EP3022345B1

EP3022345B1 - Back rest device for a weaving machine

Info

Publication number: EP3022345B1
Application number: EP14739072.8A
Authority: EP
Inventors: Patrick Debergh; Ignace Meyns; Koenraad Vandecasteele
Original assignee: Picanol NV
Current assignee: Picanol NV
Priority date: 2013-07-15
Filing date: 2014-06-23
Publication date: 2019-04-03
Anticipated expiration: 2034-06-23
Also published as: WO2015007461A2; WO2015007461A3; EP3022345A2; TR201909154T4; CN105378170A; CN105378170B; BE1021709B1

Description

The invention relates to a back rest device for guiding warp threads coming from a warp beam on a weaving machine, wherein the back rest device comprises a first guiding bar and a second guiding bar, which second guiding bar in use is arranged in parallel to the first guiding bar and upstream of the first guiding bar for deflecting warp threads coming from the warp beam. The invention further relates to a weaving machine comprising a back rest device and a method for arranging a back rest device on a weaving machine.
Back rest devices arranged between a warp beam and shed forming elements are known from the prior art. For example US 3,125,128 discloses a back rest device comprising a warp tensioning beam supported by one or more springs. The device further comprises a carrier beam and a shaft, wherein the warp tensioning beam is rotatably supported by arms connected to the shaft. Further, an outer tube rotatably supported by the carrier beam and surrounding the carrier beam, and a rod connected to the outer tube by means of brackets and disposed between the warp tensioning beam and the outer tube are provided. Warp threads unwound from a warp beam run over the warp tensioning beam. A portion of the warp threads runs directly from the warp tensioning beam to shed forming elements, whereas the remaining warp threads pass beneath the rod disposed between the outer tube and the warp tensioning beam. Depending on the angle of the outer tube supporting the rod, these warp threads are more or less tensioned. DE 2103406 discloses to provide a sheet passed over the warp beam for applying a braking pressure. FR 694.058 discloses a back rest device comprising a first guiding bar and a second guiding bar, which second guiding bar in use is arranged in parallel to the first guiding bar and upstream of the first guiding bar for deflecting warp threads coming from the warp beam, wherein in use the position of the second guiding bar with respect to the first guiding bar is not fixed and the second guiding bar is held in position by means of a counterweight.
US 1,573,777 discloses a back rest device comprising a first guiding bar and a second guiding bar, which second guiding bar in use is arranged fixed in position in parallel to the first guiding bar and upstream of the first guiding bar for deflecting warp threads coming from the warp beam. For an adjustment to different requirements, guiding bars of different sizes can be combined.
It is the object of the invention to provide a simplified back rest device allowing for a reliable tensioning of warp threads. It is further the object of the invention to provide a weaving machine with a simplified back rest device and a method for arranging a back rest device on a weaving machine and for tensioning warp threads.
This object is solved by a back rest device with the features of claim 1, a weaving machine with the features of claim 12 and a method with the features of claim 13. Preferred embodiments are defined in the dependent claims.
According to a first aspect, a back rest device for guiding warp threads coming from a warp beam is provided, comprising a first guiding bar, a second guiding bar, which second guiding bar in use is arranged in parallel to the first guiding bar and upstream of the first guiding bar for deflecting warp threads coming from the warp beam, a mounting device, which mounting device is arranged for mounting the first guiding bar in a fixed mounting position and in a non-rotatable manner, and a supporting device, which supporting device is arranged for supporting the second guiding bar so that in use the longitudinal axis of the second guiding bar is fixed in position with respect to the longitudinal axis of the first guiding bar, wherein the second guiding bar is mounted on the first guiding bar by means of the supporting device, and wherein the position of the longitudinal axis of the second guiding bar with respect to the longitudinal axis of the first guiding bar is settable, wherein in order to bring the longitudinal axis of the second guiding bar into a set position with respect to the longitudinal axis of the first guiding bar the first guiding bar is rotatable about its longitudinal axis to orient the first guiding bar in an angular position.
The second guiding bar is supported so that in use its longitudinal axis is fixed in position with respect to the first guiding bar. In other words, the second guiding bar is mounted fixed in position with respect to the first guiding bar in a plane perpendicular to the longitudinal axis of the second guiding bar. However, the second guiding bar in one embodiment is moveable with respect to the first guiding bar in the direction of its longitudinal axis.
The back rest device according to the invention is in particular suitable for weaving a heavy fabric. In the context of the application, a fabric having a cover factor in the order of magnitude of forty is defined as a heavy fabric. In the context of the application, the cover factor is the ratio of the area of the fabric covered by the threads to the whole area of the fabric, in other words the cover factor as expressed by the known basic model of Pierce. For weaving a heavy fabric, a first guiding bar having a sufficient rigidity is provided. Rigid elements made for example of stainless steel, tend to have a higher weight than less rigid elements. As the first guiding bar is mounted in a fixed mounting position, a higher weight is acceptable.
