Method for introducing and pulling back weft yarns at a loom, prewinder device for a loom and loom

Abstract

In a method for introducing and pulling back a weft thread (5) at a weaving machine (1), the weft thread (5) to be introduced is temporarily stored on a bobbin (8), wherein during the temporary storage the weft thread (5) is fixed on the bobbin (8) by a fixing element (11) which is located in a fixed position, the weft thread (5) is released for the weft insertion, wherein the fixing element (11) is moved from the fixed position into a release position and the weft thread (5) is unwound from the bobbin (8) in an unwinding direction and introduced with formation of a thread loop. The weft thread (5) is pulled back after the weft insertion has been completed by means of a pulling back device (9). Here, the weft thread (5) is gripped and pulled back in the area of the thread loop behind the fixing element (11) in a picking position. In a corresponding pre-twist device (7) for a weaving machine (1), the pulling back device (9) is arranged behind the fixing element (11) in the thread run in the pre-twist device (7) and the pulling back device (9) has a driving element (13) for the weft thread (5), which grips the weft thread (5) in the picking position. A corresponding weaving machine (1) has a weft insertion system (4) and such a pre-twist device (7).

Description

Methods for introducing and pulling back weft yarns at the loom, pre-winding devices for the loom, and the loom itself. Technical Field

[0001] This invention relates to a method for introducing and retracting weft yarn in a loom, particularly an air-nozzle type loom, in which the weft yarn to be introduced is temporarily stored on a drum, wherein, during temporary storage, the weft yarn is secured to the drum by a fixing element located in a fixed position, the weft yarn is released for weft introduction, wherein the fixing element moves from the fixed position to the release position, and the weft yarn is unwound from the drum and introduced in the unwinding direction while forming a yarn air loop, and in the method, the weft yarn is pulled back by means of a retraction device after weft introduction. The invention also relates to a pre-winding device for a loom and a loom. Background Technology

[0002] Methods and apparatus for introducing and pulling back the weft yarn are known at the loom in various embodiments. For example, weft yarn pull-back devices are known for tensioning the weft yarn after weft introduction.

[0003] Furthermore, it is known in rapier looms (or Greiferwebmaschinen) that the weft end supplied to the gripper is pulled back a short distance by means of a pullback device before being grasped by the gripper. For this purpose, a lever is used to pivot the fingers into the weft's travel, and the now shortened weft end is supplied to the gripper. Such a yarn pullback unit is shown, for example, in DE 35 24 727 A1.

[0004] In contrast, a common problem in air-nozzle looms is that the weft yarn ends are damaged over a longer length due to pressure pulses when the yarn is raised in the main nozzle. This damage is visible as a fabric defect in the finished fabric. To avoid this defect, the weft yarn length is typically increased so long in air-nozzle looms that the defect caused by compressed air at the weft yarn is discharged from the loom shed (or shed) on the right side of the fabric and falls into the waste on the right side.

[0005] US 3,370,618 A discloses an output and measuring device for accurately measuring the length of a weft yarn to be introduced. Furthermore, the device should also be able to pull the weft yarn end back into the nozzle. This is done by means of a linearly movable tube, wherein the yarn is then clamped by a clamping element.

[0006] DE 102 10 911 A1 proposes that the weft yarn be pulled back from the blowing area of ​​the main blowing nozzle after weft insertion. For this purpose, a pull-back device is arranged between the pre-winding device and the main blowing nozzle. The pull-back device has a pivot arm with a reversing element for the weft yarn. By means of the suction action of the main blowing nozzle, the weft yarn remains taut after pull-back, and the weft yarn end is not exposed to excessively strong, damaging blowing airflow. Fabric defects can also be reduced as a result. Furthermore, the pull-back unit can also be used as a yarn brake, which brakes the weft yarn near the end of weft insertion.

[0007] Similar to DE 35 24 727 A1, SE 154 756 C1 also pivots the needle-equipped finger into the weft yarn's travel to pull the weft yarn back. The needle actively pulls back in order to release the weft yarn again. This pull-back element is also positioned between the nozzle and the pre-winding device.

[0008] WO 2005 / 064059 A1 also illustrates a similar pullback device, which is arranged directly after the funnel-shaped air ring limiter. This device can be used as both a yarn brake and a pullback device. However, when the yarn accelerates in the main nozzle, damage to the weft yarn can still occur, which degrades the quality of the fabric. Summary of the Invention

[0009] The objective of this invention is to provide a method for introducing and pulling back weft yarns, which avoids fabric defects and achieves improved weft introduction. Furthermore, a corresponding pre-winding device and a loom having such a pre-winding device should be provided.

[0010] The task is accomplished by a method, a pre-winding device, and a loom, which are characterized according to the invention.

[0011] In a method for introducing and retracting weft yarn on a loom, particularly an air-nozzle loom, the weft yarn to be introduced is temporarily stored on a drum. During temporary storage, the weft yarn is secured to the drum by a fixing element located in a fixed position. The weft yarn is released for weft introduction, wherein the fixing element moves from the fixed position to the release position, and the weft yarn is unwound from the drum and introduced in the unwinding direction while forming a yarn air loop. After weft introduction is completed, the weft yarn is pulled back by a retraction device.

[0012] It is proposed that the weft yarn is grasped and pulled back in the extraction position after the fixing element and in the area of ​​the yarn air loop.

