AU611890B2 - Gable-top container closure system - Google Patents

Description

1.4 111111.6laIHoQ9 3 01. 1.25 1.4 6 F r I I- I--r I. -r _Jii i61189 FORM 10 F Ref: 53859 COMMONWEALTH OF AUSTRALIA PATENTS ACT 1952 COMPLETE SPECIFICATION

(ORIGINAL)

FOR OFFICE USE: Class Int Class 00 a 0 0 o 00 0 Complete Specification Lodged: Accepted: Published: Priority: Related Art: 0 0 000 0 Name and Address of Applicant: Minnesota Mining and Manufacturing Company 3M Center Saint Paul Minnesota 55144-1000 UNITED STATES OF AMERICA Spruson Ferguson, Patent Attorneys Level 33 St Martins Tower, 31 Market Street Sydney, New South Wales, 2000, Australia Address for Service: o0 0 0 ,0 Complete Specification for the invention entitled: Gable-Top Container Closure System The following statement is a best method of performing it full description of this invention, .ncluding the known to me/us 5845/5 TO: THE COMMISSIONER OF PATENTS

AUSTRALIA

SBR/TGK/152T 7

ABSTRACT

A gable-top thermoplastic coated container with controllably enhanced sealing and opening characteristics includes at least one fillet attached to the panels which form the pouring spout. The fillet comprises a thin strip of stiff material coated with a layer of adhesive. The strip extends along a portion of the panel length to increase the applied opening force which may be transmitted to the tip of the spout where the gable rib panels are adjoined and prevent buckling of the spout panels. The unadhered surface of the strip does not strongly adhere to the opposing thermoplastic coated panel, so that the spout o 0 may be opened with a controlled low force, without tearing or delamination of the carton panels. The portion of the o 0o fillet-carrying panel not covered by the fillet will bond o0 oo S° to the opposing panel by thermoplastic fusion. Preferably, s0o C, the adhesion layer is of such a thickness that a portion 00000, thereof is extruded during the carton sealing process, forming a bead of adhesive along the edges of the strip to bond opposing panels together. The result is a hermetic 0o°a0 seal which is readily opened without destruction of the 0 00 0o"0 spout panels.

O OoOo 0 00 00 0 00 0 00 00 0 00 1 A Declared at Minnesota, ti10h day of March 1988 U.S.A. ti 0h1 SFP4 ~TO: The Commissioner of PatentsSgntrofecrnts18 Vice President 42324AUS6A GABLE-TOP CONTAINER CLOSURE SYSTEM Background of the Invention 1. Field of the invention T-his invention relates to, packaging, aP~d particularly to an improved package construction using a pressure sensitive adhesive tape material to improve the opening characteristics of a disposable gable-top container suitable for the packaging of liquids. More particularly, this invention relates to a blank from which the container is formed.

2. Description of the _Prior Art Containers for beverages such as milk, fruit juices, and drinks are conventionally constructed from 00 15 blanks of thermoplastic coated paperboard. The most widely used of such containers have a rectangulai. cross-sectional a 0a 0 C' body surmounted by a gable-top closure inuorporating an 00 00 extensible pouring spout. Blanks from which the containers 000000are constructed are divided into a plurality of panels 0 a which are adapted to form the walls and closure members.

The panels are formed and separated by score lines at which 0 4 0 the blank is folded. Particular panels are intended to be 0 00bojoined together 1n a lapped arrangement in the completed 0O 00 0 a0 25 heated or exposed to high frequency radiation to fuse the adjoining thermoplastic surfaces and form a generally strong seal. To finially Seal the filled container, two or 00 0 0 0 11more panels are finally joined and sealed to form a rib 30 along the top edge of the roof panels. Exemplary of such 0 00 30 container blanks are those shown in Alden U.S. Patent No.

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

conitainers of this type are opened for access to the contents by a two-step toggle action process. First, the gable edges. of the roof panels at the front of t'he -2container are pushed outward 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 backward past the point at which the lip panels are joined, to nearly touch the roof panels.

Second, the gable edges are pushed forward and inward. The 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 -,napping the spout outward to a po-ring position.

In early models of gable-top containers, the Soopanels comprising the lips of the pouring spout were bonded 0 o 0 00 15 to the underside 3 000 of the roof panels. The resulting sealed spout was difficult to open, generally requiring insertion of a tool 00 00 0 0o behind the lips to separate them from the roof underside.

0 The cardstock panels often tore or delaminated, producing an unsightly and unsanitary container. In those cases where an adhesive was applied to only those panels which were to 0O00 .0.0o0 be joined, it was simple to eliminate adhesive from the 00000 spout panels to reduce the forces required to open the z 00 spout. The resulting container, of course, was not 0 0 o° 25 effectively sealed and was subject to leakage.

An improvement in gable-top containers to provide a hermetic seal for an extended shelf life package 00 0 0 0 consisted of coating the inner surface of the container o oo o 0 blank with a foil and an overcovering layer of thermoplastic such as polyethylene, The panels to be sealed are bonded by heating the thermoplastic surface coatings to a softening or melting temperature, compressing the panels togethar and cooling. The use of thermoplastic coatings or foil adds some stiffness to the panels, and the container is made resistant to wicking by liquids. However, the strong bonding of the lip panels results in buckling, tearing and delamination of the cardstock upon opening ,.he -3seal. Thus, the spout is difficult to open, and the opened panels are unappealing in appearance.

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

As used in the food packaging .Justry, the term hermetic refers to a container designed and intended to be secure against the entry of oxygen which degrades flavor.

The term is also used to designate containers used for aseptic filling and storage, i.e. containers secure against the entry of microorganisms. The hermetic barrier of such cartons typically comprises an aluminum or other barrier film coating the inner surface, overcovered with a thermoplastic such as polyethylene. The carton wall t'f "thickness is thus increased, resulting in larger channels where the edges of overlying panels have a stepped relationship in the gable rib area, increasing the chance for leakage.

4 *08 Attempts to provide an easily opened spout seal ihave included perforations in the spout panels which tear open to expose pouring lips, improved control of the sealing temperatute, the use of added scoreline 0 00t o oo 0 patterns to concentrate the opening forces, and the use 0" 0 of anti-adhesion agents, i.e. abhesives, to reduce the required opening forces.

