Pneumatic spinning apparatus and spinning method

Abstract

The present invention concerns a spinning method and a spinning apparatus for producing a yarn (13) from fibres (7). In a spinning chamber (2) the fibres (7) are subject to a rotating air vortex (15) and in this process are twisted into a yarn (13) in an inlet opening of a spindle duct (11) of a spindle (12). The fibres to be processed (7) are guided via at least one fibre feed duct (20, 21) into the spinning chamber (2). The present invention proposes that fibres (17), which are not caught into the yarn formation process are eliminated via an exhaust air duct (16), that these eliminated fibres (17) are regenerated, and that the regenerated fibres (17) are fed back into the yarn forming process.

Description

[0001] The present invention concerns a pneumatic spinning apparatus and a spinning method according to the introductory part of the independent patent claims.

[0002] According to the state of the art spinning of a yarn in an air stream is known. It concerns a vortex-air-spinning method in which in a chamber fibres from a fibre supply duct are fed into a rotating air vortex. In this rotating air vortex the fibres are subject to a twist and in this manner are spun into a yarn, which subsequently is taken off through a spindle duct of a rotating or stationary spindle, which is arranged essentially opposite the fibre supply duct. In this process at least one end each of the fibres fed into the vortex freely remains in the rotating air stream over a certain period of time. The advantages of this spinning method are seen in that at a high processing speed a relatively high yarn quality, comparable to ring spinning quality, can be achieved.

[0003] In the method described the air vortex required is generated by compressed air nozzles arranged tangentially oriented in the spinning chamber. The compressed air leaving the spinning process is drained via an exhaust air duct extending along, and arranged coaxially with, the spindle. As the spinning chamber and the exhaust duct are of relatively small dimensions and as the pressure of the air supplied is high the airflow speeds are correspondingly high. They range close to the sonic speed in certain zones.

[0004] The spinning method known according to the state of the art, described e.g. in U.S. Pat. No. 5,528,895, is characterised in that upstream from the spindle duct inlet a sun corona of fibres is formed supported by the air vortex. One end of the fibres each of this fibre sun corona is located in the spindle duct and there forms part of the yarn, which continually is taken off. An important part-task of this fibre sun corona is seen, simplified, in that it catches freely floating fibres and takes them into the spinning process. Even in this arrangement the problem persists that part of the fibres is not caught by the fibre sun corona and thus escapes in the exhaust air stream. A major portion of these lost fibres are short fibres, which seen quantitatively are of significant economic importance and which in the spinning methods known according to the state of the art are lost.

[0005] It is the objective to propose a spinning method and a spinning apparatus, using which an improved yarn quality can be obtained and a reduction of the fibre losses is achieved.

[0006] This objective is achieved using the spinning method and the spinning apparatus as defined in the patent claims.

[0007] The present invention is based on the fact, that in the method described above fibres carried by the exhaust air are caught, regenerated and are fed back into the spinning process at a defined location. The fibres in this process in a first step are separated from the exhaust air stream, and in a second step are freed of impurities if required and oriented, and in a third step using suitable means are fed back into the spinning process. Depending on the field of application different feedback points are provided, which exert different influences on the yarn formation process. Preferred variants will be described in the following.

[0008] A first variant of the fibre feedback is laid out in such a manner that regenerated fibres are fed back into the zone of the rotating fibre sun corona. In a zone of the centre of the rotating fibre sun corona, just as in the eye of a tornado, comparatively low flow speeds prevail. Fibres fed into this zone are not subject to the high flow speeds prevailing at the periphery and thus are deflected correspondingly less. Using this arrangement a yarn is produced, which contains a core consisting of relatively low twist fibres wrapped by a sleeve of twisted fibres.

[0009] Feeding fibres into the centre of the rotating fibre sun corona preferentially is effected through a fibre feed duct centrically arranged separately and/or through one or a plurality of eccentrically arranged fibre feed ducts. Fibre guide means are applied in order to ensure that the fibres reach the centre of the rotating fibre sun corona under optimum conditions. These means are e.g. conical elements, which are formed and arranged symmetrically and essentially point towards the centre of the rotating fibre sun corona. Suitable shapes also are cone-shaped guide means tapering off towards the centre of the rotating fibre sun corona and at their front ends are provided with the outlet of the fibre feed duct or ducts. Asymmetric layouts also may be applied.

