EP0089299A2 - Drawing method for a fibrous textile structure, and apparatus therefor - Google Patents

Abstract

1. Method for stretching a textile structure constituted of discontinuous fibers, arranged, for the most part at least, in parallel to the length of said structure, which structure can be either in fibersheet or in top or roving form, characterized by the fact the stretching is obtained by subjecting the moving fibrous structure to external pressures causing a simple shear effect which tends to make the fiber layers slide one with respect to the other, according to a speed gradient which results in the displacement, at different regularly staged speeds, of elementary fiber layers, on which normal forces are exerted to this effect, especially in the layers situated in the sliding area.

Description

The present invention relates to a process for drawing a textile structure based on fibers, said structure being both in surface form (mattress, tablecloth, veil, etc.) and in linear form (ribbon, wick, etc.). ; it also relates to a device allowing the implementation of this process.

It is well known in the textile industry that obtaining articles based on staple fibers and in particular when passing through yarns, requires at the various stages of manufacture, subject the fibers to stretching, that is to say reductions in the mass of the cross section, both at the stage of preparation where the fibers are arranged in the form of a web as at the stage spinning proper where they are in the form of a ribbon or a wick.

FIGS. 1 to 5 annexed illustrate, in a schematic manner, the various methods and devices proposed and used to date for carrying out these stretching operations. In all these solutions, the actual stretching is obtained essentially between a pair of input cylinders (1,2) (also frequently designated by the term "food cylinders"), having the same tangential speed Vl and, a pair of output cylinders (1'-2 ') having the same tangential speed V2 greater than that VI of the input cylinders. The ratio V2 of these speeds determines the rate of stretching. This drawing rate is a theoretical rate which does not take account of any slippage in the fibers. Furthermore, the clamping of the material between the cylinders (1,2) and (l ', 2') is done only by the pressures (15-16).

Such a drawing process is therefore based on a speed difference given by a positive call from the cylinders outlet (l ', 2') relative to the inlet cylinders (1, 2); it is implemented in practically all systems known to date and this, whatever the adaptations made and which result from the nature of the material worked (long fibers, short fibers) and / or from the form in which it is presented this material (wick, ribbon, tablecloth). This is clearly shown in Figures 2 to 5 which are diagrams of the different stretching systems used to date and which comprise, arranged between the inlet cylinders (1,2) and outlet (1 ', 2 '), additional members such as for example intermediate cylinders (3) or guide strips (4) (FIG. 2) or also, as in the case of using long fibers (wool or bast fibers for example), "hedgehog" cylinders (5) (Figure 3), fields of movable needles (6) (Figure 4) or any other rotary or mobile intermediate support (6 ') (Figure 5). All the aforementioned conventional drawing systems have the drawback of not being able to allow precise control of the movement of the fibers, these fibers being able to break up (as indicated by the reference 17 in FIGS. 1 and 2), which can result in an irregularity of section, therefore by defects in the finished product.

In addition, it should be noted that apart from these quality problems in the product produced, the stretching systems proposed to date produce only relatively low stretching rates, generally at most of the order of 20 to 30, which therefore limits production speeds and / or leads to carrying out successive drawing operations on different materials, therefore increasing production costs. In addition, depending on the length and length distribution of the fibers to be worked, it is necessary to adjust the distance d between the pair of input (or food) cylinders and the pair of output (or drawing) cylinders in order to avoid on the one hand the breaking of the long fibers if the distance d is too small, and on the other hand, the loss of control of the fibers if the distance d is too large; despite all the additional organs and systems added to compensate for the lack of pressure necessary for correct control of the slip of the fibers.

However, we have found, and this is what is the subject of the present invention, a process which not only makes it possible to obtain drawing rates even very high, whatever the lengths of fibers because in principle , this system ensures the control of fibers during their sliding, but also leads to products having very good textile characteristics. Furthermore, the method according to the invention can be used to stretch fibrous textile structures which are present both in the form of a web or the like, for example in preparation for the conventional threshing or the carding classic, as well as the shape of a ribbon or wick between carding and up to the actual spinning.

