Compressor device

Abstract

The invention relates to a compacting device (40) for compacting a fiber sliver that is drawn in a drafting system of a textile machine. The compacting device is designed as a channel compactor and has a guide channel that is helically shaped in the direction of travel of the fiber sliver (4), the inlet opening of which has its greatest width in the horizontal direction and the outlet opening of which is arranged rotated by at least 30° with respect to the inlet opening, the rotation between the inlet opening and the outlet opening of the guide channel being between 30° and 160°.

Description

[0001] The invention relates to a compacting device for compacting a fiber sliver which is drawn in a drafting system of a textile machine, and to a drafting system comprising such a compacting device.

[0002] In connection with textile machines, in particular spinning machines, both drafting systems and associated compression devices have been known for a long time and are described in detail in numerous patent applications.

[0003] The familiar drafting systems are located upstream of the spinning units of textile machines and draw an incoming feed material, usually a fiber sliver or roving, to the desired fineness. Such drafting systems have several pairs of rollers arranged one behind the other in the direction of travel of the fiber sliver, which rotate at different circumferential speeds and transport the fiber sliver to the corresponding spinning units.

[0004] Since the peripheral speed of the roller pairs increases in the direction of travel of the fiber sliver, the fiber sliver is continuously accelerated within the drafting system and subjected to a so-called draw draft. In conventional drafting systems, the total draw draft of the fiber sliver varies greatly depending on the textile machine in question.

[0005] In the drafting systems of air-jet spinning machines, for example, the total draft of the sliver can be 180 times higher, while the drafting systems of roving machines, for example of flyers, generally operate with significantly lower total drafts.

[0006] The compactness and hairiness of the drawn fiber sliver are among the decisive factors for the quality of the fiber material delivered by the drafting system.

[0007] This means that when entering the drafting system, the fiber sliver has a width that is initially reduced to a significantly smaller width during the drafting process. At the exit side of the drafting system, in the area of ​​the so-called spinning triangle, the width should then be significantly less than the intermediate width of the incoming material.

[0008] During the drawing process, however, there is the problem that edge fibers are often either not integrated and cause increased fiber fly, or that the edge fibers are integrated in a disordered manner, which leads to increased hairiness and a larger width of the spinning triangle and thus to a reduction in the quality of the drawn fiber sliver.

[0009] In order to ensure reliable guidance and the best possible compaction of the fiber sliver during drafting of the feed material and thus the smallest possible width of the spinning triangle, the known drafting systems often also have so-called compaction units.

[0010] DE 102011 015 748 A1, for example, describes a drafting system for a roving machine which has a pre-drafting zone, a main drafting zone and a downstream compression zone.

[0011] A compression unit, referred to as a condenser component in DE 10 2011 015 748 A1, is positioned in the compression zone. The condenser component has an upwardly open guide slot for the fiber sliver, with the guide slot being significantly taller than it is wide. The condenser component is intended to even out the thickness of the fiber sliver and reduce its hairiness, thus improving the quality of the feed material.

[0012] Furthermore, DE 10 2013 017 636 A1 discloses drafting systems for the air-jet spinning units of air-jet spinning machines, which are equipped with comparable compressor units.

[0013] One of the embodiments shown shows and describes a drafting system which is designed as a so-called four-roller drafting system and has a pre-drafting zone, a middle drafting zone and a main drafting zone.

[0014] In this well-known four-roll drafting system, a pre-compressor is located in front of the drafting system's input roller pair, and a second compressor is positioned in the pre-drafting section. Furthermore, the main drafting section of the drafting system is equipped with a third compressor.

[0015] In this well-known splicing system, the compression units are also intended to reduce the hairiness of the drawn fiber sliver or increase the number of wrapped fibers.

[0016] A four-roller drafting system for the air-jet spinning units of air-jet spinning machines is also described in DE 10 2015 110 980 A1.

[0017] This well-known drafting system is also equipped with a special device to improve the quality of the drawn fiber sliver. This four-roller drafting system features a false twist device located in the pre-drafting section of the drafting system, which twists the fiber sliver with alternating directions of rotation before it is drawn to the desired yarn count in the main drafting section and fed to an air-jet spinning unit.

[0018] The alternating direction of rotation of the fiber sliver is intended to minimize fiber deflections of the edge fibers, which occur particularly due to the air flow in the area of ​​the output rollers of the drafting system rotating at relatively high speed.

