CA2033950A1

CA2033950A1 - Method and apparatus for constructing gable-top container closure system

Info

Publication number: CA2033950A1
Application number: CA002033950A
Authority: CA
Inventors: Gregory R. Wyberg
Original assignee: Minnesota Mining and Manufacturing Co
Current assignee: 3M Co
Priority date: 1990-01-26
Filing date: 1991-01-10
Publication date: 1991-07-27
Also published as: BR9100120A; NO910294D0; EP0439958A1; JPH0769339A; AU635379B2; AU6923191A; NO910294L

Abstract

ABSTRACT OF THE DISCLOSURE

A method and apparatus for constructing a gable-top container having a stiffening fillet applied to the inner or outer surface of one or more panels of the pouring spout. A pair of sealing jaws are compressed against first portions of the first and the second roof rib panels with a force sufficient for reciprocal sealing of the first and second roof rib panels and the first and the second gable rib panels of the container, while compressing the portions of the first and second roof rib panels generally overlying the stiffening fillets with a force sufficient for reciprocal sealing of the first and the second roof rib panels and the first and the second gable rib panels overlaying the stiffening fillet without substantially displacing the stiffening fillet from the desired location.

Description

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PP~TENT

METHOD AND APPARATUS FOR CONS~RUCTING
GABLE-TOP CONTAI~ER CLOSURE 8YSTEM

Background of the Inventlon 1. Field of the Invention This invention relates to packagingt and particularly to a method and apparatus for constructlng a gable-top container having improved opening characteristics.

2. Description of the Prior Art Containers for beverages such a6 milk, frult juices, and drinks are conventionally constructed from blanks of thermoplastic coated paperboard. The most widely u6ed of such containers have a rectangular cross-sectional body surmounted by a gable-top closure incorporating an extensible pouring spout. Blanks from which the containers are constructed are divlded lnto a plurality of panels which are adapted to form the walls and closure members. The panels are formed and separated by ~core llnes at which the blank is folded. Partlcular 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 adjoinLng thermoplastic surfaces and form a generally strong ~eal.
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 Wilcox U.S. Patent No. 3,245,603.
Containers of this type are opened or access to the contents by a two-step toggle action process.
First, the gable edges of the roof panels at the front ~33~

o the container are pushed outward and upward toward the rear of the container by thumb pressure, breaklng the seal between the outside surfaces of the two lip panels, and breaking the seal in the rib panels surmounting the roo~ above the pouring spout. The gahle edges are forced backward past the point at which the lip panels are joined, to nearly touch the roo~ panel~.
Second, the gable edges are pushed forward and towards each other. 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 panel~ and snapping the spout outward to a pouring position.
In early models o gable-top containers, the p~nels comprising the lips of the pour~ng spout were bonded to the underside of the roof panels. The resulting ~ealed spout was difficult to open, generally requiring insertion of a tool behind the lip6 to separate them from the roof underside. The cardstock panels often tore or delaminated, producing an unsightly and unsanitary container. In tho~e ca6es where an adhes~ve was applled to only those panels which were to be joined, it was simple to eliminate adhesive from the spout panels to reduce the forces required to open the ~pout. The resulting container, o course, was not effectively sealed and was subject to leakage.
An improvement in gable-top containers to provide a hermetic seal for an extended shelf life package consisted 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 thermopla6tic coatings or oil adds some 6tiffnes6 to the panel~, and the container is made resi6tant to wicking by liquid6. However, the strong bonding of the _3 2~33~

lip panels results ~n buckling, tearlng and delamination o~ the card6tock upon opening th~ seal. Thus, the ~pout i6 dlfficult to open, and the opened panels are unappealing in appearance.
~s used in the food packaging industry, 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 microorganism6.
The hermetic barrier of such carton6 typically comprises an aluminum or other barrier film coating the inner ~urface, overcovered with a thermoplastic such as polyethylene. The carton wall thickne~s 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 leakaqe.
Attempts to provide an easily opened spout seal have included (a) perforation6 in the spout panels which tear open to expose pouring lip6, ~b) improved control of the 6ealing temperature, (c) the use of added scoreline patterns to concentrate the opening forces, and (d) the use of anti-adhesion agents, i.e. abhesives, to reduce the required opening forces.
U.S. Patent Nos. 4,712,727; 4,813,547; and 4,B69,373, all entitled "Gable-Top Container", all generally describe an improvement in the formation of a gable-top container of paneled flexible material to stlffen the package material ad~acent the sealed area to be opened. This results in a more reliable, consistently openable hermetically sealed opening for gaining access to the content6.
Referring now to the drawings, a gable-top container is depicted such as may be utilized in conjunction with the above '727; '547; and '373 patents.
~igure 1 shows a typical container 1 in a closed, sealed condition as for storage oE beverages and the like. The _4~ c container i6 self-~ustainlng ln shap~ and i8 hermetlcally sealed. Container 1 is comprisQd oP a series of panels, including a container body haviny four body panels 2-5. Front body panel 4 and second side body panel 5 are shown in Figure 1, while rear body panel 2 and flrst 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 bottom of the container 1 is closed. First roof panel 28 0 iB connected to the upper edge of first side panel 3.
Second roof panel 30 is connected to the upper edge of seco~d side panel 50 When the container ls in the closed conditlon, the roof panels 28 and 30 converge upwardly to form a gable roof construction. Roof rib panel 54 i6 attached to roof panel 30 and extend~ upwardly therefrom. Likewise, upper rib panel 55 is attached to roof rib panel 54 and extends upwardly therefrom.
Flrst triangular end panel 29 is connected to the upper edge of the front body panel 4. When the container is closed, end panel 29 is folded under the 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 of roof panel6 28 and 30, respectively. A second triangular end panel, not shown in this Figure, is usually adapted to remain folded under the opposite gable roof, unless it is desired to open both gable ends of the contalner.
Figure 2 shows the container of Figure 1 in which the spout has been partially opened. The first and second foldback panels 41 and 42 and overlapping roof wing panels 40 and 43 are typically pushed outward and backward with thumb pressure to break the seal between the inner surfaces 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 vi~ible in this drawing. The gable rib panel6 are connected to the upper edge of foldback panels 41 and 42,:and extend upwardly therefrom.

