WO2012079877A2

WO2012079877A2 - Method and device for feeding weft thread

Info

Publication number: WO2012079877A2
Application number: PCT/EP2011/070012
Authority: WO
Inventors: Patrick Puissant
Original assignee: Picanol
Priority date: 2010-12-14
Filing date: 2011-11-14
Publication date: 2012-06-21
Also published as: WO2012079877A3; CN103370463A; EP2652186A2; CN103370463B; BE1019702A3

Abstract

Method and device for feeding weft thread (2) in a weaving machine, wherein a reference moment in the weaving cycle is determined that is a measure of the stretching moment in which during the insertion of weft thread (2) into the weaving shed (6) the weft thread (2) stored in the storage element (11) changes from stored condition into stretched condition and wherein a thread holder (20) arranged between a prewinder (3) and a storage element (11) is controlled by a control unit (31) as a function of the determined reference moment in the weaving cycle.

Description

Method and device for feeding weft thread.

The invention concerns a method for feeding weft thread in a weaving machine. The invention also concerns a device for feeding weft thread in a weaving machine that is designed for applying a method according to the invention.

A device for feeding weft thread to a weaving shed of an airjet weaving machine is known from US 4,947,898 or WO 2010/006774 A2. The device comprises a storage element for storing weft thread, which storage element comprises a cavity delimited by side walls, which cavity has an inlet and an outlet for weft thread. In the side walls, openings are provided allowing compressed air to escape. The device comprises a clamping element for clamping weft thread, which clamping element is arranged near the out!et of the cavity. The clamping element can be closed for storing weft thread and can be opened for removing weft thread. The c!amping element can also close off the outlet of the cavity for compressed air. The device also comprises a blowing device to blow weft thread into the storage element, so that weft thread can be stored in the storage element. The blowing device is arranged near the inlet of the storage element and serves for blowing weft thread to the storage element and for blowing weft thread in the direction from the inlet to the outlet of the storage element. Further the device comprises a prewinder for releasing weft thread. The device allows weft thread to be stored under low tension in the storage element, so that weft thread under low tension can be removed from the storage element, aliowing higher weaving speeds to be reached or to insert weft thread with Iower air consumption and with iower tension into the weaving shed. The prewinder allows to release a weft thread with a suitable length.

A method for feeding weft thread to a weaving shed of an airjet weaving machine is, for example, known from US 4,947,898 and WO 2010/006774 A2. Such a method describes the controiling of a thread holder of a prewinder, a blowing device of a storage element, a thread holder of a storage element and a main blower. Such a method has the disadvantage that if a certain weft thread is supplied too slowly to the storage element, this weft thread will be inserted too slowly into the weaving shed, so that the weft thread arrives too late in the weaving cycle at the opposite side of the weaving shed and a weft fault can occur. Such a method also has the disadvantage that if a certain weft thread is supplied too fast to the storage element, this weft will be inserted too fast into the weaving shed, so that the weft thread arrives too early in the weaving cycle at the opposite side of the weaving shed and so that the weft thread at arrival is subjected to a high tension, so that a breaking of the weft thread can occur.

It is an object of the invention to improve such a method, so that weft thread is supplied under a relatively low tension and with a desired speed to the storage element and so that weft thread is inserted under a relatively low tension and with a desired speed into the weaving shed.

This object is achieved by a method for feeding weft thread in a weaving machine, wherein a length of weft thread is released from a prewinder in order to be inserted into a weaving shed, wherein weft thread coming from the prewinder is supplied to a storage element via an inlet of the storage element, wherein weft thread is removed from the storage element via an outlet of the storage element in order to be inserted into the weaving shed, wherein before the start of the insertion of weft thread into the weaving shed weft thread is stored in the storage element, wherein at least during a part of a period of the insertion of weft thread into the weaving shed a simultaneous store and removal of weft thread is carried out, wherein at least at the end of the simultaneous store and removal of weft thread, the weft thread stored in the storage element is removed from the storage element faster than weft thread coming from the prewinder is supplied to the storage element, so that at a stretching moment in the weaving cycle during the period of the insertion of weft thread into the weaving shed the weft thread stored in the storage element changes from stored condition into stretched condition, wherein the stretching moment is determined as reference moment.

In the context of the description with the term "stretching moment" is meant the moment in the weaving cycle at which during the insertion of weft thread into the weaving shed the weft thread stored in the storage element changes from stored condition into stretched condition. In the context of the description with the term "stored condition" is meant stored in non-stretched condition in the storage element, for example stored in zigzag form in the storage element. The "reference moment" is a measure of the "stretching moment", but as is further evident from the description this "reference moment" does not necessarily have to coincide exactly with the "stretching moment".

The invention offers the advantage that by determining a reference moment that is a measure of the moment in the weaving cycle at which the weft thread is stretched in the storage element, it is possible to influence or set specific control parameters for influencing the reference moment in order to control the reference moment. In an embodiment, to control the reference moment, the speed at which weft thread is supplied to the storage element is adapted to the speed at which weft thread is inserted into the weaving shed.

According to a preferred embodiment, the start of the storing of weft thread in the storage eiement is controlled by an opening of a second thread holder that is arranged between the prewinder and the storage element, wherein the opening of the second thread holder is controlled in function of the reference moment in the weaving cycle. This means that in dependence of the speed at which weft thread is supplied to the storage element and in dependence of the speed at which weft thread is inserted into the weaving shed, the second thread holder that is arranged between the prewinder and the storage element is opened at a suitable moment, so that the weft thread changes from stored condition in the storage element into stretched condition in the storage element at a desired moment in the weaving cycle, This also allows keeping the tension in the weft thread relatively low during the storing in the storage element and during the insertion into the weaving shed .

According to a preferred embodiment the moment of the opening of the second thread holder that is arranged between the prewinder and the storage element is determined so that the determined reference moment is related to a set moment in the weaving cycle. The choosing of a set moment in the weaving cycle allows controlling the moment of opening of the second thread holder so that the determined reference moment is related to this set moment. The reference moment in the weaving cycle can be determined depending on the moment in the weaving cycle at which the first thread holder that is arranged between the storage element and the weaving shed is opened and/or the moment in the weaving cycle at which the weft thread is expected to arrive at the opposite side of the weaving shed. The method according to the invention has as result that the opening of the second thread holder is also influenced by the moment in the weaving cycle at which the weft thread is expected to arrive at the opposite side of the weaving shed.

According to an embodiment, a method is provided wherein a length of weft thread is released from a prewinder in order to be inserted into a weaving shed, wherein weft thread coming from the prewinder is supplied to a storage element via an inlet of the storage element, wherein weft thread is removed from the storage element via an outlet of the storage element in order to be inserted into the weaving shed, wherein before the start of the insertion of weft thread into the weaving shed weft thread is stored for example in zigzag form in the storage element, wherein at the start of the insertion of weft thread into the weaving shed weft thread is simultaneously stored in the storage element and removed from the storage element, wherein at the end of the insertion of weft thread into the weaving shed weft thread is inserted into the weaving shed in stretched condition from a prewinder via the storage element, wherein the start of the insertion of weft thread into the weaving shed is controlled by the opening of a first thread holder that is arranged between the storage element and the weaving shed, wherein the end of the insertion of weft thread into the weaving shed is controlled by the closing of a second thread holder that is arranged between the prewinder and the storage element, wherein the start of the storing of weft thread in the storage element is controlled by the opening of the second thread holder that is arranged between the prewinder and the storage element, wherein a reference moment in the weaving cycle is determined that is a measure of the moment in the weaving cycle at which during the insertion of weft thread into the weaving shed the weft thread stored in the storage element changes from stored condition into stretched condition, and wherein the opening of the second thread holder that is arranged between the prewinder and the storage element is controlled in function of the determined reference moment in the weaving cycle.