[0019] Although the drafting systems described above offer various possibilities for improving the quality of a hidden sliver, they cannot completely solve the problem that edge fibers are formed during drafting of the sliver or that the sliver has insufficient compactness, so that a relatively wide spinning triangle is often formed at the output side of the drafting system.

[0020] Based on the aforementioned prior art, the invention is based on the object of developing a compression unit for a drafting system arranged upstream of the spinning device of a textile machine, which is designed in such a way that it is ensured during the drafting process that the width of the fiber sliver to be drawn is reliably minimized both in the area of ​​the main draft and in the area of ​​the spinning triangle created on the output side of the drafting system.

[0021] This object is achieved by a compressor device according to the features of claim 1. The compressor device is designed as a channel compressor and has a guide channel which is helically formed in the running direction of the fiber sliver, the inlet opening of which has its greatest width in the horizontal direction and the outlet opening of which is arranged rotated by at least 30° with respect to the inlet opening.

[0022] Advantageous embodiments of the invention are the subject of the subclaims.

[0023] The design of a channel compactor has the particular advantage that the fed fiber sliver, which initially enters the inlet of the channel compactor's guide channel in a flat horizontal orientation, is slightly rotated within the channel compactor, temporarily imparting a false twist. This means that upon exiting the channel compactor's guide channel, the fiber sliver is twisted in such a way that the edge fibers are immediately compacted in the subsequent pair of draw rollers, thus resulting in an initial compaction of the fiber sliver.

[0024] This means that by compacting the twisted sliver, the edge fibers are incorporated to a high degree, which not only leads to a reduction in fiber fly, but also to a minimization of the width of the spinning triangle, with the result that there is an overall increase in the quality of the produced feedstock material.

[0025] According to the invention, the rotation between the inlet opening and the outlet opening of the guide channel of the channel compressor is between 30° and 160°, preferably 90°.

[0026] Such a twisted arrangement of the inlet and outlet openings of the guide channel not only temporarily imparts a so-called false twist to the fiber sliver, which leads to a positive stabilization of the feed material, but it is also prepared for further compaction by the downstream drafting rollers.

[0027] It has proven particularly advantageous if the sliver is rotated by 90°, i.e. if the sliver, which originally runs in a horizontal orientation, is rotated into a vertical orientation in the guide channel of the channel compressor and runs in this orientation into the subsequent pair of drafting rollers.

[0028] The channel compressor is preferably manufactured from an abrasion-resistant plastic using a 3D printing process. Polyamides have proven to be advantageous as plastics, as they can be three-dimensionally produced in virtually any shape using fused deposition modeling. This means that the production of the channel compressor according to the invention using a 3D printing process represents an advantageous, relatively simple manufacturing process.

[0029] The channel compressor according to the invention can of course also be manufactured using another 3D printing process.

[0030] Different locations are also possible with regard to the installation position of the channel compressor according to the invention.

[0031] In the case of drafting systems of textile machines that operate with relatively high draft values, such as the drafting systems of air-jet spinning machines, positioning the channel compressor according to the invention both in the area of ​​the pre-drafting zone of the drafting system and in the area of ​​the middle drafting zone of the drafting system of the air-jet spinning unit can be advantageous.

[0032] Such an arrangement keeps the distance between the channel compressor and the pair of output rollers of the drafting system relatively small, which has a very positive effect on the development of the width of the spinning triangle that is set on the output side of the pair of output rollers of the drafting system.

[0033] In connection with drafting systems for air spinning units, however, it has been found that arranging the channel compressor in front of the input roller pair of the drafting system or arranging several channel compressors simultaneously at different positions of a drafting system can be quite advantageous.

[0034] In particular, when several channel compactors are arranged simultaneously, the twisted sliver processed by the roller pairs of the drafting system is compacted several times, so that the width of the sliver in the area of ​​the drafting system and in the area of ​​the spinning triangle is minimized.

[0035] Even in textile machines whose drafting systems operate with relatively low draft values, for example in flyers, various arrangements of the channel compressor according to the invention can be advantageous.

[0036] For example, tests have shown that both an arrangement of the channel compressor in front of the pair of feed rollers of the drafting system and an arrangement of the channel compressor in the area of ​​the pre-drafting field of the drafting system are quite advantageous.

