US Patent 7794354 Variable speed transmission

A variable speed transmission is disclosed. In one embodiment, a two shaft and two opposing planetary gearset arrangement is utilized. Drive and driven shafts are connected as respective inputs and outputs to opposing planetary gears of the planetary gearsets. Respective sun gears are rotatably coupled to each end of an intermediary shaft which traverses the span between the planetary gearsets. Respective ring gears are meshed to a pair of spur gears coupled to a secondary shaft which also traverses the span. In operation, the coordinated actuation of a pair of clutch-brake assemblies associated with the intermediary and secondary shafts substantially continuously varies the transmission of torque from the drive shaft to the driven shaft.