EP3146101B1

EP3146101B1 - Stretching device for a weft thread

Info

Publication number: EP3146101B1
Application number: EP15723937.7A
Authority: EP
Inventors: Marnix Ghesquiere
Original assignee: Picanol NV
Current assignee: Picanol NV
Priority date: 2014-05-22
Filing date: 2015-05-19
Publication date: 2020-02-26
Anticipated expiration: 2035-05-19
Also published as: EP3146101A1; CN106460260B; WO2015177155A1; CN106460260A; BE1021879B1

Description

This invention relates to a stretching device for stretching a weft thread that has been inserted into a weaving shed in a weaving machine, wherein the stretching device is arrangeable opposite to a U-shaped insertion channel of a reed. The invention further relates to a weaving machine comprising a stretching device and a method for stretching a weft thread.
A stretching device for stretching a weft thread is arranged at the end of the weaving shed of a weaving machine in order to catch and keep taut a weft thread inserted into the weaving shed. This allows amongst others to avoid that an inserted weft thread springs back or rebounds into a weaving shed at the end of the weft thread insertion. This also allows to keep the weft thread taut when beating up the weft thread.
Stretching devices that are arrangeable opposite to a U-shaped insertion channel of a reed to blow on an end of an inserted weft thread are known amongst others from CS 262455 B1 .
US 4,487,236 shows a pneumatic weaving machine with a number of relay nozzles, wherein a component of an air jet from said relay nozzles is directed transverse to a weft thread insertion direction, further named as an insertion direction, in order to influence a stretching. BE1017893 A5 also shows a weaving machine with a number of relay nozzles and a stretching device with a tubular guide element fixed along a movement direction of a weft thread in the U-shaped insertion channel of the reed.
It is an object of the invention to provide a stretching device that allows a weft thread to be kept sufficiently stretched without disturbing an airflow present in the U-shaped insertion channel. It is further an object of the invention to provide a weaving machine comprising a stretching device and to provide a method for stretching a weft thread.
These objects are solved by the stretching device according to claim 1, the weaving machine according to claim 9, and the method according to claim 11.
According to a first aspect a stretching device is provided comprising a holder, a first blowing nozzle for providing a first air-jet acting on an end region of an inserted weft thread and a second blowing nozzle for providing a second air-jet acting conjointly, in other words together with the first air-jet on the end region of the inserted weft thread, which second blowing nozzle is arranged downstream of the first blowing nozzle in a first direction, which first direction upon mounting the stretching device to the weaving machine is parallel to the insertion direction, wherein both of the first blowing nozzle and the second blowing nozzle are formed as a hollow needle with an outflow aperture near the tip of the hollow needle, wherein the hollow needle of the first blowing nozzle and the hollow needle of the second blowing nozzle are aligned in the first direction, and in that the first blowing nozzle and the second blowing nozzle are arranged on the holder in such a manner that a plane of the second outflow aperture forms a wider angle with a plane perpendicular to the first direction than a plane of the first outflow aperture, so that the second air-jet forms a wider angle with the first direction than the first air-jet.
For a weft thread insertion, the weft thread is transported through the insertion channel by means of a main nozzle device and a number of relay nozzles. The stretching device is arranged downstream of relay nozzles. In contrast to the relay nozzles blowing sequentially on regions of the weft thread transported through the weaving shed, the two air-jets act conjointly on an end region of the inserted weft thread.
The stretching device works together with the reed towards which the weft thread is forced by means of the air-jets. Preferably, no additional mechanical clamping elements are provided. Therefore, a weft thread can easily enter the stretching device and easily leave the stretching device after the weft thread has been beaten up. Such a stretching device is also particularly advantageous as there is no risk that a weft thread is caught by the stretching device. The stretching device is particularly advantageous for weaving smooth filament weft threads that require a relative high force in order to be kept taut.