00 00 o 0 0 25 The use of perforations in the spout panels has generally been unsatisfactory. Such perforations produce a spout of reduced size, which requires special sealing 0o operations. The pecforations are considered by some to be a "0o o weak point in the carton, prone to develop leaks, This type of 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, efforts to reduce temperature variations in the sealing process have not produced a satisfactory hermetic sealing gable-top container. Because of narrow acceptable temporature range for obtaining the r r u -4- 0C 0o 0 0 00 0 a 000 O 0 0 0 0 00 00 0 0 0 O Q 00 0 0 00 desired adhesion, sealing variations persist in spite of improved temperature control. Moreover, the required opening forces generally exceed the panel strength, even where minimal sealing is achieved.

The use of novel scoreline patterns generally has not overcome the strong sealing forces of well-sealed spouts and buckling of the spout panels is common.

One method for preventing the difficulty in opening the completely bonded lip panels of polyethylene coated gable-top containers is shown in Crawford et al, U.S. Patent No. 3,116,002. In this reference, a thin coating of a high molecular weight organo-siloxane gum is applied to the lip panels as an abhesive, that is, to prevent permanent adhesion to the panels in contact with the lip panels, Egleston et al, U.S. Patent No. 3,270,940 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 cellulose plastic laminated to polyethylene, the latter heat-bondable to the polyethylene surface of the cardstock blank.

The release properties of abhesives are generally affected by the heat sealing parameters and are 25 inconsistent. Containets designed for hermetic use and having adhesives in the spout sealing area often require opening forces greater than the wall strength of the panels, and the spout panels buckle during the opening process.

Summary of the Invention The present invention is directed to an improvement in the formation of a package oC paneled flexible material to stiffen the package material adjacent the sealed area to be opened. The result is a more reliable, consistently openable hermetically sealed opening for gaining access to the contents. The flexible material .z may be cardstock plastic, or other material with a thermoplastic inner surface coating which is sealed by elevated temperature and pressure. The flexible material may include a gas-impermeable film or foil layer. A blank of the package material with scoreline-defined panels is folded into the package shape and overlying panels are sealed. A typical sealing process consists of heating with hot air to a temperature which melts or fuses the thermoplastic surface coatings, and compressing together the panels to be joined.

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

The container body in the illustrated embodiment includes a front body panel, a back body panel and first and second S, 15 side panels. Bottom closure panel means is provided for closing the bottom of the gable-top container, Connected tn o the upper edges of the first and second side panels are the o o 0 0 first and second roof panels, respectively. When assembled, the roof panels are oppositely disposed to converge 0 0 upwardly, and are connected at their top edges to form a gable roof, The front edges of the roof panels have score so o lines defining subpanels which comprise first and second o00oOO roof wing panel The wing panels form the rear portion of 0 00 the pouring spout.

I o 25 First and second opposed, substantially 0 0 triangular end panels are connected to the upper edges of the front and back body panels to extend upwardly ,o 0 therefrom. The first triangular end panel, the first and 0 00 o 0 3 second under panels and the panels listed below form an 0 0 o 30 extensible pouring spout connected to the top of the container body.

A first foldback panel i, 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 'o nel.

1 1 1 I L f

I

i I 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 edge of the second triangular end panel, and is adapted to be connected to the second roof panel, opposite the second foldhack panel.

First and second gable rib panels are connected to the upper edges of the first and second foldback panels, respectively, and extend upwardly therefrom. These gable rib panels are also connected to each other at a common line, and comprise lips of the pouring spout from which the container contents are discharged.

Third and fourth gable rib panels are connected to the upper edges of the third and fourth foldback panels, respectively, and extend upwardly therefrom.

First and second roof rib panels are connected to the upper edges of the first and second roof panels, respectively, and extend upwardly 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 fiLst and second roof rib panels, respectively, and extend upwardly therefrom.

At least one stiffening or reinforcement fillet 25 overlays a portion of, and is bonded to, the inner surface of at least one of the following pouring spout panels: first gable rib panel, (ii) second gable rib panel, (iii) first roof rib panel, (iv) second roof rib panel, first triangular end panel, (vi) first foldback panel, (vii) second foldback panol, (viii) first wing panel, and (ix) second wing panel.

ri i D 3 O d 9 i) D i) F i j -7- The fillet comprises a strip of material resistant to deleterious effects of Ithe conventional carton sealing process, i.e. it will not melt, or otherwise degrade at the temperature and pressure of the sealing process, and a layer of adhesive attached to one side of the strip. The layer of adhesive adheres to the inner surface of at least one of the above panel(s), strongly bonding one side of the strip to the panel or panels. The layer of adhesive is preferably adapted to be partially extruded from the fillet during the carton sealing process, forming a bead of extruded adhesive along the edge of the strip. This adhesive bead effectively bonds opposing pouring spout panels together with the exposed portions of the rib panels which become thermally bonded, provides hermetic seal. This boad, however, may be disrupted without tearing, hurkling ot rlelamination of the panels.

The fillet extenlds along a major portion of the force transmission line between the site where the opening force is applied and the intersection of the panels which receive the opening fae. The fillet strengthens the panel member to which it is bonded, so that the resistance of the panel member to hnding ort buckling increasers, and gre ater opening forces are tannsmittodl to the spout tip.

Simultaneously, the fillet controls the force required to break the hermetic seal between panel members, so that the required opening force is less than the force which will buckle or delaminate the panels. The sealing force in controlled by: controlling the area and specific locations of the panels which will be subject to thermoplastic heat---sealing, controlling the arihesion between the resistant strip and both panels, and (r) controlling the thickness of tho adhesive layr of the fillet for optional extrusion from the fillet, to adhesively join opposing panets irn the pouring spout. In opening the gable-top container from the sealed condition, the force required is I imi tec vill tear, delaminate, or cri to a value below that which imple the pouring spout panels.

I

BriefDescriptno th Daing Figure I is a perspective view of the upper end of a closed container formed from a blank according to one embodiment of the p,:esenit invention, Figure 2 is a perspectiv e vii:.- of the container end of Figure 1 with a partially opened rib.

Figure "I is a perspective view of the container end of Figure I with its sealed Lib fully open and the spout panels in the closed position.

