Patent ID: 7537536

Claim:
A two speed gearbox mounted in-line for driving a hub, the gear box comprising: a gearbox casing adapted to journal mount about an input drive shaft and output shaft; a central planetary gear carrier assembly rotatably mounted within the gearbox casing comprising: a sun gear to accommodate and be driven by the input drive shaft; a plurality of planetary gears; a ring gear with structure to accommodate and drive the output shaft; a planetary gear carrier, the planetary gear carrier supporting and interconnecting the planetary gears; a low speed clutch assembly with a plurality of fixed discs mounted to the gearbox casing adapted to selectively engage a plurality of rotating discs there between attached to the ring gear of the planetary gear carrier assembly; a high speed clutch assembly with a plurality of fixed discs mounted on the carrier mount adapted to selectively engage a plurality of rotating discs there between attached to the sun gear of the planetary gear carrier assembly; an engaging/disengaging high speed hydraulically powered spring return piston located on the planetary gear carrier and operably associated with the high speed clutch assembly; an engaging/disengaging low speed hydraulically powered spring return piston attached to the gearbox casing and operably associated with the low speed clutch assembly to selectively hydraulically secure the ring of the planetary gear assembly in a low operating range, when engaged; and hydraulic activation means to selectively activate the desired high speed and low speed hydraulically powered spring return pistons to provide the desired operating speed mode having a dynamic hydraulic valve circuit with passageways in the gearbox surrounding the planetary gear carrier joined with a dynamic seal surrounding corresponding passageways in the planetary gear carrier in communication with the high speed and low speed hydraulically powered spring return pistons, said hydraulic valve circuit adapted to hydraulically activate the low speed hydraulically powered spring return piston selectively to engage the ring gear of the planetary gear carrier assembly in a low operating range, when activated; and to hydraulically activate the high speed hydraulically powered spring return piston selectively to engage the sun gear of the planetary gear carrier assembly in a high operating range when activated.