The invention also relates to the means allowing the implementation of said method.

In general, the invention therefore relates to a process for drawing a textile structure made up of staple fibers, the average orientation of which is preferred in the direction parallel to the length of said structure, a structure which can also be present under the form of a sheet than a ribbon or a wick (or any other equivalent material), the method according to the invention being characterized in that the stretching is obtained by subjecting the fibrous structure in movement to external stresses which cause a simple shearing effect which tends to slide the fibers relative to each other, in the form of layers superimposed elementals moving at different speeds from each other and on which forces normal to the fibers are exerted, especially in the sliding zone.

In fact, according to the new approach at the origin of this invention, the process of refining the linear or surface mass of the fibers in a section can be assimilated to a flow of fibers. By analogy, with what happens for fluids (Figures 10a, 10b, 10c), the lamellar flow in parallel layers sliding parallel to each other (7) relative to each other (8), is best achieved by applying this which is called in rheology a "simple shear" either on plane layers (figure 10a), or on cocylindrical layers, telescopically (figure 10b).

According to this principle, the fastest layer of fibers (9) is driven by the application of a force (10), while the slowest layer (11) is retained relative to the intermediate layers by the application of 'a force (12). The normal effect of the couple of tangential forces (10/12) must be compensated by the application of normal forces (13) and (14) (figure 10c), otherwise the tendency to rotate would result in a dislocation of the layers. and the conditions for an ideal sliding of the layers would no longer be ensured.

To do this, the system according to the invention refines a set of fibers presented in the form of a mattress, tablecloth (= _" surface textile") or in the form of a ribbon or wick (= _" linear textile _"). ") by simple shear; the relative sliding of the layers of fibers is done by the application (fig. 6a) of an element (19) driving the fibers at the speed V2 higher (and not equal or barely different as in known systems) to the speed VI of another element (18), while applying normal forces (20-21) to the during the sliding of the fiber layers (24). In a first version which is simple and practical for carrying out the process, the elements driving the fibers are strips or flat strips, of the same type as those used in conventional drawing on a bench or on a spinning machine, normal forces are applied to the axes of the drive rollers distributed over the fibers due to the tension given by the tension (25), _r-glables or not (Figure 6a) with (1) and (2) rotating at speed Vl and (the ) (2 ') at speed V2.

Of course, the arrangement of the longitudinal axis of flow of the fibers can be horizontal, vertical, or inclined, in particular if one wishes to take advantage of gravity to perfect the guidance of the flow of the fibers and / or the maintenance on the drive elements of said fibers, or between these elements or between the supply, or even the outlet, and these elements.

In addition, the organs and devices well known to technicians such as for example the means for storing the material to be stretched, for receiving after stretching, the driving of the organs as well as the frames supporting these organs will not be described and shown (to with the exception of Figure 9a), for the sake of simplification.

• - la nature des éléments d'entraînement des fibres et leur disposition ;
• - la combinaison en "cascade" de ce système, répété pour assurer un étirage échelonné et progressif,
• - la façon d'appliquer les forces normales,
• - l'alimentation et la sortie,
• - l'extension à la fabrication d'un fil à âme en combinaison avec ce système d'étirage.

The variants relating to the system described by the invention relate to:

• - the nature of the fiber drive elements and their arrangement;
• - the "cascade" combination of this system, repeated to ensure a gradual and progressive stretching,
• - how to apply normal forces,
• - supply and output,
• - the extension to the manufacture of a core wire in combination with this drawing system.

The invention and the advantages which it brings will however be better understood thanks to the illustrations by the annexed diagrams and thanks to the examples of embodiment which follow.

