Thomson introduces SFM safety nuts for reliable backup load handling in vertical ball screw applications

Thomson Industries, Inc., a leading manufacturer of linear motion control solutions, has announced the availability of an external safety interlock option for vertical ball screw applications. The SFM safety nut is a secondary nut designed to hold a vertical load if the primary system fails.

“System designers implement ball screws for their excellent low-friction capability, but if the load-carrying nut traveling on the screw fails, the load can drop, presenting a possible hazard to both workers and machines. Our SFM safety nuts help prevent this precarious situation by taking over the load if the traveling nut cannot,” said Ojesh Singh, product manager at Thomson.

Ball screw nut failures can result from factors such as overloading and shock loading. Overheating or lax lubrication can also cause the nuts to succumb to gravitational force.

Thomson SFM safety nuts thread onto the screw below the traveling nut. During normal operation, it carries no load and has no contact with the screw threads. If there is increased axial play in the nut above specification, however, its negative thread will contact the screw thread, creating friction that will hold the load and prevent harm to nearby workers or equipment.

Safety nuts are especially valuable where human safety is at risk, such as patient tables, stage constructions, work platforms and airport people movers. Thomson offers safety nuts installed at the factory, but they can also be added at any time after shipment. The external flanged SFM safety nuts are available in a wide variety of standard dimensions capable of handling loads up to 450 kN. Integrated safety nuts (flanged and cylindrical) and customized options are available outside of the standard product offering upon request.

For more information, visit https://www.thomsonlinear.com/downloads/screws/SFM_Safety_Nut_bruk.pdf.

A video showing the proper installation of the safety nut is available at https://www.thomsonlinear.com/en/video/How-to-Install-an-External-Safety-Nut-onto-a-Metric-Ball-Screw-Assembly