An apparatus forms stacks of interfolded sheets. First and second folding rolls receive the plurality of sheets, move the plurality of sheets through the nip, and fold the plurality of sheets into a stack of interfolded sheets downstream of the nip. A packing finger is associated with each folding roll, and the respective packing fingers move between a retracted position and an extended position relative to the corresponding folding roll with alternate movement relative to each other between the retracted position and the extended position to engage the plurality of sheets and form the stack of interfolded sheets. A liquid delivery system delivers liquid to a sheet in the plurality of sheets when the sheet is on one of the folding rolls and before the sheet is moved to the stack.

A machine (1) for producing packages of napkins, tissues, towels, or similar products, comprises a support frame (100) to support a feeding group (10) which feeds a first and a second web of paper (5a, 5b). The support frame (100) supports, furthermore, a cutting group (20) which cuts the first and second webs of paper (5a, 5b) respectively in a first and a second plurality of sheets (6) of predetermined length, and a folding or interfolding group (30) which folds or interfolds the sheets of paper (6) at a folding or interfolding zone, (35) in such a way to obtain a stack (150) of folded or interfolded sheets, according to a predetermined folding or interfolding configuration. The cutting group (20) and the folding or interfolding group (30) are mounted on the same support body (110) to move between an assembled position in which is supported by the support frame (100), and a disassembled position, in which is not supported by the support frame (100). A displacement group (50) is, furthermore, provided to displace the support body (110) between the assembled position and the disassembled position. The displacement group (50) and the support body (110) are provided with respective engagement portions (58,118) to engage with each other in such a way to allow the displacement group (50) to displace the support body (110) between the assembled position and the disassembled position.

A paper creasing device includes a receiving member including a groove extending in a fixed direction; a rotary blade movable along the groove; and a movement mechanism for moving the rotary blade along the groove at a fixed height in a range between first and second edges of paper in a width direction, the paper being placed on an upper surface of the receiving member. The receiving member is formed to have shearing forces applied to the paper sandwiched between the rotary blade and the groove in an outside range and an inside range in the width direction of the receiving member, the outside range corresponding to at least one of the paper edges located on a side where the rotary blade starts contacting the paper when moving along the groove, and the shearing force in the outside range being smaller than the shearing force in the inside range.