Both of the first blowing nozzle and the second blowing nozzle are formed as a hollow needle with an outflow aperture near the tip of the hollow needle. In particular, the first blowing nozzle and the second blowing nozzle are identical in construction with each other and, preferably, also with the relay nozzles used in the weaving machine. This allows for a cost-efficient manufacturing. In order to provide two air-jets forming different angles with the insertion direction using two blowing nozzles, which are identical in construction, the blowing nozzles are arranged with different orientations with respect to a plane perpendicular to the insertion direction.
The first blowing nozzle comprises a first outflow aperture and the second blowing nozzle comprises a second outflow aperture, wherein a plane of the second outflow aperture forming a wider angle with a plane perpendicular to the first direction than a plane of the first outflow aperture. A plane of the outflow aperture is perpendicular to the air-jet. Preferably, either or both of the first outflow aperture and the second outflow aperture comprise a plurality of small outflow holes. For example, blowing nozzles having between eleven and sixteen small outflow holes are provided.
The air-jet discharged from an outflow aperture usually diverges with the distance from the outflow aperture. In the context of the application, the direction of the air-jet is defined as its main outflow direction. The first air-jet and the second air-jet both have a component in the first direction, which first direction upon mounting the stretching device is parallel to the insertion direction and a component transverse to the insertion direction. The larger the component of an air-jet transverse to the insertion direction in relation to the component in the insertion direction, the wider is an angle of said air-jet with the insertion direction. Hence, assuming that the absolute value of both air-jets is the same, the second air-jet has a larger component transverse to the insertion direction than the first air-jet.
A stretching device according to the invention offers the advantage that during stretching of a weft thread the airflow in the insertion channel coming from the main nozzle device and the relay nozzles is supported by the air-jet from the first blowing nozzle forming a smaller angle with the insertion direction and that the air-jet from the second blowing nozzle forming a wider angle with the insertion direction blows the weft thread towards the reed, wherein the air-jets conjointly act on the weft thread in order to stretch and keep taut that weft thread. The orientation of the air-jets of the stretching device is preferably chosen, so that the air-jets from both blowing nozzles of the stretching device as little as possible disturb the airflow through the insertion channel, so that the airflow through the insertion channel can continue its flow and can provide an additional force to stretch a weft thread. Providing two air-jets allows acting with a sufficient stretching force on the weft thread. Due to this stretching force the weft thread is kept under tension by the resulting airflow that acts on the end region of the weft thread, even if the end region of the weft thread onto which the air-jets of the stretching device directly act is relatively short. Because the stretching device according to the invention can exert sufficient force on a short end region, the advantage is obtained that the waste end of the inserted weft thread can be kept small, for example an end region in insertion direction smaller than 30mm past the stretching device. Using such a stretching device allows blowing on the weft thread in a region between the woven fabric and a waste band, this also allows keeping a waste end small.
The first blowing nozzle and the second blowing nozzle are aligned in a direction parallel to the first direction. It is known from the prior art, for example from WO 2008/031519 A1 , to provide an elongate fabric support having a projecting lip portion, which fabric support is fixed to a frame of the weaving machine. The alignment allows arranging both blowing nozzles in such a manner that they both pass beneath a fabric support for the woven fabric when they are moved together with a sley towards the fabric support, even in case the fabric support comprises a protruding lip portion as shown in WO 2008/031519 A1 .
Preferably, the second blowing nozzle is arranged lower than the first blowing nozzle in a second direction perpendicular to the first direction in order to avoid that the second blowing nozzle reaches into the first air-jet.
The first air-jet and the second air-jet act conjointly on the end region of the inserted weft thread. In an embodiment, the air-jets reach the weft thread at adjacent, but different positions of the end region of the inserted weft thread. According to a preferred embodiment, the second air-jet merges with the first air-jet. The first blowing nozzle and the second blowing nozzle are arranged sufficiently close to one another for allowing the second air-jet to merge with the first air-jet. As the first blowing nozzle and the second blowing nozzle are arranged sufficiently close to one another a required space is small, and a space for arranging further elements, for example weft detectors is not affected. By means of the resulting air-jet a higher force is applied compared to a device using one blowing nozzle of the same dimension that is oriented to provide an air-jet in the resulting direction.
