EP0089299B1 - Drawing method for a fibrous textile structure, and apparatus therefor - Google Patents

Description

The present invention relates to a process for drawing a textile structure based on fibers, said structure being presented 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.

de ces vitesses détermine le taux d'étirage. Ce taux d'étirage est un taux théorique qui ne tient pas compte des glissements éventuels des fibres. Par ailleurs, le pinçage de la matière entre les cylindres (1, 2) et (1', 2') se fait uniquement par les pressions (15-16).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 of these solutions, the actual stretching is obtained essentially between a pair of input cylinders (1, 2) (also frequently referred to as "food cylinders"), having the same tangential speed V1 and, a pair of output cylinders (1'-2 ') having the same tangential speed V2 greater than that V1 of the input cylinders. The report

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 (1 ', 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 of the output cylinders (1 ', 2') compared to the input 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), cylinders "hedgehogs" (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, the distance d between the pair of input (or food) cylinders and the pair of output (or draw) cylinders must be adjusted in order to d '' on the one hand avoid breaking the long fibers if the distance d is too short, 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 with respect to each other, in the form of superimposed elementary layers moving at different speeds from each other and on which forces normal to the fibers are exerted especially in the sliding area.

Indeed, according to the new approach at the origin of this invention, the process of refining the Linear or areal mass of the fibers in a section can be compared 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 done by applying this which is called in rheology a "simple shear" either on flat 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 V1 of another element (18), while applying normal forces (20-21) during the sliding of the layers of fibers (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 and distributed over the fibers due to the tension given by the tensioners (25), adjustable or not (Figure 6a) with (1) and (2) rotating at speed V1 and (1 ') (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 from the illustrations in the appended diagrams and from the following exemplary embodiments.

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 in work of the method according to the invention, of a stretching by simple shearing on telescopic cocylindrical surfaces, but which is 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 (1 '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 progressive drawing.

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 mobile 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 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 can be considered. 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 the 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 "upper and lower" elements may not be identical as in FIGS. 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'élement (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 (e1, 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 V1) 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 (e1, 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 method according to the invention can be implemented by subjecting the fibrous structure in motion to external stresses from mobile elements displaced at different speeds and on which apply normal forces exerted on the fibers in the sliding zone, it can also be envisaged at the limit, with regard to linear textiles (wicks, ribbons) to implement this method without using such additional means, these constraints being obtained by the fibers themselves same 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 FIG. (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 (8a 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 the intermediary of an element (45), commonly used in conventional spinning like carded wool, and designated by the expression "twisting whistle" as well as this is illustrated in figure (9a). It could be envisaged to use a "twisting and drawing 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, on a spindle bench, that is to say before the final drawing on continuous spinning (as has hitherto only been the case with a single 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 comprises two strips (18-19) made of synthetic elastomer 31 mm wide, the distance between the axes of the rollers (1 and 2) or (1 '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 wick, but on conventional equipment, of the type illustrated in FIG. 2, led to the same overall drawing rate:

• 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 6 ktex ribbon of acrylic fibers (type: long fibers of 3.3 dtex) was carried out by means of a device illustrated in FIG. 7b, with an overlap of the sleeves over 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 speed ratio of 19 and 18 = 72, the title of wire obtained is 97.2 tex, with a coefficient of variation of 9.6%.

By applying the same overall stretch 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" stretching 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 breaks 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 is applied 1.47 (usual rate 1.04 to 1.1).

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 such as wool as short fibers, type: cotton, or a mixture of short and long fibers: the yarns formed have, moreover, exceptional qualities, superior to previous yarns, in particular in 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 examples of 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 drawing.

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 ... making it possible to ensure better efficiency of the drive or even to achieve, at the same time time as the main stretching function, other functions such as disentangling, parallelization, or carding for which stretching by progressive gradients successively allows a much better efficiency than that given by conventional known embodiments at a single gradient made.

Claims (15)

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.

2. Method as claimed in claim 1, characterized by the fact that the stretching is obtained by one simple shear area only.

3. Method as claimed in claim 1, characterized by the fact that a progressive stretching is obtained by several successive simple shear areas.

4. Method as claimed in claim 2, characterized by the fact that the simple shear is obtained by the action of movable elements (belts, bands, ...) disposed on either side of the material, and moving at different speeds, normal forces being applied on said movable elements which forces are exerted on the fibers in the sliding area.

5. Method as claimed in claim 4, characterized by the fact that the said movable elements are offset one with respect to the other.

6. Method as claimed in claim 3, characterized by the fact that the progressive stretching is obtained by means of a sequence of elements on either side of the material, said elements being offset one with respect to the other and performing a progressive stretching.

7. Method as claimed in claim 3, characterized by the fact that a shearing operation is performed in telescopically concentric co-cylindrical layers, applied only to the case of top or roving of fibers, in which the external support is supplied by the superficial fibres themselves which are twisted for example by false twist, the centripetal effect of which ensures the application of a normal pressure, depending on the assembly in series of false twist elements.

8. Device 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 fiber sheet or in top or roving form (24), characterized by the fact that said device comprises means for subjecting the moving fibrous structure to external pressures (20, 21) causing a simple shear with a speed gradient which tends to make the fibers slide, as superimposed elementary layers all moving at different speeds, on which layers are exerted normal forces in the sliding area.

9. Device as claimed in claim 8, characterized by the fact that the external pressures are obtained by causing the material (24) to pass between two movable elements (18, 19), (belts, bands or similar fiber-driving means) placed on either side of the material and moving at different speeds V₁ and V₂.

10. Device as claimed in claim 9, characterized by the fact that the movable elements (18,19) are arranged in facing relation.

11. Device as claimed in claim 9, characterized by the fact that the movable elements (18, 19) are offset one with respect to the other.

12. Device as claimed in claim 11, characterized by the fact that the said device comprises a plurality of movable elements (18, 19, 26, 27) offset one with respect to the other and respectively driven at different speeds (V₁, V₂, V₃, V₄, ...).

13. Device as claimed in claim 8, characterized by the fact that the normal forces (20, 21) communicated by the movable elements (18, 19) to the moving material (24) are obtained by means of plates, pulleys, rollers or spring leaves.

14. Device as claimed in claim 8, characterized by the fact that the normal forces supplied on the material (24) are obtained from the fibers themselves, from one or more successive shears of a telescopic type.

15. Device as claimed in claim 14, characterized by the fact that the action of the fibers is obtained by means of one or more false twist elements.

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