EP4658493A1

EP4658493A1 - Apparatus for producing transversely extensible webs of fibrous material

Info

Publication number: EP4658493A1
Application number: EP24707621.9A
Authority: EP
Inventors: Marion Sterner; Federico Cariolaro; Giorgio Trani
Original assignee: Individual
Current assignee: Individual
Priority date: 2023-01-31
Filing date: 2024-01-29
Publication date: 2025-12-10
Also published as: IT202300001449A1; WO2024161282A1

Abstract

Apparatus for producing transversally extensible webs of fibrous material starting from a layer (4) of mouldable fibrous mixture having a dry content between 18% and 70%, preferably between 40% and 60%, comprising: - a continuous conveyor belt (2) made of material permeable to fluids and elastically stretchable at least in the transverse direction, - means (12) to cause the temporary and localized transversal stretching of at least a portion of said conveyor belt (2), - means for placing said layer (4) of mouldable fibrous mixture on said conveyor belt (2), when this is in a transversally stretched condition, and for removing it from said conveyor belt, when this has elastically resumed, at least in part, its initial configuration, - a perforated support surface (6) of at least a portion of said conveyor belt (2), at least in the phase in which it is passing from the stretched condition transversely to its initial configuration, - a vacuum source (8) acting on the side of said perforated support surface (6) opposite to the side of deposition of said layer (4) of mouldable fibrous mixture, characterized in that said perforated support surface (6) and said conveyor belt (2) are configured so as to be in direct contact each other with only from 30% to 70% and preferably from 40% to 60% of their facing surfaces.

Description

APPARATUS FOR PRODUCING TRANSVERSELY EXTENSIBLE WEBS OF FIBROUS MATERIAL.

The present invention concerns an apparatus for producing transversely extensible webs of fibrous material.

Apparatus is known for producing webs of fibrous material, in particular paper, which can be transversely extensible, i.e. in a direction defined CD (Cross Direction), meaning with this term the direction substantially orthogonal to the direction MD (Machine Direction), of formation of the of fibrous material in a paper mill machine.

Generally a paper mill machine includes a headbox, in which a mixture of cellulose material fibers and water is formed and maintained in a fluid state and from which a film of mixture containing a dry percentage of between 1 % and 2% on a fluid-permeable conveyor belt. On this conveyor belt the mixture layer is progressively deprived of its water content until it reaches a dry content between 18% and 30%, and therefore the consistency of a paper web which can be sent for subsequent processing.

In this phase, the removal of water from the layer of fibrous material is generally favored by a suction effect caused on the lower surface of the conveyor belt, i.e. on the surface opposite to that on which the layer of fibrous mixture was placed.

In the case of apparatus for producing transversely extensible webs of fibrous material, it is envisaged that the layer of fibrous mixture is made to descend onto a conveyor belt made of elastically yielding material in the transversal direction and subjected to a transversal stretching a little before the layer of fibrous m ixture has been laid on it. The subsequent elastic return of the conveyor belt to the initial configuration also determines a transverse contraction of the layer of fibrous mixture which adheres to it both due to its weight and to the effect of the suction, which is practiced on it and which also causes the removal of water from the dough.

Thanks to this transversal compaction, the product web thus obtained has a greater transversal extensibility the greater the compaction to which the fibers have been subjected.

It is also known to cause the transversal stretching of the conveyor belt in correspondence with a perforated cylinder with a horizontal axis, around which the belt itself is partially or totally wrapped depending on whether the conveyor belt is made up of a belt deferred from the perforated cylinder or by a sleeve wrapped around the perforated cylinder. Generally, the conveyor belt reaches its maximum stretching near the top of the cylinder and elastically resumes its initial configuration near the lowest part of the cylinder, in which the conveyor belt is no longer stretched transversely or is stretched transversally to a lesser extent than when it had reached its maximum transverse stretch.

