METHOD FOR SEPARATING A BROKEN WARP THREAD AT THE WARP STOP MOTION FROM THE WARP SHEET ON A WEAVING MACHINE, AND A DEVICE WHICH USES THIS METHOD

Abstract: Method for separating a broken warp thread at the warp stop motion from the warp sheet on a weaving machine on which the warp stop motion consists of several rows (1-4) of drop wires. The method consists essentially of extracting the loop (24) in the broken warp thread, caused by a sag (22) as a result of the corresponding drop wire (16) falling, from the warp stop motion, back from the fallen drop wire (16)

Description: This invention concerns a method for separating a broken warp thread at the warp stop motion from the warp sheet on a weaving machine _ in particular on weaving machines of the type in which the warp stop motion consists of one or more rows of drop wires _ in order to enable the broken warp thread to be automatically located and taken up. The invention also concerns a device which uses this method. A warp stop motion commonly used on weaving machines consists of a row of drop wires resting on the warp threads, so that when a warp thread break occurs, the corresponding drop wire makes an electrical contact or mechanical interlock, thus causing the machine to be stopped. Dutch patent application No. 8600372 _ made by the present applicant _ describes a method of automatically locating the fallen drop wire, which is then gripped and raised in order to make it visibly stand out from the row of drop wires, thus enabling the weaver to see at a glance where a thread break needs to be repaired. Dutch patent application No. 8601819 also describes a method for turning the fallen drop wire through an angle so that the neighboring drop wires are forced apart, thus forming a local opening in the unbroken warp threads, and so facilitating rethreading of the drop wire which is presented in this way. Although both of the abovementioned patent applications are aimed at automating the process of warp thread repair, they do not offer any solution to the problem of dealing with the broken warp thread, which is usually still threaded through the fallen drop wire, either by removing it and replacing it with a new one or by tying it in again. The problem is mainly that the broken warp thread which remains threaded through the fallen drop wire first has to be located, which is fairly difficult to automate since the warp thread which was under tension contracts when it breaks and gets crossed over neihboring threads. The present invention concerns a method for separating the broken warp thread at the warp stop motion from the warp sheet on a weaving machine, thus providing a solution to the problem described below. Further, the warp thread which is thus separated is also brought into the correct position with respect to the remaining warp threads, in other words not crossed over the neighboring threads. To this end, the method of the invention essentially involves extracting the sagging loop _ formed in the broken warp thread as a result of the drop wire falling _ from the warp stop motion, back from the fallen drop wire; optionally, the fallen drop wire may first be raised before extracting the broken warp thread in this way. In a preferred embodiment the loop is extracted from the warp stop motion back from the fallen drop wire by means of at least one airstream which exerts a force on the broken warp thread, starting at the point where the fallen (or raised) drop wire is located. Depending on the variant, the airstream may be provided by suction or blower nozzles. In yet another embodiment, the force is exerted by mechanical means, for example grippers or hooks. The method according to the present invention should preferably be used in combination with the method described in Dutch patent application No. 8601819, in which as well as being raised the fallen drop wire is also turned through an angle in order to facilitate the freeing of the broken warp thread. The effect of turning the drop wire in this way is to draw the neighboring warp threads away from the broken warp thread. The present invention also concerns a device for applying the method of the invention, which essentially uses one or more suction nozzles, blower nozzles or mechanical means which operate in conjunction with the drop wire. For the purpose of describing the characteristics of the invention, the following preferred embodiments are described with reference to the accompanying drawings, by way of example only and without being limitative in any way, where: fig. 1 represents a cross section of a warp stop motion, equipped with suction nozzles, at the point of the broken warp thread; figs. 2 to 8 illustrate the operation of the device; fig. 2 is a plan view (looking down on the warp sheet) and figs. 3 to 8 show the various stages of the method, in a cross section of the warp stop motion; fig. 9 shows a particular embodiment of a suction nozzle, such as may be used in the device according to the invention; fig. 10 