One shock absorber plays two roles

Farmington, MI--For years, makers of industrial shock absorbers had a rule of thumb: They could build a self-compensating shock absorber--one that handles a wide range of loads--or they could make a "soft contact" version. But they couldn't combine self-compensating features and soft contact in a single product.

Now, however, that's changing. Engineers at ACE Controls Inc. have developed an industrial shock absorber, or "load decelerator," that combines both features. Called the SC², it efficiently stops a wide range of loads and can stop them in a way pleasing to the customer's eyes and ears.

For most users, the ability to combine those qualities is critical. Most need a load decelerator that operates efficiently, thus minimizing wear and tear on their machinery. Equally important, they want a shock absorber that enables their machinery to operate faster, quieter, and longer. Self-compensating shock absorbers perform particularly well in those areas, because they offer the same performance under changing load conditions. At the same time, however, many users also want soft contact. For them, efficient shock absorbers may seem too abrupt at impact.

The SC² offers a solution to that dilemma by departing from conventional shock absorber designs. Unlike conventional models, which typically use an exponentially spaced series of holes on their inner tubes, SC² employs nearly linear hole spacing. "When you space the orifices that way, you can vary performance based strictly on orifice diameter," notes Harold Wiard, engineering manager for ACE Controls and co-designer of the new product.

ACE Controls also departed from the conventional in its use of just four orifices. In contrast, conventional shock absorbers typically use as many as a dozen orifices.

The key to obtaining soft contact and self-compensating performance in such a simple design is ACE Controls' use of a custom computer program. Over the years, the company's engineers created custom design software that relates a shock absorber's hydraulic metering area to various loading parameters. Key loading parameters include impact velocity of the mass, propelling force, and weight range.

Using this software for their design, they slice the hydraulic cylinder's stroke into five control zones--three zones for the first three orifices, two for the last orifice. Knowing the reaction forces in each zone, they then size the orifices. Afterward, they run a custom simulation program that describes how that particular shock absorber will perform under load. "Because we know the cause-and-effect relationships, we can blend the orificing so that it meets self-compensating and soft contact criteria simultaneously," Wiard says.

By employing such a simple design, ACE Controls also benefits from lower manufacturing costs. To machine a dozen exponentially spaced holes in the cylinder's inner sleeve is a slow and costly process, Wiard says. "Doing it our way results in a more manufacturable metering pattern," he says.

Most important, however, is the fact that customers can now obtain soft contact and self-compensation in a single product.

Additional details…Contact Harold Wiard, ACE Controls Inc., 23435 Industrial Park Drive, Farmington, MI 48335.