Figure 4 is a plan view of an embodliment of the container blank Laccording to the? invention, Figure 5 is a pe.rspective view of a portion of a reinforcemnetflt attached to a conta-,inelr panel according to the pvesent invention, che cross-section of the fillet and pnl are oxpandeod to show the laminar construction, Itt 88 I 8 I 8 ItO II I I I 0 8 Figure 6 is a cross-sectional view throuqh the closed upper closute along lineo 6-6 of Figutre I, Figure 7 is a persperctive view of the upper portion of a gable--top container fotmod from one ombodliment, of a blank according to the ptrsent invention, A pot tion of the containper in- cut away Ln view panel members, he-low the roof and roof rib paineIs Figures, 8 t'hrotigh 12 are plan views of the interior face of various embodiments of the preseont invention, Do-tiled Do scti~tlon Referring now to the drawingsq, the invention depicted with reference to a gable-top container in which the Invention is incocporotped. A qable-top container Is formed from a blank of poperboitr(d or other uIbe material coated on the inner plonar surfaco, or on both the inner aid outer suirfaces with a Thermoplantic material, T~he -9container blank is adapted to be erected 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 those panels are at an elevated temperature. Other alternative sealing processes may also be utilizod.

FIG. 1 shows a typical container 1 in a closed, sealed condition as for storage of beverages and 'he like.

The container is self-sustaining in shape aind is hermetic Ily sealed, Containecr I is comprised of a series of panels, including a container body having foutr body panels Front body panul 4 and second sidu body panel 5 are shown in FIG3. 1, while reari body panel 2 and first side body panel 3, not shown, oppose panels 4 and 5, respectively, forming a container of rectangular cross-.section, Usually, the cross-section is square The bottomothcntir1 is closed- First roof panel 28 Is connecteod to the upper edge of first side panel 3. Second roof panel 30 is connected to the uppPE edgel of second stde lianel 5. W1hen the container ir in the os c- onritinn, the rneof panels 28 and 30 convi-tql upwatLdly to fotm a gabile roo~f construction. Roof rib pane 1 54 it- attached Lo roif pilnol and extends: upwarcdly therofi em, Likewise', upper Lt) 2$ panel 55 is attachied to roof rib panel 54 and extends upwardly therefrom, Vir;, t trianqiular end panel 29 is connected the upper edge of tho front, body panel 4. when the oontainer is closed, end panel 29 is foldeid iuder the gable rolof formed by the two toof panels, Also s;hown (Ite. firt roof wing pancl 40 and se(rcn roof wing panel 13 'The, rnnf "Ane-1 panels 40 and 43 are suhpaneln of Loof panols 20 Ind, respective-ly, A\ second triangular end panel,, niot thown in this fiqlure, is usually adapted to remain folded undler thr.e gable roof, uinlecss it is desired to open hoth gaible ends of the contaner.

FIG. 2 ahowsi the contalnor of FIG. I 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 seal between the inner surfEace~s of 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 edge of foldback panels 41 and 42, and extend upwardly therefrom, FIG. 3 shows the container at the point where foldback panels 41 and 142 have been pushed backward about degrees from their sealed position, These panels are roughly triangular in shape, each having one edge denfinled is by scoreline 35 or 36, whr~!'e ~Hiny are attached to a latoral edge of first ttiangutat end panel 29, First and secind gable rib panels 30 and S2 act as lips of the pnuring spout, and meet at a mimon gabl rib score line 51, The upper tecminus SlA of the common rib score lino a t t heF f r re edge 53 of the pouring lip) comptises the tip of the pouting spout, First and spcond upper rib pacnols 49 and 59 extend upwardly from the first and second Loof rib panols 48 and 54 to a level higher than the free upper edqte 53 of giile rib Pa1TQ1$ 50 and 514, To complete, the unseating andI opening~ of Container 1, foldhack panels 41 anid, 42 ate puhed 1,watrrl beyond the position shown in Ml.~ 3. The roof rib panels and upper rib panels will. fold alonq foidline 57, The blank may or may not be srcored at thit looation, The gable rib panelsn ato slightly I onqer than the roof- rib panels, Trhus, after tihe panels ate, folded backward, a subsequont forward and In'war oeeto i panels 40 aind 43 transmifts openingq forces inl a togglo-.like action along the wing panel-. and gable rib pannIls $0 and toward the common lile- $1 betwoen the grible rib panels. A component of these forces ex~tends outward and upward from line 51 and from gable ocore lines 35 and 36 to pull thle Ak gable rib panels 50 and 52 away from roof rib panels 54 and 48, the latter not visible in FIG. 3, and to pull foldhack panels 41 and 42 away from roof wing panels 40 and 43, Likewise, triangular end panel 29 is forced outward, and the distended panels creaite a pouring spout. The variouts score lines delineating the paneols act as hinges for the panels as they are unEnldpd, The force reciuiired 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 I-Lcking to occur may be described as: where: C 9.87 for hinged endrs, E modulus of elasticity of heam.

I =moment of inortia of the beam, I =bh /12 whereo b width an h thirknenn oif the, beam, and L lengjth of I-he hedmii, Analys is of the open inq fo rr'e is vninpi e, in qr'ne rml however~, the gable rib pnnnels, Eoldibaek panels, and roof rib panels must he relativoly stiff to prtvont the t),itils from crumpling, and to transmit the a'ipliod opening forcors to common line 51. The, sealing forces which bond the rablo rib pa-;nels to the1 LOOf rib panelc are pref orably only ns high as required to maintain the hermotir .npal, Excessnive bonding forces will require qtteater rtiffnoso Hn the rqlrut panels to prevent qtumtplinq of HeP pnels durinq the opening procesa 4 Certain fpoturoen of this, invention will ptodiul a liquid-proof spout -eal which is oasily openied withoutL tearing, delamination, or bufeklinqr of thn ,4pout panel Mombe rs, These0 foatures, underlie the, spout panol momniI-el in VIG. 3, and ore tnot Vitsible, in thjat tiqure.Ths features includo one or miore fillets .96, shown in rI.4 and described in refetonco to the remaindqr of thoe fipuALOS.

-12- 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, and it is coated with a thermoplastic such as polyethylene.

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

The central portion of blank 1A comprises four body panels 2, 3, 4, and 5, having their lower edges along bottom score line 13, and thejir 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, Vectical score lines 7, 8 and 9 transect The blank to define the lateral edges of the body panel 2, 3, 4 and and other panels above the body panels. These and other score lines are not necessarily straight, but may be 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 oE another body member 2 by the container sealing process. Bottom closure means 26 is shown as a group of bottom closure panels 14 through 21 attached to the body members along bottom score line 13, and extending downward therefrom, Bottom closure score lines 22 through 25 enahle bottom closure panels 14, 16, and 18-21 to be folded under closure panels 15 and 17 and sealed to provide a leakproof container bottom, Such a closure means is well-known in the a:t. A separately formed structure may alternatively be used to close the bottom of the container. In fa,:t, any closure means which zestults in a satisfactorily tight seal may be used.

