EP1290253B1 - Machine for making a nonwoven by airlay technique, comprising a fibre dispersing chamber whereof the front wall is porous in the lower part - Google Patents

Abstract

The invention concerns a machine (4) for making a nonwoven by airlay technique, comprising: a surface (6a) for forming and conveying the nonwoven, which is permeable to air; a dispersion chamber (11) above the forming and conveying surface (6a); means (12) for supplying the dispersion chamber (11) with fibres designed to form the nonwoven; and means (13, 14) adapted to generate, inside the dispersing chamber (11), an air stream for dispersing the fibres inside the chamber and projecting them on the forming and conveying surface (6a). The front wall (9) of the dispersing chamber (11) is porous in its lower part, and preferably has in its lower part a slope modification such that its internal surface (17b) forms a funnel (21) with the forming and conveying surface (6a).

Description

The present invention relates to the field of the manufacture of a nonwoven by aeraulic route. Its main object is a machine for the formation of a nonwoven by aeraulic route, which has been perfected so as to reduce the risk of formation of defects in the nonwoven.

It has been known for many years a technique of manufacturing a non-woven airway, which is commonly referred to as "airlay" technique. This technique is essentially characterized by the dispersion in a chamber and the projection on a mobile receiving surface of individual fibers by means of a high velocity air flow, said receiving surface being permeable to air, and allowing the formation and transport of the nonwoven. The fibers undergo, during their course in the air flow, a random dispersion, which is commonly called "random" effect, and which advantageously contributes to obtain a homogeneous nonwoven, the mechanical properties of which are very good. isotropic.

In practice, the dispersion of the fibers is carried out in a vertical dispersion chamber which overcomes the formation and transport surface of the nonwoven. Generally, the fibers are fed to the upper part of the dispersion chamber, being transported to the periphery of a rotating cylinder, and the air flow allowing the dispersion and transport of the fibers to the formation surface and transporting the nonwoven, is created inside the dispersion chamber so as to be substantially tangential to the cylinder and to assist in detaching the fibers from the periphery of the cylinder. Preferably, but not necessarily, the rotating cylinder, which allows the introduction of the fibers into the dispersion chamber, is rotated at high speed, so as to also allow an ejection of the fibers inside the dispersion chamber, under the effect of the centrifugal force.

A machine permitting the manufacture of a nonwoven by aerodynamic means is described, for example, in US Pat. No. 3,512,218. In this embodiment, the surface for forming and transporting the nonwoven is produced by means of a porous conveyor belt. The dispersion chamber comprises two longitudinal vertical walls which extend parallel to the direction of movement of the conveyor belt, and two rear and front walls, which extend transversely to the direction of travel of the conveyor belt, and which are referenced respectively (77) and (78) in Figure 3 of US-A-3,512,218. In the present text, the terms "back" and "front" are taken with reference to the direction of movement of the forming surface and non-woven transport. The introduction of the fibers into the dispersion chamber is carried out by means of two referenced rotary cylinders (52) and (54) in the figures of this patent. The "airlay" airflow, for dispersing and transporting fibers to the conveyor belt, is created by means of a referenced suction box (102), associated with fans that make it possible to create a flow suction through the conveyor belt, and over substantially the entire horizontal section of the dispersion chamber, and recycle the sucked air by the discharge in the upper part of the dispersion chamber. In operation, the fibers introduced inside the dispersion chamber are dispersed and projected against the surface of the conveyor belt, and accumulate on this surface in the form of a nonwoven. This nonwoven thus formed is conveyed by the conveyor belt, outside the dispersion chamber, passing to the right of the front wall of this chamber, a space being provided between the lower end of the this front wall and the surface of the conveyor belt.

A first constraint for the designers of this type of machine is to prevent air from being sucked from outside the dispersion chamber and entering the dispersion chamber passing between the walls of the chamber. and the formation and transport surface of the nonwoven. A second constraint is to limit the risk of attachment of non-woven fibers on the lower end of the front wall of the dispersion chamber, during the passage of the non-woven to the right of this wall.

To solve the first stress at the longitudinal walls and the rear wall of the dispersion chamber, the lower edge of these walls is positioned in the immediate vicinity of the formation and transport surface of the nonwoven, and is provided with a seal, coming against the forming surface and transport.

