Abstract:
Straight zipper sections are attached to a carrier tape for attachment to the mouth end of a bag. The straight zipper sections are mounted on the continuous tape in longitudinal series orientation, or in spaced side-by-side orientation across the length of the tape. The tape in either case may be fan folded and packed into a storage or shipping container. The tape provides for closing attachment across the mouth of a bag to provide a security membrane and/or a tamper evident structure required to be ruptured to gain initial access into the bag after the zipper is opened.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates in general to the bag making art, and is more particularly concerned with a new and improved method of and means for providing extruded thermoplastic reclosable fastener means, commonly referred to as zipper, for bags which may be formed from plastic film and provided with mouth ends closable by means of the zipper. 
     As heretofore generally provided, the zippers have either been extruded integrally with the bag making film, or the zippers may have been preformed in continuous strip and supplied in rolls for subsequent use in a bag making line. This is exemplified in recently issued U.S. Pat. No. 4,835,835. 
     An inherent disadvantage of the continuous rolling of thermoplastic zipper is the distortion that develops due to the memory of the winding system. This manifests itself as memory of the spool known as curvature and camber which causes deviation from a straight line. It may be noted, however, that in the accepted mode of applying zipper to substrates in packaging machines, the zipper is kept under tension in order to minimize the difficulty in application of the zipper to the substrate. In cases where zero deviation from straightness is required, the zipper must be held under extreme tension. In applications where the zipper cannot be held under tension, application of the zipper to a substrate is virtually unattainable. 
     The provision of sectional lengths of zipper to be applied to the outside of bags is disclosed in U.S. Pat. No. 4,691,373. In that disclosure, pressure sensitive adhesive is provided on the predetermined length of zipper and a peelable protective strip is applied over the pressure sensitive adhesive until the sectional length of zipper is to be used. That disclosure does not meet the problem of supplying predetermined lengths of zipper in a ready availability mode for applying separate lengths of the zipper to bags in a bag production line, especially as conducted in a bag making machine. 
     SUMMARY OF THE PRESENT INVENTION 
     The present invention provides a new and improved method and means for solving the problems discussed hereinabove. 
     An important object of the present invention is to provide a continuous line supply of reclosable zipper capable of being applied without exhibiting curvature or camber. 
     Another object of the present invention is to provide a reclosable zipper with a membrane or web material as a component of its construction. 
     A further object of the present invention is to provide a reclosable zipper capable of being supplied in such a form that either in machine direction running or head running of the bag making film, application of the zipper sections to the bag making film can be effected substantially without reducing the line speed of the packaging machine. 
     Yet another object of the present invention is to provide a new and improved reclosable zipper with sealing compatibility to substrate by use of sealing compatibility of a carrier tape. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will be readily apparent from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, although variations and modifications may be effected without departing from the spirit and scope of the novel concepts of the disclosure, and in which: 
     FIG. 1A is a more or less schematic perspective view demonstrating a method of producing sectional or predetermined length reclosable zipper according to one preferred embodiment of the invention; 
     FIG. 1B is an extension of FIG. 1A and illustrates how the straight sectional zipper product is advantageously packed for further use; 
     FIG. 2 is a more or less schematic illustration showing how the straight sectional zipper product of FIGS. 1A and 1B is adapted to be used in producing zipper equipped bags; 
     FIG. 3 is an enlarged fragmentary sectional detail view taken substantially along the line III--III in FIG. 2; and 
     FIG. 4 is a more or less schematic perspective view showing an alternate manner of packing the straight sectional zipper sections. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIGS. 1A and 1B, complementary reclosable zipper strips 10 and 11 are extruded from a desirable plastic material by extrusion means including extruder apparatus 12 disclosed schematically. It will be understood that, as is usual, the extruder apparatus will also include appropriate chilling means so that promptly after issuing of the zipper strips from the extruder nozzle, they will be satisfactorily set to retain the desired cross section, including generally hooked shape zipper profiles 13 on the strip 10 which cooperate reclosably with complementary zipper profiles 14 on the strip 11. As shown, the profiles 13 and 14 are disposed along respective margins of the strips 10 and 11 and from which margins the strips extend in respectively opposite directions to provide respective base flanges 15 on and along the strips. As soon as the strips 10 and 11 are self-sustaining after the extrusion process, they are joined together by releasably interlocking the profiles 13 and 14 by passing the cooperating strips between driving pinch rolls 17, rotatively complementally driven in any well know manner. From the pinch rolls 17, the zipper assembly travels rectilinearly through cutoff and spot sealing means 18, schematically illustrated as of generally the guillotine type including an underlying anvil member 19 and a reciprocating cutoff member 20. Combined with or associated with the members 19 and 20 is spot sealing means 21 by which the profile areas of the zipper assembly at the ends of zipper section lengths 22 are provided with spot seals 23 which flatten the profile areas to nearer the thickness of the flanges 15 to facilitate subsequent sealing of the ends of the strips into side seals of bags with which the sections are incorporated. 
