Stretching Device For A Weft Thread
[0001 ] 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 .
[0002] 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.
[0003] 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.
[0004] 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.
[0005] 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.
[0006] These objects are solved by the stretching device according to claim 1, the weaving
machine according to claim 14, and the method according to claim 17.
[0007] According to a first aspect a stretching device is provided comprising 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 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.
[0008] 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.
[0009] 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.
[00 10] 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
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.
[00 11] 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.
[00 12] In an embodiment, the first blowing nozzle and the second blowing nozzle are aligned in
a direction parallel to the insertion direction . It is known from the prior art, for example from
WO 2008/03 15 19 A 1, 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 2008/03 15 19 A 1.
[00 13] Preferably, the second blowing nozzle is arranged lower than the first blowing nozzle in a
direction perpendicular to the insertion direction in order to avoid that the second blowing nozzle
reaches into the first air-jet.
[00 14] 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 .
[00 15] In preferred embodiments, 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 insertion direction than
a plane of the first outflow aperture. A plane of the outflow aperture is perpendicular to the airjet.
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.
[00 16] In an embodiment, the first outflow aperture 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 airjet
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.
[00 17] 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.
[00 18] 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.
[00 19] In an embodiment, the first blowing nozzle and the second blowing nozzle are formed as
a unit. A unit is for example a blowing tube with two outflow apertures near the top portion of the
unit, wherein the outflow apertures provide two air-jets differing in orientation.
[0020] In preferred embodiments, either or 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 .
[0021 ] 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.
[0022] 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 costefficient
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 .
[0023] 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 airjet
on the end region of the inserted weft thread , which additional blowing nozzle is arranged in
insertion direction downstream of the second blowing nozzle, wherein the additional air-jet
forms a wider angle with the insertion 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.
[0024] 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 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.
[0025] The stretching device can be arranged at any type of weaving machine having a reed
that is provided with a U-shaped insertion channel.
[0026] 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 .
[0027] 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.
[0028] 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, 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.
[0029] 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. 11shows an alternative of the stretching device of Fig. 5.
[0030] 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.
[0031 ] 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.
[0032] 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 3 1
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).
[0033] 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.
[0034] 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 bou nd 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.
[0035] 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 3 1 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 3 1 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 3 1 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°.
[0036] 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 3 1 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 3 1.
[0037] 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 3 1 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 5 1, 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 5 1, which
direction 5 1 is parallel to the insertion direction M.
[0038] 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 5 1 as shown in Fig. 3, so that
the stretching device 3 can pass beneath a lip portion 38 of the fabric support 39.
[0039] 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.
[0040] 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 2 1 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 .
[0041 ] 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 .
[0042] 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.
[0043] 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.
[0044] 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 4,898,2 14.
[0045] 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.
[0046] 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 3 1 and/or the second air-jet 35 and the third blowing nozzle 27 does not impede the airjets
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.
[0047] In an embodiment as shown in Fig. 11, 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 3 1 and 35 as shown in Fig. 5.
[0048] 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.
[0049] 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 .
[0050] 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
1. 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 first blowing nozzle ( 1 1) 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), which second blowing nozzle (15) is arranged in insertion
direction (M) downstream of the first blowing nozzle ( 1 1) , characterized in that the
second air-jet (35) forms a wider angle with the insertion direction (M) than the first air-jet
(31 ) .
2. The stretching device as claimed in claim 1, characterized in that the first blowing nozzle
( 1 1) and the second blowing nozzle (15) are aligned in a direction (51 ) parallel to the
insertion direction (M).
3. The stretching device as claimed in claim 2, characterized in that the second blowing
nozzle (15) is arranged lower than the first blowing nozzle ( 1 1) in a direction
perpendicular to the insertion direction (M) to avoid that the second blowing nozzle (15)
reaches into the first air-jet (31 ) .
4. The stretching device as claimed in claim 1, 2 or 3, characterized in that the second airjet
(35) merges with the first air-jet (31 ) .
5. The stretching device as claimed in any one of claims 1 to 4, characterized in that the
first blowing nozzle ( 1 1) comprises a first outflow aperture (13) and the second blowing
nozzle (15) comprises a second outflow aperture (17), wherein a plane (49) of the
second outflow aperture (17) is forming a wider angle with a plane perpendicular to the
insertion direction (M) than a plane (48) of the first outflow aperture (13).
6. The stretching device as claimed in claim 5, characterized in that the first outflow
aperture (13) is arranged closer to the U-shaped insertion channel (5) than the second
outflow aperture (17).
7. The stretching device as claimed in any one of claims 1 to 6, characterized in that a first
angle (A) that the first air-jet (31 ) forms with the insertion direction (M) is about 15° to
about 25°, for example about 20° and/or that a second angle (B) that the second air-jet
(35) forms with the insertion direction (M) is about 25° to about 45°, for example about
27°.
8. The stretching device as claimed in any one of claims 1 to 7, characterized in that the
first blowing nozzle ( 1 1) and the second blowing nozzle (15) are formed as a unit (52).
9. The stretching device as claimed in any one of claims 1 to 7, characterized in that either
or both of the first blowing nozzle ( 1 1) and the second blowing nozzle (15) are formed as
a hollow needle (12, 16) with the outflow aperture (13, 17) near the tip (14, 18) of the
hollow needle (12, 16).
10. The stretching device as claimed in claim 9, characterized in that the first blowing nozzle
( 1 1) and the second blowing nozzle (15) are identical in construction.
11. The stretching device as claimed in any one of claims 1 to 10, characterized in that the
first blowing nozzle ( 1 1) and the second blowing nozzle (15) are supplied together with
compressed air.
12. The stretching device as claimed in claim 11, characterized in that the first blowing
nozzle ( 1 1) and the second blowing nozzle (15) are connected to a compressed air
source (22) via two supply ducts (19) that are arranged in parallel.
13. The stretching device as claimed in any one of claims 1 to 12, 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 insertion direction (M) downstream of the second blowing
nozzle (15), wherein the additional air-jet (37) forms a wider angle with the insertion
direction (M) 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 13.
The weaving machine as claimed in claim 14, 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 ) .
The weaving machine as claimed in claim 14 or 15, characterized in that a continuous
reed ( 1 ) is provided.
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) arranged opposite to a Ushaped
insertion channel (5) of a reed (1), wherein the stretching device (3) comprises a
first blowing nozzle ( 1 1) for providing an first air-jet (31 ) acting on an end region (36) of
an inserted weft thread (6) and comprises 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 an
inserted weft thread (6), which second blowing nozzle (15) is arranged in insertion
direction (M) downstream of the first blowing nozzle ( 1 1) , characterized in that the
second air-jet (35) is discharged at a wider angle with the insertion direction (M) than the
first air-jet (31 ) .