[0013] Similarly, in a prewinding device for a loom, particularly an air-nozzle loom, the prewinding device has a spool for temporarily storing the weft yarn to be introduced; a fixing element for the weft yarn that is associated with the spool and is movable from a fixed position to a released position; and a pull-back device for pulling back the weft yarn after weft insertion. The pull-back device is arranged in the prewinding device after the fixing element in the yarn direction, and the pull-back device has a drive for the weft yarn that grips the weft yarn in the extraction position after the fixing element and in the area of ​​the yarn air pocket formed during weft insertion.

[0014] By using a pullback device to pull the weft yarn back, it can now be pulled back to such an extent that only a relatively short segment remains in the main nozzle. If this short yarn segment is now damaged by compressed air in the main nozzle during weft acceleration, this is not a problem, because this short segment will inevitably fall into the waste on the right side.

[0015] Furthermore, the arrangement of the pull-back device in the pre-winding apparatus after the fixing element in the yarn direction allows for a very compact unit requiring only a small structural space. Additionally, the weft yarn, spread out between the drum and the immediately following guide element (e.g., an air loop limiter) after weft insertion, can be reliably gripped between the fixing and guide elements at the drum due to this arrangement. Therefore, it is not necessary for the weft yarn to be continuously guided in the pull-back device (i.e., also during weft insertion). This avoids weft insertion interference. The weft yarn can be pulled back particularly effectively because it is gripped directly after the fixing element in the weft direction; for this purpose, a pull-back device with a surrounding drive element is used.

[0016] The advantages of this invention also apply to corresponding looms, especially air-nozzle looms, which have weft yarn introduction systems and such pre-winding devices, and thus protection is also required for these looms.

[0017] Furthermore, it is advantageous that the weft yarn is pulled back by a pullback device until it reaches the main nozzle of the pneumatic weft yarn introduction system of the loom. Correspondingly advantageous in the loom is that the weft yarn introduction system is constructed as a pneumatic weft yarn introduction system having at least one main nozzle. The weft yarn is pulled back such that it remains precisely within the blowing area of ​​the main nozzle after being pulled back. This ensures, on the one hand, that the weft yarn is reliably held by the holding air of the main nozzle, but on the other hand, it also prevents severe damage to the weft yarn end from the holding air before weft insertion. By pulling back only to such an extent that the weft yarn remains within the blowing area of ​​the main nozzle with its end, damage to the weft yarn caused by acceleration in the main nozzle is limited to a very short segment, which lies ahead of the ejector of the main nozzle in the yarn direction. As shown, for example, in document DE 102 24 078 B3, the main nozzle typically comprises a mixing tube and an ejector by means of which compressed air is introduced into the mixing tube. This short segment of the weft yarn appears in the waste on the right side after weft insertion or in the catch strip (or catch selvage, i.e., Fangliste), and therefore does not negatively affect the fabric quality. Thus, there is no need to increase the weft yarn length and thereby produce unnecessary waste.

[0018] According to the invention, the weft yarn is gripped by a drive member of the pull-back device that can move around a circular track surrounding the drum, and pulled back by further movement of the drive member on the circular track. In the case of the pull-back device, the drive member can move around a circular track surrounding the drum. For this purpose, the pull-back device advantageously has a drive mechanism for driving the drive member. Thus, the pull-back device can be implemented in a very simple structure. The yarn can be reliably and consistently gripped near the drum in the same extraction position by the drive member process, without the need for costly adjustments. Due to its relatively simple technical implementation, the pull-back device is also suitable for retrofitting various looms.

[0019] According to an advantageous embodiment of the pullback device, it is further advantageous that the drive element is constructed as an open hook. With the aid of the open hook, the weft yarn spread between the fixing element and the immediately following yarn guide element (e.g., an air ring limiter) can be gripped in a particularly reliable manner.

[0020] Advantageously, the drive element is discontinuously driven on the circular track. The drive element moves periodically between the take-up position and the release position, in which the weft yarn is released again. The drive element thus grasps the weft yarn in the take-up position and releases it again in the release position in each weaving cycle, so as to return to the take-up position to grasp and pull back the weft yarn for the next weaving cycle.

[0021] According to an advantageous embodiment, the drive member moves around on a circular track, wherein the drive member moves from the extraction position back to the extraction position via a pull-back area, and wherein the drive member moves at a reduced speed and / or temporarily stops in the pull-back area after the weft yarn is pulled back. Correspondingly advantageously in the pull-back device is that the drive member can move discontinuously from the extraction position back to the extraction position via the pull-back area on the circular track. For this purpose, the pull-back device advantageously has a stepper motor or servo motor as the drive device. For example, the pull-back area can be used to keep the drive member outside the influence area of ​​the formed yarn air loop during weft insertion, for which the drive member is driven at a reduced speed. The drive member can also be temporarily stopped in a stationary position located within the pull-back area. A short stop of the drive member can also be used to keep the drive member outside the influence area of ​​the formed yarn air loop during weft insertion. However, according to another embodiment, the stationary position can also be used to reliably hold the weft yarn still connected to the drive member and position the weft yarn end in the desired position in the main blower nozzle. It is also conceivable to provide two different stationary positions for the drive member.

[0022] However, according to another embodiment, the drive can also be continuously driven without reducing the speed in the pull-back area or without stopping in the stationary position.

