A method and an interfolding machine for producing a pack of interfolded sheets

Abstract

A pack (P) of interfolded sheets (S) comprising interfolded sheets (S) of a same length (SI) between a first end (I) and a second end (F) thereof, both ends being separated from those of the other sheets (S), with the W-interfolded sheets (S), that is with four panels (Span) having an identical extension, and having a same orientation; each sheet (S), with the exception of the end sheets (S), is interfolded with two sheets (S) that are both on the same side with respect to the sheet (S) and each of the two sheets (S) is interfolded with the sheet (S) by two panels (Span). Also described are a method and a machine for operating an interfolding machine (1000) which realise the pack (P) from a first succession (T1 ) and from a second succession (T2) of sheets (S) flanked and staggered by half a length (SI), pulling the sheets (S) from the side of the first succession (T1 ) at the first ends (I) and at the second ends (F).

Description

[0001] A METHOD AND AN INTERFOLDING MACHINE FOR PRODUCING A PACK OF INTERFOLDED SHEETS

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to the technical sector concerning production of packs of interfolded sheets, i.e. with the sheets, or sheet articles, folded in a zigzag with respect to one another; typically the sheets are made of paper material and the packs can, for example, be packs of paper handkerchieves, paper napkins, or paper hand-towels. In detail, the invention relates to sheets with a plurality of folds, also known as multi-fold.

[0004] DESCRIPTION OF THE PRIOR ART

[0005] In this technical sector, the sheets that are to be folded in an interfolded way for the formation of a stack of sheets (pack) are usually supplied in the form of continuous strips, or continuous reels, typically obtained from unwinding means starting from reels of paper, which pass through cutting means that define the sheet articles and then reach folding means which are configured and predisposed for folding the sheet articles in an interfolded way by carrying out one or more folds. The stack of sheets under formation is usually supported by support means and the separation between packs of sheets, once a desired number of interfolded sheets has been reached, is carried out by separation means.

[0006] The cutting means can define the sheet articles by separating the sheets from one another, by means of neat cuts, also known by the name of Clean cuts, or by making lines or points of pre-perforations, also known by the name of Tab-bonds (TB), between the sheet articles.

[0007] When the sheets are folded in a zig-zag format, one with the other, by the folding means, in each sheet portions are formed, separated from one another by a respective fold: each of these portions is usually called a panel. It is thus possible to realise packs of interfolded sheets with sheets having 2 panels, 3 panels, 4 panels and so on. 4-panel sheets with panels having, or having approximately, a same length, are also known by the name of W-folded sheets. The expert in the sector will understand how the length of the panels might not exactly correspond since minimal variations in the positioning of the components of the interfolding machines can lead to dimensional variations. To this it can be added that the machines typically operate at high velocities and that typically the sheets are made of paper material, or, in any case, of a material with similar characteristics; the paper material can be subjected to different levels of tension which can in turn determine dimensional variations.

[0008] Figure 1 reflects figure 1 C of international patent application W02023100048A1 . Figure 1 shows a schematic sequence of sheets of a pack of interfolded sheets that are W-folded, i.e. with 4 panels. The example of figure 1 has the sheets interfolded in half, i.e. two panels of a sheet of a line are facing two panels of a sheet of the other line, and includes the use of Tab-bonds (TB) on one line and Clean-cuts on the other line.

[0009] Figure 2 shows a schematic sequence of sheets of a pack of interfolded sheets that are W-folded according to an approach described in W02010031529A1 : the superposing takes place by differences in velocity between the successive sheets of a same succession of sheets, as illustrated by way of example in figure 9 of W02010031529A1 . In the packs of W02010031529A1 two lines of sheets are not present, but the successive sheet will always be on the left, as shown by way of example in figure 2, or will be always be on the right of the sheet that has been previously folded. Figure 3 shows a schematic sequence of sheets of a pack of interfolded sheets in an asymmetric way and W-folded according to an approach illustrated in figure 11 of EP2379435A1 : three panels of a first sheet of a line are facing three panels of a second sheet of the other line and a panel of the first sheet is facing a panel of the other sheet of the other line.

[0010] The solution of WO2023100048A1 does not allow having successive sheets separated from one another in both lines and the pack is not homogeneous and balanced as on one side there is the material of the Tab-bond (TB) connections while on the other side there are the gaps left by the Clean-cuts. With reference to figure 1 , during use there is a high risk that the extraction of one sheet from the dispenser also leads to the extraction of the successive sheet connected by Tabbonds (TB) and, often, by the sheet of the other line which is interfolded with both of these sheets.

[0011] The solution of W02010031529A1 has, primarily, significant limits in terms of productivity as the superposing taking place by differences in velocity between the sheets allows only a slowed interfolding velocity with respect to the velocity of interfolding obtainable by the superposing of two successions of sheets that are distinct from one another, such as for example in W02023100048A1 . The packs obtained in W02010031529A1 , especially during the increase of sheets in the pack, hang more towards one side making management of the pack more difficult in the successive steps of production and use.

[0012] The solution of EP2379435A1 realises a product having a variable behaviour since on the extraction of a sheet from the dispenser the successive sheet can be secured to the pack with three panels or with only one panel. Especially critical is a case in which when the sheet is secured by only one panel, as three panels exit the dispenser, which panels can more easily get dirtied. Further, the orientation of the sheet or sheets exiting the dispenser varies. For these reasons the type of pack of interfolded sheets, schematically illustrated in figure 3, is not widely demanded on the market.

[0013] There is therefore an established need for a pack of sheets, or sheet articles, interfolded and well distributed internally of the volume occupied and which guarantees easy removal.

[0014] These characteristics are obtained in a pack of interfolded sheets which comprises interfolded sheets, with each sheet having, or approximately having, a same length between a first end and a second end thereof. Each sheet is W-folded, i.e. has, between the first end and the second end, two folds and a central fold which is interposed between the two folds, with each of the two folds and the central fold separating panels of sheet, i.e. portions of sheet, of an identical extension, equal to a quarter of the same length, or approximately of an identical extension.

[0015] The first end and the second end of each sheet are separated from the first end and second end of the other sheets.

[0016] The sheets have the same orientation, i.e. have all the central folds on a same side with respect to the respective two folds.

