TECHNICAL FI ELD AND PRIOR ART

[0001 ] The invention relates to an arrangement and a method for optimizing a weaving process. More particular, the invention relates to an arrangement and a method for avoiding weaving errors due to an incorrect threading of a weft thread preparation device of a weaving machine.

[0002] A fabric consists of warp threads and weft threads. In a weaving machine, the weft threads are inserted in between warp threads during an insertion cycle of the weaving process. Weft threads are fed to the weaving machine and are wound on bobbins which are typically placed on bobbin racks or bobbin creels arranged on one side of the weaving machine, generally on the left side. Before starting to weave a new fabric style, a weaving machine has to be equipped with raw materials. From the rack, the weft thread of each bobbin is manually threaded to a prewinder that prepares the weft thread for the weft insertion. A weaving machine can have one prewinder or up to sixteen prewinders. Usually, one prewinder contains weft thread coming from one bobbin. In so called multi thread weaving applications, two or more weft threads coming from an associated bobbin can be wound simultaneously on a common prewinder. Also, in so called multi thread weaving applications, two or more weft threads coming from an associated prewinder can be inserted simultaneously in a weaving shed, for example by means of a gripper or a main nozzle. Often, a leading end of a second bobbin is tied to the trailing end of a first bobbin, to enable longer machine running cycles without interventions to supply new bobbins. For example, a weaving machine is equipped with sixteen prewinders and with one or more racks that form together sixteen platforms for bobbins, wherein each platform comprises one or two pins, on which a bobbin is placed.

[0003] In a control device for the weaving machine so called machine channels or weft insertion channels are used to determine the sequence in which the different weft threads are inserted. This sequence is often referred to as a "color pattern". One or more element(s) is/are assigned to each virtual channel, which is/are driven by the control device for drawing off a weft thread from a bobbin and/or to insert a weft thread threaded or otherwise coupled to said element. In the context of the application, said elements assigned to virtual channels are referred to as weft insertion channel elements. A group of weft insertion channel elements assigned to one virtual channel is referred to as weft insertion channel group. [0004] In a gripper weaving machine, also named rapier weaving machine, weft threads are manually threaded to prewinders of a weft thread preparation device and are threaded from the prewinders through weft thread brakes to one weft presenter, also named weft thread presenter. The prewinders are operated in order to wind the weft thread on the prewinder and thereby to draw off weft thread from the bobbin. An operation is triggered for example upon reaching a defined minimum length of weft reserve on the prewinder. This can be detected by means of a sensor arranged at the prewinder. The weft presenters are driven for example by a control device to present a particular weft thread coming from the associated prewinder to a bringer gripper for an insertion of said weft thread. In this case, the weft insertion channel elements comprise the prewinders and the weft presenters.

[0005] In an airjet weaving machine, weft threads from prewinders are fed to one main nozzle or to a set of main nozzles, wherein the main nozzles are driven by the control device in order to select the weft thread to be inserted during a weaving machine cycle. In this case, the weft insertion channel elements comprise the prewinders and the main nozzles. [0006] In order to have a control device that regulates the complete insertion process, it is essential that the type of weft thread threaded to the weft insertion channel element(s) and, thus, added or allocated to a weft insertion channel is known. In the context of the application "threaded to a weft insertion channel element" means that weft thread is coupled along its movement path in a certain way to the weft insertion channel element. [0007] From US 2004/0133297 A1 it is known to provide bobbins with identification elements, and to identify a bobbin provided on a platform, wherein the identification of the bobbins is used in order to weave an article according to a weft insertion pattern that is determined as a function of the kind of weft threads. A weft insertion pattern can be entered in a machine terminal or a central server as a function of the kind of weft thread to be inserted. Using the identification elements and the knowledge about the path of the weft thread in the weaving machine, in particular the knowledge about the prewinder and the main nozzle or the weft presenter used for a particular weft thread coming from the bobbin rack, the weaving machine can determine, for each kind of weft thread, the weft insertion channel corresponding to that kind of weft thread, and can convert the entered weft insertion pattern as a function of the kind of weft thread to a weft insertion pattern as a function of the weft insertion channels.

[0008] However, even with such identification elements there remains the risk that the weft thread coming from a prewinder is threaded to a different weft presenter or main nozzle than assumed in the control device and, hence, the weft thread property is added to an incorrect weft insertion channel.

SUMMARY OF THE I NVENTION

[0009] It is therefore, the object of the present invention to provide an arrangement and a method for avoiding weaving errors due to an incorrect threading of a weft thread preparation device of a weaving machine.

[0010] This object is solved by the arrangement and the method with the features of claims 1 and 8. Preferred embodiments are defined in the dependent claims.

