AU607471B2 - Gable-top container - Google Patents

Description

'I

S F Ref: 53846 FCRk: COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATiON

(ORIGINAL)

FOR OFFICE USF: Class Int Class C S 0 Complete Specification Lodged: Accepted: Published: Priority: Related Art: 'I I (I I I t Cc*1t I; I M A1.i: l) [l L Name and Address of Applicant: Address for Service: Minnesota Mining and Manufacturing Company 3M Center Saint Paul Minnesota 55144-IOQO UNITED STATES OF AMERICA Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Males, 2000, Australia Complete Specification for the Invention entitled: Gable-Top Container The following statement 15 a full description of this invention, Including the best method of performing it known to me/us b845/3

ABSTRACT

A gable-top thermoplastic coated container with controllably enhanced sealing and opening characteristics includes at least one stiffening fillet attached to the panels which form the spout. The fillet comprises a thin strip coated with a layei of adhesive, and is bonded to at least one of the pouring spout panels. The strip is resistant to the thermal container-sealing process, and extends along a major portion of the panel length to increase the force which may be transmitted to the tip of the spout where the foldhack panels are adjoined, and prevent buckling of the spout panels. An adhesive web is delaminably bonded with a controlled release adhesive to the opposite surface of the strip, and is bonded to an opposed panel by the container sealing process.

Delamination from the leakproof or hermetically sealed condition occurs at the interface between the strip and the delaminable adhesive, and is accomplished with a low opening force. The strip [rovides additional stiffness to the spout panels, enabling relatively high forces to be transferred to the spout tip where the opening forces act Sto open the container spout. The spout may; be opened o readily without significan, tearing or delamination of the spout panels.

S« 00 4l5lOALJS2A GABL[E-TOP CONTAINER B a k or ou nc of t he Inven tio n I. Field o~f the Inventioni ThI~is invention relates to packaging, and particularly to an improved package construction using a pressure sensitLive adhesive tape, material to improve the opening chara-;cteristics of a disposable gable-toip container suitable for the packaging of liquids. More particul~arly, this invention relates to a blank from which the container is formed.

2. Dc tip ion or)f_ th le PLrior, Ar~t Containers for- beverages such as milk, fruit juices, and dirinks are convent innally cons tructedl fro m blanks of thermopl.astic coated priperhoard. TrJh most widely used of such containers have a rectangutlar cross-sectional body surmounted by a yahle-top closurve inrorporating an extensible pouring qpout. Blanks from which the containcers are constructed are divided into a plw ality of panels wh4Ih are adapted to form the walls aod closure members.

The pannels are formed and separated by score. linos at which the blank is folded. Particular panels are intenided to be joined together in a lapped arrangemont in the completed] container. Typically, thorie panels are pressed together and heated or exposed to high fuequency rodia Lion, to fuse the adjoining thermoplastic stmr~oces, frming a gnrl strong seal. To finally seial the, fl.ied cointainer, [wo or more panels are linally joined and sealed to form a I lb along the top edge of the roof panels, Exemplary of such cotitaner blanks are those shown in Alden U.S. Patent No.

2,750,095 and Wilcox UI.S. Patent No. 3,245,603.

Containers of this type are openedl for access to the contents by a two-step toggle action procoss. First, the gable edges of the roof panecls, at the front of the -2container are pushed outwnrd and upward toward the rear of the container by thumb pressure, breaking the seal between the outside surfaces of the two lip panels, and breaking the seal in the rib panels surmounting the roof above the pouring spout. The gable edges are forced ba. ward past the point at which the lip panels are joined, to nearly touch the roof panels.

Second, the qabl. o dgers are pushed forward and inward. The second stage opening forces are communicated through spout panels to the tip of the pouring spout, breaking the seal between the lip panels and the underside of the roof panels and snapping the spout outward to a pouring position.

The first step in the opening process primarily produces tension forces in the spout panels, while the second step produces compression forces, and these latter forces are transmitted over a greater distance. Thus, the second opening stage is more likely to result in bent and crumpled spout panels, In early models of gable-top containers, the panels comprising the lips, gable rib panels of the pouring spout were bonded to the underside of the roof panels. The resulting sealed spout was difficult to open, generally requiring insertion of a tool behind the lips to separate them from the roof unders.de. The cardstock panels often tore or delaminated, producing an unsightly and unsanitary container. In those cases where an adhesive was S, applied to only those panels which were to be joined, it was simple to eliminate adhesive from the spout panels to reduce the forces required to open the spout. The resulting container, of course, was not effectively sealed and was subject to leakage.

An improvement in gable-top containers to pcovide a hermetic seal for an extonded shelf life package consists of coating the inner surface of the container blank with a foil and an overcovering layer of thermoplastic such as polyethylene. The panels to be sealed C Y -3are bonded by heating the thermoplastic surface coatings to a softening or melting temperature, compressing the panels together and cooling. The use of thermoplastic coatings or foil adds some stiffness to tho panels, and the container is made resistant to wicking of liquids. However, the strong bonding of the lip panels results in buckling, tearing and delamination of tlhe cardstock upon opening the seal. Thus, the spout is difficult to open, and the opened panels are unappealing in appearance.

Polyethylene has a low modulus of elasticity, so the stiffness added by the coating is minimal.

As used in the food packaging industry, the term hermetic refers to a container designed and intended to he secure against the entry of oxyqrn which degrades flavor and other food pLoperties. The term is also used to designate containers used for aseptic filling and storage, containers secure against the entry of microorganisms. The hermetic barrier of such cartons typically comprises an aluminum or othr barrier film coating the inner surface, overcovteled with a thermoplastic such as polyethylene. The carton wall thickness is thus increased, resulting in larigr channols who:r the Pdges of overlying panels have a stopped relnionship in the qnble rib area, increasing the chance for leakage, Attempts to provide an easily opened spout seal have included perforations in the spout panels which tear open to expose pouring lips, improved control of the sealing temperature, the use of added scorelinP .patterns to concentrate the opening forces, and the use of anti-adhesion agents, abhesives, to eliminate the sealing between panels and thus reduce the required opening forces.

The use of perfotations in the spout paneJs has generally been unsatisfactory. such perforations produce a 3b spout of reduced size, which requires special sealing operations. The perforations are considered by somr to be a weak point in the carton, prone to develop leaks. This type -4of carton spout requires external forces such as thumbnail pressure to open, and this procedure is considered unsanitary. The carton cannot be effectively closed, once opened, and shaking of the carton results in spillage.

Likewise, effotts to reduce temperature variations in the sealing process have not produced a satisfactory hermetic sealing gable-top container. Because of narrow acceptable temperatuLe range for obtaining the desired adhesion, sealing variations persist in spite of improved temperature control. moreover, the required opening forces generally exceed the panel strength, evon where minimal sealing is achieved.

The use of novel scoreline patteLns generally has not overcome the strong sealing forcos of well-sealed e 15 spouts and buckling of the spout panels is common.

'aiJ One method for preventing the difficulty in a opening the completely bonded lip panels of polyethylene coated gable-top containers is shown in Crawford et al., US. Patent No. 3,116,002. In this ref,-rence, a thin coating of a high molecular weight organo-siloxane gum is o, applied to the lip panels as an abhesive, that is, to prevent permanent adhesion to the panels in contact with a a. the lip panels.

a. Egleston et al., U.S. Patent No. 3,270,940 4 Q 25 discloses the use of an anti-adhesive composition applied to both the outside and inside surfaces of the pouring lip of a gable-top container. Abhesive agents disclosed include a *acellulose plastic laminated to polyethylene, the latter 4 heat-bondable to the polyethylene surface of the catdstock blank. The cellulose plastic adds insignificant reinforcing stiffness to the pour.ng lip because of its low modulus of elasticity.

The release propertie- of abhesives are generally affected by the heat sealing parameters and are inconsistent. Containers designed for hermetic use and having adhesives in the spout sealing area often require opening forces greater than the w-JIi strength of the 0 @0 0 0 00 00 004 0* 4* 4 0 0 4 0* 0* 0 0 0 o 4 4 000004 0 4 4 O 0 4 0 *4 0 *o 00 4 0 04 00 04 04 4 0 0 04 0 0 4s 04 0 0 00 0 04 panels, and the spout panels buckle during the opening process.

