Patent application title: Process for Preventing Ribbon Windings
Dietmar Greis (Ingolstadt, DE)
RIETER INGOLSTADT GMBH
IPC8 Class: AB65H5438FI
Class name: Preventing superposed convolutions in successively wound layers (i.e., ribbon breaker) by control of guide guide traverse speed
Publication date: 2012-10-18
Patent application number: 20120261504
A process is provided for preventing ribbon windings when cross-wound
bobbins are wound in random winding on a textile machine. The thread from
a thread guide is traversed over a double stroke. The traversing
frequency of the thread guide is continuously varied during the bobbin
travel within a predetermined deviation range around a nominal frequency.
A random stringing together of individual interference patterns is
generated by a random generator by selecting a target value for the
traversing frequency from the deviation range for every interference
pattern. The traversing frequency is adjusted by a control device on the
selected target value.
1. Process for preventing ribbon windings during the winding of
cross-wound bobbins (4) in random winding on a textile machine (1),
wherein the thread (3) is traversed from a thread guide (6) passing
through a double stroke (DS) moving back and forth and wherein, for
generating anti-patterning, the traversing frequency (F) of the thread
guide (6) is varied continuously during the bobbin travel within a preset
deviation range (DR) around a nominal frequency (NF), characterized in
that a random stringing together of individual interference patterns (13)
is generated by a random generator (11) that selects for every
interference pattern (13) a nominal frequency (NF) for the traversing
frequency (F) from the deviation range (DR) and the traversing frequency
(F) is adjusted by means of a control device (14) on the target value
(TV) set in each case, wherein for every double stroke (DS) or for every
single stroke of the thread guide (6) another value of the traversing
frequency (F) is maintained constant over the further course of the
single stroke (SS) or double stroke (DS).
 This invention refers to a process and a device for preventing
ribbon windings when cross-wound bobbins are wound in random winding in a
textile machine. Here, the thread is traversed from a thread guide
through a double stroke moving back and forth, wherein the traversing
frequency of the thread guide is varied continuously around a nominal
frequency within a preset deviation range for generating anti-patterning.
 When cross-wound bobbins are wound in random fashion, they are circumferentially driven by a frictional roller with constant circumferential speed so that the bobbin speed depends on the bobbin diameter, which gradually builds up. Thus, with increasing bobbin diameter the bobbin speed decreases. On the other hand, the thread guide is driven by a constant speed, so that the winding ratio (i.e. the number of bobbin revolutions per double stroke of the thread guide) decreases with increasing diameter. As a result of this, so-called ribbon windings--in which the threads from several successive layers are laid on the bobbin circumference, on the same place or directly beside it--occur in winding ratio areas in which the winding ratio takes on a whole number. This leads to compressed areas on the bobbin and therefore to an irregular yarn body, which can cause problems in subsequent manufacturing processes such as dyeing. There is also the danger of a possible jamming or catching of the threading devices lying beside or on top of one another, so that the unwinding properties of the bobbin in question are also affected.
 Therefore, many different devices and processes for preventing ribbon windings or for generating anti-patterning have been suggested; basically, the generation of an anti-patterning can take place by changing the bobbin speed or traversing frequency. If the bobbin is driven by a frictional roller, however, only one anti-patterning is available by changing the traversing frequency owing to the reasons described above. In open-end spinning machines, in which generally all thread guides are driven by means of a single central traversing drive, there is an additional limitation because it is not possible to match the anti-patterning on the bobbin diameter or limit it to areas with critical winding ratios because a machine's individual bobbins are in a different winding state. In such machines, a continuous anti-patterning must take place over the entire bobbin travel through a change in the traversing frequency.
 Known rotor spinning machines such as the applicant's R40 rotor spinning machine, for example, have a mechanical device for anti-patterning in the form of anti-patterning mechanism, which encompasses a cam disk that acts upon the revolutions that drive the traversing mechanisms that move the thread guides. This cam disk turns once through several double strokes of the thread guides (through 15 double strokes, for example), thereby varying the frequency of the traversing drive within a certain area that deviates from the nominal frequency. Afterwards, the cam disk turns once again through the next 15 double strokes so that the same interference cycle is always periodically carried out. The disadvantage in this case is that ribbon windings can nonetheless occur--especially starting from a certain larger diameter ribbon--and consequently the diameter of the bobbins to be generated is limited. Furthermore, owing to the continuous repetition of the same interference, an irregular bobbin build-up with compressed areas can occur. In addition, the ribbon breaker is subject to wear and needs regular maintenance.
