Method for Producing a Yarn in a Jet Spinner

Abstract

During a jet spinning method, the rotating fibre ends or the subsequent wound fibres of the spun yarn (70) cause a spinning tension Fs. In tests, a direct correlation has been established between the spinning result and the spinning tension Fs. The aim of the invention therefore is to provide a method for spinning yarn in a jet spinner that permits an ideal spinning tension Fs despite high spinning speeds, thus achieving an optimal spinning result, in particular with regard to the yarn quality. According to the invention, a jet spinner is operated with a spinning tension Fs<20 cN by means of a configuration of spinning box elements.

Description

The invention relates to a method for producing a yarn in a jet spinner according to the preamble of patent claim 1.

The present invention relates to the field of jet spinners. Jet spinners have a multiplicity of spinning stations. In each spinning station, a yarn is spun from a longitudinal fiber structure which is supplied. In this case, the longitudinal fiber structure is first refined, that is to say the fiber quantity per unit length is reduced by drafting. Then, in the spinning station, the refined fiber composite is spun into a yarn by imparting twist to it. For this purpose, the spinning station has a fiber guide element which guides the fiber composition into a swirl chamber where a yarn is produced on a spindle by means of the known vortex jet spinning method.

Tests have shown that there is a direct relation between the spinning tension and the spinning result. FIG. 1 shows a diagrammatic illustration of the components of a jet spinner. As explained above, the longitudinal fiber structure 1 is refined in a drafting arrangement 69, spun into a yarn 70 in the spinning box 5 and supplied to a yarn bobbin 68 via a thread transfer device 67 by means of take-off rollers 64. The term spinning tension F_s is understood in this context to mean the force F_s, to be given in the units [N] or [cN], which acts on the yarn between the spinning box 5 and take-off 63.

For a further explanation, then, reference is made to FIG. 2. The spinning box 5 has a swirl chamber 10 in which the air flowing in through the air inlet port 61 generates a swirl flow which rotates around edge fibers 62 located on the surface of the fiber composite 1 and thereby spins the fiber composition 1 into a yarn 70. The abovementioned spinning tension F_s is caused mainly by the run-on of edge fibers 62 at the inlet mouth 9 of the spindle 7. These forces consequently have a particular characteristic which is basically different from the tension characteristics of other methods, such as, for example, ring, rotor or two-nozzle spinning.

Since, in the jet spinning method (an example of a machine corresponding to this may be gathered from the publication EP 1 335 050 A2 [2]), essentially the rotating fiber ends or the subsequent wrap-around fibers of the spun yarn 70 cause the spinning tension F_s, there is a direct correlation between the spinning result, that is to say the yarn produced, and the actual measurable spinning tension F_s. The term “spinning result” embraces the properties of yarn quality and spinning process reliability. By reduction in the spinning speed, the spinning tension can also be reduced to values which permit an improved spinning result. However, in the case of the high spinning performances required, with spinning speeds v_L>300 m/min required for this purpose, this, on the one hand, is not practicable and, on the other hand, leads to an impairment of the spinning result for the following reason: the edge fibers should ideally be spun into a yarn 70 at an angle of approximately 45° around the fiber composite 1. This angle, then, taking into account the air vortex, is determined essentially by the spinning speed, and this must therefore move within a customary range toward 300 m/min.

The object on which the present invention is based is, therefore, to specify a method for spinning a yarn in a jet spinner, in which, despite high spinning speeds, an ideal spinning tension can be set, with the result that an optimal spinning result, particularly with regard to the yarn quality, is achieved.

This object is achieved by means of the method specified in patent claim 1.

By virtue of the method parameters according to the invention, according to which the spinning tension F_s has a value range F_s<20 cN, a method is provided which in the case of high speeds allows a spinning tension which ensures, in particular, high reliability, so that, for example, the risk of yarn breaks is greatly reduced.

In order to achieve this sought-after value range for the spinning tension F_s and consequently to optimize the spinning result, for example, one or more of the following measures may be taken:

• • Adaptation of the spinning draft s_v between the drafting arrangement exit and the take-off rollers downstream of the spinning box, so that s_v≦1.0.
  • Adaptation of the compressed air pressure p of the air which flows into the swirl chamber to values of 3 to 6 bar, preferably of 4 to 5 bar.
  • Achievement of a high suction action by the air vortex generated in the swirl chamber, in order to suck in air from the gusset region downstream of the exit nip line of the drafting arrangement. There are various configuration possibilities for this purpose which are described in the embodiments listed below.
  • Optimal configuration of the swirl chamber. There are various configuration possibilities for this purpose, too, which are likewise specified in the exemplary embodiments listed below.