shows a device which uses blower nozzles mounted above the warp sheet; fig. 11 shows a variant of the embodiment in fig. 10, in which the blower nozzles are mounted under the warp sheet; figs. 12 and 13 show yet another variant which uses a hook to move the sagging loop. figs. 14 and 15 show a particular embodiment of a suction nozzle or extraction tube. Fig. 1 shows a cross section of a warp stop motion consisting essentially of a number of rows of drop wires 1 to 4 which are suspended on the warp threads of the warp sheet 5, and which when they fall make an electrical contact with one the electrodes 6 to 9 respectively. The warp sheet 5 is led over supporting elements 10 to 14 on either side of the rows of drop wires 1 to 4. In fig. 1 a broken warp thread 15 is shown such that the corresponding drop wire 16 has fallen. Also in fig. 1 there is a gripping device 17, more particularly as described in Dutch patent application No. 8601819, which manipulates the fallen drop wire 16. The actual mechanism of the invention consists, in the embodiment illustrated, of a series of suction nozzles 18 to 21 which can move in such a way that each suction nozzle 18 to 21 can be presented opposite one of a particular row of drop wires 1 to 4. The operation of the device according to the invention, using the method outlined above, is described below with the aid of the successive figures. In fig. 1 a warp thread break has occurred, in particular in warp thread 15. Here it should be noted that as a result of the drop wire 16 falling a sag 22 has been formed in the warp thread 15. The fallen drop wire 16 is located and gripped by the gripping device 17. In the next step, the fallen drop wire 16 is gripped by its end 23, turned and raised by gripping device 17, as shown in fig. 2. At the same time the suction nozzles 18 to 21 are lowered towards the warp sheet 5, almost right up to the supporting elements 11 to 14, as shown in fig. 3. Obviously, the result of raising the fallen drop wire 16 will be that where previously there was a sag 22 in the warp thread 15 there will now be a free-hanging loop 24. At this stage, shown in fig. 2, the suction nozzle 19 is activated, with the result that the warp thread 15 is drawn taut and perhaps also partly sucked in. As shown in fig. 4, the suction nozzles 18 to 21 are now moved upwards, with the result that said loop 24 is displaced over a short distance, arriving over the supporting element 12, since the suction nozzle 19 drags the warp thread 15 towards it. When the nozzles arrive in their highest position, suction nozzle 19 is deactivated and suction nozzle 20 is activated (the activation and deactivation times may overlap slightly). The series of suction nozzles is once more presented to the warp sheet 5, resulting in a situation as shown in fig. 5. The warp thread 15 is then moved along by the action of suction nozzle 20, so that the loop is farther displaced to nozzle 20, as shown in fig. 6. As shown in figs 7 and 8, the above sequence is then be repeated for the last suction nozzle 21, so that the loop 24 is drawn out of the warp stop motion, away from the fallen drop wire 16. A hooking or gripping mechanism 25 may be positioned in proximity to the last suction nozzle 21 in order to take over the warp thread 15 from the suction nozzle 21, so that the latter may be deactivated. Said hooking or gripping mechanism 25 may then be used for further manipulation of the warp thread 15; however such manipulation is outwith the scope of this invention. On commencement of the operation according to the method of the invention, it may be advantageous to first activate the nozzle 18 beside the fallen drop wire 16, this is opposite to the direction in which the loop 24 will be transported, in order to raise the warp thread 15 and so facilitate the transfer of said loop 24 between the other suction nozzles 19 to 21. Clearly, other variations of the method according to the invention are also possible. In one important variant, there is only one suction nozzle, which is first lowered beside the fallen drop wire 16, then activated and raised so as to draw the loop 24 with it, and subsequently deactivated and positioned over the following row of drop wires. This sequence is repeated until the suction nozzle arrives outside the warp stop motion, at which point the abovementioned hooking or gripping mechanism 25 can take over the thread. It also clear that in addition to the suction nozzles, the device must include the necessary transport, activation, deactivation and control functions necessary for the cycle to be carried out automatically. The loop 24 can of course be carried either to side 26 or side 27 of the warp stop motion; in the latter case, there must be another suction nozzle 28 at the other side 27 of the warp stop motion. In a variant, the operating cycle of the suction nozzles 18 to 21 is as follows. When a warp break is detected, all the suction nozzles 18 to 21 are lowered. The suction nozzle nearest the fallen