METHOD FOR ADJUSTING THE LENGTH OF THE WEFT THREAD TO BE INSERTED INTO THE SHED OF WEAVING LOOMS AND DEVICES USED FOR THIS OBJECT

Abstract: Method for adjusting the length of the weft thread to be inserted into the shed of weaving looms, characterized by the fact that it mainly comprises the automatic correction during each weaving cycle of the weaving process, in other words, the retaining or the releasing to a more or less large extent of the free length of weft thread (10) in such a way that the desired thread length is inserted into the shed.

Description: The object of the present invention is a method for adjusting the length of the weft thread to be inserted into the shed of weaving looms as well as devices, to put this method into practice. It is already known that the weft yarn of weaving looms can be guided through a thread preparation device in such a way that weft thread lenghts can be made free from this device in order to be inserted into the shed. According to known embodiments, use is made of a weft storing device equipped with a drum, whereby a magnetically actuated pin is mounted on the front side along its periphery. This way the weft yarns are coiled on the drum, on the one hand and, on the other hand, a given number of turns of these yarns are loosened step-wise by the adequate actuation of the aforesaid pin. The drum surface is mainly composed of several pins which are essentially oriented in axial direction and which are radially movable in order to achieve a length adjustment of the weft thread length made free. The adjustments must be carried out manually beforehand. Quite obviously, this is a tedious job that renders automatic adjustment impossible. It is already known to provide several thread locking elements along the periphery of the aforesaid drum like magnetically actuated pins, in such a way that a complete turn not necessarily must be made free at each time. Such a device has, however, the disadvantage that automatic adjustment can only achieve a gradual length adjustment and that, consequently, in most of the cases, a small thread length is lost for each weft thread. In this respect, it should not be forgotten that even a small thread excess for each weft thread corresponds to a relatively large total thread loss for the woven fabric. Thus, the object of the present invention is a method in order to adjust the length of the weft thread to be inserted into the shed of weaving looms, whereby this method does not have the aforesaid disadvantage. To this object, the method mainly comprises the automatic correction during the weaving process, in other words, the retaining or the loosening to a more or less large extent of the free length of weft thread, in such a way that at each insertion the desired thread length is inserted into the shed. According to a first possibility, the weft thread is retained respectively loosened to a more or less large extent by guiding the weft thread before the weft insertion side of the shed along a way with an adjustable path length. According to another possibility, a weft storing device is used, whereby along the periphery of the drum of this device thread locking elements are provided, which can be displaced automatically in axial or tangential direction with respect to the drum, in function of the thread length. Further on, the present invention also concerns devices in order to put this method into practice. In order to explain better the characteristics of the invention, a few preferred embodiments will be described hereafter by way of examples, without any limitative character and with reference to the figures in appandix which are illustrating respectively : figure 1 is a schematic view of a first embodiment of the device in accordance with the invention. figure 2 and 3 use of two different embodiments in accordance with the principle of figure 1 figure 4 a view of a device in accordance with the invention, whereby the weft storing device is equipped with several rows of magnets. figure 5 a view of a device in accordance with the invention, whereby the weft storing device is equipped with an axially movable thread locking element. figure 6 a view of a de vice in accordance with the invention, whereby the thread locking elements which are mounted around the drum of the weft storing device, can carry out a tangential movement. figure 7 a schematic view of an alternative embodiment in accordance with figure 6. figure 8 a practical embodiment in accordance with the embodiment of figure 7. Figure 1 illustrates schematically a weft storing device 1, two thread guiding elements 2 and 3, a main blower 4 and the weft insertion side 5 of a shed 6. The weft storing device 1 is made in this case of a stationary or rotatable weft storing drum 7 or respectively of a rotatable or stationary coiling arm 8 and of a locking element 9 which can be magnetically actuated for instance. In this case, a weft thread 10 is coiled on the drum 7 in a well known manner while the adequate actuation