WO2024156592A1

WO2024156592A1 - Method for operating an air-jet spinning machine and air-jet spinning machine

Info

Publication number: WO2024156592A1
Application number: PCT/EP2024/051166
Authority: WO
Inventors: Oliver Straub; Martin Janousek
Original assignee: Rieter Ag
Priority date: 2023-01-26
Filing date: 2024-01-18
Publication date: 2024-08-02
Also published as: DE102023101946A1

Abstract

The invention relates to a method for operating an air-jet spinning machine with multiple spinning positions, wherein the spinning positions each comprise a spinning nozzle (1), which is supplied with a fibre composite (3) during a spinning operation using a delivery device (2) of the respective spinning position, wherein the fibre composite (3) is made to rotate within the spinning nozzle (1) using a swirling air flow, such that a yarn (4) is formed from the fibre compsite (3), and wherein the yarn (4) is withdrawn from the spinning nozzle (1) in a predefined spinning direction using a withdrawal device (5) of the respective spinning position. According to the invention, the ratio between the delivery speed of the delivery device (2), with which the fibre composite (3) is supplied to the spinning nozzle (1), and the withdrawal speed of the withdrawal device (5), with which the yarn (4) is withdrawn from the spinning nozzle (1), determining the spinning tension, is altered at least at one of the spinning positions during the spinning operation. The invention also relates to an air-jet spinning machine with multiple spinning positions.

Description

Method for operating an air spinning machine and air spinning machine

The present invention relates to a method for operating an air spinning machine with several spinning stations, wherein the spinning stations each comprise a spinneret to which a fiber structure is fed during a spinning operation with the aid of a delivery device of the respective spinning station, wherein the fiber structure is given a rotation within the spinneret with the aid of a vortex air flow so that a yarn is produced from the fiber structure, and wherein the yarn is drawn out of the spinneret in a predetermined spinning direction with the aid of a draw-off device of the respective spinning station.

Furthermore, an air spinning machine with several spinning stations is proposed, wherein the spinning stations each comprise a spinneret to which a fiber structure is fed during a spinning operation with the aid of a delivery device of the respective spinning station, wherein the fiber structure is given a rotation within the spinneret with the aid of a vortex air flow so that a yarn is produced from the fiber structure, and wherein the yarn is drawn out of the spinneret in a predetermined spinning direction with the aid of a draw-off device of the respective spinning station.

Air spinning machines of this type are used to produce a yarn from an elongated fiber structure with the aid of a vortex air flow generated by corresponding air nozzles within the vortex chamber. For this purpose, a fiber structure is conveyed in the direction of the spinneret with the aid of a delivery device, which is preferably and in particular also in the case of the present invention formed by a pair of output rollers of a drafting system arranged upstream of the spinneret in the spinning direction, and is sucked in by it by means of negative pressure. The fiber structure finally reaches the interior the spinneret and there into the area of the inlet opening of a spindle-shaped yarn forming element. The outer fibers of the fiber structure are wound around the inner fibers (core) in the area of the inlet opening with the help of the vortex air flow generated by the air nozzles, so that a stable yarn is created as a result, which is finally drawn out of the vortex chamber via the draw-off channel with the help of a draw-off device arranged outside the spinneret and wound onto a tube by means of a winding device (the elements or features mentioned are preferably also implemented in the spinneret or air spinning machine described below).

The object of the present invention is to exert a positive influence on the yarn properties or the productivity of the air spinning machine during the spinning process.

The problem is solved by a method and an air spinning machine having the features of the independent patent claims.

In principle, the air spinning machine according to the invention has a spinneret for producing a yarn, as well as a delivery device for a fiber structure upstream of the spinneret and a take-off device downstream of the spinneret for the yarn produced in the spinneret. The delivery device is preferably a pair of output rollers of a drafting device upstream of the spinneret in the spinning direction, with the help of which the fiber structure is drawn to a defined fineness or uniformity before entering the spinneret. Of course, the delivery device can also be formed by a pair of delivery rollers in addition to a drafting device.

