Device and method for clamping a weft thread
Technical Field
The invention relates to a device and a method for clamping a weft thread
in a weaving machine, more particularly in a rapier weaving machine.
Prior Art
When weaving, a weft thread positioned in the path of a gripper is gripped
by the gripper and inserted into the shed. The inserted weft thread is cut off
on the insertion side in order to allow a subsequent weft thread to be
inserted. It is known to position a weft thread to be inserted in the path of
the gripper by using a presenting element of a presenting device that is
arranged on the weaving machine next to the shed, for example as
described in EP 0 598 264 A .
It is further known to provide a clamping device arranged between a weft
presenting device and a weft thread cutter. For example, EP 0 644 286 A 1
relates to an apparatus for presenting weft threads on a rapier weaving
machine comprising a movably mounted weft thread clamping unit having
at least three weft thread clamps which are spaced apart in the direction of
movement of the clamping unit, a positioning device for moving each of the
weft thread clamps into a reference plane, which positioning device
comprises a stepping motor.
EP 0 421 349 A 1 describes a clamping device for a rapier weaving
machine. The clamping device comprises a first and a second gripping
body, which are movable up and down and are forced in a direction
towards a middle position, and a gripper element, which is movable up and
down between the first and the second gripping body, wherein the gripper
element is able to make contact with the first and second gripping body,
when positioned in the middle position between the first and second
gripping body, and is able to make contact with one of the gripping bodies
so that an open section is defined between the gripper element and the
other gripping body when positioned against one of the gripping bodies.
The drive means for moving the gripper element up and down are
designed as a cam and a lever, two solenoids or an electrical drive.
5
Brief description of the invention
It is the object of the invention to provide a device and a method for
clamping an inserted weft thread that allows a reliable clamping of an
l o inserted weft thread.
This object is solved by a device for clamping a weft thread in a weaving
machine, more particularly in a rapier weaving machine, the device
comprising a central clamping element, a first outer clamping element and
15 a second outer clamping element, wherein the central clamping element is
forced in two opposite clamping directions towards an intermediate
position, wherein the central clamping element being sandwiched between
the first outer clamping element and the second outer clamping element,
when the central clamping element is positioned in the intermediate
0 position, the device comprises further a drive device adapted for displacing
the central clamping element out of the intermediate position in two
clamping directions, a first clamping direction to at least one first position
and a second clamping direction to at least one second position, wherein in
the first position the central clamping element is at a distance from the first
5 outer clamping element and in the second position the central clamping
element is at a distance from the second outer clamping element, and
wherein the drive device comprises a pneumatic cylinder with at least one
piston, which piston is directly coupled to the central clamping element for
a transmission of motion.
0
The device for clamping a weft thread is also referred to as clamping
device. In the context of the invention with clamping direction is meant a
movement direction wherein the clamping elements move during the
opening or the closing of the clamps.
A pneumatic cylinder allows the central clamping element to be displaced
with a high reliability and at high speeds. In an embodiment, the central
clamping element is formed integrally with a piston and/or a piston rod. In
other embodiments, the elements are formed as separate parts, which are
mechanically coupled. The mechanical coupling in one embodiment is a
releasable connection, for example using screw elements. In other
embodiments, a permanent connection is chosen, for example by welding
or gluing the elements together. When using a pneumatic cylinder, desired
forces may be applied. The direct coupling of the central clamping element
to the piston allows to achieve a light-weight device suitable for co
operating with a pneumatic cylinder. In this case the piston is directly
coupled to the central clamping element for a transmission of movement in
the clamping direction.
Further, when providing a pneumatic cylinder, a compact structure may be
obtained. In absence of weft thread, the central clamping element makes
contact with the first outer clamping element and with the second outer
clamping element when the central clamping element is positioned in the
intermediate position.
According to an embodiment, the pneumatic cylinder is a double acting
pneumatic cylinder, more particularly a double acting pneumatic cylinder
which can be held in a first position, a second position and a third
intermediate position. The piston of the pneumatic cylinder is moveable in
the clamping direction. Providing a double acting pneumatic cylinder
allows the piston to adopt three positions and, hence, also to couple the
central clamping element directly to the piston to adopt three positions. In
a preferred embodiment, the piston is arranged vertical or essentially
vertical. With this arrangement, the piston may adopt a first upper piston
position when only the lower chamber of the pneumatic cylinder is
pressurized, adopt a second lower piston position when only the upper
chamber of the pneumatic cylinder is pressurized, and adopt a third
intermediate piston position when the loads applied on the piston are
balanced. Preferably, the loads applied on the piston are balanced when
none of the two chambers is pressurized. In this case, the central
clamping element will adopt an intermediate position when no pressurized
fluid is supplied. However, in other solutions, the intermediate position may
be adopted when the both chambers are pressurized.