[0037] It has been shown, for example, that with such arrangements of the channel compressor with the drafting systems, flyer slivers can be produced that are significantly more compact and less hairy than the flyer slivers known to date.

[0038] This means that with the drafting systems of flyers, in which a channel compactor according to the invention is positioned in front of the draw-in roller pair of the drafting system or in the area of ​​the pre-drafting field of the drafting system, flyer rovings can be produced which have considerable advantages in their subsequent processing on ring spinning machines.

[0039] These improved flyer slivers, for example, resulted in spinning triangles being created during the spinning process on the drafting systems of the ring spinning machines, which are significantly wider than the previously usual spinning triangles, which is a good sign of excellent quality of the drawn sliver.

[0040] Different designs are also conceivable with regard to the exact design of the guide channel of the channel compressor.

[0041] In a first embodiment, the guide channel of the channel compressor can, for example, be designed such that it has its maximum width in the region of its horizontally arranged inlet opening. This maximum width then tapers along the guide channel and finally has its minimum width in the region of the outlet opening, which is arranged vertically rotated relative to the inlet opening.

[0042] In another advantageous embodiment, it is provided that the guide channel of the channel compressor has a width in the region of its horizontally arranged inlet opening, which changes in the sense of "growing" over the course of the guide channel and has a maximum width in the region of the outlet opening arranged rotated in the vertical direction with respect to the inlet opening.

[0043] Which of the two embodiments described above is more advantageous may depend on various factors, for example the material of the sliver or the flyer sliver, the desired fineness of the drawn material, the degree of sliver drawing, etc.

[0044] The invention is explained in more detail below with reference to the embodiments shown in the drawings.

[0045] It shows: Fig. 1 schematically shows in front view an air-jet spinning machine with a plurality of spinning stations, each having an air-jet spinning unit with an upstream drafting system, Fig. 2 in side view a drafting system arranged in front of an air-jet spinning unit, designed as a four-roller drafting system, with a channel compressor according to the invention in the area of ​​the central drafting zone, Fig. 3 in side view a four-roller drafting system according to Fig.2 , with a channel compressor according to the invention in the area of ​​the pre-drafting field of the drafting system, Fig. 4 the four-roller drafting system according to Fig.2in side view, with a channel compressor according to the invention in front of the input roller pair of the drafting system, Fig. 5 in side view a working station of a flyer, with a three-roller drafting system which has a channel compressor according to the invention in the region of the pre-drafting field of the drafting system, Fig. 6 a first embodiment of the channel compressor, Fig. 7 a further, second embodiment of the channel compressor.

[0046] The Figure 1 shows a front view, very schematically, of an air-jet spinning machine 1. As shown, such air-jet spinning machines 1 have, between their end frames 15, 16 arranged at the ends, a plurality of work stations 2 arranged next to one another in a row, which are often also referred to as spinning stations.

[0047] At these spinning stations 2, feed material, for example, fiber sliver 4 stored in a spinning can 3, is processed. This means that at these spinning stations 2, the fiber sliver 4 is spun into a yarn.

[0048] The spinning stations 2 are equipped with various devices for this purpose. For example, the spinning stations 2 each have a drafting system 5, an air-jet spinning unit 6, a yarn take-off device 7, a yarn clearer 8, and a winding device 11.

[0049] The drafting system 5, which can be designed, for example, as a four-roller drafting system or as a three-roller drafting system, also has a Fig. 1 The channel compressor according to the invention, not shown for reasons of clarity.

[0050] This channel compressor 40 according to the invention will be explained in detail below with reference to Figures 2 to 9.

[0051] As in Fig. 1As indicated, the yarn produced from the fiber sliver 4 in the air spinning unit 6 is wound in intersecting layers onto a winding bobbin 17 by an associated thread traversing device 9, so that a cross-wound bobbin is produced.

[0052] The cross-wound bobbin 17 is held, as usual, in a bobbin frame (not shown) and is rotated during spinning by a bobbin drive (also not shown). As in Figure 1 As further shown, the work stations 2 of the air-jet spinning machine 1 are supplied by an automatically operating operating unit 12 which, guided on rails 13, 14, can be moved along the work stations designed as spinning stations 2.

[0053] The Figures 2 , 3 and 4 each show a positioning possibility of a channel compressor 40 according to the invention arranged in the area of ​​a drafting system 5.

[0054] In the exemplary embodiments, the drafting system 5, which draws a fiber sliver 4, is designed as a four-roller drafting system and is arranged in front of an air-jet spinning unit 6 of an air-jet spinning machine 1.