To solve the second constraint, a front wall is used which has a slope change at the bottom, which results in an enlargement of the section of the dispersion chamber, taken in a plane parallel to the formation and transport surface of the dispersion chamber. nonwoven. The inner face of this lower part of the front wall of the dispersion chamber thus forms with the formation and transport surface, a funnel (channel whose section, taken in a plane transverse to the formation and transport surface, decreases gradually), which allows a progressive guide of the nonwoven to the exit of the dispersion chamber. Preferably, the lower part of the funnel-shaped front wall has a substantially arcuate shape.

To solve the aforementioned first constraint at the front wall, it is ensured that the outlet of the aforementioned funnel has a low height, which is in practice fixed so that in operation the nonwoven is slightly compressed in Release the funnel, which ensures a sufficient air tightness. Preferably, this height of the outlet of the funnel is adjustable, so as to allow adjustment of the thickness or weight of the nonwoven.

In the machine described in the aforementioned patent US-A-3,512,218, the aforementioned funnel at the front wall of the dispersion chamber is obtained by virtue of the implementation, in the lower part of this front wall, of a plate substantially in the shape of an arc and referenced (81) in Figure 3 of this patent. This plate is pivotally mounted so as to allow the aforementioned adjustment of the outlet section of this funnel.

By making a nonwoven with a machine of the type described in US-A-3,512,218 it has been found that small defects occur randomly in the nonwoven. These defects result in the formation in the non-woven of small areas of over-accumulation of fibers; these areas are elongate and oriented essentially according to the width of the nonwoven.

The present invention aims to provide a machine for the formation of a nonwoven by aeraulic route, which has been improved so as to produce a nonwoven of better quality having a number of aforementioned defects, and in the best of case free from any of the above defects.

• une surface de formation et de transport du non-tissé, qui est perméable à l'air,
• une chambre de dispersion surmontant la surface de formation et de transport,
• des moyens permettant d'alimenter la chambre de dispersion avec des fibres destinées à former le non-tissé,
• et des moyens qui sont aptes à créer, à l'intérieur de la chambre de dispersion, un flux d'air permettant de disperser les fibres à l'intérieur de la chambre et de les projeter sur la surface de formation et de transport.

This object is achieved by the machine of the invention, which is known, in particular from US-A-3,512,218, in that it comprises:

• a surface for forming and transporting the nonwoven, which is permeable to air,
• a dispersion chamber surmounting the formation and transport surface,
• means for supplying the dispersion chamber with fibers intended to form the nonwoven,
• and means which are able to create, within the dispersion chamber, a flow of air to disperse the fibers within the chamber and project them onto the forming and transporting surface.

Characteristically according to the invention, the front wall of the dispersion chamber is porous in its lower part.

• la figure 1 représente une ligne complète de production d'un non-tissé mettant en oeuvre une machine de fabrication d'un non-tissé par voie aéraulique, conforme à l'invention,
• la figure 2 est une représentation en perspective simplifiée des parties essentielles de la machine de fabrication d'un non-tissé par voie aéraulique de la ligne de production de la figure 1,
• la figure 3 est une vue en coupe transversale de la machine de fabrication d'un non-tissé par voie aéraulique de la ligne de production de la figure 1
• la figure 4 est une vue en coupe transversale simplifiée et agrandie de la machine de la figure 3,
• la figure 5 représente de manière schématique une deuxième variante de réalisation d'une machine de fabrication d'un non-tissé par voie aéraulique conforme à l'invention, et mettant en oeuvre un cylindre poreux ;
• la figure 6 est une vue de détail du cylindre poreux de la machine de la figure 5,
• et la figure 7 représente de manière schématique une troisième variante de réalisation d'une machine de fabrication d'un non-tissé par voie aéraulique conforme à l'invention

Other features and advantages of the invention will appear more clearly on reading the following description of several preferred embodiments of a machine for forming a nonwoven according to the invention, which description is given as a non-limiting example and with reference to the accompanying drawings in which:

• FIG. 1 represents a complete line of production of a nonwoven using a machine for manufacturing a nonwoven by the aerodynamic route, according to the invention,
• FIG. 2 is a simplified perspective representation of the essential parts of the aerated nonwoven manufacturing machine of the production line of FIG. 1,
• FIG. 3 is a cross-sectional view of the machine for manufacturing a nonwoven by the aerodynamic route of the production line of FIG. 1
• FIG. 4 is a simplified and enlarged cross-sectional view of the machine of FIG. 3,
• FIG. 5 is a schematic representation of a second variant embodiment of a machine for manufacturing a nonwoven by aerodynamic means according to the invention, and using a porous cylinder;
• FIG. 6 is a detailed view of the porous cylinder of the machine of FIG. 5,
• and FIG. 7 schematically represents a third variant embodiment of a machine for manufacturing a nonwoven aeraulic way according to the invention

FIG. 1 shows a complete production line of a nonwoven comprising, at its inlet, a conventional feed chimney 1, which in operation is fed at the top with fibers, and which delivers on a conveyor 2 a fiber pile mat (not shown). Downstream of the conveyor 2, the line comprises a card 3 of traditional design, which feeds an output machine 4 according to the invention for the production of a nonwoven by aeraulic route.

In the particular example illustrated, the card 3 comprises an input feed roller 3 has, associated with a takerin 3 b. The takerin 3 b used for supplying fiber, a first rotating carding cylinder 3c, more commonly called "front end", and whose surface is coated in the usual manner of a card clothing allowing it to resume fibers of the periphery of the breaker cylinder 3 b . On the periphery of the carding cylinder 3 b are mounted conventional doffer means, that allow to work the fibers taken into the cylinder card clothing 3c, so as to individualize and to parallelize. In the illustrated example, these combing means are constituted by several successive pairs of a stripping roll 3 d and a worker roller 3 e . Downstream of these means doffer the fibers are taken from the periphery of said first carding cylinder 3 c, and is transferred in the state at the periphery of a second rotary carding cylinder 3 g, f 3 by a transfer cylinder , still called "communicator". The second carding cylinder 3 g , still commonly called "large drum" or "main drum", is also coated with a card lining or the like and is provided on its periphery with combing means (3 d , 3 e ) identical to those equipping the first carding cylinder 3 c . The card 3 has a double output, each card outlet consisting of two successive cylinders 3 h and 3 i . This type of card exit is already known and described in particular in the European patent application EP-A-0 950 733, to which the skilled person can refer.

The machine 4 for producing a nonwoven by aerodynamic means which is described in detail below, is not necessarily implemented with an upstream card, but may be implemented generally with any upstream fiber feeder device, this device may or may not as appropriate have a function of working and working fibers. When the machine 4 is provided downstream of a card, this card is not necessarily identical to that of Figure 1 which is given by way of non-limiting example. Indeed, depending on the type of fiber and the desired degree of processing, it is possible to envisage a longer card using a larger number of successive carding rolls, or on the contrary a shorter card using a single cylinder. carding. Furthermore, the rollers 3 d and 3 e could be arranged by being juxtaposed one behind the other alternately, according to a configuration commonly called "Garnett". These rollers could also be replaced by any means of different structure, and fulfilling the same function, that is to say, to individualize and parallelize the fibers transported by the carding rolls. In particular, these rollers 3 d and 3 e could be replaced by static plates, more commonly known as "carding plates", mounted on the periphery of the carding cylinder, and having a plurality of carding points in the form for example of grooves or splines.

The machine 4 for manufacturing a nonwoven by air means comprises a conveyor 5 employing a porous conveyor belt 6 mounted stretched on drive rollers 7. In operation, the upper run 6 a of this conveyor belt 6, which in the particular example illustrated is substantially horizontal, is driven at predetermined constant speed in the direction of transport shown in Figure 1 by the arrow D. This upper strand 6 has an air permeable surface, which allows the formation and transport of the nonwoven.

Machine 4 also comprises a vertical shaft 8, which surmounts the upper strand 6a of the conveyor belt 6 and extends over the entire width (L) of the upper strand 6a (Figure 2). This chimney 8 essentially comprises a front wall 9 and a rear wall 10, which extend transversely to the direction of movement (D) of the conveyor belt 6, and two longitudinal walls connecting the two front walls 9 and rear 10, and extending substantially parallel to the direction of displacement (D), that is to say in a plane parallel to the plane of FIGS. 1, 3 and 4. For the sake of simplification and clarity of the drawing, these two longitudinal walls n ' it is not shown in the perspective of Figure 2. This chimney 8 forms a chamber 11 for dispersing the fibers. This chamber is open at both its upper ends 11a and lower 11b.