Thus, if FIGS. 1 to 5 illustrate, as seen previously, conventional stretching systems, FIGS. 6a, 6b, 6c, 7a, 7b, 7c, 7d, 7e illustrate different modes of implementing the method according to the invention , of a stretching by application of a simple shear on flat sliding surfaces and which apply to the fibrous structures to be stretched, in the form of a sheet or ribbon, while FIGS. 9a, 9b, 9c illustrate the placing work of the method according to the invention, of a stretching by simple shearing on co-surfaces. cylindrical telescopic, but limited to linear textiles.

FIGS. 6a, 6b, 6c illustrate the first embodiment of the method according to the invention in which the external stresses applied to the fibrous material to cause a simple shearing effect, are obtained by means of a pair of elements upper and lower movable, for which the speed of the upper drive rollers (l'-2 ') is different from the speed of the lower drive rollers (1,2): the ratio of these two speeds giving the theoretical stretch ; the two movable elements (18-19) ensure contact with the upper layer and the lower layer respectively of the sheared fibrous system, having the same contact surface, being exactly superimposed.

FIGS. 7a, 7b, 7c, 7d, 7e, illustrate variants according to which the stresses are also obtained by means of a pair of movable elements, said upper and lower elements being offset by c (FIG. 7a) one by relative to the other, without necessarily having the same respective contact surfaces with the upper layer and with the lower layer.

Figures 8a and 8b illustrate variants in which the fibrous material is subjected to a succession of external stresses ensuring a progressive stretching.

Figures 9a, 9b, 9c illustrate different embodiments of the method according to the invention in which the external stresses are obtained by the action of the fibers themselves.

FIGS. 10a, 10b and 10c are diagrams illustrating how the stretching process obtained by implementing the method according to the invention can be explained theoretically.

In the following description, for the sake of simplification, the same or similar elements will be designated by the same references.

Figures 6a, 6b, 6c, 7a, 7b, 7c, 7d, 7th, 8a, 8b illustrate different embodiments of the method according to the invention in which the fibrous structure (24), in the form of a sheet or ribbon , materials in which the staple fibers are arranged at least for the most part substantially parallel with respect to the length, is stretched in accordance with the invention, by subjecting said fibrous structure (24) in movement, to external stresses which cause an effect of Simple shear tending to slide the fibers relative to each other in the form of superimposed elementary layers, moving at different speeds relative to each other. In these embodiments, the material passes between a pair of movable elements (18-19) driven at different speeds, the upper element (19) having a speed V2 higher than the speed V1 of the lower element ( 18). In practice, the elements (18-19) entraining the fibers can be flat strips or bands, metallic or not, fixed or extensible, grooved, notched, or covered with any other lining (spiked, toothed, with more or less rough) or for example, of the same type as those used in conventional drawing on a bench or on a spinning machine. These mobile elements (19-18) are carried by pairs of rollers (1,1 'and 2,2') driven in rotation in a known manner. Furthermore, means are associated with these mobile elements so that they exert, on the material (24) passing between them, forces (20-21) in the region of sliding of the fibers. These normal forces (20-21) can be obtained, as shown in FIG. 6a, by the tension given to the supports, possibly by means of tensioners (25), adjustable or not, acting on each of the elements (18-19 ) for driving the fibers themselves driven respectively at the speed V1 and V2. These normal forces can be obtained by any suitable means such as springs, jacks, electromagnets, loaded levers or the like. They can be transmitted as shown in Figure (6a) by means of a roller but other equivalent means could be envisaged. Thus in FIG. (6b), the normal forces (20-21) are transmitted by means of plates (22-23) on which the elements (18-19) slide. These plates distribute the applied forces over said elements (20-21).

One can also consider using a solution such as that shown in Figure (6c) in particular to avoid the disadvantage of parasitic friction of the elements on the fixed plates. In this variant, the forces (20-21) are transmitted via rollers (28), rollers (29) or any other device keeping the elements under a pressure corresponding to the normal force required in the interval _" a , b ".

