CA1314849C - Gable-top container - Google Patents

Abstract

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 layer 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 foldback 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 provides additional stiffness to the spout panels, enabling relatively high forces to be transferred to the spout tip where the opening forces act to open the container spout. The spout may be opened readily without significant tearing or delamination of the spout panels.

Description

-1- 131484q GABI.E:-TOP CONT/:~INER

Back~und of the Invention _ , _ _ _ 1. Field of the Invention This invention relates to packaging, and 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 li~uids. More particularly, this invention relates to a blank -from which the container is formed.

2. Descrl~_ion of the Prlor Art Containers for beverages such as milk, fruit lS juices, and drinks are conventionally constructed from blanks of thermoplastic coated paperboard. The most widely used of such containers have a rectangular cross-sectional body surmounted by a gable-top closure incorporating an extensible pouring spout. slanks from which the containers are constructed are divided into a plurality of panels which are adapted to form the walls and closure members.
The panels are formed and separated by score lines at which the blank is folded. Particular panels are intended to be joined together in a lapped arrangement in the completed container. Typically, those panels are pressed together and heated or exposed to high frequency radiation, to fuse the adjoinillg thermoplastic surfaces, forming a generally strong seal. To finally seal the filled container, two or more panels are finally joined and sealed to form a rib along the top edge of the roof panels. Exemplary of such container blanks are those shown in Alden U.S. Patent No.
2,750,095 and Wi]cox U.S. Patent No. 3,245,603.
Containers 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 the ~ -2- 1 31 ~849 , container are puched ol~twarcl and upward toward the rear of the container by thllmb pressure, breaking the seal bet~een the outside surfaces of the two lip pane]s, and hreaking the seal in the rib panels surmounting the roof above the 5 pouring spout. ~he gable edges are forced backward past the point at which the llp panels are joined, to nearly touch the rooE panels.
Second, the gable edges are pushed forward and inward. ~he second stage operling forces are communicated through spout panels to the tip of the pouring spout, breaking the seal between the ]ip 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 mode]s of gable-top containers, the panels comprising the lips, i.e., gable rib panels of the pouring spout were bonded to the underside of the roof panels. The resulting sealed spout was diEficult to open, generally requiring insertion of a tool behind the lips to separate them from the roof underside. The cardstock panels often tore or delaminated, producirlg an unsightly and unsanitary container. In those cases where an adhesive was applied to only those pane]s 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 provide a hermetic seal for an extended she]f 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 are bonded by heating the thermoplastic surface coatings to a softening or melting temperature, compressing the panels together and cooling. The use of thermopla.stic coatings or foil adds some stiEfness to t'ne panels, an~ the container is made resistant to wicking of liquids. ~lowever, the strong bonding of the lip panels results in buckling, tearing and delamination of the carclstock upon opening the seal. Thus, the spout is difficult to open, and the opened panels are unappealing in appearance.
Polyethylene has a low modulus oE elasticity, so the stiffness added hy the coating is minimal.
As used in the food packaging industey, the term hermetic refers to a container designed and intended to be secure against the entry of oxygen which degrades flavor and other ~ood properties. 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 wal] thickness is thus increased, resulting ;n larger channels where the edges of overlying panels have a stepped re]ationship in the gable rib area, increasing the chance for leakage.
Attempts to provide an easily opened spout seal have included (a) perforations in the spout panels which tear open to expose pouring lips, (b) i.mproved control of the sealing temperature, (c) the use of added scoreline patterns to concentrate the opening forces, and (d) the use oE anti-adhesion agents, i.e., abhesives, to eliminate the sealing between panels and thus reduce the required opening forces.
The use of perEorations in the spout pane!s has generally been unsatisfactory. Such perEorations produce a spout of reduced size, which requires special sealing operations. The perforations are considered by some to be a weak point in the carton, prone to develop leaks. This type 1 31 484q of carton spout requires externa] forces such as thumbnail pressure to open, ancd this procedure is considered unsanitary. ~rhe carton cannot be effectively closed, once opened, and shaking of the carton results in spillage.
Likewise, effo~ts to reduce temperature variations in the sealing process have not procluced a satisfactory hermetic sealing gable-top container. secause of narrow acceptable temperature range for obtaining the desired adhesion, sealing variations persist in spite of improved temperatuce control. riOreover, the required opening forces general:Ly exceed the pane] 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., ~.S. Patent No. 3,116,002. In this reference, a thin coating of a high molecular weight organo-silo~ane gum is applied to tile 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. ~bhesive agents disclosed include cellulose plastic laminated to polyethylene, the latter heat-bondable to the po]yethylene surface of the carclstock blank. The cellulose plastic adds insignificant reinforcing stiffness to the pouring lip because of its low modulus of elasticity.
The release properties of abhesives are generally affectecl 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 wall strength of the 1 3 1 484q 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 of paneled flexible material to stiffen the package material adjacent the sealed area to be opened. The result is a more reliable, consistently openable spout for gaininy access to the container contents. The container may be sealed to a leakproof or even a hermetically sealed condition if desired, yet is readily opened wi-th minimal force. The flexible material 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.
The invention provides a sheet material blank for constructing a sealed gable-top container with a thermoplastic inner surface coating responsive to a container sealing process, the blank including a container body having sides, a bottom and a top and an extensible pouring spout including a substantially triangular end panel connected to the container body top, first and second foldback panels, the first foldback panel connected to the container body top and to at least one lateral edge of the first triangular end panel, and the second foldback panel connected to the container body top and to the other lateral edge 1 31 ~849 of the triangular end panel, a first roof wing panel adjoining the first foldback panel and connected thereto, a second roof wing panel adjoining the second foldback panel and connected thereto, third and fourth Eoldback panels, the third foldback panel connected to the Eirst roof panel and to one lateral edge of the second triangular end panel and adapted to be connected to the second roof panel, and said fourth foldback panel connected to the other lateral edge of said second triangular end panel and connected to said second roof panel, first and second gable rib panels connected to upper edges of the first and second foldback panels, respectively, to extend upwardly therefrom, having upper edges and lateral edges, and connected to each other at a common line, third and fourth gable rib panels connected to upper edges of said third and fourth foldback panels, respectively, and to each other, Eirst and second roof rib panels connected to upper edges of the first and second roof panels, respectively, each of the roof rib panels connected at one side thereof to one of the first and second gable rib panels, first and second upper rib panels connected to upper edges of the first and second roof rib panels, respective].y, and pouring spout panels comprising said first triangular end panel, said first and second foldback panels, said first and second roof wing panels, and said first and second gable rib panels, the sheet material blank further comprising at least one stiffening fillet overlying a portion of and bonded to the inner surface of at least one of said pouring spout panels for simultaneously stiffening said at least one overlain pouring spout panel to transfer applied opening forces therealong for opening at a controlled low opening force, said fillet comprising:

~' ~ 1 31 4849 a strlp of material resistant to the temperature and pressure of said container sealing process, a first layer of adhesive attached to a first surface of said strip and to said inner surface of said at least one overlain pouring spout panel for bonding said strip thereto, and an adhesive web including a controlled release adhesive delaminably 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.
The invention also provides a hermetically sealed gable-top container for extended shelf life having a thermoplastic inner surface coating, said container including a container body having sides, a bottom and a top and an extensible pouring spout including a substantially triangular end panel connected to the container body top and extending upwardly therefrom, first and second foldback panels, the first foldback panel connected to the container body top and to one lateral edge of said first triangular end panel, and said second foldback panel connected to said container body top and to the other lateral edge of said first triangular end panel, a first roof wing panel adjoining said first foldback panel and connected thereto, a second roof wing panel adjoining said second foldback panel and connected thereto, third and fourth foldback panels, said third foldback panel connected to said first roof panel and to one lateral edge of said second triangular end panel, and said fourth foldback panel connected to the other lateral edge of said second triangular end panel and connected to said second roof panel, first and second ~' ---` 1314849 7a 60557-3402 gable rib panels connected to upper edges of said first and second foldback panels, respectively, and extending upwardly therefrom, and connected to each other at a common line, third and fourth gable rib panels connec-ted to upper edges of said third and fourth foldback panels, respectively, and to each other, first and second roof rib panels connected to upper edges of said first and second roof panels, respectively, each said roof rib panel connected at one side thereof to one of said first and second gable rib panels, first and second upper rib panels connected to the upper edges of said first and second roof rib panels, respectively, and pouring spout panels comprising said first triangular end panel, said first and second foldback panels, said first and second roof wing panels, and said first and second gable rib panels, the container further comprising at least one sti:Efening fillet disposed between and adhesively bonded to at least one of said pouring spout panels for stif:Eening the at least one overlain pouring spout panel to transfer applied opening forces therealong and for controlling the force required to open the container, said fillet comprising: a strip of material constructed of material resistant to the temperature and pressure of a container sealing process; a first layer of adhesive disposed between a first surface of said strip of material and said at least one pouring spout panel and adhesively joining said strip thereto; and an adhesive web including a controlled release adhesive delaminably bonded to the opposite surface of said strip and bonded to an opposed panel, wherein said opening forces transmitted along said strip delaminate said adhesive web from said opposite surface of said strip.

. .~

1 31 484q 7b 60557-3402 The adhesive web is thus delaminable from the surface oE
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 required to delarninate the web from the strip is precisely controllable because the adhesive properties as well as interfacial area may 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 ]ow opening force, combined with the added stiffening from the strip and strong adhesive, prevents buckling or delamination of the gable rib panels which otherwise occur ~uring opening of s~ch 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 delaminate, tear or buckle as is common in the prior art 1~ gable-top containers.
he adhesive web may be a layer of a controlled release adhesive which delaminably bonds to the strip su~face 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 adhesive and second, a thermoplastic ribbon to which the delaminable adhesive is bonded. The ribbon melts or softens during the container sealing operation and becomes strongly fused to the thermoplastic coating of the container panels. Thus, the thermoplastic ribbon also acts as an adhesive.

Brief Description of the Dr _ ings Figure 1 is a perspective view of the u~per end oE a closed container formed from a blank according to one embodiment of the present invention.
Figure 2 is a perspective view of the container end of Figure 1 with a partially opened rib.

9 13148~q Fiqure 3 is a perspecti~Je vie/ of the container end of Figure 1 with its sealed rib fully open and the spout panels in the closed position.
Figure ~ is a plan view of an embodiment of the container blank acco~ding to the invention.
Figure 5 is a perspective view of the upper portion of a gable-top container formed from one embodiment of a blank acording to the present inventi.on, sealed, and subsequently opened. A portion of the container is cut away to view panel members below the roof and roof rib panels;
Figure 6A is a sectional view along line 6-6 of Figure 3, showing the gable rib panel, roof rib panel and fillet, prior to the container .sealing proces.s;
Figure 6s is a sectional view along line 6-6 of Figure 3, showing the gable rib panel, roof rib panel and fillet in the seal.ed condition;
Figure 6C is a sectional view along line 6-6 of Figure 3, showing the gable rib panel, roof rib panel and ~0 fillet following opening of the spout seal;
Figure 7A is a sectional view along line 6-6 of Figure 3, showing the gable rib panel, roof rib panel and fillet of a further embodiment, prior to the container sealing process;
Figure 7s ls a sectlonal view along line 6-6 of Figure 3, showing the gable rib panel, roof rib panel and fillet of Figure 7A in the sealed condition;
Figure 7C is a sectional view along line 6-6 of Figure 3, showing the gable rib panel, roof rib paneJ. and fillet of Figure 7A following opening of the spout seal;
and Figures 8 through 12 are plan views of the interior face of various emhodiments of the present invention.

-lo- 1 ~ 1 4849 Detailed Description _ _ _ Referring now to the drawings, the invention is clepicted 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, or on both the inner and outer surfaces with a thermoplastic material. The container blank is adapted to be erected and have certain panels sealed to each other by a container sealing process.
Typically, the sèaling 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 utili~ec].
FIG. 1 shows a typical container 1 in a closed, sealed condition as for storage of ~everages and the like.
The container is self-sustaining in shape and may be hermetically sealed.
~ ontainer 1 is comprised of a series of panels, including a container body having four body panels 2-5.
Front body panel 4 and second side body panel 5 are shown in FIG. 1, while rear 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. Tlle bottom of the container l is closed. First roof panel 2~ is connected to the upper edge of first side panel 3. Second roof panel 30 is connected to the upper edge of second side panel 5. When the container is in the closed conclition, the roof panels 28 and 30 converge upwardly to form a gable roof construction. Second roof rib panel 5~ is attached 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.

