clothings of the feed roll 10 and the preliminary roll 16 1 is increased in order to reestablish the required initial distance between the feed roll 10 and the preliminary roll 16 1 according to fig5 a in a second step according to fig5 c the preliminary roll 16 1 is swung in the direction of the arrow h about the axis m 3 of the preliminary roll 16 2 in this manner the distance between the clamping location defined by the feed roll 10 and the feed tray 14 and the transfer location defined between the feed roll 10 and the preliminary roll 16 1 is reduced as compared to that shown in fig5 a and also the distance between the two rolls 10 and 16 1 is re established while in the preceding description the invention was set forth in connection with a roller card and roller card feeder it will be understood that in the same manner a mobile card feeder incorporating the feeding device 10 14 and a carding machine may be used 0023 fig6 shows an embodiment in which the feeding device 10 14 is an integral part of the fiber processing machine such as a schematically and partially shown carding machine cm the feeding device 10 14 is followed by three licker ins 16 3 16 4 and 16 5 the feeding device 10 14 receives the fiber tufts as a fiber batt from for example a non illustrated card feeder and advances the fiber material to the licker in 16 3 the fiber material is then consecutively transferred to the licker ins 16 4 and 16 5.