WO2002088441A1

WO2002088441A1 - Machine for making a nonwoven by airlay technique, comprising a fibre dispersing chamber whereof the front wall is porous in the lower part

Info

Publication number: WO2002088441A1
Application number: PCT/FR2002/001104
Authority: WO
Inventors: Jean-Louis Dupont; Xavier Catry; Marc Brabant
Original assignee: Thibeau
Priority date: 2001-04-26
Filing date: 2002-03-28
Publication date: 2002-11-07
Also published as: FR2824082A1; EP1290253A1; FR2824082B1; DE60215735D1; ATE344340T1; EP1290253B1

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

MACHINE FOR THE MANUFACTURE OF A NONWOVEN BY TRACK

AERAULIC, COMPRISING A CHAMBER OF DISPERSION OF

FIBERS OF WHICH THE FRONT WALL IS POROUS IN THE LOW PART

The present invention relates to the field of manufacturing a nonwoven by air. Its main purpose is a machine for the formation of a nonwoven by air, which has been improved so as to reduce the risks of formation of defects in the nonwoven. There has been known for many years a technique for manufacturing a nonwoven by air, which is commonly referred to as the "airlay" technique. This technique is essentially characterized by the dispersion in a chamber and the projection onto a mobile receiving surface, of individual fibers, by means of a high speed air flow, said receiving surface being permeable to air, and allowing training and transportation of the nonwoven. The fibers undergo, during their course in the air flow, a random dispersion, which is commonly called "random" effect, and which contributes advantageously to obtain a homogeneous nonwoven, whose mechanical properties have a very good isotropic.

In practice, the dispersion of the fibers is carried out in a vertical dispersion chamber which surmounts the surface for forming and transporting the nonwoven. Generally, the fibers are fed into the upper part of the dispersion chamber, by being transported to the periphery of a rotary cylinder, and the air flow allowing the dispersion and the routing of the fibers to the formation surface and for transporting the nonwoven, is created inside the dispersion chamber so as to be substantially tangential to this cylinder and to assist in the spotting of the fibers from the periphery of the cylinder. Preferably, but not necessarily, the rotary cylinder, which allows the introduction of the fibers into the dispersion chamber, is rotated at high speed, so as to also allow ejection of the fibers inside the dispersion chamber, under the effect of centrifugal force. A machine allowing the manufacture of a nonwoven by air is for example described in patent US-A-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 movement of the conveyor belt, and which are referenced respectively (77) and (78) in FIG. 3 of patent US-A-3,512,218. In the present text, the terms "rear" and "front" are taken in reference to the direction of movement of the formation surface and for transporting the nonwoven. The fibers are introduced into the dispersion chamber by means of two rotary cylinders referenced (52) and (54) in the figures of this patent. The “airlay” air flow, for dispersing and transporting the fibers to the conveyor belt, is created by means of a suction box referenced (102), associated with fans which make it possible to create a flow suction through the conveyor belt, and over substantially the entire horizontal section of the dispersion chamber, and to recycle the air sucked in by discharging it into 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 this front wall and the surface of the conveyor belt.

A first constraint for the designers of this type of machine is to avoid that air is sucked in from the outside of the dispersion chamber and enters the interior of the dispersion chamber passing between the walls of the chamber. and the surface for forming and transporting the nonwoven. A second constraint is to limit the risks of the fibers of the nonwoven catching on the lower end of the front wall of the dispersion chamber, when the nonwoven passes through the wall. To resolve the first constraint 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 nonwoven formation and transport surface, and is provided with a seal, which is applied against the forming and transport surface.

To resolve the second constraint, a front wall is used which has a change in slope at the bottom, which results in an enlargement of the section of the dispersion chamber, taken in a plane parallel to the surface for forming and transporting the nonwoven. The internal 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 progressive guiding of the nonwoven fabric until it leaves the dispersion chamber. Preferably, the lower part of the front wall forming a funnel has a curved shape substantially in an arc.

