Folding, or interfolding, unit of a web, or sheet, of paper in a paper converting machine

Abstract

Folding or interfolding unit of a web, or sheet, of paper, comprising a first and a second folding or interfolding roll, of a web, or sheet, of paper, configured to fold or interfold, the web or sheet of paper according to a predetermined folding or interfolding configuration, at a folding or interfolding zone arranged between the first and the second folding or interfolding roll. The folding or interfolding unit comprise, furthermore, a first and a second plurality of detaching fingers configured to cause the web or sheet of paper to be detached from the external surface of the respective folding or interfolding roll.

1 . A folding or interfolding unit of a web, or sheet, of paper, comprising:
 a first and a second folding or interfolding roll of a web or sheet of paper configured to fold or interfold said web or sheet of paper according to a predetermined folding or interfolding configuration at a folding or interfolding zone arranged between said first and said second folding or interfolding roll;   a first and a second plurality of detaching fingers configured to cause said web or sheet of paper to be detached from an external lateral surface of the respective folding or interfolding roll;   a first and a second actuation group configured, respectively, to cause a back-and-forth oscillatory motion of said first and second plurality of detaching fingers towards/from said folding or interfolding zone, in such a way to cause a respective web or sheet of paper to be detached, respectively, from said first and second folding or interfolding roll, said folding or interfolding unit being characterized in that said first and second actuation group are, furthermore, configured to postpone or anticipate said oscillatory motion, respectively, of said first and of said second plurality of detaching fingers with respect to a predetermined reference oscillatory motion, in such a way to delay or anticipate, the instant (tr) in which said first and second pluralities of detaching fingers are arranged to cause said web or sheet of paper to be detached, respectively, from said first folding roll and from said second folding roll.   
     
     
         2 . The folding or interfolding unit of a web, or sheet, of paper according to  claim 1 , wherein each said first and second folding or interfolding roll, comprises:
 a tubular body configured to rotate about a longitudinal rotation axis in a predetermined sense of rotation, said tubular body being provided with an external lateral surface and with an internal lateral surface pneumatically communicating with each other through a plurality of suction holes organized according to plurality of longitudinal rows;   a suction chamber defined within said folding or interfolding roll and pneumatically connected to a vacuum generation device configured to generate a predetermined vacuum degree;   a vacuum distribution device configured to selectively pneumatically connect said suction chamber with at least one row of suction holes of said plurality, at determined angular positions of said tubular body in such a way to cause the processed sheet or web of paper to be sucked, and to adhere at a corresponding portion of said external lateral surface of said folding or interfolding roll arranged between a catching point and a releasing point (P 1 ,P 2 ) having determined angular positions.   
     
     
         3 . The folding or interfolding unit of a web, or sheet, of paper according to  claim 2 , wherein a displacement device is, furthermore, provided configured to move said vacuum distribution device, in such a way to change the angular position of said catching point (P 1 ) and/or of said releasing point (P 2 ) of said web or sheet of paper, and, therefore, to anticipate, or postpone, the instant in which said web or sheet of paper adheres to or leaves said external lateral surface of said first, or second, folding or interfolding roll. 
     
     
         4 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 3 , wherein said displacement device is configured to move said vacuum distribution device during said rotation of said tubular body about said longitudinal rotation axis. 
     
     
         5 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 3  wherein said vacuum distribution device comprises a fixed tubular body coaxially mounted within said tubular body, said fixed tubular body being pneumatically connected with said device for generating a predetermined vacuum degree and being provided with at least one aperture and wherein said displacement device is configured to cause a rotation of said fixed tubular body about said longitudinal rotation axis. 
     
     
         6 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 3  wherein said displacement device comprises an actuation device selected from the group comprising:
 a linear actuator; 
 a mechanical actuator; 
 an electric actuator; 
 an electromechanical actuator; 
 a pneumatic actuator; 
 or a combination thereof. 
 
     
     
         7 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 5 , wherein said vacuum distribution device comprises a first and a second sealing member integral to said fixed tubular body at opposite sides with respect to said or each aperture, said first and second sealing members being positioned longitudinally to said tubular body. 
     
     
         8 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 2 , wherein said vacuum distribution device comprises a plurality of sealing members integral to said tubular body and positioned longitudinally to the same, each sealing member of said plurality being associated to at least one row of suction holes arranged to pneumatically connect said external surface with said device for generating a predetermined vacuum degree. 
     
     
         9 . The folding or interfolding unit according to  claim 1 , wherein said first and second actuation group comprise, respectively:
 a first and a second motor group configured to cause a rotation of a first and of a second motor shaft about respective axes of rotation;   a first and a second oscillator device configured to convert the rotational motion of said first and of said second motor shaft on an inlet axis, to an oscillatory motion on an outlet axis, to transmit said oscillatory motion to said first and to said second plurality of detaching fingers.   
     
     
         10 . The folding or interfolding unit according to  claim 9 , wherein said first and second motor group are, furthermore, configured to change the speed of rotation of said first and of said second shaft of rotation with respect to a reference speed of rotation (vm*) for a determined interval of time (Δt*), in such a way anticipate, or postpone, respectively, the oscillatory motion of said first and of said second plurality of detaching fingers. 
     
