MECHANISM AND METHOD FOR SUPPLYING WEFT THREADS ON WEAVING MACHINES

Abstract: Mechanism for supplying weft threads on weaving machines, characterized in that it consists essentially of at least three weft supply mechanisms (2, 3, 4, 5), of which at least one operates with at least two thread supplies (7, 8, 9) with different sorts of weft thread (6A, 6B, 6C).

Description: This invention concerns a mechanism and a method for supplying weft threads on weaving machines. As is generally known, on weaving machines the weft threads are supplied to the shed by first winding them off yarn packages or suchlike by means of thread supply mechanisms and then inserting them into the shed. These thread supply mechanisms consist firstly of prewinders which are essentially formed by a drum on which a quantity of thread is wound, so that a number of turns can be drawn off at each weaving cycle, so providing the required length of weft thread per insertion, and secondly of insertion mechanisms in order to insert the lengths of weft thread one by one into the shed. When making a cloth which contains different kinds of weft thread, for example weft threads of different colours or weft threads of different types, then of course there are at least as many weft supply mechanisms as there are used different kinds of weft threads. On modern weaving machines, the aim is to automate them as far as possible in order to avoid weaving machine stops or to reduce stops to a minimum. In order to limit weaving machine stops due to faults in the weft thread supply, from EP-A-0 195 469 (BE-A-901 969) held by the present applicant it is known for a reserve mechanism to be held in readiness for each weft supply mechanism. When a fault in the supply of a weft thread occurs, the machine automatically switches over to the reserve mechanism with the same type of weft thread. Although machine stops can be avoided with this known mechanism, it has the disadvantage that the weft supply mechanisms must be duplicated, so that the weaving machine is bulkier and also considerably more expensive than a conventional weaving machine. The present invention concerns a mechanism for the supply of weft threads which does not have the above-mentioned disadvantages. To this end, the invention concerns a mechanism characterized in that it consists of at least three weft supply mechanisms, of which at least one operates with at least two thread supplies with different sorts of weft thread. Said mechanism also includes a device by which the weft supply mechanism which works with the different sorts of weft thread can be supplied with one of the weft threads according to choice, as well as a control unit which controls said device. Use of the mechanism according to the invention makes it possible for the weft supply mechanism which operates with several sorts of weft threads to be fed with the same sorts of weft thread as is being woven during the normal weaving process, where said weft supply mechanism is kept on standby as a reserve mechanism, and is activated whenever a fault in the supply of one of the weft threads normally used occurs. At that moment the weft supply mechanism placed on standby is provided with the same sort of thread as the weft supply mechanism in which the fault occurs. Clearly, this means that it is only necessary to have one reserve weft supply mechanism, which can replace any of the other weft supply mechanisms which are normally in use. The invention also concerns a method for supplying weft threads on weaving machines, in which different weft threads are inserted successively into the shed in a particular pattern, characterized in that it consists essentially in: supplying the different weft threads during the normal weaving process via respective weft supply mechanisms; during the normal weaving process, holding on standby at least one weft thread supply mechanism which operates with different thread supplies, where said thread supplies contain at least the same sorts of weft thread as is being woven during the normal weaving process; detecting faults in the supply of the weft threads during the normal weaving process; and, if a fault is detected, switching over from the weft supply mechanism in which the fault has occurred to the weft supply mechanism on standby, such that the latter is fed with the weft thread of the same sort as the weft thread in which the fault has occurred. In order to better explain the characteristics according to the invention, the following preferred embodiments are described below, by way of example only and without being limitative in any way, with reference to the accompanying drawings, where: fig. 1 is a schematic diagram of the mechanism according to the invention, in which the weft supply mechanism which operates simultaneously with several weft threads is kept on standby; fig. 2 is a schematic diagram of the mechanism shown in fig. 1, at the moment that a fault in the normal supply of the weft threads occurs, where the weft supply mechanism which operates with several thread