EP2435609B1

EP2435609B1 - Method for inserting a weft thread and airjet weaving machine

Info

Publication number: EP2435609B1
Application number: EP10723927.9A
Authority: EP
Inventors: Bianca Smet; Patrick Puissant
Original assignee: Picanol NV
Current assignee: Picanol NV
Priority date: 2009-05-27
Filing date: 2010-05-26
Publication date: 2017-08-16
Anticipated expiration: 2030-05-26
Also published as: EP2435609A1; CN102449216A; WO2010136194A1; BE1018762A3; CN102449216B; WO2010136194A8

Description

The invention relates to a method for inserting a weft thread into a shed of an airjet weaving machine, wherein the weft thread is transported by compressed air coming from a main nozzle device and at least one set of relay nozzles. Preferably, the compressed air which is supplied to the main nozzle device and to the at least one set of relay nozzles is controlled by shut-off valves which are controlled by a control unit. The invention also relates to an airjet weaving machine for applying such a method, in other words an airjet weaving machine which can apply a method as mentioned above.
It is known from WO 2007/057217 A1 to supply compressed air successively to the successive sets of relay nozzles while the weft thread is transported through the shed. The different sets of relay nozzles are provided with compressed air via shut-off valves. Each shut-off valve is connected to a set of relay nozzles and each shut-off valve is controlled by a control unit. Measurements are carried out on the weft thread while the weft thread is transported through the shed. For each set of relay nozzles a moment can be determined when the supply of compressed air to this set of relay nozzles is interrupted. This moment can be determined in function of said measurements. This allows that both a slow weft thread and a fast weft thread are sufficiently supported by compressed air coming from successive sets of relay nozzles. As described in WO 2007/057217 A1 , an influence on the supply of compressed air to a set of relay nozzles can be chosen strong, medium or limited.
Airjet weaving machines are known from WO 2007/057217 A1 , wherein weft threads coming from different weft thread buffers are inserted into the shed according to a pattern. For each weft thread coming from a weft thread buffer a corresponding main nozzle device with main nozzles arranged in series is provided. Further a number of sets of relay nozzles is provided for transporting the weft threads, coming from the different weft thread buffers, through the shed, more in particular for transporting the weft threads along a guide channel through the shed. For inserting a weft thread into the shed, compressed air can be supplied to each main nozzle of a main nozzle device via associated shut-off valves that are arranged between a reservoir with compressed air and a corresponding main nozzle. Compressed air is supplied to each set of relay nozzles via associated shut-off valves that are arranged between a reservoir with compressed air and the associated set of relay nozzles. Each set of relay nozzles comprises at least one relay nozzle and for example two or three relay nozzles that are mounted next to one another.
The amount of compressed air which is supplied during a time interval to a main nozzle and/or to a set of relay nozzles can be regulated during weaving by means of a motor-controlled throttle valve that is mounted between the reservoir and a corresponding main nozzle and/or set of relay nozzles. Such a motor-controlled throttle valve comprises for example a controllable stepping motor that can be controlled in both directions with a number of steps by means of a control unit. The control of the amount of supplied compressed air during a time interval can be regulated during weaving in function of a deviation of a measured insertion parameter. It is possible for example to control the amount of compressed air which is supplied during a time interval so, that an inserted weft thread reaches the end of the shed approximately at a desired angular position of the weaving machine. According to a possibility, an average deviation is determined between the moment at which the weft thread reaches the end of the shed and the moment at which the main drive shaft of the weaving machine reaches a given angular position. The throttle valves can then be controlled in such a way that the average deviation that is determined during several insertions of weft threads coming from the corresponding weft thread buffers will be approximately equal to a given value.
DE 42 26 693 A1 shows a method, wherein upon starting a normal weaving operation, a supply of compressed air is adjusted. According to one method shown in this document, first a supply pressure to the main nozzles is increased until a weft thread is sufficiently fast, i.e. until a measured arrival time is shorter than a desired arrival time. In case the measured arrival time is longer, i.e. in case the weft thread is too slow, the pressure is increased. Then, a supply pressure to the relay nozzles is reduced until a weft thread becomes too slow, i.e. until a measured arrival time is longer than a desired arrival time. In case the measured arrival time is longer, i.e. in case the weft thread is too slow, the pressure is increased. Next, a duration of the supply of compressed air to the main nozzles is reduced until a weft thread becomes too slow. When the weft thread becomes too slow, the duration is adjusted to the previous value of the supply of compressed air to the main nozzles. Finally, a duration of the supply of compressed air to the relay nozzles is reduced until a weft thread becomes too slow. When the weft thread becomes too slow, the duration is adjusted to the previous value of the supply of compressed air to the relay nozzles.
It is an object of the invention to provide a method and an airjet weaving machine for reducing the amount of compressed air which is used for the insertion of weft threads into a shed, while weaving errors are avoided during reducing the amount of compressed air which is used for inserting weft threads into a shed.
This object is solved by a method according to claim 1 and an airjet weaving machine according to claim 10.
A method for inserting a weft thread into a shed of an airjet weaving machine comprising a main nozzle device and at least one set of relay nozzles is provided, wherein a standard setting for the supply of compressed air to the main nozzle device and to the at least one set of relay nozzles is determined, the standard setting for the supply of compressed air to the main nozzle device and to the at least one set of relay nozzles is adjusted in order to reduce the supply of compressed air, a stability of insertions of a weft thread with the adjusted standard setting is observed, the standard setting for the supply of compressed air to the main nozzle device and to the at least one set of relay nozzles is adjusted such that the supply of compressed air to the at least one set of relay nozzles is decreased until a weft insertion becomes unstable, and if a weft thread insertion becomes unstable when an adjusted standard setting for the supply of compressed air to the main nozzle device and to the at least one set of relay nozzles is applied, the supply of compressed air to the main nozzle device is decreased in order to avoid the instability.