Summar y of the I-T'nv "e nt ion 59 Th'e pres~ent invention is directed to an improvement in the formation of a package nf panepled flexible material to stiffen the package material adjacent the sealed area to be, opened. The result is a more reliable, consistently openable, spout for rjoinin'j ccess Ltr the container contents. Trhr rnntainei: may hip sealnd to a leakproof or even a hermetically sealed condition if desi.red, yet is readily opened with minimal force. The flexible material may be catdf;toc-k, plastic, or other mate rial with a the rmopl astij inone r surface coatVi ng whi rh 15 is sealed by elevoteri tomppratui e and pressure. The flexible material may include1 a ras-i mpormpahIp film or foil layer. A blank of the package motrrial with scoreline-clefined panels is foldorl into the package shape and overlying panels, aro sealedl. A typi cal sealing process consists of heating with hot) air to a temperature which melts or fuses the thermoplastic skir. face coatincgs, and compressing together the panels to he joined.

A container bodly is provided having sides, a bottom and a top suitable for the packaging of liquids.

25 The container body in the illustrated embodliment ini-ludes a front body panel, a bark body patnel cind first and second side panels, Bottom closure panel means in ptovidedr for closing the bottom of the gahl e-top container, Connoreted to the upper edges of the first and 5econdl side panels are tho first anid second roof panels, respectively. Whenr assoemblri, tOe roof panels ore oppositely disposedi to converge upwardly, and are connected at their top edges to formo a gable roof. rhe front edges of the roof pnels have 8 orp lines defining subpanels which comprise first anid secondj roof wing panels. The wing panels form the rear portion of the pouring spout. The first triangular ernd panel, the first and second wing panels and the panels listedl below form an extensible pouring spout connected to the top of the container body.

First and second opposed, substantially triangular end panels are connected to the upper edges of the front and back body panels to extend upwardly therefrom.

A first foldback panel is connected to the first roof wing panel and to one lateral edge of the first triangular end panel. A second foldback panel is connected to the second roof wing panel and to the other lateral edge of the first triangular end panel.

A third foldback panel is connected to the other end of the first roof panel and to one lateral edge of the second triangular end panel. A fourth foldback panel is connected to the other lateral adge of the second triangular end panel, and is adapted to he connected to thi second roof panel, opposite the seonnd foldback panel.

First and second gable rib panels are connected to the upper edges of the first and second foldback panels, respectively, and extend upwardly thlrefrom. These gable rib panels are also connected tn ear'h other at a commnn line, and comprise lips of the pouring spout from which the container contents are discharrged, Third and fourth gable vib panels are connected to the upper edges of the third and fourth foldback panels, respectively, and extend upwardly thorefrom, First and second Croof rib panels are connected to i the upper edges of the first and second nnof panels, respectively, and extend upwatrlly therefrom. Each roof rib panel is connected at one side thereof to one of the first and second gable rib panels.

First and second upper rib panels are connected to the upper edges of the first and second rof rilb panes]n, respectively, and extend upwardly thI.erofrom.

A stiffening or reinforcement fillet overlays a portion of, and is bonded to, the inner surface of at leasione of the pouring spout panels.

77-- 7i

I

t t 1 0 0 0 0 0 0 00 00 0000 00 0 .0 0 0 .0 0.

0 0 0 0 0.

000 0 a 0 0 0a 0 0 0 00 The fillet comprises a strip of reinforcing material resistant constructed of material resistent to deleterious effects of the conventional carton sealing process, it will not melt, or otherwise degrade at the temperature and pressure of the sealing process, a first layer of high strength adhesive attached to one side of the strip, and an adhesive web including a controlled release adhesive delaminably attached to the opposite surface of the strip of resistant material and adapted to seal to the panels or (xx) opposite the panels overzlain by the fillet, when the container is erected, closed and sealed.

The first layer of high strength adhesive adheres to the inner surface of one of the sets of panels, strongly 15 bonding one side of the strip to the panels, to which it remains bonded during opening of the container.

The reinforcing strip and high strength first adhesive layer of the fillet extend along a major portion of the opening force transmission line of the closed and 20 sealed container, that is, the line between the site where opening force is applied an the intersection of the gable rib panels which receives the opening force. The gable rib panels are pushed outward along the intersection by the transmitted opening force. The strip and adhesive stiffen 25 the panel member to which they are bonded, so that the ristance of the panel member to bending or buckling increases, and the opening force. required to open the spout atre transmitted to the spout tip, The adhesive web is delamiriable from the strfce of the strip at a relatively low peel strength, but remains bonded to the container panels, having a higher peel strength at the web-panel interface. The force roquired to delaminate the web from the strip is precisely controlla~ble because the adhesive properties as well as interfacial area -8may be closely controlled. At the same time, a tight seal, including a hermetic seal, may be readily achieved even when the force required for delamination is very low, Thus, a hermetically sealed container having a very low opening force may be produced, provided the blank includes a gas-impermeable layer. The low opening force, combined with the added stiffening from the strip and strong adhesive, prevents buckling or delamination of the gi ile rib panels which otherwise occur during openinj of such containers. Furthermore, the clean separation of adhesive web from the reinforcing strip results in a smooth nonporous inner surface of the gable rib panels, enhancing sanitation considerations. The gable rib panels do not Sdelaminate, tear or buckle as is common in the prior art S 15 gable-top containers, The adhesive web may be a layer of a controllid release adhesive which delaminably bonds to the strip surface at a relatively low, controllable peel strength but bonds to the panels with a higher peel strength.

Preferably, the adhesive web includes two members: first, a delaminable controlled release adh'esive and second, a thermoplastic ribbon to which the delaminable adhesive is bonded. The ribbon melts or softens during the container sealing operation and b comes strongly fused to the S 25 thermoplastic coating of the container panels, Thus, the thermoplastic ribbon also acts as an adhesive.

*?Brief Description of the Dtawings \o Figure 1 is a perspective view of the upper ond of a clored container formed from a blank arcordling to one embodiment of the present invention, Figure 2 is a perspective view of the container end o Figure 1 with a partially opened rib.

-9- Figure 3 is a perspective view of the container end of Figure 1 with its sealed rib fully open and the spout panels in the closed position.

Figure 4 is a plan view of an embodiment of the container blank according to the invention.

Figure 5 is a perspective view of the upper portion of a gable-top containr'r for~med from one embodiment of a blank acording to the present invention, sealed, and subsequently opened. A portion of the container is cut away to view panel members bc-low the roof and Voof rib panels; Figure 6A is a sectional view along line 6-6 of Figure 3, showing the gahlt, rib p~anol, roof rib panel and fillet, prior to the containrL tscaling process; Figure 651 is a sectironral view along lint, 6-6 of *Figure 3, showing the gabic, rib Fanel, roof rilb pnel an(] fillet in the seailed condition; Figure 6C is a sectional view along line 6-6 of Figure 3, showing the gable rib panel, roof rib panel and 20 fillet following opening of th( spout seal; Filgure 7A i~s a rpecti.unal view Maong 1 Inc 6-63 of Figure 3, showInq the gablo rib pnnc, ronf W11 panol and fillet of ii further embodirnont, prior to thr" container sealing provtess;.

14 253 Figure 7B Is aosetional view along line A of Figure 3, showing the gable Lib panell roof rib panel andl '>flit of Figure 7A in the spaloed condition; Figure 7C is a soctional view along line 6~-6 rif Figure 3, showing, the gablo 0.ib panel, roof rib panel andl S 30 fillet of Figure 7A following opening oit the npout seal *0Figures 8 through are plan. vie ws of the interior face of VAcious ombodlmnLt of tho prppmnt invenition, Detailed Description Referring now to the drawings, the invention is depicted with reference to a gable-top container in which the invention is incorporated. A gable-top container is formed from a blank of paperboard or other suitable material coated on the inner planar surface, cr on both the inner and outer surfaces with a theLmoplastic material. The container blank is adapted to be prected and have certain panels sealed to each other by a container sealing process.

Typically, the sealing process consists of compressing together the panels to be joined while toiose panels are at an elevated temperature. Other alternative sealing processes may also be utilized, FIG, 1 shows a typical container 1 in a closed, sealed condition as for storage of beverages and the like.

The container is self-sustaining in shape and may be ,o hermetically sealed, e 0 0 nContainer 1 is comprised of a series of panels, 00 oincluding a container body having four body panels S°°o 20 Front body panel 4 and second side body panel 5 are shown 0,o o in FIG, 1, while Lear body panel 2 and first side bcdy 0 0 panel 3, not shown, oppose panels 4 and 5, respectively, forming a container of retangular cross-.setion. Usually, o0°'0 0 the cross-section is square, The bottom of the container 1 0 25 is closed. First roof panel 28 is connected to the upper edge of first side panel 3. Second roof panel 30 is :°.00o connected to the upper edge of second side panel R. When 0 0 the container is in the closed condition, the root panels 28 and 30 converge upwardly to form a gable roof coot 30 construction. Second roof rib panel 54 is attachrd to second roof panel 30 and extends upwardly therefrom, Likewise, upper rib panel 55 is attached to roof rib panel 54 and extends upwardly therefrom, Ir I First triangular end panel 29 is connected to the upper edge of the front body panel 4. When the container is closed, end panel 29 is folded under the gnble roof formed by the two roof panels. Also shown are first roof wing panel 40 and second roof wing panel 43. The roof wing panels 40 and 43 are subpanels of roof panels 2P and respectively. A second triangular end panel, not shown in this figure, is usually adapted to remain folded under the opposite gable roof, unless it is desired to open both gable ends of the container.

