Twin Variator Transmission Arrangement

A transmission arrangement comprising two variators each of which comprises a first race, a second race, and a plurality of rollers arranged to run upon the first and second races to transfer drive from one to the other, all of the races being mounted for rotation about a common axis with the first races arranged between the second races, the inclination of one variator's rollers being variable independently of the inclination of the other variator's rollers so that the two variators provide independently and continuously variable drive ratios, the arrangement further comprising a biasing device for exerting a force upon at least one of the races to urge the races into engagement with the rollers, and a shaft, lying along the common axis, which passes through the first races and by means of which the second races are coupled, via at least one thrust bearing, to resist movement of one away from the other so that the force of the biasing device is referred through the shaft and the thrust bearing, the arrangement still further comprising two shunt gear trains which are coupled to the respective variators and are coaxial with the variator's races, each shunt gear train having a first gear operatively coupled to the first race of its associated variator, a second gear operatively coupled to the second race of its associated variator, and an output gear whose speed is a function of the speeds of the first and second gears.