INTERFOLDING MACHINE

Abstract

An interfolding machine (1) for producing stacks (100) of interfolded sheets according to a predetermined interfolding configuration, starting from a web (50) of paper, or similar materials, provides a feeding section (10), which provides to apply a tension on the web (50) and to move the same along a feeding direction (101) to feed the same to a cutting section (20), in which the web of paper (50) is cut into a series of sheets (11) of length predetermined, at a cutting point arranged between a cutting roller (25) and a counter-cutting element (26). Downstream of the cutting section (20) a folding section (30) is provided comprising a first and a second folding rollers (31,32) counter-rotating one with respect to the other. The first and second folding rollers (31,32) are arranged to rotate about respective rotation axes (131,132), in such a way to have a first peripheral velocity vP and are configured to fold, at a folding zone (35), the aforementioned plurality of sheets (11) in a plurality of panels and to form the stack (100) of interfolded sheets. The cutting roller (25) is configured in such a way to alternately distribute the aforementioned sheets (11) between a transfer roller (45) of transfer section (40), and the first folding roller (31).

Claims

1. An interfolding machine for producing stacks of interfolded sheets from a web of paper, or similar materials, said machine comprising: a feeding section configured to cause said web of paper to move along a predetermined feeding direction; a cutting section comprising a cutting roller having an external surface, and a counter-cutting element configured to cooperate with each other in such a way to cut said web of paper in a plurality of sheets of predetermined length; and a folding section comprising a first and a second folding rollers counter-rotating one with respect to the other, said first and second folding rollers being configured to fold, at a folding zone, said plurality of sheets in a plurality of panels and to form said stack of interfolded sheets according to a predetermined interfolding configuration; wherein: said cutting roller is configured to alternately distribute said plurality of sheets to said first folding roller forming a first plurality of sheets arranged to reach said folding zone through a first feeding path, and to a transfer roller provided in a transfer section forming a second plurality of sheets arranged to reach said folding zone through a second feeding path, said transfer roller is configured to transfer said second plurality of sheets to said second folding roller, and said cutting roller is provided with: first holding elements configured to hold said sheets on a first portion of said external surface of said cutting roller; and second holding elements configured to hold said sheets on a second portion of said external surface positioned downstream of said first portion of said cutting roller, in such a way that, when said second holding elements are arranged to hold said sheets on said second portion, a sheet of said plurality is transferred from said cutting roller to said transfer roller, whilst, when said second holding elements are not arranged to hold said sheets on said second portion, a sheet is transferred from said cutting roller to said first folding roller.

2. The interfolding machine, according to claim 1, wherein: said transfer roller is provided with third holding elements configured to hold said second plurality of sheets on the external surface of said transfer roller, and said third holding elements are configured to alternatively move between: an activation configuration in which said third holding elements are arranged to hold said second plurality of sheets on said external surface of said transfer roller, and a deactivation configuration, in which said third holding elements are not arranged to hold said sheets of said second plurality and, therefore, all the sheets of said plurality are arranged to be transferred from said cutting roller to said first folding roller.

3. The interfolding machine, according to claim 2, further comprising an activation/deactivation device configured to arrange said third holding elements in said activation configuration, or in said deactivation configuration.

4. The interfolding machine, according to claim 2, wherein: said second holding elements are configured to move between an activation configuration, in which are arranged to hold said sheets on said second portion, and a deactivation configuration, and said second holding elements are not arranged to hold said sheets on said second portion whereby all the sheets of said plurality are arranged to be transferred from said cutting roller to said folding zone through said first feeding path.

5. The interfolding machine, according to claim 4, wherein an additional activation/deactivation device is provided configured to arrange said second holding elements in said activation configuration, or in said deactivation configuration.

6. The interfolding machine according to claim 1, wherein said cutting roller has a circumference having a length equal to a multiple of the length of a panel.

7. The interfolding machine according to claim 1, wherein said transfer roller has a circumference having a length equal to a multiple of the length of a panel.

8. The interfolding machine according to claim 1, wherein said cutting roller and said transfer roller have circumferences having equal lengths.