This known method for causing the transversal stretching of the conveyor belt around the perforated cylinder involves retaining the portion of belt wrapped around the cylinder at the two edges by a pair of disks which are rotated together with the perforated cylinder and are kept inclined in the direction opposite to the rotation shaft of the cylinder itself, so that the distance between their tops is always maximum and the distance between their lowest points is always minimum. In this way the synchronous rotation of the two disks, kept thus inclined with respect to the shaft of the perforated cylinder, causes a transversal stretching on the conveyor belt, which is generally maximum when the belt is close to the top of the two inclined disks and is minimum at the lowest point of these, or in any case, if the conveyor belt is made up of a continuous web, after this has been detached from the disks. Obviously, as the maximum inclination of the two discs with respect to their rotation shaft varies within the limits imposed by the physical characteristics of the system, the difference varies between the maximum and minimum transverse stretching to which the conveyor belt is subjected.

In the particular case in which the conveyor belt is made up of an elastic sleeve fitted onto the perforated cylinder, it is subjected to a cyclic transversal stretch which reaches its maximum at the top of the two disks and is minimum at their lowest point.

However, regardless of whether the conveyor belt is made up of a tape partially wrapped around the perforated cylinder or is made up of a sleeve wrapped totally around the perforated cylinder, if the part of the conveyor belt which is in a transversely stretched condition and is about to return to initial configuration, a layer of mouldable fibrous mixture is made to adhere; with the rotation of the perforated cylinder and the disks, this layer of fibrous material is subjected to a transversal contraction which, combined with the loss of liquid, is transformed into a web of fibrous material having its own consistency and a certain degree of transversal extensibility. Generally, the separation of the web of fibrous material from the conveyor belt is done at the instant in which the belt has returned to its minimum transversal extension or shortly before it has reached that instant.

This process of transversal compaction of the fibrous material and extraction of water can be favored if a suction chamber, in the shape of a cylindrical segment, is created inside the perforated cylinder, capable of creating on the strip of the conveyor belt, which is returning to its initial configuration , a depression suitable for keeping the layer of fibrous material adherent to the conveyor belt, and for removing a large part of the liquid present in it from the layer itself.

Regardless of the methods of transversal stretching of the trampoline, the known solutions now described have revealed some limitations linked to the difficulties of obtaining uniform stretching across the entire width of the conveyor belt due to the high friction existing between it and the perforated support cylinder , friction which is accentuated by the depression which is generally created inside the cylinder itself to keep the layer of mixture adherent to the belt during its elastic return to its initial configuration.

In order to reduce this friction, which involves the production of a web of fibrous material and in particular of paper having non-homogeneous transversal extensibility characteristics across its entire width, and more particularly of a web of fibrous material that is more extensible in its lateral bands and less extensible in the central band, it was proposed to place between the conveyor belt and the perforated support cylinder a sort of support grid for a plurality of spheres, which form a sort of rolling bearing distributed over their entire contact surface and protrude from both sides of the grate to adhere to the perforated support cylinder and to the surface of the elastic conveyor belt.

This solution made it possible to obtain webs of fibrous material and in particular paper presenting a significantly uniform behavior in terms of transversal extensibility but revealed its criticality both in terms of construction complexity of the system, and therefore cost, and in terms of quality of obtainable product, as the effective support points of the elastic belt are located in correspondence with the spheres, which for obvious geometric reasons cannot be sufficiently close together and create a support discontinuity which negatively affects the quality of the product obtained. Furthermore, the presence of the spheres and their support grid does not allow a uniform and effective depression to be created on the conveyor belt and this constitutes a further obstacle to obtaining a high quality product. Finally, this solution has proven to be rather rigid in the sense that it does not allow the creation of webs of fibrous material with transversal extensibility characteristics diversified according to needs.

The aim of the invention is to propose an apparatus for producing transversally extensible webs of fibrous material and even capable of overcoming these limitations found in the state of the art.

In particular, the aim of the invention is to propose an apparatus for producing webs of fibrous material that are transversally extensible and have a high uniformity of this degree of transversal extensibility.

