Roll top bag constructions

[0001] This application is a continuation of and claims priority, under 35 U.S.C. 120, to PCT/US01/31525, filed Oct. 10, 2001, which claims priority to U.S. Application Serial No. 60/240,496, filed on Oct. 13, 2000.

[0002] This invention relates generally to the field of bags adapted to be closed by folding or rolling down their upper ends, such as for the packaging of granular material and other consumable items. The invention is particularly related to reclosable surface closures for gusseted roll-top bags.

[0003] A conventional roll top bag closure employs one surface fastener element (e.g., a section of loop material) at the top edge of the front external face of the bag, and a matable fastener element (e.g., a width of hooking material) spaced approximately two widths of the fastener element down the back face of the bag. To secure the top of the bag in a rolled state, the top is folded down toward the back bag face, the width of the fastener element, and then rolled over again to engage the matable surfaces of the fastener elements. Once so mated, the fastener elements are loaded primarily in peel (i.e., the separation load is generally normal to the plane of the fastener elements), due to the tendency of the rolled top to unroll.

[0004] It has been realized that hook and loop closures, as well as some adhesive closures, are stronger when loaded in shear (i.e., when resisting loads applied generally parallel to their engagement plane) than in peel. One improvement in roll top bag constriction was introduced by Rinicker in U.S. Pat. No. 3,655,118, in an attempt to place the hook and loop engagement under shear by facing the lower surface fastener element toward the bag face on a flexible flap. To secure the Rinicker bag closure, one would roll the bag top down and, lift the flap, and insert the rolled top between the bag face and the flap to engage the hooks and loops.

[0005] Improved closure constructions are desired, especially ones that are readily accommodated by modern bag making and filling equipment, are easy to use, and are designed for compatibility with various bag constructions, such as gusseted roll top bags for such commodities as coffee and the like.

[0006] In one aspect the invention relates to a gusseted bag of disposable packaging material having a roll-top closure defined during use by two releasably engageable fastener components, one component being associated with an upper edge of a rollable top of the bag, and the other component being carried on a flexible flap secured to a lower portion of a face of the bag. Each of the components is in the form of a plastic base layer carrying respective hook or loop elements.

[0007] In one preferred construction, the flexible flap is secured to the face of the bag along the upper edge of the flap, with its fastener component facing away from the face of the bag and disposed below the attachment of the flap to the bag face. The top of the bag is folded down toward the flap, which is then folded upward to engage the two fastener components and secure the folded top between the bag face and the flap.

[0008] In another preferred construction in which the flexible flap is secured to the face of the bag along the upper edge of the flap, with its fastener component facing away from the face of the bag and disposed below the attachment of the flap to the bag face, the top of the bag is folded down over the flap to engage the two fastener components. When the folded top is released and tends to unfold, the flap is bent upward to follow the unfolding top and redirect at least a significant portion of the peel load applied to the fastener into a shear load.

[0009] In certain preferred embodiments the packaging material from which the gusseted bag is formed has an outer layer of thermally weldable plastic, in the form of a film or coating, and the plastic base layers of the plastic components are of a compatible thermally weldable material. In many of the preferred embodiments the plastic of each of the layers is of substantially the same molecular type. In one case each comprises polyethylene, in another case each comprises polypropylene, in another each comprises copolymers of EVA and polyethylene and in another case each comprises polyester.

[0010] According to another group of preferred embodiments, the outer surface of the gusseted bag is defined by paper, and the fastener components carry upon them an adhesive layer, preferably in many embodiments pressure-sensitive adhesive, or in other cases heat-activatable adhesive, and appropriate pressure and/or heat are applied during manufacture to secure these components to the bag. In a particular example the outer surface of the bag is paper and adhesive (e.g., moisture-sensitive or gum adhesive) is pre-applied to the base layers of the closure components.

[0011] In preferred embodiments of the invention, the loop material is a non-woven material (e.g., formed of needled fibers), such as is available from Velcro USA of Manchester, N.H. under the trademark ASPEN. Various detailed features of this preferred loop material can be found in co-pending U.S. Ser. No. 09/262,159, the contents of which are incorporated herein by reference as if fully set forth.