In an embodiment, the pneumatic cylinder comprises at least a spring,
preferably two springs, loading the piston. The springs are adapted to hold
the piston in the third intermediate piston position, wherein also the central
clamping element is in its intermediate position. When using two springs, in
the third intermediate position the loads applied by the two springs are
balanced. When using only one spring the load applied by this spring in the
third intermediate position for example is almost negligible.
In preferred embodiments, the clamping device comprises a first force
element forcing the first outer clamping element towards the central
clamping element, a second force element forcing the second outer
clamping element towards the central clamping element, and at least one
abutment element for limiting a displacement of the first and the second
outer clamping element caused by the displacement of the central
clamping element and a force applied by the first and the second force
element on the first and the second outer clamping element, respectively.
The first and the second force element in preferred embodiments are
realized as spring elements. In an embodiment, the first and the second
force elements assume the functions of the springs of the pneumatic
cylinder, wherein the springs of the pneumatic cylinder may be omitted. In
other embodiments, the force elements are co-operating with the springs of
the pneumatic cylinder, wherein the loads applied by the force elements
are preferably chosen smaller than the forces applied by the springs of the
pneumatic cylinder.
According to another embodiment, at least one abutment element is
arranged between the first and the second outer clamping element,
wherein a height of the central clamping element is larger than a total
height of the at least one abutment element. In the context of the invention,
the total height of the at least one abutment element arranged between the
first and the second outer clamping element is defined as the distance
between two abutment surfaces limiting a movement of the first and the
second outer clamping element towards each other. If only one abutment
element is provided, the total height equals the height of this abutment
element. In preferred embodiments, the at least one abutment element is
centred with the central clamping element when the central clamping
element is arranged in the intermediate position. In other embodiments, the
at least one abutment element is a little off centre in one of the two
clamping directions. In both cases, the total height of the at least one
abutment element is smaller than the height or the thickness of the central
clamping element, in order to allow that both the first and the second outer
clamping element abut against the central clamping element in an
intermediate position. Because of that smaller height of the at least one
abutment element a play is achieved between the clamping elements and
the at least one abutment element which is advantageous to keep the
clamps in the intermediate position closed, in other words against the
central clamping element, what allows to always clamp a weft thread, even
if the clamping elements due to their sudden movements move or vibrate a
bit up and down, more in particular vibrate after the contacting of a
clamping element with the central clamping element, this means after the
closing of a clamp. In this case all clamping elements can vibrate together
over that play without one of the clamps opening and releasing a weft
thread.
According to an embodiment, the first outer clamping element and/or the
second outer clamping element are formed as a plate being fixed to a
guiding shaft. The length of the guiding shafts is chosen in an embodiment
in order to limit a movement of the outer clamping elements. The guiding
shafts may therefore assume the function of the at least one abutment
element. In other embodiments, the guiding shafts co-operate with an
abutment element provided between the outer clamping elements. The
plates provide a light-weight solution.
According to another embodiment, guiding shafts for the central clamping
element, the first outer clamping element and second outer clamping
element are coaxially arranged. In preferred embodiments, the piston rod
of the pneumatic cylinder functions as a guiding shaft for the central
clamping element. The piston rod extends through the central clamping
element, the first outer clamping element and the second outer clamping
element. The central clamping element is arranged in a fixed position on
the piston rod or is formed integrally with the piston rod. The first outer
clamping element and the second outer clamping element are provided
with feed-through openings for the piston rod. The guiding shafts for the
first outer clamping element and for the second outer clamping element are
formed as tubular shaped shafts arranged concentrically around the piston
rod.
In an embodiment, a receiving section of the clamps formed by the central
clamping element and the outer clamping elements are arranged
approximately perpendicular to the weft thread when the weft thread is
taken up by the associated clamp, because such an arrangement is
advantageous for catching the weft thread.
In alternative or in addition according to another embodiment, the distal
end of the central clamping element that is directed towards a weft thread
to be clamped forms an intake funnel with the distal end of the first outer
clamping element and/or with the distal end of the second outer clamping
element. This allows the weft thread to be taken up by the clamping device
more easily. The clamping device can be arranged in a fixed position on
the weaving machine.
