Device for catching and stretching a weft thread, weaving machine and
method for catching and stretching a weft thread
Description
The invention relates to a device for catching and stretching weft
threads, to a weaving machine provided with a device of this type, and to
a method for catching and stretching weft threads.
For catching a leading end of a weft thread inserted into a shed (also
referred to as "inserted weft thread" in the following) and for holding the
inserted weft thread with a desired tension, the use of so-called "catch
ing threads" is known from the prior art. The catching threads run in
parallel to the warp threads next to the shed and form a separate shed
which may be closed earlier than the normal shed via associated shedforming
means, so as to bind the inserted weft thread at an appropriate
moment and with an appropriate tension. By holding the end parts of
the inserted weft thread, it is avoided that the weft threads, which extend
beyond the fabric edge after the insertion, are pulled back into the fabric.
In order to avoid catching threads, US 6,206,051 B 1 provides a mecha
nism for removing a weft thread end including a weft thread suction de
vice and a weft thread tensioning device. During weaving, a leading end
part of an inserted weft thread reaching the arrival side is caught and
held tensioned by the weft thread tensioning device. Then, the weft
thread thus held in the shed is beaten into the fabric fell by the beat-up
motion of the reed. The weft thread suction device is provided with a first
and a second suction opening. When the leading end part of the weft
thread approaches the first suction opening, the sucking operation of the
weft thread tensioning device is stopped in order to suck the leading end
part of the weft thread through the first suction opening into the weft
thread suction device. An additional blower arranged on a member
combined with the reed may be provided to blow air towards the first
suction opening from behind the dents of the reed.
GB 2 009 798 A discloses a weft yarn end treating device comprising a
sucking device arranged stationary on the weaving machine in an exten
sion of an insertion path of a weft thread and a plurality of loop-shaped
belts for holding weft thread ends. The device further comprises a hook
member which reciprocally moves and is arranged to hitch the end po r
tion of an inserted weft thread caught by the sucking device and then to
thrust this end portion between the belts.
It is an object of the invention to provide a device for catching and
stretching weft threads, a weaving machine with a device of this type
and a method for catching and stretching weft threads, wherein the weft
thread is held with sufficient tension until the free end of the weft thread
is cut off, wherein the free end is kept short and wherein the use of
catching threads can be avoided.
This object is solved by a device according to claim 1, more in particular
a device for catching and stretching a weft thread inserted into a shed of
a weaving machine, comprising a weft thread stretching device arranged
stationary on the weaving machine in an extension of an insertion path
of the weft thread for catching the leading end part of the inserted weft
thread and stretching the caught weft thread, a weft thread holding device
arranged stationary on the weaving machine in a region of the beatup
line for holding the leading end part of at least one beaten up weft
thread, and a moveable guiding device for guiding the caught weft
thread towards the weft thread holding device, wherein the guiding de
vice is adapted for limiting a displacement of the inserted weft thread in
a direction transverse to the moving direction of the guiding device upon
guiding the caught weft thread towards the weft thread holding device,
wherein the guiding device is arranged on the sley for movement with
the sley, and wherein the guiding device is positioned at a distance from
the reed away from the beat-up line in order to avoid interference of the
guiding device with weft threads upon insertion of the weft threads.
A weft thread inserted into a shed is caught and stretched in order to
avoid that the inserted weft thread is pulled back into the shed and/or the
fabric. The caught and stretched weft thread is referred to as caught
weft thread in the following. In one embodiment, the caught weft thread
is held by means of the weft thread stretching device until the weft
thread is transferred to the weft thread holding device. In other embodiments,
additional clamping devices are provided for holding the caught
weft thread at least partly upon the movement of the weft thread to the
weft thread holding device. A weft thread introduced into the weft thread
holding device is referred to as "introduced weft thread" in the following.
When the guiding device is moved, the caught weft thread is brought
towards the weft thread holding device. A stationary arrangement of the
weft thread stretching device is advantageous in order to avoid a heavy
load on the sley of the weaving machine. However, a stationary weft
thread stretching device may exert a pulling action on a caught weft
thread in a direction transverse to a movement direction of the guiding
device, while guiding the caught weft thread towards the weft thread
holding device. By providing a guiding device that is adapted for limiting
a displacement of the caught weft thread in a direction transverse to the
moving direction of the guiding device upon guiding the caught weft
thread towards the weft thread holding device, a reliable transfer of the
caught weft thread towards the weft thread holding device is achieved
while the weft thread is held with a defined tension.
The guiding device is arranged on the sley for movement with the sley in
order to avoid the necessity of an additional mechanism for moving the
guiding device. Further, the guiding device is positioned on the sley at a
distance from the reed away from the beat-up line in order to avoid inter
ference with inserted weft threads upon insertion of the weft threads.
Upon insertion, the weft thread needs to pass the guiding device for
reaching the weft thread stretching device provided beyond the reed.
Only after the weft thread is caught by the weft thread stretching device,
an interaction between the caught weft thread and the guiding device is
desired for moving the caught weft thread towards the weft thread hold
ing device.
In a preferred embodiment the weft thread holding device is provided
with an entry slit between a fabric edge of the fabric and the movement
path of the guiding device, which entry slit is adapted for receiving a weft
thread transversally to its longitudinal direction.
