Patent Publication Number: US-4929225-A

Title: Method of making bags and bag material having hinged zipper strips

Description:
PRIOR APPLICATIONS 
     The present application is a continuation-in-part of copending application Ser. No. 812,467 filed Dec. 23, 1985 (now abandoned) and continuation thereof application Ser. No. 106,920 dated Oct. 6, 1987, now U.S. Pat. No. 4,792,240 and Ser. No. 075,636 dated July 20, 1987, now U.S. Pat. No. 4,787,880 which is a division of Ser. No. 812,467, now Ser. No. 106,920. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention relates to the art of making bags and bag making material equipped with reclosable extruded plastic zippers, that is, fasteners which have resiliently flexible releaseably interlockable profiles for extending across the tops of reclosable bags. 
     As heretofore constructed, bags equipped with extruded zippers have generally been provided with separately formed zipper strips extending across the respective tops of bag walls and having the opposite ends of the separate zipper strips secured together as by heat sealing. This has required producing and handling two separate zipper strips in the bag making process where the strips are separably formed and attached to the bag body sheet or web material. On the other hand, where profiles are integrally extruded with the film, it has been required to extrude separate complementary profile portions of the zipper on separate panels or panel portions of a bag making film. 
     In recent developments in this art, as covered in copending patents, all assigned to the same assignee as the present application, it has been proposed to provide zippers formed from extruded profiled continuous strips folded upon themselves so that the profiles on the folded strip portions interlock to provide reclosabIe zippers for the bags. 
     Attention is directed to U.S. Pat. No. 4,666,536 dated May 19, 1987, wherein opposite ends of the zipper strips are heat sealed to the bag wall film, and there is also disclosure of providing a tack or seal at fold in the zipper where the zipper fold is located at a fold in the bag film. Such tacking or sealing of the zipper strip ends or folds facilitates registration of the zipper profiles for closing the zipper 
     In U.S. Pat. Nos. 4,617,683 dated Oct. 14, 1986 and 4,655,862 dated Apr. 7, 1987, is disclosed that the folding of the zipper strips on themselves can be facilitated by notching the profiles at the folds. 
     All three of the identified patents disclose applying the zipper strips across the formation axis of the plastic bag forming sheet or film material which provides definite advantages in converting continuous ribbon film into bags, especially in the type of bag filling machines commonly referred to as form, fill and seal machines, such as exemplified in U.S. Pat. No. 4,617,683. 
     A problem that must be addressed in bags according to the indicated construction resides in avoiding inadvertent opening of the bags due to internal pressures after the bags have been filled. 
     SUMMARY OF THE PRESENT INVENTION 
     An important object of the present invention is to provide new and improved method of and means for resisting inadvertent opening of bags equipped with reclosable extruded plastic zippers, especially of the kind wherein the zippers extend across the formation axis of the bag film material. 
     Another object of the invention is to provide a new and improved attachment of profiled fastener strips on bag making material. 
