EP3460113B1 - Method for incorporating a warp knitting machine and warp knitting machine - Google Patents

Description

The invention relates to a method for incorporating a warp knitting machine with a new pattern in which threads of a warp are drawn into guide needles and at least one row of stitches is formed by the interaction of the guide needles with knitting needles.

The invention also relates to a warp knitting machine with at least one main shaft, at least one guide bar, at least one knitting needle bar, a thread compensation device, at least one delivery drive and at least one fabric take-off.

The necessary data are generally available for a known knitted fabric, which can also be referred to as a “sample” for short. The data include the laying, a size for the thread inlet and a size for the goods take-off. So if a warp knitting machine has to be incorporated, for example because a warp beam has been completely processed or the warp knitting machine has been converted to a different pattern is to be, the operator pulls the threads into the needles, creates one or more rows of stitches, pulling the threads taut by hand after each stitch formation process, then switches on the supply drive with a predetermined thread inlet value, lets the machine create a series of additional stitches , until you are able to pull off the resulting knitted fabric with the goods take-off, then switch on the goods take-off and can start production. However, if a new pattern is to be generated, not all or not all of the required data is necessarily available. As a rule, the laying is specified, ie the course of movement of the laying needles in relation to the knitting needles. However, the thread inlet must be determined empirically, for example. This requires a certain amount of experience and a corresponding feeling on the part of the operator. With every work step there is accordingly the risk of operating errors and a lack of specialist knowledge. This can result in damage to the active elements and / or also to the process material, for example the yarn. Training is accordingly time-consuming and costly.

DE 102 34 545 A1 shows a method and a device for supplying threads to a textile machine, which is specified as a knitting machine, in which individual threads are supplied by individual thread bobbins and controlled by individual thread feeding devices. The thread feeding devices try to deliver threads with a predetermined thread tension. Depending on the thread consumption of each connected knitting point, this results in individual delivery quantities or

Yarn feed speeds on the individual yarn feeders. These yarn delivery quantities or yarn speeds are recorded and used as the basis for determining a target value, which can then be used as a basis for later operation.

EP 1 289 239 shows a device for adapting the speed of rotation of warp beams in a warp knitting machine as a function of the warp thread tension. The invention is based on the object of making it easier to incorporate a warp knitting machine into a new pattern.

In a method of the type mentioned at the outset, this object is achieved in that the tension of the incoming threads is determined and limited to a predetermined maximum value by regulating a delivery drive.

Limiting the thread tension avoids excessively high thread tensions. This considerably reduces the risk of damage to the knitting tools or the thread material. In addition, the limitation of the tension of the incoming threads allows a restriction with regard to the freely selectable parameters, so that the operator can only work in a limited work area. This further facilitates the incorporation because the possibilities for variation and thus also the possibilities for errors can be kept small. The tension of the circulating threads is preferably determined on a component that is not directly thread-guiding. Nor is it a question of the tension of an individual thread, but rather of the tension prevailing in the entirety of the threads supplied by a tree. The delivery drive actively drives a warp beam from which the threads of the warp are pulled. In the later production operation, in which the knitted fabric is continuously produced, the delivery drive is operated with a constant thread inlet value. The thread inlet value is usually given in "mm / R", ie millimeters per rack. One of the tasks involved in training a warp knitting machine with a new pattern is to determine an appropriate thread inlet value. This thread inlet value can be determined by specifying the tension and operating the supply drive in a closed control loop in such a way that the tension is reached, but not exceeded. If the supply drive is too much thread length per Emits loop forming process, the tension is too low. If the supply drive gives too little thread length per loop formation process, the tension is too high. Accordingly, the "delivery speed" in the delivery drive can be set to the correct thread inlet value with a relatively simple regulation. It is not absolutely necessary here that the supply drive is already running continuously at this stage of familiarization. It can also be operated intermittently, i.e. deliver some thread for a short time and then stop again. This is only intended to avoid excessively large voltage peaks. Moreover, very little or no tension at all can sometimes prevail in the threads during a loop-forming process. In any case, the delivery drive is only operated in a positive drive direction, i.e. in a direction in which it releases threads.

The row of stitches is preferably formed in a creep speed. So you can run the warp knitting machine at a very low speed as long as you work in the new pattern. The tensions of the threads are practically independent of the working speed of the warp knitting machine.