The take-off device is preferably designed as a pair of take-off rollers, whereby the yarn is clamped between the two take-off rollers, which are driven by a drive, and is thereby drawn out of the spinneret is drawn off. A winding device is preferably arranged downstream of the drawing-off device, with the aid of which the drawn-off yarn is wound onto a tube to produce a yarn spool (hereinafter also sometimes referred to as spool).

According to the invention, the method for operating an air spinning machine is characterized in that the ratio determining the spinning tension between the delivery speed of the delivery device with which the fiber structure is fed to the spinneret and the withdrawal speed of the withdrawal device with which the yarn is withdrawn from the spinneret is changed during spinning operation at least at one of the spinning stations. Preferably, the spinning tension is changed at the individual spinning stations simultaneously or individually.

Since the composite of the fibre structure entering the spinneret and the yarn drawn off from the spinneret is a continuous fibre strand, the ratio between the draw-off speed of the draw-off device (i.e. the speed of the yarn drawn off by the draw-off device) and the delivery speed of the delivery device (i.e. the speed of the fibre structure conveyed by the delivery device) influences the so-called spinning tension (the spinning tension is the longitudinal tension acting on the fibre strand mentioned).

Normally, yarns with defined properties (hairiness, yarn thickness, length-related yarn weight, etc.) are produced at the individual spinning stations over a certain period of time or until a certain number of yarn spools have been produced. In other words: in the state of the art, it is usual that for a certain batch (specified fiber material, yarn with desired yarn properties, certain number of finished spools) before the spinning process begins, A spinning tension is selected for the spinning stations involved in the batch, which is maintained until the end of the batch.

In contrast to this, the present invention provides that the spinning tension mentioned is changed in a targeted and controlled manner during the spinning process and thus during the production of the respective batch in order to influence the yarn properties or the productivity of the respective spinning station. The spinning tension can be changed suddenly (i.e. within a few milliseconds) or over a longer period of time (i.e. over a period of more than 1 second, preferably more than 10 seconds).

The present invention therefore provides that a spinning tension, preferably the same for all spinning stations, is selected for all spinning stations involved in a batch at the beginning of the batch, wherein the spinning tension is subsequently changed as required at individual or all spinning stations during the completion of the batch.

In any case, the spinning tension affects one or more characteristics of the yarn, as it influences the behaviour of the fibre ends in the area of the inlet opening of the yarn forming element and also the longitudinal tension acting on the drawn-off yarn.

It is advantageous if the spinning tension is changed during spinning operation if the value of a previously defined parameter of the yarn produced by the spinning station falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value. The respective parameter is preferably monitored with a yarn sensor that is part of the spinning station. Possible parameters of the yarn are listed below, such as hairiness, thickness or length-related mass. However, what is said below also applies to other parameters that are not explicitly mentioned (for example, the yarn speed at which the yarn passes the yarn sensor of the spinning station would be conceivable).

In general, it should be noted for the entire description that when a lower and an upper limit are mentioned, both limit values or just one of the mentioned limit values can be taken into account in the method according to the invention. It is therefore not necessary to take a first and a second limit value into account.

Likewise, the spinning tension could be changed depending on one or more parameters that do not directly characterize the yarn. For example, it would be conceivable to use the yarn breakage rate (i.e. the number of yarn breaks per unit of time) at one or more spinning stations or the productivity of one or more spinning stations (i.e. the length or weight of the yarn produced per unit of time) as a basis for changing the spinning tension.

It is particularly advantageous if the spinning tension is changed during spinning if the hairiness of the yarn produced by the spinning station falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value. The hairiness of a yarn is a measure of the protrusion of free fiber ends, i.e. the more fiber ends protrude from the yarn at the side, or the longer the fiber ends are that protrude from the yarn, the higher the hairiness. If the hairiness falls below a certain first limit value or reaches the first limit value, this can be an indication that the spinning tension is too high or too low (this depends, among other things, on the material of the fiber band). The same applies applies if the hairiness at one or more spinning stations exceeds or reaches a previously defined second limit value. Whether the hairiness is reduced or increased by increasing the spinning tension depends on further settings at the spinning station or the material and properties (e.g. thickness) of the fiber material that is fed to the respective spinning station for yarn production. There are therefore cases in which the spinning tension is increased in order to reduce the hairiness. Cases are also conceivable in which the spinning tension must be reduced in order to reduce the hairiness.

