chambers 5 and 8 have been provided with the same reference numerals for this purpose fig1 schematically shows a cross sectional view of the feed roller pair 3 and the feed chamber 5 and a lateral view of the exit roller pair 6 with the exit chamber 8 two sealing rollers 4 1 and 4 2 which can be driven form the feed roller pair 3 the lower sealing roller 4 1 is mounted rotatably in a bearing block 13 and is coupled to a drive not illustrated the upper sealing roller 4 2 is mounted rotatably on a pivot support 11 and is likewise coupled to a drive not illustrated the pivot support 11 is l shaped and is mounted on its side that is turned towards the steam chamber 1 by means of a pivot axis 12 on the bearing block 13 an actuator designed as a cylinder piston unit 14 engages at the pivot support 11 the sealing rollers 4 1 and 4 2 are held in such a way in relation to one another that a predetermined nip 10 is formed between the circumference of the sealing rollers 4 1 and 4 2 the nip 10 represents a feed cross section for guiding a fiber strand into the feed chamber 5 on that side of the feed roller pair 3 which is turned towards the steam chamber 1 the feed chamber 5 is directly connected to the sealing rollers 4 1 and 4 2 the feed chamber 5 is formed by means of a top plate 15 and a bottom plate 16 each of which is connected tightly to the circumference of the sealing rollers 4 1 and 4 2 and two side plates 17 1 and 17 2 the formation of the seal.