supplies is in operation; fig. 3 shows a practical embodiment of the mechanism according to fig. 1, used on an airjet weaving machine; figs. 4 to 6 show the mechanism according to fig. 3 in various conditions; fig. 7 shows another practical embodiment of the invention; figs. 8 to 10 show the different conditions of the invention according to fig. 7; fig. 11 shows a practical embodiment of the mechanism according to fig. 1 on a rapier weaving machine. As shown in fig. 1, the mechanism 1 according to the invention consists essentially of a number of weft supply mechanisms 2 to 5, in which different sorts of weft threads, 6A, 6B and 6C respectively, can be drawn from thread supplies 7 to 12, for example yarn packages, in order for lengths of the different sorts of weft thread to be inserted one by one into the shed 13 of the weaving machine, in a known way according to the weave pattern. The particular feature of the present invention is that at least one of the weft supply mechanisms - weft thread supply mechanism 2 in figs. 1 and 2 - operates with several thread supplies 7 to 9 with different sorts of weft thread 6A, 6B and 6C. Further, use is made of a device 15, controlled by a control unit 14 in order to supply according to choice one of the weft threads 6A, 6B or 6C from the thread supplies 7 to 9 to the corresponding weft thread supply mechanism 2. In a preferred embodiment of the invention, the mechanism 1 enables a particularly advantageous method to be used for supplying the different sorts of weft thread. For this purpose, as shown in fig. 1, during the normal weaving process the different sorts of weft thread 6A, 6B and 6C are inserted into the shed 13 according to a particular pattern, such that each passes via its own weft supply mechanism, 3 to 5 respectively. The particular feature is that the weft supply mechanism 2 is kept on standby and operates with the same sorts of weft thread 6A to 6C, drawn from the thread supplies 7 to 9. When a particular fault occurs in the supply of one of the weft threads 6A to 6C coming from the thread supplies 10 to 12, the corresponding weft supply mechanism is deactivated and the weft thread supply mechanism 2 is activated in its places, such that by means of the device 15 the latter is supplied with the same sort of weft threads 6A, 6B or 6C as that in which the fault has occurred. Such a fault can for instance consist of a thread break or the fact that one of the thread supplies has run out. Fig. 2 is a schematic diagram of an example in which a fault 16, for example a thread break, has occurred in the supply of the weft thread 6B coming from thread supply 11. As a result of this fault being detected, the control unit 14 can control the device 15 in such a way that the weft thread 6B from the thread supply 8 is supplied to the weft supply mechanism 2, which is then activated to replace the weft supply mechanism 4, for instance until the thread break 16 has been repaired. The particular configuration of the mechanism 1 according to figs. 1 and 2 and the method used here offer the advantage that only one weft supply mechanism 2 can be used to supply any of the reserve weft threads 6A, 6B or 6C. Fig. 3 shows a practical embodiment of the mechanism 1, for an airjet weaving machine. Here, the weft threads 6A to 6C are inserted into the shed 13 by means of main nozzles 17 to 20 and a number of relay nozzles 21. The above-mentioned weft supply mechanisms 2 to 5 consist in this case essentially of prewinders which each consist for example of a prewinder drum 22, a rotating winding tube 23 in order to lay a certain number of turns 24 on the prewinder drum 22, an electromagnetic retaining mechanism 25 which acts on the surface of the prewinder drum 22, and one or more turn detectors 26 positioned along the winding drum 22, together with the insertion mechanism formed by the above-mentioned main nozzles 17 to 20. The control unit 14 is connected to a number of detectors, namely thread break detectors 27 to 32 - for example thread motion detectors, positioned along the path of the weft threads 6A to 6C from the respective thread supplies 7 to 12, together with the weft stop motion 33 mounted in the conventional manner at the far side of the shed 13. The control unit 14 is also connected to the above-mentioned turn detectors 26. It controls the activation and deactivation of a number of components, including the main nozzles 17 to 20, the drives of the winding tubes 23, the retaining mechanism 25, the relay nozzles 21, the main drive 34 of the weaving machine and the above-mentioned device 15. The above-mentioned device 15 consists of an apparatus 35 for tying the weaving threads and a device 36 for holding the different weft threads 6A, 6B and 6C from the thread supplies 7 to 9 and presenting them to each other. The apparatus 35 can consist of a tying apparatus which itself is known, or a splicing unit. The device 36 can be made up of a number of mobile thread clips and thread eyes such that two of the threads, 6A, 6B or 6C according to choice, can