[0012] The male fastener elements (e.g., hooks) are preferably formed integrally (e.g., molded) with the plastic base layer of the fastener component.

[0013] In certain preferred embodiments packaging material, prior to being formed into gusseted bags, has pre-applied to it one or both of the two fastener components.

[0014] In some preferred embodiments the two fastener components are introduced to the bag making process as a single unit (e.g., as parallel portions of a wide closure strip), which is then split into the two components and applied to the packaging material.

[0015] In another preferred embodiment, a closure strip that defines both of the components has a dividing tear strip between them, the components being secured to the bag as a unit, the tear strip adapted to be removed by the purchaser to divide the unit into the two separate components.

[0016] In some embodiments, the flexible flap is secured to the face of the bag along a lower edge of the flap, with its fastener component facing toward the face of the bag, such that the fastener components are engageable by moving the flap away from the face of the bag, folding the top of the bag down between the flap and the face of the bag, and then moving the flap back toward the face of the bag to engage the fastener components and secure the folded top between the face of the bag and the flap.

[0017] According to another aspect of the invention, a bag of disposable packaging material has a closure comprising two releasably engageable fastener components, wherein each fastener component comprises a plastic base layer carrying either hook or loop elements. One fastener component extends in a strip from an upper edge of a foldable top of the bag down one face of the bag, and the other fastener component extends in a strip from an upper edge of the foldable top of the bag down an opposite face of the bag, such that when the top of the bag is folded downward, one fastener component will engage the other fastener component to hold the top closed.

[0018] Preferably, one or both of the fastener components extends from the top of the bag to a gusseted bottom of the bag. One of the fastener components covers a fin seal of the bag in some cases.

[0019] In some embodiments, the bag has gusseted sides formed between the faces along which the fastener components extend.

[0020] Various embodiments may also contain features described in U.S. Pat. No. 6,202,260, and PCT Serial Number US99/26261, published May 18, 2000 as WO 00/27721, the entire contents of both of which are hereby incorporated by reference as if fully set forth.

[0021] According to another aspect of the invention, a method is provided for forming a bag of packaging material having a roll-top closure comprising two releasably engageable fastener components, each fastener component comprising a plastic base layer carrying either hook or loop elements. The method includes forming a roll-top bag of the packaging material, with the first fastener component disposed on one face of a foldable top of the bag, and a flap extending from a lower portion of an opposite face of the bag and carrying the second fastener component positioned to be engageable with the first component when the top of the bag is rolled downward.

[0022] In some embodiments the method includes, before forming the roll-top bag, pre-applying the first fastener component to the packaging material, and securing the flap to the packaging material, the flap carrying the second fastener component.

[0023] In some cases, the method includes introducing the two fastener components to a bag making process as parallel portions of a unitary closure strip, splitting the closure strip into the two fastener components, and then applying the fastener components to the packaging material.

[0024] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims.

[0025] FIG. 1 is a perspective view of a roll top bag.

[0026] FIG. 2A is an end view of the roll top bag of FIG. 1, with the top rolled and held down to engage the surface fastener components.

[0027] FIG. 2B shows the bag of FIG. 2A after the rolled top has been released.

[0028] FIG. 3 is a cross-sectional view, taken along line 3-3 in FIG. 2B.

[0029] FIG. 4 is an enlarged side view of the top portion of the bag, showing the placement of the surface fastener components.

[0030] FIG. 5 is a perspective view of a second roll top bag.

[0031] FIG. 6 is a perspective view of the bag of FIG. 5, in its unfilled state.

[0032] FIGS. 7A and 7B are alternate cross-sectional views, taken along line 7-7 in FIG. 6.

[0033] FIGS. 8A-8C sequentially illustrate the opening and reclosing of a third roll top bag construction.

