Interfolding machine for producing stacks of interfolded sheets, and method for producing stacks of interfolded sheets

Abstract

An interfolding machine (1) for producing stacks (100) of sheets interfolded according to a predetermined interfolding configuration, starting from at least one web (50) of paper, or similar products, comprises an advancement section (10), which carries out the tensioning and the unwinding of the web (50) along a predetermined advancement path (101) for feeding the same to a cutting section (20), where the web of paper (50) is divided in a series of sheets (11) of predetermined length, at a cutting point positioned between a cutting roll (25) and a counter-cutting device (27). Downstream of the cutting section (20) an interfolding section (30) is provided comprising a first folding roll (31) and a second folding roll (32) counter-rotating to each other. The first and second folding rolls (31,32) are adapted to rotate about a respective rotation axis (131, 132), and are configured to fold, at a folding zone (35), the aforementioned plurality of sheets (11) in a plurality of panels and to form a stack (100) of interfolded sheets. A threading group (200) is, furthermore, provided to engage a wing (51) of the or each web of paper (50) during a threading step preceding the production step and to cause the same to move along a predetermined threading path (105).

Description

[0001] TITLE

[0002] INTERFOLDING MACHINE FOR PRODUCING STACKS OF INTERFOLDED SHEETS, AND METHOD FOR PRODUCING STACKS OF INTERFOLDED SHEETS

[0003] DESCRIPTION

[0004] Field of the invention

[0005] The present invention relates to machines for producing packages of sheets of paper material , in particular packages of interfolded sheets , and relates to a structure of machine for interfolding such sheets .

[0006] The invention also relates to a method for producing packages of such products of interfolded sheets .

[0007] Description of the prior art

[0008] As it is known, many machines and processes are used in the paper industry, for producing packages having a certain height of napkins , towels and similar articles of paper material .

[0009] In many applications , the packages are obtained by folding the sheets in an "interf olded" way, that means enclosing within each fold a wing of the previous sheet and a wing of the following sheet . In this way, when a sheet is extracted from the package , at the moment of using the product , also a wing of the following sheet is extracted with consequent practicality of use for certain types of users . Among the possible ways to interfold are known L, or V, interfolded, with two panels ( single- fold) , or Z or W, respectively, with three and four panels

[0010] (multi- fold) . In other applications , the packages are obtained by folding the sheets in a not interfolding way, by folding the not overlapped sheets , or overlapped sheets , but holding them at one side such that no panel of a previous sheet is enclosed in a wing of the immediately successive sheet .

[0011] The interfolding machines normally provide to unwind a web of paper starting from a reel . The web of paper is cut in sheets of predetermined length that are , then, fed overlapped to each other for a predetermined portion at folding rolls counter-rotating to each other .

[0012] More precisely, as for example described in US 6228014 , the cut in sheets of the webs is carried out on cutting rolls which alternatively interact with relative counterblades . In the case of "L" or "V" interfolded ( singlefold) the webs are cut in order to form a staggered sequence of sheets coming from two di f ferent directions . Therefore , the sheets coming from one or the other direction are fed in a staggered and alternated way to the folding rolls in such a way that the sheet coming from a first direction is overlapped to a portion of the sheet coming from the second, and vice versa . Generally, the overlap is about hal f a sheet .

[0013] In the case of " Z" or "W" interfolding machine (multifold) only one web of paper is fed and is cut forming a continuous sequence of single sheets of predetermined length . The sheets are , then, staggered one another, that means partly overlapped to one another in order to form a continuous flow of partly overlapped sheets which is fed to a couple of folding counter-rotating rolls .

[0014] Other types of interfolding machine of prior art can produce both packages of interfolded sheets with a single fold, that means of "L", or "V", type, and packages of interfolded sheets with multiple folds, that means of "Z", or "W" type. In the case that the machine produces packages of interfolded sheets of "L", or "V", type, it, generally, provides a series of rolls comprising a cutting roll which alternately distributes the cut sheets towards a first or a second feeding line. Each feeding line moves the sheets to respective folding rolls which, therefore, fold or interfold the sheets depending on the set mode. Among the cutting roll and the folding rolls, a transfer group is provided comprising a series of rolls which carries out a difference of length 81 between the path of the second feeding line and the path of the first feeding line. In this way, the sheets of the first and second feeding lines arrive at the interfolding section staggered from each other of the portion that is needed to obtain the desired interf olding . The transfer group has the function of lengthening the path of the feeding line where are introduced with respect to the other feeding line, of a length Al equal to half a sheet, or of a length equal to odd multiples of half a sheet, for example a sheet and half, or two sheets and half. In the case that the machine produces "Z" or "W" folding products, the cutting roll feeds only one line of the machine where the partial overlap is provided of the continuous flow of sheets which, then, are moved towards the couple of folding rolls. However, overall, this type of interfolding machines from the cut to the folding need at least of 8 rolls. Machines of this type are, for example, described in EP2462044. In the single- fold machines two webs of paper unwound starting from two reels are provided . The two webs of paper are wrapped on two respective cutting groups each comprising a cutting roll and a counter-cutting element cooperating with each other to form two continuous flows of sheets of predetermined length . Downstream of the two cutting groups two folding counter-rotating rolls are present to which the two flows of sheets are fed in a staggered way, that means in order to obtain an overlap of a portion of the sheets necessary to carry out the desired interfolding configuration . In this type of machine it is , therefore , necessary to have two unwinders for each web of paper, and, in case , two embossing groups in case of embossed products . Machines of this type are , for example , described in patents EP1630118 , EP0982256 .

[0015] In all the existing interfolding machines , however, before starting the machine for producing the stacks of interfolded products , it is necessary that a worker manually positions the or each web of paper on the or each respective cutting roll , and, therefore , he starts the machine for beginning the production of the stacks of interfolded sheets . This operation that is called in j argon "threading" , however, as anticipated above , is manually carried out by a worker and, therefore , it requires long times to be completed with consequent loss of productivity . Furthermore , i f the threading of the web of paper has to be carried out once that the machine has been already started, that means during a production cycle , for example the need to discharge a portion of web on which defects are present , or due to a sudden breakage of the web of paper, the drawbacks linked to this operation are even more evident . In fact , in these circumstances , it is necessary to stop the machine and to call a worker who has promptly to intervene with consequent loss of time , raw material and productivity .

[0016] Other technical solutions of prior art with analogous drawbacks are described in JP2015016355 , W02005 / 092614 and EP4067276 .

[0017] Summary of the invention

[0018] It is , therefore , an obj ect of the present invention to provide an improved interfolding machine of sheets which is able to overcome the aforementioned drawbacks of the interfolding machines of prior art .

