Note: Descriptions are shown in the official language in which they were submitted.
1 3 ~ 5 7 5 3
~ABI.E-'rOP CON'rAI NER
sackground 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 liquids. More particularly,
this invention relates to a blank from which the container
is formed.
2. Description of the Prior ~rt
Containers for beverages such as milk, fruit
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 higll frequency radiation to f~se the
adjoining thermoplastic surfaces and form a generally
strong seal. To finally seal the filled container, two or
more panels are finally joined and sealed to form rib alonq
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 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- ~ 3
container are pushed outward and upward toward the rear of
the container by thumb pressllre, breaking the seal ~-etween
the outside surfaces of the two lip panels, and breaking
the seal in the rib panels surmountin~ the roof above the
pouring spout. The gable edges are forced backward past the
point at which the lip panels are ~oined, to nearly tough
the roof panels.
Second, the gable edges are pushed forward and
inward. l'he second stage opening forces are communica~ed
through spout panels to the tip of the pouring spout,
breaking the seal between the lip panels and the underside
of the roof panels and snapping the spout outward to a
pouring position.
The first step in the opening process primarily
produces tension forces in the spout panels, while the
second step produces compression forces, and these forces
are transmitted over a greater distance. Thus, the second
opening stage is more likely to result in bent and crumpled
spout panels.
In early models of gable-top containers, the
panels comprising the lips, i.e. gable rib panels of the
pouring spout were bonded to the underside of the roof
panels. I'he resulting sealed spout was difficult to open,
generally requiring insertion of a tool behind the lips to
separate them from the roof underside. The carclstock panels
often tore or delaminated, producing an unsightly and
unsanitary container. In those cases where an adhesive was
applied to only those panels which were to 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 shelf life package
consisted of coating the inner surface of the container
blank with a foil or other gas-impermeable layer and an
overcovering layer of thermoplastic such as polyethylene.
` ~ -3- ~3~
The panels to be sealed are honded by heating the
thermoplastic surface coatings to a softening or melting
temperature, compressing the panels together and cooling.
The use of thermoplastic coatings or foil adds some
stiffness to the panels, and the container is made
resistant to wicking by liquids. However, polyethylene has
a low modulus of elasticity, and the added stiffness is
minimal. The strong thermoplastic bonding of the lip panels
results in buckling, tearing and delamination of the
cardstock upon opening the seal. Thus, the spout is
difficult to open, and the openecl panels are unappealing in
appearance.
As 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 microorganisms. The hermetic barrier of such
cartDns typically comprises an aluminum or other barrier
film coating the inner surface, overcovered with a
thermoplastic such as polyethylene. The carton wall
thickness is thus increased, requiriny significantly
greater forces to open the container, particularly in the
second step of the opening process. Attempts to provide an
easily opened spout seal for hermetically sealed and other
gable-rib cartons have included (a) perforations in the
spout panels which tear open to expose pouring lips, (b)
improved control of the sealing temperature, (c) the use of
added scoreline patterns to concentrate the opening forces,
and (d) the use of anti-adhesion agents, l.e. abhesive, to
reduce the required opening forces.
The use of perforations in the spout panPIs has
generally been unsatisfactory. Such perforations prodlJce 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. 'l'his type
oE carton spout requires external forces such as thumbnail
pressure to open, and this procedure is considered
unsanitary. The carton cannot be effectively closed, once
opened, and shaking of the carton results in spillage.
Likewise, efforts to reduce temperature
variations in the sealing process have not produced a
satisfactory hermetic sealing gable-top container. I'he
desired adhesion is obtained within a narrow range of
temperature, and temperatures either higher or lower may
produce excessive or inadequate sealing. Variations in
sealing persist in spite of improved temperature control.
Moreover, the required opening forces generally exceed the
panel strength, even where minimal sealing is achieved.
The use of novel scoreline patterns generally has
not overcome the strong sealing forces of well-sealed
spouts and buckling of the spout panels is common.
One method for preventing the difficulty in
opening the completely bonded lip panels of po]yethylene
coated gable-top containers is shown in Crawford et al,
U.S.. Patent No. 3,116,002. In this reference, a thin
2~ coating of a high molecular weight organo-siloxane gum is
applied to the lip panels as an abhesive, that is, to
prevent permanent adhesion to the panels in contact with
the lip panels.
Egleston et al, U.S. Patent No. 3,270,9Q0
discloses the use of an anti-adhesive composition a~plied
to both the outside and inside surfaces of the pouring lip
of a gable-top container. Abhesive agents disclosed include
cellulose plastic laminated to polyethylene, the latter
heat-bondable to the polyethylene surface of the carrlstock
blank.
The release properties of abhesives are generally
affected by the heat sealing parameters and are
inconsistent. Containers designed for hermetic use and
having adhesives in the spout sealing area often require
opening forces greater than the wall strength of the
panels, and the spout panels buckle during the opening
process.
7~ 60557 3400
Summa!ry oE the Invention
The present invention is directed to an improvement in
the Eormation 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 opening for
gaining access to the contents. 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 having inner and outer
surfaces 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 first 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 one lateral edge of the first
triangular end panel, and the second foldback panel connected to
the container body top and to the o-ther lateral edge of the -Eirst
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
~IS
6 ~ 60557-3~00
and Eourth foldback panels, the third foldback panel connected to
the first roof panel and to one lateral edge of a second
triangular end panel, and the fourth foldback panel connected to
the other lateral edge of the second triangular end panel and
adapted to be connected to the second roof panel, first and second
gable rib panels connected to upper edges of the first and second
foldback panels, respectively, to extend upwardly t'nerefrom,
having upper edges and la-teral edges, and connected to each other
at a common line, third and four-th gable rib panels connected to
upper edges of the 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 Eoldback 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 sti:Efening fillet overlying a portion oE and bonded
to the outer surface of at least one of said pouring spout panels,
for stiffening said at least one pouring ~.pout panel to transfer
applied opening forces therealong to open the container, said
fillet comprising: a strip of material resistant to the container
sealing process and having a modulus of elasticity of at least 0.1
x 106 psi, and a layer of adhesive attached to one side of said
strip and to the outer surface of said at least one pouring spout
panel for bonding said strip thereto.