9. The interfolding machine according to claim 1, wherein said cutting roller has a diameter equal to the diameter of said first and second folding rollers, or a multiple of the same.

10. The interfolding machine, according to claim 1, wherein said transfer roller has a diameter equal to the diameter of said first and second folding rollers, or a multiple of the same.

11. The interfolding machine according to claim 1, wherein said cutting roller and said transfer roller have a circumference having a length that is six times the length of a sheet of said plurality of sheets.

12. The interfolding machine, according to claim 1, wherein said first and second folding rollers have a circumference having a length that is four times the length of a sheet of said plurality of sheets.

13. The interfolding machine, according to claim 1, wherein said first and second folding rollers are arranged to rotate about a respective rotation axis in such a way to have a first peripheral velocity v.sub.P, and wherein said cutting roller and said transfer roller are arranged to rotate about respective rotation axes in such a way to have a second peripheral velocity vT, said first peripheral velocity v.sub.P being less than said second peripheral velocity vT.

14. The interfolding machine, according to claim 13 wherein said first peripheral velocity v.sub.P is equal to half of said second peripheral velocity vT, i.e. v.sub.P=½ vT.

15. The interfolding machine, according to claim 13 wherein said prima peripheral velocity v.sub.P is equal to ⅔ of said second peripheral velocity vT, i.e. v.sub.P=⅔ vT.

16. The interfolding machine, according to claim 1, wherein said first and/or said second holding elements are of pneumatic type.

17. The interfolding machine, according to claim 16, wherein said first and second holding elements are suction holes arranged to be selectively put in pneumatic communication with a vacuum generation device to hold said sheets respectively on said first portion d1 and on said second portion of said external surface of said cutting roller.

18. The interfolding machine, according to claim 17, wherein a device for adjusting the level of vacuum generated by said vacuum generation device, in such a way to adjust the level of vacuum at least of said second holding elements.

19. The interfolding machine, according to claim 1, wherein said first and/or said second holding elements are of mechanical type.

20. The interfolding machine, according to claim 1, wherein: said first portion extends substantially from said counter-cutting element to a first tangent point positioned between said cutting roller and said first folding roller, and said second portion extends substantially from said first tangent point positioned between said cutting roller and said first folding roller and a second tangent point positioned between said cutting roller and said transfer roller.

21. The interfolding machine, according to claim 1, wherein: said cutting roller comprises a plurality of holes, wherein said first holding elements are configured to put in pneumatic communication said holes with a vacuum generation device at said first portion of said cutting roller to hold on said first portion said sheets arranged to be transferred to said first folding roller, and said second holding elements are configured to selectively put in pneumatic communication said holes with said vacuum generation device at said second portion of said cutting roller to hold on said second portion said sheets arranged to be transferred to said transfer roller.

22. The interfolding machine according to claim 1, wherein said second holding elements of said cutting roller are arranged to hold said sheets on said portion of said external surface of said cutting roller only at predetermined angular positions of said cutting roller during the rotation of the same about its rotation axis, in such a way that: when said cutting roller is positioned at said predetermined angular positions, said second holding elements are arranged to hold said sheets on said second portion in order to feed a sheet of said plurality from said cutting roller to said transfer roller, whilst, when said cutting roller is not arranged at said predetermined angular positions, said second holding elements are not arranged to hold said sheets on said second portion, and therefore a sheet is transferred from said cutting roller to said first folding roller.

23. A method for producing stacks of interfolded sheets starting from a web of paper, or similar material comprising: feeding of said web of paper along a predetermined feeding direction; cutting of said web of paper in a plurality of sheets of predetermined length; and folding by a first and a second folding rollers counter-rotating one with respect to the other said sheets at a folding zone to form said stack of interfolded sheets interfolded according to a predetermined interfolding configuration; wherein: said cutting of said web into said sheets is carried out on a cutting roller configured to alternately distribute said plurality of sheets to said first folding roller forming a first plurality of sheets arranged to reach said folding zone through a first feeding path, and to a transfer roller of transfer section forming a second plurality of sheets arranged to reach said folding zone through a second feeding path, said transfer roller (being configured to transfer said second plurality of sheets to said second folding roller and in that said cutting roller is provided with: first holding elements configured to hold said sheets on a first portion of said external surface of said cutting roller; and second holding elements configured to hold said sheets on a second portion of said external surface of said cutting roller positioned downstream of said first portion, in such a way that, when said second holding elements are arranged to hold said sheets on said second portion a sheet of said plurality is transferred from said cutting roller to said transfer roller, whilst, when said second holding elements are not arranged to hold said sheets on said second portion, a sheet is transferred from said cutting roller to said first folding roller.