It is also advantageous if the spinning tension is changed during spinning operation if the thickness of the yarn produced by the spinning station falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value. Here, too, it can depend on the fiber material to be spun and other parameters of the respective spinning station whether the spinning tension has to be increased or decreased in order to increase or decrease the thickness of the yarn produced. As a rule, increasing the spinning tension will lead to a thinner yarn because the fibers of the fiber material or the yarn produced from it are pulled apart more. The spinning tension is therefore preferably reduced if the thickness of the yarn falls below or reaches a previously defined first limit value and increased if the thickness exceeds or reaches a previously defined second limit value.

It is particularly advantageous if the spinning tension is changed during spinning if the linear mass of the yarn produced by the spinning station falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value. It is particularly useful to reduce the spinning tension if the linear mass of the yarn is to be increased. Likewise the spinning tension should be increased if the linear mass of the yarn exceeds or reaches the first limit value mentioned above.

It is also advantageous if the spinning tension is changed when the hairiness, thickness and/or length-related mass of the yarn produced by the spinning station (or another characteristic of the yarn or the spinning station) falls below or exceeds a previously defined limit by a defined amount and/or for a defined period of time. It is therefore often not necessary and also not sensible to change the spinning tension immediately if a previously defined limit is exceeded or undershot. Rather, it is advantageous if the spinning tension is only changed when the respective characteristic at the respective spinning station exceeds or falls below a corresponding limit over a longer period of time (e.g. at least 10 seconds). Certain deviations from a defined limit can also be tolerated, so that the spinning tension does not have to be adjusted if a limit is exceeded or undershot even the smallest time. For example, it would be conceivable that the spinning tension at a spinning station is only changed when a defined limit value of a defined parameter is exceeded or undercut by an amount X and for a period of time Y at this spinning station.

It is also conceivable that the spinning tension is changed at individual or multiple spinning stations if defined parameters of the yarn at multiple spinning stations deviate from a specified reference value or fall below or exceed a specified limit. Alternatively, the spinning tension can also be changed individually at each spinning station, whereby when determining whether the spinning tension is changed, only parameters of the yarn at precisely this spinning station can be taken into account. It is also advantageous if the spinning tension is changed during spinning by an amount of 0.1% to 10.0% of the spinning tension specified for the start of spinning. Compliance with the above range ensures that the spinning tension is not changed so much that the change has a negative effect on the yarn properties or that the yarn production is stopped (i.e. the yarn separates from the fiber material fed to the spinning station).

It is also advantageous if the spinning tension is changed during spinning by changing the take-off speed while keeping the delivery speed constant. This has the advantage that the fiber structure can be fed to the spinneret at a constant delivery speed.

This is particularly advantageous if the delivery speed is specified by a pair of delivery rollers which is part of a drafting system of the spinning station or is arranged between the drafting system and the downstream spinneret. If the pair of delivery rollers is operated at a constant delivery speed, the drafting system can also be operated under constant conditions. In particular, the drafting system comprises several pairs of rollers, whereby the rotational speed of the pairs of rollers can be kept constant during the spinning process and when the spinning tension changes.

Of course, the speed of the tube onto which the yarn is wound should also be changed depending on the change in the take-off speed, so that the yarn does not break between the take-off device and the rinsing device or the yarn sags.

It is advantageous if the take-off speed is changed during spinning by an amount that is 0.1% to 10.0% of the speed required for the start of spinning operation. In general, within the scope of the invention, the start of spinning operation at a spinning station is understood to mean the start of a new batch at the respective spinning station or the start-up of the spinning station after a longer standstill. The range mentioned for changing the take-off speed has proven to be useful in order to have a positive influence on the yarn properties on the one hand and to prevent the spinning process from being interrupted by the yarn separating from the fiber structure fed to the spinning station on the other.