If in the embodiments illustrated by the figures: (6a, 6b, 6c) the elements (18-19) are arranged face to face, it could be envisaged, as illustrated in figure (7a), to shift one relative to each other in the direction of advance of the fibrous material (24). This offset, designated by the reference (c) in FIG. 7a, will have a value which will not normally exceed the length of the longest fibers worked. The "lengths" of the contact surfaces of the lower and upper "elements" may not be identical as in Figures 7c, 7d and 7e.

From the variant illustrated in FIG. (7a), it can be envisaged to carry out successive, progressive draws, as shown in the figures (8a and 8b).

...

...

et en nombre variable ou fixe.In these variants, a successive repetition of devices is used to ensure stretching of the draws and / or to change the speed gradient applied, according to constant or variable speed ratios.

...

...

and in variable or fixed number.

alors que l'élément (26), à vitesse V3, assure un deuxième étirage théorique de

et l'élément (27) (à vitesse V4) assure le troisième étirage théorique de

. En fonction de la nature des fibres traitées, et plus particulièrement de leur longueur, on peut modifier les écartements (el, e2, e3, e4) en prévoyant, éventuellement, l'utilisation dans les écartements (afin d'assurer le maintien desdites fibres dans ces zones d'écartement (e) où elles ne sont en contact qu'avec un seul support), d'un ou plusieurs soutiens ou guides, tels que des galets (28), rouleaux (29) (pouvant être lisses, rainurés ou décolletés) ou encore de condenseur et/ou (demi) entonnoir.In the embodiment illustrated by the figures (8a and 8b), the installation comprises three stages of drawing. The element (19) (at speed V2) offset with respect to the element (18) (at speed Vl) ensures a first theoretical stretching of

while the element (26), at speed V3, provides a second theoretical stretching of

and the element (27) (at speed V4) provides the third theoretical stretching of

. Depending on the nature of the fibers treated, and more particularly their length, the spacings (el, e2, e3, e4) can be modified, possibly providing for use in the spacings (in order to maintain said fibers) in these spacing zones (e) where they are in contact with only one support), one or more supports or guides, such as rollers (28), rollers (29) (which can be smooth, grooved or necks) or condenser and / or (half) funnel.

If the process according to the invention can be implemented work by subjecting the fibrous structure in movement to external stresses from mobile elements moved at different speeds and on which apply normal forces exerted on the fibers in the sliding zone, it can also be envisaged to the limit, with regard to linear textiles (wicks, ribbons) to implement this process without using such additional means, these constraints being obtained by the fibers themselves of the ribbon. This is obtained by communicating a twist whose centripetal effect makes it possible to ensure normal pressure by twisting the fibers, which leads to a shear of the telescopic but frustoconical type, as illustrated in the figure (10b), a similar way to what would happen for the flow of a fluid in a capillary. Such a possibility is illustrated by the figures (9a and 9b), as well as by the figure (9c) in which, as in the embodiments illustrated by the figures (Sa and 8b), a succession of draws is communicated by means of elements arranged in cascade.

This twist can be communicated by means of a conventional false-twist member, for example by means of an element (45), commonly used in conventional spinning of the carded wool type, and designated by the expression "twist siiflet" as well as this is illustrated in figure (9a). It could be envisaged to use a “twisting stretching system” of the type of that illustrated in FIG. (9b). It can also be envisaged to use a cascade assembly, with two or more elements in series, with false twist alternating or not, as illustrated in the figure (9c) which comprises three stages with three elements (30-31-32 ) with false alternating twists, which makes it possible to obtain sufficient and effective stretching. Such stretching systems can be used for example at the spindle bench, that is to say before the final stretching on continuous spinning (as is only the case so far with only one stage).

Example 1:

Drawing a wick of 500 tex cotton (100% Russian cotton with an average fiber titer of the order of 2.5 dtex) using a device of the type illustrated in Figure (6a). The stretching system has two strips (18-19) of synthetic elastomer 31 mm wide, the distance between the axes of the rollers (1 and 2) or (l 'and 2') is 50 mm.