 DE 195 48 257 A1 describes the problems of a non-homogeneous bobbin design and the insufficient anti-patterning during the typical periodic interference functions such as the saw tooth, sinus or rectangle functions and suggests executing the gradient of the periodic interference function in the zero crossings very steeply and furthermore passing through the areas in the extreme points with brief resting time, if possible, to prevent the occurrence of ribbon windings even more effectively. Furthermore, it describes how to make a periodic interference function a reality by electronically controlling the driving motor of the thread guides. This makes it possible, within limits, to vary the amplitude and/or the period duration of the periodic interference function for improving anti-patterning. Nonetheless, this electronic anti-patterning is also based on the periodic repetition of the same interference cycle so that the danger of having quality problems in the bobbins persists.
 The task of this invention is therefore to generate a sustainable anti-patterning with good bobbin quality.
 The task is solved with the characteristics of the independent claims.
 In a process for preventing ribbon windings when cross-wound bobbins are wound randomly on a textile machine, the thread is traversed from a thread guide through a double stroke moving back and forth, wherein the traversing frequency of the thread guide during bobbin travel is varied continuously within a preset deviation range around a nominal frequency for generating anti-patterning. A corresponding device for preventing ribbon windings comprises a control device for controlling the drive of the thread guide and for generating anti-patterning by changing the traversing frequency. According to the invention, a random stringing together of individual interference patterns is generated by a random generator that selects a target value for the traversing frequency from the deviation area for every interference pattern and a control device setting the traversing frequency to the selected target value. In this case, another value of the traversing frequency is set, at least for each double stroke, according to a variant of the invention for every single stroke of the thread guide. After the set target value is reached, the value of the traversing frequency can be constantly maintained over the subsequent course of the single stroke or double stroke. Contrary to the state of the art, in which an interference cycle is periodically repeated over several double strokes and in which a largely continuous change of the traversing frequency takes place over the duration of the interference cycle, another value of the traversing frequency is now allocated to every double stroke or single stroke of the thread guide with the help of a random generator, so that the anti-patterning takes place with a high degree of flexibility and also with larger bobbin diameters without repetitions. A pattern build-up can therefore be sustainably prevented even with larger bobbin diameters. Furthermore, the traversing frequency that differs for every double or single stroke of the thread guide reliably prevents localized compressions in the bobbins, thus leading to better quality and improved bobbin delivery.
 According to an advantageous further development of the process, a change of the traversing frequency takes place in each case exclusively within a single stroke of the thread guide. Even if merely one target value is allocated to every double stroke and not to every single stroke, the change of the traversing frequency takes place in each case only within a single stroke. This results in no acceleration over the reverse points of the thread guide; instead, the thread is deposited with constant speed. It has been determined that the tendency to form imperfections can be significantly reduced because of this.
 According to a first embodiment of the invention, an interference pattern extends exactly over one double stroke, in which case another target value for the traversing frequency is selected and set for every double stroke. Since both the size and separation of the successive preset target values differs in each case for one double stroke, an optimal anti-patterning can take place so no repetition of a pre-set pattern occurs. The device for preventing ribbon windings can be operated in a first mode for this purpose, in which every single interference pattern extends over exactly one double stroke. However, the advantages mentioned above can also be achieved if another target value (TV) for the traversing frequency (F) is already selected and set for every single stroke (SS). The essential factor here is that after the preset target value is reached within the single or double stroke, no change in the traversing frequency takes place any longer, since this ensures that no whole-number winding ratios occur.
 According to another embodiment of the invention, an interference pattern extends over several double strokes, wherein the target value selected by the random generator is set stepwise and wherein in each case one step is allocated to one double or single stroke. This process allows one to have a particularly smooth anti-patterning because the change in speed is relatively small from one double or single stroke to the next one. Such a process is therefore especially suitable for higher delivery speeds. The device for preventing ribbon windings can be operated in a second mode for this purpose, in which case the device can be switched between the first and second mode preferably at any time and at will, also while the textile machine is operating.
 Particularly advantageous is also when in this case the target is set in uniform steps. This also contributes to a smoother anti-patterning, since only a small, consistently equal change in speed is carried out per double or single stroke. It is also advantageous for the changing rate of the traversing frequency to be the same in every step so the climbing angle of the speed increase remains the same. This contributes to uniform bobbin winding.
 According to an especially advantageous further development of the invention, a change in traversing frequency occurs in this case outside of the edge-laying areas of the cross-wound bobbin. The edge-laying areas are especially sensitive so that one must take great care to achieve an especially precise thread deposit. As a result of this, imperfections can be prevented and a quiet bobbin build-up is made possible, as a change in speed of the thread winding takes place only along the less sensitive bobbin body. For this purpose, the drive of the thread guide is controlled accordingly.
