Note: Descriptions are shown in the official language in which they were submitted.
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RETORT-RESISTANT PLASTIC CONTAINER
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of United States Provisional
Application No.
61/394,248, filed October 18, 2010, which is hereby incorporated by reference
as though fully
set forth herein.
TECHNICAL FIELD
[0002] The present invention relates in general to retort-resistant plastic
containers,
including molded plastic containers with improved structural characteristics
for resisting retort.
BACKGROUND
[0003] Metal cans have been used to hold product contents for some time.
More recently,
with increases in the costs of metals, such as steel, there has been an
interest in providing cans
and other forms of containers made of plastic. However, plastic cans and
containers have been
commonly considered less suitable for some applications due to the physical
stresses placed on
the material, which for some applications may be significantly greater than
those encountered in
common plastic container "hot-fill" applications. Retort processes provide an
example of
applications in which, due to high temperatures and internal pressures,
plastic containers have
been considered to be undesirable. A common industry objective is to provide a
plastic container
that can practically withstand such processing with minimal or sufficiently
recoverable
deformation.
[0004] Consequently, there exists a desire to, among other things, provide
plastic, retort-
resistant containers that are capable of serving as replacements for
applications involving
relatively higher physical stresses, such as microwave applications or other
retort processes.
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SUMMARY
[0005] A retort-resistant plastic container includes a base portion, a
sidewall portion, and a
neck portion. The base portion includes a domed portion and a lower annular
portion. The
sidewall portion extends upwardly from the base portion, and typically has a
minimum thickness
of 0.020 inches. The neck portion extends upwardly from the sidewall portion
and includes an
annular flange. In embodiments, the outer diameter of the lower annular
portion is less than the
inner diameter of the annular flange. Further, in some embodiments, the
sidewall is substantially
smooth absent various sidewall structural reinforcements (e.g., vacuum panels
or reinforcement
ribs). Moreover, for embodiments, the sidewall portion is at least 0.80 of the
total vertical length
of the container.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] Embodiments of the invention will now be described, by way of
example, with
reference to the accompanying drawings, wherein:
[0007] FIG. 1 is a perspective illustration of an embodiment of a plastic
container
generally illustrating certain teachings of the present invention;
[0008] FIG. 2 is perspective illustration of an embodiment of a plastic
container similar to
that generally illustrated in FIG. 1;
[0009] FIG. 3 is a top view of the container generally illustrated in FIG.
2;
[00010] FIG. 4 is a side elevation view of the container generally
illustrated in FIG. 2;
[00011] FIG. 5 is a side cross-sectional elevation view of the container
taken along lines A-
A in FIG. 4;
[00012] FIG. 6 is a side elevation view of a container similar to that
shown in FIG. 2,
generally illustrating split lines for the container;
[00013] FIG. 7 is a cross-sectional view of the container taken along lines
B-B in FIG. 6;
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[00014] FIG. 8 is a cross-sectional view of an embodiment of a base portion
for a container,
the view generally illustrating aspects of the inventive concept;
[00015] FIG. 8A is a cross-sectional view of another embodiment of a base
portion for a
container;
[00016] FIG. 8B is a cross-sectional view of an embodiment of a base
portion similar to that
shown in FIG. 8A, generally showing a base portion in a different
configuration;
[00017] FIG. 9 is a cross-sectional view of a portion of the neck of a
container;
[00018] FIG. 10 is perspective view of two containers generally shown in a
stacked
configuration;
[00019] FIG. 11 is an elevation view of two containers generally shown in a
stacked
configuration; and
[00020] FIG. 12 is an enlarged sectional view of an annular flange and
closure.
DETAILED DESCRIPTION
[00021] Reference will now be made in detail to embodiments of the present
invention,
examples of which are described herein and illustrated in the accompanying
drawings. While the
invention will be described in conjunction with embodiments, it will be
understood that they are
not intended to limit the invention to these embodiments. On the contrary, the
invention is
intended to cover alternatives, modifications and equivalents, which may be
included within the
spirit and scope of the invention as defined by the appended claims.