[0010] The fibre guide means can be provided at its front end with a protruding means, e.g. a tube, which additionally lengthens the outlet of the fibre supply duct. The fibre guide means do not present any sharp edges nor steps, which negatively affect the air flow conditions; steps advantageously are laid out smoothly. The fibre guide means also assist as twist stop devices, preventing the main fibre stream, which is fed in through one or a plurality main feed ducts arranged peripherally, from suffering unwanted twisting oriented backwards and extending back into the feed zone.

[0011] The regenerated fibres are short fibres mainly, which in first feeding step are disadvantaged all the more the farther away from the centre of the rotating fibre sun corona they are located. If now these regenerated fibres, collected owing to natural selection, are fed back to the centre, a yarn is produced presenting more shorter fibres at the centre of its cross-section, twined outside by longer fibres. Depending on the type and manner of the fibre feedback the fibres will be located more or less at the centre of the yarn cross-section.

[0012] In addition to the regenerated fibres fed back also external fibres can be fed in. These fibres can be e.g. endless (endless filaments), or elastic fibres fed in e.g. in their drawn state, which thus exert an influence on the resulting yarn.

[0013] A further possibility is the previous separation of fibres, in particular of short fibres, from the fibre stream to be processed in order to feed these fibres, as described above, back into the spinning process at the centre of the rotating fibre sun corona. Owing to this procedure the probability is reduced, that short fibres are eliminated in the exhaust air stream.

[0014] In order to assist the yarn formation process a suction air stream directed in the yarn transport direction can be generated in the spindle duct. This measure is aimed at assisting fibres, in particular short fibres, to enter the inlet opening of the spindle duct. A corresponding suction air stream, however, is not necessarily connected with the processing of fibres fed in centrally.

[0015] The apparatus for feeding in fibres can also be used to facilitate the spinning start-up process, if a guide yarn is inserted. The fibres fed in centrally in certain cases prevent uncontrolled twisting of the wrapping fibres up to the feed zone. The distance between the feed opening of the regenerated fibres and the inlet opening of the spindle duct is adjusted in function of the fibre material to be processed.

[0016] In the described apparatus the spinning process can be influenced in many ways. In addition to feeding in regenerated fibres, or alternatively, the feed-in opening can be laid out also as an additional air nozzle, using which the yarn formation process can be influenced. Injection of an additional controlled air volume renders the fibres at the centre fluidised. Owing to an injector effect the fibres are actively involved into the yarn formation process. Furthermore central injection of air influences the zone of low flow speed at the centre of the vortex.

[0017] In the spinning method described, upstream from the actual spinning device containing the spinning chamber, a fibre preparation means is arranged serving for preparing the fibres of a fibre sliver for the spinning process. In principle two variants of fibre preparation means are known using which the fibres are prepared for the spinning forming process. In a first variant the fibre sliver is refined (drafted) and paralleled in a drafting system, as shown e.g. in EP 0 488 007. In a second variant the fibre sliver is dissolved or opened into individual fibres using one or a plurality of opening rolls. Intermediate layout arrangements of these two variants also are known. Based on these two variants described further layout variants of the present invention are derived.

[0018] The drafting system applied in the first variant as opening means in a simplified layout comprises, seen in the direction of fibre transport, a first pair of rolls, a subsequently arranged pair of belts and a second pair of rolls. In principle it is possible that regenerated fibres are fed back upstream from the first pair of rolls and/or upstream from the pair of belts or upstream, or downstream, from the second pair of rolls. If the regenerated fibres are to be subject to a renewed drafting process, it makes sense if they are fed in upstream from the drafting system. In contrast to the layout example described above, in which the fibres are fed into the centre of the rotating fibre sun corona, in the variant considered here the resulting yarn as a rule is not discernible from a conventional yarn.