 It is especially advantageous here if a minimum of one sensor monitors at least one terminal position of the thread guide. If the sensor does not emit a signal, the change in the traversing frequency is blocked. As a result of this, it can be favorably ensured that a change in speed will only take place when the thread guide is at the start of the bobbin's winding area and the terminal position or the reversal point has just been passed. For this purpose, the device for preventing ribbon windings has a respective sensor connected to the control device that emits the corresponding signal when it registers the terminal position. The change in traversing frequency to the next target value generally concludes within one single stroke, so that it is enough to register only one of the terminal positions. According to a further development of the invention, however, both terminal positions can also be registered for safely ruling out a change in the sensitive edge-laying areas.
 According to a further development of the invention, it is advantageous to preset the size of the deviation area from the nominal frequency according to the machine's operational parameters and/or the yarn material to be wound in an operational unit of the control device. Thus, for example, in a stepwise process a relatively large deviation area can be set, since the changes take place very smoothly, whereas in an interference cycle--which extends merely over only one single or double stroke--the size of the deviation range can be set correspondingly lower in order to prevent excessively large jumps in the traversing frequency from one single or double stroke to the next.
 It is furthermore advantageous if during the change in traversing frequency a preferably optical signal is displayed on the selected target value. For this purpose, the device comprises a display unit, especially an optical display unit. In this way, a user can easily control anti-patterning activity.
 Further advantages of the invention will be described with the help of the following embodiments, which show:
 FIG. 1 an overview of a textile machine with a device for preventing ribbon windings,
 FIG. 2 a drawing of the process according to the invention for preventing ribbon windings according to a first embodiment,
 FIG. 3 another embodiment of the process according to the invention for preventing ribbon windings, and
 FIG. 4 a drawing of the process according to the invention for preventing ribbon windings according to a second embodiment.
 FIG. 1 shows an example of a textile machine 1, here a spinning machine, in which the process according to the invention and the device according to the invention can be favorably applied. The spinning machine 1 has numerous working positions 2 arranged beside each other in which in each case a spun yarn 3 is wound on a cross-wound bobbin 4. For this purpose, the bobbin 4 is driven by a frictional roller 5, while at the same time the thread 3 is traversed back and forth through a thread guide 6 over the stroke S of the bobbin so that the thread 3 is finally deposited cross-wise on the bobbin 4.
 The frictional rollers 5 are connected to one another by a continuous shaft 7 and centrally driven by a mechanism 8 located in one end of the spinning machine 1. The thread guides 6 of all working positions 2 are connected to one another by a machine-long traversing rod 9 that is also driven by a central drive 10. Here, the drive of the traversing rod 9 contains a special stroke cam mechanism that converts the turning motion of the central drive 10 to a back and forth movement of the traversing rod 9. Since the bobbins 4 are always driven with the same speed along their circumference and, on the other hand the traversing frequency F remains constant along the entire bobbin travel, the yarn 3 is in random winding, i.e. it is wound on the bobbins 4 with a constant thread crossing angle. On the other hand, the winding ratio--defined as the number of bobbin revolutions per double stroke DS--becomes smaller with increasing bobbin diameter.
 To prevent the recurring ribbon windings occurring with this type of winding and changing winding ratio, a device 12 for preventing ribbon windings is provided for varying the traversing frequency F within a certain deviation range D around a nominal frequency NF in order to prevent the appearance of whole-number winding conditions. For this purpose, the device 12 comprises a control device 14 with a random generator 11, which is connected to the drive 10 of the traversing rod 9 and controls it accordingly. In this case, the drive 10 of the thread guides 6 is an electronically controlled central drive, wherein the drive 10 drives a stroke cam mechanism for generating the double stroke (DS). However, the invention can also be used with an electronically-driven individual traversing for every spinning position. Furthermore, the control device 14 is connected to, and controlled by, the drive 8 of the spooling, which is here also executed as a central mechanism and connected through the control. The speed of the spooling drive 8 is recorded by a speed sensor (not shown here) and constitutes the input quantity of the control device 14 for calculating the nominal frequency NF of the traversing drive. Additionally, it is also possible to record the speed of the traversing drive 8, represented here by a dotted line. As described in more detail below, the random generator 11 issues a target value TV that also constitutes an input quantity of the control device 14. The control device 14 now generates from this an interference pattern 13 and the drive 10 of the thread guide is correspondingly impinged until the next target value TV is given by the random generator 11. In this case, the drive 10 is controlled in such a way that another traversing frequency F is set for every double stroke DS.