In the context of the application, an entry slit is defined as a narrow
opening through which a weft thread can be introduced into the weft
thread holding device. The entry slit extends at least partially essentially
in the longitudinal direction of the weft thread to be introduced and,
hence, is adapted for receiving a weft thread transversally to the longitu
dinal direction of the weft thread. In preferred embodiments, the entry
slit extends at least essentially in parallel to the beat-up line of the fabric.
The weft thread is introduced into the weft thread holding device via the
entry slit by a movement of the guiding device with the caught weft
thread beyond the entry region of the entry slit. The entry slit has a lim
ited width transverse to the moving direction of the guiding device. As
the displacement of the weft thread transverse to the moving direction is
limited by means of the guiding device, it is avoided that the guiding de
vice pushes the weft thread above or below the entry slit, instead of
through the entry slit and into the weft thread holding device. Thereby, a
reliable introduction is ensured despite a potential pulling action of the
weft thread stretching device on the caught weft thread, in particular pulling
actions in a direction transverse to the moving direction. A risk of
damaging the weft thread upon insertion is minimized, which damaging
could otherwise result in a broken weft thread, of which the remaining
part is not long enough to be held by the weft thread holding device.
In a preferred embodiment, the entry slit is adapted for retaining a weft
thread introduced into the weft thread holding device via the entry slit.
Thereby, the entry slit prevents that the weft thread introduced into the
weft thread holding device is pulled backwards and out of the weft
thread holding device by the guiding device when the guiding device is
moving away from the beat-up line and the weft thread is not yet bound
by the warp threads. In particular in high speed weaving machines,
such a retention is advantageous.
In one embodiment, a width of the entry slit is delimited, in order to allow
a retention function of the entry slit. In one embodiment, the entry slit is
delimited by at least one retaining edge, preferably two mutually oppos
ing retaining edges. The retaining edges avoid or at least restrict a retraction
or withdrawal of introduced weft threads from the weft thread
holding device. In one embodiment, the retaining edges are provided in
the form of barbs or hooks. In other embodiments, the retaining edges
are formed as undercut regions.
In a preferred embodiment, the guiding device comprises a hook-shaped
guiding element provided with a recess having inwardly converging
sidewalls for receiving the weft thread. The recess is formed for exam
ple wedge-shaped and has one or two inclined sidewalls. Upon move
ment of the guiding device, the caught weft thread is pulled rearwards
into the recess, for example by means of the stationary weft thread
stretching device. The inwardly converging sidewalls allow an entry re
gion of the recess to be chosen sufficiently high in order to avoid an in
terference of the guiding device with the weft threads upon insertion pri
or to a catching of the weft thread by the weft thread stretching device
and/or for allowing a reliable introduction of the caught weft thread into
the recess. At the bottom of the recess, weft threads are guided upon
their movement towards the weft thread holding device for an introduc
tion of the weft threads into the entry slit having a limited width.
When weaving with the same weaving machine, the position of the beatup
line may vary, for example due to the use of different warp threads
and/or weft threads, due to different weaving patterns and/or weaving
speeds and/or due to other influences on a weaving machine setup.
Hence, a distance between a rearmost reversal point of the sley and the
beat-up line may vary when beating up a weft thread. In case the guid
ing device is not fixed on the sley, a movement path of the guiding de
vice may be adjusted. However, according to the invention, the guiding
device is arranged on the sley in order to avoid the need of an additional
moving mechanism. In order to compensate the variance in the position
of the beat-up line and to ensure that the caught weft thread is int ro
duced with a defined introduction depth into the weft thread holding de
vice, in one embodiment the weft thread holding device is adjustably arranged
on the weaving machine and the position of the weft thread hold
ing device is matched to the beat-up line.
In another embodiment, the guiding device comprises an adjustable
stopping element for adjusting the depth of the recess. By use of an adjustable
stopping element, the depth of the recess of the guiding element
can be adjusted, thereby an introduction depth of the weft thread into the
weft thread holding device via the entry slit may be varied. The adj usta
ble stopping element allows matching the depth of the recess to a posi
tion of the beat-up line chosen under certain weaving conditions for ensuring
an essentially constant introduction or a constant introduction
depth of the weft thread via the entry slit. In this way it is possible to
avoid the necessity of changing a position of the weft thread holding de
vice, which position also influences how the already beat-up weft
threads are presented to and cut by a cutting device. In one embodiment,
the adjustable stopping element may be formed as a small plate,
arranged on the guiding device in such way that the adjustable stopping
element reduces the depth of the recess. In other words, the adjustable
stopping element is arranged close to a ground of the recess. Preferably,
the stopping element is replaceable mounted on the guiding device
allowing for a replacement of the stopping element in case the stopping
element is worn out. As the stopping element is the element of the guid
ing device most subjected to wear, the overall lifetime of the guiding device
is extended.
In preferred embodiments, the weft thread holding device comprises a
suction nozzle with a suction opening, at which suction opening the entry
slit is provided. The suction nozzle of the weft thread holding device is
also referred to as holding nozzle. The holding nozzle is provided with
the suction opening having an aperture on the rear side, facing the reed.
The suction opening in preferred embodiments is in the form of a suction
pipe or suction tube. Via the suction nozzle a continuous suction force
or suction action may be exerted for holding the introduced weft threads
after these weft threads are released from the weft thread stretching de
vice. In preferred embodiments, the holding nozzle has a waste duct
arranged to remove weft thread end parts, which have been cut off by a
thread cutting device, by sucking the end parts through the waste duct.