Moreover, advantageous refinements of the invention are specified in further dependent claims.

The invention is explained in more detail below by way of example, with reference to drawings in which:

FIG. 1 shows a diagrammatic illustration of the components of a jet spinner;

FIG. 2 shows a partial illustration of a spinning box, particularly to explain the entry of a fiber composite into the spindle;

FIG. 3 shows a fiber conveyance duct with a tunnel lining;

FIG. 4 shows a more detailed illustration of the shoulder of the tunnel lining and, of the air inlet port in the first embodiment;

FIG. 5 shows a more detailed illustration of the shoulder of the tunnel lining and of the air inlet port in a second embodiment;

FIG. 6 shows an illustration of a fiber guide face having a deflection edge, in a fiber guide duct.

FIG. 1 shows a diagrammatic illustration of the components of a jet spinner: the speeds which occur are shown by v_exit and v_take-off, and reference symbol 71 indicates the location at which the method parameter, spinning tension F_s, relevant to this invention occurs.

FIG. 2 shows a detailed illustration of a spinning box 5, such as corresponds to the prior art and has already been explained in the description introduction.

FIG. 3 shows a first configuration within a spinning box 5 to ensure that the desired spinning tension F_s is achieved. The spinning box 5 has a fiber guide element 3 and, thereafter, a spindle 7 with a yarn guide duct 8. The fiber guide element 3 is surrounded by a hollow-cylindrical tunnel lining 17. The tunnel lining 17 may be produced in one piece or in a plurality of pieces. The fiber conveyance duct 4 is encased by the tunnel lining 17. The tunnel lining 17 is shaped in such a way that a shoulder 18 toward the swirl chamber housing 15 occurs at the end of the fiber conveyance duct 4. The end face of the shoulder 18 serves as a guide face for the fluid, normally air, emerging from the jet nozzles 13.1. The outlet ports for the jet nozzles for the fluid into the swirl chamber 14.1 have an elliptic shape. In this case, the fiber guide element 3 and the associated tunnel lining 17 are installed in the swirl chamber housing 15. As is also shown in the following FIGS. 4 and 5, the swirl chamber housing 15 does not necessarily also have to comprise the fiber guide element 3 and its tunnel lining 17. The two last-mentioned elements may also have a specific housing which is contiguous to the swirl chamber housing 15 (see FIG. 5). Overall, four individual jet nozzles 13.1 are provided. The jet nozzles 13.1 have an angle of inclination a with respect to the fiber transport-direction 19. The angle of inclination a lies in a value range of 45° to 88°. In this first embodiment, the angle of inclination of the end face of the shoulder 18 with respect to the material flow direction has the same amount. In this case, it can be seen clearly how that end face 20 of the fiber guide element 3 which is contiguous to the swirl chamber 14.1 has the same angle of inclination with respect to the material flow direction 19 as the bores of the jet nozzles 13.1.

FIGS. 4 and 5 show two further embodiments of the shoulder of the tunnel lining to ensure that the desired spinning tension F_s is achieved. The swirl chamber housing 15 in this case adjoins a housing 32 for the fiber guide element 3 and the tunnel lining. The embodiment shown according to FIG. 4 possesses a tunnel lining 26 which is shaped in such a way that the shoulder 29 occurs at the end of the fiber conveyance duct 4 with an angle of inclination β. The tunnel lining 26 preferably has a thickness (a) which lies in a value range of 0.1 to 3 mm. The bore of the jet nozzle 13.1 is arranged in the immediate vicinity of the end face of the shoulder 29 in the swirl chamber housing 15. The shoulder 29 is in this case arranged so near to the opening to the jet nozzle 13.1 that the end face of said shoulder serves as a guide face for the emerging flow. The shoulder 29 is arranged in alignment with the bore which is itself arranged in alignment with the inner face or surface area of the swirl chamber 14.1, so that the bore 13.1 runs “tangentially in alignment” into the inside of the swirl chamber housing 15 or tangentially into the swirl chamber 14.1. However, angles of inclination α with respect to the material flow direction which lie in a value range of 60° to 70° are preferred. The angle of inclination β of the end face of the shoulder 29 may have a different value from the angle of inclination α. The most suitable angle of inclination β can best be determined empirically for the actual application. Tests have shown that, in most cases, an angle of inclination β which has the same value as the angle of inclination α is suitable. However, a design with ≠#β is also possible. In FIG. 5, the bore 13.1 is arranged at a distance d from the shoulder 31 of the tunnel lining 28. The distance d in this case lies in a value range of 0.5 mm to 2 mm, preferably 0.9 mm to 1.3 mm, preferably 1.1 mm.