-Flgure 3 shows the contalner at the point where oldback 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 are attached to a lateral edge of fir~t triangular end panel 29. First and second gable rib panels 50 and 52 act as lips of the pouring spout, and meet at a common gable rlb 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.
To complete the unsealing and openlnq of container 1, foldback panels 41 and 42 are pushed backward beyond the position shown in Figure 3. The roof rib panels and upper rib panels will fold along foldline 57. The blank may or may not be scored at that location.
The gable rib panels are slightly longer than the roof rlb panels. Thus, after the panels are folded backward, a subsequent forward and inward movement of wing panels 40 and 43 transmits opening forces in a toggle-like action along the wing panels and gable rib 25 panels 50 and 52 toward the common line 51 between the gable rib panels. A component of these forces extends outward and upward from line 51 and from gable score lines 35 and 36 to pull the gable rib panels 50 and 52 away from roof rib panels 54 and 48, the latter not visible in Figure 3, and to pull foldback panels 41 and 42 away from roof wing panels 40 and 43~ Likewise, triangular end panel 29 is forced outward, and the distended panels create a pouring spout. The various scora llnefi delineating the panels act as hinges for the panels as they are unfolded.

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Certain feature6 of the gable-top container construction of the '727; '547; and '373 patents will produce a li~uid-proof spout seal which ls easily opened without tedring, delamination, or buckling of the spout panel members. These features underlia the spout panel members in ~igure 3, and are not visible in that Figure.
These features include one or more ~illets 56, shown in Figure 4.
Figure 4 illustrates an exemplary flat sheet material blank for constructing a gable-top container as descr~bed in the '727; '547; and '313 patents. 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 a~ walls of the container and its closure parts when the contalner is erected.
The central portion of blank lA comprise6 four body panels 2, 3, 4, and 5, having their lower edges ' along bottom score line 13, and thelr upper edges along top score line 31. These transverse score lines are shown as extendlng from blank edge 6 to opposite blank edge 12 in substantially parallel relationship across the face of the blank. Vertical score lines 7, 8 and 9 transect the blank to define the lateral edges of the body panel 2, 3, 4 and 5, and other panels above the body panels. These and other score lines are not necessarily straight, but may be slightly offset in certain sectors of the blank to improve the fit of the varlous panels in the erected container.
In the example shown in Figure 4, side seam flap ll is connected to one lateral edge lO of a body member for sealing to the edge of another body member 2 by the container sealing process. ~ottom closure means 26 is shown as a group of bottom closure panels l4 ~33~

through 21 a~tached to the body members along bottom score line 13, and extending downward therefrom. ~ottom closure score lines 22 through 25 enable bottom closure panels 14, 16, and 18-21 to be folded under closure panels lS and 17 and sealed to provide a leakproof container bottom. Such a closure means is well-known in the art. A separately formed structure may alternatively be used to close the bottom of the container. In fact, any closure means which results in a satisfactorily 1 tight seal may be used.
The gable-top of the container t 6 formed ~rom 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 panel~ 3 and 5, respect~vely. 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 upper edge of the front panel 4 is a first substantially 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 i6 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 roo~
wing panel 40 along score line 8. Panel 41 has a score line 44 as its upper edge. Similarly, second foldback panel 42 is connected to triangular end panel 29 along edge 36, and to second roof wing panel 43 along score line 9. It has score line 44 as its upper edge.
Similarly, third and fourth foldback panels 39 and 38 are connected to triangular end panel 27 along lateral edges 33 and 32, respectively. The third 3S foldback panel 39 is attached to the first roof panel 28 :', -8- 2~33~

along score line 7, and the fourth foldback panel 3~ is connected to the second roof panel 30 by side saam flap ll when the container i 6 erected.
Attached to the upper edqe o 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 30 are flr~t and second roof rib panels 48 and 54, respectively. Fir~t and second gable rib panel6 50 and 52 are connected to each other at a common ~core line 51, and third and fourth gable rib panels 46 and 45 are connected to each other at common æcore 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 ~, and is adjacent first oldback 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 foldback panel when the erected container is closed.
A first upper rib panel 49 is connected to the upper edge of the first roo rlb 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 upper edge 53 of the first and second gable rib panels 50 and 52. The lattee panels serve as lips of the pouring spout of the erected container.

