Method and apparatus for manufacturing packaging bags, and bags obtained thereby

Abstract

The present invention relates to a method of manufacturing packaging bags having lateral bellows, the method being characterized by the fact that it comprises the stepsof forming respective cutouts ( 150, 160 ) in each of the two lateral, bellows-forming zones of a packaging bag sheet ( 100 ) so that the bag has only two thicknesses superposed at the mouth of said bellows, at least over a portion of its width; and heat-sealing ( 184, 186 ) the adjacent edges of the sheet to the peripheries of the cutouts ( 150, 160 ) to close the bag. The invention also provides apparatus for implementing the method and bags obtained thereby.

1 . A method of manufacturing packaging bags comprising the steps of: 
 providing a packaging bag sheet, having a longitudinal extent, for forming a packaging bag;    folding said packaging bag sheet so as to form a pair of laterally spaced bellow regions within side edge portions of said packaging bag sheet;    forming cutouts within each one of said pair of laterally spaced, bellow regions of said packaging bag sheet so that said bag has only two sheet thicknesses superposed with respect to each other within a mouth region of said bellows;    placing complementary male/femelle closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag and transversely with respect to said longitudinal feeding direction; and    heat-sealing edges portions of said sheet to edge portions of said cutouts so as to close and seal said bag.    
     
     
         2 . A method according to    claim 1   , wherein said cursor has two lateral flanges interconnected by means of a web and which co-operate with an elongate central tongue placed between the closure strips to define two converging passages for the closure strips.  
     
     
         3 . A method according to    claim 1   , wherein the closure strips are provided on respective main support walls which are adapted to be fixed on the packaging bag sheet and which are connected together by an auxiliary wall adapted to be broken when the bag is opened the first time.  
     
     
         4 . A method according to    claim 1   , further comprising the steps of: 
 feeding said packaging bag sheet in a direction parallel to said longitudinal extent of said packaging bag sheet; and    forming said pair of laterally spaced bellow regions by making two Z-folds which extend parallel to said longitudinal feeding direction of the said packaging bag sheet.    
     
     
         5 . A method according to    claim 4   , wherein: 
 each one of said Z-folds is formed by a pair of blades that are partially superposed with respect to each other so as to partially overlap each other and thereby form a baffle within which a side edge portion of said packaging bag sheet is engaged.    
     
     
         6 . A method according to    claim 4   , wherein: 
 said cutouts are formed within said pair of laterally spaced bellow regions after said folds have been formed within said packaging bag sheet so as to form said pair of laterally spaced bellow regions.    
     
     
         7 . A method according to    claim 4   , wherein: 
 said cutouts are formed within said pair of laterally spaced bellow regions before said folds are formed within said packaging bag sheet so as to form said pair of laterally spaced bellow regions.    
     
     
         8 . A method according to    claim 5   , wherein: 
 said cutouts are formed within said pair of laterally spaced bellow regions by using one of said pair of fold-forming blades as an anvil for a cutting-out punch thereby leaving one of the faces of said packaging bag sheet intact.    
     
     
         9 . A method according to    claim 1   , further comprising the step of: 
 initially holding said complementary closure strips in position upon said packaging bag sheet by spot heat-sealing ends of said closure strips to said packaging bag sheet.    
     
     
         10 . A method according to    claim 4   , further comprising the step of: 
 fixing said Z-folds by spot heat-sealing said Z-folds at zones where transverse lines of heat-sealing are to be formed so as to close said bag.    
     
     
         11 . A method according to    claim 10   , wherein said formation of said transverse lines of heat-sealing comprises the step of: 
 forming two mutually parallel transverse lines of heat-sealing such that one of said transverse lines of heat-sealing forms the bottom of a bag while the other one of said transverse lines of heat-sealing forms the mouth of a bag.    
     
     
         12 . A method according to    claim 11   , further comprising the step of: 
 forming a rectilinear cut line between said two transverse lines of heat-sealing so as to separate said formed packaging bag into two separate adjacent bags.    
     
     
         13 . A machine for manufacturing packaging bags from packaging bag sheets, comprising: 
 means for feeding a packaging bag sheet having a longitudinal extent;    means for folding said packaging bag sheet so as to form a pair of laterally spaced bellow regions within side edge portions of said packaging bag sheet;    means for forming cutouts within each one of said pair of laterally spaced bellow regions of said packaging bag sheet such that said packaging bag has only two superposed sheet thicknesses within a mouth region of said bellows;    means for placing complementary male/femelle closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal extent of said packaging bag sheet;and    means for heat-sealing together edges portions of said packaging bag sheet to edge portions of said cutouts so as to close and seal said bag.    
     
     
         14 . A machine according to    claim 13    wherein said cursor has two lateral flanges interconnected by means of a web and which co-operate with an elongate central tongue placed between the closure strips to define two converging passages for the closure strips.  
     
     
         15 . A machine according to    claim 13    wherein the closure strips are provided on respective main support walls which are adapted to be fixed on the packaging bag sheet and which are connected together by an auxiliary wall adapted to be broken when the bag is opened the first time.  
     
     
         16 . A machine according to    claim 13   , further comprising: 
 means for forming said pair of laterally spaced bellow regions so as to comprise a pair of Z-folds which extend parallel to said longitudinal extent of said packaging bag sheet.    
     
     
         17 . A machine according to    claim 16   , wherein: 
 said means for forming said pair of laterally spaced bellow regions comprises two partially superposed blades that overlap each other and thereby form a baffle into which said packaging bag sheet is engaged so as to form said pair of Z-folds.    
     
     
         18 . A machine according to    claim 17   , further comprising: 
 a cut-out punch; and    one of said fold-forming blades comprises an anvil for said cut-out punch when said cut-out punch is used to make said cutouts so as to leave one of the faces of said packaging bag sheet intact.    
     
