Festo Pneumatic Bellows Cylinder

Bellow cylinders are pneumatic actuators that serve as both drive components (providing mechanical motion) and pneumatic springs (offering shock absorption properties). The design consists of two metal plates connected by ribbed rubber bellows and no piston rod. They generate high force from the compressed air acting on the large surface area of the end faces. As pressure increases in the bellows, the force is applied outward on the movable end face. When the pressure decreases, there is no need for a return spring, as the return motion is typically achieved by the weight of the applied load.

Festo bellow cylinders are available in diameters from 80 mm to 385 mm, offering strokes up to 230 mm and a maximum carrying force of 70 kN at 8 bar. They are ideal for a wide range of pneumatic actuator applications due to their high force output, compact installation, and smooth, consistent movement.

Key features of Festo bellows cylinders

• Operates effectively in harsh, dusty environments
• Suitable for underwater applications
• Robust construction for durability and long life
• Offers a force range from 1 to 50 kN
• Compact design ideal for space constraints
• Ensures smooth and consistent operation (no stick-slip effect)
• Maintenance-free as there are no moving parts or sealing components

Function

The Festo EB series bellows cylinders are single acting, meaning they generate force in one direction when pressurized and return to their original position through an external force. These cylinders serve as both driving and cushioning components. When pressurized and exhausted, they function as driving components, with the force getting weaker as they extend. When kept under constant pressure, they act like cushions. The design includes two metal connecting plates and an attached rubber bellows, with no sealing components or moving mechanical parts. This reduces maintenance needs, increases durability, and minimizes the risk of leaks or mechanical failures. These cylinders are single-acting and do not require spring returns, as the reset is achieved by the application of external force.

Festo single and double bellows cylinders

Single bellows cylinders consist of one set of bellows and are designed to generate force in one direction when pressurized. They are compact and suitable for applications with limited space and moderate stroke requirements.

Double bellows cylinders have two sets of bellows stacked together. This configuration allows for larger strokes compared to single bellows cylinders while still generating force in one direction when pressurized. Both single and double bellows cylinders are single acting and the distinction is solely based on the number of bellows in each type.

Table 1: Festo single and double bellows cylinder features

Feature	Single bellows cylinder	Double bellows cylinder
Structure	One bellows unit	Two bellows units stacked together
Stroke length	20 mm to 115 mm	45 mm to 230 mm
Thrust force	1.7 kN to 31.6 kN	1.4 kN to 31.5 kN
Recommended operating height	60 mm to 145 mm	90 mm to 250 mm
Resetting force	120 N to 400 N	200 N to 400 N
Weight	500 g to 5900 g	500 g to 6900 g
Tilt angle	10° to 20°	15° to 30°

Note: As the size increases, the amount of material required for the double-bellows configuration grows more substantially than for the single-bellows configuration. This is because each additional bellows adds more weight, and the connecting components must be more robust to handle the increased forces and strokes. The smallest size for both single and double-bellows cylinders weighs approximately the same.

Installation and usage

Table 1: Festo bellows cylinder installation and usage requirements

Installation considerations	Description	Illustration
Space requirements	Ensure the bellows cylinder does not contact other machine parts during expansion.
Combined installation	When using multiple cylinders, mounting plates must be inserted to prevent lateral spreading.
Lateral offset and tilt	Adhere to maximum lateral offset and tilt angle to prevent damage.
Height constraints	Do not exceed the minimum and maximum height limits to avoid damage.

Technical specifications

• Pneumatic connection: Varies from G1/4 to G3/4 depending on the size
• Operating pressure: 0 to 8 bar
• Ambient temperature: Operates effectively in temperatures ranging from -40 °C to 70 °C
• Corrosion resistance: Moderate corrosion resistance suitable for indoor applications with condensation

Application example

Consider a manufacturing plant that requires a reliable method to maintain consistent tension in their conveyor belt system, which operates in a dusty and harsh environment.

Select a bellows cylinder, for example a model like the EB-145-60 single-bellows cylinder provides a thrust capacity (up to 3.2 kN) and stroke length of 60 mm. The bellows cylinders are mounted on the conveyor frame with the pneumatic connections linked to the plant's compressed air system. The cylinders are positioned to apply tension to the conveyor belt by pushing against an adjustable tensioning roller.

Compressed air is supplied to the bellows cylinders, which expand to maintain the desired tension on the conveyor belt. As the belt stretches or contracts due to load variations, the bellows cylinders automatically adjust to keep the tension consistent.

Advantages

• The robust design of the bellows cylinders ensures reliable operation in dusty and harsh industrial conditions.
• The simple construction with no moving mechanical parts minimizes maintenance requirements.
• The bellows cylinders provide smooth and continuous tension adjustment, preventing belt slippage and improving operational efficiency.