' ~
` 7 ~3~ 60557-3400
The invention also provides a sealed gable-top container
having a thermoplastic outer surEace coating, the container
including a container body having sides, a bottom, and a top, and
an extensible pouring spout including a first 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 one lateral edge of the -Eirst
triangular end panel, and the second foldback panel connected to
the container body top and to a second lateral edge of the first
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 a second
triangular end panel, and the fourth foldback panel connected to
the other lateral edge of the second triangular end panel and
connected to the second roof panel, first and second gable rib
panels connected to upper edges of the 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 the third and fourth
foldback panels, respectively, and to each other, first and second
roof rib panels connected to the upper edges of the first and
second roof panels, respectively, each said roof rib panel
connected at one side thereof to one o:E 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,
`` ~` 7a ~ ~ ~ 5 7 ~ 3 60557-3~00
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 stif:Eening fillet
overlying a portion of, and bonded to the outer surface of at
least one of said pouring spout panels, Eor stiffening said at
least one pouring spout panel to transfer applied opening forces
therealong to open the container, said fillet comprising: a strip
of material resistant to a container sealing process and having a
modulus of elastici-ty of at least 0.1 x 106 psi, and a layer of
adhesive attached to one side of said strip and to the outer
surface of said at least one pouring spout panel for bonding said
strip thereto.
The fillet stif:Eens the panels to which it is bonded,
enabling higher applied opening forces to be transferred to the
common line connecting the gable rib panels of the spout of the
erected, sealed container, to open -the seal.
The fillet extends along a major portion of the force
transmission line between the site where the second stage opening
force is applied and the intersection of the gable rib panels
which receives the opening Eorce. The fillet strengthens the
panel to which it is bonded, so that the force transmitted
therethrough will break the spout seal betwaen the gable rib
panels and roof rib panels before those panels fold, tear or
delaminate.
Brief Description o~ the Drawinos
Figure 1 is a perspective view of the upper end of a
closed container formed from a blank according to an embodi~ent of
7b ~L 3 ~ ~ 7 ~ ~ 60557-3400
the present invention.
Figure 2 is a perspective view oE the container end of
Figure 1 with a partially opened ribO
Figure 3 is a perspective view of the container end of
Figure 1 with its sealed spout rib fully open and the spout panels
in the closed position.
Figure ~ is a perspective view of a portion of a
stiffening fillet attached to a container panel according to the
present invention. The cross-section of the fillet and panel are
enlarged to show the laminar construction.
Figure 5 is a plan view of an embodiment o-E the
container blank according to the invantion.
Figure 6 is a cross-sectional view through the closed
upper closure of one embodiment of the invention, taken along line
6-6 of Figure 1.
,~ .
,,
Figure 7 is a cross-sectional view through the
closed upper closure of a further embodiment oE the
invention, taken along line 6-6 of Figure 1.
Figure 8 is a perspective view of a portion of a
stiffening fillet attached to a container panel according
to a furtller embodiment of the invention, with the fi]let
and panel enlarged in cross-section.
Figure 9 is a cross-sectional view through the
closed upper closure of another embodiment of the
invention, taken along line 6-6 of Figure 1.
Figures 10 through 13 are plan views of a portion
of the outer face of various embodiments of the present
invention.
Detailed Description_
Referring now to the drawings, the invention is
depicted with reference to a gable-top contalner in which
the invention is incorporated. A gable-top container is
formed from a blank of paperboad or other suitable material
which may optionally be coated on the inner planar sur~ace
and/or outer planar surface with a thermoplastic material.
The container blank is adapted to be folded along
horizontal and vertical fold lines, erected, and have
certain panels sealed to each other by a container sealing
2~ process. For thermoplastic coated container blanks, the
sealing process typically consists of compressing to~ether
the panels to be joine~ while those panels are at an
elevated temperature. Other alternative sealing processes
may also be utilized, such as the application of adhesive
to the panels to be sea]ed.
FIG. l shows a typical container 1 in a closecl,
sealed condition as for storage of beverages and the like.
The container is self-sustaining in shape.
Container 1 is comprise~l of a series of panels,
including a container body having four body panels 2-5
which make up the body 2~. Front body panel ~ and secon~
side body panel 5 are shown in FIG. l, while rear body
.. .. .
_9~ 7~
panel 2 and Eirst side hody pane~ 3, not shown, opp-se
panels q and 5, respectively, forming a container of
rectangular cross-section. Usually, the cross-section is
square. The bottom of the container 1 is closecl. First
roof panel 31 is connecte~ to the upper edge of first side
panel 3. Second roof panel 32 is connected to the upper
edge of second side panel 5. When the container is in the
closed condition, the roof panels 31 and 32 converye
upwardly to form a gable roof construction. Second roof
rib panel 55 is attached to second rooE panel 32 and
extends upwardly therefrom. Likewise, second upper rib
panel 58 is attached to second roof rib panel 55 and
extends upwardly therefrom.
In the same manner, Eirst roof rib panel 5~ is
attached to first roof panel 31 and extends upwardly
therefrom. First upper Lib pclnel 57 is attached to first
roof rib panel 5~ and extends upwards therefrom.
First triangular end panel 29 is connected to the
upper edge of the front body panel ~. When the container
is closed, end panel 29 is folded under the gable rcof
formed by the two roof panels. Also shown are first roof
wing panel 38 and second roof winq panel 39. The roof wing
panels 38 and 39 are subpanels of roof panels 31 and 32,
respectively. A second triangular end panel, not shown in
this figure, is usually adapted to remain folded under ~le
opposite gable roof, unless it is desired to open hoth
gable ends of the container.