24. The method according to claim 23 wherein: said transfer roller is provided with third holding elements arranged to hold said second plurality of sheets on a respective portion of the external surface of said transfer roller to transfer said second plurality of sheets from said cutting roller to said second folding roller, and the method further comprises deactivating said third holding elements of said transfer roller in such a way that all the sheets of said plurality of sheets are arranged to move from said cutting roller to said first folding roller reaching said folding zone through said first feeding path.

25. The method according to claim 23, further comprising deactivating said second holding elements in such a way that all the sheets of said plurality of sheets are arranged to move from said cutting roller to said first folding roller reaching said folding zone through said first feeding path.

26. An interfolding machine for producing stacks of interfolded sheets starting from a web of paper, or similar material, said machine comprising: a feeding section configured to cause said web of paper to move along a predetermined feeding direction; a cutting section comprising a cutting roller having an external surface, and a counter-cutting element configured to cooperate with each other in such a way to cut said web of paper in a plurality of sheets of predetermined length; a folding section comprising a first and a second folding roller counter-rotating one with respect to the other, said first and second folding rollers being configured to fold, at a folding zone, said plurality of sheets in a plurality of panels and to form said stack of interfolded sheets according to a predetermined interfolding configuration; and a transfer roller configured to alternatively move between: a working configuration, in which said cutting roller is arranged to alternately distribute said plurality of sheets to said first folding roller forming a first plurality of sheets arranged to reach said folding zone through a first feeding path, and to said transfer roller forming a second plurality of sheets arranged to reach said folding zone through a second feeding path, said transfer roller being configured to transfer said second plurality of sheets to said second folding roller, and a rest configuration, in which said transfer roller is not arranged to hold said sheets whereby all the sheets of said plurality of sheets are arranged to move from said cutting roller to said first folding roller and therefore to reach said folding zone through said first feeding path only.

27. The interfolding machine according to claim 26, wherein said transfer roller is provided with third holding elements configured to hold said sheets on a portion of the respective external surface of said transfer roller, said third holding elements being configured to move between: an activation configuration, in which are arranged to hold said sheets whereby said transfer roller is arranged in said working configuration, and a deactivation configuration, in which said third holding elements are not arranged to hold said sheets and, therefore, said transfer roller is arranged in said rest configuration.

28. The interfolding machine according to claim 27, further comprising an activation/deactivation device configured to arrange said third holding elements in said activation configuration, or in said deactivation configuration.

29. The interfolding machine according to claim 26, wherein said second holding elements are configured to move between: an activation configuration, in which said second holding elements are arranged to hold said sheets on said second portion, and a deactivation configuration, wherein said second holding elements are not arranged to hold said sheets on said second portion d2 whereby all the sheets of said plurality are arranged to be transferred from said cutting roller to said folding zone through said first feeding path.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0048] The invention will now be shown with the following description of its exemplary embodiments, exemplifying but not limitative, with reference to the attached drawings in which:

[0049] FIG. 1 diagrammatically shows a side elevational view of a first embodiment of the interfolding machine, according to the invention;

[0050] FIGS. from 2 to 10 diagrammatically show a possible sequence of steps that can be carried out by the machine of FIG. 1 for producing stacks of interfolded sheets according to the invention.

DETAILED DESCRIPTION OF SOME EXEMPLARY EMBODIMENTS OF THE INVENTION

[0051] With reference to FIG. 1, according to an embodiment of the invention, an interfolding machine 1 for producing stacks 100 of interfolded sheets according to a predetermined interfolding configuration, for example a “V”, “Z” or “W”, configuration starting from a web 50 of paper, or similar materials, provides a feeding section 10, which, for example by feeding rollers 5a and 5b provide to apply tension on the web 50 and to move the same along a feeding direction 101 at a predetermined feeding speed.

