A ctuator nuts made of a non-metallic filament-wound material commonly used for bearings are designed to carry higher loads with less weight, and without lubrication.
The design is the latest innovation using filament-wound bearing material with non-cylindrical inside configurations. An earlier product used a filament-wound bearing with a helical, hexagonal inside shape riding on a helical, hexagonal shaft to convert the shaft's rotary motion into linear motion. By moving the shaft linearly, the bearing could be made to rotate.
The new actuator nut is designed to be used with rolled thread forms. The rolled thread provides a combination of low cost and smooth finish. "The goal was to come up with the best combination of a low-cost mating surface with good finish to replace the machined helical hex or helical square forms that were used in earlier actuator nut designs," explains Engineering and Marketing Manager, Bernard Harris.
"The self-lubricating Duralon bearing material is a composite made of Teflon and polyester fibers woven into a bondable fabric and supported by a filament-wound fiberglass and epoxy shell. When applied to a matching rolled stainless-steel thread form, it provides an actuator, or cam action," adds Harris.
A key element of the latest design is the use of a modified shape and multiple starts to achieve increased load-carrying capacity. According to Harris, the thread form of the actuator nut was developed by taking the chord across the tooth instead of following the arc. This provides a larger contact area than the line contact that would otherwise be used. With multiple starts, the load is transferred through a number of flats on the multi-threaded form, which reduces the unit load per tooth.
Additional Details… Rexnord Corp., DuralonBearing Div., Downers Grove, IL 60515; Tel: (630) 719-2323; www.rexnord.com.