| 摘要 |
<p>A gearbox includes an input shaft (2), an output shaft (4) and a plurality of pairs of meshing gearwheels (8, 10, 12, 14, 16, 18, 20, 22, 24, 26), at least one gearwheel of one meshing pair including a selectively operable rotary lock which is adapted to lock the gearwheel to the associated shaft, which is intended normally to rotate in a predetermined direction. The gearwheel has a circular section internal engagement surface, which defines a space accommodating two or more brake shoes (30), each brake shoe being mounted to pivot about an axis (32) parallel to the axis of the associated shaft and having an inwardly projecting nose (36) which extends into a cavity (34) in the associated shaft. Actuation means (50) within the shaft is arranged to move the nose (36) outwardly and thus to pivot the brake shoe (30) about its axis (32) and into engagement with the engagement surface on the gearwheel. The nose (36) is spaced from the pivotal axis (32) in the direction opposite to the predetermined direction, whereby all the brake shoes (30) are leading brake shoes, whereby when the brake shoes (30) are in engagement with the engagement surface, the shaft is locked to the gearwheel and torque is transmitted between the shaft and the gearwheel via the two engaging thrust surfaces. <IMAGE></p> |
