FR2811603A1 - Non-woven sheet material perforating procedure and machine uses cylinder with sharp-edged hollow inserts and roller with perforating fingers - Google Patents

Abstract

The procedure consists of passing the sheet material (N) between a perforated cylinder (2) and a roller (4) with spring-loaded perforating fingers (9). The cylinder's perforations are formed by a series of detachable inserts (8) with holes in their flat outer surfaces (S) having sharp edges (8g), while the roller's fingers are designed to rotate as their interact with the perforations, shearing the fibres of the sheet material.

Description

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  PROCESS FOR PERFORATING A NONWOVEN TABLECLOTH

  The present invention relates to the field of non-woven tablecloths, consisting of fibers or filaments, intended, in particular but not exclusively to be used for the production of hygienic articles, for example, for diapers for babies or for incontinence adults or even female protections. It relates more particularly to a method of perforating a nonwoven web and a

  device adapted to the implementation of this process.

  There are different methods of perforating nonwoven webs.

  Document EP 0214608 describes a method of perforating a nonwoven which specifically comprises thermoplastic fibers or filaments. This process involves perforating the nonwoven web

  between a plurality of studs which cooperate with a plurality of recesses.

  Under the action of the pads, the fibers of the nonwoven web are locally repelled and in order to maintain the vacuum thus formed, the pads and the contour of the recesses are heated so as to cause the thermoplastic fibers to merge. After hardening of the molten fibers, a perforation is obtained having the shape of the stud and the contours of which are delimited and

  consolidated by fused fibers and therefore linked to each other.

  This method has the drawback, on the one hand of requiring the use of a nonwoven containing thermoplastic fibers and on the other hand, of bringing a certain rigidity to the nonwoven due to the presence

  hardened areas at the periphery of the perforations.

  Document EP 0974433 describes a perforation process applicable to any type of nonwoven web. According to this method, the ply is pushed inside a through orifice formed in a piece of thin thickness so that the nonwoven ply protrudes beyond this orifice. Cutters then cut the

  fibers protruding beyond the part so as to form perforations.

  This process requires a relatively complex device including in particular a hollow cylinder whose interior is provided with cutting members and requires the use of a thin piece in which are

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  provided the orifices. In addition, this method does not guarantee perforations having a circular perimeter. Indeed, the shape of the perforations tends to vary and after a certain period of implementation of this process, the perforations obtained are oval. However, in the case of a hydrophobic nonwoven web as frequently used for the production of hygiene articles, it is important that the perforations made in this web are circular. Indeed, only circular perforations allow water or any other liquid to pass through the hydrophobic nonwoven without wetting the surface of the latter,

  which allows to absorb a liquid while having a dry surface.

  The object of the present invention is to propose a new method for perforating a nonwoven web which in particular overcomes all or part of the drawbacks associated with the use of the methods of the prior art. This object is achieved by means of a method of perforating a nonwoven web comprising fibers or filaments according to which, in a characteristic manner, the web is brought into contact with the first face of a part which is provided in an area plane of at least one orifice which has a sharp edge formed by the intersection of the internal surface of the orifice with the planar area and a portion of the ply is cut by shearing the fibers or filaments arranged in line with

  the orifice against the sharp edge of the latter.

  This process has the advantage of producing clear perforations which do not tend to close due to the rearrangement of the fibers (the fibers are indeed cut which prevents their rearrangement) and which have a circular edge whatever the duration of setting artwork

of the process of the invention.

  The Applicant has in fact demonstrated that the fact of using an orifice which has a sharp edge formed by the intersection of the internal surface of the orifice with a plane makes it possible to cut the fibers or filaments of the sheet by shearing. non-woven all over

perimeter of the edge of the orifice.

  According to the method of the invention, the cutting by shearing of the fibers against the sharp edge of the orifice can be carried out gradually along the edge of the orifice or all at once

  the perimeter of the orifice, the sheet is then cut with a cookie cutter.

  In all cases it is a portion of the sheet which is removed by cutting. The present invention also relates to a device for perforating a nonwoven web which, typically comprises a part provided at least on its first face with at least one orifice disposed on a flat area of this first face, the orifice having a sharp edge formed by the intersection of the internal surface of the orifice with the flat area of the first face and a cutting member which cooperates with the sharp edge of the orifice so as to cut the fibers or filaments by shearing of the tablecloth located to the right of the orifice

against the sharp edge of the latter.

