Patent ID: 6884195

Claim:
An integrated hydrostatic transaxle comprising: a housing; a hydrostatic transmission disposed within said housing and comprising a variable-displacement axial piston pump and a fixed-displacement axial piston motor, said pump and said motor hydraulically interconnected together, said pump having a rotary pump cylinder barrel defining an array of pump cylinders and a pump piston disposed in each of said pump cylinders, said pump pistons protruding from said pump cylinders and bearing against an adjacent swash plate, said pump pistons having stroking axes parallel to the rotational axis of said rotary pump cylinder barrel, said motor having a rotary motor cylinder barrel defining an array of motor cylinders and a motor piston disposed in each of said motor cylinders, said motor pistons protruding from said motor cylinders and bearing against an adjacent inclined thrust plate, said motor pistons having stroking axes parallel to the rotational axis of said rotary motor cylinder barrel; an input drive shaft having a vertical axis of rotation disposed in a first vertical plane in said housing, said input drive shaft rotatably supported in said housing and protruding outwardly of said housing to be driven by a power input source, said input drive shaft extending inwardly of said housing to engage said rotary pump cylinder barrel via a spline connection for rotation at equal speed therewith; a one-piece casting at least partially disposed in said housing and surrounded from below by said housing; a pump fluid coupling surface disposed in a first horizontal plane inside said housing and formed or mounted on said one-piece casting, said pump fluid coupling surface being spaced from underlying interior surfaces of said housing; a motor output shaft having a horizontal axis of rotation disposed in a second horizontal plane in said housing, said motor output shaft engaging said rotary motor cylinder barrel via a spline connection for rotation at equal speed therewith; a motor fluid coupling surface disposed in a second vertical plane inside said housing and formed or mounted on said one-piece casting, said one-piece casting having a bore receiving said motor output shaft and an outer shoulder portion surrounding said bore, said outer shoulder portion supported by an interior surface of said housing in at least one location radially adjacent said bore and where said at least one location lies above said second horizontal plane, and said rotary pump cylinder barrel and said rotary motor cylinder barrel rotatably mounted on said pump fluid coupling surface and said motor fluid coupling surface, respectively; a mechanical differential disposed in said housing; reduction gearing disposed in said housing drivingly connecting said motor output shaft with said mechanical differential; axle shafts rotatably supported in said housing and extending outwardly from said housing, said mechanical differential being drivingly connected between said reduction gearing and said axle shafts.