Square bottomed plastic bag and method of making same

Abstract

A square bottom plastic bag is designed to stand upright when opened. The bags are constructed with open tops, side gussets, side handle openings or with t-shirt style handles. The t-shirt bags may have apertures through the handles to suspend the bags on a rack. The bags may have detachable or rupturable center tabs. The bags may have openings, microperforations, or are formed of porous material to dissipate heat or moisture. The bags are formed from a flattened gusseted tube of polyethylene cut into bag blanks of a selected length. The blank is slit upwardly from its lower end and portions of the front and back panels and side gussets are folded and sealed to form a square, flat bag bottom.

1 . A square bottomed plastic bag, comprising: 
 front and rear polyethylene film walls, each of said front and rear walls having first and second side edges, a top edge and a bottom edge;    each of said bags having a pair of longitudinally oriented side gussets attached to said first and second side edges;    each of said bags having a flat, rectangular bottom formed of lower portions of said front and rear walls and lower portions of said side gussets;    lower corners of said each side gusset being folded outwardly and together to form downward pointing triangular panels;    said triangular panels being folded inwardly from said side gussets;    lower portions of said front and rear walls being folded inwardly and sealed together to form the bag bottom;    said bag bottom being sealed to said side gussets adjacent upper edges of said triangular panels;    said triangular panels being sealed to an upper surface of said bag bottom; and    whereby, when said bag is opened, it will stand erect upon said flat bottom.    
   
   
       2 . The square bottomed plastic bag as described in  claim 1 , wherein said bag is folded inwardly at said side gussets and upwardly from either of said front wall and said rear wall at a point spaced upwardly from said bottom edge, to form a flattened bag.  
   
   
       3 . The square bottomed plastic bag as described in  claim 1 , further comprising at least one handle opening, said handle opening extending through said front and rear walls in an upper portion of each of said bags.  
   
   
       4 . The square bottomed plastic bag as described in  claim 1 , wherein said bags are formed of a porous material.  
   
   
       5 . The square bottomed plastic bag as described in  claim 1 , wherein said bags are formed of material having microperforations penetrating at least a portion of any of said bag walls and side gussets.  
   
   
       6 . The square bottomed plastic bag as described in  claim 1 , wherein said bags have a plurality of ventilating openings penetrating at least a portion of any of said bag walls and side gussets.  
   
   
       7 . The square bottomed plastic bag as described in  claim 1 , wherein said bag further comprises: 
 an upper seal, said upper seal joining said front wall to said rear wall at said top edges of said bag walls and joining top edges of said side gussets; and    a U-shaped cutout, said cutout commencing at a first point on said upper seal spaced from said first side edge and extending downwardly toward said bottom edges, across an upper portion of said bag walls and upwardly to a second point on said upper seal spaced from said second side edge, thereby forming an open bag mouth and a pair of bag handles terminating at said upper seal.    
   
   
       8 . The square bottomed plastic bag as described in  claim 7 , wherein said bag further comprise a pair of apertures, each of said apertures penetrating said bag handles at a point spaced downwardly from said upper seal, said apertures permitting said bag to be suspended from a dispensing rack.  
   
   
       9 . The square bottomed plastic bag as described in  claim 7 , further comprising: 
 a central tab, said central tab extending upwardly from at least one of said front wall and said rear wall at said open mouth; and    said central tab having an opening therethrough for suspending said bag from a dispensing rack.    
   
   
       10 . The square bottomed plastic bag stack as described in  claim 7 , wherein said central tab is attached to at least one of said front wall and said rear wall at said open mouth at a weakened area, said weakened area permitting said central tab to be torn from said open mouth of said bag as said bag is removed from a dispensing rack.  
   
   
       11 . The square bottomed plastic bag stack as described in  claim 10 , wherein said central tab includes a weakened area, said weakened area extending from said opening to an edge of said central tab, said weakened area parting under pressure as said bag is removed from a dispensing rack.  
   
   
       12 . A method of making a square bottomed plastic bag, comprising the steps of: 
 extruding a tube of thermoplastic material;    forming side gussets in said tube and flattening same;    cutting said flattened tube perpendicular to said side gussets to a first predetermined length, thereby forming a bag blank, said bag blank having front and rear walls, front and rear top edges, front and rear bottom edges, first and second side edges;    slitting said bag blank at intersections of said side gussets and said front and rear walls from said front and rear bottom edges upwardly for a first predetermined distance;    folding lower corners of said each side gusset outwardly and together to form downward pointing triangular panels;    folding said triangular panels inwardly from said side gussets;    folding lower portions of said front and rear walls inwardly;    sealing said front and rear wall together adjacent said front and rear bottom edges to form a bag bottom;    sealing said bag bottom to said side gussets adjacent upper edges of said triangular panels; and    sealing said triangular panels to an upper surface of said bag bottom.    
   