According to an embodiment, the device also comprises an abutment
which limits the movement of the first outer clamping element in the second
position and/or an abutment which limits the movement of the second outer
clamping element in the first position. This limits vibrations that may arise
after reaching the first or second position of the clamping elements,
whereby it is avoided that a clamped weft thread is laying free in the clamp,
this means is let free, shortly after reaching the first or second position.
In preferred embodiments, the clamping device is arranged in a module.
The module allows an easy and reliable positioning on the weaving
machine. In an advantageous embodiment, the device is arranged in a
fixed position on the weaving machine, this means in a fixed position with
respect to a gripper path, a cloth line and a cloth edge. In preferred
embodiments, the fixed position is adjustable and may be chosen suitably
with respect to the gripper path, the cloth line and the cloth edge of the
woven cloth in order to clamp the inserted weft threads.
In an embodiment, the module further comprises at least one thread
guiding element arranged upstream of the clamping device according to
the invention in insertion direction. In the context of the invention with
insertion direction is meant the direction of the gripper movement. In
preferred embodiments, the thread guiding element is arranged close to
the gripper path in the vicinity of an area where the weft thread is taken up
by the gripper. Integrating a guiding element in a module allows a reliable
and simple assembly.
According to another embodiment, the module comprises in an alternative
or in addition at least one cutting device arranged downstream of the
central clamping element in weft direction. By providing a cutting device in
a position adjacent to the cloth edge between the clamping device
according to the invention and the cloth edge, inserted weft threads may be
cut essentially to the same length and the weft thread ends protruding
beyond the cloth edge may be kept to a minimum. In an embodiment, the
cutting device comprises a stationary jaw and a movable jaw, for example
of the type shown in WO 2009/007076 A . The content of which is hereby
incorporated by reference. In preferred embodiments, the module
comprising the clamping device and the cutting device is arranged next to
the cloth edge, wherein the weft thread ends may be cut to a length of less
than 10mm, for example to lengths between 4mm and 8mm. According to
an embodiment, the cutting device and the clamping device may be
arranged in a certain position and also mutually arranged at a certain
settable distance from each other. This setting may be either in the
insertion direction as in the warp direction. The cutting device and the
clamping device may herein be arranged as a unit or separately in a
certain position.
In an embodiment, the module is arranged to be moveable towards and
away from a gripper in a plane approximately parallel or parallel to the cloth
edge of the woven cloth. According to an embodiment, the module is
arranged at least partly on a rotatable shaft to be moved towards and away
from the gripper. The arrangement allows to bring the device close to the
gripper path in the vicinity of an area where a weft thread is taken up by the
gripper, because such an arrangement is advantageous for keeping a weft
thread end protruding beyond the thread clamp in the gripper short, which
allows to keep the thread end protruding beyond the cloth edge at the
opposite side of the shed under control, this means short.
The object is further solved by a method for clamping a weft thread in a
weaving machine, more particularly in a rapier weaving machine, wherein
an inserted weft thread is introduced in a device for clamping a weft thread
arranged next to a cloth edge of the woven cloth, wherein the device
comprises a central clamping element, a first outer clamping element and a
second outer clamping element, wherein the central clamping element
being forced in two opposite clamping directions to an intermediate
position, wherein the central clamping element being sandwiched between
the first outer clamping element and the second outer clamping element,
when the central clamping element is positioned in the intermediate
position, wherein the device further comprises a drive device adapted for
displacing the central clamping element from the intermediate position in
two clamping directions, a first clamping direction to at least one first
position and a second clamping direction to at least one second position,
wherein in the first position the central clamping element is at a distance
from the first outer clamping element and in the second position the central
clamping element is at a distance from the second outer clamping element,
and wherein compressed air is supplied to the drive device for displacing or
moving the central clamping element in at least one of the intermediate
position, the first position or the second position.
An actuating by supplying compressed air allows the central clamping
element to be displaced with a high reliability and at high speeds.
According to an embodiment, the drive device is a double acting pneumatic
cylinder having a first chamber and a second chamber, wherein the first
chamber is pressurized for moving the piston in the first position and a second
chamber is pressurized for moving the piston in the second position.
The weft thread is clamped by the clamping device before the cutting
device cuts the weft thread. For the subsequent insertion, the weft thread
is released by the clamping device. According to a further embodiment, the
gripper takes up a weft thread and the weft thread taken up by the gripper
is pulled out of a clamp of the clamping device while the clamp is still
closed. The clamp only opens afterwards by supplying compressed air.