If the supply of compressed air to the main nozzle device is decreased, the inserted weft thread is less pushed into the shed. Correspondingly, the speed of the weft thread at the entrance of the shed will also fall, so that a leading end of the weft thread will not be slower than the trailing end of the inserted weft thread. This allows a setting for the supply of compressed air wherein the supply of compressed air to the sets of relay nozzles is interrupted at an earlier moment, without the risk that the inserted weft thread will form loops due to differences in speed, in particular due to a higher speed at the entrance of the shed than at the end of the shed. As a result, after decreasing the supply of compressed air to the main nozzle device, the setting can be further adjusted by decreasing the supply of compressed air to the at least one set of relay nozzles.
Preferably, after the supply of compressed air to the main nozzle device has been decreased, the standard setting is again further adjusted by decreasing the supply of compressed air to the at least one set of relay nozzles until insertions of a weft thread become again unstable.
A standard setting can be defined as a function of a weaving pattern, a yarn type and other parameters, under which previously determined data, such as measurements on transported weft threads during their transport. By observing the stability of the insertion of the weft thread it is possible to optimize the standard setting, while weaving errors are prevented. If the observed weft thread insertion is stable, the standard setting can be further adjusted, for example a supply of compressed air can be further decreased.
Preferably, the interruption of the compressed air supply to the at least one set of relay nozzles is further delayed or advanced with respect to a standard setting in function of measurements on a transported weft thread during transport of this weft thread as described in WO 2007/057217 . If the weft thread insertion is stable, the standard settings can be adjusted, in particular, a period during which compressed air is supplied to a corresponding nozzle, can be shortened, in other words the interruption of the supply of compressed air for the standard setting can be advanced in relation to the weaving cycle. The adjustment can be repeated until the weft thread insertion becomes unstable. When the weft thread insertion becomes unstable, the standard settings can be adjusted by extending the period of air supply, in particular by delaying an interruption of air supply to the sets of relay nozzles, and/or adjusting an air supply to the main nozzle device. Thereby, a limit for decreasing the air supply to the sets of relay nozzles is determined. According to a preferred embodiment, a user or operator can choose to what extent the standard setting for the at least one set of relay nozzles may be influenced. For example, the user or operator can choose between low influence, medium influence or high influence.
According to an embodiment, an interruption of a compressed air supply to the main nozzle device and/or to the at least one set of relay nozzles is adjusted in function of measurements on a transported weft thread in order to adjust the standard setting. The moments for interrupting and/or commencing the compressed air supply to the main nozzle device and/or to the sets of relay nozzles can be alternately adjusted. According to another embodiment first only the setting for the air supply to the sets of relay nozzles is adjusted, and if a limit for decreasing the air supply to the sets of relay nozzles is reached, the moment for interrupting the supply of compressed air to the main nozzle device is also set earlier. The air supply to the main nozzle device is preferably only reduced to an amount which allows that the weft thread is still accelerated with sufficient force during the start of the insertion, so that this reaches a desired speed, which is determined by the force, i.e. the pressure and/or the air flow per time unit, exerted by the main nozzle device. Thereby it is accomplished that the relay nozzles support the weft thread with a minimum force and that an unnecessary acceleration of the weft thread by the main nozzle device at the entrance of the shed is avoided.
According to another embodiment, the main nozzle device is provided with a first main nozzle and a second main nozzle, wherein the supply of compressed air to the first main nozzle is decreased, when a weft thread insertion becomes unstable. The first main nozzle is also called auxiliary main nozzle or fixed main nozzle, in case the first main nozzle is fixedly mounted on the frame of the weaving machine. Preferably, viewed in the moving direction of the weft thread the first main nozzle is arranged so, that this precedes the second main nozzle which is mounted near the shed, in particular mounted next to the reed on the sley. The second main nozzle is also called moveable main nozzle, in case the second main nozzle is mounted on the sley. In this way, the second main nozzle, which is arranged next to the reed, can further insert the weft thread into the shed, in other words this can blow as long as necessary to insert the weft thread into the shed. Preferably, the setting for the supply of compressed air to the moveable or second main nozzle is not changed or is changed only limited by adjusting the setting. In order to avoid loops at the entrance of the shed, the pressure of the supplied compressed air to the moveable main nozzle is preferably higher than the pressure of the supplied compressed air to the fixed main nozzle. In an embodiment, the first, in particular the fixed main nozzle can be set to only assist to pull the weft thread from a prewinder, while the second, in particular the moveable main nozzle blows the weft thread into the shed.
Preferably, a number of successive sets of relay nozzles is provided, wherein the standard setting for a compressed air supply to the number of sets of relay nozzles is adjusted making use of a belly pattern or bell-shaped curve. According to the invention, a belly, belly pattern or bell-shaped curve is defined as a pattern, according to which in a row of successive sets of relay nozzles, sets of relay nozzles mounted near a centre of the shed are influenced stronger than sets of relay nozzles mounted on the sides of a shed. For example, if nine sets of relay nozzles are provided, then the 4^th, 5^th and 6^th set are the most strongly influenced, while the 1^st, 2^nd, 8^th and 9^th set are not or almost not influenced and the 3^rd and 7^th set are slightly influenced. In another example, a belly pattern is chosen such that it is symmetrical with respect to a central set of relay nozzles. For example, at the middle sets of relay nozzles a setting of an interruption moment can be adjusted in a first step to occur 5% earlier with respect to a previous standard interruption moment for the middle sets of relay nozzles, e.g. the 5^th set of relay nozzles when nine sets are provided. For the 1^st, 2^nd, 8^th and 9^th set of relay nozzles the moment of interruption of an air supply can first be kept constant, for the 3^rd and 7^th set of relay nozzles can be chosen to occur 1% earlier, and the interruption moment for the 4^th and 6^th set can be chosen to occur 3% earlier. If the weft thread insertion remains stable after the adjustment, the interruption moment can be further adjusted until the weft thread insertion becomes unstable or until limit values for adjusting an interruption moment are reached. Limit values can be set dependent on a chosen influence setting. When for example, a low influence setting is chosen, a limit value can be set on 30% at the deepest belly point, i.e. the middle sets of relay nozzles. When an average or a high influence setting is chosen, a limit value can be set on 40% or 50% at the deepest belly point, respectively. In addition, the settings for each inserted weft thread can be adjusted according to the measurements on the determined inserted weft thread. For example, when a slow weft thread is detected, a later actual moment of interruption is used than in cases when a fast weft thread is detected. Slow and fast weft threads can be distinguished for example depending on a time difference between a moment or a point of time that an unwinding of a weft thread winding is accomplished, for example the second weft winding and a previously chosen moment in the weaving cycle. When a slow weft thread is detected, a moment for the interruption of an air supply can be chosen that lies between the adjusted standard moment set in accordance with the adjusted standard setting according to the invention and an original standard moment set by an operator, in other words a standard moment of an initial setting.