[0017] Each sheet, with the exception of the end sheets of the pack, is advantageously interfolded with two sheets which are both on the same side withe respect to the sheet and each of the two sheets is interfolded with the sheet with two panels.

[0018] A like interfolded pack is visible in figures 4 and 5 and is apparently schematised in figures 12 and 13 of the patent application published with number US 2011 / 0129633 A1. According to the above patent application, the pack would be obtainable with a length-fold converting line. SUMMARY OF THE INVENTION

[0019] The present invention intends to obviate one or more drawbacks of the solutions of the prior art.

[0020] An aim of the present invention is to ensure high productivity with respect to the existing solutions, given same performances obtained in the final product, i.e. in the production of a pack of interfolded sheets, with sheets having a plurality of folds, in particular a pack of sheets, or sheet articles, interfolded and well distributed internally of the volume occupied and which guarantees easy removal from the pack.

[0021] An aim of some embodiments is to simplify the realisation and / or ensure the quality of the product obtained, especially with an increase in the speed of interfolding.

[0022] These and other aims, which will be obvious to the expert in the sector from a reading of the following text, are attained by means of a method for realising a pack of interfolded sheets and an interfolding machine for realising a pack of interfolded sheets according to the contents of the claims.

[0023] In accordance with the teachings of the present document, the method comprises steps of: providing a first succession of sheets and a second succession of sheets; flanking the sheets of the first succession and of the second succession; interfolding the flanked W-folded sheets.

[0024] The sheets of the first succession and of the second succession, have, or have approximately, a same length between a first end and a second end thereof, a central part halfway between the first end and the second end and two intermediate parts respectively halfway between the first end and the central part and halfway between the central part and the second end.

[0025] In the step of flanking the sheets, the sheets are flanked in such a way that the sheets of the first succession are staggered by half the same length, or approximately by half the same length, with respect to the sheets of the second succession.

[0026] In the step of W-interfolding, the flanked sheets of the first succession and the second succession are advantageously drawn together on the side of the first succession at the first ends and the second ends and on the side of the second succession at the intermediate parts so as to form, in each sheet, two folds and a central fold which is interposed between the two folds.

[0027] In accordance with the teachings of the present document, the interfolding machine comprises an interfolding unit which W-interfolds sheets, support means for supporting interfolded sheets, a first supply line of sheets and a second supply line of sheets.

[0028] The interfolding unit comprises a first roller which has a lateral surface for receiving sheets, which comprises means for holding sheets and which rotates with respect to a first rotation axis, a second roller which has a respective lateral surface for receiving sheets, which comprises respective means for holding sheets and which rotates, with respect to a second rotation axis, first folding elements and second folding elements.

[0029] The support means are configured for supporting interfolded sheets beneath the first roller and the second roller.

[0030] The first supply line supplies a first succession of sheets on the lateral surface.

[0031] The second supply line supplies a second succession of sheets on the respective lateral surface. The second rotation axis is parallel to the first axis of rotation and both bear on a joining plane.

[0032] The first roller and the second roller rotate at a same tangential velocity, with opposite rotation directions to one another.

[0033] The first folding elements, at a first folding area, move the sheets from the lateral surface towards the support means.

[0034] The second folding elements, at a second folding area, move the sheets from the respective lateral surface towards the support means.

[0035] The first supply line and the second supply line are advantageously configured to supply sheets which have, or have approximately, a same length between a first end and a second end thereof, and in such a way that the sheets of the first supply line cross the joining plane staggered by half the same length, or approximately by half the same length, with respect to the sheets of the second supply line.

[0036] Further, the means for holding are configured in such a way as to hold both the sheets of the first supply line and the sheets of the second supply line at the first ends and the second ends of the sheets for a first portion which is between the joining plane and the first folding area so that the first folding elements form a central fold, which is central between the first end and the second end of the sheet alternatingly on a sheet of the first supply line or on a sheet of the second supply line.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Specific embodiments of the invention will be described in the following part of the present description, according to what is set down in the claims and with the aid of the accompanying drawings, in which: figures from 1 to 3 are each a schematic view of a sequence of sheets of a respective pack of W-interfolded sheets folded in W fashion of the prior art; figure 4 and figure 5 are each a schematic view of a sequence of sheets of an embodiment of a pack of interfolded sheets obtainable with the method and the interfolding machine of the present invention; figure 6 and figure 7 each illustrate a representative diagram of an interfolding machine according to the invention which realises the pack of interfolded sheets respectively of figure 4, and figure 5; figure 8 is a representative diagram, represented as a section, which is representative of the suction arcs of an embodiment of the interfolding machine according to the invention which realises the pack of interfolded sheets of figure 4; figure 9 is a schematic lateral view of the cutting roller of figure 8 indicating the position of the section; figure 10 is a diagram, represented as a section, which is representative of the suction arcs of an embodiment of the interfolding machine according to the invention which realises the pack of interfolded sheets of figure 4; figure 11 is a schematic lateral view of the cutting roller of figure 10 indicating the position of the section, as will be more fully illustrated in the following; figure 12 illustrates a section, passing through a median plane that is perpendicular to the axes of the rollers, of an embodiment of the interfolding machine according to the invention; figure 13 is a partial view in larger scale of figure 12; figures from 14 to 16 each show the section of figure 12 in successive moments of the production of a pack of interfolded sheets by the embodiment of figure 12. DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] With reference to the appended figures, reference P indicates a pack (P) of interfolded sheets (S), comprising interfolded sheets (S), each having, or having approximately, a same length (SI) between a first end (I) and a second end (F).

[0040] Each sheet (S) of the pack (P) of interfolded sheets (S) is W-folded, i.e. has two folds (Sp) and a central fold (Scentr), which is interposed between the two folds (Sp), between the first end (I) and the second end (F). Further, each of the two folds (Sp) and the central fold (Scentr) separates panels (Span), or portions of sheet (S) having an identical extension, equal to a quarter of the same length (SI), or approximately of an identical extension.