drop wire 16 is activated and raised so that the broken warp thread 15 is raised with it; in the accompanying figures, the suction nozzles concerned would be nozzle 19. When the suction nozzle 19 arrives in its raised position, it is deactivated and the next suction nozzle 20, which is still in the lowered position, is activated and then raised. This process is repeated in a similar way until the loop 24 has been carried out of the warp stop motion. In yet another operating cycle which may be used in the method according to the invention, only the suction nozzle 19 is lowered towards the fallen drop wire 16 and then raised, taking the broken warp thread 15 with it when it is raised. The other suction nozzles are then activated and deactivated successively, so that the loop 24 is passed from one to the other until it arrives outside the warp stop motion, either on side 26 or on side 27, in other words going directly from the stage shown in fig. 4 to the stage shown in fig. 6, without moving the suction nozzles up and down. In order to prevent the warp thread 15 remaining stuck inside a suction nozzle after it has been deactivated, due to the stiffness of the thread, thus preventing the loop 24 being passed from one to the other, positive pressure can be applied to the first nozzle when one nozzle is deactivated and the next activated, thus making sure that the loop 24 is released. A warp thread which gets stuck in a nozzle can also be freed by some mechanical device, eg. rings or tubes 29 mounted concentrically on the suction nozzles 18 to 21 and which move up and down. The suction nozzles 18 to 21, and also nozzle 28 if provided, can also be mounted underneath the warp sheet 5 instead of above it. In the variant shown in fig. 10, the method of the invention is accomplished by using a succession of airjets at various points to displace the loop 24 in the broken warp thread 15, starting at the fallen drop wire 16 and progressing to one of the sides of the warp stop motion, in this case side 26. To this end the suction nozzles 18 to 21, and nozzle 28 if provided, are replaced to blower nozzles 30 to 34. No up and down motion is necessary if such blower nozzles are used. The operation of the device may be simply deduced from fig. 10, and is more or less analagous to the method using suction nozzles. It is possible to provide extraction tubes 35 to 39 mounted opposite the blower nozzles 30 to 34, in order to promote evacuation of the airstream from whichever blower nozzles are activated. The extraction tubes may also operate as suction nozzles, so that there is a combined action of blower and suction nozzles. In the variant shown in fig. 11, the blower nozzles 30 to 33, and also blower nozzle 34 if provided, are mounted underneath the warp sheet 5. This has the advantage that they can be mounted on the same transport mechanism as the rotatable gripper device 17. As shown in figs. 12 and 13, the loop 24 can also be transported out of the warp stop motion by means of hooking or gripping devices. In the variant illustrated, the suction nozzles are replaced by hooks 42 to 45, and also hook 46 if provided, which move up and down, thus raising the loop 24, starting at the fallen drop wire 16. The particularity of this method is that, as shown in the two figures, it is not necessary for the fallen drop wire 16 to be presented and raised by a special gripping device 17, since the corresponding drop wire will be raised by the action of gripper 43 in fig. 13. The motion of the hooks must of course be controlled in such a way that they operate separately one after the other so that they carry the loop 24 in the warp thread 15 with them. In order to avoid unwanted effects on the loop 24, it is also possible for a guide 47 for the broken warp thread to be lowered. Clearly, suitably controlled gripping or clamping devices may be used instead of the hooks 42 to 45. The hooking, gripping or clamping devices may of course also be mounted under the warp sheet 5. In a preferred embodiment as shown in fig. 14 the suction nozzles 18 to 21 or the suction nozzle 28 may be provided with a sieve-shaped element 48 which prevents the broken warp thread 15 being sucked completely into the suction nozzles 18 to 21 or 28. In the same way the extraction tubes 35 to 39 may also be provided with a sieve-shaped element 48 which prevents the broken warp thread 15 being blown completely into the extraction tubes 35 to 39. As shown in fig. 15 the sieve-shaped element 48 may be provided with holes 49 whereby the diamter of the holes 49 is less than the diameter of the warp thead 15 in order to prevent the warp thread being sucked into the holes 49. The present invention is no way limited to the variants described by way of example and shown in the accompanying figures; on the contrary, such a method and device for extracting a broken warp thread from the warp sheet in weaving machines may be made in all sorts of variants while still remaining within the scope of the invention.