• - vitesse d'entrée de la matière : V1 (vitesse de lanière : 18) = 0,22 m/mn,
• - vitesse de la sortie de la matière V2 (vitesse de la lanière 19) = 10 m/mn.

The operating conditions are as follows;

• - material entry speed: V1 (strap speed: 18) = 0.22 m / min,
• - speed of exit of the material V2 (speed of the strap 19) = 10 m / min.

Hence a drawing ratio of 10: 0.22 = 46.

The title of the yarn obtained = 10.9 tex; its toughness: 10.8 cN / tex, its elongation at break = 5.8%, its fracture energy (working capacity) = 31.3 (cN / tex) x (mm / mm); its irregularity in quadratic coefficient of variation = 16.8%.

• Le titre du filé obtenu = 10,9 tex ; sa ténacité 8,5 cN/tex ; son allongement à la rupture = 4,4 % ; son énergie de rupture (capacité de travail) = (18,7 cN/tex) x (mm/mm), son irrégularité en coefficient de variation quadratique = 18,7 %.

Tests carried out in parallel on the same drill bit, but on conventional equipment, of the type illustrated in FIG. 2, led to the same overall drawing error:

• The title of the yarn obtained = 10.9 tex; its tenacity 8.5 cN / tex; its elongation at break = 4.4%; its breaking energy (working capacity) = (18.7 cN / tex) x (mm / mm), its irregularity in quadratic coefficient of variation = 18.7%.

This shows the superiority of the new system compared to the classic system.

Example 2:

• - Rapport des vitesses de 19 et 18 = 36 ; le titre du fil obtenu = 167 tex ; l'irrégularité en coefficient de variation est de 6,8 %.

The stretching of a 6ktex ribbon of acrylic fibers (type: long fibers of 3.3 dtex) was carried out by means of a device illustrated in FIG. 7b, with a sleeve overlap on 20 mm. These strap sleeves are 50 mm wide, and made of synthetic elastomer. The operating conditions are as follows:

• - Ratio of speeds of 19 and 18 = 36; the title of the yarn obtained = 167 tex; the irregularity in coefficient of variation is 6.8%.

By applying a conventional stretch of 36 (FIG. 2) to the same ribbon, a thread of 167 tex is also obtained, but with a coefficient of variation of 8.25%.

Still on the same system with stretching by shearing, according to FIG. 7b, entering with a ribbon of 7 ktex, and applying a 3rd gear ratio of 19 and 18 = 72, the yarn titer obtained is 97.2 tex, with a coefficient of variation of 9.6%.

By applying the same overall rag of 72 on the same ribbon, but on conventional equipment (FIG. 2), a 92 tex thread is obtained but with a coefficient of variation of 14.6%.

Example 3:

In "carded wool" type spinning, a mixture based on 22.5% virgin wool, 8.5% carded wool, 60% "renaissance" wool, 9% polyamide (recovered on rags), "telescopic" drawing according to FIG. 9b with a rate of 1.47 and with a coefficient of twist 18 (giving a false twist of 650 rpm), made it possible to obtain a spun yarn of 120 tex, with only 2 , 1 breakage per 10,000 m of yarn, whereas in conventional spinning, without twisting stretcher, without telescopic drawing, the breakage rate is between 20 and 100 per 10,000 m if a drawing rate of 1.47 (usual rate 1.04 to l, l).

The foregoing examples clearly show the advantages provided by the invention and in particular the fact that it is possible to obtain much higher rates than with the previous stretching systems, rates which can reach 50 and much more, and this as well from wicks of long fibers like wool than short fibers, type: cotton, or of a mixture of short and long fibers: the yarns formed have, moreover, exceptional qualities, superior to the previous yarns, in particular as regards mass regularity , cleanliness, dynamometric properties and this compared to yarns of the same title obtained with the same materials on conventional ring spinning machines for cotton on the one hand and for wool on the other hand, but with drawing rates which cannot exceed 30 for cotton and 20 for wool per drawing stage.

