synchronism with the rotatory speed of the needle cylinder by means of a conventional drive 35 fig1 and in the above example they have circumferential velocities which at the maximum cylinder rotatory speed are approximately a hundred times lower than the circumferential velocity of the card cylinder 10 at the same time the feed rate of the feed rolls 7 can be varied according to the weight of the strand on account of the great difference between the rate of feed of the fiber strand 8 and the circumferential speed of the card cylinder 10 a great draft is exerted on the fiber strand 8 and therefore an extremely good singling of the fibers is accomplished the centrifugal forces occurred at the high rotatory speeds or circumferential velocities of the card cylinder 10 normally suffice in the embodiments described to release one hundred percent of the fibers from the hooks 14 and this is essential for the achievement of a great uniformity of the density of the enmeshed fibers since these centrifugal forces however do not always suffice an opening 36 fig3 and 7 but not shown in fig4 for sake of clarity connected to a vacuum machine or blower can be provided in the shroud 15a 15d respectively of fig3 and 7 for the purpose of producing an auxiliary air current in the throw off section 19a 19d respectively to assist in the release of the fibers from the hooks 14 of the card cylinder 10 if the centrifugal forces produced by the rotation of the card cylinder 10 are too weak in circular knitting machines of the kind described above the hooks 4 of the knitting.