Self opening bag pack, apparatus and method of making same

Abstract

A plurality of stacked polyethylene film bags comprising about 40-48 wt. % high density, high molecular weight polyethylene, 12-20 wt. % high density, medium molecular weight polyethylene, 20-30 wt. % linear low density polyethylene, 0-8 wt. % color concentrate, are releasably adhered together in substantial registration. Each of the bags includes front and rear polyethylene film walls and each of the front and rear walls have first and second side edges, a top edge and a bottom edge. The front and rear walls are integrally joined at their first and second side edges and secured together at their bottom edges. An open mouth portion is defined adjacent the top edges of the bag. At least an upper portion of the outer surface of the front and rear walls of each of the bags has been corona treated. T-shirt style bags using the above formulation are also described.

1 . A self-opening bag pack comprising:
 a plurality of stacked thermoplastic film bags, each of said bags having front and rear walls, each of said front and rear walls having first and second side edges, a top edge and a bottom edge;   said front and rear walls being integrally joined at their first and second side edges and secured together at their bottom edges and defining an open mouth portion adjacent said top edges;   at least an upper portion of an outer surface of said front and rear walls of each of said bags having been corona treated;   means for attaching said bag pack to a dispensing rack;   front and rear walls of each of said bags in said bag pack being penetrated by at least one knife cut, said knife cut having first and second ends and first and second edges;   thermoplastic material adjacent said knife cut adhering said rear wall of a first bag to said front wall of a subsequent bag in said bag pack; and   whereby, when said bag pack is attached to said dispensing rack and said first bag is pulled outwardly from said bag pack, said front wall of said subsequent bag will be adhered to said rear wall of said first bag, thereby causing said first bag to open.   
     
     
         2 . The self-opening bag pack, as described in  claim 1 , wherein said thermoplastic film comprises less than 49 wt. % high density, high molecular weight polyethylene. 
     
     
         3 . The self-opening bag pack, as described in  claim 1 , wherein said corona treatment on said outer surfaces of said front and rear walls of each of said bags is an amount sufficient to result in a surface tension on said corona treated surface of 35-39 dynes/cm. 
     
     
         4 . The self-opening bag pack, as described in  claim 1 , wherein said first and second edges of said knife cut are spaced apart by a distance ranging from 0.02 inches to 0.3 inches. 
     
     
         5 . The self-opening bag pack, as described in  claim 1 , wherein said knife cut is orthogonal to said first and second side edges and centrally disposed below said mouth portion. 
     
     
         6 . The self-opening bag pack, as described in  claim 1 , wherein said knife cut is S-shaped. 
     
     
         7 . The self-opening bag pack, as described in  claim 1 , wherein said knife cut is Z-shaped. 
     
     
         8 . The self-opening bag pack, as described in  claim 1 , wherein said knife cut is in the form of a straight line, said straight line having at least one curved section at either of first and second ends of said straight line. 
     
     
         9 . The self-opening bag pack, as described in  claim 1 , wherein each of said bags includes longitudinally oriented side gussets. 
     
     
         10 . The self-opening bag pack, as described in  claim 1 , wherein the means for attaching said bag pack to a dispensing rack further comprises:
 first and second openings, said first and second openings penetrating and extending transversely through said bag pack in an upper portion of the bags; and   said openings being spaced downwardly from said top edge, spaced inwardly from said first and second side edges and serving to support said bag pack on horizontal arms of a dispensing rack.   
     
     
         11 . The self-opening bag pack, as described in  claim 9 , wherein each of the bags of the bag pack further comprises:
 an upper seam, said upper seam sealing said front wall to said rear wall at their respective top edges; and   a U-shaped cut-out, said U-shaped cut-out being disposed in an upper portion of said bag and commencing at a first point along said upper seam spaced inwardly from said first side edge and extending to a second point along the upper seam spaced inwardly from said second side edge, said cut-out extending downwardly toward said bottom edges, thereby forming an open mouth portion and a pair of bag handles.   
     
     
         12 . The self-opening bag pack, as described in  claim 1 , further comprising at least one cold staking area piercing and extending transversely through said bag pack for maintaining the bags in said bag pack in substantial registration. 
     
     
         13 . The self-opening bag pack, as described in  claim 1 , further comprising at least one hot melt pin area piercing and extending transversely through said bag pack for maintaining the bags in said bag pack in substantial registration. 
     