[0034] FIG. 9 is a transverse cross-sectional view of a first, one-piece closure strip, and FIG. 9A shows such a closure strip as installed on a bag.

[0035] FIG. 10 is a transverse cross-sectional view of a first, one-piece closure strip, and FIG. 10A shows such a closure strip as installed on a bag.

[0036] FIGS. 11A-11C show bags with three different top fold multiples.

[0037] Like reference symbols in the various drawings indicate like elements.

[0038] Referring to FIG. 1, gusseted bag 10 is formed to have a generally flat bottom 12 to stand up on a horizontal support surface (not shown), as is common in the packaging of coffees, for example. The body 14 of the bag is formed of plastic film, such as a laminate of polyethylene (on the inner surface of the bag, to promote freshness) and polyester (on the outer surface of the bag for durability). A transverse end seal 16 and a vertical fin seal 18 help to form the film into a pouch as shown, having an inner cavity as shown in cross-section in FIG. 3.

[0039] Still referring to FIG. 1, bag 10 has two surface fastener components for releasably retaining the top of the bag in a closed, rolled condition for storage. A male surface fastener 20 is attached to the rear face 22 of the bag along the upper edge of fastener 20, with the lower majority of the area of fastener 20 extending freely from the bag. Fastener 20 is preferably in the form of a width of plastic resin molded to have an array of integrally-formed male, loop-engageable fastener elements extending from its broad outer surface. Such fasteners may be formed by the process described in Fisher in U.S. Pat. No. 4,794,028, hereby incorporated by reference. In this embodiment, the faster is applied with its longitudinal forming direction extending across the bag face, with hook-shaped fastener elements that are directed across the width of the bag. However, other shapes of male fastener elements may be employed, or hook shapes that face upward and/or downward as applied to the bag. Preferably, fastener 20 is of a resin compatible with the outer surface of bag 10, such that the upper edge of the fastener may be permanently attached by heat-staking, for example. Other suitable attachment means include pressure-sensitive adhesive (PSA) or moisture-sensitive adhesive (MSA), such as gum coatings.

[0040] A female surface fastener 24 is applied across the front face 26 of bag 10, toward the top of the bag. Fastener 24 carries a field of engageable loops or fibers for mating with the fastener elements of fastener 20, and is permanently secured to the bag film at least along its two long edges (e.g., by heat-sealing), preferably across its entire back face (e.g., by heat-sealing or adhesives). The field of fibers exposed on the outer surface of fastener 24 may be, for example, the ASPEN material referred to above. As shown, fasteners 20 and 24 extend across substantially the full width of bag 10.

[0041] To close bag 10, the top of the bag is first folded above the upper edge of loop fastener 24, as indicated by arrow A. The bag top is folded over again, this time below the lower edge of fastener 24, as indicated by arrow B. The bag top is then folded a third time, this time just above the upper, attached edge of hook fastener 20, to engage the exposed, mating surface of fasteners 20 and 24 (as shown in FIG. 2A). Were the lower edge of fastener 20 attached to the bag face, releasing the rolled bag top in this position would place a normal (i.e., peel) separation load upon the surface fasteners due to the resiliency of the rolled bag top and its associated tendency to unroll. However, because the lower portion of fastener 20 is unattached, the resiliency of the rolled bag top pulls fastener 20 upward, bending it about its attached upper edge, until it is directed upward, on the outer surface of the rolled bag top as shown in FIG. 2B. I have round that with thin, flexible hook substrates, fastener 20 can be pulled up to an orientation of 10 to 30 degrees from vertical. Further tendency of the rolled bag top to unwind places a load between the surface fasteners that is predominantly in shear (i.e., parallel to their engagement plane), a loading mode known to be more readily resisted by surface fasteners than peel. As FIGS. 2A and 2B illustrate, the lowest fold of the rolled top almost completely unfolds after the rolled top is released and allowed to deflect the lower fastener 20 up into a shear loading orientation. It should be understood that other folding multiples are envisioned for this general bag closure construction, with the last fold of any such multiple at least partially sacrificed to pull the closure into a shear loading orientation. FIGS. 11A-11C, for example, show various folding multiples. The more folds, the more sealed the closure.

