Abstract:
An improved method and apparatus for providing end seals on vertical stand up packages that prevents pleat formation and gusset variation. A clamping device is mounted below sealing jaws. A bottom end seal is made by the sealing jaws to form an open-ended tube. The open-ended tube is moved downward. The clamping device engages the tube to prevent twisting when product is placed into the tube. Product then enters an open-ended tube of flexible film packaging and the top seal is made.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a vertical stand-up package made from a modified vertical form, fill, and seal packaging machine, and the apparatus and method for making same, that provides for a single piece construction of a vertical stand-up package. In particular, the invention reduces the pleating that can occur when filling a vertical stand-up package with minimal cost increase and minimal modification. 
     2. Description of Related Art 
     Vertical form, fill, and seal packaging machines are commonly used in the snack food industry for forming, filling, and sealing bags of chips and other like products. One such packaging machine is seen diagrammatically in  FIG. 1 . This drawing is simplified and does not show the cabinet and support structures that typically surround a machine, but it demonstrates the working of the machine well. Packaging film  110  is taken from a roll  112  of film and passed through tensioners  114  that keep it taut. The film then passes over a former  116 , which directs the film into a vertical tube around a product delivery cylinder  118 . As the tube is pulled downward by drive belts  120  the vertical tube of film is sealed along its length by a vertical sealer  122 , forming a back seal  124 . The machine then applies a pair of heat sealing jaws  126  against the tube to form a transverse seal. This transverse seal acts as the top seal  133  on the bag  130  below the sealing jaws  126  and the bottom end seal  131  on the bag  132  being formed above the jaws  126 . After the transverse seal has been formed, a cut is made across the sealed area to separate the finished bag  130  below the seal from the partially completed bag  132  above the seal. The tube is then pushed downward to draw out another package length. Before the sealing jaws  126  form each transverse seal the product to be packaged is sent through the product delivery cylinder  118  and is held within the tube above the bottom end seal  131 . The material that is fed into the form, fill and seal machine is typically a packaging film such as polypropylene, polyester, paper, polyolefin extrusions, adhesive laminates, and other such materials, or from layered combinations of the above. For many food products, where flavor retention is important, a metalized layer will form the inner most layer. 
     One modification to a vertical form, fill, and seal packaging machine is disclosed in U.S. Pat. No. 6,722,106 (“the &#39;106 Patent”), which is assigned to the same assignee as the present invention. The &#39;106 Patent discloses a method for making a free standing package called a vertical stand up pouch. The modification uses two forming plates  104  and a tension bar  102  to hold the packaging film tube in tension from inside the tube. Tension is applied on the outside of the film and in the opposite direction of the tension provided by the forming plates  104  by a fixed or stationary tucker mechanism  106  positioned between the forming plates  104 . The tucker bar  106  provides a crease or fold in the tube of the packaging film between the two forming plates  104 . The crease is formed prior to formation of the transverse seal by the seal jaws  126 . Consequently, once the transverse seal is formed, the crease becomes an integral feature of one side of the package. The vertical form and fill machine thereafter operates basically as previously described in the prior art, with the sealing jaws  126  forming a lower transverse seal  131 , product being introduced through the forming tube  118  into the sealed tube of packaging film which now has a crease on one side, and the upper transverse seal being formed, thereby completing the package. An example of the vertical stand up package formed shown in FIGS.  2   a  and  2   b , which show the outside layer of packaging film  116  with the graphics oriented 90 degrees clockwise from graphics orientation normally present on a pillow pouch formed by a standard prior art vertical form, fill and seal machine. As shown in  FIGS. 2   a  and  2   b  the transverse seals  131 ,  133  of the vertical stand up package are oriented vertically once the bag stands up on one end as shown in  FIG. 2   b.    
       FIG. 2   a  shows the crease  176  that was formed by the tucker bar  106  and forming plates  104  to create a gusset  180  base bounded by an edge that permits the package to stand upright. Various modifications of the vertical stand up pouch, methods for making the pouch, and apparatuses for making the pouch are disclosed in U.S. Pat. Nos. 6,729,109 and 6,679,034. 
     Referring back to  FIG. 1 , after the transverse seal is formed by the pair of sealing jaws  126 , an open-ended tube is created. The open-ended tube is pulled downward by drive belts  120 , product is dropped into the open-ended tube and the bag is formed upon completion of the second end seal  133 . Unfortunately, the weight of the product dropping into the open-ended tube can apply pressure to the gusset portion  180  of the open-ended tube and can cause the flexible film tube to twist or rotate below the fill tube about the fill tube axis. If the flexible film tube is twisted when the sealing jaws  126  are brought together to make the end seals  131   133 , the gusset  180  can be sealed at the ends at the location indicated by numeral  141  and  143 , thus forming a pleat  151   153 . Pleats  151   153  are undesirable for several reasons. 
       FIG. 2   c  is a perspective view of a vertical stand up package having pleats. There are several problems associated with pleats. First, as shown by the Figure, a pleat can cause edge erosion. Edge erosion can inhibit the ability of the vertical stand up package to stand upon the gusset  180 . Second, bags having pleats can have higher propensity to produce a non-hermetic seal and result in reduced shelf life. This can be especially true if pleats are in unpredictable or inconsistent locations. Third, pleats can interfere with easy opening features of a bag. For example, to provide an easy opening feature, a cut out  155   156  can be provided on the end seals  131   133  in communication with a score line  152  placed on the container by methods known in the art. Normally, upon tearing in the vicinity of the cut out  155   156 , the film will continue to tear along the score line  152 . The cut out  156 , however, can be sealed by a pleat  141 , preventing initiation of a tear along the score line  152 . Consequently, a need exists for a vertical stand-up package having no pleats. The method and apparatus should be economical and should permit modification to existing vertical form, fill, and seal machines. In addition, the method and apparatus should minimize the breakage of frangible product within the package. 
     SUMMARY OF THE INVENTION 
     The proposed invention involves producing a vertical stand up package having a gusset and no pleats at the end seals using a vertical form, fill, and seal machine modified with a clamping mechanism. A first end seal is made in a flexible film to form an open ended tube. The open ended tube is pulled downward and a gusset is formed. The open ended tube is held in place by a clamping mechanism and product is added to the open ended tube. A second end is then made to form a bag having no pleats. 
     The method works on existing vertical form, fill, and seal machines requiring very little modification. The same metalized or clear laminations used as materials in pillow pouches can also be used with the invention. The above as well as additional features and advantages of the present invention will become apparent in the following written detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features believed characteristic of the invention are set forth in the appended claims. The invention itself, however, as well as a preferred mode of use, further objectives and advantages thereof, will be best understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a prior art form, fill, and seal machine. 
         FIGS. 2   a ,  2   b  and  2   c  are perspective views of prior art vertical stand up packages. 
         FIG. 3  is a perspective view of a vertical form, fill, and seal machine according to one embodiment of the present invention. 
         FIG. 4   a  is a perspective view of a bag straightening device in accordance with one embodiment of the present invention. 
         FIG. 4   b  is a side view of a bag straightening device depicted in  FIG. 4   a.    
     
    
    
     DETAILED DESCRIPTION 
     An embodiment of the innovative invention will now be described with reference to  FIG. 3 .  FIG. 3  is a perspective view of a vertical form, fill, and seal machine according to one embodiment of the present invention. As shown, a bag straightening device  300  is placed on the gusset side of the open-ended tube below the sealing jaws  126 . Prior to this invention, larger bags, especially those having an end seal length L greater than about 10 inches could not be efficiently used for a vertical stand up pouch because of pleating that occurred during end seal formation performed by the sealing jaws  126 . 
     The sealing jaws  126  provide three functions simultaneously. First, they make a bottom transverse seal  131  to form an open ended tube above the sealing jaws  126 . Second, they form a top transverse seal  133  to close the open-ended tube and thereby from a closed package below the sealing jaws  126 . Third, they provide a cut  130  between the top transverse seal  133  of the closed package below the sealing jaws  126  and a bottom transverse seal  131  to an open ended tube above the sealing jaws  126 . 
     Once the sealing jaws  126  have provided a bottom end seal  131  to form an open ended tube, the open ended tube is pulled downward by drive belts  120  or other means. A bag straightening device  300  then engages the open-ended tube. The purpose of the bag straightening device  300  is to prevent the open-ended tube from twisting or rotating below the fill tube about the fill tube axis prior to transverse seal  131   133  formation. It should be noted that the undesirable rotation occurs when the weight of the product placed into the bag exceeds a certain threshold. The product density of tortilla chips and potato chips causes this threshold to be exceeded when the end seal length L greater than about 10 inches, however, other products may cause this threshold to be exceeded at other lengths. Prevention of such rotation reduces or eliminates pleats and promotes a substantially symmetrical gusset  180  about the crease line  176 , depicted in  FIG. 2   a . A substantially symmetrical gusset  180  lessens gusset variation and aids package stability. 
       FIG. 4   a  is a perspective view of a bag straightening device  300  in accordance with one embodiment of the present invention.  FIG. 4   b  is side view of a bag straightening device  300  depicted in  FIG. 4   a . Referring to  FIGS. 3 ,  4   a , and  4   b , once the open-ended tube has reached its pre-determined fill position, two opposing supports  350  close to provide a clamp that prevents twisting or open tube rotation when product is subsequently dropped through the fill tube  118  into the open tube made of flexible film. After product has dropped into the open tube, the sealing jaws  126  close to form the top end seal  133  of the closed package and the bottom end seal  131  of the open tube. Because of the clamp provided by the clamping device  300 , open tube rotation is prevented during the filling and sealing steps. Further, because the sealing jaws  126  simultaneously provide the bottom seal  131  of the open tube at the same time it provides the top seal  133  of the closed package, the clamp prevents pleating at both seals  131   133 . Thus, a vertical stand up package having a substantially symmetrical gusset is made with no pleats. The clamp then disengages the closed package and the process repeats. 
     In one embodiment, the clamp is provided at least one inch above the first end seal. In one embodiment, the clamp location height can be easily adjusted by manipulation of a screw (not shown) to vary the distance of the clamping device support member  322  in relation to the sealing jaws  126 . 
     In one embodiment, the bag straightening device  300  shown is pneumatically operated. Thus, compressed air can be used to actuate a clamping mechanism. In alternative embodiments, the bag straightening device can be hydraulically or electrically operated. In one embodiment, the clamping mechanism comprises a piston  315  mounted to a pair of arms  325 . Each arm  325  is attached to a support  350 . In one embodiment, each arm comprises an elbow  320 . 
     To close the bag straigtening device or clamping mechanism  300 , compressed air  310  causes the piston  315  to be pulled in the direction as indicated by the arrow  317 . This causes the arms  325  to rotate inward about the elbows  320  causing the support  350  to reciprocate towards each other in the direction depicted by the arrows  327 . In one embodiment, the actuating can be reversed such that compressed air  305  causes the piston  315  to be pulled in the direction as indicated by the arrow  317 . 
     In one embodiment, the clamping mechanism  300  engages and holds the open-ended tube before the tube is filled with product. This can help to minimize gusset variation that may occur if product is first placed into the open-ended tube. This also helps to prevent breakage of potentially frangible product, such as potato or tortilla chips. In one embodiment, the piston  315  is attached to an adjustable member  330  such that the tension applied by the clamping mechanism  300  can be adjusted. 
     In one embodiment, the portion of the support  350  that engages the open-ended tube comprises a resilient material  360 . Once the open-ended tube is filled with product, the end seals  131   133  are created before the clamping mechanism disengages. 
     To open the clamping mechanism, compressed air  305  causes the piston to be pushed upward. The arms  325  rotate outward about the elbows  320  causing the supports  350  to reciprocate away from each other. The above embodiment is just one example of a bag straightening device. 
     The present invention can be achieved with relatively inexpensive modification of existing form, fill, and seal machinery to produce a relatively large vertical stand up package with minimal pleating and a substantially symmetrical gusset. In one embodiment, the gusset width is greater than about 3 inches. As used herein, the gusset width is the length of film from the substantially parallel edges of the gusset and is perpendicular to the crease line  176 . (The non-parallel edges of the gusset are located near the end seals.) The gusset length is the distance from end seal  131  to end seal  133 . 
     While the invention has been particularly shown and described with reference to a preferred embodiment, it will be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention. For example, shapes other than a circular shape as defined by a support  350  can be used in the clamping mechanism.