US Patent 7662240 Seal for worm gear speed reducer

The performance of a worm assembly seal is improved by (1) the use of a hardened steel worm with a bronze worm gear; (2) a tribological coating on one or both of the worm thread or spiral and the gear teeth; 3) a tribological coating on one or both of the input or output shaft or shaft sleeves; or (4) a tribological coating applied to the worm thread, the gear teeth, the input and output shafts or shaft sleeves, or combinations thereof. In each of the approaches, the worm, worm gear, and input and output shafts or shaft sleeves can have surface finishing treatments. Additionally, in each of the three approaches, carbon or carbon/nitrogen concentration gradients can be added to the worm.