     In accordance with the principles of the present invention, there is provided a method of making reclosabIe bag material, comprising providing bag making film; providing an extruded plastic profile reclosable fastener strip across a portion of the formation axis of the film to be located at the open end of a bag made from the film, and the strip having a base web for attachment to the film; and bonding the base web to the film with at least a portion of the base web attached to the film at a location only above the centerline of the profile on the strip. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the invention will be readily apparent from the following description of representative embodiment thereof, taken in conjunction with the accompanying drawing, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts embodied in the disclosure, and in which: 
     FIG. 1 is a fragmentary elevational view of a bag embodying the present invention: 
     FIG. 2 is an enlarged fragmental sectional detail view taken substantially along the line II--II in FIG. 1; 
     FIG. 3 is a schematic illustration showing how bag making material for the present invention may be made; 
     FIG. 4 is an enlarged fragmentary sectional detail view taken substantially along the line IV--IV in FIG. 3; 
     FIG. 5 is a schematic illustration showing a modified way of producing bag making material for the present invention; 
     FIG. 6 is an enlarged fragmentary sectional detail view taken substantially along the line VI--VI in FIG. 1; 
     FIG. 7 is a fragmentary sectional detail view similar to FIG. 6, but showing the zipper in an alternative interlocked interengagement; 
     FIG. 8 is a schematic illustration of a manner of extruding zipper strips in a mass production manner; 
     FIG. 9 is an enlarged sectional detail view of a modified form of the zipper strip; 
     FIG. 10 is a fragmental, enlarged sectional detail view showing another modified form of the zipper strip; 
     FIG. 11 is a view similar to FIG. 10, but showing still another modified form of the zipper strip; 
     FIG. 12 is a fragmentary perspective view of bag making material showing a still further modification of the zipper strip; 
     FIG. 13 is an enlarged sectional detail view taken substantially along the line XIII--XIlI in FIG. 12; 
     FIG. 14 is a fragmentary perspective view of bag making material, similar to FIG. 12, but showing a modification thereof; 
     FIG. 15 is an enlarged sectional detail view taken substantially along the line XV--XV in FIG. 4; 
     FIG. 16 is an enlarged fragmentary sectional detail view taken substantially along the line XVI--XVI in FIG. 14; 
     FIG. 17 is a fragmentary perspective view of bag making material, similar to FIG. 14, but showing still another modification; 
     FIG. 18 is an enlarged sectional detail view taken substantially along the line XVIII--XVIII in FIG. 17; 
     FIG. 19 is an enlarged fragmentary section detail view taken substantially along the line XIX--XIX in FIG. 17. 
     FIG. 20 is a perspective view of a bag fabricated in accordance with the method of the present invention; 
     FIG. 21 is a fragmentary sectional detail view taken substantially along the line XXI--XXI of FIG. 20; 
     FIG. 22 is a plan view illustrating a manner of bonding the fastener strip to the film where opposite sides of the film are folded in upon the film; and 
     FIG. 23 is a perspective view illustrating a way in which a bag can be fabricated from film in general according to the disclosure in FIG. 22. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, a bag 10 has confronting wall panels 11 which may be made from any suitable sheet material but in a popular form may comprise plastic film such as polyethylene, polypropylene, or the like, either in single thickness material or a laminate where the desirable characteristics of different plastic materials are desired, according to conventional practice. 
     The panels 11 are connected together along opposite side edges 12 and 13 and along a bottom end 14. At its upper end, the bag 10 has a top opening 15 best visualized in FIG. 6. The side edge 12 may be a fold juncture while the side edge 13 and bottom end 14 may be heat seal seamed closed. 
     A reclosable zipper 17 is sandwiched between the upper portions of the wall panels 11 and extends lengthwise between the side edges 12 and 13. The zipper 17 comprises a continuous length of extruded profiled plastic strip having a plurality of spaced parallel profile parts, in this instance comprising two parts 18 and 19. The strip is folded upon itself to provide confronting complementary portions 20, which extend from a fold 21. One of the zipper portions 20 is attached to one of the wall panels 11 and the other of the portions 20 is attached to the other of the wall portions 11. Desirably the zipper strip foId 21 is located in the folded side 12 of the bag 10. The zipper profile parts 18 and 19 are releasibly interengagable with one another for closing the top opening 15. 
     In order to retain the folded zipper strip portions 20 against springing open at the fold 21, the strip portions 20 are spot sealed together as shown at 21a, as visualized in FIGS. 1 and 2. Where the material of the bag wall panels 11 is fusibly compatible with the material of the zipper strips 17, the portions of the waIl panels contiguous to the fold spot seal 21a may be fusibly sealed to the spot seal 21a. In addition, the opposite, originally free ends of the zipper strip portions 20 are desirably spot sealed together as shown at 22. The spot seal 22 may extend inwardly from the heat sealed closure seam 13. 
