Method of forming zipper gusset bag

Abstract: A method of forming a gusseted plastic zipper bag. The zipper profiles (26,28) are provided intermittently on a carrier web (18), the thickness of which is less than the bag film (14). The carrier web (18) is attached to the bag film (14) that has windows (16) cut therein that are aligned transversely so that a profile-free section (27) of the carrier web (18) covers the windows (16). During bag formation the sections of the bag film (14) with windows (16) covered by the carrier web (24) are folded to form gussets (54).

Description: This invention relates to the manufacture of gusseted plastic zipper bags, and particularly to a method for manufacturing such bags with the zipper running transversely to the film feed direction of a vertical form, fill and seal machine on which the bags are formed. It has heretofore been suggested to provide gusseted zipper bags wherein profile-free sections of the gusset are captured between the zipper profiles. The zipper-free areas of such bags have the thickness of the bag film and hence the mating zipper profiles which capture these areas has to be sufficiently loose fitting to permit such capture which compromises the tightness and security of the zipper closure or requires unduly thin bag walls. An object of this invention is to provide a method of forming gusseted zipper bags, wherein the portions of the gusset which are captured between the mating zipper elements are relatively thin with respect to the remainder of the bag walls. A further object is to provide such a method which may be practiced on a conventional form, fill and seal equipment with relatively minor modification. The above and other beneficial objects and advantages are attained in accordance with the present invention by cutting transversely aligned windows into a bag making film. The windows are provided at locations corresponding to the gusseted walls of the bags to be formed and aligned with the locations at which the profile is to be attached. A carrier web bearing intermittent lengths of zipper is attached to the film with profile-free areas covering the windows. The thickness of the carrier web is relatively thin with respect to the thickness of the bag film. A particular embodiment in accordance with this invention will now be described with reference to the accompanying drawings; in which:- Fig. 1 is a schematic perspective view showing attaching a transversely positioned carrier web with intermittent zipper sections to a bag film with windows cut out; Fig. 2 is a fragmentary detail view of the carrier web bearing zipper profile being attached to the bag film Fig. 3 is a perspective view of the fill tube of a form-fill seal machine about which the bag film is formed into a side-gusseted bag; Fig. 4 is a sectional view taken along line A-A of Fig. 3 showing initial formation of the side gussets; Fig. 5 is a sectional view taken along line B-B of Fig. 3 showing a later stage of gusset formation and a longitudinal side seal; and, Fig. 6 is a sectional view taken along line C-C of Fig. 3 showing the bottom seal step in the bag construction. In Fig. 1 a carrier web 18 bearing intermittent zipper elements is fed transversely onto a bag film 14 which has transversely aligned cutouts or windows 16. These window areas 16 are provided in the portions of the bag film 14 that will be folded to form the gusset walls of the bag with said window areas being then captured between the mating zipper profile elements of the completed bag. In this manufacturing stage carrier web 18 is supplied from a source 20 (not shown) and moved in a direction traverse to the feed direction of bag film 14. The carrier web 18 has a repeating pattern of a central zipper section 26, a pair of zipper-free areas 27 at opposite ends of the central zipper section 26, and a pair of shorter zipper end elements 28 at opposite ends of the zipper-free areas 27. Margin portions 24 are provided adjacent both sides of the zipper extending to the edges of carrier strips. Finally, there is a pair of end seal areas 29 at the opposite ends of the zipper end elements. As further indicated in Fig. 1 a length of carrier web 18A including a repeat of the above pattern has been positioned to overlie transversely the bag film 14 and to extend between the opposite side edges 15 of the film. The length of carrier strip 18A is substantially the same as the width W between the side edges 15 of film 14. The same reference numbers are used for components of carrier web 18 and the single repeat 18A. The movement of the carrier strip 18A, and movement of the film 14 is coordinated or indexed so that the zipper-free areas 27 of the carrier web will overlie the windows 16 of the bag film; then the seal bar 42 descends to seal the carrier strip along its margins 24 to the bag film. The attachment phase of the carrier web 18 to the bag film 14 is further illustrated in Fig. 2 which shows seal bar 42 which descends to seal the edges 24 of the carrier web to the bag film 14. Atop carrier web 18A the zipper profile 26 is schematically shown as four unisex projections of a multi-track zipper, the shape of the profile of the zipper being such as to enable it to engage and interlock with itself. While a unisex zipper construction will reduce alignment problems when the zipper is folded on itself around the fill tube, other male, female constructions with provided alignment means can also be used. Above the carrier web profile is recess area 44 in the seal bar to allow sealing of the side margins of the carrier web without interference with or damage to the zipper profile. The seal bar also includes end sections to seal the end-seal areas 29 of the carrier web to the bag film. As noted above, the areas of the gussets to be captured within the bag profiles is to be formed of thinner film than the remainder of the gusset to facilitate that portion being captured by the profiles. Figs. 3-6 illustrate how a bag film prepared according to Figs. 1 and 2 with the thinner film covering the window areas may be formed into a side-gusseted reclosable bag. Accordingly, fig. 3 shows the filling or forming tube 50 of a vertical form, fill and seal machine having a forming collar at a top end 52, tapered neck 54, gusset-forming recess 56 and bottom end 58. The bag film 14 is brought downward over the forming collar and wrapped around fill tube 50. As the bag film is moved downward and wrapped, the opposite side edges 15 are brought together and sealed along longitudinal seal 60 seen in Fig. 5 formed by side seal bars 62. Fig. 4 shows the initial phase of side gusset formation as gusset-forming bars 64 begin to press the film inward into recesses 56 of the filling tube 50 extending lengthwise and radially inward on opposite sides of fill tube 50. Fig. 5 shows further and almost complete gusset formation which occurs lower down on the fill tube. Finally, as seen in Figs. 3 and 6, below the bottom of the fill tube the lower seal bars 66 will converge against the front and rear bag surfaces, with the upper part of the lower seal bar 66A pressing the zipper together into interlocking relationship and the lower part of the lower seal bar 66B sealing these surfaces to each other thereby closing the bottom of the newly formed bag. In typical apparatus this seal operation simultaneously seals the top of the previously formed bag which has been filled by product entering through the fill tube. The sealing bars further serve to cut the seal area to separate the formed and filled lower bag from the bag being formed and filled.