[0019] The opening means mentioned with the second variant is based on the arrangement that a fibre sliver of fibres to be processed is guided through a supply duct, is taken over by a feed roll and transferred there from to an opening roll provided with teeth or needles. In the process the fibre sliver is compressed between the feed roll and a feed trough to be transferred to the opening roll. The fibres of the fibre sliver have been at least carded already or drafted and thus are aligned essentially parallel. The fibres are transferred from the opening roll to a suction roll the circumferential speed of which is lower. The suction roll as rule is laid out as a roll with a porous surface through which air is sucked in to the inside in such a manner that the fibres adhere to the roll surface. In this second variant of an opening means the regenerated fibres are fed back into the process in the zone of the supply duct, of the opening roll or in the zone of the suction roll. In order to provide optimum preparation of the regenerated fibres for the yarn forming process they preferentially are fed back in the zone of the supply duct.

[0020] The present invention is explained in more detail in the following with reference to the drawings. It is shown schematically and much simplified in the:

[0021] FIG. 1 Possible fibre feed back points in a drafting system;

[0022] FIG. 2 The feedback of fibres into the centre of the rotating fibre sun corona;

[0023] FIG. 3 Two further variants of feedback to the centre of the fibre sun corona;

[0024] FIG. 4 A further variant of fibre feedback;

[0025] FIG. 5 A spinning device with opening means and with a spinning chamber.

[0026] In the FIG. 1 a spinning apparatus 1 is shown in a section. Upstream from a spinning chamber 2 a drafting system 3 is arranged. The drafting system 3 serves for preparing the fibres of a fibre sliver 4 for the spinning process in the spinning chamber 2. The drafting system 3 comprises a first pair of rolls 5, a further pair of rolls 5.1 and a pair of drafting belts 6 arranged between them. These elements run at different speeds, which are chosen in such a manner that the fibres passing through are oriented and refined, in which process they are presented arranged parallel side by side and in the right quantity desired to be fed into the yarn forming process.

[0027] The fibres 7 to be processed reach the inside room of the spinning chamber 2 through a fibre supply duct 8. In this room a rotating fibre sun corona 9 is present formed by fibre ends 10. The fibre sun corona is supported by a vortex 15 generated using compressed air nozzles (not shown in more detail), indicated by arrows 15, seen either from the front side (circle with a point at its centre) or from the back (circle wit a cross at its centre). One end of the fibres 10 each of the rotating fibre sun corona 9 is located in the inlet of a spindle duct 11 of a spindle 12. The spindle duct 11 serves for continually taking off a yarn 13 from the spinning chamber 2. The fibres 7 supplied from the fibre supply duct 8 are guided via a fibre guide means 14 to the inlet opening of the spindle duct 11, in such a manner that they are taken up by the rotating fibre ends and are twisted into a yarn.

[0028] The compressed air supplied via the compressed air nozzles (not shown in detail) into the spinning chamber 2, serving for generating the vortex 15, is drained off through an annular exhaust air duct 16 extending parallel to, and surrounding, the spindle 12. As not all the fibres are caught in the spinning process, part of the fibres are carried off with the exhaust air escaping through the exhaust air duct 16. These fibres 17 predominantly are short fibres. The fibres 17 eliminated are separated from the exhaust air stream, as shown schematically by the arrow A. In the regeneration process (not shown in detail here) the fibres 17 are freed of any thrash particles and remaining impurities, are oriented and re-integrated into the spinning process. The various feedback points are indicated by the arrows B through E. The choice of the feedback point depends on the fibre material to be processed and on the type of regeneration process applied. If the fibres are to be subject to a further drafting process, they preferentially are fed back at the point indicated by the arrow B.

[0029] In the FIG. 2 a further form of realisation of the present invention is shown. In this arrangement the fibres 17 present in the exhaust air stream are separated therefrom, are regenerated and through a separate second fibre feed duct 20, which is arranged essentially coaxial with the spindle 12, are fed into the zone of the centre of the fibre sun corona 9 rotating in the spinning chamber 2. This step is indicated schematically by an arrow F. The first and/or the second fibre feed duct can be laid out forming an angle or can be provided with other means, which prevent unwanted twisting of the fibres.