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The score line6 may be applied to blank lA
before or after the thermoplastic coating is applled to the blank. The score lines may be applied to either ~urfaca ~r both sucface~ of the blank. For purpo~es of clearer delineation of the various panels, score line6 are shown in the drawings on either or both o~ the inner and outer surfaces o~ the blank and container.
In the embodiment shown in Figure 4, two stiffening fillets 56 overlie portions of the first and second gable rib panels S0 and 52, and extend downwardly to overcover portion of the flrst and second foldback panels 41 and 42 and small upper portions of first end panel 29.
Each fillet 56 comprises a strip 66 of material resistant to the container sealing process, and a layer 72 of adhesive. This adhe~lve layer 72 i~
attached to any of the panels forming the pouring spout of the gable-top container.
The material of the strip may he constructed rom any suitable material, but is preferably constructed from unoriented polypropylene, such as th~t utilized a~ a film backing in a pressure sensltive adhesive tape marketed under the trademark "Y-8450" by Minnesota Mining and Manufacturing Company of St. Paul, Minnesota. A fillet constcucted of unoriented S polypropylene exhibits several advantages over strips constructed of other materials and specifically polyester. Specifically, unoriented polypropylene has a lower modulus of elasticity than polyester ~i.e. as low as 0.2 x 10 p.s.i.). Therefore, a more compliant strip may be constructed which is better able to conform to the scorelines between the pouring spout panels. The optimum temperature ranye per bonding the unoriented polypropylene strip is 260 - 320 F. Unoriented polypropylene is the preferred material for the strip in that it i~ dimen~ionally stable, even when 6ub~ected to the;elevated temperatures and pressures experienced when a containsr is ~ealed. Oriented polypropylene, although having incrsased tensive strength, has a tendency to return to its unoriented state when exposed to temperatures li.e., 180 - 200 F) below the sealing temperatures. ~his distortion of oriented polypropylene results in buckling and separation of the polypropylen0 from a mounting surface.
The strip 66 and adhesive layer 72 may be preformed as a tape which is applied by machine to the blank lA.
For hermetic sealing containers, the modulus of elasticity of strip 66 may be as low as 0.2 x 106 p.s.i. ~1.4 x 108 kg/m2), but preferably for materials other than polypropylene is at least 0.4 x 106 p.s.i.
(2 8 x 10a kg/m2) 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 during the first sealing process, a portlon of the adhesive of layer 72 extrudes from between the panel or panels and strip 66 of resistant material. The extruded adhe~ive fills channels otherwise open to leakage and effectively seals the container. The adhesive used may be sealable by pressure, heat, or other proces6.
Figure 5 is an enlarged cross-sectional view through the rib portion of a container formed from this invention, showing the panel members and fillet exaggerated in thickness for the sake of clarity. It is understood 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 coatlng.
First and second roof rib panels 48 and 54 overlie first and second gable rib panels 50 and 52. I'he gable rib panels are separated from foldback panels 41 2~33~

and 42 by scorelines 44, and ths roof rib panel~ are likewise separated from roof wing panels 40 and 43 by scorelines 44. Upper rlb panels 49 and 55 are separated by score lines 60 and 61 from the roof rib panels 4B and 54~ and extend upwardly therefrom. Each of the panels shown in the Figure includes a coating o thermoplastic on at lea~t the inner surface. Stifening f~llet 56 i6 shown attached to the inner face of gable rib panels 50 and 52, and to an upper portion of foldback panel~ 41 and 42. The fillet includes resistant strip 66 and adhesive layee 72.
Fillet 56 may comprises a tape having a relatively thick backing or strip 66 of a 6tiff material whose bond to the thermoplastic surface of the panels is weaker than its bond to adhesive layer 72. 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. ~owever, the thermal carton zeallng process has been found to significantly enhance the sealing strength of the pressure-6ensitive adhesives (PSA's) which were tested. Typical pressure sensitive adhe6ives can be formed into stable thick layers at room temperature, and will readily extrude at the temperatures and pressures used to thermally seal polyethylene. Thus, when an extruded bead of adhesive is desired, PSA's appear to work well.
In Figure 5, the container contents occupy the 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 às shown in Figure 5. The upper rib ~1~339~

panel~ ara bonded on their inner surfacee at lnterface 69, and gable rib panels 50 and 52 are preferably mutually bonded on their outer surfaces at interace 70.
A further seal~ng feature may be produced i~
desired. A thick layee 72 of an extrudable adhesive may be used in the fillet. Compression at an elevated temperature during the carton sealing process extrude~
the adhesive from between the gable rib panels and ~trip 66, and the extruded bead 79 of adhesive bonds overlying panels 50 and 52 just above the upper edge 75 o~ 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 are ~oined, and along the exposed portion of the common gable rib score line. A hermetic seal is achieved where the adhe~ive extrudes, even when the bead of extruded adhesive is minimal. The quantity of extruded adhesive may be varied by controll~ng the type of adhesive, the thickne~s o the adhesi~e 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 correspondinq llne 47 of the third and ~ourth 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. This seal is especially enhanced by features to be later described.
~ ecause the bead bonding 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 pre~erably produce a peel strength greater than 50 oz.

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per lnch of wldth l612 grams per cm. width) at room temperature, so that the fillet will remain an lntegral part of the panel ~o which it is attached, both before and a~ter the spout panels are un8ealed and un~olded.
The fillet may be adhesively attached to at least one of . the pouring spout panels listed above, dependlng upon what is desired for the partlcular application.
Preferably, the thickness of adhesive layer 72 is considerably greater than would be required for 1~ 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 exceedlng 0.001 inch ~0.0025 cm) in thic~ness 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 adhesives, a thickness of up to 0.004 inch (0.0102 cm) may be used. However, in conjunction with a strip constructed of unor~ented polypropylene, an adhesive layer o~ approxlmately 0.003 inches (0.009 cm) has been found to be preferred.
Figure 6 shows a gable-top container 1 formed from the blank of Figure 4 and sealed according to conventional contalner sealinq process, and ~ubsequently opened from the closed and sealed condition. Second roof panel 30 and first roo~ panel 28 converge upwardly so that their upper edges 44 meet or almost meet. Roof rib panels 48 and 54 are sealed along approximately ane-half of the length of the rib structure, and enclose third and fourth gable 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 scorellnes is a vertical channel which when filled with adhesive w~ll prevent leakage. First and second upper ri~ panels 49 and 55 ars joined by the container sealing ~,,.