  According to the invention, the part provided with at least one orifice can be

  fully flat or have flat areas.

  According to a particular embodiment, the part provided with at least one orifice being a rotating cylinder which has on its first face a plurality of orifices, each of said orifices is equipped with an insert which comprises a body fixed in the orifice and provided with a perforation which

  emerges in a plane at the level of the first face of the cylinder.

  It is also possible according to the invention to use a rotating cylinder which has on its first face a plurality of orifices, the zones surrounding the orifices being machined so as to form flats,

that is to say flat areas.

  The present invention will be better understood and its characteristics

  and advantages will appear better on reading the description which follows and

  refers to the accompanying drawings showing a preferred embodiment of the device of the present invention, presented by way of nonlimiting example and in which: - Figure 1 is a partial schematic representation in section of the preferred embodiment of the present invention ;

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  - Figure 2 is an enlarged partial view of the device of Figure 1, in the area where a pad cooperates with an orifice of the first cylinder in order to perforate the nonwoven web; and - Figure 3 shows an alternative embodiment of the device of the invention. The preferred embodiment of the device of the present

  The invention will now be described with reference to FIG. 1.

  The device 1 designed for the perforation of a nonwoven web comprises a first cylinder 2 which is a perforated cylinder. This cylinder 2 is driven in rotation about its longitudinal axis 3. The device 1 also includes a second cylinder 4 driven in rotation around

  its longitudinal axis 5 parallel to the axis 3 of the first cylinder 2.

  The first cylinder 2 has on its outer periphery a cylindrical part 6 provided with a plurality of through orifices 7. This part 6 is rotated in the direction of the arrow F. Each through orifice 7 is equipped with an insert 8 which will be more fully described with reference to FIG. 2. The second cylinder 4 is provided on its periphery with studs 9 which are arranged to cooperate with the inserts 8

  orifices 7 made in the outer part 6 of the first cylinder 2.

  In the preferred embodiment shown here, the cylinder 2 also includes a suction zone A which allows the sheet N to be pressed by suction against the first face 6a of the piece 6 and to evacuate the pieces M of the sheet which have been cut out. In addition, to facilitate the removal of the pieces M, the wall A1 which delimits the zone A comprises a scraper A2 which, due to the rotation of the first cylinder 2, comes

  tear off the pieces of cut tablecloth coming out of the holes 7.

  Referring to Figure 2, each insert 8 comprises a body 8a provided with a perforation 8b. This perforation 8b opens out in the example shown but may also, according to the invention, have a bottom. The external surface 8c of the body 8a is equipped with a thread 8d which cooperates with a reverse thread 7a disposed inside each orifice 7 in order to fix each insert 8 in an orifice 7. The body 8a has at one of its ends a flat collar 8e. The 8th shape collar with

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  the internal surface 8f of the perforation 8b a sharp edge 8g and can advantageously serve as a gripping means for fixing the

inserts 8 in the holes 7.

  In an alternative embodiment shown in FIG. 3, the insert 8 does not have a collar 8e and the perforation 8b opens at a flat end 8h of the insert. Such an insert does indeed have a sharp edge 8g formed by the intersection of the internal surface 8f of the perforation 8b with the planar end 8h which corresponds to the thickness of the body 8a. In this case, the orifices 7 and the perforations 8b of the inserts 8 may have an increasing diameter from the first face 6a of the part 6 towards the second face 6b of the latter, this flared shape.

  to facilitate the removal of the pieces M of the perforations 8b.

  In an alternative embodiment of the means for cutting the nonwoven web shown in FIG. 2, the stud 9 is mounted in an external part 10 of the second cylinder 4 by means of a housing 11 at the bottom of which is a spring 12. The stud 9 is arranged in the housing 11 so that it turns on itself when it moves in the direction of the arrow H during the compression of the spring 12. More precisely, the stud 9 is provided with 'a pin 13 projecting inside the housing 11, this pin penetrating into a slide 14 formed in the wall of the housing 11 and which is inclined relative to the direction H of

  translational movement of the stud 9.

