A stack of paper sheets, particularly for use as dispenser napkins, includes a plurality of folded sheets. Each folded sheet is folded along a first folding line so that a part of a free edge opposite to the first folding line is located on an outer surface of the folded sheet and inward of the outer peripheral edges of the folded sheet, whereby a starter fold is formed. Each folded sheet is further folded along a second folding line non-parallel to the first folding line, the second folding line separating the folded sheet in two panels connected at the second folding line. Two consecutive folded sheets are interfolded so that one panel of one folded sheet is disposed between two panels of the consecutive folded sheet. Also, a method for manufacturing such a stack and folding the sheets included in the stack as well as a dispenser containing such a stack are disclosed.

A roll (1) for folding, or interfolding, a web, or sheet, of paper, (100) fed along an advancing direction in a paper converting machine, or similar machines, comprises a tubular body (10) configured to rotate about a longitudinal rotation axis (101), and having an external lateral surface (11) and an internal lateral surface (12) pneumatically communicating through a plurality of suction holes (3a, 3b) organized in a predetermined number of suction groups (60). Each suction group (60) comprises a predetermined number of close longitudinal rows (30a, 30b) of suction holes (3a, 3b) distributed along the tubular body (10). A suction chamber (20) is, then, provided arranged internally to the roll (1) for folding, or interfolding, and pneumatically connected to a suction device generating a predetermined vacuum level. Each suction group (60) comprises at least 3 close longitudinal rows (30a, 30b, 30c) of suction holes (3a, 3b, 3c) configured to hold each sheet, or web, of paper (100) on the roll (1) at a respective portion of the external lateral surface (11).

A roll (1) for folding, or interfolding, a web, or sheet, of paper, (100) fed along an advancing direction in a paper converting machine, or similar machines, comprises a tubular body (10) configured to rotate about a longitudinal rotation axis (101), and having an external lateral surface (11) and an internal lateral surface (12) pneumatically communicating through a plurality of suction holes (3a, 3b) organized in a predetermined number of suction groups (60). Each suction group (60) comprises a predetermined number of close longitudinal rows (30a, 30b) of suction holes (3a, 3b) distributed along the tubular body (10). A suction chamber (20) is, then, provided arranged internally to the roll (1) for folding, or interfolding, and pneumatically connected to a suction device generating a predetermined vacuum level. Each suction group (60) comprises at least 3 close longitudinal rows (30a, 30b, 30c) of suction holes (3a, 3b, 3c) configured to hold each sheet, or web, of paper (100) on the roll (1) at a respective portion of the external lateral surface (11).

A method for producing stacks of individual web sections involves: (a) directing the continuous web to a perforating station; (b) perforating the continuous web at predetermined intervals and forming sheets of web material between consecutive perforation lines extending laterally across the continuous web, the perforating being carried out via at least one perforation element arranged at the circumference of a perforation roller; (c) directing the continuous web to a cutting station; (d) cutting at second predetermined intervals the continuous web into web sections via a cutting element acting against an anvil element, to generate a clear cut or a tab-bond; (e) folding the web sections via a folding roll; and (f) stacking the folded web section to generate a stack of folded sheets.

A method for producing stacks of individual web sections involves: (a) directing the continuous web to a perforating station; (b) perforating the continuous web at predetermined intervals and forming sheets of web material between consecutive perforation lines extending laterally across the continuous web, the perforating being carried out via at least one perforation element arranged at the circumference of a perforation roller; (c) directing the continuous web to a cutting station; (d) cutting at second predetermined intervals the continuous web into web sections via a cutting element acting against an anvil element, to generate a clear cut or a tab-bond; (e) folding the web sections via a folding roll; and (f) stacking the folded web section to generate a stack of folded sheets.

The folding roller includes a rotation axis and at least a gripping member extending longitudinally along the folding roller, controlled by at least a piezoelectric actuator. The piezoelectric actuator causes a pivoting movement of the gripping member about its pivoting axis parallel to the rotation axis of the folding roller.

The folding roller includes a rotation axis and at least a gripping member extending longitudinally along the folding roller, controlled by at least a piezoelectric actuator. The piezoelectric actuator causes a pivoting movement of the gripping member about its pivoting axis parallel to the rotation axis of the folding roller.

A conveying unit includes a rotatable roller having a first through-hole between the inside and the outside of the roller. A cylindrical member inside the roller has an opening and defines an annular chamber between the member and the roller. An insert borne by the roller inserted in the first through-hole thereof and contacting an external surface of the cylindrical member has a second through-hole in communication with the outside of the roller and extending through the first through-hole and the annular chamber. The first through-hole of the opening is configured such that, when the roller rotates, the insert transits at the opening, temporarily placing the outside of the roller in fluid communication with the annular chamber via the second through-hole, so that a sheet outside the roller and at the first through-hole is pulled against the roller by aspirating means and is conveyed.

A conveying unit includes a rotatable roller having a first through-hole between the inside and the outside of the roller. A cylindrical member inside the roller has an opening and defines an annular chamber between the member and the roller. An insert borne by the roller inserted in the first through-hole thereof and contacting an external surface of the cylindrical member has a second through-hole in communication with the outside of the roller and extending through the first through-hole and the annular chamber. The first through-hole of the opening is configured such that, when the roller rotates, the insert transits at the opening, temporarily placing the outside of the roller in fluid communication with the annular chamber via the second through-hole, so that a sheet outside the roller and at the first through-hole is pulled against the roller by aspirating means and is conveyed.

An interfolding machine (1) is described, including folding rollers (3). Such a roller has a cylindrical sleeve (3C) having a rotation axis (3A), an outer surface (3X) and an inner surface (3Y) defining an inner axial cavity (23) of the cylindrical sleeve (3C). The cylindrical sleeve includes, furthermore, a plurality of suction holes (41, 43) which extend from the outer surface (3X) to the inner surface (3Y) of the cylindrical sleeve (3C). The suction holes are arranged depending on longitudinal alignments (42, 44), parallel to the rotation axis (3A) of the cylindrical sleeve (3C) and angularly staggered in relation to one another. Inside a suction chamber (23A) in the cylindrical sleeve (3C), shutters are stationarily arranged having closing surfaces (37A) cooperating with the inner surface (3Y) of the cylindrical sleeve (3C) to selectively close the suction holes.