[00022] FIGS. 1 and 2 generally illustrate embodiments of plastic
containers 10, 20
including teachings and aspects of the present invention. As generally
illustrated, the container
20 may include a base portion 30, a sidewall portion 40 that extends upwardly
from the base
portion 30, and a neck portion 50 that may include an annular flange 60. A top
view of the
container 20 is generally illustrated in FIG. 2.
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[00023] In an embodiment, the plastic container 20 may be comprised of
polypropylene
(PP). However, the container is not limited as such, and other plastic
materials, such as
polyethylene terephthalate (PET), high density polyethylene (HDPE), and
various plastic
monomers, may also be employed for some applications. The container may also,
if desired
include one or more barrier materials/layers and/or oxygen scavengers,
including conventional
oxygen scavengers that do not haze, provide a clear appearance, and do not
have a negative
impact on recyclability. It is noted that the container according to the
disclosure may be
monolayer. However, if desired such containers can instead be provided in the
form of a multi-
layer construction. For example and without limitation, in an embodiment, a
container may be
provided with two polymer layers (e.g., two polypropylene (PP) layers)
separated, for instance,
by a barrier/scavenger layer (e.g., ethylene vinyl alcohol (EVOH)), and, if
desired, the layers
may be held together by some form of adhesive.
[00024] Further, while various molding techniques may be employed to form
the container,
in embodiments, the plastic container may be injection molded. With injection
molded
embodiments, the plastic container 20 may comprise an amorphous plastic, as
opposed to a
biaxially oriented plastic that may be produced by a different process, such
as injection stretch
blow molding (ISBM). Notably, for embodiments of the container, the wall
thicknesses at the
majority of portions of the container will exceed 0.020 inches, for other
embodiments the wall
thicknesses at the majority of portions of the container will exceed 0.030
inches, and for some
embodiments, the minimum wall thickness for all portions of the container may
be 0.030 inches.
Moreover, and without limitation, for some embodiments, the average wall
thickness may be
0.070 inches or more.
[00025] FIG. 4 generally illustrates a side view of the container 20. The
base portion 30 is
shown including a lower angular portion 70 and a lower annular portion 80. As
generally
depicted in the illustrated embodiment, in embodiments, the sidewall portion
40 may comprise a
substantial portion of the vertical length of the container 20. In
embodiments, without limitation,
the sidewall may comprise at least 0.80 of the total vertical length of the
container, and for some
embodiments may comprise at least about 0.89 of the total vertical length.
Moreover, for
comparison purposes, and without limitation, in an embodiment the total
vertical length L1 of the
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container 20 may be approximately 3.35 inches, L2 may be approximately 3.19
inches, and L3
may be approximately 3.09 inches. Further, also for comparative purposes, and
without
limitation, the diameter of the container 20 at or about D1 may be, for
example, about 2.69
inches; while the diameter at the position labeled D2 may have about a 0.25
inward taper
moving toward the base portion 30.
[00026] FIG. 5 includes a cross-sectional view of the container 20 viewed
along lines A-A
in FIG. 4. For illustration and comparison purposes, and without limitation,
in an embodiment
the thickness of the sidewall portion 40 at T1 may be, for example, about
0.070 inches; the
diameter at D3 may be about 2.52 inches; the diameter at D4 may be about 2.97
inches; and the
diameter at D5 may be about 2.37 inches. Moreover, as additionally depicted,
vertical lengths L4
and L5 may, for example, be about 3.18 and 3.07, respectively. Further, the
illustrated angle 0
may, for example, be about 35 10 . It is noted that the container is not
limited to the
aforementioned dimensions, which merely illustrate aspects and features of the
inventive concept
in an illustrative context. It is noted that FIG. 5 also identifies two
regions, generally identified
as C and CDS (custom double seam), which are discussed further hereinafter in
connection with
FIGS. 8 and 9. For some embodiments, D5 will not be less than 0.75 the
diameter of D3. For
example, without limitation D5 may be about 0.89 times D3.
[00027] FIG. 6 generally includes other dimensions of container 20 in an
illustrative
context, generally illustrating possible mold split lines. For example,
without limitation, L6,
which may generally represent a vertical length for a stripper ring, may be
about 0.022 inches;
L7, which may generally represent a vertical length for a cavity (top), may be
about 2.49 inches;
and L8, which may generally represent a vertical length for a cavity (bottom),
may be about
0.085 inches. It is noted that the invention is not limited to the split lines
illustrated, and other
and/or more split lines may be employed as known to persons skilled in the
field.