[001 1 ] According to a first aspect of the invention an arrangement for optimizing a weaving process is provided, the arrangement comprising a control device and a number of weft insertion channel groups, wherein each weft insertion channel group comprises a first weft insertion channel element and a second weft insertion channel element downstream of the first weft insertion channel element, wherein each first weft insertion channel element is adapted to temporarily store weft thread coming from at least one associated bobbin, wherein weft thread coming from at least one of the first weft insertion channel elements can be fed to at least two different second weft insertion channel elements for forming a weft insertion channel group, wherein each of the number of first weft insertion channel elements is arranged to be operated in a regular mode, wherein in the regular mode each of the number of first weft insertion channel elements is driven for drawing off at least one weft thread fed to said first weft insertion channel element from the associated bobbin upon or after a defined minimum length of weft reserve stored in said first weft insertion channel element is reached, and wherein each of the number of first weft insertion channel elements is further arranged to be operated in a set-up mode, wherein in the set-up mode upon or after an insertion of weft thread coming from one of the number of first weft insertion channel elements is detected a second weft insertion channel element used for said insertion is identified and prior to operating said first weft insertion channel element in the regular mode, in particular prior to driving said first weft insertion channel element for drawing off weft thread from the at least one associated bobbin, said first weft insertion channel element and said identified second weft insertion channel element used for said insertion are allocated in the control device to one weft insertion channel group. [0012] In theory, a weft thread fed by a bobbin could be manually threaded or otherwise coupled to any of a number of first weft insertion channel elements, in particular prewinders, and from the first weft insertion channel elements to any of the number of second weft insertion channel elements, for example to a weft presenter or a main nozzle. In practice, there are some spatial limitations. Nevertheless, in many weaving machines weft threads coming from one first weft insertion channel element, in particular coming from a prewinder, can be manually threaded or otherwise coupled to at least two different second weft insertion channel elements, such as weft presenters or main nozzles, without difficulty. This may result in weaving errors. For example, for weaving a particular weaving pattern, the control device assumes that a first weft thread of a first type is inserted using a first weft insertion channel group comprising a first prewinder and a first weft presenter, and a second weft thread of a second type is inserted using a second weft insertion channel group comprising a second prewinder and a second weft presenter. However, if by setting up the weaving machine, the first weft thread of the first type is threaded to the first prewinder and the second weft presenter, and the second weft thread of the second type is threaded to the second prewinder and the first weft presenter, this will result in a weaving error, which cannot be detected with prior art control devices.

[0013] According to the invention, the first weft insertion channel elements can be operated in a set-up mode. The set-up mode is also referred to as "wait for identification mode". In this mode, a normal weaving or a weaving of a test pattern is possible until weft thread is drawn off from the first weft insertion channel element being in the set-up mode. In other words, until weft thread temporarily stored in said first weft insertion channel element has been inserted. In case an insertion of weft thread coming from one particular first weft insertion channel element, which is in a set-up mode is detected, then the second weft insertion channel element used for said insertion is identified and the two elements are allocated to the same weft insertion channel group. After the insertion of weft thread from one first weft insertion channel element a defined minimum length of weft reserve stored in said first weft insertion channel element may be reached, which in a regular mode would cause driving said first weft insertion channel element for drawing off weft thread from an associated bobbin. However, in the set-up mode drawing off weft thread from the associated bobbin is delayed until at least the step of adding or allocating the first weft insertion channel element and the second weft insertion channel element to a weft insertion channel group is completed.

[0014] According to preferred embodiments, at least some of the first weft insertion channel elements are associated with a detector arranged at or downstream of the respective first weft insertion channel elements, wherein an insertion of weft thread coming from one of the number of first weft insertion channel elements is detected by means of said detector, in particular by means of a weft reserve detector provided at the first weft insertion channel element, by means of a winding detector provided at the first weft insertion channel element and/or by means of a weft thread movement detector arranged downstream of the first weft insertion channel element. In a regular mode, the first weft reserve detector in one embodiment is used to detect that a defined minimum length of weft reserve stored in a first weft insertion channel element is reached, which will trigger an operation of said first weft insertion channel element for drawing off weft thread from an associated bobbin. [0015] According to an embodiment, the control device is arranged to compare first weft insertion channel elements and second weft insertion channel elements allocated to one weft insertion channel group in the set-up mode with first weft insertion channel elements and second weft insertion channel elements previously allocated to said weft insertion channel group and/or expected to be allocated to said weft insertion channel group. In particular, the control device is arranged to compare the elements allocated to one weft insertion channel group with the elements allocated to one machine channel or weft insertion channel in the control device. In case the result of the comparison is negative, this means in case the first and second weft insertion channel elements are allocated to other groups than expected, in one embodiment, the control device adjusts a weft insertion pattern defined by weft threads having an expected threading to match the weft insertion pattern to the identified threading of the weft threads. In other embodiments, an error signal is issued and a user is prompted to correct the threading.