FIG, 2 shows the container of FIG. 1 in which the spout has been partially opened, The first and second foldback panels 41 and 42 and overlapping roof wing panels and 43 are typically pushed outward and backward with thumb pressure to break the sRPa between the inner surfaces o. the first and second upper rib panels 49 and 55, and between the outer surfaces of the first and second gable rib panels 50 and 52, the latter not visible in this drawing, The gable rib panels are connected to the upper 20 edge of foldback panels 41 and 42, and extend upwardly therefrom.

FIG. 3 shows the container at the point where foldback panels 41 and 42 have been pushed backward about degrees from their sealed position. These panels are roughly triangular in shape, each having one edge defined by scoreline 35 or 36, where they adjoin the first triangular end panel 29, First and second gable rib paneland 52 act as lips of the pouring spout, and meet at a common gable rib score line 51, The upper tLeminus 1A of 30 the common rib score line at the fro edge 53 of the pouring lip comprises the tip of the pouring spout. First and second upper rib panels 49 and 55 extend upwardly from the first and second roof rib panels 48 and 51 to a lvel higher than the free upper edge 53 of gable rib panels and 52.

7 -12- To complete the unsealing and opening of container 1, foldback panels 11 and 42 are pushed backward beyond the position shown in FIG. 3. The roof rib panels and upper rib panels will fold along line 57. The blank may or may not be scored at that location.

The gable rib panels are slightly longer than the roof rib panels. Thus, after the panels are folded backward, a subsequent forward and inward movement of wing panels 40 and 43 transmits oponing forces in a toggle-like i0 action along the wing panels and gable rib panels 50 and 52 toward the common line 51 between the gabl rib panels. A component of these forces extends outward and upward from line 51 and from gable score lines 35 and 36 to pull the gable rib panels 50 and 52 away from roof rib panels 54 and 48, the latter not visib l e in FIG. 3, and to pull foldback panels 41 and 42 away from roof wing panels 40 and 43.

Likewise, triangular end panel 29 is forced outward, and the distended panels create a pourinq spout. The various Oto score lines delineating the panels act as hinges for the o 20 panels as they are unfolded.

,,The force required to distend the spout in this fashion may be calculated theoretically. If the gable rib panels are looked upon as a beam which is to be buckled in the center, the force P required for buckling to occur may be described as: lP CEI/(L 2 where: C =(pi) 2 9.87 for hinged ends.

S, 30 E =modulus of elasticity of beam.

I I moment of inertia of the beam.

I bhl/12 where b width and h thickness of the beam.

and L length of the beam.

Analysis of the opening forces is complex. In general -13however, the gable rib panels, foldback panels, and roof rib panels must be relatively stiff to prevent the panels from crumpling, and transmit the applied opening forces to common line 51. The sealing forces which bond the gable rib panels to the roof rib panels are preferably only as high as required to maintain the desired leakproof or hermetic seal. Excessive bonding forces require higher opening forces to be transferied to the spout tip, necessitating greater stiffness in the spout panels to prevent crumpling of the panels during the opening process.

Certain features of this invention produce a liquid-proof spout seal which is easily opened without tearing, delamination, or buckling of the spout panel members. These features underlie the spout panel members in FIG. 3, and are not visible in that figure. These features include one or more fillets 56, shown in FIG. 4 ,I and described in reference to the remainder of the figures.

FIG. 4 illustrates an exemplary flat sheet material blank of this invention for constructing a gable-top container. The inner surface or face is shown, 4 0and it is coated with a thermoplastic such as polyethylene.

Typically, the outer surface is also similarly coated. The sheet material may include a gas impermeable layer such as aluminum foil. An appropriate pattern of score lines divides blank IA into a pluraity of panels and sub-panels which are used as walls of the container and its closure .parts when the container is erected.

The central portion of blank IA comprises four body panels 2, 3, 4, and 5, having their lower edges along 30 bottom score line 13, and their upper edges along top score line 31. These transverse score lines are shown as extending from blank edge 6 to opposite blank edge 12 in substantially parallel relationship across the face of the blank. vertical score lines 7, 8, 9, and ]0 transect the blank to define the lateral edges of the body panel 2, 3, 4, and 5, and other panels above the body panels. These and other score lines are not neceas'.ily straight, but may -14be slightly offset in certain sectors of the blank to improve the fit of the various panels in the erected container.

In the example shown in FIG. 4, side seam flap 11 is connected to one lateral edge 10 of a body member for sealing to the edge of another body member by the container sealing process. Bottom closure means 26 is shown as a group of bottom closure panels 1.4 through 21 attached to the body members along bottom score line 13, and oxtending downward therefrom. Bottom closure score lines 22 through enable bottom closure panels 14, 16, and 18-21 to be folded under closure panels 15 and J.7 and sealed to provide a leakproof container bottom. Such a closure means is well-known in the art. A separately formed structure may alternatively be used to close the bottom of the container.

In fact, any closure moans which results in a satisfactorily tight seal may be used.

The gable top of the container is formed from a series of panels above top score line 31. First and second roof panels 28 and 30 are connected to the upper edges of the first and second side panels 3 and 5, respectively.

The roof panels 28 and 30 aire oppositely disposed and when erected, converge upwardly to mee.t along score line 44 to form a gable roof. Connected to the upper edge of thfront panel 4 is a first substantially triangular end panel 29 whose two lateral edges 35 and 36 formed by score lines aO 0a extend upwardly to score line 44. Similarly, second triangular end panel 27 is connected to the upper edge of back panel 2, and has lateral edges 32 and 33 which extend upwardly to score line 44i On each side of triangular end panel 29 is a foldback panel. First foldback panel 41 is connected to triangular end panel 29 along edge 35, and to first roof wing panel 40 along score line 8. Panel 41 has a score line 44 as its upper edge. Similarly, second foldback panel 42 is connected to triangular end panel 29 along edge 36, and to second roof wing panel 43 along score line 9.

It has score line 44 as its upper edge.

Similarly, third and fourth foldback panels 39 and 38 are connected to triangular end panel 27 along lateral edges 33 and 32, respectively. The third foldback panel 39 is attached to the first roof panel 28 along score line 7, and the fourth foldback panel 38 is connected to the second roof panel 30 by side seam flap 11 when the container is erected.

Attached to the upper edge of each foldback panel 38, 39, 41, and 42 along score line 44 is a gable rib panel 46, 50, and 52, respectively. Similarly, attached to the upper edge of first and second roof panels 28 and a are first and second roof rib panels 48 and 54, respectively. First and second gable rib panels 50 and 52 are connected to each other at a common score line 51, and third and fourth gable rib panels 46 and 45 are connected a.

20 to each other at common score line 47. The uppermost end 51A of line 51 is the tip of the pouring spout of the erected container.

First gable rib panel 50 is connected to first 4. roof rib panel 48 at score linz 8, and second gable rib 25 panel 52 is connected to second roof rib panel 54 at score line 9.

4 -l First roof wing panel 40 comprises a triangular portion of first roof panel 28 defined by score lines 34, 44, and 8, and is adjacent first foldback panel 41. Second o 30 roof wing panel 43 comprises a triangular portion of second roof panel 30 defined by score lines 37, 44, and 9 and is adjacent second foldback panel 42. These roof wing panels 28 and 43 are more or less coextensive with the adjacent foldback panel when the erected container is closed.

A first upper rib panel 49 is connected to the upper edge of the first roof rib panel 48. Likewise, a second upper rib panel 55 is connected to the upper edge of -16the second roof rib panel 54. The score lines 60 and 61 .separate the upper rib panels from the adjacent roof rib panels, and are substantially continuous with the free upper edge 53 of the first and second gable rib panels and 52. The latter panels serve as lips of the pouring spout of the erected container.

The score lines may be applied to blank 1A before or after the thermoplastic coating is applied to the blank. The score lines may be applied to either surface or both surfaces of the blank. For purposes of clearer delineation of the various panels, score lines are shown in the drawings on both of the inner and outer surfaces of the blank and container.

In the embodiment shown in FIG. 4, two stiffening fillets 56 overlie portions of the first and second gable rib panels 50 and 52, and extend downwardly to overcover portion of the first and second foldback panels 41 and 42 and small upper portions of first end panel 29.