FIG. 6 shows a cross section through a spinning box 5 in another embodiment, in order to achieve the method parameter value according to the invention of the spinning tension F_s<20 cN. The fiber guide element 3c shown has a fiber guide face 16 with a deflection point 72. The deflection point 72 is formed by the fiber guide face 16: the fiber guide face 16 in this case consists of two planar faces, the common intersection line of which forms the deflection point 72. By virtue of this configuration of the fiber guide face 16, the fibers of the fiber composite 1 (not illustrated in FIG. 6) are guided in an arrangement in which they lie essentially flat next to one another. The fiber discharge edge 6 also makes a contribution to this flat arrangement. The deflection point 72 is in this case dimensioned such that the fibers of the fiber composite 1 are deflected in such a way that the free fiber ends of the fibers which are located in the fiber composite can lift off. At the deflection point 72, both the front and the rear fiber ends above all of those fibers which are located on the surface of the fiber composite 1 or directly below it are lifted off. At the deflection point 72, both front and rear fiber ends are lifted off. By fiber ends being lifted off at the deflection point 72, the number of free fiber ends in the fiber composite rises. The term “free fiber ends” is to be understood as meaning those ends which do not lie within the staple fiber composite or are not connected to other fibers and can consequently be picked up by the swirl flow. Due to the rise in the number of free fiber ends, the number of wrap-around fibers in the yarn and the quality of the spinning process per se are increased. This configuration of the fiber guide face surprisingly has a further advantage, as compared with the prior art. The result of the reduction in the cross section A of the fiber conveyance duct 4 within a region was that the air quantity V flowing through was surprisingly increased. Owing to the increased air quantity V, fiber guidance between the exit rollers and the entrance of the fiber guide element 3c, that is to say upstream of the fiber guide element 3c, can be appreciably improved. The number of production interruptions caused by breaks in the fiber composite directly downstream of the exit rollers, can thereby be reduced. It was likewise possible to detect a measurable improvement in the yarn quality. Tests have shown that particularly good results are achieved when the cross section A of the fiber conveyance duct 4 remains constant as far as the deflection point 72 and, beyond the deflection point or additional edge 72, the following cross section B of the fiber conveyance duct 15 increases. The area of the cross section A of the fiber conveyance duct 4 as far as the deflection point 72 preferably lies in a value range of 0.5 mm² to 10 mm². Table 1 contains dimensional particulars relating to the variables C, D, E and F contained in FIG. 6, which make it possible to have a spinning tension F_s<20 cN.

TABLE 1
Dimensional particulars relating to the embodiment according to FIG. 6
			Preferred
	Symbol	Value	value
Description	unit	range	range
Horizontal distance between	C	1 . . . 4	1.5 . . . 2.5
deflection point 72 and fiber	[mm]
discharge edge 6
Vertical distance between	D	0.2 . . . 1	0.4 . . . 0.7
deflection point 72 and fiber	[mm]
discharge edge 6
Horizontal distance between	E	0.1 . . . 1	0.3 . . . 0.7
fiber discharge edge 6 and inlet	[mm]
mouth 9
Vertical distance F between	F	10 . . . 40
fiber discharge edge 6 and	[in %
center line of yarn guide duct 8	diameter
	of yarn
	guide
	duct]

In order to make it possible to have the desired spinning tension F_s<20 cN, the air (fluid) to be supplied preferably has a pressure p which lies in the following value range:
3 bar<p<6 bar.

In a further refinement of the present invention, a spinning draft S_v≦1.0. In this case, the spinning draft S_v is defined by the following quotient:
S_v:=v_take-off/v_exit.