     In an efficient arrangement, the zipper strip 17 comprises a flanged base 23 secured either by fusion or adhesively to the bag wall panels 11. From one face of the base 23 the profile parts 18 and 19 project integrally in spaced parallel relation. The profile part 18 has a curved neck 24 toped by an arrow shaped head 25. On the other hand, the profile part 19 has a curved neck 27 and an arrow shaped head 28. In order to facilitate separable interlocking interengagement of the profile parts of the folded zipper strip, the necks 24 and 27 are formed on approximately a common radius and are spaced apart sufficiently to provide a groove 29 receptive of one of the profile part heads 25 or 28 as the case may be. At their confronting sides, the heads 25 and 28 are spaced apart a distance somewhat greater than the thickness of the necks 24 and 27, but less than the overall width of either of the respective heads 25 and 28. Thereby, the respective profile part heads can engaged within the groove 29 of the companion folded zipper strip portion as shown in FIGS. 6 and 7. In FIG. 6 of the profile part head 28 is engaged in the groove 29 of one of the zipper strip portions 20 and the head 25 is engaged in the groove 29 of the other zipper strip portion 20. As shown in FIG. 7, just the reverse interengagement of the heads within the grooves prevails. In either event, the zipper is thoroughly closed. Both in the closing manuever and in the separating manuever, the necks 24 and 27 enable resilient flexing of the profile parts for the heads 25 and 28 to pass one another. 
     In order to provide for thorough resistance to opening of the zipper due to pressures within the bag 10, without inhibiting the opening of the bag by opening manuever applied at the outside of the bag opening 15, the zipper profile part 18 is constructed stiffer than the part 19 by a somewhat greater mass in at least the profile head 25, and desirably also in the connecting neck 24. This stiffening of the profile rib parts 18 also facilitates interengagement of the zipper portions to assure that the profile part 18 of the folded strip always engages with itself in mutually resistive fashion relative to pressure from the inside of the bag tending to separate the zipper. 
     Desirably, the zipper base flange 23 extends to both sides of the zipper profile parts, a flange portion 30 which is relatively narrow extending toward the inside of the bag. A flange portion 31 which may be substantially wider extends outwardly toward the top of the bag, and together with the upper portions of the bag side walls 11 provides respective pull flanges which project outwardly from the zipper 17 and facilitate grasping to pull the zipper open when desired. The zipper 17 is easily closed by applying pressure inwardly on the side wa-1 panels in line with the zipper. 
     By having one of the flange portions 30 or 31, and in this instance the flange portions 31 extending to a substantial width beyond the profile parts 18 and 19, manipulation and attachment of the zipper strip 17 is facilitated. Another advantage of the wider flange portion 31 is that it facilitates folding of the zipper strip 17 upon itself because the web portion 31 allows more readily for the shift in the profiles 18 and 19 when they are folded on each other, and the slipping of the profiles into locking interengagement. 
     In producing bag material, as indicated in FIG. 3, a continuous ribbon of bag wall web W may be provided. Across the width of the web W and at suitable bag length intervals therealong the zipper strips 17 are attached to the web in any suitable fashion, such as by heat sealing where that is feasible or by means of adhesive, all according to known techniques. Each of the zipper strips 17 may be notched at 32 to facilitate folding of the zipper strip when each bag section is separated from the ribbon W as along a line 33 and then folded along the bag side edge line 12. 
     The zipper strips 17 may be economically produced in a mass production manner by extruding a plurality of the strips in a tubular extrusion 34 (FIG. 8). For example, eight of the zipper strips 17 may be produced in one extrusion 34 and the extrusion separated along longitudinal lines 35 to divide the same into individual zipper strips 17. 
     Where it is preferred to produce the web and the zipper profile as a one piece extrusion, the arrangement shown in FIG. 5 may be employed wherein the web ribbon W&#39; has zipper 17&#39; integrally extending lengthwise therealong. The overall width of the web w&#39; will be the same as the desired length of the bags to be made from the web. Then the web is divided into sections as shown which are equivalent to twice the width of the bags to be made therefrom, with each of the bag sections being folded along the line 37 extending through a notch 32&#39; in the zipper strip to facilitate folding. Of course, if it is preferred to supply the web W&#39; with the zipper 17&#39; separately fabricated, that may be done, the zipper 17&#39; being either secured by heat sealing or adhesively, as may be preferred. The end result will be the same as the bag sections derived from the web W in FIG. 3, namely, each bag material section will result in a bag such as the bag 10 in FIG. 1. 
