METHOD FOR RELEASING FAULTY WEFT THREADS IN WEAVING MACHINES AND DEVICE USED FOR THE PURPOSE

Abstract: Method for releasing faulty weft threads in weaving machines, characterized in that it essentially consists in the combination of : - eliminating the binding between the faulty weft thread (6) and the warp threads (1, 2) ; - initially releasing or holding the weft thread (6) free near the fabric edge or edges (14, 16) by moving the associated thread end or both thread ends thereof away from the cloth line (5) or holding it apart ; - positioning at least one releasing element or releasing elements (12, 13 ; 26-33) between the cloth line (5) and the released thread end or released thread ends ; - releasing the thread end or the thread ends over a further distance (A) by moving the releasing element or releasing elements (12, 13 ; 26-33) away from the cloth line (5) in the direction of the reed ; - repositioning a releasing element (12 ; 26-33) between the weft thread section or weft thread sections (8, 9) thus released and the cloth line (5) ; - in turn releasing over a further distance (B) the weft thread (6) by moving the last-mentioned releasing elements (12, 13 ; 26-33) away from the cloth line (5) in the direction of the reed ; - and continuing the last-named two steps in the shed (3) stepwise until the weft thread (6) is released over the desired length.

Description: This invention relates to a method for releasing faulty weft threads in weaving machines, in other words, a method for freeing a beaten-up faulty weft thread again in the shed in a manner such that it can readily be removed therefrom. The invention furthermore relates also to devices which use said method. A weaving machine is known from the Dutch Patent Application no. 82 04665 which contains means for removing defective weft threads from the shed. The means used in this case provide for an element which can be moved to and fro through the shed to be introduced from the insertion side of the weaving machine, which element is passed between the cloth line and the thread to be released. However, this device has the disadvantage that the element which can be moved to and fro moves along the weft direction over the warp threads and consequently can catch on the latter and damage them. Another disadvantage of said device is that it is only suitable for releasing sections of thread which are located at the insertion side of the machine. In the case of a broken weft thread, the other section of thread is not released. Yet another disadvantage of this device is that it requires a lot of space at the entrance of the shed and this entails difficulties in siting the other necessary components. A device is also known from the Dutch Patent Application no. 82 02215 for releasing faulty weft threads. In this case, the faulty weft thread is released at a number of points in the shed and then drawn through the uppermost warp threads. The actual release of the faulty weft thread is carried out by allowing a hook-shaped element to slide over the cloth until it reaches the vicinity of the cloth line, the beaten-up faulty weft thread, which has already been beaten-up but not yet fixed in position, being released and taken to the centre of the shed. This device does not, however, offer complete reliability in relation to releasing the faulty weft thread since, if the latter is securely clamped between the warp threads, the needle-shaped element will slide over the faulty weft thread and completely miss its object. A shuttleless weaving machine is known from the British Patent no. 1.430.520 in which a faulty weft thread, more particularly a broken weft thread, is removed from the shed from either side by means of devices installed next to the shed. The present invention relates to a method for releasing faulty weft threads and also to a device which uses said method, the above-mentioned disadvantages being systematically eliminated. According to this invention, the method for releasing faulty weft threads has the characteristic that it essentially consists in : - eliminating the binding between the faulty weft thread and the warp threads ; - initially releasing or holding the weft thread free near the fabric edge or edges by moving the associated thread end or both thread ends thereof away from the cloth line or holding it apart ; - positioning at least one releasing element or releasing elements between the cloth line and the released thread end or the released thread ends ; - releasing the thread end or the thread ends over a further distance by moving the releasing element or releasing elements away from the cloth line in the direction of the reed ; - repositioning a releasing element between the weft thread section or weft thread sections thus released, and the cloth line ; - in turn releasing over a further distance the weft thread by moving the last-mentioned releasing element away from the cloth line in the direction of the reed ; - and continuing the last-named two steps in the shed stepwise until the weft thread is released over the desired length. With the intention of demonstrating the characterizing features according to the invention more satisfactorily, the method and a number of devices according to the invention are described below, as examples without any limiting nature, with reference to the accompanying drawings in which : figures 1 to 5 inclusive show diagrammatically the me­ thod according to the invention ; figure 6 shows a device according to the invention ; figure 7 to 13 inclusive show diagrammatically the me­ thod according to the invention in which both thread sections of a broken weft thread ahve to be removed ; figure 14 shows a device according to the invention ; figures 15 