[0041] In other words, the four panels (Span) are identical to one another or approximately so, taking account of the dimensional variations which, as mentioned in the foregoing, can be generated in the interfolding machines. Dimensional variations can be caused by the structure or the dynamic behaviour of the interfolding machines as well as by the flexibility of the material, typically paper material, which can be more or less stretched; for example, the sheets (S) can be obtained from portions of strip (N1 , N2) subjected to different tensions or the different tensions can modify the position of the folds (Sp, Scentr) in the sheet (S). In the remaining part of this description too, the term “approximately” is intended to mean taking the dimensional variations into consideration that can occur in the technical sector of reference, especially for the above-described reasons.

[0042] The first end (I) and the second end (F) of each sheet (S) are separated from the first end (I) and from the second end (F) of the other sheets (S), i.e. a clean cut is provided for all the sheets (S). The sheets (S) have the same orientation, having all the central folds (Scentr) on a same side with respect to the respective two folds (Sp). For example all the folds (Scentr) are on the left of the two folds (Sp) of the same sheet (S), as in figure 4, or are on the right of the two folds (Sp) of the same sheet (S), as in figure 5.

[0043] Each sheet (S), with the exception of the end sheets (S), is interfolded with two sheets (S) which are both on the same side with respect to the sheet (S), and each of the two sheets (S) is interfolded with the sheet (S) by two panels (Span).

[0044] As illustrated in figures 4 and 5, the above-described condition takes place for each sheet (S) of the pack (P) of interfolded sheets (S) occurs with the exception of the end sheets (S), which can be interfolded with a single sheet (S), by two panels (Span).

[0045] The sheets (S) internally of the pack (P) of interfolded sheets (S) as described above are interfolded with the following sheet (S) by two panels (Span) and each time a sheet (S) is extracted the mouth formed by two the panels (Span) of the end sheet (S) is always facing in the same direction, i.e. the fold between the extracted two panels (Span) is always on the same side.

[0046] Further, the sheets (S) are well distributed internally of the pack (P) of interfolded sheets (S).

[0047] The invention relates to a method for realising the pack (P) of interfolded sheets (S) described in the foregoing.

[0048] An embodiment of the method comprises steps of:

[0049] - providing a first succession (T1 ) of sheets (S) and a second succession (T2) of sheets (S) with the sheets (S) having, or approximately having, a same length (SI) between a first end (I) and a second end (F), a central part (S) which is halfway between the first end (I) and the second end (F) and two intermediate parts (Si) respectively halfway between the first end (I) and the central part (Sc) and halfway between the central part (Sc) and the second end (F);

[0050] - flanking the sheets (S) of the first succession (T1 ) and of the second succession (T2) in such a way that the sheets (S) of the first succession (T1 ) are staggered by half the same length (SI), or approximately by half the same length (SI), with respect to the sheets (S) of the second succession (T2);

[0051] - W-interfolding the flanked sheets (S), by pulling the flanked sheets (S) of the first succession (T1 ) and of the second succession (T2) together on the side of the first succession (T1 ) at the first ends (I) and the second ends (F) and on the side of the second succession (T2) at the intermediate parts (Si) so as to form, in each sheet (S), two folds (Sp) and a central fold (Scentr) which is interposed between the two folds (Sp).

[0052] The above-illustrated method enables realising the pack (P) of interfolded sheets which has the advantages as illustrated in the foregoing.

[0053] Though in figures from 12 to 16 the sheets (S) are shown while evidencing the detachment between them in order to make the functioning of the interfolding machine (1000) according to the invention more evident, generally the sheets (S) of each succession, between the first succession (T1 ) and the second succession (T2), are separated (cut using the clean cut method) from one another, but substantially in mutual contact. It might therefore be stated that in both the first succession (T1 ) and in the second succession (T2), the sheets (S) follow upon one another substantially without empty spaces.

[0054] The arrows of figure 6, and those of figure 7, give an example of the pulling positions in the step of W-interfolding the flanked sheets (S). Figure 6 shows how the flanked sheets (S) are pulled from the side of the of the first succession (T1 ), i.e. displaced in a direction which goes from one sheet (S) of the second succession (T2) to the flanked sheet (S) of the first succession (T 1 ), at the first end (I), of the central part (Sc) and the second end (F) of the sheets (S) of the first succession (T1 ). This formulation is equivalent to the one described in the foregoing as the first ends (I) and the second ends (F) of the sheets (S) of the second succession (T2) are at the central parts (Sc) of the sheets (S) of the first succession (T1 ).

[0055] Preferably, the step of providing a first succession (T1 ) of sheets (S) and a second succession (T2) of sheets (S) comprises steps of:

[0056] - providing a first strip (N1 );

[0057] - transversally cutting the first strip (N1 ) repeatedly at a distance equal to a same length (SI), or approximately equal to a same length (SI), so as to obtain a first succession (T1 ) of sheets (S) having, or having approximately, the same extension between the first end (I) and the second end (F);

[0058] - providing a second strip (N2);

[0059] - transversally cutting the second strip (N2) repeatedly at a distance equal to a same length (SI), or approximately equal to a same length (SI), so as to obtain a second succession (T2) of sheets (S) having, or having approximately, the same extension between the first end (I) and the second end (F).

[0060] In this way productivity can be maximised, given the same performance, with respect to the case of use of a single strip.

[0061] The invention also relates to an interfolding machine (1000) for producing a pack (P) of interfolded sheets (S) as described above and, typically, the interfolding machine (1000) is configured to realise the above-described method.

[0062] An embodiment of the interfolding machine (1000) comprises:

[0063] - an interfolding unit (10) which W-interfolds sheets (S) and which comprises: o a first roller (1 ) which has a lateral surface (11 ) for receiving sheets (S), which comprises means for holding (15) sheets (S) and which rotates with respect to a first rotation axis (X1 ), o a second roller (2) which has a respective lateral surface (21 ) for receiving sheets (S), which comprises respective means for holding (25) sheets (S) and which rotates with respect to a second rotation axis (X2) parallel to the first rotation axis (X1 ) and which insists together with the first rotation axis (X1 ) on a joining plane (U), o first folding elements (3) and o second folding elements (4);

[0064] - support means (5) for supporting interfolded sheets (S) beneath the first roller (1 ) and the second roller (2);

[0065] - a first supply line (100) of sheets (S) which supplies a first succession (T1 ) of sheets (S) on the lateral surface (11 );

[0066] - a second supply line (200) of sheets (S) which supplies a second succession (T2) of sheets (S) on the respective lateral surface (21 ).

