Abstract:
A method for repairing a weft thread on a weaving machine, in particular for repairing thread breaks between a yarn supply package and an accumulator, includes the step of providing at least two yarn supply packages, a second package automatically replacing the one in use when the one in use becomes empty. Additional steps include using a thread clip to hold a thread end of the second supply package, monitoring the weft thread for breaks between the supply package in use and the accumulator, and when a thread break is detected, gripping the thread end of the second supply package and joining it to the broken weft section which is connected to the accumulator. An apparatus is provided which includes means for carrying out each of the above-described steps.

Description:
FIELD OF THE INVENTION 
     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, itself common technology, for forming a particular thread accumulation necessary for inserting a weft thread into the shed. 
     The method is particularly applicable to a weaving loom which uses a rotating package frame preferably of the type where the supply packages are presented one after the other to the insertion mechanism by a conveyor belt. 
     BACKGROUND OF THE INVENTION 
     In conventional weaving machines, a disadvantage exists in that thread breaks which occur between the yarn supply and the yarn accumulator must be repaired manually, and in that the accumulator must then be rethreaded manually. Furthermore, manual rethreading has generally been required when the yarn supply, for example a yarn package, becomes empty. 
     In connection with the latter disadvantage, devices exist which ensure a continuous supply of thread by tying together two yarn packages and automatically switching from one to the other, as disclosed in U.S. Pat. No. 4,450,876. However, this type of device still suffers from the disadvantage that repair and rethreading after a thread break must be done manually. 
     SUMMARY OF THE INVENTION 
     The method according to the invention includes the steps of continually 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 and tying it to the weft section of broken thread which is still connected to the thread accumulating device. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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 are schematic diagrams illustrating 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, 13 to 14, and 16 respectively show four variants of the invention. 
     FIG. 15 is a schematic diagram showing control means for carrying out the method of FIGS. 1 to 3. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 shows a weft insertion mechanism which, as is known, includes 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 an 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 8 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 each supply package 8 is brought into the corresponding thread clip 11 during installation of the package on 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 e.g., in the manner shown in Belgian Pat. No. 1,000,368, and U.S. Pat. No. 4,054,159 and 4,756,341, 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 reference numeral 19. A known knotting device is shown, for example, in U.S. Pat. No. 4,423,586. 
     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. 15, the conveyor belt 9 can be driven by means of a motor 53. This motor is controlled by means of a control unit 54 which in turn is coupled to detector 13. Upon detecting a thread break, motor 53 is switched on to move the conveyor over a distance which is equal to the distance between the two packages. The displacement can be controlled by means of a proximity switch 55 or the like. An exact displacement can also be obtained by using a stepper motor. 
     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, e.g., by a pneumatic or hydraulic cylinder, 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 end 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. This can be accomplished, as shown in FIG. 16, by providing a valve system 50 which can be switched into at least two positions, respectively connecting the nozzle 23 with a suction source 51 or with compressed air supplying means 52. 
     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 come in front of the detector 13 and the thread eye 12, whereupon the thread can be drawn through. 
     If the weft section 17 is no longer located at the point at which it is to he 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. 
     The present invention is in no way limited to the embodiments described by way of example .and shown in the figures; on the contrary, such a method according to the invention can be implemented in all sorts of variants while still remaining within the scope of the invention.