Astir Technologies, Concord, MA, astirtechnologies.com, has developed a fully automated device called the PowerNurse that lets a single nurse safely and comfortably transfer even the heaviest of patients between hospital beds, stretchers, and exam tables without risk of back injury. The company says other less-expensive friction-reducing transfer devices decrease but do not eliminate this risk. Motors and gearboxes from Maxon Precision Motors Inc., Fall River, MA, maxonmotorusa.com, were critical to the successful automation of the PowerNurse.

The low-profile (74 × 28 × 2.3 in.) assembly rides over a standard hospital stretcher. A series of conveyor belts, motors, and gearboxes in the device work to lift and move the patient. The first prototype easily transferred 400 lb using only one-fifth of the capacity of Maxon 250-W EC45 motors. The designer thereby downsized to 120-W ECmax 40 motors for the PowerNurse, while reserving the larger motors for another product in development.

Originally, the PowerNurse traveled at only one speed (1 in./sec). This was fine for patient pick-up and delivery, but too slow for lateral transfers. Consequently, Astir President and developer of the PowerNurse Chris McNulty included a two-speed option in the beta model. “Maxon's wide selection of gearbox diameters, gear ratios, and number of gear stages let us fine-tune overall speed while maintaining a high torque. In addition, using the DEC 50/5 motor control smoothed operation of the device,” he says.

The PowerNurse includes four Maxon ECmax 40 motors, four GP 42C, three-stage, 43:1 gearboxes, and four DEC50/5 servo-amplifiers, along with a 400 W, 48 Vdc power supply. The push-button device operates in burrow, pad align, and transfer modes. In burrow mode, conveyor belts carry the patient onto the device, while other belts move the device under the patient. This action happens simultaneously, so the patient feels a smoother transfer than with many other devices. In pad align mode, only the top conveyor belts are energized, for example, to align the patient with an incontinence pad. Transfer mode energizes the bottom belts, which transfers the PowerNurse with the patient on top to an adjacent surface.