Furthermore, it is advantageous if the change in spinning tension is reversed if the result desired by changing the spinning tension does not occur, in particular within a defined period of time. The desired result can be, for example, an increase and/or decrease in one of the characteristics of the yarn (such as hairiness or fineness or one or more of the other characteristics mentioned above or below). It is also conceivable that after a change in spinning tension, it is monitored whether the productivity or the number of yarn breaks at the spinning station at which the spinning tension was changed exceeds or falls below a defined limit value. If the desired result does not occur after the change in spinning tension, this is a sign that the change in spinning tension is not suitable for achieving the desired result. In this case, the spinning tension is reset to the value that existed before the change at the corresponding spinning station.

Alternatively, it is also conceivable that the amount of the change is reduced or increased if the desired result from the change in the spinning tension does not occur, in particular within a defined period of time. In this case, the spinning tension is not reset to the value that existed before the change in the spinning tension at the corresponding spinning station. was present. Rather, only the amount of the change is changed. Then it is checked again whether the desired result has been achieved or not. After this, the spinning tension can either be changed back to the previous value or the original value at the corresponding spinning point, or the spinning tension can be increased or decreased again by a defined amount until the desired result is achieved.

At this point, it should be noted generally for the entire description that the spinning tension at all or individual spinning stations can also be reduced or increased with the purpose of increasing productivity at the respective spinning stations or reducing the occurrence of defined yarn defects over time. For example, it would be conceivable to increase or reduce the spinning tension at individual or several (preferably all) spinning stations until the yarn breakage rate at selected or all affected spinning stations falls below or reaches a defined limit.

It is also advantageous if a message is issued to an operator of the air-jet spinning machine if the desired result from the change in the spinning tension does not occur, in particular within a defined period of time. The message can be issued if the desired result does not occur at all or a group of spinning stations at which the spinning tension was changed. It is also conceivable that individual messages are issued, each individually for the spinning stations at which the spinning tension was changed. The message can be optical or acoustic. For example, it would be conceivable that a light signal (e.g. in the form of an LED) is activated at the affected spinning station or at a central control. A message could also be issued on a display of the respective spinning station or a central display of the air-jet spinning machine, which informs the operator of the air-jet spinning machine. machine signals that the change in spinning tension resulted in a defined change in one or more selected parameters at one or more spinning stations. It is also conceivable that the message contains the information that the change in spinning tension at one or more spinning stations did not lead to the desired result.

It also has advantages if the spinning tension is changed at several spinning stations together during spinning operation. For example, it would be conceivable to change the spinning tension at all spinning stations that are involved in the production of a common batch of yarn spools. It would also be conceivable to change the spinning tension at all spinning stations where it has been detected, for example with the help of a yarn sensor, that one or more parameters do not correspond to the desired specifications. Likewise, one or more parameters of the yarn produced at a selected spinning station could be monitored and the corresponding measured value of the parameter used to change the spinning tension at other spinning stations as well. In this case, the selected spinning station would act as the reference spinning station.

Alternatively, it can also be advantageous if the spinning tension is changed individually at individual spinning stations during spinning operation and preferably independently of the other spinning stations. In this case, one or more parameters of the yarn or spinning station are individually monitored at the respective spinning station and the spinning tension is changed if the parameter(s) fall below or exceed a defined limit value or reach(s) one of the limit values.

In general, the spinning tension does not have to be changed immediately if one or more limit values are exceeded or undershot. values or when one is reached. Rather, it is also conceivable that the spinning tension is only changed when the limit value(s) is exceeded or not reached for a defined period of time.

It is also extremely advantageous if the spinning tension is changed during spinning in order to produce an effect yarn. In this context, it would be conceivable, for example, that the spinning tension is repeatedly increased and decreased within defined limits and at defined time intervals in order to change the characteristics of the yarn produced. If, for example, the spinning tension were repeatedly reduced for a short time at short intervals and then increased again to an initial value, a yarn could be produced which has defined thick spots depending on the time intervals and the duration of the change in the spinning tension. It would also be possible to change the hairiness or thickness of the yarn only for a short time by changing the spinning tension, so that a yarn with alternating high and low hairiness or with alternating thin and thick spots is produced. In general, it is therefore conceivable to change the spinning tension during spinning in such a way that the yarn is not produced with constant yarn properties, but rather with yarn properties that change over the length of the yarn. The spinning tension is preferably changed in such a way that the corresponding yarn properties change continuously.