°As is also illustrated in an enlarged perspective 9 20 view in FIG. 5 and in FIGS. 6A, 6B and 6C, each fillrt 56 comprises a strip 66 of material resistant to the rnrainer sealing proce cind a first layer 72 of adhesive, This adhesive layer 72 is attached to a first planar surface 86 of strip 66 and to the inner '-hermoplastic coating 82 of one or more of the pouring spout panels as described herein. The strip 66 of material is thus sealed to the 4 thermoplastic inner coating 82 of one or more of thesp panels.

Strip 66 may be formed from any solid material 9"o S 30 which is resistant to any deleterious effect of the container sealing process, and is sufficiently rigid so that, together with adhesive layer 72, it provides sufficient strength to reinforce the panel to the nocesRar y stiffness. Thus, strip 66 must not melt, or otherwise degrade at the tpmperature and pressure conditions nf the container sealing process.

wp -17- Material such as metallic foil, polyester film, and polycarbonate film are examples of strip materials which are unaffected by the temperatures used for sealing panels coated with polyethylene. Such thermoplastic coatings are typically sealed at temperatures of 250 to 400°F (01 to 205 0 In one preferred embodiment of the invention, the material of the strip is unoriented polypropylane, such as that utilized as a film backing in a pressure sensitive adhesive tape marketed under the trademark "Y-8450" by Minnesota Mining and Manufacturing Company of St. Paul, Minnesota. A fillet constructed of unoriented polypropylene exhibits several advantages over strips constructed of other materials. Specifically, unoriented polypropylene has a lower modulus of elasticity than polyester as low as 0.2 x 10'psi). Therefore, a more compliant strip may be constructed which is better able to conform to the scorelines between the pouring spout panels. Thus, a notch, such as is shown in Figures 9, and 12 and discussed hereinafter, is not required. T'his S 20 simplifies the process of positioning and aliening the m fillet on the panels. The optmium temperature range per 0 bonding the unoriented polypropylene strip is 260' 320'F.

The stiffening fillet 56 further includes an adhesive web 73 including a controlled release adhesive, 25 having a first surface 80 delaminab]y attached to the opposite surface 68 of strip 66. During the container sealing process, the opposite surface 79 of web 73 is bonded to the opposite panel by the sealing process conditions. This web 73 may comprise a single controlled 30 release adhesive material which strongly arheres to the container panel coating, typically polyethylene, and bonds delaminably to strip 66 with less adhesion. When the sealed container is opened, the adhesive web 73 peels from the strip 66, leaving a smooth surfaced pouring lip. The adhesive material comprising the web of this embodiment may be a pressure sensitive adhesive such as a rubber/resin combination or which becomes bonded to the container panel surface at the con -ainer se aling conditions, achieving an adhesion strength of 5 to 50 az/in (61 to 612 g/cm) of width.

In the preferred embodiment, web 73 comprises two members, a thermoplastic ribbon 74 and a layer 76 of controlled release adhesive delaminably attached to one side of the ribbon 76. The various embodiments of web 73 are further explained with reference to the remaining figures, The strip 66 and ad~hesive layer 72 may he preformed as a tape which is applied by machine to the blank lA. The adhesive web 73 may be preformed as part of the tape, or may be applied to strip 66 during or after the application of the tape to the blank. A web 73 comprised of a thermoplastic ribbon 74 and adhesive layer 76 may be 41preformed as a second tape whichi is app ]e to the st-rip 66 of a first tape, or La the panel opposite that to which 2strip 66 and layer 72 are attachied. optionally, strip 66, adhesive layer 72, ribbon 74, and adhesive layer 76 may be together preformed as a single tape to be applied to blanks

IA.

For hermetic sealing containers, the modulus of elasticity of strip 66 may be as low as 0.2 x 106 psi (1.4 x 108 kg/in but for materials other than unoriented S 25 polypropylene preferably is at least 0.4 x 106 psi (2.0 x $kg/rn) The stiffness, of the fillet 56 must, be such that the panel with the attached fillet has greater stiffness than a panel without the fillet. This relationship may be expressed as follows:

VIE

2 El( hi)/h "I where: E,=modulus if elasticity of panel.

r, 2 =modulus of elasticity of panel fillet.

hi=thickness of panel.1 h 2 =thickness of panel fillet.

-19- It is preferred that E 2 be greater than 0.2 x 10 pounds per square inch (1.406 x 10 kg per square meteL) to provide the lesired stiffness.

The first adhesive layer 72 may be of such an adhesive type and thickness that when the fillet 56 is compressed between gable rib panel 50 and 52 and roof rib panels 48 and 54 during the container sealing process, a portion of the adhesive of layer 72 extrudes from between the panel or panels and strip 66 of resistant material.

The extruded adhesive fills channels otherwise open to leakage and effectively seals the container. The adhesive used may be sealable by pressure, heat, or other process, but is preferably a pressure sensitive adhesive whose bond is strengthened by the heat and pressure of the container sealing process.

FIG. 5 shows a gable-top container 1A formed from the blank of FIG. 4, sealed according to the container sealing process, and subsequently opened from the closed and sealed condition. Second roof panel 30 and first roof Panel 28 converge upwardly so that their upper edges 44 meet or almost meet. Roof rib panels 48 and 54 are sealed along approximately one-half of the length of the rib structure, and enclose third and fourth gable rib panels and 46. When the container is closed, common scoreline 47 0 25 between the third and fourth gable rib panels is somewhat spaced from common scoreline 51. The void between those 0 scorelines is a vertical channel which when filled with adhesive will prevent leakage. First and second upper rib panels 49 and 55 are joined by the container seali.ng process. The spout panels of the rib structure arp sho.wn to have been opened by first breaking the seal between the upper rib panels 49 and 55, and then breaking the seal between gable rib panels 50, 52 and roof rib panels 48, 54.

First triangular end panel 29, and first and second foldback panels 41 and 42 are folded outward to extend the pouring spout.

I Stiffening fillet 56 is shown within the pouring spout, having strip 66 overlying and attached to first gable rib panel 50, and second gable rib panel 52, not visible in this view. Adhesive web 73 is shown attached to first roof rib panel 48, having delaminated from strip 66 by the ope:' ng forces applied to the container. Conforming to a preferred embodiment, the strip 66 also extends downward over scoreline 44 to overcover a portion of foldback panels 41 and 42. The advantages of such extension will be later described.

FlGS. 6A-6C and 7A-7C are enlarqed cross-sectional views through the rib portion of a hermetically sealing container 1 formed from this invention, showing the panel members and an embodiment of the fillet 56 exaggerated in thickness for the sake of clarity. The panel members 54, 52 include a film or foil 81 of gas-impermeable material such as aluminum, bonded to the inside surface of fiberboard layer 83 by adhesive 84, and overcovered by the thermoplastic coating 82. The outside surface of the fiberboard 83 is shown as also being coated with a layer of thermoplastic It is understood that while the adhesive layer 72 of fillet 56 is shown as being directly attached to the gable rib panel 52, it may optionally be attached to roof 25 rib panel 54. In other words, fillet 56 is reversed within the space between the panels.

Although fillet 56 is shown as being first attached to gable rib panel 52 by adhesive layer 72, and subsequently attached to roof rib panel 54 by web 73 during 30 the container sealing process, the orm.t may be revePrsed if desired, without changing the members that are adhesively joined. In other words, adhesive web 73 of fillet 56 maiy be first attached to roof rib panel 54 of blank 1A, with adhesive layer 72 subsequontly bonded to gable rib panel 52 during the container sealing process. Preferably, the fillet 56 is first bonded to the gable rib panel 52 because proper placement of strip 66 and layer 72 on panel 52 is -21more critical than the placement of web 73 on the roof rib panel. During the container erection and sealing processes, the gable rib panels 50 and 52 may not always be precisely aligned with the roof rib panels 48 and 54.

It is to be understood that FIGS. 6A-7C apply equally to the first gable rib and roof rib panels 50 and 48, although the second gable rib and roof rib panels 52 and 54 aLe shown.

Turning now to FIGS. GA through 6C, fillet 56 is shown in FIG. 6A attached to gable rib panel 52 of blank IA. The fillet comprises, in order, a layer 72 of adhesive bonded to the inner thermoplastic coating 82 of the gable rib panel 52. The first surface 86 of reinforcing strip 66 is bonded to coating 82 by intervening adhesive layer 72.

An adhesive web 73 is delaminably bonded on first surface to opposite strip sutirface 68. Web 73 is adapted to be bonded on its opposite surface 79 to roOEf ib panel 54 during the container sealing prncess.

