WO2010073221A2

WO2010073221A2 - Device for treatment of a card web

Info

Publication number: WO2010073221A2
Application number: PCT/IB2009/055924
Authority: WO
Inventors: Paolo Olivo; Nicola Olivo
Original assignee: Texnology S.R.L.
Priority date: 2008-12-23
Filing date: 2009-12-23
Publication date: 2010-07-01
Also published as: ITPD20080382A1; IT1392408B1; WO2010073221A3

Abstract

A device for treatment of a card web (V), comprising a first conveyor belt (2) and a second conveyor belt (3) in overlapped relationship along one section to define a conveyor channel (4) for the web (V); a plurality of first rotating and axially fixed rollers (7) with the conveyor belts (2, 3) wound thereon; a first axially movable accumulator carriage (8) which collide with a portion of the conveyor channel (4) to move it in a first direction (X), and thus change the length of the conveyor channel (4); first compensation means (11) which compensate for length changes in the conveyor channel (4) defining section of the first conveyor belt (2) and second compensation means (12) which compensate for length changes in the conveyor channel (4) defining section of the second conveyor belt (3). The second compensation means (12) include a second accumulator carriage (13), axially movable in a second direction (Y) other than the first direction (X).

Description

DEVICE FOR TREATMENT OF A CARD WEB

Field of the invention

The present invention finds application in the field of textile processing machines and is particularly suitable for use in the field of nonwoven fabric processing machines..

Namely, the present invention relates to a device for treatment of a card web.

Background art

In the process for obtaining nonwoven textile surfaces, textile fibers first undergo carding, whereby a web is formed, also known as card web, which is later subjected to a web-laying process, i.e. laid on multiple overlapped layers, to obtain a multilayered structure of the desired thickness, to be later consolidated by needlefelting or other methods.

Though the above steps, the web is carried by conveyor belts driven by rollers or rotating cylinders. The web is generally placed on at least one conveyor belt, although it is usually inserted in a conveyor channel formed between two overlapping conveyor belts, with the purpose of retaining and protecting the card web during processing.

Indeed, the quality of the resulting nonwoven fabric, that can be assessed in terms of uniform thickness and fabric density, depends on many factors, including the uniform size of the card web in each processing step. Particularly, the desired predetermined web thicknesses should be preserved, with the web being required to have uniform width and no breaking point during web-laying. In order to ensure uniform treatment and coherence of web fibers from carding to web-laying, the movement of the web shall be as constant as possible, with no abrupt changes. Nevertheless, it may be appreciated that each processing step requires generally different speeds from the others and, among other things, one step often has variable speeds during processing. This involves web motion discontinuity in the process between carding and web-laying.

Particularly, a web drafting step is provided between carding and web-laying, for changing web thickness in certain predetermined sections.

In the background art, web-laying of a card web of constant thickness provides a substantially parallelepipedal multilayered structure. Nevertheless, further consolidation processing tends towards a higher compression of the multilayered structure in the middle section of its longitudinal section, and thus provides a consolidated multilayered structure of non uniform thickness. In order to compensate for the above, the web is drafted to reduce its thickness in the sections designed for web-laying at the ends of the longitudinal section of the multilayered structure. Therefore, the latter no longer has a parallelepipedal shape, but has a longitudinal section with a profile that substantially slopes towards the edges.

Since this and other discontinuities may cause web ruptures or degradations of the quality of the consolidated nonwoven fabric, a plurality of dynamic card web storage devices have been added, to be interposed between the various processing stages.

These devices generally consist of a plurality of movable rotating rollers that subtend the card web conveyor belts, and may move towards and away from each other to increase or reduce the space through which the card web moves from one processing station to the next. Therefore, these devices are dynamic card web storage devices, which provide variable storage according to the differences of processing speeds between one station and the stations directly upstream and downstream from it.

Examples of devices for treatment of a card web, adapted to provide dynamic storage of the web are disclosed in patent EP 0,659, 220 and patent US 7,320,154.