The holding nozzle in this embodiment has two functions, it serves both
to keep introduced weft threads tensioned and to remove the cut off weft
thread ends. The suction opening is provided with the entry slit for a l
lowing the caught weft thread to be inserted transversely to the longitu
dinal direction of the weft thread by the guiding device. In one embodi
ment, the entry slit is formed integrally or at least partially integrally with
the suction opening. In preferred embodiments, the entry slit is not
symmetrical with respect to a plane perpendicular to the fabric and par
allel to the fabric edge, wherein a depth of the entry slit at a side facing
away from the fabric edge is less than the depth of the entry slit on the
side facing the fabric edge.
In another embodiment, at least at an entry region of the entry slit a
cross section of the entry slit decreases from a distal end towards the
suction nozzle for leading the weft thread towards the suction nozzle. In
other words, the entry slit is wider on the rear side, that is facing the
reed, and narrows towards the front side, that is facing away from the
reed. Thereby, the walls of the entry slit may support the guiding device
when guiding the weft thread towards the inside of the weft thread holding
device. However, when guiding a caught weft thread towards the
holding nozzle via walls of the entry slit, the weft thread is pushed for
ward into the weft thread holding device. A pushing force is more dam
aging to a weft thread than the pulling force exerted by the weft thread
stretching device for pulling the weft thread into the recess of the guiding
element. Therefore, in preferred embodiments, the recess of the guiding
element is chosen sufficiently narrow at a bottom or ground thereof for
allowing a precise positioning of the weft thread with respect to the weft
thread holding device, wherein only little or no guiding support is re
quired from the walls of the entry slit.
In another embodiment, at least one auxiliary nozzle is provided in the
region of the entry slit of the weft thread holding device blowing towards
the inside of the weft thread holding device in a direction away from the
reed. The auxiliary nozzle provides an additional holding force for holding
already introduced weft threads and for hindering introduced weft
threads from being pulled out the weft thread holding device. Thereby,
the auxiliary nozzle supports the introduction of a weft thread into the
weft thread holding device and the holding of introduced weft threads.
The weft thread stretching device is arranged stationary on the weaving
machine, next to the reed and the guiding element in the extension of
the insertion path. Preferably, the weft thread stretching device com
prises a suction nozzle, in particular a ring-jet suction nozzle, the open
ing of which is directed towards a guiding channel of the reed if the reed
is in its most rearward position, away from the beat-up line. Preferably,
a ring-jet suction nozzle with a sufficient large diameter is chosen as a
stretching nozzle in order to allow a good catching and stretching of the
weft thread and in order to allow large amounts of weft thread to pass
easily through it, in case a removal of a wrongly inserted weft thread is
necessary. In one embodiment, a ring-jet suction nozzle as disclosed in
WO201 1/000561 is used, the content of which is herewith incorporated
by reference.
In other embodiments, a stationary auxiliary suction nozzle is provided
for removing wrongly inserted weft threads. The stationary auxiliary suc
tion nozzle comprises a large opening and is only operated when a re
moval of wrongly inserted weft threads becomes necessary.
According to a preferred embodiment, the weft thread stretching device
is connected to a control unit, wherein the weft thread stretching device
is controlled by the control unit so that the weft thread stretching device
is activated upon insertion of a weft thread into the shed for catching the
inserted weft thread and is deactivated when or after the caught weft
thread is beaten up or has been beaten up. For example, in case the
weft thread stretching device is a suction nozzle, in one embodiment, the
weft thread stretching device is connected to a compressed-air tank via
a valve, wherein the valve is controlled so that the weft thread stretching
device is activated upon insertion of a weft thread into the shed for
catching the inserted weft thread and is deactivated when or after the
caught weft thread is beaten up or has been beaten up.
In one embodiment, the end part of the inserted weft thread is caught by
the weft thread stretching device and held by the weft thread stretching
device until the weft thread is transferred to the weft thread holding de
vice and held by the weft thread holding device.
In an alternative embodiment, the guiding device is provided with a
thread clamp, in particular an active thread clamp. In one embodiment,
at least one jaw or both jaws of the thread clamp are arranged for form
ing a hook-shaped guiding element. In this case, the weft thread is inserted,
stretched by the weft thread stretching device and, thereafter,
held by the thread clamp.
When providing a thread clamp, arrangement is made for providing that
during the forward movement and/or during beat-up, an inserted weft
thread, in particular the end part of the inserted weft thread, is still held
by the weft thread stretching device and, therefore, is pulled into the
thread clamp between the two clamping elements. After the weft thread
is clamped and held with sufficient force by the thread clamp, the weft
thread stretching device may be deactivated. The thread clamp is posi
tioned for guiding the end part of the clamped weft thread into the weft
thread holding device via the entry slit of the weft thread holding device.
In one embodiment, the thread clamp is provided with an adjustable
stopping element, which defines the depth of the opening defined by the
two clamping elements.
Preferably, an active thread clamp is provided. In the context of the a p
plication, a thread clamp which may be opened or closed by exerting a
defined force, for example a hydraulically, pneumatically or motor driven
thread clamp is referred to as an active thread clamp. An active thread
clamp allows for an independent operation of the thread clamp. In one
embodiment, a thread clamp as described in WO 20 1/000561 is used.
The object is further solved by a weaving machine comprising a device
for catching and stretching a weft thread.