always be presented to each other. Since such a device 36 can be made up in various ways and is within the scope of any person skilled in the art, for the sake of clarity it is only shown schematically in the figures. Finally, also shown in fig. 3 are the sley 37, essentially consisting of the batten beam 38 with the reed 39 mounted on it, a suction nozzle 40 at the far side of the shed 13, the upper warp sheet 41 and the lower warp sheet 42. The operation of the mechanism and the method by which it is preferably used are now described with reference to figs. 3 to 6. Fig. 3 shows the same condition as in the schematic diagram in fig. 2. As can be seen, the thread break 16 has been detected by the detector 31. As a result, weft supply mechanism 4 is deactivated by means of the control unit 14. Weft supply mechanism 2 is activated in its place. If as shown in fig. 3 the same sort of weft thread 6B is still present in the weft supply mechanism 2 as in the weft supply mechanism in which the thread break 16 has occurred, then weaving can continue immediately from thread supply 8, without a weaving machine stop. A minimum quantity of weft thread Q, corresponding to one pick length to be inserted into the shed 13, is always kept on the prewinder drum 22 of the weft supply mechanism on standby. Clearly, the control unit 14 can activate a signalling device 43 in order to warn the weaver that a repair needs to be carried out. In the case where a second thread break occurs before the first has been repaired, the weaving machine will come to a stop. In the case shown in fig, 4, a thread break 44 is present in a weft thread 6A which is different in sort, type or colour from the weft thread 6B present in the weft supply mechanism 2 on standby. When the thread break detector 30 detects the fault, the above-mentioned device 15 comes into operation and the end of the weft thread 6A from the reserve thread supply 7 is presented to the weft thread 6B which is present in the weft supply mechanism 2 and joined to it by the apparatus 35, which itself is provided with the necessary cutting device 45 in order to cut the thread supply 8 loose, such that the join 46, consisting of e.g. a knot, is made. If the weaving pattern permits, the weaving machine can continue working in the meantime, so that other weft threads are inserted into the shed 13, for example 6C from thread supply 12. Once the join 46 has been made, a certain quantity of weft thread 6A from the thread supply 7 is already wound on the prewinder drum 22 of the weft supply mechanism 2, as shown in fig. 5. If the weaving pattern permits, then preferably one more length of weft thread 6B present in weft supply mechanism 2 is released from the prewinder drum 22, inserted into the shed 13 in the normal way and cut off by means of the weft cutter 47. In this way, any remaining quantity of weft thread 6B in weft supply mechanism 2 is kept to a minimum. Subsequently, when a length of weft thread 6A has to be inserted into the shed 13, then as shown in fig. 6 the retaining mechanism 25 of the weft supply mechanism 2 is opened sufficiently long to release at least enough turns 24 for the join 46 to reach the far side of the shed 13 opposite the main nozzles. The above-mentioned remaining part of the weft thread 6B is sucked up into the suction nozzle 40 and cut off at the far side of the shed 13 by a cutting device, for instance a cutter 48. Clearly, for this to be done a large quantity of weft thread, consisting of part of the weft thread 6B and a complete length of the weft thread 6A, must be led through the shed 13, so that as a consequence more time will be required than for a normal pick. In order to allow for this the main drive 34 of the weaving machine can be halted briefly, or can be set to a lower speed. If however as in fig. 5 the weaving pattern does not permit the quantity Q of the weft thread 6B also to be inserted into the shed before the weft thread 6A is demanded, then said quantity Q must first be led in its entirety through the shed 13, which of course will make a slightly longer machine stop necessary. In a variant of the method according to the invention, the above-mentioned join 46 is made between the thread preparation mechanism and the component which inserts the thread into the shed 13, i.e. in the case of an airjet weaving machine between the prewinder drum 22 and the main nozzle 17. The quantity of weft thread present in the weft supply mechanism 2 placed on standby is then wound off the corresponding prewinder drum 22 and cut off. In this way the quantity of thread which has to be led the whole way through the shed 13 is kept to a minimum. In order to achieve this, the mechanism 1 includes a device 15 which, as shown in figs. 7 to 10, consists essentially of: a rotating package frame 49 on which the above-mentioned yarn packages 7 to 9 mounted, where the respective weft threads 6A to 6B are led through nozzles 50 and 52; a cutter 53 mounted before the weft supply mechanism 2; a device 54 to remove the weft thread present in the