[0016] According to preferred embodiments, the arrangement further comprises a bobbin rack with a number of platforms each having a weft thread property identifying sensor, wherein weft threads of bobbins placed on at least some of the platforms, and preferably on all platforms, are fed to at least some of the weft insertion channel groups, wherein at least at some of the platforms a weft thread movement detector arranged for detecting a weft thread movement is provided, wherein the first weft insertion channel elements of the weft insertion channel groups are arranged to be driven for drawing off the at least one weft thread fed to said weft insertion channel group from the associated bobbin placed on a platform, and wherein the control device is arranged

a) to determine the platform of the bobbin from which the at least one weft thread is drawn off by evaluating detector signals of the weft thread movement detectors provided at the platforms, and

b) to identify at least one weft thread property of the at least one weft thread fed to the weft insertion channel element by evaluating a sensor signal of the weft thread property identifying sensor provided at the determined platform.

[0017] Platforms can be provided with one pin or more than one pin, in particular two pins. On each pin of each platform a weft thread property identifying sensor can be provided. In theory, a weft thread from a bobbin placed on any pin of any platform could be manually threaded or otherwise coupled to any of a number of first weft insertion channel elements, in particular prewinders, and from the first weft insertion channel elements, in particular from the prewinder, to any of the number of second weft insertion channel elements, for example to a weft presenter or a main nozzle. As mentioned above, in practice, there are some spatial limitations. Nevertheless, in many weaving machines weft threads fed from at least some of the bobbins placed on the platform can be manually threaded or otherwise coupled to at least two different prewinders without difficulty. This may result in weaving errors. For example, when weaving with a particular weft insertion pattern, the control device assumes that a first weft thread of a first type has been threaded to a first prewinder and a second weft thread of a second type has been threaded to a second prewinder. However, if by setting up the weaving machine the first weft thread of a first type is threaded to the second prewinder and a second weft thread of a second type is threaded to the first prewinder, this will result in a weaving error, which cannot be detected with prior art control devices. According to an embodiment of the invention, the platforms of the bobbins from which weft threads are drawn off are determined by means of the control device and properties of the weft thread arranged on the determined platform are identified. This allows an unambiguous determination of properties of weft threads inserted using weft insertion channel elements allocated in the control device to a particular weft insertion channel. Thereby, the actual set-up of the weaving machine can be determined, and, weaving errors can be avoided.

[0018] Suitable weft thread movement detectors, also named movement detectors, may be chosen by the person skilled in the art. In one embodiment, an optical detector is provided for detecting a ballooning or movement of a weft thread during operation. In another embodiment, a piezo-electronic detector is provided for detecting an electrical charge induced upon the movement of the weft thread. In another embodiment, a detector using capacitive effects is provided, wherein for example a change in the capacitance upon movement of the weft thread is detected. In still another embodiment, natural electrical charges on the weft thread are detected using for example charge detectors. Suitable detectors are described for example in EP 0195469 A2 and/or US 4215728 A, which are incorporated herein by reference. However, the invention is not limited to the use of such detectors.

[0019] In preferred embodiments, the control device is further arranged to compare identified weft thread properties with weft thread property information allocated to weft insertion channels in the control device. As mentioned above, weft insertion channels are used in the control device to determine the sequence by which the different weft threads are inserted and the weft insertion channel elements assigned to the weft insertion channels are driven accordingly. When comparing identified weft thread properties with weft thread property information allocated to weft insertion channels in the control device weaving errors due to an incorrect threading can be avoided. For example, in case the control device has identified that a red weft thread is threaded to the weft insertion channel element associated to a first weft insertion channel. However for obtaining a desired fabric, a green weft thread has to be inserted using said weft insertion channel elements, an error message can be generated and weaving may be inhibited until the threading is corrected.

[0020] In an embodiment, the control device is arranged for adjusting a previous or expected allocation of weft insertion channel elements to a weft insertion channel based on an identified threading of a weft thread. For example, a first prewinder has been previously used to insert a weft thread coming from a first platform, and, thus, has been allocated to the associated weft insertion channel. However, upon a new set-up, the weft thread has been threaded to a second prewinder. In this case, in an embodiment the second prewinder will be allocated to the weft insertion channel instead of the first prewinder by the control device without further action required by the user. In alternative or in addition, the control device is arranged for adjusting a weaving sequence for obtaining a particular fabric based on identified weft thread properties. For example, in case the control device has identified that a red weft thread is threaded to the weft insertion channel element associated to a first weft insertion channel, however for obtaining a particular fabric a green weft thread is required, and a green weft thread is threaded to the weft insertion channel element associated to a second weft insertion channel, however for weaving said particular fabric a red weft thread is required, in the weaving sequence the first weft insertion channel and the second weft insertion channel are exchanged. Of course, such an adjustment is not possible in case that no red weft thread has been provided.