The object is further solved by a method according to claim 14, more in
particular a method for catching and stretching a weft thread inserted
into a shed of a weaving machine using a device with a weft thread
stretching device, a weft thread holding device arranged stationary on
the weaving machine in a region of a beat-up line, and a moveable guid
ing device, arranged for movement with the sley and positioned at a distance
from the reed away from the beat-up line, wherein the method
comprises catching and stretching the leading end part of the weft
thread at an extension of an insertion path of the weft thread by means
of the weft thread stretching device, guiding the caught weft thread towards
the weft thread holding device by means of the guiding device
while limiting a displacement of the caught weft thread in a direction
transverse to the moving direction of the guiding device, and introducing
the caught weft thread into the weft thread holding device via an entry
slit.
According to a preferred embodiment, the weft thread holding device is
continuously activated for taking over and holding inserted weft threads,
and the weft thread stretching device is activated upon insertion of a
weft thread into the shed for catching the inserted weft thread and is deactivated
when or after the caught weft thread is beaten up or has been
beaten up. In one embodiment, the weft thread holding device and/or
the weft thread stretching device comprise a suction nozzle, wherein in
an activated state a suction force is provided for example by exerting a
negative pressure.
Further features and advantages of the invention will emerge from the
following description of the embodiments illustrated in the drawings.
figure 1: is a schematic plan view of a part of a weaving machine with
a device according to a first embodiment of the invention during insertion
of a weft thread;
figure 2: is a perspective view of a part of the weaving machine
shown in figure 1;
figure 3: is a perspective view of a part of the weaving machine with
the device shown in figure 1 seen from the rear side of a reed;
figure 4: is a schematic drawing showing a detail of a weft thread
holding device and a guiding device of the weaving machine with the
device shown in figure 1;
figure 5: is a schematic plan view of the weaving machine shown in
figure 1 during movement of a sley towards a beat-up line;
figure 6: is a schematic plan view of the weaving machine shown in
figure 1 during beat-up;
figure 7: is a schematic plan view of the weaving machine shown in
figure 1 during a backward movement of the sley away from the beat-up
line;
figure 8: is a schematic plan view of the weaving machine shown in
figure 1 during binding;
figure 9: is a perspective view of a part of a weaving machine similar
to figure 2 with a device according to a second embodiment of the inven
tion;
figure 10: is a schematic side view of a detail of the device shown in
figure 9;
figure 11: is a schematic side view of a variant embodiment of a weft
thread holding device to be used in a device shown in figure 1 or 9 ; and
figure 12: is a schematic plan view of the variant shown in figure 11.
Figure 1 is a schematic plan view of a part of a weaving machine with a
device 1 according to a first embodiment of the invention during insertion
of a weft thread 2 . Fig. 2 and 3 show perspective views of a part of a
weaving machine similar to Fig. 1.
The weft thread 2 is inserted in a shed 30 formed between planes of
warp threads 3 by selectively raising and lowering warp threads 3. Dur
ing insertion, the weft thread 2 is supported in a known way by relay
nozzles 4 (see Fig. 1) and guided in a guiding channel 509 (see Fig. 2)
of a reed 5 , which guiding channel 509 determines the insertion path
510 of the inserted weft thread. In the depicted embodiment, a weft de
tector 6 is arranged at the end of the insertion path next to the reed 5 to
detect the arrival of the weft thread 2 .
The leading end part 2f of the inserted weft thread 2 is caught and
stretched with a predetermined tension by a weft thread stretching de
vice 7. As schematically shown, the weft thread stretching device 7 is
arranged stationary on the weaving machine in an extension of an insertion
path of the weft thread 2 determined by the guiding channel 509, for
example by means of a cantilever or beam 700.
The reed 5 is attached to the sley 500 (see Fig. 3) and moved towards a
beat-up line 800 of a fabric 8 for a beat-up motion. The weft thread 2,
that is caught and stretched by the weft thread stretching device 7, as
schematically shown in Fig. 1, is moved with the reed 5 towards the
beat-up line 800 and is beaten into the fabric 8.
In accordance with the application, a weft thread holding device 9 is arranged
stationary on the weaving machine in a region of a beat-up line
800 for holding the leading end parts of a number of beaten up weft
threads 2d. As mentioned above, the weft thread stretching device 7 is
also arranged stationary on the weaving machine, at a distance from the
beat-up line 800 in the extension of an insertion path of the weft thread
2 . A moveable guiding device 10 is provided for guiding the caught weft
thread 2 towards the weft thread holding device 9. As shown in Fig. 1,
the guiding device 10 is positioned at a distance from the reed 5 away
from the beat-up line 800 in order to avoid interference of the guiding
device 10 with weft threads upon insertion of the weft threads.
The stationary arranged weft thread stretching device 7 exerts a pulling
action in a direction transverse to a movement direction B of the guiding
device 10 on the caught weft thread (not shown in Figs. 2 and 3) when
the caught weft thread is moved towards the weft thread holding device
9. As can be seen in Figs. 2 and 3 , the guiding device 10 is adapted for
limiting a displacement of the caught weft thread in a direction transverse
to the moving direction of the guiding device 10 upon guiding the
caught weft thread towards the weft thread holding device 9.
The weft thread holding device 9 is provided with an entry slit 900 (as
can be seen in Figs. 2 and 3) between the fabric edge 801 of the fabric 8
and the movement path 110 of the guiding device 10. The entry slit 900
extends parallel to the beat-up line 800 and is adapted for receiving a
weft thread transversally to the longitudinal direction of the weft thread.