to 17 inclusive illustrate the operation of the device according to figure 14 in steps ; figures 18 to 31 show diagrammatically a variation of a device which uses the method according to the invention and also the operation thereof ; figure 32 shows a releasing element according to the in­ vention ; figure 33 shows diagrammatically the way in which the releasing elements according to the invention are moved. The diagrammatic depictions in figures 1 to 5 inclusive show the uppermost warp threads 1, the undermost warp threads 2, the shed 3, the fabric 4 and the cloth line 5. Furthermore, a faulty weft thread 6 is indicated which consists, for example as a result of a thread break 7, of two weft thread sections 8 and 9. The weft thread 6 is still connected to the thread feed 10, for example via a thread eye or thread clamp 11. According to this embodiment, use is furthermore made of two movable needle- or pin-type releasing elements 12 and 13. During the normal weaving process, said releasing elements 12 and 13 are located outside the shed 3 and in front of the fabric edge 14 or the extension thereof. If a thread break 7 is now detected as in figure 1, which can be done automatically by known detection devices, the weaving machine is stopped. If the faulty weft thread 6 has already been fixed in position by the warp threads 1 and 2, said fixing should first be eliminated by turning the weaving machine backwards, all this being done in a manner such that a situation is achieved as shown in figure 1. The releasing element 12 is then lowered and moved away from the cloth line 5 in the direction of the reed 15 (figure 2). This forces the weft thread 6 free and it is released over a distance A from between the warp threads 1 and 2. After this, the second releasing element 13 is placed next to the first as shown in figure 3. As shown in figure 4, the first releasing element 12 is then moved upwards, moved over the warp threads 1, moved back in the direction of the cloth line 5 and then lowered through the warp threads 1 into the shed, all this in a manner such that said releasing element 13 is positioned just next to the cloth line 5 inside the above-mentioned distance A and behind the weft thread 6. By now moving the releasing element 12 away from the cloth line 5 in the shed 3 (in other words, towards the reed 15), the weft thread 6, more particularly the thread section 8 is released over a further distance B. The releasing element 13 ensures that the weft thread 6 always remains taut, otherwise the latter could not be released by the releasing element 12. As shown in figure 5, the releasing element 13 is again placed next to the first releasing element 12 in a subsequent step. By repeating the above-mentioned cycle, a complete operation is build up in which, in a stepwise advancing movement V, the faulty weft thread 6, or at least the weft thread section 8, is released. The released weft thread section 8 can then easily be removed from the shed by thread removal means known per se. Thus, this weft thread section 8 will be removed, for example at the other fabric edge 16, from the shed 3, as shown in figure 6, by introducing a new weft thread 17 which is entrained by the section 8 in the form of a loop. Since the releasing elements 12 and 13 are always positioned between an already previously removed section of the weft thread 6 and the cloth line 5, the thread to be released is gripped in a positive manner, this being in contrast to the device of the above-mentioned Dutch Patent Application no 82 02215 in which the releasing elements have to be forced between the cloth line and the faulty weft thread. It is clear that the operation to free the weft thread 6 may start not only from the fabric edge 14, but that it can also start from the opposite fabric edge 16 (figure 6), in other words by executing an operation by means of releasing elements 12 and 13 following a movement W, this being in order to free the second weft thread section 9. Since the thread end of the weft thread 6 is completely woven in near the fabric edge 16, it should first be pulled free by means of movable clamping means 18 known per se, for example a mechanical clamp or a suction nozzle, in a manner such that a free space 19 is created for the initial positioning of the releasing elements 12 and 13. The release of the weft thread section 9 then takes place in an analogous manner as described with reference to figures 1 to 5 inclusive. It is clear that, if, in the event of a thread break 7, it is desired to release one of the weft thread sections 8 or 9 completely, the releasing elements 12 and 13 should be moved in the respective V or W over the complete weaving widths, this being because it is not known where the thread break is situated in the shed. If it is now desired to release both thread sections 8 and 9 of a broken weft thread 6 according to the method of the invention, it is possible to proceed as shown in figures 7 to 13 inclusive. According to figures 7 to 12 inclusive, in this process a first operation is executed from left to right. As specifically shown in figure 11, the releasing elements 12 and 13 cannot finish up behind the second thread section 9 in this process, with the result that it is not released. In order, therefore, to release said section 9, a second operation is provided in which the releasing elements 12 and 13 execute a movement from right to left, the start of which is shown in figure 13. According to a variation not shown in the figures, it is also possible to employ two devices which release the thread sections 8 and 9 respectively from the oppositely situated fabric edges 14 and 16, the devices executing a crossing movement. Figure 14 shows an example of a