A stable insertion of a weft thread is hereby determined as an insertion wherein no instability takes place, more particularly wherein no weaving error occurs. According to an embodiment, an unstable weft thread insertion is identified by detecting at least one weaving error. For example, according to the invention a weaving error, also called a weaving irregularity, is defined as a situation wherein a leading end of a weft thread is not supported sufficiently for allowing the weft thread to be transported in a stretched condition through the shed.
For example, a weaving error is detected when the time difference between a measured moment wherein an inserted weft thread arrives at a first measurement point and a measured moment wherein the inserted weft thread arrives at a second measurement point exceeds a predetermined threshold. A weaving error can also be detected when the average time difference between a measured moment wherein an inserted weft thread arrives at a first measurement point and a measured moment wherein the inserted weft thread arrives at a second measurement point exceeds a predetermined threshold.
For example, a weaving error is detected when the time difference between an expected arrival moment of an inserted weft thread at a measurement point and the measured arrival moment of at least one weft thread at this measurement point exceeds a predetermined threshold. A number of measurement points can be defined, wherein each measurement point can be chosen in the shed and/or at the end of a shed. According to an embodiment, an unwinding moment of a weft thread, for example at a prewinder, and an arrival moment at a measurement point, for example at an exit of the shed, are measured and a time difference is determined. According to an example, the time difference is determined between a signal of the last but one winding, i.e. in case of five windings the fourth winding, and the signal of the arrival of a weft thread at a detector which is mounted at the exit of the shed. Alternatively or additionally the time difference is determined between a last winding, in this example the fifth winding, and the arrival of a weft thread at the said detector. I n case of a constant speed of the weft thread, each of these two time differences is essentially constant. When the weft thread speed decreases towards the end of the shed, one or each of the said time differences will increase, so there can be concluded that the weft thread is not supported sufficiently.
According to a preferred embodiment, an average arrival moment for a certain number of insertions is determined and a weaving error is detected if the time difference between an expected arrival moment of an inserted weft thread at a measurement point and the average arrival moment at this measurement point exceeds a predetermined threshold. Preferably, a number of weft thread insertions that is used for determining an average arrival moment is adjusted to a deviation between values measured during different insertions as described in WO 2006/114187 .
According to another embodiment, an unstable weft thread insertion is identified upon reaching at least one pre-set limit value for the standard setting. In determining an unstable weft thread insertion upon reaching a limit for the standard setting for the sets of relay nozzles the supply of compressed air to main nozzle device can be reduced, in particular, the moment for interrupting an air supply to the main nozzle device can be advanced in the weaving cycle. After reducing the air supply to the main nozzle device, the supply of compressed air to the sets of relay nozzles can be further reduced, in particular the moment of interrupting an air supply to the sets of relay nozzles can be advanced in the weaving cycle. This allows a further reduction of air supply to the sets of relay nozzles until the weft thread insertion becomes unstable again.
Preferably, the setting for a compressed air supply to the main nozzle device and/or to the at least one set of relay nozzles is adjusted when the average speed of inserted weft threads is changed, in particular is slackened. I n order to compensate a change of the average speed of weft thread insertions, a blowing force, i.e. a pressure and/or an air current per time unit, of a main nozzle device can be changed. Methods for compensating changes in an average speed are described for example in WO 2007/071350 . When weaving with certain yarn types, in particular with filament yarns, a weft thread speed increases when weaving off a bobbin. This increase can be compensated by a reduction of a blowing force. In other cases the average speed of the weft thread slackens. In accordance with the methods described in WO 2007/071350 , a pressure and/or an air current per time unit increases or slackens in response to this, in order to keep the average insertion speed or arrival of the weft thread at a measurement point at an essentially constant level. I n order to avoid conflicts between both regulating ways, one method can be interrupted or stopped under certain conditions. For example, an adjustment of the standard settings for an air supply can be stopped if a limit value for an applied pressure and/or air current per time unit is reached.
According to still a further embodiment, the weaving speed of the weaving machine is adjusted in accordance with a standard setting for a compressed air supply to the main nozzle device and/or to the at least one set of relay nozzles, for example as described in WO 2007/071350 . Again, in order to avoid conflicts between a method for regulating the weaving speed in order to compensate changes in an average weaving speed and the adjustment according to the invention, one of both methods can be interrupted or stopped under certain conditions. For example, an adjustment of the standard settings for an air supply can be stopped if a limit value for the weaving speed is reached.
The object is also solved by an airjet weaving machine provided with a main nozzle device and at least one set of relay nozzles, wherein the airjet weaving machine comprises a device for applying a method for adjusting standard settings for a compressed air supply to the main nozzle device and the at least one set of relay nozzles.
Preferably the airjet weaving machine comprises a device with a control unit and a number of shut-off valves which can be controlled by the control unit. The shut-off valves allow a regulation of an air supply, in particular an interruption of an air supply to certain sets of relay nozzles and/or the main nozzle device.
