Patent Principle Animation:Planetary Gear Reducer Lab

The sun sits in the middle with planets around it, an internal ring outside, and the planet pins mounted on the carrier. Not every tooth count works: ring teeth equal sun plus twice the planet, and (Zs + Zr) must divide evenly by the number of planets. Try switching to four planets.

With the ring fixed, each planet orbits the sun while spinning, rolling inside the ring. Its outer edge is at rest, its inner edge matches the sun, and its centre moves at half that—so the carrier slows down: i = 1 + Zr/Zs = 5. The three lines in the speed diagram show exactly this.

Holding the ring gives a large reduction; holding the carrier makes an ordinary gear train with reversed output; holding the sun with the ring as input gives a mild reduction. Automatic gearboxes shift by locking different members with clutches, and patents often claim these modes as separate dependent claims.

Independent claim 1 splits into features 1a–1d, each of which must be found in the product; dependent claims add the tooth relations and ratio. Infringement analysis, validity defence and due diligence all work through the chart cell by cell like this.