[0023] A particular advantage is that the drive member grasps the weft yarn directly after the fixing element with respect to the yarn direction. Similarly, it is advantageous in the pull-back device to be arranged in the pre-winding apparatus such that the extraction position is directly after the fixing element in the yarn direction. Preferably, the drive member grasps the weft yarn at a distance of 1 mm to 50 mm from the fixing element. At this position, the weft yarn can be grasped particularly well by the drive member. Furthermore, with the aid of the surrounding pull-back device, the weft yarn can be pulled back with a particularly large stroke and therefore particularly effectively by grasping it early in the yarn direction close to the fixing element.

[0024] Additionally or alternatively, it is advantageous that the drive element grips the weft yarn with respect to the yarn direction before the yarn guide element immediately following the drum. As already described, this allows the weft yarn to be gripped particularly well. Furthermore, in this arrangement, a yarn guide element is unnecessary in the pull-back device, which could interfere with weft insertion due to its frictional action. The weft yarn is adequately guided between the drum or fixing element and the immediately following yarn guide element (e.g., the main nozzle).

[0025] According to another advantageous embodiment, the weft yarn is connected to a drive member located in the pull-back zone until the next weft insertion. In this case, as described above, the weft yarn connected to the drive member is reliably held in the desired position, and the weft yarn end is reliably positioned in the desired position in the main blower nozzle. If the drive member moves in the pull-back zone and does not stop, the drive member will only move slowly in any case. Furthermore, when moving on the circular track, the distance between the drive member and the fixed element in the pull-back zone increases only very slightly, so that even if the drive member continues to move, the weft yarn hardly changes its position.

[0026] Another significant advantage of this method is that the drive element is driven in the unwinding direction of the weft yarn. This simplifies the process of the weft yarn disengaging from the drive element for the next weft insertion.

[0027] Therefore, it is particularly advantageous that after the weft yarn is released by the fixed element for weft insertion, the weft yarn automatically disengages from the drive member due to the yarn tension and centrifugal force acting on it during weft insertion. Thus, this disengagement can be achieved solely through the loop-like unwinding motion of the weft yarn. However, the disengagement of the weft yarn from the drive member can also be additionally supported by having the drive member stop in a stationary position as described above. However, it is entirely unnecessary to operate the drive element for release. Since the weft yarn automatically disengages from the drive member without active control during weft insertion, there is no delay or timing error in release due to the pull-back device during weft insertion.

[0028] Advantageously, after releasing the weft yarn for weft insertion, the drive member is accelerated and moved further into the extraction position. Therefore, the drive member can continue its circular motion during weft insertion and quickly return to the extraction position to grab and pull back the next weft yarn. Particularly advantageously, the drive member only accelerates after the weft yarn has disengaged from the drive member, or if the drive member stops, it is put back into motion and moved further into the extraction position. This supports the disengagement of the weft yarn from the drive member. Furthermore, the drive member can thus be well kept outside the influence range of the formed yarn air pocket and does not obstruct weft insertion.

[0029] Advantageously, the weft yarn extends unguidedly through the pull-back device during weft insertion. Thus, the weft yarn extends freely between the drum and the following guide element during weft insertion and is therefore completely free from friction, which can negatively affect weft insertion. Weft insertion can thus be performed more reliably and quickly.

[0030] According to a particularly advantageous improvement of the method, weft insertion begins even before the weft yarn introduction channel of the loom is released by the opened loom frame. For example, weft insertion begins when the loom angle is less than 50°, preferably less than 40°, and particularly preferably less than 35°. Since the weft yarn is pulled back a considerable distance to the main nozzle by means of a pullback device, the weft yarn can now begin much earlier than is typically the case in the prior art. Therefore, weft insertion can be accelerated, thereby selectively achieving higher speeds or more economical weft insertion with less pressure. Furthermore, by starting the yarn earlier, the weft yarn tip already has a high speed when leaving the main nozzle, thus allowing the yarn tip to fly stably and therefore achieving reliable weft insertion.

[0031] Furthermore, it is advantageous in the pullback device that the diameter of the circular track of the drive element is larger than the diameter of the drum. This allows for reliable gripping of the weft yarn at the extraction position. Preferably, for this purpose, the drive element has a slightly longer capture profile, which is oriented from the diameter of the circular track of the drive element towards the center point of the circular track. The pullback device can thus cover different drum diameters.

[0032] Another advantage is that the rotation axis of the drive is offset relative to the axis of the drum. This allows the drive to receive the weft yarn well in the take-up position without obstructing the next weft insertion.

[0033] Therefore, the combination of the axial offset and the larger diameter of the circular track of the drive, as described above, is particularly advantageous. This allows the drive to be positioned very close to the periphery of the drum in the take-up position to grip the weft yarn. However, after the weft yarn disengages from the drive, the drive moves away from the periphery of the drum and thus does not interfere with the unwinding of the weft yarn loops.

[0034] Furthermore, it is advantageous that the pull-back device has an annular member with external teeth, the drive member is arranged at the annular member with external teeth, and the annular member with external teeth can be driven by the drive device. This achieves the following: the pull-back device is arranged directly at the pre-winding device, for example, directly at the air ring limiter of the pre-winding device. Here, the yarn direction can pass through the interior of the annular member in a particularly advantageous manner. Thus, the weft yarn engages with the pull-back device only during pull-back, but extends through the interior of the annular member without engagement during weft insertion. This eliminates the need for an active release element that must be controlled by the loom controller, which also helps to avoid weft insertion interference. Attached Figure Description

[0035] Other advantages of the invention are described in the following embodiments, which are illustrative of each:

[0036] Figure 1 shows a loom in a first scenario shortly after weft insertion, the loom having a pre-winding device with a pull-back device;

[0037] Figure 2 shows the loom of Figure 1 in a second scenario, after weft insertion and after weft yarn cutting;

[0038] Figure 3 shows the loom of Figure 1 in the third case after the weft yarn has been pulled back;

[0039] Figure 4 shows a view of the pre-winding device with a pull-back device on the drum, seen from the loom grid when the weft yarn is being grasped in the first case.