The tension is preferably determined at a point in time at which the guide needles have reached their reversal point behind the knitting needles. This is where the maximum deflection of the guide needles takes place. The distance between the various active elements is greatest at this point. Accordingly, the tension of the threads is also greatest here. It is sufficient to determine the tension here and make it the basis for further action. A goods take-off is preferably switched on and, after the goods take-off has been switched on, the control of the delivery drive continues for a predetermined time. Switching on the fabric take-off results in a change in the appearance of the knitted fabric. Without a fabric take-off, the individual rows of stitches are created "on a block", so to speak. The stitches of the individual rows of stitches practically lie against one another in the direction of production of the knitted fabric. Switching on the goods take-off then results in a slightly different appearance. Depending on the speed at which the fabric take-off is operated, the result is a looser or firmer knitted fabric structure. The regulation of the supply drive then also has an influence on the structure of the knitted fabric, because if the supply drive supplies a greater length of thread per stitch formation process, a looser knitted fabric can be achieved than in the case of shorter thread length per stitch formation process. After switching on the fabric take-off, the operator can then check whether the knitted fabric meets the requirements or wishes. If this is not the case, you can change the voltage specification.

A thread entry value of the delivery drive is preferably displayed. The thread tension results in a thread inlet value, for example mm / R, i.e. millimeters per rack. If the knitted fabric has the desired look and feel, this thread run-in value can be displayed so that it can be used again in later production processes of the same pattern. The indication can take place optically via a display. However, the display can also consist of printing out the thread inlet value or storing it in some other way. It is only important that the thread entry value is available later, i.e. when the same pattern is produced again, and can be entered into the knitting machine.

The predetermined maximum value is preferably specified as a fraction of a basic value. The basic value is known for every machine and can be specified by the manufacturer. It results, for example, from measurements on the respective warp knitting machine, whereby fluctuations can also be taken into account here. You can then, for example, specify a certain percentage of the basic value as the voltage. It is therefore not necessary to specify an absolute value.

The object is achieved in a warp knitting machine of the type mentioned at the outset in that a thread tension measuring device is connected to a control device which regulates the delivery drive in a learning phase.

With the thread tension measuring device, as explained above in connection with the method, one can determine the thread tension of the threads of the warp and make this tension the basis for setting the thread inlet value of the supply drive. On the one hand, this avoids overloading the active elements and the thread material. On the other hand, the operator has a simple possibility to change the appearance and the feel of the resulting knitted fabric. He only has to change a setpoint with which the control device regulates the delivery drive.

The thread tension measuring device is preferably arranged on the thread compensation device. The thread compensation arrangement is necessary in the production of a knitted fabric in a warp knitting machine because the thread consumption fluctuates during a loop formation process. The fluctuations within this thread consumption can be compensated for using the thread compensation device. You can now use this thread compensation device in a simple manner to determine the thread tension. "Measuring" in the sense of a numerical result is often not necessary. The thread tensioning device can also be arranged on the fastening of the thread compensation device.

The thread tension measuring device preferably determines a total tension of several threads. This results in a certain compensation across the width of the warp knitting machine. The influence of a single thread and its tension is thus kept small, while the total tension of several or even all threads gives a meaningful quantity.

It is preferred here that the thread tension measuring device determines a tension on a crosshair. In the simplest case, the crosshair is a spring-mounted rod over which the threads of the chain are guided before they enter the thread guide opening of the guide needles. The crosshair has its greatest deflection when the locating needles are behind the knitting needles at their reversal point. At this moment the maximum thread tension can be determined. The thread tension is preferably determined on a stationary part, for example in an area between a spring arrangement that carries the crosshairs and the frame of the warp knitting machine.

The thread tension measuring device is preferably synchronized with the main shaft. The thread tension measuring device can then determine the corresponding tension precisely at the moment indicated above, in which the guide needles are at their greatest distance from the knitting needles.

Fig. 1

eine stark schematisierte Ansicht von Teilen einer Kettenwirkmaschine, und

Fig. 2

eine schematische Darstellung von Spannungsverläufen.

The invention is described below using a preferred exemplary embodiment in conjunction with the drawing. Show here:

Fig. 1

a highly schematic view of parts of a warp knitting machine, and

Fig. 2

a schematic representation of voltage curves.