Brief description of the drawings
In the following, embodiments of the invention will be described in detail
based on several schematic drawings. Throughout the drawings, the same
elements will be denoted by the same reference numerals.
Fig. 1 is a perspective view of a device for clamping a weft thread
arranged on a rapier weaving machine;
Fig. 2 is a top view of the device for clamping a weft thread of Fig. 1;
Fig. 3 is a perspective detailed view of a device for clamping a weft thread
of Fig. 1;
Fig. 4 is a perspective schematic partially cut and detailed view of a
central clamping element of the device for clamping a weft thread of
Fig. 1;
Fig. 5 is a perspective detailed view of an outer clamping element of the
device for clamping a weft thread of Fig. 1;
Fig. 6 is a perspective detailed view of the device for clamping a weft
thread of Fig. 1 in the intermediate position;
Fig. 7 is a view of the device of Fig. 6 in the first position;
Fig. 8 is a view of the device of Fig. 6 in the second position;
Fig. 9 is a perspective view of a device for clamping a weft thread
according to a second embodiment;
Fig. 10 is a second perspective view of the device for clamping a weft
thread of Fig. 9.
Fig. 11 is a top view of another device for clamping a weft thread according
to the invention.
Detailed description of embodiments
Fig. 1 and 2 show a perspective view and a top view of a device 1 for
clamping a weft thread, arranged on a rapier weaving machine, also
named gripper weaving machine. The rapier weaving machine is only
partly shown. The rapier weaving machine comprises presenting devices 2
for weft thread and a gripper 3. In the depicted embodiment, also a thread
guiding element 4 and a cutting device 5 for weft thread are provided. In
the depicted embodiment, the cutting device 5 is attached to the frame of
the device 1 for clamping weft thread 6 and forms an assembly with the
device 1 for clamping weft thread 6 .
Weft threads 6 are schematically shown in Fig. 2 . According to the
insertion direction N, a weft thread 6 runs from the presenting device 2 , via
the gripper 3 , the thread guiding element 4 , the device 1 for clamping a
weft thread 6 , and the cutting device 5 to the cloth edge 8 and the woven
cloth 9 with the cloth line 7 . The cloth 9 can in this case support on a cloth
support not shown. As indicated in Fig. 2 the cloth edge 8 is a side edge of
the cloth 9 that extends in warp direction, while the cloth line 7 is the
beat-up edge of the cloth 9 that extends in weft direction.
The thread guiding element 4 is preferably fixedly arranged on the weaving
machine. The thread guiding element 4 comprises a guide plate 1
arranged near the gripper 3 , which guide plate 11 is directed in the
insertion direction N. Further a guide plate 12 is provided between the
gripper 3 and the presenting device 2 which is directed in the insertion
direction N in order to support a weft thread 6 to be inserted close to the
presenting device 2 at the gripper 3 .
The device 1 for clamping a weft thread is described in more detail with
reference to Figures 3 to 8 , showing the device 1 for clamping a weft
thread and parts of the device 1 for clamping a weft thread in detail.
The device 1 comprises a central clamping element 10 shown in more
detail in Fig. 4 , a first outer clamping element 15 , and a second outer
clamping element 16 , as shown in Fig. 5 . As best seen in Fig. 6 , the central
clamping element 10 is movable supported, this means is forced in two
opposite clamping directions to an intermediate position P shown in
amongst others Fig. 6 . The central clamping element 10 is sandwiched
between the first outer clamping element 15 and the second outer
clamping element 16 and makes contact with the first outer clamping
element 15 and the second outer clamping element 16 when positioned in
the intermediate position P. In other words, both the first clamp 20 formed
by the central clamping element 0 and the first outer clamping element 5
and the second clamp 2 1 formed by the central clamping element 10 and
the second outer clamping element 16 are closed in the intermediate
position P in order to clamp a weft thread, each. In the depicted
embodiment, two force elements 8 , 19 designed as springs are provided
in order to force the first outer clamping element 15 towards the central
clamping element 10 , and the second outer clamping element 16 towards
the central clamping element 10 , respectively.
The device 1 further comprises a drive device 22 adapted for displacing,
this means moving the central clamping element 10 out of the intermediate
position P as shown in Fig. 6 in two clamping directions K and L, this
means in a clamping direction K to at least one first position and in a
clamping direction L to at least one second position, for example in one
clamping direction K downwards and in the other clamping direction L
upwards in the orientation of the device 1 as shown in the figures 6 to 8 ,
wherein as shown in Fig. 7 , in the first position the central clamping
element 10 is at a distance from the first outer clamping element 15 , for
example in case of an opened first clamp 20, and as shown in Fig. 8 , in the
second position the central clamping element 10 is at a distance from the
second outer clamping element 16 , for example in case of an opened
second clamp 2 1.