Claims: 1. Method for separating a broken warp thread at the warp stop motion from the warp sheet on a weaving machine on which the warp stop motion consists of several rows (1-4) of drop wires, with the characteristic that the method consists essentially of extracting the loop (24) in the broken warp thread, caused by a sag (22) as a result of the corresponding drop wire (16) falling, from the warp stop motion, back from the fallen drop wire (16) 2. Method as in claim 1, with the characteristic that the fallen drop wire (16) may or may not be raised before the loop (24) in the broken warp thread (15) is extracted from the warp stop motion. 3. Method as in claim 2, with the characteristic that extracting the loop (24) from the warp stop motion, back from the fallen drop wire (16), is accomplished by exerting a force on the broken warp thread (15) by means of an airstream which acts in turn behind each of the rows of drop wires (1-4), beginning at the row of drop wires (2) in which the fallen, or raised, drop wire (16) is located. 4. Method as in claim 3, with the characteristic that the airstream is provided by means of suction nozzles (18-21). 5. Method as in claim 3, with the characteristic that the airstream is provided by means of blower nozzles (30-34). 6. Method as in claims 1 or 2, with the characteristic that the loop (24) is extracted from the warp stop motion, back from the fallen drop wire (16), by means of a series of hooking or gripping devices mounted behind each of the rows of drop wires (1-4) and which one after the other exert a tractive force on the broken warp thread (15), beginning at the row of drop wires (2) in which the fallen, or raised, dropwire (16) is located. 7. Method as in claim 4, with the characteristic that it consists of successively: bringing a series of suction nozzles (18-21) up to the point where the fallen, or raised, dropwire (16) is located, and presenting each of the suction nozzles (18-21) behind one of the rows of drop wires (1-4); presenting at least one suction nozzle (19) to the warp sheet (5), namely the suction nozzle (19) situated behind the row of drop wires (2) in which the raised drop wire (16) is located; activating the suction nozzle (19) which is situated behind the raised drop wire (16); moving at least the activated suction nozzle (19) away from the the warp sheet (5) so that it drags the broken warp thread (15) with it; deactivating the last activated suction nozzle (19) and activating the next suction nozzle (20); presenting the suction nozzle now activated (20) to the warp sheet (5); once more moving the suction nozzle now activated (20) away from the warp (5) so that it drags the broken warp thread (15) with it; and repeating this cycle with the remaining suction nozzles until the warp thread is carried to the outside (26) of the warp stop motion. 8. Method as in claim 7, with the characteristic that all the suction nozzles (18-21) in the abovementioned series are moved simultaneously. 9. Method as in claim 7, with the characteristic that the series of suction nozzles (18-21) is presented to the warp sheet (5), following the suction nozzles (18-21) are moved in turn one by one away from the warp sheet (5), starting with the nozzle nearest the fallen drop wire and progressing towards the side of the warp stop motion, after which the nozzles remain in this position. 10. Method as in claim 4, with the characteristic that it consists of successively: bringing a suction nozzle to the warp sheet (5), near to the point where the raised dropwire (16) is located; activating and raising the suction nozzle so that the broken warp thread (15) is carried with it over a certain distance; deactivating the suction nozzle; moving the suction nozzle to behind the next row of drop wires (3) and lowering it to the warp sheet (5) once more; reactivating the suction nozzle, raising it and moving it over a distance once more so that the broken warp thread (15) is carried with it; and repeating this cycle in the same way until the suction nozzle arrives on the outside (26) of the warp stop motion. 11. Method as in claim 4, with the characteristic that it consists of successively: bringing a series of suction nozzles (18-21) up to the point where the fallen, or raised, dropwire (16) is located, and presenting each of the suction nozzles (18-21) behind one of the rows of drop wires (1-4); presenting only one of the suction nozzles (19) to the warp sheet (5), namely the suction nozzle (19) situated behind the row of drop wires (2) in which the raised drop wire (16) is located; activating the suction nozzle (19) which is situated behind the raised drop wire (16); moving the activated suction nozzle (19) away from the warp sheet (5) so that it drags the broken warp thread (15) with it; and passing the loop (24), which has been separated from the warp sheet (5), to the successive action of the remaining suction nozzles (20-21). 12. Method as in one of the claims 7 to 11, with the characteristic that activation of the suction nozzles (18-21) is overlapping. 