A transmission for changing the rotational speed of an engine input shaft to a driven output shaft. The transmission includes a first and second face gears. Each face gear has first and second sets of teeth formed on it. Each set of teeth forms an annular pattern about a central axis. The second...http://www.google.com.au/patents/US5807202?utm_source=gb-gplus-sharePatent US5807202 - Differential speed transmission