[0052] The feeding section 10 feeds the web of paper 50 to a cutting section 20, in which the web of paper 50 is cut into a series of sheets 11 of predetermined length, at a cutting point positioned between a cutting roller 25 and a counter-cutting element 26. Downstream of the cutting section 20a folding section 30 is provided comprising a first and a second folding rollers 31 and 32 counter-rotating one with respect to the other. The first and second folding rollers 31 and 32 are arranged to rotate about respective rotation axes 131, and 132, in such a way to have a first peripheral velocity vP and are configured to fold, at a folding zone 35, the aforementioned plurality of sheets 11 into a plurality of panels, and to form the stack 100 of interfolded sheets. In particular, with the term “panel” it is intended to indicate each portion of sheet that is obtained by folding a sheet 11 a determined number of times.

[0053] According to the invention, the cutting roller 25 is configured in such a way to alternately distribute the aforementioned sheets 11 between a transfer roller 45 of a transfer section 40, and the first folding roller 31. More precisely, the sheets 11 which are transferred from the cutting roller 25 to the first folding roller 31 form a first plurality of sheets 11a which reach the folding zone 35 through a first feeding path 102. This comprises a first portion d1 of the surface of the cutting roller 25 and a portion of the first folding roller 31.

[0054] The sheets 11 which, instead, are transferred from the cutting roller 25 to the transfer roller 45 form a second plurality of sheets 11b which reach at the folding zone through a second feeding path 103. In particular, the second feeding path 103 comprises a second portion d2 of the external surface of the cutting roller, a portion of the surface of the transfer roller 45 and a portion of the second folding roller 32. In particular, the cutting roller 25 and the transfer roller 45 can have a circumference of equal length. The cutting roller 25 and the transfer roller 45 are arranged to rotate about respective rotation axes 125, and 145, in such a way to have a second peripheral velocity vT. More in detail, the first peripheral velocity vP of the folding rollers 31 and 32 is equal to half of the second peripheral velocity vT, i.e. vP=½ vT. In the case that is shown in the FIG., the cutting roller 25 and the transfer roller 45 have a circumference having a length that is 6 times the planar development of a sheet 11, i.e. 6 times the cut-off. The first folding roller 31 and the second folding roller 32 have, advantageously, a circumference having a length that is 4 times the length of the planar development of the sheet 11, i.e. 4 times the cut-off. In other embodiments that are not shown for reasons of simplicity, the cutting roller 25 and the transfer roller 45 have a circumference having a length that is a multiple of the length of a panel of the sheet 11. This configuration is particularly advantageous when the sheet 11 has 3, or 4 panels.

[0055] In particular, as diagrammatically shown in the FIGS. from 2 to 7, the ratio between the peripheral velocity vT of the cutting rollers 25 and the transfer roller 45, and the peripheral velocity vP of the folding rollers 31 and 32, allows to carry out the interfolding, according to a determined interfolding configuration, of the sheets 11a coming from the first feeding path 102 with those 11b coming from the second feeding path 103. More precisely, since the peripheral velocity vP of the first folding roller is half of the peripheral velocity vT of the cutting roller 25, each sheet 11 that is transferred to the first folding roller 31 and, therefore, reaches the interfolding zone 35 along the first feeding path 102, is positioned rearward of a position with respect to the sheet 11 which follows the same that is transferred from the cutting roller 25 to the transfer roller 45 and reaches the interfolding zone 35 through the second feeding path 103. In other words, the peripheral velocity vT of the cutting roller 25 is about twice the one of the folding rollers 31 and 32, because the cutting roller 25 has to continuously feed both the folding rollers 31 and 32 with a stream of sheets which will be, therefore, continuous and staggered at the interfolding zone 35. When the peripheral velocity vT of the cutting roller 25 is about twice the vP of the folding rollers 31 and 32, the sheets coming from the first feeding path 102 and those coming from the second feeding path 103 are staggered of half a sheet, thus forming a stack 100 of “V” interfolded sheets that means formed by two panels.

