FR2824082A1 - MACHINE FOR THE MANUFACTURE OF A NON-WOVEN BY AIR, COMPRISING A FIBER DISPERSION CHAMBER THE FRONT WALL IS POROUS IN THE LOW 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

18. Metal treated with a composition according to one of claims 1 to

10.

  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 perfected 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

  breathable, and allowing the formation and transport of non-

  woven. 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, being transported to the periphery of a rotary cylinder, and the air flow allowing the dispersion and the routing of the fibers to the surface of formation and transport of 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 way

  ventilation is for example described in 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 0 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 with reference to the direction of movement of the surface training and transportation of 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 the dispersion and transport of 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 non

  woven fabric 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,

  during the passage of the nonwoven to the right of this wall.

  0 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 formation and transport surface of the nonwoven, and is provided with '' a seal, which comes to rest against the forming surface

and transportation.

  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, decot 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 level of the front wall of the dispersion chamber is obtained by using, in the lower part of this front wall, 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 section of

exit from 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 permeable to air, - a dispersion chamber surmounting the formation and transport surface, 3 o - 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 onto the training 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 a preferred embodiment of a training machine

  0 of a nonwoven according to the invention, which description is given as

  non-limiting example and with reference to the accompanying drawings in which:

  - Figure 1 shows a complete production line for a non

  woven using a machine for manufacturing a nonwoven by air, according to the invention, - Figure 2 is a simplified perspective representation of the essential parts of the machine for manufacturing a nonwoven by ventilation of the production line of FIG. 1, FIG. 3 is a cross-section view of the machine for manufacturing a non-woven fabric by the ventilation of the production line of FIG. 1 - and FIG. 4 is a simplified and enlarged cross-sectional view

of the machine of figure 3.

  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 to a conveyor 2 a fluff fiber mat (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 3:, more commonly called "front end", and the surface of which is usually coated with a card lining allowing it to take up the fibers. from 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 35, so as to individualize them and to 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 3g, and are transferred unchanged to the periphery of a second rotary carding cylinder 3g, by a transfer cylinder 3_ also called " communicator>. The second carding cylinder 3g, also commonly called "large tam bour" or "main tam bour", is also coated with a card lining or the like and is provided on its periphery with combing means (3d, 3) identical to those fitted to the first carding cylinder 3c. Carding 3 has a double outlet, each carding outlet being made up of two successive cylinders 3h and 3i. This type of carding outlet is already known and described in particular in the patent application. European EP-AO 950

  733, to which a person skilled in the art can 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. the 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 using a larger number of successive carding cylinders, or on the contrary a shorter card using a single cylinder carding. In addition, 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 0 different structure, and filling the same function, that is to say 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 on 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 using a porous conveyor belt 6 tensioned mounted 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 FIG. 1 by the arrow D. This upper strand 6a forms a surface permeable to air, which allows formation and transport of

2 5 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 3 o 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 extending substantially parallel to the direction of movement (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 have not been represented on the perspective of the figure

  2. This chimney 8 forms a chamber 11 for dispersing the fibers.

  This chamber is open at its two upper ends 11a and

lower 11 b.

  At the open upper end 11a of the dispersion chamber 0, the machine 4 comprises a cylinder 12, hereinafter referred to as a "disperser" cylinder, which allows the fibers to be supplied to the dispersion chamber. This dispersing cylinder 12 is adjacent to the two card exit cylinders 3 ', 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 3. The cylinder disperser 12 is preferably provided on its periphery with a lining whose points or teeth 12a (FIGS. 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. This cylinder 12 can be directly rotated by a motor whose rotor is directly coupled 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 carding machine 3 (for example the carding cylinder 3) by a transmission system judiciously sized mechanical gears and belts. Preferably, in operation, this dispersing cylinder 12 is driven at high speed, so that the fibers 3 o which are taken in its lining tend to come out of this

  packing under the action of centrifugal force.

  The machine 4 also comprises an air intake 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 dispersion chamber 11. 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 (Figure 1). When the fan is on, the internal chamber 14a is placed under vacuum. It thus forms a suction chamber 0 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) of the open lower end 11b of the dispersion chamber 11, that is to say -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 area

  of suction 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 dispersion chamber 11, which air flow substantially tangents the tips 1 2a 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 force centrifugal. The fibers are thus ejected individually inside the chamber 11. 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 distant 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 outside of the dispersion chamber 11, in

  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 flat and 0 impermeable to air, and in the lower part of a thin curved sheet 17, having a profile substantially in arc of a 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 attached piece and fixed to 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 from a thick solid sheet 19, which is airtight.

  2 0 The two sheets 16 and 19 are not perfectly vertical and parallel, but diverge slightly from one another (Figure 4 / angles o: and 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

especially on its lower edge.