FIG. 2 shows the container of FIG. 1 in which the
spout has been partially openecl. The first and second
foldback panels ~1 and ~2 and overlapping roof wing ~-anels
38 and 39 are typically pushed outward and backwar-1 with
thumb pressure to break the seal between the inner su~faces
of the first and second upper rib panels 57 and 58, and
between the outer surfaces of the first and second yable
-lo- ~3~
rib panels 46 and 47, the latter panels not visible in this
drawing. The gable rib panels 46 and Q7 are connected to
the upper edge of foldback panels 41 and 42, and e~tend
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 trianglllar in shape, each having one edge defined
by scoreline 34 or 35, where they are attached to a lateral
edge of first triangular end panel 29. First and second
gable rib panels 46 and 47 act as lips of the pouring
spout, and meet at a common gable rib score line 51. The
upper terminus 52 of the common rib score line 51 at the
free edge 53 of the pouring lip comprises the tip oE the
pouring spout. First and second upper rib panels 57 and 58
extend upwardly from the first and second roof rib panels
54 and 55 to a level higher than the free upper edge 53 of
gable rib panels 46 and 47.
To complete the unsealing and openinq of
container l, foldback panels 41 and 42 are pushed backward
beyond the position shown in FIG. 3. The roof rib panels
54 and 55 and upper rib panels 57 and S8 will fold along
foldline 6~. The blank may or may not be scored at that
location.
When opened, the gable rib panels 46 and 47 are
slightly longer than the unfolded portion of the roof rib
panels 54 and 55. After the panels are folded backward, a
subsequent forward and inward movement of wing panels 38
and 39, gable rib panels 46 and 47, roof rib panels 54 and
55, and uppPr rib panels 57 and 58 transmits opening forces
in a toggle-like action along the wing panels and gable rib
panels and toward the common line 51 between the gahle rih
panels. The forces further shorten the folded portion of
the r~of rib panels 54 and 55. A component of the applied
forces extends outward and upward from line 51 and from end
panel lateral edges 34 and 35 to pull the gable rib panels
46 and 47 away from roof rib panels 54 and 55, the latter
3 ~ 5 1~ 3
not visible in FIG. 3, and to p~lll foldback panels ~1 and
g2 away from roof wing panels 38 and 39. 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 force P required for bucking to occur may
be described as:
P = CEI/(L )
15 whare: C = (pi2) = 9.~7 for hinged ends.
E = modulus of elasticity of beam.
I = moment of inertia of the beam.
I = 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
however, the gable rib panels, foldback panels, and roof
rib panels must be relatively stiff to prevent the panels
from crumpling, and to transmit the applied opening forces
to common line 51. The sealing forces which bond the gable
rib panels to the roof rib panels are preferably only as
high as required to maintain the desired seal. ~ nomillal
liquid-tight seal common in milk cartons may be achieved
with minimal or no bonding of gable rib panels to roof rib
panels, while a hermetic seal requires relatively lligh
strength bonding over the continuous panel interface.
~ligh bonding forces between the gable rib panels
and the roof rib panels will require greater stiffness in
the spout panels to prevent huckling of the panels cluring
the opening process.
The features of this invention will produce an
openable container spout seal, regardless of whether the
-12- 131~53
seal is merely liquid-tight or is hermetic, i.e.,
gas-tight. ~s illustrated in FIG. 3, one or more fillets
56 overlie a portion of one or both o~ the gable rib panels
46 and 47. The construction of fillet 56 is further
described in reference to FIG. q.
As shown in an enlarged perspective sectional
view in FIG. 4, each fillet 56 comprises a stiffening strip
61 and an adhesive layer 62 by which the strip is attached
to the outside surface 63 of a portion of one of the
pouring spout panels, such as gable rib panels 46 and 47 as
shown. In this embodiment, one surface 69 of strip 61
remains free of adhesive. When the container spout is
closed, surface 69 on one gable rib panel abuts surface 69
on the other gable rib panel. The bond between the two
surfaces 69 may be weak or strong, but in any case is less
than the strong bond created by the layer 62 of adhesive
which bonds the strip or strips 61 to the respective gable
rib panels.
- FIG. 5 illustrates an exemplary flat sheet
material blank of this invention for constructing a
gable-top container. The outer surface or face is shown,
and it may be coated with a thermoplastic such as
polyethylene. The inner surface may also be similarly
coated. The sheet material may include a gas impermeable
layer such as aluminum foil. An appropriate pattern of
score lines divides blank lA into a plurality of panels and
sub-panels which are used as walls of the container and its
closure parts when the container is erected.
The central portion of blank lA comprises a body
28 with four body panels 2, 3, 4, and 5, having their lower
edges along bottom score line 13, and their upper ed~es
along top score line 33. These transverse score lines are
shown as extending from blank edge 6 to opposite blank ed~e
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 panels 2, 3,
4 and 5, and other panels above the body panels. ~hese and
-13- ~ 3 ~ 3
other score lines are not necessari]y straight, but may be
slightly offset in certain sectors oE the blank to improve
the fit of the various panels in the erected container.
In the ecample shown in FIG. 5, side seam flap 11
is connected to one lateral edge l0 of a body member for
sealing to the edge of another body member 2 by the
container sealing process. Bottom closure means 26 is
shown as a group of bottom closure panels 14 throu~l~ 21
attached to the body members along bottom score line 13,
and extending downward therefrom. Bottom closure score
lines 22 through 25 enable bottom closure panels 14, 16,
and 1~-21 to be folded under closure panels 15 and 17 and
sealed to provide a leakproof container bottom. Such a
closure means is well-known in the art. A separately
formed structure may alternatively be used to close the
bottom of the container. In fact, any closure means wllich
results in a satisfactorily tight seal may be used.
The gable top of the containPr is formed from a
series of panels above top score line 33. First and second
roof panels 31 and 32 are connected to the upper edges of
the first and second side panels 3 and 5, respectively.
