Abstract:
A stand up bag having a flat bottom is formed from a weldable material. The bag includes a seam that closes the bag&#39;s bottom wall. The seam is welded flat so that the bag is free of protruding elements. A method for manufacturing the bag includes the step of overlapping the leading edge of a tube and welding the overlapped edge to form the flat, welded seam that allows the bag stand on end in an open condition. The apparatus for manufacturing the bag includes a former that may be moved between retracted and expanded positions with an actuator. The former holds the lower portion of the bag in an expanded position while clamp plates form the overlap seam. A bottom welder is used to weld the overlap seam while the clamp plates hold the bottom of the bag against a portion of the former.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application claims priority from United States Provisional Patent Application serial No. 60/323,588 filed Sep. 19, 2001; the disclosures of which are incorporated herein by reference. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Technical Field  
           [0003]    The present invention generally relates to storage containers in the field of flexible bags and, more particularly, to stand-up bags that may be folded flat and that have a flat bottom when unfolded to support the bag in a stand-up position. Specifically, the present invention relates to flat-bottom, stand-up bags that are fabricated from a polymer material wherein the seams of the bag are welded in a manner that yields a flat seam on the bottom surface of the bag.  
           [0004]    2. Background Information  
           [0005]    Stand-up bags are used in a wide variety of applications. One of the most common uses for stand-up bags is to hold food at a fast food retail establishment. Stand-up bags provide a relatively inexpensive package to deliver multiple items of food and drink to a customer who may be standing at a counter inside the retail establishment or who may be sitting in a vehicle at a drive-up window. Some fast food establishments may use multiple people to fill an order that is placed in a single bag. In this situation, the clerk who receives the order may fill the drink order for while allowing other employees to fill the food portion of the order. While the customer waits for the order to be filled, the bag may be standing on the counter or at a station behind the counter where orders are filled. Bags that stand up in an open configuration allow the workers to view the contents of the bag and insert items into the bag without repeatedly handling the bag and disturbing the contents of the bag. Stand-up bags that remain in the open configuration also have the advantage that they are easier to fill with the various order items by store employees. Stand-up bags also have the advantage that consumers can place them in their vehicles and on tables without upsetting the contents of the bags.  
           [0006]    The most common type of a stand-up bag is fabricated from a paper material. Although paper may be coated with a substance, such as wax or a polymer, that will resist liquid spills and grease absorption, a large liquid spill will destroy the integrity of the bag causing the bag to fail. The art thus desires a stand-up bag that may be fabricated from a polymer material that is substantially resistant to moisture absorption.  
           [0007]    Some polymer bags include a flange that extends from the bottom surface of the bag that prevents the bags from standing upright. In some paper bags, a separate patch is used on the bottom of the bag to cause the bag bottom to be flat and to increase the strength of the bag. The art thus desires a polymer stand-up bag that has a flat bottom free of extending flanges and patches. Such a bag must be able to be efficiently manufactured from a variety of materials.  
         BRIEF SUMMARY OF THE INVENTION  
         [0008]    The invention provides a stand up bag having a flat bottom that is formed from a material that may be welded. The bag includes a seam that closes the bottom wall of the bag. The seam is welded flat so that the bag is free of protruding elements that would prevent the bag from standing in an upright position.  
           [0009]    The invention also provides a method for manufacturing a bag having a flat bottom with no protruding seam. The bottom of the tube that forms the sidewall of the bag is folded into the bottom wall of the bag with the leading edge of the tube being overlapped and welded to form the flat, welded seam that allows the bag to stand on end in an open condition.  
           [0010]    The invention also provides an apparatus capable of manufacturing a bag having a flat bottom with no protruding seam. The apparatus includes a former that may be moved between retracted and expanded positions with an actuator. The former holds the lower portion of the bag in an expanded position while clamp plates form the overlap seam. A bottom welder is used to weld the overlap seam while the clamp plates hold the bottom of the bag against a portion of the former.  
       
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0011]    [0011]FIG. 1 is a perspective view of the first embodiment of the bag of the present invention.  
         [0012]    [0012]FIG. 2 is a front view of the bag of FIG. 1.  
         [0013]    [0013]FIG. 3 is a side view of the bag of FIG. 1.  
         [0014]    [0014]FIG. 4 is a bottom view of the bag of FIG. 1.  
         [0015]    [0015]FIG. 5 is an enlarged view of one portion of the bottom of the bag.  
         [0016]    [0016]FIG. 6 is a perspective view of the second embodiment of the bag of the present invention.  
         [0017]    [0017]FIG. 7 is a front view of the bag of FIG. 6.  
         [0018]    [0018]FIG. 8 is a side view of the bag of FIG. 6.  
         [0019]    [0019]FIG. 9 is a bottom view of the bag of FIG. 6.  
         [0020]    [0020]FIG. 10 is an enlarged view of one portion of the bottom of the bag.  
         [0021]    [0021]FIG. 11 is a schematic side view of the first step in the process for making the bags of FIGS. 1 and 6.  