[0067] The first roller (1 ) and the second roller (2) rotate at a same tangential velocity (w1 , w2), with opposite rotation directions to one another.

[0068] The first folding elements (3), at a relative first folding area (P1 ), move the sheets (S) from the lateral surface (11 ) towards the support means (5), and the second folding elements (4), at a second folding area (P2), move the sheets (S) away from the respective lateral surface (21 ) towards the support means (5).

[0069] The first supply line (100) and the second supply line (200) are advantageously configured to supply sheets (S) which have, or have approximately, a same length (SI) between a first end (I) and a second end (F) and in such a way that the sheets (S) of the first supply line (100) cross the joining plane (U) staggered by half the same length (SI), or approximately by half the same length (SI), with respect to the sheets (S) of the second supply line (200).

[0070] Further, the means for holding (15) are configured in such a way as to hold both the sheets (S) of the first supply line (100) and the sheets (S) of the second supply line (200) at the first ends (I) and the second ends (F) of the sheets (S) for a first portion (T1a) which is between the joining plane (U) and the first folding area (P1 ) so that the first folding elements (3) form a central fold (Scentr), which is central between the first end (I) and the second end (F) of the sheet (S), alternatingly, on a sheet (S) of the first supply line (100) or on a sheet (S) of the second supply line (200).

[0071] The expert in the sector will understand how the second folding elements (4) consequently form two folds (Sp) on each sheet (S) thus obtaining W-interfolded sheets (S) that have, between the first end (I) and the second end (F), two folds (Sp) and a central fold (Scentr) which is interposed between the two folds (Sp), with each of the two folds (Sp) and the central fold (Scentr) separating panels (Span) of sheet (S) having an identical extension, equal to a quarter of the same length (SI), or approximately an identical extension.

[0072] The interfolding machine (1000) of the invention enables obtaining the pack (P) of interfolded sheets (S) which has the advantages as described in the foregoing and with greater productivity with respect to the case in which the sheets (S) are interfolded in half by a difference in velocity. In the interfolding machine (1000) according to the invention, the productive limit is generally determined by the time required for holding the sheets (S) furthest from the roller, whether the first roller (1 ) or the second roller (2); typically by the time necessary for passing one sheet (S) from the first roller (1 ) to the second roller (2), or vice versa.

[0073] As shown by way of example in figures 8, 10 and 13, according to a known method the interfolding units with folding rollers hold portions of two adjacent sheets (S) so as to bring the portions into a first folding area (P1 ) or a second folding area (P2), alternatingly, holding in a first portion (T1a) and a respective first portion (T1 b) until the first folding elements (3) and second folding elements (4) move the sheet (S) away. The first portion (T1a) and the respective first portion (T1 b) theoretically correspond to the arc between the joining plane (U) and the first folding area (P1 ) and between the joining plane (U) and the second folding area (P2). However, for various reasons, for example the quantity of motion of the sheets (S), the delays of the means for holding (15) and the respective means for holding (25) or the superiority in moving the sheets (S) of the first folding elements (3) and second folding elements (4), the first portion (T1a) and the respective first portion (T1 b) can terminate prior to the respective first folding area (P1 ) or second folding area (P2) or, possibly, thereafter.

[0074] The first portion (T1a) preferably extends between the joining plane (U) and the first folding area (P1 ). The second portion (T2a) more preferably extends from the joining plane to the second folding area (P2).

[0075] The first portion (T1a) typically extends from the joining plane (U) and the respective first portion (T1 b) also extends from the joining plane (U).

[0076] Although another theoretical possibility is that the first supply line (100) and the second supply line (200) supply the sheets (S) between the first roller (1 ) and the second roller (2) at the joining plane (U), in practice, this option tends to incur drawbacks in realisation or performance. In other words, the option schematically illustrated in figures 6 and 7 would be realisable, for example, with the use of plate conveyors or with vacuum belt conveyors but with the risk of not holding the sheets (S), incorrect alignment of the sheets (S), etc.

[0077] It is therefore preferable that:

[0078] - the first supply line (100) supplies the sheets (S) to the first roller (1 ) at an inlet area (11 ) in such a way that the lateral surface (11 ) receives at least a fraction of the sheets (S) before the sheets (S) pass from the joining plane (U) and

[0079] - the second supply line (200) supplies the sheets (S) to the second roller (2) at a respective inlet area (I2) in such a way that the respective lateral surface (21) receives at least a fraction of the sheets (S) before the sheets (S) pass from the joining plane (U).

[0080] In this way at least a fraction of each sheet (S) is arranged on the lateral surface

[0081] (11 ) or on the respective lateral surface (21 ) before the means for holding (15) or the respective means for holding (25) hold the sheet (S) and a flanking sheet (S).

[0082] In the embodiments of the appended figures the inlet area (11 ) is located above the joining plane (U), i.e. on the side opposite the support means (5), and the respective inlet area (I2) is located above the joining plane (U), i.e. on the side opposite the support means (5), but the inlet area (11 ) and the respective inlet area

[0083] (12) might also be positioned by the side, although the upper position allows, in general, best exploiting the extension of the interfolding machine (1000) in the vertical direction.

[0084] The means for holding (15) more preferably hold the first ends (I) of the sheets (S) of the first supply line (100) from the inlet area (11 ) to the end of the first portion (T1a).

[0085] Consequently, this also occurs for the second ends (F) and for the central parts (Sc) of the sheets (S) of the first supply line (100).

[0086] This guarantees a precise alignment of the half of the sheets (S) of the pack (P) of interfolded sheets (S), even with an increase in the speed of interfolding and a gain in productivity.

[0087] Further, this guarantees the correct positioning of the sheets (S) when the passage between the first cutting roller (130), introduced following, and the first roller (1 ), and the passage between the second cutting roller (230), introduced following, and the second roller (2), is direct, as shown by way of example in figure 12.

[0088] The means for holding (15) preferably comprise suction holes (16, 17), which more preferably aspirate from the inlet area (11 ) to the end of the first portion (T 1 a).

[0089] Likewise the respective means for holding (25) preferably comprise respective suction holes (26, 27) which aspirate in the respective first portion (T1b).