To resolve the first aforementioned stress 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 sufficient airtightness. Preferably, this height of the outlet of the funnel is adjustable, so as to allow an adjustment of the thickness or the 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 the implementation, in the lower part of this front wall, of a plate substantially in the form of an arc of a circle and referenced (81) in FIG. 3 of this patent. This plate is pivotally mounted so as to allow the aforementioned adjustment of the outlet section of this funnel.

By manufacturing a nonwoven with a machine of the type described in US Pat. No. 3,512,218, it has been observed that small dimensions defects appear randomly in the nonwoven. These defects result in the formation in the nonwoven of small areas of over-accumulation of fibers; these areas are elongated and oriented essentially along the width of the nonwoven.

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

This objective 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 breathable,

a dispersion chamber surmounting the formation and transport surface, means making it possible to supply the dispersion chamber with fibers intended to form the nonwoven, and means which are capable of creating, inside the dispersion chamber, an air flow making it possible to disperse the fibers inside the chamber and to project them onto the formation and transport surface. Typically according to the invention, the front wall of the dispersion chamber is porous in its lower part.

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

FIG. 1 represents a complete production line for a nonwoven using a machine for manufacturing a nonwoven by air, in accordance with the invention,

FIG. 2 is a simplified perspective representation of the essential parts of the machine for manufacturing a nonwoven by air from the production line of FIG. 1,

- Figure 3 is a cross-sectional view of the machine for manufacturing a nonwoven by air from the production line of Figure 1

FIG. 4 is a simplified and enlarged cross-sectional view of the machine of FIG. 3,

- Figure 5 shows schematically a second alternative embodiment of a machine for manufacturing a nonwoven by air according to the invention, and using a porous cylinder;

- Figure 6 is a detailed view of the porous cylinder of the machine of Figure 5, - and Figure 7 shows schematically a third alternative embodiment of a machine for manufacturing a nonwoven by air flow according to the invention

FIG. 1 shows a complete production line for a nonwoven comprising, at the inlet, a usual supply chimney 1, which in operation is supplied at the top with fibers, and which delivers at the outlet on a conveyor 2 a fiber fleece mattress (not shown). Downstream of the conveyor 2, the line comprises a card 3 of traditional design, which feeds a machine 4 according to the invention allowing the production of a nonwoven by air. In the particular example illustrated, the card 3 comprises as input a food roller 3a, associated with a breaker cylinder 3b. The breaker cylinder 3b makes it possible to supply fibers, a first rotary carding cylinder 3c, more commonly called “front end”, and the surface of which is usually coated with a carding lining allowing it to take up the fibers of the periphery of the breaker cylinder 3b. On the periphery of the carding cylinder 3b are mounted conventional combing means, which make it possible to work the fibers taken from the carding lining of the cylinder 3c, so as to individualize and parallelize them. In the example illustrated, these combing means consist of several successive pairs of a 3d cleaning roller and a working roller 3e. Downstream of these combing means, the fibers are taken from the periphery of the first carding cylinder 3c, and are transferred as they are to the periphery of a second rotary carding cylinder 3g, by a transfer cylinder 3f_, also called "Communicator". The second carding cylinder 3g, also commonly called “large drum” or “main drum”, is also coated with a carding lining or the like and is provided on its periphery with combing means (3d, 3e) identical to those fitted to the first carding cylinder 3ç. Card 3 has a double outlet, each card outlet consisting of two successive cylinders 3h and 3 [. This type of carding out is already known and described in particular in European patent application EP-A-0 950 733, to which a person skilled in the art may refer.

