Driveline for a track laying vehicle

Claim 1

A driveline for a track-laying vehicle having a prime mover and a pair of output shafts (L, R) connected to drive left- and right-hand tracks at a predetermined range of speeds, the driveline comprising: two similar continuously-variable-ratio transmission units (10, 20) of the toroidal race-rolling traction type, each having an input adapted to receive input drive from the prime mover and an output; a cross shaft (CS); two similar summing epicyclic gear output units (12, 22), each having a first input (70, 80) geared to the output of a respective transmission unit, an output connected to a respective output shaft (73, 83), and a second input (72, 82) connected to the cross shaft; rotating clutch means (51) connecting the input drive to drive the cross shaft at a first predetermined ratio at which a variation of transmission ratio of the transmissions towards zero will correspond to an increase in track speed, for low regime operation; a middle regime differential gear arrangement (40); rotating clutch means (52) connecting the middle regime differential gear arrangement to have two inputs connected at second and third predetermined gear train ratios respectively to the corresponding outputs of the transmission units and an output connected at a fourth predetermined gear train ratio to the cross shaft such that the cross shaft is driven by the outputs of the two transmission units, to be operable in a middle regime; and means (50) for connecting the input drive to the cross shaft at a fifth predetermined gear train ratio, for high regime operation.