In spite of their differences, the devices disclosed in these two patents, as well as all the other prior art devices, have certain common features. First, two conveyor belts are provided, both in a closed-loop arrangement, which overlap along at least one section comprising a substantially U-shaped portion. These two conveyor belts define a web conveyor channel, in which they define an inlet and an outlet.

The belts are tensioned and driven by a plurality of first axially fixed rotating rollers around which they are wound. Furthermore, at least one first rotating roller is found, which can axially move in the direction of extension of the U- shaped portion to extend or shorten it Particularly, the movable roller is placed at the bottom of the U-shaped section and moves away from and towards the fixed rollers located at the top of the U-shaped section. Any movement of the movable roller in one of its two opposite directions causes the U-shaped section to be extended or shortened.

Since the conveyor belts have a closed-loop configuration, each conveyor belt shall obviously have at least one second rotating roller, which can axially move relative to the fixed rollers to compensate for the motion of the first movable rotating roller of the corresponding conveyor belt.

As shown, for instance, in US 7,320,154, the second rollers are movable in a direction that coincides with the direction of the first movable roller. It can be noted that such solution have particularly large space requirements, because any motion of a given amplitude of the first roller involves a corresponding movement of the same amplitude of each of the second rollers. The space subtended by the displacements of the rollers in their common direction is three times the space subtended by the motion of the first roller.

The case disclosed in EP 0,659,220 is only seemingly different, as one of the second rollers is replaced by a movable carriage comprising two rotating rollers. Although the latter are displaced in directions other than the direction of displacement of the first roller, the element to be considered is obviously the movable carriage whose direction of displacement coincides with the direction of displacement of the first roller. Once again, this involves the drawback that the space subtended by the displacements of the rollers and the carriages in their common direction is three times the space subtended by the motion of the first roller.

In addition to the above described need for card web storage areas, web drafting may involve further degradations of the nonwoven fabric quality.

A card web is drafted by at least two rotating rollers that rotate at different speeds. Namely, the web is introduced into the nip between a first one of, these rollers and an opposing element, i.e. through a web retaining and feeding area which utilizes the compression friction between the web and the roller to assist feeding. Then, the web passes between the second one of such rollers and an additional opposing element, i.e. through a further retaining and feeding area. The opposing elements shall also be movable with and at the same with as their respective rollers, to prevent web damages. They generally consist of additional rotating rollers or conveyor belts wound on rotating rollers.

When the fifth roller rotates at a higher speed than the first, the card web section within the retention areas is pulled, and is thus drafted. Nevertheless, as it passes between the retention areas during drafting, the web acts as a rubber band, and rends to reduce both its thickness and its width. This is an undesired effect of drafting, which degrades the quality of the final product and forces the user to cut the lateral edge of the nonwoven fabric due to the presence of step-like formations.

One way to avoid or minimize this effect is to reduce the nip between the rotating rollers that perform the drafting action. Namely, the shorter is the free space, i.e. the one in which the web is not accompanied by rollers or conveyor belts between drafting areas, the smaller is its transverse skrinkage. During drafting, the pulled web comes out of a retention area and goes into the next retaining area in the direction defined by the tangent to the two rollers of the retaining areas, therefore the reduction of the free space between rollers is obtained by minimizing the distance therebetween.

A first solution is disclosed in EP 1 ,386,990, in which two lamellar rollers are provided, which can be drawn towards each other and allowed to partially intermesh. While this solution can reduce the distance between rollers, it still cannot totally obviate the drawback of web width shrinkage, as the free section covered by the web is still considerable, although minimized.

This drawback might be alleviated by reducing the diameter of the rollers, but there would still be a limit, in that excessively small-diameter rollers would cause the web to roll and jam therearound, thereby stopping the process and irremediably spoiling the web.