The roof panels are oppositely disposed and when erected,
converge upwardly to meet along score line ~5 to form a
gable roof. Connected to the upper edge of the front panel
~ is a first substantially triangular end panel 29 whose
two lateral edges 3~ and 35 formed by score lines extend
upwardly to score line ~5. Similarly, second triangular
end panel 30 is connected to the upper edge of back panel
2, and has lateral edges 36 and 37 which extend upwardly to
score line ~5.
On each side of triangular end panel 29 is a
foldback panel. First foldbaclc panel ~1 is connected to
triangular end panel 29 along edge 3~, and to first roof
wing panel 38 along score line ~. Panel ~1 has score line
-14- 13~7~3
45 as its upper edqe. Similarly, second foldback panel 42
is connected to triangular end panel 29 along edge 35, and
to second roof wing panel 39 along score line 9. It has
score line 45 as its upper edge.
Similarly, third and fourth foldback panels q3
and 44 are connected to triangular end panel 30 along
lateral edges 37 and 36, respectively. When the carton is
erected, the fourth foldback panel 44 is attached to the
second roof panel 32 by flap 11~ ~dge 6 is then generally
continuous with scoreline 10. The third foldback panel 43
is connected to the first roof panel 31 along scoreline 7.
Attached to the upper edge of each foldback panel
41, ~2, ~3 and 44 along score line 45 is a gable rib panel
46, 47, 48 and 49, respectively. Similarly, attached to
the upper edge of first and second roof panels 31 and 32
are first and second roof rib panels 54 and 55,
respectively. First and second gable rib panels 46 and 47
are connected to each other at a common score line 51, and
third and fourth gable rib panels 48 and 49 are connected
to each other at common score line 50. I'he uppermost end
52 of line 51 is the tip of the pouring spout of the
erected container.
First gable rib panel 46 is connected to first
roof rib panel 54 at score line 8, and second gable rib
panel 47 is connected to second roof rib panel 55 at score
line 9.
First roof wing panel 38 comprises a triangu1ar
portion of first roof panel 31 defined by score lines 40,
45 and 8, and is adjacent first foldback panel 41. Second
roof wing panel 39 comprises a triangular portion of second
roof panel 32, and is defined by score lines 40, 45 and 9.
Panel 39 is adjacent second fo]dhack panel 42. These roof
wing panels are more or less coe~tensive with the adjacent
foldback panel when the erected container is closed.
: 35 A first upper ~ib panel 57 is connected to the
upper edge of the first roof rib panel 54. Likewise, a
second upper rib panel 58 is connected to the upper edge of
-15- 13~ 575~
the second roof rib panel 55. The score line 59 separates
the upper rib panels from the adjacent roof rib panels, and
is substantially continuous with the free upper edge 53 of
the first and second gable rib panels ~6 and ~7. The
latter panels serve as lips of the pouring spout of the
erected container.
The score lines may be applied to hlank lA
before or after an optional thermoplastic coating is
applie~ to the blank. ~rhe score lines may be applied to
either surface or both surfaces of the blank. For purposes
of clearer delineation of the various panels, score lines
are shown in the drawings on either or both of the inner
and outer surfaces of the blank and container.
In the embodiment shown in FIG. 5, a single
stiffening fillet 56 overlies portions of the first and
second gable rib panels 46 and 47. Fillet 56 ~omprises a
strip 61 of stiff material having a layer 62 of adhesive on
one surface, by which the strip is bondingly attachetl to
the outer surface 63 of the gable rib panels 46 and 47.
Strip 61 may be formed from any solid material which is
resistant to deleterious effects of the container sealing
process, and is sufficiently rigid so that, together with
adhesive layer 62, it provides sufficient strength t~
reinforce the panel to achieve the necessary stiffness.
Thus, ~or some containers, the modulus of elasticity of
strip 61 must be at least 100,000 psi (0.7 x 108 kg/m2),
and is preferably at least 200,000 psi (1.4 x lOd kg/m~).
For hermetic sealing cartons and other containers with
relative]y heavy gauge walls, the modulus of the strip is
preferably at least 400,000 psi (2.~ x 108 kg/m2).
Strip 61 must not melt, or otherwise degrade at
the conditions, e.g., elevated temperature and pressure, of
the container sealing process. Of course, a containe~:
sealing process of significant compression of the panels at
an elevated temperature my tend to increase the area of
intimate contact and relieve elastic stresses, causin~
adhesion of the abutting strip surfaces 69, or adhesion of
-16- ~3~ ~7~3
strip surface 69 to the p~nel outer surface 63, if fillet
56 is present on only one o~ the gable rib panels ~6 or 47.
The bond strength of this pressure-produced adhesion will,
however, be signi~icantly less than the bond strenqth of
the adhesive layer 62 which bonds strip 61 to the gable rib
panel ~6 or ~7.
Material such as metallic foil, polyester film,
and polycarbonate ~ilm are examples of strip materials
which are unaffected by the temperatures used for sealing
panels coated with polyethylene, and have a su~ficiently
high modulus of elasticity. Thermoplastic coatin~s like
polyethylene are typically sealed at temperatures of 250 to
400F (81 and 205C). In one preferred embodiment of the
inventlon, the material of the strip is unoriented
polypropylane, sucl- as that utilized as a film backing in a
pressure sensitive adhesive tape marke~ed under the
trademark "Y-~50" by ~innesota Mining and Manufacturing
Company of St. Paul, Minnesota. A fillet constructed of
unoriented polypropylene exhibits several advantayes over
strips constructed of other materials. Specifically,
unoriented polypropylene has a lower modulus of ela~sticity
than polyester ~i.e. as low as 0.2 x 10~psi). ~herefore, a
more compliant strip may he constructed which is better
able to conform to t:he scorelines between the pouring spout
panels. Thus, a notch, such as is shown in Figures 9, 10
and 12 and discussed hereinafter, is not required. This
simplifies the process of positioning and aligning tile
fillet on the panels. The optmium temperature range per
bonding the unoriented polypropylene strip is 260 - 3~0F.
