What are air bellows and how are they used

What are air bellows and how are they used?

By Martin Lissenburg, Product Specialist

You have an application requiring a high thrust over a short stroke; there is a significant amount of vibration and the location makes maintenance free an ideal.

In these situations, air bellows (or bellows) are a perfect solution. A 12 inch diameter unit can deliver an initial force of around 35,000 Newtons at the recommended operating pressure of 5.5 bar, has a high vibration isolation level and is frictionless in operation..

How are air bellows constructed?

The flexible bellows are made from fabric reinforced rubber and usually have one, two or three convolutions, depending on the stroke required. The air bellow is fixed between two chrome steel end caps and chrome steel studs are welded to each end cap; this makes bellows easy to install, particularly as they have higher tolerance to mis-alignment than other linear actuators. However, the full surface of the metal endcaps must be used to bear the force and lateral guides should be used.

What are typical applications?

As stated above, air bellows are ideally suited to high load, short thrust applications and where vibration is a problem. Good examples are handling applications, like scissor or platform lifts, machine stops or footings, hopper vibration dampers, reel tensioning, stamping presses and vehicle suspension.

There are more such applications where the air bellows are used either to produce motion (as an actuator) or to provide isolation in high vibration situations.

What are the operational considerations?

As a design point, it should be noted that thrust is not constant - it decreases as the height of the bellows increases; this is due to the change in the effective area of the bellows itself as stroke changes. Manufacturers provide graphs showing the change in force generated, for various operating pressures, as the height, or stroke, varies.

Clearly, the bellows must not be inflated until they are installed and end stops should be designed in to prevent operation beyond the minimum and maximum recommended heights. If removal is required the bellows should be fully deflated before any dismantling commences.

Although the materials are robust in normal use, the bellows should not be constantly in contact with hydraulic oils, lubricants, solvents, metal cuttings and welding sparks. 

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