This shortcoming has been obviated in patent application WO 2006/051294, in which, particularly referring to Figure 6 of the application, small diameter rollers are used as apices of four closed-loop conveyor belts which form in pairs the two retention areas between which drafting occurs. While it can be appreciated that the free space covered by the card web is particularly small, this is still obtained by means of a highly complex device. Furthermore, such free space covered by the web in the drafting area is not completely eliminated, therefore the web still undergoes some minor width shrinkage.

Patent EP 1 ,381 ,721 , provides multiple point drafting, to divide the pulling force that has to be exerted on the web to obtain the desired drafting effect. This alleviates the width shrinkage problem, but does not totally eliminate it.

Disclosure of the invention

A general object of the present invention is to overcome the above drawbacks, by providing a device for treatment of a card web that can obviate the drawbacks and limitations of the prior art.

Particularly, one object of the invention is to provide a device for treatment of a card web that can improve the quality of the final nonwoven fabric as compared with equivalent prior art devices, while maintaining the uniformity of the card web.

Notwithstanding these general objects, a particular object of the invention is to provide a device that is particularly compact and can be easily manufactured, as compared with equivalent prior art devices.

Another desired object is to provide a device that can perform drafting of predetermined sections of the card web, while reducing or totally eliminating lateral shrinkage of the web.

These and other objects, as better explained hereafter, are fulfilled by a device for treatment of a card web as defined in the main claim.

Particularly, in one aspect of the invention, the device may include at least one first conveyor belt and at least one second conveyor belt, in overlapped relation along at least one section, to define a web conveying channel having an inlet and an outlet.

Furthermore, the device may comprise a plurality of first axially fixed rotating rollers, around which the conveyor belts are wound to be at least tensioned thereby.

In another aspect of the invention, the device may comprise at least one first accumulator carriage, that is capable of axial movement and is susceptible to collide with and deform at least one portion of the conveyor channel, by extending or shortening it in a direction lying on a first line.

In a further aspect of the invention, the device may also comprise first compensation means, susceptible of changing the path of the first conveyor belt, to maintain its length and tension unchanged as the conveyor channel is extended or shortened, and second compensation means susceptible of changing the path of the second conveyor belt to maintain its length and tension unchanged as the conveyor channel is extended or shortened.

In another aspect, the second compensation means may comprise at least one second accumulator carriage, which is capable of axial movement in a second direction, lying on a second line, separate from the first line, to collide with and deform the path of the second conveyor belt. Thus, the length and tension of the second conveyor belt can be maintained unchanged even when the conveyor channel has been shortened or extended.

In a further aspect of the invention, the first compensation means comprise at least one third accumulator carriage, which is capable of axial movement in a third direction, lying on a third line, to collide with and deform the path of the first conveyor belt, and thus maintain its length and tension unchanged as the conveyor channel is shortened or extended. It can be noted that at least one of the compensation means operates on a line that is different from the line of motion of the first accumulator carriage. Particularly, since the line of motion of the second accumulator carriage moves is different from the line of motion of the first accumulator carriage, then, as better explained below, although a movement of a given width of the first accumulator carriage must cause a movement of the same width of each of the second and third accumulator carriages, there will be no longer a directrix along which the space covered by the displacements is three times the space covered by the first accumulator carriage, but such space will be at the most twice, if one of the second and third carriages is aligned with the first, or equal to the displacement of the first carriage, if both are movable on directrices other than that of the first carriage and different from each other.

Preferably, but without limitation, the first accumulator carriage comprises at least one second rotating roller, the second accumulator carriage comprises at least one third rotating roller and the third accumulator carriage comprises at least one fourth rotating roller.

In one aspect of the invention, the device comprises, upstream from the inlet of the conveyor channel, card web drafting means, which in turn comprise at least one first drive unit for driving the card web at a first driving speed and at least one second drive unit for driving the card web at a second driving speed.