As may be seen best in Fig. 4 , the drive device 22 is a pneumatic double
acting cylinder 30 comprising a piston 23, which piston 23 is directly
coupled to the central clamping element 10 for a transmission of motion via
the piston rod 24 of the piston 23. The central clamping element 10, the
piston rod 24 and the piston 23 are mechanically coupled or manufactured
as an assembly, so that the central clamping element 10 is moved directly
by the piston 23. The piston 23 is herein balanced by two springs 13, 14
each provided in a chamber 27 or 28, also named pressure chamber,
which springs 13 , 14 force the piston 23 in a central position as long as no
compressed air is fed. In consequence, without a pressure supply, the
central clamping element 10 is held in the intermediate position. In other
embodiments, the intermediate position is obtained by feeding compressed
air to both chambers 27, 28. However, in this case it has to be ensured that
no unbalancing due to pressure losses or similar effects occurs in order to
avoid that the central clamping element 10 is forced in a direction, while
supplying compressed air to both chambers 27, 28.
The outer clamping elements 15 and 16 are movable arranged and the two
force elements 18 , 19 ensure that the first clamp 20 and the second clamp
2 1 initially remain closed upon displacement of the central clamping
element 10 . The device 1 further comprises an abutment element 17
arranged between the first outer clamping element 15 and the second
outer clamping element 16 in the movement path of the outer clamping
elements 15 , 16 , wherein a height H 1 of the central clamping element 10 is
larger than a height H2 of the abutment element 17, as may be seen in
Figures 5 and 6 . The difference in height between H 1 and H2 defines the
play over which the clamping elements 15 and 16 , which are part of a
mass and spring system, are able to move or vibrate without making
contact with the abutment element 17 and without the clamps 20 and 2 1
are opened and release a weft thread. The play is herein chosen taking
into account the properties of the mass and spring system and the
damping present in this mass and spring system. When the central
clamping element 10 is arranged in the intermediate position as shown, the
abutment element 17 does not make contact with any of the outer clamping
elements 15 or 16. The depicted abutment element 17 is fork shaped,
wherein the two tips of the fork shaped element surround the central
clamping element 10 without limiting a movement of the central clamping
element 10 in the two clamping directions K and L . The two tips of the
abutment element 17 may limit the movement of the clamping elements 15
and 16 by abutting against broadenings provided at the clamping elements
15 and 16 .
According to an embodiment not shown two abutment elements are
provided, for example each of which formed by a fork shaped element.
These two abutment elements are arranged at a distance from one another
and can each co-operate with an associated outer clamping element 15 or
16, and in this way function together as the one piece clamping element
17 .
When moving the central clamping element 10 downwards in clamping
direction K, the force element 18 loads the first outer clamping element 15
in order to follow the movement of the central clamping element 10 until the
first outer clamping element 15 abuts against the abutment element 17 so
that the first clamp 20 opens, while the second clamp 2 1 remains closed.
When moving the central clamping element 10 upwards in clamping
direction L , the force element 19 loads the second outer clamping element
16 in order to follow the movement of the central clamping element 10 until
the second outer clamping element 16 abuts against the abutment element
17 so that the second clamp 2 1 opens, while the first clamp 20 remains
closed. In an embodiment, the abutment element 17 and the central
clamping element 10 are aligned in an intermediate position, wherein
through a slit 65 a positioning screw 29 is provided for aligning the
abutment element 17 in relation to the central clamping element 10 in the
intermediate position. As may be seen in Fig. 4 an alien screw 60 is
arranged rotatable in the housing 22. By screwing the alien screw 60 more
or less into the housing 22, the intermediate position of the piston 23 can
be set relatively accurately and also the force applied by the springs 13
and 14 on the piston 23 can be set.
As mentioned above, the drive device 22 is a pneumatic acting double
cylinder 30 comprising a piston 23, arranged between two chambers 27
and 28, wherein a spring 13, 14 is provided in each chamber 27, 28.
Compressed air is supplied to each of the two chambers 27, 28 via
respective ducts 3 1, 32 with valves 33, 34 for interrupting the air supply.
