ABSTRACT
Planetary gears have enjoyed an increasing application over a period of years partly because of the design improvements but also, and especially, because of the advantages associated with planetary gears in comparison with ordinary gear trains. Applications of planetary gears range from hoisting units in cranes to use in helicopters, tanks, airplane engines, turbines, pumps, textile machines, paper and cardboard-fabricating machinery, printing presses, and controls for a variety of instruments. When two gears mesh, a friction loss occurs when opposing teeth roll and slide on each other, and the sliding is proportional to the distance between the point of contact between opposing teeth and the pitch point. The efficiency of a planetary gear train is found by comparing it with an ordinary gear train having the same losses. An obvious solution to obtain nonuniform motion from planetary gear trains is to interpose a noncircular gear train between the input shaft and the planetary gear train.