of the thread locking element 9 by means of the pulling force of the main blower 4 can result in the removal of a given number of turns at adequate moments. According to the present invention, the weft thread is guided now from the locking element 9 to the main blower 4 along a path 11 with adjustable path lengths. For instance, the path length of the weft thread 10 is adjusted by moving the latter one between the thread guiding elements 2 and 3 along an arrow X. The previous process can be achieved for instance with devices illustrated on figures 2 and 3. On figure 2, such a device includes a thread guiding element 12 as well as a thread cyclet which is placed between the aforesaid guiding elements 2 and 3 and is equipped of driving means 13 which are actuated by control devices not illustrated on the figures, in such a way that an adequate length of weft thread 10 can always be inserted into the shed 6. Preferably, the aforesaid device is used in the following way. At the moment of the insertion, the thread guiding element 12 is moved in the A position in order to avoid braking of the thread. Just before braking the weft thread 10 this thread guiding element 12 is moved in the C position so that the weft thread has not be pulled back afterwards. Finally, the thread guiding element 12 is put to a B position which is required in order to provide an exact length of the weft thread. Quite obviously, the adjustment along the direction X can occur in a lot of different ways and is strongly dependent upon the distance D between two successive locking elements 9. If, for instance, the desired length of the weft thread is equal to 40,5 times the distance D, in other words, the distance between thread blocking elements 9, at the first insertion a thread length equal to 41 times the distance D is released while the thread guiding element 12 is placed on a point D in such a way that the location of the point B has an influence on the path length of the weft thread 10 corresponding to an elongation of this thread equal to 0,5 D. At the following insertion, the thread guiding element 12 is put back in the A position and a length of weft thread equal to 40 times D is released, resulting in the insertion into the shed 6 of a weft thread 10 having a total length of 40,5 D. Quite obviously it is possible provide more than one adjustable thread guiding element 12. Figure 2 illustrates consequently in dotted-pointed lines still a second adjustable thread guiding element 12A as well as a stationary thread guiding element 2A which is mounted between both movable thread guiding elements 12 and 12A. According to figure 3 the elongation of the path length between the thread guiding elements 2 and 3 is achieved using a rotatable construction 14 which is equipped with rolls 15 and 16, whereby the weft thread 10 is guided in zig-zag between the rolls 15 and 16. If the rotatable construction 14 is rotated over a determined angle by means of driving devices 13, the desired effect can also be obtained in accordance with the invention. The functioning of the device is clearly shown on figure 3. According to an alternative solution not illustrated on the figures, the length adjustment occurs by moving the thread eyelets 2 and 3 with respect to each other. Figure 4 illustrates still another alternative solution, whereby use is made of two or more rolls of locking elements, respectively 9 and 20 which are selectively actuated in such a way that the distance between a locking element 9 and the main blower 4, and more specially between locking element 9 and the thread guiding element 2 can be modified. In such a case, two rows of locking elements A and B are provided. The figure clearly shows that if a magnet 20 from row B is or is not energized in combination with a magnet 9 from row A, it is possible to adjust the path length 11. As shown on figure 5, use is made of a weft storing device 1 composed of a drum 7 already known, of a coiling arm 8 and of one or several thread locking elements 9 mounted along the periphery of the drum 7, as for instance electro-magnetically actuated pins. According to the present invention, the weft thread 10 is compensated in this case, more specially retained or respectively released to a more or less large extent by the correspondng thread locking element 9 which must be provided for locking the weft thread introduced into the shed, this locking element being mainly axially moved. This way, the path length between the locking element 9 and the main blower 4 is adjusted. It is also possible to move several thread locking elements 9 along a common axial path. Figure 6 illustrates schematically still an alternative solution, whereby the thread locking elements 9 can be moved separately on a well determined distance in tangential direction with respect to the drum. This way, the path length is also adjusted by comparison with stationary magnets. According to an alternative solution illustrated on figure 7, the adjustment of the length of