FIG. 60 shows the same panels 52, 54 and fillet a 20 56, following sealing. Strong honding forces exist between adhesive layer 72 and thermoplastic coating 02 of gable rib panel 52, between adhesiv layer 72 and strip 66, and between web 73 and thermoplastic coating 82 of the roof rib panel 54. The bond between the first surface 80 of web 73 and the opposite surface 68 of strip 66 has the least strength of the fillet bonds, and web 73 is designed to So cleanly separate or delaminate at surface 68 upon application of opening forces, Adhesive web 73 is designed to extrude during the container sealing process of high temperature and prmssure, to penetrate a'eas of possible leakage between the panels and provide a leakproof or hermetic seal in the spout, The resistance to delamination of web 73 from strip 66 it relatively low, compared to the other sealing forces, so a oeal expansion of wob 73 on surface 68 has little effect on the required opening force, The separation or delamination is illustrated in FIG, 6C, which shows web 73 soparatiny from strip 66 and

MMM

remaining bonded to the inner the rropli 51 rotnr 82, of roof rib panel 51. qThe clean separation pro'vidos a smooth inner surface on the gable rib panels 50, 52.

FIGS. 7A-7C corrospond to FIGS, 6A-6C, hut show another embodiment of theu web fillet 56. The webh 73 of this fillet 56 is comprised of a thermoplastic ribbon 71 which is drlaminahly bonde.d to side 68 of strip 66 by a layer 76 of delarninahie arlhosi vo. Diu.inrj [he onntai nr sealing process of elevated tompreraturr. and pressuire, IQ ribbon 74 mlts and fuses, to the inner thermoplastic coating 82 on roof L1ib panel 54 Lo provideo a strong seal.

The thermoplastic extrudes. into open areas b-etwee,-.n the two panels to effectively prevent leakage, producing a rsell usu~ful for hermeti' sealing rontainors, The oxt rusion which occur4 is not shown in Vm~s. 7r3 or 7C~, and has; little efect upon the force, roqui red for opening, becauser thr, thermoplastic will not effectively adhere to strip r6. As illustrated in F-1G. 7C, HeP r'ntainor seal is ope-ned by separating or delaminating layer 76 from surface 68 of strip 66, The layer 76 of delIAminahle adlhesive remains attached to the roof rib paneJ 131, providing a clean, smooth surface on tho innor facerr of tHe, rgable lb Linel- ";1 0 th~ck Fillet il6 niay compi is a Lape having a relat Lvoly tikbacking or ntrilp 66 of a n fi f[ mitr ial which bondis 4 j '25 relatively weakly to the thet mop) o!st ic suiLriro of thepanels Vie adlhesive layer- 72 mny ho thormoplnqtie in 4' 4'nature, but prefe rably i!s a ptrs~r>snitieadhesnive, The latter affordis easir posit ininj dlurtig appl ir'at in tr) the blank 1A, andI does nnt reui er the. application of hent for positioning, Unover, the thermal eeontainor seaIling process. has been foundl to sirnfiantly ronhanct, the noealing stroagth of the ptrsure nonsiliv, irlhesive-s (PISA-) wehirh were tested. Typical pressure nen i tiv( ae nho~ivor, C P"Ar;) can be form~ed into stable, thick layer s, if rlpitr, and wil1, readily extvrde at the ternperitutrs andl ptrsqures u to thermally seal polyethylene. In qomor, s, it ma,*y bs desirable to produce an extru~ied bqad of adhosive alonq the 4' A kt~.a Se 7 -23edges of the fillet 56 to Eur th(er enhance the sealingj. in such cases PSA' s appear to work wel b-ing e1XtrU(1ed by the pressure of the container sealing process. The quanitity of extrudeod adhensive may hep varied by controlling the type of -ahesive, the thickne-ss of the adhesive layer, and the tempe rature' and pressuir of the ra rton sel log Process. Thle quantity of extrude-d adhersive may hcontrolled to fill the srnall rhannnen w hich typical ty dev.elop along the free, uppe.r edger 53 of the gable rib IQ panels, and provide additional sealing in the areas immediately surrounding the, strip 66.

Furthermore, the spare ait the tip of the pourin3 spout, that is, tht, space, in FIG. 5 betweenn common ur1ic 51 and the corresponding line 47 (if tHe t-hirrl and fourth riable rib panels, usuilly not securely 8ealcd in the orlor art by the container sealing process, may also he controllably filled with ai bead of extruded Adhe.sive dutring the sealing process to enhance the seal.

Becausge thes hoad b)onding the qtible rih pan-rls to the roof rib panels is relatively narrow, ihe seail may 1w broken with minimial force dutinrg openinq rif the spout Thre adhesion of strip 66 to the crinlaine r panol throur.h adhesive layer 72 shouild p~rbypoueapeel rit rngtb greater than 50 poL inch at width (6112 grams' per c m, 25 width) at ,oomn temperature, so that tho strip) 66 will remain a'u integral part of the panel to which it is, attached, both before and aftr the spout piinolr, atoe unsealed. and unfolded, Ithe fillet may be adhesively attoched to at loast Oo of tho piouring spout panels depend~ng Upon What Is depsire'd for the plarticulllr application, A strip 66 and adhosive, layer 72 atta-hed to the roof rib panela are somewhat lots effectivQ at transferring the opening fores than when ahtahedl toi the, gable rib panelq. However, thir coincimi ttrint toruct ion fi 4, 0 00 0 0 0 04 00 0 0 4 00 44 0 0 0 0 0 -24a an a required opening forces resulting f rom ".hi k; invra1 enables a strip 66 attcched to the rooF rif to satisfactorily transfer the required forPS open the container spout.

In this invention, the thickness of layer 72 may be made considerably greater than wo1 required for merely handing strip 66 to a pan-al. it(,r example, while the iat i, my he attained oih monomolecular layot of arlhonive?, with rsome contain'?tn, thlis invention may requiir. an adhesive layer exc'odionj 0,001 inch (0.0029 cm) in thirknos fot achievinrj rlesitedl additional 5tiffnoss nnd lookptoof or hermotic sptlinrj, An adhesive layer of about 0,002 inch (0,001, rm) has pt-nven optimal. for CerLCO, n pressur sns tivo adhesives, user to seal polyethylene coated cont.ainors, With other adhosives, a thlokness of up to 0.00d inoh (0,01.02 rm) may he sed ItoWeVer, in ccnjunction with ii strip constructed of uno r ionted pnlypropylone, onu dhs ir'aynl a1ppr o ma I ely 0,003 inches 0,000 oum) has- broen fwundl tor fir prefort H.

Strip 66 is mad(- of. a telatively !itiff material which is not matt.i ally offeetw~l hy the trmperature andl pres~sure of the coninor rwali iri pr rs, hat in, it, will not melt, extrudo, ot ruhs tant ially bond to the, thermoplastic panel. cuatinqr; .t tho neaiiigr condi tion, Thtp MOditlUS Of elasticity must he at leanst 0.1 X 1.0" psi .'10 kq/n') anld is pr~rferahily at leat 0,2xiO' psi 14t kq'm') ,0intl pi frt ai y( ai mitor i al wit h a modudos, cit at leant 0,4x10' pni (2 ,8xto" ,t i Iausr for the strip rMI) onabllnqj th r t(-Piir e ii I jonal sti ffness Loc be achieved with a thin Pttrip rCr tla teriialro nurh a r me tal I i r foil1, polye(stert f ilm,1 arid( Pl yea-bona1(in 1 fil maI y he used, at. thi ekne~rr rn tancr.1i n f rom frou t, 0. 000n5 t r) 0 n6 inches 0 o0013 to 0 02 Zemn, deopend i nvj uprin the oponi ogl force whirch must lip transform h y the f iilet and the: materorll modullus of o'1astircity, 'rho delaminabl, adhosivo of web 73 or layer '76 is ar pret~sure sonaltivre adhesn:ive which providesn a c~nnt-rolledl 0 4.10 A A, after-sealing pool strength adh~esion to thec thermoplastic coating 82 or to the therinop.Ldstic ribbon 7/1, of 5-50 ounces/inch (61.2-612 gram-force/cm) of width. For many applications, a peel StLength of atbout 20 ounces/inch (245 gram-force/cm) of width is Optimal. The adhesive must be delaminable or peelable from strip 66 at a controlled release force, while maintaining its bond integrity with container panel 54. Withi natural rubber/resin adhesive combinaitions, for exnmple., the, delaminahie idhiesion rcin be closely controlled by varying the percent taockifier in the adhesive, mixture to achieve then desired container opening force of about 5-7 pounds 2.3--3.2 kg) when a two-part adhesive web 73 is used, thormnplristic. ribbon 74 may be comprised of the same material as the thormoplastic coatings 82 on the panols. For thiv copmon polyethyl erie coated containers, a ribbon( mIt(.riL of lo dnt polyethylene works well, Such miatrial has a lwmodulus Of elasticity, approximately 0.02,110' Psi (0,14X10P K 0 kg/mt) The ribbon material should have a me-lt index of 0.2 30 g/10 minutes, and preferably q/10 minutes, as, defined by ASTM Test No. D1238. Rilibon 74 may have a thickness of 0. 001~-0 o006 inches 0. 0025-0 .015 cm) with 0.004 inches (0.001 cm) as ther preferred thickness Prior tn Asealing, During the sealing process, the ribbon 74 is extruded and fused to the paneol coating, typically beoming compressed to become o much thinner member, Because of it low modulus of elasticity and its ultimate thinness, the ribbon 74 contributes little, it~ any, stiffness to the panels, Ribbon 74 may bp advantageously formed of thermoplastic which is different in color from the Panel coatings 82, Thte effect of the partticmlac ealing conditions may then be easily Pvalua- tod merely by oppning a sealed container ond visually de(tormininq the fusing (oF the differcintially colored thermoplastic layers. Trhu'3, at the correct sealinq temperature,, Orhe entire coloredl rIbibon 74 will be firmly bonded to the container panel, if the -26sealing temperaure is too low, the colored ribbon 74 will be found to be still attached to the strip 66 by the delaminable adhesive 76. If the temperature is sufficient in some areas of the seal but insufficient in other area, ribbon 74 will be inconsistently bonded to the container panel, and delamination of adhesive layer 76 to strip 66 may even be erratic. Prior to this time, such a method for quickly and easily evaluating the seal has not been available.

