| 摘要 |
<p>At least one gearwheel of each meshing pair of gearwheels (10, 12, 14, 16, 20, 22, 24, 26) includes two respective selectively operable rotary locks which are adapted to lock the gearwheels to the associated shaft so that it rotates therewith in respective opposite directions. Each rotary lock comprises a plurality of rollers (34), whose positions relative to one another are maintained by a respective cage (36, 38) and which are received in respective spaces defined between an internal cylindrical surface on the associated gearwheel and a respective portion (32) of the surface of the associated shaft. The spaces associated with the two sets of rolling bodies (34) have a width in the radial direction of the shaft which progressively decreases from a maximum value in opposite circumferential directions of the shaft, whereby the two cages (36, 38) are movable in respective opposite circumferential directions between a freewheel position and a locked position. Each cage (36, 38) is acted on by at least one actuating mechanism (44) which is selectively operable to move the cage and thus the associated rollers in the circumferential direction in which the width of the associated spaces decreases from the freewheel position to the locked position.</p> |