  During the translational movement of the stud 9, the pin 13 moves correlatively in the slide 14. Due to the inclination of the slide 14, the stud 9 performs a slight rotation on itself in a first direction of rotation R1 during of its displacement in translation in the direction H (outside the orifices 7) and in a second direction of rotation R2 during its displacement in the direction G opposite to H, that is to say in the direction of the orifice 7 In this preferred embodiment, the thread 8d fitted to each of the inserts 8 is such that the movement in rotation in the direction R1 of the studs 9 tightens the fixing of each of the

inserts 8 in the holes 7.

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  The stud 9 is of a diameter D slightly greater than the diameter d of the perforation 8b of the insert 8 so as to be able to press the sheet N against the sharp edge 8g of the insert 8 or close to the latter which cuts the sheet N. The operation of the device of the invention will now be explained. Due to the rotation of the cylinders 1 and 2, the ends of the studs 9 penetrate slightly inside the perforations 8b of the inserts 8 and press the portions of the ply N located at the right of the perforations 8b against the sharp edges 8g or close to it of these. The end of the studs 9 being of a diameter D greater than that of the perforation 8b and the edge 8g being inscribed in a flat area, the sheet N is therefore locally compressed against the sharp edge 8g and thus cut by

  cutting of the fibers or filaments constituting the sheet N on the edge 8g.

  In the example shown which implements a cylindrical part provided with a plurality of orifices 7, it is important that the flange 8e is planar. In fact, the Applicant has demonstrated that when the surface of the flange 8e which comes into contact with the sheet N is not strictly planar, it seems, without however that the Applicant is linked to this explanation, that it is not possible, due in particular to the relative rotation of the first and second cylinders 2 and 3 and of the pad 9, to obtain contact between the end of the pad 9 and the entire perimeter of the perforation 8b (at the level of the end of the insert 8 corresponding to the collar 8e) so that it is not possible to press the ply N uniformly and sufficiently against the sharp edge 8g of the insert 8 so as to

cut it out.

Claims (8)

  1. A method of perforating a nonwoven web (N) comprising fibers or filaments characterized in that: - said web (N) is brought into contact with the first face (6a) of a part which is provided in a flat area (8e) of at least one orifice (7), said orifice having a sharp edge (8g) formed by the intersection of the internal surface (8f) of said orifice (7) with said planar area (8e); - A portion of the sheet (N) is cut by shearing the fibers or filaments arranged in line with the orifice (7) against said sharp edge (8g). 2. Device for perforating a nonwoven web (N) characterized in that it comprises: - a part (6) provided at least on its first face (6a) with at least one orifice (7) disposed on a planar area of said first face (6a), said orifice (7) having a sharp edge (8g) formed by the intersection of the internal surface (8f) of said orifice with said planar area of said first face (6a); and - a cutting member (9) which cooperates with said sharp edge (8g) of said orifice (7) so as to cut by shearing the fibers or filaments of said ply (N) situated at the right of said orifice (7) against said edge vivid (8g). 3. Device according to claim 2, characterized in that said orifice (7) has an increasing diameter from the first face (6a)   towards the second face (6b) of said part (6).   4. Device for perforating a nonwoven web according to claim 2 or 3, characterized in that the part provided with at least one orifice being a rotating cylinder (6) which has on its first face a plurality of orifices ( 7), each of said orifices (7) is equipped with an insert (8) which comprises a body (8a) fixed in said orifice (7) and provided with a perforation (8b) which opens into a plane at the level of the first face of said cylinder. 8 2811603   5. A perforation device according to claim 4, characterized in that said insert (8) has at one of its ends, at said level   perforation (8b) a flat collar (8e).   6. Device according to one of claims 4 or 5, characterized in that   that said cutting member (9) is driven in a first direction (R1) of rotation during its translational movement in the direction (H) opposite to said orifice (7) and driven in a second direction (R2) of rotation opposite to said first direction of rotation during its movement in   translation in the direction (G) of said orifice (7).   7. Device according to one of claims 2 to 6, characterized in that   that said insert (8) is fixed by screwing in said orifice (7).   8. Device according to claims 6 and 7, characterized in that the   direction of screwing said insert (8) into said orifice (7) corresponds to   first direction of rotation (R1) of said cutting member (9).