[0019] It is , in particular, an obj ect of the invention to provide an interfolding machine of sheets which allows to simpli fy and speed up the threading step of the or each web of paper material up to a zone positioned downstream of the cutting rolls before starting a production step .

[0020] It is , furthermore , an obj ect of the present invention to provide a method for producing stacks of interfolded sheets having the same advantages .

[0021] These and other obj ects are achieved by the interfolding machine , according to the present invention, for producing stacks of interfolded sheets starting from at least one web of paper, or similar material , said machine comprising :

[0022] - an advancement section configured to cause said web of paper to move along a predetermined advancement path;

[0023] - a cutting section comprising a cutting roll having an external surface , and a counter-cutting device configured to cooperate with each other in order to cut said or each web of paper in a respective plurality of sheets of predetermined length, said cutting roll being provided with suction holes configured to cause said web to adhere on a predetermined portion of said external surface ;

[0024] - an interfolding section comprising a first folding roll and a second folding roll counter-rotating to each other, said first and second folding rolls being configured to fold, at a folding zone , during a production step said plurality of sheets in a plurality of panels and to form said stack of sheets interfolded according to said predetermined interfolding configuration; whose main characteristic is to provide , furthermore , a threading group configured to engage a wing of said or each web of paper during a threading step which precedes said production step and to cause said or each web of paper to move along a predetermined threading path which coincides with said advancement path at least up to said cutting roll .

[0025] Other technical characteristics of the present invention are set out by the dependent claims .

[0026] In particular, the threading group can be , furthermore , configured to disengage the wing of web of paper at a predetermined position of the threading path such to allow the suction holes of the cutting roll to suck the web of paper and to cause the same to adhere to the external surface .

[0027] In particular, a displacement device can be , furthermore , provided configured to arrange said counter- cutting device between a cutting position where is positioned at a first predetermined distance dl from said cutting roll such to cut said web in said plurality of sheets during said production step, and a rest position where said counter-cutting device is positioned at a second distance d2 from said cutting roll during said threading step .

[0028] In particular, the aforementioned threading group can comprise at least one flexible threading element , preferably at least one threading belt . More in particular, the threading member, for example the threading belt, can be wrapped around a plurality of rolls arranged to define a predetermined closed path configured in such a way to move the web of paper along the aforementioned threading path . More in particular, the aforementioned threading path can coincide with said predetermined advancement path at least up to said cutting roll .

[0029] In an embodiment of the invention, the threading group can comprise at least one deviating roll configured to deviate the web of paper along a branch del predetermined threading path which diverges from said predetermined advancement path .

[0030] In particular, the threading group can comprise dragging elements configured to cause the aforementioned displacement of the web of paper along said predetermined threading path .

[0031] More in particular, the aforementioned dragging elements can comprise a first and a second roll counterrotating with respect to each other .

[0032] In particular, the aforementioned threading group can comprise a cutting device configured to cut the web of paper in a predetermined position of the aforementioned branch of the threading path which diverges from said predetermined advancement path .

[0033] More in particular, the aforementioned cutting device can be arranged to cut the web of paper, once that the suction holes of the cutting roll are arranged to suck a determined portion of said web of paper positioned upstream of the aforementioned dragging elements .

[0034] In particular, a push device can be , furthermore , provided configured to push the web towards the cutting roll at a predetermined position of the predetermined threading path, in such a way to facilitate the web to be sucked by the aforementioned suction holes and to adhere to the external surface of the cutting roll .

[0035] In particular, the aforementioned push device can be of pneumatic type .

[0036] In an alternative embodiment of the invention, the aforementioned push device is of mechanical type .

[0037] According to another aspect of the invention, a method for producing stacks of sheets interfolded according to a predetermined interfolding configuration starting from at least a web of paper, or similar material , comprises the steps of :

[0038] - advancing said web of paper along a predetermined advancement path;

[0039] - cutting by a cutting roll having an external surface and a counter-cutting device configured to cooperate with each other in a respective plurality of sheets of predetermined length, said cutting roll being provided with suction holes configured to cause said web to adhere on a predetermined portion of said external surface ;

[0040] - folding at a folding zone , during a production step, by a first and a second folding roll counterrotating to each other, said plurality of sheets in a plurality of panels in such a way to form said stack of interfolded sheets according to said predetermined interfolding configuration; wherein a threading step is , furthermore , provided which precedes said production step and wherein said threading step is carried out by a threading group configured to engage a wing of said or each web of paper, and to cause said or each web of paper to move along a predetermined threading path which coincides with said advancement path at least up to said cutting roll .

[0041] In particular, a step can be , furthermore , provided for disengaging said wing of said web of paper at a predetermined position of said threading path such to allow said suction holes of said cutting roll to suck said web of paper and to cause the same to adhere to said external surface .

[0042] In an embodiment of the invention, the aforementioned step for engaging the wing of the or each web of paper provides to engage the wing in a flexible element of a threading group comprising a dragging member configured to cause the web of paper to move along the aforementioned predetermined threading path .

[0043] In particular, the threading step can comprise , furthermore , the steps of :

[0044] - stopping the advancement of the wing of said or each web of paper by stopping the advancement of said flexible element ;

[0045] - feeding the web of paper by the dragging member ;

[0046] - cutting the web of paper by a cutting device ;

[0047] - holding the web of paper on the external surface of the cutting roll by activating the suction holes .

[0048] More in particular, the step for holding the web of paper on the external surface of the cutting roll can be carried out by activating the suction holes before the cutting step of the web of paper by a cutting device .