The main nozzle device preferably comprises a fixed main nozzle or auxiliary main nozzle and a moveable main nozzle.
Further characteristics and advantages of the invention will appear from the following description of example embodiments presented in the drawings and from the dependent claims.

Figure 1: shows a schematic view of a part of an airjet weaving machine according to the invention.
Figure 2: shows a graphic of a standard setting for the supply of compressed air to the main nozzle device and to successive sets of relay nozzles.
Figure 3: shows a graphic for an adjusted standard setting for the supply of compressed air to the main nozzle device and successive sets of relay nozzles.
Figure 4: shows a graphic for a further adjusted standard setting for the supply of compressed air to the main nozzle device and successive sets of relay nozzles.
Figure 5: shows a graphic for another further adjusted standard setting and an actual setting for the supply of compressed air to the main nozzle device and successive sets of relay nozzles.
Figure 6: shows a graphic for an adjusted standard setting for the supply of compressed air to the main nozzle device at a further adjusting moment.
Figure 7: shows a graphic for an adjusted standard setting and an actual setting for the supply of compressed air to successive sets of relay nozzles at another further adjusting moment.

Figure 1 shows a device for transporting or inserting a weft thread through a schematically indicated shed 1 of an airjet weaving machine. This device comprises two supply channels 2, 3 for the supply of a weft thread 4 or 5, respectively. Each supply channel 2, 3 comprises a thread buffer 6, a prewinder 7, and a main nozzle device 70 which comprises a main nozzle 8 and an auxiliary main nozzle 9. The main nozzle 8 and the auxiliary main nozzle 9 are mounted in series next to the shed 1, in particular the main nozzle 8 is mounted near the shed 1, while the auxiliary main nozzle 9 precedes the main nozzle 8 according to the moving direction of the weft thread. The main nozzle 8 is also called the second or moveable main nozzle, and the auxiliary main nozzle 9 is also called the first or fixed main nozzle. Further the airjet weaving machine comprises a reed 10 wherein a guide channel 40 is provided which allows a weft thread to be transported through the shed 1 via this guide channel 40 by means of compressed air. Near this guide channel 40, successive sets of relay nozzles 11, 12, 13, 14, 15, 16, 17, 18 and 19 are mounted along the shed 1, in particular mounted along the guide channel 40 in order to successively support a weft thread making use of compressed air.
The main nozzles 8 are each connected to a compressed air source 23 via associated shut-off valves 21 and throttle valves 22. The auxiliary main nozzles 9 are each connected to a compressed air source 23 via associated shut-off valves 24 and throttle valves 25. Each set of relay nozzles 11, 12, 13, 14, 15, 16, 17, 18 and 19 is connected in a similar way via a shut-off valve 31, 32, 33, 34, 35, 36, 37, 38, 39 and an associated throttle valve 26 to the compressed air source 23. According to a not shown variant the throttle valves 26 can be omitted. The compressed air source 23 can comprise at least one compressed air reservoir associated to respective nozzles. In addition, a stretching nozzle 27 is shown which serves to keep a weft thread stretched once this is inserted. The stretching nozzle 27 is connected to a compressed air source 23 via a shut-off valve 28 and a throttle valve 29. At the end of the guide channel 40 which is situated opposite the end, on which the main nozzles 8 are mounted, a thread detector 41 is mounted which is equipped for determining when a weft thread 4, 5 arrives or passes at this thread detector 41.
The shut-off valves 21, 24, 28, 31, 32, 33, 34, 35, 36, 37, 38 and 39 and the throttle valves 22, 25, 26 and 29 are controlled by a control unit 42 of the airjet weaving machine, as illustrated in figure 1. The shut-off valves are for example electromagnetic valves which can be controlled by the control unit 42. I n this case, the throttle valves can be designed such that they can be driven by a motor and controlled by the control unit 42. A device 71 for applying the method according to the invention comprises at least the control unit 42 and a number of said shut-off valves.
A weft thread 4, 5 is blown into the guide channel 40 by a main nozzle 8 and is then blown further along the guide channel 40 by jets of compressed air from sets of relay nozzles 11 to 19. The guide channel 40 is for example mounted in a reed 10 and is brought in a known way into a shed during the insertion of a weft thread 4, 5. At the end of the guide channel 40 a thread detector 41 is arranged to detect the arrival of a weft thread. The main nozzles 8, the sets of relay nozzles 11 to 19, the stretching nozzle 27, the reed 10 and the thread detector 41 are attached in a known way on a not shown sley which moves to and fro. The thread buffer 6, the prewinders 7 and the auxiliary main nozzles 9 are attached on the frame of the airjet weaving machine.
The thread detector 41 is for example connected to a control unit 43 by means of a connecting line 44. The control unit 43 is connected to the control unit 42 by means of a connecting line 45. According to a not illustrated variant, the control unit 42 and the control unit 43 can be part of one single control unit. The shut-off valves and the throttle valves are connected to the control unit 42 by means of a common connecting line 50. Each prewinder 7 comprises a magnetic pin 46 in order to release a desirable length of weft thread 4 or 5 at a desired moment. The magnetic pins 46 are connected to the control unit 42 by means of a common connecting line 49.
Figure 1 also shows next to each prewinder 7 a thread detector 47, which thread detector 47 sends a signal to the control unit 43 each time a winding 48 is unwound from a wind-up drum of a prewinder 7, more in particular each time a part of a weft thread arrives at or passes along the thread detector 47. Such a thread detector 47 is also called a winding sensor. The signals of the thread detectors 47 are in this case guided to the control unit 43 via a connecting line 57. The measurements on the transported weft thread 4, 5 during the transport of this weft thread 4, 5 are obtained here by the signals of the thread detector 47. Herewith, the moment when a winding 48 arrives at a thread detector 47 is measured with respect to a reference moment, more in particular what is known as winding time. For example, the moment when a winding 48 passes at a thread detector 47 is measured with respect to the moment when the magnetic pin 46 is activated to release the weft thread 4 or 5 and this moment can be indicated as the winding time. The successive signals of a thread detector 47 can be used as measurements on the transported weft thread 4, 5 during its transport. Herewith it is possible to measure or determine an absolute time for unwinding one or more windings.