By providing a first guiding bar mounted in a non-rotatable manner, a tension is applied to the warp threads guided along the surface of the first guiding bar. The tension depends among others on a wrap angle. In the context of the application, the wrap angle is defined as the contact angle of the warp threads against the first guiding bar.
A diameter of a warp beam and, hence, a withdrawal angle of the warp threads from the warp beam is varying over time due to warp thread consumption. When deflecting the warp threads coming from the warp beam and supplied to the first guiding bar by means of the second guiding bar mounted so that its longitudinal axis is in a fixed position with respect to the longitudinal axis of the first guiding bar, the warp threads are supplied to the first guiding bar from a fixed position and with a fixed direction. Therefore, with the assumption that the withdrawal angle of warp threads leaving the first guiding bar is at least substantially constant, the warp threads are wrapped around the first guiding bar with a fixed wrap angle. Thereby, a known tension is applied to the warp threads by means of the first guiding bar during weaving from a full warp beam to an empty warp beam. In case the angle of warp threads leaving the second guiding bar is not constant, the influence of the variation of this angle on the tension applied to the warp threads by means of the second guiding bar during weaving is small.
Due to a contact with the warp threads, the second guiding bar will also tension the warp threads. As the second guiding bar is arranged substantially fixed in position in a plane perpendicular to its longitudinal axis, a wrap angle of the warp threads coming from the warp beam and deflected by the second guiding bar varies over time due to warp thread consumption. However, the second guiding bar is arranged so that the tension applied due to frictional effects is significantly less than the tension applied by the first guiding bar. For example, the second guiding bar is arranged rotatable and/or a supporting surface of the second guiding bar is chosen smaller in size. As a result, the variance of the wrap angle around the second guiding bar has no or at least no relevant influence on the tension applied.
The first guiding bar is mounted in a fixed mounting position, wherein in one embodiment, the fixed mounting position is settable for example by means of a support table.
As mentioned above, the tension depends among others on the wrap angle against the first guiding bar.
The position of the longitudinal axis of the second guiding bar with respect to the longitudinal axis of the first bar defines the wrap angle of the warp threads against the first guiding bar. By setting a position of the longitudinal axis of the second guiding bar with respect to the longitudinal axis of the first guiding bar, a wrap angle is chosen for applying a defined tension. In one embodiment, the second guiding bar is provided in a position for allowing a wrap angle of the warp threads against the first guiding bar between approximately 120 degrees and approximately 290 degrees.
When mounting the second guiding bar on the first guiding bar, a relative positioning of the second guiding bar and the first guiding bar is independent from the absolute mounting position of the first guiding bar.
The second guiding bar in one embodiment is mounted on the first guiding bar by two support elements provided at the two ends of the second guiding bar. Preferably, the supporting device comprises a plurality of support elements distributedly arranged over the length of the first guiding bar for supporting the second guiding bar. Thereby, a reliable support of a second guiding bar is ensured even when weaving a heavy fabric and using a second guiding bar having only a small stiffness or rigidity.
In one embodiment, plate-like elements arranged perpendicular to the first guiding bar and provided with through holes for receiving the second guiding bar are provided on the first guiding bar, wherein the second guiding bar is inserted from the side into the support elements.
In a preferred embodiment, hooks are provided as support elements, which hooks are distributedly arranged over the length of the first guiding bar. The second guiding bar is attached to or detached from such hooks by a radial and/or tangential displacement allowing for an easy handling.
According to one embodiment, the second guiding bar is supported moveably, in particular rotatably, in the hooks. When supporting the second guiding bar moveably, a force applied by the second guiding bar on the warp threads is reduced. When supporting the second guiding bar in a rotatable manner, for example a reciprocating rotatable manner, the second guiding bar in some embodiments is moveable with respect to the first guiding bar in the direction of its longitudinal axis.
Preferably, limit stops are provided for delimiting or preventing a movement of the second guiding bar in the direction of its longitudinal axis .
In one embodiment, the outer circumference of the first guiding bar is larger than the outer circumference of the second guiding bar, wherein in particular an outer circumference of the first guiding bar is larger than 500 mm, in particular between approximately 550 mm and approximately 800 mm and/or an outer circumference of the second guiding bar is between approximately 90 mm and approximately 230 mm. In other words, preferably, the outer circumference of the first guiding bar is larger than the outer circumference of known guiding bars. The larger outer circumference results in a more rigid structure allowing for a stronger tensioning of the warp threads. On the other hand, the second guiding bar is provided with a smaller outer circumference. Thereby, a lightweight product is provided allowing for an easy handling. In addition, the friction applied by the second guiding bar on the warp threads is negligible even when supporting the second guiding bar in a non-rotatable manner.
