| 摘要 |
A traversing mechanism of the kind in which a carriage is alternately releasably clamped to a respective one of two parallel runs of an endless belt so as to be reciprocated along a guided path. A coupling wheel is rotatably mounted on the carriage at a location between the two belt runs and has a plurality of radially projecting lobes provided around its outer periphery. In operation, the wheel is rotated in stepwise fashion as permitted by a sliding escapement, to sequentially adopt a plurality of operative positions in each of which a run of the belt is clamped between a wheel lobe and one of the backing surfaces. Each backing surface is mounted for movement towards and away from the respective adjacent belt run under the influence of a camming actuator. The actuator is movable between an engage position in which it urges the two backing surfaces into a position in which it can adopt clamping engagement with the belt, and a disengage position in which the backing surfaces cannot adopt clamping engagement with the belt. |