According to an embodiment, weft thread coming from a prewinder is blown by means of a blowing device that is arranged between the prewinder and the storage element via an inlet of the storage element into the storage element, wherein this blowing device is activated at a moment in the weaving cycle that is determined in function of the determined reference moment in the weaving cycle. This allows that this blowing device is activated so that the blowing device has already blown on the weft thread over a short time before opening the second thread holder that is arranged between the prewinder and the storage element. This allows blowing weft thread into the storage element from the moment at which the second thread holder is opened. This means that the opening of the second thread holder determines the moment in the weaving cycle at which weft thread is stored in the storage element.

According to a preferred embodiment the blowing device is deactivated at a deactivation moment in the weaving cycle so that the blowing of the blowing device on the weft thread decreases before the reference moment. In other words, the activating of the blowing device ends before the weft thread changes into stretched condition in the storage element. This is advantageous to influence the moment in the weaving cycle that the weft thread in the storage element changes to stretched condition. A short time before reaching the stretched condition weft thread is blown only by a residual airflow of the blowing device with iow speed into the storage element. To this purpose, the start and the end of blowing of this blowing device in the weaving cycle are determined in function of amongst others the speed at which is woven.

According to an embodiment the deactivation moment in the weaving cycle is determined in function of a set part of weft thread coming from the prewinder being supplied to a storage element via an inlet of the storage element.

Further, the force of the blowing of this blowing device is chosen so that the weft thread is not blown to the outlet of the storage element when a part of the stored weft thread has already been removed from the storage element. To this end, for example, the pressure of the compressed air that is delivered to the blowing device and the flow rate of compressed air that is delivered via the blowing device to the storage element are adapted to the type of weft thread, to the speed at which is woven and/or to other similar parameters. The force of the air flow of the blowing device has to be sufficient to blow a weft thread with a desired speed into the storage element, but has however to be limited so that it is avoided that weft thread gets entangled during the storing of weft thread into the storage element.

According to another embodiment, the start of the insertion of weft thread into the weaving shed is controlled by the opening of a first thread holder that is arranged between the storage element and the weaving shed and/or the end of the insertion of weft thread into the weaving shed is controlled by the closing of a second thread holder that is arranged between the prewinder and the storage element. The terms "first" and "second" in the "first thread holder" and the "second thread holder" are only intended to indicate that there are two different thread holders and in order to indicate which of both thread holders is meant.

According to a preferred embodiment, the reference moment is determined on the basis of signals of a thread detector or a number of thread detectors that are arranged at the prewinder, more particularly a so-cailed winding detector that delivers each time a signal if a winding coming from the drum of the prewinder is moved past the thread detector. The reference moment in embodiments is determined on the basis of time differences, average time differences and/or statistical deviations of time differences between signals of a thread detector that is arranged at the prewinder.

According to another embodiment, the reference moment is alternatively or in addition determined on the basis of signals from a presence sensor or a number of presence sensors that are arranged at the storage element.

According to another embodiment, the reference moment is alternatively or in addition determined on the basis of signals of a tension sensor for weft thread, that is arranged between a prewinder and a storage element and/or a tension sensor for weft thread, that is arranged between a storage element and the weaving shed .

According to another embodiment, the reference moment is alternatively or in addition determined on the basis of signals of a movement sensor for weft thread, for example a movement sensor for weft thread that can detect the movement, in particular the speed of a weft thread moving along the movement sensor. The movement sensor in preferred embodiments is arranged between a prewinder and a storage element and/or between a storage element and the weaving shed.

This object is also achieved by a device with a prewinder, a storage element for weft thread and a thread holder that is arranged between the prewinder and the storage element, wherein the thread holder is controlled by a control unit in function of the determined reference moment in the weaving cycle. The storage element can be a storage element that allows to store a weft thread in the storage element in zigzag form, for example a storage element as known from WO 2010/006774 A2.

The invention also offers the advantage that weft thread that is stored in the storage element with a low tension, can be inserted into the weaving shed with low tension and/or with higher speed. This allows in airjet weaving machines amongst others to increase the weaving speed or to decrease the consumption of compressed air necessary for the insertion of a weft thread. The consumption of compressed air can be decreased by decreasing the pressure of the compressed air and/or by decreasing the amount of delivered compressed air. The amount of delivered compressed air is, for example, determined amongst others by the flow through opening to the blowers and/or the time interval of blowing. The invention also offers the advantage that the influence of an alteration of the air friendliness of a weft thread on the supplying of weft thread to the storage element and on the insertion of a weft thread into the shed can easily be taken into account.

Further featu res and advantages of the invention emerge from the following description of the embodiments represented in the drawings.

Fig . 1 shows a perspective view of a part of a weaving machine according to the invention with a number of devices for feeding weft threads.

Fig . 2 shows a cross section according to a rrow F2 in Fig . 1 of a blowing device and a storage element of a device according to the invention before the storing of a weft thread in the storage element.

Fig. 3 shows schematically a state before the storing of the weft thread in the storage element of Fig . 2.

Fig . 4 shows a state during the storing of the weft thread into the storage element of Fig . 2.

Fig . 5 shows a state at the start of the removing of the weft thread from the storage element of Fig . 2, while weft thread is further stored in the storage element of Fig. 2. Fig . 6 shows a state before the stretching moment when further removing the weft thread from the storage element of Fig. 2.

Fig. 7 shows a state after the stretching moment when further removing the weft thread from the storage element of Fig . 2.

Fig . 8 shows a state before the end of the removing of the weft thread from the storage element of Fig . 2.

Fig . 9 shows a state at the end of the removing of the weft thread from the storage element of Fig . 2.

Fig . 10 shows schematica lly a view according to arrow F10 in

Fig . 1 of a drum of a prewinder.

Fig . 1 1 shows successive signa ls of thread detectors that are arranged at a prewinder.

shows a variant of Fig. 2.

shows curves of signals of tension sensors measuring the tension of the weft thread.

shows a view according to arrow F14 in Fig. 1 of a further storage element.

shows curves of signals of movement sensors measuring the movement of the weft thread. The weaving machine shown in Fig. 1 comprises four devices 1 for feeding weft threads 2. Such a device 1 is known from WO 2010/006774 A2 of which the description forms part of this patent application. Each device 1 comprises a prewinder 3 onto which a weft thread 2 coming from a bobbin 4 is wound. Each device 1 further comprises a main blower 5 that is located next to the weaving shed 6 and is arranged to blow the weft thread 2 into the weaving shed 6. The weaving shed 6 is formed by warp threads 7 and 8. Each device 1 also comprises a thread brake 9, a blowing device 10 and a storage element 11 that are arranged in order to guide a weft thread 2 successively from a prewinder 3 via the thread brake 9, the blowing device 10 and the storage element 11 to a main blower 5. A number of relay nozzles 12 are shown that can enter into the weaving shed 6 and that are arranged to support a weft thread 2 inserted into the weaving shed 6. In preferred embodiments, the main blowers 5 and the relay nozzles 12 are mounted on a sley 13 of the weaving machine to move to and fro with the sley 13. Near the weaving shed 6 a weft cutter 14 is positioned . At the end of the weaving shed 6 located opposite to the main blowers 5 a thread detector 15 is located that is arranged to detect a weft thread 2 inserted through the weaving shed 6. The blowing device 10 comprises a blowing unit 16 and a guide tube 17, also cailed fill tube, that connects to the storage element 11. The main blower 5 comprises a blowing unit 18 and a guide tube 19 that is located near the weaving shed 6. A main b!ower 5 and a blowing device 10 are, for example, implemented as described in EP 985.062 Bl.