  In the particular example illustrated, this thin cover 17 is flexible and in the absence of nonwoven comes, at its lower end 1 7g, in contact with the upper strand 6a of the conveyor belt 6. In operation (Figure 4 ), the nonwoven (W) lifts the sheet 17 by slightly modifying its curvature, said sheet coming to exert on the nonwoven a low pressure force, which compresses it slightly. In operation, this prevents the suction flow 0 created by the suction box 14 from generating an incoming air flow which would penetrate inside the dispersion chamber 11 passing between the lower end of the front wall 9 and the strand

  upper 6, such an air flow being detrimental to the quality of the non-

  woven. Also, to prevent the suction flow created by the suction box 14 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 11, the lower edge of these walls is positioned in the immediate vicinity of the upper strand 6, and is fitted 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 micro

  perforations made in the sheet 17.

  Preferably, as illustrated in the appended figures, the sheet 17 is impermeable to air, over 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 sheet 17 is used.

  perforated over its entire surface, and the non-porous lower part (B) 0 is obtained fixing on the internal face of this lower part a coating 22 (FIG. 4) sealing the micro-perforations in an airtight manner. 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 microperforated sheet 17 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 hood 14 inside the dispersion chamber generates through the micro-perforated part (A) of the sheet 17 a flow of incoming air from the outside , in the form of a plurality of mini air jets, distributed over all the width (L) of the sheet metal wall 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 nonwoven formation surface (upper strand 6a of the conveyor belt 6) with a

  low horizontal component for these air speeds.

  Comparatively, in the hypothesis where one uses as a sheet 17, a solid sheet impermeable to air, 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 velocities 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 are formed 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

  example shown) airtight.

  In a specific example given as an indication, the sheet 1 7 was made of stainless steel with a thickness of 300 μm; the opening rate of the micro-perforated sheet (ratio between total surface

  open and total area) was about 25%; each micro-

  perforation had a substantially circular section, with a

diameter of the order of 320 m.

  The invention is not limited to the preTried variant of 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 even a flat sheet in the central part and ending in lower and upper end portions substantially in

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 transport bar. Preferably, it is not necessarily required, in this case the height of this space is adjustable, so as to adjust the thickness or the weight of the nonwoven leaving the chamber.

dispersion 1 1.

  In another alternative embodiment, the sheet 17 could be porous over its entire surface; The disadvantage, however, of this variant, compared with the implementation of a sheet 17 whose lower end portion is impermeable to air, is the increased risk of the nonwoven hanging on the wall.

  before leaving dispersion chamber 11.

  In another alternative embodiment of the invention, the sheet 17 2 o (that is to say the porous part of the front wall 9) could be replaced by a rotary hollow table or cylinder, for example made of stainless steel, and micro-perforated over its entire periphery, the axis of this tube or cylinder extending transversely to the direction of movement (D) of the conveyor belt 6. In this case, a slight space is provided between this tube or cylinder and the upper strand 6a of the conveyor belt. This variant has the advantage of reducing the

friction with the nonwoven.

  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 bottom edge of plate 16), eVou the front wall 9 could be

made in one piece.

  In the preTerated variant of embodiment which has been described, the

  air intake channel 13 opens into the open air at the top.

  In another alternative embodiment, the air sucked by the suction bode 14 could be used in a closed circuit while being in all

  or part pushed back inside the channel 13.

Claims (12)

  1. Machine (4) for the manufacture of a nonwoven fabric (W) by air flow, of the type comprising: - a surface (6) for forming and transporting the nonwoven fabric, which is breathable, - a dispersion chamber (11) surmounting the formation and transport surface (6), - means (12) making it possible to supply the dispersion chamber (11) with fibers intended to form the nonwoven, - and means (13,14), which are capable of creating, inside the dispersion chamber (11), an air flow making it possible to disperse the fibers inside the chamber and to project them onto the surface forming and transport (6), characterized in that the front wall (9) of the   dispersion (11) is porous in its lower part.   2. Machine according to claim 1 characterized in that the front wall (9) of the dispersion chamber has a change in slope at the bottom so that its internal face (170 forms a funnel (21) with the forming surface and of transport (6).   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 (17) closest to the surface (6) for forming and transporting the non-woven, being oriented   substantially parallel to said surface (6).   4. Machine according to claim 3 characterized in that the front wall (9) of the dispersion chamber has in the lower part   3 o 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 (6) for forming and transporting the nonwoven .   7. Machine according to one of claims 1 to 6 characterized in that   that the porous part of the front wall (9) of the dispersion chamber is produced by means of a thin micro-perforated sheet (17).   0 8. Machine according to one of claims 1 to 7 characterized in that   that the front wall (9) of the dispersion chamber is impermeable to air on a part (B) which extends from its lower edge (17).   9. Machine according to claim 8 characterized in that on the internal face of the front wall (9), at its lower part (B) impermeable to air, is fixed a coating (22) to   lower coefficient of friction.   10. Machine according to one of claims 1 to 9 characterized in that   that the means (13,14), which make it possible to create, inside the dispersion chamber (11), an air flow making it possible to disperse the fibers inside the chamber and to project onto the formation and transport surface (6), comprise a suction chamber (14) which allows a suction to be created at   through the training and transport surface (6).   11. Machine according to one of claims 1 to 10 characterized in that   that the porous part of the front wall (9) is formed by a rotary hollow tube or cylinder, micro-perforated over its entire periphery. 12. 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 non