Method for Avoiding Ribbon Windings

Abstract

A method for avoiding ribbon windings in producing cross-wound bobbins at the workstations of textile machines in the “random winding” type of winding, by changing the traversing speed at which the thread is wound onto the bobbin. Each workstation has a single motor drive activated for the rotation of the cross-wound bobbin, and a single motor drive activated for a traversing thread guide. The diameters (DSP k) of the bobbin (8) which are critical with regarding to the development of ribbon windings depending on the width (BSp) of the bobbin (8) and a cross-winding angle (α) are determined, and, shortly before reaching each critical diameter (DSP k), the cross-winding angle (α) is changed to a value (α1), which avoids development of ribbon windings in this diameter region, and the cross-winding angle (α1) is reset to its original value (α) after the critical diameter (DSP k) has been passed.

Description

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of German patent application 10 2005 054 356.1, filed Nov. 15, 2005, herein incorporated by reference.]

BACKGROUND OF THE INVENTION

The invention relates to a method for avoiding ribbon windings during the production of take-up bobbins Method for avoiding ribbon windings in the production of take-up bobbins which are wound at the workstations of textile machines producing cross-wound bobbins in the “random winding” type of winding, by changing the traversing speed at which the thread is wound onto the take-up bobbin, the workstations in each case having a single motor drive, which can be activated in a defined manner for the rotation of the cross-wound bobbin, and a single motor drive which can be activated in a defined manner for a traversing thread guide.

During the production of take-up bobbins at workstations of textile machines producing cross-wound bobbins, a thread which is manufactured in an open-end spinning device, for example, and supplied at a virtually constant speed to a winding device when running onto a bobbin is displaced by a traversing thread guide in such a way that it runs in crossing layers onto the bobbin and thus forms a so-called cross-wound bobbin. During the production of cross-wound bobbins in the “random winding” type of winding, there is, however, the problem that if no particular measures are taken, so-called ribbon windings repeatedly occur in the course of the bobbin travel. Such ribbon windings always occur if a whole-number winding ratio is present, in other words, if the cross-wound bobbin carries out one or more complete revolutions per double stroke of the traversing thread guide. In a case such as this, the reversal points of the thread are substantially located over the reversal points of the previous stroke, so the thread is repeatedly placed on the same or a directly adjacent point on the winding periphery which leads to ribbon-like thread layers which are designated ribbon windings.

As the stripping-off of complete yarn layers from the bobbin surface often occurs when there is such a non-homogeneous structure of the yarn layers when unwinding the cross-wound bobbins, and this leads to serious operating disruptions, ribbon windings of this type absolutely have to be avoided.

Various methods and devices which are to be used during the bobbin build-up to overcome the aforementioned problems have therefore been known for a long time to avoid ribbon windings. With these so-called ribbon disrupting methods and mechanisms, the winding ratio is influenced in the regions of the cross-wound bobbin at risk of ribbon winding.

DE 25 34 239 C2, for example, describes a device and a method for ribbon disruption, in which it is attempted, by means of constant changing of the cross-winding angle, to prevent the development of whole-number winding ratios. The traversing thread guides of one machine side can be driven here together by a first drive at least two different speeds and the winding rollers of this machine side can be driven together by a second drive. The two drives are also connected to one another by an electronic gearing in such a way that the winding rollers and therefore the cross-wound bobbins are driven in such a way, synchronously and as a function of the movement of the traversing thread guides, that the quotient of the rotational speed of the cross-wound bobbins and the cosine of half the thread cross-winding angle is constant.

In other words, in this known method, an attempt is made both to avoid whole-number winding ratios and also to keep the resulting winding speed of the thread and therefore the thread tension virtually constant.

A ribbon disruption method is also known from DE 43 37 891 A1, in which a thread supplied at a constant speed and wound onto a cross-wound bobbin in the “random winding” type of winding is wound on at a changeable traversing speed to avoid ribbon windings. The mechanism has a single motor driven winding roller and a single motor driven traversing thread guide. In this known ribbon disrupting method, the traversing speed of the thread guide is subjected to a non-periodic change. The maximum and minimum values of the traversing speed, at which in each case a changeover takes place from an acceleration to a deceleration and vice versa, and the time intervals between the reversal points, are changed in this case by means of a computer within predetermined limits.

A ribbon disrupting method is furthermore known from DE 196 28 402 A1, in which, similarly to in the mechanism according to DE 25 34 239 C2, the winding rollers of one machine side are driven together by a first drive and the thread guides of this machine side are driven together by a further drive.

The traversing speed of the thread guides and the rotational speed of the winding rollers are constantly changed here in opposite directions between predetermined top and bottom values around an average value.

One of the two speeds in this case forms the reference variable which the other speed is made to follow as a following variable of the method. In each case, if the reference variable has reached a top or bottom value, at the beginning of its change in the opposite direction a signal is generated which triggers the change of the following variable in the opposite direction.