Another aim of the invention is to propose an apparatus that can be manufactured in a simple and inexpensive manner.

Another aim of the invention is to propose an apparatus that can be created with limited modifications to existing equipment.

Another aim of the invention is to propose an apparatus that guarantees optimal and constant results over time.

Another aim of the invention is to propose an apparatus that allows the creation of webs of fibrous material with transversal extensibility characteristics diversified according to needs.

Another aim of the invention is to propose an apparatus suitable for use alone (off-line) or in a flat paper machine.

According to the invention, all these aims and others that will result from the following description can be achieved both jointly and separately with an apparatus for producing transversally extensible webs of fibrous material as defined in claim 1 .

The present invention is further clarified below in some of its preferred practical embodiments reported for purely illustrative and non-limiting purposes with reference to the attached drawings, in which:

Figure 1 shows a vertical schematic section and in a first embodiment the portion of the apparatus according to the invention, in which the transversal (axial) contraction occurs of a conveyor belt consisting of an elastic sleeve wrapped around a perforated cylinder and bound with the two edges to two inclined disks,

Figure 2 shows it according to the vertical section ll-ll of fig. 1 ,

Figure 3 shows it in perspective view and partially in transparency,

Figure 4 shows, in a view similar to fig. 2, the complete path of the layer of fibrous mixture from the moment it is made to descend onto the axially stretched elastic sleeve to when it is transformed into a transversely extensible web of fibrous material,

Figure 5 shows it in the same view as fig. 1 in a second embodiment,

Figure 6 shows it in the same view as fig. 2 in this second embodiment,

Figure 7 shows it in the same view as fig. 3 in this second embodiment,

Figure 8 shows it in the same view as fig. 1 in a third embodiment, Figure 9 shows it in the same view as fig. 2 in this third embodiment,

Figure 10 shows it in the same view as fig. 3 in this third embodiment,

Figure 11 shows it in the same view as fig. 1 in a fourth embodiment, Figure 12 shows it in the same view as fig. 2 in this fourth embodiment,

Figure 13 shows it in the same view as fig. 3 in this fourth embodiment,

Figure 14 shows it in the same view as fig. 1 in a fifth embodiment, Figure 15 shows it in the same view as fig. 2 in this fifth embodiment, Figure 16 shows it in the same view as fig. 3 in this fifth embodiment.

As can be seen in the figures, in a first embodiment the apparatus according to the invention, illustrated in figures 1 - 4, includes a conveyor belt 2, made of material permeable to fluids and elastically yielding at least in the transverse direction.

This conveyor belt 2 can for example be made up of one or more layers of elastomer, possibly expanded, or of a single or multiple fabric of elastic or even non-elastic threads but in any case intertwined according to an elastic weave, or of a composite layer of the previous ones or finally it can include a plurality of springs of metallic or plastic material possibly incorporated into an elastomeric structure. It can also constitute the belt of the so-called flat table, which in a traditional paper machine receives the mixture coming from the headbox.

In all the embodiments described here, the conveyor belt 2 is made up of an elastic sleeve completely wrapped around a hollow cylinder 6, which houses inside it a suction chamber 8 in the shape of a cylindrical segment with the perforated cylindrical surface facing to the perforated side wall of the cylinder 6 and developing according to a circular arc, which runs from the top of the cylinder 6, has a width preferably between 90° and 180°, for example about 135°, and is fixed, i.e. it does not rotate when the perforated cylinder 6 is rotating.

The suction chamber 8 is connected in the traditional way to a vacuum pump (not shown).

In different embodiments, the conveyor belt 2, instead of being made up of a sleeve, could be made up of a continuous belt closed in a ring and developping with a trend linked to the configuration of the system on which it is mounted. Therefore, even if in the present description, it will be always and only spoken of elastic sleeve 2, in reality this term also means a continuous conveyor belt closed in a ring, elastically compliant in the transverse direction and partially wrapped around the perforated cylinder 6, which also constitutes a return roller of the continuous belt itself.

