PROCESS AND RELATED APPARATUS FOR THE ON-LINE REALIZATION OF THE DRAWING AND WARPING STEPS OF POLYAMIDE MONOFILAMENTS

Abstract: A process and apparatus for the on-line realization of the drawing and warping steps of mono-filament threads (10) from polyamide comprising a first pre-tensioning step (4-4a; 6-6a-6b) of the mono-filament threads unwinding from cheeses positioned on a creel, by passage through a tension compensator for said threads, and a drawing step on a plurality of rolls (11-13, etc.) arranged by groups, each group being spaced with respect to the other one. Each group of rolls is contained in a separator-container (7-9) and, at the outlet of the threads from each group, they are positioned on a thread-guide-reed (18-18a-18b) and an ionizing bar (19) for the elimination of the electrostatic charges accumulated by the threads on their translation on said rolls. The plurality of simultaneously treated threads provides for a number of about 1200 threads kept spaced from one another by a value of between 1.4-1.6 mm.

Description: PROCESS AND RELATED APPARATUS FOR THE ON-LINE REALIZATION OF THE DRAWING AND WARPING STEPS OF POLYAMIDE MONOFILAMENTS . DESCRIPTION The present invention relates to a process for the realization of the drawing step together with the warping step (collection on a fractional type beam) of mono-filament polyamide threads, in order to impart said threads the characteristics required during the warp-knitting step. The present invention also relates to an apparatus for the practical realization of said process. As is known, the present techniques that comprise the drawing of polyamide threads (Nylon) together and on-line with warping are at presenc utilizable only for multi-filament threads for Nylon. In fact, the present warping apparatuses for multi- filament threads for Nylon (equidistant and unwinding from cheeses located on a creel) provide for the sliding of a multiplicity of threads on a multiplicity of rolls (up to 17) possibly heated and enclosed in one only assembly; said rolls are mounted in such a manner as to rotate at different speeds, precisely to realize the drawing. Said known apparatuses are also provided on said creel with a device for the tension compensation of the threads of the adjustable spring type, having the aim of regularizing the tension of the threads before submitting them to the drawing step. Besides, in this apparatus the multi-filament threads are fed in a driven manner and kept at mutual distances ranging from 0.8 mm to 1.2 mm, so that the width of the apparatus can be contained between 1.25-1.30 m. These known types of apparatuses for the drawing and simultaneous warping of multi-filament Nylon threads have always proved not to be suitable for the simultaneous drawing and warping of mono- filament Nylon threads. In fact, at present, in order to realize the drawing step and the warping step of the mono- filament threads, apparatuses are used that provide separately for the spinning step, the drawing step and lastly the warping step. The reasons why said known techniques and related apparatuses for the drawing together with the warping of multi-filament threads could not been utilized to realize also the treatment of mono- filament Nylon threads are due to the fact that the said one- filament threads treated by means of the processes employed for multi-filament threads of the known art often broke and did not overcome the actual drawing step because of the many entanglements that caused the subsequent on-line step to be impossible, said threads tending towards collapsing among each other, with ensuing frequent interruptions of the process, continuous need of the intervention of an operator, with ensuing working times that were unacceptable on an industrial scale. Besides, the product obtained was entirely unsatisfactory as it did not respect the characteristics required to be then employed in the warp-knitting step. Given the impossibility of utilizing the apparatuses known at present for the treatment of multi-filament threads to realize the drawing step together with the warping step for polyamide mono- filament threads, various modifications have been experimented for said apparatuses for multi- filament threads, trying to exploit as much as possible the working principle and the basic structure . For instance, the heating of drawing rolls has been avoided, but this contrivance did not give acceptable results as mono-filament threads tended to "stick" with each other also at room temperature during the drawing, creating severe problems downstream on the drawing rolls. Then, it has also been tried to utilize a reduced number of mono-filament threads, for instance, about half the number normally utilized in the case of multi-filament threads, so as to space them more from each other, but also this solution did not give the results hoped for, especially because of the fact