The guiding device 10 guides a caught weft thread to be introduced into
the weft thread holding device 9 via the entry slit 900 and to be transferred
to the weft thread holding device 9 while upholding a sufficient
tension of the weft thread in order to avoid that the weft thread is pulled
back into the fabric 8 or the shed.
A cutting device 11 (see Figs. 1 and 3) is provided between a fabric
edge 801 of the fabric 8 and the weft thread holding device 9 for cutting
the ends of weft threads after they are bound by the warp threads 3.
The cutting device 11 is arranged close to the fabric edge 801 for mini
mizing the length of the ends of the bound weft threads protruding be
yond the fabric 8. The cut-off ends are removed via a duct 901 (see Fig.
1) provided with the weft thread holding device 9.
In the depicted embodiment, an auxiliary suction nozzle 12 is provided
for removing wrongly inserted weft threads. A weft detector 120 (see
Fig. 1) is arranged near, i.e. just before, in or just after, the auxiliary suc
tion nozzle 12 for removing a wrongly inserted weft thread. The wrongly
inserted weft threads are removed via a duct 121 provided with the auxil
iary suction nozzle 12.
In the depicted embodiment, the weft thread stretching device 7 and the
weft thread holding device 9 comprise a ring-jet suction nozzle, each. In
the context of the application, a ring-jet suction nozzle is defined as a
suction device, wherein a suction effect is obtained by blowing compressed
air into the suction device. For this purpose, in the depicted
embodiment, the weft thread stretching device 7 and the weft thread
holding device 9 are each connected to a compressed-air tank 13 via
supply lines 130 with a valve 131 and a pressure regulator 132 (see Fig.
1) . According to one embodiment, the valve 13 1 between the weft
thread stretching device 7 and the compressed-air tank 13 is activated
upon insertion of a weft thread into the shed for catching the inserted
weft thread and is deactivated when or after the caught weft thread 2a is
beaten up or has been beaten up. In other embodiments, at least the
valve 131 between the weft thread holding device 9 and the compressed-
air tank 13 is omitted, wherein a continuous suction action is
exerted by the weft thread holding device 9.
The suction nozzle 902 of the weft thread holding device 9, more par
ticular the ring-jet suction nozzle, is provided with a suction opening 903
in the form of a suction trunk or suction tube. The suction opening 903
or suction tube has an essentially V-shaped distal end that opens toward
the reed 5 with two entry regions 904 (see Fig. 3), which are inclined
with respect to the plane of the fabric 8 for forming the entry slit 900.
The entry slit 900 extends essentially perpendicular or perpendicular to
the longitudinal direction of the tubular suction opening 903 for introduc
ing the weft thread into the weft thread holding device 9 transversally to
the longitudinal direction of the weft thread. In preferred embodiments, a
continuous suction force or suction action is exerted by the suction nozzle
902 for holding the ends of introduced weft threads and of bound
weft threads 2d with a defined tension after these weft threads are re
leased from the weft thread stretching device 7.
Further, in the depicted embodiment an auxiliary nozzle 14 is provided in
the region of an entry slit 900 (see Figs. 2 and 3) of the weft thread hold
ing device 9 blowing towards the inside of the weft thread holding device
9 in a direction away from the reed 5 and towards the suction nozzle 902
for supporting the introduction of a weft thread 2 into the weft thread
holding device 9. The auxiliary nozzle 14 is connected to the com
pressed-air tank 13 via a supply line 130 with a valve 13 1 and a pres
sure regulator 132. In preferred embodiments, a suction action of the
auxiliary nozzle 14 is applied only upon the introduction of the caught
weft thread into the entry slit 900 for reducing an air-consumption.
At an entry region of the entry slit 900, a cross-section of the entry slit
900 decreases from a distal end towards the suction nozzle 902 of the
weft thread holding device 9 allowing the caught weft thread 2b to be
guided towards the inside of the weft thread holding device 9 along entry
regions 904 of the entry slit 900. The entry slit 900 is further adapted for
retaining an introduced weft thread 2b. For this purpose, in the embod
iment shown in Fig. 4, the entry slit 900 is delimited by two mutually o p
posing retaining edges 905. The retaining edges 905 are slightly in
clined towards the inside of the weft thread holding device 9 allowing for
an undisturbed introduction of a weft thread into the weft thread holding
device 9, while restricting a retraction of the introduced weft thread 2b.
In the depicted embodiment, the retaining edges 905 are formed on a
panel element 906 attached to the suction opening 903 in the region of
the entry slit 900 on the side not facing the fabric edge 801 .
Fig. 4 is a schematic drawing showing a detail of the weft thread holding
device 9 . More particular, Fig. 4 shows the panel element 906 of the
weft thread holding device 9 provided with the retaining edges 905, and
the guiding device 10 of the device 1 shown in Figs. 1 to 3 . Further, in
Fig. 4 a caught weft thread 2a, which is guided by the guiding device 10,
and an introduced weft thread 2b, which is introduced into the weft
thread holding device 9 , are shown. As explained above, in the embodiment
as shown in Fig. 3 , the auxiliary nozzle 14 is provided in the region
of the entry slit 900 of the weft thread holding device 9, which auxiliary
nozzle 14 is blowing towards the inside of the weft thread holding device
9 as shown by arrows 140 in Fig. 4.
