US Patent 7708663 Continuously variable constant mesh epicyclic transmission

A transmission includes a ring gear driven by a first primary gear train, a carrier driven by a second primary gear train and a sun gear driven by a third primary gear train. Clutches are utilized to lock and unlock the ring gear, carrier and sun gear. When locked each rotate at the same speed and the torques are added together at an output shaft to provide a high torque low speed output from the transmission. As the transmission accelerates the clutches are disengaged allowing the ring gear, carrier and sun gear to rotate separately and achieve higher speeds, providing a continuous output from high torque to high speed operation.