A ribbon disrupting method for cross-wound bobbins, which are wound in the “random winding” type of winding, is also described in DE 102 09 851 A1. In this known method, as a function of the delivery speed of the thread, the degree of tensioning drawing and the cross-winding angle, the rotational speed of the winding roller is fixed and the cross-winding angle is changed by changing the speed of the traversing thread guide for the purpose of ribbon disruption. The drive for the winding rollers and the drive for the traversing thread guides are configured as speed-controllable motors, to which a signal representing the value of the desired cross-winding angle is supplied, from which the motors derive the required motor speed.

The aforementioned ribbon disrupting methods or ribbon disrupting mechanisms have the disadvantage, however, that they are all relatively complicated or expensive.

In other words, to carry out the known methods, either a high mechanical and control outlay is required or the ribbon disrupting methods lead to unsatisfactory results during the winding of the cross-wound bobbins.

SUMMARY OF THE INVENTION

Proceeding from the aforementioned prior art, the invention is based on the object of providing a relatively simple method for avoiding ribbon windings, which method is advantageous to use in particular in workstations, which have single motor drives for the winding rollers and the traversing thread guide.

This object is achieved according to the invention by a method as described in claim 1. Method for avoiding ribbon windings in the production of take-up bobbins which are wound at the workstations of textile machines producing cross-wound bobbins in the “random winding” type of winding, by changing the traversing speed at which the thread is wound onto the take-up bobbin, the workstations in each case having a single motor drive, which can be activated in a defined manner for the rotation of the cross-wound bobbin, and a single motor drive which can be activated in a defined manner for a traversing thread guide, characterised in that the diameters (D_{SP k}) of the cross-wound bobbin (8) which are particularly critical with regarding to the development of ribbon windings and depend on the width (B_Sp) of the cross-wound bobbin (8) and a cross-winding angle (α) selected during the winding of the cross-wound bobbin (8), are determined, in that, in each case, shortly before reaching one of these critical diameters (D_{SP k}), the cross-winding angle (α) is changed to a value (α₁), which rules out the development of ribbon windings in this diameter region and in that the cross-winding angle (α₁) is reset again to its original value (α) after the critical diameter (D_{SP k}) has been passed.

Advantageous configurations of the invention are the subject of the sub-claims.

The method according to the invention offers the possibility of reliably preventing right from the start the production of ribbon windings in that suitable measures are already taken to disrupt ribbons before a critical region is reached during the winding of a cross-wound bobbin. In other words, shortly before reaching a critical region of this type predetermined by the bobbin width and the cross-winding angle, the winding ratio is adjusted in a defined manner by changing the cross-winding angle in such a way that the production of ribbon windings are reliably ruled out. The changed cross-winding angle is retained here until the critical diameter region of the cross-wound bobbin has been passed. The original cross-winding angle is then reset and winding continues with this cross-winding angle until in the course of the bobbin travel, the diameter of the cross-wound bobbin approaches the next critical diameter region.

As shown in claim 2, the critical diameter regions of a cross-wound bobbin wound by the “random winding” type of winding is advantageously calculated by the formula: D_{SP k}=A×B_SP/π×tan(α/2), wherein D_{SP k} stands for a critical diameter region of the cross-wound bobbin, A stands for a whole number, B_SP stands for the respective bobbin width of the cross-wound bobbin and a stands for the selected cross-winding angle of the cross-wound bobbin. The diameter data can be calculated, for example, in a workstation computer and processed such that before a critical diameter region of the cross-wound bobbin is reached, a change in the cross-winding angle is in each case initiated in a timely manner. The regions of the cross-wound bobbin are called a critical diameter region, in which a whole-number winding ratio is present, in other words, in which the cross-wound bobbin carries out one or more complete revolutions per double stroke of the traversing thread guide because of the present diameter.

As described in claim 3, it is provided, in this case, in an advantageous embodiment that the cross-winding angle is reduced shortly before reaching a critical cross-wound bobbin diameter, by reducing the speed of the traversing thread guide.

The reduction in the cross-winding angle leads directly to a change in the winding ratio with the result that ribbon windings cannot occur in this per se critical diameter region of the cross-wound bobbin.

As shown in claim 4, to change the cross-winding angle, the workstation computer preferably initiates a speed change of the traversing thread guide. At the same time, the rotational speed of the winding roller and therefore the winding speed of the cross-wound bobbin are also adjusted in such a way that the thread tension of the running-on threads remains virtually constant. In other words, the speeds of the traversing thread guide and winding roller are adjusted in such a way that the resultant force of the displacement speed of the traversing thread guide and the rotational speed of the winding roller constantly remain virtually the same.