     
         11 . The folding or interfolding unit according to  claim 10 , wherein said first and second actuation groups comprise, respectively:
 a first and a second motor group configured to cause a rotation of a first and of a second motor shaft about respective axes of rotation;   a first and a second oscillator device configured to convert the rotational motion of said first and of said second motor shaft to an oscillatory motion of said first and of said second plurality of detaching fingers;   and wherein a first and a second adjustment device are, furthermore, provided respectively associated to said first and to said second oscillator device and configured to anticipate or postpone, the instant (tr) in which said first and second pluralities of detaching fingers are arranged to hit said web or sheet of paper to cause said web or sheet of paper to be detached, respectively, from said first and from second folding or interfolding roll.   
     
     
         12 . The folding or interfolding unit according to  claim 11  wherein said first and second adjustment devices comprise, respectively, a first and a second phase-shifter gearbox. 
     
     
         13 . The folding or interfolding unit according to  claim 12 , wherein said first and second phase-shifter gearbox are, respectively, provided with a first and with a second epicycloidal gear, said first and second phase-shifter gearbox being operatively connected, respectively, to a first and to a second motor configured to operate, respectively, said first and second epicycloidal gear in such a way to accelerate, or decelerate, said oscillatory motion of said first and second pluralities of detaching fingers. 
     
     
         14 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 4  wherein said displacement device and/or said first and second actuation group are configured to be operated by an operator through an interface panel, or HMI “Human Machine Interface”. 
     
     
         15 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 14  wherein said displacement device and/or said first and second actuation group are operated by an electronic control unit as a function of at least one of the following parameters:
 instantaneous operating speed of the first and of the second folding or interfolding roll; 
 length of the sheet of paper; 
 paper weight. 
 
     
     
         16 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 2  wherein said plurality of longitudinal rows of rows of suction holes are organized according to a plurality of suction groups, each suction group of said plurality comprising at least 2 longitudinal rows of holes close to each other. 
     
     
         17 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 2  wherein said plurality of longitudinal rows of suction holes are organized according to a plurality of suction groups, each suction group of said plurality comprising at least 3 longitudinal rows of holes close to each other. 
     
     
         18 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 16 , wherein the distance between two following suction groups of said plurality is equal to the length of the processed sheet. 
     
     
         19 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 12 , wherein said first and second phase-shifter gearboxes are operatively connected, respectively, to said first and to said second motor group by a first and a second transmission belt. 
     
     
         20 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 19 , wherein said first and second phase-shifter gearboxes are, furthermore, operatively connected to a first and to a second actuation device by a first and a second transmission belt, said first and second actuation devices being arranged to transmit the rotational motion caused by said first and second motor groups, respectively, to said first and to said second oscillator device. 
     
     
         21 . The folding or interfolding unit of a web, or sheet, of paper, according to  claim 20 , wherein said first and second phase-shifter gearboxes are, respectively, provided with a first and with a second electric motor arranged to adjust the speed of rotation of said first and of said second actuation device. 
     
     
         22 . The folding or interfolding unit according to  claim 9 , wherein said first oscillator device and said second oscillator device are, respectively, provided with a first and a second desmodromic cam. 
     
     
         23 . The folding or interfolding unit according to  claim 9 , wherein said first and second oscillator devices are connected at respective first ends of said first and of said second transmission group, said first and second transmission groups being operatively connected, at a respective second end opposite to said first end respectively, to said first and to said second plurality of detaching fingers. 
     
     
         24 . A method for folding or interfolding, a web or sheet of paper in a paper converting machine comprising the steps of:
 feeding at least one web or sheet of paper along an advancing direction;   folding, or interfolding, said web or sheet of paper at a predetermined folding or interfolding zone, of a paper converting machine, said folding or interfolding step, being carried out by a first and a second folding or interfolding roll at a folding or interfolding zone, defined between them;   detaching by a first and a second plurality of detaching fingers said web or sheet of paper from the external lateral surface of the respective folding or interfolding roll, said detaching step being carried out causing a back-and-forth oscillatory motion of said first and second plurality of detaching fingers towards/from said folding or interfolding zone;   said method being characterized in that an adjustment step is, furthermore, provided for adjusting the phase between said first and second pluralities of detaching fingers and said first and second folding or interfolding rolls, respectively, said adjustment step being arranged to delay or anticipate, said oscillatory motion of said first and second plurality of detaching fingers, in particular with respect to a predetermined reference oscillatory motion, in such a way to postpone or anticipate, at least the instant (tr) in which said first and second pluralities of detaching fingers are arranged to cause the detachment of said web or sheet of paper, respectively, from said first and from second folding or interfolding roll.   
     
     
         25 . The method for folding or interfolding a web or sheet of paper, according to  claim 24  wherein said oscillatory motion of said first and second plurality of detaching fingers is adjusted by an electronic control unit as a function of at least one of the following parameters:
 instantaneous operating speed of the folding or interfolding roll; 
 operative speed of the folding or interfolding roll; 
 length of the sheet; 
 paper weight. 
 
     
     
         26 . The method for folding or interfolding a web or sheet of paper, according to  claim 25  wherein said electronic control unit automatically adjusts said oscillatory motion of said first and second pluralities of detaching fingers, or adjust said oscillatory motion of said first and second pluralities of detaching fingers on the basis of a command received by an interface panel or HMI (Human Machine Interface).