[0090] However, the means for holding (15) or the respective means for holding (25) might comprise openings or pliers, with each plier movable in the opening between a gripping position and a release position and the other roller having protuberances for pushing a sheet (S) into an opening. In this case, the pliers are in a gripping position at least in the first portion (T1a), preferably in the inlet area (11 ), or in the respective first portion (T1 b). The use of pliers and protuberances, at least without further specifications, prevents direct passage as described above between the first cutting roller (130) and the first roller (1 ) and between the second cutting roller (230) and the second roller (2) due to the interferences among components; this can be resolved, for example, by interposing a specially conformed transfer roller.

[0091] More preferably, the suction holes (16, 17) are connected to an internal tube (150) of suction which has a suction arc (150a) that covers the passage of the suction holes (16, 17) from the inlet (11 ) to the end of the first portion (T1a).

[0092] With respect to other suction methods, the one having an internal tube (150) facilitates high speed of transfer of the sheets (S). Further, a suction arc (150a) that covers the passage of the suction holes (16, 17) from the inlet (11 ) to the end of the first portion (T1a) ensures the correct positioning of the sheets (S) as far as the first folding area (P1 ).

[0093] Owing to the high velocities of transfer allowed, it is preferable for the suction along the respective first portion (T1 b) to utilise a respective internal suction tube with a respective suction arc, as illustrated by way of example in figure 13.

[0094] In a known realisation, the means for holding (15) can comprise rows of suction holes (16, 17) arranged in the direction of the first rotation axis (X1 ) and connected to the suction arc (150a) which is made as a cylindrical opening which extends for a portion of circumference and is connected to an aspirating conduit, i.e. to means for distributing the depression. In other words, the suction holes (16, 17) aspirate exclusively when they flank the cylindrical opening during the rotation.

[0095] Likewise the respective means for holding (25) can comprise rows of respective suction holes (26, 27) arranged in the direction of the second rotation axis (X2) and connected to a respective cylindrical opening which extends by a portion of circumference and is connected to a respective aspirating conduit, i.e. to respective means for distributing the depression.

[0096] In a realisation of an interfolding machine (1000) known to the technical expert in the field, the means for holding (15) are arranged in such a way as to divide the lateral surface (11 ) into two or more parts (11a, 11b, 11c) each having a circumferential extension equal to half the same length (SI), or approximately half the same length (SI). Each part of the two or more parts (11a, 11 b, 11c) has two ends (12a, 13a, 12b, 13b, 12c, 13c) and an equidistant part (14a, 14b, 14c) which is equidistant, or is approximately equidistant, from the two ends (12a, 13a, 12b, 13b, 12c, 13c).

[0097] The respective means for holding (25) are arranged in such a way as to divide the respective lateral surface (21 ) into two or more portions (21a, 21 b, 21c) each having a circumferential extension equal to half the same length (SI), or approximately half the same length (SI). Each portion of the two or more portions (21a, 21 b, 21c) is configured for holding a sheet (S) and has two respective ends (22a, 23a, 22b, 23b, 22c, 23c) and a respective equidistant part (24a, 24b, 24c) which is equidistant, or is approximately equidistant, from the two respective ends (22a, 23a, 22b, 23b, 22c, 23c).

[0098] In the technical language the two or more parts (11a, 11 b, 11c) and the two or more portions (21a, 21b, 21c) are known as fold areas.

[0099] The first supply line (100) supplies half a sheet (S), or approximately half a sheet (S), on each of the two or more parts (11a, 11 b, 11c); and the second supply line supplies half a sheet (S), or approximately half a sheet (S), on each of the two or more portions (21a, 21b, 21c).

[0100] The first rotation axis (X1 ) and the second rotation axis (X2) are spaced from one another in such a way that, at the joining plane (U), two flanked sheets (S) can be interposed between the lateral surface (11 ) and the respective lateral surface (21 ), the means for holding (15) can act on the sheet (S) interposed more closely to the respective lateral surface (21 ) and the respective means for holding (25) can act on the sheet (S) interposed more closely to the lateral surface (11 ).

[0101] The first roller (1 ) is orientated with respect to the first rotation axis (X1 ) and the second roller (2) is orientated with respect to the second rotation axis (X2) so that during the rotation thereof an end 12a, 13a, 12b, 13b, 12c, 13c) crosses the joining plane (U) together with a respective equidistant part (24a, 24b, 24c) facing towards the first roller (1 ) and, vice versa, a respective end (22a, 23a, 22b, 23b, 22c, 23c) crosses the joining plane (U) together with an equidistant part (14a, 14b, 14c) facing towards the second roller (2).

[0102] The means for holding (15) are configured to hold at least when each of the two ends (12a, 13a, 12b, 13b, 12c, 13c) moves along the first portion (T1a) and the respective means for holding (25) are configured to hold at least when each of the respective two ends (22a, 23a, 22b, 23b, 22c, 23c) moves along a respective first portion (T1b) between the joining plane (U) and the second folding area (P2).

[0103] The means for holding (15) preferably hold only at the two ends (12a, 13a, 12b, 13b, 12c, 13c) and the respective means for holding (25) preferably hold only at the two respective ends (22a, 23a, 22b, 23b, 22c, 23c).

[0104] The functioning and, possibly, the structure of the interfolding machine (1000) is therefore simpler while guaranteeing the correct movement of the sheets (S) and there are fewer risks that the passage of the sheets (S) from the first roller (1 ) to the second roller (2’), and vice versa, will not occur.

[0105] As can be observed in figure 12, while in the inlet area (11 ) the first roller (1 ) receives the first ends (I) and the second ends (F) at the means for holding (15), this does not occur with the second roller (2). Typically, in a case where the second roller (2) receives the sheets (S) for a portion between the respective inlet area (12) and the joining plane (U), the second roller (2) comprises respective means of holding (28) at the respective equidistant parts (24a, 24b, 24c) configured to hold the first ends (I) and the second ends (F) of the sheets (S) of the second supply line (200) from the respective inlet area (12) to the joining plane (U).