     For larger size bags and which may be required to handle large volume contents, a zipper 38 (FIG. 9) may be provided having a plurality of spaced parallel profile parts greater than two. For example, five profile parts 39 are shown carried by a base panel strip 40. In this instance, the profile part 39 along one edge of the base 40 has a neck 41 and an arrow shaped head 42 which is of greater mass than necks 43 and arrow heads 44 of the remaining profile parts. It will be appreciated that the zipper strip 38 is adapted to be used in the same manner as the zipper strip 17, that is the zipper strip 38 is secured to the bag body web, may be notched, and folded upon itself in the same manner. The heavier or greater mass section profile part 41, 42 will be located at the inside o±the bag and thus resist opening of the zipper due to internal pressures within the bag. 
     Where the zippers are prefabricated and then assembled with prefabricated film or web, and one side of the zipper in each instance is equipped to provide internal bag pressure resistance as has been described, it is important that the side of the zipper which is so equipped be properly placed when attaching the zipper to the web. Such proper placement is visually determinably by ready identification or recognition of the resistance equipped side of the zipper, that is the side which is provided by the heavier section profile parts 24, 25 (FIGS. 5 and 7) and 41, 42 (FIG. 9) previously described herein. 
     In FIG. 10, there is shown another zipper 47 wherein a single strip is folded upon itself and secured to opposite wall panels 48 of a bag. In this construction, which comprises four generally arrowshaped profiles on a base panel strip 49, there is on the side which is at the mouth end of the bag a side flange 50 which is of substantial width, and not only provides together with the contiguous portions of the bag walls 48 a substantial pull flange, but also facilitates attachment of the components and facilitates folding of the zipper on itself. The three profiles 51 which are closest to the pull flange 50 have groove spaces 52 between them which are all equal but somewhat wider than the width of the arrowhead rib portions of the profiles. On the other hand, a spacing groove 53 between a fourth, innermost profile 54 and the adjacent profile 51 is narrower than the groove spaces 52, but just wide enough to accommodate the rib head of the profile 54. In this manner, the lateral flanges of the rib head of the profile 54 will in each instance oppose to a maximum extent the head flanges of the profiles 51 and 54 alongside the groove space 53 into which the opposite profile 54 is assembled when closing the zipper 47 by interlocking the profiles. In contrast lesser rib head flange surface opposition exists in the groove spaces 52. As a result, the innermost profile 54 affords substantially greater resistance to separation from separating forces which may develop at the inside of the bag, as compared to separating forces applied to the zipper 47 at the outerside of the bag by manipulation of the pull flanges 50. 
     In another arrangement as shown in FIG. 11, a zipper 55 has opposite zipper strip bases 57 which are secured to opposite wall panels 58 of a bag. Substantially wider flange portions 59 along the outer sides of the zipper strip bases 57 cooperate with the mouth end portions of the bag wall panels 58, and provide substantial pull flanges, as well as the additional advantages of facilitating attachment of the zipper to the wall panels and folding of the zipper strip on itself. In this instance there are four generally arrowshaped zipper profiles on each base strip 57, comprising three identical profiles 60 inwardly from the flange portions 59, and a fourth generally arrowshaped profile 61 at the inner side o±each base strip 57. All of the profiles 60 and 61 of the zipper 55 are, in this instance, equally spaced from one another and define grooves 60a between the profiles 60 and a respective groove 61a between each of the profiles 61 and the adjacent profile 60. Greater resistance to opening due to forces from within the bag is achieved by tilting or biasing the arrowhead of each of the innermost profiles 61 toward the adjacent profile 60, by curving necks 62 of the profiles 61 toward the adjacent profile 60. Through this arrangement, when the profiles are interlocked, a side flange 63 on the profile 61 in groove 61a interlocks with an adjacent side flange 64 of the nearest profile 60 close to a neck 65 of the profile 60. Thereby, forces interiorly of the bag tending to separate the zipper are resisted by the interengagement of the side flanges 63 and 64. On the other hand, the normal interengagement of the opposing head side flanges of the profiles 60 permits easier opening of the zipper at the mouth end of the bag as may be effected by manipulation of the pull flanges 59. 