The gable top of the container is formed from a 5845/5 ml 4 0 I 0 4 -13series 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 are oppositely disposed and when erected, converge upwardly to meet along score line 44 to form a gable roof. Connected to the up-:r edge of the front panel 4 is a first substantially triangular end 'janel 29 whose two lateral edges 35 and 36 formed by score lines extend upwardly to score line 44. Similarly, second triangular end panel 27 is connected to the upper edge of back panel 2, and has lattitl edges 32 and 33 which extend upwardly to score line 44, On each side of triangular end panel 29 is a foldback panel. First foldback panel dl is connected to 15 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 14 as its upper edge.

Similarly, third and fourth foldback panels 39 and 38 are connected to triangular end panel 27 :long lateral edges 31 and 32, respectively. The third foldback panel 39 is attached to the first coof panel 28 along score 25 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 45, 46, 50 and 52, respectively. Similarly, attached to the upper edge of first and second roof panels 28 and ale first and second roof rib panels 48 and 54, respectively. First and secrind gable rib panels 50 and 52 are connected to each other at a common score line 51, and P 'P i~ ;i -14third and fourth gable rib panels 46 and 45 are connected toeach 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 roof rib panel 48 at score line 8, and second gable rib panel 52 is connected to second roof rib panel 54 at score line 9.

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 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 are more or less coextensive with the adjacent foldhack o ao panel when the erected container is closed.

0 A first upper rib panel 49 is connected to the upper edge of the fiist roof rib panel 48, Likewise, a second upper rib panel 55 is connected to the upper edge of the 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 o 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 IA 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 S* 30 delineation of the various panels, score lines are shown in 0 a the drawings on either or both of the inner and outer surfaces of the blank and container.

In the embodiment shown in FIG. 4, two ,tiffening 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 illustrated in an enlarged perspective view in SFIG. 4, each fillet 56 comprises a strip 66 of material resistant to the container sealing process, and a layer 72 of adhesive. This adhesive layer 72 is attached to a first planar surface 67 of strip 66 and to the inner thermoplastic surface 62 of one or more of the first gable rib panel 50, (ii) the second gable rib panel 52, (iii) the first roof rib panel 48, and (iv) the second roof rib panel 54, the first triangular end panel, (vi) the first fold back panel, (vii) the second fold back panel, (viii) the first wing pail, and (ix) the seccnd wing panel.

The strip 66 of material is thus sealed to the thermoplastic inner surface 62 of one or more of these panels.

ola Strip 66 may be formed from any solid material which is resistant to any deleterious effect of the container sealing process, and is sufficiently rigid so Schat, together with adhesive layer 72, it provides sufficient strength to reinforce the panel to achieve the .necessary stiffness. Thus, the bond strength between the adhesive-free surface 68 of strip 66 to the thermoplastic coating must be significantly less than the bond strength a° between the strip 66 and the adhesive layer 72, or between °o 25 the adhesive layer 72 and the strip 66. Furthetmore, strip 66 must not melt, extrude, or otherwise degrade at the temperature and pressure conditions of the container sealing process. Of course, a container sealing process of significant compression of the panels at an elevated f% 30 temperature may tend to increase the area of intimate Soo contact and relieve elastic stresses, causing adhesive of strip 66 to the thermoplastic inner surface 62. The adhesive strength of this pressure-produced bond will be significantly less than the adhesive strength of the adhesive layer 72, however.

Material such as metallic foil, polyester film, polycarbonate film are examples of strip materials which I I -16are unaffected by the temperatures used for sealing panels coated with polyethylene. Such thermoplastic coatings are typically sealed at temperatures of 250 to 400°F (81 and 205 0

C).

The material of the strip may also be constructed from unoriented polypropylene, 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 and specifically polyester. Specifically, unoriented polypropylene has a lower modulus of elasticity than polyester as low as 0.2 x 106psl). Therefore, a more compliant strip may be constructed which is better able to o conform to the scorelines between the pouring spout panels.

o Thus, a notch, such as is shown in Figures 9, 10 and 12 and discussed hereinafter, is not required. This simplifies the process of positioning and aligning the fillet on the 20 panels. The optimum temperature range per bonding the unoriented polypropylene strip is 260' 3201F. Unoriented polypropylene is the preferred material for the strip in o that it is dimensionally stable, even when subjected to the *elevated temperatures and pressures experienced when a oa 25 container is sealed, Oriented polypropylene, although having increased tensive strength, has a tendency to return to its unoriented state when exposed to temperatures 180'-200'F) below the sealing temperatures. This distortion of oriented polypropylene results in buckling o 30 and separation of the polypropylene from a mounting S surface.

The strip 66 and adhesive layer 72 may be preformed as a tape which is applied by machine to the blank IA.

For hermetic sealing containers, the modulus of elasticity of strip 66 may be as low as 0.2 x 10" psi (1.4 -17x 108 kg/m 2 but preferably for materials other than polypropylene is at least 0.4 x 106 psi (2.8 x 108 kg/m 2 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: E 2>E I(h~ where: E modulus of elasticity of panel.

E modulus of elasticity of panel fillet.

h thickness of panel.

h thickness of panel fillet, It is preferred that E, he greater than 0.2 x 10' pounrds per square inch (1.406 x 10" kg per square meter) to provide the desired stiffness.

The layer 72 is 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 a during the first sealing process, a portion of the adhesive of layet 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 containc-r. The adhesive used may be sealable by pressure, heat, or other process.

FIG. 6 is an enlarged cross-sectional view through the rib portion of a container formed from this invention, showing the panel members and fillet exaggerated S 30 in thickness for the sake of clarity. It is understood So that all of the panel members shown include a thermoplastic coating on at least the inner surfaces, and preferably on both the inner and outer surfaces. Additionally, the panel members may include a film or foil of gas-impermeable material such as aluminum, overcovered by the thermoplastic coating.

iji_ I -18- First and second roof rib panels 48 and 54 Soverlie first and second gable rib panels 50 and 52. The gable rib panels are separated from foldback panels 41 and 42 by scorelines 44, and the roof rib panels are likewise separated from roof wing panels 40 and 43 by scorelines 44.

