EP1891257B1

EP1891257B1 - Method for introducing weft threads and weaving machine for applying this method

Info

Publication number: EP1891257B1
Application number: EP06754173A
Authority: EP
Inventors: Kristof Roelstraete
Original assignee: Picanol NV
Current assignee: Picanol NV
Priority date: 2005-06-15
Filing date: 2006-06-07
Publication date: 2011-01-26
Anticipated expiration: 2026-06-07
Also published as: DE602006019859D1; EP1891257A1; WO2006133833A1; CN101198733A; BE1016639A6; CN101198733B; ATE497039T1

Abstract

Weaving machine and method for introducing a weft thread (2, 3, 4) in a weaving machine, comprising introducing a specific weft thread (2, 3, 4) into a shed (8) at a lower speed than the normal speed for this specific weft thread (2, 3, 4), if a knot or irregularity (39, 41) has been detected in a specific weft thread (2, 3, 4).

Description

The invention relates to a method for introducing a weft thread in a weaving machine, more particularly in a gripper weaving machine.
Gripper weaving machines in which a plurality of weft threads are successively introduced into a shed according to a specific pattern by means of grippers are known. With most gripper weaving machines, the weft thread remains connected to the fabric selvedge between the successive introductions and the weft thread is cut by weft scissors from the fabric selvedge at the beginning of the introduction. Weft scissors of this type are described, inter alia, in US 3621885 .
A gripper weaving machine usually comprises a thread monitor in order to detect a broken weft thread, which thread monitor is arranged between a thread stock, such as a spool and the shed. In addition, a gripper weaving machine may comprise detection means in order to detect irregularities, such as a knot, a relatively thin or thick section in a weft thread and the like.
It is known to connect or tie the end of a spool which supplies weft thread to the start of an auxiliary spool and to provide a spool switching sensor between both spools in order to detect such a connection or knot.
From EP 656.437 B1 , it is known to interrupt the introduction of a specific weft thread once a knot has been detected in said weft thread, so that a length of weft thread containing a knot is not introduced into the shed. This offers the advantage that it is possible to produce a fabric without knots. The abovementioned method can be used when a specific type of weft thread can be provided from a plurality of feeders. With the abovementioned method a length of weft thread is lost, which may be a disadvantage, particularly with expensive yarns. With weak weft threads, the intermediate distance between two knots may in this case be in the order of magnitude of the length of weft thread which has to be removed. This may lead to no weft thread being supplied through the respective feeder for a long time. In addition, the length of weft thread which has to be removed using the method according to EP 656.437 B1 is usually significantly larger than strictly necessary to remove the knot, as a safety margin has to be observed due to the fact that it is impossible to determine the exact position of the knot which in turn depends on the weft thread stock on a prewinder.
If the fabric is allowed to have knots and the introduction of a specific weft thread is not interrupted once a knot has been detected in said weft thread, there is a risk with gripper weaving machines, and particularly with fast gripper weaving machines, that as a result of the continuous pull on a weft thread containing a knot by means of a gripper, this weft thread will break at this knot.
It is an object of the invention to minimize the breaking of a weft thread during the introduction of a weft thread, more particularly during the introduction of a weft thread using at least one gripper in a gripper weaving machine.
In order to achieve this object, a method according to the invention comprises introducing a specific weft thread at a lower speed than the normal speed for this specific weft thread, if a knot or irregularity has been detected in a specific weft thread.
The invention offers the advantage that it prevents a knot or irregularity in a specific weft thread giving rise to a thread break and thereby stops of the weaving machine as a result of thread breaks are prevented. With certain fabrics, the presence of knots and irregularities in the fabric does not present a problem. Furthermore, the method does not necessarily require additional mechanical or pneumatic means in order to remove a knot before it is woven into the fabric.
The invention is particularly advantageous for weaving weak weft threads which already contain a significant number of knots due to preparatory processes such as spinning, winding, twisting and the like. With weft threads of this type, the knots are usually also relatively weak and can be pulled apart from a certain yarn tension upwards.
According to a preferred embodiment, a method comprises introducing a specific weft thread at a relatively low speed once the knot or irregularity has been detected and before the knot or irregularity is introduced. This makes it possible to reduce the speed only after a certain time or a certain number of introductions after a knot or irregularity has been detected.
According to a preferred embodiment, a method comprises introducing a specific weft thread at a relatively low speed at least up to the point in time when the knot or irregularity is introduced. This makes it possible to increase the speed again once it has been ascertained that a knot or irregularity has been introduced.
According to a preferred embodiment, a method comprises lowering the speed of the weaving machine after a knot or irregularity has been detected in that specific weft thread. This method is particularly suitable for use with a weaving machine in which the speed of the weft thread is determined by the speed of the weaving machine, more particularly with a weaving machine such as a gripper weaving machine.
According to one embodiment, a method comprises detecting a knot or irregularity which is located between the thread supply and the fabric selvedge. This may be effected using detection means for detecting a knot or irregularities which comprise a spool switch sensor arranged between two spools and producing a signal when a switch from one spool to the other spool takes place. Such detection means may also comprise a thread sensor which can detect a knot or irregularity in a weft thread. An irregularity may consist of a knot, a relatively thin or thick section and the like. If an irregularity is present, the local tensile strength of the weft thread can be assumed to be significantly lower than the nominal tensile strength of the weft thread, i.e. the tensile strength when no irregularity is present. With some weft threads, the irregularities usually consist of knots.
The invention also relates to a weaving machine, more particularly a gripper weaving machine, which employs a method according to the invention and which comprises a drive unit, for example a drive motor, the speed of which can be controlled.
In order to illustrate the features according to the invention more clearly, the invention will be explained in more detail below with reference to drawings of exemplary embodiments, in which:

