EP0131170B1 - Method and device for false spinning - Google Patents

Abstract

A fiber sliver is drafted to a yarn count in a drafting mechanism and is fed to a false twist unit with a sliver width B1 of 10 to 19 mm. In accordance with the method, by means of the width B1, the fiber sliver leaving the delivery roller pair is divided into a yarn core rotated by the false twist member with a spinning triangle of the width B2 and into edge fibers delivered thereto. The edge fibers are taken up by the rotating yarn core in the suction passage of the false twist unit. The taking-up of the edge fibers occurs in that the front ends of the delivered edge fibers are caught by the rotating yarn core in the region of the narrowest portion of the suction passage and are wound about the yarn core with the same rotational direction as the fiber core but with a substantially larger inclination until the rear end of the edge fibers is wound into the yarn core in the spinning triangle. To maintain the width of the fiber sliver, as delivered by the apron pair and determined by the funnel, until catching of the sliver by the nip line of the delivery roller pair, one of the two aprons is extended into the converging space of the delivery roller pair and both aprons are guided so close to the corresponding roller of the delivery roller pair that the spacings between the aprons and the delivery rollers are close to zero. The spacing between the nip line and the narrowest portion of the suction passage is shorter than the average length of the procesed edge fibers, in order to ensure that the rear end of the edge fibers is not released from the nip line before the edge fibers are wound in the spinning triangle.

Description

The invention relates to a method for false twist spinning with the method steps that a sliver is drawn in a drafting system to a desired yarn number, the spread sliver in the converging space of the output roller pair being limited to a width by suitable means that the sliver in such a Width is output from the pair of output rollers that only a portion of the original width of the drawn fiber sliver is gripped by the spinning triangle and turned to an incorrectly twisted yarn core, and that the edge fibers resulting from the difference in width to the smaller width of the spinning triangle are sucked into a tapered suction channel and at the latest at the narrowest point of the intake duct, d. H. in front of the throttling point of a false twist spinning unit following the drafting device and containing the intake duct are detected by the rotating incorrectly rotated yarn core, the elongation of the yarn core being generated by the pneumatic false twist element downstream of the throttling point, and also a device according to the preamble of claim 10 for carrying out this method.

The problems of the yarns produced by means of the false twist spinning process with regard to the further processing into the finished fabric lie essentially in the uniformity, strength and elongation. For example, non-measurable, recurring weak points, even with the highest measured strength of the yarn, are major disadvantages in the slip and weaving processes, or neps also reduce the value of the finished fabric in the case of yarns which are problem-free for the subsequent processing processes.

A method and a device according to the preamble of the first method and the first device claim are known from CR-A-615 467.

In this known method or in this known device, shown schematically and partly in section with FIG. 1, a delivered sliver 2 is calibrated in a drafting device 1 by a hopper 5 or 6 provided in front of a pair of input rollers 3 and in front of an intermediate roller 4 and guided by a pair of straps 8 directed by the intermediate roller pair 4 against an output roller pair 7 (the roller pairs are indicated by dashed lines).

In the converging space of the pair of output rollers 7, a further funnel 9 is provided for collecting the edge fibers F or to avoid as far as possible that these edge fibers are lost.

In the prior art method, the sliver 2 is released from the pair of straps 8 (only the lower strap is shown) with a width BA and fed to the clamping line K formed by the pair of output rollers 7.

In the converging space of the pair of output rollers 7, the sliver experiences a spread due to the circumferential air of the rotating pair of output rollers which is conveyed into this space and escapes in the axial direction, which is limited to a width BB by the funnel 9.

The difference in the width BB to the smaller width BC of the spinning triangle gives rise to the edge fibers F mentioned, which are sucked into an intake duct 10 and at the latest at the narrowest point of the intake duct, i.e. in front of the throttle point 11 are largely caught by the rotating incorrectly rotated yarn core 12. The rotation of the yarn core 12 is caused by the pneumatic false twist element 13 connected downstream of the throttle point 11.

The main disadvantage of this method is insufficient yarn uniformity with regard to mass uniformity, weak points and nits. The strength of the yarn is also much lower than that of normal ring spun yarns. This insufficient uniformity is essentially due to the fact that the fiber spreading mentioned is random and uncontrolled, and that the edge fibers mentioned are wound around the yarn core without pretensioning.