13148~9 First triangular end panel 29 is connected to t'ne upper edge of the front hody panel 4. ~7hen the container is closed, end panel 29 is folded under the gable 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 oE roof panels 28 and 30, respectively. A second triangular end panel, not shown in this figure, is usually adapted to remain folded under the opposite gable roo~, 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 ~2 and overlapping roof wing panels 40 and 43 are typically pushed outward and backward with thumh pressure to break the seal between the inner surfaces of the first and second upper rib panels q9 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 42 have been pushed backward about 90 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 rih panels 50 and 52 act as lips of the pouring spout, and meet at a common gable rib score line 51. The upper term;nus 51A of the common rib score line at the free 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 54 to a level higher than the free upper edge 53 of gable rib panels 50 and 52.

-12- 131484q , .,. .~

To complete the unsealing and opening of container 1, foldback panels ~1 and 42 are pushed hackwar~1 beyond the position sho~n in FIG. 3. ~he 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 ~3 transmits opening forces in a toggle-like action along the wing panels and gable rib panels 50 and 52 toward the common line 51 between the gable rib panels. A
component of these ~orces extends outward and upward from line Sl 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 ~isible in FIG. 3, and to pull foldback panels ~1 and 42 away from roof wing panels 40 and 43.
Likewise, triangular end panel 29 is forced outward, and the distended panels create a pouring spout. The various score lines delineating the panels act as hinges for the 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 Eorce P required for buckling to occur may be described as:

P = CEI/(L ) where: C = (pi)2 = 9.87 for hinged ends.
E = modulus of elasticity of beam.
I = moment of inertia of the beam.
= bh3/12 where b = width and h = thickness of the beam.
and L = length of the beam.
Analysis of the opening forces is complex. In general -13- 1 31 4 8 4 q , .\ , however, the gable rib p~ne]s, foldback panels, and roof rib panels must be relatively stiff to prevent the panels ~rom crumpling, and transmit the applied opening forces to common line 51. The sealiny 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 transferred to the spout tip, necessitating greater stiffness in the spout panels to prevent crump]ing of the panels during the openin~ process.
Certain features of this invention prodnce 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 and described in reference to the remainder of the figures.
FIG. 4 illustrates an exemplary flat sheet material blank of thls invention for constructing a gable~top container. The inner surface or face is shown, and 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 lA into a plurality of panels and suh-panels which are used as walls of the container and its closure parts when the container is erected.
The central portion of blank lA comprises four body panels 2, 3, 4, and 5, having their lower edges along 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 lO transect the blank to define the lateral edges o the body panel 2, 3, 4, and 5, and other panels above the body panels. These and other score lines are not necessarily straight, but may ~ 1 31 484~
be slightly offset in ceLtain sectoLs 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 ll 5 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. sOttOm closure means 26 is shown as a group of bottom closure panels 1~ through 21 attached to ( the body membe~s along bottom sc~e line 13, and extending 1~ downward therefrom. sottom closure score lines 22 through 25 enable bottom closure panels 1~, 16, and 18-21 to be folded under closure panels 15 and 17 and sealed to provide a leakproof container bottom. Such a closure ~eans 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 means 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 are oppositely disposed and when erected, converge upwardly to meet along sco~e line 44 to form a gable roof. Connected to the upper edge of the front panel 4 is a first ~ubstantially triangular end panel 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 lateral 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 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 . . . .

-15- l 31 4~4q 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 g.
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, respective]y. The third foldback panel 39 is attached to the first roof panel 28 along scDre 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 eclge of each foldback panel 38, 39, 41, and 42 along score line 44 is a gable rih panel 45, 46, 50, and 52, respectively. Similarly, attached to the upper edge of first and second roof panels 28 and 30 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 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 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 clefined by score lines 37, 44, and 9 ancl is adjacent second foldback panel 42. These roof wing panels 28 and 43 are more or less coextensive with the acljacent foldback panel when the erectecl 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 -16- ~ 31 4849 the second rooE rib panel 5~. The score lines 60 and 61 separate the upper rib panels from the adjacent roof rib panels, and are substantially continuous with the Eree upper edge 53 of the first and second gable rib panels 50 and 52. The latter panels serve as lips of the pouring spout of the erected container.
The score lines may be applied to blank 1~
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 shnwn 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 e~tend downwardly to overcover portion of the first and second foldback panels ~1 and 42 and small upper portions of first end panel 29.
As is also illustrated in an enlarged perspective 2~ view in FIG. 5 and in FIGS. 6A, 6s and 6C, each fillet 56 comprises a strip 66 of material resistant to the container sealinq process, and a first layer 72 of adhesive. This adhesive layer 72 is attached to (a) a first planar surface 86 of strip 66 and to (b) the inner thermoplastic coating 2S 82 of one or more of the pouring spout panels as described herein. The strip 66 of material is thus sealed to the thermoplastic inner coating 82 of one or more of these panels.
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 that, together with adhesive layer 72, it provides sufficient strength to reinforce the panel to the necessary stiffness. Thus, strip 66 must not melt, or otherwise degrade at the temperature and pressure conditions o~ the container sealing process.