[0042] FIG. 4 shows a preferred spacing of fasteners 20 and 24 to enable the folding described above. Loop fastener 24 has a width w of about inch (12.5 millimeters), and is spaced down from the upper edge 28 of the bag a distance equal to its width minus a fraction x of about inch (3.2 millimeters). Hook fastener 20 is attached to the bag face a distance down from loop fastener 24 equal to the width w of fastener 24 plus fraction x. These fraction adjustments aid in the rolling of the bag top, by accounting for the fold thickness. The array of fastener elements carried upon fastener 20 is also of about width w.

[0043] FIG. 5 shows a bag 20 with a roll top closure that is functional with the top folded over any one of several numbers of times. Such a bag construction is particularly useful, for example, for applications in which the user desires to incrementally collapse the bag as its contents are depleted. Bags for charcoal briquettes, for example, are one such application. A strip of loop fastener 24 is carried vertically all the way up the front face 32 of the bag, and a matable strip of hook fastener (not shown in this view) extends in parallel fashion up the rear face 34 of the bag. When the bag top is folded over one or more times, its two opposite faces, and the respective fasteners they carry, engage to form a releasable fastening. In this embodiment, the hook and loop strips are both permanently attached to the bag film along their entire length, which also corresponds to the entire length of the bag. It will be understood that this particular construction does not obtain the advantages of predominant shear loading, but does obtain many of the other advantages noted above.

[0044] FIG. 6 shows the same bag 30 empty and open, as before filling, for example. The loop component 24 is shown in dashed outline only, to illustrate that the longitudinal fin seal 18 of the bag extends up its front face and is covered by the loop component for an aesthetically pleasing appearance. The loop component 24 may be attached to the bag film on both sides of the longitudinal fin seal with adhesive 36, as shown in FIG. 7A, or may have one edge aligned with the free edge of the fin seal, as shown in FIG. 7B. Both approaches have distinct advantages, as the fasteners as shown in FIG. 7A can be applied to the bag after formation of the fin seal, and even after completion of the form and fill process, if desired. On the other hand, the fasteners as shown in FIG. 7B, which are heat-staked or welded directly to the bag film, may be applied to the sheet-form bag film in advance of forming and filling the bags, with the fastener strips introduced directly to the bag forming equipment as continuous lengths, or applied to a respective edge and middle region of the bag film as it is spooled from a roll, to name two preferred examples.

[0045] FIGS. 8A-8C illustrate a roll top bag construction that combines the advantages of shear loading and variable adjustability. A strip of loop component 24 is permanently attached to the front face of bag 40, similar to the arrangement of the loop strip on the bag of FIG. 5. On the back face of the bag, however, hook component 20 is attached only at its upper and lower ends to the bag, with its array of hook elements facing toward the bag film along its entire length. As shown in FIG. 5A, the upper edge of filled bag 40 is sealed to form a pouch suitable for perishable goods, with the upper seal of the bag forming a tear strip 42 to be torn from the bag upon its initial opening. Hook component 20 is attached at its upper end only to tear strip 42, and contains an upper frangible joint (e.g., a transverse score line or tear notch, not shown) adjacent the tear strip, such that when the tear strip is torn away, the upper end of hook component 20 is freed from the bag as shown in FIG. 8B. To reclose the bag, the top is rolled up as much as desired, then the extended hook strip 20 is wrapped over the top of the bag (as shown in FIG. 8C), engaging the loop strip 24 over a wide area in predominantly shear loading.

