Abstract: An infinitely variable hydrostatic transmission includes an input shaft connected to drive a hydraulic pump unit, a grounded hydraulic motor unit, and an output shaft. A swashplate assembly is connected to impart output torque to the output shaft resulting from the pumped exchanges of pressured hydraulic fluid between the hydraulic pump and motor units. A ratio controller is linked to independently, variably position input and output members of the swashplate assembly and thus vary nutating magnitudes of cylinder blocks of the hydraulic pump and motor units, pursuant to adjustably setting ratio conditions of the transmission.

Abstract: A hydromechanical transmission receives split power inputs from a vehicle engine, one split input driving a hydrostatic power unit and the other split input driving a mechanical power input. The infinitely variable hydrostatic power output is combined in the mechanical power unit with multiple ratios of its split input power to achieve multiple ratios of hydromechanical output power for smoothly propelling a vehicle from rest through multiple transmission ranges to maximum speed, with synchronous shifting between ranges. The hydromechanical transmission is particularly applicable to off-road vehicles, such as agricultural tractors.