Fiber tape preparation

Abstract

The invention relates to a drawing unit for conveying a fiber strip towards an inlet opening of a vortex chamber of an air spinning device and to a method for operating a drawing unit comprising an output roller pair and at least one further drawing unit roller pair and / or belt roller pair, by means of which a fiber strip for the production of a thread is fed to a vortex chamber of an air spinning device at a spinning station of an air spinning machine, wherein the output roller pair can be driven independently of the at least one further drawing unit roller pair and / or belt roller pair.In order to provide a method for operating a drafting unit comprising a pair of output rollers and at least one further pair of drafting rollers and / or belt rollers, as well as a drafting unit which enables reliable preparation of the fiber strip end before the spinning process, it is provided that the pair of output rollers for combing the fiber strip end after a spinning interruption is driven at a predetermined combing speed and that the at least one pair of drafting rollers and / or belt rollers upstream of the pair of output rollers in the fiber strip direction is stopped or operated at a holding speed corresponding to the combing speed, which is a maximum of 10% of the combing speed.

Description

[0001] The invention relates to a drafting unit for conveying a fiber strip towards an inlet opening of a vortex chamber of an air spinning device and to a method for operating a drafting unit comprising an output roller pair and at least one further drafting roller pair and / or belt roller pair, by means of which a fiber strip for the production of a thread is fed to a vortex chamber of the air spinning device at a spinning station of an air spinning machine, wherein the output roller pair can be driven decoupled from the at least one further drafting roller and / or belt roller pair.

[0002] Drafting devices of this type, as well as methods for operating them at a spinning station of an air-jet spinning machine, are known in various embodiments from the prior art, as documented in EP 1 219 737 A1. At the spinning stations of such air-jet spinning machines, the drafting devices serve to feed a fiber sliver into a vortex chamber of an air-jet spinning device at the spinning station, whereby the sliver is first drafted.

[0003] During the spinning process, errors repeatedly occur, resulting in thread segments whose parameters, such as thread thickness, hairiness, thread strength, etc., deviate from a specified target value. Such thread defects are detected by a thread sensor and must be removed in a cleaning cut that interrupts the spinning process. Similarly, thread breaks occur during the spinning process, requiring the thread end to be reattached to the fiber sliver fed into the air-jet spinning machine's vortex chamber by the drafting unit.

[0004] To carry out the spinning process, it is necessary to pick up each yarn end that has wound onto a take-up bobbin using a yarn receiving device located either at the spinning station or one that can be moved past the spinning station, particularly on the air-jet spinning machine. This device then transfers the yarn end, contrary to the actual yarn path, into the vortex chamber of the air-jet spinning unit during the spinning process, where it can be joined to the supplied fiber sliver. To prepare the yarn end for joining to the supplied fiber sliver, it is necessary to prepare the yarn end before spinning. This is done using a yarn preparation device, which is located downstream of the vortex chamber in the yarn path. This device serves to cut the yarn end to a predefined length and to unravel the yarn end, i.e.,to free it from its existing twist so that it can be connected to the supplied fiber tape. After the thread end is released, it is transported into the vortex chamber, for example by means of blown air, by releasing a clamp that positions the thread end in the thread preparation device, and held there.

[0005] In the subsequent spinning process, the fiber strip is fed into the vortex chamber via the drawing unit and the output roller pair, forming a thread which is connected to the free thread end placed in the vortex chamber and then drawn off from the vortex chamber via the take-off device.

[0006] At the start of the spinning process, the drafting unit is first raised, which conveys the fiber sliver towards the vortex chamber. Only after the drafting unit has started raising is the take-up unit started, resulting in a dwell time of the yarn end in the vortex chamber at the beginning of the spinning process. During this time, the fiber sliver fed via the drafting unit is bonded to the yarn end in the vortex chamber. After this dwell time has elapsed, both the take-up unit and the output roller pair are accelerated to a predetermined take-up speed, at which the spinning process then continues.

[0007] Careful preparation of the free fiber end is crucial for a flawless connection between the yarn end and the fiber strip during the spinning process. However, known drafting machines and methods for fiber strip preparation using these machines only partially achieve the desired conditioning of the fiber strip end before the spinning process.