[00028] FIG. 7 includes a cross-sectional view of the container 20 viewed
along lines B-B
in FIG. 6. For illustration and comparison purposes, and without limitation,
vertical lengths L9
and L10 may, for example, be about 3.33 and 0.64, respectively.
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[00029] The base portion region generally identified as region C in FIG. 5
is illustrated in
additional detail in FIG. 8. In addition to the lower angular portion 70 and
the lower annular
portion 80, the figure also generally illustrates a domed portion 90, which is
shown comprising
an upward angular portion 100, a curved portion 110, and a dimpled portion
120. It is noted that,
the base portion 30 of the container may, if desired, be configured to
facilitate container-on-
container stackability. That is, portions of the base portion 30 may be
configured to receive
and/or retain upper portions associated with similarly configured containers.
For illustration and
comparison purposes, and without limitation, the diameter at D6 may be about
1.77 inches; the
diameter at D7 may be about 2.53 inches; and the diameter at Dg may be about
2.66 inches.
Further, the vertical length L11 may be, for example, about 0.47 inches; and
the illustrated
thicknesses at T2, T3, T4, T5, T6, and T7 may be about 0.070, 0.070, 0.071,
0.079, 0.069, and
0.070 inches, respectively. Upward angular portion 100 may have an angle, as
measured from
the standing surface, of about 15 . For some embodiments, the angle between
the upward
angular portion 100 and the standing surface may be at least 5 . However, for
some
embodiments, the angle may be between about 5 and about 45 , and may further
be between
about 5 and 25 . The upward angular portion 100 provides space for stacking
with respect to
features of a container stacked vertically below it. For example, a clearance
(or head space) may
be created by lower annular portion 80, which may, for example, have a
vertical height H1 of at
least about 0.030 inches, and for some embodiments may have a vertical height
H1 of at least
about 0.100 inches. The clearance may provide sufficient room for a raised
formation, e.g., a
raised tab, or pull tab, that can extend vertically upward from a lower
container. The clearance,
or head space, may further be increased at portions vis-a-vis an associated
upward angular
portion 100. An upward angular portion, for example and without limitation as
generally
illustrated in FIG. 8, may provide a further increased vertical height H2.
Additionally, for some
embodiments, D7 may not be less than 0.85 the diameter of Dg. For example,
without limitation
D7 may be about 0.95 times D8.
[00030] Turning to FIG. 8A, another embodiment of a base portion region is
shown. The
illustrated embodiment of a base portion 30' includes a lower angular portion
70', a lower
annular portion 80', and a domed portion 90'. With some embodiments, such as
that illustrated,
the base portion 30' may include wall portions, or at least segments thereof,
that are
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comparatively thinner than other portions of the base portion, and/or in
comparison to a
container with a base portion that is intended to be substantially rigid in
service. If desired, the
domed portion 90' may include an upward angular portion 100', a curved portion
110', and a
dimpled portion 120'. Further, the base portion 30' can also be configured to
facilitate
container-on-container stackability.
[00031] While some embodiments of the base portion may be substantially
"fixed," in that
there is little or no intended flexing, embodiments of a base portion, such as
base portion 30',
may instead include portions that are configured to be flexible and/or to
promote movement
(e.g., in response to internal pressure or a vacuum) as a filled container
takes commercial form.
That is, in embodiments, portions of base portion 30' may, for instance, be
formed to be
comparatively thinner than surrounding portions, and such thinner portions may
be configured to
move or flex between inward and outward positions. To illustrate the point,
and without
limitation, FIG. 8B generally illustrates a base portion 30' similar to the
base portion shown in
FIG. 8A. As shown in FIG. 8B, the base portion can have portions that, at
least at a point in time
(e.g., prior to contents cooling and creating a vacuum force), extend
downwardly. As shown in
the illustrated embodiment, a portion of the base portion ¨ e.g., the segment
where the upward
angular portion 100' and curved portion 110' generally come together ¨ can
extend downward to
a vertical height/level that is at or near the same vertical height/level as
the lowermost
height/level of the lower annular portion 80' (which may be a lower resting
plane or standing
surface for the container). Then upon sufficient internal force, the
aforementioned portion of the
base portion can flex or translate to an upward position, such as generally
illustrated in FIG. 8A.