     
         19 . A machine according to    claim 13   , wherein: 
 said machine comprises a form, fill, and seal machine.    
     
     
         20 . A machine according to    claim 19   , wherein said form, fill, and seal machine comprises: 
 a forming throat having an inlet that receives said packaging bag sheet in a planar state, and an outlet that delivers said packaging bag sheet shaped into a tube,    a filling chute which opens out into said forming throat and consequently into said tube so as to deposit material into said tube,    longitudinal heat-sealing means for closing and sealing said tube longitudinally, and    means for sequentially generating transverse lines of heat-sealing so as to close and seal said formed bag.    
     
     
         21 . A machine according to    claim 13   , further comprising: 
 means for initially securing said closure strips in position upon said packaging bag sheet by spot heat-sealing ends of said closure strips to said packaging bag sheet.    
     
     
         22 . A machine according to    claim 16   , further comprising: 
 means for fixing said Z-folds by spot heat-sealing said Z-folds at zones that are subsequently to include transverse lines of heat-sealing so as to close and seal said bag.    
     
     
         23 . A machine according to    claim 22    further comprising: 
 heat-sealing means for forming two mutually parallel transverse lines of heat-sealing such that one of said transverse line of heat-sealing forms the bottom of a bag while the other one of said transverse lines of heat-sealing forms the mouth of a bag.  
 
     
     
         24 . A machine according to    claim 23   , further comprising: 
 means for forming a rectilinear cut line between said two transverse lines of heat-sealing so as to separate said formed packaging bag into two separate adjacent bags.    
     
     
         25 . A packaging bag comprising: 
 a folded packaging sheet, having a longitudinal extent, for forming a packaging bag;    a pair of laterally spaced bellows formed within side edge portions of said folded packaging bag sheet;    cutout portions respectively formed within each one of said pair of laterally spaced bellows so that said packaging bag has only two sheet thickness superimposed with respect to each other within a mouth region of said bag;    complementary male/female closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal exent of said packaging sheet; and    heat-sealed regions for closing and sealing said packaging bag.    
     
     
         26 . A bag according to    claim 25   , wherein: 
 said heat-sealed regions of said packaging bag comprises a line of heat-sealing defined between edge portions of said packaging bag sheet and edge portions of said cutouts.    
     
     
         27 . A packaging bag as set forth in    claim 25   , wherein said packaging bag sheet comprises: 
 a planar main face;    first longitudinal flaps disposed upon and integrally connected to opposite sides of said planar main face;    second longitudinal flaps disposed upon and integrally connected to opposite sides of said first longitudinal flaps, and    auxiliary segments disposed upon and integrally connected to said second longitudinal flaps.    
     
     
         28 . A packaging bag as set forth in    claim 25   , wherein: 
 each cutout portion is defined by two rectilinear longitudinal edges coinciding respectively with outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely to said longitudinal extent of said packaging bag sheet, and a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.    
     
     
         29 . A packaging bag as set forth in    claim 25   , wherein: 
 each cutout portion is defined by two rectilinear longitudinal edges which are respectively set back from the outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely to said longitudinal extent of said packaging bag sheet, and a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.    
     
     
         30 . A packaging bag as set forth in    claim 28   , wherein: 
 said second transverse edge comprises a dihedral made up of two rectilinear segments.    
     
     
         31 . A packaging bag comprising: 
 a folded packaging sheet, having a longitudinal extent, for forming a packaging bag;    a pair of laterally spaced bellows formed within side edge portions of said folded packaging bag sheet;    cutout portions respectively formed within each one of said pair of laterally spaced bellows so that said packaging bag has only two sheet thickness superimposed with respect to each other within a mouth region of said bag;    complementary male/female closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal exent of said packaging sheet; and    heat-sealed regions for closing and sealing said packaging bag,    each one of said cutout portions being defined by two rectilinear longitudinal edges coinciding respectively with outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely to said longitudinal extent of said packaging bag sheet, and a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.    
     
     
         32 . A packaging bag comprising: 
 a folded packaging sheet, having a longitudinal extent, for forming a packaging bag;    a pair of laterally spaced bellows formed within side edge portions of said folded packaging bag sheet;    cutout portions respectively formed within each one of said pair of laterally spaced bellows so that said packaging bag has only two sheet thickness superimposed with respect to each other within a mouth region of said bag;    complementary male/female closure strips provided with a control cursor upon said packaging bag sheet within the vicinity of said mouth region of said bag such that said closure strips extend transversely with respect to said longitudinal event of said packaging sheet; and    heat-sealed regions for closing and sealing said packaging bag,    each one of said cutout portions being defined by two rectilinear longitudinal edges which are respectively set back from the outer definition lines of said laterally spaced bellows, a rectilinear transverse edge extending transversely with respect to said longitudinal extent of said packaging bag sheet, and    a second transverse edge that is not rectilinear and is concave towards said mouth region of said bag.    
     
     
         33 . A bag according to    claim 32   , wherein: 
 said heat-sealed regions of said packaging bag comprises a line of heat-sealing defined between edge portions of said packaging bag sheet and edge portions of said cutout portions.    
     
     
         34 . A packaging bag as set forth in    claim 32   , wherein said packaging bag sheet comprises: 
 a planar main face;    first longitudinal flaps disposed upon and integrally connected to opposite sides of said planar main face;    second longitudinal flaps disposed upon and integrally connected to opposite sides of said first longitudinal flaps, and    auxiliary segments disposed upon and integrally connected to said second longitudinal flaps.    
     
     
         35 . A packaging bag as set forth in    claim 32   , wherein: 
 said second transverse edge comprises a dihedral made up of two rectilinear segments.