METHOD FOR REPAIRING A WEFT THREAD ON WEAVING MACHINES

Abstract: Method for repairing a weft thread (3) on weaving machines, in particular for thread breaks between the yarn supply package (8A) and the device (2) for forming a particular thread accumulation. This method consists essentially of: continually providing yarn supply packages (8A, 8B, 8C, 8D); using a thread clip (11B, 23, 24) to hold the thread end (15) of at least the supply package (8B) following the supply pakcage (8A) in use; monitoring the weft thread (5) for breaks between the supply package (8A) in use and the device (2) for forming a particular thread accumulation; then, when a thread break (10) is detected, gripping the above-mentioned thread end (15) of the next supply package (8B) and joining said thread end to the broken weft section (17) which is connected to the device (2) for forming a thread accumulation (3).

Description: This invention concerns a method for repairing a broken weft thread on weaving machines, in particular for repairing thread breaks which occur between the yarn supply package in use and the device for forming a thread accumulation necessary for inserting a weft thread into the shed. In a particular embodiment of the invention, a rotating package frame is used, preferrably of the type where supply packages are presented one after the other to the insertion mechanism by a conveyer belt. From EP-A-0 171 057 it is known that a broken weft thread can be repaired by means of a thread of a new weft thread supply package which, after detecting the broken weft thread, is cut off and wound around the storage drum and is threaded to the main nozzle. This method has the disadvantage that the action of cutting off and of rethreading the storage drum and the main nozzle is time-consuming. The present invention relates to a method not having the abovesaid disadvantage. To this end the method according to the invention comprises the steps of providing yarn supply packages; using a thread clip to hold the thread end of at least the supply package following the yarn supply package in use; monitoring the weft thread for breaks between the supply package in use and the device for forming the above-mentioned thread accumulation; and when a break is detected, gripping the thread end of the following supply package which is not in use in order to use the latter for repairing the weft thread, whereby this method is characterised in that the yarn supply packages are continually provided and that the gripped thread end is joined to the broken weft section which is still connected to the device for forming a thread accumulation. In order to explain the characteristics of the invention, the following preferred embodiments are described, without being limitative in any way, with reference to the accompanying drawings, where: figs. 1 to 3 show the different steps of the method according to the invention; fig. 4 shows a variant of the step shown in fig. 3; figs. 5 to 9, 10 to 12 and 13 to 14 respectively show three variants of the invention. Fig. 1 shows a weft insertion mechanism which, as is known, consists essentially of a package frame 1, a device 2 on which a particular thread accumulation 3 can be formed, and a weft insertion device 4 for inserting the weft thread 5 into the shed 6 on the weaving machine, where this thread 5, as is known, is beaten up between the warp threads by a reed 7. The package frame 1 is of the type where in addition to the supply package in use 8A, at least one second supply package 8B is held in readiness to be used as soon as the previous package is empty or is no longer connected to the device 2 as the result of a thread break. In this embodiment, this is achieved by using a package frame 1 consisting of a conveyor belt 9, such that as shown schematically by the arrow 10 the empty supply packages can be evacuated automatically, while a full supply package is presented automatically. The device 2 used to form a weft accumulation 3 can consist of e.g. a prewinder which itself is common technology. Clearly, on a airjet weaving machine the insertion device 4 will consist of a main injector or similar, while on a gripper machine it will be formed by grippers. Also in fig. 1, use is made of: a number of thread clips 11A to 11D which in this case are mounted on the conveyor belt 9; a thread eye 12 through which the weft thread 5 is led from the package frame 1 to the device 2 for forming a thread accumulation 3; a detection device 13; and a threading device 14 or suchlike. The detection device 13 monitors the thread 5 for breaks, either by detecting the absence of the thread or by detecting that the thread is not moving. The method according to the present invention consists of gripping the thread end 15 of at least the supply package 8B following the supply package in use 8A, by means of a thread clip 11B. In the embodiment shown in fig. 1, the thread end 15 of any supply package 8 can be brought into the corresponding thread clip 11 by positioning the conveyor belt 9. Here it should be noted that either mechanical or pneumatic thread clips (thread catchers) 11A-11D can be used. Pneumatic thread catchers, consisting of e.g. suction nozzles, offer the advantage that the thread is always held kept stretched between the thread catcher and the supply package, even if the distance between the thread catcher and the supply package changes as a result of rotation of the conveyor belt 9 of the package frame 1. If a thread break 16 occurs, as shown in fig. 1, this is detected by the detector 13. As a result of this detection, the threading device 14 is actuated, such that said threading device moves through the thread eye 12 and grips the thread end 15 of the next supply package 8B, as shown in fig. 2. The clip 14A of the threading device 14 can be either mechanical or pneumatic, e.g. in the form of a suction nozzle. The threading device 14 is then drawn back, thus threading the detector 13 and the thread eye 12, after which the thread end 15 is joined to the weft section 17, preferably by means of a welded splice 18, as shown in fig. 3. The join can be made by devices which themselves are common technology, for example a tying-in device or a splicer, represented in the figures by 19. The free end 20 formed on the supply package 8A previously in use can be brought back into the thread clip 11A in various ways. As shown in fig. 3 this is done by means of a suction nozzle 21 which scans the outer surface of the corresponding supply package 8A, catches the thread end 20 and then brings it into the thread clip 11A. As shown in fig. 4, the supply package 8A is first brought back into the position where new supply packages are normally mounted on the conveyor belt 9, in order for the thread end 20 to be led into the thread clip 11A by the suction nozzle 22. Clearly, in this case when a new supply package is mounted the suction nozzle 22 also has the function of finding its thread end 15 and leading said thread end into the corresponding thread clip. In the embodiment shown in figs. 5 to 9, instead of the above-mentioned thread clips 11 a single pneumatic thread catcher or suction nozzle 23 is used. By means of this suction nozzle 23 the thread end 15 of the next new supply package 8B is found and caught, whereupon said suction nozzle 23 is brought to a particular point P, as shown in fig. 6. When the detector 13 detects a thread break 16, the package frame 1 is actuated such that said package 8B is brought into the same position as the package previously in use 8A, so that, as shown in fig. 7, the thread end 15 is situated in front of the thread eye 12 and the detector 13. As shown in fig. 8, it is then simple for the thread end 15 to be drawn through the detector 13 and the thread eye 12 by means of the threading device 14 and then connected to the the weft section 17, as shown in fig. 9. The embodiment shown in figs. 10 to 12 uses a fixed thread clip 24, in which the thread end 15 of each new package 8B is placed, and an auxiliary device 25 with a fork 26 which moves so as to bring the thread end 15 of the supply package 8B into line with the thread eye 12 and the detector 13. Clearly in this case after the broken thread 5 has been repaired the package frame 1 is turned so that, as shown in fig. 12, the supply package 8B is brought into the position shown for supply package 8A. In another variant of the invention, the thread end 15 of the supply package 8B following the supply package in use 8A is caught by a suction nozzle 23, in exactly the same way as shown in figs. 5 and 6, after which when a thread break 16 is detected, the suction nozzle 23 is moved so that the thread end 15 is brought into the vicinity of the thread eye 12 and/or the detector 13. The position obtained in this way is shown in fig. 13. Then, as shown in fig. 14 the thread from the supply package 8B is drawn through the thread eye 12 by means of the threading device 14. In another variant, not shown in the figures, the suction nozzle 23 is presented to the thread eye 12, whereupon the suction is cut off and compressed air supplied, so that the thread end 15 is blown through the thread eye 12. Then either the threading device 14 brings the thread end 15 to the device 19, or thread end 15 is blown directly into the vicinity of the device 19. In yet another variant not shown in the figures, instead of the fork 26 shown in fig. 10 a suction nozzle is used, e.g. suction nozzle 23, where the auxiliary device 25 with suction nozzle 23 can be moved as in the embodiments shown in figs. 5 and 13, i.e. in order to bring the thread to a particular point P, after which when a thread break occurs the bar with the suction nozzle 23 mounted on it extends until it comes in front of the detector 13 and the thread eye 12, whereupon the thread can be drawn through. If the weft section 14 is no longer located at the point at which it is to be connected to the thread end 15, it can be fetched by means of e.g. the method described in Belgian patent application No. 8700566 made by the present applicant.

