A rodless cylinder that could be a breakthrough product for high-temperature applications is being tested in Europe, according to one of its designers. Mechanical applications engineer Stephan Barry, of Hoerbiger-Origa Corp, Glendale Heights, Ill., said that late last year, the company's OSP-series rodless pneumatic cylinder, called Thermocylinder, was tested in oven-door opening applications to 500º, the limit of the thermal test equipment used in the trials.

"The test ended only because the sensors maxed out," Barry said. "Rodless cylinders usually have a maximum operating temperature around 150º. The unique barrel design allows coolant to flow through the entire length of the cylinder."

Designed for applications like food processing ovens, glassworks furnaces, and metals foundries, the cylinders are equipped with special end caps that keep them air- and fluid-tight throughout the entire pressure range, Barry noted.

The cylinders meet the challenge by using high-temperature gaskets. Coolant is passed through the cylinder and out to a heat exchanger in a continuous cooling cycle. The end caps separate the coolant flow into five paths as it cools the cylinder, and back into one outflow path as it exits.

In a test that ran 270 minutes, the coolant temperature remained under 150º F as the oven temperature went up. The internal air temperature remained just above that mark. A chiller, like those used in plastic molding machines, would be an effective way of lowering coolant temperature rapidly, Barry said.

And, depending upon the application, the heat removed could be used in another part of the factory, Barry added.

"The amount of heat energy removed has been calculated at 9240 BTU's/hr. for a 40mm bore with a 65-inch stroke. The product is very different because of that heat-exchanging set-up," he said.

"All the results are very positive," Barry said. "The modifications of the end caps and seals have been successful. The cylinder is in testing in Europe, but we don't have a fixed date for a product release. We've been working on the project for two-and-a-half years."

Chris Christensen, unit president of fluid power at Applied Industrial Technologies based in Cleveland, Ohio, has several glass and primary metals manufacturering customers waiting to test the Hoerbiger-Origa cylinders.

"We see a technological breakthrough in that application. While it's not industry-changing, we do have some specific customers that can use this product. Hoerbiger-Origa is ahead of everyone on this niche technology so we hope to have some successful results," Christensen said.

While less enthusiastic about rodless pneumatic products in general, Joseph O'Brien of Gibson Engineering in Norwood, Mass., said that there are some possible applications for the product as long as its use is closely monitored. O'Brien is vice president for external affairs for the Fluid Power Distributors Assn. His company specializes in pneumatic products.

"Sometimes, the seals used in [rodless] cylinders are asked to perform beyond their normal capacity. If the application is strictly engineered and monitored, they can be a useful item," he said. "If you look inside one of those carriages, you can see it is very complex. However, if [users] are very meticulous about monitoring the guiding and physical components, it may do well."