Unoriented polypropylene is tlle preferred material Eor the
strip in that it is dimensionally stahle, even when
subjected to the elevated temperatures and pressures
experienced when a container is sealed. Oriented
polypropylene, although having increased tensive strength,
has a tendency to return to its unorientefl state whe
exposed to temperatures ~i.e., 180-200F) below the
sealing te~peratures. This distortion of oriented
-17- ~ L57~3
polypropylene results in buckling and separation of the
polypropylene from a mounting surEace.
The strip 61 and adhesive layer 62 may be
preformed as a tape which is applied by machine to the
blank lA.
Neither strip 61 or adhesive layer 62 has direct
contact with the container contents, so governmental
approval for the materials from which the fillet components
are fabricated may not generally be required.
Nevertheless, strip materials and adhesives approved Eor
food contact are available.
The stiffness of the fillet 56 must be such that
the panel with the attached Eillet has greater stiffness
than a panel without the fillet. Expressecl in another way,
the fillet 56 must enable the panel ~6 and/or ~7 to carry
and transfer a greater longit~dinal force to open the
container. This relationship may be expressed as follows:
E2>El(hl) /(h2)
where: El = modulus of elasticity of panel.
E2 = modulus of elasticity of panel ~ fillet.
h1 = thickness of panel.
h2 - thickness of panel + fi~let.
~5 For hermetic sealing containers, it is preferred that E2 be
greater than 0.2 x 106 pounds per square inch (1.~06 x lOe
kg per square meter) to provide the desired stiffness. The
thickness of the panel or panel plus fillet affects the
resistance to buckling and bending. Tlle adhesive is
important in rigidity spacing strip 61 from the panel
surface to provide the necessary effective thickness of the
panel and fillet. The adhesive usecl may be sealable hy
pressure, heat, or other process, but is preferably a
pressure-sensitive adhesive whose bonding strength is
incr0ased by the container sealing process.
FIG. 6 is an enlarged cross-sectional view
through the rib portion of a container formed from this
~ 3 ~ 3
invention, showing the panel members ancl fi]let exaggerated
in thickness for the sake of clarity. It is understood
that all of the panel members shown may include a
thermoplastic coating on at least one of the blank
surfaces, and preferably on both the inner and outer
surfaces. Additionally, the panel members may include a
film or foil of gas-impermeable material such as aluminum,
overcovered by the thermoplastic coating.
First and second roof rib panels 54 and 55
overlie first and second gable rib panels 46 and 47. The
gable rib panels q6 and ~7 are separated from foldback
panels ~1 and q2 by scorelines q5, and the roof rib panels
5~ and 55 are likewise separated from roof wing panels 38
and 39 by scorelines ~5. Upper rib panels 57 and 5~ are
separated by score line 59 from the roof rib panels 5~ and
55, and extend upwardly therefrom. Each of the panels
shown in the figure may include a coating of thermoE-lastic
on at least one of the surfaces. Stiffening fillet 56 is
shown attached to the outer face 63 of gable rib panels 46
and 47. The fillet includes resistant strip 66 and
adhesive layer 72, so that when the container is closed and
sealed, as shown here, the surfaces 69 of the folded strip
: 61 form a strip-strip interface 6~ with an intervening
adhesive.
Fillet 56 may comprises a tape having a
relatively thick backing or strip 61 of a stiff ~aterial
whose bond to itself is weaker than its bond to ac]hesive
layer 62. The adhesive layer 62 may be tllermoplastic in
nature, but preferably is a pressure-sensitive adhesive.
The ~atter affords easier positioning cluring application to
the blank lA, and does not require the application of heat
for positioning. However, the thermal carton sealing
process has been found to significantly enhance the sealing
strength of the pressure-sensitive adhesives (PSA's) which
were tested.
In FIG. 6, the container contents occupy the
space between panel 38 and panel ql, and the space between
-19- ~3~7~3
panel 39 and panel ~2. The spout sea] interface 65 between
gable rib panels ~6, ~7 and respective roof rih panels 5~,
55 may include an adhesive layer, if bonding of the panels
is not desirable. In other cases, such as in hermetic
seals, these panels are bonded by fusing of the
thermoplastic coating on the panels, by adding adhesives,
or by other means. If the panels are bonded tightly along
interface 65, the force required to break the seal and open
the container spout may be considerably greater than the
gable rib panels can transfer. Use of the fillet enhances
the force carrying capability of the gable rib panels to
provide an openable container.
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 coa-ting, and compressed together
as shown in FIG. 6. The upper rib panels are bonded 011
their inner surfaces at interface 67, provicling the major
bonding to maintain the integrity of the gable top during
handling and storage.
The adhesion of strip 61 to the pouring spout
panels such as gable rib panels ~6 and/or ~7 should
preferably produce a peel strength greater than 50 oæ. per
inch of width (612 grams per cm width) at room temperature,
so that the fillet will remain an integral part of the
panel to which it is attached, both before and after the
spout panels are unsealed and unfolded.
The thickness of both the strip 61 and the
adhesive layer 62 will depend upon the ~orce which must be
transferred by the gable rib panels, the modulus of
elasticity of the strip, and to a lesser extent, the
adhesive properties. The same resistance to buckling can
be achieved with various combinations of adhesive
thickness, strip thickness, strip material and type of
adhesive. For example, when a polyester strip is used, a
strip thickness of 0.001-0.00~ inch ~0.0025-0.01 cm) is
generally desirable, and an adhesive layer of the same
-20-
range of thickness may be optimal for achieving the clesired
additional stiffness. A fillet adhesive layer of ahout
0.002 inch (0.005 cm) has proven optimal for certain
pressure-sensitive adhesives used in fillets to reinforce
polyethylene coated containers. With other adhesives, a
thickness of up to 0.004 inch (0.0102 cm) may be used.
Even monomolecular layers of adhesives may be used in the
fillet. However, for strips constructed of unoriented
polypropylene, an adhesive layer havinq a thickness of
approximately 0.003 inches (0.008 cm) has been found to be
preferred.