At the open upper end 11a of the dispersion chamber 11, the machine 4 comprises a cylinder 12, said cylinder thereafter "Dispenser", which allows the supply of fibers to the dispersion chamber. This dispersing cylinder 12 is adjacent to the two cylinders 3 i of the card outlet 3, and allows to recover and superimpose on its periphery the card webs, from the card 3 and transported on the periphery of these two cylinders 3 i . The disperser roll 12 is preferably provided on its periphery with a covering whose teeth or spikes 12 has (Figures 3 and 4) are oriented towards the front (that is to say in the direction of rotation of the cylinder) . This dispersing cylinder 12 is further provided to be rotated with a circumferential speed greater than or equal to the circumferential speed of the two upstream cylinders 3 i . This cylinder 12 can be driven directly in rotation by a motor whose rotor is coupled directly to the rotation shaft of the cylinder 12, or be driven indirectly, its rotation shaft being mechanically coupled to the rotation shaft of one of the cylinders of the card 3 (for example the carding cylinder 3 (g ) a properly sized mechanical transmission system with gears and belts. Preferably, in operation, this dispersing cylinder 12 is driven at high speed, so that the fibers which are taken in its lining tend to come out of this lining under the action of the centrifugal force.

Machine 4 also comprises an air supply channel 13, whose open upper end 13 a communicates with the open air, and the lower end 13 b of which is connected to the open upper end 11a of the dispersion chamber 11. at the opposite channel 13, under the upper strand 6a of the conveyor belt 6 is mounted a box (or box) suction 14, which defines an internal chamber 14 a which is connected to a fan (not shown) by a conduit 15 (Figure 1). When the fan is running, the internal chamber 14a is depressurized. It thus forms a suction chamber and makes it possible to create, through the upper run 6 a of the conveyor belt 6, a suction which generates inside the dispersion chamber 11 a substantially vertical flow of air, indicated by arrows in figures 3 and 4. this suction is created over the entire section (taken in a plane parallel to the strand 6a of the conveyor 6) from the lower open end 11b of the dispersion chamber 11, that is that is to say on a surface which extends in the direction (D) over a width l (FIGS. 3 and 4) and in the transverse direction over the width L of the conveyor belt. Preferably, the front wall 14b of the suction box is translatable in the direction (D) so as to allow a case-by-case adjustment of the width (I) of the suction surface, which makes it possible to adapt the suction zone to different sections of dispersion chamber.

In operation, the fibers which are conveyed inside the dispersion chamber 11, at the periphery of the dispersing cylinder 12, are detached from the lining of this cylinder by the action of the air flow created inside the the dispersion chamber 11, which air flow is substantially tangential to the tips 12a of the trim cylinder disperser 12. a high rotational speed of the disperser roll 12 also facilitates the detaching of the fibers under the action of the force centrifugal. The fibers are thus ejected in an individualized manner inside the chamber 11. These fibers are dispersed by the flow of air over the entire horizontal section of the dispersion chamber 11 and are projected by the air flow on the Upper strand 6 at a distance from the conveyor belt 6. A nonwoven is thus formed inside the chamber 11 and at the surface of the conveyor belt 6, which nonwoven is conveyed by the conveyor belt 6 to the conveyor belt 6. outside the dispersion chamber 11, passing right of the front wall 9 of this chamber.

The front wall 9 of the dispersion chamber is formed in the upper part of a solid plate 16, which is flat and impervious to air, and in the lower part of a curved thin sheet 17, having a substantially arcuate profile. circle, and of which the part 17a closest to the upper strand 6a of the conveyor 6 (that is to say in the illustrated example the lower end portion of the sheet 17) is oriented substantially parallel to the strand top 6a of the conveyor belt. This sheet 17 is an insert and fixed on the lower edge of the sheet 16 by any appropriate means and for example by screws 18 or rivets.

In contrast, the rear wall 10 of the dispersion chamber 11 is formed of a solid thick plate 19, which is impervious to air. The two sheets 16 and 19 are not perfectly vertical and parallel, but slightly divergent from each other (FIG. 4 / angles α and β of the sheets 16 and 19 with respect to the vertical), so that the dispersion chamber 11 forms a cone whose cross-section (taken in a plane parallel to the upper strand 6a of the conveyor 6) increases towards the upper strand 6a of the conveyor belt 6. Thus, a better dispersion of fibers .