In an embodiment, the first outflow aperture upon mounting the stretching device is arranged closer to the U-shaped insertion channel than the second outflow aperture. Thereby, the second blowing nozzle aligned with the first blowing nozzle in the direction parallel to the insertion direction does not reach into the air-jet coming from the first blowing nozzle as this allows that the first air-jet coming from the first blowing nozzle can pass above the second blowing nozzle.
According to embodiments, a first angle that the first air-jet forms with the insertion direction M is about 15° to about 25° and/or a second angle that the second air-jet forms with the insertion direction M is about 20° to about 45°. By means of the first air-jet forming a small angle with the insertion direction, it is prevented that the weft thread is blown against the reed by the force of the second air-jet forming a wider angle. Hence, the weft thread is less decelerated during insertion in insertion direction compared to a stretching device as shown in CS 262455 B1 . On the other hand, by means of the second air-jet forming a wider angle with the insertion direction, the second blowing nozzle blows sufficiently towards the reed to prevent springing back of the weft thread after the weft thread has been stretched.
Suitable angles of the air-jets depend on different weaving parameters and may be different for different weaving conditions. In an embodiment, for example, an optimum stretching force is obtained with a first angle of about 20° and a second angle of about 27° with respect to the insertion direction. This orientation offers the advantage that the resulting air-jet acts sufficiently on the end region of the weft thread in order to stretch that weft thread, without the end region of the weft thread being blown considerably against the back of the reed.
In an embodiment, the first blowing nozzle and the second blowing nozzle are supplied together with compressed air. Hence, both blowing nozzles always blow at least almost at the same time and with at least almost the same pressure. This offers the advantage that a direction of the resulting air-jet from both blowing nozzles remains mainly the same independent of a pressure of the compressed air supplied.
In an embodiment, the first blowing nozzle and the second blowing nozzle are connected to a compressed air source via two supply ducts arranged in parallel. This allows for a cost-efficient manufacturing as supply ducts used for the relay nozzles may also be used for the stretching device. Preferably, the first blowing nozzle and the second blowing nozzle are mounted on a holder, wherein the holder comprises two supply ducts for a supply of compressed air, leading to a common air chamber to which air chamber both blowing nozzles are connected.
In an embodiment, the stretching device comprises at least one additional blowing nozzle for providing an additional air-jet acting conjointly with the first air-jet and the second air-jet on the end region of the inserted weft thread, which additional blowing nozzle is arranged in the first direction downstream of the second blowing nozzle, wherein the additional air-jet forms a wider angle with the first direction than the second air-jet. Providing additional blowing nozzles allows applying a higher blowing force. However, the dimension of the stretching device in the insertion direction is increased. A suitable number of blowing nozzles can be chosen by the person skilled in the art in accordance with boundary conditions of the weaving machine.
According to a second aspect of the invention, a weaving machine is provided, the weaving machine comprising a reed with a U-shaped insertion channel and a stretching device for stretching a weft thread arranged opposite to the U-shaped insertion channel, which stretching device is arranged downstream of relay nozzles in the insertion direction and comprises a first blowing nozzle for providing an first air-jet acting on an end region of an inserted weft thread and a second blowing nozzle for providing a second air-jet acting conjointly with the first air-jet on the end region of an inserted weft thread, which second blowing nozzle is arranged in insertion direction downstream of the first blowing nozzle, wherein the second air-jet forms a wider angle with the insertion direction than the first air-jet.
The stretching device can be arranged at any type of weaving machine having a reed that is provided with a U-shaped insertion channel.
According to an embodiment, the stretching device is fixed to a sley of the weaving machine adjustable in position in the length direction of the reed. Hence, the stretching device can be arranged in any position with respect to the reed, for example, a position adjusted to the weaving width of the fabric to be woven. Hence, when changing the weaving width, the position of the stretching device in the insertion direction can easily be adjusted.
Preferably, a continuous reed is provided, i.e. a reed that extends beyond the fabric edge of the woven fabric, in particular even beyond a waste band woven next to the woven fabric.