Preferably, either or both of the first guiding bar and the second guiding bar is a tubular element, in particular a circular tubular element. According to a variant, the first guiding bar and/or the second guiding bar has an oval cross-section. However, circular tubular elements are generally less expensive. In addition, a circular tubular element may be rotated in the mounting device prior to closing the mounting device for fixing the first guiding bar. As will be described in more detail below, such a rotation allows for a user friendly installation process. In one embodiment, bearing taps are provided on a tubular element having a non-circular cross section for allowing a rotation thereof during mounting.
According one embodiment, a wall thickness of the first guiding bar is between approximately 8 mm and approximately 15 mm and/or a wall thickness of the second guiding bar is between approximately 1 mm and approximately 5 mm. The wall thickness is chosen in order to reduce material costs and weight of the guiding bars, while ensuring a sufficient rigidity.
As mentioned above, preferably a position of the longitudinal axis of the second guiding bar with respect to the longitudinal axis of the first guiding bar is settable. To this end, in preferred embodiments, markers and/or limit stops are provided for indicating a plurality of pre-set positions for the longitudinal axis of the second guiding bar. This allows an aid for the operator when setting up the back rest device.
In one embodiment, the first guiding bar is mounted by a mounting device provided at least partly inside the first guiding bar. In preferred embodiments, the mounting device comprises two clamping elements for clamping the first guiding bar at its ends, in particular at its ends at the height of its outer circumference. Thereby, a more rigid mounting structure is provided.
According to a second aspect, a weaving machine comprising a back rest device arranged near a warp beam, in particular between a warp beam and shed forming elements is provided. The weaving machine is preferably designed to allow the weaving of heavy fabric. Preferably, when weaving heavy fabric also other parts of the weaving machine, such as a reed, a reed holder, a sley drive, healds, heald frames, heald frame drives, the warp beam, a warp beam drive, a cloth take up drive, and other elements are designed more rigid and/or more durable and/or are reinforced.
According to a third aspect, a method for arranging a back rest device comprising a first guiding bar, a mounting device, a second guiding bar, and a supporting device, on a weaving machine is provided, wherein the first guiding bar is inserted into the mounting device, warp threads supplied by a warp beam are arranged over the first guiding bar, and the second guiding bar is fixed to the supporting device to deflect the warp threads, wherein the second guiding bar is mounted on the first guiding bar by means of the supporting device, wherein after attaching the second guiding bar to the supporting device, the first guiding bar is rotated about its longitudinal axis for bringing the longitudinal axis of the second guiding bar into a set position with respect to the longitudinal axis of the first guiding bar, and the first guiding bar is mounted by the mounting device in a non-rotatable manner after the longitudinal axis of the second guiding bar is in the set position. In other words, the first guiding bar is rotated for positioning the second guiding bar in a plane perpendicular to its longitudinal axis.
By setting the position, a tension applied to the warp threads is adjusted.
In the following, embodiments of the invention will be described in detail based on several schematic drawings in which

Fig. 1: is a schematic perspective view of a back rest device;
Fig. 2: is a schematic side view of the back rest device similar to the back rest device of Fig. 1 configured for weaving a heavy fabric;
Fig. 3: is a schematic side view of the back rest device of Fig. 2 before setting up the back rest device;
Fig. 4: is a schematic side view of the back rest device of Fig. 2 set for weaving a very heavy fabric;
Fig. 5: is a schematic perspective view of a hook used in a supporting device of the back rest device of Fig. 1;
Fig. 6: is a schematic perspective view of the hook of Fig. 5 with a fixation element;
Fig. 7: is a schematic cross section of the first guiding bar with a hook from a first side of the guiding bar;
Fig. 8: is a schematic side view of the first guiding bar with a hook from the side opposite to the first side as in Fig. 7;
Fig. 9: is a schematic front view of a first guiding bar of the back rest device of Fig. 1;
Fig. 10: is a schematic side view of the back rest device similar to Fig. 2 set for weaving a heavy fabric.

Throughout the drawings, the same or similar elements will be denoted by the same reference numerals.
