Invention makes it possible for single caregiver to move patients

May 07, 2001

(Blacksburg, Va., May 8, 2001) -- In 1995, after seeing people with rigid, heavy power wheelchairs struggle with transporting them, Virginia Tech human factors engineer John Casali invented and patented a light-weight, front-mounted, detachable power drive for folding wheelchairs. Although the device could provide a low-cost alternative for thousands of wheelchair users unable to afford power chairs and the large, modified vans required to transport them, and be a flexible alternative for others among the 1.2 million wheelchair users in the United States alone, it has not yet been commercialized for wheelchairs. However, T.H.E. Medical, a Canadian manufacturer of mobile patient lifts, saw the wheelchair drive and asked Casali to develop a power assist device for patient lift and transport units.

Such units are used in hospitals, nursing homes, and private homes. While they often have a power assist for lifting a patient, they do not have any power assist for moving the unit and patient. The effect is a front-heavy unit that is difficult to push and steer, and difficult to stop once moving. "The caregiver is usually a nurse trying to push a patient down a hallway or negotiate with a suspended patient in close quarters, such as over a bed or bath," explains Casali, who is the Grado professor and head of industrial and systems engineering (ISE).

He and ISE research machinist Randy Waldron were happy to have the opportunity to help caregivers and reduce injury for these workers. In conjunction with T.H.E. Medical, they have invented a power unit that "not only improves ease and convenience in transporting nonambulatory patients, but also reduces back and shoulder injuries for nursing attendants and enhances safety for patients being transported," Casali explains.

An attendant grasps the lift's handlebars and presses an acceleration control. Movement starts smoothly, with a minimum of patient swinging. Stopping, with release of the spring-loaded acceleration device, is also smooth. The researchers integrated the drive unit with a four-wheel, 360-degree rotation caster chassis, adding stability and allowing the lift to spin within its own wheelbase. "Such a lift can turn around in a narrow hallway, which is very difficult without the power assist," Casali says.

A patent is pending on the drive and it has already been licensed by Virginia Tech Intellectual Properties (VTIP), Inc. to T.H.E. Medical of Barrie, Ontario.

Meanwhile, the quick-connect, power drive and steer attachment for wheelchairs has been improved. Dr. Laura L. Clark, as part of her dissertation research at Virginia Tech, worked with Waldron, Casali, and other faculty members of the Human Factors Engineering Center at Virginia Tech to make improvements. Then Clark, who received her Ph.D. in 1997, tested the second generation of the power add-on unit (PAU) with seven wheelchair users.

The resulting third-generation prototype snaps on with a small battery and is attachable and detachable by the wheelchair user. "It does 80 percent of what a power chair does for about one-fifth of the cost and only weighs about six pounds," says Casali. "Its beauty is in its simplicity."

Clark, in her dissertation conclusion, expounds the potential social benefits of the power assist unit, pointing out that it provides independence not previously available to the disabled, would be useful to temporarily disabled people who can't transport a bulky electric wheelchair, and would be convenient for companies who lease equipment.

Casali believes the power unit has not been commercialized because there is a much larger profit margin for the more expensive rigid frame power wheelchairs, making them more attractive strictly from a commercial standpoint.
Contact for more information:
John Casali 540-231-9081 or, or visit

Laura Clark's dissertation is at

Michael Martin, executive vice president of VTIP, at 540-951-5292 or, or visit

Joe Bailey, T.H.E. Medical,, 705-733-0022, or

Photos available at

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