     
         14 . The self-opening bag pack, as described in  claim 11 , wherein the means for attaching said bag pack to a dispensing rack further comprises:
 first and second openings, said first and second openings penetrating and extending transversely through said bag pack in an upper portion of said bag handles; and   said openings being spaced downwardly from said upper seam and serving to support said bag pack on horizontal arms of a dispensing rack.   
     
     
         15 . The self-opening bag pack, as described in  claim 1  or  claim 11 , further comprising:
 a central tab portion connected to said open mouth portion of said bags in said bag pack; and   an aperture, said aperture extending transversely through said bag pack within said central tab portion for suspending said bag pack from a dispensing member.   
     
     
         16 . The self-opening bag pack, as described in  claim 15 , wherein said central tab portion is disposed above an upper edge of said open mouth portion and attached thereto, thereby providing stress relief for said open mouth portion. 
     
     
         17 . The self-opening bag pack, as described in  claim 15 , wherein said central tab portion of each bag in said bag pack is detachably connected to said open mouth portion of said bags. 
     
     
         18 . The self-opening bag pack, as described in  claim 15 , wherein:
 said central tab portion of each bag in said bag pack includes a frangible section;   said frangible section extending between said aperture and an outer edge of said central tab portion; and   said frangible section rupturing upon removal of said bag from said dispensing member.   
     
     
         19 . The self-opening bag pack, as described in  claim 17 , wherein said at least one knife cut is disposed below said central tab portion. 
     
     
         20 . The self-opening bag pack, as described in  claim 18 , wherein said at least one knife cut is disposed within said central tab portion. 
     
     
         21 . The self-opening bag pack, as described in  claim 11 , wherein said at least one knife cut is disposed within said bag handle. 
     
     
         22 . The self-opening bag pack, as described in  claim 1 , further comprising 0.5 wt. % slip and antiblock compound. 
     
     
         23 . The self-opening bag pack, as described in  claim 1 , further comprising 1-3 wt. % calcium carbonate. 
     
     
         24 . The self-opening bag pack, as described in  claim 1 , further comprising 10-20 wt. % recycled material, said recycled material comprising about 40-49 wt. % high density, high molecular weight polyethylene, 12-20 wt. % high density, medium molecular weight polyethylene, 20-30 wt. % linear low density polyethylene, 0-8 wt. % color concentrate. 
     
     
         25 . The self-opening bag pack, as described in  claim 1 , wherein 10-15 wt. % of said linear low density polyethylene has a density ranging from 0.923-0.924 gm/cc. 
     
     
         26 . The self-opening bag pack, as described in  claim 1 , wherein 10-15 wt. % of said linear low density polyethylene has a melt index ranging from 0.25-0.30 gm/10 minutes. 
     
     
         27 . The self-opening bag pack, as described in  claim 1 , wherein said high density, medium molecular weight polyethylene has a density ranging from 0.937-0.947 gm/cc. 
     
     
         28 . The self-opening bag pack, as described in  claim 1 , wherein said high density, medium molecular weight polyethylene has a melt index ranging from 0.10-0.30 gm/10 minutes. 
     
     
         29 . An apparatus for making a self-opening bag pack comprising:
 a supply of thermoplastic material;   an extruder, said extruder forming a continuous tube of thermoplastic film;   a flattener, said flattener forming a continuous flattened tube;   a corona treater, said treater corona treating at least one surface of said flattened tube;   a first sealer, said first sealer forming a bottom seam across a width of said flattened tube at a predetermined interval;   a cutter, said cutter cutting said flattened tube into bag blanks at a predetermined distance from said bottom seam;   a stacker, said stacker forming said bag blanks into a bag pack an aperture maker, said aperture maker penetrating said bag pack and forming means for suspending said bag pack from a dispensing rack;   an adhesion knife, said knife penetrating said bag pack and adhering adjacent bag blanks together in said bag pack; and   whereby, when said bag pack is attached to said dispensing rack and a first bag is pulled outwardly from said bag pack, said front wall of said subsequent bag will be adhered to said rear wall of said first bag, thereby causing said first bag to open.   
     
     
         30 . The apparatus for making a self-opening bag pack, as described in  claim 47 , wherein said first and second edges of said knife cut are spaced apart by a distance ranging from 0.02 inches to 0.3 inches. 
     