Fig. 1 is a schematic perspective view of a back rest device 2 mounted on a weaving machine 1 for guiding warp threads 7 coming from a warp beam 10. In figure 1, only one warp thread 7 is schematically shown. Of course, in use a plurality of warp threads is provided. A warp detector 12 is provided downstream of the back rest device 2, whereas the back rest device 2 is provided downstream of the warp beam 10. The back rest device 2 comprises a first guiding bar 3, a mounting device 4 at both side parts 16 of the weaving machine, a second guiding bar 5, and a supporting device 6. The back rest device 2 is arranged near the warp beam 10, in particular between the warp beam 10 and shed forming elements 15 (schematically shown in Fig. 2).
The first guiding bar 3 is a circular tubular element. Hence, the first guiding bar 3 is also referred to as tube. In the embodiment shown, the outer diameter of the first guiding bar 3 is between approximately 200 mm and approximately 250 mm. A wall thickness of the first guiding bar 3 is chosen to allowing for a sufficient stiffness of the first guiding bar 3. In one embodiment, the wall thickness is between approximately 10 mm and approximately 15 mm.
The first guiding bar 3 is provided with a smooth surface for preventing any damaging of the warp threads 7. The first guiding bar 3 is, for example, made of steel. In one embodiment a surface treatment is provided, so that the first guiding bar 3 has a hard chrome surface. Such a first guiding bar 3 is strong and durable. In another embodiment, the first guiding bar 3 is made of stainless steel, that is also strong and durable, but more expensive.
The mounting device 4 is arranged for mounting the first guiding bar 3 in a fixed mounting position and in a non-rotatable manner. In the embodiment shown, the mounting device 4 comprises two clamping elements 40 provided at both side parts 16 of the weaving machine 1 for clamping the two ends 34 of the first guiding bar 3. Each clamping element 40 comprises a fixed clamping part 41 and a moveable clamping part 42, between which the first guiding bar 3 is clamped. Before closing the clamping element 40 by means of the moveable clamping part 42, the first guiding bar 3 is rotatably supported by the fixed clamping part 41 having a semi-circular supporting surface. After closing the clamping element 40 by means of the moveable clamping part 42, the first guiding bar 3 is mounted in a non-rotatable manner, in other words is clamped in a non-rotatable manner. The clamping parts 41, 42 are clamped around the first guiding bar 3, for example using fastening means 43 such as screw means. The clamping elements 40 are arranged for allowing the application of a high clamping force. The position of the mounting device 4 is adjustable by means of the support tables 14 or along the support tables 14 of the weaving machine 1, so that the position is adjustable as well in horizontal direction as in vertical direction.
The second guiding bar 5 in use is arranged in parallel to the first guiding bar 3 and upstream of the first guiding bar 3 for deflecting warp threads 7 coming from the warp beam 10. The supporting device 6 is arranged for supporting the second guiding bar 5 with its longitudinal axis in use at least substantially fixed in position with respect to the longitudinal axis of the first guiding bar 3. In other words, in a plane perpendicular to the longitudinal axis of the first guiding bar 3 and perpendicular to the longitudinal axis of the second guiding bar 5, the second guiding bar 5 is arranged at least substantially fixed in position with respect to the first guiding bar 3.
In the embodiment shown in Fig. 1, the second guiding bar 5 is also in the form of a circular tubular element. The outer diameter of the second guiding bar 5 is significantly smaller than the outer diameter of the first guiding bar 3. Preferably, the second guiding bar 5 has an outer diameter that is less than half the outer diameter of the first guiding bar 3. In particular, the outer diameter of the second guiding bar 5 is between approximately 35 mm and approximately 80 mm. In one embodiment, the wall thickness is between approximately 1 mm and approximately 5 mm. A small second guiding bar 5 takes up less space, so that a warp beam 10 can be arranged closer to the first guiding bar 3, which usually allows to use a lager warp beam 10. Hence, the second guiding bar 5, for example, made of the same material as the first guiding bar 3, for example of steel, in particular stainless steel, has a lower weight than the first guiding bar 3 and can be handled more easily. The second guiding bar 5 in one embodiment is provided in a rotatable manner. In other embodiments, the second guiding bar 5 is provided in a non-rotatable manner, wherein the warp threads 7 slide over the surface of the second guiding bar 5. In particular, in case of a relative movement between the second guiding bar 5 and the warp threads 7, the second guiding bar 5 has a smooth surface for guiding the warp threads without damaging the warp threads 7.
In the embodiment shown, the supporting device 6 has a plurality of hooks 60 provided as support elements 8 for the second guiding bar 5, namely seven hooks 60, distributedly arranged over the length of the first guiding bar 3 for supporting the second guiding bar 5. The second guiding bar 5 is held by the hooks 60 with its longitudinal axis fixed in position with respect to the longitudinal axis of the first guiding bar 3.
