Ravigneaux planetary gearset

The Ravigneaux gearset is a double planetary gear set, invented by Pol Ravigneaux, who filed a patent application on July 28, 1949, in Neuilly-sur-Seine France. This planetary gear set, commonly used in automatic transmissions, is constructed from two gear pairs, ring–planet and planet–planet.

The Ravigneaux set has two sun gears, a large sun and a small sun, and a single planet carrier, holding two sets of planetary gears, inner planets and outer planets. The carrier is one sub-assembly but has two radii to couple with the inner and outer planets, respectively. The two sets of planet gears rotate independently of the carrier but co-rotate with a fixed gear ratio with respect to each other. The inner planets couple with the small sun gear and co-rotate at a fixed gear ratio with respect to it. The outer planets couple with the large sun gear and co-rotates with a fixed gear ratio with respect to it. Finally, the ring gear also couples and co-rotates with the outer planets in a fixed gear ratio with respect to them.