For about 80% of us, back pain at some point will be our worst enemy. While the causes and treatments are many and varied, one well-received approach is spinal decompression on Axiom Worldwide’s DRX9000™. And bearings from NB Corp keep the system working smoothly.
Engineering the Therapy
High tech approaches to back pain relief include spinal decompression, where brief periods of increased and then reduced tension on the lower body alleviate pain associated with herniated and bulging discs, facet joint pain, and sciatica. Jim Gibson, president/CEO, and Nick Exarhos, executive vice president, founded Axiom Worldwide of Tampa, FL and started developing the DRX9000™ in 2000.
Spinal decompression systems on the market at that time were poorly engineered and didn’t provide for individualized treatment, plus few systems attempted to accommodate motion of the patient spine via a moving mattress. Where a moving mattress was used, plastic slides or other composite materials were relied on to facilitate that motion. Friction resulted in decreased performance and inconsistent “stick and slip” movement. Precise, controlled movement was lacking.
"Friction, slip-stop, gearbox binding and other such obstacles must be removed before you can focus on the patient," says Scot Johnson, Axiom’s engineering director. "These problems exist in all mechanical systems and we have gone to great lengths to produce a device that provides proper logarithmically applied forces. One major advantage of our device is that we utilize steel bearing and shafting technology in our floating lower mattress.”
How It Works
A patient lies flat on a padded, two-part table contoured to keep the knees slightly bent. The floating lower mattress supports the lower body and can move independently of the upper mattress half, traveling up to 3 ½ in. away from it. Sensors in the table weigh the patient and measure various parameters. The upper body is secured to the upper mattress; the lower body is secured to a strap that exits the tower in front of the patient, applying tension to the lower body. As the body elongates, pressures on the spine’s intervertebral discs are reduced.
“One of the most critical parts of the DRX9000™ is the floating lower mattress,” explains Scot Johnson. “While the upper half of the body remains stationary, we want the lower body to be able to extend freely as our system provides a tension pull. As the spine elongates and decompresses, instead of having the body dragged along a stationary mattress, we let it float freely and elongate at its own rate and direction. The floating lower mattress really facilitates that. We think it is a competitive advantage over our competitors. Very few spinal decompression products have a floating lower mattress.”
Precise Motion Makes It Work
To ensure that the electronically controlled motions are realized precisely, the floating lower mattress moves via linear bearings on precision ground shafts. NB Corp designs and manufactures these unique bearings -- its Topball line. Each bearing’s load plate is precision-ground – not stamped – and checked for consistency during manufacture. These unique bearings have load plates whose ends are thinner than their centers, making the center a fulcrum for self-alignment. Because wiper seals on the bearings are floating, they don’t restrict self-alignment and the floating load plate adjusts the clearance automatically. Axiom uses both the single and double wide block-housed Topball bearings identified as TWA 12 UU.
The bed can support patients who weigh as much as 400 pounds, so the bearings have to accommodate loads far in excess of that. NB Corp recommended the Topball line for this high load capacity because it has greater ball contact in its ground circular arches, thereby tripling load capacity. The bearings can actually carry a load of up to one ton (2,000 lb).
The DRX9000C™ also provides spinal decompression for the neck, which requires moving horizontally on a different type of linear bearing -- the NB Corp SYT Slideway. Because it has great roller-to-rail contact, though more compact than other crossroller bearings, it, too, can support a ton.
Finding the Perfect Lubricant
Axiom engineers continue to improve their technology, focusing on what they refer to as the “five critical subsystems,” of which the floating lower mattress is one. Taking the next step, Axiom sought to reduce friction by improving the bearing lubricant. X-1R Corp’s lubricant line seemed an ideal candidate. X-1R’s lubricant technology had been used successfully in NASCAR racing engines and had been adopted by NASA for use in the Space Shuttle Crawler.
Axiom requested that NB perform static and kinetic friction and lifetime testing on the steel bearings and shafting used in the DRX9000™, comparing NB’s current lubricant with the X-1R lubricant. Completed in late 2007, the testing demonstrated a decrease in static and kinetic friction by up to 27% over the current lubricant.
X1R lubricant technology impregnates certain metal surfaces, increasing density of those surfaces and decreasing friction. The bearings can go without additional lubricant for a longer period of time, extending their life. In addition, X-1R lubricants are eco-friendly.
Understanding How to Facilitate New Product Development
“NB went out of their way to get product to us, sample, and stock what we needed,” says Scot Johnson, describing the NB working relationship during product development. “We were incorporating some very low profile table slides into the DRX9000C™ for neck vertebral decompression. That bearing is a precision part and not easy to come by. I recall there were times when they, of their own accord, would have additional parts made (and stock them) when they knew we were in the development and problem-solving mode. There was no purchase order. They were just doing that so that if we placed a purchase order they would have it in stock. I was very impressed.”