A Place At The Table

How new linear weight bearing capabilities expanded X-ray table functionality

By Jeff Reinke, Editorial Director

Arcoma is one of the world's leading providers of automatic X-ray equipment. However, in re-designing one its flagship products, the Arcoma mobile imaging table, the company encountered a significant design obstacle.

alt="The Arcoma mobile imaging table faced serious design challenges throught the product's redesign"> Arcoma's original plan for the mobile imaging table included creating a flexible, easy-to-operate, ergonomic unit that could provide a safer way of lifting patients. ADVERTISEMENT

The original plan called for creating a flexible, easy to operate, ergonomic unit that could provide a safer way of lifting patients. In upgrading the unit, it would also need to perform radiographs on trauma patients without having to re-position them. This translated to the table requiring support for as much as 500 lbs. of weight.

According to Brian Gogan, executive vice president of Arcoma North America, the new applications for the table fell within pain management and orthopedic studies, so the re-design would have to support obese patients in order to comply with FDA requirements.

"The increased load capacity would have been too great a strain on our existing tables, so the key was to find a linear motion system that could not only hold the weight, but also have a long enough stroke for the application," explains Gogan. "Because the tables move around the imaging equipment, rather than moving the patients themselves, there is a huge strain on the bearings."

Furthermore, Gogan explains that in addition to the extra load capacity, Arcoma needed a highly reliable linear bearing system. "It's simply not an option for our products to fail in the field, because of patient safety," he adds.

So regardless of the FDA regulations, simply from an operational perspective these tables needed to be able to support a 350-lb. person. When moving people, safety factors of at least three times-and as high as 10 times-are usually used. In this situation increasing the safety factor could not impact friction or deflection.

Feeling vibrations would only add to whatever discomfort and apprehension the patient may already have due to the particular test he or she is undergoing. These factors make smooth movement a crucial performance variable.

"We investigated several linear motion options," states Gogan, "but only ROLLON's telescopic rail provided the combination of load capacity and extended stroke. The rails act like industrial drawer slides so they are able to telescope beyond the mounting structure. In testing, even with extremely high loading, the slides showed zero deflection, and with reach strokes of over 200 cm, they provided the flexibility required for mobile imaging. They also have hardened 60 HR raceways to ensure a smooth movement."

In creating the telescopic rail family, ROLLON's engineers created a telescopic linear bearing - similar in movement to a drawer slide but closer, in function, to a linear bearing. Some of the keys specs include:

• A composition of cold-drawn bearing steel. (These rails are never produced by bending sheet metal.)
• The capacity to reach strokes of over 2 m (6.5') in one direction and can double that by doing the same out of the other side.
• A family of products that contains telescopic slides with hardened races, telescopic slides with non-hardened races and semi-telescopic slides with rails that extend more than half of their length out of either side of the fixed part of the slide.

With more medical situations involving MRIs, shorter bearings that put less steel closer to the machinery are becoming very important. With the type of solution described here, less steel is placed in a closer proximity to the huge magnets found in MRI machines when the rail telescopes outward.

The results? "Arcoma's new mobile imaging table was launched in January 2007," Gogan states, "and so far we have a total of 53 units in use across the U.S. without any failures."