If you look at Google search, the rotary actuator goes by many names: it is also referred to as a rotary drive or rotary actuator, as well as rotary cylinder, rotary motor, swivel cylinder, or swivel drive. What unites all these synonyms is their ability to deliver maximum torque in tight spaces.

The rotary actuator is based on a drive concept that allows you to rotate and pivot even the heaviest objects. Typically, these actuators operate within a range of 45° to 360°, and in extreme cases, they can even rotate up to 1440° or more. Eckart Hydraulics' rotary actuators are considered the absolute benchmark, often referenced in various educational and technical publications.

The term "rotary actuator" is defined by ISO 5598, so there is actually no other designation for this type of actuator. However, various names can be found, especially in online searches. Rotary actuators, or rotary drives, are composed of compact units that use hydraulic or pneumatic pressure to move a driveshaft in both directions. This driveshaft can rotate a digging bucket, pivot a train door, or move the basket on a fire department ladder, close heavy savety doors.. to name just a few applications.

What makes them outstanding is their ability to generate maximum power in a compact design. They are secure, powerful, fast, and precise, yet easy to control. Eckart Hydraulics employs the steep thread principle for absolute power density in their rotary actuators. Our rotary actuators operate within a pressure range of 20 to approximately 250 bar.

In the field of hydraulic rotary actuators, the helical spline (steep thread) plays a major role.

The helical spline in hydraulic rotary drives enables precise control and stabilization of intermediate rotation angles. It achieves this by converting the linear movement of the piston into an effective rotational movement of the output shaft. This conversion takes place under hydraulic pressure in a very compact space, generating impressive torque.

The outstanding feature of the helical spline principle lies in the generation of high torque and excellent holding power. It is also highly adaptable in terms of external dimensions. Although this principle may seem simple at first glance, manufacturing functional and highly reliable drives requires a maximum level of precision and extensive engineering expertise.

Hydraulic rotary actuators based on the helical spline principle are known under various terms internationally. In English-speaking markets, designations such as "Hydraulic Rotary Actuator", "Limited Rotation Actuator", "Semi-Rotary Actuator", "Swing Actuator", or "Helical Rotary Actuator" are particularly common.

Depending on the industry, region, and specific application, terms like "Rotary Drive", "Swivel Drive", or "Rotary Cylinder" are also frequently used.

In the global market environment, you will sometimes also find the informal term "HELAC-Type". Similar to how well-known brand names in other industries are occasionally used as a general term for a specific technology, this term often serves as a collective designation for hydraulic rotary actuators utilizing a helical or spiral operating principle, regardless of the actual manufacturer.

Eckart Hydraulics has been developing and manufacturing hydraulic rotary actuators based on the helical spline principle for decades, catering to applications with the highest demands on torque, precision, installation space, and reliability.

Depending on the country, industry, and manufacturer, hydraulic rotary actuators are referred to by various names. In practice, however, different technical concepts, designs, and driving principles are often mixed up or grouped together under similar terms.

Some of the following terms are frequently used synonymously in common language or search engines, even though they may refer to fundamentally different technical systems — such as rotary actuators based on the helical spline principle, the rack-and-pinion principle, the vane principle, or continuously rotating hydraulic motors.

The following overview serves primarily to provide a technical and international classification of terms related to hydraulic rotary and swivel movements.

Video Key Takeaways and Technical Details

How the Hydraulic Rotary Actuator Works in Detail:
In this video, you can see how hydraulic pressure moves an internal piston linearly inside the housing. This linear movement is then converted into a precise rotary motion via high-precision helical gears, resulting in a smooth and continuous rotational movement across the entire swivel range. Built-in damping ensures controlled and smooth deceleration at the end of the rotation.