weft supply mechanism 2 - or at least the part present on the prewinder drum 22; and the above-mentioned apparatus 35 for joining weft threads. The device 54 consists essentially of a suction nozzle 55 mounted in the path of the reserve weft thread, as well as a transversely-oriented suction nozzle 56. In addition there are a number of thread clips 57 to 61, together with cutters 62 which operate in conjunction with the suction nozzle 56. The prewinder used is of the type which can be automatically rethreaded pneumatically. The operation of the mechanism can be simply deduced from figs. 7 to 10. In fig. 7 the same situation applies as in fig. 4. The weft supply mechanisms 3 to 5 are not shown any longer. In fig. 7, the weft thread 6B is cut by means of a cutter 53 at a short distance after the nozzle 51. The retaining mechanism 25 of the weft supply mechanism 2 is opened while the suction nozzle 56 is in operation. As a result the quantity of weft thread 6B present on the prewinder drum 22 is entirely sucked up into the suction nozzle 56. Clearly, in so doing the thread clip 60 must be kept closed in order to prevent the weft thread 6B being pulled out of the main nozzle 17. The package frame 49 is then rotated, such that the nozzle with the correct sort of weft thread, in this case nozzle 50 with weft thread 6A, is presented precisely at the intake of the winding tube 23 of the weft supply mechanism 2. As shown in fig. 8, by activating the nozzle 50 the weft thread 6A is led into the winding tube 23 and along the prewinder drum 22 of the weft supply mechanism 2, and taken up by the suction nozzle 55. The thread clip 57 is subsequently closed. Clearly, during this stage the suction nozzle 56 is deactivated and the thread clip 61 is kept closed. In the next step, the suction nozzle 56 is activated once more, such that both sorts of weft thread 6A and 6B are sucked up by their ends and can be joined together by means of the apparatus 35, as shown in fig. 9. To make the join, the free ends are cut off by the cutter 62 and removed by the suction nozzle 56, in the normal way. In the meantime the retaining mechanism 25 is closed once more and a quantity of the weft thread 6A is built up in the weft supply mechanism 2, after the thread clip 57 has been opened once more. Finally a state is reached as shown in fig. 10, from which it can be seen that at the moment a quantity of weft thread 6A has to be inserted into the shed 13, the remaining length of weft thread 6B which has to be led through the whole width of the shed is very small, so that it is not always necessary for the weaving machine to be stopped in order to do this. According to a variant of the invention, in the case where a thread break 44 occurs in a weft thread 6A which is different from the weft thread 6B present in the weft supply mechanism 2 on standby - i.e. a situation analogous to that shown in fig. 7 - the weaving machine is brought to a halt, the thread 6B is cut by the cutter 53 and the quantity of weft thread 6B remaining in the weft supply mechanism 2 is blown into the suction nozzle 40 by means of the main nozzle 17 and relay nozzles 21 until it has been removed completely. The package frame 49 is then rotated until the nozzle 50 for the correct sort of weft thread 6A is presented precisely at the intake of the winding tube 23 of the weft supply mechanism 2, as shown in fig. 8. By means of the nozzle 50, the weft thread 6A is then led into the winding tube 23, along the prewinder drum 22, through the suction nozzle 55 and into the main nozzle 17 whereupon the weft thread 6A is brought into the suction nozzle 40 by means of the main nozzle 17 and the relay nozzles 21. The corresponding retaining mechanism 25 is closed and a certain number of turns 24 are laid on the prewinder drum 22 by means of the winding tube 23. The section of weft thread present in the shed is then cut off by the weft cutter 47 and removed by means of the suction nozzle 40. The weaving machine is then started, after which the supply of the weft thread 6A is ensured by the weft supply mechanism 2. Using the nozzles 50, 51 and 52 offers the advantage that the threads 6A, 6B and 6C can be presented directly at the intake of the winding tube 23 of the weft supply mechanism 2, thus enabling rapid rethreading of this mechanism. Obviously, the above-mentioned weft supply mechanism 2 which is kept on standby is not necessarily inactive. It is always possible for the weft supply mechanism 2 to be used alternately with one of the other weft supply mechanisms 3 or 5, in order to ensure the supply of the same sort of weft thread during the normal weaving process. In the embodiment shown in fig. 4, this means for example that the weft thread 6B is inserted into the shed 13 via weft supply mechanisms 2 and 4 alternately. If the thread break occurs in the weft thread 6B of the weft supply mechanism 4, weft thread 6B continues to be supplied by weft supply mechanism 2 only. If on the other hand a thread break 44 occurs in one of the weft threads 6A or 6C, then