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proce~s. The spout panels o~ the rib structure are ~hown to have been opened by first breaking tha seal between the upper rib panels 49 and 55, and then breaking the seal between gabls rib panels 50, 52 and roof rib panels 48, 54. First triangular end panel 29, and fir~t and second foldback panels 41 and 42 are folded outward to extend the pouring spout.
Stiffening fillet 56 is shown at the inside of the pouring spout, o~erlyinq and attached to a portion of the inside surface of the first gable rib panel 50 and the second gable rlb panel 52, not visible in this view. Conformlng 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 described.
Fillet 56 is shown as spaced from roof wlng panel 40 and roof rib panel 48 to form side spacing 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 adhesive 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 5 when the carton is sealed. Fillet 56, being resifitant to the container sealing process, does not strongly adhere to 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 s,eal 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 o~ the strip, nevertheless prevents fluid leakage.
A he~met~c seal results from (a) the thermoplastic heat seal between exposed portions of the gable rib panels 2~33~

and oppo~ing roof rib panel~, or (b) a baad o~ adhe~lv~
extruded from beneath the strip, to be descrlbed later, or the seal between surface 68 and the overlying panel, or (d) a combination of the two.
The sealing temperature is dificult to accurately control, and if the fillet adhesive softens exce6~ively, the fillet ~trlp may slide downward, not retainlng its proper alignment on the gable rib panel or panel6. ~he portion of the fillet below the gable rib panels will be much les6 affected because o~ 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.
It was discovered in the '727; '547; and '373 patents that enhanced sealing results from cuttlng, notching or slotting the strip 66 where it overcovers the common gable rib scoreline 51, especially the portion of the common line just below its upper terminus 51A. 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 melted 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.
U.S. Patent Nos. 4,726,234; 4,813,548; and 4,872,562, all entitled "Gable-Top Container", the contents of which are all hereby incorporated herein by reference, also disclose a gable-top container con~truction in which a stiffening fillet is utilized in the same manner as herein described with respect to the '727t '547; and '373 patents. However, in the case of the '234; 548; and 562 patents, the stiffening fillet is ~16- 2~339~

applied to the outer surface of one or more correspondin~ panels of the container, as shown in Figures 7 and 8.
V.S. Patent Nos. 4,756,426; 4,792,048; and 4,869,372, all entitled "Gable-Top Contalner Closure System", the contents of which are all hereby incorporated herein by reference, also disclose a gable-top container construction 1 in which a stiffening flllet 56 i6 utili2ed in the same manner as herein 10 descrlbed with respect to the '727; '547; and '373 patents in that the fillet 56 is applied to the inner surface of one or more panels forming the pouring ~pout.
However, in the case of the '426; '048; and '372 patents, the stiffening ~illet 56 includes two layer6 laminated to each other, as shown in Figures 9-11.
More speci~ically, the fillet compri6es (a) a strip 56a of reinforcing material constructed of mat~rial resistant to deleterious effects of the conventional container sealing process, i.e. it will not melt, or otherwise degrade at the temperature and pressure of the container sealing proces6, tb) first layer of high strength adhesive 56b attached to one side of the strip, and (c) an adhesive web 56c including a controlled release adhesive delaminably attached to the opposite side of the strip of resistant material and adapted to seal to the panels opposite the panels overlain by the fillet, when the container is erected, closed and sealed.
Collectively, the '234; '54~; and '562; '426;
'048; '372; '727; '597; and '373 patents shall hereinafter be jointly referred to as the "Fillet"
patents. In the '727; '547; and '373 Fillet patents, it has been observed that unoriented polypropylene is the preferred material for the reinforcing strip in that it is dimensionally stable, even when subjected to the elevated temperatures and pressures experienced when a container i6 sealed. Oriented polypropylene, although iJ

having increased tensive strength, has a tendency to return to its unoriented state when exposed to temperatures (i.e. 180 - 200) below the sealing temperature. This distortion of oriented polypropylene results in buckling and separation of the polypropylene from a mounting surface.
It i6 to be understood that the Fillet patents all disclose a specific gable-top container construction, it is to be understood, for the purposes of this invention, that the use of a stiffening fillet may be utilized in any gable-top container construction, regardless o the particular agreement, size or shape of panels, provlded that a pouring spout is included having at least the first triangular end panel, the first and second fold back panels, the flrst and second wlng panels, the first and second gable rib panels, along with the first and second roof rib panels.
However, although an improvement over existing gable-top containers, the use of the stiffening fillets deiscribed above in the ~illet patents provides gable-top containers that are more difficult to seal properly when the stiffening fillets overly any one or more of the first and second roof rib panels or the first and second gable rib panels. That is, the overall thickness of the rldge or rib of the gable-top container is increased over a portion of its length.
Typically, the first and second roof rib panels and first and second gable rib panels are sealed together to form the ridge or rib of the gable-top container by the compressive application of a pair of parallel sealillg jaws or bars after heating with hot air to a temperature which melts or fuses the thermoplastic surface coatings, to seal together the panels to be joined. When the thickness of the gable-top ridge structure varies along the length of the gable ridge, as with the eeinforcing fillets, effective sealing o the container is diminished in at least two respects. First, ~3~

the non~reinforced portion of the gable ridge structure do not receive an even appllcatlon of compressive force from the sealLng jaws. Second, and as a consequence of the first disadvantage, increased pressure ~s applied to to the portions of the first and second roof rib panels or the first and second gable rib panel6 that overly the stiffening fillets so that the stifening fillets have a tendency to be squeezed out of position (i.e.
di~placed), with apparent adverse con6equence~. Such displacement includes deformation or damage to the reinforcing strip of the fillet, as well. Reduction of the overall compressive force applied by the sealing jaw6 to prevent the stiffening fillets from bein~
displaced may prevent effective reciprocal sealing of the first and second roof rib panels and the first and the second gable rib panels and therefore, of the container.