By supplying compressed air via the duct 3 1 and the valve 33 in the
chamber 27 of the spring 13, the central clamping element 10 and the two
outer clamping elements 15 , 16 are moved downwards until the first outer
clamping element 5 abuts against the abutment element 17 so that the
first clamp 20 opens and the second clamp 2 1 remains closed. If
compressed air is supplied via the duct 32 and the valve 34 in the chamber
28 of the spring 14, the central clamping element 10 and the two outer
clamping elements 15 , 16 are moved upwards until the second outer
clamping element 16 abuts against the abutment element 17 so that the
second clamp 2 1 opens and the first clamp 20 remains closed. If no
compressed air is fed, then the springs 13 , 14 force the central clamping
element 0 in its intermediate position. The strength of the springs 3 and
14 is preferably higher than the strength of the force elements 18, 19 .
In an alternative embodiment, the force elements 18 , 19 take over the
function of the springs 13 and 14 and the springs 13 , 14 may be omitted. In
this case, a balancing of the force elements 18 , 19 is to be ensured.
In the embodiment shown, the outer clamping elements 5 , 16 are formed
as plates that are fixed on guiding shafts 25, 26. The guiding shafts 25, 26
are of tubular shape and coaxially arranged with the piston rod 24, so that
the guiding shafts 25, 26 surround the piston rod 24 and the piston rod 24
is displaceable inside the tubular shaped guiding shafts 25, 26. The tubular
shaped guiding shafts 25, 26 allow that the outer clamping elements 15
and 16 move coaxially with the guiding shafts 25, 26, but independent of
the piston rod 24. In the embodiment shown, the length of the tubular
shaped guiding shafts 25, 26 is further chosen so that the movement of the
outer clamping elements 15 , 16 is limited by additional abutments 5 1 , 52.
The abutment 5 1 forms part of a ring element 66 and limits the movement
of the first clamping element 15 in the second position, while the abutment
52 forms part of a ring element 67 and limits the movement of the second
clamping element 16 in the first position. When the first outer clamping
element 15 via the guiding shaft 25 abuts against the abutment 5 1, the first
outer clamping element 15 is almost not able to vibrate, since the first outer
clamping element 15 is held between the abutment 5 1 and the central
clamping element 10, and a weft thread is with certainty clamped further by
the clamp 20. When the second outer clamping element 16 via the guiding
shaft 26 abuts against the abutment 52, the second outer clamping
element 16 is almost not able to vibrate, since the second outer clamping
element 16 is held between the abutment 52 and the central clamping
element 10 , and a weft thread is with certainty clamped further by the
clamp 2 1. At the tubular shaped guiding shafts 25, 26 the outer clamping
elements 15 , 16 respectively have a feed-through opening 6 1, 62 where
through the piston rod 24 is movable.
In an embodiment shown, the central clamping element 10 is provided with
a distal end 53 shaped as a wedge shaped tip. The distal end 54 of the first
outer clamping element 15 and the distal end 55 of the second outer
clamping element 16 are each bent away from the central clamping
element 10 , more particularly bent in such a way that the distal ends 54, 55
each form an intake funnel 56, 57 with the distal end 53 of the central
clamping element 10. The distal ends 53 and 54 form a receiving section
58 for the one weft thread, while the distal ends 53 and 55 form a receiving
section 59 for the other weft thread.
As best seen in Fig. 3 , the device 1 is arranged in a module 35 and can be
positioned with respect to the weaving machine using two positioning
elements 36, 37. This allows a reliable and easy positioning of the device
1. The module 35, for example, comprises also the thread guiding element
4 that is arranged in insertion direction N upstream of the central clamping
element 10 of the device 1. The module 35, for example, also comprises
the cutting device 5 that is arranged in insertion direction N downstream of
the central clamping element 10 of the device 1. According to a variant not
shown, all aforementioned elements may be arranged separately at a
settable distance from each other.
Fig. 9 and 10 show an alternative embodiment, wherein the device 1 is
provided with a module 35, which module 35 is arranged to be movable
towards and away from the gripper 3 according to arrow P in a plane
parallel or approximately parallel to the cloth edge 8 of the woven cloth 9 .
The device 1 is similar to the device of Figures 1 to 8 and the same or
similar elements will be denoted by the same reference numerals. In the
depicted embodiment, an arm 38 is provided that can be moved to and fro
by a drive mechanism 39, such as a cam drive mechanism, arranged on a
frame 40. The device 1 is attached to the arm 38.