 Contrary to the state of the art, in which a given disturbance cycle extending over a vast number of double strokes is continuously repeated, the device 12 according to the invention generates now a random stringing together of individual interference patterns 13. As a result of this, the occurrence of ribbon windings can be prevented even with large bobbin diameters, whereas in the state of the art the constant repeating of the same interference cycle can nevertheless cause ribbon windings or image formations. Since in the anti-patterning according to the invention another traversing frequency F still has to be set for every double stroke DS, a very uniform bobbin build-up without compression zones can be achieved.
 FIG. 2 shows a first embodiment of the invention (in which a process for preventing ribbon windings is shown) that improves anti-patterning even more and makes a uniform bobbin build-up possible. Here, a successive quantity of double strokes DS of the thread guide 6 or of the traversing rod 9 can be seen in the upper part of the drawing symbolically represented over a certain time period, whereas the lower part of the drawing shows the course of the traversing frequency F over the quantity of double strokes DS shown or over the corresponding duration. Here, the magnitude of the traversing frequency F is indicated as a percentage deviation from the nominal frequency NF, so that according to this drawing, the value of zero corresponds exactly to the nominal frequency NF of the traversing frequency F.
 For generating every single interference pattern 13, the random generator 11 now selects a target value TV that lies within a given deviation range DR at the nominal frequency NF. Here, the deviation range DR is ±6% of the nominal frequency NF, which corresponds to the zero value. However, the deviation range DR can also lie asymmetrically to the nominal frequency NF. The preset target value TV given by the random generator 11 for the traversing frequency F is in each case set by the control device 14 to the target value TV selected and maintained for a while; afterwards, the random generator starts with the next predetermined target value TV2, which is maintained and the process continues in this way. Owing to the fact that the successive target values TV1, TV2, TV3, etc. are always randomly selected, in which case positive and negative deviations from the nominal frequency NF can be executed in any random succession, a highly flexible and sustainable anti-patterning is possible. As a result of this, the danger of ribbon windings is almost completely prevented, while the constant change of the traversing frequency allows a much more uniform bobbin build-up.
 As can also be seen in FIG. 2, for every double stroke DS of the thread guide 6 another target value TV for the traversing frequency F is given and set through the control device 14. Thus, it can almost be totally prevented that the threads 3 of two successive winding layers are deposited on top of each other or very close to one another, so that even with larger bobbin diameters almost no ribbon windings can occur.
 An especially advantageous embodiment of the invention is shown here, according to which a change in the traversing frequency F will in each case follow exclusively one single stroke SS of the thread guide 6 or of the traversing rod 9. Here, an interference pattern 13 extends over exactly one double stroke DS of the traversing rod 9, wherein a change in the traversing frequency F takes place from the current actual value to the next target value TV only within one single stroke SS of the thread guide 6. As shown here, the change in the traversing frequency F starts exactly at the start of a single stroke SS in the left terminal position LE and ends before the thread guide 6 has reached the other terminal position RE. This advantageously ensures that in the edge areas of the bobbins 4--in other words, in the terminal positions LE and RE of the thread guide 6--no change in the traversing frequency F will take place and therefore the thread 3 will not be accelerated in the sensitive edge areas. It has been demonstrated that, as a result of this, the formation of imperfections, i.e. thread pieces that slide off the edge area in the front sides of the bobbins 4 and span positions lying farther inside as peel-off edge, can be largely prevented. Such imperfections greatly impede the operational behavior and further processing of the bobbin 4, so that owing to the extensive prevention of imperfections only high-quality bobbins 4 can be produced. Furthermore, by changing the traversing frequency F only along the bobbin body, a very uniform bobbin build-up is facilitated.
 Differing from the embodiment shown, these advantages can also be achieved when another traversing frequency F is already set for every single stroke SS. In this case, an interference pattern extends exactly over one single stroke SS of the thread guide, wherein the change of the traversing frequency F also takes place here preferably only outside the edge areas, i.e. outside the terminal positions LE and RE of the thread guide.
 FIG. 3 shows an embodiment of the invention as in FIG. 2, but the deviation range DR is smaller than the one in FIG. 3. Here, a deviation range DR having ±4% of the nominal frequency NF is shown. For example, it is useful to set the deviation range DR to a somewhat lower value with higher delivery speeds in order to prevent very large jumps in the traversing frequency F between two successive double strokes DS. For this purpose, the device 12 is equipped with an operating unit 17, which also contributes to a quieter and smoother bobbin build-up. The magnitude of the deviation range DR can therefore be advantageously set according to the operational parameters of the machine 1, for example according to the delivery speed or also depending on the yarn material to be wound.
