US Patent 7578214 Preload structure for a ball screw

A preload structure for a ball screw in the inner surface of a nut is formed a helical groove whose lead is different from the lead of the adjacent helical groove to produce a lead deviation between the helical groove of the nut and the helical groove of the screw. By such arrangements, the lead deviation can be used to achieve the preload objective, thus reducing the fitting number demanded of the circulation system. Consequently, not only the single circulation system fittings can be used, but also the length of the nut is shorter and without extra machining, and the producer only needs to control the deviation of the interval helical track during rubbing to achieve various preload changes.