         [0022]    [0022]FIG. 12 is a view similar to FIG. 11 showing the second step of the process.  
         [0023]    [0023]FIG. 13 is a view similar to FIG. 11 showing the third step of the process.  
         [0024]    [0024]FIG. 14 is a view similar to FIG. 11 showing the fourth step of the process.  
         [0025]    [0025]FIG. 15 is a view similar to FIG. 11 showing the fifth step of the process.  
         [0026]    [0026]FIG. 16 is an enlarged view of the overlap and clamp plate.  
         [0027]    [0027]FIG. 17 is an enlarged view of the bottom welded.  
         [0028]    [0028]FIG. 18 is an enlarged view of the bottom former. 
     
    
       [0029]    Similar numbers refer to similar parts throughout the specification.  
       DETAILED DESCRIPTION OF THE INVENTION  
       [0030]    A first embodiment of the flat bottom, stand up bag according to the present invention is indicated generally by the numeral  10  in the accompanying drawings. Bag  10  includes a continuous sidewall  12  and a bottom wall  14  that cooperate to define a storage compartment for holding items. Bag  10  may have any of a variety of shapes such as the exemplary rectangular shape shown in the drawings. In other embodiments, the cross section of bag  10  may be square, triangular, oval, or round. In the exemplary rectangular embodiment, sidewall  12  of bag  10  includes opposed substantially flat front and back walls with opposed gusseted sidewalls. These walls are joined at corners formed by folding or creasing the material that forms sidewall  12 .  
         [0031]    Bag  10  may be fabricated from essentially any material that may be welded. Such materials generally include a large number of plastic and metal materials that are known in the art of flexible packaging. Exemplary materials include mono layer and co-extrusion blown films, laminates, multi-layered materials, and foils.  
         [0032]    Sidewall  12  includes first  16  and second  18  longitudinal edges that are joined together in an overlap seam  20  to form continuous sidewall  12  in the shape of a tube that forms the majority of bag  10 . In the first embodiment of the invention, seam  20  is centrally positioned with respect to one of the walls of bag  10 . In the exemplary rectangular embodiment, seam  20  is disposed in the center of one of the wide walls as depicted in FIG. 2. In other embodiments of the invention, seam  20  may be offset with respect to center if such offset is desired.  
         [0033]    Bottom wall  14  is formed from the same tube of material that is used to form sidewall  12 . This tube is folded to form bottom wall  14  with the ends of the tube being overlapped and welded onto themselves to form a flat seam  22  such that wall  14  is free of a projecting seam. The folding process creates gussets  24  that allow bag  10  to be folded flat. The configuration of these gussets and the general manner of folding them is known to those skilled in the art and the specific folds are not described in detail in this specification. When bottom wall  14  is folded, seam  20  extends across half of bottom wall  14 . Bottom wall  14  is thus flat and allows bag  10  to stand up in an open configuration as depicted in FIG. 1 so that bag  10  may be used in the manners described in the Background of the Invention section of this specification. In known prior art bags, the end of the tube used to form the bag would form a projecting flap when the edges of the tube are welded together. Such a projecting flap would hinder the bag from standing upright. The invention overcomes this drawback in prior art bags.  
         [0034]    A second embodiment of the flat bottom, stand up bag according to the present invention is indicated generally by the numeral  110  in the accompanying drawings. Bag  110  includes a continuous sidewall  112  and a bottom wall  114  that cooperate to define a storage compartment for holding items. Bag  110  may have any of a variety of shapes such as the exemplary rectangular shape shown in the drawings. In other embodiments, the cross section of bag  110  may be square, triangular, oval, or round. In the exemplary rectangular embodiment, sidewall  112  of bag  110  includes opposed substantially flat front and back walls with opposed gusseted sidewalls. These walls are joined at corners formed by folding or creasing the material that forms sidewall  112 .  
         [0035]    Bag  110  may be fabricated from the same materials as bag  10  described above.  
         [0036]    Sidewall  112  includes first  116  and second  118  longitudinal edges that are joined together in an overlap seam  120  to form continuous sidewall  112  in the shape of a tube that forms the majority of bag  110 . In the second embodiment of the invention, seam  120  is centrally positioned with respect to one of the walls of bag  110 . In the exemplary rectangular embodiment, seam  120  is disposed in the center of one of the short walls as depicted in FIG. 8. In other embodiments of the invention, seam  120  may be offset with respect to center if such offset is desired.  
         [0037]    Bottom wall  114  is formed from the same tube of material that is used to form sidewall  112 . This tube is folded to form bottom wall  114  with the ends of the tube being overlapped and welded onto themselves to form a flat seam  122  such that wall  114  is free of a projecting seam. The folding process creates gussets  124  that allow bag  110  to be folded flat. The configuration of these gussets and the general manner of folding them is known to those skilled in the art and the specific folds are not described in detail in this specification. When bottom wall  114  is folded, seam  120  extends across a portion of bottom wall  114 . Bottom wall  114  is thus flat and allows bag  110  to stand up in an open configuration as depicted in FIG. 6 so that bag  110  may be used in the manners described in the Background of the Invention section of this specification. In known prior art bags, the end of the tube used to form the bag would form a projecting flap when the edges of the tube are welded together. Such a projecting flap would hinder the bag from standing upright. The invention overcomes this drawback in prior art bags.  