In the embodiment shown, the second guiding bar 5 is supported rotatably and moveable in the direction of its longitudinal axis in the hooks 60. For attaching or detaching the second guiding bar 5, the second guiding bar 5 is moveable radially into the hooks 60 or out of the hooks 60. In use, the second guiding bar 5 is held substantially fixed in position in the radial direction, wherein - depending on the orientation of the hooks 60, the second guiding bar 5 is held in place due to gravitational forces. In addition, in one embodiment, in use the warp threads 7 force the second guiding bar 5 in the hooks 60 against a movement in the radial direction. The axial movement of the second guiding bar 5 can be delimited or prevented by limit stops 48, 49 that are formed in the embodiment shown, respectively, by the ends 52 of the second guiding bar 5 and an associated side surface of the clamping part 41.
According to an alternative embodiment, the second guiding bar 5 is clamped in the hooks 60, for example clamped by means of elastic hooks that act as support elements. Depending on a clamping force of the hooks, the second guiding bar 5 may be held in a determined position or may be held moveable in the direction of its longitudinal axis and/or rotatable about its longitudinal axis.
During weaving a diameter of the warp beam 10 and, hence, a withdrawal angle of the warp threads 7 leaving the warp beam 10 is varying over time due to warp thread consumption. By means of the second guiding bar 5 arranged upstream of the first guiding bar 3, the warp threads 7 coming from the warp beam 10 are deflected and supplied to the first guiding bar 3 with a determined angle. Therefore, with the assumption that the withdrawal angle of warp threads leaving the first guiding bar 3 is at least substantially constant, the warp threads 7 are wrapped around the first guiding bar 3 with a fixed wrap angle.
The warp detector 12 is arranged at a suitable height and a suitable angle with respect to the back rest device 2 in order to avoid considerable bending of warp threads 7 near the warp detector 12. A known fixed arranged tube 44 can be provided, for example, for guiding superfluous warp threads or for acting as a support for an operator.
As mentioned above, before closing the clamping element 40, the first guiding bar 3 is supported rotatably about its longitudinal axis. The hooks 60 are fixed on the first guiding bar 3. Hence, by rotating the first guiding bar 3, the position of the hooks 60 and, when attached, a position of the longitudinal axis of the second guiding bar 5 with respect to the longitudinal axis of the first guiding bar 3 is adjustable in a plane perpendicular to the longitudinal axis of the second guiding bar 5. By adjusting the position, the wrap angle of the warp threads 7 against the first guiding bar 3 and, hence, the tension applied to the warp threads 7 by means of the first guiding bar 3 is adjustable.
Fig. 2 is a schematic side view of a back rest device 2 similar to the back rest device 2 of Fig. 1 configured for weaving a heavy fabric. The back rest device 2 shown in Fig. 2 differs from that shown in Fig. 1 in the hooks 60 provided for supporting the second guiding bar 5 on the first guiding bar 3. Apart from the shape of the hooks 60, the back rest device 2 shown in Fig. 2 corresponds to that of Fig. 1 and the two embodiments are described together.
According to the embodiment shown in Fig. 2, a wrap angle of the warp threads 7 against the first guiding bar 3 of approximately 170 degrees is provided. Other wrap angles may be suitable for different fabrics to be woven. Preferably, wrap angles between approximately 170 degrees and approximately 270 degrees against the first guiding bar 3 are chosen, so that sufficient friction is exerted on the warp threads 7 for tensioning the warp threads 7. Owing to the second guiding bar 5, the wrap angle of the warp threads 7 about the first guiding bar 3 is substantially constant during weaving from a full warp beam to an empty warp beam.
The diameter of the second guiding bar 5 is substantially less than the diameter of the first guiding bar 3. In this way, the friction force exerted by the second guiding bar 5 is small. In other words, due to the large diameter of the first guiding bar 3, the warp threads 7 are guided along a long distance against the first guiding bar 3, so that sufficient frictional forces are exerted for tensioning the warp threads 7. The friction exerted by the first guiding bar 3 allows that the tension in the warp threads 7 upstream of the first guiding bar 3 is small. The diameter of the second guiding bar 5 is also small so that the friction surface about the second guiding bar 5 is also small. As the wrap angle of the warp threads 7 against the second guiding bar 5 is different for a full warp beam 10 than for an empty warp beam 10, the friction force exerted by the second guiding bar 5 will also differ. In Fig. 2 the warp threads 7 are shown for a full warp beam 10. As shown in Fig. 2 the warp threads in case of an empty warp beam run according to line 9. The difference in friction force exerted by the second guiding bar 5 is small with respect to the friction force caused by the first guiding bar 3. The withdrawal angle varies depending on the position of the warp threads in case of a full warp beam and the position of the warp threads in case of an empty warp beam.