Upper rib panels 49 and 55 are separated by score lines and 61 from the roof rib panels 48 and 54, and extend upwardly therefrom. Each of the panels shown in the figure includes a coating of thermoplastic on at least the inner surface. Stiffening fillet 56 is shown attached to the inner face of gable rib panels 50 and 52, and to an upper portion of foldback panels 41 and 42. The fillet includes resistant strip 66 and adhesive layer 72.

Fillet 56 may comprises a tape having a relatively thick backing or strip 66 of a stiff material whose bond to the thermoplastic surface of the panels is s weaker than its bond to adhesive layer 72. The adhesive layer 72 may be thermoplastic in natute, but preferably is 4, a pressure-sensitive adhesive, The latter affords easier S 20 positioning during application to the blank 1A, and does o a not require the application of heat for positioning.

However, the thermal carton sealing process has been found 0 to significantly enhance the sealing strength of the pressure-sensitive adhesives (PSA's) which were tested.

1o '0 25 Typical pressure sensitive adhesives can be formed into a 1 stable thick layers at room temperature, and will readily o extrude at the temperatures and pressures used to thermally seal polyethylene. Thus, when an extruded bead of adhesive 0 is desired, PSA's appear to work well.

oa 30 In FIG. 6, the container contents occupy the on space between panel 40 and panel 41, and the space between panel 42 and panel 43.

When the first sealing process is thermal in nature, the upper rib panels, the gable rib panels, and the roof rib panels are heated to the softening or melting point of the thermoplastic coating, and compressed together as shown in FIG. 6. The upper rib panels are bonded on i I ljF I1 I -19- 01 0) 0 0 0 (00000 0 01 (0 0( (0 0) 40 0i) 00 their inner surfaces at interface 69, and gable rib panels S50 and 52 are preferably mutually bonded on their outer surfaces at interface A further sealing feature may be produced if desired. A thick layer 72 of an extrudable adhesive may be used in the fillet. Compression at an elevated temperature during the carton sealing process extrudes the adhesive from between the gable rib panels and strip 66, and the extruded bead 79 of adhesive bonds overlying panels 50 and 52 just above the upper edge 75 of strip 66. A similar extrusion of adhesive is produced along the lateral edges of strip 66 as well, both where the gable rib panels and roof rib panels ate joined, and along the exposed portion of the common gable rib score line. A hermetic seal is achieved where the adhesive extrudes, even when the head of extruded adhesive is minimal. The quantity of extruded adhesive may be varied by controlling the type of adhesive, the thickness of the adhesive layer, and the temperature and pressure of the carton sealing process. The quantity of extruded adhesive may be controlled to fill the small channels 73 or channel 74 which typically develop along the free upper edge 53 of the gable rib panels.

Furthermore, the space at the tip of the pouring spout, that is, the space between common line 51 and the corresponding line 47 of the third and fourth gable rib panels, usually not securely sealed in the prior art by the first sealing process, may also be controllably filled with a bead of extruded adhesive during the carton sealing process to provide an aseptic or essentially hermetic seal.

30 This seal is especially enhanced by features to be later described.

Because the bead bon kg the gable rib panels to the roof rib panels is relatively narrow, the seal may be broken with minimal force to open the spout. The adhesion of strip 66 to the container panel should preferably produce a peel strength greater than 50 tz. per inch of width (612 grams per cm. width) at room temperature, so 0 o a Ai

IA

that the fillet will remain an integral part of the panel to which it is attached, both before and after the spout panels are unsealed and unfolded. The fillet may he adhesively attached to at least one of the pouring spout panels listed above, depending upon what is desired for the particular application. Fillets adhered to the roof rib panels are somewhat less effective at transferring the opening forces than fillets adhered to the gable rib panels. However, the concomitant reduction in required opening force enables fillets on the roof rib panels to transfer the required forces.

In this invention, the thickness of adhesive layer 72 is considerably greater than would be required for merely bonding strip 66 to a panel. For example, while the latter may be attained with a monomolecular layer of adhesive, this invention generally requires an adhesive layer exceeding 0.001 inch (0.0025 cm) in thickness for achieving desired additional stiffness and leakproof hermetic sealing. An adhesive layer of about 0.002 inch (0.005 cm) has proven optimal for certain pressure sensitive adhesives used to seal polyethylene coated containers. With other adhesiv.s, a thickness of up to 0.004 inch (0.0102 cm) may be used. However, in 2. .conjunction with a strip constructed of unoriented polypropylene, an adhesive layer of approximately 0.003 inches (0.008cm) has been found to be preferred.

FIG. 7 shows a gable-top container 1 formed from the blank of FIG. 4 and sealed according to the container sealing process, and subsequently opened from the closed and sealed condition. Second roof panel 30 and first roof 0 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 ,.anels and 46. When the container is closed, common scorellne 47 between the third and fourth gable rib panels is somewhat spaced from common scoreline 51. The void between those -21scorelines is a vertical channel which when filled with adhesive will prevent leakage. First and second upper rib panels 19 and 55 are joined by the container sealing process. The spout panels of the rib structure are shown to have been operned by first breaking the seal between the upper r' panels 49 and 55, and then breaking the seal between gable rib panels 50, 52 and roof rib panels 48, 54.

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

Stiffening fillet 55 is shown at the inside of the pouring spout, overlying and attached to a portion of the inside surface of the first gable rib panel 50 and the second gable rib panel 52, not visible in tnis view.

Conforming to a preferred embodiment, the fillet 56 also extends downward over scoreline 44 to overcover a portion of foldback panels 41 and 42, The advantages of such extension will be later describd., Fillet 56 is shown as spaced from roof winq panel 40 and roof rib panel 48 to form side spac'ing 59, and also spaced from the free upper edge 53 of gable rib panel 50 to form lip spacing 58. During the first sealing process, a portion of the ad,-sive is extruded from the adhesive layer of the fillet 56 into channels 73, previously described, resulting from spacings 58 and 59, to effectively seal these areas from leakage. The surface 68 of the fillet 56 which has no adhesive layer is, of course, in contact with roof rib panels 48 and 54 when the carton is scaled, Fillet 56, being resistant to the container sealing process, does not strongly adhete lo the thermoplastic surfaced roof rib panels, although the pressures and temperatures typical of the first sealing process minimally result in a close conformity of their surfaces which is subsequently maintained by the tight seal of the rib panel members, The seal between surface 68 and the overlying panel, though not as tenacious as that of the opposite adhesive coated side of the strip, nevertheless prevents L. i i -22fluid leakage. A hermetic seal results from the thermoplastic heat seal between exposed portions of the gable rib panels and opposing roof rib panels, or a bead of adhesive extruded from beneath the strip, to be described later, or a combination of the two.