In this case:

• • v_take-off means the rotational speed of the take-off rollers;
  • v_exit means the rotational speed of the exit rollers.

The condition S_v≦1.0 means that the circumferential speed of the take-off rollers 64 must be at most equal to that of the exit rollers 2 of the drafting arrangement 69. It is therefore possible to obtain this condition because, during the spinning of the fibers, the fiber composite slightly loses length. S_v in this case preferably lies in the range of 0.96 to 1.0.

A further preferred embodiment of the invention arose from numerous spinning tests. Moreover, in these spinning tests under various operating conditions (such as different spinning speeds and yarn finenesses), optimizations of the elements of the spinning device and analyses of the spun yarn quality, it was possible surprisingly to find a relation which, on the basis of the operating conditions of spinning speed and yarn fineness, predetermines an optimal spinning tension F_s,optimal: $\begin{array}{c}{F}_{s,\mathrm{optimal}}=6.6\mathrm{cN}+0.05\frac{\mathrm{cN}g}{m}·\left(100\frac{m}{g}-\mathrm{Nm}\right)+\\ 0.0096\frac{\mathrm{cN}\min }{m}·\left(v_L-350\frac{m}{\min }\right)\end{array}$
in which:

• • F_s,optimal=optimal spinning tension in [cN]
  • Nm=yarn fineness in metric number [m/g]
  • v_L=yarn delivery speed in [m/min]

This relation is not a physical formula which necessarily arises due to the operation of the spinning station. Instead, this formula indicates the optimal spinning tension which is to be achieved on account of the operating conditions of yarn delivery speed at the exit of the spinning machine and desired yarn fineness (what is known as the “metric number” of the spun yarn in [m/g]) by the adaption of the most diverse possible elements of the spinning machine. In other words, if a spinning machine is operated at a specific yarn delivery speed and a specific yarn fineness is established (for example, by setting the drafting arrangement), this does not mean that this automatically results in a spinning tension according to the abovementioned relation. A completely different actual spinning tension F_s will therefore be obtained. A yarn quality will also likewise not be optimal. What therefore has to be done is to vary the actual measurable spinning tension F_s by means of various measures described on the previous pages, such that its value corresponds to the amount of the optimal spinning tension F_s,optimal calculated by means of the above formula. This results in a yarn of optimal quality.

The following table 2 contains in the middle column the optimal spinning tension F_{s, optimal} calculated from the metric number and spinning speed; the spread values defined as ±20% are given in the first two columns.

TABLE 2
Table of values with the calculated optimal spinning tension Fs,optimal
Spinning	Spinning
tension	tension
Fs,optimal	Fs,optimal
lower limit	upper limit	Spinning	Metric	Spinning
(−20%) in	(+20% in	tension	number mN	speed vL
[cN]	[cN]	Fs,optimal [cN]	[g/m]	[m/min]
7.664	11.496	9.580	50	400
7.110	10.666	8.888	60	380
6.480	9.720	8.100	70	350
5.696	8.544	7.120	80	300

The teaching according to the invention can be implemented by means of a free combination and adaption of the configuration, explained above in FIGS. 3 to 6, of the spinning box 5 and of its spinning box elements, such as, for example, the fiber inlet edge 31, fiber discharge edge 29 or deflection point 72, and also freely by means of the abovementioned operating parameters of pressure and spinning draft. By the elements mentioned in the preceding description and claimed below being adapted, it is possible to bring the actual measurable spinning tension F_s to a value F_s<20 cN. In a preferred embodiment of the invention, the actual measurable spinning tension F_s even has a value which corresponds to the amount according to the abovementioned formula for F_s,optimal.

