intake air so as to render possible an adjustment to different fiber materials after the first whirling up the fibers again form a fleece on the surface of the cylindrical cage 3 under the influence of the stream of intake air p 1 this fleece is now pressed against the cylindrical cage 3 and smoothed by the following calendar roller 6 and stripped off with whirling up by the associated stripping and conveying roller 7 the stripping and conveying rollers always exert a beating action on the cylindrical cage 3 and so prevent blockage of the perforation of the cylindrical cage this process is repeated continuously in the manner described over the periphery of the cylindrical cage 3 until the fleece compressed by the last calendar roller 6 or 6 39 is stripped off the cylindrical cage 3 by the stripper roller 8 and the fibers are removed it can be seen that as a result of the whirling effect of the stripping and conveying rollers 7 a rearrangement of the fibers in the following fleece is effected between each pair of rollers as a result in the course of the cleaning process even the fibers which were originally further away from the screen wall come into direct contact with the screen wall of the cylindrical cage 3 this leads to a particularly intensive cleaning of the fibrous material from dust and dust like impurities by the concentration.