FIGS. 8 through 12 show a portion of the blank lA, including those panels which become the pouring spout.

These figures depict various embodiments of fillet 56 in terms of the particular panel area or areas covered thereby.

In FIG. 8, a single fillet 56 overcovers all or a portion of both gable rib panels 50 and 52. The uppermost edge of fillet 56 may be generally continuous with the upper free edge 53 of the gable rib panels, but is preferably spaced therefrom by less than 0,15 inches (0.38 cm) when a bead of extruded adhesive is to be a part of a hermetic seal of the container. When the uppermost edge of fillet 56 is lower than free edge 53 by more than 0.3 inches (0.76 cm), an excessive sealing area for the thermoplastic carton sealing process may result. This Sa produces a strong seal which may require an excessive opening force to break the seal Also extruded adhesive may not reach and fill the narrow channel which generally forms above the edge 53. The narrow spacing 58 provides 25 space which in some cases is desirably filled with extruded adhesive, minimizing the thermoplastic-to-thermoplastic seal area and substituting an extruded adhesive seal. The relatively narrow band of adhesive provides a tight seal between the gable rib and root rib panels which is nevertheless openable with an acceptable opening force.

S* When the fillet or fillets 56 are adhesively attached to both gable rib panels 50 and 52, and the uppermost edge of the fillets extend above the upper free edge 53 of the gable rib panels, the heat sealing process will bond the exposed portions of the strips 66 on each gable rib panel to each other. In addition, the amount of adhesive extruded into the space above the strips 66 may be -it -23decreased. Therefore, it is generally desirable to limit such upward extension of the fillet or fillets above the gable rib panels 50 and 52 to not more than 0.15 inches (0.38 cm).

Each end of the fillet 56 may he 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 fillet 56 and the roof rib panels is not less than 0.01W, where W is the length of the first or second gable rib or 52, The maximum spacing 59 is controlled by the length of fillet which will provide the desired stiffness to the panels, and may be as great as 0.6W, where W is as defined above.

FIG. 9 illustrates a fillet 56 overcovering a portion of the gable rib panels 50 and 52, and extending downwardly to overlie in bonded relationship a portion of the first and second foldback panels 41 and 42, The fillet also optionally overlies the upper portion of f.irt triangular end panel 29. The advantage of this downward extension 71 is evident when the container sealing process is one which affects the bonding strength of the fillet adhesive layer. 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 sealing temperatute is difficult to accurately control, and if the fillet adhesive softens excessively, the Eillet strip may slide 30 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 much less affected because of the lower temperature, and will maintain the original position of the fillet. The high adhesion of adhesive layer 72 is regained upon cooling.

The figure also shows the fillet as overlying score line apex 64 at the top of triangular end panel 29.

-24it has been discovered that enhanced sealing results from cutting, notching or slotting the strip 66 where it overcovers the common gable rib scoreline 51, especially the portion of the common line just helow its upper terminus 5lA. Thus, strip 66 may include a cut extending downwardly from the upper edge of the strip, along at least a portion of the common line 51. This enables adhesive from layer 72 and/or meltedi thermoplastic polyethylene to extrude through the cut, notch or slot to contact the opposite gable rib panels 45 and 46 at common scoreline 47, and bond thereto. This difficult-to-seal site is thus effectively sealed.

Fillet 56 is further shown in FIG, 9 with a notch extending downwardly from the upper edge of the strip, along the common line 51 between the first gable rib panel and the second gablo rib panol 592, The notch may optionally extend downwardly to expose aplex 64, (is further shown in VIG. 10, or may extend downward as a slot through the fillet to divide it into two fillets, When-t a notch or slot exposes the common line 51, thc' odqr' of the fillet strip may be separated ftom a portion of the common line by up to 023 inches (0,76 cm). When there are two fillets, each overcover-ing a portion of one of the gable tit) panels, the maximum spacing of each fillet from common line 51 is 2$ also 0,31 inches (0,76 cmfl, A groAter sparing restiults in insucdient stiffening of tho panels in the vicinity of common line 51, awd in adldition, the container nepaling process will bond an exes~poL tion of exposed cpoi rib panel along lino 51 to tht, r'nrrer~poclinq ro i ae with a the rmoplas ti c- to- tho.rmop1astic bond, such a LIqht bond at the point where the opening forces first aIct tro unseal the spout Make such unseling dif-ficult, Groatet force is required, and with .102n reinforcemont, th, end ot the spout may caumple. Whon cn aperLe7 xoo h ap~ex 64, as In FIG. 1.0, the edge 63 of the fillet in preferably spaced from the apex by less than 0.3 Inches (0-76 cm).

Optionally, the shape of fjj~ rj Ic,: (J that scorelines 35 and 36 are not covE :1z i tie forces required to open the seal ave fttrthrr x,'y )icd by so doing.

As shown in FIG, 11, a further V comprises placement of f illets on one or L 4'h of the roof rib panels 48 and 54, Tim sipe and shape olf fhe liets are such that when the seal is closed, the fi1_vt generally correspond in cnverage t~o thos :ip ir to The gable rib panels. 'jus, the uipper edqP 75 of eark fillet 56 is no more than 0, 3 inch (0,16 cm) f rom scorelinc. 61, and preferably with 0,15 Invih (0,38 cm) Lit--wi4e, it is preferred that fillet edges 77 ancl 78 ate, no more Vha n aboiut 0.3 Inche.& (0,76 cm) ftom commonn line 51 when the container spout; is a~rnled, This ensutres sealing of the space betwe'on common folcilinen 51 and 47, FIG. 12 illufctrator. an embodimont whereby fillets are attached to The inner Murfaes of both the gable rib panels and root rib panols, In this embodiment, it is imperative Thot the matotial from which the strips 66 aire made will not soften nt me]lt undor the container sealing conditions to fuse( the correspondingj fillets together in a strong bond, A limitoed dereeo of sonlingJ is acceptahlo, and may even he preferred, The previous discussion regardling the desired, fillet Gizor, and covorcige also applies.