[0021 ] The weft thread property identifying sensors are arranged to identify at least one weft thread property selected from the group comprising amongst others thread thickness, thread hairiness, thread twist, thread color, thread production time, thread supplier, thread material and/or other thread properties. In one embodiment, the weft thread property identifying sensors each comprise a contactless reader element arranged for reading data that is associated with a weft thread property from a tag attached to a bobbin placed on the associated platform. Reader elements and tags allow for a simple communication of a large number of weft thread properties of the weft threads wound on a bobbin. This allows the use of expert knowledge related to the physical properties of the weft thread in the control device. The reader element in an embodiment is an optical reader element, for example a barcode reader element or a QR code reader element. In preferred embodiments, radio frequency technology is applied, and in particular an RFID reader element is provided. In alternative or in addition, sensors detecting the color, the hairiness or other weft thread properties may be provided. It is well known to provide more than one bobbin on a common platform, wherein a trailing end of a first bobbin is attached to the leading end of a second bobbin. In case several bobbins are placed on a common platform, in an embodiment only the weft thread properties of the first bobbin from which the weft thread is unwound is identified. In preferred embodiments, the weft thread property identifying sensors each are arranged for reading data from the tags attached to each bobbin placed on any one of the pins of the associated platform and/or for each bobbin placed on any one of the pins of the associated platform an associated weft thread property identifying sensor is provided. [0022] According to a second aspect a method is provided for optimizing a weaving process in a weaving machine comprising a control device and a number of weft insertion channel groups, wherein each weft insertion channel group comprises a first weft insertion channel element and a second weft insertion channel element downstream of the first weft insertion channel element, wherein each first weft insertion channel element is adapted to temporarily store weft thread coming from at least one associated bobbin, wherein a weft thread coming from at least one of the first weft insertion channel elements can be fed to at least two different second weft insertion channel elements for forming a weft insertion channel group, wherein each of the number of first weft insertion channel elements is arranged to be operated in a regular mode, wherein in the regular mode each of the number of first weft insertion channel elements is driven for drawing off at least one weft thread fed to said first weft insertion channel element from the associated bobbin upon or after a defined minimum length of weft reserve stored in said first weft insertion channel element is reached, and wherein the method comprises driving at least one of the number of first weft insertion channel elements in a set-up mode, wherein in the set-up mode upon or after an insertion of weft thread coming from said first weft insertion channel element is detected a second weft insertion channel element used for said insertion is identified and prior to operating said first weft insertion channel element in the regular mode, in particular prior to driving said first weft insertion channel element for drawing off at least one weft thread fed to said first weft insertion channel element from at least one associated bobbin, said first weft insertion channel element and said identified second weft insertion channel element used for said insertion are allocated in the control device to one weft insertion channel group.

[0023] Driving the first weft insertion channel element in the set-up mode allows allocating a first weft insertion channel element and the second weft insertion channel element used for an insertion of weft thread coming from said first weft insertion channel element to a common weft insertion channel. In other words, the second weft insertion channel element being threaded to the first weft insertion channel element and, thus, grouped with said first weft insertion channel element in a common weft insertion channel group is identified.

[0024] The first weft insertion channel elements can be manually or automatically, for example by means of the control device, switched to the set-up mode upon or after each operation that may result in a modification of the threading of the weft threads. Preferably, the first weft insertion channel elements are manually or automatically switched to the set-up mode after a new bobbin has been threaded to at least one weft insertion channel group and/or after threading operations within at least one weft insertion channel group.

[0025] In preferred embodiment, the first weft insertion channel element and the second weft insertion channel element allocated to one weft insertion channel group in the set-up mode are compared by means of the control device with first weft insertion channel elements and second weft insertion channel elements previously allocated to said weft insertion channel group or expected to be allocated to said weft insertion channel group. In particular, the elements are compared with elements allocated to a virtual channel or weft insertion channel used in the control device. This allows for a detection of threading errors.

[0026] In an embodiment, driving the selected one of the number of first weft insertion channel elements for drawing off weft thread from an associated bobbin is avoided in case the first weft insertion channel element and second weft insertion channel element allocated to one weft insertion channel in the set-up mode deviates from first weft insertion channel elements and second weft insertion channel elements previously allocated to said weft insertion channel group or expected to be allocated to said weft insertion channel group.

[0027] In preferred embodiments, a bobbin rack with a number of platforms each having a weft thread property identifying sensor is provided, wherein a bobbin is placed on any one of the platforms and the weft thread of said bobbin is fed to one of the number of weft insertion channel groups, wherein the method further comprises driving the selected one of the number of first weft insertion channel elements for drawing off weft thread from an associated bobbin, wherein upon or after drawing off the weft thread from said bobbin, the platform of said bobbin from which the at least one weft thread is drawn off is determined by evaluating detector signals of weft thread movement detectors arranged for detecting a weft thread movement, which are provided at at least some of the platforms, and at least one weft thread property of the at least one weft thread fed to said first weft insertion channel element is identified by evaluating a sensor signal of the weft thread property identifying sensor provided at the determined platform. [0028] As described above, by determining the platform from which a weft insertion channel element draws off a weft thread, and by identifying the weft thread properties of the weft thread wound on a bobbin at said platform, weaving errors can be avoided reliably.