[0049] Brief description of the drawings

[0050] Further features and advantages of the interfolding machine according to the invention will be clearer with the following description of its exemplary embodiments , exempli fying but not limitative , with reference to the attached drawings in which :

[0051] - Fig . 1A diagrammatically shows a side elevation view, partly sectioned, a first embodiment of the interfolding machine of multi-fold type , according to the invention, during a production step ;

[0052] - Figures from IB to ID diagrammatically show a side elevation view, partly sectioned, of the interfolding machine of figure 1A in some moments of the threading step ;

[0053] - Fig . IE diagrammatically shows a side elevation view, partly sectioned, of an alternative embodiment according to the invention of the interfolding machine of multi-fold type of figure 1A;

[0054] - Fig . IF diagrammatically shows a side elevation view, partly sectioned, of another alternative embodiment according to the invention of the interfolding machine of multi- fold type of figure 1A;

[0055] - Fig . 2 diagrammatically shows a cross-sectional view of a possible embodiment of a cutting roll which can be used in the interfolding machine according to the invention;

[0056] - Fig . 3 diagrammatically shows a plan view of a possible embodiment of some components of a threading group provided from the interfolding machine according to the invention;

[0057] - Figures from 4A to 4C diagrammatically show a side elevation view, partly sectioned, of some moments of the threading step of an alternative embodiment of the interfolding machine of multi- fold type of figure 1A;

[0058] - Figures from 5A to 5C diagrammatically show a side elevation view, partly sectioned, of some moments of the threading step of another alternative embodiment of the interfolding machine of figure 1A;

[0059] - Fig . 6 diagrammatically shows a side elevation view, partly sectioned, of still another alternative embodiment according to the invention of the interfolding machine of figure 1A;

[0060] - Figures 7A and 7B diagrammatically show a side elevation view, partly sectioned, of some moments of the threading step of a further alternative embodiment of the interfolding machine of figure 1A;

[0061] - Figures 8A and 8B diagrammatically show a side elevation view, partly sectioned, of some moments of the threading step of still a further alternative embodiment of the interfolding machine of figure 1A;

[0062] - Figures 8C and 8D diagrammatically show a side elevation view, partly sectioned, some moments of the threading step of still a further alternative embodiment of the interfolding machine of figure 1A;

[0063] - Figures from 9A to 9C diagrammatically show a side elevation view, partly sectioned, some moments of the threading step of still a further alternative embodiment of the interfolding machine of figure 1A;

[0064] - Fig . 10 shows a block diagram of a possible succession of steps which can be carried out by the interfolding machine according to the invention to move from the threading step to the production step .

[0065] Detailed description of a preferred exemplary embodiment of the invention

[0066] With reference to figure 1A, in an embodiment of the invention, an interfolding machine 1 for producing stacks 100 of sheets interfolded according to a predetermined interfolding configuration, for example a "V", " Z" or "W" configuration, starting from a web 50 of paper, or similar products , provides an advancement section 10 , which, during a production step, diagrammatically shown in figure 1A, where the aforementioned stacks 100 of interfolded sheets are produced, carried out , for example by advancement rolls 15 , the tensioning and the unwinding of web 50 along a predetermined advancement path 101 at a predetermined advancement speed .

[0067] Still during the production step, the advancement section 10 feeds the web of paper 50 to a cutting section 20 , where the web of paper 50 is divided into a series of sheets 11 of predetermined length, at a cutting point placed at a cutting section 20 . This , in particular, comprises a cutting roll 25 provided with a predetermined number of cutting blades 22 , and a counter-cutting device 27 provided with a counter-blade 28 adapted to cooperate with the cutting blades 22 for carried out the aforementioned division of the web of paper 50 into sheets 11 . In particular, the aforementioned cutting point is positioned between the cutting roll 25 and the countercutting device 27 .

[0068] In particular, the cutting roll 25 , as diagrammatically shown in figure 2 , is provided with suction holes 26 . In particular, the suction holes 26 can be organi zed in a plurality of rows of holes . These are selectively put in communication with a device for generating a determined vacuum degree at predetermined portions of the external surface 21 of the cutting roll 25 . In this way, the web 50 and the sheets 11 are caused to adhere on the surface of the cutting roll 25 at the aforementioned predetermined angular portions .

[0069] Downstream of the cutting section 20 , an interfolding section 30 is provided comprising a first folding roll 31 and a second folding roll 32 counter-rotating to each other . The first and second folding rolls 31 and 32 are adapted to rotate about a respective rotation axis 131 , and 132 , and are configured to fold, at a folding zone 35 positioned between them, the aforementioned plurality of sheets 11 in a plurality of panels in such a way to form the aforementioned stack 100 of sheets interfolded according to a predetermined interfolding configuration . In particular, with the term "panel" it is intended each portion of the sheet which is obtained by folding a determined number of times the sheet 11 .

[0070] In particular, the interfolding group 30 can be , furthermore , provided, as known to a skilled person in the art , with a separation group 80 , advantageously comprising a first and a second separation member 81 and 82 , configured to separate a completed stack of interfolded sheets , from a following stack of sheets being formed . More in particular, the interfolding group 30 can, furthermore , comprise a detachment group, not shown in figure for simplicity, but however of known type to a skilled person in the art , configured to facilitate the detachment of the sheets from the surface of the folding rolls 31 and 32 .

[0071] As diagrammatically shown in the embodiment of the figures from 1A to IE , with reference ad an interfolding machine 1 of multi- fold type where , as known, only one web of paper 50 is provided which, during the production step of figure 1A is fed along an advancement path 101 by a feeding group 10 , comprising, generally, a determined number of advancement rolls 15 . In particular, according to the invention, a threading group 200 , which is not shown in figure 1A for clarity reasons , is , furthermore , provided configured to engage a wing 51 of web of paper 50 during a threading step which precedes the aforementioned production step and to cause the web of paper 50 to move along a predetermined threading path 105 ( figures 1B- 1D) .

[0072] The threading group 200 can be , furthermore , configured to disengage the wing 51 of web of paper 50 at a predetermined position of the threading path 105 such to allow the suction holes 26 of which the cutting roll 25 is provided with ( see figure 2 ) to suck the web of paper 50 and to cause them to adhere on the external surface 21 of the same , in order to convey the web 50 towards the folding rolls 31 and 32 by deviating the web 50 from the threading path 105 to the advancement path 101 downstream of the cutting section 20 ( figure ID) .

[0073] In particular, as indicated in the figures from 1A to ID, the threading path 105 coincides with the aforementioned advancement path 101 at least up to the cutting roll 25, or up to a position in proximity of this .

[0074] In an embodiment of the invention and diagrammatically shown in figure 2 , the cutting roll 25 can comprise an external tubular body 25a and an internal tubular body 25b . More precisely, the external tubular body 25a is arranged to rotate about a rotation axis 125, while the internal tubular body 25b is fixed and is provided with a longitudinal chamber 23 in pneumatic connection with a sucking device , not shown in figure for simplicity, able to generate a determined vacuum degree within the longitudinal chamber 23 same . Furthermore , the internal tubular body 25b is provided with at least an aperture , advantageously a plurality of aperture , arranged to put in pneumatic communication the suction holes 26 of the external tubular body 25a at predetermined angular portions in such a way to cause the web of paper 50 to be sucked . For example , the or each aperture 24 is associated to a first and a second longitudinal sealing member 29a and 29b in such a way to define a suction chamber at which the holes 26 are put on suction .