It is therefore an object of this invention to provide a method and an apparatus with which a more uniform yarn can be produced in relation to the properties mentioned.

According to the method, the object is achieved in that the edge fibers not covered by the spinning triangle are sucked in and guided by means of the intake air flow in such a way that the front end of a fiber with a length corresponding to the average length of the processed fibers is seen from the rotating yarn core, as seen in the direction of conveyance of the yarn core is detected when the rear end of the fiber is still clamped in the nip line of the pair of output rollers, and that the rear end of the fiber leaves the nip line only when the fiber has been caught by the spinning triangle, whereby the rear end of the fiber is bound in the yarn core .

A device for carrying out this method is characterized in that one of the two aprons protrudes further into the converging space than the other apron and both aprons are guided so close to the corresponding roller of the output rollers that the distances between the aprons and the corresponding rollers are almost zero. In this device, the distance between the clamping line of the pair of output rollers and the narrowest point of the intake duct is 60 to 75% and preferably 68 to 72% of the average fiber length.

Preferred embodiments of the method and the device can be found in subclaims 2 to 9 and 11 to 16, respectively.

The invention achieves a more uniform yarn with high strength.

• Fig. 2 einen Längsschnitt der erfindungsgemäßen Vorrichtung, schematisch und teilweise im Schnitt dargestellt,
• Fig. 3 den im Schnitt dargestellten Teil von Fig. 2, vergrößert und halbschematisch in Richtung 1 (Fig. 2) im Schnitt dargestellt.
• Fig. 4+5+5a je eine Variante des Teiles von Figur 3, halbschematisch und in derselben Richtung im Schnitt dargestellt,
• Fig. 6 - 8 je einen Verfahrensschritt, halbschematisch dargestellt,
• Fig. 9 das fertige Garn, halbschematisch dargestellt,
• Fig. 10 ein Festigkeitsdiagramm des fertigen Garnes in Abhängigkeit einer charakteristischen Kennzahl,
• Fig. 11 ein Faserverlustdiagramm des Garnes, in Abhängigkeit einer charakteristischen Kennzahl,
• Fig. 12 eine Variante der Anordnung von Fig. 2,
• Fig. 13a bis d diverse Wert-Diagramme.

In the following the invention is explained in more detail with reference to drawings, which only show exemplary embodiments; it shows:

• Fig. 2 shows a longitudinal section of the device according to the invention, schematically and partially in Section shown,
• Fig. 3 shows the part of Fig. 2 shown in section, enlarged and semi-schematic in the direction 1 (Fig. 2) shown in section.
• 4 + 5 + 5a each a variant of the part of Figure 3, shown semi-schematically and in the same direction in section,
• 6 - 8 each a process step, shown semi-schematically,
• 9 shows the finished yarn, shown semi-schematically,
• 10 shows a strength diagram of the finished yarn as a function of a characteristic characteristic number,
• 11 is a fiber loss diagram of the yarn, depending on a characteristic number,
• 12 shows a variant of the arrangement of FIG. 2,
• 13a to d various value diagrams.

In a drafting system 101 (FIG. 2), a sliver 102 is drawn to a finished yarn size in a preliminary drafting field between an input roller pair 103 and an intermediate roller pair 104 and in a main drafting field between the intermediate roller pair 104 and an output roller pair 105 and shown in a false twist spinning unit 106 (shown in section ) turned into a yarn 107.

The drafting system further comprises a condenser 108 in front of the input roller pair 103 as a first sliver guiding element, a condenser 109 in front of the intermediate roller pair 104 as a second sliver guiding element and a pair of straps 110 consisting of an upper apron 111 and a lower apron 112 as an additional sliver guiding element. The guides of the roller pairs and straps are known per se and are not the subject of the invention.

The condenser 108 serves the primary and the condenser 109 the secondary guidance of the sliver 102. The clear width of these condensers is such that the sliver has a width B1 of 10 19 mm between the straps, preferably 14 for a yarn titer of approx. 15 tex - 15 mm. In order to maintain this width B1 essentially unchanged up to the clamping line K generated by the exit rollers 105, as a first measure one of the two straps of the strap pair 110 is brought further into the converging space 113 of the exit rollers 105 than the other strap, for example the lower strap 112 .