[0055] According to Fig. 2 the channel compressor 40 according to the invention is positioned, for example, in the area of ​​the so-called central drafting field 33.

[0056] As can be seen, a fiber sliver 4 drawn off from a spinning can 3 (not shown) is drawn into the drafting system 5 by a pair of draw-in rollers 22, which is formed by an upper roller 18 and a lower roller 19, and is then transported to the air-jet spinning unit 6 by means of further pairs of rollers 24, 26, 28 and is thereby drawn.

[0057] The roller pairs 24, 26, 28 each consist of an upper roller 20 and a lower roller 25, an upper roller 21 and a lower roller 27 or an upper roller 23 and a lower roller 29. The upper roller 21 and the lower roller 27 each interact with one of the aprons 30 and 31, respectively, which are arranged in the area of ​​the so-called main drafting zone 34. The upper roller 23 and the lower roller 29 represent the output roller pair 28 of the drafting system 5. This means that in the present four-roller drafting system 5, viewed in the running direction F of the fiber sliver 4, the first two roller pairs 22, 24 form a pre-drafting zone 32 for the fiber sliver 4. The subsequent drafting system section between the roller pair 24 and the roller pair 26 forms a so-called central drafting zone 33, in which the channel compactor 40 designed according to the invention is also arranged, while the roller pairs 26, 28, as already indicated above, form the main drafting zone 34 of the drafting system 5.

[0058] As can be seen, the fiber sliver 4 is transported by the roller pairs 22, 24, 26 and 28 to the air spinning unit 6.

[0059] Since the circumferential speeds of the roller pairs 22, 24, 26, 28 increase in the running direction F of the fiber sliver, the fiber sliver 4 is stretched during transport.

[0060] The stretching of the fiber band 4 can, for example, lead to 180 times its original length.

[0061] As in Fig. 2 Further shown, the air spinning unit 6 has a nozzle device 42 on the input side, the nozzles 43, 44 of which are connected to a compressed air source 46 via a pneumatic line 45. Adjacent to the nozzle device 42 is a hollow spinning cone 47, which is surrounded by an air chamber 48, which is connected to a vacuum source 50 by means of a further pneumatic line 49.

[0062] During spinning, the air flowing out of the nozzles 43, 44 generates a rotational flow that is applied to the drawn fiber sliver 4. This means that, in the interaction of the nozzle device 42 and the spinning cone 47, a yarn 10 is formed in the air-jet spinning unit 6, which is drawn out of the air-jet spinning unit 6 through the hollow spinning cone 47.

[0063] Further details on the spinning process using such air spinning units 6 can be found, for example, in DE 199 26 492 A1.

[0064] The according to the embodiment of the Fig. 2The channel compactor 40, designed according to the invention and arranged in the region of the central drafting zone 33, ensures, during the drawing process, by means of its helical guide channel 35, that the fiber sliver 4, which initially enters the drafting system 5 in a flat horizontal orientation, is twisted in the channel compactor 40 into a vertical orientation, for example. The fiber sliver 4 is thereby temporarily given a false twist, which leads to an all-round compaction of the fiber sliver 4.

[0065] This all-round compaction of the fiber sliver 4 is not only maintained during the passage of the fiber sliver 4 through the drafting system 5, but is further reinforced in the drafting system 5.

[0066] The Fig. 3 illustrated embodiment differs from the embodiment according to Fig. 2 merely by arranging the channel compressor 40 designed according to the invention in the area of ​​the drafting system 5.

[0067] As can be seen, the channel compressor 40 according to the invention is in the embodiment of the Fig. 3 positioned in the area of ​​the pre-drafting field 32 of the drafting system 5.

[0068] Even with such an arrangement of the channel compressor 40, the fiber band 4 temporarily receives a false twist and is thereby compacted on all sides.

[0069] Also in Fig. 4 The embodiment shown differs from the embodiments according to Figure 2 and 3 essentially by the arrangement of the channel compressor 40 designed according to the invention in the area of ​​the drafting system 5.

[0070] As can be seen, the channel compressor 40 according to the invention is positioned in front of the feed roller pair 22 of the drafting system 5 in this embodiment.

[0071] Such an arrangement of the channel compressor 40 results in the fiber sliver 4 being rotated from a flat horizontal orientation into, for example, a vertical orientation before entering the drafting system 5.