Optionally, a number of thread detectors 54, 55, 56 can be mounted along the guide channel 40 in order to detect when a leading end of the weft thread arrives at one of these thread detectors. The thread detectors 54, 55, 56 can cooperate with the control unit 43 via a connecting line 51.
As indicated in figure 1, the airjet weaving machine also comprises an input unit 52 which makes it possible to input several parameters. The control unit 42 is provided to display parameters by means of a display unit 53. The connecting lines 49, 50, 51 and 57 can be for example CAN-bus lines.
While a weft thread 4, 5 is transported through the shed 1, the shut-off valves 21, 24, 31 to 39 are for example activated in accordance with the diagram as illustrated in figure 2. I n this case the shut-off valves 31 to 39 are activated successively. With airjet weaving machines it is customary to weave at a weaving speed in the order of magnitude of 800 to 1200 weft threads per minute or, expressed differently, for example with a weaving width of two meters, 1400 to 2800 meters per minute. When weaving irregular weft threads, for example when weaving spun weft insertions, it is possible that, with successive weft threads coming from a supply channel 2 or 3, a measured insertion parameter differs considerably from weft thread to weft thread, in other words that a particular weft thread arrives at a thread detector at a different moment in the weaving cycle.
Figure 2 shows, by means of blocks 61 to 69, the periods in which the nine sets of relay nozzles 11 to 19, indicated as BB11 to BB19, respectively, are provided with compressed air, in other words, periods wherein the shut-off valves 31 to 39 of figure 1 are open in order to supply compressed air to an associated set of relay nozzles 11 to 19. The periods, in which the main nozzle 8 and the auxiliary main nozzle 9 are provided with compressed air are indicated respectively by blocks 20 and 30, indicated as MMN8 and FMN9, respectively. Such blocks are explained in more detail in WO 2007/057217 . The blocks 20, 30 and 61 to 69 determine a moment for commencing the air supply and a moment for interrupting the air supply to respective nozzles. In figure 2 the time is indicated as angular positions 0 to 360 degrees of the main shaft of the weaving machine. Each angular position corresponds with a moment in the weaving cycle, in other words each angular position corresponds with a time in the weaving cycle.
In figure 2, line 58 illustrates the movement path of an average weft thread, line 59 illustrates the movement path of a fast weft thread and line 60 illustrates the movement path of a slow weft thread. The lines 58, 59 and 60 can be determined during the weaving of a large number of weft threads at a standard setting of the sets of relay nozzles according to figure 2, for example a few thousands of weft threads. A moment TG is a determined reference moment in the weaving cycle, for example a specific chosen time after the weaving machine has reached a specific angular position in the weaving cycle. The meaning of TG will be explained in more detail below.
If the weaving is done with a weaving machine which is set to a predetermined or initial standard setting of interruption moments and/or periods according to figure 2 and the method according to the invention is activated, preferably the predetermined standard setting according to figure 2 is adjusted automatically to an adjusted predetermined standard setting according to figure 3, hereafter called "adjusted standard setting". With this "adjusted standard setting" the supply of compressed air to at least one specific set of relay nozzles is interrupted earlier in the weaving cycle than in accordance with the initial standard setting according to figure 2.
A preferred adjusted standard setting with a belly pattern is shown in figure 3. According to the standard setting shown in figure 3, a setting for a central set of relay nozzles, i.e. set of relay nozzles 15 in the embodiment shown in figure 1, is adjusted by shortening a period of air supply with 5%. The periods of air supply for the two sets of relay nozzles adjacent to the central set of relay nozzles, i.e. sets of relay nozzles 14 and 16, are shortened with 3%. The periods of the next sets of relay nozzles, i.e. sets of relay nozzles 13 and 17 are only shortened with 1% and the periods for the side sets of relay nozzles, i.e. sets of relay nozzles 11, 12, 18 and 19 are not shortened at this adjustment moment. The shortened air supply periods are indicated in figure 3. For the sake of clearness, the standard setting according to figure 2 before the adjustment is indicated with dashed lines in figure 3.
For example can in a similar way as described in WO 2007/057217 , in case of a slow weft thread, i.e. a weft thread which for example arrives at a measurement point after the moment TG, this slow weft thread will be inserted with a setting as illustrated in figure 2, while a normal or fast weft thread will be inserted with a setting according to figure 3.
According to the invention a standard setting is adjusted and a stability of a weft thread insertion is observed. When the weft thread insertion seems to be stable after an adjustment step, a further adjustment of the actual standard setting can be carried out. When the weft thread insertion is found to be unstable, an executed adjustment is cancelled and/or the standard setting is adjusted in the opposite direction. So, standard settings for an air supply to the sets of relay nozzles 11 to 19 and/or the main nozzles 8, 9 are optimized.
According to a preferred embodiment, in order to optimize the compressed air supply, with an adjusted standard setting the supply of compressed air to the fixed or auxiliary main nozzle 9 is decreased. Preferably a decrease of the compressed air supply to the auxiliary main nozzle 9 is accomplished by shortening a period of air supply as indicated in dash-dot-line for block 20 in figure 3. It is preferred not to reduce the period of the supply of compressed air to the main nozzle 8, in order to guide the weft thread suitably to the shed at the entrance of the shed.
When the weft thread insertion remains stable despite a decrease of the period of air supply to the at least one set of relay nozzles 11 to 19 and/or the main nozzles 8 and/or 9 of the main nozzle device 70, the period of compressed air supply to the at least one set of relay nozzles 11 to 19 and/or the main nozzles 8 and/or 9 of the main nozzle device 70 can be further decreased. Herewith or as an alternative the compressed air supply to the sets of relay nozzles 11 to 19 can be further decreased. Preferably the decrease of the compressed air supply to the sets of relay nozzles 11 to 19 is accomplished with settings which have a belly pattern.