[0046] The two fasteners may also be provided as part of a unitary strip. For example, FIG. 9 shows a closure strip 50 that has a unitary resin substrate 52 from which both a tear rib 54 and an array of integrally molded fastener elements 56 extend in parallel, longitudinally continuous form. Loop material 58 is also carried on the substrate, with fibers of the loop material embedded in and secured by resin of the substrate. Methods of forming such unitary closure strips are described more fully in U.S. Pat. No. 6,202,260. Parallel, continuous bands of adhesive 60 are provided on the back side of the closure strip for securing the strip to a bag, as shown in FIG. 9A, for example. The narrow band of adhesive 60 on the hook side of rib 54 attaches the closure strip to the face of the bag, and the wider band of adhesive 60 on the loop side of the rib secures the strip to the rolled top of the bag after filling. With the closure strip so applied to the bag, closure strip 50 provides desirable tamper evidence, as the bag cannot be opened without damaging or tearing the closure strip. To open the bag, tear rib 54 is grasped and pulled across the face of the bag and discarded, severing the substrate 52 of the closure into two parallel portions, each carrying an associated one of the matable fasteners. Substrate 52 is provided with molded tear channels (not shown) on either side of rib 54 to assist in controlled opening. The bag can then be reclosed by rolling the top of the bag down to engage the two fasteners, as discussed above. As the lower edge of closure strip 50 remains unattached to the bag, the lower fastener component is free to be hinged about its associated adhesive attachment to the bag face, to orient the fastening plane in a shear loading direction.

[0047] FIG. 10 shows another illustrative embodiment of a unitary bag closure strip 70 useful for roll top bags. In this example, the molded male fastener elements 56 are formed on a side opposite the side carrying the tear rib 54 and loop material 58. One wide band of adhesive 60 extends below the loop material, and a narrow band of adhesive 60 is disposed under the longitudinal edge adjacent the hook elements. The narrow band of adhesive secures the lowermost edge of the bag closure 70 to the face of the bag, with hook elements 56 facing the bag film as shown in FIG. 10A. The wide band of adhesive 60 permanently secures the closure strip to the rolled or folded top of the filled bag. Tear rib 54 is grasped and pulled to tear through the substrate of the closure for initial opening of the filled bag, and the bag is thereafter reclosed by tucking the rolled top between the face of the bag and the flap formed by the severed, lower, hook portion of the closure. Although this closure sequence requires both the flap and the rolled top to be simultaneously manipulated, thereby generally requiring a two-handed operation, it does provide the shear loading advantages discussed above. Furthermore, the one-piece nature of the closure strip enhances ease of assembly and provides tamper evidence. Because the closure is attached to the bag top only after filling, the loop component can be positioned according to the actual requirements of each individually filled bag. Thus, the upper portion of the closure can be adhered to the filled bag with its top already rolled down to an advantageously very tight, space-minimizing position, the closure thus put into tension as would a piece of adhesive tape. Such tight packaging is desirable to remove air and promote sealing (e.g., for perishable items) and to reduce shipping and shelf space for retail goods.

[0048] The lower band of adhesive 60 in each of the closure strips shown on bags in FIGS. 9A and 10A could be replaced, for example, with a thermal weld. In such a case, the closure strip can be applied to the bag before filling. The closure strip can be provided in continuous form, and cut to length as applied, or can be provided as finite lengths upon a release liner and applied with typical labeling equipment.

[0049] It should be realized that the above-described drawings are not to scale, but do schematically represent the concepts claimed. The closure components discussed above, for example, typically have a substrate thickness of only about 0.003 to 0.007 inch (preferably, between about 0.004 to 0.005 inch), although as illustrated they appear much thicker than the bag film, which is preferably about the same thickness as the closure substrates. The thinness and flexibility of the closure substrate, especially for the bag construction shown in FIG. 1 and compared to the bag film itself, enables the lower closure component to be readily pulled upward into a shear loading orientation. Thicker bag films can tend to be more resilient, providing greater roll top restoring force for re-orienting the closure. The thinness of the closures also enables the use of standard handling and packaging equipment.

[0050] The contents of the following applications are all incorporated herein by reference as if fully set forth: PCT/US01/31525, filed Oct. 10, 2001 and U.S. Patent Application No. 60/240,496, filed Oct. 13, 2000.

[0051] A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. Accordingly, other embodiments are within the scope of my claims.