Originally Published MPMN March 2009

BREAKTHROUGHS

Linear Actuators Add Safety Feature to Imaging Systems

Shana Leonard

Roh’lix linear actuators, manufactured by Zero-Max Inc., have been used since the 1970s in such machinery as automated manufacturing equipment. Recently, however, the actuators have found application by enabling part movement while ensuring patient safety in medical diagnostic imaging systems.

Incorporated into the bed positioning systems of such imaging equipment as MRI machines and CT scanners, Roh’lix actuators are designed with an overload protection feature that halts motion in the event of an obstruction or upon obtaining a preset level of travel pressure. This means that in the instance of a power failure, for example, a technician would be able to pull the patient table out of the system, according to Bob Mainz, Zero-Max manager of sales and marketing. “That’s a key feature,” he adds. “And, if something went wrong in the drive system—if you had a feedback loop error or something malfunctioned—this would be the ultimate safety [feature] where it would simply slip.”
The ability to force the positioning system to slip translates into an inherently safer end product than those relying on ball screws, according to the company. An alternative to ball screw–based products, the actuators are engineered with three precision ball bearings on each end of a two-piece aluminum carrier block; all six bearings are mounted at an angle to the drive shaft axis. “[A ball screw] turns rotary motion into linear motion, and that’s what we do with this actuator,” notes Mainz. “We’re replacing that function.”
The motion control components also offer flexibility by including an adjustable thrust setting. This feature allows thrust to be set to transport loads without slipping while avoiding the buildup of unnecessary thrust prior to overloading. The actuators can handle motion thrust ranging from 5 to 200 lb, depending on the model and size.
Available in five standard sizes for 3/8- to 2-in.-diam shafts, Roh’lix actuators do not use sensors or drive motors, and do not require lubrication. Offered with steel or stainless-steel components, the compact products provide smooth, clean, quiet, and accurate operation.
Zero-Max Inc., Plymouth, MN
www.zero-max.com
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