According to a variant embodiment, the thread brake 9 is provided on or integrated in the prewinder 3 and/or functions as a thread compensator or a thread damper. According to a variant embodiment also an extra thread brake or thread clamp is provided on or integrated in each of the main blowers 5, for example as known from EP 1.389.244 Bl or EP 1.389.245 Bl. According to a variant embodiment, also each main blower 5 is replaced by a number of main blowers, for example two main blowers arranged in series that co-operate with an associated weft thread 2.

At each prewinder 3 a thread holder 20 is provided that is formed for example by a bar 21 arranged to be actuated by an actuator 22. The thread holder 20 is also named second thread holder in this description. In an embodiment, the actuator 22 consists of an electromagnet, while the bar 21 consists of a pin that can cooperate with the electromagnet. The prewinder 3 comprises for example a drum 23 and a winding arm not shown to wind weft thread 2 on the drum 23. In the embodiment of Fig. 1 the thread holder 20 is fixed to the prewinder 3. The bar 21 is arranged to move to and from the drum 23 of the prewinder 3. When the bar 21 is moved to a position to the drum 23, also called closed position, the bar 21 can prevent that weft thread 2 is released from the prewinder 3, while when the bar 21 is moved to a position at which the bar 21 is remote from the drum 23, also called opened position, weft thread 2 can be released from the prewinder 3. In this case the thread holder 20 is arranged in order to hold the weft thread 2 at a determined place when the thread holder 20 is in closed position. Each prewinder 3 a!so comprises at least one thread detector 24 that generates a signal each time when a weft thread 2 which is released from the drum 23 moves past this thread detector 24.

As explained in Fig. 2 and 3, a weft thread 2 can be blown through the guide tube 17 of the blowing device 10, via the inlet 25 into the storage element 11 and according to the moving direction B to the outlet 26 of the storage element 11 located opposite to the inlet 25. At the outlet 26 of the storage element 11 a thread holder

27 is arranged. The thread holder 27 is also named first thread holder in this description. The thread holder 27 is arranged to clamp the weft thread 2 at the outlet 26, more particularly in order to hold the weft thread 2 at a determined place. Alternatively or in addition, the thread holder 27 is arranged to essentially hermetically seal the storage element 11 at the outlet 26 and/or to brake a moving weft thread 2. In an embodiment, the thread holder 27 consists of a bar

28 that can be commanded by an actuator 29 and of a stop 30 against which the bar 28 can impact. In an embodiment, the actuator 29 consists of an electromagnet, while the bar 28 consists of a pin that can cooperate with the electromagnet. In this case, a weft thread 2 can be held by the thread holder 27 by clamping the weft thread 2 between the bar 28 and the stop 30. During the clamping, the thread holder 27 is in a closed position. If the thread holder 27 does not clamp the weft thread 2, more particularly when the bar 28 is removed from the stop 30, the thread holder 27 is in opened position.

The weaving machine comprises, as schematically shown in Fig. 1, a control unit 31 arranged to drive an actuator 22 of a thread holder 20 via a drive unit 32, to drive an actuator 29 of a thread holder 27 via a drive unit 33 and to drive the weft cutter 14 via a drive unit 34. In preferred embodiments, the control unit 31 in addition provides a blowing unit 16 of a blowing device 10 with compressed air via a controllable valve system 35 that is connected to a compressed air source 47. Further, the control unit 31 preferably provides a blowing device 18 of a main blower 5 with compressed air via a controllable valve system 36 and provides a relay nozzle 12 with compressed air via a controllable valve system 37. The control unit 31 is arranged to receive signals of a thread detector 15 and/or to receive signals of the thread detectors 24 of the prewinders 3.

In the embodiment shown in Fig. 2 and 3, the storage element 11 for the weft thread 2 comprises a cavity 38 located between the inlet 25 and the outlet 26 that is delimited by side walls 39, 40 and that has a substantially flat shape. In this case the transverse width between the side walls 39, 40 of the cavity 38 decreases from the inlet 25 to the outlet 26, so that the side walls 39, 40 mutually form a small angle, for example an angle in the order of magnitude between 1° and 8°. At a side wall 41 of the cavity 38, for example the upper side wall, several openings 42 are provided that allow compressed air to escape from the cavity 38, The storage element 11 also comprises a thread guide 43 that is arranged beyond the thread holder 27, this means between the thread holder 27 and the main blower 5.

To a blowing device 10 there is delivered compressed air from a compressed air source 47, for example an air tank that is shown schematically in Fig. 1, which compressed air source 47 is connected to the blowing device 10 via a valve system 35. The pressure and/or the air flow rate with which compressed air is delivered to the blowing device 10 in preferred embodiments are set and regulated so that weft thread 2 is supplied to the storage element 11 with a desired speed. The force with which the blowing device 10 blows has to be such that weft thread 2 is supplied to the storage element 2 with a sufficient speed. The pressure and/or the flow rate can also be adapted during weaving, for example in function of measured or set weaving parameters.

To a main blower 5 and/or relay nozzles 12 there is delivered compressed air from a compressed air source 48, for example an air tank that is shown schematically in Fig. 1, which compressed air source 48 is connected via a valve system 36 or 37 to a main blower 5 and/or a relay nozzle 12. The pressure and/or the flow rate with which compressed air is delivered to a main blower 5 and/or a relay 5 nozzle 12 in preferred embodiments are set and regulated so that the weft thread 2 is inserted into the weaving shed 6 with a desired speed. The force with which the main blower 5 and the relay nozzles 12 blow has to be such that weft thread 2 is inserted into the weaving shed 6 with a sufficient speed. The pressure and/or the flow l o rate in further embodiments are adapted during weaving, for example in function of measured or set weaving parameters, for example in a way as known from WO 2006/114187 or EP 1272699 Bl.

The thread holders 20, the thread holders 27, the blowing is devices 10, the main blowers 5 and the relay nozzles 12 are controlled according to a method according to the invention via the control unit 31. The operation for feeding weft thread 2 with a device

I according to the invention is further explained using Fig. 3 to 9.

In Fig. 3 the thread holders 20 and 27 are closed, while the 0 main blower 5, the blowing device 10 as well as the relay nozzles 12 do not blow. In Fig. 4 the thread holder 20 is opened and the blowing device 10 blows so that weft thread 2 released from the drum 23 of the prewinder 3 is supplied to the storage element 11 and is stored according to a zigzag form with a number of loops 49 5 in the storage element 11. In Fig. 5 also the thread holder 27 is opened and the main blower 5 together with a number of relay nozzles 12 blow weft thread 2 into the weaving shed 6. In Fig. 5 simultaneously weft thread 2 is removed from the storage element

II via the outlet 26 and weft thread 2 is blown and stored in the0 storage element 11 via the inlet 25.

Next, the blowing device 10 stops blowing so that weft thread 2 is only supplied to the storage element 11 by means of a residual air flow, while stored weft thread 2 is further removed from the storage element 11. Because the speed at which the weft thread 2 is removed from the storage element 11 is greater than the speed at which weft thread 2 is supplied to the storage element 11, at a certain moment the weft thread 2 will be stretched in the storage element 11. By stopping the blowing before a weft thread 2 is fully stored in the storage element 11 it is also easiiy achieved that the weft thread 2 will be stretched in the storage element 11 while the weft thread 2 is further inserted into the weaving shed 6. The moment at which the weft thread 2 is stretched in the storage element 11 is called the stretching moment.

