Continuously variable hydro-mechanical transmission

1. A transmission for use between a power source and a load, the transmission comprising:

a hydrostatic power unit, including a pump, coupled to a first input shaft adapted to be coupled to the power source, the hydrostatic power unit including a first output shaft; and

a compound planetary gear unit including a second input shaft directly coupled to the power source and selectively coupled to the first output shaft of the hydrostatic power unit by at least third and fourth input shafts each driven by a different driving gear respectively interconnecting the first output shaft and either the third or fourth input shaft,

the compound planetary gear unit further including:

a primary sun gear coupled to the second input shaft;

a secondary sun gear coupled to the third input shaft;

a ring gear coupled to the fourth input shaft;

a compound planetary gear cluster mounted on a planetary gear carrier and in engagement with the primary sun gear, the secondary sun gear and the ring gear;

a second output shaft coupled to the planetary gear carrier;

a directional clutch coupled to the second output shaft;

a load shaft adapted to be coupled to the load; and

a road range gear set selectively coupled between the load shaft and one of the third input shaft and the planetary gear carrier, whereby the transmission may be selectively operated either in a purely mechanical configuration or in a mixed hydro-mechanical configuration.