. ~

Material such as metallic foil, polyester film, and polycarbonate film are examp]es 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 ~00F (81 to 205C). In one preferred embodiment of the invention, the material of the strip is unorientecl 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, ~Inoriented polypropy]ene has a lower modulus of elasticity than polyester (i.e. as low as 0.2 x lOfpsi). Therefore, a more compliant strip may be constructed which is better able to conform to the scorelines between the pouriny spout panels. Thus, a notch, such as is shown in Figures 9, 10 and 12 and discussed hereinafter, is not required. This simpliies the process oE positioning and alien;ng the fillet on the panels. The optmium temperature range per bonding the unoriented polypropylene strip is 260' - 320`F.
The stiffening fillet 56 Further includes an adhesive web 73 including a controlled release adhesive, having a first surface ~0 delaminably attached to the opposite surface 6~3 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 release adhesive mater;al which strongly adheres 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 3~ adhesive material comprising the web of this embodiment may be a pressure sensitive adhesive such as a rubber/resill combination or which becomes bonded to the container panel surface at the container sealing conditions, achieving an adhesion strength of 5 to 50 oz/in (61 to 612 g/cm) of width.
n the preferred embodiment, web 73 comprises t~,io members, a tllermoplastic ribbon 7~ and a layer 76 of controlled release aclhesive delaminably attached to one side of the ribbon 7~. The various embodiments of web 73 are further explained with reference to the remaining figures.
The strip 66 and a~lhesive 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 preformed as a second tape which is applied to the strip 66 of a first tape, or to the panel opposite that to which strip 66 and layer 72 are attached. Optionally, strip 66, adhesive layer 72, ribbon 7q, and adhesive layer 76 may be together preformed as a single tape to be applied to blanks 1~ .
For hermetic sealing containers, the modulus of elasticity of strip 66 may be as low as 0.2 x 106 psi (1.4 x 10a kg/m2) but for materials other than unoriented polypropylene preferably is at least 0.q x 10~ psi (2.8 x 10 kg/m ).
The stiffness of the fillet 56 must be such that the panel with the attached Eillet has greater stiffness than a panel without the Eillet. This relationship may be expressed as follows:

E2>E,(hl) /(h2)3 where: E~ = modulus of elasticity of panel.
E2 = modulus of elasticity of panel ~ fillet.
ht = thickness of panel.
h2 = thickness of panel -~ fillet.

-19- l 3 1 484q It is preferred that ~ I)e greater than 0.2 x 10 pounds per square inch (1.406 x 10~ kg per square metel) to provide the desired stiffness.
The first adhesive ]ayer 7;' may be of such an adhesive type and thickness that when the fillet 55 is compressed between gahle rib panel 50 and 52 and roof rib panels 48 and 54 during the container sealing process, a portion of the aclhesive of layer 72 extrudes from ketween the panel or panels and strip 66 of resistant material.
The extruded adhesive fills channels otherwise open to leakage and effectively seals the container. qhe adhesive used may be sealable by pressllre, 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 lA formed from the blank of FIG. 4, sealed according to the container sealing process, and subsequently opened from the closed and sealed condition. Second rooE 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 l-ib structure, and enclose third and fourth gahle rib panels 45 and 46. When the container is closed, common scoreline 47 between the third and fourth gable rib panels is somewhat spaced from common scoreline 51. The void between those 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 sealing process. The spout panels of the rib structure are shown 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 ~olded outward to extend the pouring spout.

