SPEED CHANGING TRANSMISSIONS

A three-speed transmission of the planetary type having three sets of planet gears, three sun gears and three ring gears. All planet gears are mounted on and driven by one common carrier which is connected to the input shaft. The sun gears are carried by an output shaft which is rotatably mounted on the input shaft and which extends from the transmission housing to carry a driving sprocket. A shifting mechanism, including a plurality of spring-loaded shifting pawls engageable with the ring gears and operable by a slotted shifting shaft, is selectable to maintain a desired one of the ring gears stationary relative to the housing to provide the desired speed ratio between the input and output shafts. The shifting mechanism in one embodiment also includes a mechanism which engages the first speed ring gear whenever the transmission input is driven in reverse and in another embodiment also includes a mechanism which engages one of the ring gears whenever the shifting pawls are all in their neutral position and the transmission input is driven in the forward direction. The transmission is shown adapted for use as a bicycle drive and mounted such that the transmission housing is fixed against rotation relative to the bicycle frame; the pedal crank being the input shaft to the transmission and extending completely through the same and being rotatably mounted in the bicycle housing with the sun gear driven output shaft rotatably mounted on the input shaft.