The air spinning machine according to the invention comprises several spinning stations, whereby the spinning stations each comprise a spinneret to which a fiber structure is fed during spinning operation with the aid of a delivery device of the respective spinning station. The spinneret has an internal swirl chamber and a yarn forming element protruding into the swirl chamber. With the aid of air nozzles, the fiber structure within the spinneret is given a rotation by generating a swirl air flow, so that a yarn is created from the fiber structure. The yarn thus produced is finally With the help of a take-off device, the yarn is drawn out of the spinneret in a predetermined spinning direction via a take-off channel of the yarn forming element of the respective spinning station and wound onto a tube, so that a yarn spool is created.

The air spinning machine according to the invention is characterized in that the delivery device and the take-off device are operatively connected to a control which is designed to control the delivery device and/or the take-off device in such a way that the ratio determining the spinning tension between the delivery speed of the delivery device with which the fiber structure is fed to the spinneret and the take-off speed of the take-off device with which the yarn is taken off from the spinneret changes at least at one of the spinning stations during the spinning operation.

The respective spinning station is designed to change the spinning tension according to the previous and/or following description during the spinning operation. Furthermore, the general rule for the entire description is that the expression "during the spinning operation" means that the spinning tension is changed during the regular production of the yarn, i.e. after any piecing process has been carried out. Of course, it is also conceivable to change the spinning tension during the piecing process compared to a value that exists during regular yarn production.

If spinning errors occur during the spinning process (thick or thin spots in the yarn, yarn breakage, unsatisfactory supply of the fiber structure, etc.) or if the spinning machine is shut down for a certain period of time, a piecing process is necessary following the respective event that interrupts yarn production. In this process, the bobbin-side end of the yarn already produced (ie the end section of the last yarn section wound up before the interruption of yarn production) or an appropriately provided auxiliary thread is fed back against the actual spinning direction via the withdrawal channel into the vortex chamber and from there via the inlet to the area in front of the spinneret. The yarn is preferably fed back so far that it is in the area of the delivery device of the spinning station and is fixed by this. After the return, the yarn is brought into contact with the beginning of the provided fiber structure outside the spinneret by means of a service robot, a device in the spinning station or manually by mutual overlapping (the beginning of the fiber structure being formed by the area that is in the area of the delivery device at the start of the piecing process).

Finally, the yarn end and with it the beginning of the fiber structure are drawn into the interior of the vortex chamber by switching on the air jets and starting the take-off device and exposed to the vortex air flow there, whereby the delivery device is or was also put into operation at this time in order to convey the fiber structure or the yarn end towards the inlet of the spinneret. The connection or overlap area between the yarn end and the beginning of the fiber structure finally passes the inlet of the spinneret and, within the vortex chamber, the inlet opening of the yarn formation element. The spinning process is now continued as usual, i.e. the spinning station is operated in spinning mode again and produces a yarn.

Since the composite of the fiber strand entering the spinneret and the yarn drawn off from the spinneret is a continuous fiber strand, the ratio between the draw-off speed of the draw-off device (i.e. the speed of the yarn drawn off by the draw-off device) and the delivery speed of the delivery device (i.e. the speed of the fiber strand conveyed by the delivery device) during spinning and also during the piecing process influences the so-called spinning tension. It has now been shown that it is advantageous for a high-quality piecing if the spinning tension during the piecing process deviates, at least temporarily, from the spinning tension prevailing during spinning operation.

Advantageously, it can therefore be provided that the ratio between the take-off speed of the take-off device and the delivery speed of the delivery device, which determines the spinning tension, during the piecing process deviates at least temporarily from the corresponding ratio that prevails during spinning. In this way, the spinning tension can be optimally adapted to the piecing process, so that conditions are created that enable a piecing that is more stable or less visible than in the prior art. The quality, in particular the homogeneity, of the yarn produced can be improved as a result.

Finally, it is also conceivable that the respective spinning station has a yarn sensor with which the quality of the piecing (i.e. the connection point between the fiber structure and the yarn end) is monitored. Depending on the measurement data from the yarn sensor, the spinning tension can be adjusted before and/or during and/or after the fiber structure is connected to the yarn end. The aim here is to optimize relevant quality data, such as the tear resistance or hairiness, of the piecing by adjusting the spinning tension during the piecing process.