Of course, the invention is not limited to the embodiments described above but it covers all the variants produced in the same spirit. Thus, if the invention has been described more particularly for obtaining yarns of single fibers, it could be envisaged to incorporate a core inside said yarns and this at any stage of the drawing process. according to the invention before, during or at the end of the actual stretching.

Similarly, if in the embodiments where the material passes between two elements (18-19) driven at different speeds, belts similar to those used on conventional machines at all stages of spinning are used, it could be envisaged using materials representing another surface configuration, for example coated with a lining such as spikes, teeth, etc. making it possible to ensure better efficiency of the drive or even to carry out, at the same time as the main stretching function, other functions such as disentangling, parallelization, or carding for which stretching by progressive gradients successively allows _J not much better efficiency than what the conventional known embodiments give to a single fact gradient .,

Claims (15)

1 / Method for stretching a textile structure made up of staple fibers, arranged at least for the most part substantially parallel to the length of said structure, this structure being able to be in the form of a sheet as well as a ribbon or of a wick, characterized in that the stretching is obtained by subjecting the fibrous structure in motion to external stresses which cause a simple shearing effect which tends to slide the fibers relative to each other, according to a gradient of speeds resulting in the displacement at different speeds regularly staggered of elementary layers of fibers and on which forces normal to the layers are exerted, in particular in the sliding zone, to do this. 2 / A method according to claim 1, characterized by a stretch obtained by a single simple shear zone. 3 / A method according to claim 1, characterized by a progressive stretching obtained by several successive single shear zones. 4 / A method according to claim 2, characterized in that the simple shearing is obtained by actions of mobile elements (strips, strips ....) arranged on either side of the material, moved at different speeds, and on which apply normal forces exerted on the fibers in the sliding zone. 5 / A method according to claim 4, characterized in that said movable elements are offset relative to each other. 6 / A method according to claim 3, characterized in that the progressive stretching is obtained using a sequence of elements on either side of the material, these elements being offset relative to each other and ensuring progressive stretching. 7 / A method according to claim 3, characterized by a shear in concentric telescopic cocylindrical layers only applicable in the case of tape or wick, where the external support is produced by the surface fibers themselves twisted for example by false twist, whose centripetal effect ensures the application of normal pressure, according to the series connection of elements with false twists. 8 / Device for the stretching of a textile structure made up of staple fibers, arranged at least in the majority portion substantially parallel to the length of said structure, structure which can be in the form of a sheet as well as a ribbon or a wick (24) characterized in that it comprises means making it possible to subject the fibrous structure in movement to external stresses (20-21) which cause simple shearing with a speed gradient which tends to make sliding the fibers in the form of superimposed elementary layers moving at different speeds from each other, layers on which normal forces are exerted, in particular in the sliding zone. 9 / Apparatus according to claim 8, characterized in that the external stresses are obtained by passing the material (24) between two movable elements (18-19) (strips, strips or any other fiber driving element) arranged on either side of the material moving at different speeds V1 and V2. 10 / Device according to claim 9, characterized in that the movable elements (20,21) are arranged face to face. 11 / Device according to claim 9, characterized in that the movable elements (18-19) are offset from each other. 12 / Apparatus according to claim 11, characterized in that it comprises a plurality of movable elements (18,19,26,27) offset from each other and driven respectively at speeds (Vl, V2, V3 , V4 ...) different. 13 / Device according to claim 8, characterized in that the normal forces (20,21) communicated by the movable elements (18-19) to the material (24) in movement are obtained by means of plates, rollers, rollers, spring leaves. 14 / Apparatus according to claim 8, characterized in that the normal forces applied to the material (24) are obtained by the action of the fibers themselves, according to one or more successive shears of the telescopic type. 15 / Device according to claim 14, characterized in that the action of the fibers is obtained by means of one or more false twist elements.

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