[0075] In other embodiments not shown in the cutting roll 25, the suction system can be obtained in different way, for example, associating the suction holes 26 to a suction longitudinal chamber which extends substantially parallel to the rotation axis 125. Each longitudinal suction chamber is selectively put on suction for a predetermined angular portion by a vacuum distribution device arranged at an end of the cutting roll 25.

[0076] Advantageously, the suction holes 26 can be arranged according to longitudinal rows , in such a way that one or more rows of holes hold an initial portion of a sheet 11 and one or more rows of holes hold an end portion of a sheet 11 .

[0077] More in particular, as diagrammatically shown in figure 3 , the threading group 200 can comprise an engagement element 205 configured to engage the aforementioned wing 51 of web of paper 50 . In particular, the aforementioned engagement element 205 is arranged to move along a predetermined closed path 106 such to displace the web 50 along the threading path 105 .

[0078] Still with reference to figure 3 , the threading group 200 which, advantageously, develops laterally to the cutting section 20 , can comprise at least one threading member 210 , preferably at least one flexible threading element , for example one threading belt 210 wrapped around a plurality of rolls 215 in such a way to define the aforementioned closed path 106 and, therefore , to move the web of paper 50 along the aforementioned threading path 105 . This , as anticipate above , coincides , in particular, with said predetermined advancement path 101 at least up to the cutting roll 25 , or at least up to a position in proximity of this .

[0079] In an embodiment of the invention, not shown for simplicity, the engagement element 205 is not present . In this case, not shown in figure for simplicity, the wing 51 of web of paper 50 can be directly engage to the flexible element 210 , for example to the threading belt 210 , which, at this purpose , can be , advantageously, provided with at least an engagement aperture , in particular an engagement slot , arranged to engage the web 50 .

[0080] In particular, as diagrammatically shown, for example in the figures from 4A to 6 , a displacement device 60 , can be , furthermore , provided configured to move the countercutting device 27 between a cutting position ( see figures 1A and 5C ) where is arranged at a first predetermined distance dl from the cutting roll 25 such to allow to the cutting roll 25 to cooperate with the counter-cutting device 27 for cutting the web 50 in the aforementioned plurality of sheets 11 during the aforementioned production step, and a rest position, where the countercutting device 27 is , instead, positioned at a second distance d2 from the cutting roll 25 during the threading step greater than the aforementioned first distance dl , that means d2>dl ( see figures from IB to 5B ) .

[0081] Furthermore , the threading group 200 can be provided with a dragging member 203 comprising, for example dragging elements 205 and 206 configured to cause the web 50 to be moved along the predetermined threading path 105 .

[0082] In particular, the dragging elements 205 and 206 can comprise a first roll 205 and a second roll 206 counterrotating to each other, preferably having a respective external knurled, or rough, surface and arranged to form a dragging groove 207 through which the web 50 passes for tensioning the web 50 same and for causing the same to move along the aforementioned threading path 105 . the dragging member 203 can be positioned upstream of the cutting section 20 as shown in the figures from lb to le, or downstream of the cutting section 20, as, instead, shown in the alternative embodiments of figures 5a, 5b and 6. With the expression downstream of or upstream position of the cutting section 20 it should be understood a position referred to the advancement direction of web 50 along the advancement path 101 . Even more precisely in order to position downstream or upstream the cutting section 20 , it is meant a position with reference to the cooperation point between blade 22 and counter-blade 28 of the cutting group 20 , in the advancement direction of the web 50 along the advancement path 101 .

[0083] The threading group 200 can, advantageously, comprise at least one deviating roll 201 configured to deviate the web 50 along a branch 106 of the predetermined threading path 105 at which the threading path 105 diverges from said predetermined advancement path 101 .

[0084] Preferably, the deviating roll 201 is positioned upstream of the cutting section 20 in advancement direction of the web 50 along the advancement path 101 . More precisely, with position upstream of the cutting section 20 it is intended a position upstream of the point of cooperation of the blade 22 and the counter-blade 28 in the advancement direction of web 50 along the advancement path 101 .

[0085] The threading group 200 can optionally comprise a cutting device 250 configured to cut the web 50 along the threading path 105 once that the suction holes 26 of the cutting roll are arranged to suck the web 50 .

[0086] In an alternative embodiment diagrammatically shown in figure IB, the cutting device 250 can be positioned downstream of the deviating roll 201 along the threading path 105 . In a further embodiment , diagrammatically shown in the figures I F and 5C for an interfolding machine 1 of multi- fold type , in figure 7B for an interfolding machine 1 of single- fold type, and in figure 8B in the case of a further alternative embodiment of the interfolding machine 1 , the cut of the web 50 , once correctly threaded, can be carried out by the cutting group 20 .

[0087] As diagrammatically shown in figure IE , the threading group 200 can, optionally, comprise a push device 70 . This can be configured to push the web 50 towards the cutting roll 25 at a predetermined position of the aforementioned predetermined threading path 105 . For example , the push device 70 can be of pneumatic type , for example an air j et , or of mechanical type, for example comprising at least one pneumatic or electric or hydraulic actuator . For example , the push device 70 can be a roll moved by the aforementioned actuators to be move towards to or away from the cutting roll 25 .

[0088] With reference to figures from IB to ID for the case of an interfolding machine of multi- fold type , the operational threading mode can provide to operate the threading member 210 by at least a motor, not shown in figure for simplicity, in order to cause the web 50 to advance along the threading path 105 towards the cutting section 20 and, therefore , also along the advancement path 101 , which, as described above , coincides with the threading path 105 at least up to the cutting roll 25 . In order to help the web 50 to be gradually stretched on the advancement rolls 15 and, therefore , to be positioned along the advancement path 101 , it is possible to cause the advancement rolls 15 and the cutting roll 25 to rotate . In proximity of the cutting roll 25 , the web 50 is wrapped about the deviating roll 201 so that the wing 51 of web 50 can follow the threading path 105 diverting from the advancement path 101 up to move through the dragging groove 207 of the dragging member 203 .

[0089] When the wing 51 of web 50 reaches a position downstream of the dragging groove 207 , the threading belt 210 can be stopped ( figure 1C ) . In this case , the web 50 is caused to advance along the threading path 105 by operating the dragging member 203 and the advancement rolls 15 on which the web 50 is at least partly stretched . In this stage , the wing 51 of web 50 is still and engaged to the threading belt 210 while the remaining part of the web 50 is fed by the dragging member 203 forming an excess of web 50 which can be collected at an accumulation zone 38 . The accumulation zone 38 can preferably have an accumulation device 37 , for example a container, or simply an accumulation plane , as for example a platform . Preferably, the accumulation device 37 can comprise a discharging belt , not shown in figure for simplicity, for discharging the web 50 accumulated at the end of the threading procedure outside the interfolding machine 1 . In particular, the discharging conveyor can be configured to discharge the accumulated web outside the protection carter of the interfolding machine 1 .