[0056] According to an embodiment of the invention it is possible to cause the cutting roller 25 to rotate in such a way to have a peripheral velocity vT higher than the feeding speed of the web of paper 50.

[0057] The cut sheets 11 move along the surface of the cutting roller 25 from the cutting point to a first tangent point PT.sub.1 positioned between the cutting roller 25 and the first folding roller 31. As diagrammatically shown in FIG. 1, the cutting roller 25 is provided with first holding elements 25a configured to hold the sheets 11 on a first portion d1 of the surface of the cutting roller 25 and second holding elements 25b configured to hold the sheets 11 on a second portion d2 of the surface of the cutting roller 25. Preferably, as diagrammatically shown for example in FIG. 1, the second holding elements 25b can be of pneumatic type, i.e. in communication with a device for generating a determined level of vacuum. In particular, the second holding elements 25b can be arranged to hold the sheets solo at predetermined angular positions of the cutting roller 25 during the rotation of the same about its rotation axis 125. Therefore, at the aforementioned predetermined angular positions of the cutting roller 25, the second holding elements 25b are arranged to hold the sheets 11 on the second portion d2, and, therefore, a sheet 11 is transferred from the cutting roller 25 to the transfer roller 45, whilst, when the cutting roller 25 is not arranged in the aforementioned angular positions, the second holding elements 25b are not arranged to hold the sheets 11 on the second portion d2, and, therefore, the processed sheet 11 is transferred from the cutting roller 25 to the first folding roller 31. Even if it is not shown in detail for reasons of simplicity, the first and second folding rollers 31 and 32 are provided with holding elements configured to hold the sheet 11 on a respective holding portion and, therefore, to leave the same at the aforementioned interfolding zone 35.

[0058] More in particular, come diagrammatically shown in FIG. 1, the first portion d1 of the cutting roller 25 extends substantially from the counter-cutting element 26 to a first tangent point PT1 positioned between the cutting roller 25 and the first folding roller 31. Instead, the second portion d2 of the cutting roller 25 extends substantially from the first tangent point PT1 and a second tangent point PT2 positioned between the cutting roller 25 and the transfer roller 45. The sheets 11 can adhere to the portion d1 of the surface of the cutting roller 25, for example, because sucked by a series of suction holes 27 which, at an angular sector corresponding to an angle at the centre a of predetermined magnitude, are put in communication with a vacuum generation device, not shown in the FIGS., that puts under vacuum the central part of the cutting roller 25. When the sheets 11 reach point PT.sub.1 they are no more sucked by the suction holes and, if they have to be fed to the second path 103 as the sheets 11b of FIG. 1, they have to continue to adhere to the surface of the cutting roller 25. For this purpose, additional suction holes are provided which work in combination with a shaped hole. This is arranged to put in pneumatic communication the holes with the vacuum generation device at a predetermined position according to a principle that is known in the related field. In particular, the holes are put in pneumatic communication with ducts which extend longitudinally to the cutting roller. Therefore, the hole that is in pneumatic communication with the corresponding duct sucks the sheet 11 on the cutting roller 25 to move the same from the tangent point PT1 to the tangent point PT2 where is transferred on the transfer roller 45 and therefore fed to the interfolding zone 35 along the second feeding path 103 in order to be interfolded with a respective sheet 11a that is fed along the first feeding path 102. In a possible embodiment of the invention, not shown in the FIGS. for reasons of simplicity, a device can be provided for adjusting the level of vacuum generated by the aforementioned device for generating a determined level of vacuum. In particular, the aforementioned device for adjusting the level of vacuum can be configured to increase, or decrease the level of vacuum at least of the second holding elements 25b.

[0059] Downstream of the interfolding zone 35 separation elements can be provided for separating a stack being formed into small stacks 100, in a way that is not shown but that the skilled person is able to carry out for example as described in EP1415945 by folding fingers, or folding arms, or separators, etc.