When appliedl to oi container hlank whivh inicludes8 a hermetic barrier, the contaiiner seal of this invention may be adopted to Vrovide a hermetically sealed container uinder variousi conditions of carCstook thickness and, strength as well aa containec size, EXAMPIL1 1 Comercalhermotically sealed 0.5 gollon (1-9 liter) gable-top conitainers wre manually opened. After folding back the Wing panol.&, simple totward, handl presisure on the root rib panels re.itltod in buckli~ng and distottlon -26of thA gable rib panels, without opening the tip of the spout at the common fold line. in all case-, insertion of a knife blade between the gable rib panels and roof rib panels oear the common fold line woas required to open ths spout.

Container blanks of the same matorial were sealed by hand, using a Liqvipak

T

model 010 hand sealer.

Attempts to open the containers produced th same as were obtained with the commercially sealed conta-;iners.

An applied force of 15 poivids-force (6.0 kg-force) resulted in tearing and buckling of the panels, without opening the spout.

The opening force recquired by a previously opened hermetically sealed carton was determined to be abut 2,6 pounds-force (1,2 kg-forceY, F'or the sake of comparisono a common milk carton opened fcom the sealed condition with an applied force of abo-t. 3,0 pound-force (1,36 krg-forco,), without tearing of tlhe spout panels. This carton is sealed only to the extent of preventing liquid leaks, and a hermetic barrier is not 2 provided, EXAMPLE 2 Several types of fillet were applied to polyethylene coated cardstLock for determining the effect mijpon panel stiffness and ease of containnr opening.

The container material was man, faotiirod by international Paper Compziny for hermetically skialed carons an coprised paperboard having an ,alumintim film bonded to the inside surface, and both sides then contd'd with thirmoplastic polyothylene, The typis of adhesive used in the fi Ilets included ethylc-ne-vinyl avetate (EVA) copolymner, (h) Medium dens~Ity polyethylene (rIDPE)e and (c a pressuce-sensltivo adhesive (PSA), The modulus of elasticity was determined by measuring the deflection cauised by a weight placed on the -27center of a simple beam formed from the cardstock.

Mea'surements 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 3

Y

where E modulus of elasticity.

f force applied, O.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), o 7 i -28- The results were as follows: Beam Material Cardstock (unreinforced) a Thickness 0.027 in.

(0.069 cm)

Y

Deflection 0.18 in.

(0.46 cm) Cardst ck with transverse scoreline.

0.027 in. 0.33 in.

(0.069 cm) (0.84 cm) reduced modulus) (f 10 g because of Cardstock with fillet of 0.004 in. (0,010 cm) polyester and 0.002 in (0.005 em) EVA adhesive (ScotchpakT" 26 tape) Cardstock with fillet of 0.002 in. (0,005 cm) polyester and 0.003 in.

(0.0075 cm) PSA E, Modulus, PSI(kg/cm 2 393,000 (2.76 x 108) 28,000 (0.2 x 108) 332,000 (2.33 x 390,000 (2,7 x 0.036 in.

(0.091 cm) 0.032 in, (0.079 cm) 0.090 in.

(0.23 cm) 0.12 in.

(0.30 cm) o 9; (3 0 (3 (3 (3 3 (3 0 Spout panels, 0.027 in 0.080 in. 885,000 not preflexed not prelexed (0.069 cm) (0.20 cm) (6.2 x 10 Spout panels, 0.027 in. 0.21 in. 337,000 preflexed (0.069 cm) (0.53 cm) (2.4 x 10 Polyester Film 400,000 (Literature Value) (2.8 x The results indicate that the modulus of elasticity is approximatoey the same, 0.4 x 10' psi (2.8 x 108 kg/m 2 for preflexed panels, either with or without the added fillet.

Buckling force were calculated from the data of Table 2 using -29- P i CEh'b/12L 2 where Pe t is the forward-directed force at which buckling will occur, lb-force; C is pi 2 E is the modulus of elasticity, approximately 0.4 x 10O 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 (buckle the spout tip) the unsealed spout of unreinforced cardstock was pounds (0.23 kg.), The force carried by both of the unreinforced 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 bond at the tip of the spout.

Reinforcement of the gable rib panels with a S0.002 inch (0.005 cm) thick polyester strip and 0,002 inch (0.005 cm) layer of PSA adhesive provided a higher calculated 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 rm) layer 62 of EVA adhesive provided a calculated availabl' force of 4.6-0.5 4.1 pounds (2.09 kg.) for breaking the bond at the spout tip. In this case, the net panel thickness was 0.036 incLes (0.142 cm). Thus, as a thicker, stiffer reinforcement strip is added, the applied forward-directed opening force available for opening the Sspout tip greatly increases.

Measurements we.e made of the force required to open a previously opened gable top hermetic sealing caLton, using a spring gauge. The average measured force of 2.4 pounds (1.09 kg,) included the force required to buckle the Sextreme tip of the unreinforced spout, that is, the common fold line of the gable rib panels. Thus, the calcula >d 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 the greater joint strength of a sealed spout will result in 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 wore opened without buckling or delamination of the panels.

The effects of several variables upon ease of opening were subjectively evaluated. Ease of opening was o enhanced by an increase in gable rib area covered by Sthe fillet, 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 apex where the end panel touches the common fold line, and a reduction of gable rib area which is permitted to thermally seal to the roof ribs.

EXAMPLE 3 Several types of adhesive tapes were evaluated for use as fillets for ease of positioning in the spout, adhesion to the gable rib panels, and opening characteristics. The last are a function both of the additional stiffness gained by the panels and the bonding o" o forces between the roof rib (or gable rib) panels and (a) the fillet strip, the exposed portion of the opposed o #o gable rib (or roof rib) panels, and the extruded adhesive, if present.

-31- The fillet configuration of FIG. 9 was utilized.

The notch 65 extended downwardly one half of the height of the gable ribs, and the fillet extended 1.0 inch (2.5 cm) below the score line 44 separating the gable rib panels and foldback panels 41 and 42.

The tapes included: Scotchpak 26: 0.004 inch (0.01 cm) polyester backing as the strip, with 0.002 inch (0.005 cm) EVA adhesive.

Scotchpak

T

48: 0.0005 inch (0.0012 cm) polyester backing with 0,004 inch (0.01 cm) MDPE adhesive.

ScotchtabTM: 0.002 inch (0.005 cm) polyester backing as the strip, with 0.002 inch 90.005 cm) PSA adhesive.