In the embodiment shown in Figs. 1 to 4 , the guiding device 10 compris¬
es a hook-shaped guiding element 100 with a recess 10 1 having inward
ly converging sidewalls 102 for receiving the caught weft thread 2a. The
guiding device 10 further comprises an adjustable stopping element 103
for adjusting the depth of the recess 10 1 (see also Fig. 3). The adjustable
stopping element 103 is pivotable as indicated with an arrow 141 in
Fig. 4. A bolt 104 is provided for adjusting a position of the adjustable
stopping element 103. As shown in Fig. 3, the bolt 104 is arranged in a
position which is easily accessible after the device 1 is mounted on the
weaving machine.
Figs. 5 to 8 schematically show parts of a weaving machine and a de
vice 1 for catching and stretching a weft thread inserted into a shed simi
lar to the presentation of Fig. 1. For the same or similar elements, iden
tical reference signs are used. As shown in Fig. 1, the leading end part
of the weft thread 2 inserted into the shed is caught and stretched at an
extension of an insertion path of the weft thread by means of the weft
thread stretching device 7. A weft thread 2 inserted into a shed is
caught for avoiding that it is pulled back into the fabric 8 and is referred
to as caught weft thread 2a. As shown in Fig. 5, the caught weft thread
2a is guided towards the weft thread holding device 9 by means of the
guiding device 10. In preferred embodiments, the guiding device 10 is
arranged on the sley 500 (see Fig. 3) of the weaving machine and ad
vanced towards the beat-up line 800 with the reed 5. The movement
direction of the reed 5 and the guiding device 10 towards the beat-up
line 800 is schematically represented with an arrow B. The weft thread
holding device 9 is arranged between the fabric edge 801 and the
movement path 110 of the guiding device 10.
As shown in Fig. 6 , the caught weft thread 2a is introduced into the weft
thread holding device 9 during beat-up. In the depicted embodiment, the
caught weft thread 2a is still held and stretched by the weft thread
stretching device 7 upon introduction into the weft thread holding device
9 . As will be explained in more detail with respect to Figs. 9 and follow
ing, alternative arrangements for holding the weft thread upon int roduc
tion into the weft thread holding device 9 are possible. A weft thread in
troduced into the weft thread holding device 9 is referred to as int ro
duced weft thread 2b. In preferred embodiments, after the weft thread is
introduced into the weft thread holding device 9, the suction action for
stretching the caught weft thread 2a with the weft thread stretching de
vice 7 is stopped. In the meanwhile the weft thread 2b is sucked into the
weft thread holding device 9 and leaves the weft thread stretching de
vice 7 .
As shown in Fig. 7, the introduced weft thread 2b is held in the weft
thread holding device 9 and stretched by the weft thread holding device
9 during a backward movement of the sley with the guiding device 10
away from the beat up line 800. Preferably, as also shown in Fig. 7 , the
bound weft threads 2d, which are bound by the warp threads 3 are cut
by the cutting device 11 as the fabric 8 advances. The cut-off ends are
removed via the duct 901 shown in Fig. 1.
As shown in Fig. 8 , the free ends of introduced weft threads 2b (shown
in Fig. 7) that are sucked into the weft thread holding device 9, are held
and stretched by the weft thread holding device 9 until these weft
threads are bound by the warp threads 3.
Figs. 9 and 10 schematically show a second embodiment of a device 1
for catching and stretching a weft thread inserted into a shed of a weav
ing machine, wherein Fig. 9 shows a view similar to the view of the de
vice shown in Fig. 2, and Fig. 10 shows in more detail a guiding device
10. For the same or similar elements, identical reference signs are used
and no detailed description of these elements is provided. In the em
bodiment according to Figs. 9 and 10, the guiding device 10 is provided
with an active thread clamp 105. The guiding device 10 is arranged on
the sley for movement with the reed 5 . The guiding device 10 is positioned
at a distance from the reed 5 away from the beat-up line 800 in
order to avoid interference of the guiding device 10 with the weft threads
upon insertion of the weft threads.
The thread clamp 105 of Fig. 9 is shown in more detail in Fig. 10. The
thread clamp 105 is an active thread clamp, which is driven by a pneu
matic drive 15 . The thread clamp 105 comprises a bottom, fixedly a r
ranged jaw 16 and a top, movably mounted jaw 17, which is driven
pneumatically. In the depicted embodiment, the fixedly arranged jaw 16
comprises an elastically mounted clamping element 160 that is formed
by a plate 161 that is supported by an elastic layer 162. The clamping
element 160 has for example a substantially flat clamping surface. The
elastic layer 2 is for example formed by a restoring element exerting a
return force, for example an elastic layer 162 in the shape of a synthetic
layer or a rubber layer. Such an elastic layer 162 preferably also has
damping properties. This allows obtaining a correct clamping function.
The plate 161 forms a wear-resistant layer and consists for example of a
metal plate. The movably arranged jaw 17 comprises a clamping part
170 that can co operate with the clamping element 160. The clamping
part 170 has for example a substantially flat clamping surface.
The movably arranged jaw 17 is formed integrally with a drive lever arm
18 which can be driven in both directions by the pneumatic drive 15.
The pneumatic drive 15 comprises pneumatic cylinders 15 1 and 152.