[0072] Even if the channel compactor 40 is arranged in front of the feed roller pair 22 of the drafting system 5, the fiber sliver 4 temporarily receives a false twist and is thereby compacted on all sides.

[0073] The further integration of edge fibers into the fiber sliver 4 associated with the compaction of the vertically aligned fiber sliver 4 not only leads to an improvement in the quality of the fiber sliver 4 entering the air spinning unit, but also to a significant reduction in the fiber fly generated during the spinning process.

[0074] The Fig. 5shows a highly schematic side view of a working station of a roving machine, in the illustrated embodiment, the working station of a so-called flyer 51.

[0075] As is known, by means of such flyers 51, fiber slivers 4, which are twist-free, are drawn and processed into flyer slivers which already have some yarn twist.

[0076] These flyer slivers, which have a slight yarn twist, are then spun into fine yarns on textile machines downstream in the production process, such as ring spinning machines.

[0077] As shown, the working stations of such flyers 51 generally have two flyer wings 51 rotatably mounted in a wing bank 52, each of which is supplied by an upstream three-roller drafting system 5.

[0078] In the present embodiment, a channel compressor 40 designed according to the invention is also arranged in the area of ​​the pre-drafting field 32 of the drafting system 5.

[0079] As can be seen, a fiber sliver 4, preferably drawn off from a spinning can 3 (not shown), is drawn into the drafting device 5 by a pair of draw-in rollers 22, which is formed by an upper roller 18 and a lower roller 19, and is then drawn by means of the pairs of rollers 26, 28 of the drafting device 5.

[0080] As usual, the roller pairs 26, 28 each consist of an upper roller 21 or 23 and a lower roller 27 or 29, wherein, viewed in the running direction F of the fiber sliver 4, the first two roller pairs 22, 26 form a pre-drafting zone 32 in which a channel compressor 40 designed according to the invention is arranged.

[0081] The roller pairs 26, 28 form the subsequent main drafting zone 34 of the drafting system 5, wherein the roller pair 28 also represents the output roller pair 28 of the drafting system 5.

[0082] The fiber sliver 4 is transported by the roller pairs 22, 26 and 28 to the flyer wing 51 rotatably mounted in a wing bank 52 and is thereby stretched as the circumferential speeds of the roller pairs 22, 26, 28 increase in the running direction F of the fiber sliver 4.

[0083] The rotating flyer wing 51 also ensures that the drawn fiber sliver receives a slight twist, i.e., becomes a so-called shaped flyer sliver.

[0084] As with the drafting systems for air-jet spinning units, the channel compactor 40, designed according to the invention and arranged in the area of ​​the pre-drafting zone 32, also ensures, by means of its helical guide channel 35, that the fiber sliver 4, which initially enters the drafting system 5 in a flat horizontal orientation, is twisted into a vertical orientation, for example, as it passes through the channel compactor 40. The fiber sliver 4 thus temporarily acquires a false twist, which leads to all-round compaction of the fiber sliver 4.

[0085] This all-round compaction of the fiber sliver 4 is not only maintained during the passage of the fiber sliver 4 through the drafting system 5, but in the area of ​​the roller pairs 26, 28 a compaction of the vertically aligned fiber sliver 4 takes place with the result that a further increased integration of the edge fibers into the fiber sliver 4 takes place.

[0086] The resulting flyer sliver is significantly more compact and less hairy than previously known, which makes it easier to process in the subsequent operation on a ring spinning machine. This means that when processing such compact and less hairy flyer slivers, spinning triangles with a reduced width are created at the spinning stations of the ring spinning machines, which represents a significant improvement in the quality of the flyer sliver.

[0087] The Figures 6 and 7 show possible embodiments of a channel compressor 40 according to the invention.

[0088] The Fig. 6 discloses a channel compressor 40, the guide channel 35 of which has a maximum width B in the region of its horizontally arranged inlet opening 36.

[0089] As can be seen, this maximum width B tapers in the course of the guide channel 35 and finally has a minimum width BX in the region of the outlet opening 37, which is arranged rotated in the vertical direction with respect to the inlet opening 36.

[0090] The Fig. 7 shows a channel compressor 40 that is comparable in principle.

[0091] In this embodiment, the guide channel 35 of the channel compressor 40 has a minimum width B 1 in the region of its horizontally arranged inlet opening 36.

