Patent ID: 8579065

Claim:
A mower with four wheel drive, which comprises: (a) a frame supported for rolling over the ground by four ground engaging drive wheels comprising a pair of laterally spaced front drive wheels and a pair of laterally spaced rear drive wheels; (b) a grass cutting device carried on the frame; and (c) a hydraulic drive system for propelling the drive wheels, which comprises: (i) a plurality of individual hydraulic drive motors for rotating the drive wheels with one drive motor being operatively connected to each of the drive wheels such that the plurality of drive motors comprise a pair of front drive motors for the front drive wheels and a pair of rear drive motors for the rear drive wheels; (ii) a hydraulic fluid supply circuit that comprises: a pair of identical serial flow circuits, wherein each serial flow circuit comprises a hydraulic pump that serves as a source of pressurized hydraulic fluid, the pump having an outlet that is directed in a serial manner first through one rear drive motor and then through one front drive motor for one pair of rear and front drive wheels on opposite sides of the frame, the front drive motor having an outlet that is serially connected by a return line back to an inlet of the pump; and a crossover path between the outputs of the pumps, wherein the pump output crossover path contains an orifice that is sized to allow a maximum of substantially enough flow to crossover from one pump output to the other pump output such that whatever rear drive motor for the rear drive wheel is on an outside of a maximum turn receives adequate flow to permit smooth rotation of the rear drive wheel on the outside of the maximum turn without scrubbing or skidding of the rear drive wheel.