[0030] Separation of the eliminated fibres from the air is effected mechanically or under the influence of centrifugal forces, the flow e.g. being deflected in such a manner that the fibres are separated because of their inertia. Another possibility is the use of a filter, which is cleaned continually. The filter can be an endless filter tape supported on rolls, which is in constant motion. The exhaust air is guided through this filter tape in such a manner that fibres present in the air are separated. The fibre material accumulated on the filter tape is regenerated and is fed back into yarn forming process. The fibre material can e.g. be transferred from the filter tape to a suction drum, which forms part of a fibre preparatory device. In the regeneration process the fibres collected are, if required freed of any impurities, are aligned and condensed into a fibre sliver, in such a manner that they are optimally prepared for the yarn forming process. The regenerating process advantageously is performed on a drafting system, or a fibre opening means respectively, provided specifically for this purpose.

[0031] Next to the second fibre supply duct 20 a first fibre supply duct 21 is arranged. This first fibre supply duct 21 is arranged offset with respect to the axis of the spindle 12 and serves for supplying the fibres 7 to be processed, delivered from a drafting system or from a fibre opening device known as such (both not being shown in more detail). The fibres 7 are carried along a fibre guide means 14.1 into the reach of the rotating fibre sun corona 9 where their ends are caught by the rotating fibres 10 and are integrated into the yarn forming process.

[0032] The fibre guide means 14.1 is arranged coaxially with the spindle 12 and presents a fibre guide surface 22 essentially extending conically, which is partially flattened, and which tapers off towards the spindle duct 11 and at its front end can be provided with a protruding pin, as known e.g. from DE 4 431 761 or U.S. Pat. No. 5,528,895. The second fibre supply duct 20 extends inside the fibre guide means 14, and coaxially therewith, extending to its point. The outlet opening 23 of the second fibre supply duct 20 is arranged essentially opposite the spindle duct 11. The fibre guide means 14 serves as a twist stop device preventing the supplied fibres 7 from undergoing unwanted twisting action, which could extend back right into the first supply duct.

[0033] Not all fibres 7 supplied are caught into the yarn forming process and thus escape into the exhaust air duct 16. These fibres 17 primarily are comparatively short fibres, which are taken in less easily into the yarn forming process. These fibres 17 in the form of realisation shown here then are regenerated and subsequently are fed through the second fibre supply duct 20 into the centre of the rotating fibre sun corona 9. In this arrangement these fibres are placed predominantly at the centre of the yarn cross-section where longer fibres are wrapped around them. As at the centre zone of the rotating fibre sun corona 9 relatively quiet flow conditions prevail the danger of short fibres being carried away with the exhaust air is reduced.

[0034] In the FIGS. 3a and 3b two further variants of outlet openings of the fibre supply ducts 20, 21 are shown. Instead of a conically shaped fibre guide means fibre delivery edges 24 here are provided, as known from CH 1845/00. These edges present the advantage that they tend, owing to the special air flow conditions in the spinning chamber, to deliver yarns of particularly high quality.

[0035] In the forms of realisation shown, below the fibre delivery edge 24, which is arranged offset with respect to the inlet opening of the spindle duct 11 of the spindle 12, the outlet opening of a second fibre supply duct 20 is arranged. Fibres 7 to be processed are fed into the spinning chamber 2 through the first fibre supply duct 21, and via the fibre delivery edge 24 are transferred into the reach of the rotating fibre sun corona 9, where they are integrated into the yarn forming process. The fibre delivery edge 24 serves as a twist stop device and prevents unwanted twisting of the fibres 7 to be processed back into the fibre supply zone of the first fibre supply duct 21.

