Folding or interfolding unit, and method for folding or interfolding a plurality of sheets of paper

A folding or interfolding unit of a plurality of sheets of paper, comprising:

• a first and a second folding or interfolding roll configured to fold or interfold said plurality of sheets of paper according to a predetermined folding or interfolding configuration, at a folding or interfolding zone, each said first and second folding or interfolding rolls comprising:
• a tubular body configured to rotate in un a predetermined direction of rotation about a longitudinal rotation axis oriented along a horizontal direction;
• a plurality of gripping groups integral in rotation with said tubular body, each gripping group of said plurality comprising:
• a mechanical gripping member configured to move, at a gripping point having a first angular position, from a releasing configuration to a gripping configuration, where is arranged to mechanically hold said or each, sheet of said plurality of sheets up to a releasing point having a second angular position;
• at least one suction hole associated to each mechanical gripping member and configured to cause said or each sheet of paper to be sucked to introduce the same into the mechanical gripping member;
• a vacuum distribution device configured to selectively pneumatically connect at least one suction hole at a time to a device for generating a determined vacuum degree in such a way to cause said or each sheet to be sucked between a position of starting suction and a position of ending suction;
• each said first and second folding or interfolding rolls furthermore comprises:
• an actuation group configured to cause a mechanical gripping member at a time of said plurality to move from said releasing configuration to said gripping configuration at said gripping point and from said gripping configuration to said releasing configuration at said releasing point;
• an adjustment group configured to move said actuation group with respect to said respective folding, or interfolding roll, to selectively move the same in a predetermined spatial position to which correspond a first and a second angular position of said gripping point and of said releasing point respectively;
• and wherein each said folding or interfolding roll, comprises:
• a fixed tubular body positioned coaxially to said tubular body, said fixed tubular body being provided with an external lateral surface and an internal lateral surface communicating with each other by at least one aperture and a longitudinal cavity pneumatically connected to said device for generating a predetermined vacuum degree;
• and wherein said vacuum distribution device comprises:
• a suction chamber pneumatically communicating to said longitudinal cavity and delimited by an internal lateral surface of said tubular body and laterally by a first and a second sealing element arranged to extend longitudinally to said tubular body, said suction chamber being configured to selectively pneumatically connect said longitudinal cavity to a suction hole at a time between said first and second predetermined angular positions.

A method for folding or interfolding a plurality of sheets of paper, comprising the steps of:

• folding or interfolding by a first and a second folding or interfolding roll said plurality of sheets of paper according to a predetermined folding or interfolding configuration, at a folding or interfolding zone, each said first and second folding or interfolding rolls comprising:
• a tubular body configured to rotate in a predetermined direction of rotation about a longitudinal rotation axis oriented along a horizontal direction;
• a plurality of gripping groups integral in rotation with said tubular body, each gripping group of said plurality comprising:
• a mechanical gripping member configured to move, at a gripping point having a first angular position, from a releasing configuration to a gripping configuration, where is arranged to mechanically hold said or each, sheet of said plurality of sheets up to a releasing point having a second angular position;
• at least one suction hole associated to each mechanical gripping member and configured to cause said or each sheet of paper to be sucked to introduce the same into said mechanical gripping member;
• a vacuum distribution device configured to selectively pneumatically connect at least one suction hole at a time to a device for generating a determined vacuum degree in such a way to cause said or each sheet to be sucked between a position of starting suction and a position of ending suction;
• causing by an actuation group a mechanical gripping member at a time of said plurality to move from said releasing configuration to said gripping configuration at said gripping point and from said gripping configuration to said releasing configuration at said releasing point;
• moving by an adjustment group said actuation group with respect to said respective folding, or interfolding roll, to selectively position the same in a predetermined spatial position to which correspond a first and a second angular position of said gripping point and of said releasing point respectively;
• wherein each actuation group provides a guide member configured to guide each mechanical gripping member at a time along a predetermined trajectory during rotation of said folding or interfolding roll about said longitudinal axis, said guide member comprising at least one closing stretch arranged to cause each mechanical gripping member to move from said releasing configuration to said gripping configuration, and at least one opening stretch arranged to cause each mechanical gripping member to move from said gripping configuration to said releasing configuration;
• and wherein each adjustment group is configured to rotate said guide member with respect to the respective folding, or interfolding roll about said respective longitudinal axis to position said guide member in a predetermined spatial position in such a way to set the angular position of said gripping point and of said releasing point.