Fig. 1 shows a gripper weaving machine according to the invention;
Fig. 2 shows the course of the speed of the weaving machine as a function of time;
Fig. 3 shows the course of the break risk of a weft thread and the speed of the weaving machine as a function of the tensile stress in the weft thread.

Fig. 1 shows a gripper weaving machine comprising a supply 1 for the weft threads 2, 3 and 4. The supply 1 comprises, for example, three feeders 5, 6 and 7 for introducing a specific weft thread into the shed 8 during successive introductions. In this case, the weft thread of each feeder remains connected to the edge 9 between successive introductions and is detached from the edge 9 by means of diagrammatically illustrated weft scissors 10 which are driven by, for example, the weaving machine, at the start of an introduction of a weft thread of a specific feeder. The edge 9 is in this case at the first warp thread 11. In the case of weaving without waste, the edge 9 is also the fabric selvedge.
The weft scissors 10 are arranged at the edge 9 at the beat-up line 12 of the fabric. The weft scissors 10 are intended for detaching a weft thread from the edge 9 at the start of the introduction into the shed 8. In addition, the weaving machine comprises a control unit 14 which, inter alia, controls a thread feeder 13. The thread feeder 13 ensures that weft threads are fed from a specific feeder 5, 6 or 7 to a gripper, more specifically to the giving gripper 15. There, the giving gripper 15 takes the fed weft thread up, takes the weft thread which was taken up to the centre of the shed 8 and passes this weft thread onto a receiving gripper 40 in a known manner (as indicated in Fig. 1 by a dashed line). The receiving gripper 40 then takes the received weft thread further to the other side of the shed 8 in a known manner.
The supply 1 in this case also comprises a thread monitor 16 for detecting broken weft threads, more particularly for detecting a broken weft thread 2, 3 or 4. The feeder 5 comprises two spools 17, 18, the feeder 6 comprises two spools 19, 20 and the feeder 7 comprises two spools 21, 22. As diagrammatically indicated, the end of the spools 17, 19 and 21 in use is tied to the start of an associated auxiliary spool 18, 20 or 22. Furthermore, each feeder 5, 6 or 7 comprises an associated prewinder 23, 24 or 25. Spool switch sensors 26, 27 and 28 are arranged between the spools in order to detect a switch from one spool to another spool. In addition, a thread sensor 29, 30, 31 is arranged in front of every prewinder 23, 24, 25 in order to detect a knot or irregularity in a weft thread.
The spools are arranged in a fixed position on a spool stand 32, on which spool stand 32 the prewinders are also secured. Near the beat-up line 12 of the fabric 33, a guide bar 34 is also provided for guiding a weft thread between the edge 9 and a gripper 15 to the weft scissors 10. A reed 35 is also illustrated. The thread feeder 13 comprises a plurality of thread feeder needles 36, 37 and 38 which are each provided with a thread guide.
According to the invention, the gripper weaving machine comprises a control unit 14 which can interact with detection means which detect when there is a knot or irregularity between a spool and the edge 9, more particularly with the spool switch sensors 26, 27 or 28 and/or the thread sensors 29, 30 or 31. The spool switch sensors 26, 27 and 28 produce a signal when a switchover from one spool to another spool takes place, thus making these signals also representative of a knot 39 which is present there. The thread sensors 29, 30 or 31 may, for example, use the principle of thickness measurement and are in this case able to produce a different signal when a knot 41 or irregularity in the weft thread passes the thread sensor instead of a normal weft thread. Thread sensors 29, 30 or 31 of this type are preferably used when, in addition to the knots produced by connecting two spools, other knots 41 or irregularities are present in the weft thread present on the spools. The latter is mainly the case with weak weft threads.
In this case, it should be noted that the abovementioned detection means are preferably arranged in such a manner that the length of weft thread between the detection means and the edge 9 is greater than the length of a weft thread to be introduced. This allows the knot or irregularity to be detected before it is introduced into the shed 8. As there is a certain stock 42, 43 and 44 of weft thread on the prewinder 5, 6 or 7, there will always be sufficient weft length when the abovementioned detection means are arranged in front of the prewinder.
The giving gripper 15 and the receiving gripper 40 are transported through a shed 8 formed by warp threads 52 by means of gripper belts 50 and 51 in a known manner. The warp threads 52 are moved up and down by means of known shed-forming device according to a pattern. The gripper belts 50 and 51 are, for example, driven according to a specific movement path by means of a gripper drive 53 and 54. Gripper drives 53, 54 of this type are driven by a drive shaft 55 and are known, inter alia, from EP 077.087 A1 and FR 2315558 A1 . The drive shaft 55 is driven synchronously by means of the drive shaft 56 of the drive motor 57 of the weaving machine. In this case, the gripper drives 53, 54 impose a movement path on the grippers 15, 40 which is determined by the angular position of the drive shaft 56. The movement path of the introduced weft thread is in this case determined by the movement path of the gripper 15 or 40 which interacts with the weft thread.
The weaving machine comprises a drive unit 45, the speed of which can be controlled. The drive unit 45 comprises a drive motor 57. An angular sensor 58 is provided in order to determine the angular position of the drive shaft 56 of the drive motor 57. This angular sensor 58 is connected to the control unit 14. It is clear that according to a variant, the drive shaft 55 can coincide with the drive shaft 56. The drive motor 57 is controlled by means of the control unit 14 in accordance with a specific velocity profile. This may be effected in a manner as described in EP 1.032.867 B1 or WO 03/032481 . During a weaving cycle for introducing a weft thread, the drive motor 57 can be controlled using a corresponding velocity profile. In this manner, a weft thread can be introduced into a shed using a corresponding velocity profile, which is dependent on and determined by the velocity profile of the drive motor.
Furthermore, the weaving machine comprises an input unit 46 for inputting data into the control unit 14. These data contain the pattern with which successive weft threads 2, 3 and 4 have to be introduced and the pattern of the speed at which the drive motor 57 is to be driven for successive weft threads. In this case, it should be noted that, as will be explained below, each type of weft thread 2, 3 or 4 can also be introduced at a different speed during successive introductions, which operation is to be controlled in a suitable manner by the speed of the drive motor 57.
The input unit 46 is, for example, used to input the weaving pattern below. The weaving machine will then be controlled by the control unit 14, for example according to the pattern below.