[0029] In preferred embodiments, the identified weft thread properties are compared by means of the control device with weft thread property information allocated to weft insertion channels in the control device. In case the identified weft thread properties do not match with the weft thread property information, an error message can be generated and weaving can be inhibited until a user has corrected the threading.

[0030] In alternative or in addition, in an embodiment, the control device adjusts the allocation of a weft insertion channel element to a weft insertion channel based on an identified threading of the weft thread. This could be done either by the control device without further notification to the user or only after the user has approved the adjustment.

[0031 ] In an embodiment, a user is prompted to modify a position of two or more bobbins on the bobbin rack to optimize weaving a given weaving pattern. For example, it might be favorable to thread a weft thread dominating a particular weaving pattern to a weft presenter travelling only over a short distance when presenting a weft thread. The user can opt to follow the proposed modification or to maintain a set-up.

[0032] In an embodiment, weft thread properties are read by means of the weft thread property identifying sensor from a tag attached to the bobbin from which the weft thread is drawn off, wherein in particular the weft thread properties are read using a contactless reader element, in particular an RFID reader element. The weft thread properties may comprise amongst others information about the weft thread, such as color, thickness, hairiness and/or its production date, as well as its spinning date as its bobbin date. The determination of such weft thread properties also allows, for example, to start-up a weaving machine with specific settings that are stored in the control device of the weaving machine for weft threads with such weft thread properties.

BRIEF DESCRI PTION OF THE DRAWINGS

[0033] Further characteristics and advantages of the invention will emerge from the following description of the embodiments schematically illustrated in the drawings. Throughout the drawings, the same elements will be indicated by the same reference numerals. Fig. 1 shows an arrangement for optimizing a weaving process at a gripper weaving machine.

Fig. 2 shows the arrangement of Fig. 1 with a different configuration.

Fig. 3 shows a display content for an arrangement similar to Fig. 1 during a threading. Fig. 4 shows a display content for an arrangement similar to Fig. 1 with another threading.

Fig. 5 shows a display content for an arrangement similar to Fig. 1 with an incorrect threading.

Fig. 6 shows the arrangement of Fig. 1 with another different configuration.

Fig. 7 shows an arrangement for optimizing a weaving process at an airjet weaving machine.

DETAI LED DESCRI PTION OF EMBODIMENTS

[0034] Fig. 1 schematically shows an arrangement 1 for a gripper weaving machine. The gripper weaving machine comprises a bringer gripper 2 and a receiver gripper 3. For weaving a fabric 4, weft threads are inserted into a shed formed by warp threads 5. [0035] The arrangement 1 comprises a control device 6. The control device 6 in one embodiment is the central control device of the weaving machine. In another embodiment, a separate control device communicating with the central control device is provided. In still another embodiment, auxiliary control devices are provided, which each are associated to individual elements of the arrangement 1 and conjointly form the control device 6. The arrangement 1 shown in Fig. 1 further comprises a number of prewinders 7, 8, 9, a weft thread presenter device 10 with a number of weft presenters 1 1 , 12, 13 and a bobbin rack 14 with a number of platforms 15, 16, 17, each having two pins, wherein a bobbin 18, 19, 20, 21 , 22, 23 is provided at each pin. In the embodiment shown, three prewinders 7, 8, 9, three weft presenters 1 1 , 12, 13 and three platforms 15, 16, 17 are provided. In other embodiments, less than three or more than three, in particular up to sixteen prewinders, weft presenters and platforms are provided. [0036] Weft threads wound on a first bobbin 18, 20, 22 of each platform 15, 16, 17 are threaded to one of the number of prewinders 7, 8, 9 and are threaded from the prewinder 7, 8, 9 through weft thread brakes (not shown) to one of the number of weft presenters 13, 12, 1 1 . The trailing ends of the first bobbins 18, 20, 22 are tied to the leading ends of the second bobbins 19, 21 , 23. Each bobbin 18, 19, 20, 21 , 22, 23 may in principle be used as "first bobbin".

[0037] In the embodiment shown, at least one weft thread property identifying sensor 24, 25, 26 is provided at each platform 15, 16, 17. Preferably, at each bobbin of each platform an associated weft thread property identifying sensor is provided. Further, a weft thread movement detector 27, 28, 29 arranged for detecting a weft thread movement is provided at each platform 15, 16, 17. The weft thread property identifying sensors 24, 25, 26 and the weft thread movement detectors 27, 28, 29 communicate with the control device 6. The communications can be either wired or wireless. In the embodiment shown, additional weft thread movement detectors 30, 31 , 32 are provided downstream of each prewinder 7, 8, 9. Further, a human machine interface 33 for data input and data output is provided. A human machine interface 33 may consist of a computer, a tablet, a smartphone, a smartwatch, smart glasses and such apparatuses.