--20- l 3 1 4849 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 f~om strip 66 by the opening 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.
FIGS. 6~-6C and 7~-7C are enlarged cross-sectional views through the rib po~tion of a hermetically sealing contalner 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, honded to the inside surface of fiberboard layer 83 by adhesive 8~, 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 85.
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 rib panel 5A. In other words, Eillet 56 is reverse~ 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 5~ hy web 73 during the container sealing process, the order may be reversed if desired, without changing the memhers that are adhesive]y joined. In other words, adhesive web 73 of fillet 56 may be first attached to roof rib panel 54 of blank lA, with adhesive layer 72 subsequently 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 ~ 21- l 31 ~849 more c~itical than the placement of web 73 on the Loof 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 ~8 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 are shown.
Turning now to FIGS. 6A through 6C, fillet 56 is shown in FIG. 6A attached to gable rib panel 52 of blank lA. The fillet comprises, in order, a layer 72 of adhesive bonded to the inner thermoplastic coating 82 of the gable rib pane]. 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 80 to opposite strip surface 68. Web 73 is aclapted to be bonded on i~s opposite surface 79 to roof rib panel 5 during the container sealing process.
FIG. 6B shows the same panels 52, 54 and fillet 56, following sealing. Strong bonding forces exist between adhesive layer 72 and thermoplastic coating 82 of gable rib panel 52, between adhesive 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 6a o strip 66 has the least strength of the fillet bonds, and web 73 is designed to cleanly separate or delaminate at surface 68 upon application of opening forces. Adhesive web 73 is designed to extrude duriny the container sealiny process of high temperature and pressure, to penetrate aLeas o~ 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 is relatively low, compared to the other sealing forces, so a real expansion oE web 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 separating from strip 66 and ~" -22- 13148~9 remaining bonded to the inner thermop]astic coating 82 of roof rib panel 5~. The clean separation provides a smooth inner surface on the gable rib panels 50, 52.
FIGS. 7A-7C correspond to FIGS. 6A-6C, but sho,7 another embodiment of the web fillet 56. The web 73 of this fillet 56 is comprised of a thermoplastic ribbon 74 which is delaminably bonded to side 68 o~ strip 66 by a layer 76 of delaminable adhesive. During the container sealing process of elevated temperature and pressure, ribbon 7~ melts and fuses to the inner thermoplastis coating 82 on roof rib panel 5~ to provide a strong seal.
The thermoplastic extrudes into open areas between the two panels to effectively prevent leakage, producing a seal useful for hermetic sealing containers. The extrusion which occurs is not shown in FIGS. 7~ or 7C, and has little effect upon the force required for opening, because the thermoplastic will not effectively adhere to strip 66. As illustrated in FIG. 7C, the container seal is openerl by separating or delaminating layer 76 from surface 68 of strip 66. l'he layer 76 oE delaminable adhesive remains attached to the roof rib panel 5~, providing a clean, smooth surface on the inner face of the gable rib panel 52.
Fillet 56 may comprise a tape having a relatively thick backing or strip 66 of a stiff material which bonds relatively weakly to the thermoplastic surface of the panels. The adhesive layer 72 may be thermoplastic in nature, but preferably is a pressure-sensitive adhesive.
The latter affords easier positioning during application to the blank lA, and does not require the application of heat for positioning. However, tlle thermal container sealing process has been found to significantly enhance the sealing strength of the pressure sensitive adhesives (PSAs) which were tested. Typical pressure sensitive adhesives (PSAs1 can be formed into stable thick layers, if desiled, and will readily extrude at the temperatures and pressures used to thermally seal polyethylene. In somes cases it may be desirable to produce an extruded bead of adhesive along the edges of the fillet 56 to further enhancf the sealing. In such cases, PS~'s appear to ~"ork well, being extru-le~] by the pressure of the container sealing process. The quantity of extruded adhesive may be varied by controlling the type of ahesive, the thickness c,f the adhesive layer, and the temperature and pressure of the carton sealing process. The quantity of cxtruded aclhesive may be controlled to ~i]l the small cl-annels which typically develop alonq the free upper edge 53 of the gable rib panels, and provide additional sealing in the areas immediately surrounding the strip 66.
Furthermore, the space at the tip of the pouring spout, that is, the space in FIG. 5 between common lille 51 and the corresponding line ~7 of the third and fourth gable rib panels, usually not securely sealed in the prior art by the container seal;ng process, may also be controllably filled with a bead of extruded adhesive during the seallng process to enhance the seal.
secause the bead bonding the gable rib panels to the rooE rib panels is relatively narrow, the seal may be broken with minimal force during opening of the spout. The adhesion of strip 66 to the container panel through adhesive layer 72 should preferably produce a peel strength greater than 50 oz. per inch of width (612 grams per cm.
width) at room temperature, so that the strip 66 will remain an integral part of the panel to wllich it is attached, both before and after the spout panels are unsealed and unfolded. The fillet may be adhesively attached to at least one of the pouring spout panels depending upon what is desired Eor the particular application. A strip 66 and adhesive layer 72 attached to the roof rib panels are somewhat less eEfective at transferring the opening forces than when attached to the gable rib panels. However, the concom;tant reduction in ~ -24- 1 3 1 4849 required opening forces resulting ~rom this invention enables a strip 66 attached to the roof rib panels 4~, 5~
to satisfactorily transfer the re~uired forces to readily open the container spout.
In this invention, the thickness of aclhesive layer 72 may be made considerab:ly greate~ 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, with some containers this invention may require an adhesive layer exceeding 0.001 inch (0.0025 cm) in thickness for achieving desired additional stiffness and leakproof or hermetic sealing. An adhesive layer of abollt 0.002 inch (0.005 cm) has proven optimal for certain pressure sensitive adhesives used to seal polyethylene coated containers. with other adhesives, a thickness of up to 0.004 inch (0.0102 cm) may be used.
However, in conjunction with a strip constructed oE
unoriented polypropylene, an adhesive layer, approximately 0.003 inches 0.008 cm) has been found to be preferred.
Strip 66 is made oE a relatively stiff material which is not ~aterially aEEected by the temperature and pressure of the container sealing process, that is, it will not melt, extrude, or substantially bond to the thermoplastic panel coatings at the sealing condition. The modulus of elasticity must be at least 0.1 x lOfi psi (0.7x108 kg/m2) and is preferably at least 0.2xlO~ psi (l.~x108 kg/m2). Most preEerably, a material with a modulus of at least O.~x106 psi (2.8xlOn kg/m~) is used for the strip 66, enabling the required additional stiffness to be achieved with a thin strip 66. Materials such as metallic foil, polyester film, and polycarbonate film may be used, at thicknesses ranging from about 0.0005 to 0.008 inches (0.0013 to 0.02 cm.), depending upon the opening force which must be transferred by the fillet and the material's modulus of elasticity.
The delaminable adhesive of web 73 or layer 76 is a pressure sensitive adhesive which provides a controlled -25- l 31 4849 after-sealiny ,oeel strengtll adhesion to the thermoplastic coating 82 or to the thermoplastic ribbon 79, of s-~n ounces/inch (61.2-612 gram-force/cm) of ~7idth. For many applications, a peel stren~th of about 20 ounces/inch (245 gram-force/cm) of width is optimal. The adhesive must be delaminable or peelable from strip 66 at a controllec3 release force, while maintaining its bond integrity with container panel 54. With natural rubber/resin adhesive combinations, for example, the delaminable adhesion can be closely controlled by varying the percent tackifier in the adhesive mixture to achieve the desirecl container openirlg force o~ about 5-7 pounds (2.3-3.2 kg). When a two--part adhesive web 73 is used, thermoplastic ribbon 74 may be comprised of the same material as the thermoplastic coatings 82 on the panels. For the common polyethylene coated containers, a ribbon material of low density polyethylene worl~s well. Such material has a low modulus of elasticity, approximately 0.02x10'6 psi (0.14x108 kg/m2). The ribbon material should have a melt index of 0.2 to 30 g/10 minutes, and preferahly 1-2 g/10 minutes, as defined by ~STM Test No. D1238. Ribbon 74 may have a thickness of 0.001-0.006 inches (0.0025-0.015 cm), with 0.004 inches (0.001 cm) as the preferred thickness prior to sealing. During the sealing process, the ri.bbon 74 is extcuded and fused to the panel coating, typically becoming compressed to become a much thinner member. secause of its low modulus of elasticity and its ultimate thinness, the ribbon 74 contributes little, if any, stiEfness to the panels.
Ribbon 74 may be advantageously formed of thermoplastic which is different in color from the panel coatings 82. The effect of the particular sealing conditions may then be easily evaluated merely by opening a sealed container and visually determinin~ the fusing of the differentially colored thermoplastic layers. ~hus, at the correct sealing temperature, the entire colored ribbon 74 will be firmly bonded to the container panel. If the _ 26- l 31 4849 sealing temperaure is too low, the colored ribbon 74 be found to be still attached to the strip 66 hy the delaminable aclhesive 76. If the temperature is sufficierlt in some areas of the seal but insufficient in other area, ribbon 74 will be inconsistently bonded to the container pane], 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.
n In a preferred embodiment, the fillet 56 is formed on the blank lA by machine application of two tapes.
The strip 66 is the backing member of a first tape, and has one side coated with a layer of adhesive 72. l'hermopla.stic ribbon 74 is the backing member of a second tape, and has one side coated with a layer 76 of delaminable adhesive.
The first tape is applied to the desired panels of blank 1~, and the second tape is next applied to the opposite 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 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 full distance. For containers having such distance W of 0.5 inches (1.27 cm), a web width of about 0.2 inches (0.5 cm~ has been Eound optimal. In the two-part form, web 73 may, in fact, extend above free edge 53, but upwarcl extension exceeding O.lW is generally not clesired.
Preferably such upward extension is no more than 0.05W.
FIGS. 8 througll 12 show a portion of the blank 1~, 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 each case, the adhesive web 73 may comprise a single layer 76 of delaminable adhesive, or may comprise a single layer 76 and a thermoplastic ribbon 74.

