No ring gear is used in the IVT design. Rather, the rotational speed of the planetary gear, which is normally fixed at a predetermined multiple of the input rotational speed by the ratio of the pitch diameters of the ring gear to planetary gear, varies and is independently controlled using a serpentine belt interfacing a variable diameter, non-rotating "variator". The input shaft is attached to the planetary carrier plate, and the output shaft is attached to the sun gear.
A key to the controlled epicyclic drive is the design of the variator. This is where mechanical stresses are high and the dynamic range of control is determined. VeriTran has developed a variator which does not rotate with the power shafts. A serpentine belt is employed in conjunction with the variator to transfer the torque. A patented "Torque Following" design ensures that the belt does not slip before reaching the design limit of the transmission.
