Patent ID: 8667865

Claim:
A transmission for a vehicle which includes a ground engaging structure driven from an output member of the transmission, the transmission including a first input member connected to a prime mover, and a second input member drivable by the operation of a hydraulic drive motor, and the transmission being operable to transmit drive from the first input member to the output member in mechanical drive mode, and from the second input member to the output member in hydrostatic drive mode, the first input member providing a drive input from the prime mover to a mechanical drive train which includes a gear ratio selection apparatus, and for mechanical drive mode, the gear ratio selection apparatus providing for one of a plurality of alternative gear ratios to be selected by the engagement or disengagement of each of a plurality of power-shift clutch devices, and the second input member being connected via a drive path to the output member, the mechanical drive train including a gear fixed to rotate with the first input member and which is in permanent mesh with a gear fixed to rotate with a first lay shaft, a first one of the plurality of power-shift clutch devices being engageable to connect the first lay shaft to a drive shaft, the drive shaft having a gear fixed to rotate with the drive shaft and in permanent mesh with a gear fixed to rotate with a second lay shaft, and a second one of the plurality of power-shift clutch devices being engageable to connect the second lay shaft to the first input member, and a third one of the power-shift clutch devices disposed between the hydraulic drive motor and the second input member and being operative when the transmission is in hydrostatic drive mode, to transmit drive established by the operation of the hydraulic drive motor to the second input member, and wherein the hydraulic drive motor of the transmission, when the transmission is in hydrostatic drive mode, is provided with pressurized hydraulic fluid to drive the hydraulic drive motor from a hydraulic pump, the hydraulic pump being driveable by the prime mover, and wherein the hydraulic drive motor and the hydraulic pump are each variable capacity devices.