Summary of the Invention The present invention includes a method for producing a gable-top contalner, comprislng the stepz of: (a) providing a container body having sides, a bottom and a top, and an extensible pouring spout including a generally 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 the first triangular end panel, and the second oldback panel connected to the container body top and to the other lateral edge of the first triangular end panel, 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, a first roof rib panel connected to the firzt roof panel and the first roof wing panel, a second roof rib panel connected to the second roof panel and the second roof wing panel, a first gable rib panel connected to an upper edge o~ the flrst foldback pan~l, a second gable rib panel connected to an upper edge of the second foldback panel, the uppermo6t end of the first triangular end panel and the flrst and tha 6econd foldback panels orming a tip of the pouring spout; ~b) providing at least one stiffening fillet overlying at least a portion of and bonded to one or ~ore of the first and the second roof rib panels and the first and second gable rib panel for simultaneously stifening one or more of the first and the second roof rib panels and the first and second gable rib panels to transfer applied opening forces therealong and for limiting the force required to open the container from the sealed condition, the fillet comprising a strip of mate~ial resistant to the temperature and pressure of the container sealing process and a layer of adhesive attached to one side of the strip and to one or more of the first and the second roof rib panels and the first and the second gable rib panels for bonding the strip thereto; ~c) erecting a gable-top container; (d) heating the first and the second roof rib panels and the first and the second gable rib panels to a temperature sufficient for reciprocal sealing of the first and the second roof rib panels and the first and the second gable rib panels; (e) applying a first sealing pressure to first portions o the first and said second roof rlb panels sufficient for reciprocal sealing of the fir6t and second roof rib panels and the first and the second gable rib panels of the container to seal the container;
and (f) applying a second sealing pressure on portions of the first and the second roof rib panels overlying said stiffening fillet during sealing of the container sufficient for reciprocal sealing of facing portions of the stifening illet and the first and the second roof rib panels and the first and the second gable rib panels , 35 without substantially displacing the stiffenlng flllet -20- ~3~5~

from the de6ired locatlon on one or more o the firGt and the second roof r~b panels and the first and the s~cond gable rib panels.
In one embodiment, the method ~urther includes the steps of: providing a pair of sealing jaws including opposed sealing surfaces for compressive contact with exterior surfaces of the heated fir6t and second roo rlb panels; ~b) ~orming opposed recesses in the sealing surface6 of the pair of sealing ~aws, the reces6es being aligned with portions of the first and the ~econd roof rib panels overlying said stiffening fillet; ~c) compressing the sealing ~aws against the exterior of the first and the second roof rib panels after heating so that during sealing of the first and the second roof rib panels the fir.st sealing pressure is applied to the first portions of the first and the second roof rib panels and the second sealing pressure is applied to the second portions of the first and the second roof rib panels for reciprocal sealing of facing portlons of the irst and the second roof rib panels, the first and the second gable rib panels and the stiffening fillet without substantially displacing the stiffening fillet from the desired location. The present invention further provides for apparatus for use in carrying out the above method with a gable-top container including a container body having sides, a bottom and a top, an extensible pouring spout including a generally triangular end panel connected to the container body top and extending upwardly therefro~, first and second foldback panels, the first foldback panel connected to the container body top and to 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 first triangular end panel, irst roof wing panel adjoining the first foldback panel and connected thereto, a second roof wing panel adjoining the second foldback panel and connected ;

-21~ 3~

thereto, a ~irst roof rib panel connected to th~ flr~t roo~ panel and the first roof wing panel, a second roof rib panel connected to the second roof panel and the second roof wing panel, a first gable rib panel connected to an upper edge of the first foldback panel, a second gable rib panel connected to an upper edge of the second foldback panel, the uppermost end of ths first trlangular end panel and the first and second foldback panels forming a tip of the pouring spout, a stlffen~ng fillet overlying at least a portion of and bonded to one or more of the first and the second roo rib panels and the first and the second gable rib panels for simultaneously stiffening one or more o the first and the second roof rib panels and the first and second gable rib panels and to transfer applied opening force~
therealong and for limiting the force required to open the container from the sealed condition, the fillet comprising a strip of material resistant to the temperature and pre6sure of the container ~ealing ; proce6s and a layer of adhesive attached to one side of the strip and to one or more ofthe surface of the first and the second roof rib panels and the first and second gable rib panels for bonding the strip thereto, comprisinq: (a) a pair of sealing jaws including opposed sealing surfaces for compressive contact with exterior surfaces of the first and second roof rib panels~ ~b) means for heating the to a desired temperature sufficient for reciprocal sealing of the pouring spout of the container; ~c~ means for cooperative movement of the pair of sealing jaws between positions spaced from the contalner and sealing positions in contact with the exterior of the first and the second roof rib panels;
and (d~ means for compressing said pair of sealing jaws against first portions of the first and the second roof rib panels with a first sealing force sufficient for reciprocal sealing of facing surfaces of the first and the second roof rib panels and the first and the second . .