[0036] The arrangements shown in the FIGS. 3a and 3b differ in that the second fibre supply duct 20 in the arrangement according to the FIG. 3b presents a protrusion 25 serving for moving the fibres closer to the centre of the rotating fibre sun corona 9. By adjusting the distance X between the outlet opening of the second fibre supply duct 20 and the inlet opening of the spindle duct 11 the yarn forming process can be influenced additionally. The protrusion 25 in this arrangement is designed as a tube of constant cross-section protruding over the wall 26 of the spinning chamber 2. The tube essentially extends to the centre of the rotating air vortex (not shown in more detail) supporting the rotating fibre sun corona 9. The protrusion 25 is laid out in such a manner that it does not negatively affect the flow of the rotating vortex by e.g. causing detrimental turbulences.

[0037] In order to additionally influence the yarn forming process specifically, one or both of the fibre supply ducts 20, 21 can be subject to an air stream directed towards the inside of the spinning chamber 2. Additionally, or alternatively, the spindle duct also can be subject to an oriented airflow. The second fibre supply duct 20 can be, if required, and if the spinning device is laid out appropriately, used also for the spinning start-up process, if it serves for taking up a lead yarn.

[0038] In the FIG. 4 a further embodiment of the present invention is shown. In this arrangement fibres 17 are separated from the exhaust air in the exhaust air duct 16, are regenerated and through the second fibre supply duct are fed into the centre zone of the rotating fibre sun corona 9. The fibres 17 are separated from the exhaust air stream by a circulating endless filter tape 50. The filter tape 50 in this arrangement is laid out in such a manner that the fibres 17 separated are transported over a certain distance and then are transferred to a suction roll 51. The suction roll 51 in this arrangement is arranged upstream from the second fibre supply duct 20 and at the same time assists insertion. The suction roll 51 also can be co-ordinated with a fibre opening means. The filter tape 50 is laid out in such a manner that it separates fibres 17 from the exhaust air stream but remaining particles 52 are eliminated. This process is schematically indicated by the arrow 53. Instead of using the circulating endless filter tape 50 the fibres also can be fed back in an air stream, e.g. in a suitable hose.

[0039] In the FIG. 5 a spinning apparatus 1 is shown with a fibre opening device arranged upstream, similar to the arrangement described in CH 1845/00 by the same applicant. The fibre opening means 30 comprises a feed duct 31 serving for feeding in fibres 7 to be processed. At the outlet end of the feed duct 31 a feed roll 32 and a feed trough 39 are arranged, which are used for transferring the fibres 7 to be processed to an opening roll 33 provided with teeth or needles. In this transfer process thrash particles and remaining impurities 35 are eliminated in a first stage and are eliminated via a corresponding first exhaust duct 38. The fibres 7 are transferred from the opening roll 33 to a suction roll 34. The suction roll 34 as a rule is $laid out as a roll with a porous surface through which air is sucked into the inside room in such a manner that fibres 7 adhere to the roll surface. During the transfer process the fibres are sharply deflected, remaining thrash particles 35 and remaining impurities 35 are eliminated and via a further exhaust duct 38 are carried away. From the suction roll 34 the fibres 7 to be processed are guided using a transfer roll 40 into a fibre feed duct 36 through which they reach the spinning chamber 2.

[0040] In the embodiments of the present invention shown here the fibres 17 contained in the exhaust air are separated therefrom, are regenerated if required, and through a duct 37 are transferred to the opening roll 33 using which they are prepared again for the yarn forming process. The infeed of the eliminated fibres is effected in such a manner that any remaining thrash particles are separated. In the arrangement shown here the short fibres 17 separated from the exhaust air are blended with the fibres 7 to be processed from the feed duct 31. Owing to this feedback the efficiency of the spinning process is improved in contrast to the known spinning methods. As the feeding in is effected within the reach of the opening roll, and owing to the subsequent transfer to the suction roll the fibres are aligned once more and are blended into the other fibres. Owing to the regeneration process the fibres are optimally prepared for the yarn forming process in such a manner that an even yarn is obtained.

[0041] By combining the characteristics of the various embodiments shown in the Figures, further forms of realisation result.

Claims

1. Method of producing a yarn (13) from fibres (7) in a spinning chamber (2), which fibres (7) are subject to a rotating air vortex (15) and thus are twisted into a yarn (13) in an inlet opening of a spindle duct (11) of a spindle (12) arranged in the spinning chamber (2), the fibres (7) being guided through at least one fibre supply duct (20, 21) into the spinning chamber (2), characterised in that

a) Fibres (17) not caught in the yarn forming process are separated from an exhaust air duct (16);

b) The separated fibres (17) are fed back into the yarn forming process.