According to claim 5, the drive of the traversing thread guide is preferably configured as a stepping motor. Such stepping motors are economical mass produced components, which can also be very precisely activated in a relatively simple manner. In other words, very precise displacement of the traversing thread guide is possible, for example, with such stepping motors, the outlay for control being kept within reasonable limits.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention described in more detail below with the aid of an embodiment shown in the drawings, in which:

FIG. 1 shows a side view of a workstation of an open-end rotor spinning machine producing cross-wound bobbins, with a winding device which operates by the method according to the invention,

FIG. 2 schematically shows, to an enlarged scale, the winding device required to carry out the method according to the invention,

FIG. 3 shows a graph, which makes clear the connection between the rotational speed of the winding roller and the speed of the traversing thread guide, in particular when there is a change in the cross-winding angle,

FIG. 4 schematically shows the thread run in a cross-wound bobbin, which has reached a critical diameter region.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 schematically shows a side view of one half of a textile machine 1 producing cross-wound bobbins, in the embodiment of an open-end rotor spinning machine. Textile machines of this type, as known, have between their end frames (not shown) a large number of similar workstations 2, which inter alia have a spinning unit 3, in each case, as well as a winding device 4. Fibre bands 6, which are stored in spinning cans 5, are processed to form threads 7 in spinning units 3, which threads are then wound on the winding devices 4 to form cross-wound bobbins. The finished cross-wound bobbins 8 are conveyed, for example, by means of a cross-wound bobbin transporting mechanism 12 to a loading station (not shown) arranged at the end of the machine.

As also indicated in FIG. 1, the individual workstations 2, apart from the spinning unit 3 and the winding device 4, also have further handling mechanism, for example a thread take-off mechanism 10, a suction nozzle 17 or a waxing device 14. The functions of these components are known and described in detail in numerous patents.

The winding device 4 substantially has a creel 9, a winding roller 11 as well as a thread traversing mechanism 16. The winding roller 11, which can be driven by a single motor by means of a drive 13, in this case drives the cross-wound bobbin 8, which is freely mounted in the creel 9, by frictional engagement.

FIG. 2 schematically shows a front view of a winding device 4 required to carry out the method according to the invention.

As indicated in the drawing, the cross-wound bobbin 8 freely rotatably held in a creel (not shown) rests on a winding roller 11 and is entrained thereby by frictional engagement.

The winding roller 11 is in this case connected to a drive 13, which is in turn connected via a control line 23 to a workstation computer 19. To displace the thread 7 while running onto the bobbin 8, a thread traversing mechanism 16 is also provided, the traversing thread guide 18 of which is driven in an oscillating manner by its own drive, preferably a stepping motor 20. The stepping motor 20 is also connected to the workstation computer 19 via a control line 24 and can be activated thereby in a defined manner.

Furthermore, a sensor mechanism 21 is provided, which is connected via a signal line 22 to the workstation computer 19 and detects the respective rotational speed of the cross-wound bobbin 8 during the winding process. In other words, the workstation computer 19 is supplied with signals of the sensor mechanism 21 and, using the rotational speed of the winding roller, the known diameter of the winding roller and the rotational speed of the cross-wound bobbin 8 determined by the sensor mechanism 21 constantly calculates the instantaneous diameter of the cross-wound bobbin 8.

FIG. 3 shows a graph, in which the speed V_FF of the traversing thread guide 18 is shown on the abscissa and the rotational speed V_WW of the winding roller 11 is shown on the ordinate. As indicated, a thread take-up speed V_A1 is produced during the regular bobbin travel at a speed V_{1 FF} of the thread guide 18 and a rotational speed V_{1 WW} of the winding roller 11. In this case, the thread runs onto the cross-wound bobbin 8 at an angle α/2.

Shortly before reaching a critical diameter region D_{SP k} of the cross-wound bobbin 8, the value of the thread run-on angle α/2 is changed to α₁/2. In other words, the speed of the thread guide 18 is reduced to V₂ FF, as shown in FIG. 3. In order to keep the thread take-up speed V_A1=V_A2 constant, the rotational speed of the winding roller 11 is also adjusted in such a way that the winding roller 11 now rotates at V_{2 WW}. This means that the resulting thread take-up speed V_A1 or V_A2 being produced from the rotational speed V_WW of the winding roller 11 and the speed V_FF Of the thread guide 18 remains constant regardless of the thread cross-winding angle α or α₁.

FIG. 4 shows a cross-wound bobbin 8, which has reached a first critical diameter region D_{SP k} depending on the bobbin width B_SP and the cross-winding angle α. As indicated with the aid of the line 30 representing the thread run, or the associated arrows 31 to 36, a plurality of complete revolutions of the cross-wound bobbin 8 would take place at this diameter of the cross-wound bobbin 8 and a cross-winding angle α per double stroke of the traversing thread guide 18, with the result that the thread would be placed in thread deposits located one above the other.

