Patent Publication Number: US-2011052100-A1

Title: Integral closure system for a flexible bag

Description:
FIELD OF THE INVENTION 
     The present invention relates to the field of flexible bags in general and, more particularly, to flexible bags that have a cinch, tie or other closure system provided for closing the bag after filling. 
     BACKGROUND OF THE INVENTION 
     Flexible bags are made in a great number of sizes and configurations for a variety of application. For example, small-sized plastic bags are widely used for packing food and packaging other small items, medium-sized paper and plastic bags are used for grocery shopping and other retail merchandise applications, and large-sized plastic bags are widely used to contain and carry garbage or trash. Extremely large-sized plastic bags are termed flexible intermediate bulk containers (FIBCs, or “super sacks”), and have been used for example to transport large volumes of raw materials required for commercial building. 
     Paper and plastic films are particularly cost-effective materials for use in single-use bag applications. In applications where the bags may be used more than once (for example, grocery shopping), materials such as burlap, woven polyethylene and non-woven polyethylene may be used for their greater tear resistance and wear quality. 
     In single-use garbage bags, plastic film bags have become a ubiquitous component of everyday life, providing an easy and inexpensive means for gathering and securing garbage for disposal. Commonly, a soft, flexible plastic such as LDPE (Low Density Polyethylene) or, for strength, LLDPE (Linear Low Density Polyethylene) is extruded, for example, to form garbage bags for packaging in roll form. HDPE (High Density Polyethylene) is sometimes alternatively used. 
     Manufacture of plastic film garbage bags is most economically carried out using a blown film process. To begin this process, raw material in the form of small plastic beads (resin) is gravity fed from a top mounted hopper into the barrel of an extruder. Additives such as colorants and UV inhibitors, also in pellet form, may also be mixed into the resin prior to arriving at the hopper. 
     The mixed material is fed through the feed throat (an opening near the rear of the barrel) and comes into contact with a rotating screw. The rotating screw forces the plastic beads forward into the barrel which is heated to the desired melt temperature of the molten plastic (for example, around 200° C.). In most processes, a heating profile is preferably set for the barrel in which three or more independently controlled heaters gradually increase the temperature of the barrel from the rear (where the plastic enters) to the front. This allows the plastic beads to melt gradually as they are pushed through the barrel and lowers the risk of overheating, which may cause degradation in the polymer. Extra heat is contributed by the intense pressure and friction taking place inside the extruder barrel. Typically, cooling fans are used to keep the temperature below a set value. 
     At the front of the barrel, the molten plastic leaves the screw and travels through a screen pack to remove any contaminants that may have entered the melt. The screens are typically reinforced by a breaker plate (a thick metal puck with many holes drilled through it) since the pressure at this point can exceed 5000 psi (34 MPa). The screen pack/breaker plate assembly also serves to create back pressure in the barrel, which is necessary for uniform melting and proper mixing of the polymer. 
     After passing through the breaker plate, the molten plastic enters a die. The die is an upright cylinder with a circular opening similar to a pipe die. The diameter can be a few centimeters to more than three meters across. The molten plastic is pulled upwards from the die by a pair of nip rolls high above the die (4 meters to 20 meters or more depending on the amount of cooling required). In the center of the die is an air outlet from which compressed air can be forced into the center of the extruded circular profile, creating a bubble. This expands the extruded circular cross section by some ratio (a multiple of the die diameter), thus decreasing the wall thickness. This ratio, called the “blow-up ratio” can be from a few percent to 200 percent of the original diameter. The nip rolls flatten the bubble into a double layer of film, having a width (called the “layflat”) that is equal to half of the circumference of the bubble. This flattened film can then be spooled or printed on, cut into shapes, and heat sealed. 
     In order to form the plastic film bags, the flattened film is fed though heat rolls that periodically apply a thermal bond across the sheet to form a bottom portion of the bag, and then through cutting rolls or dies that that cut the sheet adjacent to each thermal bond to separate the bag from the extrusion and to form the mouth of the next bag. 
     Conventional plastic film garbage bags can be classified into two types: flat-mouth bags, and vest- or ear-style bags. For each type, after filling the bag, the mouth of the bag may be closed by tying portions of the bag adjacent to the mouth into a knot. More specifically, in the case of the flat-mouth bag, bag material along opposite rim sides of the mouth is gripped to form two handles or strips, which are tied together to form the knot. However, as described in U.S. Pat. No. 5,980,109, which is incorporated by reference herein in its entirety, as a result of the loss of the bag material used to form the handles, the utilization ratio (i.e., portion of the volume of the bag which may be filled with garbage) of a bag sealed in this manner is limited to 65%-80%. If the garbage bag happens to be over-filled, it becomes difficult to tie the knot. Even if tied, an insufficient amount of material may be used to form the strips, such that the bag may become easily untied. 
     Vest-style bags overcome this deficiency by providing additional material (i.e., the “shoulder” portions or “ears” of the vest) to form the tying strips. However, vest-style bags may not be as conveniently and inexpensively formed as flat-mouth bags in continuous bag rolls, and it may still be difficult to tie the ears of the vest to form a knot if the bag has been overfilled. 
     In order to overcome these shortcomings, several additional types of garbage bags have been developed.  FIGS. 1 and 2  depict a bag  10  with a flat mouth  12  and a tie-wire  11  pre-set (for example, adhesively) on the outside of the bag near the mouth  12 . As illustrated in  FIG. 2 , the tie-wire  11  can be removed from the outside of the bag  10  without damaging the bag  10 , and then tied around the mouth  12  of the bag  10  to close the bag  10 . However, the tie-wire  11  may be difficult for a single user to tie tightly around the mouth  12  of the bag  10 , and may be difficult to find or may be lost at the time at which the bag  10  is to be closed. In addition, setting the tie-wire  11  onto the bag  10  adds production cost and difficulty. 
     Alternatively, as shown in  FIG. 3 , a bag  13  may be formed in which an endless tie-wire  16  is placed into a folded wire channel  14  at the rim of the mouth  17  of the bag  13 . In order to close the bag  13 , the endless tie-wire  16  is pulled from the opening  15  of the wire channel  14  to and tied together to close the mouth  12 . While the endless tie-wire  16  may be easier to manipulate than the tie-wire  11 , adding the tie-wire  16  and channel  14  to the bag  13  also increases production cost and difficulty. For example, the bag  13  cannot be prepared using a blown film process as described above, but must rather be prepared by forming the channel  14  on a flat plastic sheet, adding with the tie-wire  16  to the channel, folding the sheet over and forming thermal bonds along a bottom edge, edges of the channel and a side edge of the folded sheet in order to form the bag  13 . 
     Referring to  FIGS. 4 and 5 , a third type of garbage bag as disclosed by U.S. Pat. No. 5,980,109 is shown, in which a tie-strip  3  is formed from material at an edge of a plastic bag  4 . A thermal bond line  1  extends along a portion of a lateral edge of the bag  4  between a lower point spaced from a bottom edge of the bag  4 ) and an upper point spaced from mouth of the bag  4  to define a thermal bond strip of the bag  4 . A tear line  2 , which is a rupturable separation line, extends along and within the thermal bond strip and separates it into two portions. By tearing the bag  4  along the tear line  2 , a tie-strip  3  is formed. A second thermal bond line  5  is preferably formed along an outer edge of the tear line  2  to add strength to the tie-strip  3 . While this third type of garbage bag provides the advantage of providing a closure formed from just from the extruded material of the bag  4 , it still suffers the disadvantage of requiring a user to separate the tie-strip  3  from the bag  4  and apply the tie-strip  3  to the mouth of the bag in order to close the bag. As in the case of the bag illustrated in  FIG. 1 , the tie-strip  3  may be difficult for a single user to tie tightly around the mouth of the bag  4  in order to achieve an effective closure of the bag. 
     Referring to  FIGS. 6A-6D , a fourth type of garbage bag is shown as disclosed by U.S. Pat. No. 4,778,283 is shown. U.S. Pat. No. 4,778,283 is hereby incorporated by reference herein in its entirety. 
     In  FIGS. 6A-6D , a draw band bag  20  includes a front panel  21  and a rear panel  22  formed from a polyethylene tube. Opposing sides are cut from the tube in a perpendicular direction. The tube is slit along a top  23  to form an opening. Holes  24  are punched in both of the panels  21  and  22  of the bag at a predetermined distance from the top  23 . A draw tape or band  25  is positioned on the outer surface of panel  21  parallel to the top  23  and over the holes  24 . The ends of the draw band  25  are secured to the opposite sides of the bag  20  when side heat seals  26  and  27  are made. A bottom  28  of the bag  20  is formed by the fold joining the front and back panels  21  and  22 . 
     As is further disclosed in U.S. Pat. No. 4,778,283, the draw tape  25  may alternatively be produced by folding the panels  21  and  22  over one side of the bag  20  and securing the fold to the opposite sides of the bag  20  when side heat seals  26  and  27  are made. Once the gold has been secured, an outer one of the panels  21  and  22  is slit at the fold in order to create the open top  23 . The other one of the panels  21  and  22  is perforated, so that the folded-over portion of the panels  21  and  22  can later be separated to form the draw band  25 . 
     Closure of the bag  20  is effected by inserting the middle of the band  25  as a loop through the holes  24  in both panels  21  and  22 , and pulling in the top corners of the bag  20  to the holes  14  at the center of the panels. As shown in  FIG. 6D , for example, the draw tape  25  can then be used to make a half hitch around the top  23  of the bag and pulled tight. Although the bag of  FIGS. 6A-6D  provides an integral closure systems, like the endless tie-wire bag of  FIG. 3 , it is relatively costly and difficult to produce. 
     Therefore, it would be advantageous to provide a plastic garbage bag having an inexpensive, integral closure system which can be easily manufactured and used for effectively closing the bag. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to an integral closure system for a flexible bag which may be used in any of a variety of applications (for example, in merchandise bags and in garbage or trash bags). The flexible bag includes a plurality of panels defining an interior compartment of the bag, and a mouth portion for accessing the interior compartment of the bag. In one embodiment of the invention, the closure system is implemented in two opposing panels among a plurality of panels of the bag. 
     Specifically, each one of the two opposing panels includes a first portion integrally defining a handle, and a second portion including an aperture. The first portion of each opposing panel is positioned near a top edge of the panel proximate to the mouth portion, and the second portion of each panel is positioned adjacent to and below the first portion. The handles of the two opposing panels are configured to be drawn together, inserted from an interior compartment side successively through each of the apertures, and then cinched in order to close the mouth portion of the bag. 
     The handles are preferably formed by cut lines applied at the border between the first and second portions of the opposing panels. The cut lines extend across a width direction of the panels, and have opposing ends that are spaced inwardly apart from side edges of the opposing panels. The cut lines are preferably formed as a series of spaced-apart perforations. 
     The apertures are preferably centered between the side edges of the panels, and are preferably circular or oval in shape. The apertures may be formed by cutting spaced-apart perforations into the second portion that conform to perimeters of the apertures, and then pushing out interior panel material within the cut lines to form the apertures. 
     As compared to prior art closure systems, the present invention requires no separate components to be added to or formed on the panels of the flexible bag, and results in a closure system that is integrated with the bag so that it cannot be misplaced or lost. The present invention is also cost-effective to produce as compared to prior art closure systems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The inventions will become more readily apparent from the Detailed Descriptions of the Invention, which proceeds with reference to the drawings, in which: 
         FIG. 1  shows a conventional flat-mouth garbage bag having a separate tie-wire pre-set on an exterior surface of the bag; 
         FIG. 2  shows the bag in the bag of  FIG. 1  in a closed state; 
         FIG. 3  shows another conventional flat-mouth garbage bag incorporating a tie-wire in a folded wire channel provided at the rim of the mouth of the bag; 
         FIG. 4  shows another conventional flat-mouth garbage bag incorporating a tie-strip formed from at an edge of the bag; 
         FIG. 5  shows the bag of  FIG. 4  with the tie-strip in a detached state; 
         FIGS. 6A-6D  show another conventional flat-mouth garbage bag having a draw band and an opening through which the draw band is inserted for closing the bag; 
         FIG. 7  shows a garbage bag including a closure system according to an embodiment of the present invention; 
         FIG. 8  provides a process flow diagram depicting a method for operating the closure system of  FIG. 6 ; and 
         FIGS. 9A-9D  illustrate steps in the method depicted in  FIG. 8 ; 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is directed to an improved closure system for flexible bags, including for example conventional blown film garbage or trash bags (for example, comprising one of LDPE, LLDPE and HDPE) and merchandise bags (for example, comprising one of burlap, woven polyethylene and non-woven polyethylene). The inventive system requires no additional material components be added to the bags, and forms the closure system integrally with the bag. As a result, components of the closure system cannot be misplaced or lost during use of the bag. Moreover, the closure system is cost-effective to produce, and is easily operated by a single user to effectively close the bag without significantly compromising the utilization ratio of the bag. 
       FIG. 7  depicts a flexible bag  100  having a closure system according to an embodiment of the present invention. While the bag  100  is depicted as a conventional, flat-mouth extruded plastic bag (for example, comprising one of LDPE, LLDPE and HDPE), a skilled artisan will readily understand that the bag  100  may alternatively be formed from a folded plastic sheet, may have a vest-style mouth, and/or may be formed from a reinforced paper, woven polyethylene, non-woven polyethylene or impregnated cloth material rather than as a blown-film plastic extrusion. The bag  100  may be used in a variety of applications (for example, as a grocery bag or as a bag for carrying other merchandise). 
     In  FIG. 7 , the flexible bag  100  is depicted in a “flattened” state, with overlapping panels  103  that that coextensively define a mouth  101 , side edges  102  and a bottom edge  104 . Because they are formed in a continuous extrusion and then flattened, the overlapping panels  103  are seamlessly joined at the side edges  102 . A bottom edge  104  is preferably formed by cutting the continuous extrusion, and then sealed in a fully closed state by a thermal bond  105 . 
     The panels  103  are each provided with perforations  110  and apertures  120 . The perforations  110  preferably extend in a line below and parallel to the mouth  101  of the flat-mouth bag  100 , terminating inwardly from side edges  102  of the bag  100 . The apertures  120  are provided below the perforations  110 , and are preferably centered between the side edges  102 . 
     In accordance with the present invention, the perforations  110  and apertures  120  may be provided at various positions on the panels  103 . In a preferred embodiment, the panels are configured to have a length of about 32.5 inches along the sides  102  and a width of about 23.5 inches along the bottom edge  103  and mouth  101 . In this preferred embodiment, the perforations  110  are offset by about 2 inches below the mouth  101 , and terminate inwardly about 2 inches away from each side edge  102 . The apertures  120  preferably have a diameter of about one inch, and are preferably centered between the side edges  102  and about 2 inches below the perforations  110 . 
     The perforations  110  and apertures  120  may be readily produced, for example, by passing the flexible bag  100  in its flattened state through conventional cutting rollers having elements configured to cut the continuous extrusion to form the mouth  101 , as well as elements configured to cut the perforations  110  and apertures  120 . The cutting and perforating elements may be provided on a single roller, or on a series of rollers. By passing the bag  100  through the cutting rollers in its flattened state, the perforations  110  and apertures  120  may be simultaneously cut into both panels  103 . 
     As an alternative to the blown-film plastic bag, and as previously noted, the bag  100  may be formed from a folded sheet or two overlaid sheets that are joined along open seams (for example, by thermal bonding, adhesive and/or stitching), and/or reinforced paper, woven polyethylene, non-woven polyethylene, burlap and or impregnated cloth material. With any of these alternatives, the perforations  110  and apertures  120  may preferably still be formed in the bag  100  in the above-described manner. 
     In some applications, one or more of a region surrounding the perforations  110  and/or the apertures  120  may receive additional reinforcement for extending the useful life of the bag  100 . Suitable reinforcement may include, for example, the application of an adhesive in the regions surrounding the perforations  110  and/or the apertures  120 , the application of stitching (for example, to prevent unraveling of a woven bag material, or the application of one or more additional material layers surrounding the perforations  110  and/or the apertures  120  (for example, adhesively, by thermal bonding or by stitching). The additional material layers may be formed form additional layers of the material of the bag  100 , or by other materials having more desirable reinforcement properties (for example, using a heavier gauge non-blown film plastic to reinforce the perforations  110  and/or the apertures  120  of a blown film plastic bag. 
       FIG. 8  presents a process flow diagram depicting a method for operating the closure system of  FIG. 7 .  FIGS. 9A-9D  further illustrate the steps of  FIG. 7 . 
     At step  801  of  FIG. 8 , a user begins the closure process by grabbing bag material  130  between the mouth  101  and perforations  110  of the flexible bag  100  with one hand, and pressing the fingertips of his or her hand through the perforations  110  in order to separate the material  130  from the rest of the material of the panels  103  along the perforations  110 . As further illustrated for example in  FIG. 9A , the separated material  130  from the panels  103  forms two handles  131  of the bag  100 . 
     At step  802  of  FIG. 8 , the user proceeds to thread both handles  131  through one of the apertures  120  in the panels  103  (for example, an aperture  121  in a panel  103  defining a right bag face, as illustrated in  FIG. 9B ). As the apertures  120  are preferably formed by perforations in the panels  103  along perimeters of the apertures  120 , the user at step  702  may be required to press his or her fingertips through material of the panels  103  within each perimeter in order to separate and remove this material from the panels  103  prior to the threading step. 
     Next, at step  803 , the user threads both handles  131  through the other one of the apertures  120  (for example, an aperture  122  in another panel  103  defining a left bag face, as illustrated in  FIG. 9C ). According to the user&#39;s preference, the handles may be threaded from the exterior of the bag  100  along a single direction through both apertures  121 ,  122 , or may be threaded from the interior of the bag first in a direction through one of the apertures  121 ,  122  and then in an opposing direction over the top of the bag and through the other of the apertures  121 ,  122 . 
     Finally, at step  804 , the user pulls upwardly on both handles  131  in order to draw upper side regions  132  of the panels  103  (see, e.g.,  FIGS. 7 and 9D ) and middle portions  134  of the panels in the vicinity of apertures  121 ,  122  together to close the mouth  101 . 
     The pathway taken by the handles  131  through the apertures  121 ,  122  upon pulling upwardly on the handles  121  causes a cinching effect, which assists in maintaining the mouth  101  in its closed position when the handles  131  as extended by the upward pulling are ultimately released by the user. The extended handles can then be easily employed, for example, by the user to lift the bag  100  out of a receptacle  140  in order to then carry and dispose of the bag  100 . 
     Those skilled in the art will readily recognize additional numerous adaptations and modifications which can be made to the present invention which fall within the scope of the present invention as defined in the claims. For example, the invention may be further modified in one of more of the following ways:
         by positioning the apertures at a position other than centered between side edges of the bag (for example, in the vicinity of the side edges of the bag);   by adding additional apertures for further threading of the handles;   by adding additional perforations defining additional handle pairs;   by configuring the perforations along other than a straight line (for example, curving downwardly in the vicinity of the side edges for adding strength to the handles at their points of connection to the bag;   by configuring the apertures with other than a circular shape (for example, configuring the apertures in an elliptical shape); and   by adding reinforcements surrounding the apertures and or along the handles for added strength.       

     It is intended that the scope of the present invention include all foreseeable equivalents to the elements and structures as described with reference to  FIGS. 7-9D . Accordingly, the invention is to be limited only by the scope of the claims and their equivalents.