 As also shown in FIGS. 2 and 3, the change in the traversing frequency F can be shown in each case on a new target value TV by means of a display, symbolized here by the corresponding stars. For this purpose, the control device 14 comprises a display 17 (see FIG. 1), for example an LED device installed on the control device 14 for indicating every change in the traversing frequency F by lighting up for a short time. In this way, the operating staff receives also optical (visible) information about the anti-patterning execution.
 It is especially advantageous if the control device 14 can control the change in the traversing frequency F, when at least one of the terminal positions LE and RE of the thread guide 6 is monitored by at least one sensor 15. As shown in FIG. 1, for example, the left reversal point or the left terminal position LE of the traversing rod 9 is monitored by a sensor 15. The sensor 15 can, for example, be arranged directly in the area of a thread guide 6 or also in the area of the machine-long traversing rod 9. Likewise, the sensor can also be installed directly in the area of the drive 10. The sensor 15 also constitutes an input quantity for the control device 14. If the sensor 15 does not emit a signal, the change in traversing frequency is blocked by the control device 14, so that the coordination of the change in traversing frequency F on the area outside of the edge-laying areas of the bobbin 4 is advantageously possible.
 FIG. 4 shows an alternative embodiment of the invention in which an interference pattern 13 extends over several double strokes DS. The target value TV that the random generator 11 selects is in this case set stepwise by the control device 14, wherein in each case one double stroke DS is allocated to one step. After the first target value TV1 was achieved in several steps, the nominal frequency NF is initially set stepwise and afterwards the next target value TV2 is started in several steps too. Once again, one double stroke DS is allocated to a step. According to this drawing, the selected target value TV is set in uniform steps for each instance. As with the previously described embodiments of the invention, the step-wise start of the target value TV allows the allocation of another value of the traversing frequency F to every double stroke DS. The stepwise setting of the newly given target value TV permits the generation of an especially smooth anti-patterning because the change in the traversing frequency F between two successive double strokes DS is relatively small. Even in this embodiment of the invention, it is once again possible to allocate another value of the traversing frequency F to every single stroke SS and therefore to start the target value TV stepwise, preferably in uniform steps.
 An especially uniform bobbin build-up can be accomplished here if (as shown here too) the changing rate of the traversing frequency F is the same in every step. Therefore, the described embodiment of the invention is preferably used with high delivery speeds starting at 150 meters per minute. Likewise, this especially smooth process can be used to great advantage for preventing ribbon windings in yarns that curl or stretch a lot.
 So a change in the traversing frequency F can be prevented in the edge-laying areas, the invention also provides a change in the traversing frequency F occurring exclusively within a single stroke, something that can favorably take place by a sensor 15, which comprises at least one of the terminal positions LE, RE of the thread guide 6 or of the traversing rod 9. Needless to say, a setting of the magnitude of the deviation range DR is possible according to this process too in order to facilitate an adjustment to various parameters.
 Even in this embodiment of the invention it is also advantageous if during the changing of the traversing frequency F an optical signal follows the selected target value TV. In this case, the optical display lights up until the target value given by the control unit 13 is reached after several steps, so that a LED here remains lit for a somewhat longer period. In a device 12 for preventing ribbon windings, in which it is possible to change over between two modes according to both processes described, the operating staff can therefore also recognize according to what process the picture disruption is being executed with the help of the optical display. The switching between the two modes can also be done via the operating unit 17.
 With the device according to the invention and the process according to the invention for preventing ribbon windings it is therefore for the first time possible to prevent a repetition of an interference cycle or of an interference pattern in which a different value of the traversing frequency is set for every double stroke of the thread guide. As a result of this, an especially uniform bobbin build-up can be generated that prevents compression zones and imperfections and consequently also ensures a good and uniform operational behavior as well as good dye receptivity.
 1 Textile machine, spinning machine
 2 Working positions
 3 Thread, yarn
 4 Cross-wound bobbin
 5 Frictional roller
 6 Thread guide
 7 Bobbin shaft
 8 Bobbin shaft drive
 9 Traversing rod
 10 Traversing rod drive, thread guide drive
 11 Random generator
 12 Device for preventing ribbon windings
 13 Disturbance pattern
 14 Control unit
 15 Sensor
 16 Disturbance cycle
 17 Display
 18 Operating unit
 DR Deviation range
 DS Double stroke
 F Traversing frequency
 LE Left terminal position
 NF Nominal frequency
 RE Right terminal position
 S Stroke
 SS Single stroke
 TV Target value
Patent applications by RIETER INGOLSTADT GMBH