| 摘要 |
The device includes a roller so that it can be turned in stages in one direction around a shaft by turning the roller exterior backwards and forwards. Stop pins are positioned in fixed relation to the roller, are equally spaced apart, and are at the same radial distance from the shaft. A stop head (5) is articulated at a fixed point relative to the shaft. The stop head has two teeth, and is rotatable between first and second end positions. The head is spring-loaded to return to the first position. In both end positions, only one of the stop teeth projects between stop components. |