This measure results in a deflection of the fiber sliver at the deflection point 114 of the apron 112 out of the plane (not shown) in which the clamping line K and the clamping line given by the intermediate rollers 104 (not shown) are contained. This deflection pushed into the converging space 113 also results in an additional fiber guidance on a surface piece of the upper roller 105A of the output rollers 105 characterized by the angle α (FIG. 2).

As a further measure for maintaining the width B1, the straps 111 and 112 are guided so close to the corresponding roller of the output rollers 105 that the distances M, respectively. N, are approximately zero, so that the air flow resulting from the rotating output rollers 105 is practically prevented from flowing into the converging space 113

This further measure supports the first measure, which essentially avoids spreading of the edge fibers, which are designated by F and FA in the prior art described in FIG. 1. The false twist spinning unit 106 connected downstream of the pair of output rollers essentially comprises an intake duct 115, a throttle point 116 known from Swiss Patent Specification No. 615 467 and a pneumatic false twist element 117 with at least one air inflow duct 118.

In operation, as can be seen from FIGS. 3-5 a and known from the theory of false twist spinning (also called nozzle spinning), a so-called wrongly twisted core of yarn 119 with a pitch with the angle β (FIG. 7) is created by the rotation generated in the false twist element 117. , for example as shown in Figures 3-5a with an S rotation.

This rotation creates a spinning triangle delimited by the clamping line K with a width B2 (shown in FIGS. 3 and 6) given by the intensity of the rotation, which should be substantially smaller than the previously mentioned fiber bandwidth 81, ie the width B1 becomes at Resulting width B2 selected depending on the processed average fiber length and spun yarn titer such that there is a sufficient number of edge fibers F for the winding around the yarn core 119.

It was found that the front ends, seen in the conveying direction R (FIG. 2) of the yarn core 119, of the edge fibers F sucked in by the suction channel 115 (FIG. 2) in a path essentially corresponding to a conical spiral against the high speed (e.g. B. 200000 U / min.) Rotating yarn core 119 and are usually detected in front of the narrowest point of the intake channel of the rotating yarn core 119, said web being created by an air vortex generated by the rotating yarn core. Subsequently, as shown in FIGS. 6 to 8, the following happens:

After the front end of the edge fibers F has been gripped by the rotating yarn core 119, provided that the rear end of the gripped fiber is still guided in the clamping line K, this edge fiber causes the yarn core 119 to be wound in the same direction of rotation, ie at S-twist of the yarn core 119, also S-twist of the wrapping fiber, but with a much larger pitch with the angle y. However, the angle becomes somewhat larger towards the spinning triangle and can correspond to the angle β shortly before the spinning triangle.

This larger incline is caused by walking the winding at a higher speed than the advance of the yarn core in the direction opposite to the yarn advance, i.e. towards the spinning triangle, and ensures that, provided that the rear fiber end is still gripped by the clamping line K, this end is screwed into the spinning triangle, so that this is subsequently the rear fiber end released by the clamping line K remains contained in the yarn core of the finished yarn.

The slope is so much steeper than the speed of the mentioned hiking is great. In order to ensure that the rear fiber end is twisted into the spinning triangle, the distance D between the narrowest point of the intake duct 115 and the clamping line K must be smaller than the length of the edge fiber F. A too early twisting of the said front fiber end can result in the wrapping length of the edge fiber shorten that the wrapping strength given by the adhesive length of the wrapping fiber is not sufficient to give the finished yarn sufficient tensile strength.

Furthermore, it has been shown that the spinning triangle is repeatedly and variably divided into smaller spinning triangles with the different width b2 (FIG. 6a), so that the edge fibers F not only have to occur in the edge parts of the width B1, but edge fibers F. of the whole width B1 are distributed outside and between the small spinning triangles.

• ganzheitliches Spinndreieck:
  
• aufgeteiltes Spinndreieck:

In comparison to the holistic spinning triangle explained with Figs. 6 - 8, the following relation can be established:

• holistic spinning triangle:
  
• split spinning triangle:

This division into small spinning triangles arises from the tendency to keep the fiber density in the clamping gap K so low that the free edge fibers F already mentioned which are not contained in the spinning triangle can occur.

