High-rel ball screw actuators fly high

Ball screw assemblies play a critical role in aircraft design: They actuate flap and slat controls, main landing gear, and horizontal stabilizers, to name a few functions. These devices have proved extremely reliable, having logged millions of flight hours.

For more than 50 years, Thomson Saginaw (Saginaw, MI) has been a leader in designing and producing precision ball screw actuators for aircraft and aerospace applications. Each assembly consists of a screw with a precision-ground machined, or rolled helical groove, a nut (outer race) with an internal groove, and circuits of precision steel balls that recirculate in the grooves between the screw and the nut. The anti-friction design--which operates at more than 90% efficiency--converts torque to thrust (or vice versa) as either the screw or nut turns and the remaining components move in a linear direction. Thomson's line can carry loads up to 750,000 lbs with stroke length ranging from fractions of an inch to 10 ft or more.

Hydraulics or rotary hinges could be used for the same job, says John Kinney, director of sales and marketing for aerospace and government applications. But the mechanical, structural nature of ball screws allows for many levels of redundancy, and makes them both inherently fire-resistant and robust. Using advanced manufacturing techniques, and leveraging upon years of experience, Thomson ensures that all of its ball screw products have a long, reliable life.