Particularly, the first drive unit comprises at least one fifth roller rotating at a first rotation speed and first holding means, for holding the card web against at least one working section of the surface of the fifth rotating roller, and the second drive unit comprises at least one sixth roller rotating at a second rotation speed and second holding means, for holding the card web against at least one working section of the surface of the sixth rotating roller. Furthermore, the holding means are so designed that the card web covers at least one non rectilinear path between the first drive unit and the second drive unit.

Thus, while in the prior art the card web came out of a retention area and went into the next one along the tangent to the two rollers that formed the two retention areas, in the present device the aim is to cause the web to be released from a roller and sit on the next roller in the points closest to the line that connects the centers of the circles defined by the cross section of each roller. Since the shortest distance between two rollers is determined by such connecting line, this obviously minimizes the free space covered by the web, in which transverse shrinkage thereof occurs.

In one aspect of the invention, the first and second holding means comprise at least one seventh roller, which is disposed tangent to the fifth and sixth rotating rollers to define, along the line of contact with the fifth rotating roller, a first card web holding area, and along the line of contact with the sixth rotating roller, a second card web holding area.

This advantageously eliminates any free space to be covered by the card web, with the latter being guided between retention areas by a roller.

Brief description of the drawings.

Further characteristics and advantages of the invention will be more apparent from the detailed description of a few preferred, non-exclusive embodiments of the device of the invention, which are described as non-limiting examples with the help of the annexed drawings, in which:

FIG. 1 is an operational view of the device for treatment of a card web according to the invention; FIG. 2 is a further operational view of the device for treatment of a card web according to the invention;

FIGS. 3 to 7 show details of the device of FIG. 2. Detailed description of a preferred embodiment

FIG. 1 shows a device 1 for treatment of a card web V.

Here, it is shown to include at least one first conveyor belt 2 and at least one second conveyor belt 3, in overlapped relation along at least one section, to define a conveyor channel 4 for the web V, having an inlet 5 and an outlet 6.

Particularly, the conveyor belts 2 and 3 are wound around a plurality of first axially fixed rotating rollers 7, i.e. which are only capable of rotational motion, and provide at least tensioning and possibly also driving features.

The device 1 of the invention also comprises at least one first axially movable accumulator carriage 8, i.e. capable of at least translational movement, preferably but not necessarily including at least one second rotating roller 9 that collides with and deforms at least one portion 10 of the conveyor channel 4. Such deformation occurs in a first direction, lying on a first line X, and causes a change in the length of the channel 4. It shall be understood that, in certain variant embodiments, not shown, the first accumulator carriage 8 may also collide with and deform the portion 10 of the conveyor channel 4 by specially shaped elements other than a rotating roller.

Therefore, the transverse movement of the first accumulator carriage 8 along the first line X causes the conveyor channel 4 to be extended or shortened and creates a curved section of variable size in the channel 4, at the portion 10. This provides a variable, i.e. dynamic storage for the card web V that runs through the channel 4 to preserve its integrity and more generally its quality.

While the figure shows the first accumulator carriage 8 as mainly causing the formation of a U-shaped portion 10, it shall be understood that the latter may also have a simply curvilinear shape, such as a C or L shape. Basically, the effect of the first accumulator carriage 8 is to attract a larger amount of the first conveyor belt 2 and the second conveyor belt 3 towards the portion 10 of the channel 4.

This involves the need for first compensation means 11 to compensate for any length change in the conveyor channel 4 defining section of the first conveyor belt 2, and second compensation means 12 to compensate for any length change in the conveyor channel 4 defining section of the second conveyor belt 3.

Particularly, the first compensation means 11 and the second compensation means 12 change the path of the first conveyor bent 2 and second conveyor belt 3 respectively, to maintain the length and tension thereof unchanged even when the conveyor channel 4 has been extended or shortened.

In one aspect of the invention, the second compensation means 12 comprise at least one second accumulator carriage 13, which is capable of axial movement in a second direction, lying on a second line Y, different and separate from the first line X. Particularly, the second accumulator carriage 13 comprises at least one third rotating roller 14 around which the second conveyor belt 3 is wound.