Claims: A method of forming a gusseted plastic zipper bag, comprising the steps of: a. providing a continuous bag film (14) with opposite side edges (15), b. cutting in said bag film (14) a spaced-apart pair of windows (16) aligned transversely across the lengthwise dimension of said bag film (14), c. positioning a length of carrier web (18) which has a thickness less than that of said bag film (14) to transversely overlie said bag film (14), said carrier web (18) including thereon a generally central section of zipper profile (26), a pair of zipper-free areas (27) at opposite sides of said central section of zipper profile (26), and a pair of end sections (28) of zipper profile at opposite ends of said zipper-free areas (27) aligned with said central section (26) of zipper profile, said two zipper-free areas (27) being positioned to overlie and cover said pair of windows (16), d. sealing said carrier web (18) onto said bag film (14), and, e. forming said bag film (14) with said carrier web (18) attached into a bag. A method according to claim 1, wherein said carrier web (18) has side sections (24) along its length on opposite sides of said zipper profile (26,28), and said sealing step comprises sealing said side sections (24) of said carrier web (18) to said bag film (14). A method according to claim 1 or 2, wherein said zipper profile comprises unisex projections (26) extending from said central section of zipper profile which projections are releasably engageable with similar projections extending from said end profile sections (28) when said end profile sections are positioned to overlie and engage said central profile section (26) and said bag forming step comprises joining said bag film opposite edges (15) so as to position said end profile sections (28) over said central profile sections (26). A method according to claim 1 or 2, wherein said generally central section (26) of zipper profile comprises a male profile or a female profile, and said pair of end sections (28) of zipper profile comprises the other of said male or female profiles, said profiles being adapted to interlock with one another. A method according to any one of the preceding claims, wherein said bag forming step comprises the further step of: advancing said bag film (14) with said carrier web (18) thereon longitudinally along and around a fill tube (50) of a form, fill and seal machine, with said carrier web (18) disposed transversely to the direction of movement of said bag film (14) so as to transform said bag film strip into a tube. A method according to claim 5, including the further step of: folding in, from opposite sides said tube formed from said bag film to form gussets (56) at said zipper-free areas (27) between said central section (26) of zipper profile and said end sections (28) of zipper profile. A method according to claim 6, comprising the further steps of sealing a bottom end of said tube formed from said bag film, filling product into said tube, cross-sealing the top of said tube so as to form said bag, and cutting through said top cross-seal to sever said filled bag from the section of tube above it. A method according any one of the preceding claims, wherein said carrier web (18) includes margins (24) adjacent both sides of said zipper sections (26,28) and said sealing steps comprises sealing said margins (24) to said bag film (14). A method according to any one of the preceding claims, wherein said carrier web (18) includes zipper free end sections (29) at the outer sides of said pair of end sections (28) of zipper profile and said sealing step includes sealing said zipper free end sections (29) to said bag film (14).

Inventors: AUSNIT STEVEN, AUSNIT, STEVEN
Applicants: ILLINOIS TOOL WORKS, ILLINOIS TOOL WORKS INC.
Application year: 2001
Main classification: B31B19
IPC codes: B65D33, B65D30, B31B23, B31B19, B31B1, B65B9