[0008] Based on this, the invention aims to provide a method for operating a drawing unit comprising a pair of output rollers and at least one further pair of drawing unit rollers and / or belt rollers, as well as a drawing unit which enables reliable preparation of the fiber strip end before the spinning process.

[0009] The invention solves the problem by means of a method with the features of claim 1 and by means of a drawing device with the features of claim 3. Advantageous further developments of the method are specified in dependent claim 2. Further embodiments of the drawing device according to the invention are found in dependent claims 4 and 5.

[0010] A characteristic feature of the method according to the invention is that the output roller pair for combing out the fiber strip after a spinning interruption is driven at a predetermined combing speed, and the at least one drafting roller and / or belt roller pair upstream of the output roller pair in the fiber strip direction is stopped or operated at a holding speed corresponding to the combing speed, which is max. 10% of the combing speed.

[0011] In regular spinning operation, the output roller pair of the drafting unit and the take-up device have a matching production speed, referred to as the take-up speed, whereby the at least one drafting unit roller and / or belt roller pair upstream of the output roller pair, viewed in the yarn direction, has a lower production speed due to system requirements in order to achieve the desired distortion of the fiber strip within the drafting unit.

[0012] According to the inventive method, the output roller pair, which can be driven independently of at least one further drafting roller and / or belt roller pair, is driven at a predetermined combing speed, while the at least one further upstream drafting roller and / or belt roller pair remains stationary or is operated at a low holding speed, which is a maximum of 10% of the combing speed. Such a combing operation of the drafting unit results in no or only a very small feed of the fiber strip towards the vortex chamber of the air spinning device.Rather, especially when drafting roller and / or belt roller pairs are stationary and the output roller pair is operated at the specified combing speed, the fiber strip end is conditioned by this combing process so that it can be optimally prepared for the spinning process onto the free thread end arranged in the vortex chamber.

[0013] According to a further development of the invention, the output roller pair is driven before at least one further pair of drafting rollers and / or belt rollers during the spinning process when the drafting unit is ramped up. This embodiment of the invention makes it possible to avoid fluctuations in the ramp-up of the output roller pair, which would otherwise cause fibers to be conveyed at a speed not specified by the rest of the drafting unit and which could lead to additional distortion of the fiber strip or a build-up of fibers.

[0014] In principle, it is possible, following the combing process, in which the output roller pair is decoupled from the at least one further drafting roller and / or belt roller pair (which is stationary or operated only at a specific holding speed), to raise the prepared fiber strip and convey it into the vortex chamber of the air spinning device. According to the invention, the drafting unit is stopped after combing and then raised for spinning. This embodiment of the invention ensures with particular reliability that the free fiber strip end is positioned in the vortex chamber at the beginning of the spinning process in the desired manner for connection with the free yarn end.

[0015] Characteristic of the drawing unit for conveying a fiber strip towards an inlet opening of a vortex chamber of an air spinning device, wherein the drawing unit has an output roller pair that can be driven independently of the at least one further drawing unit roller pair and / or belt roller pair, is a control unit for carrying out the method described above according to the invention or further developed for operating a drawing unit after a spinning interruption. The control unit can be arranged directly at the spinning station or, according to an advantageous embodiment of the invention, be integrated into a central control unit for more than one spinning station or the air spinning machine. The central control unit can preferably be a mobile or stationary device outside the spinning station and / or air spinning machine. Particularly advantageously, the control unit orThe control unit is designed to variably adjust the combing speed and / or the holding speed, thus enabling optimal adaptation to the fibers.

[0016] An embodiment of the invention is explained below with reference to the drawings. The drawings show: Fig. 1 in a front view of an air spinning machine with workstations, each having its own yarn receiving device and yarn preparation device to supply its air spinning device, and Fig. 2 in a sectional view in a schematic representation of an air spinning device during the spinning process.

[0017] The Fig. 1Figure 1 schematically shows a front view of a textile machine, usually referred to as a cross-coil 9, which produces coils; in this case, it is an air-jet spinning machine 1. Such textile machines 1 have a plurality of spinning stations 2 between machine frames 13a, 13b arranged at the machine ends. A spinning can 3 is positioned at each of the spinning stations 2, which is equipped with a supply of feed material, for example, fiber ribbon 25.