     Another advantage of the tilted relation of the profile 61 relative to the other profiles is that it provides visual differentiation, or recognition of profile 61 from especially the adjacent profile 60. Therefore, when assembling the prefabricated zipper with prefabricated film or web, it can be readily determined which side of the zipper is to be placed in the position of internal bag pressure resistance. 
     A zipper strip 67, as depicted in FIGS. 12 and 13, is secured to and across the bag mouth end of bag panels 68 formed from a single sheet of bag material adapted to be folded upon itself along a longitudinal line 69 to bring the panels 68 together in forming a bag. This fold line 69 intersects the zipper strip 67 so that profiles 70 of the zipper strip will interengage or separably interlock as shown in FIG. 13. At the fold 69, as well as at the opposite interlocked ends of the folded zipper strip 67, the zipper strip may be secured together by spot heat sealing, similarly as described at 21 and 22 in FIGS. 1 and 2. 
     Generally, like FIGS. 10 and 11, the zipper strip 67 has four arrowshaped profiles 70 which, in this instance, are of the same geometry and equally spaced from one another and are located inwardly from a flange portion 71 of substantial width of base panel 72. 
     To render the folded zipper 67 capable of resisting opening from the inside of the bag to a substantially greater extent relative to opening from the outer or mouth end of the bag, at which the flange portion 71 serves as part of pull flange structure 74 of the bag, only the flange portion 71 is attached to pull flange end portions 75 of the bag wall panels 68. Thereby, the wall panels 68 are flexibly divertible along hinges 77 relative to the zipper 67. It will b®observed that the hinges 77 are spaced from the outermost of the profiles 70. As a result, the bag walls 68 may balloon without placing any significant opening force on the zipper 67. On the other hand, the zipper 67 can be easily opened by manipulating the pull flanges 74. 
     For greater resilient flexibility the base 72 may be provided with indented grooves 78 extending longitudinally along the base 72 in alignment with the respective neck portions of the arrowshaped profiles 70. 
     A shown in FIG. 14, bag making material, similar to that shown in FIG. 12, may comprise sheet material 79 of any preferred type suitable for the intended purpose and adapted to be folded along a longitudinal line 80 to provide bag wall panels 81 adapted to be folded upon themselves and sealed along the joined longitudinal edges and then severed into bag length sections from a continuous strip of the material. Along the end of the sheet 79 to form the top reclosable end of a bag, a zipper strip 82 is secured. This zipper strip 82 is of a continuous length and extends across the entire width of both of the panels 81, and when the sheet 79 is folded along the line 80, the zipper strip 82 is similarly folded upon itself along that line which extends across the zipper strip. In this instance, the zipper strip 82 comprises a base 83 carrying three generally arrowshaped profiles 84 extending therealong, and which are interlockably separably interengagable when the zipper strip is folded upon itself. 
     Attachment of the zipper strip 82 to the sheet 79 is in a manner to resist opening of the zipper from the inside of the bag to a substantially greater extent relative to opening from the outer or mouth end of the bag into which the material is to be formed. And for this purpose, the entire face of the base 83 which opposes one of the panels 81 may be secured as by heat sealing or adhesive means 85 (as indicated by stippling in FIG. 14). Such securement includes a pull flange portion 87. On the other of the panels 81, only the pull flange portion 87 of the zipper strip 82 is secured to such panel by the securement means 85, the remainder of the zipper base 83 remaining unattached as shown in FIG. 16. In the finished bag, this affords stress relief avoiding opening of the closed zipper due to internal pressures within the bag. 