Insertion	Weft thread	Weaving machine speed
1	2	550 revolutions/minute
2	3	550 revolutions/minute
3	4	450 revolutions/minute
4	2	500 revolutions/minute
5	4	450 revolutions/minute
6	3	500 revolutions/minute
7	2	550 revolutions/minute
8	2	550 revolutions/minute

If the thread sensor 29 detects, for example, a knot 41 and emits a corresponding signal to the control unit 14, a method according to the invention will be used. As the prewinder 23 still contains a stock 42, the control unit 14 does not have to react immediately.
The method for introducing a weft thread in a weaving machine according to the invention comprises introducing a specific weft thread at a lower speed than the normal speed for said specific weft thread when a knot or irregularity was detected.
In the illustrated example, the speed for introducing the weft thread 2 is reduced at the fourth, seventh and eighth insertion, for example by limiting the speed of the weaving machine to 500 revolutions/minute and in this way limiting the speed of the corresponding weft thread proportionally. In this case, the weaving machine is controlled by the control unit 14, for example using the pattern below.

Insertion	Weft thread	Weaving machine speed
1	2	500 revolutions/minute
2	3	500 revolutions/minute
3	4	450 revolutions/minute
4	2	500 revolutions/minute
5	4	450 revolutions/minute
6	3	500 revolutions/minute
7	2	500 revolutions/minute
8	2	500 revolutions/minute

As the speed with which the weft thread is introduced into a shed 8 decreases proportionally with the reduced speed of the drive motor 57, the tension in the weft thread will also decrease. After all, with gripper weaving machines, the tension of the weft thread is directly dependent on the speed of the weaving machine. By reducing the speed of the weaving machine, it is possible to reduce the tension of the weft thread so that this tension definitely remains below the expected strength of the knot. This makes it possible to prevent weft threads breaking as a result of breaks at weak knots or irregularities.
In this case, it should be noted that, in the illustrated example, the speed of 500 revolutions/minute for introducing the weft thread 2 is not reduced at the fourth insertion. This speed is not reduced as this was already at such a low speed before the knot was detected. This speed for the fourth insertion was set at a low speed in order to limit the difference in speed with the previous and/or the next insertion.
If, according to a variant, it is decided to reduce the speed for the weft thread 2 to 400 revolutions/minute, then the speed for all insertions of the weft thread 2 will be reduced, for example, as indicated by the pattern below.

Insertion	Weft thread	Weaving machine speed
1	2	400 revolutions/minute
2	3	500 revolutions/minute
3	4	450 revolutions/minute
4	2	400 revolutions/minute
5	4	450 revolutions/minute
6	3	500 revolutions/minute
7	2	400 revolutions/minute
8	2	400 revolutions/minute

In the latter case, it is advisable to also reduce the speed for introducing the other weft threads, for example in order to limit the difference in speed between two insertions, so that a pattern results in which the difference in speed between two successive insertions is relatively limited.

Insertion	Weft thread	Weaving machine speed
1	2	400 revolutions/minute
2	3	450 revolutions/minute
3	4	450 revolutions/minute
4	2	400 revolutions/minute
5	4	450 revolutions/minute
6	3	450 revolutions/minute
7	2	400 revolutions/minute
8	2	400 revolutions/minute