[0106] Figure 12 shows, at the equidistant parts (14a, 14b, 14c), means of holding that comprise aspiration blocks, which are alike to the aspiration blocks of the respective means of holding (28) and which are not strictly necessary. Obviously, the aspiration blocks, as with the respective means of holding (28), must not be active on the crossing of the joining plane (U) when they are facing towards the other roller, from between the first roller (1 ) and the second roller (2), so as to enable the transfer of the sheets (S).

[0107] In a use mode, the suction line connected to the aspiration blocks is kept switched off while in a different use mode the suction line connected to the aspiration blocks is kept switched on between the inlet area (11 ) and the joining plane (U), then is switched off at the passage of the sheet (S) from the first roller (1 ) to the second roller (2).

[0108] The aspiration blocks have been illustrated to show how the interfolding machine (1000) of the invention can be made for a plurality of types of production, thus being more flexible with respect to the solutions in the prior art.

[0109] Figures 8 and 10 show, with shading, the arcs in which the first ends (I) and the second ends (F) as well as the sheets (S) of the first succession (T1 ) on the first roller (1 ) to the left, and the sheets (S) of the second succession (T2) on the second roller (2) on the right. Further, these figures show, in dotted lines, the first portion (T1a) and the respective first portion (T1b). The shading of the second roller (2) of figures 8 and 10 shows an example of the suction portions of the respective means of holding (28) which enable taking the first ends (I) and the second ends (F) of the second succession (T2) from the respective inlet area (I2) to the joining plane (U).

[0110] Figures 8 and 10, with the aid of figures 9 and 11 , also illustrate two different embodiments of the first roller (1 ) which enable taking the first ends (I) and the second ends (F) of the sheets (S) of the first succession (T1 ) from the inlet area (11 ) to the first folding area (P1 ). In figure 8 the same components of the means for holding (15), for example the suction holes (16, 17), hold from the inlet area (11 ) to the first folding area (P1 ). In figure 10, the same result is obtained with more components of the means for holding (15); in the illustrated example, the suction holes (16, 17) hold along to the joining plane (U) and other suction holes, staggered axially with respect to the suction holes (16, 17), aspirate from the joining plane (U) up to the first folding area (P1 ).

[0111] The first supply line (100) preferably comprises a first strip supply line (110) which supplies a first strip (N1 ) and cutting means (130) comprising a blade or counterblade (131 ) and a first cutting roller (132) which comprises first means for holding (133) sheets (S).

[0112] The first supply line (100) is configured in such a way that the first cutting roller (132) and the blade or counter-blade (131 ) cut the first strip (N1 ) so as to create a first succession of sheets (S) of, or approximately of, the same length (SI).

[0113] Further, the second supply line (200) comprises a second strip supply line (210) which supplies a second strip (N2) and second cutting means (230) comprising a respective blade or counter-blade (231 ) and a second cutting roller (232) which comprises second means for holding (233) sheets (S). The second supply line (200) is configured in such a way that the second cutting roller (232) and the respective blade or counter-blade (231 ) cut the second strip (N2) so as to create a second succession of sheets (S) of, or approximately of, the same length (SI).

[0114] Further:

[0115] - the first roller (1 ) is downstream of the first cutting roller (132) and receives the sheets (S) cut from the first cutting roller (132), more preferably directly therefrom;

[0116] - the second roller (2) is downstream of the second cutting roller (232) and receives the sheets (S) cut from the second cutting roller (232), more preferably directly therefrom;

[0117] - the first cutting roller (132), the second cutting roller (232), the first roller (1 ) and the second roller (2) rotate at a same tangential velocity (w1 , w2), clearly in scalar terms.

[0118] A like interfolding machine (1000) enables obtaining precise sheets (S) and facilitates correct transfer thereof up to the first roller (1 ) and the second roller (2).

[0119] In the accompanying figures, the cylindrical lateral surface (11 ) of the first roller (1 ) is subdivided into three parts, as is the respective cylindrical lateral surface (21 ) of the second roller (2). In figure 12, the first rotation axis (X1 ) and the second rotation axis (X2) are both orthogonal to the sheet and horizontal.

[0120] The same figures show how preferably the joining plane (U) is a horizontal plane and how the sheets (S) cross it vertically, arranged on a first succession (T1 ) and a second succession (T2), as they can arrive in a vertical or circular trajectory.

[0121] As can be observed in figure 12, the position of the first folding area (P1 ) is definable from the angle formed between the joining plane (U) and a plane passing through the first rotation axis (X1 ) and the distancing area of the sheets (S) from the lateral surface (11 ) and the position of the second folding area (P2) is definable from the angle formed between the joining plane (U) and a plane passing through the second rotation axis (X2) and the distancing area of the sheets (S) from the respective lateral surface (21 ).

[0122] Figure 13 also enables observing the orientation of the first roller (1 ) and the second roller (2) respectively with respect to the first rotation axis (X1 ) and the second rotation axis (X2) and therefore between one another. The angular position of the second roller (2) is such that the respective equidistant part (24a, 24b, 24c) is about to cross the joining plane (U) together with two ends (12a, 13a, 12b, 13b, 12c, 13c) of successive parts of the two or more parts (11a, 11b, 11c). Still in figure 13, note how the two or more parts (11a, 11b, 11c) define angles of circumference (alfa) that are identical to one another.

[0123] The lateral surface (11 ) and the respective lateral surface (21 ) typically have the same diameter (11diam, 21diam).

[0124] The means for holding (15) and the respective means for holding (25) shown by way of example in the embodiment of figure 12 respectively comprise suction holes (16, 17) and respective suction holes (26, 27) which operate in the first portion (T1A) and in the respective first portion (T1 b).

[0125] Several methods are known for realising means for holding (15), the respective means for holding (25), the first means for holding (133) or the second means for holding (233), as for example discussed in EP3724112B1 , in EP3067303B1 or in EP1457444B2.

[0126] The holes shown by way of example in the first means for holding (133) and in the second means for holding (233) of figure 12 are illustrated schematically as they are of known type. The support means (5) are schematically represented in figures from 12 to 16. The example diagram comprises vertically-mobile forming tables (51 ) and separating tables (52) which are mobile at least horizontally in order to be placed between a formed pack (P) of interfolded sheets (S) on the forming tables (51 ) and the sheets (S) in arrival.