The movement of the second accumulator carriage 13 is apparently coordinated with that of the first accumulator carriage 8. Particularly, the two movements cover the same distance, to maintain the second conveyor belt 3 subtended and prevent it from tearing.

Since these two carriages 8 and 13 move along separate lines, the spaces covered thereby do not sum together along the same line, and this obviously reduces the dimensions of the device 1 of the invention. Like the second compensation means 12, the first compensation means 11 comprise at least one third accumulator carriage 15, which is capable of axial movement in a third direction lying on a third line Z, and comprises at least one fourth rotating roller 16. Also, the movement of the third accumulator carriage 15 is coordinated with that of the first accumulator carriage 8. Particularly, the two movements cover the same distance, to maintain the first conveyor belt 2 subtended and prevent it from tearing.

It shall be understood that, as mentioned above concerning the first accumulator roller 8, in certain variant embodiments, not shown, the second accumulator carriage 13 and the third accumulator carriage 15 may be subtended by respective conveyor belts also through specially shaped elements other than a rotating roller.

In the accompanying figures, the third line Z is shown as coincident with the first line X, thereby causing the covered spaces to sum together on the same line. Nevertheless, if the device 1 of the invention is required to have even smaller dimensions, the third line Z may be designed to be separate from the first line X.

The figures also show that the first line X and the second line Y are parallel, but this has to be intended without limitation. However, in case of incident lines, the point of incidence must be external to the maximum extension of the portion 10 of the conveyor channel 4 in which the first accumulator carriage 8 operates. In another aspect of the invention, a particular dimensional reduction is obtained when the first accumulator carriage 8 defines, in its movement, a movement lane different from the movement lane defined by the second accumulator carriage 13.

The same applies to the third accumulator carriage 15 if the first line X and the third line Z are separate. In a further aspect of the invention, the device 1 comprises card web V drafting means 17 upstream from the inlet 5 of the conveyor channel 4, as shown in FIG. 2.

These comprise at least one first drive unit 18 for driving the card web V at a first driving speed and at least one second drive unit 19 for driving the card web V at a second driving speed.

Particularly, the second drive unit 19 is placed downstream from and proximate to the first drive unit 18 and the first driving speed is equal to or lower than the second driving speed so that, when the second driving speed is higher than the first driving speed, the section of the card web V between the two drive units 18 and 19 can be drafted.

It will be obviously appreciated that the dynamic storage shall be placed downstream from the drafting means 17, due to their variable speed action on the web V.

In a further aspect of the invention, also shown in the detailed view of FIG. 3, the first drive unit 18 comprises at least one fifth rotating roller 20 and first holding means 21 for holding the card web V against at least one working section 22 of the surface 23 of the fifth roller 20.

Conveniently, the effect of the first holding means 21 is to hold the card web V in contact with the surface 23 of the fifth rotating roller 20 as long as possible, so that the web runs along at least one non rectilinear section 24 between the first drive unit 18 and the second drive unit 19.

Thus, as anticipated above, while in the prior art the card web came out of a retention area and went into the next one along the tangent to the two rollers that formed the two retention areas, in the present device 1 the aim is to cause the web V to be released from the fifth rotating roller 20 in points that are as close as possible to the second drive unit 19.

In order to enhance such effect, the second drive unit 19 also conveniently comprises at least one sixth rotating roller 25 and second holding means 26 for holding the card web V against at least one working section 27 of the surface 28 of the sixth roller 25.

In this case, in the device 1 the aim is to cause the web V to be released from the fifth rotating roller 20 and sit on the sixth rotating roller 25 in the points closest to the line that connects the centers of the circles defined by the cross section of each roller 20, 25. Since the shortest distance between two rollers is determined by such connecting line, this obviously minimizes the free space covered by the web V, in which transverse shrinkage thereof occurs.