In the state shown in Fig. 1 and 7, the weft thread 2 that is stretched between the prewinder 3 and the main blower 5 is further supplied to the storage element 11 according to the moving direction B of the weft thread 2 via the inlet 25, while the weft thread 2 is removed from the storage element 11 via an outlet 26 located opposite to the inlet 25. In the state shown in Fig. 8, the thread holder 20 of the prewinder 3 is closed so that it is prevented by the thread holder 20 that weft thread 2 is further released from the prewinder 3 so that the insertion of weft thread 2 into the weaving shed 6 will end. In the state shown in Fig. 9, the weft thread 2 is inserted into the weaving shed 6 and the thread holder 27 is also closed again. Meanwhile also the main blower 5 and the relay nozzles 12 stop blowing and the weft thread 2 is cut by the weft cutter 14. The weft thread 2 can be cut a short time before, while or a short time after the moment that the thread holder 27 is closed. The thread holder 27 is, for example, closed while the weft thread 2 is beaten up by the sley 13. Subsequently the above mentioned cycle of Fig. 3 to 9 can be repeated.

According to a variant embodiment, the thread holder 27 can also be closed a short time before the state shown in Fig. 8 with a small force, so that the weft thread 2 is decelerated a short time before the state shown in Fig, 8. It is clear that if a thread brake 9, as shown in Fig, 1, is provided between the prewinder 3 and the storage element 11 that this thread brake 9 can be controlled, for example, at the end of the insertion of weft thread 2 into the weaving shed 6, in other words in such way that the thread brake 9 decelerates the weft thread 2 a short time before the state shown in Fig. 8. If a thread brake is provided near the main blower 5, this thread brake can decelerate the weft thread 2 similarly a short time before the state of Fig. 8. The decelerating or braking of a weft thread 2 a short time before the end of the insertion into the weaving shed 6 of the weft thread 2 is advantageous to limit the tension in the weft thread 2 when this weft thread 2 makes contact with the bar 21 of the thread holder 20.

In the embodiment shown, the valve system 36 of the main blower 5 and the valve system 37 of a relay nozzle 12 are controlled in a known way during a weaving cycle. In this case the opening of the first thread holder 27 is also controiled in a known way, which thread holder 27 determines the start of the insertion of weft thread 2 into the weaving shed 6. If, for example, the length of weft thread 2 consists of four windings 50 that were stored on the drum 23 of the prewinder 3 and that were released from the drum 23, then the closing of the thread holder 20 can take place in a known way, for example the thread holder 20 can be brought to a closed position after the penultimate winding 50, in this case the third winding 50 has passed the thread detector 24. According to the embodiment shown, the second thread holder 20 and the thread detector 24 are arranged so that a weft thread 2 only passes by the thread detector 24 each time when a winding is released from the drum 23 almost completely. The closing of the first thread holder 27 has to take place after the weft thread 2 is inserted into the weaving shed 6 and before a following weft thread 2 is stored in the storage element 11, If weaving is carried out with two devices 1 according to the invention, there is always sufficient time available to close the thread holder 27 and the closing, for example, takes place at the moment that the inserted weft thread 2 is beaten up against the fabric 51. The cutting of the weft thread 2 for example takes place a short time before the thread holder 27 is closed.

According to a preferred embodiment of the invention the subsequent signals of a thread detector 24 are used to control the valve system 35 of the blowing unit 18 and to control the opening of the thread holder 20. Based on the moments of the subsequent signals of a thread detector 24, also named winding moments, it is possible to determine when a weft thread 2 changes from stored condition in the storage element 11 to stretched condition, more particularly when the stretching moment takes place. If storing of the weft thread 2 in the storage element 11 takes longer than the insertion of the weft thread 2 into the weaving shed 6, then the time difference lapsed between two subsequent signals of a thread detector 24, also called winding time, will be larger during the storing of weft thread 2 in the storage element 11 than during the insertion of weft thread 2 into the weaving shed 6 with the weft thread 2 passing in stretched condition through the storage element 11. In this embodiment, the time difference that lapses between the opening of the thread holder 20 and the signal that is generated by the passing of the first winding past the thread detector 24 is called the winding time of the first winding, The winding times for the three subsequent windings are determined by the time differences that pass between the four respective subsequent signals of the thread detector 24. If for example a weft thread 2 for one insertion is formed by four windings 50 and the stretching moment takes place during the third winding, then the winding time for the first three windings will be substantially larger than the winding time for the fourth winding, If the stretching moment takes place during the second winding, then the winding time of the first and the second winding will be substantially larger than the winding time of the third and the fourth winding. If the stretching moment takes place during the fourth winding then the winding time of the fourth winding will not be substantially smaller than the winding time of the previous windings.

Using the winding moments and/or the winding times, it is possible to determine at which moment in the weaving cycle the stretching moment takes place. By comparing subsequent winding moments and/or winding times, a reference moment can be determined that is a measure of the stretching moment. The reference moment can for example be determined as follows. If, for example, it is determined that the stretching moment takes place during the third winding, then the reference moment during the third winding can be determined further starting from the winding times of the second, third and fourth winding. To this end use can be made for example of the rule of three to determine if the stretching moment takes place near the start, the middle or the end of the third winding. This means if the winding time of the third winding differs only slightly from the winding time of the second winding, implying that the third winding is mainly stored in the storage element 11, the stretching moment takes place near the end of the third winding. If the winding time of the third winding differs only slightly from the winding time of the fourth winding, implying that the third winding passes mainly stretched through the storage element 11, the stretching moment takes place near the start of the third winding. If the winding time of the third winding is the average of the winding time of second and the fourth winding, the stretching moment takes place near the middle of the third winding. The comparing of the winding times and/or the winding moments allows determining a reference moment in the weaving cycle that is a measure of the stretching moment.

According to an embodiment of the invention, the opening of the second thread holder 20 that is positioned between the prewinder 3 and the storage element 11 is controlled as a function of the determined reference moment in the weaving cycle. In this embodiment, the moment at which the second thread holder 20 is opened is chosen or set so that the reference moment coincides with a desired moment during the weaving cycle, for example near the middle of the third winding in case a weft thread 2 for one insertion is formed by four windings 50. This means that the opening of the second thread holder 20 during the weaving cycle is controlled to a moment earlier or later in the weaving cycle so that the determined reference moment that is a measure of the stretching moment is shifted to a desired moment in the weaving cycle. If in the example shown, it is determined that the third winding time is approximately equal to the second winding time, then in an embodiment the thread holder 20 is opened stepwise later in the weaving cycle, until the third winding time is the average of the second and the fourth winding time. If it is determined that in the example shown the third winding time is approximately equal to the fourth winding time, then in an embodiment the thread holder 20 is opened stepwise earlier in the weaving cycle, until the third winding time is the average of the second and the fourth winding time.

In this case the determined reference moment can also be compared with a desired or set moment in the weaving cycle, and the thread holder 20 can be opened earlier or later in the weaving cycle until the determined reference moment coincides with the desired or set moment in the weaving cycle. This allows controlling the start of the storing of weft thread 2 in the storage element 11 by the opening of the thread holder 20, so that the stretching moment for which the reference moment is a measure takes place at a desired or set moment in the weaving cycle.

According to the invention, the reference moment is not necessarily determined based on winding times and/or winding moments. In other embodiments, the reference moment alternatively or in addition is determined in a similar way based on average winding times, based on statistical deviations of winding times, based on average winding moments and/or based on statistical deviations of winding moments.