The machine 4 for producing a nonwoven by air, which is described in detail below, is not necessarily implemented with a carding device upstream, but may be implemented in general with any upstream fiber feeding device, this device possibly or not depending on the case having a function of working and working the fibers. When the machine 4 is provided downstream of a card, this card is not necessarily identical to that of FIG. 1 which is given by way of nonlimiting example. Indeed, depending on the type of fibers and the desired degree of processing, we can consider a longer card implementing a larger number of successive carding cylinders, or on the contrary a shorter card implementing a single cylinder carding. Furthermore, the rollers 3d and 3e could be arranged by being juxtaposed one behind the other in an alternating manner, 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 allowing to individualize and parallelize the fibers transported by the carding cylinders. In particular, these 3d and 3e rollers could be replaced by static plates, more commonly called "carding plates", mounted at the periphery of the carding cylinder, and comprising a plurality of carding points in the form for example of grooves or grooves.

The machine 4 for manufacturing a nonwoven by air comprises a conveyor 5 implementing a conveyor belt

6 porous mounted tensioned on drive rollers 7. In operation, the upper strand 6a of this conveyor belt 6, which in the particular example illustrated is substantially horizontal, is driven at a predetermined constant speed in the direction of transport indicated in Figure 1 by the arrow D. This upper strand 6a forms an air permeable surface, which allows the formation and transport of the nonwoven.

The machine 4 also includes a vertical chimney 8, which surmounts the upper strand 6a of the conveyor belt 6 and which extends over the entire width (L) of this 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 9 and rear 10 walls, and s 'extending substantially parallel to the direction of movement (D), that is to say in a plane parallel to the plane of Figures 1, 3 and 4. For the sake of simplicity and clarity of the drawing, these two longitudinal walls n' we have not been shown in the perspective of Figure 2. This chimney 8 forms a chamber 1 1 of fiber dispersion. This chamber is open at its two upper ends 1 1 a and lower 11 b.

At the open upper end 11a of the dispersion chamber 11, the machine 4 comprises a cylinder 12, hereinafter called the "disperser" cylinder, which allows the fiber to be supplied to the dispersion chamber. This dispersing cylinder 12 is adjacent to the two card output cylinders 31, and makes it possible to take up and superimpose on its periphery the card webs, coming from the card 3 and transported on the periphery of these two cylinders 3L The dispersing cylinder 12 is preferably provided on its periphery with a lining, the points or teeth 12a (Figures 3 and 4) are oriented forward (that is to say in the direction of rotation of the cylinder). This dispersing cylinder 12 is further provided to be driven in rotation with a circumferential speed greater than or equal to the circumferential speed of the two upstream cylinders 3 [. This cylinder 12 can be directly driven in rotation by a motor whose rotor is directly coupled to the rotation shaft of cylinder 12, or be driven indirectly, its rotation shaft being mechanically coupled to the rotation shaft of one of the cylinders of carding machine 3 (for example the carding cylinder 3g ) by a judiciously 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 leave this lining under the action of centrifugal force. The machine 4 also includes an air supply channel 13, the open upper end 13a of which communicates with the open air, and the lower end 13b of which is connected to the open upper end 11a of the chamber dispersion 1 1. Opposite the channel 13, under the upper strand 6a of the conveyor belt 6 is mounted a suction box (or box) 14, which delimits an internal chamber 14a which is connected to a fan (not shown) by a conduit 15 (Figure 1). When the fan is on, the internal chamber 14a is placed under vacuum. It thus forms a suction chamber and makes it possible to create, through the upper strand 6a of the conveyor belt 6, a suction which generates inside the dispersion chamber 11 a substantially vertical air flow, materialized by arrows in FIGS. 3 and 4. This suction is created over the entire section (taken in a plane parallel to the strand 6a of the conveyor belt 6) from the open lower end 1 1 b of the dispersion chamber 1 1, this is ie on a surface which extends in direction (D) over a width! (Figures 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 area with different sections of the dispersion chamber. In operation, the fibers which are conveyed inside the dispersion chamber 1 1, 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 of the dispersion chamber 1 1, which air flow comes substantially to tangent to the tips 12a of the lining of the dispersing cylinder 12. A high speed of rotation of the dispersing cylinder 12 also makes it possible to facilitate the spotting of the fibers under the action of the centrifugal force. The fibers are thus ejected individually inside the chamber 1 1. These fibers are dispersed by the air flow over the entire horizontal section of the dispersion chamber 11 and are projected by the air flow onto the upper strand 6a remote from the conveyor belt 6. A nonwoven is thus formed inside the chamber 11 and on the surface of the conveyor belt 6, which nonwoven is conveyed by the conveyor belt 6 to the exterior of the dispersion chamber 1 1, passing to the 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 thick solid sheet 16, which is planar and impermeable to air, and in the lower part of a thin curved sheet 17, having a substantially arcuate profile. of circle, and the part 17a closest to the upper strand 6a of the conveyor belt 6 (that is to say in the example illustrated the lower end part of the sheet 17) is oriented substantially parallel to the upper strand 6a of the conveyor belt. This sheet 17 is an insert and fixed to the lower edge of the sheet 16 by any suitable means and for example by screws 18 or rivets.