device for releasing the faulty weft threads. The above-mentioned releasing elements 12 and 13 are in this case embodied in needle form and are respectively mounted on two small carriages or the like, 20 and 21. Drive means which are not shown in the figures are provided in the small carriages 20 and 21 in order to move the releasing elements 12 and 13 through the warp threads 1 and 2 in and out of the shed 3 precisely in order to provide the necessary to and fro movement in the shed 3. The small carriages 20 and 21 form the means of moving the releasing elements 12 and 13 and they therefore provide the stepwise movement thereof. Said small carriages 20 and 21 are provided with a drive which is formed by cable connections 22A and 22B and stepping motors 23A and 23B. The small carriage 21 is connected to the small carriage 20 by means of elastic means 24, such as, for example, a tension spring. The small carriages 22A and 22B each furthermore contain a braking or locking mechanism in a manner such that they can be locked with respect to the guide 25. The operation of the device according to figure 14 is shown diagrammatically in figures 15 to 17 inclusive for above-mentioned movement W. In figure 15 the small carriages are up against each other. In a first step, the small carriage 20 is advanced, while the small carriage 21 is locked. The spring 24 is stretched. In the situation in figure 16, the releasing element 12 is then set in operation, a release cycle being executed as described above. The needle 13 is then removed from the shed 3 and the locking machanism of the small carriage 21 is released. The tension spring 24 pulls the second small carriage 21 back up against the first small carriage 20. The releasing element 13 is then lowered again, as shown in figure 17. The preceding steps can then be executed repeatedly. For the movement V, the functions of the small carriages 20 and 21 are reversed. Of course, the whole of the necessary control means are provided for switching the above-mentioned drive means and moving means on and off appropriately. Preferably, the control takes place via the cable connections 22A and/or 22B which are constructed as electrical conductors along which control signals can be transmitted. The device for releasing the faulty weft thread 6 does not necessarily have to be movable along the fabric. Figure 18 therefore shows diagrammatically a device in which use is made of releasing elements 26 to 33 inclusive which are distributed over the complete weaving width in the vicinity of the cloth line 5 and are situated in the rest state above or below the shed. A possible operation procedure thereof is shown stepwise in figures 18 to 31 inclusive. Here the releasing elements 26 to 33 inclusive are represented by means of small crosses if they are situated ouside the shed 3, and by means of dots if they are positioned in the shed. The weft thread 6 is, of course, first released initially near the fabric edges 14 and 16, for example by means of clamps 34 to 35. As shown in figure 19, a release element, 26 and 33 respectively, is then lowered at both ends of the shed 3, and they finish up between the cloth line 5 and the respective weft thread sections 8 and 9. The method according to the invention is then executed from both ends, by means of the movements V and W respectively. The two operations, by means of movements V and W respectively, should be executed over the complete moving width, which is clearly shown in the figures. In particular, it can be seen in figure 23 that, if the two operations were to stop in the middle of the shed 3, in other words at the point where they meet each other, then the thread section 8 would not yet have been released at the height of the releasing elements 30 and 31. The releasing elements are, of course, provided with the necessary drive and control means to execute the above-mentioned steps in a suitable manner. Preferably, the above-mentioned releasing elements 12, 13 and 16 to 33 inclusive are provided with thread detectors 36. In figure 32 these consist, for example, of two optical detection elements 37 and 38 situated opposite each other. According to a variation, however, mechanical detectors or the like can also be used. The detection elements 37 and 38 are placed in a manner such that they can detect the thread concerned during the forward movement 39. The use of the thread detectors 36 offers the advantage that the above-mentioned releasing elements do not always have to operate over the complete width of the machine, but only over the distance in which the weft thread section concerned is present. With reference to the embodiment in figures 18 to 31 inclusive, this means that the operation by means of the movement W is interrupted when the situation in figure 22 is reached since weft thread is no longer detected at the releasing element 31, while the operation by means of the movement V is continued until the situation in figure 27. By means of the thread detectors 36, it is also possible to detect whether all the thread has been removed from the shed 3. The releasing elements 12 and 13, or respectively 26 to 33 inclusive, describe preferably a rectangular path 40 as shown in figure 33. Providing first an upwards movement 41 after the forwards movement 39 and then only a return movement 42 prevents the weft thread 6 which has been forced loose being carried back to the cloth line 5, for example because it has caught on the releasing element. The present invention is by no means limited to the embodiment described as an example but such a method and device for releasing weft threads can be realized in accordance with variations of all kinds without departing from the scope of the invention.