     
         31 . The apparatus for making a self-opening bag pack, as described in  claim 47 , wherein said knife cut is orthogonal to said first and second side edges and centrally disposed below said mouth portion. 
     
     
         32 . The apparatus for making a self-opening bag pack, as described in  claim 47 , wherein said knife cut is S-shaped. 
     
     
         33 . The apparatus for making a self-opening bag pack, as described in  claim 47 , wherein said knife cut is Z-shaped. 
     
     
         34 . The apparatus for making a self-opening bag pack, as described in  claim 47 , wherein said knife cut is in the form of a straight line, said straight line having at least one curved section at either of first and second ends of said straight line. 
     
     
         35 . The apparatus for making a self-opening bag pack, as described in  claim 47 , further comprising a gusseter, said gusseter forming first and second longitudinal side gussets perpendicular to said width of said flattened tube. 
     
     
         36 . The apparatus for making a self-opening bag pack, as described in  claim 47 , further comprising:
 a second sealer, said second sealer forming an upper seam across a width of said flattened tube at a predetermined distance from said bottom seam;   said upper seam, sealing said front wall to said rear wall at their respective top edges;   a bag mouth cutter, said bag mouth cutter forming a U-shaped cut-out in said bag blank after stacking in said bag pack, said U-shaped cut-out being disposed in an upper portion of said bag blank and commencing at a first point along said upper seam spaced inwardly from said first side edge and extending to a second point along the upper seam spaced inwardly from said second side edge, said cut-out extending downwardly toward said bottom edges, thereby forming an open mouth portion and a pair of bag handles.   
     
     
         37 . The apparatus for making a self-opening bag pack, as described in  claim 47 , further comprising at least one cold staker, said cold staker piercing and extending transversely through said bag pack for maintaining the bags in said bag pack in substantial registration. 
     
     
         38 . The apparatus for making a self-opening bag pack, as described in  claim 47 , further comprising at least one hot melt pin, said hot melt pin piercing and extending transversely through said bag pack for maintaining the bags in said bag pack in substantial registration. 
     
     
         39 . The apparatus for making a self-opening bag pack, as described in  claim 36 , further comprising an aperture maker, said aperture maker forming:
 first and second openings, said first and second openings penetrating and extending transversely through said bag pack in an upper portion of said bag handles; and   said openings being spaced downwardly from said upper seam and serving to support said bag pack on horizontal arms of a dispensing rack.   
     
     
         40 . The apparatus for making a self-opening bag pack, as described in  claim 36 , wherein said bag mouth cutter forms:
 a central tab portion connected to said open mouth portion of said bag blanks in said bag pack; and   an aperture, said aperture extending transversely through said bag pack within said central tab portion for suspending said bag pack from a dispensing member.   
     
     
         41 . The apparatus for making a self-opening bag pack, as described in  claim 40 , wherein said bag mouth cutter forms said central tab portion above an upper edge of said open mouth portion and attached thereto, thereby providing stress relief for said open mouth portion. 
     
     
         42 . The apparatus for making a self-opening bag pack, as described in  claim 40 , wherein said bag mouth cutter forms said central tab portion detachably connected to said open mouth portion of said bags. 
     
     
         43 . The apparatus for making a self-opening bag pack, as described in  claim 40 , wherein said bag mouth cutter forms:
 said central tab portion of each bag in said bag pack with a frangible section;   said frangible section extending from said aperture to an outer edge of said central tab portion; and   said frangible section rupturing upon removal of said bag from said dispensing member.   
     
     
         44 . The apparatus for making a self-opening bag pack, as described in  claim 40 , wherein said bag mouth cutter forms said at least one knife cut below said central tab portion. 
     
     
         45 . The apparatus for making a self-opening bag pack, as described in  claim 40 , wherein said bag mouth cutter forms said at least one knife cut within said central tab portion. 
     
     
         46 . The apparatus for making a self-opening bag pack, as described in  claim 40 , wherein said bag mouth cutter forms said at least one knife cut within said bag handle. 
     