[0090] When the web 50 is at least partly stretched on the deviating roll 201 , in particular when is stretched at least for 10% of the width of web 50 , preferably at least for 25% , the web 50 same is caused to adhere to the external surface 21 of the cutting roll 25 . Preferably, it is possible to provide that the web 50 is completely stretched on the deviating roll 201 before causing the web 50 to adhere to the external surface 21 of the cutting roll 25 .

[0091] In order to cause the web 50 to adhere to the external surface 21 of the cutting roll 25 can be activated for sucking the suction holes 26 i f they were not previously already activated . Alternatively, it is possible to activate the suction holes 26 also during the previous steps .

[0092] Advantageously, in order to facilitate the adhesion of web 50 to the external surface 21 of the cutting roll 25 , it is possible to provide a step for stopping the advancement of web 50 by the dragging member 203 , while the remaining part of the web 50 upstream of the cutting section 20 is fed by the advancement rolls 15 .

[0093] I f present , it is possible to operate the cutting device 250 for cutting the web 50 at a zone positioned between the deviating roll 201 and the dragging member 203 ( see figure ID) . In this way, the dragging member 203 can be operated for feeding towards the accumulation zone 38 the residual web 50 arranged between the deviating roll 201 and the dragging member 203 .

[0094] The following step provides to cause the web 50 to advance by the advancement rolls 15 and the cutting roll 25 in such a way that the web 50 follows the advancement path 101 , while the part of the web 50 which is threaded along the threading path 105 , downstream of the deviating roll 201 , remains still .

[0095] In case that the cutting device 250 is present , the residual web 50 ' arranged downstream of the deviating roll 201 along the threading path 105 can be absent because the dragging member 203 can have already accumulated the same at the accumulation zone 38 . When the web 50 goes beyond the counter-cutting device 27 and, preferably, goes beyond the counter-blade 28 , it is possible to operate a displacement device 60 for positioning the counter-cutting device 27 in the cutting position . It is useful to remember that , normally, during the threading step, the cutting section 20 is open, which means in the rest position, where the counter-cutting blade is far removed from and does not cooperate with the cutting blade 22 .

[0096] In this step, i f the cutting device 250 is not present , as for example shown in the embodiment of figures IE and I F, or in the alternative embodiments of figures 4A-4C, or also in the embodiment of figures 5A-5C, or of figures 8C and 8D, the blade 22 and the counter-blade 28 cut the web 50 dividing a waste portion 50 ' which is threaded along the threading path 105 from the remaining web 50 . Then, the dragging member 203 , i f present , can be operated for feeding the portion of web 50 ' comprised between the cutting roll 25 and the dragging member towards the accumulation zone 38 ( see figure 5C ) . The web 50 threaded along the advancement path 101 is held by the suction holes 26 of the cutting roll 25 or, when they are organi zed in a plurality of rows , by at least one row of holes of the plurality of suction holes 26 as it happens during the production step .

[0097] Finally, when the web 50 is completely stretched on the cutting roll 25, the threading step is completed and it is possible to start the production step of the interfolding machine 1 in order to obtain the stacks 100 of interfolded sheets . The portion of web 50 which is not completely stretched along the advancement path 101 and on the cutting roll 25 which has been fed towards the folding rolls 31 and 32 , can be accumulated downstream of these, in particular, as in the case that is diagrammatically shown in figure 4B, at a formation device 102 , at which during the production step the interfolded sheets are accumulated to form a stack 100 at a time, for example a formation table of the type described in EP1640305, or EP1415945, or a formation device 102 which provided to move the completed stack 100 at a discharge zone, as for example described in WO2022 / 238949 . In this case , therefore , the accumulation zone 38 coincides with the formation device , or the trans fer device 102 ( figures 4B and 8B ) . In particular, in this case , the function of the accumulation device 37 can be carried out by the formation device 102 same which, at the end of the threading step, can discharge the accumulated web 50 by the conveyor belt which is, normally, used to discharge the completed stacks 100 from the interfolding machine 1 , preferably at the opposite side with respect to the direction where the completed stacks 100 are discharged during the production step . At this purpose, it is suitable to specify that in order to discharge the residual portion 50' of web 50 accumulated on the formation device 102 , a supplementary cut is , preferably, carried out to disengage the wing 51 , or however the end of web 50 , which is engaged to the threading member 210 , and, thus , allowing to discharge the residual portion 50 ' from the machine 1 as described above .

[0098] An alternative embodiment of the procedure can provide to cause the web 50 to adhere on the external surface 21 of the cutting roll 25 only at the moment that the web 50 is completely stretched on the deviating roll 201 . In this case, incompletely stretched web 50 is not formed downstream of the folding rolls 31 and 32 and all the residual web 50 ' of the threading step is accumulated at the accumulation zone 38 .

[0099] In this case when the web 50 completely stretched on the cutting roll 25 is caused to adhere to the same , the interfolding machine 1 can start the step for producing the stacks 100 . The passage of the stacks 100 from the threading step to the production step can be carried out in continuous that means without stopping the feeding of the web 50 .

[0100] Optionally, when present, it is possible to operate the push device 70 in order to facilitate the web 50 to adhere to the external surface 21 of the cutting roll 25 , when it is necessary to move the web 50 from the threading path 105 to the advancement path 101 downstream of or next to the deviating roll 201 .

[0101] In a first and a second alternative embodiment of the invention diagrammatically shown in the figures 5A-5C and 6 , the threading path 105 can extend up to downstream of the cutting roll 25 . In particular, in this case , the closed path 106 defined by the flexible element 210 , preferably by the threading belt , not shown in figure for simplicity, will be wrapped around a series of rolls arranged to make the aforementioned closed path 106 . In particular, the threading belt 210 will follow a threading path adapted to cause the wing 51 of the web of paper 50 to be introduced into the dragging groove 207 of the dragging member 203 , in such a way to be able to drag the web 50 once that the threading belt 210 is stopped .

[0102] In these embodiments , the deviating roll 201 is not present because the threading path 105 coincides with the advancement path 101 up to a position downstream of the cutting roll 25 .

