Method for fabricating a bag with a flat bottom, and a bag thus obtained

Abstract

A method for fabricating a bag with a flat bottom comprises: making a flattened tubular element with lateral bellows; obtaining a quadrilateral bottom of a single piece, the perimeter of which has a size equal to that given by the sum of the tubular element and the bellows; folding the bottom in a single piece along one of its first axes, keeping the outer sides parallel to the axis and of a size equal to the initial one; folding the other two sides to identify two opposite bellows, bringing a central folding line of the bellows thus identified into a position perpendicular to the first axis; inserting the bottom thus folded into the flattened tubular element, bringing the two opposite bellows of the bottom so that they are astride of the lateral bellows of the flattened tubular element; and welding the ends facing outwards of the flattened tubular element and of the corresponding lateral bellows respectively to the outer sides, which are parallel to the axis and are of a size equal to the initial size of the bellows and to the inner edges of the two opposite bellows obtained in the bottom. The bag has a quadrilateral bottom added to the tubular element and welded around the perimeter.

1 . Bag with flat bottom obtained from a flattened tubular element ( 12 ) with side bellows ( 13 ), characterized in that said flat bottom is obtained from a bottom element ( 16 ), which is quadrilateral and has a perimetral weld, at the ends of the sides and of the bellows of said tubular element.  
     
     
         2 . Bag with flat bottom according to  claim 1 , characterized in that said perimetral weld is made, in one of its first portions ( 22 ), between the sides in view of the flattened tubular element ( 12 ) with the first opposite sides ( 18 ) of said bottom element ( 16 ) and, in one of its second portions ( 23 ), between the sides of the internal bellows ( 13 ) of said flattened tubular element ( 12 ) with the remaining two sides or internal edges of two opposite internal bellows ( 20 ) of said bottom element ( 16 ).  
     
     
         3 . Method for fabricating a bag with flat bottom, characterized in: making a flattened tubular element ( 12 ) with side bellows ( 13 ); obtaining a quadrilateral bottom of a single piece ( 15 ), the perimeter of which has a size equal to that given by the sum of said tubular element and said bellows; folding said bottom in a single piece along one of its first axes ( 17 ), keeping the outer sides ( 18 ) parallel to said axis ( 17 ) and of a size equal to the initial one; folding the other two sides ( 19 ) to identify two opposite bellows ( 20 ), bringing a central folding line ( 21 ) of said bellows thus identified into a position perpendicular to said first axis ( 17 ); inserting said bottom element ( 16 ) thus folded into said flattened tubular element ( 12 ), bringing said two opposite bellows ( 20 ) of said bottom so that they are astride of said lateral bellows ( 13 ) of said flattened tubular element ( 12 ); and welding the ends facing outwards of said flattened tubular element and of the corresponding lateral bellows respectively to said outer sides ( 18 ) which are parallel to said axis ( 17 ) and are of a size equal to the initial size of said bellows and to the internal edges of said two opposite bellows obtained in said bottom.  
     
     
         4 . Method according to  claim 3 , characterized in that said bottom element ( 16 ) is obtained having a rectangular shape.