the released weft part is achieved when the aforesaid thread locking elements are commonly carrying out a tangential movement in relationship with the drum 7. Such can be achieved, for instance, by means of a device as illustrated on this figure 8, whereby the ring-shaped part 17, whereon the thread locking elements 9 are mounted is actuated for instance through a gear transmission by means of a step motor or a servomotor 18 which is, in turn, actuated by control devices 19, like for instance an electronic circuit. The adjustment of the thread length is achieved for instance in the following way : if 40,5 D is desired, 40 D is released and the magnets are rotated 0,5 D further in such a way that effectively 40,5 D is obtained in the yawn. Quite obviously the present invention can be put into practice according to different alternative solutions and combinations without departing from the scope of the invention. Moreover, the method of the invention, as reported in the introduction, is also applicable for thread preparation systems that don't include weft storing drum 7. Devices, as illustrated on figures 1 to 3, may be for instance also applied for weaving looms which are equipped with thread preparation devices, whereby the weft thread 10 is blown in the shape of a loop. The device in accordance with the invention can possibly be placed before the thread preparation device instead of behind it. The present invention is by no means limited to the embodiments described by way of examples and illustrated on figures, but such devices for putting the method of the invention into practice can be also built with several designs without leaving the scope of the invention.

Claims: 1. Method for adjusting the length of the weft thread to be inserted in the shed, characterized by the fact that it mainly comprises the automatic correction during each weaving cycle of the weaving process or, in other words, retaining or re leasing to a more or less large extent the free-length of weft thread (10) in such a way that at each insertion the desired length is inserted into the shed (6). 2. Method according to claim 1, characterized by the fact that the length of weft thread (10) made free is corrected by guiding it before the weft insertion-side (5) of the shed (6) along a path with adjustable length. 3. Method according to claim 1, using a weft storing drum (7) equipped with one or several thread locking elements (9) on its periphery, characterized by the fact that the length of the weft thread made free from the drum (10) is corrected by at least an automatic axial movement of the thread locking element (9) involved. 4. Method according to claim 1, using a weft storing drum (7) equipped with one or several thread locking elements (9) on its periphery characterized by the fact that the weft thread (10) made free from the drum is corrected by the thread locking elements (9) which are automatically carrying out a tangential movement around the weft storing drum (7). 5. Device in order to adjust the length of the weft thread of weaving looms according to the method of claim 2, characterized by the fact that it mainly comprises at least one thread guiding element (2, 3, 12, 14) which is automatically adjustable during the weaving process. 6. Device in order to adjust the length of the weft thread of weaving looms, in accordance with the method of claim 2, characterized by the fact that it mainly comprises at least one thread locking element (20) which is automatically adjustable during the weaving process. 7. Device in order to adjust the length of the weft thread of weaving looms, in accordance with the method of claim 3, characterized by the fact that it mainly comprises the combination of a weft storing drum (7), of several thread locking elements (9) which are mounted along the periphery of the weft storing drum (7) whereby these thread locking elements (9) can carry out automatically an axial movement with respect to the drum (7) during the weaving process, driving means (13) in order to achieve the aforesaid axial movement and control means for actuating the driving means (13) in function of the desired length of the weft thread. 8. Device for adjusting the length of the weft thread of weaving looms according to the method of claim 4, characterized by the fact that it is mainly composed of the combination of a weft storing drum (7), of thread locking elements (9) which are mounted along the periphery of the weft storing drum (7), whereby these thread locking elements (9) can carry out automatically a tangential movement with respect to the drum, driving means (13) for achieving the aforesaid movement and control means (19) for actuating the driving means (18) in such a way that the desired length of the weft thread is obtained. 9. Device in order to put into practice the methods according to the claims 1 to 4.

Inventors: AMPE, FRANK, VAN BOGAERT, PHILIPPE
Applicants: PICANOL N.V.
Application year: 1987
Main classification: D03D47
IPC codes: D03D47