A warp knitting machine 1, parts of which are shown, has guide needles 2 which are arranged on a guide bar, not shown in detail. Furthermore, the warp knitting machine has knitting needles 3 which are arranged on a knitting needle bar, not shown in detail. When the warp knitting machine is in operation, the guide needles 2 and the knitting needles 3 are moved relative to one another in order to form loops of a knitted fabric. The relative movement has sections in which the guide needles 2 are moved through alleys between knitting needles 3, and Sections in which the locating needles are moved parallel to the longitudinal extension of the knitting needle bar.

With such a movement, threads 4 that are pulled off a warp beam 5 are processed into stitches of the knitted fabric.

The threads 4 are guided to a crosshair designed as a rod 6. The rod is mounted on a spring arrangement 7. The spring arrangement 7 allows a certain mobility of the rod 6 when the tension of the threads 4 changes. Such a change in tension occurs at least once per knitting cycle, as shown in FIG Fig. 2 can be seen.

Fig. 2 shows a first curve 8, which represents the tension of an individual thread 4, and a second curve 9, which represents a corresponding tension curve of the entire warp. The voltage profile shown in curve 9 can be determined from the movement of rod 6. For this purpose, a sensor 10 is arranged on the spring arrangement 7, which sensor determines the tension of the spring arrangement 7 and thus the force applied by the rod 6 to the spring arrangement 7. It is of course also possible to use a different sensor in order to determine the tension of the chain formed by the threads 4. The sensor 10 can be formed, for example, by a strain gauge which is arranged between a frame 18 of the warp knitting machine and a holder 19 of the spring arrangement 7 fastened to the frame 18. The sensor is therefore located on a stationary part and it is located outside of a direct thread-guiding element of the warp knitting machine.

The sensor 10 is connected to a control device 11. The control device 11 is connected to a supply drive 12 of the warp beam 5.

The warp knitting machine 1 has a main shaft 13. The main shaft 13 is responsible for most of the movements of the knitting tools. In particular, it controls the movements of the guide needles 2 and the knitting needles 3. Expressed in simple terms, one rotation of the main shaft 13 causes a loop-forming process in most cases, so that one row of stitches is produced per rotation of the main shaft 13.

A rotation angle sensor 14 detects the rotary position of the main shaft 13 and also reports it to the control device 11.

A fabric take-off with which the formed knitted fabric can be removed from the working area formed by the laying needles 2 and the knitting needles 3 is not shown.

When a warp knitting machine is put into operation, the threads 4 are drawn into the laying needles 2. This is usually done with a dismantled guide bar, in which the guide needles 2 are more accessible. After the threads have been drawn in, the guide bar is brought to its normal working position and mounted there. An operator then slowly sets the machine in motion and first checks whether the laying needles 2 can run through alleys between the knitting needles 3 without colliding. Possibly. correction is required.

The operator then first carries out a first loop-forming process. The threads 4 are then tightened by hand. This is followed by one or more further loop-forming processes until at least one is over the working width of the Warp knitting machine 1 continuous row of stitches has been formed. The threads 4 are tightened by hand between each stitch formation process.

When a continuous loop formation has taken place, the delivery drive 12 of the warp beam 5 is put into operation. The warp beam 5 then delivers the threads 4. The stitches are then initially formed in a block, i.e. they are close to one another. Then the goods take-off (not shown) is put into operation and production of the goods can begin.

However, this presupposes that certain parameters of the production of the knitted fabric are known, in particular a value for the so-called thread inlet, which is typically specified in mm / R, that is, millimeters per rack. In addition to the actual laying and the stitch density, which can be influenced by the pull-off, the thread inlet is an important value in the production of the knitted fabric.

When a new pattern is to be created, the thread inlet value is not available. The thread inlet is adjusted with the experience and feeling of the operator. There is a risk at every step of the process due to operating errors and a lack of specialist knowledge. This can result in damage to the knitting elements, that is to say the locating needles 2 and the knitting needles 3. In addition, the threads 4 can also be damaged.

In order to mitigate this problem, a tension of the incoming threads 4 is determined with the aid of the sensor 10 and this actual tension is passed on to the control device 11. The control device 11 compares the actual voltage with a predeterminable setpoint voltage and now regulates the Delivery drive 12 so that this target voltage, which represents a predeterminable maximum value, is not exceeded.

If the delivery drive 12 is controlled in such a way that it delivers more threads 4, that is to say a larger thread length per rack, then the tension drops. If the supply drive 12 is driven in such a way that it supplies fewer threads, that is to say a smaller thread length per rack, then the tension increases. This automated procedure enables the warp knitting machine to approach the correct value of the thread inlet by itself, so to speak.