Figures 4 and 5 show schematically a second and a third adjustment moment according to an embodiment of the invention, wherein an interruption time is advanced in the weaving cycle with respect to a setting as shown in figure 2. For the sake of clearness, the standard setting of figure 2 before the adjustment is indicated with dashed lines in figures 4 and 5. As mentioned above in a first moment the "standard setting", as shown in figure 3, can be applied. If the weft thread insertion remains stable, the interruption times for an air supply to the sets of relay nozzles 11 to 19 are further advanced. I n the embodiment shown in figures 4 and 5 an interruption time for a central set of relay nozzles, i.e. set of relay nozzles 15 in the embodiment shown in figure 1, is adjusted by shortening a period of air supply with 10% or 15% with respect to the example of figure 2 at respectively a second or third adjustment moment. The period of air supply for the sets of relay nozzles next to central set of relay nozzles, i.e. sets of relay nozzles 14 and 16, are shortened with 6% and 9% with respect to the example of figure 2 at respectively a second and third adjustment moment. The period of air supply to the next sets of relay nozzles, i.e. sets of relay nozzles 13 and 17 is shortened with 2% and 3% with respect to the example of figure 2 at respectively a second and third adjustment moment, and the period for the sets of relay nozzles at the sides, i.e. sets of relay nozzles 11, 12, 18 and 19 are not shortened at all. The decreased air supply periods are indicated in figures 4 and 5. Of course, other belly patterns can be applied. When after the adjustment with an applied standard setting in accordance with figure 5 is carried out, an unstable weft thread insertion is detected, according to a method not in accordance with the invention the standard setting can be reset to a previous standard setting, for example to the standard setting as illustrated in figure 3. According to a variant, the standard setting according to figure 5 can hereby be reset to the standard setting as illustrated in figure 4.
For example, in a similar way as described in WO 2007/057217 , in case of a slow weft thread, i.e. a weft thread that for example arrives at a measurement point after the moment TG, this slow weft thread will be inserted with a setting as illustrated with dash-dot-line for blocks 64, 65 and 66 in figure 5, while a normal or fast weft thread will be inserted with the standard setting according to figure 5.
I n accordance with the invention, as illustrated in figure 6, if an unstable weft thread insertion is detected when a standard setting in accordance with figure 5 is applied, the instability can be avoided by decreasing the blowing period of the auxiliary main nozzle 9. For block 20 in figure 6 that illustrates the blowing period for the auxiliary main nozzle 9, the decreased blowing period is indicated with full lines, while the initial blowing period is indicated with dashed lines. More in particular, the moment in the weaving cycle or the point of time for interrupting the compressed air supply to the auxiliary main nozzle 9 can be advanced. An adjustment is accomplished for example in dependency of the average deviation of the time difference between the arrival of the weft thread at the end of the shed, measured by the thread detector 41, and the moment of detection of the last winding measured at the thread detector 47. The moment of the arrival of the weft thread at the end of the shed is also called arrival time TA. The detected moment of the last winding at the thread detector 47 is also called the last winding time TLW.
According to an embodiment, a function for an adjustment of an interruption moment for the auxiliary main nozzle 9 can be chosen with 50% of a deviation of the present difference between the arrival time TA and the last winding time TLW with respect to the initial standard setting. For example, if the time difference TA - TLW = 1 msec was indicated for an initial standard setting, and for the adjusted standard setting, the time difference is TA - TLW = 3msec, the blowing time of the auxiliary main nozzle 9 can be shortened with 50% of (3 - 1)msec or 1 msec. In other words, in this example, the interruption time of the auxiliary main nozzle 9 is advanced with 1 msec in the weaving cycle. This advancement of the interruption moment can be based on average time differences and for taking the average a method similar as described in WO 2006/114187 can be applied.
Alternatively to the above mentioned example the blowing time of the auxiliary main nozzle 9 can be shortened in steps of 0.5 msec until the value TA-TLW reaches about 1 msec again. According to still another alternative the blowing time of the auxiliary main nozzle 9 can be shortened in steps of 5% of the blowing time of the auxiliary main nozzle 9 until the value TA-TLW reaches a desired value again.
When after such an adjustment, the weft thread insertion is not stabilized a further shortening of the blowing time of the auxiliary main nozzle 9 can be carried out. If the weft thread insertion is stabilized, the blowing time for the sets of relay nozzles 11 to 19 can be shortened further. For example, by decreasing the blowing time of the auxiliary main nozzle 9, the blowing time for the sets of relay nozzles 11 to 19 can be further shortened with a belly pattern with for example an adjustment of 30% at the central set of relay nozzles 15, as illustrated in figure 7. In the embodiment of figure 7 the blowing time of the set of relay nozzles 12 are shortened too.
If an instability of the insertion occurs at this setting, again either the setting for the sets of relay nozzles 11 to 19 and/or the setting for the main nozzle device 70, in particular the auxiliary main nozzle 9 can be adjusted to a previous standard setting.
According to an embodiment, an unstable weft thread insertion is identified upon reaching at least one pre-set limit value.
Further, for the auxiliary main nozzle 9, a maximum decrease of a blowing time can be set on 20% with respect to the initial standard setting or any other value of the initial blowing time. Preferably, limit ranges are set in advance, for example when choosing a low influence of the main nozzle device 70, a limit before the decrease can be set on 15%, and when choosing an average or high influence, the limit for the decrease can be set on 20% or 25%, respectively.
For example, in order to observe the stability of a weft thread insertion, an arrival time at one or more of the weft thread detectors 41, 47, 54, 55, 56 can be measured and a measured arrival time can be compared with an expected arrival time for an inserted weft thread. If a time difference between the measured time and the expected time exceeds a threshold, it can be assumed that a weaving error may have occurred and that the weft thread insertion is unstable.