weft thread 6B is supplied via weft supply mechanism 4 only, while weft supply mechanism 2 is used to ensure the supply of the sort of weft thread 6A or 6C in which the break 44 has occurred. The invention is not limited to airjet weaving machines. To illustrate this, fig. 11 shows a mechanism 1 according to the invention which is intended in particular for rapier weaving machines of the type in which the weft threads after being inserted remain connected to the edge of the cloth 63. As is known, in this type of weaving machine the weft threads 6A to 6C are presented in the path of a gripper 65 by means of a thread presentation mechanism 64, such that they are inserted into the shed 13. In this case, each of the above-mentioned weft supply mechanisms 2 to 5 consists essentially of a prewinder, formed by a prewinder drum 22 and a winding tube 23, and a thread presentation element 66. Also shown in fig. 11 are the weft cutter 67, a cutting device 6B which can cut off all hanging weft threads along the edge 63 of the cloth, and a thread removing mechanism 69 consisting of driven thread removing rollers 70 and a suction nozzle 71. The rollers 70 are mounted along the weft threads 6A to 6B and can be moved towards each other by means of a positioning mechanism 72. Fig. 11 shows a similar situation to that in fig. 4 in which the join 46 has already been made. Subsequently the thread removing mechanism 69 is activated, such that all the weft threads held by the thread presentation mechanism 64 are gripped between the rollers 70 and carried towards the suction nozzle 71. The thread removing mechanism 69 continues to operate until it is certain that the join 46 has been sucked up into the suction nozzle 71, and preferably also until all the weft thread 6A present in the weft supply mechanism 3 has also been sucked up into the suction nozzle 71. At the same time, all weft threads are cut off from the cloth edge 63 by means of the cutting device 6B. When the join 46 has been drawn past the rollers 70, the rollers 70 are moved apart once more and weaving can start again, with the weft threads 6A, 6B and 6C being supplied via the weft supply mechanisms 2, 4 and 5 respectively. As soon as all three weft threads hanging from the thread presentation mechanism 64 into the suction nozzle 71 have been inserted into the shed 13 once, they are all cut off at the beginning of the insertion, which means that the thread waste can be completely sucked up into the suction nozzle 71. In yet another variant of the above-mentioned method, only the weft thread coming from the weft supply mechanism 2 which operates with several thread supplies 7, 8 and 9 is removed by the thread removing mechanism 69, and the thread removing mechanism 69 only continues to operate until it is certain that the join has been sucked up into the suction nozzle 71. Once the broken weft thread 6A from the weft supply mechanism 3 has been repaired, either manually or automatically, a control signal 73 can be supplied to the control unit 14, which reactivates the weft supply mechanism 3 and restores the supply to the weft supply mechanism 2 with the weft thread 6B which was present in weft supply mechanism 2 before the fault occurred. Preferably, the weft supply mechanism 2 should always be threaded with the weft thread 6B which is most likely to cause faults, as this will enable the number of machine stops to be limited. The weft supply mechanism 2 does not necessarily have to work only with the same sorts of weft thread as the weft supply mechanisms normally in use. Said weft supply mechanism 2 can also be provided with a different sort of weft thread 6D from a thread supply 74. A thread break detector 75 can also be mounted along the path of said weft thread 6D. This makes it possible, for example, after a large number of insertions have been made, for a limited number of weft threads 6D to be inserted from weft supply mechanism 2, as a result of a control signal 76 sent by e.g. the weaving machine control which was supplied to the control unit 14 in order to act a marker between two pieces of cloth. Since the weft thread 6D is only inserted in limited quantities at very large intervals, no separate weft supply mechanism has to be provided for this weft thread 6D. Clearly, the above-mentioned thread supplies 7 to 12 and 74 can consist of several yarn packages which are connected to each other. Clearly also, any weft supply mechanism of an existing weaving machine can be used as a reserve mechanism, on condition of course that the weaving machine is equipped with the above-mentioned device 15 and the control unit 14. Of course it is also possible for several weft supply mechanisms to function as reserve mechanisms. Thus for example in the case of a weaving machine which is equipped with six weft supply mechanisms and on which only four different colours are being woven, two weft supply mechanisms can be used as reserve mechanisms. The two weft supply mechanisms placed on standby can for example each be connected to two thread supplies.