that the threads could not pass successfully the drawing step with regard to the total number of rolls. Also the use of a number of rolls smaller than that of the known apparatuses has been tried, but also in this case the results were not acceptable. To sum up, all the attempts at modifying and/or improving the known apparatuses for multi-filament threads did not allow the regular treatment of mono-filament threads, also because the known apparatuses for multi-filament threads require a high number of rolls enclosed all in one only assembly whose access was difficult in case of need (repairs, inspections, etc.). There therefore exists the problem of providing a simple and reliable process for the realization of the drawing step together with the warping step for mono-filament thread from polyamide, substantially Nylon. Within the scope of this problem, the main object of the present invention is therefore to realize a process capable of carrying out the drawing step simultaneously and on-line with the warping step of mono-filament Nylon threads using structurally simple means, easily accessible in case of need and economically competitive with respect to those utilized in the present drawing procedures separated from the warping one. Another object of the invention is to realize an apparatus for the realization of said process, so structured as to be advantageously realizable not only for the treatment of mono-filament Nylon threads but also for multi-filament threads without requiring modifications and/or variants in the components of the apparatus. These and still other objects, that will be better described later on, are achieved by a process for the realization of the drawing step on-line with the warping step of a plurality of mono-filament polyamide threads, utilizing a plurality of drawing rolls rotating at different speeds, which process includes, according to the present invention, the following steps: - unwinding of a plurality of mono-filament threads from the cheeses located on a creel of a known type, - realization of the pre-tensioning step through a tension compensation step of said threads, in order to stabilize tension, - transfer of said plurality of threads so treated to a drawing section comprising a plurality of drawing rolls arranged by groups, each group being spaced with respect to the other one, said rolls being submitted to different speeds, keeping said distance between the threads by means of thread guides located at the outlet of said groups of drawing rolls, - elimination of the electrostatic charges from threads, through antistatic means associated to said thread guides, and lastly winding of the threads on a fractional beam positioned in a collection station. More particularly, said mono-filament threads are kept spaced from each other by a value comprised between about 1.4 and 1.6 mm. Mono-filament threads, in fact, become electrostatically charged due to the rubbing on the rolls and during the passage through the tension compensator; besides, while passing through the tension compensator located on the creel, they undergo partial and irregular drawings such as to cause thread distortion and therefore create problems of tension adjustment when the threads are submitted to the actual drawing step. Said tension compensation step according to the present invention is just intended for the elimination of the above described problem. Therefore, according to the present invention it has been provided to modifying the tension compensator by the insertion of a tension dial, substantially a constant pre-tensioning device, so as to prevent the mono-filament thread from undergoing "tears" or deformations at the outlet of the compensator. Always according to the present invention, the introduction of said thread-guide-reeds among the various groups of rolls also allows to prepare the threads coming out from the first group of rolls, keeping them well separated from each other, and ready to enter the subsequent group of rolls without breaks or entanglements of said threads. Besides, the insertion of said antistatic means in association with said thread guide according to the present invention, allows to systematically eliminate the electrostatic charge generated by the passage of the threads on the drawing rolls, preventing therefore threads from collapsing and "entangling", and allowing the completion of the drawing step. For the realization of said process an apparatus is provided that utilizes groups of rolls rotating at different speeds, a tension compensator coupled to the creel and a collection station with a fractional beam, which apparatus comprises, according to the present invention: a device for adjusting the tension of mono- filament threads, suitable to create a pre- tensioning of said threads, located before and online with said tension compensator and positioned, together with the latter, on said