In order to avoid ribbon windings, the value of the cross-winding angle α is changed to α₁ shortly before reaching the critical diameter region D_{SP k}. At a cross-winding angle α₁ and a bobbin width B_SP, it is ensured, in the region of the cross-wound bobbin diameter D_{SP k} that no ribbon windings can occur.

The thread run being adjusted at a cross-winding angle α₁ and a bobbin width B_SP is indicated in FIG. 4 with the aid of the line 40 or the associated arrows 41 to 49.

Functioning of the method according to the invention:

At the beginning of a batch, firstly the most important parameters of the cross-wound bobbin, for example the provided final diameter of the cross-wound bobbin 8, the bobbin width B_SP, the cross-winding angle α, with which the cross-wound bobbin 8 is to be wound, as well as a further cross-winding angle α₁ are established and input for example into the central control unit of a textile machine.

The central control unit of a textile machine is, in this case, in turn connected to the individual workstation computers 19 of the workstations 2 preferably via a bus connection or the like. The central control unit or the workstation computers 19 firstly calculates/calculate, with the aid of the aforementioned data, the critical diameter regions D_{SP k} of the cross-wound bobbin, in other words, the regions in which if no particular measures are taken, ribbon windings would occur. For example, the workstation computer 19 determines with the aid of the formula: D_{SP k}=whole number x bobbin width B_SP/π×tan cross-winding angle α/2, that at a bobbin width of, for example, 150 mm and a cross-winding angle of α=36°, the particularly critical diameter regions of the cross-wound bobbin 8 are at D_{SP k}=147 mm, 294 mm etc.

After the start of the spinning/winding process the rotational speed of the cross-wound bobbin 8 is constantly monitored by means of the sensor mechanism 21 and the current diameter D_SP of the cross-wound bobbin 8 is constantly calculated in the workstation computer 19 according to the formula: D_SP=D_WW×n_ww/n_SP.

If the workstation computer 19 establishes that the diameter D_SP of the cross-wound bobbin 8 is approaching a critical diameter region D_{SP k}, the value of the cross-winding angle α is changed to α₁, for example reduced from α=36° to α₁=30°. The reduction in the cross-winding angle α to α₁ takes place here by reducing the speed V_FF of the traversing thread guide 18. In other words, the workstation computer 19 activates the drive 20 of the thread traversing mechanism 16 in the direction of “deceleration”.

In order to continue to keep the thread tension of the thread 7 running onto the cross-wound bobbin 8 constant, the workstation computer 19 simultaneously also activates the drive 13 of the winding roller 11 in the direction of “acceleration”. In other words, the rotational speed V_WW of the winding roller 11 is increased in such a way that the take-up speed V_A of the thread 7 onto the cross-wound bobbin 8 remains virtually constant despite the change in the cross-winding angle.

The invention is not limited to the embodiment shown; in an alternative embodiment, instead of the workstation computers, section computers or the central control mechanism of the textile machine can obviously also be used as the control computer.

Claims

1. Method for avoiding ribbon windings in the production of take-up bobbins which are wound at the workstations of textile machines producing cross-wound bobbins in the “random winding” type of winding, by changing the traversing speed at which the yarn is wound onto the take-up bobbin, the workstations in each case having a single motor drive, which can be activated in a defined manner for the rotation of the cross-wound bobbin, and a single motor drive which can be activated in a defined manner for a traversing yarn guide, characterised in that the diameters (DSP k) of the cross-wound bobbin (8) which are particularly critical with regarding to the development of ribbon windings and depend on the width (BSp) of the cross-wound bobbin (8) and a cross-winding angle (α) selected during the winding of the cross-wound bobbin (8), are determined, in that, in each case, shortly before reaching one of these critical diameters (DSP k), the cross-winding angle (α) is changed to a value (α1), which rules out the development of ribbon windings in this diameter region and in that the cross-winding angle (α1) is reset again to its original value (α) after the critical diameter (DSP k) has been passed.

2. Method according to claim 1, characterised in that the critical diameters (DSP k) of the cross-wound bobbin (8) are determined according to the formula (DSP k)=(whole number) x bobbin width (BSp)/π×tan of half the cross-winding angle (α/2).

3. Method according to claim 1, characterised in that the cross-winding angle (α) is reduced shortly before reaching a critical diameter (DSP k) of the cross-wound bobbin (8).

4. Method according to claim 1, characterised in that to change the cross-winding angle (α), the speed (VFF) of the traversing yarn guide (18) is changed, the rotational speed (VWW) of the winding roller (19) being simultaneously adjusted in such a way that the yarn tension of the running-on yarn (7) remains virtually constant.

5. Method according to claim 4, characterised in that a stepping motor (20) is used as the drive for the traversing yarn guide (18).