Suction roll for paper converting machines

Abstract

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).

1 . 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, said roll ( 1 ) for folding, or interfolding, comprising:
 a tubular body ( 10 ) configured to rotate about a longitudinal rotation axis ( 101 ), said tubular body ( 10 ) providing an external lateral surface ( 11 ) and an internal lateral surface ( 12 ) pneumatically communicating with each other through a plurality of suction holes ( 3   a , 3   b ) organized in a plurality of suction groups ( 60 ) comprising a predetermined number of suction groups ( 60 ), each suction group ( 60 ) of said plurality comprising a predetermined number of close longitudinal rows ( 30   a , 30   b ) of suction holes ( 3   a , 3   b ) distributed along said tubular body ( 10 );   a suction chamber ( 20 ) provided internally to said roll ( 1 ) for folding, or interfolding, and pneumatically connected to a suction device configured to generate a predetermined vacuum level;   a vacuum distribution device ( 50 ) configured to selectively put in pneumatic connection said suction chamber ( 20 ) with at least a row of suction holes ( 3   a , 3   b ) of said plurality, at predetermined angular positions of said tubular body ( 10 ) in such a way to cause the suction of the processed sheet, or web, of paper ( 100 ), and its adhesion at corresponding portions of said external lateral surface ( 11 ) of said roll ( 1 ) for folding, or interfolding;   said roll ( 1 ) for folding, or interfolding, being characterized in that each suction group ( 60 ) comprises at least 3 close longitudinal rows ( 30   a , 30   b , 30   c ) of suction holes ( 3   a , 3   b , 3   c ) configured to hold each sheet, or web, of paper ( 100 ) on said roll ( 1 ) at a respective portion of said external lateral surface ( 11 ) in that said suction groups ( 60 ) of said plurality are distributed on said external lateral surface ( 11 ) in such a way that the arch of circumference arranged between a suction group ( 60 ) and the following suction group ( 60 ) is equal to the length of a processed sheet of paper ( 100 ) and in that said vacuum distribution device ( 50 ) is configured to selectively put each longitudinal row ( 30   a , 30   b , 30   c ) of suction holes ( 3   a , 3   b , 3   c ) of each suction group ( 60 ) in pneumatic connection with said suction chamber ( 20 ) at respective predetermined angular positions of said tubular body ( 10 ).   
     
     
         2 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to  claim 1 , wherein each suction group ( 60 ) comprises at least 4 close longitudinal rows ( 30   a , 30   b , 30   c , 30   d ) of suction holes ( 3   a , 3   b , 3   c , 3   d ). 
     
     
         3 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to any of the previous claims, wherein at least 2 of said close longitudinal rows ( 30   a , 30   b , 30   c , 30   d ) of suction holes ( 3   a , 3   b , 3   c , 3   d ) of each suction group ( 60   a , 60   b , 60   c , 60   d ) are arranged according to directions lying on incident planes (γa,γb,γc,γd) arranged to intersect each other in a line parallel to said longitudinal rotation axis ( 101 ) of said roll ( 1 ). 
     
     
         4 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to  claim 3 , wherein said line is positioned at a distance from said external lateral surface that is smaller than the radius r of said roll. 
     
     
         5 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to any of the previous claims, wherein said close longitudinal rows ( 30   a , 30   b , 30   c , 30 d) of suction holes ( 3   a , 3   b , 3   c , 3   d ) of a same group ( 60   a , 60   b , 60   c , 60   d ) are aligned with respect to the direction longitudinal to said roll ( 1 ), in such way that the axes ( 103   a , 103   b , 103   c , 103   d ) of the respective suction holes ( 3   a , 3   b , 3   c , 3   d ) lie on a same plane orthogonal to said longitudinal rotation axis ( 101 ). 
     
     
         6 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to any claims from  1  to  4 , wherein said close longitudinal rows ( 30   a , 30   b , 30   c , 30   d ) of suction holes ( 3   a , 3   b , 3   c , 3   d ) of a same group ( 60   a , 60   b , 60   c , 60   d ) are staggered to each other with respect to the direction longitudinal to said roll ( 1 ), in such way that the axes ( 103   a , 103   b , 103   c , 103   d ) of the respective suction holes ( 3   a , 3   b , 3   c , 3   d ) lie on different planes. 
     
     
         7 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to  claim 3 , wherein said incident planes (γa,γb,γc,γd) form an angle (θ 1 ,θ 2 ,θ 3 ) having an amplitude comprised between 0.1° and 5°. 
     
     
         8 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to  claim 7 , wherein said incident planes (γa,γb,γc,γd) form an angle (θ 1 ,θ 2 ,θ 3 ) having an amplitude comprised between 1° and 5°. 
     
     
         9 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to  claim 3 , wherein said incident planes (γa,γb,γc,γd) form an angle (θ 1 ,θ 2 ,θ 3 ) having an amplitude comprised between 2° and 20°. 
     
     
         10 . Roll ( 1 ) for folding, or interfolding, a web, or sheet, of paper, according to  claim 9 , wherein said incident planes (γa,γb,γc,γd) form an angle (θ 1 ,θ 2 ,θ 3 ) having an amplitude comprised between 4° and 15°. 
     
     
         11 . Machine for folding, or interfolding, a web, or sheet, of paper, characterized in that it comprises an interfolding unit equipped with first and second rolls for folding, or interfolding, according to any claims from  1  to  10 , configured in such a way to be counter-rotating. 
     
     
         12 . Method for making a roll for folding, or interfolding, a web, or sheet, of paper, ( 100 ) in a paper converting machine comprising the steps of:
 disposing a roll having a tubular body having an external lateral surface and an internal surface, said roll being provided of a longitudinal rotation axis;   disposing a drilling tool;   making by said drilling tool a plurality of suction holes arranged to put into pneumatic communication said external lateral surface with said internal surface, said plurality of suction holes being organized in a plurality of suction groups ( 60 ) comprising a predetermined number of suction groups ( 60 ), each suction group ( 60 ) of said plurality comprising a predetermined number of close longitudinal rows of suction holes distributed along said tubular body;   arranging a suction chamber ( 20 ) internally to said roll ( 1 ), said suction chamber ( 20 ) being pneumatically connected to a suction device configured to generate a predetermined vacuum level;   providing a vacuum distribution device ( 50 ) configured to selectively put in pneumatic connection said suction chamber ( 20 ) with at least a row of suction holes ( 3   a , 3   b ) of said plurality in such a way to cause the suction of the processed sheet, or web, of paper ( 100 ), and its adhesion at corresponding portions of said external lateral surface ( 11 ) of said roll ( 1 ) for folding, or interfolding;   said method being characterized in that each suction group ( 60 ) comprises at least 3 close longitudinal rows ( 30   a , 30   b , 30   c ) of suction holes ( 3   a , 3   b , 3   c ) configured to hold each sheet, or web, of paper on said roll at a respective portion of said external lateral surface ( 11 ), in such a way to control in an accurate way the folding of each said sheet ( 100 ), or web, of paper during formation of a stack ( 150 ) of folded, or interfolded, sheets, in that said suction groups ( 60 ) of said plurality are distributed on said external lateral surface ( 11 ) in such a way that the arch of circumference arranged between a suction group ( 60 ) and the following suction group ( 60 ) is equal to the length of a processed sheet of paper ( 100 ) and in that the vacuum distribution device ( 50 ) is arranged to selectively put each longitudinal row ( 30   a , 30   b , 30   c ) of suction holes ( 3   a , 3   b , 3   c ) of each suction group ( 60 ) in pneumatic connection with said suction chamber ( 20 ) at respective predetermined angular positions of said tubular body ( 10 ).