` ~22~ 3~

gable rib panels of the container, while compres6ing second portions of the irst and second roo rib panele generally overlying the stiffening fillet with a second sealing force ufficient for reciprocal sealing o~ the S first and the second roof rib panels and the first and second gable rib panels overlying the stiffening fillet without substantially displacing the stiffening fillet from the desired location.
In on embodiment of the apparatus of thi~
inventlon, the compressing means includes a rece~s formed in said sealing surface of each of said sealing ~aws, said recesses being generally coextensive with the stiffening fillet when said sealing jaws are in said contact position, whereby said first sealing pressure i~
applled to said first portions of the first and the second roof rib panels and said second sealing pressure is applied to said second portions of the first and the second roof panels.
The present invention also includes a gable-top container constructed according to the above described method.

Brief De~cription of the Drawings The present invention will be further described with reference to the accompanying drawing wherein like reference numerals refer to like parts in the several views, and wherein:
Figure 1 is a perspective view of the upper end of a closed container formed rom the container blank of Figure 1.
Figure 2 is a perspective view of the container end of Figure 1 with a partially opened rib.
Figure 3 is a perspective view of the container end of Figure 1 with its sealed rib fully open and the spout panels in the closed position.

-23- ~33~

Figure 4 is a plan view of an embodlment o~ a conventional container blank with a sti~fening fillet applied to an inner surface of one or more panel~ o the pouring spout.
Fig~lre 5 is an enlarged cross-~ectional view through the closed upper clo6ure along line 6-6 of Figure 1.
Figure 6 is a partial perspective vlew of the container end of Figure 1 with with the pouring ~pout completely opened. A portion o the container is cut away to view panel members below the roof and roof rib panels.
Figure 7 is a perspective view of an alternate container end with its sealed rib fully open and the spout panels in the closed po6ition showlng a sti~fening fillet applled to the outer surface of one or more panels of the pouring spout with the pouring spout in a closed position.
Figure 8 is an enlarged cross-sectional view through the closed upper closure of a gable~top container with a stiffening fillet applled to an outer surface of one or more of the panels of the pouring spout.
Figure 9 is a perspective view of another alternate container end wlth its pouring spout in an open position showing a stiffening fillet applied to the inner surface of one or more panels of the pouring spout with the stiffening fillet including two delaminable layers.
Figure 10 is a partial enlarged cross-sectional view through the closed upper closure of a gable-top container with a stiffening fillet applled to an inner surface of one or more of the panels of the pouring spout of Figure 9.
Figure 11 is a partial plan view oE a container blank with a stiffening fillet applied to inner surface of one or more panels of the pouring ' . spout.

~33~

Figure 12 is a top view of erected but unsealed gable-top container according to this invention with a pair of sealing jaws adjacent the exterior of the first and second roof rib panels.
Flgu~ 13 is a front view of the gable-top conta~ner and sealing jaws of Figuee 12 after the gable-top container has been sealed.
Figure 14 is side view of the sealing surface of one of the sealing jaws of Figures 12 and 13 with a rece~s portion-Figure 15 is a top view o the gable-top container of Figure 13.
Figure 16 ls a side view of the gable-top contalner of Figures 13 and 15.

Detailed Description Referring now to Figure 12, the method of this invention will now be discussed along with apparatus for carrying out that method. gable-top container 1 is as shown and discussed previously with respect to Figures 1 11. Specifically, although not shown, a stiffenlng fillet is applied to the inner or outer surfaces of one or more surfaces of the panels of the pouring spout, as described in the Fillet patents, but more specifically, the stiffening fillets overly one ~5 or more of the first and the second roof rib panels 50, 52 or the first and second gable rib panels 48, 54.
A pair of opposed sealing jaws, 100 and 102, respectively, are positioned adjacent the exterior of the first and second roof rib panels, 50 and 52, respectively. Each sealing jaw includes a sealing surface, 104 and 106, respectively, for application to the exposed surfaces of the first and the second roof rib panels. Means are provided for heating the container panels to a desired temperature sufficient for sealing of facing 6urfaces of the pouring spout panels of the gable-top container. Usually, such means takes the form . , 2~33~

of str~am~ of he~ted air directed against the panels o~
the container to be sealed, in a manner known in the art, and thus will not be discussed herein urth~r.
Means are also provided for movement o~ the sealing jaws 100 and 102, such as in opposed directions 108 and 110, from a spaced apart position as shown in Figures 12 and 13, to opposed positions in compressive : contact with the first and second roof rib panels 50 and 52, dur~ng the sealing of the gable-top container. The ;1 application of heat and the pressure of the sealing jaws will seal the gable-top container, as previously described. Such sealing jaws are known in the art and the mechanism for moving the sealing jaws against the gable-top container panels and compres-sing the panels are also known in the art and will not be discussed in greater detail hereinafter. The following companies are sources of commercially available machines for sealing gable-top containers that may utili~ed in the method and apparatus of the present invention: Cherry-Bureve of Louisville, KY and Pure-Pak of Wald Lake, Michigan.
Means are provided for applying a flrst sealing pressure to first portions 50', 52' of the first and said second roof rib panels sufficient for reciprocal sealing of the first and second roof rib panels 50, 52 and the first and second gable rib panels 48, 54 of the container and applying a second sealing pressure on portions of the first and the second roof rib panels overlying the stiffening fillet durinq sealing o the container sufficient for reciprocal sealing of facing portions of the stiffening fillet without substantially displacing the stiffening fillet from the desired location on the first and the second roof rib panels. For the purposes of this invention, the term "displacement" also includes any deformation or damage to the reinforcing strip caused by compression ~5 during sealing of the gable-top container.