Claims: 1. Method for repairing a weft thread on weaving machines, in particular for thread breaks between the yarn supply packages and the device for forming a thread accumulation, said method comprising the steps of providing yarn supply packages (8A, 8B, 8C, 8D); using a thread clip (11B, 23, 24) to hold the thread end (15) of at least the supply package (8B) following the supply package in use (8A); monitoring the weft thread (5) for breaks between the supply package in use (8A) and the device (2) for forming a thread accumulation; and, when a thread break (16) is detected, gripping the above-mentioned thread end (15) of the next supply package (8B), whereby said method is characterised in that said yarn supply packages are continually provided and that said gripped thread end (15) is joined to the broken weft section (17) which is connected to the device (2) for forming a thread accumulation (3). 2. Method as in claim 1, characterized in that it uses a package frame (1) with a conveyor belt (9), such that the thread end (15) of each new supply package (8A, 8B, 8C, 8D) is held in a thread clip (11A, 11B, 11C, 11D) mounted on the conveyor belt (9), where said thread end (15) is gripped by means of a threading device (14). 3. Method as in claim 1, characterized in that it uses a package frame (1) of the type which consists of a conveyor belt (9) along which supply packages (8A-8D) are placed, where the thread end (15) of each supply package (8B) following the supply package in use (8A) is caught by a pneumatic thread clip or suction nozzle (23) and brought to a particular point (P), such that when a thread break (16) is detected, the conveyor belt (9) of the package frame (1) is moved so that said thread end (15) is presented in front of the thread eye (12) and the detector (13) through which the weft thread (5) is normally threaded. 4. Method as in claim 1, characterized in that when a thread break (16) is detected, an auxiliary device (25) pushes the thread end (15) of the new supply package (8B) into line with the thread eye (12) and the detector (13) which are mounted between the package frame (1) and the device (2) for forming a thread accumulation whereupon the thread end (15) of the new supply package (8B) is drawn through said thread eye (12) and said detector (13) by means of a threading device (14) and joined to the remaining broken weft section (17). 5. Method as in claim 2, characterized in that when a break (16) occurs in the weft thread (5), the free end (20) on the corresponding supply package (8A) is found by means of a suction nozzle and brought back into the above-mentioned thread clip (11A). 6. Method as in claim 1, characterized in that the thread end (15) of the supply package (8B) following the supply package in use (8A) is caught and held in a suction nozzle (23), and that when a thread break (16) occurs, the suction nozzle (23) moves so as to present the thread end (15) of the new supply package (8B) in the vicinity of the thread eye (12) through which the thread is normally led. 7. Method as in claim 6, characterized in that the thread end (15) which is presented as described above is gripped by a threading device (14) and drawn through the thread eye (12) in order for it to be joined to the above-mentioned weft section (17) which is connected to the device (2) for forming the thread accumulation (3). 8. Method as in claim 6, characterized in that the suction nozzle (23) is presented in front of the thread eye (12), after which the suction is switched off and compressed air supplied so that the thread end (15) is blown at least through the thread eye (12).

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