According to a third aspect, a method is provided for stretching a weft thread that has been inserted into a weaving shed in a weaving machine by means of a stretching device arranged opposite to a U-shaped insertion channel of a reed and downstream of relay nozzles (2) in an insertion direction, wherein the stretching device comprises a first blowing nozzle for providing an first air-jet acting on an end region of an inserted weft thread and a second blowing nozzle for providing a second air-jet acting conjointly with the first air-jet on the end region of an inserted weft thread, which second blowing nozzle is arranged in insertion direction downstream of the first blowing nozzle, wherein the second air-jet is discharged at a wider angle with the insertion direction than the first air-jet.
Further features and advantages of the invention derive from the following description of the embodiments shown in the drawings and the dependent claims, wherein:

Fig. 1: shows schematically and in perspective a part of an airjet weaving machine with a stretching device according to the invention;
Fig. 2: shows the stretching device of Fig. 1 in a front view with respect to the reed;
Fig. 3: shows the stretching device of Fig. 1 in a top view with respect to the reed;
Fig. 4: shows an arrangement of the stretching device of Fig. 1 with respect to a fabric support;
Fig. 5: shows an enlarged front view of a stretching device;
Fig. 6: shows an enlarged perspective view of a stretching device;
Fig. 7: shows a partial cross sectional view of the stretching device of Fig. 5;
Fig. 8: shows an alternative of Fig. 7;
Fig. 9: shows an alternative arrangement of the stretching device of Fig. 1 in an air-jet weaving machine;
Fig. 10: shows an alternative of the stretching device of Fig. 7;
Fig. 11: shows an alternative of the stretching device of Fig. 5 not in accordance with the claimed invention.

Figs. 1 to 7 show a first embodiment of a stretching device 3, wherein Figs. 1 to 4 show the stretching device 3 together with further elements of a weaving machine, and Figs. 5 to 7 show the stretching device 3 by itself.
In Figs. 1 to 3 a part of a reed 1, one of a number of relay nozzles 2 and a stretching device 3 for stretching a weft thread 6 are shown. The reed 1 comprises a number of lamellae 4 with a U-shaped profiling that are arranged next to one another and that form together a U-shaped insertion channel 5, as shown in Fig. 4.
The stretching device 3 comprises a first blowing nozzle 11 providing a first air-jet 31 acting on an end region 36 of the inserted weft thread 6 and second blowing nozzle 15 providing a second air-jet 35 acting conjointly, in particular simultaneously with the first air-jet 31 on the end region 36 of an inserted weft thread 6, which second blowing nozzle 15 is arranged in insertion direction M downstream of the first blowing nozzle 11. The stretching device 3 cooperates with the reed 1 in order to keep an inserted weft thread 6 taut. For this purpose, the reed 1 is a continuous reed that extends farther than a fabric edge (not shown).
As in the embodiment shown in Figs. 2 and 3, the blowing nozzles 11, 15 of the stretching device 3 are arranged closer to the U-shaped insertion channel 5 of the reed 1 than the relay nozzles 2. This arrangement of the stretching device 3 allows a higher force to act on the weft thread 6.
During weaving, a weft thread 6 is inserted into a weaving shed 32, shown in Fig. 4, by means of an airflow in the U-shaped insertion channel 5, which airflow transports the weft thread 6 through the U-shaped insertion channel 5 of the reed 1. This airflow is generated by a main nozzle (not shown) and by the number of relay nozzles 2 that are arranged one after the other in an insertion direction M and are mounted on the sley 7. The inserted weft thread 6 moves in the insertion direction M through the U-shaped insertion channel 5 in the direction towards the stretching device 3 and beyond the stretching device 3. The inserted weft thread 6 is held by the stretching device 3 to prevent the weft thread 6 from springing back or rebounding. To this end, the stretching device 3 blows on the weft thread 6. The inserted and stretched weft thread 6 is bound in a known way by warp threads 43, 44 and beaten up by the reed 1 at the height of the U-shaped insertion channel 5. Expressed in numerical values: when one revolution of a weaving machine is 360° and the beat-up occurs at 0°, then, for example, the weft thread 6 arrives at the stretching device 3 at about 250°, and the weft thread 6 is bound by the warp threads at about 340°. In this example, the stretching device 3 is in preferred embodiments activated to start blowing at about 240° and is deactivated at about 350°. This means the stretching device 3 already blows when the weft thread 6 arrives at the stretching device 3 and the stretching device 3 continues to blow until the weft thread 6 is bound by the warp threads 43, 44 or is beaten up. Preferably, at least the relay nozzles 2 next to the stretching device 3 continue to blow for at least a first part of the time period in which the blowing nozzles 11 and 15 of the stretching device 3 are blowing.
