Machine for producing stacks of folded sheets of paper and method therefor

Abstract

Machine ( 1 ) for converting paper comprising a starwheel unit ( 10 ) equipped with at least one cylindrical body having a plurality of grooves ( 15 ), each of which is configured to receive a respective sheet ( 11 ) of a plurality of folded sheets ( 11 ) that are carried in turn, for example between two transmission belts ( 200, 201 ), along a feeding direction ( 101 ), for example a direction substantially tangential to the starwheel unit ( 10 ). The starwheel unit rotates about a rotation axis ( 110 ), for example in a counterclockwise direction, and discharges in turn the sheets ( 11 ) present in the grooves ( 15 ) onto a formation table ( 20, 120 ). More precisely, the folded sheets are discharged to achieve a predetermined angular release position, in order to form a stack ( 50 ) of folded sheets ( 11 ). The machine ( 1 ) can comprise a transfer means for transferring the formed stacks ( 50 ) from the table ( 20, 120 ) to said conveying means ( 30 ). The transfer means comprises a rotation means ( 60 ) arranged to transfer the stack ( 50 ) of folded sheets ( 11 ) from the table ( 20 ) to the conveying means ( 30 ) through a rotation of a predetermined angle.

1 . Machine for making stacks of folded paper sheets, or similar material, such as napkins, or paper tissues, comprising:
 a feeding means for feeding a plurality of sheets along a predetermined feeding direction;   a starwheel unit mounted rotatable about a rotation axis, said starwheel unit arranged to receive said plurality of folded sheets and to put them in turn on a table, in order to form a stack of folded overlapped sheets according to a first predetermined stack direction;   a transfer means that is arranged to transfer a completed stack of folded sheets from said table to said conveying means, said conveying means arranged to convey said stack of folded sheets along a conveying direction;   
       characterised in that said transfer means comprises a rotation means which is arranged to rotate said stack of folded sheets for transferring said stack from said table to said conveying means, said rotation means configured to bring the axis of the stack from said first predetermined stack direction, when said formed stack is located on said formation table, to a second predetermined stack direction, when said formed stack is located on said conveying means. 
     
     
         2 . Machine, according to  claim 1 , wherein said first predetermined stack direction is selected from the group consisting of:
 a substantially horizontal direction;   a substantially vertical direction;   a direction at a predetermined angle with respect to a horizontal plane.   
     
     
         3 . Machine, according to  claim 1 , wherein said second predetermined stack direction is selected from the group consisting of:
 a substantially vertical direction when said predetermined stack direction is substantially horizontal;   a substantially horizontal direction when said predetermined stack direction is substantially vertical.   
     
     
         4 . Machine, according to  claim 1 , wherein said transfer means comprises, furthermore, a translation means that is arranged to translate said stack of folded sheets from said table to said conveying means, and a means is provided for selectively operating said translation means and said rotation means for transferring said stack of folded sheets from said table to said conveying means. 
     
     
         5 . Machine, according to  claim 4 , wherein during the production of packs, or stacks, of folded sheets of “flat” type said means for selectively operating operate said translation means such that a “flat” stack of folded sheets remains substantially with vertical axis both on the table and on said conveying means once transferred. 
     
     
         6 . Machine, according to  claim 4 , wherein during the production of packs, or stacks, of folded sheets of “bulk” type said means for selectively operating is arranged to operate said rotation means for bringing said “bulk” stack of folded sheets from a configuration with substantially vertical axis when it is arranged on said table, to a configuration with axis substantially horizontal when it is located on the conveying means. 
     
     
         7 . Machine, according to  claim 1 , wherein downstream of said starwheel unit a banding section is provided in which to said stack of folded sheets a banding film is applied, said banding section arranged along said conveying direction, such that once arranged on said conveying means, said stack of folded sheets moves along a single conveying direction substantially rectilinear up to entering said banding section, in particular said conveying direction is substantially parallel to said rotation axis of said starwheel unit. 
     
     
         8 . Machine, according to  claim 1 , wherein said transfer means is arranged to transfer said stack of folded sheets from said table to said conveying means through a combination of movements that comprise a rotation of the stack of folded sheets for an angle set between 80° and 110°, in particular 90°. 
     
     
         9 . Machine, according to  claim 1 , wherein said table has is substantially “comb”-shaped, comprising a plurality of portions alternated to a plurality of empty spaces, said transfer means configured to be put at said empty spaces for picking up said stack of folded sheets from said table and transferring it onto said conveying means, in particular said rotation means comprises a first and a second grip portions that can be brought towards/away from each other between a gripping configuration of said folded sheet stacks and a release configuration of said folded sheet stacks, and vice-versa. 
     
     
         10 . Machine, according to  claim 1 , wherein said feeding means is arranged to feed a plurality of parallel rows of sheets to said starwheel unit, said starwheel unit comprising a plurality of coaxial starwheel elements each arranged to process a respective row of sheets of said plurality of rows of sheets arranging in turn said sheets on said table, in order to make a respective stack of folded sheets for each row according to an axis oriented in a predetermined stack direction. 
     