[0038] The prewinders 7, 8, 9 are driven to prepare a weft thread for the weft insertion by winding the weft thread on the prewinder 7, 8, 9, and, thereby, draw off weft thread from the respective bobbin 18, 20, 22. For a weft insertion of a particular weft thread, the respective weft presenter 1 1 , 12, 13 is driven by the control device 6 to present the weft thread to the bringer gripper 2 and the weft thread is inserted by means of the bringer gripper 2 into the shed, wherein the weft thread is drawn off from the prewinder 7, 8, 9.

[0039] Each prewinder 7, 8, 9 and each weft presenter 1 1 , 12, 13 is assigned in the control device 6 to a weft insertion channel, also named weaving machine channel. These weft insertion channels are used in the control device 6 and determine the sequence in which the different weft threads are inserted. The prewinder 7, 8, 9 and the weft presenter 1 1 , 12, 13, which due to the threading are used for the insertion of weft thread coming from one platform 15, 16, 17 are referred to as weft insertion channel group. In the configuration of Fig. 1 , the prewinder 9 and the weft presenter 1 1 belong to one weft insertion channel group, the prewinder 8 and the weft presenter 12 belong to one weft insertion channel group, and the prewinder 7 and the weft presenter 13 belong to one weft insertion channel group.

[0040] Before starting up a new fabric style, the weaving machine has to be equipped with raw materials. When the weft threads of the bobbins arranged on the platform are threaded to the prewinders 7, 8, 9 and/or are threaded from the prewinders 7, 8, 9 to the weft presenters 1 1 , 12, 13, different configurations are possible.

[0041 ] Fig. 2 shows a possible alternative configuration of the arrangement 1 of Fig. 1 . The configuration of Fig. 2 differs from that shown in Fig. 1 in that a weft thread coming from a bobbin 20 arranged in the middle is threaded to a prewinder 9 arranged at a bottom side and a weft thread coming from a bobbin 22 arranged at a bottom side is threaded to a prewinder 8 arranged in the middle. Of course, such an arrangement is only possible in case the weft threads coming from the bobbins 20 and 22 do not interfere with each other. As in the configuration of Fig. 1 , in the configuration of Fig. 2, the prewinder 9 and the weft presenter 1 1 belong to one weft insertion channel group, the prewinder 8 and the weft presenter 12 belong to one weft insertion channel group, and the prewinder 7 and the weft presenter 13 belong to one weft insertion channel group.

[0042] Generally, it is possible to weave with both configurations. However, in order to have a reliable control system that regulates the complete insertion process, it is important that the weft thread type threaded to a particular prewinder 7, 8, 9 is known in the control device 6.

[0043] According to the embodiment shown, one of the prewinders 7, 8, 9 is driven for drawing off the weft thread fed to said prewinder 7, 8, 9 from the associated bobbin 18, 20, 22 placed on the bobbin rack 14. The prewinders 7, 8, 9 can be operated in a regular mode, wherein in the regular mode each of the number of prewinders 7, 8, 9 is driven for drawing off weft thread fed to said prewinder 7, 8, 9 from the associated bobbin 18, 20, 22 upon or after a defined minimum length of weft thread reserve stored in said prewinder 7, 8, 9 is reached. An instant, at which a defined minimum length of weft reserve stored in a prewinder 7, 8, 9 is reached, is detected for example by means of a weft reserve sensor provided at said prewinder 7, 8, 9. Auxiliary control devices (not shown) allocated to the prewinders 7, 8, 9 for driving the prewinders 7, 8, 9 in one embodiment are communicated with a central control device and, thus, together with the central control device form the control device 6. In other embodiments, auxiliary control devices (not shown) allocated to the prewinders 7, 8, 9 work autonomously and in the regular mode independent of the control device 6. A movement of the respective weft thread drawn off from the associated bobbin 18, 20, 22 is detected by means of one of the weft thread movement detectors 27, 28, 29. By evaluating the detector signals of the weft thread movement detectors 27, 28, 29, the platform 15, 16, 17 at which the bobbin 18, 20, 22 from which weft thread is drawn off is placed is determined. After the platform 15, 16, 17 is determined, weft thread properties of at least the first bobbin 18, 20, 22 arranged on said platform 15, 16, 17 can be identified by evaluating a sensor signal of the weft thread property identifying sensor 24, 25, 26 provided at the determined platform.

[0044] In the embodiment shown, the weft thread properties identified by the control device 6 are visualized to a user on the human machine interface 33 comprising a display. [0045] Figs. 3 and 4 show possible display contents for an arrangement 1 similar to Fig. 1 and 2 comprising four platforms 101 , 102, 103, 104, and four prewinders 201 , 202, 203, 204.