[0040] Figures 5 and 6 show views onto the roll in Figure 4 during the pullback of the weft yarn in the second and third scenarios;

[0041] Figure 7 shows a view onto the drum of Figure 4 in a different situation after the weft yarn has been pulled back;

[0042] Figure 8 shows a view onto the drum of Figure 4 in another scenario where the weft yarn is unwinding;

[0043] Figure 9 shows a view onto the roll of Figure 4 in another scenario during weft insertion;

[0044] Figure 10 shows a view from the weft yarn storage device towards the pull-back device and the air ring limiter, and

[0045] Figure 11 shows an alternative embodiment of a loom during weft insertion, the loom having a pre-winding device with a pull-back mechanism. Detailed Implementation

[0046] In the following description of the embodiments, the same reference numerals are used for features that are identical or at least comparable in their design and / or mode of operation. Furthermore, these features are explained in detail only when first mentioned, and in the embodiments described below, only differences from the already described embodiments are discussed. Additionally, for clarity, only one or a small number of identical components or features are typically labeled.

[0047] Figure 1 shows a schematic diagram of a loom 1 in a first scenario shortly after weft insertion. The loom has a pre-winding device 7 with a pull-back device 9. The loom 1 typically has a weft yarn storage device 6 on the introduction side ES, from which the weft yarn 5 is unwound and supplied to the pre-winding device 7. The pre-winding device 7 has a bobbin 8 on which the weft yarn 5 is laid in multiple loops by means of a winding disc (not shown). The weft yarn 5 currently extends from the bobbin 8 through an air ring limiter 12 to the weft yarn introduction system 4 of the loom 1. The weft insertion direction SR is indicated by an arrow. Furthermore, a separation device 25 is arranged on the introduction side ES to separate the weft yarn 5 after weft insertion.

[0048] The loops of the weft yarn 5 laid on the drum 8 are held in place by means of a retaining element 11. The retaining element 11 is located in a fixed position I (see Figures 4-9) to hold the weft yarn 5 and is movable to a release position II (see Figures 4-9) to release the weft yarn 5. For example, the retaining element 11 is implemented as a removable pin that can be fed into the drum 8. For weft insertion, the retaining element 11 is then moved to the release position II and a predetermined number of loops of the weft yarn 5 are pulled off the drum 8 during weft insertion. Here, the number of loops pulled off can be detected by means of a sensor, so that the predetermined number of loops are always pulled off during weft insertion. After weft insertion is completed, the retaining element 11 is then moved back to the fixed position I.

[0049] Currently, the weft introduction system 4 is pneumatically configured and includes a main nozzle 20 arranged on the introduction side ES of the loom 1 in a manner known per se. Only one main nozzle 20 is shown here. However, it is also possible and common for two main nozzles 20 to be arranged sequentially on the introduction side ES. The main nozzle 20 can be loaded with compressed air. Here, to hold the weft yarn 5 until the next weft insertion, the main nozzle 20 can be loaded with a smaller airflow, i.e., so-called holding air. For weft insertion, a stronger airflow, i.e., so-called main air, can be used to load the main nozzle 20. This accelerates the end of the weft yarn 5 and introduces it into the open loom grid 2. The loom grid 2 is typically formed by alternately raising and lowering adjacent warp yarns 3. After weft insertion is completed, the weft yarn 5 is stopped (angeschlagen) by means of the reed 10 in the same known manner. In the case of the air-nozzle type loom shown here, the reed 10 has a weft yarn introduction channel 24, into which the weft yarn 5 is introduced by a main nozzle 20 and transported through the loom grid 2. For this purpose, the weft yarn introduction system 4 includes a plurality of relay nozzles (not shown here) distributed on the reed 10, which support the transport of the weft yarn 5 through the loom grid 2. On the side of the loom 1 away from the introduction side ES, the weft yarn introduction system 4 also has a suction nozzle 22 for capturing and receiving the introduced weft yarn 5. In the present case, the weft yarn 5 has just been introduced and received by the suction nozzle 22. In the present loom 1, a reversing nozzle 23 is also provided, which, by means of airflow, draws the weft yarn 5 extending from the loom grid 2 out of the suction nozzle 22 and moves it in the direction of the yarn being pulled out WR, so that the weft yarn does not interfere with further weft insertion.

[0050] In the case of this pneumatic weft introduction system 4, the weft yarn 5 is typically damaged during take-up due to the acceleration in the main nozzle 20. This problem occurs particularly in the case of untwisted filament yarn. This damage is usually visible as a defect in the finished fabric. These problems can also occur in the case of core-spun yarn. Therefore, in the prior art, the weft yarn length is usually increased, thus primarily affecting the transport of damage to the weft yarn end through the loom grid 2 and being discharged as weft yarn waste on the right side of the loom 1 opposite to the introduction side ES. Similarly, in the prior art, a pull-back device 9 has been used to pull the weft yarn 5 back from the blowing area of ​​the main nozzle. Although the weft yarn 5 is still kept taut by the main nozzle 20, the weft yarn end is no longer damaged by the strong airflow.