     
         11 . Machine, according to  claim 10 , wherein said rotation means is adapted to transfer at the same time said plurality of folded sheet stacks from said formation table to said conveying means. 
     
     
         12 . Machine, according to  claim 1 , wherein said conveying means has an end close to a banding section, said conveying means being associated with a pushing means that is arranged to push said folded sheet stacks to provide a predetermined acceleration to said folded sheet stacks, said pushing means configured to apply said push in said conveying direction for displacing said stack directly to said banding station. 
     
     
         13 . Machine, according to  claim 12 , wherein said conveying means comprises a plane support on which a plurality of handling rods, movable with respect to said plane support, move said stack of folded sheets along said conveying direction, in particular the distance between two successive handling rods being higher than the width of said stack of folded sheets, in order to cause the conveying means to work continuously. 
     
     
         14 . Machine, according to  claim 1 , comprising:
 a first starwheel unit arranged to receive from a first feeding means a first plurality of folded sheets that are carried in turn along a first feeding direction, and to overlap them on a first table, in order to form a first stack, or series of folded sheet stacks;   a second starwheel unit arranged to receive from a second feeding means a second plurality of folded sheets that are carried in turn along a second feeding direction and to overlap them on a second table, in order to form a second stack of folded sheets, in particular said first and said second starwheel units configured to work in an alternated way, in such a way that, while said first starwheel unit is creating a stack of sheets, said second starwheel unit is not supplied of folded sheets and the stack of folded sheets that has been just formed by the latter is transferred by said transfer means onto said conveying means, and vice-versa.   
     
     
         15 . Machine, according to  claim 1 , comprising:
 a first starwheel unit mounted rotatable about a first rotation axis, said first starwheel unit arranged to receive said plurality of folded sheets and to put them in turn on a first table, in order to provide a first stack of overlapped folded sheets;   a second starwheel unit mounted rotatable about a second rotation axis parallel to said first rotation axis, said second starwheel unit arranged to receive said plurality of folded sheets and to put them in turn on a second table, in order to provide a second stack of overlapped folded sheets;   
       wherein each starwheel unit among said first and said second starwheel unit has a plurality of protruding portions, between two following protruding portions a groove being obtained arranged to receive a sheet of said plurality of sheets; 
       and wherein between said feeding means and said first and second starwheel units a deviation means is arranged to deviate alternatively said plurality of sheets towards said first, or said second starwheel unit. 
     
     
         16 . Machine, according to  claim 15 , wherein said first starwheel unit is associated with a first introduction means, said first introduction means arranged to put a sheet in a groove along a first introduction direction and said second starwheel unit is associated with a second introduction means, said second introduction means arranged to put a sheet in a groove along a second introduction direction, said deviation means arranged to deviate alternatively said plurality of sheets towards said first and towards said second introduction means. 
     
     
         17 . Machine, according to  claim 15 , wherein said deviation means comprises a deviation element having at least one guide surface arranged alternatively along said first introduction direction of said sheets in said first starwheel unit, or along said second introduction direction of said sheets in said second starwheel unit. 
     
     
         18 . Machine, according to  claim 15 , wherein said deviation means comprises a deviation element having a first and a second guide surface arranged to be alternatively, and respectively, put along said first introduction direction of said sheets into said first starwheel unit and along said second introduction direction of said sheets into said second starwheel unit. 
     
     
         19 . Machine, according to  claim 15  wherein an actuating rod is provided operatively connected to said deviation means, said actuating rod arranged to move selectively said deviation means along said first, or said second, introduction direction respectively. 
     
     
         20 . Machine, according to  claim 15 , wherein said deviation means comprises at least one deviation roller equipped with:
 a first holding means for keeping said sheets on a first angular portion of the surface of said deviation roller, said first angular portion ending at said first introduction means;   a second holding means for keeping said sheets, alternatively to said first means for keeping, on a second angular portion of the surface of said deviation roller, said second angular portion ending at said second introduction means.   
     
     
         21 . Method for making stacks of folded paper sheets, or similar material, such as napkins, or paper tissues, comprising the steps of:
 feeding a plurality of folded sheets to a starwheel unit along a feeding direction;   releasing said plurality of folded sheets onto a table by said starwheel unit, in order to form a stack of overlapped folded sheets;   transferring said stack of folded sheets from said table to said conveying means, which is arranged to convey said stack of folded sheets along a conveying direction;   handling said stack of folded sheets along a conveying direction;   
       characterised in that said transfer step from said table to said conveying means is carried out through a rotation of a predetermined angle of said stack of folded sheets, said rotation configured to bring the axis of the stack from a first predetermined stack direction, when said formed stack is located on said formation table, to a second predetermined stack direction, when said formed stack is located on said conveying means. 
     
     
         22 . A conveying unit for bringing a plurality of stacks, or packs, of sheets from a stacking section to a banding section characterised in that said conveying unit comprises a pushing means that is arranged to apply, during the movement of said conveying unit, an additional push on said folded sheet stacks to provide a predetermined acceleration to said folded sheet stacks, said additional push applied by said pushing means when said folded sheet stacks are approaching said banding section.