In contrast, the rear wall 10 of the dispersion chamber 11 is formed from a thick solid sheet 19, which is impermeable to air. The two sheets 16 and 19 are not perfectly vertical and parallel, but diverge slightly from one another (Figure 4 / angles α and β of the sheets 16 and 19 relative to the vertical), so that the dispersion chamber 11 forms a cone whose section (taken in a plane parallel to the upper strand 6a of the conveyor belt 6) increases in the direction of the upper strand 6a of the conveyor belt 6. A better dispersion of the fibers is thus obtained. The curved sheet 17 makes it possible to produce a change in slope in the lower part of the front wall 9, the internal face 17b of the sheet 17 forming with the upper strand 6a of the conveyor belt 6, a funnel 21, which makes it possible to guide the not -woven formed up to the exit of the dispersion chamber. This advantageously limits the risks of the fibers of the nonwoven catching on the front wall 9, and in particular on its lower edge.

In the particular example illustrated, this thin sheet 17 is flexible and in the absence of nonwoven comes, at its lower end 17a, in contact with the upper strand 6a of the conveyor belt 6. In operation (FIG. 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. This avoids in operation that the suction flow created by the suction box 14 does not generate an incoming air flow which would penetrate inside the dispersion chamber 1 1 passing between the lower end of the front wall 9 and the upper strand 6a, such an air flow being detrimental to the quality of the nonwoven.

Also, to prevent the suction flow created by the suction box14 from generating an incoming air flow which would penetrate inside the dispersion chamber 11 passing between the upper strand 6a and the lower end rear 10 and longitudinal walls of the chamber 1 1, the lower edge of these walls is positioned in the immediate vicinity of the upper strand 6a, and is equipped with a seal 20 which is applied to the upper strand 6a. According to an essential characteristic of the invention, the front wall 9 is porous to air in its lower part, that is to say in the particular example illustrated in its part forming a funnel 21. This porous zone extends over substantially the entire width (L) of the front wall 9 of the dispersion chamber 11 (FIG. 2). More particularly, this porosity is obtained by multiple microperforations carried out in the sheet 17.

Preferably, as illustrated in the appended figures, the sheet 17 is impermeable to air, on a first sector referenced (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 sheet 16. The height h (FIG. 4) between the sheet 17 and the conveyor belt 6, at the border between the porous zone (A ) and non-porous area (B) corresponds in practice to the maximum thickness of fiber accumulation inside the dispersion chamber.