[0103] In the block diagram 300 of figure 10 , the main operational steps of the method for producing stacks of interfolded sheets according to the invention are diagrammatically shown . In particular, a step is provided for threading the web 50 by the threading belt 210 up to the dragging member 203 , block 301 . A step follows of stopping the threading belt 210 causing the web 50 to move by the dragging member 203 , block 302 . Therefore , once that the web 50 is completely stretched on the cutting roll 25 , a step is provided for operating the displacement device 60 for moving the counter-cutting device 27 from the rest position to the cutting position, block 303 . A step can be , furthermore , provided, i f they are not already activated, for activating the suction holes of the cutting roll 25 . Then, a step for cutting the web 50 by the cutting section 20 follows , block 304 . Then, a step follows for feeding by the dragging member 203 the residual web 50 ' comprised between the cutting roll 25 and the dragging member 33 towards the accumulation zone 38 .

[0104] In particular, the step for cutting the web 50 can occur without stopping the dragging member 203 .

[0105] Also in this case , once that the cutting section 20 has carried out the cut of the web 50 , the interfolding machine 1 can start the production without stopping, i . e . moving from the threading step to the production step of the stacks 100 without stopping the machine . The solution of figures 5A and 5B is di f ferent from that of figure 6 only for the threading path 105 which, in the case shown in figure 6 , provides , in particular, to move the paper, also during the threading step, between the cutting roll 25 and a trans fer roll 40 , in particular positioned downstream of the cutting roll 25 . In this case , the cutting roll 25 and the trans fer roll 40 , during the threading step, can be kept in rotation .

[0106] With reference to figure 6 , in a further alternative embodiment , the threading path 105 provides to move the web 50 through the "groove" formed by the cutting roll 25 and the trans fer roll 40 and, then, to feed the web 50 directly towards the folding rolls 31 and 32 . In this case , the dragging member 203 can be formed by the cutting roll 25 where the holes 26 are operated to suck and the accumulation zone 38 to accumulate the web 50 fed during the threading step can be positioned in the formation device 102 of the stacks 100 . In this case , furthermore , the function of the accumulation device 37 can be carried out by the formation device 102 of the stacks 100 which, at the end of the threading, can discharge the accumulated web 50 by the conveyor belt which is normally used to discharge the completed stacks 100 from the interfolding machine 1 .

[0107] The threading group 200 as described above , can be implemented in an interfolding machine of " single- fold" type for example described in US 6228014 , or in WO2020 / 161571 . In particular, in this case , as diagrammatically shown in the figures 7A and 7B, the webs 50a and 50b are cut in respective pluralities of sheets I la and 11b, at a first and a second cutting group 20a and 20b, respectively, each of which comprising a cutting roll 25a and 25b arranged to cooperate with each other with a respective counter-cutting device 27a and 27b . In particular, in WO2020 / 161571 the cutting rolls 25a and 25b are also folding rolls 31 and 32 . In particular, in figure 7A, two di f ferent possible configurations for the threading device 200 are shown, and precisely one acting at the left side of machine 1 of figure 7A, and one acting at the right side of machine 1 . In particular, the interfolding machine 1 can provide for both the webs 50a and 50b the same threading group 200 , that means only one among those shown for webs 50a and 50b .

[0108] In the first case , which relates to the web 50a, the dragging member 203 is positioned downstream of the cutting section 20a in the advancement direction of the advancement path 101 or in the threading path 105 which coincide with each other up to the cutting section 20a . In this case , preferably in order to avoid accidental breakage of the web 50 , the threading device 200 can comprise a deviating roll 201 for slackening the web 50 from the counter-cutting device 27 . In this case , the deviating roll 201 can be positioned downstream of the cutting section 20 in the advancement direction of the web 50 along the advancement path 101 . More precisely, for position downstream of the cutting section 20 it is intended the position following the point of cooperation between the blade 22 and the counter-blade 28 in the advancement direction of the web 50 along the advancement path 101 .

[0109] In the second case , which relates to web 50b, on the right of figure 7B, the dragging member 203b is positioned upstream of the cutting section 20b in the advancement direction of the advancement path 101 . In this case , the threading path 105 diverges from the advancement path 101 at a position upstream of the cutting section 20b .

[0110] In the configuration shown for the threading device 200 of web 50b the deviating roll 201 can be omitted . The operational step for the threading path 105a of web 50a is the same described with reference to figure 5 while the operational mode for threading the web 50b is the same described with reference to figure IB, or figures 4A-4C .

[0111] With regard to the threading step illustrated for web 50b, once that the web 50 is suf ficiently stretched on the advancement rolls 15b, for example at least for 20% of the total width of the web 50b, it is possible also to provide the stopping step of the dragging member 203b while the web 50b is fed by the advancement rolls 15b for creating a bag of web 50b which gradually approaches the cutting roll 25b . The adhesion and the treatment of the web 50b, at least partly stretched on the external surface 21 of the cutting roll 25b, is carried out by activating the suction of the suction holes 26 of the cutting roll 25b .

[0112] It is optionally possible to provide to use a push device 70b adapted to facilitate the approaching and the adhesion of the web 50b to the cutting roll 25b . The push device 70b can be like that which has been previously described . Preferably, the approaching step of the web 50 can occur when the web 50b is completely stretched on the advancement rolls 15b and / or the dragging member 203b .

[0113] Preferably, the web in excess which is fed by the dragging members 203a and 203b can be accumulated at respective accumulation zones 38a and 38b which, preferably, comprise accumulation devices 37a and 37b analogously to what has been previously described .

[0114] In a further alternative embodiment not shown, each threading path 105a, 105b of an interfolding machine of single- fold type , can coincide with the advancement path 101 up to the interfolding groove formed by the folding rolls 31 and 32 ( or 25a and 25b in the case of WO2020 / 161571 ) . In practice , it is expected to move the respective web 50a, 50b, between the cutting roll 25a, 25b and the respective counter-cutting device 27a, 27b and to directly feed each web 50a, 50b towards the folding rolls 31 and 32 without using the dragging members 203a, 203b which, therefore , can be omitted . Once that the flexible element 210 has led the wing 51 and, therefore , the web 50 through the folding rolls 31 and 32 , the dragging of web 50a and 50b is carried out by causing the folding rolls 31 and 32 to counter-rotate with respect to each other .

[0115] When the web 50 is stretched at least for 10% on the folding rolls 31 and 32 , or the cutting rolls 25a, 25b, it is possible to operate the displacement device 60 in order to position the counter-cutting device 27 in the cutting position and to start the cut of the web 50 . At this stage , the web 50 is caused to advance by the advancement rolls 15 and to the rotation of the cutting rolls 25a and 25b which hold the respective webs 50a and 50b by activating the suction holes 26 . The residual web 50 engaged to the flexible element 210 is brought out by the formation device 102 of the stacks 100 of the interfolding machine 1 going along the closed path 106 .