In a preferred embodiment, the fillet 56 is formed on the blank IA by machine application of two tapes.

The strip 66 is the backing member of a first tape, and has one side coated with a 2iyer of adhesive 72. Thermoplastic ribbon 74 is the backing member of a second tape, and has one side coated with a layer 76 of delaminable adhesive.

%:oQ The first tape is applied to the desired panels of blank So 1A, and the second tape is next applied to the opposite o* surface 68 of strip 66 of the first tape, While strip 66 may overcover adjacent panels below the gable rib panels, one-part or two-part web 73 is

S""

0 0 preferably restricted in application to the gable rib panels 50, 52 or roof rib panels 48, 54. The vertical width of the web is preferably at least 1/5 of the distance W betwen score line 44 and free edge 53, and may extend the o 25 full distance. For containers having such distance W of 0.5 inches (1.27 cm), a web width of about 0.2 inches 00 0 cml) has been found optimal. In the two-part form, web 73 may, in fact, extend above fLee edge 53, but upward extension exceeding 0,1W is generally not desired.

30 Preferably such upward extension is no more than 0.05T'I.

o "o FIGS. 8 through 12 show a portion of the blank IA, including those panels which become the pouringi spout.

These figures depict various embodiments of fillet 56 in terms of the particular panel area or areas covered thereby. In each case, the adhesive web 73 may comprise a single layer 76 of delaminable adhesive, or may compr,.se a single layer 76 and a th^rmoplastic ribbon 74.

J

^-Y

-27- Regardless of the type of fillet, corresponding thermoplastic covered areas of gable rib panels and roof rib panels which are not covered by the fillet and are compressed together during the container sealing process will be bonded together, providing the coatings attain a melting or fusing temperature.

In FIG. 8, a single fillet 56 overcovers a portion of both gable rib panels 50 and 52. Shown are strip 66 h ving an underlying layer of adhesive 72, not visible, and adhesive web 73, which preferably 'xtends from one end of the strip to the opposite end without interruption, but may also optionally extend beyond the strip ends. The web 73 is within the scorelines defining the gable rib panels 50, 52. The uppermost edge 63 of fillet 56 is generally continuous with the upper free edge 53 of the gable rib panels, but may be spaced upwardly f therefrom by up to 0.2W, where W is the distance between score line 44 and free edge 53. The uppermost edge 63 of S4 the fillet 56 may also be below free edge 53, When the S 20 uppermost edge 63 of fillet 56 is below the free edge 53 by .more than 0.3 inches (0.76 cm), an excessive panel sealing area may result. This produces a strong panel-panel thermoplastic seal which may require an excessive opening force to break. In such cases, torn or dclaminated panel 25 portions may result in the directly sealed areas, As previously depicted in-FIG. 4, a separate strip 66 may be bonded to each of the gable rib panels 52. In this case, adhesive web 73 preferably bridges the space between the two strips 66 to provide additional thermoplastic along common line 51, to effectively seal this area.

FIG. 9 depicts other features which may optionally be incorporated in the seal of this invention.

strip 66 and underlying layer 72 of adhesive overcovor portions of both gable rib panels 50, 52, and extend downward to overcover and bondr to portions of first triangular end panel 29 and first and second foldback -28panels 41, 42. The advantage of this downward extension 71 is evident when the container sealing pLocess is one which affects the bonding strength of the fillet adhesive layer 72. In common heat sealing processes used to seal polyethylene coated blanks, heat is directly applied to the panels to be sealed, the rib panels. Panels below the rib panels are only incidently heated and attain a considerably lower temperature. The sealling temperature is difficult to accurately control, and if the adhesive layer 72 softens excessively, the fillet strip 66 may slide downward, not retaining its proper alignment on the gable rib panel or panels. The portion of the fillet below the gable rib panels will be muich less affected because of the lower temperature, and will maintain the original position of the strip 66, regardless of the typical temperature variations. The high adhesion of adhesive layer 72 is regained upon cooling.

The downward extontion 71 also provides additional stiffness for easing the opening of the spout 20 seal, Each end of the strip 66 may be spaced from the roof rib panels 48 and 54 to form spaces 59. The spacing provides room for the panels to fold around the fillet at scorelines 8 and 9. Preferably, the spacing 59 between 25 strip 66 and the roof rib panels is at least 0,01?, where P is the length of the first or second gable rib panel 50 or 52. The maximum spacing 59 is controlled by the lenqth of strip which will provide the desired stiffness to the panels, and may be as great as 0.3P, where P is as defined 30 above, The figure also shows a notch in strip 66 which exposes common line 51 between the two gable rib panels 52. Line 51 acts as a hinge between the gable rib panels.

A notch, slot or slit in strip 66 along line 51 reduces the force required to bend the gable rib panels outward to open the spout. Thus, strip 66 may onclude a cut extending downwardly from the upper edge 63 of the strip, along at -29least a portion of the common line 51. This also enables adhesive from layer 72 and/or melted thermoplastic from the panel coating and the adhesive web to extrude through tho cut, notch or slot to contact th, opposite gable rib paneJ- 45 and 46 at common scoreline 47, and bond thereto. This difficult-to-seal site is thus effectively sealed. When a notch or slot exposes the. common line 51, the edge of the fillet strip may be separated ft.rom a portion of the common line by up to 0.3 inches (0.76 cm). When there aLe two strips 66,, each overcovering a portion of one of the gable rib panels, the maximum spacing of each fillet from common line 51 is also 0.3 inches (0.76 cm). A greater spacing may result in insufficient stiffening of the panels in the vicinity of common line 51 and, in addition, the container sealing process will bond an excessive portion of exposed gable rib panel along line 51 to the corresponding roof rib panel with a thermoplastic-to-tlermoplastic bond. Such a tight bond at the point where the opening forces first act to unseal the spout make such unsealing difficult. Greater 1 0 force is required, and with less reinforcement, the end of the spout may bend, tear, andl delaminate.

In the exemplary embodiment of FIG. 10, an aperture 69 in strip 66 and adhesive layer 72 exposes both the score line intersection 64 and common line 51. The &2 25 sealing of first and second gable rib panels along common line 51 is enhanced, and the opening force is reduced.

o oOpening forces may be further reduced by exposing scorelines 35 and 36 with slits, or by limitation of the downward extension 71 of strip 66. The edge of aperture 69 30 is preferably spaced from the score line intersection 64 by less than 0,3 inches (0.76 cm).

As shown in FIG. 11, a further embodiment comprises placement of fillets 56 on one or both of the roof rib panels 48 and 54. The Size and shape of the fillets are such that when the seal is closed, the fillets generally correspond in coverage of the gable rib panels to fillets which would have been applied to the gable rib panels as shown in FIGS. 8-10. When applied to a container blank which includes a hermetic barrier, the container seal of this invention may be adapted to provide a hermetically sealed container under various conditions of cardstock thickness and strength as well as container size.

In FIG. 12 is illustrated a version of this invention in which strip 66 is honded to the gable rib panels 50,52 by adhesive layer 72, and adhesive web 73 is bonded to the roof rib panels 48, 54. When the container blank 1A is erected and sealed, each of the webs 73 becomes delaminably bonded to a side of the strip 66, sealing the container spout. The preferred web 73 of this embodiment comprises a pressure sensitive adhesive (PSA).