Claims: 1. Mechanism for supplying weft threads on weaving machines, characterized in that it consists of at least three weft supply mechanisms (2, 3, 4, 5), of which at least one operates with at least two thread supplies (7, 8, 9) with different sorts of weft thread (6A, 6B, 6C). 2. Mechanism according to claim 1, characterized in that it has a device (15) by means of which the weft supply mechanism (2) which operates with several sorts of weft thread (6A, 6B, 6C), can be supplied with one of said weft threads (6A, 6B, 6C) according to choice, together with a control unit (14) which controls said device (15). 3. Mechanism according to claim 1 or 2, characterized in that a number of the above-mentioned weft supply mechanisms (3, 4, 5) each operate with one thread supply (10, 11, 12), in which thread supplies with different sorts of weft thread (6A, 6B, 6C) are used, and in which the weft supply mechanism (2) which operates with several thread supplies (6A, 6B, 6C) uses at least the same sorts of weft thread (6A, 6B, 6C). 4. Mechanism according to claim 1 or 2, characterized in that a number of the above-mentioned weft supply mechanisms (3, 4, 5) each operate with one thread supply (10, 11, 12), in which thread supplies with different sorts of weft thread (6A, 6B, 6C) are used and in which the weft supply mechanism (2) which operates with several thread supplies (6A, 6B, 6C) uses the same sorts of weft thread (6A, 6B, 6C). 5. Mechanism according to claim 1 or 2, characterized in that a number of the above-mentioned weft supply mechanisms (3, 4, 5) each operates with one thread supply (10, 11, 12), in which thread supplies with different sorts of weft thread (6A, 6B, 6C) are used and in which the weft supply mechanism (2) which operate with several thread supplies (6A, 6B, 6C) uses at least two of the same sorts of weft thread (6A, 6B). 6. Mechanism according to claim 2, 3, 4 or 5, characterized in that the device (15) used in order to supply one of the weft threads (6A, 6B, 6C) according to choice consists of an apparatus (35), placed between the respective thread supplies (7, 8, 9) and the corresponding weft supply mechanism (2), which is used to join the weft thread (6A) according to choice with the weft thread (6B) which is still connected to the weft supply mechanism (2), and a cutting device (45) to cut off the thread supply (8) from which the last-mentioned weft thread (6B) comes. 7. Mechanism according to claim 2, 3, 4 or 5, characterized in that the weft supply mechanism (2) which operates with several thread supplies (7, 8, 9) is of the type which can be threaded automatically, and that the device (15) for supplying said weft supply mechanism (2) according to choice with one of the weft threads (6A, 6B, 6C) from the above-mentioned thread supplies (7, 8, 9) contains a package frame (49) by means of which the weft threads (6A, 6B, 6C) from the above-mentioned thread supplies (7, 8, 9) can be presented according to choice at the intake of the weft supply mechanism (2). 8. Mechanism according to claim 2, 3, 4 or 5, characterized in that the weft supply mechanism (2) which operates with several thread supplies (7, 8, 9) is of the type which can be threaded automatically, and the device (15) for supplying said weft supply mechanism (2) according to choice with one of the weft threads (6A, 6B, 6C) from the above-mentioned thread supplies (7, 8, 9) consists of a package frame (49) by means of which the weft threads (6A, 6B, 6C) from the above-mentioned thread supplies (7, 8, 9) can be presented according to choice at the intake of the weft supply mechanisms (2), together with a device (54) to partially or completely remove the quantity of weft thread (6B) of an unwanted sort present in the corresponding weft supply mechanism (2). 9. Mechanism according to claim 7 or 8, characterized in that each thread supply (7, 8, 9) of the above-mentioned package frame (49) is equipped with at least one nozzle (50, 51, 52), where said nozzles (50, 51, 52) hold the respective weft threads (6A, 6B, 6C) in readiness to be supplied to the above-mentioned weft supply mechanism (2). 10. Mechanism according to claim 9, characterized in that the yarn packages (7, 8, 9) are mounted on a rotating package frame (49), so that by rotating the package frame (49) the weft threads (6A, 6B, 6C) from said thread supplies (7, 8, 9) can be presented according to choice to the intake of the weft supply mechanism (2). 11. Mechanism according to any of claims 8 to 10, characterized in that the weft supply mechanism (2) which operates with several thread supplies (7, 8, 9) consists of a prewinder and at least one main nozzle (17); that the device (54) for removing the weft thread (6B) present in the corresponding weft supply mechanism (2) consists of a suction nozzle (56) and a cutter (62) which operates with it, where said suction nozzle and cutter are located between said prewinder and said main nozzle (17); that there is also an apparatus (35) for joining threads, where the above-mentioned components enable the quantity of weft thread (6B) from the prewinder which has to be removed to be sucked up into the suction nozzle; that said weft thread (6B) can be cut between said suction nozzle (56) and said main nozzle (17), such that a part of said weft thread (6B) remains present in the main nozzle (17); and that by means of said apparatus (35) a new supplied weft thread (6A) is joined to the section of thread still present in the main nozzle (17). 