The drive lever arm 18 and the movably arranged jaw 17 are part of a
unit, which is mounted rotatable about an axis 19. The pneumatic cylin
ders 15 1, 152 are respectively connected to a compressed air source
(not shown) via shut-off valves (not shown). The compressed air source
can be the same as the compressed-air tank 13 shown in Fig. 1. In pre
ferred embodiments, a control unit is provided for controlling the shut-off
valves. In preferred embodiments, the control unit used for controlling
the shut-off valves can also control various other components of the
weaving machine, for example the valve 13 1 shown in Fig. 1. According
to the depicted embodiment, the thread clamp 105 further comprises a
stop lever arm 20 that can co-operate with a stop 2 1. The stop 2 1 can be
mounted in an adjustable position by a positioning element 22, for ex
ample a setting screw. Further, in the embodiment shown the stop 2 1
comprises a stopping element 23 that can co-operate with the stop lever
arm 20 and that for example is formed of a material with damping prop
erties.
The operation is as follows: When the thread clamp 105 is closed with a
certain force, the clamping part 170 and the clamping part of the clamping
element 160 contact each other and the stop lever arm 20 beats up
against the stop 2 1, so that the clamping force is restricted and the
moveable jaw 17 does not act with full force on the plate 161 of the f ix
edly arranged jaw 16.
According to a variant, the stopping element 23 features damping prop
erties and this allows an elastic deformation during the co-operation with
the stop lever arm 20. When the stop lever arm 20 beats up against the
stop 2 1, impact forces are damped. Therefore, it is possible to control
the pneumatic drive 15 with a large force, so that the thread clamp 105
can close fast enough and there is also sufficient clamping force present
just after the closing, while the damping properties of the stopping ele
ment 23 are advantageous to restrict the impact of the beating up
against the stop 2 1.
The pneumatically driven thread clamp 105 is adapted to allow to be
controlled for opening or closing in any position of the sley 500. In pre
ferred embodiments, the thread clamp 105 is controlled for clamping an
inserted weft thread upon the beat-up motion of the reed 5. The inserted
weft thread is caught and stretched by the weft thread stretching device
7 and transferred to the thread clamp 105 when the thread clamp 105
passes the weft thread stretching device 7. The weft thread 2a caught
by the thread clamp 105 is subsequently introduced into the weft thread
holding device 9 . Upon this transfer to the weft thread holding device 9
the thread clamp 105 is operated to release the caught weft thread 2a.
Preferably the guiding device 10 comprising a thread clamp 105 is also
provided with an adjustable stopping element 103, which defines the
depth of the opening formed by the two clamping elements 160, 170. In
case the drive 15 of the thread clamp 105 is not driven, the thread clamp
105 of Fig. 10 can herewith act as the hook-shaped guiding element 100
of Fig. 4. In case the drive 15 of the thread clamp 105 is driven, the
thread clamp 105 of Fig. 10 can also act as the hook-shaped guiding
element 100 of Fig. 4 that guides the caught weft thread 2a towards the
weft thread holding device 9 and can thereby, for example for relatively
elastic weft threads, in addition to the weft thread stretching device 7
prevent that the weft thread is pulled back into the fabric.
Fig. 11 and 12 show a variant embodiment of a weft thread holding de
vice 9 to be used in a device 1 shown in Fig. 1 or 9. The weft thread
holding device 9 shown in Figs. 11 and 12 comprises a suction opening
903, which is formed by a tube. The aperture of the suction opening 903
faces the reed 5. At a distal end of the suction opening 903 the entry slit
900 is provided.
The entry slit 900 is formed by two grooves 907, 908, which are a r
ranged into the tube that is forming the suction opening 903. The two
grooves 907, 908 are provided in two parallel planes. The groove 908
which is arranged in use of the weft thread holding device 9 closer to the
fabric edge 801 (see Fig. 1 or 9) is sufficiently long in order to allow in
troduced weft threads to be held and stretched until these are bound by
the warp threads 3 without bending the introduced weft threads about a
ground of the groove 908, i.e. for allowing the weft threads to extend in
an essentially straight line between the weft thread holding device 9 and
the fabric edge 801 . The groove 907 at the opposite side of the suction
opening 903 is provided with two mutually opposing retaining edges 905.
The retaining edges 905 are slightly inclined towards the inside of the
weft thread holding device 9 in order to allow an undisturbed introduction
of a weft thread (not shown), while restricting a retraction or withdrawal
of the introduced weft thread. The retaining edges 905 are preferably
provided at an entry region 904 of the entry slit 900 as shown in Figs. 11
and 12. Therefore, the groove 908 is longer than the groove 907. In
other embodiments, the groove 907 extends beyond the retaining edges
905 provided for example in the form of a number of barbs and has the
same length as the groove 908.
An auxiliary nozzle 14 is provided in the region of the entry slit 900 of the
weft thread holding device 9, which auxiliary nozzle 14 is blowing to
wards the inside of the weft thread holding device 9.
The device, the weaving machine with the device and the method according
to the invention are of course not limited to the embodiments,
which have been described by way of example and are illustrated in the
figures. The device, the weaving machine and the method can likewise
be embodied within the claims in accordance with variant embodiments,
shapes and dimensions. Combinations of the illustrated embodiments
that fall under the claims are also possible.