The first blowing nozzle 11 and the second blowing nozzle 15 both discharge an air-jet acting on the weft thread 6. As can be seen in Figs. 1 to 7, in particular Fig. 6, the second air-jet 35 discharged by the second blowing nozzle 15 forms an angle B with the insertion direction M that is wider than the angle A that the first air-jet 31 discharged by the first blowing nozzle 11 forms with the insertion direction M. In other words, the first air-jet 31 is oriented more towards the insertion direction M than the second air-jet 35. In the embodiment shown, the first blowing nozzle 11 is arranged to generate a first air-jet 31 which is essentially directed in the insertion direction M, for example the angle A between the first air-jet 31 and the insertion direction M is less than 20°. By means of the first air-jet 31 it is prevented that the weft thread 6 is blown too excessively against the reed 1 by the force of the second air-jet 35. The angle B between de second air-jet 35 and the insertion direction M is for example wider than 27°.
As shown in more detail in the embodiment of Figs. 5 to 7 the first blowing nozzle 11 is formed as a first hollow needle 12 with a first lateral outflow aperture 13 provided near the tip 14 of the first hollow needle 12. The second blowing nozzle 15 is formed as a second hollow needle 16 with a second lateral outflow aperture 17 provided near the tip 18 of the second hollow needle 16. Both lateral outflow apertures 13, 17 are formed by a plurality of small outflow holes, for example small outflow holes as known from US 3,978,896 . As can be best seen in Fig. 5, a plane 48 of the first outflow aperture 13 and a plane 49 of the second outflow aperture 17 are both slightly inclined with respect to a middle axis of the respective hollow needle 12, 16 and the air- jets 31 and 35 extend essentially perpendicular with respect to the respective plane 48, 49. In the embodiment shown, the first blowing nozzle 11 and the second blowing nozzle 15 are identical in construction. However, the first blowing nozzle 11 and the second blowing nozzle 15 are oriented in different directions so that the planes 48, 49 of the first outflow aperture 13 and the second outflow aperture 17, respectively are not in parallel. In this case the air- jets 31 and 35 discharged at the first outflow aperture 13 and at the second outflow aperture 17 are not in parallel, and the second air-jet 35 forms a wider angle with the insertion direction M than the first air-jet 31.
The first blowing nozzle 11 and the second blowing nozzle 15 are arranged on a holder 8. The holder 8 comprises a first mounting surface 40 to which the first blowing nozzle 11 is mounted. The holder 8 also comprises a second mounting surface 41 that is directed inclined with respect to the first mounting surface 40 and to which the second blowing nozzle 15 is mounted. In this case the first blowing nozzle 11 and the second blowing nozzle 15 are arranged on the holder 8 in such a manner that the plane 49 of the second outflow aperture 17 forms a wider angle with a plane perpendicular to the insertion direction M than the plane 48 of the first outflow aperture 13. An inclined arrangement defines the difference in orientation of the first air-jet 31 discharged and the second air-jet 35 discharged. The orientation of the planes 48 and 49 and thus also the direction of the air- jets 31 and 35 can be set by rotating the first hollow needle 12 and/or the second hollow needle 16 around their length axis with respect to the holder 8. Further, the second mounting surface 41 is arranged so that the second blowing nozzle 15 is arranged lower than the first blowing nozzle 11 on the holder 8. Hence, the second blowing nozzle 15 is arranged in such manner that its tip 18 does not reach into the first air-jet 31. As can be best seen in Fig. 1, upon mounting the stretching device 3 to the weaving machine, the first blowing nozzle 11 is arranged closer to the U-shaped insertion channel 5 than the second blowing nozzle 15. On the other hand, as can be best seen in Fig. 3, the first blowing nozzle 11 and the second blowing nozzle 15 are aligned in a direction 51, which upon mounting the stretching device 3 coincides with the insertion direction M, in other words the first blowing nozzle 11 and the second blowing nozzle 15 are arranged in a direction 51, which direction 51 is parallel to the insertion direction M.