[0051] In the current loom 1, a pull-back device 9 for pulling back the weft yarn 5 after weft insertion is arranged between the drum 8 and the air ring limiter 12. The pull-back device 9 has its own drive unit 15. Its exact function is described in detail with reference to Figures 4-9. It goes without saying that there is a pre-winding device 7 with its own pull-back device 9 for each color.

[0052] However, the air pocket limiter 12 is not necessarily required. According to an alternative embodiment of the loom shown in Figure 11, only one yarn guide element 28 is arranged after the pre-winding device 7. The yarn guide element 28 can also be arranged directly at the pre-winding device 7. For example, the yarn guide element 28 can be constructed as a ceramic eyelet. Figure 11 shows the loom 1 during weft insertion. Here it can also be seen that the weft yarn 5 is unwound from the drum 8 while forming the yarn air pocket 21. In other respects, the loom 1 corresponds to the situation shown in Figure 1.

[0053] Figure 2 now shows the loom 1 of Figure 1 in a second case after weft insertion and after the weft yarn 5 has been cut. As can be seen, in this case, the weft yarn 5 on the guide side ES has been cut. Similarly, the weft yarn end on the side opposite to the guide side ES has also been redirected by the reversing nozzle 23 toward the article pulling direction. The weft yarn end cut on the guide side ES of the loom 1 still protrudes from the end of the main nozzle 20.

[0054] Figure 3 also shows the loom 1 of Figure 1 in a third scenario after the weft yarn 5 has been pulled back. After weft insertion, during the intermediate time, the fixing element 11 is brought from release position II to fixing position I, where it fixes the weft yarn 5 wound on the drum 8. The now-stopped weft yarn 5 is pulled back by the pull-back device 9. As can be seen from Figure 3, the weft yarn 5 is pulled back in the main nozzle 20 to such an extent that only a very short section remains. The weft yarn 5 is pulled back to such an extent that it is still within the blowing area of ​​the main nozzle 20, i.e., just before the nozzle of the ejector (not shown). Through this pull-back of the weft yarn 5, only a very short section is exposed to the damaging effects of the main air when the weft yarn 5 accelerates. However, since there is always unavoidable waste on the right side caused by the process, severe damage to this very short section is not a problem. After the weft insertion, this short section will inevitably be located in the waste on the right side and will be cleaned up along with the waste. Due to the further pull back of the weft yarn 5, the damaged weft yarn end leaves the loom grid 2 on the side opposite to the insertion side, and thus does not cause fabric defects.

[0055] However, this not only reduces weft waste on the right side by approximately 10-14 cm, but also achieves many other advantages due to the very short weft end protruding from the loom grid 2 on the right side (as can be seen, especially from Figure 2). For example, the shortened weft end significantly reduces the likelihood of clogging of the suction nozzle 22 and the reversing nozzle 23. Similarly, in the prior art, the spreader (not shown) frequently becomes clogged due to the long, laterally protruding weft end. This is also avoided by the now significantly shorter, laterally protruding weft end from the loom grid 2 or the article. Likewise, the problem of winding of the catch strip on the right side (also not shown) is avoided.

[0056] Furthermore, it is particularly advantageous that, since the weft yarn 5 is almost pulled back to the nozzle of the main nozzle 20, the weft yarn has already been accelerated in the main nozzle 20 and can therefore leave at a high speed. Thus, the weft yarn 5 leaves the main nozzle 20 in a stretched state and at a high speed, and can be more easily introduced into the weft yarn introduction channel 24 of the reed 10. This results in more stable weft insertion. Problems such as "crutch formation," where the further rear weft yarn 5 extends beyond the front weft yarn end, can also be avoided.

[0057] Furthermore, it is advantageous that the weft yarn 5 can be started up before the weft yarn introduction channel 24 is released from the open loom grid 2, because the weft yarn is still within the main nozzle 20 when it is started up. The loom grid is fully open until the end of the weft yarn has traveled the distance to the loom grid 2. Therefore, starting up can occur earlier, thereby enabling an increase in the speed of the loom 1 and thus an increase in production. For example, starting up can be achieved when the loom angle is approximately 30°.

[0058] Since the weft yarn 5 can accelerate earlier, it also reaches its maximum speed almost as early as when it reaches the loom slot 2. Therefore, weft insertion is performed with low gas pressure in the same advantageous way, thereby enabling the loom 1 to operate energy-efficiently.

[0059] By pulling the yarn back into the main nozzle 20, weft insertion interference, which could be caused by the holding air in the adjacent main nozzle 20, is also avoided. During acceleration or take-up, the weft yarn end remains within the main nozzle 20 and is therefore not affected by the air turbulence of the adjacent main nozzle 20.

[0060] The pullback device 9 according to the invention and its operation will now be described with reference to Figures 4 to 10. Figures 4 to 9 show schematic top views of the pullback device 9 and the roll 8 of the pre-winding device 7, viewed from the loom grid 2. In contrast, Figure 10 shows a schematic top view of the pullback device 9 and the air ring limiter 12, viewed from the weft yarn storage device 6.