As can be seen in Fig. 2, the warp threads 7 are directed downwards when leaving the first guiding bar 3. In preferred embodiments, when weaving heavy fabric, a line of symmetry of the shed is under a line between the area where the warp threads 7 leave the first guiding bar 3 and the cloth line. This allows for an equal tension of warp threads moved for crossing of the shed and warp threads remaining in an extreme positioning as explained in US 5,273,079 the content of which is herewith incorporated by reference.
A method for installing the back rest device 2 on a weaving machine 1 is described with reference to Figs. 2 to 4, showing a schematic side view of the back rest device 2 during weaving a fabric, before installation of the back rest device and during weaving a very heavy fabric, respectively.
When installing the back rest device 2, the first guiding bar 3 is moved in the mounting device 4 without fixing the first guiding bar 3 in the mounting device 4. The warp threads 7 are arranged over the first guiding bar 3. The hooks 60 extend through the warp threads 7 as shown in Fig. 3. Before moving the first guiding bar 3 with the hooks 60 to the position shown in Fig. 3, the tube 44 is removed. Then the second guiding bar 5 is arranged in the hooks 60.
After arranging the second guiding bar 5, the first guiding bar 3 is rotated from the position as shown in Fig. 3 according to direction R, wherein the warp threads 7 are moved along with the second guiding bar 5 and wound in a defined wrap angle against the first guiding bar 3. The first guiding bar 3 is hereby oriented in angular position in order to bring the second guiding bar 5 into a desired position, for example the position as shown in Fig. 2.
Fig. 4 is a schematic side view of the back rest device 2 of Fig. 2 configured for weaving a very heavy fabric. In this embodiment, a wrap angle of the warp threads 7 against the first guiding bar 3 is approximately 270 degrees.
As mentioned above, when weaving a heavy fabric, at least a wrap angle as shown in Fig. 2 is preferably provided. In order to obtain that as well as for a full warp beam as for an empty warp beam still a wrap angle is present around the second guiding bar 5, the second guiding bar 5 has to be arranged at least past the line 11 shown in Fig. 2, which line 11 indicates the direct connection between the empty warp beam 10 and the first guiding bar 3.
In one embodiment, markers 45 (shown in Fig. 1) are provided on the first guiding bar 3 and/or markers 46, 47 are provided on the mounting device 4 to allow to position and to fix the first guiding bar 3 in several pre-set positions, for example markers 45 indicating wrap angles from 0 degrees to 360 degrees and/or markers 46, 47 indicating respectively vertical and horizontal positions of the first guiding bar 3 with respect to the mounting device 4. Hereby, it is possible based on the markers 45 to determine the angular position of the first guiding bar 3, and based on the markers 46 and 47 to determine the vertical and horizontal position of the first guiding bar 3.
In one embodiment, a warp tension sensor (not shown) is provided that measures the tension of the warp threads 7. For example, a separate warp tension measurement device is provided that measures the tension in some or all of the warp threads 7 directly on the warp threads. Preferably, such a sensor is provided between the back rest device 2 and the warp detector 12. In another embodiment, the warp tension is measured indirectly by measuring the forces of the first guiding bar 3 acting in the region of the mounting device 4. In both cases, a measured tension can be used for bringing the warp tension to a desired value.
Fig. 5 to 8 schematically show a hook 60 and support elements 8 used in a supporting device 6 of the back rest device 2 of Fig. 1, whereas Fig. 7 to 9 schematically show an associated first guiding bar 3.
As shown in Fig. 9, the first guiding bar 3 is provided at its two ends 34 with bearing taps 36 that can be received in the clamping elements 40 of the mounting device 4 shown in Fig. 1. The bearing taps 36, for example, are formed by machining.
The hook 60 shown in Fig. 5 is provided with a curved part 600 for receiving the second guiding bar 5. The hook 60 can be fixed with its distal end 601 near the first guiding bar 3. In an embodiment as shown in Figs. 5 to 8, a fixation element 61 is fixed with bolts 62 to the hook 60, wherein the bolts 62 extend through openings 602 in the hook 60. The fixation element 61 is fixed with bolts 63 to the first guiding bar 3, which first guiding bar 3 is provided to this end with a bore hole 603 having screw thread. Further a pin 64 is provided for positioning the fixation element 61 in an accurate position with respect to the hook 60, which pin 64 can co-operate with a slot 604 in the hook 60. Further a pin 65 is provided to set the fixation element 61 in an accurate position with respect to the first guiding bar 3, which pin 65 can co-operate with a bore hole 605 in the first guiding bar 3.