The sleeve 2 is intended to receive a layer 4 of mixture of mouldable fibrous material having a dry content between 18% and 70%.

Two rigid disks 12, preferably metallic, are attached to the same rotation shaft 10 of the cylinder 6, which are provided with traditional means, which constrain them in rotation to the shaft itself but at the same time always keep them inclined with respect to it in the opposite direction, so that these always have the maximum distance in correspondence with a their certain angular position with respect to the axis of the shaft 10, for example in correspondence with their top and the minimum distance in correspondence with their diametrically opposite point, for example in correspondence with the their lowest point. This can be achieved in various ways and preferably by mounting the two disks on the shaft 10 via traditional spherical joints 14 and keeping with pushers the lower part of each disk 12 closer to the lower part of the other disk . These pushers 16 can for example be made up of rollers free to rotate around the respective vertical axis and kept with their edge adhering to the external surface of the respective disk 12 (see fig. 3).

Each disk 12 has its edge provided with means to retain the corresponding edge of the sleeve 2 during rotations, and these means can for example consist of a groove configured to receive the thickened edge portion of the sleeve 2, which in this way is held by the disks 12 and at the same time is subjected to cyclic axial stretching alternating with axial elastic contractions as the disks 12 rotate.

Approximately near the generator of the hollow cylinder 6, in correspondence with which the suction chamber 8 ends at the bottom, against the cylinder 6 a second cylinder 18 is placed, made or covered with perforated rubber and housing inside another suction chamber, which extends approximately from the generator in contact with the cylinder 6 up to the generator in contact with a third drying cylinder 20, preferably made of steel and having a substantially smooth surface heated to a temperature between 40°C and 100 °C , preferably between 50°C and 80°C .

In this first embodiment, the sleeve 2, which can advantageously be made of elastomeric polymers, is provided along its entire axial length with small circumferential undulations 22, which have the function of making contact between the sleeve 2 and the hollow cylinder 6 only at the top of these undulations and therefore to reduce the effective contact surface between the two to a fraction between 30% and 70% and preferably between 40% and 60% of the contact surface that would exist in the absence of such undulations .

The operation of the apparatus according to the invention in this first embodiment is as follows: the sleeve 2 is rotated with the hollow cylinder 6 and with the disks 12, which subject it to cyclic transverse stretching, which corresponds to the transversal distension of the undulations 22. This distension and therefore the localized axial elongation of the sleeve 2, reaches its maximum at the top of the hollow cylinder 6 and then progressively returns to its initial value, thanks to the elastic return of the material no longer stressed, when the sleeve 2 has reached the lowest point of hollow cylinder 6. During the rotation of the sleeve 2, the layer 4 of fibrous mixture is made to adhere to it, preferably at the top of the perforated cylinder 6, i.e. the most transversely stretched part of the sleeve 2, which after reaching the sleeve 2 is made advance with this and at the same time, following its axial contraction, it is subjected to transversal compaction and is kept adhering to the sleeve itself also due to the effect of the depression generated in the suction chamber 8.

The axial stretching of the sleeve 2 and its return to the initial configuration involves its sliding in an axial direction on the perforated surface of the cylinder 6, but thanks to the presence of the corrugations 22 the surfaces of effective mutual contact are reduced, to an extent linked to the dimensions of the corrugations, to the thickness of the sleeve and to the nature of the elastic material with which it is made, but from tests carried out and from considerations on the behavior of the materials they can be estimated in 30% - 70% or more particularly in 40% - 60% of the surface of the cylinder and the friction generated during this sliding is the same and correspondingly reduced. It follows that the web 4, now transformed into a continuous band 24 compacted transversely and having a dry content between approximately 35% and 70%, can be detached from the sleeve 2 following both the cessation of the effect of the depression present in the chamber 8 and of the depression created inside the second cylinder 18 and can adhere to this until it reaches the third cylinder 20, to which it can then adhere automatically following the cessation of the suction effect by the second cylinder 18 . Then in contact with the smooth and heated surface of the third cylinder 20, the layer of fibrous mixture 4 completes its transformation into a web 24 of fibrous material, in particular paper, having a dry content between 40% and 100%, preferably between 50% and 80%. Thanks to the uniform return of the sleeve 2 to its initial configuration, the transversal compaction of the paper tape 24 is also uniform and makes the tape itself extensible in a transverse direction to an almost uniform extent over its entire width.