For example, it would be conceivable to reduce the spinning tension during the piecing process if the yarn sensor detects that the strength of the piecing is too low. It would also be conceivable to increase the spinning tension during the piecing process if the piecing is thicker than the rest of the yarn.

Of course, the system described can control the spinning tension adjust automatically, ie the control of the spinning station or the air spinning machine checks the measured values of the yarn sensor at regular intervals and adjusts the spinning tension regularly until the measured data of the yarn sensor are in a defined target range. This procedure can be carried out individually at each spinning station.

Furthermore, it is advantageous in principle (i.e. during spinning operation and/or during a piecing process) if the spinning tension is changed by changing either the delivery speed of the delivery device or the take-off speed of the take-off device or both speeds compared to an initial value or a value that existed before the change.

It is advantageous if the delivery device and the take-off device each have a separate drive. In particular, the drives should be individual drives so that the take-off speed and the delivery speed can be selected or changed independently of each other. This makes it possible to change the spinning tension either by changing the delivery speed or by changing the take-off speed or by changing both speeds differently during spinning.

The drives are preferably electric motors, for example stepper motors. Alternatively, it would also be conceivable for the delivery device and the withdrawal device to be operatively connected to a common drive, with the withdrawal device and/or the delivery device being connected to the drive via a gear, so that a change in the drive speed of the drive results in the delivery speed and the withdrawal speed changing by different amounts. It is also advantageous if the spinning stations each comprise a yarn sensor, with the aid of which one or more parameters of the yarn produced by the respective spinning station is monitored during spinning, the control being designed to control the delivery device and/or the take-off device on the basis of the measurement data from the yarn sensor. The yarn sensor can be designed to monitor one or more of the following parameters of the yarn or parameters of the spinning station having the yarn sensor: hairiness of the yarn, length-related mass of the yarn, thick or thin spots of the yarn, number of yarn breaks per yarn length or per unit of time, speed of the yarn, diameter of the yarn. The yarn sensor or the control connected to the yarn sensor can be designed to detect or monitor one or more of the parameters mentioned as absolute amounts or as a change over time compared to a reference value or an average value determined over a defined period of time.

Particular advantages are achieved if the control system is designed to operate the air spinning machine according to one or more of the process features described above or below.

Further advantages of the invention are described in the following embodiments. They show, schematically:

Figure 1 shows selected sections of a spinning station of an air spinning machine according to the invention during spinning operation, and

Figure 2 is a sectional view of a spinneret of a spinning station of an air spinning machine according to the invention.

Figure 1 shows a section of a spinning station of an air spinning machine according to the invention (the air spinning machine is of course a The air spinning machine can, if required, comprise a drafting system 8 with a plurality of drafting system rollers 9, which is supplied with a fiber structure 3, for example in the form of a doubled drafting belt. Furthermore, the spinning station shown comprises a spinneret 1, shown in more detail in Figure 2, with an internal swirl chamber 19, in which the fiber structure 3 or at least some of the fibers of the fiber structure 3 are given a rotation after passing through an inlet 13 of the spinneret 1 (the exact mode of operation of the spinning station is described in more detail below).

In addition, the spinning station has a take-off device 5 arranged downstream of the spinneret 1 and having, for example, two take-off rollers 10, and preferably a rinsing device (not shown) arranged downstream of the take-off device 5 for winding the yarn 4 leaving the spinning station onto a tube so that a bobbin 12 is formed. The spinning station according to the invention does not necessarily have to have a drafting device 8. The take-off rollers 10 can also be replaced by an alternative take-off device 5.

The spinning station shown generally works according to an air spinning process. To form the yarn 4, the fiber strand 3 is guided in a spinning direction S and with the aid of a delivery device 2 (which can be formed, for example, by the pair of output rollers of the drafting system 8) via a fiber guide element 14 having the aforementioned inlet 13 into the vortex chamber 19 of the spinneret 1. There it is given a rotation, ie at least some of the free fiber ends of the fiber strand 3 are caught by a vortex air flow that is generated by air nozzles 16 arranged accordingly in a vortex chamber wall surrounding the vortex chamber 19, the air nozzles 16 being fed with compressed air via an air duct 18 (e.g. annular and connected to an air supply line 17). At least some of the fibers are thereby drawn out of the fiber strand 3. Pulled out a little and wound around the tip of a yarn forming element 15 projecting into the vortex chamber 19.