The division into small spinning triangles has the advantage that these edge fibers, as shown in FIG. 6a, can be distributed over the width B1, which results in a statistically uniform occurrence of these edge fibers F.

It is also possible that certain fibers of a fiber structure forming a spinning triangle are nevertheless not contained in the spinning triangle when leaving the clamping line K, namely if, for example, the adhesive force between these fibers and the rollers is greater than that of the other fibers forming the spinning triangle. Such fibers, like the so-called edge fibers F, remain free at their front ends until, like the edge fibers F, they are caught by the rotating yarn core 119 and also form wrapping fibers.

Furthermore, the optimal distance D should correspond to approximately 70% of the average spun fiber length, but should not be less than 60% of this average fiber length. The usable range for the distance D is 60-75% of the average spun fiber length.

The finished yarn, which is passed on from a pair of take-off rolls (not shown) provided after the false twist unit to a spool unit (not shown), consists of an essentially untwisted yarn core 120 (FIG. 9), which is held together by surrounding fibers F, now called winding fibers F1 becomes.

The slope A A (FIG. 9) of these wrapping fibers F1 essentially corresponds to the slope difference A (FIG. 7), which results from the difference between the slope (β) of the yarn core 119 and the slope (y) of the edge fibers F. However, the winding direction of the wrapping fibers F1 is opposite to that of the edge fibers F, i.e. if the edge fibers in front of the swirl organ had an S direction, the wrapping fibers had a z direction. During the untwisting, the wound fibers have a position over part of their length and for a short moment, which is parallel to the longitudinal axis of the yarn core, until they increasingly take on the opposite direction of twist as the untwisting continues.

The advantages of this method compared to the previously known methods result from the fact that by grasping the front free fiber end and wrapping around it during a time in which the rear end of the edge fibers is still held by the clamping line K, the wrapping underneath a certain tension of the edge fibers happens and in the further the rear end is clearly and firmly wrapped in the yarn core and held there. By wrapping under tension, a tight wrap is created, in which the wrapping fibers are under a certain pretension within their stretch, so that when the yarn core is unhooked, not only the lengthening of the yarn core and the enlargement of the yarn core diameter, but also the pretension helps that the wrapping fibers do not detach from the core fibers in the transitional position, in which they are partly parallel to the Garnachse for a short time.

This pretension can neither arise in those processes in which the fiber end belonging to the wrapping part of the fiber is freely protruding during the unwinding process, nor in those processes which guide the edge fiber parallel to the core fibers according to the clamping line and the wrapping without the inclusion of one or the other End of the wrapping fibers happens.

The fact that the width B, which can be selected, for example, by the action of the condensers 108, 109, also provides a sufficient and secure number of edge fibers F which are essentially constant over time can be provided for the winding.

FIG. 4 shows a variant of the false twist unit 106 in that a suction part 123 is provided between the suction channel 115A and the throttle point 116. This suction part consists of a short space 124 connecting the suction channel 115A and the throttle point 116 and a space between them suction bore 125 connecting to the surroundings of the false twist unit. A suction system (not shown) is connected to this suction bore, with which an additional amount of air is sucked in through suction channel 115A in addition to the false twist element.

This additional amount of air serves to increase the air speed in the intake duct, so that the spiral path in which the front ends of the edge fibers F are conveyed has a greater gradient. This greater incline, respectively higher suction speed, rather ensures that the front fiber ends mentioned are better aligned and are not detected too early, but as close as possible to the narrowest point of the suction duct 115A mentioned. This suction also reduces possible edge fiber loss between the pair of output rollers 105 and the inlet of the intake duct.

FIG. 5 shows, with the intake duct 115B, an additional variant of the intake duct in this latter endeavor of the fiber end guide. This suction channel 115B is designed in a bell-shaped manner in such a way that the tendency that the fiber ends mentioned are caught too early by the rotating fiber core 119 can be additionally counteracted.