The arm 38 is arranged on a rotatable shaft 4 1, which shaft 4 1 is driven via
a rod 42, a coupling rod 43 and a lever 44 by the cams 48. The position of
the coupling rod 43 on the lever 44 may be adjusted by using a bolt 45
arranged in a slot 46 provided on the lever 44 in order to set the moving
course of the device . A spring 47 forces the lever 44 into contact with the
cams 48. In preferred embodiments, the drive axis 49 for the cams 48 is
synchronised with the movement of the weaving machine, for example via
a mechanical coupling or via a drive by an own controllable drive motor, in
order to avoid that the device 1 according to the invention may come into
contact with a reed 50 or with a sley 63 on which a reed can be fixed,
shown in Fig. 2 . In an alternative embodiment, instead of a drive system
with cams, a pneumatic system and/or an electromagnetic system can be
provided for moving the device 1 towards and away from the gripper 3 . In
an embodiment, the valves 33, 34 for regulating the supply of compressed
air via the ducts 3 1, 32 are fixedly arranged on the frame 40. By moving
the arm 38 in the rotation direction R, the device 1 according to the
invention may be positioned towards or away from the gripper 3 . Herein the
device 1 can be arranged close to the gripper 3 during the taking up of a
weft thread by the gripper 3 and during the taking up of a weft thread by
the device 1 be arranged away from the gripper 3 and almost be arranged
in the elongation of the cloth line 7 .
According to the embodiment of Fig. 11 at the thread guiding element 4 , for
example at the guiding plate 1 at the side of the thread guiding element 4
faced away from the cloth edge 8 , a suction nozzle 64 may be arranged for
catching and holding weft threads that are released unwanted from the
device 1 for clamping a weft thread. This allows to still catch and keep such
weft threads in the suction nozzle 64, so that these weft threads still can be
taken up and inserted by the gripper 3 during a next insertion and
subsequently be clamped again in the device 1 for clamping weft thread
according to the invention.
During the insertion of a weft thread, the device 1 is brought in such a
position that the inserted weft thread can be taken up in an opened clamp
20 or 2 1 and subsequently be clamped by closing this clamp 20, 2 1.
Preferably, the device 1 is arranged so that during the taking up the weft
thread extends almost perpendicular to the direction of the taking up of the
weft thread in the clamp 20 or 2 . Subsequently the clamped weft thread is
cut off by the cutting device 5 between the device 1 and the cloth 9 . During
a subsequent insertion a weft thread presented by the presenting device 2
is taken up by the gripper 3 and inserted in the shed, wherein this weft
thread is pulled out of the device 1 by the gripper 3 while the associated
clamp 20, 1 is preferably still closed and the weft thread is released by the
device 1. Preferably, the associated clamp 20 or 2 1 is opened afterwards
in order to take up an inserted weft thread.
The device 1 for clamping a weft thread is adapted to co-operate with two
weft threads. However, in embodiments not shown several such devices
for clamping a weft thread are provided. The devices for clamping a weft
thread are preferably each arranged on a movable frame, which thus
allows to weave with more than two weft threads and more than two
presenting devices for weft thread. In an embodiment, two devices
according to the invention are used which are arranged mirror symmetrical
to each other. At the cloth edge 8 the cloth 9 can be bound by so-called
leno-threads which are arranged approximately parallel to and next to the
warp threads.
The device and the method for clamping a weft thread according to the
invention are not limited to the embodiments shown and described by way
of example, but can also comprise variants and combinations of these
embodiments that fall under the claims.
Claims
1. Device for clamping a weft thread (6) in a weaving machine, the
device ( 1) comprises a central clamping element ( 10), a first outer
clamping element ( 15) and a second outer clamping element ( 16),
wherein the central clamping element ( 10) is forced in two opposite
clamping directions (K, L) to an intermediate position (P), wherein
the central clamping element ( 10) is sandwiched between the first
outer clamping element ( 15) and the second outer clamping element
( 16) when the central clamping element ( 10) is positioned in the
intermediate position (P), the device ( 1) further comprises a drive
device (22) adapted for displacing the central clamping element ( 10)
out of the intermediate position (P) in two clamping directions (K, L),
a first clamping direction (K) to at least a first position and a second
clamping direction (L) to at least a second position, wherein in the
first position the central clamping element (10) is at a distance from
the first outer clamping element ( 15) and in the second position the
central clamping element ( 10) is at a distance from the second outer
clamping element ( 16), characterized in that the drive device (22)
comprises a pneumatic cylinder (30) comprising at least a piston
(23), which piston (23) is directly coupled to the central clamping
element ( 10) for a transmission of motion.
2 . The device according to claim 1, characterized in that the pneumatic
cylinder (30) is a double acting pneumatic cylinder, which is
displaceable to the intermediate position, the first position and the
second position.