[0018] The spinning stations 2 each also have a drafting unit 4, an air spinning device 5, a take-up device 6, a yarn cleaner 7, and a yarn changing device 8, which ensures that the yarn 36 spun or produced from the fiber sliver 25 in the air spinning device 5 is wound onto a winding bobbin 9 in intersecting layers. The resulting cross-wound bobbin 9 is held, as usual, in a bobbin frame (not shown) and is rotated by a bobbin drive (also not shown).

[0019] Each of the spinning stations 2 is also equipped with a thread receiving device 39, which makes it possible to receive a thread end 37 of a manufactured thread 36 that has run up onto the cross bobbin 9 after a spinning interruption and to transfer it to a so-called thread preparation device 40 located in the area of ​​the take-off device 6.

[0020] The Fig. 2 Figure 5 shows, in side view and on a larger scale, an air spinning device 5 suitable for carrying out the method according to a preferred embodiment during the spinning process.

[0021] As can be seen, the air spinning device 5 shown in the cross-section is preceded by the drawing unit 4 for drawing the fiber spool 25. In the fiber spool direction R behind the air spinning device 5, a single-motor-driven and reversible take-up device 6 is installed, which ensures that the produced thread 36 can be conveyed towards the take-up spool 9 and in the opposite direction.

[0022] In the area of ​​the thread take-up device 6, the thread preparation device 40, which is not shown in detail here, is also arranged, which prepares the thread end 37 of the finished thread 36, which has been retrieved by the thread take-up device 39, for the subsequent spinning process.

[0023] As in Fig. 2 As shown, the air spinning device 5 essentially consists of a two-part outer housing 14, 15, an expansion housing 16, a nozzle block 17, a fiber belt guide 18 and a hollow spinning cone 19.

[0024] The expansion housing 16, in conjunction with the front housing part 14 of the outer housing, forms a front annular space 20, which is connected to a pressure source 22 via a pneumatic line 21 and is connected to the expansion space 28 located in the rear housing part 15 of the outer housing.

[0025] While the expansion chamber 28 is indirectly connected to the ambient atmosphere via an exhaust duct 29, the annular space 20 is pneumatically connected throughout to at least one blowing air nozzle 23, which is arranged in the nozzle block 17.

[0026] The blowing air nozzle 23 opens into a vortex chamber 33 in the area in front of the inlet opening 35 of the spinning cone 19 and is directed towards the head 24 of the spinning cone 19 in such a way that a rotating airflow is established at the head. The spinning cone 19 is preferably made of a highly wear-resistant material, for example, a technical ceramic material.

[0027] To control the compressed air supply, the pneumatic line 21 is equipped with a valve 32, the actuation of which is preferably carried out by a spinning station-specific control unit 38, which is connected to the valve via appropriate control lines.

[0028] During the normal, previously known spinning process (not shown here), the fiber sliver 25, stored in a spinning can 3, first passes through the drafting unit 4 on its way to the cross-wound bobbin 9, where it is strongly drawn out. Via the output roller pair 26 of the drafting unit 4, the drawn fiber sliver 25 is then transferred to the area of ​​the inlet opening 27 of the air spinning device 5 and, under the influence of a vacuum flow present there, is drawn into the vortex chamber 33 of the air spinning device 5. Inside the air spinning device 5, the drawn fiber sliver 25 passes via the fiber guide 18 and the nozzle block 17 to the inlet opening 35 of the hollow spinning cone 19 and is drawn into the spinning cone 19 by the thread 36 forming inside the spinning cone 19. The fiber ribbon 25 is exposed in the area of ​​the head 24 of the spinning cone 19 to the influence of a rotational flow, which is generated by the airflow exiting the nozzle block 17.

[0029] To direct this airflow, initiated by the overpressure source 22, to the nozzle block 17, the valve 32 is open. To allow the airflow entering via the nozzle block 17 to escape through the exhaust duct 29 to the ambient atmosphere or to a machine-integrated extraction system during the spinning process, a valve 34, connected to the control unit 38 via a corresponding control line, is open.

[0030] During the spinning process, the continuous movement of the fiber strip 25 in the fiber strip direction R continuously draws the fiber strip 25 into the hollow spinning cone 19, whereby the outer fibers are helically wound around the core fibers of the fiber strip 25. The resulting yarn 36 is drawn from the air spinning device 5 by means of the yarn take-up device 6 and then wound onto a cross-wound bobbin 9.