     As the continuous zipper strip assembly is fed forwardly by the feed pinch rolls 17, the sectional lengths 22 of the zipper assembly are advanced, before being cut off, to and between feed rolls 24 and 25. At this point there is advanced from a suitable supply, such as a roll 27 or other suitable supply, a continuous carrier tape 28 somewhat wider than the overall width of the zipper sections 22 and trained over the feed roll 24 into engagement with the underfaces of the successive zipper sections 22. The relationship is such that with the zipper sections 22 centered along the length of the tape 28, the tape projects substantially uniformly, in this instance, to each side of the zipper strips. 
     At the feed rolls 24, 25, the flanges 15 of the discontinuous lengths of zipper sections 22 are desirably attached onto the carrier tape 28 travelling at a predetermined rate to insure accurate positioning of the zipper lengths thereon. While attachment of the flanges 15 to the carrier tape 28 may be effected in various ways known in the art, the feed roll 25 may be provided in the form of spaced parallel sections which press the flanges 15 against the tape 28 and simultaneously effect welding 25a (FIG. 3) of the flanges 15 to the tape. For this purpose, the flanges 15 and the tape are desirably formed from sealingly compatible thermoplastic material. 
     As the carrier tape 28 travels downstream with the attached uniformly relatively closely spaced zipper sections 22 thereon, it is, as shown in FIG. 1B longitudinally fan folded and received in a storage or shipping container, such as a carton 29. 
     If desired, of course, the carrier tape 28 and supported succession of zipper section lengths 22 thereon may be utilized directly, and without packaging, on a bag making production line, such as depicted in FIG. 2. Of course, if the bag making line is located apart from the zipper production facility, then the packaged carrier tape and zipper assembly arrangement of FIG. 1B may serve as the zipper source. In any event, the zipper sections 22 as carried by the tape 28 are adapted to be continuously applied to the mouth end of bag sections 30 of bag making film material 31 which may be fed from a supply roll 32. As each zipper section 22 registers with a bag section 30, the leading bag section carrying thereon one of the zipper section 22 and the length of carrier tape 28 associated therewith, may be cut off from the next succeeding bag section 30 along a median cutoff line 33 between the spaced ends of the zipper sections 22 on the respective bag sections. 
     As shown in FIGS. 2 and 3, the bag sections 30 may be in what may be termed a J-fold wherein the bag mouth end of one wall 34 of the bag projects sufficiently beyond the bag mouth end of the opposed bag wall 35 so that the width of the tape 28 will substantially bridge between the opposite margins of the mouth ends of the bag walls 34 and 35. Attachment of the tape 28 to the bag walls may be along respective seals 37. For this purpose, the carrier tape 28 may be constructed from any preferred materials which are sealably compatible with the substrate bag film for effective bonding. If preferred, the carrier tape may comprise one or more materials designed to enhance the sealing of the tape onto the substrate. Through this arrangement, the tape may serve as a vapor retaining security membrane across the mouth of the bag and may also serve as a tamper evident device since in order to gain access into the filled and closed bag, the tape membrane must be fractured. 
     To facilitate deliberate fracturing of the tape membrane, a line of weakening 38 may be formed along the tape behind the zipper profiles 13, 14. Thereby not only must the zipper be opened for initial access into the bag, but the tape membrane 28 must also be opened, as by rupturing the same in order to gain such access. 
     While the longitudinal folding of the carrier tape as depicted in FIG. 1B is suitable for equipping bags where the zipper assembly is applied along the travelling axis of the bag material, where it is desired to apply the zipper sections 22 across the travelling axis of the bag material, the arrangement shown in FIG. 4 is adaptable for such purpose. Accordingly, the straight zipper sections 22 are secured across the longitudinal axis of the carrier tape 39 which may then be fan folded between the edges of the contiguous zipper strips, substantially as shown, and received in a storage/shipping container 40, unless the carrier and zipper section assembly is to be immediately used on a bag making line. 
     From the foregoing, it will apparent that the new and improved straight zipper section and carrying tape combination of the present invention is thoroughly compatible with productivity of bag making or packaging lines and is not detrimentally affected by the heretofore generally accepted difficulties of sealing similar materials of uneven thickness to incompatible substrates. Furthermore, there is no need for placing the straight zipper sections under tension for applying the same to the packages or bags since the zipper sections are free from curvature or camber. Also, the carrier tape serves as an advantageous membrane material in association with the zipper sections. The zipper section and carrier tape arrangement is adaptable to either machine or head-to-head applications without reducing the line speed of the packaging machine. By use of sealingly compatible carrier tape, the reclosable zipper is advantageously sealing compatible with respect to the bag material substrate. 
     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.