Scotchpak 26 with 0.003 inch (0.0075 cm) PSA adhesive applied over the EVA adhesive.

Polyester/PSA: 0.002 inch (0.005 cm polyester film backing as the strip, with 0.003 inch (0.0076 cm) co.

a PSA adhesive.

20 Control; No fillet.

o 0 The pressure-sensitive adhesive (PSA) used in this test was a typical rubber-resin adhesive, S The results of the tests were as follows: o Scotchpak" 26 with EVA adhesive was difficult to position for sealing, and required preliminary heat sealing to provide a good seal. The scaled carton spout opened a. easily without buckling or delamination.

Scotchpak" 48 with MDPE adhesive was difficult to position and required preliminary heat sealing.

Insufficient stiffness was added by the fillet to 0 consistently transfer the required opening forces to the S° spout tip. Scotch tab™ with PSA adhesive was easy to position, and required heat sealing to strongly bond to the panels. The se ,led carton spout opened easily without buckling or delamination.

I

-32- Scotchpak T 26 with PSA adhesive was easy to position, and heat-sealing provided a ood seal. The sealed spout opened easily without buckling or delamination.

The control gable top carton spout, heat-sealed according to the commercial process, could not be opened without buckling and delamination of the cardstock.

EXAMPLE 4 There are no standard tests for evaluating the seal integrity of "hermetically sealed" containers.

However, a dye penetration test was performed on "hermetically sealed" cartons both with and without a fillet attached to the gable rib panels. Several configurations of the fillet were tested. The dye comprised 1.2 grams of Rhodamine B in 600 grams of isopropyl alcohol. The dye solution was introduced into an inverted carton having its gable-top sealed, and held for 10 minutes. The solution was then p[.ouied out and the carton rinsed with water. The spout was opened and the degree of dye penetration into the seal area was noted, 0 Containers formed from blanks without the fillets of this invention and sealed conventionally to form "hermetic seals" could not be opened without directly applying force to the inside of the spout. Tearing and delamination resulted. All of the containers formed from blanks of this invention were easily opened without significant tearing or delamination of the spout panels. Little dye penetration was noted in any of the opened container spouts, but the penetration was greater in containers without the fillet or fillets.

While the present invention has been particularly set forth in terms of specific embodiments thereof, it will 2, be understood in view of the instant disclosure that numerous variations upon the invention are enabled to those skilled in the art, which variations yet reside within the scope of the present teaching. Accordingly, this invention -33is to be broadly construed, and 1 S' and spirit of the claims now appe ij imited only by the scope nded hereto.

I

0f 0 0 O 0 0I) EXAMPLE An unoriented polypropylene adhesive tape was evaluated as a stiffening filet in a one-half gallon gable top container blank, which was then heat sealed with a Liquipak Model 010 heat sealer.

The tape was applied to the inside of the spout flush to the spout edge. The fillet was one and one-half inches wide and three inches long and was centered on the spout tip. No notch was cut in the fillet.

The tape had a 0.0035 inch thick unoriented polypropylene backing and a 0.003 inch thick rubber/resin pressure sensitive adhesive.

The carton was opened in the normal manner and a spring gauge measured the opening force at 8.3 pounds. A similar carton without the fillet would have a force in excess of 12 pounds applied and would buckle and not open, The polypropylene softned and filled the gaps and channels in the spout. The polypropylene bonded sufficiently to the polyethylene coating on the carton at the back of the spout to provide a hermetic seal that was easily separated during the spout opening. The hermetic seal was determined by pouring an isopropyl alcohol dye solution into the carton and examining the gable joint for dye penetration. No dye pEnetration was observed.

EXAMPLE 6 An unorionted polypropylene adhesive tape was evaluated as a stiffening filet in a one-half gallon gable top container blank, which was then heat sealed with a Liquipu Model 010 heat sealeri The tape was applied to the inside of each side of the carton in line with the spout edge. The fillets were one-half of an inch wide and one-and-three-quartert. of an inch long.

P -34- The tape had a 0.0035 inch thick unoriented polypropylene backing and a 0.003 inch thick rubber/resin pressure sensitive adhesive.

The carton was opened in the normal manner and a spring gauge measured the opening force at 8.1 pounds. A similar carton without the fillet would have a force in excess of 12 pounds applied and would buckle and not open.

The polypropylene softned and filled the gaps and channels in the spout. The polypropylone bonded sufficiently to the polyethylcne coating on the carton at the back of the spout to provide a hermetic seal that was easily separated during the spout opening. The hermetic seal was determined by pouring an isopropyl alcohol dye solution into the carton and examining the gable joint for dye penetration. No dye penetration was observed,

Claims (5)

1. A sheet material blank for constructing a sealed gable-ton container, said blank being substantially rectangular and comprising a first upper portion, a central portion and a lower portion, each of said portions being Impressed with predetermined scorellnes so that upon sequential folding along said scorellnes said upper portion might form the roof, said central portion the wall(s) and 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 container sealing process having a modulus of elasticity of at least 0.2 x 106 psi, and a 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 thersto,

2. The blank according to claim 1 further characterized in that said layer of adhesive is adapted to be partially extruded from said fillet during said container sealing process to form a bead of extruded adhesive along upper and lateral edges of said at least one said panel to further seal opposing panels together,

3. The blank according to claim 1 further characterized In that said fillet comprises a tape having pre-applied layer of pressure-sensitive adhesive on one side thereof.

4. The blank according to claim 3 further characterized In that the adhesion peel strength of said tape to the thermoplastic surfaced sheet material of said one of said pouring spout panels to which said fillet is adhered equals or exceeds 50 ounces force per Inch (612 gram-force per cm., of tape width. The blank according tc claim 1 further characterized In that said fillet comprises two\ strips of said resistant material, each said strip overlying and bonded to a portion of a respective panel of said at lodst two panels. 0 LF/1223h ~i 36 .T The blank according to claim 1 further characterized in that said resistant material comprises one'of metallic foil, polyester film, polycarbonate film and unoriented polypropylene,

7. A hermetically sealed gable-top container formed from a blank as defined in any one of the preceding claims, A- A 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 to 7 of the accompanying drawings. DATED this THIRTIETH day of NOVEMBER 1990 Minnesota Mining and Manufacturing Company Patent Attorneys for the Applicant SPRUSON FERGUSON R 'II.jt"C3 clL1 223h