-27- 131~849 , ~

Regardless of the type of Eillet, corresponding thermoplastic covered areas of gable ri.b panels ~nd roof rib panels which are not covered by the fillet and are compressed together during the container sealing proce.ss will be bonded together, providing t.he coatings attain a melting or fusing temperature.
In FIG. 8, a single fillet 56 overcovers a portion of both gable rib panel.s 50 and 52. Shown are strip 66 having an underlyi.ng layer of adhesive 72, not visible, and adhesive web 73, which preferably P~.tends 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 lS fillet 56 is genera].ly continuous with the upper free edge 53 of the gable rib panels, but may he spaced upwardly therefrom by up to 0.2~, where W is the distance between score line 44 and free edge 53. The uppermost edye 63 of the fillet 56 may also be below free edge 53. When the uppermost edge 63 oE 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 delaminated panel portions may result in the directly sealed areas.
~s previously depicted in FIG. ~, a separate strip 66 may be bonded to each of the gable rib panels 50, 52. ~n this case, adhesive web 73 pre:Eerably bridges the space between the two strips 66 to provide additional thermoplastic along common line 51, to efEectively seal this area.
FIG. 9 depicts other features which may optiona].ly be incorporated in the seal of this invention.
Strip 66 and underlying layer 72 of adhesive overcover portions of both gable rib panels 50, 52, and extend downward to overcover and bond to portions of first triangular end panel 29 and first and second foldback 28- l 31484~
, .

panels 41, ~2. 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 72. In common heat sealing processes used to seal polyethylene coated blanks, heat is directly applied to the panels to be sealed, i.e., the rib panels. Panels below the rib panels are only incidently heated and attain a considerably lower temperature. The sealing 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 ~uch 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 extention 71 also provides additional stiffness for easing the opening of the spout seal.
Each end of the strip 66 may be spaced from the roof rib panels ~8 and 5~ to form spaces 59. The spacing provides room for the panels to fold around the illet at scorelines 8 and 9. Preferably, the spacing 59 between strip 66 and the roof rib panels is at least O.OlP, where P
is the length of the first or second gable rib panel 50 or 52. The maximum spacing 59 is controlled by the length of strip which will provide the desired stiffness to the panels, and may be as great as 0.3P, where P is as defined above.
The figure also shows a notch in strip 66 which exposes common line 51 between the two gable rib panels 50, 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 include a cut extending downwardly from the upper edge 63 of the strip, along at -2'~- 1314849 least a portion of the common line 51. ~his also enables adhesive from layer 72 and/or melted thermoplastic from the panel coating and the adhesive web 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. When a notch or slot exposes the common line 51, the edge of the fillet strip may be separated from a portion of the common line by up to 0.3 inches (0.76 cm). When there a~e 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 stifEening 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 rooE rib panel with a thermoplastic-to-thermoplastic bond. Such a tight bond at the point where the opening forces first act to unseal the spout make such unsealing difficult. Greater force is required, and with less reinforcement, the end of the spout may bend, tear, and delaminate.
In the exemplary embodiment of FIG. 10, an aperture 69 in strip 66 and adhesive layer 72 exposes hoth the score line intersection 64 and common line 51. The sealing of first and second gable rib panels along common line 51 is enhanced, and the opening force is reduced.
Opening forces may be furtller 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 is preferably spaced Erom the score line intersection 6~ 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 ~enerally correspond in coverage of the gable rib panels to fillets which would have been applied to the gable rib ~ -30- l 31 4849 panels as shown in FIGS. 8-10. When applie~ 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 carclstock thickness and strength as well as container size.
Ill FIG. 12 is illustrated a version of this invention in which strip 66 is bonded to the gable rib panels 50,52 by adhesive layer 12, and adhesive weh 73 is bonded to the roof rib panels ~8, 54. When the container blank lA is erected and sealed, each of the webs 73 becomes delaminably bonded to a side of the strip 66, sealing tlle container spout. The preferred web 73 of this embodiment cornprises a pressure sensitive adhesive (PSA).

EX~MPLE 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 resultecl in buckling and distortion of the gable rib panels, without opening the tip of the spout 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 reyuired to open the spout.
The container material was manufactured by International Paper Company Eor heemetically 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~M moclel 010 hand sealer.
Attempts to open the contairlers produced the same results as were obtained with the commercially sealed containers.
~n applied force of 15 pounds-force (6.8 kg-force) resulted in tearing and buckling of the panels, without opening the spout.

-31- l 3l 4 8 4 q ~rhe opening force required by a previously opened hermetically sea]ed carton was determined to be abo~t 2.5 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 togetheri 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 generally acceptable for 1/2 gallon (2 liter) gable-top containers.

Several thermoplas-tic 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 degree peel adhesion of at least 50 ounces per inch (612 yram-force per cm) of tape width was required to properly seal the joint. In most cases, the heat sealing process enhanced the peel adhesion of the delaminable adhesive.
Rubher 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 inclu~ed ~a) ethylene-vinyl acetate (EVA) copolymer, (b) medium density polyethylene (MDPE), and (c) a pressure-sensitive adhesive (PS~).
lhe modulus of elasticity was determined hy measuring the deflection caused by a weight placed on the 32-- l 3 1 4849 center of a simple beam formecl frc)m the cardstock.
Measurements were made on the cardstock itself, on a pair of gable rib panels from a blank, and from the entire onter spout assembly comprising the gable rib panels, triangular end panel, and foldback panels. The formula used to calculate the modulus was:
E = f~ /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:

