News Releases

July 2006

No hissing and stamping with rage using simple, even-tempered Airstrokes

One of the simplest forms of pneumatic actuation can also be one of the most effective for applications such as pressing, forming and stamping.

The uniquely flexible air spring is, like a conventional air cylinder, essentially a contained column of air that is pressurised to actuate machinery.

In the case of a conventional cylinder, a piston extends to provide force. In the case of an air spring, the bellows itself extends.

Each type of cylinder can be superior to the other in particular applications, but sometimes the more familiar conventional cylinder may be specified for materials handling applications simply because it is better known than the alternative, rather than better suited.

Some of the advantages for air springs in particular applications arise from the fact that, whereas conventional cylinders contain their air in a rigid metal jacket, air springs contain theirs in a flexible but immensely strong rubber and fabric-reinforced bellows.

The shape of the bellows may vary - it may be tubular, like the air bags used in truck suspensions, or it may be convoluted. While air springs are available in a variety of styles, sporting differing components that control the shape and path of axial extension, their basic design is the same. Each style is, in essence, a heavy-duty balloon that offers 40-40,000kg of pushing or lifting power and strokes (extensions) of up to 350mm, powered by simple, basic compressor equipment found in nearly every factory.

The design of all air springs (or Airstrokes®, as our Firestone actuators are known) differs substantially from conventional cylinders in that they contain no pistons, rods, seals or other wear parts prone to hissing leaks and energy wastage. This simplicity means that in many applications they cost less, last longer and are less expensive to operate than conventional cylinders. They can also significantly reduce downtime, compared with conventional pneumatic or hydraulic cylinders.

Because friction is reduced, and there are no internal moving parts to break or wear, they are very suitable for high-repetition tasks, such as powering stamping presses. Bear in mind that Firestone - the world's number one supplier of air springs, engineers its market-leading product to be so robust as to function for hundreds of thousands of kilometres in heavy truck and bus suspensions. As a result, they are certainly sufficiently flexible and robust to survive millions of cycles in industrial applications (and have in numerous applications we can point to).

Flexible Airstrokes are far less affected by side loads generated by the material beneath them (they can bend with the load, rather than break down as a rigid cylinder may) and are impervious to dirt and contaminants the material or environment may carry. In addition, air springs are far more tolerant of shock loads then conventional pneumatic cylinders. Such shock may damage conventional cylinders and, where they cannot absorb the bumps and grinds of production, the shock may transfer into the workpiece and damage that.

Also valuable to a production engineer is the flexible air springs ability to arc without a clevis - to bend and to tolerate uneven and fluctuating loads. This built-in flexibility makes them suitable for materials handling tasks in which they must exert force across uneven surfaces, such as in different pressing and forming applications.

One of their salient advantages in these latter applications, moreover, is their ability to exert even pressure across the surface of the material to which they are applied. Rather than exerting pressure from a point - such as the rod of a conventional pneumatic or hydraulic cylinder - the thrust of an air spring is exerted evenly across the entire diameter of the bellows (which can vary from just a few centimeters to about a metre).

This even pressure capability can be very helpful also where the air spring is used to apply counter pressure, such as against the rams of large hydraulic presses, for example. The even force exerted by such counter pressure assists production engineers in precision forming metal components with fine tolerances when they are fitted together (such as vehicle component pressing produced by Ford Australia, which uses Airstrokes to provide counter pressure in enormous presses up to 200 tonnes capacity)

Where space is at a premium, Airstroke actuators' short collapsed height and angular capability are further pluses. Though a conventional pneumatic cylinder is limited to a stroke that is approximately equal to its collapsed height, an air spring stroke is up to four times its collapsed height, providing more motion from a smaller space.

Conclusion

The author of this article does not pretend that Airstrokes are the ideal solution for every pressing, forming and stamping application. There are many quality actuation products in the market that have particular advantages for particular types of job. What this article sets out to demonstrate is that there are many applications for which Airstrokes may be suitable but for which they have not been considered.

Free technical information

Would you like to learn more about the technology discussed in this exclusive report as it relates to particular applications? Readers can receive more information by contacting Air Springs Supply Pty Ltd, PO Box 215 West Ryde, 2114, ph (02) 9807 4077, fax (02) 9807 6979.

About the author: A man with more than 20 years experience in pneumatic actuation and isolation, Simon Agar is National Sales Manager for Air Springs Supply Pty Ltd, Australia's oldest and largest distributor of air springs. The company represents the world's largest producer of Air Springs, Firestone, and Europe's premium brand, Continental. Projects for which Mr Agar has provided advice on air spring selection, positioning and use span such industries as food and beverage processing, manufacturing, materials handling, metal forming, mining and mineral processing, process engineering, packaging, transport and construction.