[0060] According to further embodiments that are not shown, the first and/or the second holding elements 25a, 25b can be of mechanical type. In particular, the first and/or the second holding elements 25a, 25b can comprise mechanical clamps operated by cams, or other devices arranged to close and open the mechanical clamps according to suitable times and modality. For example, piezoelectric actuators can be used as for example described in WO2019/207434.

[0061] According to an embodiment of the invention that is diagrammatically shown in FIG. 8, the transfer roller 45 is provided with third holding elements 45b arranged to hold the sheets on a portion of the external surface 46. In FIG. 8, the portion 47 of the external surface 46 of the transfer roller that extends between the tangent points of the transfer roller 45 with the cutting roller and with the second folding roller 32.

[0062] According to an embodiment of the present invention, the third holding elements 45b can be configured to alternatively move between an activation configuration, in which the third holding elements 45b are arranged to hold the second plurality of sheets 11b on the portion 47 of the external surface 46, in such a way to transfer the same from the cutting roller 25 to the second folding roller 32, and a deactivation configuration, in which the third holding elements 45b are not arranged to hold the sheets of the second plurality of sheets and, therefore, all the sheets cut by the cutting roller 25 are arranged to be transferred from the cutting roller 25 to the first folding roller 31.

[0063] In the example of FIG. 8, the third holding elements 45b are of pneumatic type, and, therefore, comprises suction holes 45b which are pneumatically connected with a vacuum generation device. In this case, therefore, in the activation configuration, the third holding elements 45b, for example suction holes and a suction sector 49b, or a bell-shaped vacuum system, are arranged in pneumatic connection with the vacuum generation device, whilst in the deactivation configuration, the third holding elements 45b are not arranged in pneumatic communication with the aforementioned vacuum generation device and, therefore, in this configuration they do not hold the sheets 11 cut by the cutting roller 25 that, therefore, all reach the folding, or interfolding, section 35 through the first feeding path. For example, a vacuum generation device can be provided that is operatively connected through a pneumatic circuit only to the suction holes 45b. In this case, the activation/deactivation device 250 can be arranged to turn on or off the aforementioned vacuum generation device to arrange the third holding elements 45b, respectively, in a deactivation, or activation, configuration.

[0064] According to an embodiment of the invention, an activation/deactivation device 250 can be provided configured to arrange the aforementioned third holding elements 45b in the activation configuration, or alternatively, in the deactivation configuration. In the case in which the third holding elements 45b are of pneumatic type, as disclosed above with reference to FIG. 8, the aforementioned activation/deactivation device 250 can be an electro-valve positioned along the pneumatic circuit 200 which connects the vacuum generation device 350 with the suction holes 45b and that can be alternatively opened, or closed, for example operated by control unit 300 (FIG. 9).

[0065] According to an alternative embodiment of the invention, alternatively, or in addition to the third holding elements 45b of the transfer roller 45, the second holding elements 25b of the cutting roller 25 can be configured to be alternatively positioned in an activation configuration, in which are arranged to hold the sheets on the external surface at the second portion d2, as described above, or in a deactivation configuration, in which they are not arranged to hold the sheets 11 at the second portion d2 of the external surface. For example, analogously to what described above with reference to FIG. 9, the activation/deactivation device 250, diagrammatically shown in FIG. with a rectangular block, can be an electro-valve configured to connect, or disconnect, only the second holding elements 25b of the cutting roller 25, or also the third holding elements 45b of the transfer roller 45, this case is shown in FIG. 10, in order to arrange the only second holding elements 25b of the cutting roller 25, or the second holding elements 25b of the cutting roller 25 and the third holding elements 45b of the transfer roller 45, in the respective aforementioned activation configuration, or in the aforementioned deactivation configuration. Still in the case of FIG. 10, it is possible to provide a single vacuum generation device 350 pneumatically connected with the first holding elements 25a through the branch 251, con the second holding elements 25b through the branch 252 and with the third holding elements 45b through the branch 253. More in particular, in the example of FIG. 10, a first activation/deactivation device 250a for connecting or disconnecting (case shown in FIG. 10) the second holding elements 45b with/from the vacuum generation device 350, and a second activation/deactivation device, 250b for connecting or disconnecting (case shown in FIG. 10) the third holding elements 45b with/from the vacuum generation device 350, are provided.