[0092] This minimum width B 1 changes in the course of the guide channel 35 and then has a maximum width B 1 +X in the area of ​​the outlet opening 37, which is also arranged rotated in the vertical direction with respect to the inlet opening 36.

[0093] The inlet opening 36 and the outlet opening 37 are preferably each designed as an elongated hole with rounded ends and a constant opening width therebetween, wherein the guide channel 35 connects the inlet opening 36 to the outlet opening 37 in a manner that continues this shape cross-sectionally and communicates with each other, and wherein the width of the guide channel 35 continuously decreases or increases from the inlet opening 36 to the outlet opening 37. In this context, the width is understood to mean the direction between the ends of the inlet opening 36 or the outlet opening 37 or the guide channel 35, with the opening width extending perpendicular thereto. List of reference symbols

[0094] 1 Air-jet spinning machine 2 Spinning station 3 Spinning can 4 Sliver 5 Drafting system 6 Air-jet spinning unit 7 Yarn take-off device 8 Yarn clearer 9 Yarn traversing device 10 Yarn 11 Winding device 12 Operating unit 13 Rail 14 Rail 15 End frame 16 End frame 17 Cross-wound bobbin 18 Top roller 19 Bottom roller 20 Top roller 21 Top roller 22 Pair of feed rollers 23 Top roller 24 Pair of rollers 25 Bottom roller 26 Pair of rollers 27 Bottom roller 28 Pair of rollers 29 Bottom roller 30 Apron 31 Apron 32 Pre-draft zone 33 Middle draft zone 34 Main draft zone 35 Guide channel 36 Inlet opening 37 Outlet opening 40 Channel compressor 41Locking device 42Nozzle device 43Nozzle 44Nozzle 45Pneumatic line 46Compressed air source 47Spinning cone 48Air chamber 49Pneumatic line 50Vacuum source 51Flyer 52Vent bank 53Vent FLanging direction

Claims

1. Compressor device (40) for compacting a fiber sliver (4) which is drawn in a drafting device (5) of a textile machine (1, 51), wherein the compressor device (40) is designed as a channel compressor and has a guide channel (35) which is helically designed in the running direction (F) of the fiber sliver (4), the inlet opening (36) of which has its greatest width in the horizontal and the outlet opening (37) of which is arranged rotated by at least 30° with respect to the inlet opening (36), the rotation between the inlet opening (36) and the outlet opening (37) of the guide channel (35) being between 30° and 160°.

2. Compressor device (40) according to claim 1, characterized in that the rotation between the inlet opening (36) and the outlet opening (37) of the guide channel (35) is 90°.

3. Compressor device (40) according to one of the preceding claims, characterized in thatthe compressor device (40) designed as a channel compressor is manufactured from an abrasion-resistant plastic using a 3D printing process.

4. Compressor device (40) according to one of the preceding claims, characterized in that the guide channel (35) of the channel compressor (40) has a maximum width (B) in the region of its horizontally arranged inlet opening (36), which tapers in the course of the guide channel (35) and has a minimum width (BX) in the region of the outlet opening (37) which is arranged rotated in the vertical direction with respect to the inlet opening (36).

5. Compressor device (40) according to one of the preceding claims 1 to 3, characterized in that the guide channel (35) of the channel compressor (40) in the region of its horizontally arranged inlet opening (36) has a width (B 1) which changes along the guide channel (35) and has a maximum width (B 1 +X).

6. Drafting system (5) for an air spinning unit (6) or a flyer (51), wherein the drafting system (5) comprises a pre-drafting field (32), characterized in that a compressor device (40) according to one of the preceding claims is arranged in the region of the pre-drafting field (32).

7. Drafting system (5) for an air spinning unit (6), wherein the drafting system (5) comprises a central drafting field (33), characterized in that a compressor device (40) according to one of the preceding claims 1 to 5 is arranged in the region of the central drafting field (33).

8. Drafting device (5) for an air spinning unit (6) or a flyer (51), wherein the drafting device (5) comprises a pair of input rollers (22), characterized in thata compressor device (40) according to one of the preceding claims 1 to 5 is arranged in front of the input roller pair (22) in the running direction of the fiber band (4).

9. Drafting system (5) according to one of the preceding claims 6 to 8, characterized in that several compressor devices (40) according to one of claims 1 to 5 are arranged at different positions of the drafting system (5).

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