The sheet curve 17 enables a change of slope in the lower part of the front wall 9, the inner face 17b of the sheet 17 forming the upper side 6a of the conveyor 6, a funnel 21 for guiding the nonwoven formed to the exit of the dispersion chamber. This advantageously limits the risk of attachment of non-woven fibers on the front wall 9, and in particular on its lower edge.

In the particular example illustrated, this thin plate 17 is flexible and in the absence of non-woven is, at its lower end 17a in contact with the upper strand 6a of the conveyor belt 6. In operation (Figure 4), the nonwoven (W) raises the sheet 17 by slightly modifying its curvature, said sheet coming to exert on the nonwoven a low pressure force, which compresses it slightly. It is thus avoided in operation that the suction flow created by the suction box 14 does not generate a flow of incoming air that would penetrate inside the dispersion chamber 11 passing between the lower end of the wall front 9 and the upper strand 6a, such air flow being detrimental to the quality of the nonwoven.

Also, to avoid that the suction created by the flow aspiration14 box does not come generating an air stream entering that penetrate inside the dispersion chamber 11 by passing between the upper strand 6a and the end lower rear walls 10 and longitudinal of the chamber 11, the lower edge of these walls is positioned adjacent the upper strand 6a, and is equipped with a seal 20 which is applied on the upper strand 6 a .

According to an essential characteristic of the invention, the front wall 9 is porous to the air in its lower part, that is to say in the particular example illustrated in its funnel portion 21. This porous zone extends over substantially the entire width (L) of the front wall 9 of the dispersion chamber 11 (Figure 2). More particularly, this porosity is obtained by multiple micro-perforations made in sheet 17.

Preferably, as shown in the accompanying figures, the sheet 17 is impervious to air, on a first referenced sector (B) which extends over a short length from the lower edge 17c of the sheet 17, and is porous on its remaining surface (sector referenced A) which extends to the upper plate 16. The height h (FIG. 4) between the sheet 17 and the conveyor belt 6, at the level of the boundary between the porous zone ( A) and nonporous zone (B) corresponds in practice to the maximum thickness of accumulation of fibers inside the dispersion chamber.

In an alternative embodiment, a sheet 17 is used micro-perforated over its entire surface, and the bottom portion (B) non-porous is obtained fixing on the inner face of this lower part a coating 22 (Figure 4) closing off airtight micro-perforations. Preferably, it was a coating 22 with a lower coefficient of friction (compared to the coefficient of friction of the internal face of the sheet 17), such as for example polytetrafluoroethylene (PTFE).

In another variant, it would also be possible to use a sheet 17 micro-perforated only in the porous part (A) of the front wall 9. In this variant, it may also be advantageous to use a coating 22 with a low coefficient of friction so that to improve the sliding of the nonwoven relative to the front wall 9.

In operation, the suction created by the suction box 14 inside the dispersion chamber generates through the micro-perforated portion (A) of the sheet 17, a flow of incoming air coming from the outside, in the form of a plurality of mini-jets of air, distributed over all the width (L) of the wall This air intake advantageously makes it possible to maintain an orientation of the air velocities in the funnel 21, which is essentially transverse (that is to say vertical in the illustrated example) to the formation surface of the nonwoven (upper strand 6a of the conveyor 6) with a small horizontal component for these air velocities.

Comparatively, in the case where sheet metal 17 is used, a solid sheet that is impermeable to air, air funnel 21 is observed in the funnel, which increasingly tends to deviate from the vertical. the closer we get to the sheet 17, the air velocities near the exit of the nonwoven (nonwoven nipping zone between the sheet 17 and the conveyor belt 6) having a large horizontal component. However these air speeds with a high horizontal component are the source of defects in the structure of the nonwoven. These defects materialize in the form of short areas of over-accumulation of fibers, which are local, oriented substantially along the width of the nonwoven. and which form randomly in the surface of the nonwoven.