[0046] Fig. 3 shows a possible display content after bobbins have been placed on the four platforms 101 , 102, 103, 104 and the weft thread properties of bobbins have been identified. The identified weft thread properties of bobbins at the platforms 101 , 102, 103, 104 are indicated in a window 1 A, 2A, 3A, 4A, 1 B, 2B, 3B, 4B associated to a bobbin that is placed on a pin of the platform. The identified weft thread properties are compared by the control device 6 (see Fig. 1 ) with weft thread property information allocated to weft insertion channels in the control device 6. The windows 1 A, 2A, 3A, 4A that are associated to the pin on which a bobbin is placed, wherein the identified weft thread properties match with the weft thread property information in the control device 6, are for example marked green. The windows 1 B, 2B, 3B, 4B that are associated to a pin on which no bobbin is placed are for example marked grey.

[0047] Fig. 4 shows a possible display content similar to Fig. 3. In contrast to Fig. 3, a wrong bobbin has been placed on platform 104. The wrong bobbin will be indicated for example by marking the window 4A red, that is shown hatched in Fig. 4. Hereby, starting the weaving process is inhibited. In alternative driving the prewinder 201 , 202, 203, 204 is inhibited, that will be signaled to a user by an arrow 36, for example a white arrow.

[0048] After the weft threads are for example moved one by one, and a movement of the respective weft thread is detected by means of one of the weft thread movement detectors 27, 28, 29 (see Fig. 1 ), then it is determined which prewinders 201 , 202, 203, 204 are associated to which platform 101 , 102, 103 , 104. In case all identified weft thread properties match with the weft thread property information allocated to weft insertion channels in the control device 6, the correct threading is indicated to the user for example by means of an arrow 34, that is shown hatched in Fig. 3 but in reality is for example a green arrow. In case a weft thread is not yet threaded to a prewinder 201 , 202, 203, 204, this will be signaled to a user by an arrow 35, for example an orange arrow, and starting the weaving process is inhibited. After the threading is correctly completed, a user may start weaving. [0049] Fig. 5 shows another possible display content similar to Fig. 3. In contrast to Fig. 3, a user has threaded the prewinders 203 and 204 with weft thread coming from bobbins of another platform 103, 104 than expected by the control device 6. This mismatch is shown on the display by means of arrows 37, that are shown vertically hatched in Fig. 5 but in reality are for example red arrows. Thereafter, the user in an embodiment has three options:

1 ) exchange the threading of the weft threads coming from the bobbins placed on platforms 103, 104,

2) exchange the positions of the bobbins on the bobbin rack, or

3) adjust the weft insertion channels in the control device 6. [0050] In an embodiment, the adjustment is carried out by the control device 6 after the user has made an input. In another embodiment the adjustment can also take place without further input from the user.

[0051 ] Fig. 6 shows a possible alternative configuration of the arrangement 1 of Fig. 1 . The configuration of Fig. 6 differs from that shown in Fig. 1 in that a weft thread coming from a prewinder 9 arranged at the bottom side is threaded to a weft presenter 13 arranged closest to the fabric 4 and a weft thread coming from a prewinder 7 arranged at the top side is threaded to a weft presenter 1 1 arranged furthest from the fabric 4. In other words, the configuration of Fig. 6 differs from that shown in Fig. 1 , wherein the prewinder 9 and the weft presenter 13 belong to one weft insertion channel group, the prewinder 8 and the weft presenter 12 belong to one weft insertion channel group, and the prewinder 7 and the weft presenter 1 1 belong to one weft insertion channel group. In the embodiment shown, additional weft thread movement detectors 30, 31 , 32 are provided downstream of the prewinders 7, 8, 9, that are each associated to one of the prewinders 7, 8, 9. Preferably, the weft thread movement detectors 30, 31 , 32 are arranged at the exit of the respective prewinder 7, 8, 9. The additional weft thread movement detectors 30, 31 , 32 allow to determine from which prewinder 7, 8, 9 a weft thread is drawn off by the bringer gripper 2 while a particular weft presenter 1 1 , 12, 13 presents a weft thread to the bringer gripper 2. Hence, the configuration shown in Fig. 6 can be distinguished from the configuration shown in Fig. 1 by the control device 6.

[0052] For this purpose, according to the invention, the prewinders 7, 8, 9 can be switched to a set-up mode or "wait for identification mode", for example after threading operations due to weft thread breaks. In the set-up mode, weaving can be continued or a test fabric can be woven until an insertion of weft thread from one prewinder 7, 8, 9 switched into the set-up mode is detected. In the set-up mode, driving the prewinder 7, 8, 9 for drawing off weft thread from an associated bobbin 18, 19, 20, 21 , 22, 23 is deferred or blocked. Hence, upon or after an insertion of weft thread coming from said prewinder 7, 8, 9 is detected by means of the associated weft thread movement detectors 30, 31 , 32 the weft presenter 1 1 , 12, 13 used for said insertion, this means the immediately preceding or present insertion, is identified and prior to driving said prewinder 7, 8, 9 for drawing off at least one weft thread fed to said prewinder 7, 8, 9 from the associated bobbin(s) 18, 19, 20, 21 , 22, 23, the prewinder 7, 8, 9 and the weft presenter 1 1 , 12, 13 used for said insertion are allocated in the control device 6 to one weft insertion channel group.