In a second embodiment, illustrated in figures 5 - 7, the sleeve 2 has a substantially smooth surface in contact with the cylinder 6, while the lateral surface of the cylinder 6 is provided with a plurality of circumferential grooves 26 which limit the surface of effective contact with the sleeve 2 at the top of the ribs which separate the adjacent grooves 26 each other from.

Also in this case, the surfaces in mutual contact of the sleeve 2 and the perforated cylinder 6 during the contraction phase of the sleeve itself can be reduced to the same extent indicated for the previous embodiment, to the benefit of the uniformity of the characteristics of the paper tape 24 obtained.

Similar results can also be obtained with a third embodiment, illustrated in figures 8 - 10. In it, the sleeve 2 is provided, on the surface destined to come into contact with the surface of the perforated cylinder 6 , with a plurality of transversal grooves 28 which, in the phase of transversal stretching of the sleeve and elastic return to the initial configuration, slide on the surface of the perforated cylinder 6 only with the top of the ribs separating the adjacent grooves 28 and therefore with limited friction and with a consequent uniformity of behavior of the paper 24 transversally extensible thus obtained.

In a fourth embodiment, illustrated in figures 11 - 13, the surface of the sleeve 2 intended to come into contact with the perforated cylinder 6 is substantially smooth, while the surface of the perforated cylinder 6 is provided with a plurality of grooves 30 parallel to the axis of the cylinder itself and such as to reduce, for the reasons already seen and to a similar extent to what has already been indicated for the previous embodiments, the friction between the two during mutual sliding.

In a fifth embodiment, illustrated in figures 14 - 16, the surface of the sleeve 2 intended to come into contact with the perforated cylinder 6 is substantially flat, while the surface of the perforated cylinder 6 is provided over its entire extension with reliefs 32 preferably in the form of a spherical segment, which are configured and sized so as to reduce the effective contact surface between the two to a fraction between 30% and 70% and preferably between 40% and 60% of the contact surface that would occur in the absence of such findings.

In a sixth embodiment, not shown in the drawings, the surface of the perforated cylinder 6 is smooth while the surface of the sleeve 2, intended to come into contact with it, is provided with reliefs of substantially similar dimensions to those of the reliefs 32 of the perforated cylinder 6 of the previous embodiment.

In a seventh embodiment, also not illustrated in the drawings, the sleeve 2 is made of fabric with weft and/or warp threads in elastic material of different diameters, so as to protrude in a differentiated manner from the surface of the sleeve 2 intended to come into contact with the perforated cylinder 6 in discrete areas, in order to reduce friction during mutual sliding.

The weft and/or warp threads can be single or multiple twisted together and can constitute the sleeve, which in this case is monolayer, or they can constitute a layer of a multilayer sleeve.

As an alternative to the suction chamber 8 now described for the various embodiments, which has its own well-defined and immutable configuration, the invention also foresees the use of a suction chamber (not shown in the drawings) which always has the shape of cylindrical segment, but has at least one of the two radial flat walls adjustable in its angular position with respect to the other so as to vary the width of the chamber itself. In this case the free rectilinear edge of the mobile wall, parallel to the axis of the hollow cylinder 6, can slide tightly on the perforated surface of the latter, without the suction chamber having to have its own perforated cylindrical wall. This possibility of varying the width of the suction chamber, which corresponds to the portion of the lateral surface of the hollow cylinder 6, to which the web 4 of fibrous material is made to adhere, is particularly advantageous as it allows the width to be adjusted in a circumferential direction of the suction chamber 8 and therefore the extent of the transversal compaction of the layer 4 of fibrous mixture.

