning is an important factor to consider for highly dynamic applications, such as when the actuator needs to function as an end stop in a load. End-cushioning acts as a hydraulic break to slow down the movement of the actuator so that it doesn’t slam into the end position causing damage to the device or the workpiece. The end-cushioning effect can be finely tuned using orifices and set screws.

Mounting

Actuators can be mounted in different ways, along with shaft style. The actuator might have a flange mount, foot mount, or threaded holes in the actuator body. The shaft could be male or female with splines (keyed or a different shape).

Temperature

Typical hydraulic systems operate in an oil temperature range from -4°F to +240°F (-20°C to +60°C) in the same range. Actuators operate in the same range. If actuators need to operate above or below the standard temperature range, then special steels or special seal material may need to be used.

Mediums

The same applies to different mediums. Different mediums could require non-standard seals and different actuator materials.

Side Loads

If the application and actuator have side loads, the side loads need be absorbed separately from the actuator, or the actuator needs to be designed to accommodate the side loads. This is often done through the use of bearings. Eckart usually includes 4-point contact bearings as standard.

General Applications

Finally, it’s important to understand the general application. For example, will the device be going offshore? This might require special paint and special seals to protect the actuator from harsh seawater environments. As mentioned above, it’s important to know if the actuator will be used in testing applications, as special attention would be needed to make low-friction seals and a servo valve adapter plate.

Eckart Rotary Actuators

After determining these important factors, we can help you find an actuator design to best fit your application from our Eckart line. Eckart is the leading technological innovator in developing custom-made rotary actuators and valve actuators based on helical gear technology.

SM4 Rotary Actuator

Our SM4 rotary actuator is a heavy-duty and highly-customizable rotary actuator designed for the toughest and most-demanding applications with an operating pressure rating at 3,625 psi (250 bar) and maximum toques up to 2,200,000 Ibs-in (250,000 Nm).

HSE4 Rotary-Linear-Actuator

Our HSE4 rotary-linear-actuator is a combination of a rotary actuator and a dual-action linear cylinder and is commonly used for applications that require lifting and turning. It has an operating pressure of 1,450 psi (100 bar).

E3 Rotary Actuator

For mobile applications where a flange shaft, cantilever mounting style is desirable, our E3 rotary actuator is an appropriate choice. It has a maximum operating pressure of 3,046 psi (210 bar) and is available with torques up to 31,800 Ibs-in (3,600 Nm).

E1 Rotary Actuator

The E1 rotary actuator is the latest rotary actuator in our product line and was designed for low-pressure hydraulic systems with typical operating pressure ratings of up to 1,450 psi (100 bar) and is available in torques up to 22,000 Ibs-in (2,500 Nm). 

HyRAV Rotary Actuator

The HyRAV quarter-turn valve actuators have 12 drive sizes with torques up to 2,200,000 Ibs-in (250,000 Nm) and an operating pressure up to 3,046 psi (210 bar). 

Custom Rotary Actuators

More than 70% of our actuator line was custom-designed to meet specific customer needs. If you have a specific project in mind, we will present you with a customized, optimum solution.