5a, the front ends of the edge fibers F are fed to the suction duct 115C in the upper region E, and are guided in the central region M in such a way that they are as narrow as possible for as long as possible without being caught by the rotating fiber core 119 of the intake duct 115C and are guided in the lower region U into a position in which the ends of the edge fibers F are more likely to assume a position parallel to the yarn core. In this latter position, the ends of the edge fibers F can be better grasped by the fiber ends (not shown) projecting from the rotating yarn core than in a position perpendicular to the fiber core.

However, the intake duct is not limited to the shapes shown in Figs. 4-5a. Variations of this can be optimized through trials. Likewise, the suction bore 125 can open tangentially into the intermediate space 124 in such a way that the aforementioned rotation of the intake air is supported.

There were spinning tests with the false twist spinning units specified below. Suction channels performed. The yarn values listed are partially range values and serve as comparison values because they were always measured with the same method or with the same device.

• - Streckenband 3000 tex; 65 % PES (Faserlänge 40 mm)/35 % gekämmte BW. (PES = Polyesterfaser/BW = Baumwollfaser)
• - Garn 16 tex
• - Bandbreite B1: 15 mm
• - Lichte Weite W (nur in Fig. 4 und 5a gezeigt): ca. 22 mm
• - Durchmesser 0 (nur in Fig. 4 gekennzeichnet) der engsten Stelle des Ansaugkanales 115A, 115B und 115C: 2,5 mm
• - Drosselstelle 116 a) Durchmesser: 0,8 mm, b) Länge: 3 mm
• - Angesaugte Luftmenge:

• a) betreffend Ansaugkanal 115: ca. 5 Normalliter/min.
• b) betreffend Ansaugkanäle 115A, 115B, 115C: 23 - 25 Normalliter/min.

• - Streckwerksanordnung gemäß Fig. 2. Weiter sind die angegebenen CVUster-Werte Massengleichmässigkeitswerten d.h, je größer der Wert desto schlechter die Gleichmässigkeit.

The following values remained unchanged in connection with this experiment:

• - stretch band 3000 tex; 65% PES (fiber length 40 mm) / 35% combed BW. (PES = polyester fiber / BW = cotton fiber)
• - yarn 16 tex
• - Band width B1: 15 mm
• Clear width W (only shown in FIGS. 4 and 5a): approx. 22 mm
• - Diameter 0 (marked only in Fig. 4) of the narrowest point of the intake duct 115A, 115B and 115C: 2.5 mm
• - Throttle restriction 116 a) Diameter: 0.8 mm, b) Length: 3 mm
• - Air intake:

• a) regarding intake duct 115: approx. 5 normal liters / min.
• b) regarding intake ducts 115A, 115B, 115C: 23-25 normal liters / min.

• 2. The drafting arrangement according to FIG. 2. Furthermore, the CVUster values given are mass uniformity values, ie the larger the value, the worse the uniformity.

Spinning with a diameter 0 (FIG. 4) of the narrowest point of more than 2.5 mm is possible, but gives progressively worse values with increasing diameter 0. For example, the values for a diameter 0 of 4 mm are significantly worse.

On the other hand, it has been shown that with a diameter 0 of 2.5 mm finer and coarser yarns, for. B. 8 tex and 30 tex can be spun with good yarn values.

Diameter 0 values of less than 2.5 mm require higher negative pressures (higher output) for an equal air flow rate (liters / min.) And, depending on the value, result in such an increased air speed that free front fiber ends may not be able to rotate from the rotating yarn core , but are detected by the suction air, so that the corresponding edge fiber F is fed as an outlet to the suction system.

• Δp . 5⁴ ₌ konstant

The relationship between vacuum Δp (at the narrowest point) and diameter 0 value d (Fig. 4) can be expressed for a given exhaust air flow using the following formula:

• Δp. 5 ⁴ ₌ constant

The influence of the bandwidth B1 on the yarn values shown with FIGS. 10 and 11 relates to the aforementioned stretch band of 3000 tex and to the yarn of 16 tex, spun with a false twist unit according to FIG. 4.

10 shows the ordinate for the strength values in kilometers of travel (Rkm) and the abscissa for the bandwidth B1. It can be seen that the Rkm value begins to stabilize from a width of 14 mm B1.

From Fig. 11 the fiber losses in grams per hour can be seen from the ordinate and the bandwidth B1 from the abscissa.

A comparison of the two diagrams shows that a bandwidth B1 of 15 mm is optimal for this yarn.