Technical Features Highlighted in the Video:
The system offers scalable performance across 13 distinct sizes to perfectly fit your application's requirements.
It supports flexible standard rotation angles from 90 to 360 degrees, customizable intermediate positions, and options exceeding 360 degrees.
Designed for heavy-duty performance, it operates reliably from approximately 10 to 250 bar and in extreme environments from -25 to +70 degrees Celsius.
Additionally, the drive shaft features an adjustable zero-position and offers fine-tuning of the end positions by plus or minus 5 degrees.

Why this Engineering Principle is Used in Practice:
By converting linear piston movement directly into rotation within a fully enclosed, robust housing, the Eckart principle achieves an exceptionally compact yet powerful design. This allows for maximum torque output in minimal installation spaces, ensures excellent holding of the reached position, and guarantees maintenance-free and highly reliable operation even under the most demanding environmental conditions.

In the realm of rotary actuators, as well as in hub-rotary units and multi-axis devices, Eckart Hydraulics is considered a significant pioneer. We take an uncompromising approach, thanks to the incorporation of the latest material research and the individual construction of rotary drives.

More than 50 years of development are invested in Eckart's drives. Over half a million rotary actuators shipped worldwide speak for themselves. They are also used in critical and highly sensitive areas, such as personal safety and rescue operations, as well as in other safety systems, the food industry, aircraft landing gear testing, ship hatches, or offshore drilling rigs. Top-quality materials, the highest manufacturing precision, lifelong support, and repair options are part of our standard. In short, Eckart Hydraulics is a name you can rely on.

Electric actuators make sense when no hydraulics are available, when a very clean setup is required, or when you’re moving light to medium loads. For many automation and drive tasks, that’s a good fit.

However, when high torque, limited installation space, and tough operating conditions come together, a hydraulic rotary actuator is often the more robust and economical choice. Depending on the application, it may also be referred to as a rotary drive, slew drive, rotary motor, or rotary cylinder. In mobile hydraulics and harsh industrial environments, hydraulics show their strengths when high forces are required and shock loads, vibration, dirt, and temperature fluctuations are part of everyday operation. Speed is not a disadvantage either: depending on the design, very fast motion is possible, for example 180° in well under one second.

Key advantages of hydraulic rotary actuators:

•High power density: high torque in a compact design
•Robustness: resistant to shock loads and harsh environments
•Controlled motion: defined end positions even with heavy masses
•Application-specific design: torque, rotation angle (typically 0° to 360°), load profile, and duty cycle are engineered to match the task

When robustness, high force, and reliable performance are required in demanding environments, and safety factors in the design are critical, the helical spline / helical gear principle used in our Eckart-hydraulic rotary actuators provides a particularly durable solution.

Our rotary actuators are utilized in a wide range of sectors and industries. They particularly demonstrate their strengths in mining, both surface and underground: in these environments, extreme loads, shocks, vibrations, dirt, and the toughest continuous operations are part of everyday life.

Industries where our rotary actuators are typically found:

• Mining (surface & underground)
• Mobile hydraulics & construction machinery
• Heavy industry & steel mills
• Vehicle manufacturing & commercial vehicles
• Mechanical engineering & special machinery
• Power plants & energy systems
• Onshore / Offshore
• Shipbuilding & marine applications
• Food industry
• Pharmaceutical industry
 
 

A special form of rotary actuator is the linear-rotary actuator. In this case, the classic rotary motor is combined with a double-acting linear cylinder. This allows both rotary and linear movements in a confined space. Eckart Hydraulics offers the HSE4 linear-rotary combination, providing full flexibility in tight spaces.

Both units can be controlled hydraulically separately. This enables all possible movement sequences: pivoting left and right, linear extension and retraction. Because the rotary actuator and the linear cylinder can be controlled simultaneously, movements can also be executed synchronously.

It goes without saying that for these complex and diverse applications, customizations are often necessary. At Eckart Hydraulics, this is part of our fundamental concept. We fulfill customer wishes 100%. You can have a rotary actuator custom-made by us, precisely according to your requirements and with our expertise.

Each specially tailored drive is based on our proven three model series: SM4, E1, or E3.