FIG. 7 shows a cross-section through another
embodiment of this invention. ~his embodiment difEers from
that of FIG. 6 in that the fillet 56 not only overcovers a
portion of the gable rib panels ~6 and 47, but also extends
downward to overcover portions of the outside surfaces 66
of the foldback panels 41 and 42. Such downward extension
adds stiffness to the entire spout, strengthening the gable
rib panels 46 and 47. Furthermore, in a thermal container
sealing process, the temperature of the foldback panels is
not as high as that of the gable rib panels, and ~i]let 56
will not slip from its proper position. Some pressure-
sensitive adhesive materials tend to hold the strip less
tightly when they are heated to a temperature of 250-400~F
(81-205 C).
~ IGS. 8 and 9 depict a modification of the
invention in which a secondary layer 70 of adhesive
overcovers surface 69 o-~ strip 61. The panel 46, adhesive
layers 62 and 70, and strip 61 are shown with exagyerated
thickness for clarity. The secondary adhesive ~ay be
pressure-sensitive or activated by the container sea]illg
process, e.g., elevated temperature. The bond stren~th of
the secondary layer 70 is substantially less than the bond
strength o~ the primary adhesive layer 62. Thus, in FIG.
8, strip 61 is shown fixedly attached to the outer surface
63 of gable rib panel 46 by adhesive layer 62. Secondary
adhesive layer 70 overcovers the opposite surface oE strip
-2l~ ~3~3~3
61. when the container gable top is folded for closure,
the mirror image fillets 56 on each of the gable rib panels
46 and ~7 abut one another. The secondary adhesive layers
70 become joined, so that the outer surfaces 63 of the
gable rib panels are sealed togetller.
FIG. 9 shows an exaggerated section throuqh the
rib portion of a closed and sealed container according to
this embodiment. Roof wing panels 38, 39, foldback panels
~ 2, roof rib panels 54, 55, gable rib panels 46, ~7,
and upper rib panels 57, 58 are shown in the same manner as
in FIGS. 6 and 7. A fillet 56 comprising strip 61,
adhesive layer 62, and secondary adhesive layer 70 is
attached to the outside surface 63 of each of the gable rib
panels 46, 47. In this sealed condition, the two secondary
layers 70 become joined to eEfectively form a single layer
71. Layer 71 may be adapted to delaminate within the layer
itself, or to peel from one of the strip surfaces 69. The
bond strength of layer 71 is substantially less than that
of adhesive layer 62, so that the fillet or fillets 56
remain Eirmly attached to the gable rib panels 46, ~7
during the use of the container.
If desired, the fillet or fillets 56 may extend
downwardly to over-cover portions of foldback panels ql and
42 in a manner similar to that previously shown in ~IG. 7.
An advantage of this embodiment is that the
secondary bonding strength can be varied over a wide range
to achieve the desired first stage opening force
req~irement. The bonding strength may range from
essentially zero up to a strength slightly less than the
strength of the gable rib panels 46 an~ ~7.
FIGS. 10 through 13 show a portlon of the blank
lA, including those panels which become the pouring spout.
These figures depict various embodiments of fillet 56 in
terms of the particular panel area or areas coverecl
thereby. Each figure shows panels 3-5, 29, 31-32, 3~-39,
~ 2, ~6-47, 54-55, and 57-5~, with one or more fillets 56
attached to the qable rib panels ~6, 47.
~ -22-
~-3 ~rJ~
In FIG. 10, a single fillet 56 overcovers all or
a portion of both c3able ~ib panels 46 and 47. The upper
edge 72 of fillet 56 is shown as generally continuous with
the upper free edge 53 of the qable rib panels, but it may
be spaced therefrom, either upward or downward.
Preferably, upper edge 72 does not extend above free edge
53 by more than 0.15 inch (0.38 cm). When the gable rib
panels are coated with thermoplastic, a fillet covering all
of the panels effectively removes the adhesive effect of
the thermoplastic upon the required first stage opening
force. When the upper edge 72 of fillet 56 is lower than
free edge 53 by more than 0.3 inches (0.76 cm), an
excessive sealing area for the thermoplastic carton sealing
process may result. This produces a strong seal which may
require an excessive opening force to break the seal.
When the fillet or fillets 56 are adhesively
attached to both gable rib panels 46 and 47, and the uL~per
edge 72 of the fillets extend above the upper free edge 53
of the yable rib panels, the exposed portion of adhesive
layers 62 will become bonded to the roof rib panels 54 and
55. Therefore, it is generally desirable to limit such
upward extension of the fillet or fillets 56 above the
gable rib panels 46 and 47 to not more than 0.15 inches
(0.38 cm), unless the adhesive of layer 62 has a relat;vely
low bonding strength. Iligh ~ond strength in layer 62 may
result in tearing or delamination of the roof rib panels 54
and 55.
Each enc-l of the fillet 56 may be spaced from
scorelines 8 and 9, if desired.
3~ FIG. 11 illustrates a blank with two fillets 56
overcovering a portion of the gable Lib panels 46 and 47.
Each fillet 56 is spaced from scoreline 51. This spacinc3
73 permits the gable rib panels 46, 47 to more readily folcl
along scoreline 51 when the container is closed and sealed.
In order to transfer the required opening forces to
scoreline 51, however, spacing 73 must be reasonably
limited. IhuS, for a half-gallon container with gable rib
-23- ~ 7 5 3
panels ~6, ~7 or 1.5-2.0 inches lenyth, fillet 56 must not
be spaced from scoreline 51 hy more than 0.6 inches (1.5
cm). PreEerably, the spacing 73 between scoreline 51 and
fillet 55 is no more than 0.3 inches (0.76 cm).
Fillet 56 may also extend downwardly to overlie
an upper portion of foldback panels 91 and ~2.
Furthermore, this downward extension may overcover an upper
portion of first triangular end panel 29. This mode is
illustrated in both FIGS. 12 and 13.