In addition, according to an embodiment of the invention the blowing device 10 is activated at a moment in the weaving cycle that is determined in function of the determined reference moment in the weaving cycle. The moment for activating the blowing device 10 is determined in a similar way as the moment in the weaving cycle that the thread holder 20 opens, and for example is influenced so that the blowing device 10 is activated in order to blow slightly earlier in the weaving cycle than the opening of the thread holder 20, for example a few millisecond earlier. This allows that the blowing device 10 already blows on the weft thread 2 when the thread holder 20 opens.

According to a preferred embodiment of the invention, the blowing device 10 is deactivated at a deactivation moment in the weaving cycle, wherein the deactivation moment is set so that the blowing of the blowing device 10 on the weft thread 2 decreases before the weft thread 2 in the storage element 11 changes to stretched condition . If the reference moment, and thus also the stretching moment, in the embodiment in which a weft thread 2 for one insertion consists of four windings, takes place during the third winding, then the blowing device 10 in an embodiment is deactivated after the signal of the second winding in such a way that also the blowing decreases after the second winding. This method offers also the advantage that mainly only two windings are stored in the storage element 11, so that the reference moment can be determined based on for example the time difference between the third and the fourth winding time. By the advanced deactivating of the blowing device 10 it is avoided that loops of the weft thread 2 are blown over one another in the storage element 11 a short time before the stretching moment. By the advanced deactivating of the blowing device 10 it is also assured that the stretching moment takes place before the third winding passes at the thread detector 24, in other words before the fourth winding 50 is removed from the drum 23.

Of course the device 1 according to the invention allows to further use known methods for controlling for example the thread brake 9. Because in the described example the fourth winding is removed directly from the prewinder 3, the insertion of the fourth winding will take place in a similar way as in a weaving machine wherein no storage element 11 is provided. Hereby the thread brake 9 can be activated in a known way a certain time after the passing of the penultimate winding at the thread detector 24. The device 1 also allows to control based on signals of the thread detector 24, for example signals for the first winding and for the second winding, the relay nozzles 12 in a way as known from WO 2007/057217 Al, despite the signals of the thread detector 24 for the first and second winding not being determined during the insertion of this weft thread 2 into the weaving shed 6. Nevertheless, these signals are representative for the speed with which the same weft thread 2 will be inserted into the weaving shed 6, because these signals are measured on the same part of the weft thread 2 that later will be inserted into the weaving shed 6.

In another embodiment, the pressure and/or the flow rate of the compressed air delivered to the main blowers 5 are controlled in a known way in function of signals of the thread detector 15 that detects when a weft thread 2 arrives in the weaving cycle at the opposite side of the weaving shed 6. In a similar way, in another embodiment the pressure and/or the flow rate of the compressed air delivered to the blowing device 10 are controlled in function of signals of the thread detector 15, so that the pressure and/or the flow rate of the compressed air delivered to the blowing device 10 also alters with an alteration of the pressure and/or flow rate of the compressed air delivered to the main blowers 5. The pressure and/or flow rate of the compressed air delivered to the blowing device 10 can also be altered so that for example during a weaving cycle the time for the removing from a prewinder 3 of the first two windings 50 from the drum 23 remains approximately constant. Also the opening of the thread holder 27 can be controlled in a know way during a weaving cycle, for example in a way as a thread holder 20 of the prewinder 3 is opened in an airjet weaving machine without storage element 11.

In the embodiment described, wherein a weft thread 2 for one insertion is formed by four windings 50 and the stretching moment takes place during the third winding, this means during the penultimate winding, the advantage is obtained that the weft thread 2 can be inserted in a safe manner into the weaving shed 6, more particularly in a way in which the weft thread 2 can be braked in a known way during the end of the insertion, but the weft thread 2 can still be inserted into the weaving shed 6 at high speed and low tension during the largest part and from the start of the insertion.

In Fig . 10 the mutual position of the thread holder 20 and the thread detector 24 is shown wherein with arrow R the direction is indicated in which during the weaving cycle the weft thread 2 is removed from the prewinder 3. Here, the thread holder 20 and the thread detector 24 are mutually located so that the thread detector 24 delivers a first signal when the first winding has been removed from the prewinder 3, delivers a second signal when the second winding has been removed from the prewinder 3, delivers a third signal when the third winding has been removed from the prewinder 3 and a fourth signal when the fourth winding has been removed from the prewinder 3. The fourth signal is delivered a short time before the weft thread 2 is stopped by the thread holder 20. According to an embodiment as shown in Fig. 10, also a second thread detector 52 is provided at each prewinder 3 in addition to the thread detector 24, which for example with respect to the circumference of the drum 23 is arranged opposite to the thread detector 24. This allows during the removing of a winding 50 of a prewinder 3 to obtain two signals, in other words one signal of the thread detector 24 and one signal of the second thread detector 52. In the example, wherein a weft thread 2 for one insertion consists of four windings, during a weaving cycle eight signals are generated that occur each time at the removal of a subsequent half winding. In this case according to the invention the activating of the thread holder 20 can be controlled so that the stretching moment or the reference moment that is a measure of the stretching moment for example takes piace after "3,25" windings, in other words a short time after the third signal of the thread detector 24 and a short time before the fourth signal of the thread detector 52.

According to a further embodiment along the circumference of the drum 23 several thread detectors are arranged that each can detect the passing of a winding, for example four thread detectors that are shifted by 90°, more particularly the thread detectors 24 and 52 and two further thread detectors 53 and 54 shown in dashed lines in Fig , 10. In this case a reference moment can be determined based on time differences between subsequent signals of thread detectors 24, 53, 52 and 54. To this end there can be determined subsequently time differences 55 between signals of the thread detectors 24 and 53, time differences 56 between signals of the thread detectors 53 and 52, time differences 57 between signals of the thread detectors 52 and 54 and time differences 58 between signals of the thread detectors 54 and 24. Such time differences 55, 56, 57, 58 are set out in Fig. 11 wherein electrical signals of the thread detectors 24, 53, 52 and 54 are set out according to a time scale. The reference moment can be determined as the moment in the weaving cycle a short time before the moment at which a substantial drop in the subsequent time differences 55, 56, 57, 58 takes place, as indicated with moment 59 in Fig . 11. This allows to determine a reference moment according to the invention with a comparatively higher accuracy, than the reference moment determined in a way as described above based on signals of only one thread detector 24.

According to a variant, a first value of a reference moment is determined as described above based on only signals of the thread detector 24, while based on only signals of the thread detector 52, the thread detector 53 and the thread detector 54 respectively a second, third and fourth value for a reference moment are determined. Subsequently, a reference moment according to the invention in an embodiment is determined statistically, for example as an average of the first, second, third or fourth value for the reference moment. According to a variant not shown for example also three thread detectors are provided along the circumference of the drum 23 that are for example mutually shifted by 120°.

As shown in Fig. 12, in an embodiment a presence sensor 44, for example an optical sensor, is provided at the storage element 11 for observing the storing, this means the filling up of the storage element 11 with weft thread 2 and/or the removing of weft thread 2 from the storage element 11. If a stretched weft thread 2 is present in the storage element 11, the presence sensor 44 in an embodiment generates a low signal, while if a weft thread 2 stored in zigzag form is present in the storage element 11, the presence sensor 44 generates a high signal . Other embodiments are feasible. In an embodiment several presence sensors 45 and 46, designed similarly as presence sensor 44, are arranged at the storage element 11 in order to observe the presence of a weft thread that is whether or not in stretched condition in the storage element 11.