thread-cheese- bearing creel, - a drawing station made up by a plurality of rolls arranged by groups separated from each other, submitted to different speeds, - a plurality of on-line roll assemblies spaced from each other, containing each one of said rolls groups, - a thread-guide-reed, located at the outlet of each of said containers and associated to at least an ionizing bar that discharges the electrostatic charges accumulated by the threads during the drawing step, each of said creels having a number of dents equal to the number of threads fed to said rolls . More particularly, in an embodiment of the present invention, said rolls come in a total number of nine, arranged by groups of three and are kept at room temperature. More particularly, always according to the present invention, said mono-filament threads are fed at a distance from one another of about 1.4-1.6 mm. Besides, also on the winding beam of the treated threads there are provided a thread-guide-reed and an ionizing bar. The mono-filament threads obtained with the process of the present invention can be directly submitted to warp-knitting once the drawing-warping step has ended, as described above. Said warp-knitting step may be for instance advantageously realized on a knitting machine having one or more reeds and, depending on the yarn employed in warp-knitting, it can lead to the realization of warp-knitted fabrics having different characteristics. For instance, a convenient type of warp-knitted fabrics obtained according to the process in object of the present invention, is made up for about 2/3 by mono- filament threads and for about 1/3 by multi- filament threads, and is advantageously employed in the application sector of mechanical fasteners (hook and loop system) , and in particular in the health-sanitary sector. When the warp-knitting step is carried out directly at the end of the drawing-warping step according to the present invention, the so obtained warp-knitted fabrics is advantageously employed as it is, and it is not necessary to perform subsequent treatments such as washing, scouring, cleaning and so on. The warp-knitted fabrics as obtained at the end of the warp-knitting step that follows the drawing-warping step according to the invention, can be directly submitted to lamination to a film or foam united and printed of different composition, self-adhesive or not self-adhesive, and possibly then cut into different size rolls. The so obtained warp-knitted fabrics can then be directly utilized also when it is intended for the health-sanitary sector, wherein the requirements concerning the characteristics of the end product are rigidly defined. The possibility of using directly the warp-knitted fabrics at the end of the waving step, without the necessity of performing further treatments, as said, involves a remarkable advantage from the viewpoint of the economy of the production process. The elimination of submitting to washing, scouring and the like on the final product (warp-knitted fabrics) obtained by means of the process according to the present invention is caused to be possible by the use in the spinning step and possibly also the drawing step of a mix of lubricating oils in a suitable amount and composition. It has in fact been observed that, while in the realization of the processes according to the known art, the amount of lubricating oil to be used during spinning always exceed 1%, in the process according to the invention it never exceeds 0.7%. Said lubricating oils may be formed by a combination of fat acid esters, emulsifying agents and antistatic agents. In this case, the composition of oils utilized is entirely free from mineral oils and alkyl phenols. Only by way of example, there are shown in Figures 4, 5 and 6 some examples of textile structure for the realization of warp-knitted fabrics according to the process of the present invention. Further characteristics and advantages of the present invention will be more clearly stressed by the following detailed description, made with reference to the attached drawings reported only by way of non-limiting example. In said drawings: Figure 1 shows, schematically and in cross- section, an apparatus for the realization of the drawing step together and on-line with the warping step, realized according to the present invention; - Figure 2 shows the end part of the apparatus with the collection head of the threads treated on the beam; - Figure 3 shows, in perspective view, a tension compensator with adjustable springs of a known type to which a pre-tensioning device realized according to the invention is associated; Figures 4-6 show some particular diagrams of textile structures that are advantageously employed to realize warp-knitted fabrics according to the invention . With reference to said figures, the apparatus in object of the present invention is substantially made up by: - a section comprising a