Drive Transmission Unit Incorporating Expansible-Pulley Stepless Speed Changer

1. In a motor vehicle, a drive transmission unit adapted to be operatively interposed between the vehicle's engine and a differential unit connected to the half shafts of the vehicle's driving wheels, said unit incorporating an expansible-pulley stepless speed changer and comprising: a support structure, a primary shaft rotatably mounted in said support structure and connectable at one end to the drive shaft from the engine of said vehicle, a secondary shaft rotatably mounted in said support structure parallel to said primary shaft, two expansible pulleys respectively mounted fast for rotation on said primary and secondary shafts, each pulley comprising two facing frusto-conical discs one of which is rigidly connected to its respective mounting shaft and the other of which is axially slidable therealong, a trapezoidal belt passing around said pulleys at respective radii of engagement dependent on the position of the said slidable disc of the corresponding pulley axially of its mounting shaft, hydraulic means operable to control the axial displacement of the said slidable disc of each pulley whereby to vary said radii of engagement and change the transmission ratio between said primary and secondary shafts, said hydraulic means including a mechanical pump arranged adjacent the end of the primary shaft remote from said drive shaft, said primary shaft being hollow and the transmission unit further including a pump-driving shaft connected at one end to the said drive shaft and extending through said primary shaft to drive said pump, an output shaft rotatably mounted by said support structure and adapted to drive said differential unit, said output shaft being arranged adjacent one end of the secondary shaft in coaxial alignment therewith, and an epicyclic reversing unit coaxial with said secondary shaft and driven from said one end thereof, the said reversing unit providing a reduction gear stage for the transmission unit and having a rotatable output member connected to said output shaft, the reversing unit being remotely selectively settable into one of three operating states in the first of which said output shaft is arranged to rotate in the same sense as said secondary shaft, in the second of which said output shaft is arranged to rotate in the opposite sense to said secondary shaft, and in the third of which said output shaft is drivingly disengaged from said secondary shaft.

2. A drive transmission unit according to claim 1, wherein said epicyclic reversing unit comprises: a first sun wheel rotatably mounted on said secondary shaft, a second sun wheel mounted on said secondary shaft adjacent the first sun wheel and fast for rotation with said secondary shaft, an internally-toothed ring gear coaxially surrounding the said first and second sun wheels, a planet carrier fast for rotation with the said output shaft and constituting the said rotatable output member, a first and a second trio of planet wheels rotatably mounted by said planet carrier with each planet wheel of the first trio meshing with a corresponding planet wheel of the second trio, the planet wheels of the first trio also meshing with said first sun wheel and with said ring gear, and the planet wheels of the second trio also meshing with said second sun wheel, remotely-controllable means selectively operable to secure said first sun wheel against rotation relative to said support structure, and remotely-controllable means selectively operable to secure said ring gear against rotation relative to said support structure.