The advantage of this downward extension is
evident when the container sealing process is one which
affects the bonding strength of the fillet adhesive layer
62. In common hea. sealing processes used to seal
polyethylene coated blanks, heat is directly applied to the
panels to be sealed, i.e., the rib panels. Panels helow
the rib panels are only incidentally heated and attain a
considerably lower temperature. The sealing temperature is
difficult to accurately control, and if the fillet adhesive
layer 62 softens excessively, the fillet strip 61 may slide
downward, not retaining its proper alignment on the gable
rib panel or panels ~6 and 47. The portion of the fillet
56 below the gable rib panels will be much less affected
because of the lower temperature, and will maintain the
desired original position of the fillet. The adhesion of
adhesive layer 62 is regained upon cooling.
FIG. 12 shows the fillet as overlying score line
intersection 7~ at the top of triangular end panel 29, and
extending downward to overcover portions of the foldhack
panels 41, ~2 and triangular end panel 29.
It has been discovered that enhanced sealing
results from slotting the fillet 56 where it overcovers the
common gable rib score]ine 51. ~hus, in FIG. 13, fillet 56
includes a slot 75 extending downwardly from the upper edge
72 of the fillet, along at least a portion of the common
line 51. This enables easier folding of the gable rib
panels ~6, ~7, without distortion along line 51. The notch
may optionally extend downwardly to expose intersection 7~,
~3:~7~
or may extend downward as a slot through the fillet to
di~ide it into two fillets. When a notch or slot exposes
the common line 51, the edge of the fillet strip is
preferably separated form a portion oE the common line by
no more than 0.3 inches (0.76 cm). When there are two
fillets, each overcovering a portion of one of the ga~le
rib panels, the maximum spacing of each fillet from common
line 51 is also preEerably 0.3 inches (0.76 cm). A greater
spacing may result in insufficient stiffening of the panels
in the vicinity of common line 51.
EXAMPI.E 1
Commercial hermetically sealed 0.5 gallon (1.9
liter) gable-top containers were manually opened. ~fter
folding back the wing panels, simple forward hand pressure
on the roof rib panels resulted in buckling and clistortion
of the gable rib panels, without opening the tip of the
spout at the common fo]d line. In all cases, insertion of
a k~ife blade between the gable rib panels and rooE rib
panels near the common fold line was required to open the
spout.
Container blanks of the same material were sealed
by hand, using a LiquipakqM model 010 hand sealer.
Attempts to open the containers produced the same results
as were obtained with the commercially sealed containers.
An applied force of 15 pounds-force (6.8 kg-force) resulted
in tearing and buckling of the panels, without opening the
spout.
The opening force required by a previously opened
hermetically sealed carton was determined to be abut 2.6
pounds-force (1.2 kg-force).
For the sake of comparison, a common milk carton
opened from the sealed condition with an applied force of
about 3.0 pound-force (1.36 kg-force), without tearing of
the spout panels. This carton is sealed only to the e~tent
of preventing liyuid leaks, and a hermetic barrier is not
provided.
-25- ~3~ ~r)rJ3
EXAMPLE 2
Several types of fillet were applied to
polyethylene coated cardstock for determining the eEfect
upon panel stiffness and ease of container opening
The container material was manufactured by
International Paper Company for hermetically sealed
cartons, and comprised paperboard having an aluminum film
bonded to the inside surface, and both sides then coated
with thermoplastic polyethylene.
The types of aclhesive used in the fillets
included (a) ethylene-vinyl acetate (EV~) copolymer, (b)
medium density polyethylene (MDPE), and (c) a
pressure-sensitive adhesive (PSA).
Tlle modulus oE elasticity was determined by
measuring the deflection caused hy a weight placed on the
center of a simple beam formed from the cardstock.
Measurements were made on the cardstock itself, on a pair
of ~able rib panels from a blank, and from the entire outer
spout assembly comprising the gable rib panels, triangular
end panel, and foldback panels. The formula used to
calculate the modulus was:
E = fL /Qba Y
where E = modulus of elasticity.
f = force applied, 0.11 pound (50 g) Eor most
tests.
a = thickness of beam.
b = width of beam, 1.0 inch (2.5Q cm).
Y = deflection, inches (cm).
L = length of heam = 3.7 inches (9.Q cm).
The results were as follows:
~ -2~-
~3~7~3
a Y E, Moclulus,
seam MaterialThickness ~eflection PSI(k~,/cm2)
Cardstock
(unreinforced) 0.027 in. 0.18 in. 393,000
(0.069 cm) (0.46 cm) (2.76 x 108)
Cardstock with
transverse 0.027 in. 0.33 in. 28,000
scoreline.
(0.069 cm) (0.89 cm) (0.2 x ]o8)
~f = 10 g because oE reduced modulus)
Cardstock with
fillet of 0.004 0.036 in. 0.090 in. 332,000
in. (0.010 cm)
polyester and (0.091 cm) (0.23 cm) (2.33 x 108)
0.002 in tO.005
cm) EVA adhesive
(ScotchpakT'~
26 tape~
Cardstock with
fillet of 0.002 0.032 in. 0.12 in. 390,000
in. (0.005 cm)
polyester and (0.079 cm) (0.30 cm) (2.7 x 10'3)
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)
2S Spout panels, 0.027 in. 0.21 in. 337,000
preflexed
(0.069 cm) (0.53 cm) (2.9 x 108)
Polyester Film - 900,000
(Literature
Value) (2.8 x 108)
The results inclicate that the moclulus of
elasticity is approximately the same, i.e., 0.9 x lO' lsi
(2.8 x 108 kg/m2) for preflexed panels, either Witil or
without the added fillet.
Buckling forces were calculated from the lata of
Table 2 usin~
PCrit = CEh3b/12L2 ~
where PCrit is the forward-directed force merely
required to open the preElexed spollt from a
closed but unsealed condition, lb-force;
C is pi '
E is the modulus of elasticity, approximately
O . ~ x 106 psi;
h is thickness, 0.027 inches (0.069 cm);
b is width, 1.0 inch (2.5~ cm); and
L is length, 3.7 inches (9.40).