A broad fiber distribution between the aprons also has the advantage of better fiber distribution in this drafting zone which carries out the main draft. This better fiber distribution results in a more even warping in this zone and a longer apron life.

Different yarn numbers and different fiber lengths result in different dimensions of the spinning triangle and accordingly require different bandwidths B1. The optimal bandwidth B1 must be determined on a case-by-case basis. For example, with the false twist spinning unit according to FIG. 4 it was found that an optimal width B1 for a yarn of 8 tex is between 10 and 12 mm and for a yarn of 30 tex between 15 and 19 mm.

Furthermore, it has been shown that a loop, marked with the angle λ (FIG. 2), supports one of the two output rollers by the fiber sliver to separate the edge fibers from the spinning triangle. This wrapping can be achieved either by, as shown in FIG. 2, the false twist spinning unit 106 with the angle λ deviating from an imaginary plane tangential to the clamping line K, or by the false twist spinning unit as shown in FIG 106 is arranged offset parallel to the plane mentioned. The offset (Fig. 12) is measured in millimeters.

In the latter arrangement, spinning tests were carried out to determine the influence of a deviation from the optimal distance D. The tests were carried out using a false twist spinning unit according to FIG. 4 offset parallel to the aforementioned plane by 5.5 mm and the unchanged values mentioned for the test described earlier. The results of these tests are shown graphically with FIGS. 13a-d. The abscissa of FIG. 13d also applies to FIGS. 13a-c and shows values for the distance D in percentages above and below the optimal distance of 70% of the average fiber length. The ordinates of FIGS. 13a-d show the CV-Uster value, the number of nits per 1000 m with a setting level 3, the travel kilometers Rkm (CN / Tex) and the departure in percent. These values are internationally standardized measurement methods.

The diagrams show that as the distance decreases, the CV-Uster value, the number of nits and the drop in the area shown are reduced in an essentially linear function, while the travel kilometer value Rkm is reduced before and after the optimal distance D.

Ultimately, the false twist element does not need to be pneumatic, as shown in FIGS. 2-5a, but it is quite possible that following the intake duct 115A or. 115B, resp. 115C, a purely mechanical false twist device (not shown) is used. The essential inventive concept of the relation of the width B1 to the length D can also be realized in the use of a purely mechanical false twist device.

The invention defined by the claims is therefore not restricted to the use of a pneumatic false twist device.

Claims (16)

1. Method of false twist spinning with the method steps,

- that a fibre band is drafted in a drafting arrangement (101) to a desired yarn count, with the spread fibre band being restricted in the convergent space of the output roller pair (105) by suitable means to a width (B1),

- that the fibre band is released from the output roller pair (105) in a width such that only a part (B2 or Σ b₂ respectively) of the original width (B1) of the drafted fibre band is embraced by the spinning triangle and twisted into a false twisted yarn core (119), and

- that the marginal fibres (F) arising through the difference of the width (B1) from the smaller width (B2 or I b₂ respectively) of the spinning triangle are sucked into a tapering suction channel (115-115C) and are embraced by the rotating false twisted yarn core (119) at the latest at the narrowest point of the suction channel, i.e. before the restrictor location (116) of a false twist spinning unit (106) which follows the drafting arrangement (101) and contains the suction channel (115-115C), with the extension of the yarn core (119) being generated by the pneumatic false twist device (117) following the restrictor location (116),
characterised in that

- the marginal fibres (F) which are not embraced by the spinning triangle are so sucked in and guided by means of the suction airstream that the front end of a fibre - as seen in the conveying direction R of the yarn core (119) - with a length corresponding to the mean length of the processed fibres is embraced by the rotating yarn core (119) when the rear end of the fibres is still clamped in the clamping line (K) of the output roller pair (105); and in that the rear end of the fibre only leaves the clamping line when the fibre has been embraced by the spinning triangle, whereby the rear end of the fibre is bound into the yarn core (119).

2. Method in accordance with claim 1, characterised in that the width (B,) of the drafted fibre band is 10 - 30 % larger than the width (B₂ or Σ b₂ respectively) of the spinning triangle.

