| 摘要 |
A driver for oblong material having three arms carrying the driving elements which swing vertically with respect to the material path of movement. For a selected setting angle of the arms, the point of contact of a driving roller with the material is displaced such that, on the diameter of the test material becoming smaller, the point of contact is moved towards the edge of the roller. This feature has three desirable consequences: First, wear is not concentrated on a single track of the roller surface; second, the pressing-on force of the rollers is decreased with the decreasing diameter of the test material; and third, when using three rollers, the seeing angle can be adjusted such that for the narrowest approach of the rollers possible, one edge each of a roller meets with the respective edges of the other rollers in one point.
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