In an alternative embodiment, a micro-perforated sheet 17 is used over its entire surface, and the non-porous lower part (B) is obtained fixing on the internal face of this lower part a coating 22 (FIG. 4) closing off so 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, one could also 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 in order to improve the sliding of the nonwoven with respect to the front wall 9. In operation, the suction created by the suction box

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

Comparatively, on the assumption that as a sheet 17, a solid sheet impermeable to air is used, one observes in the funnel 21 air speeds which tend more and more to deviate from the vertical the closer we get to the sheet 17, the air speeds near the outlet of the nonwoven (gripping area of the nonwoven between the sheet 17 and the conveyor belt 6) having a significant horizontal component. However, these air velocities with a strong horizontal component are the source of defects in the structure of the nonwoven. These defects materialize in the form of short zones 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 straightening of the air speeds, which therefore have a greater vertical component, which limits the phenomenon of formation of the aforementioned defects. In other words, in operation, the air speeds in the funnel 21 of the dispersion chamber have a greater vertical component and a lower horizontal component, than the respectively vertical and horizontal components of the air speeds which would be obtained in the funnel 21 with a front wall 9 (sheet 17 in the example illustrated) 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 sheet 17 can be replaced by any equivalent wall, porous or micro-porous . It could be a flat sheet, or a flat sheet in the central part and ending in lower and upper end portions substantially in an arc.

In another alternative embodiment, the sheet 17 could, in the absence of nonwoven, not be in contact with the conveyor belt, a slight space 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 from the dispersion chamber 11.

In another alternative embodiment, the sheet 17 could be porous over its entire surface; the disadvantage, however, of this variant, compared to the use of a sheet 17 whose lower end part is impermeable to air, is the increased risk of the nonwoven catching on the front wall. at the outlet of the dispersion chamber 1 1.

In another variant not shown in the figures, the porous part (A) of the front wall could extend over a more limited area (that is to say over a weaker 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 into the open air at the top. In another alternative embodiment, the air sucked in by the suction box 14 could be used in a closed circuit by being wholly or partly forced back inside the channel 13.

FIG. 5 shows another alternative embodiment of a nonwoven production machine of the invention, in which, compared to the variant of FIGS. 1 to 4, the porous part of the front wall 9 is produced in the form of a hollow porous rotary tube or cylinder 22. The axis of rotation 22a of this 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 hollow tube or cylinder 22 comprises a thin cylindrical sheet 23, for example made of stainless steel, and micro-perforated over its entire surface, said sheet 23 being fixed on two end flanges 24 The assembly is mounted on a rotary shaft 25. This shaft 25 is designed to be driven in rotation by means of a motor (not shown) via a belt type transmission system 26.

Referring to Figure 5, the cylindrical sheet 23 is mounted above the upper strand 6a of the conveyor belt 6, so that it comes into contact with the upper strand 6a according to the tangency generator T. In another variant , a very slight space could be provided between the upper strand 6a and the cylindrical sheet 23, this space being sufficiently small for the nonwoven produced to be compressed during its passage under the cylinder 22.

In operation, the cylindrical sheet 23 is rotated in the same direction as the upper strand 6a of the conveyor belt 6, and with a circumferential speed at least equal to the linear speed of said upper strand 6a. In particular, the cylindrical sheet 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 example given as an indication, the sheet 17 or the cylindrical sheet 23 was thick stainless steel 300μm; the opening rate of the micro-perforated sheet (ratio between total open area and total area) was around 25%; each micro-perforation had a substantially circular section, with a diameter of the order of 320 μm. According to an additional characteristic, in the variant of FIG. 5, a brush 27 is fixed on the periphery of the cylinder 22. It makes it possible to sweep the external surface of the sheet 23 during the rotation of said sheet. This brush 27 thus makes it possible to remove from the sheet 23 the fibers or dirt which can be deposited on and be entrained 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 makes it possible, during operation, to suck up the nonwoven at the outlet from the nip ( T) between the cylinder 22 and the upper strand 6a of the conveyor belt, pressing it against the upper strand 6a. This suction is implemented over the entire width of the nonwoven. In addition, the suction zone 28a extends over a length L. The position of the suction box 28 is preferably adjustable. This suction allows 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 implementation of a cowling 29, allowing enclosing the cylinder 22 in a chamber 29a which comprises in the upper part an air intake opening 30 of width (e) preferably adjustable. This opening 30 extends in the direction of the axis of the cylinder 22 (direction transverse to the plane of FIG. 5) over substantially the entire length of the cylindrical sheet 23). This cowling 29 makes it possible to obtain a better orientation of the air flow sucked through the cylindrical sheet 23. In the two variants of FIGS. 5 and 7, the front wall 9 of the dispersion chamber 11 comprises a plate 9a which extends in the lower part beyond the cylinder 22, the lower edge 9b of this plate 9a being situated at a height ( h) of the upper strand 6a of the conveyor belt 6. This plate 9a acts as a deflector and makes it possible in operation to limit the risks of over-accumulation of fibers immediately upstream of the cylinder 22. The height (h) will be adjusted on a case-by-case basis by the skilled person.