     
         47 . A method of making a self-opening bag pack comprising the steps of:
 providing a supply of thermoplastic material;   extruding a continuous tube of thermoplastic film;   flattening said continuous flattened tube;   corona treating at least one surface of said flattened tube;   forming a bottom seam across a width of said flattened tube at a predetermined interval;   cutting said flattened tube into bag blanks at a predetermined distance from said bottom seam;   stacking said bag blanks into a bag pack;   cutting at least one aperture penetrating said bag pack and forming means for suspending said bag pack from a dispensing rack;   forming a knike cut, said knife cut penetrating said bag pack and adhering adjacent bag blanks together in said bag pack; and   whereby, when said bag pack is attached to said dispensing rack and a first bag is pulled outwardly from said bag pack, said front wall of a subsequent bag will be adhered to said rear wall of said first bag, thereby causing said first bag to open.   
     
     
         48 . The method of making a self-opening bag pack, as described in  claim 47 , wherein said first and second edges of said knife cut are spaced apart by a distance ranging from 0.02 inches to 0.3 inches. 
     
     
         49 . The method of making a self-opening bag pack, as described in  claim 47  wherein said knife cut is orthogonal to said first and second side edges and centrally disposed below said mouth portion. 
     
     
         50 . The method of making a self-opening bag pack, as described in  claim 47 , wherein said knife cut is S-shaped. 
     
     
         51 . The method of making a self-opening bag pack, as described in  claim 47 , wherein said knife cut is Z-shaped. 
     
     
         52 . The method of making a self-opening bag pack, as described in  claim 47 , wherein said knife cut is in the form of a straight line, said straight line having at least one curved section at either of first and second ends of said straight line. 
     
     
         53 . The method of making a self-opening bag pack, as described in  claim 47 , comprising the further step of forming first and second longitudinal side gussets perpendicular to said width of said flattened tube. 
     
     
         54 . The method of making a self-opening bag pack, as described in  claim 47 , comprising the further steps of:
 forming an upper seam across a width of said flattened tube at a predetermined distance from said bottom seam;   said upper seam, sealing said front wall to said rear wall at their respective top edges;   forming a U-shaped cut-out in said bag blank after stacking in said bag pack, said U-shaped cut-out being disposed in an upper portion of said bag blank and commencing at a first point along said upper seam spaced inwardly from said first side edge and extending to a second point along the upper seam spaced inwardly from said second side edge, said cut-out extending downwardly toward said bottom edges, thereby forming an open mouth portion and a pair of bag handles.   
     
     
         55 . The method of making a self-opening bag pack, as described in  claim 47 , comprising the further step of cold staking said bag pack for maintaining the bags in said bag pack in substantial registration. 
     
     
         56 . The method of making a self-opening bag pack, as described in  claim 47 , comprising the further step of hot pinning said bag pack for maintaining the bags in said bag pack in substantial registration. 
     
     
         57 . The method of making a self-opening bag pack, as described in  claim 54 , comprising the further steps of:
 forming first and second openings, said first and second openings penetrating and extending transversely through said bag pack in an upper portion of said bag handles; and   said openings being spaced downwardly from said upper seam and serving to support said bag pack on horizontal arms of a dispensing rack.   
     
     
         58 . The method of making a self-opening bag pack, as described in  claim 54 , comprising the further steps of:
 forming a central tab portion connected to said open mouth portion of said bag blanks in said bag pack; and   forming an aperture, said aperture extending transversely through said bag pack within said central tab portion for suspending said bag pack from a dispensing member.   
     
     
         59 . The method of making a self-opening bag pack, as described in  claim 58 , comprising the further step of forming said central tab portion above an upper edge of said open mouth portion attached thereto, thereby providing stress relief for said open mouth portion. 
     
     
         60 . The method of making a self-opening bag pack, as described in  claim 58 , comprising the further step of forming said central tab portion detachably connected to said open mouth portion of said bags. 
     
     
         61 . The method of making a self-opening bag pack, as described in  claim 58 , comprising the further step of:
 forming said central tab portion of each bag in said bag pack with a frangible section;   said frangible section extending from said aperture to an outer edge of said central tab portion; and   said frangible section rupturing upon removal of said bag from said dispensing member.   
     
     
         62 . The method of making a self-opening bag pack, as described in  claim 58 , comprising the further step of forming said at least one knife cut below said central tab portion. 
     
     
         63 . The method of making a self-opening bag pack, as described in  claim 58 , comprising the further step of forming said at least one knife cut within said central tab portion. 
     
     
         64 . The method of making a self-opening bag pack, as described in  claim 58 , comprising the further step of forming said at least one knife cut within said bag handle.