the air emerges from individual cylinders 11 1 through 11 4 the broken line 43 indicate how the box is constructed in two parts so that it can be opened in order to provide access to the cylinders in this embodiment the gas guiding bodies 14 of the cylinders 11 1 through 11 4 extend somewhat beyond the end faces of the rotatable cylinders and are held at their ends in semicircular mounts in the two halves of the box 38 for example in such a way that the gas guiding bodies have peripheral grooves into which the side edges of the box engage in this manner the cylinders are fixed in a problem free manner and upon opening the box the individual cylinders with the bodies can easily be removed for example in order to ensure ready insertion of the carded sliver as shown here on introducing the carded sliver the cylinders 11 2 and 11 4 are first arranged in the lower part of the box the carded sliver is then laid over these two cylinders and the cylinders 11 2 and 11 4 are then likewise arranged in the lower part of the box 38 on top of the sliver so that the carded sliver adopts the desired snake like course then the upper part of the box is set in place and fixed in its final position for example by clips thereafter the arrangement can be taken into operation fig4 and 5 show a perforated cylinder 50 which is drivably journalled and rotatable about.