[0127] The first folding elements (3) and second folding elements (4) are known in the sector and described, for example, in EP2437994B1 . As shown by way of example in figures from 12 to 16, the movement thereof is coordinated with that of the first roller (1 ) and the second roller (2) between an upper position internally of a recess and a lower position between the first roller (1 ) or the second roller (2) and the support means (5).

[0128] It is understood that the above has been described by way of non-limiting example and that any constructional variants are considered to fall within the protective scope of the present technical solution, as claimed in the following.

Claims

CLAIMS1 ) A method for producing a pack (P) of interfolded sheets (S), comprising interfolded sheets (S), each having, or having approximately, a same length (SI) between a first end (I) and a second end (F), wherein:- each sheet (S) is W-folded having, between the first end (I) and the second end (F), two folds (Sp) and a central fold (Scentr) which is interposed between the two folds (Sp), with each of the two folds (Sp) and the central fold (Scentr) separating panels (Span) of sheet (S) having an identical extension, equal to a quarter of the same length (SI), or approximately of an identical extension;- the first end (I) and the second end (F) of each sheet (S) are separated from the first end (I) and from the second end (F) of the other sheets (S);- the sheets (S) have the same orientation, having all the central folds (Scentr) on a same side with respect to the respective two folds (Sp);- each sheet (S), with the exception of the end sheets (S), is interfolded with two sheets (S) that are both on the same side with respect to the sheet (S) and each of the two sheets (S) is interfolded with the sheet (S) with two panels (Span), the method comprising steps of:- providing a first succession (T1 ) of sheets (S) and a second succession (T2) of sheets (S) with the sheets (S) having, or approximately having, a same length (SI) between a first end (I) and a second end (F), a central part (S) which is halfway between the first end (I) and the second end (F) and two intermediate parts (Si) respectively halfway between the first end (I) and the central part (Sc) and halfway between the central part (Sc) and the second end (F);- flanking the sheets (S) of the first succession (T1) and of the secondsuccession (T2) in such a way that the sheets (S) of the first succession (T1 ) are staggered by half the same length (SI), or approximately by half the same length (SI), with respect to the sheets (S) of the second succession (T2);- W-interfolding the flanked sheets (S), by pulling the flanked sheets (S) of the first succession (T1 ) and of the second succession (T2) together on the side of the first succession (T1 ) at the first ends (I) and the second ends (F) and on the side of the second succession (T2) at the intermediate parts (Si) so as to form, in each sheet (S), two folds (Sp) and a central fold (Scentr) which is interposed between the two folds (Sp).2) The method of the preceding claim, wherein the step of providing a first succession (T1 ) of sheets (S) and a second succession (T2) of sheets (S) comprises steps of:- providing a first strip (N1 );- transversally cutting the first strip (N1 ) repeatedly at a distance equal to a same length (SI), or approximately equal to a same length (SI), so as to obtain a first succession (T1 ) of sheets (S) having, or having approximately, the same extension between the first end (I) and the second end (F);- providing a second strip (N2);- transversally cutting the second strip (N2) repeatedly at a distance equal to a same length (SI), or approximately equal to a same length (SI), so as to obtain a second succession (T2) of sheets (S) having, or having approximately, the same extension between the first end (I) and the second end (F).3) An interfolding machine (1000) for producing a pack (P) of interfoldedsheets (S), comprising interfolded sheets (S), each having, or having approximately, a same length (SI) between a first end (I) and a second end (F), wherein:- each sheet (S) is W-folded having, between the first end (I) and the second end (F), two folds (Sp) and a central fold (Scentr) which is interposed between the two folds (Sp), with each of the two folds (Sp) and the central fold (Scentr) separating panels (Span) of sheet (S) having an identical extension, equal to a quarter of the same length (SI), or approximately of an identical extension;- the first end (I) and the second end (F) of each sheet (S) are separated from the first end (I) and from the second end (F) of the other sheets (S);- the sheets (S) have the same orientation, having all the central folds (Scentr) on a same side with respect to the respective two folds (Sp);- each sheet (S), with the exception of the end sheets (S), is interfolded with two sheets (S) that are both on the same side with respect to the sheet (S) and each of the two sheets (S) is interfolded with the sheet (S) with two panels (Span), the interfolding machine (1000) comprising:- an interfolding unit (10) which W-interfolds sheets (S) folded in a W shape and which comprises a first roller (1 ) which has a lateral surface (11 ) for receiving sheets (S), which comprises means for holding (15) sheets (S) and which rotates with respect to a first rotation axis (X1 ), a second roller (2) which has a respective lateral surface (21 ) for receiving sheets (S), which comprises respective means for holding (25) sheets (S) and which rotates with respect to a second rotation axis (X2) parallel to the first rotation axis (X1 ) and which insists together with the first rotation axis (X1 ) on a joining plane (U), first folding elements (3) and second foldingelements (4);- support means (5) for supporting interfolded sheets (S) beneath the first roller (1 ) and the second roller (2);- a first supply line (100) of sheets (S) which supplies a first succession (T1 ) of sheets (S) on the lateral surface (11 );- a second supply line (200) of sheets (S) which supplies a second succession (T2) of sheets (S) on the respective lateral surface (21 ); wherein:- the first roller (1 ) and the second roller (2) rotate at a same tangential velocity (w1 , w2), with opposite rotation directions to one another;- the first folding elements (3), at a first folding area (P1 ), move the sheets (S) away from the lateral surface (11 ) towards the support means (5);- the second folding elements (4), at a second folding area (P2), move the sheets (S) away from the respective lateral surface (21 ) towards the support means (5);- the first supply line (100) and the second supply line (200) are configured to supply sheets (S) which have, or have approximately, a same length (SI) between a first end (I) and a second end (F), characterised in that the first supply line (100) and the second supply line (200) are configured to supply sheets (S) in such a way that the sheets (S) of the first supply line (100) cross the joining plane (U) staggered by half the same length (SI), or approximately by half the same length (SI), with respect to the sheets (S) of the second supply line (200);- the means for holding (15) are configured in such a way as to hold both the sheets (S) of the first supply line (100) and the sheets (S) of the second supply line (200) at the first ends (I) and the second ends (F) of the sheets (S) for a first portion (T1a) which is between the joining plane (U) and the first folding area (P1 )so that the first folding elements (3) form a central fold (Scentr), which is central between the first end (I) and the second end (F) of the sheet (S), alternatingly, on a sheet (S) of the first supply line (100) or on a sheet (S) of the second supply line (200).4) The interfolding machine (1000) of the preceding claim, wherein the first portion (T 1 a) extends from the joining plane (U) to the first folding area (P1 ).5) The interfolding machine (1000) of claim 3 or 4, wherein:- the first supply line (100) supplies the sheets (S) to the first roller (1 ) at an inlet area (11 ) in such a way that the lateral surface (11 ) receives at least a fraction of the sheets (S) before the sheets pass from the joining plane (U);- the second supply line (200) supplies the sheets (S) to the second roller (2) at a respective inlet area (I2) in such a way that the respective lateral surface (21) receives at least a fraction of the sheets (S) before the sheets (S) pass from the joining plane (U);- the means for holding (15) hold the first ends (I) of the sheets (S) of the first supply line (100) from the inlet area (11 ) to the end of the first portion (T 1 a).6) The interfolding machine (1000) according to claim 5, wherein the means for holding (15) comprise suction holes (16, 17) which aspirate from the inlet area (11 ) unti the end of the first portion (T 1 a).7) The interfolding machine (1000) of the preceding claim, wherein the suction holes (16, 17) are connected to an internal tube (150) of suction which has a suction arc (150a) that covers the passage of the suction holes (16, 17) from the inlet (11 ) to the end of the first portion (T 1 a).8) The interfolding machine (1000) of any one of claims from 3 to 7, wherein:- the means for holding (15) are arranged in such a way as to divide the lateralsurface (11 ) into two or more parts (11a, 11 b, 11c) each having a circumferential extension equal to half the same length (SI), or approximately half the same length (SI);- each part of the two or more parts (11a, 11 b, 11c) has two ends (12a, 13a, 12b, 13b, 12c, 13c) and an equidistant part (14a, 14b, 14c) which is equidistant, or is approximately equidistant, from the two ends (12a, 13a, 12b, 13b, 12c, 13c);- the respective means for holding (25) are arranged in such a way as to divide the respective lateral surface (21 ) into two or more portions (21a, 21 b, 21c) each having a circumferential extension equal to half the same length (SI), or approximately half the same length (SI);- each of the two or more portions (21a, 21b, 21c) has two respective ends (22a, 23a, 22b, 23b, 22c, 23c) and a respective equidistant part (24a, 24b, 24c) which is, or is approximately, equidistant, from the two respective ends (22a, 23a, 22b, 23b, 22c, 23c);- the first supply line (100) supplies half a sheet (S), or approximately half a sheet (S), on each of the two or more parts (11a, 11 b, 11 c);- the second supply line supplies half a sheet (S), or approximately half a sheet (S), on each of the two or more portions (21a, 21 b, 21c);- the first rotation axis (X1 ) and the second rotation axis (X2) are spaced from one another in such a way that, at the joining plane (U), two flanked sheets (S) can be interposed between the lateral surface (11 ) and the respective lateral surface (21 ), the means for holding (15) can act on the sheet (S) interposed more closely to the respective lateral surface (21 ) and the respective means for holding (25) can act on the sheet (S) interposed more in proximity to the lateral surface (11 );- the first roller (1 ) is orientated with respect to the first rotation axis (X1 ) and thesecond roller (2) is orientated with respect to the second rotation axis (X2) in such a way that during the rotation thereof an end (12a, 13a, 12b, 13b, 12c, 13c) crosses the joining plane (U) together with a respective equidistant part (24a, 24b, 24c) facing towards the first roller (1 ) and, vice versa, a respective end (22a, 23a, 22b, 23b, 22c, 23c) crosses the joining plane (U) together with an equidistant part (14a, 14b, 14c) facing towards the second roller (2);- the means for holding (15) are configured to hold at least when each of the two ends (12a, 13a, 12b, 13b, 12c, 13c) moves along the first portion (T1a); and- the respective means for holding (25) are configured to hold at least when each of the respective two ends (22a, 23a, 22b, 23b, 22c, 23c) moves along a respective first portion (T1 b) between the joining plane (U) and the second folding area (P2).9) The interfolding machine (1000) of any one of claims from 3 to 8, wherein the means for holding (15) hold only at the two ends (12a, 13a, 12b, 13b, 12c, 13c) and wherein the respective means for holding (25) hold only at the two respective ends (22a, 23a, 22b, 23b, 22c, 23c).10) The interfolding machine (1000) of claim 8 or 9 when dependent also on claim 5, wherein the second roller (2) comprises respective means of holding (28) at the respective equidistant parts (24a, 24b, 24c) configured to hold the first ends (I) and the second ends (F) of the sheets (S) of the second supply line (200) from the respective inlet area (I2) to the joining plane (U).11 ) The interfolding machine (1000) of any one of claims from 3 to 10, wherein:- the first supply line (100) comprises a first strip supply line (110) which supplies a first strip (N1 ) and cutting means (130) comprising a blade or counter-blade (131 ) and a first cutting roller (132) which comprises first means for holding (133) sheets(S);- the first supply line (100) is configured so that the first cutting roller (132) and the blade or counter-blade (131 ) cut the first strip (N1 ) so as to create a first succession of sheets (S) of, or approximately of, the same length (SI); - the second supply line (200) comprises a second strip supply line (210) which supplies a second strip (N2) and second cutting means (230) comprising a respective blade or counter-blade (231 ) and a second cutting roller (232) which comprises second means for holding (233) sheets (S);- the second supply line (200) is configured in such a way that the second cutting roller (232) and the respective blade or counter-blade (231 ) cut the second strip(N2) so as to create a second succession of sheets (S) of, or approximately of, the same length (SI);- the first roller (1 ) is downstream of the first cutting roller (132) and receives the sheets (S) cut from the first cutting roller (132); - the second roller (2) is downstream of the second cutting roller (232) and receives the sheets (S) cut from the second cutting roller (232);- the first cutting roller (132), the second cutting roller (232), the first roller (1 ) and the second roller (2) rotate at a same tangential velocity (w1 , w2).

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