         [0038]    Either of bags  10  or  110  may be fabricated according to the following method. The method is described for bag  10  with it being understood by those skilled in the art that bag  110  may be fabricated by the same or an equivalent method.  
         [0039]    A sheet of material that will form bag  10  or  110  is first drawn into a tube  200  such that the longitudinal edges  16  and  18  of tube  200  may be overlapped and welded together to form seam  20 . The apparatus that is used to form tube  200  is known to those skilled in the art. This apparatus bends a flat sheet of material into a tube such that the edges are adjacent. The flat sheet of material may be stored in a large roll if desired. The creases that form gussets  24  and the corners of bag  10  are formed into the material the forms the tube before tube  200  is formed or immediately after tube  200  is formed. In the exemplary embodiment of this step depicted in FIG. 11, tube  200  is partially collapsed as it is moved over an actuator  202  such as an air cylinder or a linear actuator. In other embodiments of the invention, tube  200  may be passed over actuator  202  in an expanded condition.  
         [0040]    A former  204  is connected to the movable element  206  of actuator  202 . Former  204  is positioned downstream of actuator  202  such that the material of tube  200  passes over the body of actuator  202  before it reaches former  204 . In one embodiment of the invention, former  204  is capable of being expanded from a collapsed position (FIG. 11) to an expanded position (FIG. 13) by actuating actuator  202  from a retracted position to an extended position.  
         [0041]    Former  204  includes two outer links  206  that are pivotally connected to a fixed frame  208  at a first pivot  210 . Frame  208  may be connected to actuator  202  or the same supports that support actuator  202 . Frame  208  may be used to help guide tube  200 . Former  204  further includes a pair of bottom former plates  212  that are pivotally connected to outer links at second pivots  214 . The inner ends of bottom former plates  212  are pivotally connected together at a third pivot  216 . The extendable and retractable portion of actuator  202  is also connected to former plates  212  so that plates  212  may be moved between the collapsed position depicted in FIG. 11 and the forming position depicted in FIG. 13. In the embodiment of the invention depicted in the drawings, actuator  202  is connected to third pivot  216 .  
         [0042]    The apparatus for forming bag  10  further includes first  220  and second  222  overlap and clamp plates and a welder  224 . The apparatus also includes a cutter that severs tube  200  as is known in the art of bag forming.  
         [0043]    The method for forming bag  10  includes the step of forming tube  200  and moving tube  200  over former  204 . Tube  200  may be moved with appropriate mechanisms known to those skilled in the art. When tube is initially moved over former  204 , former  204  is in the collapsed position. Tube  200  is moved over former  204  until enough material to form bottom wall  14  extends beyond second pivots  214 .  
         [0044]    At this point, actuator  202  is moved from the retracted position to the extended position. As actuator  202  is extended, overlap and clamp plates  220  and  222  are moved into position as shown in FIG. 12. Plates  220  and  222  engage the portion of tube  200  that extends beyond second pivots  214  to start folding the material into bottom wall  14 . As actuator  202  extends, former  204  moves toward the expanded position with bottom former plates  212  pushing outer links  206  outwardly about first pivots  210 . As these elements move in FIG. 12, welder  224  moves into position.  
         [0045]    The movement of overlap and clamp plates  220  and  222  is coordinated so that plates  220  and  222  arrive at their clamping position just after bottom former plates  212  reach the expanded position as shown in FIG. 13. Plates  212 ,  220 , and  222  cooperated to clamp bottom wall  14  in place with the leading edge of tube  200  being overlapped to form seam  22 . The overlap is formed by the movement of plates  220  and  222 . Once plates  220  and  222  are in position, welder  224  heats seam  22  until the material is welded into a flat, non-protruding seam as described above.  
         [0046]    Once seam  22  is welded, plates  220  and  222  as well as welder  224  are removed as shown in FIG. 14. At this time, former  204  is collapsed by retracting actuator  202 . As former  204  collapses, the end of bag  10  folds up as shown in FIG. 15 so that bag  10  will be in a flat condition after it is formed. Tube  200  continues to move over former  204  until sidewall  12  reaches a desired length. The cutter then severs tube  200  to form bag  10 . The process is then repeated for the next bag  10 .  
         [0047]    In the foregoing description, certain terms have been used for brevity, clearness, and understanding. No unnecessary limitations are to be implied therefrom beyond the requirement of the prior art because such terms are used for descriptive purposes and are intended to be broadly construed.  
         [0048]    Moreover, the description and illustration of the invention is an example and the invention is not limited to the exact details shown or described.