The calculated force requi~ed to open the unseal~d spout of
unreinforced cardstock was 0.5 pounds (0.23 kg.).
The force carried by both of the unreinforced
gable rib panels prior to buckling was calculated to be 1.9
pounds (0.86 kg.), using L = 1.85 inches. This leaves
1.9 - 0.5 = 1.4 pounds (0.64 kg.) of force for breaking the
bond at the tip of the spout.
Reinforcement of the gable rib panels with a
0.002 inch (O.OOS cm) thick polyester strip and 0.002 inch
~0.005 cm) layer of PSA adhesive provicled a higher
calculated available force of 2.9 - 0.5 = 2.4 pounrls for
breaking the bond at the spout tip. In this case, the net
panel thickness was 0.031 inches (0.079 cm.).
Reinforcing the gable rib panels with 0.009 inch
~OoO10 cm) thick polyester and a 0.002 inch (0.005 cm)
layer 62 of EVA adhesive provided a calculatecl availa~,le
force of 4.6-0.5 = 4.1 pounds (2.09 kg.) for breaking the
bond at the spout tip. In this case, the net panel
thickness was 0.036 inches (0.142 cm). Thus, as a thicker,
sti~fer reinforcement strip is added, the ability to
transfer applied forward-directed opening Eorces for
opening the spout tip greatly increases.
Measurements were macle of the force requi~ed to
open a previously opened gable top hermetic sealing c.-lrton,
using a spring gauge. I'he average measured force of 2.4
pounds (1.09 kg.) includecl the force requiled to buckle the
~3~1~'75~
-2~-
extren~e tip of the unreinforced spout, that is, the common
fold line of the gable rib panels. Thus, the calculated
value of the force transmitted by the unreinforced spout
panels is only 1.9 pounds (0.86 kg.), nearly equal to the
measured force of 2.4 pounds (1.09 kg) required to open the
previously opened carton. This demonstrates that the
greater joint strength of a sealed spout will result in
buckling of the cardstock when openin~ forces are appiied
to the spout panels. On the other hand, when the gable rib
panels were reinforced with a fillet according to this
invention, the added stiffness provided an available
opening force greater than 2.~ pounds to the common fold
line, and the containers were opened without bucklincJ or
delamination of the panels.
With polyethylene coated blanks made for hermetic
sealing, and similar gable top containers, ease of se(-ond
stage opening will be enhanced by (a~ an increase in gable
rib area covered by the fillet, (b) fillets of greater
stiffness, (c) slotting the fillet 56 along tile common fold
line 51 between the gable rib panels, (d) leavill-3 ~Incovered
the score line intersection 79 where the triangular entl
panel 29 touches the common fold line, and (e) a redllction
of fillet 56 area which extends above the gable rib panels
46, 47 to seal to the roof rib panels 54 and 55.
EX~MPLE 3
Several types of adhesive tapes were evaluated
for use as fillets, that is, for ease of positioning on the
gable rib panels and adhesion to the gable rib panels. ~he
following tapes were applied to gable rib panels o~
polyethylene-coated container blanks, which were tl
heat-sealed.
ScotchpakTM 25: 0.004 inch (0.0~. cm) polyester backing
as the strip, with 0.002 inch (0.005 cm) EV~.
adhesive.
ScotchpakTM 48: 0.0005 inch (0.0012 cm) polyester
-29- ~ 3 ~ 3
backing with 0.00~ inch (0.01 cm) MDPE adhesive.
ScotchtabT~: 0.002 inch (0.005 cm) polyester backing as
the strip, with 0.002 inch (0.005 cm) PSA
adhesive.
ScotchpakTM 26 with 0.003 inch (0.0075 cm) PSA adhesive
applied over the EVA adhesive.
Polyester/PSA: 0.002 inch (0.005 cm) polyester film
backing as the strip, with 0.003 inch ~0.0076 cm)
PSA adhesive.
Control: No fillet.
The pressure-sensitive adhesive (PSA) used in
this test was a typical rubber resin adhesive.
The resu]ts of the tests were as follows:
Scotchpak M 26 with EVA adhesive was difficult to
position for sealing, and required preliminary
heat sealing to provide a good seal.
5cotchpakTM ~8 with MDPE adhesive was difficult to
position and required preliminary heat sealing.
Insufficient stiffness was added by the fillet to
consistently transfer the reyuired opening forces
to the spout tip.
Scotchtab M with PSA adhesive was easy to positi,-,n, and
required heat sealing to strongly bond to the
panels. Sufficient opening forces were
transferred.
ScotchpakTM 26 with PSA adhesive was easy to position,
and heat-sealing provided a good seal.
Sufficient opening forces were transferrecl to
open the seal.
The control gable top carton spout, heat-sealed
according to the commercial process, could not be opened
without buckling and delamination of the cardstock.
-30- ~ 3 ~ 3
~XAMPLE 4
An unoriented polypropylene adhesive tape was
evaluated as a stiffening fillet in a one-half gallon gable
top container blank, which was then lleat sealed with a
Liquipak ~odel 010 heat sealer.
'rhe tape was applied to the outside of the spout
flush to the spout edge. The fillet was one-and-one halE
o~ an inch wide and three and three eights of an inch long.
The fillet was centered on the spout tip.
The tape had a 0.0065 inch thick unoriented
polypropylene backing and a 0.003 inch thick rubher/lesin
pressure sensitie adhesive.
The carton was opened in the normal manner. The
carton opened with difficulty but dicl open. The inside
spout lips had fully bonded and llad full paper tear when
opened. A similar carton without the fillet would have a
force in excess of 12 pounds applied and would buckle and
not open.
. The polypropylene was not significantly bonded to
itself.
While the present invention has been particularly
set forth in terms of specific emhodiments thereof, it will
be understood in view of the instant disclosure that
numerous variations upon the invention are enablecl to those
skilled in the art, which variations yet reside within the
scope of the present teaching. Accordingly, this invention
is to be broadly construed, ancl limited only by the scope
and spirit of the claims now appended hereto.