   
       13 . The method of making a square bottomed plastic bag, as described in  claim 12 , comprising the additional step of folding said bag inwardly at said side gussets and upwardly from either of said front wall and said rear wall at a point spaced upwardly from said bottom edge, to form a flattened bag.  
   
   
       14 . A method of making a square bottomed plastic bag, comprising the steps of: 
 extruding a tube of thermoplastic material;    forming side gussets in said tube and flattening same;    cutting said flattened tube perpendicular to said side gussets to a first predetermined length, thereby forming a bag blank, said bag blank having front and rear walls, front and rear top edges, front and rear bottom edges, first and second side edges;    forming a crease line in said bag blank, said crease line being parallel to said bottom edges and spaced upwardly from said bottom edges by approximately one half of a width of one of said side gussets;    slitting said bag blank from said bottom edges of said walls to said crease line at each intersection of said front and rear walls and said side gussets;    folding lower corners of said each side gusset outwardly to said crease line and together to form downward pointing triangular panels;    folding said triangular panels inwardly from said side gussets at said crease line;    folding lower portions of said front and rear walls inwardly from said crease line;    sealing said front and rear wall together adjacent said front and rear bottom edges to form a bag bottom;    sealing said bag bottom to said side gussets adjacent said crease line and upper edges of said triangular panels; and    sealing said triangular panels to an upper surface of said bag bottom.    
   
   
       15 . The method of making a square bottomed plastic bag, as described in  claim 14 , comprising the additional step of folding said bag blank inwardly at said side gussets and upwardly from either of said front wall and said rear wall at said crease line, to form a flattened bag.  
   
   
       16 . The method of making a square bottomed plastic bag, as described in  claim 12 , further comprising the step of cutting at least one handle opening in said bag, said handle opening extending through said front and rear walls in an upper portion of said bag.  
   
   
       17 . The method of making a square bottomed plastic bag, as described in  claim 12 , further comprising the step of forming said bag of a porous material.  
   
   
       18 . The method of making a square bottomed plastic bag, as described in  claim 12 , further comprising the step of forming microperforations penetrating at least a portion of any of said bag walls and side gussets.  
   
   
       19 . The method of making a square bottomed plastic bag, as described in  claim 12 , further comprising the step of forming a plurality of ventilating openings penetrating at least a portion of any of said bag walls and side gussets.  
   
   
       20 . The method of making a square bottomed plastic bag, as described in  claim 12 , further comprising the steps of: 
 joining said front wall to said rear wall at said top edges of said bag walls and joining top edges of said side gussets, thereby forming an upper seal; and    forming a U-shaped cutout, said cutout commencing at a first point on said upper seal spaced from said first side edge and extending downwardly toward said bottom edges, across an upper portion of said bag walls and upwardly to a second point on said upper seal spaced from said second side edge, thereby forming an open bag mouth and a pair of bag handles terminating at said upper seal.    
   
   
       21 . The method of making a square bottomed plastic bag, as described in  claim 20 , further comprising the step of cutting a pair of apertures, each of said apertures penetrating said bag handles at a point spaced downwardly from said upper seal, said apertures permitting said bag to be suspended from a dispensing rack.  
   
   
       22 . The method of making a square bottomed plastic bag stack, as described in  claim 20 , further comprising the step of forming a central tab, said central tab extending upwardly from at least one of said front wall and said rear wall at said open mouth, said central tab having an opening therethrough for suspending said bag.  
   
   
       23 . The method of making a square bottomed plastic bag, as described in  claim 22 , further comprising the step of forming a weakened area, said weakened area attaching said central tab to at least one of said front wall and said rear wall at said open mouth, said weakened area permitting said central tab to be torn from said open mouth of said bag as said bag is removed from a dispensing rack.  
   
   
       24 . The method of making a square bottomed plastic bag, as described in  claim 22 , further comprising the step of forming said central tab with a weakened area, said weakened area extending from said opening to an edge of said central tab, said weakened area parting under pressure as said bag is removed from a dispensing rack.