In all the embodiments now described, it has been spoken of a layer 4 of fibrous mixture which is deposited at the top of the perforated cylinder 6, but the invention provides that, depending on the result to be obtained, the layer 4 could be placed not at of the top of the perforated cylinder 6, but also in a further downstream position, with reference to the direction of rotation of the cylinder itself, provided that inside the hollow cylinder 6 the suction chamber is started in correspondence with the generator on which it begins to be placed the web 4 and is made to end in correspondence with the generator of detachment of the web itself from the cylinder 6.

Furthermore, in all the embodiments now illustrated it is possible to vary the extent of the axial stretching of the sleeve portion 2, on which the web of fibrous material 4 must be placed, and therefore the extent of the transversal contraction of the web itself and the consequent degree of transversal extensibility of the web of fibrous material 24 obtained, by varying the inclination of the disks 12 with respect to their rotation shaft 10. In this case, however, it is appropriate that an increase in the opposing inclination of the two disks 12 also corresponds to a spacing them, to prevent an unwanted accumulation of relaxed sleeve from being created in the part of the sleeve 2 opposite to that subjected to stretching. Finally, in all the embodiments now illustrated it is also possible that the sleeve 2, instead of being made entirely of elastically stretchable material, includes a central circumferential band of elastically stretchable material, on which the layer 4 of fibrous mixture is placed, and two bands lateral circumferential bands of non-stretch material which do not perform any compacting function on the layer of fibrous material but have the function of concentrating the stretching only on the band involved in the treatment on said layer 4.

The apparatus according to the invention can be used in various contexts and more specifically it can constitute a separate unit or it can be part of a flat paper machine.

Claims

C L A I M S

1 . Apparatus for producing transversally extensible webs of fibrous material starting from a layer (4) of mouldable fibrous mixture having a dry content between 18% and 70%, preferably between 40% and 60%, comprising:

- a continuous conveyor belt (2) made of material permeable to fluids and elastically stretchable at least in the transverse direction,

- means (12) to cause the temporary and localized transversal stretching of at least a portion of said conveyor belt (2),

- means for placing said layer (4) of mouldable fibrous mixture on said conveyor belt (2), when this is in a transversally stretched condition, and for removing it from said conveyor belt, when this has elastically resumed, at least in part, its initial configuration,

- a perforated support surface (6) of at least a portion of said conveyor belt (2), at least in the phase in which it is passing from the stretched condition transversely to its initial configuration,

- a vacuum source (8) acting on the side of said perforated support surface (6) opposite to the side of deposition of said layer (4) of mouldable fibrous mixture, characterized in that said perforated support surface (6) and said conveyor belt (2) are configured so as to be in direct contact each other with only from 30% to 70% and preferably from 40% to 60% of their facing surfaces.

2. Apparatus according to claim 1 characterized in that said conveyor belt (2) is constituted by an elastic sleeve completely wrapped around a perforated cylinder (6), the lateral surface of which constitutes said perforated support surface.

3. Apparatus according to claim 2 characterized in that said sleeve (2) has its edges fixed to the edges of two disks (12) integral in rotation with the rotation shaft (10) of said perforated cylinder (6), but kept inclined in the opposite direction and in a fixed position with respect to the apparatus itself when said shaft (10) rotates.

4. Apparatus according to claim 1 characterized in that said conveyor belt (2) is made up of a continuous belt closed in a ring and returned by a perforated cylinder (6), the lateral surface of which constitutes said perforated support surface.

5. Apparatus according to one or more of the previous claims characterized in that said vacuum source (8) is constituted by a suction chamber which is configured to remain fixed during the movements of said support surface (6), and is shaped to cylindrical segment with the cylindrical surface facing said perforated support surface.

