METHOD FOR REPAIRING A WEFT THREAD IN A WEAVING MACHINE, AND A WEAVING MACHINE WHICH USES THIS METHOD

Abstract: Method for repairing a weft thread in the weft preparing device of a weaving machine, with the characteristic that, when a thread break (1) occurs before the thread accumulation space (4) of the weft accumulator (2), the method consists of using the thread reserve (R) present in the corresponding weft accumulator (2) in order to lead the broken section of thread (21) back, and then joining this thread section (21) with the end (22) of a weft thread (7, 25) which is connected to a yarn package (1, 24).

Description: This invention concerns a method for repairing a weft thread in a weaving machine, in particular in the weft preparing device of the weaving machine, more especially on weaving machines in which the weft thread is taken from a yarn package, via a weft accumulator to a pick insertion device. More especially, the invention also provides a method for repairing breaks in the weft thread before it reaches said weft accumulator. The method also concerns weaving machines which use said method. See, for example EP-A-269140 (document to be considered only under Article 54 (3)). The method according to the invention for carrying out a thread repair, as outlined above, in particular when a thread break occurs before the thread accumulation space of the thread accumulator, consists essentially of using the thread reserve present in the corresponding thread accumulator in order to lead the broken section of thread back over a certain distance, and then joining this section of thread to the end of the weft thread coming from the yarn supply. In two variants, the broken section is either joined to the weft thread from the yarn supply previously in use, or is not. Clearly, the weaving machine according to the invention must incorporate a weft preparing device which is equipped with the necessary detection device in order to detect a thread break, as well as a thread-joining device in order to join the thread ends together, and a mechanism for leading said thread reserve back. The weft preparing device used for this purpose is described in greater detail in the following description. In order to explain the characteristics of the invention, several variants according to the invention are described below, together with the weft preparing devices used, by way of example only and without being limitative in any way, with reference to the accompanying drawings, where: figs. 1 to 4 are schematic representations of the method of the invention, using a weft preparing device designed for the purpose; fig. 5 shows a variant of the part indicated by F5 in fig. 1; fig. 6 shows the same part as in fig. 5, but in a different position. As shown in fig. 1, the weft preparing device consists essentially of a yarn supply 1, at least one weft accumulator 2 and a pick insertion device 3. The yarn supply 1 can consist of a yarn package, as shown in the figures. The weft accumulator 2 has a thread accumulation space 4 and, in the embodiment shown, incorporates a prewinder consisting essentially of a prewinder drum 5 and a winding tube 6. By thread storage space 4 is meant the actual place in the thread accumulator 2 where the thread accumulation is formed. In the variants shown, this is the prewinder drum 5. The pick insertion device 3 here consists of a main nozzle for inserting the weft thread 7 into the shed 8, after which the weft thread can be beaten up by the reed 9. Clearly, the pick insertion device 3 can also consist of several nozzles, or a weft gripper or any other insertion device. In the present invention, the weft preparating device in particular also incorporates: a detection device 10 in order to monitor the weft thread 7 for a possible break 11; a thread-joining device 12, a thread-backing device, here consisting of an automatic threading device 13, as known from BE-A-1000 368 made by the present applicant, a thread-freeing device 14; and a number of thread clips 15 to 17. The detection device 10 and the thread-joining device 12 can operate on the weft thread 7, in particular between the yarn supply 1 and the weft accumulator 2. Here it should be noted that the operation of the detection device 10 can be based either on detection of the presence of the thread, or on detection of whether or not the thread is in motion. The automatic threading device 13 enables a section of thread to be drawn back through a number of the abovementioned components, in order to rethread them. This automatic rethreading device is explained in detail further on. The thread-freeing device 14 can be of any type; for example it may consist of a hooking device 18 or a tube 19 into which the thread can be drawn up pneumatically, or a combination of both. Note that the thread-freeing device 14 can operate in conjunction with weft accumulator 2. The method in which the weft preparating device described above is used is now described with reference to figs. 1 to 4. In the state shown in fig. 1, a thread break 11 has just occurred and been detected by the detection device 10. As a consequence, e.g. by means of a control unit 20 (shown only in fig. 1, for the sake of clarity), at least one thread reserve R consisting of a sufficient length of the broken section remains available in the weft accumulator 2. As shown in fig. 2, the thread-freeing device 14 is then activated, as a result of which, in this variant, the thread reserve R is completely freed, essentially by drawing it off the prewinder drum 5 by means of the hooking device 18, or by the suction of the tube 19, or by means of a blower or suchlike operating in conjunction with the tube 19. Meanwhile the automatic threading device 13 is activated. As shown in fig. 3, the free thread reserve R thus obtained is drawn back opposite the normal direction of motion of the weft thread 7 by the threading device 13, thus, in this variant, automatically rethreading the weft accumulator 2, the thread-joining device 12 and the thread clip 17. In this way the state shown in fig. 4 is reached, in which the thread ends 22 and 23 formed as a result of the thread break are presented to each other and joined together by means of the thread-joining device 12. Here it should be noted that the thread-joining device 12 may consist of a tying device, a splicing device or suchlike. Clearly, the thread clips 15 to 17 also have to be controlled accordingly, more particularly as shown in the figures. Thread clip 15 prevents the broken thread section 21 being drawn out of the pick insertion device 3 when the thread is led back. Thread clips 16 and 17 hold the weft thread 7 and the broken section of thread 21 stretched out while their ends, 22 and 23 respectively, are being joined. If the thread break 11 occurs before the thread clip 16, the end 22 of the weft thread 7 connected to the yarn supply 1 can be brought into thread clip 16. Sufficient devices for doing this are already known. If the thread break 11 occurs after the thread clip 16, then said end 22 can be gripped in the thread clip 16 directly. Figs. 5 and 6 show yet another variant which makes it clear that the broken section of thread 21 does not necessarily have to be tied on to the thread end 22 from which it has broken off; instead, a suitable positioning mechanism can be used to switch over to a second yarn supply 24 whose weft thread 25 is held with its end 26 in thread clip 16, which is positioned at a different point. The switch-over can be carried out as shown in figs. 5 and 6. This variant is particularly advantageous whenever the end 22 of the weft thread 7 previously in use is rather difficult to find. Naturally, more than one weft accumulator 2 can be used, so that as soon as a thread break occurs it is possible to switch over quickly to a second weft accumulator 2 which is already threaded; in this way, it is only necessary for the thread ends to be joined, while in the meantime the operation of threading the weft accumulator previously in use begins. When the next thread break occurs, the system switches over in a similar manner to the first weft accumulator 2, which in the meantime will have been rethreaded once more. Clearly, it is also possible to use two completely independent weft preparating devices such as shown in fig. 1, so that while a weft thread 7 is being repaired in the first one, another weft thread can be supplied to the pick insertion device 8 from the second, and vice versa.