Because the fiber structure 3 is drawn out of the vortex chamber 19 through an inlet opening 22 of the yarn forming element 15 via a withdrawal channel 20 arranged within the yarn forming element 15 and finally out of the spinneret 1 via an outlet 11, the free fiber ends are also drawn in the direction of the inlet opening 22 and wind themselves around the centrally running core fibers as so-called wrapping fibers - resulting in a yarn having the desired twist.

The compressed air introduced via the air nozzles 16 finally leaves the spinneret 1 via the exhaust channel 20 and a possibly present air outlet 21, which can be connected to a vacuum source not shown if required.

Furthermore, there is at least one yarn sensor 23 per spinning station, with the aid of which one or more parameters of the yarn 4 or a yarn break in the area of the spinning station can be monitored or detected. The yarn sensor 23 can be arranged between the take-off device 5 and the winding device or also between the spinneret 1 and the take-off device 5.

In order to be able to select or change the delivery speed and the withdrawal speed independently of each other, the withdrawal device 5 and/or the delivery device 2 can be operatively connected to a separate drive 7 (single drive), as indicated in Figure 1.

Preferably, the drives 7 of the extraction device and the delivery device 2 are operatively connected to a control 6, wherein the control 6 is designed to control the two drives 7 individually if necessary such that the ratio between the delivery speed and the take-off speed is changed in order to thereby change the spinning tension during the spinning operation.

Furthermore, the spinning station or individual components, such as the drives 7 or one or more drive units (not shown) of the drafting system 8 or the winding device, are operatively connected to the control 6, whereby the control 6 can in principle be part of the spinning station. It is also conceivable that the control 6 is a central control 6 that interacts with several spinning stations.

According to the invention, it is now provided that the spinning station-specific or central control 6 is designed to change the delivery speed and/or the take-off speed as required during the spinning operation in such a way that the spinning tension changes compared to an initial value.

By changing the spinning tension, one or more parameters of the yarn 4 can be influenced, such as its hairiness, or the productivity of the spinning station (amount of yarn produced per unit of time) or the number of yarn breaks per unit of time.

In particular, the spinning tension can be changed at individual or multiple spinning stations together within defined limits. It is also conceivable that the yarn sensor 23 can be used to monitor whether and to what extent the change in spinning tension has an influence on one or more parameters of the yarn 4 produced or the productivity of the spinning station or the yarn breakage rate. As a result, the quality or quantity of the yarn 4 produced at the spinning stations can be influenced and thus optimized by specifically influencing the spinning tension during spinning. With regard to possible embodiments of the change in spinning tension, reference is made to the above description, whereby individual features can be implemented individually or together.

The present invention is not limited to the embodiments shown and described. Modifications within the scope of the patent claims are possible, as is any combination of the described features, even if they are shown and described in different parts of the description or the claims or in different embodiments, provided that no contradiction with the teaching of the independent claims arises.

List of reference symbols

1 spinneret

2 Delivery device

3 Fibre bandage

4 yarn

5 Trigger device

6 Control

7 Drive

8 Drafting system

9 Drafting roller

10 Take-off roller

11 Outlet

12 Coil

13 Entrance

14 Fiber guide element

15 Yarn forming element

16 Air nozzle

17 Air supply line

18 Air duct

19 Vortex chamber

20 Exhaust channel

21 Air outlet

22 Inlet opening of the yarn forming element

23 Yarn sensor

S spinning direction

Claims

Patent claims

1 . Method for operating an air spinning machine with several spinning stations, wherein the spinning stations each comprise a spinneret (1) to which a fiber structure (3) is fed during a spinning operation with the aid of a delivery device (2) of the respective spinning station, wherein the fiber structure (3) is given a rotation within the spinneret (1) with the aid of a vortex air flow so that a yarn (4) is produced from the fiber structure (3), and wherein the yarn (4) is drawn out of the spinneret (1) with the aid of a draw-off device (5) of the respective spinning station in a predetermined spinning direction (S), characterized in that the ratio determining the spinning tension between the delivery speed of the delivery device (2) with which the fiber structure (3) is fed to the spinneret (1) and the draw-off speed of the draw-off device (5) with which the yarn (4) is drawn out of the spinneret (1) is changed during the spinning operation at least at one of the spinning stations.