-33- l 31 484~

a Y E, Modulus, _am Material Thickness Deflection _SI(kg/cm ) Cardstock (unreinforced) 0.027 in. 0.18 in. 393,000 8 (0.069 cm) (0.46 cm) (2.76 x 10 ) Cardstock with transverse0.027 in. 0.33 in. 2B,000 scoreline.(0.069 cm)(0.84 cm) (0.2 x 10~) (f = 10 g because of reduced modu]us) Cardstock with fillet of 0.004 0.036 in. 0.090 in. 332,000 in. (0.010 cm) (0.091 cm) (0.23 cm) (2.33 x 10~) polyester and 0.002 in (0.005 cm) EVA adllesive ( Scotchpak~M
26 tape) Cardstock with fillet of 0.002 0.032 in. 0.12 in. 390,000 8 in. (0.005 cm) (0.079 cm) (0.30 cm) (2.7 x 10 ) polyester and 0.003 in.
(0.0075 cm) PSA
Spout panels,0.027 in 0.080 in. 885,000 not preflexed(0.069 cm)(0.20 cm) (6.2 x 108) Spout panels,0.027 inØ21 in. 337,000 preflexed(0.069 cm) (0.53 cm) (2.4 x lOB) Polyester Film 400,000 (Literatttre (2.8 x 10 ) Value) The results indicate that the modulus o elasticity is approximately the same, i.e., 0.4 x 105 psi (2.8 x 10'3 kg/m2) for preflexed panels, either with or without the added fillet.
Buckling forces were calculated from the data of I'able 2 using Pcrit = CEh3b/12L2, r~ ~ 3 ~ 3 1 4 8 4 9 where P is the forward-directed Eorce merel~
c~ t required to open the pre~lexed spout from a closed but unsealed condition, lb~force;
C is pi2;
E is the modulus of elasticity, approximately 0.4 x 106 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 (~.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 unLeinforced ~5 gable rib panels prior to buckling was calculated to be 1.9 pounds (0.86 kg.), using L = 1.~5 inches. I'his leaves 1,9 - 0.5 = 1.4 pounds (0.6~ kg.) of force for breaking the bond at the tip of the spout.
Reinforcement of tile gable rib panels with a 0.002 inch (0.005 cm) thick polyester strip and 0.002 inch (0.005 cm) layer of PSA adhesive provide-l 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.).
ReinEorcing the gable rib panels with 0.00~ inch (0.010 cm) thick polyester and a 0.002 inch (0.005 cm) thickness oE E~A adhesive provided a calculated available force of 4.6-0.5 = ~.1 pounds (2.09 kg.) for breaking the bond at the spout tip. In thls case, the net panel thickness was 0.036 inches (0.1~2 cm). Thus, as a thicker, sti~fer reinforcement strip is added, the applied forward-directed opening force avai]able for opening the spout tip greatly increases.
Measurements were made oE the force required to open a previously opened gable top hermetic sealing carton, using a spring gauge. The average measured force oE 2.~
pounds (1.09 kg.) included the force required to buck]e the extreme tip of the unreinforced spout, that is, the common fold line of the gable rib panels. ~rhus, the calculate~l value of the force transmitted by the unreinforced spout panels is only 1.9 pounds (0.86 kg.), 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 (e.g., a better seal) over that of the opened 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 thls invention, the added stiffness provided an available opening Eorce 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 0.00]-0.006 inch (0.0025-0.015 cm) thickness have been Eound to work, with strip thickness of 0.002-0.004 inch (0.005-0.01 cm) being preferred.
The effects of several variables upon ease of opening were subjectively evaluated. Ease of opening was enhanced by (a) an increase in gable rib area covered by the fillet, (b) Eillets of greater stiEfness, (c) cutting, notching or slotting the fillet strip 66 along the common fold line between the gable rib pane]s, (d) leaving uncovered the score line intersection 64 where the triangular end panel 29 touches the common fold line 51, 30 and (e) a reduction of gable rib area which is permitted to thermally seal to the roof ribs.

EX~MPLE 3 A tape was made using a strip of 0.003 inch (0.0076 cm) thick polyester as 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 , .

bonding the strip to the gable 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 gable rib panels of a container blank describecl in Example 1. ~ container was erected from the hlank anc] thermcllly sealed. ~rhe container satis~ied the re~uirements o~ an environmental seal, i.e., (a) the tape remainecl at the clesired location on the blank panels during the contaienr sealing process, (b) the spout opening was fully sealed by the sealing process, (c) the added stiEfness enabled opening of the spout without buckling, tearing, or delamination of the panels, at a relatively low opening force of 6-7 pounds (2.7-3.2 kg), and (d) the spollt was opened by delamination of the EVA
adhesive from the strip, the EVA adhesive remaining attached to the roof rib panels.

EXAMPLE ~
Two tapes were prep~red for making a fillet in the spout of a gable top container. The first tape comprised an 0.003 inch (0.0076 cm) thick polyester backing as a strip 66, with a 0.002 inch (0.005 cm) layer of a tackified rubber resin adhesive coated on one surface. The second tape was an adhesive web comprising an 0.25 inch wide by O.OOq inches thick (0.64 cm by 0.01 cm) ribbon of low density polyethylene (LDPE), blue in color and having a melt index of about 1-2 g/10 minutes, coated on one surface with a delaminable adhesive comprising a natural rubber/resin PSA.
The two tapes were applied to a container blank made by International Paper Company for hermetic sealing.
The first tape, 1.5 inches (3.81 cm) wide and notched to expose the common line 51 between the panels, was applied to the gable rib panels. The delaminable adhesive of the second tape was then applied to the opposite sur~ace of the strip 66 to bond the second tape to the first tape. The location ok the tapes was as shown in ~IG. 9. A carton was then formed from the taped blank and thermally sealerl. 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 separation, the de]aminable adhesive layer from the strip, producing a smooth strip surface.
Additional blanks sealed at lower temperatures were opened. The effectiveness of the sealing temperature was readily determined by noting the integrity of the bond between the blue polyethylene rihbon and the aluminum-colored roof rib panels.

There are no standard tests for eva]uating the seal integrity of "hermetically sealed" containers.
~owever, a dye penetration test was performed on "hermetic sealing" cartons both with and without a fillet attached to the gable rib panels. Several configurations of the fillet were tested. The dye com~rised 1.2 grams of Rhodamine s 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 poured out and the carton rinsed with water. The spout was opened and the degree of dye penetration into the seal area was noted. Containers formed from blanks without the fillets of this invention and sealed conventionally to form "hermetic sea]s" 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 tearin~ 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.

