METHOD AND ASSOCIATED DEVICE FOR JOINING TOGETHER THREE THREADS HAVING THEIR OWN TWISTING MOMENT

The present invention relates to a method and a device for joining together three threads having their own twisting moment.

It is known that in the technical sector of textiles there exists the need to have yarns, which consist of a strong and continuous structure of fibres bound together by means of a twisting action imparted to the fibres which, passing through special thread-guiding devices, tend to be stably joined together. It is also known that one ©f the methods for imparting a twisting action to the fibres is based on the use of pairs of so-called "rubbing" cylinders which, rotating in opposite directions, at the same time perform an alternating translatory movement in either direction so as to impart a twist to the fibres which are made to pass through the said cylinders, creating a continuous structure known as "thread".

As a result of the alternating translatory movement of the cylinders, twisting occurs in one direction (S) along a longitudinal thread section and in the opposite direction (Z) along a thread section. When the threads leave the rubbing cylinders they are subject to a twisting moment which forces them to bind together, such that they twist and create a stable and strong structure suitable for the subsequent twining operation. Said devices are used to produce two-ply yarns for use mainly in weaving and four-ply yarns for use mainly in knitwear.

The main component of the thread-joining devices is the thread-guide which consists of a series of rollers

suitably arranged so as to define the path of the said threads leaving the rubbing cylinders and fed to the thread-guiding device; as they pass through the latter the threads are joined together as a result of the twisting moment imparted upstream by the rubbing cylinders .

These thread-guiding devices of the known type are designed so as to obtain the said joining together of two plies and/or four plies. Although performing their function, the present techniques, however, result in defects in terms of distribution of the final twist and limited use of the threads which, owing to a less uniform surface appearance, cannot be used for all types of fabric. The technical problem which is posed, therefore, is that of providing a method and a device with which it is possible to obtain yarns which have a high strength, are easy to process and are able to ensure an improved final quality of the fabric obtained with a two-ply yarn and/or a reduction in the quantity of raw material used compared to a four-ply yarn.

In connection with this problem it is also required that this device should have small dimensions, be easy and inexpensive to produce and assemble and be able to be installed also on ready existing equipment without the need for special adaptation.

These results are achieved according to the present invention by a method for joining together three threads having their own twisting moment, comprising the following steps: separate feeding of a first and a second thread to a thread-guiding device of the roller type; joining together of said first and second thread; feeding of a third thread to the said thread-guiding device; joining of the third thread to the other two threads already joined together.

The present invention relates furthermore to a device for joining together a first, second and third thread, each of which has its own. twisting moment, comprising three entry rollers, a middle roller and an exit 5 roller.

Further details may be obtained from the following description of a non-limiting example of embodiment of the present invention provided with reference to the accompanying drawings, in which:

10 - Figure 1 shows a functional diagram of an example of embodiment of the thread-guiding device according to the present invention;

- Figure 2 shows a view, similar to that of Fig. 1, of a second example of embodiment of the thread-guiding

15 device according to the present invention;

- Figure 3 shows a view, similar to that of Fig. 1, of a third example of embodiment of the thread-guiding device according to the present invention.

As shown in Fig. 1, a thread-guiding device according

20. to the present invention essentially comprises a surface 10 supporting the rotating spindles of a plurality of entry rollers HA, 12B for guiding the first thread A and the second thread B, respectively, a middle roller 13AB for guiding the two threads A and B

25 joined together, an entry roller 14C for a third thread C which is in turn supplied by the rubbing cylinders schematically denoted by 1 in the Figure and which, when passing through said roller 14C, is bound to the other two threads already joined together.

30 The device is completed by a guiding and exit roller 15ABC for the three threads A, B, C which are joined together.

As can be seen, the arrangement of Fig. 1 is such that the first two threads A and B enter into the device

35 substantially at the same point, i.e. on the inner side

of the roller HA and on the outer side of the roller 12B and are joined together at an instant when they are still subject to 100% of the twisting moment and with zero relative phase-displacement, so as to produce joining together of the sections SA, SB and ZA, ZB.