Claims: 1.- Method for releasing faulty weft threads in weaving machines, characterized in that it essentially consists in the combinations of : - eliminating the binding between the faulty weft thread (6) and the warp threads (1, 2) ; - initially releasing or holding the weft thread (6) free near the fabric edge or edges (14, 16) by moving the associated thread end or both thread ends thereof away from the cloth line (5) or holding it apart ; - positioning at least one releasing element or releasing elements (12, 13 ; 26-33) between the cloth line (5) and the released thread end or released thread ends ; - releasing the thread end or the thread ends over a further distance (A) by moving the releasing element or releasing elements (12, 13 ; 26-33) away from the cloth line (5) in the direction of the reed ; - repositioning a releasing element (12 ; 26-33) between the weft thread section or weft thread sections (8, 9) thus released and the cloth line (5) ; - in turn releasing over a further distance (B) the weft thread (6) by moving the last-mentioned releasing elements (12, 13 ; 26-33) away from the cloth line (5) in the direction of the reed ; - and continuing the last-named two steps in the shed (3) stepwise until the weft thread (6) is released over the desired length. 2.- Method for releasing faulty weft threads according to claim 1, characterized in that the stepwise release of the faulty weft thread (6) is carried out from both fabric edges (14, 16), this being done by providing a first operation (V) of the releasing elements (12, 13 ; 26-33) from one fabric edge (14) to the other (16), and then a second operation (W) in the opposite sense. 3.- Method for releasing faulty weft threads according to claim 1, characterized in that the stepwise release of the faulty weft thread (6) is carried out from both fabric edges (14, 16), this being done by providing two oppositely directed operations (V, W), which cross each other, at the same time from the oppositely situated fabric edges (14, 16). 4.- Method for releasing faulty weft threads according to claims 2 or 3, characterized in that during the releasing movements which are executed by the releasing elements (12, 13 ; 26-33) a check is also performed on the presence of the faulty weft thread (6) for the respective releasing elements when they are situated in the shed, and that, in the event that a weft thread (6) is no longer detected in front of the last releasing elements set in operation, the above-mentioned releasing movements of the operation (V, W) concerned is interrupted. 5.- Method for releasing faulty weft threads according to one of the preceding claims, characterized in that the initial releasing of the weft thread (6) near the fabric edge or edges (14, 16) takes place by pulling free the extremity or extremities thereof by means of movable clamping means (18 ; 34, 35). 6.- Device for releasing faulty weft threads in weaving machines according to the method of one of the preceding claims, characterized in that it essentially consists in : - at least one needle-type releasing element (12 ; 26-33) which can penetrate between the warp threads (1, 2) ; - drive means to move the needle-type releasing element (12 ; 26-33) through the warp threads (1, 2) respectively in and out of the shed (3), and also to and fro (from the cloth line (5) to the reed (15) and back) ; - moving means to move the needle-type releasing element (12 ; 26-33) along the cloth line (5) and drive means thereof ; - control means for switching the drive and moving means on and off in a manner such that the needle-type element (12 ; 26-33) describes cycles in which it is positioned just next to the cloth line (5) in the shed (3), is then moved in the direction of the reed (15), is then brought back out of the shed (3) and moved further along the cloth line (5) in order to again be brought next to said cloth line (5) through the warp threads (1, 2) in to the shed (3). 7.- Device according to claim 6, characterized in that the moving means consists of the combination of two small carriages (20, 21) which can be moved over the width of the fabric (4) and which are connected mutually to each other by means of elastic means (24), each small carriage being provided with a needle-type releasing element (12, 13) with drive means therefor ; a drive (22A, 22B) for the small carriages (20, 21) which is instructed by the above-mentioned control means ; and a locking device for the small carriages (20, 21), the foremost small carriage (20) being able to entrain (in the function of the sense of movement) the other small carriage (21) stepwise with a certain delay by means of the tension force of the elastic means (24). 8.- Device according to claim 7, characterized in that the drive for the small carriage consists of cable connections (22A - B) and motors (23A-B) which the cables instruct, the cable connections (22A-B) consisting of conductors which transmit the control signals for the drive means of the needle-type releasing elements (12, 13). 9.- Device for releasing faulty weft threads in weaving machines in accordance with the method according to one of the claims 1 - 5 inclusive, characterized in that they consist essentially in : - a row of movable needle-type releasing elements (26-33) which are arranged along the cloth line (5) and can be positioned in the shed (3) next to said cloth line through the warp threads (1, 2) ; - drive means for moving the needle-type elements (26-33) separately in and out of the shed (3) and to and fro with respect to the cloth line (5) (away from and towards it) ; - control means for instructing the needle-type releasing elements (26-33) in a sequential manner starting from one or both fabric edges (14, 16), in other words for switching the above-mentioned drive means on and off. 10.- Device according to one of the claims 6 to 9 inclusive, characterized in that the releasing elements (12, 13 ; 26-33) are provided with thread detectors (36).

Inventors: SHAW, HENRY
Applicants: PICANOL N.V.
Application year: 1987
Main classification: D03D51
IPC codes: D03D51