As there is a thread stock 42 present, it is possible, according to the invention, to wait for the normal speed v1 for introducing a weft thread to be reduced to the reduced speed v2. As illustrated in Figure 2, this wait can last from the instant t1 where a knot is detected until the instant t2 where the knot has usually not yet been introduced. The instant t3 represents the instant where the knot is introduced. From the instant t4 where the knot has definitely been introduced, the speed can be increased again from the reduced speed v2 to the normal value v1. As, normally, thread stock 42 is present for at least three and at most five insertions of a specific weft thread 2, it is possible, for example, to wait for another two insertions before reducing the speed. In order to be sure that the knot has been introduced, the speed cannot be increased again until for example seven insertions have been introduced.
It is clear that detecting a knot in a specific weft thread results in a reduction in speed with certain insertions of this weft thread. However, this speed does not have to be reduced for all insertions of this weft thread if the speed was already sufficiently low before the detection of the knot. Obviously, a speed reduction for a specific weft thread may also result in the speed for the insertion of another weft thread having to be reduced in order, for example, to limit variations in speed between two successive insertions.
In the illustrated example, the detection devices 26, 27, 28, 29, 30 and 31 for detecting a knot or irregularity are located between a thread stock and the edge 9, more particularly between the prewinder 23, 24 and 25 and an associated spool. This offers the advantage that it is possible to reduce the speed before the respective weft thread is introduced.
By successively introducing weft threads according to a pattern, with each successive weft thread being introduced at a corresponding speed determined in accordance with the pattern, it is possible to reduce the respective speed of at least one insertion of a specific weft thread if a knot or irregularity in a specific weft thread is detected, in order to prevent a break of said weft thread at the knot or irregularity. In the illustrated example of a gripper weaving machine, the speed of the weft thread is determined by the speed of the weaving machine, more particularly by the speed of the drive motor 57. In this case, the velocity pattern of the speed of the weaving machine is adjusted in order to adjust the speed of the weft thread.
The weaving machine also comprises a storage unit 47 for storing data relating to the speed at which weft threads are introduced, the sequence in which weft threads are introduced and, for example, an abovementioned pattern. The data in the storage unit 47 can be input via the input unit 46.
When one of the detection devices 26 to 31 sends a signal to the control unit 14, the control unit 14 also sends a signal to a counter 48 which counts, for example, the number of introductions from a specific feeder 5, 6 or 7. Depending on the number of insertions counted, the control unit 14 will adjust the pattern as mentioned above and reduce the speed for introducing specific weft threads at a suitable point in time and subsequently increase it again. The number of insertions obviously depends on the stock 42, 43 or 44.
According to a variant, the counter 48 is able to count the time instead of the number of insertions after such a signal. In this case, the time taken is dependent on the speed of the weaving machine and on the pattern. This time may be defined as the time required for introducing the number of insertions from a specific feeder. The abovementioned number of insertions or the abovementioned time can be set using an input unit 46, for example a keyboard.
The invention allows weaving to continue from each feeder 5, 6 and 7, so that the supply does not have to be interrupted from any of the feeders. The successive pattern for introducing weft threads can thus also be retained. However, if a thread break is detected, it is of course possible to stop the respective feeder and, provided that the same type of weft thread is used for several feeders, weaving can continue from the other feeders in a manner as known from EP 195.469 B2 . In this case, the speed of introducing weft threads can also be reduced in order to prevent a subsequent thread break.