According to the embodiment shown in Fig . 12, a number of presence sensors 44, 45 and 46 are arranged distributed along the length of the storage element 11 in order to determine a reference moment according to the invention. If for example a weft thread 2 is stored in the area of such a presence sensor 44, 45 or 46 in zigzag form, the presence sensor generates a high signal, while if weft thread 2 passes in stretched condition by such a presence sensor 44, 45 or 46, the presence sensor generates a low signal. This means that before the storing of weft thread 2 in the storage element 11 the presence sensors 44, 45 and 46 each deliver a low signal. If during the weaving cycle at least one of the presence sensors 44, 45 or 46 generates a high signal and at a certain moment delivers a low signal again, this indicates that at this presence sensor the weft thread 2 stored in zigzag form has become stretched . The presence sensors 44, 45 and 46 can for example be arranged so that normally the presence sensors 44 and 45 during the weaving cycle generate a high signal, while the presence sensor 46 never generates a high signal. The signal of the presence sensor 46 is then used as a verification signal.

A reference moment according to the invention in one example is determined as follows. If for a weft thread 2 only the presence sensor 45 generates a high signal during a certain time, for example during a period of 3msec, followed by a low signal, then the reference moment can be determined as a certain time, for example 2msec, after the moment that the signal of the presence sensor 45 got low again, If for a weft thread 2 as well the presence sensor 45 as the presence sensor 44 both generate a high signal and then again a low signal, then the reference moment can be determined as a certain time, for example 2msec, after the moment that the signal of the presence sensor 44 got low again. According to a possibility the moment that the signal of the presence sensor 45 got low again can also be taken into account. During the storing of a weft thread 2 in the storage element 11, the signal of the presence sensor 45 will get low again a certain time, for example 2msec, before the signal of the presence sensor 44. In this case the reference moment is for example determined as a short time after the moment that the signal of the presence sensor 44 gets low again, if the signal of the presence sensor 45 got low again slightly before, for example 2msec. This allows with a great certainty to determine a reference moment according to the invention and excludes for example that an alteration of a signal of a presence sensor caused by a weft thread not correctly stored in zigzag form is interpreted incorrectly as a weft thread being stretched. If as well the presence sensors 44, 45 as 46 generate a high signal and then again a low signal, the reference moment can be determined as a moment a certain time after the signal of the presence sensor 46 got low, if successively the signals of the presence sensors 45 and 44 got low again a short time there before.

In accordance with an embodiment, the thread holder 20 is subsequently controlled according to the determined reference moment. To this end the thread holder 20 can be controlled for example so that during the storing of weft thread 2 in the storage element 11 the presence sensors 44 and 45 generate a high signal during the weaving cycle, while the presence sensor 46 never generates a high signal, wherein the stretching moment can be determined as the moment at which the generated signals of the presence sensors 45 and 44 alter from a high signal to a low signal short time one after another. This embodiment allows determining the reference moment according to the invention relatively accurate, which allows the opening of the thread holder 20 to be controlled in function of this reference moment. If this reference moment takes place for example too early in the weaving cycle on average, which implies that few weft thread 2 is stored in zigzag form in the storage element 11, for a next insertion of weft thread 2, in an embodiment the thread holder 20 is opened earlier in the weaving cycle. If this reference moment takes place for example too late in the weaving cycle on average, which impiies that much weft thread 2 is stored in zigzag form in the storage element 11, for a next insertion of weft thread 2 the thread holder 20 in an embodiment is opened later in the weaving cycle.

The reference moment determined with signals of the presence sensors 44, 45 or 46 can of course also be used to control the valve system 35 of the blowing device 10, as well as to control the valve system 36 of a main blower 5 or the valve system 37 of a relay nozzle 12.

According to another embodiment as shown in Fig. 12, a tension sensor 60 for the weft thread 2 is arranged at the thread guide 43 and a tension sensor 61 for the weft thread 2 is arranged at the blowing device 10. Each tension sensor 60, 61 delivers a signal that is a measure of the tension in the weft thread 2. In Fig. 13 with curves 62 and 63 examples of electrical signals of the tension sensors 60, 61, respectively, during the insertion of a weft thread 2 are shown as a function of the weaving machine angle. As shown the signal of the tension sensor 60 increases at a moment 68, while also the signal of the tension sensor 61 increases at the same moment. Such an increase of tension is due to the stretching of the weft thread 2 at a stretching moment and the moment of this increase determines the reference moment according to the invention.

According to a further embodiment as shown in Fig. 14, a movement sensor 64 for the weft thread 2 is arranged at the thread guide 43 and a movement sensor 65 for the weft thread 2 is arranged at the blowing device 10. Each movement sensor 64, 65 delivers a signal that is a measure of the movement course and/or the speed of movement of the weft thread 2. In Fig. 15 with curves 66 and 67 examples of electrical signals of the movement sensors 64, 65, respectively, during the insertion of a weft thread 2 are shown as a function of the weaving machine angle. As shown, the signal of the movement sensor 64 increases at a moment 69, while the signal of the movement sensor 65 decreases at the same moment. Such alteration in speed of the weft thread 2 is due to the stretching of the weft thread 2 at the stretching moment and the moment of this alteration determines the reference moment according to the invention.

According to an embodiment the stretching moment is for example chosen during the last winding, at the fourth winding in the example with a weft thread 2 for one insertion formed by four windings 50, which allows to weave at high speed, but with the risk that the decelerating of the weft thread 2 can happen less controlled. With such a setting of the weaving machine, the use of at least one tension sensor 60, 61 and/or at least one movement sensor 64, 65 in order to determine the reference moment is particularly suitable in order to allow the stretching moment to take place as late as possible in the weaving cycle. In this case, the reference moment can be determined accurately, more particularly the stretching moment can be determined easily even when the stretching moment takes place at the end of the insertion of the weft thread 2 in the weaving shed 6.

It is known that successive weft threads 2 from a same bobbin 4 can have an air friendliness that alters and that the force necessary to draw a weft thread from a bobbin 4 can alter slowly according to the diameter of the bobbin 4. As a resu!t, weft threads coming from a same bobbin 4 supplied using the same setting of the pressure and/or the air flow rate of the blowing unit 16 during the storing in the storage element 11 can be stored with a different speed. Further, as a result weft threads coming from the same bobbin 4 inserted using the same setting of the pressure and/or the air flow rate of the blowing unit 18 during the insertion into the shed 6 can move with a different speed. In a device 1 according to the invention, in preferred embodiments a weft thread 2 is accelerated at the start of the insertion into the shed 6, then further inserted with an approximately constant speed into the weaving shed 6 and decelerated or braked at the end of the insertion into the shed 6. The determining of a reference moment according to the invention and the use of a reference moment according to the invention for controlling the opening of the thread holder 20 is especially suitable to be used for the weaving of weft thread 2 wherein the air friendliness of successive weft threads 2 inserted alters. This particular advantage of the invention will be explained more in detaii hereafter.

During the weaving, the drive unit 33 of the thread holder 27 is opened for example at a certain moment in the weaving cycle, which moment is in preferred embodiments set in function of the moment at which a weaving shed 6 is formed. The valve system 36 of the main blower 5 is in preferred embodiments set so that a weft thread 2 arrives at a desired moment in the weaving cycie at the thread detector 15, for example as known from EP 0.239.137 Bl. The valve system 37 for the relay nozzles 12 is in preferred embodiments set so that the weft thread 2 is supported by the air flow from the relay nozzles 12, for example as known from EP 2.163.670 Al or WO 2007/057.217 Al.