The third thread C is introduced into the device opposite an associated roller 14C towards which the other two threads A ₇ B already joined together are fed and is fastened to the latter, making use of its twisting moment which is substantially still at 100%, while the twisting moment of the other two threads has been reduced both because of joining together performed and because of the travel path through the guide rollers . Fig. 2 shows a further embodiment of the invention where the thread A enters in a position outside the roller HA and the thread B enters in a position inside the roller 12B in such a way that the two threads are joined together on the entry roller HA for the first thread A after the thread B has travelled along a section equal to K of roller 12B and Vi of roller UA; therefore the twisting moment at the time of joining together is suitably reduced, thereby benefiting distribution of the final twist after twining. In addition to this, the phase-displacement introduced results in joining together of sections SA-ZB; ZA-ZB; ZA-SB; SA-ZB.

Fig. 3 shows a further embodiment of the device, similar to that shown in Fig. 2, where joining together of the first thread A and the second thread B occurs on the entry roller 12B for the second thread B, namely when the thread A, which has travelled over a section with a length corresponding to the arcs of rollers HA and 12B, has lost part of its twisting moment. In addition to this, a phase-displacement between the

two threads is introduced so that sections SA-ZB; ZA- ZB; ZA-SB; SA-SB are joined together, resulting in the advantage of improved distribution of the final twist after twining of the threads . As shown, the spindles of the rollers are movable inside respective seats 10a able to allow variation in the relative distance between the various spindles is so as to calibrate suitably the device depending on the conditions (twisting moment) to be defined for the various joining operations, so as to ensure greater strength of the said joined structure or better distribution of the final twist following final twining. The present invention also envisages a method for joining together three threads A, B, C having their own twisting moment imparted to them, for example, by means of pairs of rubbing cylinders, which envisages the following steps: a) separate feeding of two threads A, B to a thread- guiding device (10) of the roller-type; b) joining together of the first two threads A, B; c) feeding of a third thread C to the said thread- guiding device (10) ; d) joining of the third thread C to the other two threads A, B already joined together.

According to preferred embodiments of the method it is envisaged that:

-) the length of the section travelled along by the first two threads A, B already joined together in order to reach the point where they are joined to the third thread C must be between 40% and 80% of the translatory movement of the rubbing cylinders which have imparted the twisting moment to the said threads; preferably said length is between 50% and 70% of the translatory movement of the rubbing cylinders;

-) the first two threads A, B are joined together in phase synchronism, namely with longitudinal sections having a corresponding twist S/Z;

-) the first two threads A, B are joined together with phase-displacement namely with alternate longitudinal sections SA-ZB; ZA-ZB; ZA-SB; SA-SB having a twist S/Z; -) the first two threads are fed simultaneously to the joining roller so that joining takes place in conditions where the threads A, B still have 100% of the twisting moment received;

-) the first two threads are fed to two different respective entry rollers and joining is performed after the second thread B has travelled along a section with a length such as to reduce its twisting moment useful for performing joining to the first thread A;

-) the first two threads A, B are fed to two different respective entry rollers and joining is performed after the first thread A has travelled along a section with a length such as to reduce its twisting moment useful for performing joining to the second thread B.

According to preferred modes of implementation of the method described above, it is envisaged that the basic threads A, B, C fed to the thread-guide;

I) have, in all three cases, the same composition, preferably of a discontinuous nature; in this case it is also envisaged that, if necessary, the thread B is reinforced with a continuous filament which is normally much finer than the basic threads;

II) have the same structure in the case of two basic threads, normally A and C, while the third thread, B, has a different structure in terms of its count

(diameter) , type and/or length of the fibres used to form it; in this case also it is envisaged that the thread B may be reinforced with a continuous filament which is normally much finer than the basic threads;

III) have the same discontinuous structure in the case of two basic threads (A=B,-A=C,-B=C) , while the third basic thread (C;B;A) is a continuous filament;

IV) have the same continuous structure in the case of two basic threads, normally A and C, while the third thread B has a discontinuous structure determined by the discontinuous fibres.

For the purposes of the above description, "filament" is understood as meaning a continuous thread consisting of several strands, such as, for example, silk and/or nylon used for manufacturing with women's stockings. It is therefore clear how with the method and the device according to the invention it is possible to obtain, during use for knitwear, joining together of three threads such as to provide a final quality comparable to that which can be obtained with the four threads, but with a considerable saving in the amount of material and a simultaneous reduction in the spinning preparation costs. In addition to this, it must be noted how the three threads are all bound together, thus obtaining, during use for weaving, a better strength than two-ply yarns, with a simultaneous reduction in the twisting costs associated with the smaller number of twisting turns required.