WO 2013/117564 PCT/EP2013/052280
Claims
1. Device for catching and stretching a weft thread (2) inserted into a
shed of a weaving machine, comprising a weft thread stretching device
(7) arranged stationary on the weaving machine in an extension of an
insertion path of the weft thread (2) for catching the leading end part of
the inserted weft thread (2) and stretching the caught weft thread (2a), a
weft thread holding device (9) arranged stationary on the weaving ma
chine in a region of a beat-up line (800) for holding the leading end part
of at least one beaten up weft thread, and a moveable guiding device
(10) for guiding the caught weft thread (2a) towards the weft thread hold
ing device (9), wherein the guiding device ( 0) is adapted for limiting a
displacement of the caught weft thread (2a) in a direction transverse to
the moving direction of the guiding device ( 10) upon guiding the caught
weft thread (2a) towards the weft thread holding device (9), character
ized in that the guiding device ( 10) is arranged on a sley (500) for
movement with the sley (500), wherein the guiding device ( 10) is posi
tioned at a distance from a reed (5) away from the beat-up line (800) in
order to avoid interference of the guiding device ( 10) with weft threads
(2) upon insertion of the weft threads (2).
2. Device for catching and stretching a weft thread according to claim
1, characterized in that the weft thread holding device (9) is provided
with an entry slit (900) between a fabric edge (801 ) of the fabric (8) and
the movement path of the guiding device ( 10), which entry slit (900) is
adapted for receiving a weft thread (2) transversally to its longitudinal
direction.
3. Device for catching and stretching a weft thread according to claim
2 , characterized in that the entry slit (900) is adapted for retaining a weft
thread introduced into the weft thread holding device (9) via the entry slit
(900), for example the entry slit (900) is delimited by at least one retain
ing edge (905), preferably two mutually opposing retaining edges (905).
4. Device for catching and stretching a weft thread according to claim
1, 2 or 3, characterized in that the guiding device ( 10) comprises a hookshaped
guiding element ( 100) provided with a recess ( 10 1) having in
wardly converging sidewalls (102) for receiving the weft thread (2).
5 . Device for catching and stretching a weft thread according to claim
4 , characterized in that the guiding device ( 10) comprises an adjustable
stopping element ( 103) for adjusting the depth of the recess (101 ) .
6 . Device for catching and stretching a weft thread according to any
one of claims 1 to 5 , characterized in that the weft thread holding device
(9) comprises a suction nozzle (902) with a suction opening (903), at
which suction opening (903) the entry slit (900) is provided.
7. Device for catching and stretching a weft thread according to claim
6, characterized in that at least at an entry region of the entry slit (900) a
cross section of the entry slit (900) decreases from a distal end towards
the suction nozzle (902) for leading the weft thread towards the suction
nozzle (902) of the weft thread holding device (9).
8. Device for catching and stretching a weft thread according to any
one of claims 2 to 7, characterized in that at least one auxiliary nozzle
(14) is provided in the region of the entry slit (900) of the weft thread
holding device (9) blowing towards the inside of the weft thread holding
device (9) in a direction away from the reed (5).
9. Device for catching and stretching a weft thread according to any
one of claims 1 to 8, characterized in that the weft thread stretching de
vice (7) comprises a suction nozzle, in particular a ring-jet suction nozzle,
the opening of which is directed towards a guiding channel (509) of
the reed (5), if the reed (5) is in its most rearward position, away from
the beat-up line (800).
10. Device for catching and stretching a weft thread according to any
one of claims 1 to 9 , characterized in that an auxiliary suction nozzle
(12) is provided for removing wrongly inserted weft threads.
11. Device for catching and stretching a weft thread according to any
one of claims 1 to 10, characterized in that the weft thread stretching de
vice (7) is connected to a control unit, wherein the weft thread stretching
device (7) is controlled by the control unit so that the weft thread stretch
ing device (7) is activated upon insertion of a weft thread into the shed
for catching the inserted weft thread and is deactivated when or after the
caught weft thread (2a) is beaten up or has been beaten up.
12. Device for catching and stretching a weft thread according to any
one of claims 1 to 11, characterized in that the guiding device ( 10) is
provided with a thread clamp, in particular an active thread clamp (105).
13. Weaving machine, characterized in that the weaving machine
comprises a device ( 1) for catching and stretching a weft thread accord
ing to any one of claims 1 to 12.
14. Method for catching and stretching a weft thread (2) inserted into a
shed of a weaving machine, using a device ( 1) according to any one of
claims 1 to 12 with a weft thread stretching device (7), a weft thread
holding device (9) arranged stationary on the weaving machine in a re
gion of a beat-up line (800), and a moveable guiding device (10), a r
ranged for movement with a sley (500) and positioned at a distance from
a reed (5) away from the beat-up line (800), wherein the method com
prises: catching and stretching the leading end part of the weft thread (2)
at an extension of an insertion path of the weft thread (2) by means of
the weft thread stretching device (7), guiding the caught weft thread (2a)
towards the weft thread holding device (9) by means of the guiding de
vice ( 10) while limiting a displacement of the caught weft thread (2a) in a
direction transverse to the moving direction of the guiding device (10),
and introducing the caught weft thread (2a) into the weft thread holding
device (9) via an entry slit (900).
15 . Method for catching and stretching a weft thread according to
claim 14, characterized in that the weft thread holding device (9) is con
tinuously activated for taking over and holding inserted weft threads, and
the weft thread stretching device (7) is activated upon insertion of a weft
thread into the shed for catching the inserted weft thread and is deac
tivated when or after the caught weft thread (2a) is beaten up or has
been beaten up.