A possible embodiment of the holding means 21 , 26 is shown in the detailed view of FIG. 4, where they are shown as comprising a plurality of through holes 50 formed on the peripheral surface of the fifth rotating roller 20 for negative pressure air to flow from the exterior to the interior of the fifth rotating roller 20.

Likewise, the second holding means 26, if any, comprise a plurality of through holes formed on the peripheral surface of the sixth rotating roller 25 for negative pressure air to flow from the exterior to the interior of the sixth rotating roller 25.

Thus, the web V is held against the rotating roller 20, 25 by vacuum.

In a different embodiment, the first 21 and second 26 holding means comprise at least one seventh rotating roller 60, which is disposed tangent to the fifth rotating roller 20 and the sixth rotating roller 25 to define, along a first line of contact with the fifth rotating roller 20, a first card web V holding area 62, and along a second line of contact with the sixth rotating roller 25, a second card web V holding area 63.

Thus, the web V is forced to run along a curvilinear section 24, and is thus released from the fifth roller 20 and comes into contact with the sixth roller 25 in points as close as possible to the minimum distance between the rollers 20, 25.

Furthermore, the section 24 covered by the card web V is not free, but lies on the seventh rotating roller 60. This further reduces, or even eliminates any transverse shrinkage of the web during drafting.

In another aspect of the invention, as shown in the detailed view of FIG. 6, the seventh roller 60 is of lamellar type and defines on the fifth rotating roller 20 a plurality of first card web V holding segments 64 aligned along the first line of contact between the fifth rotating roller 20 and the seventh rotating roller 60 and spaced by first interstices 65 in which the card web V is free.

This allows combing of the card web V as it is drafted, i.e. as it moves from the first drive unit 18 to the second drive unit 19. In other words, this completely prevents shrinkage of the card web V during drafting.

Nevertheless, this might cause uneven drafting, because the web V is only held along sections corresponding to the first holding segments 64.

Therefore, an additional lamellar roller 66 is provided, as shown in FIG. 7, which is placed downstream from the seventh roller 60 and tangent to the fifth rotating roller 20 to define thereon a plurality of second card web V holding segments, not shown, which are aligned and spaced by second interstices, also not shown, in which the card web V is free. Particularly, the second interstices correspond to the first holding segments 64, whereas the second holding segments correspond to the first interstices 65. This ensures uniform drafting of the web.

The provision of the seventh lamellar roller 60 and the additional multilayer roller 66 also allows air to be removed from within the card web V before drafting and before access to the conveyor channel 4, where the flattening effect on the web V and the resulting egress of air might degrade the quality of the web V.

In the light of the above, it will be understood that the present device fulfills the intended objects and obviates the prior art drawbacks and limitations.

Particularly, the device for treatment of a card web can improve the quality of the final nonwoven fabric as compared with equivalent prior art devices, while maintaining the uniformity of the card web.

Also, the device of the invention is particularly compact and can be easily manufactured as compared with equivalent prior art devices, and allows drafting of predetermined sections of the card web, while limiting or totally eliminating lateral shrinkage of the web.

The device of this invention is susceptible of a number of changes and variants, within the inventive concept as disclosed in the appended claims. All the details thereof may be replaced by other technically equivalent parts, without departure from the scope of the invention.

While the device has been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

Claims

1. A device for treatment of a card web (V), comprising: at least one first conveyor belt (2) and at least one second conveyor belt (3), in overlapped relation along at least one section, to define a conveyor channel (4) for the web (V), having an inlet (5) and an outlet (6) defined therein; a plurality of first axially fixed rotating rollers (7), around which the conveyor belts (2, 3) are wound to be at least tensioned thereby; - at least one first accumulator carriage (8), that is capable of axial movement and is susceptible to collide with and deform at least one portion (10) of the conveyor channel (4), by extending or shortening it in a direction lying on a first line (x). first compensation means (11) susceptible of changing the path of said first conveyor belt (2) to maintain its length and tension unchanged as said conveyor channel (4) is so extended or shortened; second compensation means (12) susceptible of changing the path of said second conveyor belt (3) to maintain its length and tension unchanged as said conveyor channel (4) is so extended or shortened; characterized in that said second compensation means (12) comprise at least one second accumulator carriage (13), which is capable of axial movement in a second direction, lying on a second line (Y), separate from said first line (X) to collide with and deform the path of said second conveyor belt (3), and thus maintain its length and tension unchanged as said conveyor channel (4) is shortened or extended.