[0061] As can be seen from Figure 10, the pullback device 9 includes a drive member 13 for the weft yarn that is currently configured as a hook and encircled on a circular track 14. The drive member 13 currently has a capture profile 27 by which it can grasp the spread weft yarn 5, as also described below. The drive member 13 is arranged at a rotatably supported annular member 18, which is connected to and driven by a gear 26 via external teeth 19. The gear 26 itself is driven by a drive unit 15, which is shown only partially here. The annular member 18 with external teeth and therefore the drive member 13 encircle the circular track 14 about the axis of rotation 16 of the drive member 13. To achieve controllable and (if configured) discontinuous or intermittent drive of the drive member 13, the drive unit 15 is preferably configured as a stepper motor. The inner peripheral surface of the air ring limiter 12 can also be seen inside the annular member 18 with external teeth. Furthermore, for informational purposes, the drum 8 of the pre-winding device 7 with a diameter DT is indicated by a dashed line, and is not visible in this view. As can be seen from Figure 10, the drive member 13 also wraps around the drum 8. Additionally, the diameter of the circular track 14 of the drive member 13 is indicated by DK.

[0062] However, as already presented with respect to Figure 11, the air ring limiter 12 is not necessarily required; only a yarn guide element 28 may be provided. In any case, the operation of the pullback device 9 is the same. According to another embodiment of the pullback device 9, not shown here, instead of having an annular member 18 with external teeth, the pullback device 9 has a capture hook fixed to the driven shaft. This capture hook rotates 360° about its own axis. For the remainder, the operating principle of this embodiment corresponds to that described with respect to Figure 10. Therefore, the following description with respect to Figures 4-9 explicitly relates to different embodiments of the pullback device 9 and the loom 1.

[0063] The pullback process of weft yarn 5 is now described based on Figure 4-9.

[0064] Figure 4 shows a view of the drum 8 with the pull-back device 9 from the loom grid during the first scenario of gripping the weft yarn 5. This scenario corresponds to that shown in Figure 2, where the weft yarn 5 is cut directly after introduction. Similarly, in this scenario, the retaining element 11 has moved back from release position II (see Figure 8) to fixed position I after weft insertion, in which the retaining element secures the weft yarn 5 to the drum 8. In this scenario, the drive member 13, which encircles the circular track 14, is located in the extraction position AP, where it grips the weft yarn 5, which is spread between the retaining element 11 and the air ring limiter 12 (see Figure 1). The air ring limiter 12 itself is not visible here and in Figures 5-9 and is located in front of the drawing plane. In the current example, the extraction position AP is directly behind the retaining element 11 along the weft insertion direction. There, the weft yarn 5 can be gripped particularly well by the drive member 13.

[0065] Figure 5 illustrates a second scenario when the weft yarn 5 is pulled back. In this scenario, the drive element 13 has moved counterclockwise along the circular track 14 from the extraction position AP and here uses its capture profile 27 to receive the weft yarn 5. The weft yarn 5 is now spread out between the fixing element 11, the drive element 13, and the air ring limiter 12 (or alternatively, the yarn guide element 28). Since the weft yarn 5 is fixed to the drum 8 by the fixing element 11, but the weft yarn end is movably held in the main nozzle 20, the weft yarn 5 is now pulled back into the main nozzle 20 by further movement of the drive element 13.

[0066] Figure 6 shows a third scenario when the weft yarn 5 is pulled back. In this scenario, the drive element 13 continues its journey on the circular track 14 and has pulled the weft yarn 5 back a certain distance. The fixing element 11 remains in the fixed position I.

[0067] Figure 7 shows an alternative scenario when weft yarn 5 is pulled back, in which weft yarn 5 is now almost completely pulled back. This scenario corresponds to the illustration in Figure 3.

[0068] Figure 7 also shows the pullback zone RB for the drive member 13. According to an advantageous embodiment of the pullback device 9 of the invention, the drive member 13 is driven discontinuously and at a reduced speed in the pullback zone RB. If the drive member 13 is located in the pullback zone RB, it does not interfere with the unwinding of the loop during weft insertion. It is also possible that the drive member 13 is also temporarily stopped in a rest position (not shown) at the beginning of the pullback zone RB. In this case, the weft yarn 5 remains connected to the drive member 13, which is stopped in the rest position RP, until weft insertion. This facilitates the unwinding of the weft yarn 5 and the start of weft insertion. However, discontinuous driving and stopping in the rest position are not absolutely necessary. It is also conceivable that the drive member 13 can be continuously wound.

[0069] Figure 8 now shows an alternative scenario where weft insertion has just begun and the weft yarn 5 has just disengaged from the drive member 13. At this moment, the drive member 13 is in the release position AGP. For weft insertion, the fixing element 11 is moved from the fixing position I to the release position II, thereby releasing the weft yarn 5 for weft insertion. Thus, the weft yarn 5, accelerated by the main nozzle 20, begins to unwind from the drum 8 in the unwinding direction AR while forming the yarn air loop 21 (see Figures 9 and 11) and is then introduced into the loom grid 2. The unwinding direction AR here corresponds to the rotation direction of the drive member 13 and is therefore also counterclockwise according to the current illustration. Due to the centrifugal force present here and the unwinding motion along the unwinding direction AR, the weft yarn 5 now begins to automatically disengage from the drive member 13.

[0070] According to the implementation scheme of the pullback device, the disengagement of the weft yarn 5 can also be supported by temporarily stopping the drive component 13 as described above.

[0071] The release position AGP also defines the start of the pullback zone RB, in which the drive 13 moves away from the drum 8 after the weft yarn 5 has disengaged. The release position AGP is variable and, if possible, adjustable. For example, the release position depends on the degree of pullback of the weft yarn 5, but remains substantially constant within the weaving process in the same machine setup.