If the weaving machine is stopped following a thread break in one of more feeders, the weaver can also remove the knot or irregularity from the disconnected feeder when repairing the thread breaks and stop the method according to the invention using the input unit 46. As a result, the feeder in which the knot or irregularity occurred can immediately be restarted and/or an immediate return to weaving at normal speed is possible after the weaving machine has been started.
The method according to the invention can of course, also be stopped by means of input unit 46, for example if weft threads are woven in which the knots do not result in thread breaks. The counter 48 can also be used to record or count the number of knots or irregularities. Furthermore, the control unit 14 can also be connected to a display unit or monitor 49.
It is clear that the method according to the invention can be used with a weaving machine with any number of feeders. According to a variant, the prewinders 23, 24 and 25 may be provided with a known winding detector with which the approximate number of windings on a respective prewinder 23, 24 and 25 can be determined. On the basis of this number of windings, the control unit 14 is able to determine the number of insertions for which the speed has to be reduced and for which the speed can be increased again. This makes it possible to determine in a more accurate way when a knot or irregularity will be introduced into the shed 8 and thus to reduce the time or the number of insertions taking place at reduced speed.
The speed does not only have to be reduced for a specific weft thread containing knots, but may also be reduced for all other weft threads which do not contain knots. Obviously, the aim will always be to weave at as high a speed as possible. After all, it is advantageous to introduce weft thread at normal speed for as long as possible, as well as to return to introducing weft thread at normal speed as quickly as possible.
It will be clear that the detection means are not limited to the detection means illustrated. It is likewise possible to provide detection means of this type for detecting knots or irregularities at the output or even downstream of the prewinder. In this case, it is preferable if the speed is reduced immediately after the knot is detected and therefore during the introduction of this weft thread. This allows the risk of a thread break due to a knot to be reduced by decreasing the introduction speed of a weft thread. Should the knot be detected too late and thus already have been partially introduced by the giving gripper 15, it is nevertheless advantageous to reduce the speed during said introduction. As a result, it may, for example, still be possible to prevent the weft thread breaking as a result of the movement of the receiving gripper 40 due to a knot or irregularity.
Although the method is particularly suitable for use with gripper weaving machines, in which the speed of the weaving machine determines the speed with which the weft threads are introduced, the invention can also be used in other types of weaving machines. For example, the invention can be used with air weaving machines, in which not only the speed of the weaving machine is then reduced, but also, for example, the pressure of the compressed air is reduced or decreased in order to cause the weft thread to be moved through the shed relatively slowly. Although the invention is particularly suitable for use with gripper weaving machines, the invention can of course also be used with gripper shuttle weaving machines, projectile weaving machines, water jet weaving machines, multiphase weaving machines and other types of weaving machine.
If, during weaving at reduced speed, another knot is detected in the same feeder, weaving can continue at a lower speed until the next knot is also definitely weaved in. If, during weaving at reduced speed, a knot is also detected in another feeder, the speed of a weft thread from this other feeder is likewise adjusted according to the invention and the speed of the weft threads of the other feeders can also be adjusted. If two or more thread breaks are detected, weaving can be carried out according to the following pattern, for example.