As can be seen in Fig. 4, the first blowing nozzle 11 and the second blowing nozzle 15 of the stretching device 3 are arranged, in particular in a direction 51 as shown in Fig. 3, so that the stretching device 3 can pass beneath a lip portion 38 of the fabric support 39.
As shown in Fig. 7, the holder 8 is provided with an air chamber 9. The air chamber 9 is connected to a compressed air source 22 via two supply ducts 19 and an associated shut off valve 20. In this embodiment two supply ducts 19 are provided. This allows supplying sufficient compressed air to the stretching device 3 while using supply ducts having a small diameter, in particular using supply ducts as commonly used for the relay nozzles 2. In other embodiments, compressed air is supplied to the air chamber 9 via only one supply duct, the diameter of which is chosen sufficiently large. When the blowing nozzles 11, 15 are connected to the compressed air source 22 via a common shut off valve 20, the blowing nozzles 11, 15 are activated and/or deactivated at least almost simultaneously.
As shown in Figs. 4 and 6, the holder 8 is fixed by means of two identical fixation elements 10 onto the sley 7. In the embodiment shown, the holder 8 is an essentially cuboidal block comprising a tongue 23 protruding from a side facing the sley 7. As shown in Fig. 4, a reed beam 21 provided on the sley 7 has a groove, and the tongue 23 is clamped between a key 24 and the reed beam 21 for fixing the holder 8 to the sley 7. The fixation elements 10 are for example embodied similar as the known fixation elements for a relay nozzle 2, for example as known from US 5,020,574 . The fixation elements 10 shown allow arranging the stretching device 3 in a desired position along the reed 1, wherein the distance of the stretching device 3 with respect to the U-shaped insertion channel 5 of the reed 1 remains retained. A desired position is for example determined by the weaving width. Such a holder 8 to which both blowing nozzles 11, 15 are mounted also allows a compact construction.
The stretching device 3 offers the advantage that the weft thread 6 and the airflow in the U-shaped insertion channel 5 due to the blowing action of the main nozzles and the relay nozzles 2 can pass almost unhindered beyond the stretching device 3, in other words the weft threads 6 inserted can continue almost unhindered their linear movement. In this way, the airflow in the U-shaped insertion channel 5 is used to provide an additional stretching force. This offers the additional advantage that a sufficient stretching force can be obtained with reduced air consumption.
In the embodiment of Fig. 8 compressed air is supplied to the first blowing nozzle 11 via a first air chamber 46 and to the second blowing nozzle 15 via a second air chamber 47. This allows to provide the blowing nozzles 11 and 15 separately with compressed air.
Fig. 9 shows a second embodiment of using the stretching device 3 as shown in Figs. 5 to 7 in a weaving machine. In this case the stretching device 3 is arranged next to a woven fabric 33 and between the woven fabric 33 and a waste band 34. Such an arrangement between the woven fabric 33 and the waste band 34 is possible, as the stretching device 3 is dimensioned small in the insertion direction M. This offers the advantage that can be woven with a short waste end of weft threads, that is much shorter than in the prior art shown in CS 262455 B1 .
In the embodiment shown in Fig. 9, a first weft detector 25 is arranged in the insertion direction M upstream the stretching device 3, and as also shown in Fig. 9, a second weft detector 26 is arranged in the insertion direction M downstream the stretching device 3. This allows using two weft detectors 25, 26, one upstream and one downstream, which is particularly advantageous for detecting too long weft threads or broken weft threads. The stretching device 3 is particularly suitable for being used together with an optical weft detector that is arranged in front of the reed 1. The stretching device 3 is also advantageous when using a so called weft removal device, for example a weft removal device as known from US 4,898,214 .
Fig. 10 shows an alternative embodiment of a stretching device 3. The stretching device 3 shown in Fig. 10 is similar to the stretching device 3 shown in Figs. 5 to 7 and identical reference numbers will be used for similar or identical elements. In this case a third or additional blowing nozzle 27 is provided downstream of the second blowing nozzle 15. The third blowing nozzle 27 is formed as a third hollow needle 28 with a third lateral outflow aperture 29 provided near the tip 30 of the third hollow needle 28. A third air-jet 37 is discharged via the lateral outflow aperture 29 in a direction perpendicular to a plane 50 of the third lateral outflow aperture 29. In the embodiment shown, the third blowing nozzle 27 is identical in construction to the first blowing nozzle 11 and the second blowing nozzle 15. However, all blowing nozzles 11, 15, 27 are oriented in different directions so that the planes 48, 49, 50 of the first outflow aperture 13, the second outflow aperture 17 and the third outflow aperture 29, respectively are not in parallel. The third blowing nozzle 27 is arranged so that the third air-jet 37 forms a wider angle with the insertion direction M than the second air-jet 35.
The third blowing nozzle 27 is mounted on a third mounting surface 42 provided at the holder 8. The third mounting surface 42 is provided so that the third blowing nozzle 27 is arranged lower than the first blowing nozzle 11 and the second blowing nozzle 15. Hence, the third blowing nozzle 27 is arranged in such manner that its tip 30 does not reach into the first air-jet 31 and/or the second air-jet 35 and the third blowing nozzle 27 does not impede the air- jets 31 and 35 coming from the other blowing nozzles 11 and 15. In further embodiments, even further blowing nozzles can be provided. Providing additional blowing nozzles allows applying a higher blowing force compared to the embodiment shown in Figs. 1 to 9. However, the dimension of the stretching device 3 in the insertion direction M is increased.
In an embodiment as shown in Fig. 11, not in accordance with the invention, the first blowing nozzle 11 and the second blowing nozzle 15 are formed as a unit 52. The unit 52 is formed by a blowing tube that is mounted on the holder 8 and that comprises two outflow apertures 13 and 17 near the top portion 54 of the unit 52, wherein the outflow apertures 13 and 17 provide two respective air- jets 31 and 35 differing in orientation. In this case the air- jets 31 and 35 are directed for example as the air- jets 31 and 35 as shown in Fig. 5.
Notwithstanding only one single relay nozzle 2 is shown in the figures, it is clear that a number of relay nozzles are arranged along the reed 1 in a known way. As shown in Figs. 1, 2, 3 and 9 the relay nozzles 2 provide an air-jet 55 directed more in insertion direction M than the air- jets 31, 35 of the stretching device 3, for example the angle A between the air-jet 55 and the insertion direction M is less than 10°. As shown in Fig. 9 another one or a number of relay nozzles 53 can be provided downstream of the stretching device 3 in order to blow on a faulty inserted weft thread for example. The air-jet 56 can be directed similar as the air-jet 55.
The stretching device 3 according to the invention can be arranged at any type of weaving machine with a reed 1 that is provided with a U-shaped insertion channel 5. The stretching device 3 can also be arranged in the length direction of the reed 1 in any position with respect to the reed 1, for example, a position adapted to the weaving width of the fabric 33 to be woven.
The stretching device and the weaving machine are not limited to the embodiments described by way of example and illustrated in the drawings, also alternatives and combinations of the described and illustrated embodiments are possible that fall under the claims.

Claims

A stretching device for stretching a weft thread (6) that has been inserted into a weaving shed (32) in a weaving machine, wherein the stretching device (3) is arrangeable opposite to a U-shaped insertion channel (5) of a reed (1), wherein the stretching device (3) comprises a holder (8), a first blowing nozzle (11) for providing a first air-jet (31) acting on an end region (36) of an inserted weft thread (6) and a second blowing nozzle (15) for providing a second air-jet (35) acting conjointly with the first air-jet (31) on the end region (36) of the inserted weft thread (6), and wherein the second blowing nozzle (15) is arranged downstream of the first blowing nozzle (11) in a first direction (51), which first direction (51) upon mounting the stretching device (3) to the weaving machine is parallel to the insertion direction (M), characterized in that both of the first blowing nozzle (11) and the second blowing nozzle (15) are formed as a hollow needle (12, 16) with an outflow aperture (13, 17) near the tip (14, 18) of the hollow needle (12, 16), wherein the hollow needle (12) of the first blowing nozzle (11) and the hollow needle (16) of the second blowing nozzle (15) are aligned in the first direction (51), and in that the first blowing nozzle (11) and the second blowing nozzle (15) are arranged on the holder (8) in such a manner that a plane (49) of the second outflow aperture (17) forms a wider angle with a plane perpendicular to the first direction (51) than a plane (48) of the first outflow aperture (13), so that the second air-jet (35) forms a wider angle with the first direction (51) than the first air-jet (31).
The stretching device as claimed in claim 1, characterized in that the second blowing nozzle (15) is arranged lower than the first blowing nozzle (11) in a second direction perpendicular to the first direction (51) to avoid that the second blowing nozzle (15) reaches into the first air-jet (31).
The stretching device as claimed in claim 1 or 2, characterized in that the second air-jet (35) merges with the first air-jet (31).
The stretching device as claimed in any one of claims 1 to 3, characterized in that a first angle (A) that the first air-jet (31) forms with the first direction (51) is 15° to 25°, for example 20°, and/or in that a second angle (B) that the second air-jet (35) forms with the first direction (51) is 25° to 45°, for example 27°.
The stretching device as claimed in any one of claims 1 to 4, characterized in that the first blowing nozzle (11) and the second blowing nozzle (15) are identical in construction.
The stretching device as claimed in any one of claims 1 to 5, characterized in that the first blowing nozzle (11) and the second blowing nozzle (15) are supplied together with compressed air.
The stretching device as claimed in claim 6, characterized in that the first blowing nozzle (11) and the second blowing nozzle (15) are connected to a compressed air source (22) via two supply ducts (19) that are arranged in parallel.
The stretching device as claimed in any one of claims 1 to 7, characterized in that the stretching device (3) comprises at least one additional blowing nozzle (27) for providing an additional air-jet (37) acting conjointly with the first air-jet (31) and the second air-jet (35) on the end region (36) of the inserted weft thread (6), which additional blowing nozzle (27) is arranged in the first direction (51) downstream of the second blowing nozzle (15), wherein the additional air-jet (37) forms a wider angle with the first direction (51) than the second air-jet (35).
A weaving machine comprising a reed (1) with a U-shaped insertion channel (5) and a stretching device (3) for stretching a weft thread (6) arranged opposite to the U-shaped insertion channel (5), characterized in that the weaving machine comprises a stretching device (3) for stretching a weft thread (6) according to any one of claims 1 to 8, which is arranged downstream of relay nozzles (2) in the insertion direction (M).
The weaving machine as claimed in claim 9, characterized in that the stretching device (3) is fixed to a sley (7) of the weaving machine adjustable in position in the length direction of the reed (1).
A method for stretching a weft thread (6) that has been inserted into a weaving shed (32) in a weaving machine, by means of a stretching device (3) as claimed in any one of claims 1 to 8, which stretching device (3) is arranged opposite to a U-shaped insertion channel (5) of a reed (1) and downstream of relay nozzles (2) in an insertion direction (M), the method comprising discharging the second air-jet (35) at a wider angle with the insertion direction (M) than the first air-jet (31), wherein the second air-jet (35) acts conjointly with the first air-jet (31) on the end region (36) of the inserted weft thread (6).