[0066] According to an alternative embodiment not shown in the FIG. for reasons of simplicity, only an activation/deactivation device 250, for example an electro-valve, can be provided arranged to connect, or disconnect, at the same time, the second and the third holding elements 25b and 45b with/from the vacuum generation device 350.

[0067] The embodiments described above in particular with reference to the FIGS. from 8 to 10, allows to obtain a machine that is highly flexible, because it is able to produce both product of single fold type, when the aforementioned third holding elements 45b and/or the aforementioned second holding elements 25b are arranged in the activation configuration (analogously to what is shown in FIG. 1), and products of multi fold type, i.e. with 3, or 4, panels, when the aforementioned third holding elements 45b and/or the aforementioned second holding elements 25b are arranged in the aforementioned deactivation configuration (FIGS. 8, 9 and 10) and, therefore, using only the first feeding path 102 to feed the sheets 11 to the folding zone 35. In this case, the overlapping of the sheets 11 is obtained by the difference in the velocity between the velocity vT of the cutting roller 25 and the velocity vP of the folding rollers 31 and 32. In particular, when the velocity vT is about 3/2 of the velocity vP an overlapping of two successive sheets 11 is obtained for ⅓ of their length when the sheets move from the cutting roller 25 to the folding roller 31. More precisely, in this working configuration, the head of the sheet 11 coming from the cutting roller 25 immediately moves on the folding roller 31, whilst the tail of the same sheet, due to the aforementioned difference in the velocities of the cutting roller 25 and the folding roller 31, is lifted forming a bent and, then, falls on the head of the following sheet (see FIGS. 8-10).

[0068] Furthermore, the length of each sheet 11, will be such to be folded two times by the folding rollers 31 and 32 obtaining a sheet with three panels overlapped for a panel to the following sheet.

[0069] In general, using the first feeding path 102 only, it is possible to obtain a stack 100 of sheets of “multi-fold” type having also more than three panels, i.e. obtained by folding more than two times a single sheet, changing the ratio between the velocity vT and the velocity vP. In any case, the velocity vT is, advantageously, always higher than the velocity vP. By changing the aforementioned ratio of velocity it is possible to change, according to the desired product, also the amount of the overlapping of two following sheets.

[0070] According to another embodiment not shown in the FIGS. for reasons of simplicity, the first, the second and the third holding elements 25a, 25b, 45b can be put in pneumatic communication with respective devices for generating vacuum through respective pneumatic circuits. In this case, in order to activate, or deactivate, the first, the second and the third holding elements 25a, 25b, 45b it is possible, respectively, to turn on or off the respective devices for generating vacuum, independently with respect to the others.

[0071] In a further embodiment the interfolding machine 1, according to the invention, in the case the second and the third holding elements 25b and 45b are of pneumatic type, when the third holding elements 45b are arranged in the deactivation configuration and, instead, the second holding elements 25b of the cutting roller 25 are arranged in the aforementioned activation configuration, these can be advantageously arranged, for example by an adjustment device, not shown in the FIG. for simplicity reasons, in such a way to have a level of vacuum lower than the case in which the third holding elements are arranged in the activation configuration and the machine produces the aforementioned stacks of single-fold sheets.

[0072] In another embodiment of the invention not shown in the FIGS. for simplicity reasons, the transfer roller 45 can be arranged in a deactivation configuration simply removing the same, for example by a displacement system, in particular an automatic sliding system, or a carousel, from the working position of FIG. 1. In this case, an activation/deactivation device can be provided arranged to move, as described above, the transfer roller 45 closer to or away from the cutting roller 25.

[0073] The foregoing description exemplary embodiments of the invention will so fully reveal the invention according to the conceptual point of view, so that others, by applying current knowledge, will be able to modify and/or adapt for various applications such embodiment without further research and without parting from the invention, and, accordingly, it is therefore to be understood that such adaptations and modifications will have to be considered as equivalent to the specific embodiments. The means and the materials to realize the different functions described herein could have a different nature without, for this reason, departing from the field of the invention. It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation.