Abstract:
Packages having improved openable and reclosable interlocking seals and a method and apparatus for making the same from a novel continuous web of composite packaging film, the seal having male and female portions of arrowhead shape in cross section, snap detents, and being formed transversely to the direction of film flow during package formation at line speed. The packaging film is provided at package length intervals with thermoformable strips secured thereto transversely to the running length of the film, and is fed to a modified standard vertical form, fill and seal packaging machine where the film is formed into a bag with the thermoformable strip inside in ends abutting folded facing relationship at the upper end of the bag, product deposited into the bag, the bag sealed, the reclosable interlocking seal formed, and the bag severed from the next bag being formed. The package reclosable seal provides positive auditory and tactile indications of the closing of the reclosable seal so that the consumer is assured that the package has been resealed even in the absence of visual package inspection. The form-fill apparatus is provided with a novel bottom press for effecting the the package sealing and reclosable seal formation, and a novel fill tube forming collar oriented within a particular angular range for feeding the composite film to the packaging machine,

Description:
This application is a continuation in part of application Ser. No. 09/364,180 filed on Jul. 29, 1999 which is a continuation in part of application Ser. No. 08/861,576, filed May 22, 1997, now U.S. Pat. No. 5,944,425. 
    
    
     This invention relates generally to packaging systems, and more particularly to flexible packages of the kind shown in my copending earlier application having an openable and reclosable interlocking seal which may be further provided with a center hinge and lateral side snap detents spaced along the length of the seal, the reclosable interlocking seal having male and female parts with the detents being formed in the female part and extending into the male part. The novel seal structure provides tactile and auditory snap indications of the state of the seal during opening and closing of the package. Also disclosed are methods and apparatus for making such packages and seals from a continuous web of flexible film, the seals being formed during package formation at line speed. 
     BACKGROUND OF THE INVENTION 
     In the past, the methods of making reclosable flexible packages have usually involved either the extrusion of a two part zipper type locking structure along with the film extending longitudinally in the direction of film extrusion along the opposite edges of the film, or by heat sealing a separately made extruded zipper type locking structure to the package film. The first type of package formation results in packages having the reclosable feature in the consumer non-preferred position along the long edge of the package, while the second type of package formation results in packages which are expensive to make because of the need to inventory and store rolls of the separate zipper structure for attachment to the packaging film and the need to insure that the separately obtained packaging film and zipper are made of compatible materials. Consumer focus groups have disclosed dissatisfaction with both types of zipper structure for various reasons, such as user frustration because of difficulty in reclosing the zippers, and no feedback to the user that the zipper has in fact been engaged. 
     Shown and described in my earlier application is a resealable interlocking closure of the same general kind as shown and described in this application, but which does not utilize the film and strip technology of the present invention, and does not include the improved features of the present invention. 
     SUMMARY OF THE INVENTION 
     The package and system according to the present invention utilize a novel composite packaging film structure comprising the packaging film with strips of formable plastic laminated to the film at package length intervals. The composite packaging film structure may be preformed and stored as roll stock material or may be concurrently made by a Sig Pack, Inc. Easy Snap™ Laminator mounted atop or adjacent to the packaging apparatus to form the novel composite packaging film structure, which composite film is then fed into the packaging apparatus to form the finished package incorporating the novel reclosable seal formed in the film and strip composite. The laminator functions with both horizontal and vertical form/fill/seal wrapping machines and with overwrap packagers, and laminates various plastic strip materials to diverse heat seal packaging films. 
     The packaging films could be for example, polypropylene, polyethylene, polystyrene, polyvinylchloride, thermoplastic heat seal coated non-plastic films, and various film laminations of two to four layers, while the plastic strip could be formed of one to three layers. In some applications the strip could be a single thickness of polyvinylchloride (PVC) heat sealed to a PVC film at a temperature of about 230° F. for ½ to ¾ seconds, while in other applications the strip could be of two layers such as PVC plus a sealing layer, or three layers such as a center layer coated on opposite sides respectively with a sealing layer and a release layer to prevent the strip from self adhering during formation of the reclosable interlock seal. A commonly used packaging film is a four layer film consisting of two layers of polypropylene separated by a layer of low density polyethylene and having a heat seal layer of low density polyethylene coated on one face. 
     The invention is shown and described in conjunction with a modified vertical form, fill and seal packaging machine having a novel fill tube forming collar and novel package sealing press which latter also forms the novel resealable closure, the packaging machine being for example a Sig Pack, Inc. Eagle Infinity, Model 1524, 
     Packages made according to the invention incorporating the novel reclosable seal address the consumer complaints relating to prior art zipper seals by providing clear auditory and tactile indications of the closing of the reclosable seal by incorporation of snap detents, so that the consumer is assured that the package has been resealed even in the absence of visual package inspection. 
     Accordingly, it is a primary object of the invention to provide novel openable and reclosable interlocking seals for packages. 
     Another object of the invention is to provide packages having novel openable and reclosable interlocking seals. 
     A further object of the invention is to provide a novel composite packaging film structure comprising packaging film with strips of formable plastic laminated to the film at package length intervals. 
     An additional object of the invention is to provide a package having a novel openable and reclosable interlocking seal as aforesaid in which the bulk of the seal structure is provided by an added layer of strip material secured in a specific way to the packaging film at package length intervals. 
     A yet further object of the invention is to provide a package having a novel openable and reclosable interlocking seal as aforesaid in which the ends of the strip material are positioned in abutment at substantially the center of one face of the package to provide a hinge to assist in package opening. 
     Still another object of the invention is to provide a reclosable interlocking package seal having male and female parts with snap detents being formed in the parts, the novel closure structure providing tactile and auditory snap indications of the state of the closure during opening and closing of the package. 
     A yet further object of the invention is to provide novel packages as aforesaid in which the reclosable interlocking seal is formed from the packaging film and a heat sealable strip heat sealed to the packaging film. 
     A still further object of the invention is to provide novel packages as aforesaid in which the packages may be formed from a variety of packaging films such as polypropylene, polyethelene, polystyrene, polyvinylchloride, and various film laminates. 
     An additional object of the invention is to provide a novel method and apparatus for making packages and reclosable seals according to the invention. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     The foregoing and other objects of the invention will be more clearly understood from a reading of the following description in conjunction with an examination of the appended drawings, wherein: 
     FIG. 1 is a diagrammatic side view of the apparatus according to the invention showing the method and stages of package forming, filing, sealing, and severing, and showing the novel fill tube forming collar; 
     FIG. 1A is a diagrammatic side view of a prior art conventional form, fill and seal packaging machine showing the standard type of fill tube forming collar; 
     FIG. 2 is a diagrammatic front view of the apparatus seen in FIG. 1; 
     FIG. 3 is a plan view of a portion of one form of the composite film showing the packaging film and the placement of the attached strip suitable for making a package having an overlapped longitudinal seal; 
     FIG. 4 is a diagrammatic cross section view through a package formed from the film of FIG. 3 having a longitudinally extending overlap seal; 
     FIG. 5 is a plan view of a portion of another form of the composite film showing the packaging film and the placement of the attached strip suitable for making a package having a longitudinal fin seal; 
     FIG. 6 is a diagrammatic cross section view through a package formed from the film of FIG. 5 having a longitudinally extending fin seal; 
     FIG. 7 is a fragmentary enlarged view of a composite packaging film composed of a single layer film and a single layer strip; 
     FIG. 8 is a fragmentary enlarged view of a composite packaging film composed of a multi-layer film and a multi-layer strip; 
     FIG. 9 is an enlarged diagrammatic cross section through a bag being sealed and severed and through the novel sealing and reclosable seal forming press, shown with the press open before the sealing and seal forming step takes place; 
     FIGS. 9A through 9C show successive steps in the ends sealing, reclosable seal forming, and package severing process; 
     FIGS. 9D and 9E show two views of an alternative form of package having a top pull-open tab usable with a package top end seal formed with a thermoformable bond which can be pulled apart; 
     FIG. 10 is an isometric view showing the forming dies which form the snap detents in the reclosable interlocking seal, with the reclosable seal shown in phantom outline; 
     FIG. 11 is an enlarged fragmentary isometric view of the inner and outer parts of the reclosable seal in separated position, showing the snap detents in the sidewalls of the seal adjacent to the arrowhead interlock; 
     FIG. 12 is an enlarged cross section through the reclosable seal shown in the phantom circle on FIG. 9C showing the placement of the forming dies of FIG.  10  and between the snap detents; 
     FIG. 13 is an enlarged cross section through the reclosable seal and the snap detents which are formed between the teeth of the forming dies, as would be seen when viewed along line  13 — 13  on FIG. 10; 
     FIG. 14 is an isometric view of a package according to the invention showing showing the longitudinally extending overlap package seal uppermost, the package end seals, the integrally formed reclosable seal with the female portion uppermost and the seal side detent snaps; 
     FIG. 15 shows the package of FIG. 14 with the top end seal removed and the package opened; 
     FIG. 16 is is an enlarged cross sectional diagrammatic showing of the upper end of a package including the novel reclosable interlocking seal according to the invention in its closed condition, and the package top heat seal spaced above the reclosable seal with an intervening length of unsecured package film; 
     FIG. 17 is an enlarged cross sectional diagrammatic showing of the novel reclosable interlocking seal according to the invention in its closed condition with the package top heat seal shown in FIG. 16 removed by cutting through the intervening length of unsecured package film; and 
     FIG. 18 is an enlarged cross sectional diagrammatic showing of the novel reclosable interlocking seal according to the invention similar to FIG. 17 but with the reclosable seal partly pulled open from the top; 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the several figures, like elements are denoted by like reference characters. 
     Considering first the side and front diagrammatic elevational views of FIGS. 1 and 2, there is seen a modified conventional vertical form-fill packaging apparatus designated generally as  20 , and which could be for example a Sig Pack, Inc. Eagle Infinity, Model 1524, comprising a vertical cylindrical fill tube  21  surmounted by a conical feed horn  22  into which the material to be packaged is deposited. Disposed adjacent to the feed horn  22  at an angle of about fifteen degrees above the horizontal and turned downward around the feed horn  22  and fill tube  21  with a slight space therebetween is a fill tube forming collar  23 , the purpose of which, together with the fill tube  21 , is to form a composite web of packaging material  24  being fed over the forming collar  23  into a tube having a longitudinally extending seal  26  formed by the heat seal device  27 . To avoid problems in reliably feeding the composite web packaging material, the angle of the MI tube forming collar is best kept to not less than horizontal but can be steeper than the fifteen degrees illustrated, although too high an elevation can cause film bunching and machinery headroom problems. 
     A pair of belt drives  28 , by pulling downward on the tube  25 , pull the web  24  downward off of the supply roll  29  or from the composite web forming apparatus  30  which laminates thermoformable strips  31  to the packaging material  32  to form the composite web of packaging material  24 . The apparatus  30  may be a a Sig Pack, Inc. Easy Snap™ Laminator. The filled descending tube  25  passes through the bottom press  33  where it pauses for formation of the top seal  35  and the reclosable seal  36 , severing of the completed package  34  from the above lying tube, and formation of a bottom seal  37  of the next descending package. The completed package  34  is carried away by the conveyor  38 . 
     The apparatus of FIGS. 1 and 2 departs from conventional vertical form-fill apparatus in two particulars. First, as shown in FIG. 1A, prior art conventional apparatus has the front edge of its fill tube forming collar  23 ′ disposed substantially orthogonally to the surface of the conical feed horn  22 , and this conventional orientation causes the thermoformable strips  31  to be tom off of the web of packaging film  32 . This problem was solved in the apparatus according to the invention by reorienting the forming collar  23  as shown and providing a leading edge tack to the strips  31 , as will become clear from FIGS. 3 and 4 to be next described. The second difference is the inclusion of the novel bottom press  33  which forms the reclosable seal, to be subsequently described. 
     Considering now FIGS. 3 and 5, there is seen in both, the packaging film material  32  and a thermoformable strip  31  secured to the film  32  substantially continuously along the strip trailing edge  39  by heat seals  40 , along the strip ends  41  as at  42 , and by a short tack  43  at the center of the strip leading edge  44  to insure that the leading edge is against the packaging film as the composite web passes into the space between the feed horn  22  and forming collar  23  to prevent tearing off the strip from the film. The only difference between FIGS. 3 and 5 is that, in FIG. 3 one end of the strip  31  is congruent with one edge  45  of the packaging film material  32  and the other end of the strip is spaced inward from the other edge  46  of the packaging film material  32  to form a side margin  47 , while in FIG. 5 both ends  41  of the strip are spaced inward from the edges  45  and  46  of the packaging film material  32  to form a pair of opposite side margins  48 . The strips  31  are also provided with apertures  49  through the strips which in the completed package act as a weakened region allowing a hinge fold to occur when the package is opened. Another hinge is provided in the completed package opposite the first hinge by the substantially abutting apposed ends  41  of the strip  31 , as seen in FIGS. 4 and 6. FIGS. 4 and 6 respectively show an overlap longitudinal package seal  26  as seen in FIG. 2 formed by the side margin  47  of FIG. 3, and a fin seal formed by the two side margins  48  of FIG. 5 which may be made by other vertical form-fill machines. 
     FIG. 7 illustrates a single layer strip  31  heat sealed to a single layer packaging film  32  in which typically the strip could be 3 to 15 mil polyvinylchloride and the film could be 1.5 to 4 mil polyvinylchloride. FIG. 8 illustrates a three layer strip  31 ′ sealed to a four layer packaging film  32 ′. The strip  31 ′could typically have a thermoformable plastic center layer  50  of 3 to 15 mil thickness, a heat seal layer  51  of 0.5 to 3 mil thickness, and a release layer  52  of 3 to 50 microns thickness. The release layer is sometimes needed to prevent the engaged faces of the folded strip from fusing together when the reclosable seal is formed in the manner subsequently to be described. The commonly used four layer film  32 ′ is composed of two layers of polypropylene  53  separated by a layer  54  of low density polyethylene and having a heat seal layer  55  of low density polyethylene. Two layer strips and two and three layer films can also be used. 
     Turning now to FIGS. 9 through 9C which illustrate the formation of the package end seals and reclosable seal, there is seen in FIG. 9 a package  34  which has been filled with product  56  while descending, and has stopped at a position where the upper part of the package is within the bottom press  33  just prior to completion by the formation of the top seal and reclosable seal. The package  34  is stopped so that the thermoformable strip  31  is positioned between the reclosable seal forming horizontally reciprocable heated female die  58  and the two part heated male die  57 , with an above-lying length  59  of the tube  25  positioned below the composite heated dies  60  and  61  and the package severing cutter  62  and anvil  63 . The female die  58  is provided with a forming recess  68 , and the male die is provided with a forming wedge  69  carried by the male die part  57 B and shaped complementally to the female die recess  68 . The composite dies  60  and  61  consist of a pair of dies  64  which form the top seal  35  of the package  34  being completed, and a pair of above-lying dies  65  which form the bottom seal  37  of the next package to descend. Disposed above and below the forming recess  68  of female die  58  are a pair of heated reclosable seal detent forming toothed dies  66  reciprocable with the female die  58  and pivotable toward one another on pivots  67 . 
     FIG. 9A shows the reclosable seal forming heated dies  57  and  58  moved toward one another and into engagement, heat forming the package film  32  and thermoformable strip  31  into the recess of the female die  58  to form the point of the arrowhead shaped reclosable seal. For clarity, the strip  31  is not shown in FIGS. 9A through 9C, but its location is seen clearly from FIGS. 9 and 11 to  13 . At the same time, the heated dies  60  and  61  heat seal the tube  25  entirely widthwise for a vertical interval  70  and define the unsecured interval  59  between the bottom of the top seal  35  and the top of the reclosable seal  36 , the portion of the seal  70  heated by the dies  64  becoming the package top seal  35 , and the portion of the seal  70  heated by the dies  65  becoming the bottom seal  37  of the next descending package when the seal  70  is subsequently severed widthwise by the cutter  62 . 
     The next step is a hybrid between FIGS. 9A and 9B in which the conditions are as shown in FIG. 9A except that the detent forming dies  66  have pivoted inward and closed sufficiently to begin formation of the inwardly sloping bottom surfaces  72  of the arrowhead shaped interlock, but not sufficiently to clamp the male die forming wedge  69 . 
     FIG. 9B shows the immediately following condition in which the cutter  62  has moved laterally to sever the heat seal  70  against the anvil  63  and separate the package  34  from the above-lying tube  25 . At the same time, male die part  57 B carrying the wedge  69  party retracts from the recess  68  of female die  58  and from between the teeth  71  of the dies  66 , and the dies  66  pivot further inward driving the detent forming die teeth  71  toward one another to their maximum closed position, the teeth  71  pinching the packaging film  32  and thermoformable strip  31  therebetween to form the film and strip into the female die recess to continue forming the inwardly sloping bottom surfaces  72  of the arrowhead shaped reclosable seal  36 , and forming the snap detents  73  best seen in FIGS. 11 and 13. The female die  58  is then moved somewhat left toward the dies  66  to set the arrowhead shape between itself and the facing surfaces of teeth  71  of detent forming dies  66 . The detents  73  are formed because as the softened thermoformable material of the film and strip are compressed between the teeth  71  the only direction that the compressed material can move is laterally into the spaces between the teeth  71 , and then bulge outward between the teeth, forming the detents  73 . 
     FIG. 9C shows the male and female dies  57  and  58  outwardly retracted with the female die laterally carrying the package  34  held within it by the unopened detent forming dies  66 , and the package end seal dies  60  and  61  and the cutter  62  have been retracted. The dies  66  remain engaged for a short time to complete setting of the detents, after which they open and release the completed package which drops to the conveyor  38  as shown in FIG. 1, and the sequence commencing with FIG. 9 is repeated. Sequencing and timing controls and drives for the sequential movements of the various dies is provided by standard commercially available components. 
     A variation  34 ′ of the package  34  is shown in FIGS. 9D and 9E in which it is seen that a flap or tab  74  extends centrally above the top heat seal  35 ′, and that a cutout  74 ′ corresponding in shape to the tab  74  is located just below the bottom heat seal  37 ′, with flanking flaps or tabs  75  disposed at both sides of the cut-out  74 ′. This configuration is readily achievable by vertically upwardly shifting the heat seal die  65  to provide an interval between it and the die  64 , and configuring the cutter  62  to provide the cut-out pattern for the tabs  74  and  75 . While this uses more package film, if a pull-apart heat seal material is provided at  35 ′, the unsecured parts of the tab  74  can be grasped and used to pull open the top of the package. 
     FIGS. 10 through 13 show in greater detail the detent forming toothed dies  66  and the structure of the reclosable seal  36 . FIG. 10 shows more clearly the relationship between the dies and the reclosable seal, and shows the shorter die teeth  76  in the central region of the die corresponding to the region of the overlap longitudinal package seal  26  formed by the film margin  47 , as best shown in FIG.  11 . FIG. 11 also shows more clearly the snap detents  73  which are formed in the seal male part  36 A and female part  36 B by an outward bulging of the thermoformable material between adjacent teeth  71  of the dies  66  when the dies close. The heat softened material between the apposed die teeth is compressed and can only move laterally, but such movement causes the outward bulging of the material which forms the detents since material is moving from opposite sides into the same space between the adjacent die teeth and can not move inward. This is also shown in FIG. 12 in which the detents  73  are shown behind the die teeth  71 . FIG. 13 is a section taken through the detents and shows the interfitted arrangement. 
     FIG. 14 shows a completed package about to be opened by cutting off the top heat seal  35  with scissors  77 , and FIG. 15 shows the package with the top heat seal removed and pulled open, the bag remaining open because of the hinging folds  78  and  79 . The hinge  78  results from the weakening produced by the strip  31  aperture  49  which is formed into the relatively rigid male part  36 A of the reclosable seal  36 , while the hinge  79  is formed at the abutment of the ends of the strip  31  located in the female part  36  B. The package is simply closed by inward directed finger pressure on the outside of the hinges  78  and  79  which causes the package sides to snap to each other, and by then applying finger pressure to press the the male and female parts  36 A and  36 B together so that the snap detents interlock. 
     FIGS. 16 to  18  show the upper end of a package  34  in enlarged diagrammatic cross section to illustrate the opening of the package. As shown in FIG. 16, the top seal is removed by cutting below it to provide the free top tabs of packaging film  32  shown in FIGS. 17 and 18. These top tabs are pulled away from each other as shown in FIG. 18 to open the female part  36 B of the reclosable sealand disengage it from the inner male part  36 A. The opening leverage is materially increased because the strip  31  is sealed to the film  32  by the trailing edge heat seal  40  and the opening pull is transmitted through the strip  31 . Conversely, inadvertent opening of the package from the body side of the package is discriminated against because the strip  31  is unsecured to the package film  32  at its leading edge  44  inside the package and there is no reinforcement of pull on the film by the strip. 
     Having now described the invention in connection with particularly illustrated embodiments thereof, it will be understood that modifications and variations of the invention may now occur from time to time to those normally skilled in the art without departing from the essential scope or spirit of the invention, and accordingly it is intended to claim the invention both broadly and specifically as indicated in the appended claims.