According to an embodiment, an unwinding time of a weft thread at the prewinders 7 and an arrival time at the exit of the shed 1, are measured by means of thread detectors 47 and 41, respectively, and a time difference is determined. If the time difference exceeds a threshold, it may be assumed that an error has occurred and that the weft thread insertion is unstable.
In order to avoid measurement errors and unstable adjustments, average arrival times for a certain number of insertions are determined and a weaving error is assumed when the time difference between an expected arrival time for an inserted weft thread at a measurement point and the average arrival time at this measurement point exceeds a predetermined threshold.
As mentioned above, slow weft threads and fast weft threads can be distinguished by weaving according to a method according to WO 2007/057217 . Based on measurements on a particular transported weft thread, the supply of compressed air can be interrupted later than specified by the applied standard setting, if it has been determined that a relatively slow weft thread is transported through the shed 1. In this case, the period during which compressed air is supplied to a number of sets of relay nozzles during transport of a slow weft thread is extended with respect to the applied standard setting.
For example, it is possible to determine the time or the period by which the supply of compressed air will be extended based on the time difference between for example a predetermined moment TG and a moment on which for example a certain winding is detected which passes along the thread detector 47. The moment TG is a pre-set time or threshold value with respect to a reference moment in the weaving cycle, for example a specific chosen time after the moment on which the weaving machine has reached a certain angular position in the weaving cycle or for example a specific chosen moment in the weaving cycle that passes a certain winding normally at the thread detector. With this purpose the moment TG can be entered via the input unit 52 in the control unit 42, optimized by the control unit 42 or adjusted manually by the operator in a way as explained in WO 2007/057217 .
In an embodiment as illustrated in figure 7 it is assumed that a weft thread has a length of five windings, wherein the signals for the windings are t1w, t2w, t3w, t4w and t5w, respectively, and for example the signal of the second winding t2w, in other words the second signal of the thread detector 47, is used in order to control the interruption of the compressed air supply to a certain set of relay nozzles. In this case, the moment of the signal of the second winding t2w will be compared with the moment TG in the weaving cycle.
If this measured signal of the second winding t2w occurs after the moment TG in the weaving cycle, i.e. a relative slow weft thread is inserted, the compressed air supply will be interrupted later to a set of relay nozzles 13 to 17, for example the period can be extended to the actual setting as indicated in dash-dot-lines in figure 7. I n other words, the supply of compressed air to a set of relay nozzles is extended and an interruption is delayed with respect to the adjusted standard setting indicated in full lines in figure 7. This extended supply can take place in a way as explained in WO 2007/057217 .
According to a variant, as also explained in WO 2007/057217 , slow weft threads can be inserted with an adjusted standard setting for interrupting the compressed air supply, for example the standard setting of figure 6, while normal or fast weft threads can be inserted with an actual setting wherein the interruption of the compressed air supply is advanced to an earlier moment in the weaving cycle, for example to a moment earlier in the weaving cycle than the moment of the standard setting of figure 6.
When this measured signal of the second winding t2w occurs at or before the moment TG in the weaving cycle, i.e. a normal or relative fast weft thread is inserted, the compressed air supply to a set of relay nozzles 13 to 17 will be interrupted according to the predetermined applied standard setting, as illustrated in full lines in figure 7.
It is clear that a set of relay nozzles may consist of at least one single relay nozzle or a number of relay nozzles connected to a compressed air source via an associated shut-off valve. The devices for the supply of compressed air can be any device which can set, control or adjust the supply of compressed air. As is known from EP 442.546 B1 or WO 2006/077063 , the regulating of the compressed air supply to a main nozzle 8 or to an auxiliary main nozzle 9 can comprise the operation of the throttle valves 22 and 25 in such a way that each weft thread arrives, for example at average the same moment in the weaving cycle, for example at a thread detector 41. This means for example that irrespective of changes in the properties of successively inserted weft threads, which can for example be the case with filament weft threads, the line 58 indicated in figure 2 for the movement path of an average weft thread does not change for successive weft threads.
The invention allows to adjust in successive steps a standard setting so that the moment for interrupting the air supply to the at least one set of relay nozzles 11 to 19 and/or to at least one main nozzle 8, 9 of the main nozzle device 70 is advanced. The successive adjustment of the standard setting can stop, if either an instability of the insertion is determined, if a limit for the advancement of the interruption for at least one set of relay nozzles is reached, for example 30%, 40%, 50% or 60% for the central set of relay nozzles, and/or if a limit for the advancement of the interruption for a main nozzle is reached, for example 15%, 20% or 25% for the fixed main nozzle 9. If the invention for example is applied in combination with a method according to WO 2007/071350 the adjustment of the standard setting can stop, if the value for the pressure and/or the air current per time unit reaches for example 98% of its maximum value and/or if the speed of the weaving machine during carrying out the method according to the invention falls with a certain percentage, for example a percentage of 3% or 5%.
If an above mentioned limit of 30% for the central set of relay nozzles is provided, for example the method according to the invention can be applied in steps of 5% towards a limit value of 40%. If with 40% still no instability occurs, can be limited again to the set limit value of 30%. In this case the adjusted standard setting is reset to the standard setting of two adjustments before, which herewith corresponds with the limit of 30%. If in this case with 35% an instability occurs, it can be reset as security or certainty to 25% or two adjustments before, notwithstanding with the limit of 30% no instability was observed yet.
Of course, the invention is not limited to the use of standard settings as illustrated in figures 2 to 7, but other standard settings can be set. According to a possibility in the control unit 42 for example can being entered to which set of relay nozzles adjustments are possible, for example to the set of relay nozzles 17. This means that the settings of the sets of relay nozzles 17, 18 and 19 are not adjusted according to the invention. There can also be entered from which set of relay nozzles adjustments of the standard setting are possible, for example from the set of relay nozzles 13. This means that the settings of the sets of relay nozzles 11 and 12 cannot be adjusted according to the invention. According to another possibility for example can be entered or avoided that the settings cannot be adjusted for a certain set of relay nozzles according the invention.