2. Device as claimed in claim 1, characterized in that said first compensation means (11) comprise at least one third accumulator carriage (15), which is capable of axial movement in a third direction, lying on a third line (Z), to collide with and deform the path of said first conveyor belt (2), and thus maintain its length and tension unchanged as said conveyor channel (4) is shortened or extended.

3. Device as claimed in claim 1 or 2, characterized in that said first accumulator carriage (8) defines a movement lane different from the movement lane defined by said accumulator carriage (13), said first accumulator carriage (8) comprising at least one second rotating roller (9), said second accumulator carriage (13) comprising at least one third rotating roller (14), said third accumulator carriage (15) comprising at least one fourth rotating roller (16).

4. Device as claimed in any preceding claim, characterized by comprising, upstream from said inlet (5) of said conveyor channel (4), card web (V) drafting means (17) comprising at least one first drive unit (18) for driving the card web (V) at a first driving speed and at least one second drive unit (19) for driving the card web (V) at a second driving speed, said second driving unit (19) being placed downstream from and close to said first drive unit (18), said first driving speed being equal or lower than said second driving speed so that, when said second driving speed is higher than said first driving speed, the section of the card web (V) between said first drive unit (18) and said second drive unit (19) can be drafted.

5. Device as claimed in claim 4, characterized in that said first drive unit (18) comprises at least one fifth rotating roller (20) and first holding means (21) for holding the card web (V) against at least one working section (22) of the surface (23) of said fifth rotating roller (20), said card web (V) covering at least one not rectilinear section (24) between said first drive unit (18) and said second drive unit (19), due to the effect of at least said first holding means (21).

6. Device as claimed in claim 4 or 5, characterized in that said second drive unit (19) also comprises at least one sixth rotating roller (25) and second holding means (26) for holding the card web (V) against at least one working section (27) of the surface (28) of the sixth roller (25).

7. Device as claimed in claim 6, characterized in that said first holding means (21) comprise a plurality of through holes (50) formed on the peripheral surface of the fifth rotating roller (20) for negative pressure air to flow from the exterior to the interior of said fifth rotating roller (20).

8. Device as claimed in claim 6 or 7, characterized in that said second holding means (26) comprise a plurality of through holes formed on the peripheral surface of said sixth rotating roller (25) for negative pressure air to flow from the exterior to the interior of said sixth rotating roller (25).

9. Device as claimed in claim 6, characterized in that said first (21) and said second (26) holding means comprise at least one seventh rotating roller (60), which is disposed tangent to said fifth rotating roller (20) and said sixth rotating roller (25) to define, along a first line of contact with said fifth rotating roller (20), a first card web (V) holding area (62), and along a second line of contact with said sixth rotating roller (25), a second card web (V) holding area (63).

10. Device as claimed in claim 9, characterized in that said seventh roller (60) is of lamellar type and defines on said fifth rotating roller (20) a plurality of first holding segments (64) for holding said card web (V) aligned along said first line of contact and spaced by first interstices (65) in which said card web (V) is free.

11. Device as claimed in claim 10, characterized in that it comprises an additional lamellar roller (66) located upstream from said seventh roller (60) and tangent to said fifth rotating roller (20) to define on said fifth rotating roller (20) a plurality of second holding segments for holding said card web (V), which are aligned and spaced by second interstices in which said card web (V) is free.

12. Device as claimed in claim 11 , characterized in that said second interstices correspond to said first holding segments (64), and said second holding segments correspond to said first interstices (65).