Claims: 1. Method for repairing a weft thread in the weft preparating device of a weaving machine, in which the weft thread is taken from a yarn package, via a weft accumulator to a pick insertion device, with the characteristic that, when a thread break (11) occurs before the thread accumulation space (4) of the weft accumulator (2), the method consists of using the thread reserve (R) present in the corresponding weft accumulator (2) in order to lead the broken section of thread (21) back and then joining this thread section (21) with the thread end (22) of the weft thread (7, 25) which is connected to the yarn package (1, 24). 2. Method as in claim 1, with the characteristic that the method consists of: using a detection device (10) to monitor the weft thread (7, 25) for a thread break (11); using a thread-joining device (12) which can be presented to the path of the weft thread (7, 25) between the yarn package (1) and the weft accumulator (2) and which can operate on the weft thread; using a threading device (13) to draw the thread reserve (R) back in the opposite direction; and using a control unit (20) connected to the detection device (10) so that when a thread break (11) is detected by the detection device (10) then successively: the thread accumulator (2) is stopped; the thread reserve formed by means of the threading device (13) is drawn back, thus at the same time rethreading the weft accumulator (2), and finally the corresponding thread ends (22, 23/25, 23) are joined together by means of the thread joining device (12). 3. Method as in claim 1 or 2, in which the weft accumulator (2) is of the type which uses a prewinder, consisting essentially of a prewinder drum (5) and a winding tube (6), with the characteristic that the thread reserve present on said weft accumulator (2) is drawn off said prewinder drum (5) by means of a thread-feeding device (14) before being led back through said winding tube (6). 4. Method as in any of the above claims 1 to 3, with the characteristic that more than one yarn package (1) is used and that after each thread break (11) the broken section of thread (21) after being drawn back is joined alternatively to the weft thread (25) of another yarn package (24), where the weft thread (25) of the second yarn package (24) has previously been prepared with its end (26) ready to be joined. 5. Weaving machine which uses the method as in any of the above claims 1 to 4, incorporating a weft supply mechanism consisting of a combination of: a yarn package (1); a weft accumulator (2); a pick insertion device (3); a detection device (10) positioned along the path of the weft thread (7) between the yarn package (1) and the weft accumulator (2) in order to detect thread breaks (11); a thread-joining device (12) which operates on the weft thread (7, 25) between the yarn package (1) and the weft accumulator (2); a threading device (13) in order to draw the thread reserve (R) in the weft accumulator (2) back over a certain distance in the direction opposite to the normal direction of motion on the weft thread (7); and a control unit (20) which acts on the signal from the detection device (10) to control the thread-joining device (12) and the threading device (13), so that when a thread break (11) is detected by the detection device (10), the thread reserve (R) in the weft accumulator (2) is first drawn back over a certain distance and then joined to the weft thread (7, 25) from the yarn package (1). 6. Weaving machine as in claim 5, with the characteristic that the weft preparing device also incorporates a thread-freeing device (14) in order to free the thread reserve (R) in the weft accumulator (2). 7. Weaving machine as in claim 6, with the characteristic that the thread-freeing device (14) consists of a hooking device (18). 8. Weaving machine as in claim 6, with the characteristic that the thread-freeing device (14) consists of a tube (19) into which the thread can be drawn up pneumatically. 9. Weaving machine as in any of claims 5 to 8, with the characteristic that it has more than one yarn supply (1, 24), and also a a positioning mechanism which, when a thread break (11) occurs, switches over to the other yarn supply (24) from the previous one (1).

Inventors: SHAW, HENRY
Applicants: PICANOL N.V.
Application year: 1988
Main classification: D03D47
IPC codes: D03D47, D03J1