According to an embodiment the fixation element 61 has a shape that makes contact with the outer circumference of the first guiding bar 3. According to a variant embodiment the fixation element 61 has a flat wall that in use makes contact with a flat part that is provided at the height of the bore hole 603 on the first guiding bar 3, which flat part is made, for example, with a milling machine.
According to another possibility the pin 65 can co-operate with a bore hole 606 in the first guiding bar 3. This allows to arrange the hook 60 in a position 180 degrees turned. Because as shown in Fig. 9, the first guiding bar 3 is designed symmetrical around an axis of symmetry 35, the first guiding bar 3 can be turned around its axis of symmetry 35 over 180 degrees. In case the first guiding bar 3 is worn due to contact with warp threads 7, the other side of the first guiding bar 3 can be used to make contact with the warp threads 7. This allows to double the lifetime of the first guiding bar 3, in particular when the warp threads 7 are guided over less than 180 degrees over the first guiding bar 3.
It is preferred to fix the hooks 60 accurately with respect to the first guiding bar 3. In other embodiments, the hooks 60 are fixed in any other suitable way to the first guiding bar 3, or are welded to the first guiding bar 3.
The hooks 60 are flat, this means have a comparatively small extension in the direction of the longitudinal axis of the second guiding bar 5. Such hooks 60 do not open the plane of warp threads substantially, so that no "stripes" in the fabric will occur. The fixation elements 61, the bolts 62 and 63, and the pins 64 and 65 do not come into contact with the warp threads 7.
As mentioned above, the second guiding bar 5 is preferably of low weight and has a comparatively small outer diameter. Due to the small dimensioning, the second guiding bar 5 in one embodiment has only a limited rigidity. A sufficient number of hooks 60 is provided in order to avoid or at least delimit a bending of the second guiding bar 5 caused by the tension in the warp threads 7.
As mentioned above, in one embodiment, the second guiding bar 5 is not clamped in the hooks 60, but held in a moveable manner. In order to avoid a too extensive shifting movement of the second guiding bar 5 in a longitudinal direction, in one embodiment, limit stops 48 are arranged at the ends 52 of the second guiding bar 5 to avoid or delimit such shifting. The curved part 600 allows a movement of the second guiding bar 5 relative to the hooks 60 in a radial direction for attaching or detaching the second guiding bar 5. In one embodiment, closure elements are provided closing the opening of the curved part 600 for avoiding a displacement of the second guiding bar 5 in radial direction and/or in tangential direction.
According to a variant (not shown), a second guiding bar 5 having a higher rigidity is provided, wherein the number of support elements can be reduced. To this end, in one embodiment a dimension of the second guiding bar is increased.
Fig. 10 shows another embodiment, wherein a second guiding bar 105 having an oval cross-section supported in support elements 8 such as hooks 160 is provided. The orientation of the second guiding bar 105 in this embodiment is chosen so that the warp threads 7 exert a force on the second guiding bar 105 in a direction where the second guiding bar 105 is more rigid against bending. As the second guiding bar 105 having an oval cross-section is prevented from rotating in the support elements 8, a frictional force is exerted on the warp threads 7 by means of the second guiding bar 105 which may be slightly higher than that exerted by the second guiding bar 5 shown in Figs. 1 to 4. Apart from the shape of the second guiding bar 105 and the associated hooks 160, the back rest device 2 shown in Fig. 10 corresponds to that of Fig. 2 and for a detailed description, reference is made to Fig. 2.
As shown in Fig. 1, at the height of both side parts 16 the first clamping part 41 is fixed via a fixation block 50 to the support table 14. In the clamping part 41, as schematically shown in Figs. 2, 3, 4 and 10, different bore holes 51 are arranged to be able to position the clamping part 41 via the fixation block 50 in different positions with respect to the support table 14. This allows to set the first guiding bar 3 in a desired position. Of course this setting of position can be done in other known ways.
In the context of the application "first" and "second" are only used to distinguish between the first guiding bar 3 and the second guiding bar 5. It is, for example, also possible to call the first guiding bar 3 that is mounted fixedly "back rest bar" or "back rest roller", and the second guiding bar 5 "tension bar" or "tension roller".
The warp threads 7 move from the warp beam 10 firstly via the second guiding bar 5 and subsequently via the first guiding bar 3 to shed forming elements 15, so that in use according to the movement direction of the warp threads 7 from the warp beam 10, the second guiding bar 5 is arranged upstream of the first guiding bar 3, in other words the first guiding bar 3 is arranged downstream of the second guiding bar 5.
Although in the embodiments shown, as well as the first guiding bar 3 as the second guiding bar 5 are executed as a hollow guide bar, in other words as a tubular element, according to a variant, it is also possible to execute at least one of the guiding bars 3, 5 as a solid guiding bar, for example the second guiding bar 5.