[0116] The webs 50a and 50b fed during the threading step are accumulated at the accumulation zone 37 which, in this case , is positioned at the formation device 102 of the stacks 100 . At the end of the threading step, the webs 50a and 50b can be discharged by the discharging device , normally a conveyor, used for discharging the completed stacks 100 from the interfolding machine 1 , advantageously, in the direction opposite to that one along which, during the production, the stacks of completed product 100 are discharged .

[0117] As diagrammatically shown in the figures 8A and 8B, respectively at a starting stage and at a final stage of a threading step, in an alternative embodiment of the invention, the threading group 200 can be used for threading the web 50 in a machine of the type described in W02011015893 . In this case , the interfolding machine 1 provides a first feeding group 10a for feeding the plurality of sheets 11 along a first advancement path 101a ( on the left in the figure ) and a second feeding group 10b for feeding a plurality of sheets 11 along a second advancement path 101b ( on the right in the figure ) . The interfolding machine 1 is , furthermore , provided with an interfolding section 30 comprising a couple of folding rolls 31 and 32 having a folding peripheral speed VP . The folding rolls 31 and 32 are arranged to receive a series of sheets 11 of length L, in case overlapped to each other for a fraction Y of their length L, and to fold them in a series of panels P . Furthermore , rolls 41 and 42 , are provided arranged to feed at the folding speed VP the series of sheets 11 cut but not yet folded towards the folding rolls 31 and 32 . The rolls 41 and 42 are positioned at the confluence of the two feeding paths 101a and 101b . Upstream of the first and second advancement paths 101a and 101b a single cutting section 20 is provided adapted to cut a web of paper 50 which moves along an advancement direction at an advancement speed V ( l ) , where V ( l ) has a ratio X ( l ) with respect to the folding speed VP . The sheets 11 can be fed along the first and second advancement paths 101a and 101b selectively and independently from each other, that means separately from each other, or at the same time , according to the type of interfolding configuration desiderata, in such a way to obtain, in particular an interfolding machine 1 which operates in "multi- fold" mode or in " single- fold" mode .

[0118] The type of threading group 200 is of the type described with reference to the figures 5A-5C and 6 , that means with the dragging member 203 arranged downstream of the cutting section 20 in the advancement direction along the threading path 105.

[0119] Also in this case , it is optionally possible to provide the use of a deviating roll 201 to move the web 50 away from the counter-blade 28 of the counter-cutting device 27 during the threading of the web 50 . In this case , preferably to avoid accidental breakage of the web 50 , the threading device 200 can comprise a deviating roll 201 to move the web 50 away from the counter-cutting device 27 . In this case , the deviating roll 201 can be arranged downstream of the cutting section 20 in advancement direction of the web 50 along the advancement path 101 .

[0120] Preferably, the threading group 200 can comprise an accumulation zone 38 to accumulate the web 50 in excess fed by the dragging members 203 during the threading step .

[0121] The operational procedure is similar to what has been described above with reference to figures 5A-5C .

[0122] In the alternative embodiment diagrammatically shown in figure 8C of the machine of figures 8A and 8B, the threading path 105 provides to move the web 50 through the groove formed by the cutting roll 25 and the trans fer roll 40 . Preferably, the web 50 can be directly fed towards the folding rolls 31 and 32 by rotating the cutting roll 25 wherein the suction holes 26 are put on suction . In this case , the function of the dragging member 203 is , therefore , directly made by the folding roll 25 . When the web 50 is stretched on the cutting roll 25at least for 10% , it is possible to operate the displacement device 60 for positioning the counter-cutting device 27 at the cutting position and starting the cut of the web 50 at least partly stretched .

[0123] During the threading step the suction is activated of the rolls 41 and 42 and the folding rolls 31 and 32 in order to cause the sheets 11 cut by the cutting section 20 to move forward .

[0124] The web 50 divided into sheets 11 formed during the threading step, can be accumulated at the accumulation zone 38 which, in this case , is positioned at the formation device 102 of the stacks 100 . In this case , the function of the accumulation device 37 can be carried out by the formation device 102 of the stacks 100 which, at the end of the threading, can discharge by the conveyor which is normally used to discharge the completed stacks 100 from the interfolding machine 1 .

[0125] In the further embodiment diagrammatically shown in figure 9 , the threading group 200 is used in an interfolding machine of the type described in WO2023209621 . In particular, in this case , downstream of the cutting group 20 a transfer roll 40 is provided having an external surface 45 and adapted to rotate at a first predetermined angular velocity about a longitudinal rotation axis 145 and to hold, alternatively, on a first and on a second predetermined portion of the external surface 45 the wing of head and the wing of tail of the sheets 11 coming from the cutting group 20 . Downstream of the transfer roll 40, a displacement group 130 is, furthermore, provided arranged to move a plurality of catching members 135 along a displacement traj ectory comprising at least a curvilinear portion and at least a rectilinear portion to move the sheets 11 , which are in a partly overlapped configuration, along a predetermined advancement traj ectory up to the interfolding section 30 where a first and a second folding roll 31 and 32 carry out the interfolding of the same in the desired interfolding configuration .

[0126] The configuration of the threading group 200 and the threading procedure can be analogous to what has been described with reference to figure 8 , or figure 5. In this case the threading group 200 comprises a dragging member 203 and a deviating roll 201 , both of them arranged downstream of the cutting section along the direction of the threading path 105. Preferably, the threading group 200 comprises also an accumulation zone 37 , which is, as previously described, positioned downstream of the dragging member 203.

[0127] 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 modi fy 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 modi fications will have to be considered as equivalent to the speci fic embodiments . The means and the materials to reali ze the di f ferent functions described herein could have a di f ferent 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 .

Claims

CLAIMS1. Interfolding machine (1) for producing stacks (100) sheets interfolded according to a predetermined interfolding configuration starting from at least a web (50) of paper, or similar material, said machine (1) comprising:- an advancement section (10) configured to cause said web of paper (50) to advance along a predetermined advancement path (101) ;- a cutting section (20) comprising a cutting roll(25) having an external surface (21) , and a countercutting device (27) configured to cooperate with each other in order to cut said or each web of paper (50) in a respective plurality of sheets (11) of predetermined length, said cutting roll (25) being provided with suction holes configured to cause said web of paper to adhere on a predetermined portion of said external surface (21) ;- an interfolding section (30) comprising a first folding roll (31) and a second folding roll (32) counter-rotating with respect to each other, said first and second folding rolls (31,32) being configured to fold, at a folding zone (35) , during a production step, said plurality of sheets (11) in a plurality of panels and to form said stack (100) of sheets interfolded according to said predetermined interfolding configuration; said machine (1) being characterized in that a threading group (200) is, furthermore, provided configured to engage a wing (51) of said or each web of paper (50) during a threading step which precedesaid production step and to cause said or each web of paper (50) to move along a predetermined threading path (105) which coincides with said predetermined advancement path (101) at least up to said cutting roll (25) .

