The invention relates to an auxiliary nozzle for supporting a weft thread in a weaving machine, which auxiliary nozzle comprises a hollow needle, wherein the needle comprises a tip and an outflow aperture for an air jet, wherein the outflow aperture is provided in a side wall adjoining the tip and is arranged to direct an air jet to a weft insertion channel when the auxiliary nozzle is mounted on the weaving machine. The invention also relates to a weaving machine, in which such an auxiliary nozzle is arranged.

Such an auxiliary nozzle is known amongst others from US 3, 978, 896, US 4, 794, 958, US 5, 020, 574 and

US 6,536,482. Such auxiliary nozzles are intended to support a weft thread during inserting of the weft thread into the shed of a weaving machine. To this end a plurality of such auxiliary nozzles is arranged distributed across the width of the weft insertion channel of the reed of the weaving machine, each supplying an air jet that supports the transportation of a weft thread blown through the weft insertion channel. Thereby the auxiliary nozzles are arranged in a certain position with respect to the weft insertion channel. The air jets out of the outflow apertures are directed to a weft thread, more in particular substantially in longitudinal direction of the weft insertion channel. The air jets directed to the weft thread also comprise an oblique upward directed component, more in particular a component directed to the upper wall and to the back wall of the weft insertion channel. During weaving the auxiliary nozzles move with each insertion of a weft thread through the lower plane of warp threads into the shed. It is also known that an air jet out of an auxiliary nozzle with one single circular shaped outflow aperture is unfavorable, more in particular is influenced by the feed pressure to the auxiliary nozzle. In order to improve this, it is known to replace the one single circular shaped outflow aperture by several small outflow apertures, which small outflow apertures are however subjected to dust, so that the air jet out of such an auxiliary nozzle is also adversely affected.

It is an object of the invention to improve an auxiliary nozzle of the abovementioned type in such a way that the air jet is less adversely affected, and thus a regular air jet is obtained, so that the air jet can blow with a good efficiency on a weft thread and, thus, the air consumption is reduced.

This object is solved by the auxiliary nozzle of claim 1 and the weaving machine of claim 8.

According to the invention an elliptical outflow aperture, also named elliptical shaped outflow aperture, is arranged close to the tip of the auxiliary nozzle, wherein the height of the outflow aperture along the length axis of the auxiliary nozzle is smaller than the width of the outflow aperture transversely to the length axis of the auxiliary nozzle . The elliptical outflow aperture is determined by a formula :

x ² /a ² + y ² /b ² = 1

wherein x is the position with respect to the center of the outflow aperture transversely to the length axis, wherein y is the position with respect to the center of the outflow aperture along the length axis, wherein a en b are constants, and wherein a is smaller than b. The air jet outflowing from the outflow aperture diverges in vertical direction and in horizontal direction. It is the basic idea of the invention to provide an elliptical outflow aperture in order to obtain that at a distance from the outflow aperture the extension of the outflowing diverging air jet is substantially similar in vertical direction and in horizontal direction, so that at a distance from the outflow aperture an air jet with a substantially circular cross-section is obtained that can act on a weft thread. With a circular outflow aperture as known from the prior art, the air jet diverges strongly in vertical direction due to deviation at the height of the outflow aperture, while the air jet diverges less strong in horizontal direction. Due to the strong diverging in vertical direction an air jet is obtained that can act less favorable on a weft thread. Due to the elliptical shape of the outflow aperture according to the invention, and a different divergence of the air jet in the vertical direction and in the horizontal direction, it is possible by appropriate choice of the values a and b, to obtain an air jet that, in a region at a distance from the outflow aperture, which region is used for blowing on a transported weft thread, extends substantially similar in vertical direction as in horizontal direction. In other words, the appropriate choice of the values a and b allows at a certain feed pressure to obtain an air jet with a substantially circular cross-section at the height of a region where the air jet acts on a weft thread. An air jet out of an elliptical outflow aperture can as a result thereof act with a higher force on a weft thread, so that not only the force at which the air jet blows on a weft thread increases, but also the air consumption necessary to support a weft thread decreases. The advantage of such an elliptical outflow aperture with respect to a circular outflow aperture with the same outflow surface is that the cross-section of the air jet at the height of the reaching of the transported weft thread is more circular and thus can act with more force on the transported weft thread. In a preferred embodiment the values a and b are chosen so that at a certain pressure the horizontal half value and the vertical half value of the outflowing diverging air jet are equal at a certain distance, which certain distance is the distance between the outflow aperture and a region where the air jet acts on a weft thread. In the context of the invention with half value of the air jet is meant the transverse distance to the center of the air jet, in a plane perpendicular to the air jet at a distance between the outflow aperture and a region where the air jet acts on a weft thread, where the force of the air jet is half that of the force that is exerted in the center of the air jet. This offers the advantage that the force that the air jet can act on a weft thread is larger than with an air jet wherein these half values considerably differ. In one embodiment the top edge of the tip of the auxiliary nozzle has a shape that is similar to the shape of the upper border of the elliptical outflow aperture. This means that the upper border of the outflow aperture has a shape that is similar to the top edge of the tip. In one embodiment the top edge of the tip of the hollow needle extends substantially parallel to the upper border of the outflow aperture.

In one embodiment the shape of the top edge of the tip of the auxiliary nozzle is determined starting from the shape of the elliptical outflow aperture and by a formula :

x ² / (a + c) ² + y ² / (b + c) ² = 1

wherein x is the position with respect to the center of the outflow aperture transversely to the length axis, wherein y is the position with respect to the center of the outflow aperture along the length axis, wherein a en b are constants that determine the outflow aperture as above mentioned, and wherein c is a constant for determining the top edge.

In this case the value c is chosen as small as possible, but still sufficient according to the wall thickness of the auxiliary nozzle. This allows that the ellipse, more in particular the center of the ellipse, can be arranged as high as possible in the auxiliary nozzle, in other words as close as possible to the tip of the auxiliary nozzle. In one embodiment of the invention the distance between the upper border of the outflow aperture and the top edge of the tip is determined by the wall thickness of the auxiliary nozzle.

As a result thereof the outflow aperture of the auxiliary nozzle according to the invention can be arranged close to the weft insertion channel and thus close to a weft thread, so that the air consumption is limited. This is possible as the upper border of the elliptical outflow aperture can be arranged close to the top edge of the closed tip of the auxiliary nozzle. Hence the upper border of the elliptical outflow aperture can also be arranged close to the weft insertion channel of the reed. This is not only advantageous for the air consumption, but also allows an air jet to be advantageously directed to a weft thread so that the air jet can act with a large force on a weft thread. This means that because the outflow aperture is arranged higher, the blowing angle of the air jet can be chosen smaller. In the context of the invention the blowing angle means the angle between the air jet and the weft insertion channel. In this case the blowing angle in horizontal direction as well as in vertical direction can be chosen smaller. This results in an air jet that is more directed along the longitudinal direction of the weft insertion channel that determines the moving direction of the weft thread and can thus act with more force in order to insert a weft thread. For an auxiliary nozzle according to the invention, in one embodiment the blowing angle amounts 6° in horizontal direction and 8,7° in vertical direction. In addition this allows the outflow aperture of the auxiliary nozzle to be arranged more parallel to the warp threads, so that the auxiliary nozzle needs to be rotated less with respect to the warp threads and thus also exerts less friction on the warp threads.

In addition the auxiliary nozzle also allows that the air jet blows less on the warp threads, as the outflow aperture is arranged closer to top edge of the tip, more in particular the lower border of the outflow aperture is arranged closer to the tip of the auxiliary nozzle. In order to facilitate the motion of the auxiliary nozzles into the shed and out of the shed through the lower plane of warp threads, in one embodiment of the invention it is provided that the top edge of the closed tip is rounded and adjoins the side wall that comprises the outflow aperture. In one embodiment of the invention it is provided that the inner space of the hollow needle evenly flows into the outflow aperture.

Due to the invention it is possible to arrange the cross-sectional surfaces required for the air jet closer to the tip of the hollow needle. This also offers the advantage that the outflow aperture moves earlier along the warp threads upon entering into the shed and moves later along the warp threads upon moving out of the shed, so there is more time available to let flow an air jet out of the auxiliary nozzle in order to blow on a weft thread, without this air jet blows on the warp threads .

Further features and advantages of the invention will emerge from the following description of the embodiments illustrated in the drawings and the dependent claims.

Figure 1 shows in a schematic view a part of a weaving machine with a plurality of auxiliary nozzles, more in particular a part of an air jet weaving machine,

Figure 2 shows a cross-section along the line II-II, wherein the reed and the auxiliary nozzles are located in the rearmost position,

Figure 3 shows a side view of an auxiliary nozzle according to the invention in enlarged scale, Figure 4 shows a cross-section of the auxiliary nozzle shown in figure 3,

Figure 5 shows a perspective view of the auxiliary nozzle of figures 3 and 4 mounted along the reed on a weaving machine,

Figure 6 shows a perspective view of the auxiliary nozzle of figures 3 and 4, wherein the air jet is directed towards a test device.

The weaving machine shown in figures 1 and 2 comprises a reed 3 consisting of a number of dents, each comprising a cross-section in order to form a U-shaped weft insertion channel 4, also named guiding channel. Along this weft insertion channel 4, weft threads 1, 2 are inserted into a shed 21, formed between an upper plane of warp threads 17 and a lower plane of warp threads 18. The weft threads 1 or 2 are each blown into the weft insertion channel 4 by a main nozzle 5, 6. The further transportation of the weft threads 1 or 2 is supported by air jets 7 which are blown into the weft insertion channel 4 by auxiliary nozzles 8. The air jets 7 are substantially directed in longitudinal direction of the weft insertion channel 4 and comprise a slightly oblique upward directed component, which is directed to the upper wall 15 and to the back wall 16 of the weft insertion channel 4 on the weft threads 1, 2. The reed 3, the main nozzles 5, 6 and the holders 9 of the auxiliary nozzles 8 are fastened to a sley profile 10 of a sley, as for example known from US 5, 020, 574. A holder 9 is shown in more detail in figures 5 and 6. The sley profile 10 is fastened for example via sley supports to an axis (not shown) of the sley, which is driven to and fro.

The upper plane of warp threads 17 and the lower plane of warp threads 18 run together in the beat-up line 19, against which the weft threads are beaten up by the reed 3, so that a fabric 20 is formed. The beat-up of a weft thread is effected by the back wall 16 of the U-shaped weft insertion channel 4, which belongs to the central part 24 of the reed 3. The upper part 23 of the dents of the reed 3 forms an upper wall 15 of the weft insertion channel 4. The lower wall 14 of the weft insertion channel 4 is formed by the lower part 22 of the dents of the reed 3. The auxiliary nozzles 8 are moved by means of the movement of the sley by each insertion of a weft thread through the warp threads of the lower plane of warp threads 18 into the shed 21 and after the beat-up of the weft thread through the lower plane of warp threads 18 back out of the shed 21. In this case the tip 12 of the auxiliary nozzle 8 moves along a path 31.

As illustrated in figures 3 and 4 the auxiliary nozzle 8 is configured as a hollow needle 11, which is provided with an outflow aperture 25 according to the invention near its tip 12 in a side wall 26. In other words the hollow needle 11 of the auxiliary nozzle 8 is in the region of the closed tip 12 provided with an outflow aperture 25 which is arranged in a side wall 26 of the auxiliary nozzle 8, which side wall 26 adjoins close to the closed tip 12. As illustrated in figures 2 and 3, when the auxiliary nozzle 8 is mounted on the weaving machine, the length axis 27 of the hollow needle 11 is arranged opposite the weft insertion channel 4 at an angle with respect to the reed 3. When the auxiliary nozzle 8 is mounted on a weaving machine, the top edge 13 of the tip 12 is arranged substantially close to the weft insertion channel 4 of the reed 3 and the outflow aperture 25 is arranged to direct an air jet 7 towards the weft insertion channel 4. The air jet 7 outflowing from the elliptical outflow aperture 25 diverges in vertical direction and in horizontal direction. The outflowing air jet 7 diverges stronger in the vertical direction than in the horizontal direction, wherein the difference in divergence depends on the pressure of the compressed air fed to the auxiliary nozzle 8. In order to achieve a regular air jet 7 in the weft insertion channel 4 in order to blow on the transported weft thread 1, 2, the auxiliary nozzle 8 according to the invention has an outflow aperture 25 with a height H along the length axis 27 that is smaller than the width B.

More in particular, the auxiliary nozzle 8 comprises close to the tip 12 an elliptical outflow aperture 25, wherein the height H of the outflow aperture 25 along the length axis 27 of the auxiliary nozzle 8 is smaller than the width B of the outflow aperture 25 transversely to the length axis 27 of the auxiliary nozzle 8. The elliptical outflow aperture 25 is determined by a formula:

x ² /a ² + y ² /b ² = 1

wherein x is the position with respect to the center 30 of the outflow aperture 25 transversely to the length axis 27, wherein y is the position with respect to the center 30 of the outflow aperture 25 along the length axis 27, wherein a en b are constants, and wherein a is smaller than b .

For an auxiliary nozzle 8 according to the invention, wherein compressed air is fed at a feed pressure of 5 bar, as commonly used in weaving machines, in one embodiment the height H amounts in the order of magnitude of 1,41mm, while the width B amounts in the order of magnitude of 1,57mm. Such an auxiliary nozzle 8 can easily be used at a feed pressure between 4 bar and 6 bar, although the auxiliary nozzle 8 is designed to be used at a feed pressure of 5 bar. In case the feed pressure is higher, it is advantageous to choose the ratio between the height H and the width B smaller. In case the feed pressure is lower, it is advantageous to choose the ration between the height H and the width B larger. In one embodiment wherein the feed pressure is 6 bar, for example, the height H is chosen 1,38mm and the width B is chosen 1,60mm. In case the feed pressure is 4 bar, for example, the height H is chosen 1,44mm and the width B is chosen 1,54mm.

In one embodiment the top edge 13 of the tip 12 of the auxiliary nozzle 8 has a shape that is similar to the shape of the upper border 28 of the elliptical outflow aperture 25 and/or the top edge 13 of the tip 12 of the hollow needle 11 extends substantially parallel to the upper border 28 of the outflow aperture 25. As shown in figure 3 the shape of the top edge 13 of the tip 12 of the auxiliary nozzle 8 is determined starting from the shape of the elliptical outflow aperture 25 and by a formula :

x ² / (a + c) ² + y ² / (b + c) ² = 1

wherein x is the position with respect to the center 30 of the outflow aperture 25 transversely to the length axis 27, wherein y is the position with respect to the center 30 of the outflow aperture 25 along the length axis 27, wherein a and b are constants that determine the outflow aperture 25 as mentioned above, and wherein c is a constant for determining the top edge 13. As shown in figure 5, the air jet 7 outflowing from the outflow aperture 25 is directed towards the weft insertion channel 4 and diverges stronger in the vertical direction than in the horizontal direction. As shown in figure 6, an air jet 7 with a substantially circular cross-section, also named circular air jet, is obtained in a plane 33 perpendicular to the air jet 7 and at a certain distance from the outflow aperture 25, which certain distance, for example, is equal to the distance between the outflow aperture 25 and a region where the air jet 7 acts on a weft thread. If the auxiliary nozzles 8 are arranged on a weaving machine at a distance from each other of 74 mm, then the above mentioned certain distance is for example between 45 mm and 74 mm, and preferably between 45 mm and 60 mm. By an auxiliary nozzle 8 according to the invention it is established, that in case an air jet with a substantially circular cross-section at the above mentioned certain distance is obtained, that this air jet from this distance on then shows a substantially circular cross-section. Due to the elliptical outflow aperture 25 an air jet with a substantially circular cross-section is obtained at the above mentioned certain distance. In this case the horizontal half value and the vertical half value are substantially equal at the above mentioned certain distance. In figure 6 half values are schematically shown by the circumference 32. For an auxiliary nozzle 8 according to the invention, in one embodiment at the height of the above mentioned certain distance a circular air jet 7 is obtained with a central axis 34 and a cone angle K in the order of magnitude of 9,2°.

In addition the auxiliary nozzle 8 also allows that the air jet 7 does blow less on the warp threads, as the outflow aperture 25 is arranged closer to top edge of the closed tip 12, more in particular the lower border 29 of the outflow aperture 25 is arranged closer to the tip 12 of the auxiliary nozzle 8. In order to facilitate the motion of the auxiliary nozzles 8 into the shed 21 and out of the shed 21 through the lower plane of warp threads 18, in one embodiment of the invention it is provided that the top edge 13 of the closed tip 12 is rounded and adjoins the side wall 26 that comprises the outflow aperture 25.

Due to the invention it is possible to arrange the cross-sectional surfaces of the outflow aperture 25 required for the air jet 7 closer to the tip 12 of the hollow needle 11. Due to the shape of the outflow aperture 25 the outflow aperture 25 according to the invention offers the advantage that de outflow aperture 25 can be arranged close to the weft insertion channel 4, so that the air jet 7 out of the outflow aperture 25 can act with large force on a weft thread.

The invention is not limited to the embodiments described by way of example and illustrated in the drawings. Variant embodiments concerning shapes and dimensions that fall under the claims and combinations of the described and illustrated embodiments are also possible .