Claims

1. Machine (4) for manufacturing a nonwoven fabric (W) by the airway, of the type comprising: - a surface (6a) for forming and transporting the nonwoven fabric, which is breathable,

- a dispersion chamber (1 1) surmounting the formation and transport surface (6a),

- Means (12) for supplying the dispersion chamber (1 1) with fibers intended to form the nonwoven, and means (13,14), which are capable of creating, inside the dispersion chamber (1 1), an air flow for dispersing the fibers inside the chamber and for projecting them onto the forming and transport surface (6a), characterized in that the front wall (9 ) of the dispersion chamber (1 1) is porous in its lower part.

2. Machine according to claim 1 characterized in that the front wall (9) of the dispersion chamber has in the lower part a change in slope so that its internal face (17b) forms a funnel (21) with the surface of training and transport (6a).

3. Machine according to claim 2 characterized in that the front wall (9) of the dispersion chamber has in the lower part a curved profile, its part (17a) closest to the surface (6a) for forming and transporting the nonwoven, being oriented substantially parallel to said surface (6a).

4. Machine according to claim 3 characterized in that the front wall (9) of the dispersion chamber has in the lower part a curved profile substantially in an arc.

5. Machine according to one of claims 1 to 4 characterized in that that the front wall (9) is flexible at the bottom.

6. Machine according to claim 5 characterized in that in the absence of nonwoven, the lower end (17a) of the front wall is in contact with the surface (6a) for forming and transporting the nonwoven .

7. Machine according to one of claims 1 to 6 characterized in that the porous part of the front wall (9) of the dispersion chamber is made by means of a thin sheet (17) micro-perforated.

8. Machine according to one of claims 1 to 7 characterized in that the front wall (9) of the dispersion chamber is impermeable to air on a part (B) which extends from its lower edge (17c) .

9. Machine according to claim 8 characterized in that on the inner face of the front wall (9), at its lower part (B) impermeable to air, is fixed a coating (22) with a lower coefficient of friction.

10. Machine according to one of claims 1 to 9 characterized in that the means (13,14), which allow to create, inside the dispersion chamber (1 1), an air flow for dispersing the fibers inside the chamber and projecting them onto the formation and transport surface (6a), have a suction chamber (14a) which makes it possible to create a suction through the formation and transport surface (6a).

1 1. Machine according to one of claims 1 to 10 characterized in that the porous part of the front wall (9) is formed by a rotary hollow tube or cylinder (22).

12. Machine according to claim 1 1 characterized in that the tube or cylinder (22) comprises a cylindrical sheet (23) micro-perforated.

13. Machine according to claim 1 1 or 12 characterized in that that it comprises means (25, 26) making it possible to rotate the cylindrical sheet (23) in the same direction as the forming surface (6a) and with a circumferential speed at least equal to the linear speed of said surface training (6a).

14. Machine according to one of claims 1 to 13 characterized in that it comprises suction means (28) of the nonwoven at the outlet of the dispersion chamber (11).

15. A production line for an air-woven nonwoven, characterized in that it comprises a card (3) making it possible to supply fibers to a machine (4) for manufacturing a nonwoven in accordance with one of claims 1 to 14.