13. Method as in claim 4, with the characteristic that it consists of successively: bringing a series of blower nozzles (30-34) up to the point where the fallen, or raised, dropwire (16) is located, and presenting each of the blower nozzles (30-34) behind one of the rows of drop wires (1-4) and activating and deactivating each of the blower nozzles in turn. 14. Method as in claim 6, with the characteristic that it consists of successively: bringing a series of gripping devices, eg. hooks (42-46), up to the point where the fallen, or raised, dropwire (16) is located, and presenting each of the gripping devices behind one of the rows of drop wires (1-4); and letting these gripping devices (42-46) operate on the broken warp thread (15), from the fallen drop wire (16) to one of the sides (26-27) of the warp stop motion, in such a way that each gripping device acts separately in turn to draw the warp thread out of the warp sheet (5). 15. Method as in one of the above claims, with the characteristic that the loop (24) carried to the outside (26) of the warp stop motion is held by hooking or gripping devices (25). 16. Method as in one of the above claims with the characteristic that the fallen drop wire (16) can be twisted with respect to its original position. 17. Device which uses one of the methods as in claims 7, 8, 9 or 11, with the characteristic that it consists essentially of: a series of movable suction nozzles (18-21) arranged in the direction of the warp threads and whose suction nozzles (18-21) can operate on the warp sheet (5) in the region of the rows of drop wires (1-4); and transport mechanism to enable the suction nozzles (18-21) to be brought up to a fallen drop wire (16) and to enable the suction nozzles to be moved towards and away from the warp sheet (5); and activation and control devices to enable the suction nozzles to be activated in turn. 18. Device which uses the method as in claim 10, with the characteristic that it consists essentially of: one suction nozzle which can operate on the warp sheet (5); means of transport to enable the suction nozzle to be presented to the warp sheet (5), behind a fallen drop wire (16), and move the suction nozzle in stages so that it is positioned beside each of the rows of drop wires (1-4) in turn, at the level of the fallen drop wire; and control devices for activating and deactivating the nozzle. 19. Device which uses the method as in claim 13, with the characteristic that it consists essentially of: a series of blower nozzles (30-34) arranged in the direction of the warp threads and whose blower nozzles (30-34) can operate on the warp sheet (5) in the region of the rows of drop wires (1-4); a transport mechanism to enable the blower nozzles (30-34) to be brought up to a fallen drop wire (16) and to enable the blower nozzles to be moved towards and away from the warp sheet (5); and activation and control devices to enable the blower nozzles (30-34) to be activated in turn, with or without overlaps. 20. Device which uses the method as in claim 6, with the characteristic that it consists essentially of: a series of movable hooks (42-46) arranged in the direction of the warp threads and whose hooks (30-34) can operate on the broken warp thread (15) in the region of the rows of drop wires (1-4); a transport mechanism to enable the series of hooks (42-46) to be brought up to the fallen drop wire (16) and to enable the hooks to be moved towards and away from the warp sheet (5); and control devices to enable the hooks (42-46) to be moved in turn. 21. Device as in one of claims 17 to 20, with the characteristic that the suction nozzles (18-21), blower nozzles (30-34) or hooks (42-46) are mounted above the warp sheet (5). 22. Device as in one of claims 17 to 20, with the characteristic that the suction nozzles (18-21), blower nozzles (30-34) or hooks (42-46) are mounted underneath the warp sheet (5). 23. Device as in claim 22, with the characteristic that the suction nozzles (18-21), blower nozzles (30-34) or gripping devices (42-46) are mounted on a transport mechanism (41), on which a clamping device (17) may or may not also be mounted for the purpose of gripping the end of the fallen drop wire (16) in order to raise it and turn it through an angle. 24. Device as in one of the claims 17 to 23, with the characteristic that it incorporates a clamping device (17) for the purpose of gripping the end of the fallen drop wire (16) in order to raise it and turn it through an angle. 25. Device as in one of the claims 17 to 24, with the characteristic that on one side (26-27) of the warp stop motion there is a hooking or gripping mechanism (25) which can operate on the broken warp thread (15) once it has been extracted. 26. Device as in one of the claims 17 to 25, with the characteristic that a suction nozzle (18-21, 28) is provided with a sieve-shaped element (48). 27. Device as in one of the claims 17 to 25, with the characteristic that an extraction tube (35-39) is provided with a sieve-shaped element (48). 28. Device as in claim 27 or 28, with the characteristic that the holes (49) have a diameter less than the warp thread diameter.

Inventors: GRYSON, DIRK
Applicants: PICANOL N.V.
Application year: 1988
Main classification: D03D51
IPC codes: D03J1, D03D51