-3~- l 3 1 48~q EX~MPLE 6 An unoriented polypropylene adheslve tape having a polyethylene sealing tape attached, was evaluated as a stiffening fillet with a sealing layer in a one-half gallon gable top container blank, which was then heat sealed with a Liquipak Model 010 heat sealel.
The combined tape was appliecl to the inside of the spout flush to the spout edge. The fillet ~tas one inch wide an~ three inches long and was centered on the spout tip. No notch was cut in the fil]et.
~ rhe tape had a 0.0035 inch thick unoriented polypropylene backing and a 0.003 inch thick rubber/resin pressure sensitive adhesive. ~ 0.2 inch wide piece of low density polyethylene was heat sealed to the uper edge of the polypropylene backing. The polyethylene was 0.00 inches thiclc.
The carton was opened in a normal manner and a spring gauge measured the npening force at 6.~ pounds. A
similar carton, without the fil],et, would have buckled instead of opening.
The pol,yethylene sealing layer bonded to the back oE the spout and f;lled the gaps and channels in the spout.
I'lle joint separated at the polypropylene/polyethylene interface during opening.
While the present invention has been partlcularly set forth in terms of specific embodiments thereof, it will be understood in view of the instant disclosure that numerous variations upon the invention are enab]ed to those skilled in the art, which variations yet reside within the scope of the present teaching. Accol-dingly, this invention is to be broadly construed and limited only by the scope and spirit of the claims now apperlded hereto.

Claims (16)

1. A sheet material blank for constructing a sealed gable-top container with a thermoplastic inner surface coating responsive to a container sealing process, the blank including a container body having sides, a bottom and a top and an extensible pouring spout including a substantially triangular end panel connected to the container body top, first and second foldback panels, the first foldback panel connected to the container body top and to at least one lateral edge of the first triangular end panel, and the second foldback panel connected to the container body top and to the other lateral edge of the triangular end panel, a first roof wing panel adjoining the first foldback panel and connected thereto, a second roof wing panel adjoining the second foldback panel and connected thereto, third and fourth foldback panels, the third foldback panel connected to the first roof panel and to one lateral edge of the second triangular end panel and adapted to be connected to the second roof panel, and said fourth foldback panel connected to the other lateral edge of said second triangular end panel and connected to said second roof panel, first and second gable rib panels connected to upper edges of the first and second foldback panels, respectively, to extend upwardly therefrom, having upper edges and lateral edges, and connected to each other at a common line, third and fourth gable rib panels connected to upper edges of said third and fourth foldback panels, respectively, and to each other, first and second roof rib panels connected to upper edges of the first and second roof panels, respectively, each of the roof rib panels connected at one side thereof to one of the first and second gable rib panels, first and second upper rib panels connected to upper edges of the first and second roof rib panels, respectively, and pouring spout panels comprising said first triangular end panel, said first and second foldback panels, said first and second roof wing panels, and said first and second gable rib panels, the sheet material blank further comprising at least one stiffening fillet overlying a portion of and bonded to the inner surface of at least one of said pouring spout panels for simultaneously stiffening said a-t least one overlain pouring spout panel to transfer applied opening forces therealong for opening at a controlled low opening force, said fillet comprising:
a strip of material resistant to the temperature and pressure of said container sealing process, a first layer of adhesive attached to a first surface of said strip and to said inner surface of said at least one overlain pouring spout panel for bonding said strip thereto, and an adhesive web including a controlled release adhesive delaminably 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 40a 60557-3402 process to form a bead of extruded adhesive along said upper and lateral edges of the at least one panel, to seal the at least one panel to another of the panels.

3. The blank according to claim 1, further characterized in that the blank is coated on its inner surface by a thermoplastic material for forming into a container by a container sealing 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 panels to be sealed are compressed together.

5. 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 adhesive 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 modulus of elasticity of at least 0.2 x 106 psi.

10. The blank according to claim 1, further characterized in that said adhesive web comprises:
a thermoplastic ribbon bondable on a first surface to the at least one panel by said container sealing process, and a layer of controlled release adhesive delaminably 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 10, further characterized in that said thermoplastic ribbon comprises low density polyethylene.

12. The blank according to claim 1, further characterized in that said resistant material comprises one of metallic foil, polyester film, and polycarbonate film.

13. A hermetically sealed gable-top container for extended shelf life having a thermoplastic inner surface coating, said container including a container body having sides, a bottom and a top and an extensible pouring spout including a substantially triangular end panel connected to the container body top and extending upwardly therefrom, first and second foldback panels, the first foldback panel connected to the container body top and to one lateral edge of said first triangular end panel, and said second foldback panel connected to said container body top and to the other lateral edge of said first triangular end panel, a first roof wing panel adjoining said first foldback panel and connected thereto, a second roof wing panel adjoining said second foldback panel and connected thereto, third and fourth foldback panels, said third foldback panel connected to said first roof panel and to one lateral edge of said second triangular end panel, and said fourth foldback panel connected to the other lateral edge of said second triangular end panel and connected to said second roof panel, first and second gable rib panels connected to upper edges of said first and second foldback panels, respectively, and extending upwardly therefrom, and connected to each other at a common line, third and fourth gable rib panels connected to upper edges of said third and fourth foldback panels, respectively, and to each other, first and second roof rib panels connected to upper edges of said first and second roof panels, respectively, each said roof rib panel connected at one side thereof to one of said first and second gable rib panels, first and second upper rib panels connected to the upper edges of said first and second roof rib panels, respectively, and pouring spout panels comprising said first triangular end panel, said first and second foldback panels, said first and second roof wing panels, and said first and second gable rib panels, the container further comprising at least one stiffening fillet disposed between and adhesively bonded to at least one of said pouring spout panels for stiffening the at least one overlain pouring spout panel to transfer applied opening forces therealong and for controlling the force required to open the container, said fillet comprising:
a strip of material constructed of material resistant to the temperature and pressure of a container sealing process;
a first layer of adhesive disposed between a first surface of said strip of material and said at least one pouring spout panel and adhesively joining said strip thereto; and an adhesive web including a controlled release adhesive 43a 60557-3402 delaminably bonded to the opposite surface of said strip and bonded to an opposed panel, wherein said opening forces transmitted along said strip delaminate said adhesive web from said opposite surface of said strip.

14. The container according to claim 13, further characterized in that said adhesive web is bonded to another of said panels by said container sealing process.

15. The container according to claim 13, further characterized in that said adhesive web comprises:

a thermoplastic ribbon bonded on a first surface to said other one of the panels by said container sealing process, and a layer of controlled release adhesive bonded to the other surface of said ribbon, and delaminably bonded to said opposite surface of said strip.

16. The blank according to claim 13, further characterized in that said resistant material comprises one of metallic foil, polyester film, and polycarbonate film.