Insertion	Weft thread	Weaving machine speed
1	2	400 revolutions/minute
2	3	400 revolutions/minute
3	4	400 revolutions/minute
4	2	400 revolutions/minute
5	4	400 revolutions/minute
6	3	400 revolutions/minute
7	2	400 revolutions/minute
8	2	400 revolutions/minute

In this way, all possible speeds for all weft threads of a feeder can be stored in the storage unit 47, based on the feeder and/or the feeders where a knot or irregularity was detected. These stored data may relate to the speed at which weft threads are introduced and may depend on the and/or the number of feeders in which knots or irregularities were detected.
It will be clear that irregularity is understood to mean any irregularity in a weft thread, for example a relatively thin section, a relatively thick section, a nub, a burl, a knot, a splice weld or any other kind of irregularity. It will be clear that where the term knot was used in the above description, every mention relating to a knot also refers to any other kind of irregularity. This means that the term knot can be replaced by the term irregularity throughout the description and that this also forms part of the description of this patent application.
The invention makes it possible to prevent thread breaks as a result of knots by continuing to weave at a relatively low speed after a knot has been detected until it is highly probable that the knot has been woven in, and subsequently increasing the speed again to the original value. By weaving at a relatively low speed, the tension of the weft thread is also reduced, as a result of which the risk of a thread break, particularly a thread break at the location of a weak knot, can be prevented.
It will be clear that the speeds of the weaving machine are only mentioned by way of example. Of course, the normal speed may be 700, 800, 900, 1000, 1100 and even 1200 revolutions/minute, while a respective associated reduced speed may be between 300 and 800 revolutions/minute. The reduced speed may, for example, be 100 to 400 revolutions/minute lower than the normal speed, i.e. the reduced speed is significantly lower than the normal speed. This reduced speed can be determined both in absolute and in relative terms, in other words a specific reduction of the speed or a relative or percentage reduction of the speed, for example a speed which is approximately 25% lower than the normal speed.
The curve 60 in Fig. 3 shows the risk of breakage "f" of a weft thread as a function of the tensile stress "T", which is expressed in cN, for example. A thread break commonly occurs at a value tA, whereas the risk of thread break is low at a value lower than tB. This value tB is a tensile stress which may be reached at a speed "v" of the weaving machine of, for example, 700 revolutions/minute. When the weft thread contains a knot 41, in the example illustrated, the risk of breakage follows a curve 61 having a mean break value tC and a value tD below which the risk of thread break is low. This value tD is in this case representative of a speed of, for example, 475 revolutions/minute. Thus, without a knot 41, weaving at 700 revolutions/minute or weaving at normal speed are possible and cause no problems, while if a knot is present, weaving without problems is only possible at 450 revolutions/minute or at a relatively low speed. With a gripper weaving machine, the curve 62 for the tensile stress of the weft thread as a function of the associated speed is virtually linear.
The method and weaving machine according to the invention are of course not restricted to the embodiments described by way of example and illustrated in the figures, but various variants and combinations of the illustrated embodiments are possible without departing from the scope of the claims.