EXAMPLE 1 Commercial hermetically sealed 0.5 gallon (1,9 liter) gable-top containers were manually opened. After folding back the wing panels, simple forward hand pressure on the roof rib panels resulted in buckling and distortion of the gable rib panels, without opening the tip of the Sspout at the common fold line. In all cases, insertion of a knife blade between the gable rib panels and roof rib panels near the common fold line was required to open the spout.

25 The container material was manufactured by International Paper Company for hermetically sealed cartons, and comprised paperboard having an aluminum film bonded to the inside surface, and both sides then coated with thermomplastic polyethylene.

Container blanks of the same material were sealed by hand, using a Liquipak" model 010 hand sealer.

Attempts to open the containers produced the same results as were obtained with the commercially sealed containers.

An applied force of 15 pounds-force (6,8 kg-force) resulted in tearing and buckling of the panels, without opening the spout.

-31- The opening force required by a previously opened hermetically sealed carton was determined to be about 2.6 pounds-force (1.2 kg-force).

For the sake of comparison, a common milk carton opened from the sealed condition with an applied force of about 3.0 pound-force (1.36 kg-force), without tearing of the spout panels. This carton is sealed only to the extent of preventing gross liquid leaks, that is, the upper rib panels are thermally sealed together; a hermetic barrier is not provided between the gable rib panels and roof rib panels.

An opening force of about 3.0 to 7.0 pounds (1.36 to 3.2 kg) has been found to be geneLally acceptable for 1/2 gallon (2 liter) gable-top containers, EXAMPLE 2 Several thermoplastic elastomer/resin PSA's were ~evaluated for use as layer 72 in bonding the strip 66 to the rib panels. Tapes were made by applying varied thicknesses of the PSA to an 0.003 inch (0.0076 cm) thick backing strip of polyester. Adhesive thicknesses ranged from about 0.0012 to 0,003 inch (0.003 to 0.0076 cm).

Several adhesives did not adhere sufficiently to the polyester backing. It was found that, in general, a 180 25 degree peel adhesion of at least 50 ounces per inch (612 gram-force per cm) of tape width was required to properly seal the joint. In most cases, the heat sealing process .4 oenhanced the peel adhesion of the delaminable adhesive, Rubber resin adhesives at 0.002-0.003 inches (0,005-0.0076 cm) thickness were generally superior to other types of adhesives, providing a high peel adhesion.

The types of adhesive used in the fillets included ethylene-vinyl acetate (EVA) copolymer, medium density polyethylene (HDPE), and a pressuresensitive adhesive (PSA).

The modulus of elasticity was determined by measuring the deflection caused by a weight placed on the i- I'? rar -32center of a simple beam formed from the cardstock.

Measurements were made on the cardstock itself, on a pair of gable rib panels from a blank, and from the entire outer spout assembly comprising the gable rib panels, triangular end panel, and foldback panels. The formula used to calculate the modulus was: E fL, /4ba'Y where E modulus of elasticity.

f force applied, 0.11 pound (50 g) for most tests.

a thickness of beam.

b width of beam, 1,0 inch (2.54 cm).

Y deflection, inches (cm).

L length of beam 3.7 inches (9.4 cm).

The results were as follows: ra a 3 j! -01 -33- Beam~ material Cardstock (unreinforced) Cardstock with transverse sco reline.

(f 10 g because of reduced modul us) Carcdstock with fillet of 0,004 in. (0.010 cm) polyester and 0,002 in (0.005 cm) EVA adhesive (Sea tchpak

TM

26 tape) Carcistock with fillet of 0.002 in, (0.Q05 cm) polyester and 0.003 in.

(0.0075 cM) PSA Spoult panels, not preflexed Spout panel's, p refl1ex~eci Polyester Fil~m (Lite ratLure Value) Thickness 0.027 in.

(0.069 cm) 0.027 i n.

(0.069 cm) 0.036 in.

(0.091 cm) 0 .0 32 in.

(0 .0Q79 cm) 0.027 in (0,069 cm) 0.027 in.

Q(0.Q6 9 cm

Y

Deflect ion 0.18 in.

(0.46 cm) 0.33 i n, (0.84 cm) 0.090 in.

(0.23 cm) 0,12 in.

30 cm) 0.080 in.

(0,20 cm) 0.21 in.

(0.53 cm) E, Modulus, 393,000 8 (2 .76 x 20,000 (0.2 x~ 332,000 (2.33 x I0Q 3 90, 000 Q (2.7 x 8005,j00 0 (6,2 x 337,000 (2.4 x 108) 400,000 (2,8 x 4 44 44 4 4 44 4 44 44 4 44 44 44 44 4 4 4 44 4 4 44 4 4~ 44 The results indicate that the modulus of 30 elasticity is approximately the seline, 0,4 x 10r' psi (2.8 x 108A kg/in 2 for preflexed panels, eithrer with or without the added fillet.

Bu~ckling forces were calculated from the data of rlable 2 usingj Pvi CEII'b/12b 2 I -34where is the forward-directed force merely required to open the preflexed spout from a closed but unsealed condition, lb-force; C is pi 2 E is the modulus of elasticity, approximately 0.4 x 10 psi; h is thickness, 0.027 inches (0.069 cm); b is width, 1.0 inch (2.54 cm); and L is length, 3.7 inches (9.40).

The calculated force required to open the unsealed spout of unreinforced cardstock was 0.5 pounds (0.23 kg.).

The force carried by both of the unreinEorced gable rib panels prior to buckling was calculated to be 1.9 pounds (0.86 using L 1.85 inches, This leaves 1.9 0.5 1.4 pounds (0.64 kg.) of force for breaking the o bond at the tip of the spout.

4 Reinforcement of the gnble rib panels with a S20 0.002 inch (0.005 cm) thick polyester strip and 0.002 inch 8 (0.005 cm) layer of PSA adhesive provided a higher o o ocalculated available force of 2.9 0.5 2.4 pounds for breaking the bond at the spout tip. In this case, the net panel thickness was 0.031 inches (0.079 cm.), Reinforcing the gable rib panels with 0.004 inch (0.010 cm) thick polyester and a 0.002 inch (0.005 cm) thickness of EVA adhesive provided a calculated available o o force of 4.6-0.5 4.1 pounds (2.09 kg.) for breaking the bond at th spout tip. In this case, the net panel thickness was 0.036 inches (0.142 cm). Thus, as a thicker, stiffer reinforcement strip is added, the applied forward-directed opening force available for opening the spout tip greatly increases.

Measurements were made of the force required to open a previously opened gable top hermptic sealing carton, using a spring gauge. The average measured force of 2,4 pounds (1.09 kg.) included the force required to buckle the extreme tip of the unreinforcod spout, that is, the common told line of the gable rib panels. Thus, the calculated value of the force transmitted by the unreinforced spout panels is only 1.9 pounds (0.86 nearly equal to the measured force of 2.4 pounds (1.09 kg) required to open the previously opened carton. This demonstrates that an increase in joint strength a better seal) over that of the opened spout will result ir buckling of the cardstock when opening forces are applied to the spout panels. On the other hand, when the gable rib panels were reinforced with a fillet according to this invention, the added stiffness provided an available opening force greater than 2,4 pounds to the common fold line, and the containers were opened without buckling or delamination of the panels.

The requried thickness, width, and length of the strip 66 to provide the desired stiffness for opening may be calculated from the above equation, when the modulus of elasticity of the strip material is known, In general, polyester strips of 0.001-0.006 inch (0,0025-0.015 cvi) thickness have been found to work, with strip thickness of 0.002-0.004 inch (0.005-0.01 cm) being preferred.

2 The effects of several variables upon ease of opening were subjectively evaluated, Ease of opening was enhanced by an increase in gable rib area covered by the ftllet, fillets of greater stiffness, cutting, notching or slotting the fillet strip 66 along the common fold line between the gable rib panels, leaving uncovered the score line intersection 64 where the triangular end panel 29 touches the common fold line 51, and a reduction of gable rib area which is permitted to 'thermally seal to the roof ribs.

EXAMPLE 3 A tape was made using a strip of 0.003 inch (0.0076 cm) thick polyester eu the backing material. A 0.002 inch (0.005 cm) layer of tackified rubber resin adhesive was applied to one surface of the strip for -36bonding the strip to the giable rib panels of a 1/2 gallon container. A 0.0002 inch thick layer of Elvax"~ 260 ethylene-vinyl acetate copolymer (EVA) adhesive was applied to the opposite strip surface as a delaminable adhesive web.