thread pre-tensioning device associated to a tension compensator, said device being mounted on a creel bearing the cheeses of mono-filament threads from polyamide to be submitted to drawing before the winding on the beam (Fig. 3), - an actual drawing section (Fig. 1) and a section for the collection and winding of the treated threads (Fig. 2) . Said first section is constituted of a tension compensator, indicated as a whole by 1 in Figure 3, which is of a known type with springs adjustable via a hand wheel la, so that a mono-filament thread 10 entering through hole 2a obtained in the supporting plate 2 comes out from a thread guide 3 having a prefixed constant tension, so as to be treatable in the actual drawing section (Fig. 1) . There are provided as many tension compensators 1 as there are mono-filament threads 10 to be submitted to drawing. Behind each of said supporting plates 2 there is anchored a flat top fixed support 4a, that ends with a common disc 4 having a width such as to prevent the possible entanglement or overlapping of the threads entering through the central hole 4b and directed towards hole 2a of plate 2 from hampering the regular passage of said threads in the direction of the compensator. Above said fixed support 4 there are freely mounted ceramic rings 6- 6a-6b through which thread 10 coming from a cheese located on the creel (not shown) is caused to pass. Said rings 6-6a-6b have a calibrated weight, so as to regularize thread tensioning, and are in touch with top 4a of the fixed support 4. The device constituted of the fixed top and the calibrated weight rings constitutes a thread pre- tensioning means, which is necessary to prevent the mono-filament thread, differently from the multi- filament one, from undergoing an irregular jerklike tensioning within compensator 1. As said, both the pre-tensioning means 4-4a and the tension compensator 1 are mounted on the creel that supports the different cheeses of mono-filament thread. The plurality of threads 10, coming from the thread guide 3 of each compensator 1 enter then into the actual drawing station illustrated in Figure 1. Each drawing station is substantially constituted of the assemblies 7-9 (Fig. 1), separated from each other and positioned on-line with the compensators; in the inside of each assembly there is positioned a group of three drawing rolls 11-12-13, lla-12a- 13a and llb-12b-13b, kept at room temperature and activated at different speeds starting from the group of rolls 11-13. Said rolls are caused to rotate through means and controls of a known type. Besides, the mono-filament threads 10, exiting the related compensators, as indicated in Figure 3 and Figure 1, are kept at a prefixed spacing between each other, exiting from each group of rolls through the use of thread-guide-reeds 18-18a-18b, having each a number of dents equal to the number of threads that come from each group of treated threads . In practice, it has been observed that the most correct number of mono-filament threads that can be simultaneously treated in the present apparatus amounts to about 1200. Besides, in order to prevent mono-filament threads that charge with electrostatic electricity especially during the drawing step, from tending towards "sticking" with one another, causing marked treatment differences, there is provided, in association with each thread-guide-reed 18a, an ionizing bar 19 performing the function of electrostatic discharger. Always according to the invention, also on the collection head 20 (Fig. 2) there may be positioned a thread-guide-reed 22 and the related ionizing bar 21. The apparatus described above and illustrated in the figures is also provided with a general electric board, not shown being realizable in a known manner, capable of controlling the whole process of treatment of the mono-filament threads by sensing the picking up the signals emitted by the various sensors (also not shown) positioned along the whole thread treatment line; in particular, it is possible, by means of said sensors, to control the drawing speed ratios between the rolls groups, the tension of threads during the drawing step and the winding step on beam 20, the feeding of the electrostatic dischargers (ionizing bars), and other parameters of high importance for the good running of the apparatus . Lastly, it was possible to observe that the apparatus described for the treatment of mono- filament threads for polyamide may be advantageously utilized, virtually without changes, also for the on-line treatment of multi-filament threads, allowing thereby to realize the steps of on-line drawing and warping of both types of threads, with an identical process and the same apparatus . Obviously, modifications and variants structurally and functionally equivalent may be introduced in the invention as described and illustrated, without falling outside the protection scope of said invention.