Claims

Method for introducing a weft thread (2, 3, 4) in a weaving machine, characterized in that the method comprises introducing a specific weft thread (2, 3, 4) into a shed (8) at a lower speed than the normal speed for this specific weft thread (2, 3, 4), if a knot or irregularity (39, 41) has been detected in a specific weft thread (2, 3, 4).
Method according to claim 1, characterized in that the method comprises introducing a specific weft thread (2, 3, 4) at a relatively low speed once the knot or irregularity (39, 41) has been detected and before the knot or irregularity (39, 41) is introduced.
Method according to claim 1 or 2, characterized in that the method comprises introducing a specific weft thread (2, 3, 4) at a relatively low speed at least up to the point in time when the knot or irregularity (39, 41) has been introduced.
Method according to one of claims 1 to 3, characterized in that the method comprises lowering the speed of the weaving machine after a knot or irregularity (39, 41) has been detected in that specific weft thread (2, 3, 4).
Method according to one of claims 1 to 4, characterized in that the method comprises detecting a knot or irregularity (39, 41) which is located between a thread supply (17, 18, 19, 20, 21, 22) and the edge (9).
Method according to one of claims 1 to 5, characterized in that the method comprises successively introducing weft threads (2, 3, 4) according to a pattern, with each successive weft thread (2, 3, 4) being introduced at a corresponding speed determined in accordance with the pattern, with the respective speed of at least one insertion of a specific weft thread (2, 3, 4) being reduced if a knot or irregularity (39, 41) in a specific weft thread (2, 3, 4) is detected.
Method according to one of claims 1 to 6, characterized in that the method comprises storing a plurality of patterns for introducing weft threads (2, 3, 4) comprising data relating to the speed at which weft threads (2, 3, 4) are introduced and being dependent on the feeders (5, 6, 7) in which knots or irregularities (39, 41) have been detected.
Weaving machine for applying a method according to one of claims 1 to 7, characterized in that the weaving machine comprises a drive unit (45), the speed of which can be controlled, and further comprises detection means (26, 27, 28; 29, 30, 31) for detecting a knot or an irregularity (39, 41) of a weft thread (2, 3, 4) to be introduced into a shed (8) which detecting means (26, 27, 28; 29, 30, 31) are connected to a control unit (14) which reduces the speed of the drive unit (45) to a lower than normal speed if a knot or an irregularity is detected.
Weaving machine according to claim 8, characterized in that the weaving machine is a weaving machine in which the speed of a weft thread (2, 3, 4) is determined by the speed of the weaving machine, more particularly is a gripper weaving machine.
Weaving machine according to claim 8 or 9, characterized in that the weaving machine comprises a storage unit (47) for storing data relating to the speed at which weft threads (2, 3, 4) are introduced, and which data are dependent on the feeders (5, 6, 7) in which knots or irregularities (39, 41) have been detected.