[0031] If the spinning process is interrupted, for example due to a break in the fiber band 25 or due to a controlled cut of the already spun thread 36 by the thread cleaner 7, a start-up process must first be carried out before restarting the spinning process.

[0032] As is known, to carry out a spinning process, on the one hand the stretched fiber ribbon 25 and on the other hand the already completed thread 36 that has wound onto the cross-spool 9 are required.

[0033] After a spinning interruption, the yarn receiving device 39 of the affected spinning station 2 first retrieves the yarn end 37 of the already completed yarn 36 from the cross-wound bobbin 9 and transfers it to a yarn preparation device 40 located downstream of the air spinning device 5 in the fiber sliver direction R. There, the yarn end 37 is largely freed from twist and loose fibers and then transferred to the swirling chamber 33 for spinning and positioned there.

[0034] To prepare the fiber strip 25, during the return of the thread end 37 to the vortex chamber 33, the drafting unit 4 is operated by the control unit in a combing operation, in which the first drafting unit roller pair 42, the second drafting unit roller pair 43 and the belt roller pair 41 are stationary, whereas the output roller pair 26 is operated at a combing speed and thereby optimally prepares the free end of the fiber strip 25 for the spinning process. Reference symbol list

[0035] 1 air spinning machine 25 Fiber tape 2 Spinning site 26 Output roller pair 3 spinning can 27 Entrance 4 Stretching 28 Expansion area 5 Air spinning device 29 Exhaust duct 6 Extraction device 31 Retention / dissolving tube 7 Thread cleaner 32 valve 8 Thread changing device 33 Vortex chamber 9 ramp-up coil 34 valve 13a, 13b machine frame 35 Entrance opening 14 outer casing 36 thread 15 outer casing 37 Thread end 16 Expansion housing 38 control unit 17 Nozzle block 39 Thread pickup device 18 Fiber tape guide 40 Thread preparation device 19 Spin cone 41 Belt roller pair 20 annular space 42 first pair of draft rollers 21 Pneumatic line 43 second pair of draft rollers 22 Overpressure source 44 Thread guide channel 23 Air nozzle R Fiber tape direction 24 Head

Claims

1. A method for operating a drafting system (4) having an exit roller pair (26) and at least one additional drafting system roller pair (42, 43) and / or apron roller pair (41), by means of which a sliver (25) is supplied at a spinning station (2) of an air-jet spinning machine (1) for the production of a yarn (36) to a vortex chamber (33) of the air-jet spinning device (5) of the spinning station (2), wherein the exit roller pair (26) can be driven decoupled from the at least one additional pair of drafting system rollers (42, 43) and / or apron rollers (41), characterized in that the exit roller pair (26) for combing out the sliver end after an interruption of spinning is driven at a predetermined combing-out speed, wherein the sliver end is conditioned by the exit roller pair (26) during combing, the at least one pair of drafting system rollers (42, 43) and / or apron rollers (41) located upstream of the exit roller pair (26) in the sliver running direction (R) is operated at a holding speed which is associated with the combing-out speed and which amounts to a maximum of 10% of the combing-out speed, and the drafting system (4) is stopped after combing and then started up for piecing.

2. The method according to claim 1, characterized in that the exit roller pair (26) is driven before the at least one additional drafting system roller pair (42, 43) and / or apron roller pair (41) when the drafting system (4) is started up during piecing.

3. A drafting system for conveying a sliver (25) in the direction of an inlet opening (35) of a vortex chamber (33) of an air-jet spinning device (5), wherein the drafting system (4) has an exit roller pair (26) which can be driven decoupled from at least one additional drafting system roller pair (42, 43) and / or apron roller pair (41), characterized by a control unit (38) for carrying out the method for operating a drafting system (4) after an interruption of spinning according to one or more of claims 1 and 2.

4. The drafting system according to claim 3, characterized in that the control unit (38) is integrated into a central control unit of the air-jet spinning machine (1).

5. The drafting system according to claim 3 or 4, characterized in that the control unit (38) is designed to variably adjust the combing-out speed and / or holding speed.

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