[0072] Figure 9 illustrates an additional scenario during weft insertion. During this period, the weft yarn 5 has completely disengaged from the drive 13 and is introduced into the loom compartment 2 while forming the yarn air loop 21 (see Figures 1-3). During this period, the retaining element 11 remains in the release position II. Meanwhile, the drive 13 accelerates and continues its journey on the circular track 14 to return to the take-up position AP.

[0073] However, according to an alternative embodiment of the pullback device 9 and the method, it is also possible for the drive element 1 to remain stationary in the already described rest position during weft insertion or to remain stationary in another rest position after a short further movement on the circular track 14, so as not to interfere with weft insertion.

[0074] Next, a section of the weft yarn 5 can then be reapplied to the drum 8 as a loop. Similarly, the retaining element 11 can then move from the release position II to the retaining position I to secure the weft yarn 5 to the drum 8. Subsequently, the drive 13 continues its journey back to the extraction position AP, where it can re-grasp the weft yarn 5, which is now spread apart between the retaining element 11 and the air ring limiter 12.

[0075] As can be seen from Figures 4-10, the drive member 13 has a relatively long capture profile 27, which allows it to effectively grip the weft yarn 5. Furthermore, since the capture profile 27 is inclined towards the rotation axis 16 of the drive member, gripping the weft yarn 5 is further facilitated. Therefore, even when the diameter DT of the drum 8 is different, the weft yarn 5 can be reliably gripped.

[0076] In the example shown, the diameter DK of the circular track 14 of the drive 13 is slightly larger than the diameter DT of the drum 8. This allows for reliable gripping of the weft yarn 5 at the extraction position AP. Simultaneously, this also allows for reliable reception of the weft yarn 5, even when the diameter DT of the drum 8 is different, in conjunction with the longer capture profile 27.

[0077] According to the example shown, the rotation axis 16 of the drive member 13 and the axis 17 of the drum 8 are further offset from each other by an axial offset A. Due to this axial offset A, the circular track 14 of the drive member 13 is located near the diameter DT of the drum 8 in the region of the extraction position AP and therefore in the region of the fixing element 11. In contrast, on the side of the drum 8 away from the fixing element 11 or the extraction position AP, the circular track 14 of the drive member 13 has a larger gap from the diameter DT of the drum 8. As a result, the drive member 13 can grip the weft yarn 5 well in the extraction position AP. But then, the drive member 13 moves away from the drum 8 and thus does not interfere with the unwinding of the loop from the drum 8.

[0078] Advantageously, in the described pull-back device 9, the weft yarn 5 can automatically disengage from the drive member 13. Therefore, no active release element is needed for weft insertion into the pull-back device 9. This avoids weft insertion interference caused by erroneous release of the weft yarn 5 in time. Similarly, sudden excessive release of the weft yarn length and the resulting weft insertion interference can be avoided. Furthermore, it is particularly advantageous that, in the case of the described pull-back device 9, the weft yarn 5 is never subjected to friction caused by the guide element or similar objects during weft insertion.

[0079] The present invention is not limited to the embodiments shown and described.

[0080] Therefore, even though the pneumatic weft yarn introduction system 4 is currently shown, the described pull-back device 9 can in principle be used in conjunction with other weft yarn introduction systems 4.

[0081] Other variations within the scope of the claims of this patent are also permissible as any combination of the described features, provided they do not contradict the teachings of the independent claims, even if they are shown and described in different parts of the specification or claims or in different embodiments.

[0082] List of reference numerals

[0083] 1 loom

[0084] 2 loom grids

[0085] 3 warp yarns

[0086] 4-weft yarn introduction system

[0087] 5 weft yarns

[0088] 6-weft yarn storage device

[0089] 7 Pre-wound equipment

[0090] 8 rolls

[0091] 9 pullback devices

[0092] 10 reeds

[0093] 11. Fixing elements for weft yarns

[0094] 12-Gas Limiter

[0095] 13 drive components

[0096] 14 circular tracks

[0097] 15 drive units

[0098] 16. Rotation axis of the drive component

[0099] 17. Axis of the drum

[0100] 18 ring parts

[0101] 19 external teeth

[0102] 20 main nozzles

[0103] 21 yarn air pocket

[0104] 22 suction nozzle

[0105] 23 Reversing Nozzle

[0106] 24 weft yarn introduction channel

[0107] 25 Separation Equipment

[0108] 26 gears

[0109] 27 Capture the Outline

[0110] 28 yarn guide elements

[0111] I fixed position

[0112] II Release Position

[0113] RB pullback area

[0114] AP extraction location

[0115] AGP release position

[0116] The diameter of the circular track driven by DK

[0117] DT drum diameter

[0118] A-axis offset

[0119] AR Unwinding Direction

[0120] ES introduction side

[0121] SR weft direction

[0122] WR item pull direction

Claims

1. A method for introducing and pulling back weft yarn (5) at an air-nozzle type loom, wherein the weft yarn (5) to be introduced is temporarily stored on a bobbin (8), wherein, During temporary storage, the weft yarn (5) is fixed to the drum (8) by a fixing element (11) located in a fixed position (I), the weft yarn (5) is released for weft insertion, wherein the fixing element (11) moves from the fixed position (I) to the release position (II), and the weft yarn (5) is unwound from the drum (8) and introduced in the unwinding direction (AR) while forming a yarn loop (21), and in this method, the weft yarn (5) is pulled back by a pullback device (9) after weft insertion. The pull-back mechanism is characterized in that the weft yarn (5) is gripped and pulled back in the extraction position (AP) after the fixing element (11) and in the area of ​​the yarn air ring (21), wherein the weft yarn (5) is gripped by a drive member (13) of the pull-back device (9) that is movable on a circular track (14) around the drum (8), and pulled back by further movement of the drive member (13) on the circular track, wherein the drive member (13) moves circumferentially on the circular track (14).