2. Method according to the preceding claim, characterized in that the spinning tension is changed during the spinning operation when the amount of a previously defined characteristic value of the yarn (4) produced by the spinning station falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value.

3. Method according to the preceding claim, characterized in that the spinning tension is changed during the spinning operation when the hairiness of the fiber produced by the spinning station Yarn (4) falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value.

4. Method according to one of the preceding claims, characterized in that the spinning tension is changed during the spinning operation when the thickness of the yarn (4) produced by the spinning station falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value.

5. Method according to one of the preceding claims, characterized in that the spinning tension is changed during the spinning operation when the linear mass of the yarn (4) produced by the spinning station falls below a previously defined first limit value or exceeds a previously defined second limit value or reaches the first limit value or the second limit value.

6. Method according to one of the preceding claims, characterized in that the spinning tension is changed when the hairiness, the thickness and/or the linear mass of the yarn (4) produced by the spinning station falls below or exceeds a previously determined limit value by a defined amount and/or for a defined period of time.

7. Method according to one of the preceding claims, characterized in that the spinning tension is changed during the spinning operation by an amount which is 0.1% to 10.0% of the spinning tension determined for the start of the spinning operation.

8. Method according to one of the preceding claims, characterized in that the spinning tension is changed during the spinning operation by changing the take-off speed while maintaining the delivery speed.

9. Method according to one of the preceding claims, characterized in that the take-off speed is changed during the spinning operation by an amount which is 0.1% to 10.0% of the take-off speed determined for the start of the spinning operation.

10. Method according to one of the preceding claims, characterized in that the change in the spinning tension is reversed or the amount of the change is reduced or increased if the result desired by the change in the spinning tension does not occur, in particular within a defined period of time.

11. Method according to one of the preceding claims, characterized in that a message is issued to an operator of the air spinning machine if the result desired by changing the spinning tension does not occur, in particular within a defined period of time.

12. Method according to one of the preceding claims, characterized in that the spinning tension is changed during the spinning operation at several spinning stations together or at individual spinning stations individually and preferably independently of the remaining spinning stations.

13. Method according to one of the preceding claims, characterized in that the spinning tension is changed during the spinning operation in order to thereby produce an effect yarn.

14. Air spinning machine with several spinning stations, wherein the spinning stations each comprise a spinneret (1) to which a fiber structure (3) is fed during a spinning operation with the aid of a delivery device (2) of the respective spinning station, wherein the fiber structure (3) is given a rotation within the spinneret (1) with the aid of a vortex air flow so that a yarn (4) is produced from the fiber structure (3), and wherein the yarn (4) is drawn out of the spinneret (1) in a predetermined spinning direction (S) with the aid of a take-off device (5) of the respective spinning station, characterized in that the delivery device (2) and the take-off device (5) are operatively connected to a control (6) which is designed to control the delivery device (2) and the take-off device (5) in such a way that the ratio determining the spinning tension between the delivery speed of the delivery device (2) with which the fiber structure (3) is fed to the spinneret (1) is fed, and the withdrawal speed of the withdrawal device (5) with which the yarn (4) is withdrawn from the spinneret (1) changes at least at one of the spinning stations during the spinning operation.

15. Air spinning machine according to the preceding claim, characterized in that the delivery device (2) and the take-off device (5) each comprise a separate drive (7).

16. Air spinning machine according to claim 14 or 15, characterized in that the spinning stations each comprise a yarn sensor (23) with the aid of which one or more parameters of the chamois (4) produced at a respective spinning station is monitored during the spinning operation, wherein the controller (6) is designed to control the delivery device (2) and/or the take-off device (5) on the basis of the measurement data of the chamois sensor (23).

17. Air spinning machine according to one of claims 14 to 16, characterized in that the control (6) is designed to operate the air spinning machine according to one or more of claims 1 to 13.