Planetary Gear Trains with High Speed Reduction Ratio

A class of planetary gear trains (PGTs) with very high speed reduction ratio (SRR), is presented. The PGTs which comprise of profile shifting gears are constituted by one compound planetary gear, one carrier, and at least one sun or ring gears to form as a two-stage speed reducer. Such PGTs are compact, lightweight and easy to manufacture. Although multiple-stage PGTs and the use of profile shifting gear have been studied intensively for years, combination of the two concepts in the design of PGTs with extremely high SRR is novel. By the deliberated selection of the number of tooth of the profile shifting gears used in the PGTs, a very high SRR of up to several thousand to one can be easily obtained. Depending on the structure of PGTs, three distinct structures for such a class of PGTs are proposed. Feasibility and practicableness of the high-SRR PGTs are justified through the numerical modeling and the construction of mock-up models built by the additive manufacturing method and the machine tooling as well.