3. Method in accordance with claim 1 and claim 2, characterised in that the width (B_I) of the drafted fibre band is achieved by a correspondingly broad guidance of the fibre band before the input roller pair (103) and before the output roller pair (105) and preferably, that the fibre band is additionally correspondingly broadly guided in front of the intermediate roller pair (104).

4. Method in accordance with claim 1 and claim 2, characterised in that the fibre band (102) is directly guided into the convergent space (113) of the output roller pair (105).

5. Method in accordance with claim 1 and claim 2, characterised in that the penetration of the peripheral air of the rotating output rollers into the converging space (113) is substantially prevented.

6. Method in accordance with claim 1, characterised in that the front end of the marginal fibre is embraced by the rotating yarn core when the fibre has left the clamping line (K) by an amount of 60 - 75 % and preferably 68 to 72 % of the mean fibre length of the processed fibres.

7. Method in accordance with claim 1, characterised in that the false twist device is a false twist nozzle (117) and the suction airstream is generated by this false twist nozzle (117); and optionally in that the suction airstream is generated as a supplement to the false twist nozzle (117) by a suction part (123) provided between the false twist nozzle and the tapering channel (115).

8. Method in accordance with claim 7, characterised in that a rotation is imparted to the suction airstream so that the sucked in free ends of the marginal fibres (F) are set in rotation about the yarn core on the way to the region in which they are embraced by the rotating yarn core (119), and are subjected through the resulting centrifugal force to a force directed towards the wall of the suction channel, so that these fibre ends reach the said region on a conical, spiral-like, path around the yarn core (119).

9. Method in accordance with claim 8, characterised in that this rotation of the suction air is generated by the rotating yarn core itself and optionally, in that the rotation of the suction air is additionally generated by an appropriately shaped suction part (123).

10. Apparatus for carrying out the method of one of the claims 1 to 9 for false twist spinning with a drafting arrangement (101) which delivers a drafted fibre band to a suction channel (115 - 115C) and also with a false twist device (117) arranged after the tapering suction channel,

- wherein the drafting arrangement (101) has, before its output roller pair (105) which delivers the fibre band to the suction channel (115, 115C), means which guide the fibre band in the drafting arrangement in such a way that the drafted fibre band delivered by the output roller pair (105) has a width (B1) whiph is larger than the width (B2 of Σ b₂ respectively) of the spinning triangle of the yarn core (119) twisted by means of the false twist device, and

- wherein the suction channel (115 - 115C) has a tapered form such that free front fibre ends which are guided in the airstream and delivered by the output roller pair (105) but which are not bound into the rotating yarn core (119) generated by the false twist device are so guided towards the rotating yarn core (119) that they are embraced by the rotating yarn core, with the said means being a pair of belts (111 and 112 respectively) ,
characterised in that
one of the two belts (111 and 112) projects further into the converging space (113) than the other belt, with both belts (111 and 112) being guided so close to the corresponding rollers of the output rollers (105) that the distances (M and N respectively) between the belts and the corresponding rollers are approximately zero.

11. Apparatus in accordance with claim 10, characterised in that the distance (D) between the clamping line (K) and the narrowest point of the suction channel amounts to 60 - 75 % and preferably 68 - 72 % of the mean fibre length.

12. Apparatus in accordance with claim 10, characterised in that the false twist device (117) is so designed that the suction airstream is generated by the false twist device.

13. Apparatus in accordance with one of the claims 10 to 12, characterised in that the narrowest point of the suction channel (115) is a restrictor location (116) provided between the suction channel and the twist device (117).

14. Apparatus in accordance with claim 13, characterised in that a suction part (123) is provided between the suction channel (115A, 115B and 115C) and the restrictor location (116) with the suction part increasing the suction airstream; and preferably in that the narrowest point of the suction channel (115A, 115B and 115C) is the diameter of the suction part (123) which adjoins it.

15. Apparatus in accordance with claim 14, characterised in that the suction part includes an intermediate space (124) which adjoins the suction channel and has a suction bore (125); and preferably in that the suction bore (125) opens tangentially into the intermediate space (124).

16. Apparatus in accordance with claim 10, characterised in that the suction channel is a substantially uniformly tapering channel (115.115A). or a substantially bell-shaped tapering channel (115B), or a substantially calyx-like tapering channel (115C).

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