[0053] In addition or in alternative, in one embodiment weft reserve detectors 50, 51 , 52 are provided at the prewinders 7, 8, 9. In a regular mode, reaching a minimum length of weft reserve stored in one of the prewinders 7, 8, 9 is detected by means of the associated weft reserve detector 50, 51 , 52. In the regular mode, the respective sensor signal triggers driving said prewinder 7, 8, 9 to draw off weft thread from the associated bobbin 18, 20, 22. In case the prewinder 7, 8, 9 is in a set-up mode, driving said prewinder 7, 8, 9 to draw off weft thread from the associated bobbin 18, 20, 22 is blocked or at least deferred. Prior to driving said prewinder 7, 8, 9 to draw off weft thread from the associated bobbin 18, 20, 22, the weft presenter 1 1 , 12, 13 used for the immediately preceding or still ongoing present insertion is identified and said weft presenter 1 1 , 12, 13 as well as the prewinder 7, 8, 9 at which reaching a defined minimum length of weft reserve stored are allocated in the control device 6 to a common weft insertion channel group. [0054] In the embodiment shown, the control device 6 is further arranged to compare the prewinder 7,8, 9 and the weft presenter 1 1 , 12, 13 as allocated to one weft insertion channel group in the set-up mode with expected configurations of a weft insertion channel group. In case the identified configuration of the weft insertion channel group requires neither a user input nor any other form of correction, said prewinder 7, 8, 9 can be set to a regular mode or normal operation mode and be driven for drawing off weft thread from an associated bobbin 18, 19, 20, 21 , 22, 23. On the other hand, in case the configuration as shown in Fig. 1 is expected, but the configuration shown in Fig. 6 is detected, the user can be prompted to take appropriate measures for a correction.

[0055] Similar to the situation described in the context of Fig. 5, the user in preferred embodiments has several options. In this case, two options are available, namely

1 ) exchange the path of the weft threads or

2) adjust the elements allocated to a weft insertion channel in the control device 6. [0056] Figs. 1 , 2 and 6 schematically show the use of the arrangement 1 in a gripper weaving machine. In alternative, the arrangement 1 may be used in an airjet weaving machine, as shown in Fig. 7.

[0057] The arrangement 1 for an airjet weaving machine shown in Fig. 7 is similar to the arrangement of Fig. 1 and for identical or similar elements the same reference numerals are used. In an airjet weaving machine, weft threads are inserted by means of nozzle arrangements comprising main nozzles 41 , 42, 43.

[0058] In the embodiment shown in Fig. 7 each prewinder 7, 8, 9 is provided with a weft reserve detector 50, 51 , 52 for detecting an instant at which a defined minimum length of weft reserve stored in a prewinder 7, 8, 9 is reached. As reaching a defined minimum length of weft reserve stored in a prewinder 7, 8, 9 occurs upon drawing off weft thread from said prewinder 7, 8, 9, the weft reserve detectors 50, 51 , 52 can be used for detecting a drawing off of weft thread coming from the prewinder 7, 8, 9. Hence, by means of the weft reserve detectors 50, 51 , 52 it is possible to identify the prewinder 7, 8, 9 from which weft thread is threaded to a main nozzle 41 , 42, 43. While weaving with at least one of the prewinders 7, 8, 9 being in a set-up mode, upon or after an insertion of weft thread coming from said prewinder 7, 8, 9 is detected by means of the weft reserve detectors 50, 51 , 52, said prewinder 7, 8, 9 and the main nozzle 41 , 42, 43 used for said insertion are allocated in the control device 6 to one weft insertion channel group prior to driving said prewinder 7, 8, 9 for drawing off weft thread from the bobbin. [0059] In other embodiments, instead of or in addition to the weft reserve detectors 50, 51 , 52, so called winding detectors 53, 54, 55 that detect the drawing off of windings from a prewinder 7, 8, 9 are provided, which can also be used as weft thread movement detectors in order to determine from which prewinder a main nozzle draws off weft thread to be inserted into a shed. Weft reserve detectors and winding detectors are generally known, for example from US 471541 1 .

[0060] In the embodiment of Fig. 7, for each bobbin 18, 20, 22, 19, 21 , 23 an associated weft thread property identifying sensor 24, 25, 26, 44, 45, 46 is provided near an associated pin on each platform 15, 16, 17. In an alternative embodiment, only one weft thread property identifying sensor 24, 25, 26, 44, 45, 46 is provided at each platform. [0061 ] The arrangement and the method according to the invention are not limited to the embodiments described by way of example and illustrated in the drawings. Alternatives and combinations of the described and illustrated embodiments that fall under the claims are also possible. All described and illustrated embodiments can be used in gripper weaving machines, airjet weaving machines or other types of weaving machines.