Abstract: Nutating drives of the prior art have suffered from a problem of rotational unbalance. Such drives (10) include an outer rotatable structure (14) rotatable about its axis (16) and having a generally cylindrical cavity (18) axially therein, an axis (20) of said cavity being at an angle from the axis of rotation (16) of the rotatable structure (14), a generally cylindrical nutatable member (22) nutatably mounted within said cavity and a generally conically surfaced member (26) in contact with a generally cylindrical surface (28) of the nutatable member (22), said generally conically surfaced member (26) having an output shaft (30) generally coaxial with the axis of the rotatable structure. This problem of the prior art is solved by a structure which does not create rotational unbalance and which allows full nutation of the nutatable member while preventing it from rotating.

Abstract: A hydromechanical vehicle transmission system for an engine most efficiently operated at a single speed is disclosed providing an infinitely variable reduction ratio for a given constant input speed requiring minimum operator skill in operation of the vehicle speed control and the engine torque control in both full and part load operation. The transmission consists of a multi-speed hydrostatic mechanical arrangement using a variable displacement hydrostatic pump-motor in conjunction with a fixed displacement hydrostatic pump-motor providing two power paths through the transmission, one hydrostatic and one mechanical. The preferred embodiment discloses four gear ranges although three gear ranges are sufficient to fulfill the objects of the invention.

Abstract: A hydrostatic mechanical transmission is disclosed having an infinitely variable split torque, planetary drive unit driving a set of range gears, in part mechanically and the remainder through a hydrostatic path comprising variable displacement hydrostatic devices acting alternately as a pump or motor and controlled through a system of hydraulic valves utilizing the same fluid as the hydrostatic devices. Five forward and two reverse ranges are provided in a relatively small package. Control is effected through a manually operated shift lever providing control signals to both the variable displacement hydrostatic devices and range selector unit, with appropriate control and safety features being provided to assure positive and smooth range changes, to prevent reverse rotation in the hydraulic unit, to sense a zero speed condition in the hydraulic units, and to insure positively synchronizing and matching speed conditions for gear engagement.