It is clear that adjusting the standard setting does not have to be done necessarily with steps of 5%, 3% or 1%, but that the adjustments can be carried out in various ways, for example according to various functions that are saved for example in the control unit 42.
According to a not illustrated variant the standard settings for controlling the shut-off valve 28 for the stretching nozzle 27 can also be determined and adjusted according to a method according to the invention.
Each graphic in accordance with figures 2 to 7 for the supply of compressed air to the above-mentioned successive sets of relay nozzles is expressed in angular degrees of the main shaft of the weaving machine. When the speed of the weaving machine is known, each graphic can be easily converted to time units, e.g. milliseconds.
The method according to the invention has the advantage that the air consumption is appropriately decreased. In accordance with the invention, there can be saved most compressed air by interrupting the sets of relay nozzles which are arranged approximately near the centre of the shed more early with respect to the initial setting than the sets of relay nozzles outside the centre.
It is clear that the airjet weaving machine is not limited to an airjet weaving machine wherein a weft thread is blown into a guide channel 40 by means of compressed air. The sets of relay nozzles of the airjet weaving machine can also blow onto a holder for a weft thread which transports a weft thread through the shed. In addition, instead of ordinary compressed air, any desired fluid can be used for inserting a weft thread into a shed of a weaving machine of this type. In this case, it is also possible to use ordinary compressed air mixed with a gas, a liquid or a vapour.
It is clear that irrespective of the fact that the present description mentions time, this time can also be expressed in angular degrees of the weaving machine. I n this case, one angular degree of the weaving machine corresponds for example with a number of milliseconds or one millisecond corresponds with a number of angular degrees.
It is clear that the method according to the invention can be used for the insertion of each of the weft threads 4 or 5. Herewith, for each weft thread 4 or 5 an individual graphic for the supply of compressed air to the successive sets of relay nozzles and/or to the main nozzle device 70 can be provided. The graphics for inserting each weft thread can be different of one another, in particular if the weft threads 4 or 5 are woven at a different weaving speed or transporting speed. This is particularly applied when the speed of the weaving machine is adjusted to the weft thread to be inserted. Of course, the method according to the invention can also be applied if one or more than two different types of weft thread are used.
The method and the airjet weaving machine in accordance with the invention presented in the claims are not restricted to the as example given embodiments which have been shown and described, but can also include variants and combinations thereof which fall within the scope of the claims.

Claims

Method for inserting a weft thread (4, 5) into a shed of an airjet weaving machine comprising a main nozzle device (70) and at least one set of relay nozzles (11 to 19),
wherein
- a standard setting for a supply of compressed air to the main nozzle device and to the at least one set of relay nozzles (11 to 19) is determined,

- the standard setting for the supply of compressed air to the main nozzle device (70) and to the at least one set of relay nozzles (11 to 19) is adjusted in order to reduce the supply of compressed air,

- a stability of the weft insertions with the adjusted standard setting is observed, and

- the standard setting for the supply of compressed air to the main nozzle device (70) and to the at least one set of relay nozzles (11 to 19) is adjusted such that the supply of compressed air to the at least one set of relay nozzles (11 to 19) is decreased until a weft insertion becomes unstable,
characterized in that
if a weft thread insertion becomes unstable when an adjusted standard setting for the supply of compressed air to the main nozzle device (70) and to the at least one set of relay nozzles (11 to 19) is applied, the supply of compressed air to the main nozzle device (70) is decreased, in order to avoid the instability.
Method according to claim 1, characterised in that after the supply of compressed air to the main nozzle device (70) has been decreased, the standard setting is further adjusted by decreasing the supply of compressed air to the at least one set of relay nozzles (11 to 19).
Method according to claim 1 or 2, characterised in that for adjusting the standard setting an interruption of the supply of compressed air to the main nozzle device (70) and/or to the at least one set of relay nozzles (11 to 19) is adjusted in function of measurements on the inserted weft threads (4, 5).
Method according to one of claims 1 to 3, characterised in that the main nozzle device (70) is provided with a first main nozzle (9) and a second main nozzle (8), wherein the supply of compressed air to the first main nozzle (9) is decreased, when a weft insertion becomes unstable.
Method according to one of claims 1 to 4, characterised in that a number of successive sets of relay nozzles (11 to 19) is provided, wherein the standard setting for a compressed air supply to the number of sets of relay nozzles (11 to 19) is adjusted making use of a belly pattern.
Method according to one of claims 1 to 5, characterised in that an unstable weft thread insertion is identified by detection of at least one weaving error.
Method according to claim 6, characterised in that a weaving error is detected when the time difference between a measured moment wherein an inserted weft thread (4, 5) arrives at a first measurement point and a measured moment wherein the inserted weft thread (4, 5) arrives at a second measurement point exceeds a predetermined threshold.
Method according to claim 6 or 7, characterised in that a weaving error is detected when the average time difference between a measured moment wherein an inserted weft thread (4, 5) arrives at a first measurement point and a measured moment wherein the inserted weft thread (4, 5) arrives at a second measurement point exceeds a predetermined threshold.
Method according to one of claims 1 to 8, characterised in that an unstable weft thread insertion is identified upon reaching at least one pre-set limit value for the standard setting.
An airjet weaving machine provided with a main nozzle device (70) and at least one set of relay nozzles (11 to 19), characterised in that the airjet weaving machine comprises a device (71) which applies a method according to any one of claims 1 to 9.
The airjet weaving machine according to claim 10, characterised in that the device (71) comprises a control unit (42) and a number of shut-off valves (21, 24, 28, 31 to 39) which can be controlled by the control unit (42).
The airjet weaving machine according to claim 10 or 11, characterised in that the main nozzle device (70) comprises a fixed main nozzle (9) and a moveable main nozzle (8).