Integrated hydro-mechanical transmission

A hydrostatic transmission incorporating gear-type hydraulic pump and motor elements;

• the hydraulic pump and motor each being of the internal gear type, wherein said hydraulic pump and motor each have an internal gear, an external gear and a crescent that separates the respective internal gear and external gear;
• the internal gears being capped off by means of laterally constrained and rotatably supported internal gear plugs, and the external gears being capped off by means of external gear plugs sandwiched between the two internal gears creating respective pump and motor working chambers;
• the internal gears and associated external gear plugs being laterally moveable by means of a concentrically-spanned control shaft which is positionally displaceable in an axial direction causing the internal gears to engage a greater or lesser portion of the respective laterally-constrained external gears such that the volumetric capacity of both pump and motor working chambers are made inversely variable to one another;
• the internal gear of the pump portion of said hydrostatic transmission being spline-coupled and driven via a support input shaft, said support input shaft also being spline coupled to a sun gear of a sun and planetary gear set;
• the internal gear of the motor portion of said hydrostatic transmission being spline coupled to a planet carrier of said sun and planetary gear set;
• the motor element of said hydrostatic transmission being coupled hydraulically to the pump element such that it rotates in the same direction as the pump but at a generally slower speed;
• gear ratios of said sun and planetary gear set being chosen in conjunction with the relative volumetric capacities of said hydraulic pump and motor elements such as to achieve a continuously variable, through zero output;
• and an output shaft being integral with a ring gear of the sun and planetary gear set.