“Spring-loaded” (also “spring-preloaded”) refers to a type of preload used in double-nut systems in which two individual nuts are held apart not by a rigid spacer ring but by a spring assembly. The two nuts are mounted in a common housing in a manner that prevents them from rotating.
Operating Principle
The spring assembly maintains a constant preload, regardless of manufacturing tolerances, wear, or thermal expansion of the components. Unlike with a rigid preload achieved using a spacer ring, these factors do not affect the friction torque.
Advantages and Limitations
- Consistent, reliably backlash-free preload throughout the entire service life
- A low preload force is sufficient, as tolerances are compensated for by the spring
- The structure is larger and more complex than that used with rigid prestressing
- Coaxiality can be easily compromised by the sliding nut
- Permissible axial force limited to about two-thirds of the preload force
Practical relevance
Spring-loaded double nuts are particularly well-suited for miniature ball screws, high-precision adjustment axes, and slim spindles, where tight manufacturing tolerances make it difficult to achieve rigid preload in a cost-effective manner.