LIST OF REFERENCE SYMBOLS USED IN FIGS. 1 TO 6

• 1 Fiber, fiber composite, staple fiber composite
• 2 Pair of exit rollers, exit rollers
• 3, 3c Fiber guide element
• 4 Fiber guide duct, fiber conveyance duct
• 5 Spinning box
• 7 Spindle
• 8 Yarn guide duct
• 9 Inlet mount of the spindle 7
• 10 Swirl chamber
• 11 Inflowing air
• 12 Drafting arrangement
• 13 Fluid device
• 13.1 Jet nozzles
• 14 Space
• 14.1 Swirl chamber
• 15 Swirl chamber housing
• 16 Fiber guide face, planar fiber guide face
• 17 Tunnel lining
• 17.1 Half-shell of the tunnel lining
• 18 Shoulder
• 19 Material flow direction, transport direction
• 20 End face of the fiber guide element 3 in the swirl chamber
• 23 Center line of the yarn guide duct
• 26 Tunnel lining
• 28 Tunnel lining
• 29 Shoulder with angle of inclination β
• 31 Shoulder
• 32 Housing for fiber guide element and tunnel lining
• 60 Spinning station
• 61 Inlet port air flow
• 62 Edge fibers
• 63 Take-off
• 64 Take-off rollers
• 65 Friction roller
• 66 Thread stop motion
• 67 Thread transfer device
• 68 Yarn bobbin
• 69 Drafting arrangement
• 70 Yarn
• 71 Location where the spinning tension occurs and is measurable
• 72 Deflection point

LIST OF REFERENCE SYMBOLS USED IN FIG. 7

• 20 Nozzle block
• 21 Jet nozzles
• 22 Swirl chamber
• 23 Ventilation duct
• 25 Conveying direction of the suction-intake air
• 26 Fiber conveyance duct
• 27 Fiber conveyance element
• 28 Fiber guide face
• 29 Fiber discharge edge
• 30 End face
• 32 Fiber reception edge
• 32 Spindle
• 36 Cone of fiber conveyance element 27
• 37 Carrying element for a fiber conveyance element 27
• 38 Center line of jet nozzles 21 and blowing direction
• 39 Fiber conveyance roller
• 45 Yarn guide duct
• 47 Center line

LIST OF SYMBOLS USED

• v_take-off Rotational speed of the take-off rollers
• v_exit Rotational speed of the exit rollers
• α Angle of inclination of the jet nozzles with respect to the fiber or material transport direction
• β Angle of inclination of the shoulder with respect to the material flow direction 19
• a Thickness of the tunnel lining 26
• d Distance between jet nozzles 13.1 and shoulder 31
• A Cross section upstream of deflection point
• B Cross section downstream of deflection point
• C Distance parallel to the center line 23 from the deflection point 72 as far as the fiber discharge edge 6
• D Distance vertically with respect to the center line 23 from the deflection point 72 as far as the discharge edge 6
• E Distance parallel to the center line 23 from the fiber discharge edge 72 as far as the inlet mouth 9 of the spindle 7
• F_s Spinning tension in [cN]
• F_s,optimal Optimal spinning tension in [cN] according to formula
• F Distance vertically with respect to the center line 23 from the fiber discharge edge 72 as far as the center line 23 of the yarn guide duct 8
• G Width of the reduced fiber discharge edge 6
• Nm Metric number in [m/g], length per mass; reference in [1]
• p Pressure in [Bar]
• S_v Spinning draft
• v_L Spinning speeds in m/min

LIST OF ABBREVIATIONS USED

ISO International Standard Organization

LIST OF UNITS USED

Bar   Pressure; ISO dimension unit
N, cN Newton, Centi-Newton; ISO dimension unit
m     Meter; ISO dimension unit
min   Minute

LITERATURE SOURCES

• [1] Fachwissen Bekleidung, 5th edition ISBN 3-8085-6205-6; 1998 Verlag Europa-Lehrmittel, Nourney, Vollmer GmbH & Co., 42781 Haan-Gruiten
• [2] EP 1 335 050 A2 Textile processing machine with a fiber conveyance duct and with a fiber guide face; Maschinenfabrik Rieter AG, 8406 Winterthur.

Claims

1. A method for producing a yarn (70) from a fiber composite (1) in a jet spinner which contains:

a pair of exit rollers (2);

a spinning box (5), following the pair of exit rollers (2) in the spinning direction, for spinning a yarn (70), the spinning box (5) containing: a swirl chamber (14.1) having a spindle (7) and containing at least one air inlet port (13.1, 61);

a following take-off (63), containing take-off rollers (64), for leading away the yarn (70), a spinning tension Fs being exerted on the yarn (70) by the latter being led away;

Characterized by the method parameter:

the spinning tension Fs has the following value range: Fs<20 cN.

2-13. (canceled)