of a pawl drive not shown but described in detail in u s pat no 3 479 699 swiss patent 485 873 in the lower nipper plate 16 which is in the form of a hollow body there is an air chamber 26 which is connected for instance by an elastically expandable hose 27 continuously to a source of compressed air not shown also during the stroke movements in the clamping surface of the lower nipper plate 16 which cooperates with the upper nipper plate 21 there debouches a slot nozzle 28 fig5 a which extends substantially over the width thereof or a series of slot openings or holes fig5 b c through which the blast air can emerge from the air chamber 26 in the direction against the detachment rolls 6 below the fiber tuft 10 when the nipper head 3 is closed the upper nipper plate 21 rests against the slot nozzle opening and closes it the upper nipper 14 consists in principle of an upper nipper arm 20 which is pivoted to the swivel pin 17 and of the upper nipper plate 21 fastened thereto as well as of a lever firmly attached to the upper nipper arm 20 furthermore there is mounted on the upper nipper 14 an adjustable insertion comb 19 which retains those fibers of the fiber tuft 10 which do not have the length of the tearing distance 34 ecartement 34 from being pulled into the detachment rolls 6 the upper.