2. The method according to claim 1, characterized in that, The weft yarn (5) is pulled back by the pullback device (9) until it reaches the main nozzle (20) of the pneumatic weft yarn introduction system (4) of the loom (1), so that the weft yarn (5) is still in the blowing area of ​​the main nozzle (20) after being pulled back.

3. The method according to claim 1 or 2, characterized in that, The drive member (13) is driven discontinuously on the circular track (14), wherein the drive member (13) moves periodically between the extraction position (AP) and the release position (AGP), in which the weft yarn (5) is released again.

4. The method according to any one of claims 1 to 2, characterized in that, The drive member (13) moves circumferentially from the extraction position (AP) back to the extraction position (AP) via the pull-back area (RB), wherein the drive member (13) moves at a reduced speed and / or temporarily stops in the pull-back area (RB) after the weft yarn (5) is pulled back.

5. The method according to any one of claims 1 to 2, characterized in that, The drive member (13) grips the weft yarn (5) directly after the fixed element (11) with respect to the yarn direction, and / or the drive member (13) grips the weft yarn (5) before the yarn guide element (28) immediately following the spool (8) with respect to the yarn direction.

6. The method according to claim 4, characterized in that, The weft yarn (5) remains connected to the drive (13) located in the pull-back area (RB) until the next weft insertion.

7. The method according to any one of claims 1-2, characterized in that, The drive element (13) is driven around the circular track along the unwinding direction (AR) of the weft yarn (5).

8. The method according to any one of claims 1-2, characterized in that, After the weft yarn (5) is released by the fixing element (11) for weft insertion, the weft yarn (5) automatically detaches from the driving element (13) due to the yarn tension and centrifugal force acting on the weft yarn during weft insertion.

9. The method according to any one of claims 1-2, characterized in that, After the weft yarn (5) is released for weft insertion, the drive (13) is accelerated and further moved to the extraction position (AP).

10. The method according to any one of claims 1-2, characterized in that, After the weft yarn (5) is disengaged from the drive member (13), the drive member (13) is accelerated and further moved to the extraction position (AP).

11. The method according to any one of claims 1-2, characterized in that, The weft yarn (5) extends unguidedly through the pullback device (9) during weft insertion.

12. The method according to any one of claims 1-2, characterized in that, Weft insertion begins before the weft yarn introduction channel (24) of the loom (1) is released by the open loom grid (2).

13. A prewinding device (7) for an air-nozzle type loom, the prewinding device having a drum (8) for temporarily storing a weft yarn (5) to be introduced; having a fixing element (11) for the weft yarn (5) mating with the drum (8), the fixing element being movable from a fixed position (I) to a release position (II) for releasing the weft yarn (5) for weft insertion; and having a pull-back device (9) for pulling back the weft yarn (5) after weft insertion is completed, characterized in that, The pullback device (9) is arranged in the pre-winding device (7) after the fixing element (11) in the yarn direction, and the pullback device (9) has a drive (13) for the weft yarn (5), which grabs the weft yarn (5) in the area after the fixing element (11) and in the area of ​​the yarn air (21) formed during weft insertion in the extraction position (AP), wherein the drive (13) can move circumferentially on a circular track (14) around the drum (8).

14. The pre-wound appliance (7) according to claim 13, characterized in that, The pull-back device (9) has a drive device (15) for driving the drive member (13).

15. The pre-wound appliance (7) according to claim 13 or 14, characterized in that, The drive member (13) is capable of moving discontinuously from the extraction position (AP) back to the extraction position (AP) via the pull-back area (RB) on the circular track (14).

16. The pre-wound appliance (7) according to any one of claims 13-14, characterized in that, The pull-back device (9) is arranged in the pre-winding device (7) such that the extraction position (AP) is directly behind the fixing element (11) in the yarn direction.

17. The pre-wound appliance (7) according to any one of claims 13-14, characterized in that, The drive element (13) is constructed as an open hook.

18. The pre-wound appliance (7) according to any one of claims 13-14, characterized in that, The diameter (DK) of the circular track (14) of the drive member (13) is larger than the diameter (DT) of the drum (8).

19. The pre-wound appliance (7) according to any one of claims 13-14, characterized in that, The rotation axis (16) of the drive member (13) is offset (A) relative to the axis (17) of the drum (8).

20. The pre-wound appliance (7) according to claim 14, characterized in that, The pullback device (9) has an annular member (18) with external teeth, the drive member (13) is arranged at the annular member with external teeth and the annular member with external teeth can be driven by the drive device (15).

21. An air-nozzle type loom, the loom having a weft yarn introduction system (4) and a pre-winding device (7) according to any one of claims 13-20.

22. The air-nozzle type loom according to claim 21, characterized in that, The weft yarn introduction system (4) is constructed as a pneumatic weft yarn introduction system (4), and the weft yarn introduction system has at least one main nozzle (20).

Images