-26- ~33~

In the illustrated embodim~nt, the ~eans for applying a differential sealing pressure to the portion6 of the first and second roof panels overlying the stiffening fillet incl~de a paic of recesses or indents 112 and 114, shown in greater detail in Figure 14, each formed in aligned, opposing locations on the sealing surfaces 104 and 106 of the sealing jaws 100 and 102.
The rece~se6 112, 114 are constructed so as to generally overly the second portions 50', 52' of the first and 1 second roof rlb panels that overly the 6tiffening flllet 56, as ~s also shown in cross section in Figure~ S and 8. It will be appreciated that the pair of indents or recesses reduce and limit the level of compressive sealing force applied to the stiffening fillet (not shown), compared to the compressive sealing force applied to remainder of the first and the second roof rib panels. By constructing the recesses in an appropriate manner, the level of compre~sive force applled to each portion of the first and second roof rib panels can be carefully controlled. The relief or reces6 should be at least nominally the thickness of the stiffening fillet but is preferably 0Ø005 cm to 0~013 cm deeper in each jaw. It is one of the advantages o~
thls invention that the method may be practiced and the apparatus constructed by relatively minor and inexpensive modifications of conventional container sealing systems.
Although the illustrated embodiment of the invention include a pair of one piece sealing jaws, each having a recess formed in a sealinq surface, it is within the spirit and scope of the present invention to provide sealing jaws having independent portions aligned with the location of the stiffening fillet and the remainder of the roof rib panels. In this arrangements, the independent portions of the sealing j~ws could be 35 applied to thc allgned portions of the first and the -27- 2~33~3 second roof rib panels with lndependent level6 o~
compressive sealing forces by a mechanism ~not shown) adapted for this purpose.
Figures 13, 15 and 16 each show a gable-top container l sealed according to the method and apparatus of this lnvention. Portions 50', 52' of the ~ir~t and second roof rib panels 50, 52 overlying the stiffenlng fillet (not shown) have A thickness that i8 perceptively larger relative to the remainder of the first and the second roof rlb panels. Although not directly affecting the functional aspects of the gable-top container and stiffening fiIlet as disclosed in the Fillet patents, the method and apparatus of the present inventton prevents damage to the stiffening fillet and en6ures the proper location and functioning of the stiffening fillet during opening of the gable-top container, and in all other respects the gable-top container constructed accordlng to the method and by the apparatus of this invention operates as described in the Fillet patent~.
The following are examples of gable-top contalner6 constructed according to the method and using the apparatus of the present invention:

Example 1 A two (2) liter foil lined gable-top carton from Tetra Pak AB of Lund, Sweden was formed on a ~iquipak Model 1800 Form/Fill/Seal machine. The machine is available from Liquipak, Inc. The carton thickness was 0.066 cm (0.026 inches) so the two portions forming the roof rib panels together are 0.132 cm (0.52 inches) thick and the panels forming the two wing panels together are 0.264 cm (0.104 inches) thick~ A YR~921 tape, available from Minnesota Mining & Manufacturing Co. of St. Paul, Minnesota, measuring 0.017 cm x 2.54 cm x 7.0 cm was applied to the inside surface of the tip of the pourlng spout as the stiffening fille'~. The gap ~etting of the jaws when closed was 0.18 cm and jaws are 2 ~

closed to a gap of 0.23 cm. over the two wing panel6.
Each jaw had a relief of 0.025 cm in the area contacting and surrounding the fillet. The sealing width (from the top of the tape to the bottom of the tape) was approximately 1.0 cm. The top portion of the carton was heated with hot air to a temperature of between 250 F
and 400 ~ and sealed with unheated jaws. The carton seale~ ~atisfac~orily and showed no displacement o~ the fillet or damage to the foll.

Example 2 A carton was prepared as described in Example 1 except that the jaws used for sealing were flat and had no recess.
The resulting carton showed the fillet squeezed through the top of the spout producing an unsightly ,ragged edge. Part of the fillet was also squeezed ~ownward into the spout causing severe wrinkling of the fillet and channels to form between the fillet and the inside wall of the carton. The foil also fractured which could cause seepage of liquid into the wall of the carton.

Examplo 3 A one-half gallon foil lined gable-top container was obtained from International Paper Company and prepared sealed with sealing ~aws having a recess as described in Example 1. The resulting carton showed satisfactory sealing with no displacement of the fillet or damage to the foil.

Example 4 one-hal gallon foil lined gable-top container ~rom International Paper Company was sealed as described in 1 except that jaws used or sealing were flat and had no receSs. The resulting carton showed displacement 2~33~

o~ fillet through the top of the spout and wrlnkling oS
the illet inside of the spout. The foil was al~o fractured it was sealed.