If the air friendliness of successive weft threads 2 coming from a certain bobbin 4 increases during weaving from this bobbin 4, at equal setting of the valve system 35 of the blowing device 10 a weft thread 2 will be stored faster in the storage element 11. If the thread holder 27 is opened at the same moment in the weaving cycle, at this moment a large part of the weft thread 2 will already be stored in the storage element 11, so that a large part of the weft thread 2 also is inserted with large speed from the storage element 11 into the weaving shed 6 before the weft thread 2 in the storage element 11 is stretched, so that then only a small remaining part of the weft thread 2 is inserted with lower speed directly from the prewinder 3. Due to this effect, when weaving with a more air f iendiy weft thread 2, this means a weft thread moving faster with a same blowing force, the speed with which the weft thread 2 is transported through the weaving shed 6 is additionally raised because this weft thread 2 is stored over a larger part in the storage element 11. This means that the stretching moment for a fast weft thread 2 will take place later in the weaving cycle than the stretching moment for a slower weft thread 2. If according to the invention the reference moment is determined that is a measure of the stretching moment and in case the actual stretching moment takes place later in the weaving cycle, at a following insertion of weft thread 2 the moment that the thread holder 20 is opened can be controlled in function of this determined reference moment, and so that the control is carried out so that if the reference moment takes place later in the weaving cycle, the moment that the thread holder 20 is opened is controlled later in the weaving cycle. Due to the opening of the thread holder 20 later at a following insertion of weft thread 2, less weft thread 2 will be stored in the storage element 11, so that less weft thread 2 previously stored in the storage element 11 is inserted into the weaving shed 6 and more weft thread 2 will be inserted directly and, thus, slower from the prewinder 3. With the invention it is possible during the insertion of a fast weft thread 2 into a weaving shed 6 to decelerate this weft thread 2 earlier, so that the effect of the fast weft thread 2 is opposed.

If the air friendliness of successive weft threads 2 coming from a certain bobbin 4 decreases during the weaving from this bobbin 4, at equal setting of the valve system 35 of the blowing device 10 a weft thread 2 will be stored slower in the storage element 11. If the thread holder 27 is opened at the same moment in the weaving cycle, at this moment only a small part of the weft thread 2 will be stored in the storing element 11, so that a small part of the weft thread 2 is inserted with large speed from the storage element 11 into the weaving shed 6 before the weft thread 2 in the storage element 11 is stretched, so that then a large remaining part of the weft thread 2 is inserted with lower speed directly from the prewinder 3. Due to this effect, when weaving with a less air friendly weft thread, this means a weft thread moving slower with a same blowing force, the speed with which the weft thread is transported through the weaving shed 6 is additionally lowered because for one insertion only a smaller part of this weft thread is previously stored in the storage element 11. This means that the stretching moment for a slow weft thread 2 will take place earlier in the weaving cycle than the stretching moment for a faster weft thread 2. If according to the invention the reference moment is determined that is a measure of the stretching moment and in case the actual stretching moment takes place earlier in the weaving cycle, at a following insertion of weft thread 2 the moment that the thread holder 20 is opened can be controlled in function of this determined reference moment, and so that the control is carried out so that if the reference moment takes place earlier in the weaving cycle, the moment that the thread holder 20 is opened is controlled earlier in the weaving cycle. Due to the opening of the thread holder 20 earlier at a following insertion of weft thread 2, more weft thread 2 will be stored in the storage element 11, so that for one insertion more weft thread 2 previously stored in the storage element 11 is inserted into the weaving shed 6 and less weft thread 2 will be inserted directly and thus slower from the prewinder 3. With the invention it is possible during the insertion of a slow weft thread 2 into a weaving shed 6 to decelerate this weft thread 2 later, so that the effect of the slow weft thread 2 is opposed.

By controlling the moment that the thread holder 20 is opened in function of the reference moment in the weaving cycle that is a measure of the stretching of the weft thread 2 in the storage element 11, it is possible to oppose the effect of a fast or a slow weft thread, more particularly to decelerate a fast weft thread 2 more and to decelerate a slow weft thread 2 less. The invention also allows further using all regulations and settings of the valve systems 36 and 37 that are used in a device 1 in which no storage element 11 is provided. The valve system 35 in an embodiment is activated so that the blowing device 10 blows approximately at the moment of the opening of the thread holder 20, for example slightly before the opening of the thread holder 20 so that the blowing device 10 already blows on the weft thread 2 while the weft thread 2 is released by the thread holder 20. Of course the valve system 35 of the main blower 5 can also be controlled in a known way so that a weft thread 2 passes at a thread detector 15 at a desired moment in the weaving cycle.

According to the invention it is also possible to regulate the valve system 35 of the blowing device 10 so that the reference moment takes place or is in relation to the removing of a certain winding 50 from a prewinder 3. The invention in preferred embodiments is carried out with a setting so that the reference moment takes place during the removal of the penultimate winding . According to another possibility the invention is used with a reference moment during the removal of the last winding, which allows to weave faster but implies more risk for the braking of the weft thread 2.

According to an embodiment, the blowing device 10 blows on the weft thread 2 during a certain time interval. According to another embodiment, the blowing device 10 blows on the weft thread 2 until a set moment in the weaving cycle. According to a preferred embodiment of the invention the blowing device 10 is deactivated at a deactivation moment in the weaving cycle, which is defined as a moment at which a certain part of weft thread 2 coming from the prewinder 3 is supplied to the storage element 11 via an inlet 25 of the storage eiement 11, for example a certain time after two windings 50 are removed from the prewinder 3. The deactivation moment is for example in the shown embodiment determined in function of the second signal of the thread detector 24 and/or in function of the moment that the presence sensor 45 generates a high signal. This means that for a fast weft thread 2, wherein for example a certain time after two windings 50 are removed takes place earlier in the weaving cycle than the set time or the set moment in the weaving cycle until which moment the blowing device 10 normally blows, the blowing device 10 stops blowing at an earlier moment in the weaving cycle than the set time or the set moment in the weaving cycle. Due to this, the blowing device 10 blows during a shorter time interval on a fast weft thread 2, so that the amount of stored weft thread 2 in the storage element 11 is limited and so that also the speed with which a fast weft thread 2 is inserted into the weaving shed 6 is limited . Due to this also the stretching moment or the reference moment according to the invention takes place earlier than in case the blowing device 10 blows as set. For a slow weft thread 2 the blowing device 10 for example blows as set, so that as much weft thread 2 as possible is stored in the storage element 11 and the insertion of slow weft thread 2 into the weaving shed 6 can still happen with sufficient speed . Due to this, also a fast weft thread 2 is braked earlier in the weaving cycle and a slow weft thread 2 is braked later in the weaving cycle. In order to avoid that a fast weft thread 2 is inserted too fast and that a slow weft thread 2 is inserted too slow, according to the invention the blowing device 10 is not activated any more from the moment that a certain length of weft thread 2 is stored in the storage element 11. This embodiment is particularly advantageous in order to oppose the influence of random fast or slow weft threads.

Despite the first winding times and/or winding moments, more particularly the winding times and/or winding moments of the windings that are stored in the storage element 11 before the reference moment, are not influenced by the insertion of weft thread 2 into the weaving shed 6, these winding times and/or winding moments are representative for the air friendliness of the weft thread 2 concerned. Therefore, it may be assumed that if the first winding times are short, the weft thread 2 will be inserted into the weaving shed 6 relatively fast, and that if the first winding times are long, the weft thread 2 will be inserted into the weaving shed 6 relatively slow. This also allows that the first winding times and/or winding moments determined with a device 1 according to the invention can also be used for a method according to WO 2007/057.217 Al.

