regulator 26 actual pressure values are compared with nominal pressure values and in case of a deviation signals representing such a deviation are applied to the motor 28 during operation through the air inlet openings 21 a and 21 c respective air streams b and c are drawn from the atmosphere by means of the vacuum prevailing in the gap between the cylinder cover 17 and the surface of the cylinder 4 the air streams b and c impinge on the short fibers carried by the cylinder clothing 4 a and loosen the hold of the clothing 4 a on such short fibers thereafter the short fibers are drawn through the waste outlet opening 18 a into the suction chamber 19 a and are removed via a conduit 36 which is coupled to a non illustrated vacuum source by means of the inflowing air streams b and c which exert a pressure on the short fibers and the vacuum stream d which exerts a pulling force on the short fibers the removal force on the short fibers is greater than the retaining force of the cylinder clothing 4 a in this manner the short fibers are removed from the cylinder.