The present invention has now been described with re~erence to several embodiments thersof. It will be apparent to those skilled in the art that many changes can be made in the embodiments described without departing from the scope of the present invention. Thus, the scope of the present invention should not be limited to the structures described in this application, but only by structures described by the language of the claims and the equivalents of those structures. For in~tance, the stiffening fillet described herein, and as disclosed in the Fillet patents, may include ~ slngle strip, or more include two or more independent 6trip8, each applied to one or more of the first and the ~econd roof rib panels and the first and the second gable rib panels, all of which is included in the term "fillet"
for the purposes of this invention. Further, although the gable-top container described hereln has been referred to as hermetically sealed, the method and apparatu~ of this invention are also applicable to non-hermetic sealing of a gable-top container, if desired

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A method for producing a gable-top container, comprising the steps of:

(a) providing a container body having sides, a bottom and a top, and an extensible pouring spout including a generally 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 the first triangular end panel, and the second foldback panel connected to the container body top and to the other lateral edge of the first triangular end panel, 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, a first roof rib panel connected to the first roof panel and the first roof wing panel, a second roof rib panel connected to the second roof panel and the second roof wing panel, a first gable rib panel connected to an upper edge of the first foldback panel, a second gable rib panel connected to an upper edge of the second foldback panel, the uppermost end of the first triangular end panel and the first and the second foldback panels forming a tip of the pouring spout;

(b) providing at least one stiffening fillet overlying at least a portion of and bonded to one or more of the first and the second roof rib panels and the first and second gable rib panel for simultaneously stiffening one or more of the first and the second roof rib panels and the first and second gable rib panels to transfer applied opening forces therealong and for limiting the force required to open the container from the sealed condition, the fillet comprising a strip of material resistant to the temperature and pressure of the container sealing process and a layer of adhesive attached to one side of the strip and to one or more of the first and the second roof rib panels and the first and the second gable rib panels for bonding the strip thereto;

(c) erecting a gable-top container;

(d) heating the first and the second roof rib panels and the first and the second gable rib panels to a temperature sufficient for reciprocal sealing of the first and the second roof rib panels and the first and the second gable rib panels;

(e) applying a first sealing pressure to first portions of the first and said second roof rib panels sufficient for reciprocal sealing of the first and second roof rib panels and the first and the second gable rib panels of the container to seal the container; and (f) applying a second sealing pressure on portions of the first and the second roof rib panels overlying said stiffening fillet during sealing of the container sufficient for reciprocal sealing of facing portions of the stiffening fillet and the first and the second roof rib panels and the first and the second gable rib panels without substantially displacing the stiffening fillet from the desired location on one or more of the first and the second roof rib panels and the first and the second gable rib panels.

2. A gable-top container constructed according to the method of claim 1.

3. The method of claim 1, further including the steps of:

(a) providing a pair of sealing jaws including opposed sealing surfaces for compressive contact with exterior surfaces of the heated first and second roof rib panels;

(b) forming opposed recesses in the sealing surfaces of the pair of sealing jaws, the recesses being aligned with portions of the first and the second roof rib panels overlying said stiffening fillet; and (c) compressing the sealing jaws against the exterior of the first and the second roof rib panels after heating in step (d) in claim 1 so that during sealing of the first and the second roof rib panels the first sealing pressure is applied to the first portions of the first and the second roof rib panels in step (e) of claim 1 and the second sealing pressure is applied to the second portions of the first and the second roof rib panels in step (f) of claim 1 for reciprocal sealing of facing portions of the first and the second roof rib panels, the first and the second gable rib panels and the stiffening fillet without substantially displacing the stiffening fillet from the desired location.

4. A gable-top container constructed according to the method of claim 3.

5. Apparatus for use with a gable-top container including a container body having sides, a bottom and a top; an extensible pouring spout including a generally 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 the first triangular end panel, and the second foldback panel connected to the container body top and to the other lateral edge of the first triangular end panel, 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, a first roof rib panel connected to the first roof panel and the first roof wing panel, a second roof rib panel connected to the second roof panel and the second roof wing panel, a first gable rib panel connected to an upper edge of the first foldback panel, a second gable rib panel connected to an upper edge of the second foldback panel, the uppermost end of the first triangular end panel and the first and second foldback panels forming a tip of the pouring spout, a stiffening fillet overlying at least a portion of and bonded to one or more of the first and the second roof rib panels and the first and the second gable rib panels for simultaneously stiffening one or more of the first and the second roof rib panels and the first and second gable rib panels and to transfer applied opening forces therealong and for limiting the force required to open the container from the sealed condition, the fillet comprising a strip of material resistant to the temperature and pressure of the container sealing process and a layer of adhesive attached to one side of the strip and to the surface of one or more of the first and the second roof rib panels and the first and the second gable rib panels for bonding the strip thereto, comprising:

(a) a pair of sealing jaws including opposed sealing surfaces for compressive contact with exterior surfaces of the first and second roof rib panels;

(b) means for heating the to a desired temperature sufficient for reciprocal sealing of the pouring spout of the container;

(c) means for cooperative movement of the pair of sealing jaws between positions spaced from the container and sealing positions in contact with the exterior of the first and the second roof rib panels;
and (d) means for compressing said pair of sealing jaws against first portions of the first and the second roof rib panels with a first sealing force sufficient for reciprocal sealing of facing surfaces of the first and the second roof rib panels and the first and the second gable rib panels of the container, while compressing second portions of the first and second roof rib panels generally overlying the stiffening fillet with a second sealing force sufficient for reciprocal sealing of the first and the second roof rib panels and the first and second gable rib panels overlying the stiffening fillet without substantially displacing the stiffening fillet from the desired location.

6. The apparatus of claim 5, wherein said compressing means includes a recess formed in said sealing surface of each of said sealing jaws, said recesses being generally coextensive with the stiffening fillet when said sealing jaws are in said contact position, whereby said first sealing pressure is applied to said first portions of the first and the second roof rib panels and said second sealing pressure is applied to said second portions of the first and the second roof panels.