Claims

Back rest device for guiding warp threads (7) coming from a warp beam (10) comprising a first guiding bar (3) for guiding warp threads (7), a second guiding bar (5, 105) for guiding warp threads (7), which second guiding bar (5, 105) in use is arranged in parallel to the first guiding bar (3) and upstream of the first guiding bar (3) for deflecting warp threads (7) coming from the warp beam (10), a mounting device (4), which mounting device (4) is arranged for mounting the first guiding bar (3) in a fixed mounting position and in a non-rotatable manner, and a supporting device (6), which supporting device (6) is arranged for supporting the second guiding bar (5, 105) so that in use the longitudinal axis of the second guiding bar (5, 105) is mounted fixed in position with respect to the longitudinal axis of the first guiding bar (3), characterized in that the second guiding bar (5, 105) is mounted on the first guiding bar (3) by means of the supporting device (6), and in that the position of the longitudinal axis of the second guiding bar (5, 105) with respect to the longitudinal axis of the first guiding bar (3) is settable, wherein in order to bring the longitudinal axis of the second guiding bar (5, 105) into a set position with respect to the longitudinal axis of the first guiding bar (3) the first guiding bar (3) is rotatable about its longitudinal axis to orient the first guiding bar (3) in an angular position.
Back rest device according to claim 1, characterized in that the supporting device (6) comprises a plurality of support elements (8) distributedly arranged over the length of the first guiding bar (3) for supporting the second guiding bar (5, 105).
Back rest device according to claim 2, characterized in that hooks (60, 160) are provided as support elements (8), which hooks (60, 160) are distributedly arranged over the length of the first guiding bar (3).
Back rest device according to claim 3, characterized in that the second guiding bar (5, 105) is supported moveably, in particular rotatably, in the hooks (60, 160).
Back rest device according to any one of claims 1 to 4, characterized in that limit stops (48, 49) are provided for delimiting or preventing a movement of the second guiding bar (5, 105) in the direction of its longitudinal axis.
Back rest device according to any one of claims 1 to 5, characterized in that the second guiding bar (5, 105) is arranged so that the tension applied due to frictional effects is significantly less than the tension applied by the first guiding bar (3).
Back rest device according to any one of claims 1 to 6, characterized in that the outer circumference of the first guiding bar (3) is larger than the outer circumference of the second guiding bar (5, 105), wherein in particular an outer circumference of the first guiding bar (3) is larger than 500 mm, in particular between approximately 550 mm and approximately 800 mm and/or an outer circumference of the second guiding bar (5, 105) is between approximately 90 mm and approximately 230 mm.
Back rest device according to any one of claims 1 to 7, characterized in that either or both of the first guiding bar (3) and the second guiding bar (5, 105) is a tubular element, in particular a circular tubular element.
Back rest device according to claim 8, characterized in that a wall thickness of the first guiding bar (3) is between approximately 8 mm and approximately 15 mm and/or a wall thickness of the second guiding bar (5, 105) is between approximately 1 mm and approximately 5 mm.
Back rest device according to any one of claims 1 to 9, characterized in that markers (45, 46, 47) are provided for indicating a plurality of pre-set positions for the longitudinal axis of the second guiding bar (5, 105).
Back rest device according to any one of claims 1 to 10, characterized in that the mounting device (4) comprises two clamping elements (40) for clamping the first guiding bar (3) at its ends (34).
Weaving machine comprising a back rest device according to any one of claims 1 to 11, characterized in that the back rest device (2) is arranged near a warp beam (10), in particular between a warp beam (10) and shed forming elements (15) .
Method for arranging a back rest device according to any one of claims 1 to 11 comprising a first guiding bar (3), a mounting device (4), a second guiding bar (5, 105), and a supporting device (6), on a weaving machine (1), wherein the first guiding bar (3) is inserted into the mounting device (4), warp threads (7) supplied by a warp beam (10) are arranged over the first guiding bar (3), the second guiding bar (5, 105) is attached to the supporting device (6) to deflect the warp threads (7), wherein
the second guiding bar (5, 105) is mounted on the first guiding bar (3) by means of the supporting device (6), and wherein after attaching the second guiding bar (5, 105) to the supporting device (6), in order to bring the longitudinal axis of the second guiding bar (5, 105) into a set position with respect to the longitudinal axis of the first guiding bar (3) the first guiding bar (3) is rotated about its longitudinal axis to orient the first guiding bar (3) in an angular position, and the first guiding bar (3) is mounted by the mounting device (4) in a non-rotatable manner after the second guiding bar (5, 105) is in the set position.