The tape was applied to the gabir, vlb panels of a container blank described in Example 1. A container was erected from the blank and thpirmcilJy sealed. The container satisfied the recjuireCMentS o[ ain environmental seal, i.e,f the tape remained at the desired loca--tion on the blank panels during the contaienr sealing pr~ocess, thle s pou t opening was fully sealed by the sealing process, the added stiffness enabled opening of the spamt without buckling, tearing, or delamination of the panels, at a relatively low opening force of 6-7 pounds (2.7-3.2 kg), and the spout was oponed by delamination of the EVA adhesive from the strip, thle E~VA adhensive remaining attached to the roof rib panels.

d.

Two t~pes were prepared for making a fillet in the spout of a gable top con ti ne r. The fitist tape comprised an 0.001 inch (0.0076 cm) thick polyester backIng ais a strip 66, with a 0,00Z inch (0.005 cm) layer of a 2$ taokkfiled irubber resin adhesive, coatod on one surface, The second tape was an adhesive wob comprisingj an 0.25 inch wide by 0.004 inches thick (0,64 cm by 0. 1 cm) ribb'-on of low density polyothyleneo (DP blue in color and hovinq a melt index of about 1-2 g/10 minutes, coated1 on one surface with a delaminable adhesive comprising a natural vubber/rezin PSI\.

Thle two tapes were applied to ai eontainer blank made by International Paper Company for hermetic soaling.

Tile first tape, 1.5 inches (3.81 cm) wtd, and notchrl o expose the common litle 51 botwoen the pantel i was ippied to the gable Cib panels. Thle delaminable adhesijve oE thle second, tape Was then applied to thle opposite surface of the -37- .4 strip 66 to bond the second tape, to the' fir-st tape. 'The location of the tapes was as shown in FIG. 9. A carton was then formed from the taped blank and thermally sealedl. The resulting hermetic seal was readily opened, without tearing or delamination of the gable rib panels, with an, opening force less than 7 pounds (3.2 kg) The opening forces delaminated, in a clean snparation, the rdelaminahle adhesive layer from the strip, producing a smooth strip suirface, Additional blanks sealed at lower temperatutns were opened. The Pffectiveness o[ the se-aling temperature was readily dceterminei by noting the integrity of the bond between the blue polyethylene ribbon and tile aluminumcolored roof rib panpls.

Fl"xAr4PLA Thl :e are no standard tests for eva) watinci the seal integrity of "hermetically seale-d' oontainer.

However, a dye penetration test was performed on "hermetic sealing" cattons- both with and without a. fillet attached to the gable rib panels, Several configurations of the fillet were tosted, Ther. dye comprised 1,2 grams of flhocamlne D in 600 grams of isopropyl -alcohol, The dye solution was introduced Into in invoetod carton haivinq itn q;ablo-top sealed, and held for 10 minutes, Tho solution was then poured out and the carllon rinsed wi th water, The Spout was opened and the K igrnn of dye peinetration, Into thle seal area was noted, Containers formed from hiani's without tho fillets of this inve-ntion and soalod conventlonitly to form tlhermotic seials"1 conuld not he nonedr without ditrctly applying force to the inside of the spout, Teartinq andl delamination resulted, All of the cerntninors formedi from blanks of this invention were reaily opo'no1 without significant teavlnq or drlamination of the npout Vannels~ Little dye penetration was notod in any of the openedl Qontainev spouts# hut the pono-ration was greater in contdners without the fillet or fillets, EXA~MPLE 6 An unoriented polypropylene adhesive tape having a polyethylene scaling tape attached, was evaluated as a rtiffening fillet with a snaling layr in a one-half gallon gable top contailer hlank, which war, then heait soaledl with a Licjuipak Model 010 heat srea irlo The combined tapo vmr,; app] ieo to the, nsirdo efr the spout f lush to t heF spout Fe dqr E ii1 lr t w a oneo inch wide and three inrlhes long andl was renteredl on the spout tip, No notch was cut in the fillet.

The tape had a 0,0035 inch thick unovionterd polypropylene backinq arid a 0,003 inc~h thick rubber./resin pressure Sensitive adlhesive, A 0.2 inch wide piece of low density polyethylene was hoat sealed to the upet: edqe of :the polypropylene baickinq. The- polyethylene was 0.004 thick The carton war. openedr in a, normal. manner; ond a spring gauge measured the npeni nq force at 6,8] pounds,. A 2Q Similar cartonl, without the fillet, twouild have buckledl Instead of opening, Trhe polyethyloen cwril i. nq layet bondeod to t ho hiark of the Apout and fille-d the, qaps, and channels In the, spout.

The joint sparated at the ripnpin/olh~~ 0 60 s interface during Oonlncj.

while the present invontion has been particutarly set forth inl terms of speelfic rombolimponts thotOf It will be understood in view of t~he inst ant di F losme tO at numerous vat atlons upon the invent ion ore PnobJ or I o thnr~ skilled in the at t, which variations yet resider Wlihin thF* 4scope of the presenit teachin. Acc'ord1.ngi.y, this, Invontion is, to be broadly construeid andr limited only by Ohe n:ope AndI spirit of the claims now appo.tidrloi hereto.

Claims (8)

1. A sheet material blank for constructing a sealed gable-top container, said blank being substantially rectangular and ccmprising a first upper portion, a central portion and a lower portion, each of said portions being impressed with predetermined scorelines so that upon sequential folding along said scorelines said upper portion might form the roof, said central portion the wall(s) ad said lower portion the base of said sealed container, said upper portion comprising at least two panels defined by relevant said scorelines, said at least two panels being adapted when said sealed container is formed for at least partial separation from the remainder of said roof to form a pouring spout, characterized by at least one stiffening fillet overlying a portion of, and bonded to the inner 'surface of at least one of said pouring spout panels, said fillet comprising a strip of material resistant to the temperature and pressure of the crntainer sealing process, a first layer of adhesive attached to one side of the strip and to the inner surface of said at least one panel for bonding said strip thereto, and an adhesive web including a controlled Srelease adhesive d9laminably attached to the opposite surface of said strip and adapted to bond by said container sealing process to another of the pouring spout panels wherein the opening forces transmitted along said strip delaminate said adhesive web from said opposite surface of said strip.

2. The blank according to claim 1, further characterized in that said first layer of adhesive is of a material which can be partially extruded from said fillet during said container sealing process to form a bead of extruded adhesive along said upper and lateral edges of said at least one pouring spout panel, to seal said at least one pouring spout 0 panel to another of said at least two panels. S3 The blank according to claim 1, further characterized in that 0 the blank is coated on at least one surface by a thermoplastic material fori forming Into a container by a container sealina process of heat and pressure, 4, The blank according to claim 1, further characterized in that the blank is adapted to be formed into a container by a container sealing process at a temperature of 260-320°F wherein parts of said blank to be sealed are compressed together, jRLF/1225h eIro* 40 The blank according to claim 1, further characterized in that .said fillet comprises a tape comprised of said strip having a pre-applied first adhesive layer on one side thereof and a pre-applied layer of controlled release aci.esive delaminably bonded to the opposite side thereof.

6. The blank according to claim 1, further characterized in that said first layer of adhesive comprises one of a pressure sensitive adhesive and a thermoplastic material.

7. The blank according to claim 1, further characterized in that said controlled release adhesive is an ethylene vinyl acetate copolymer.

8. The blank according to claim 1, further characterized in that said controlled release adhesive is a rubber-resin adhesive.

9. The blank according to claim 1, further characterized in that said strip has a modu(us of elasticity of at least 0.2 x 106 psi. The blank according to claim 1, further characterized in that S' said adhesive web comprises: a thermoplastic ribbon bondable on a first surface to the at least one panel by said container sealing process, end a layer of control ed release adhesive dalaminably bonded to said opposite surface of said strip and bonded to the opposite surface of said thermoplastic ribbon, wherein said opening forces transmitted along said strip delaminate said layer of controlled release adhesive from said opposite surface of said strip,

11. The blank according to claim 11, further characterized in that said thermoplastic ribbon comprises low density polyethylene, 12, The blank according to claim 1, further characterized ir that said resistant material comprises one of metallic fC1l, polyester film, and polycarbonate film. n 13. A hermetically sealed gable-top container formed from a blank as defined in any one of claims 1 to 12.

14. 1" sheet material blank substantially as described herein with reference to and as Illustrated by Fig, 4 of the accompanying drawings, A gable-top container substantially as described herein with reference to and as illustrated by Figs. 1 to 3 and Figs, 5, 6A, 6B, 6C, 7A, 7B and 7C of the accompanying drawings, DATED this THIRTIETH day of NOVEMBER 1990 Minnesota Mining and Manufacturing Company Patent Attorneys for the Applicant SPRUSON FERGUSON RLF/1225h r