Notwithstanding in the embodiments shown a weft thread 2 for one insertion is formed by four windings 50, it is of course possible that a weft thread 2 for one insertion is formed by another number of windings 50, for example five or more windings 50. In this case the described method can be adapted suitably, for example so that in the description the first and the second winding are retained and in the description the third and fourth winding are respectively replaced by the penultimate and ultimate winding. Other variants are possible.

It is clear that the controlling of the moment to open the thread holder 20 does not necessary have to happen continuously, but can happen in steps, for example steps of 2msec, If the determined reference moment in the weaving cycle, for example, alters on average less than 2msec from weft thread to weft thread, then in an embodiment the moment of opening of the thread holder 20 is not adjusted. If the determined reference moment is altered for example more than 2msec, then the moment of opening in an embodiment is adjusted with a step of 2msec, more particularly advanced or delayed.

By the invention it is achieved that the opening of the thread holder 20 takes place early enough in the weaving cycle, so that a sufficient length weft thread 2 is stored in the storage element 11, which length allows inserting the weft thread 2 with high speed and with low tension into the weaving shed 6. By the invention it is also 5 achieved that the opening of the thread holder 20 takes place late enough in the weaving cycle, so that during the insertion of weft thread 2 into the weaving shed 6 the stored weft thread 2 in the storage element 11 is stretched and so that the weft thread 2 during the insertion of the last part of weft thread 2 into the weaving shed l o 6 is removed directly from the prewinder 3 and in this way is braked.

The invention also offers the advantage that when weaving with several devices 1 according to the invention that feed weft thread 2 into the weaving shed 6 according to a pattern, the storing of weft is thread 2 in the storage element 11 can already take place during the insertion of a weft thread 2 from another device 1. This means that in an embodiment the storing of weft thread 2 in a storage element 11 takes place during several weaving cycles, while the removing of weft thread 2 from the storage element 11 takes place only during 0 one single weaving cycle.

According to an embodiment not shown, the thread holder 27 shown in the drawings is replaced by a thread holder that is arranged near the main blower 5 and that is arranged to command the releasing of weft thread 2 at the start of the insertion of a weft 5 thread 2.

When weaving with several weft threads according to a pattern and if several weft threads are woven with other weaving parameters, for example as known from WO 01/79597 Al, it is also possible for each weft thread to combine a method according to the 0 invention with a method as known from WO 01/79597 Al. A method according to the invention can of course also be combined with a method as known from WO 2006/114187 Al, more particularly in an embodiment the reference moment is determined as an average of a number of reference moments, whereby the number of reference moments that is used to determine the average reference moment is for example determined based on the number of alterations that is carried out with respect to the moment for the opening of the thread holder 20.

It is of course also possible to store no weft thread 2 in the storage element 11 and to weave with a device 1 according to the invention in a known classical way, wherein weft thread 2 is always removed directly form the prewinder 3, In this case the method according to the invention is also not used.

Notwithstanding that in the weaving machine shown four devices according to the invention are used, in other embodiments use is made of only one device according to the invention or of another number of devices according to the invention. If a weft thread 2 is not suitable for being stored in a storage element the blowing device 10 can be used together with a main blower 5 in order to remove a weft thread 2 from the prewinder 3 and to insert the weft thread 2 into a weaving shed 6.

The shown embodiments only serve to explain the invention .

Variants are possible, in particular with respect to the embodiments of the blowing device, the storage element, the thread holders and the sensors. Also combinations of the shown embodiments are possible that fall under the claims.

Claims

Claims,

1. Method for feeding weft thread (2) in a weaving machine, wherein a length of weft thread (2) is released from a prewinder (3)

5 in order to be inserted into a weaving shed (6), wherein weft thread (2) coming from the prewinder (3) is supplied to a storage element (11) via an inlet (25) of the storage element (11), wherein weft thread (2) is removed from the storage element (11) via an outlet (26) of the storage element (11) in order to be inserted into the

10 weaving shed (6), wherein before the start of the insertion of weft thread (2) into the weaving shed (6) weft thread (2) is stored in the storage element (11), wherein at least during a part of a period of the insertion of the weft thread (2) into the weaving shed (6) a simultaneous store and removal of weft thread (2) is carried out, i s characterised in that at least at the end of the simultaneous store and removal of weft thread (2), the weft thread (2) stored in the storage element (11) is removed from the storage element (11) faster than weft thread (2) coming from the prewinder (3) is supplied to the storage element (11), so that at a stretching

20 moment in the weaving cycle during the period of the insertion of weft thread (2) into the weaving shed (6) the weft thread (2) stored in the storage element (11) changes from stored condition into stretched condition, wherein a reference moment is determined that is a measure of the stretching moment.

25

2, Method according to claim 1, characterised in that the start of the storing of weft thread (2) in the storage element (11) is controlied by an opening of a second thread holder (20) that is arranged between the prewinder (3) and the storage element (11),

30 wherein the opening of the second thread holder (20) is controlled in function of the reference moment in the weaving cycle.

3. Method according to claim 2, characterised in that the moment of the opening of the second thread holder (20) that is arranged between the prewinder (3) and the storage element (11) is determined so that the determined reference moment is related to a set moment in the weaving cycle.

4. Method according to claim 1, 2 or 3, characterised in that weft thread (2) coming from the prewinder (3) is blown into a storage element (11) by means of a blowing device (10) that is arranged between the prewinder (3) and the storage element (11) via an inlet (25) of a storage element (11), wherein this blowing device (10) is activated at a moment in the weaving cycle that is determined in function of the reference moment in the weaving cycle.

5. Method according to claim 4, characterised in that the blowing device (10) is de-activated at a de-activation moment in the weaving cycle so that the blowing of the blowing device (10) on the weft thread (2) decreases before the reference moment.

6. Method according to claim 5, characterised in that the de-activating is determined in function of a set part of weft thread (2) coming from the prewinder (3) being supplied to a storage element (11).

7. Method according to any one of claims 1 to 6, characterised in that the start of the insertion of weft thread (2) into the weaving shed (6) is controlled by the opening of a first thread holder (27) that is arranged between the storage element (11) and the weaving shed (6) and/or the end of the insertion of weft thread (2) into the weaving shed (6) is controlled by the closing of a second thread holder (20) that is arranged between the prewinder (3) and the storage element (11).

8. Method according to any one of claims 1 to 7, characterised in that the reference moment is determined based on signals of at least one thread detector (24, 52, 53, 54) that is arranged at the prewinder (3).

9. Method according to claim 8, characterised in that the thread detector (24, 52, 53, 54) delivers each time a signal if a winding (50) coming from the drum (23) of the prewinder (3) is moved past the thread detector (24, 52, 53, 54).

10. Method according to any one of claims 1 to 7, characterised in that the reference moment is determined based on signals from at least one presence sensor (44, 45, 46) that is arranged at the storage element (11).

11. Method according to any one of claims 1 to 7, characterised in that the reference moment is determined based on signals of a tension sensor (60, 61) for weft thread (2).

12. Method according to any one of claims 1 to 7, characterised in that the reference moment is determined based on signals of a movement sensor (64, 65) for weft thread (2), for example a movement sensor (64, 65) for weft thread (2) that can detect the movement of a weft thread (2) moving along the movement sensor (64, 65).

13. Device for applying a method according to any one of claims 1 to 12, characterised in that the device (1) comprises a prewinder (3), a storage element (11) for weft thread (2) and a thread holder (20) that is arranged between the prewinder (3) and the storage element (11), wherein the thread holder (20) is controlled by a control unit (31) as a function of the determined reference moment in the weaving cycle.

14. Device according to claim 13, characterised in that the storage element (11) is a storage element (11) in which a weft thread (2) is stored in zigzag form.