2. Method according to the claim 1, characterised in that the separated fibres (17) are regenerated, in which process they are freed of any thrash particles and, if required, are aligned.

3. Method according to the claim 1 or 2, characterised in that the fibres (17) are separated from the exhaust air stream using a circulating endless filter tape (50).

4. Method according to the claim 3, characterised in that using the circulating endless filter tape (50) the separated fibres (17) are moved to a suction roll (51).

5. Method according to the claim 4, characterised in that the suction roll (50) co-operates with a fibre opening means (30).

6. Method according to the claim 5, characterised in that the suction roll (50) serves for feeding in the eliminated fibres (17) into the second fibre supply duct (20).

7. Method according to one of the preceding claims, characterised in that the fibres (7) to be processed are guided through a first fibre supply duct (21) and the separated fibres (17) are guided through a second fibre supply duct (20) into the spinning chamber (2).

8. Method according to the claim 7, characterised in that the separated fibres (17) using the second fibre supply duct (20) are fed into the centre of the rotating air vortex (15).

9. Method according to the claim 2, characterised in that the fibres (17) separated from the exhaust air stream are transferred, in order to be regenerated, to a fibre preparing means (30), where they are blended with fibres (7) to be processed and jointly with these are prepared for the yarn forming process.

10. Method according to the claim 9, characterised in that the fibre preparing means (30) is a drafting system.

11. Method according to the claim 9, characterised in that the fibre preparing means (30) is a fibre opening means, which fibre opening means comprises a feed roll (32), an opening roll (33) and a suction roll (34).

12. Method according to the claims 7, characterised in that the regenerated fibres (17) are fed in at the zone of the feed roll (32) and/or of the opening roll (33).

13. Spinning apparatus (1) for implementing the method according to the claim 1, with a spinning chamber (2), at least one fibre supply duct (21) merging into the spinning chamber (2) serving for feeding in fibres (7) to be processed, a spindle (12) arranged in the spinning chamber (2) presenting a spindle duct (11), which spindle duct (11) serves for taking off a yarn (13) spun, and an exhaust air duct (16), characterised by means (50) serving for separating fibres (17) present in the exhaust air duct (16) and by means (37, 50) serving for feeding the separated fibres (17) back into the spinning process.

14. Spinning apparatus according to the claim 13, characterised in that the means for separating the fibres (17) is a circulating endless filter tape (50).

15. Spinning apparatus according to the claim 14, characterised in that a suction roll (51) is provided for taking over the fibres (17) from the filter tape (50).

16. Spinning apparatus according to one of the claims 13 through 15, characterised in that the means for feeding back the separated fibres is a second fibre supply duct (20) serving for feeding the separated fibres (17) into the spinning chamber (2).

17. Spinning apparatus according to the claim 16, characterised in that the second fibre supply duct (20) is arranged in such a manner that the separated fibres are fed into the centre of a rotating air vortex (15).

18. Spinning apparatus according to the claim 16 or 17, characterised in that the first and/or the second fibre supply duct (20, 21) are laid out in such a manner that unwanted twisting of the fibres (7, 17) is prevented.

19. Spinning apparatus according to the claim 16, characterised in that the first and/or the second fibre supply duct (20, 21) present a bend or an angle.

20. Spinning apparatus according to one of the claims 13 through 19, characterised in that the at least one fibre supply duct (20, 21) is provided with a fibre delivery edge.

21. Spinning apparatus according to one of the claims 13 through 19, characterised in that the at least one fibre supply duct (20, 21) merges into an essentially conical fibre guide surface.

22. Yarn (13) produced according to one of the method claims 1 through 12, characterised in that in the centre of the yarn cross-section fibres (17) are arranged, which mainly were supplied from the second fibre supply duct (20), and which are surrounded by fibres (7), which mainly were supplied from the first fibre supply duct (21).