Claims: CLAIMS 1. A process of the on-line realization of the drawing step with the warping step of a plurality of mono-filament threads from polyamide, utilizing a plurality of drawing rolls rotating at different speeds, which process includes, according to the present invention, the following steps: - unwinding of a plurality of mono-filament threads (10) from the cheeses located on a creel of a known type, - realization of the pre-tensioning step through a tension compensation step of said threads, in order to stabilize tension, - transfer of said plurality of threads (10) so treated to a drawing section comprising a plurality of drawing rolls (11-13) arranged in groups, each group being spaced with respect to the other one, and said rolls being submitted to a different speed, - keeping of the distance between the threads during the drawing step by means of thread guides (18) located at the outlet of said groups of drawing rolls, elimination of the electrostatic charges from threads, through antistatic means (19) associated to said thread guide (18), and lastly - winding of the threads on a fractional beam (20) positioned in a collection station. 2. The process according to claim 1, characterized in that said mono-filament threads (10) are fed spaced from one another of a value comprised between 1.4 and 1.6 mm. 3. An apparatus for the realization of the process of drawing and simultaneous warping of claim 1, utilizing groups of rolls rotating at different speeds, a tension compensator (1) coupled to the creel and a collecting station (20) with a fractional beam, characterized in that it comprises : - a device 4-4a for adjusting the tension of mono- filament threads (10), suitable to create a pre- tensioning of said threads, located before and on- line with said tension compensator (1) and positioned, together with the latter, on said thread-cheese-bearing creel, - a drawing station made up by a plurality of rolls (11-13; lla-12a-13a; llb-12b-13b) arranged by groups separated from each other, submitted to different speeds, - a plurality of on-line assemblies (7-9) spaced from each other, containing each one of said rolls groups, - a thread-guide-reed (18), located at the outlet of each of said containers (7-9) and associated to at least an ionizing bar (19) that discharges the electrostatic charges accumulated by the threads during the drawing step, each of said thread-guide- reed (18) having a number of dents equal to the number of threads fed on said rolls. 4. The apparatus according to claim 3, characterized in that it provides for the simultaneous treatment of a number of mono-filament threads (10) equal to about 1200, kept flush and spaced from one another by about 1.4-1.6 mm. 5. The apparatus according to claim 3, characterized in that said rolls are in number of nine, arranged by groups of three. 6. The apparatus according to claim 3, characterized in that said rolls are kept at room temperature . 7. The apparatus according to claim 3, characterized in that said device of pre-adjustment of thread tension, associated to said tension compensator (1), is made up by a fixed support (4), having a flat surface (4a) at the top and ending with a vertical disc (5) , with a central hole (4b) , to prevent possible entanglements of threads (10) , during the unwinding of the cheeses from causing irregularities of thread feeding to the compensator (1) , there being freely mounted above said flat surface (4a) ceramic rings (6-6a-βb), gone through by the thread coming from the cheese, and all the weight being calibrated in such a manner as to adjust the tensioning of thread (10) , all of them remaining always in touch with said contrast plane (4a) . 8. The apparatus according to claim 3, characterized in that a thread-guide-reed (22) and an ionizing bar (21) are associated to the fractional beam (20) present in the collection station. 9. The apparatus according to claims 3-8, characterized in that it can be utilized also for the treatment of multi-filament threads from polyamide. 10. A mono-filament thread from polyamide realized by means of a continuous process comprising the step of on-line drawing together with the warping step. 11. A warp-knitted fabrics of any type realized by warp-knitting machine of at least a mono-filament thread according to claim 10. 12. A warp-knitted fabrics of any type realized for 2/3 from mono-filament threads according to claim 10, and for 1/3 by multi-filament threads. 13. The warp-knitted fabrics according to claim 11, characterized in that it is obtained by warp- knitting directly following the drawing-warping step, in very short times. 14. The warp-knitted fabrics according to claim 11, characterized in that it is obtained by using a mix of lubricating oils to an amount lower than 0.7%. 15. The warp-knitted fabrics of any type according to claims 11-14, employed as is, without subsequent treatments such as washing, scouring or the like. 16. The warp-knitted fabrics according to claims 10-15, realized according to the following types of textile structure: a) generically all hook-and-loop warp-knitted fabrics or in any case with a prevalence of hooks-and loops in particular on the surface, of a different shape and different heights, different weight with a different number of stitches, different intertwining and composition, according to the structure indicated in Figures 4 and 5 ; b) generically all reaseled warp-knitted fabrics of a different thickness, weight, height, intertwining and composition, a different number of stitches, according to the structure indicated in Figure6. 17. Use of the warp-knitted fabrics according to claims 11-16 in the field of pressure sensitive fasteners .

Inventors: PEZZOLI LUIGI, PEZZOLI, LUIGI
Applicants: PEZZOLI LUIGI, SITIP SPA, PEZZOLI, LUIGI, SITIP S.P.A.
Application year: 2000
Main classification: D03D
IPC codes: D02J1, D04B21