This "learning process" is continued when the goods take-off is switched on and the meshes become larger. A greater length of the threads 4 is thus also required for each stitch. Accordingly, the supply drive has to turn the warp beam 5 a little faster in order to supply a greater length of the threads 4 per stitch formation process. Here, too, the voltage is determined and the delivery drive 12 is regulated in such a way that a maximum voltage is not exceeded.

The voltage does not have to be entered as an absolute value. Each warp knitting machine 1 usually has a basic value which, for example, can be specified by the manufacturer or can be determined when the warp knitting machine is started up for the first time. The operator can then use an input device 15, for example, to specify a percentage of this basic value, that is to say a fraction, in order to set the maximum voltage. The operator can then check visually or by feeling whether this tension value has resulted in the desired quality of the knitted fabric. If this is not the case, the percentage value can be changed via the input device 15.

As soon as the knitted fabric has been produced with a satisfactory quality, the value of the thread inlet can be displayed via a display device 16. The display device is shown here schematically. It is not absolutely necessary to use a display or a printer here. It is also possible to simply save the value of the thread inlet so that the saved value is then available for later production processes.

With the value of the thread inlet, later knitted fabrics that contain the same pattern can be produced.

The described process preferably takes place in crawling speed, so that the operator can continuously check at slow speed whether the knitted fabric is actually being produced with the desired look and feel.

The crosshairs with the rod 6 and the spring device 7 form a thread compensation device which is required during operation in order to compensate for the fluctuating thread consumption during a loop formation process. You can now also use it to continuously determine the tension of the threads.

As out of the curves of the Fig. 2 can be seen, the tension of the threads 4 fluctuates quite considerably in a loop formation process. This is because the thread consumption also fluctuates in a knitting process. The tension is greatest when the locating needles 2 are at a reversal point behind the knitting needles 3, specifically on the side of the hook 17 of the knitting needles 3. Here, the locating needles 2 have the greatest deflection compared to the knitting needles 3. By means of the angle of rotation sensor 14, which detects the angle of rotation position of the main shaft 13, it is now possible to detect this position of the locating needles 2, so that the Control device 11 also only detects the corresponding voltage value at this point in time. The control device 11 thus forms, so to speak, a snapshot of the voltage at a point in time at which the main shaft 13 is in a predetermined rotational angular position, and only compares the voltage at this point in time with the predetermined or predeterminable maximum value.

Claims (11)

1. Method for starting up a warp-knitting machine (1) with a new pattern, in which threads (4) of a warp are drawn into guide needles (2) and at least one row of stitches is formed by interaction of the guide needles (2) with knitting needles (3), characterized in that a tension of the incoming threads (4) is determined and limited to a predetermined maximum value by regulating a delivery drive (12).
2. Method according to claim 1, characterized in that the row of stitches is formed in the creed speed.
3. Method according to claim 1 or 2, characterized in that the tension is determined at a point in time at which the guide needles (2) have reached their reversal point behind the knitting needles (3).
4. Method according to any of claims 1 to 3, characterized in that a fabric take-off is switched on and, after switching on the fabric take-off, the control of the delivery drive (12) is continued for a predetermined time.
5. Method according to any of claims 1 to 4, characterized in that a thread infeed value of the delivery drive (12) is displayed.
6. Method according to any of claims 1 to 5, characterized in that the predetermined maximum value is set as a fraction of a basic value.
7. Warp-knitting machine (1) having a main shaft (13), at least one guide bar, a knitting needle bar, at least one thread equalizing device (6, 7), at least one delivery drive (12) and at least one fabric take-off, characterized in that a thread tension measuring device (10) is connected to a control device (11) for controlling the delivery drive (12) in a learning phase.
8. Warp-knitting machine according to claim 7, characterized in that the thread tension measuring device (10) is arranged on the thread equalizing device (6, 7).
9. Warp-knitting machine according to claim 8, characterized in that the thread tension measuring device (10) determines a total tension of several yarns (4).
10. Warp-knitting machine according to claim 9, characterized in that the thread tensioning measuring device (10) determines a tension at a thread cross (6).
11. Warp-knitting machine according to any of claims 7 to 10, characterized in that the thread tension measuring device (10) is synchronized with the main shaft (13).

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