Advantageously according to the invention, the porosity in the lower part of the front wall 9 makes it possible to obtain, in the funnel part 21, a rectification of the air velocities, which consequently have a larger vertical component, which limits the phenomenon of formation of the aforementioned defects. In other words, in operation, the air velocities in the funnel 21 of the dispersion chamber have a larger vertical component and a lower horizontal component, than the respectively vertical and horizontal components of the air velocities which would be obtained in the funnel 21 with a front wall 9 (sheet 17 in the example shown) impermeable to air.

The invention is not limited to the preferred embodiment which has just been described with reference to FIGS. 1 to 4. In particular, the micro-perforated plate 17 may be replaced by any equivalent wall, porous or microporous . It could be a flat sheet, or a flat sheet in the central part and ending with lower and upper end portions substantially in a circular arc.

In another alternative embodiment, the sheet 17 could, in the absence of non-woven, not being in contact with the conveyor belt, a slight gap being for example provided between the lower end 17a of the sheet 17 and the upper strand 6a of the conveyor belt. Preferably, but not necessarily, in this case the height of this space is adjustable, so as to adjust the thickness or the weight of the nonwoven at the outlet of the dispersion chamber 11.

In another variant embodiment, the sheet 17 could be porous over its entire surface; the disadvantage of this variant, however, compared to the implementation of a sheet 17 whose lower end portion is impervious to air, is the increased risk of attachment of the nonwoven on the front wall at the outlet of the dispersion chamber 11.

In another variant not shown in the figures, the porous portion (A) of the front wall could extend over a more limited area (that is to say on a lower sector not reaching the lower edge of the plate 16), and / or the front wall 9 could be made in one piece.

In the preferred embodiment which has been described with reference to Figures 1 to 4, the air supply channel 13 opens in the open air in the upper part. In another variant embodiment, the air sucked by the suction box 14 could be used in a closed circuit by being completely or partially repressed inside the channel 13.

FIG. 5 shows another variant embodiment of a nonwoven production machine of the invention, in which, compared with the variant of FIGS. 1 to 4, the porous part of the front wall 9 is made in the form of a hollow porous hollow tube or cylinder. The axis of rotation 22 a of the tube or cylinder 22 extends transversely to the direction of movement (D) of the conveyor belt 6.

More particularly, with reference to FIG. 6, this tube or hollow cylinder 22 comprises a cylindrical thin sheet 23, for example made of stainless steel, and micro-perforated over its entire surface, said sheet 23 being fastened to two end flanges 24 The assembly is mounted on a rotating shaft. This shaft 25 is provided to be rotated by means of a motor (not shown) via a belt type transmission system 26.

With reference to FIG. 5, the cylindrical plate 23 is mounted above the upper run 6 a of the conveyor belt 6, so that it comes into contact with the upper run 6 a along the tangency generator T. In another Alternatively, a small gap could be provided between the upper strand 6a and the cylindrical plate 23, this space being sufficiently small for the nonwoven product is compressed as it passes under the roller 22.

In operation, the cylindrical plate 23 is rotated in the same direction as the upper strand 6a of the conveyor belt 6, and a circumferential speed at least equal to the linear speed of said upper strand 6a. In particular, the cylindrical plate 23 could be rotated so that its circumferential speed is slightly greater than the linear speed of the upper strand 6a of the conveyor belt 6.

In a specific exemplary embodiment given as an indication, the plate 17 or the cylindrical plate 23 was made of thick stainless steel 300μm; the rate of opening of the micro-perforated sheet (ratio between total open area and total area) was about 25%; each micro-perforation had a substantially circular section, with a diameter of the order of 320 microns.

According to an additional feature, in the variant of Figure 5, a brush 27 is fixed on the periphery of the cylinder 22. It allows to scan the outer surface of the sheet 23 during the rotation of said sheet. This brush 27 thus removes from the sheet 23 the fibers or dirt that can be deposited on and be driven by the sheet 23. This brush 27 is optional.

According to another additional characteristic, in the variant of FIG. 5, a suction box 28 is mounted immediately downstream of the cylinder 22, and allows, in operation, to suck the nonwoven at the outlet of the nipping zone ( T) between the cylinder 22 and the upper strand 6a of the conveyor belt, in the plating against the upper strand 6 a. This suction is implemented over the entire width of the nonwoven. In addition, the suction zone 28 extends over a length L. The position of the suction box 28 is preferably adjustable. This suction makes it possible to obtain a better transfer of the web beyond the cylinder 22.