2. Interfolding machine (1) , according to claim 1, wherein said threading group (200) is, furthermore, configured to disengage said wing of said web of paper (51) at a predetermined position of said predetermined threading path (105) such to allow said suction holes (26) of said cutting roll (25) to suck said web of paper (50) and to cause the same to adhere on said external surface.

3. Interfolding machine (1) , according to claim 1 or 2, wherein a displacement device is, furthermore, provided configured to place said counter-cutting device between a cutting position where is arranged at a first predetermined distance (dl) from said cutting roll such to cut said web in said plurality of sheets during said production step of said stacks (100) of interfolded sheets, and a rest position, where said counter-cutting device is positioned at a second predetermined distance (d2) from said cutting roll during said threading step.

4. Interfolding machine (1) , according to any previous claim, wherein said threading group comprises at least one threading belt wrapped around a plurality of rolls defining a predetermined closed path (106) configured in such a way to move said web of paper (50) along said predetermined threading path (105) .

5. Interfolding machine (1) , according to any previous claim, wherein said threading group (200) comprises at least one deviating roll (201) configured to deviate said web of paper (50) along a branch (106) of said predetermined threading path (105) .

6. Interfolding machine (1) according to claim 5, wherein said deviating roll (201) is configured to deviate said web of paper (50) along a branch (106) of said predetermined threading path (105) which diverges from said predetermined advancement path (101) .

7. Interfolding machine (1) , according to any previous claim, wherein said threading group (200) comprises a dragging member (203) configured to cause said web of paper (50) to move along said predetermined threading path (105) .

8. Interfolding machine (1) , according to claim 7, wherein said dragging member (203) comprises dragging elements (205,206) comprising a first and a second roll counter-rotating to each other configured to stretch said web of paper (50) between them and to cause the same to move.

9. Interfolding machine (1) , according to one or more of the previous claims, wherein said threading group (200) comprises a cutting device (20,250) configured to cut said web of paper (50) once that said suction holes (26) of said cutting roll (25) are arranged to suck said web of paper (50) forming a waste portion ( 50 ’ ) of said web of paper (50) .

10. Interfolding machine (1) according to claim 9, wherein said cutting device (20,250) coincides with saidcutting section (20) .

11. Interfolding machine (1) according to claim 9 or 10, wherein said cutting device (20,250) is configured to cut said web of paper (50) when this is stretched on said cutting roll (25) or on the deviating roll (201) at least for 10% of the total width of the web (50) , in particular at least for 50%, preferably for the total width of the web (50) .

12. Interfolding machine (1) , according to claim 7, or 8, wherein said cutting device (20,250) is arranged to cut said web of paper (50) forming said determined waste portion (50' ) of said web of paper (50) upstream of said dragging member (203) .

13. Interfolding machine (1) , according to one or more of the previous claims, wherein a push device (70) is, furthermore, provided configured to push said web of paper (50) towards said cutting roll (25) at a predetermined position of said predetermined threading path (105) .

14. Interfolding machine (1) according to claim 7, or 8, or 12, comprising an accumulation zone (38) configured to accumulate the web of paper (50) downstream of said dragging member (203) during the threading step.

15. Interfolding machine (1) according to claim 14, wherein said accumulation zone (38) comprises an accumulation container (37) where said web of paper (50) , downstream of said dragging member (203) comprises a discharging device arranged to remove said web of paper (50) from said accumulation container16. Interfolding machine (1) according to one or more of the previous claims, wherein said predetermined threading path (105) coincides with said predetermined advancement path (101) at least up to a transfer roll (40) positioned downstream of said cutting section (20) .

17. Interfolding machine (1) according to any previous claim, wherein said predetermined threading path (105) coincides with said predetermined advancement path (101) at least up to the interfolding section (30) .

18. Interfolding machine (1) according to claim 14, wherein said dragging member (203) coincides with said cutting roll (25) and wherein said accumulation zone (38) is positioned at a formation device (102) on which said interfolded sheets are positioned in order to form said stack (100) of interfolded sheets.

19. Method for producing stacks (100) sheets interfolded according to a predetermined interfolding configuration starting from at least one web (50) of paper, or similar material, said method comprising the steps of:- feeding said web of paper (50) along a predetermined advancement path (101) ;— cutting by a cutting roll (25) having an external surface (21) and a counter-cutting device (27) configured to cooperate with each other in a respective plurality of sheets (11) of predetermined length, said cutting roll (25) being provided with suction holes (26) configured to cause said web to adhere on a predetermined portion of said externalsurface (21) ;- folding, during a production step, by a first folding roll (31) and a second folding roll (32) counter-rotating to each other, at a folding zone (35) , said plurality of sheets (11) in a plurality of panels in such a way to form said stack (100) of interfolded sheets according to said predetermined interfolding configuration; said method (1) being characterized in that a threading step, which precedes said production step, is, furthermore, provided and in that said threading step is carried out by a threading group (200) configured to engage a wing (51) of said or each web of paper (50) and to cause said or each web of paper (50) to move along a predetermined threading path (105) which coincides with said advancement path (101) at least up to said cutting roll (25) .

20. Method according to claim 19, wherein a step is, furthermore, provided for disengaging said wing of said web of paper (50) at a predetermined position of said threading path (105) such to allow said suction holes (26) of said cutting roll (25) to suck said web of paper and to cause the same to adhere on said external surface (21) .

21. Method according to claim 19, or 20, wherein said threading group (200) comprises a flexible element (210) arranged to engage said wing (51) of said web of paper ( 50 ) .

22. Method according to any claim from 19 to 21, wherein said threading group (200) comprises a dragging member(203) configured to cause said web of paper (50) to move along said predetermined threading path (105) .

23. Method according to any claim from 19 to 22, wherein said threading step comprises, furthermore, the steps of :- stopping said wing (51) of said or each web of paper (50) to advance by stopping said flexible element (210) ;- feeding said web (50) by said dragging member (203) ;- cutting said web of paper (50) by a cutting device (20,250) ;- holding said web of paper (50) on the external surface (21) of said cutting roll (25) by activating said suction holes (26) .

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