     The construction in FIG. 17 is similar to the construction in FIG. 14, and therefore primed reference numerals are applied in FIG. 17 to identify substantially similar parts. As noted, a film or sheet 79&#39; in a continuous ribbon or strip of desired width to be formed into successive bag sections is arranged to be divided longitudinally along a line 80&#39; to provide panels 81&#39; to be folded onto themselves and then secured together at their longitudinal edges. A zipper strip 82&#39; having a base 83&#39;  and generally arrowshaped profiles 84&#39; extends across the sheet 79&#39; at the place which will provide the top or reclosable end of a bag when the material is folded upon itself, including the strip 82&#39; wherein the proiles 84&#39; are releasably interlockable. Along what will be the top of the bag, the strip 82&#39; has a pull flange extension 87&#39; which is secured by means 85&#39; to the bag wall sections 81&#39;. In this instance, the zipper strip 82&#39; has an inward lateral flange extension 88 projecting in the opposite direction from the flange 87&#39;. The flange 88 may be secured by means 89 such as heat sealing or adhesive to one of the panels 81&#39; but, as shown in FIG. 17 and 18, remain unsecured to the other of the panels 81&#39; as shown in FIG. 17 and 19. This serves to relieve the closed zipper from internal pressures within the ultimate bag which might tend to open the zipper from the inside. It will be observed that except for the securing means 85&#39; and 89, the base portion of the zipper strip 82&#39;, including the flange 88, remains unattached to the sheet 79&#39;. 
     As shown in FIG. 20, a bag 90 is formed by doubling, i.e. folding, the bag material on itself and securing the free edges together at 91. A zipper strip 90a extends across the entire width of the top end portion of the unfolded film and is folded with the film, and the fold of the fastener strip 90a is then desirably spot sealed at 92. 
     As will be observed in FIG. 21, bag film wall panels 93 and 94 have complementary fastener strip portions 95 and 97 attached at the top of the bag 90. However, the strip portion 95 is bonded only by its web 98 at a location above the centerline of its profiles 96 to the wall panel 93. The strip portion 97 is similarly bonded only by its web 99 at a location above the centerline of its profiles 96 to the wall panel 94. Thereby, both of the strip portions 95 and 97 are hinged to the respective bag walls 93 and 94 and opening stress on the closed zipper by pressures within the bag is avoided as is evident. 
     As depicted in FIG. 22, bag making material 100 has an extruded plastic zipper strip 101 extending entirely across from side-to-side of the bag making film which is adapted to be folded along longitudinal fold lines 102 spaced, for example about 1/4 of the distance in, from side edges 103, thereby dividing the bag film into a center portion 104 and respective side portions 105. In this instance, the fastener strip 101 is attached entirely across the full width of the film 100 by its upper web 107. Along its lower web, the zipper strip 101 is attached only at its 1/4-inward portions 108 to the film side portions 105, while center portion 109 of the lower film strip web remains unattached to the center portion 104 of the film at a location above the centerline of strip profiles 106. Thus, when the film 100 is folded into a bag along the fold lines 102 in the manner shown in FIG. 23 so that the profiles 106 of both of the fourth of the strip side portions interlock with the center strip portion, the fastener strip will be attached only above the profiles 106 of the strip along the top of the strip at the center film portion 104 providing one wall panel of the bag, whereas at the other wall panel of the bag, made up of the side portions 105 folded onto the center portion 104, the strip will be attached both above and below the profiles, and which includes across the entire profile base. This affords desirable opening stress relief at the inside of the bag with respect to the zipper. If desired, the edges 103 may be extended sufficiently to provide a fin 110 at the center joinder of the side portions. It will be apparent that it is equally possible to make the bag shown in FIG. 20 with the sealing arrangement shown in FIG. 22. 
     It will be understood that variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the present invention.