3 . The device according to claim 1 or 2 , characterized in that the
pneumatic cylinder (30) comprises at least a spring ( 13 , 14),
preferably two springs, loading the piston (23).
4 . The device according to any one of claims 1 to 3 , characterized in
that the device ( 1) further comprises a first force element ( 18) forcing
the first outer clamping element ( 15) towards the central clamping
element ( 0), a second force element (19) forcing the second outer
clamping element (16) towards the central clamping element ( 10),
and at least one abutment element ( 17) for limiting a displacement of
the first and the second outer clamping element ( 15, 16) caused by
the displacement of the central clamping element ( 0) and a force
applied by the first or the second force element ( 18 , 19) on the first
and the second outer clamping element ( 15, 16), respectively.
5 . The device according to claim 4 , characterized in that at least one
abutment element ( 17) is arranged between the first and the second
outer clamping element ( 15, 16), wherein a height (H1 ) of the central
clamping element ( 10) is larger than the total height (H2) of the at
least one abutment element ( 17).
6 . The device according to any one of claims 1 to 5, characterized in
that the first outer clamping element ( 15) and/or the second outer
clamping element ( 16) are formed as a plate, which plate being fixed
to a guiding shaft (25, 26).
7. The device according to any one of claims 1 to 6 , characterized in
that the outer clamping elements ( 15 , 16) comprise a guiding shaft
(25, 26) that is guided coaxiaily with respect to a piston rod (24) of
the piston (23).
8 . The device according to any one of claims 1 to 7 , characterized in
that the central clamping element ( 10) comprises a distal end (53),
wherein the distal end (53) facing a weft thread (6) to be clamped
forms an intake funnel (56, 57) with the distal end (54) of the first
outer clamping element ( 15) and/or with the distal end (55) of the
second outer clamping element ( 16).
9 . The device according to any one of claims 1 to 8, characterized in
that the device ( 1) comprises an abutment (51 ) which limits the
movement of the first outer clamping element (15) in the second
position and comprises an abutment (52) which limits the movement
of the second outer clamping element ( 6) in the first position.
10 . The device according to any one of claims 1 to 9 , characterized in
that the device (1) is arranged in a module (35).
11. The device according to claim 10 , characterized in that the module
(35) further comprises at least a thread guiding element (4) arranged
upstream of the central clamping element ( 10) in insertion direction
(N).
The device according to claim 10 or 11, characterized in that the
module (35) comprises at least a cutting device (5) arranged
downstream of the central clamping element ( 10) in insertion
direction (N).
The device according to any one of claims 10 to 2 , characterized in
that the module (35) is arranged to be movable towards and away
from a gripper (3) in a plane approximately parallel or parallel to the
cloth edge (8) of the cloth (9).
Method for clamping a weft thread (6) in a weaving machine,
wherein an inserted weft thread is introduced in a device ( 1) for
clamping a weft thread (6) arranged next to a cloth edge (8) of the
cloth (9), wherein the device ( 1) comprises a central clamping
element ( 10), a first outer clamping element ( 15) and a second outer
clamping element (16), wherein the central clamping element ( 0) is
forced in two opposite clamping directions (K, L) to an intermediate
position (P), wherein the central clamping element ( 10) is
sandwiched between the first outer clamping element ( 15) and the
second outer clamping element ( 16) when the central clamping
element ( 10) is positioned in the intermediate position (P), wherein
the central clamping element ( 10) is displaceable from an
intermediate position (P) in two clamping directions (K, L), a first
clamping direction (K) to at least a first position, wherein the central
clamping element ( 0) is at a distance from the first outer clamping
element (15), and a second clamping direction (L) to at least a
second position, wherein the central clamping element ( 10) is at a
distance from the second outer clamping element (16), characterized
in that compressed air is supplied to a drive device (22) for
displacing the central clamping element (10) in at least one of the
intermediate position, the first position or the second position.
15 . Method according to claim 14, characterized in that the drive device
(22) is a double acting cylinder (30) with a first chamber (27) and a
second chamber (28), wherein the first chamber (27) is pressurized for
moving the cylinder (30) in the first position and a second chamber (28) is
pressurized for moving the cylinder (30) in the second position.
16. Method according to claim 14 or 15, characterized in that the weft
thread (6) is taken up by a gripper (3) and the weft thread (6) taken
up by the gripper (3) is pulled out of the clamp (20, 21) while the
clamp (20, 21) is still closed.