6. Apparatus according to one or more of the previous claims characterized in that it also includes a second cylinder (18), which has a perforated surface, houses a suction chamber inside it and is kept in contact with the portion of the conveyor belt ( 2), on which said layer of fibrous mixture (4) is intended to be deposited during transversal contraction, and also comprises a third metal cylinder (20), which is kept in contact with said second cylinder (10) in proximity to the generator, at which its suction chamber ends, said third cylinder (20) having a smooth lateral surface heated to a temperature between 40°C and 100°C .

7. Apparatus according to one or more of the previous claims characterized in that said conveyor belt (2) is made up of one or more layers of elastomer, possibly expanded, or of a single or multiple fabric of elastic or non-elastic threads but in any case intertwined according to an elastic texture, or from a composite layer of the previous ones or from a plurality of springs of metallic or plastic material possibly incorporated into an elastomeric structure.

8. Apparatus according to one or more of the previous claims characterized in that said conveyor belt (2) is provided, on its entire surface intended to come into contact with said perforated support surface (6), which is substantially smooth, with undulations (22) configured so as to be in direct contact each otherwith only at the top of said corrugations.

9. Apparatus according to claim 8 characterized in that the axis of said corrugations (22) develops in the direction of advancement of said conveyor belt (2).

10. Apparatus according to one or more of claims 1 to 7 characterized in that said conveyor belt (2) has substantially smooth surfaces, while said perforated support surface (6) is provided with closely spaced grooves (26) having an axis developing in the direction of advancement of said conveyor belt (2).

11 . Apparatus according to one or more of claims 1 to 7 characterized in that said perforated support surface (6) is substantially smooth, while said conveyor belt (2) is provided with transverse undulations (28) over its entire intended surface to come into contact with said perforated support surface (6).

12. Apparatus according to one or more of claims 1 to 7 characterized in that the surface of said conveyor belt (2) intended to come into contact with said perforated support surface (6) is substantially smooth, while said perforated support surface (6) is provided with closely spaced grooves (30) with an axis extending transversally to the direction of advancement of said conveyor belt

13. Apparatus according to one or more of claims 1 to 7 characterized in that said perforated support surface (6) is substantially smooth while the surface of said conveyor belt (2) intended to come into contact with said perforated support surface (6) is provided with reliefs (32) substantially having the shape of spherical caps.

14. Apparatus according to one or more of claims 1 to 7 characterized in that said conveyor belt (2) has substantially smooth surfaces, while said perforated support surface (6) is provided with reliefs in the shape of spherical caps.

15. Apparatus according to one or more of claims 1 to 7 characterized in that said conveyor belt (2) is made of fabric with weft and/or warp threads in elastic material of different diameters, protruding in different ways from the surface of the carpet intended to come into contact with said support surface (6) in distinct areas.

16. Apparatus according to claim 15 characterized in that said warp and/or weft threads are single or multiple twisted together and constitute said singlelayer conveyor belt (2), or a layer of a multi-layer sleeve.

17. Apparatus according to one or more of the previous claims characterized in that said perforated support surface (6) is constituted by the lateral surface of a cylinder, around which said continuous conveyor (2) is totally or partially wrapped , and said source of vacuum (8) consists of a chamber associated with a suction pump and shaped like a cylindrical segment with two substantially flat walls arranged at an angle each other to and delimiting an opening facing a corresponding portion of the lateral surface of said cylinder (6).

18. Apparatus according to claim 17 characterized in that said suction chamber (8) has the shape of a spherical segment and at least one of its two flat radial delimiting walls is adjustable in its angle with respect to the other.

19. Apparatus according to claim 3 characterized in that said disks (12) are mounted on their rotation shaft (10) so as to be adjustable in their inclination with respect to it and to be able to slide along it.

20. Apparatus according to one or more of the previous claims characterized in that said conveyor belt (2) includes a central band, which is made of elastically stretchable material and has a width linked to the width of said perforated support surface (6), and two side bands made of substantially non- ironable material.

21 . Paper machine characterized in that it comprises an apparatus according to one or more of claims 1 to 20.