12. Mechanism according to any of claims 8 to 10, characterized in that the device (54) for removing the weft thread (6B) present in the corresponding weft supply mechanism (2) consists of a suction nozzle (40) located at the far side of the shed (13). 13. Mechanism according to any of claims 8 to 10, characterized in that the device (54) for removing the weft thread (6B) present in the corresponding weft supply mechanism (2) consists of a suction nozzle (71) located immediately in front of the entrance of the shed (13). 14. Mechanism according to any of claims 8 to 10, characterized in that the device (54) for removing the quantity of weft thread (6B) present in the above-mentioned weft supply mechanism (2) consists of a thread removing mechanism (69) formed by driven thread removing rollers (70) which are located immediately in front of the entrance to the shed (13) and which can operate on at least the weft thread coming from the weft supply mechanism (2) which operates with several thread supplies (7, 8, 9). 15. Mechanism according to claim 3 or 4, characterized in that it is equipped with a control unit (14) which is connected to thread detectors (30, 31, 32) which monitor the weft threads (6A, 6B, 6C) which are led to the weft supply mechanisms (3, 4, 5) which are each provided with only one thread supply (10,11,12) respectively, and that during the normal weaving process said control unit (14) controls the weft supply mechanisms (3, 4, 5) which each have only one thread supply (10, 11, 12), and that if one of the detectors (31) detects a fault (16), said control unit (14) deactivates the corresponding weft supply mechanism (4) and in its place activates the weft supply mechanism (2) which is connected to several thread supplies (7, 8, 9). 16. Method for supplying weft threads on weaving machines, which uses a mechanism according to one of the above claims 1 to 15 in which several sorts of weft threads (6A, 6B, 6C) are inserted successively into the shed (13) of the weaving machine according to a particular pattern, comprising the steps of in supplying the different weft threads (6A, 6B, 6C) via respective weft supply mechanisms (3, 4, 5) during the normal weaving process; also during the normal weaving process, holding on standby at least one weft supply mechanism (2) which operates with several thread supplies (7, 8, 9), where said thread supplies contain at least the same sorts of weft thread (6A, 6B, 6C) as the sorts which are used during the normal weaving process; detecting faults (16) in the supply of weft threads (6A, 6B, 6C) which are supplied during the normal weaving process; and if a fault (16) is detected, switching over from the weft supply mechanism in which the fault has occurred to the weft supply mechanism (2) on standby, where the latter is then fed with the weft thread of the same sort as the weft thread in which the fault (16) has occurred. 17. Method for supplying weft threads on weaving machines, which uses a mechanism according to one of claims 1 to 15, in which several sorts of weft thread (6A, 6B, 6C, 6D) are inserted successively into the shed (13) of the weaving machine according to a particular pattern, comprising the steps of supplying the different weft threads (6A, 6B, 6C) during the normal weaving process via the respective weft supply mechanisms (3, 4, 5); during the normal weaving process, holding on standby at least one weft supply mechanism (2) which operates with several thread supplies (7, 8, 9, 74), where said thread supplies contain at least the same sorts of weft thread (6A, 6B, 6C) as the sorts which are used during the normal weaving process; supplying a control signal (73, 76); switching over to the weft supply mechanism (2) on standby, where said weft supply mechanism (2) is fed with the weft thread (6A, 6B, 6C, 6D) determined by the control signal supplied (73, 76). 18. Method according to one of claims 16 to 17, characterized in that the weft supply mechanism (2) on standby which operates with several thread supplies (7, 8, 9) is used alternately with one of the other weft supply mechanisms (3, 4, 5) in order to ensure the supply of the same sort of weft thread (6A, 6B, 6C) during the normal weaving process. 19. Method according to claim 18, characterized in that the supply mechanism (2) on standby is supplied with the sort of weft thread (6A, 6B, 6C) in which faults are most likely to occur.

Inventors: LIGNEEL, ROGER, SHAW, HENRY, TACQ, JO
Applicants: PICANOL N.V.
Application year: 1989
Main classification: D03D47
IPC codes: D03D47