FIG. 7 shows another alternative embodiment of a nonwoven production machine of the invention, which differs from the variant of FIG. 5 only by the use of a cowling 29, allowing enclosing the cylinder 22 in a chamber 29 which comprises a top portion an air inlet opening 30 width (e) is preferably adjustable. This opening 30 extends in the direction of the axis of the cylinder 22 (direction transverse to the plane of Figure 5) over substantially the entire length of the cylindrical plate 23). This cowling 29 makes it possible to obtain a better orientation of the flow of air sucked through the cylindrical plate 23.

In both variants of Figures 5 and 7, the front wall 9 of the dispersion chamber 11 has a plate 9A which extends in the lower part beyond the cylinder 22, the lower edge 9b of the plate 9a being located at a height (h) of the upper strand 6a of the conveyor belt 6. the plate 9a is deflector office and enables in operation to limit the risks of over-accumulation of fibers immediately upstream of the cylinder 22. the height (h) can be adjusted on a case by case by the skilled person.

Claims (15)

1. Machine (4) for manufacturing a nonwoven (W) by airlay technique, of the type comprising:

   - a surface (6a) for forming and conveying the nonwoven, which is permeable to air,

   - a dispersion chamber (11) surmounting the forming and conveying surface (6a), and comprising a front wall (9) and a rear wall (10),

   - means (12) to supply the dispersion chamber (11) with fibres intended to form the nonwoven,

   - and means (13,14) able to set up an airflow inside the dispersion chamber (11), allowing the fibres to be dispersed inside the chamber and to be propelled onto the forming and conveying surface (6a),

   characterized in that the front wall (9) of the dispersion chamber (11) is porous in its lower part.
2. Machine as in claim 1, characterized in that the dispersion chamber's front wall (9), in its lower part, has a change in slope so that its inner surface (17b) forms a funnel (21) with the forming and conveying surface (6a).
3. Machine as in claim 2, characterized in that the dispersion chamber's front wall (9), in its lower part, has a curved profile, its part (17a) closest to the forming and conveying surface (6a) of the nonwoven being oriented substantially parallel to said surface (6a).
4. Machine as in claim 3, characterized in that the dispersion chamber's front wall (9), in its lower part, has a curved profile substantially in an arc of a circle.
5. Machine as in any of claims 1 to 4, characterized in that the front wall (9) is flexible in its lower part.
6. Machine as in claim 5, characterized in that when there is no nonwoven present, the lower end (17a) of the front wall is in contact with the forming and conveying surface (6a) of the nonwoven.
7. Machine as in any of claims 1 to 6, characterized in that the porous part of the front wall (9) of the dispersion chamber is made of thin, micro-perforated sheet metal (17).
8. Machine as in any of claims 1 to 7, characterized in that the front wall (9) of the dispersion chamber is impermeable to air over a part (B) which extends from its lower edge (17c).
9. Machine as in claim 8, characterized in that on the inner surface of the front wall (9), at its lower part (B) impermeable to air, a covering (22) is attached having a lower coefficient of friction.
10. Machine as in any of claims 1 to 9, characterized in that the means (13,14) enabling an airflow to be set up inside the dispersion chamber(11) allowing the fibres to be dispersed inside the chamber and propelled onto the forming and conveying surface (6a), comprise a vacuum chamber (14a) setting up a vacuum across the forming and conveying surface (6a).
11. Machine as in any of claims 1 to 10, characterized in that the porous part of the front wall (9) is formed of a rotating, hollow tube or cylinder (22).
12. Machine as in claim 11, characterized in that the tube or cylinder (22) comprises a micro-perforated cylindrical metal sheet (23).
13. Machine as in claim 11 or 12, characterized in that it comprises means (25,26) allowing the cylindrical metal sheet (23) to be driven in rotation in the same direction as the forming surface (6a) and at a circumferential speed at least equal to the linear speed of said forming surface (6a).
14. Machine as in any of claims 1 to 13, characterized in that it comprises means (28) for aspirating the nonwoven on exiting the dispersion chamber (11).
15. Production line for a nonwoven using an airlay technique characterized in that it comprises a carding unit (3) supplying fibres to a machine (4) for manufacturing a nonwoven in accordance with any of claims 1 to 14.

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