The intentional reduction in internal volume of the container provided by the
upward flexing of a
portion of the base portion can accommodate internal pressure (e.g., vacuum
pressure) associated
with the container, such as in connection with the cooling of contents in a
retort or hot-fill
application.
[00032] For example, and without limitation, a wall thickness of a "flex"
base portion may
have wall portions with a thickness of about 0.025 inches, while the wall
thickness for a
comparable portion of a "fixed" base portion might have a thickness several
times thicker (e.g.,
about 0.100 inches). For illustration and comparison purposes, and without
limitation, the
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illustrated thicknesses at T9, T10, T11, and T12 may for instance be about
0.069, 0.025, 0.070, and
0.070 inches, respectively.
[00033] The upper region generally identified as region CDS in FIG. 5 is
illustrated in
additional detail in FIG. 9. For illustration and comparison purposes, and
without limitation,
thickness T8 may be about 0.022 inches; lengths L12, L13, and L14 may be about
0.040, 0.128,
and 0.217 inches, respectively; and diameters D9, D10, D11, D12, and D13 may
be about 2.85, 2.61,
2.61, 2.58, and 2.55 inches, respectively.
[00034] FIGS. 10 and 11 generally illustrate an embodiment of plastic
containers 20 shown
in a stacked configuration.
[00035] In embodiments, the neck portion 50 may include a finish with
flange configured to
accept a double seam closure. Such a finish may be configured with respect to
desired closure
features. For a number of applications, metallic seals and closures are
envisioned. For some
embodiments, such as generally illustrated in FIG. 12, the annular flange 60,
which serves as a
sealing flange, may be sealed via a double-seemed closure 130. Further, for
some embodiments
the neck portion will be configured to be compatible with a metal closure
having a pull tab, and
may be sealed to the neck portion 50 using induction or other known processes.
While easy-
open pull tab closures may be employed, other closures, including standard
metallic closures
without a pull tab may also be used.
[00036] Plastic containers provided in accordance with the teachings of the
present concept
may, for example, have a minimum top load strength of 100 pounds. However,
some
embodiments provide for a plastic container having a minimum top load strength
of 200 pounds
or more, with some embodiments providing a minimum top load strength of 400
pounds or more.
Embodiments of the invention may be employed with a number of different retort-
related
processes. By way of example, without limitation, embodiments of containers
provided in
accordance with teachings of the present concept may be used in connection
with low-acid
foods, such as those having has an initial temperature of 140 F, a retort
temperature of 250 F,
with 25 minutes circulating in a rotary cooker at 28 psig. Such containers may
also be employed
with another process that would ramp up the temperature to 265 F over a 20
minute time frame
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before ramping down for 20 minutes. Embodiments of plastic containers
constructed in
accordance with the teachings of the present invention may be cylindrical and
are rigid ¨ even
when provided with smooth sidewall portions that are absent various sidewall
structural
reinforcements (e.g., vacuum panels or reinforcement ribs) - and such plastic
containers may
exhibit little or no deformation. That is, such plastic containers may be
provided so that, under
normal retort conditions, the container will exhibit no more than 5%
deformation, and preferably
less than 1-2% deformation.
[00037] It is noted that embodiments of containers provided in accordance
with the
teachings disclosed herein may balance a number of design considerations. For
instance, if the
diameter of the base is too large, the container may not rest on a surface
properly; if the wall
thickness of the base portion is made too thick, it will not fit between a tab
and a sidewall
properly; and if the height of the base portion is made too short, the base
portion will not clear
tabs or other formations associated with the closure of a similar container
stacked below it.
[00038] The foregoing descriptions of specific embodiments of the present
invention have
been presented for purposes of illustration and description. They are not
intended to be
exhaustive or to limit the invention to the precise forms disclosed, and
various modifications and
variations are possible in light of the above teaching. The embodiments were
chosen and
described in order to explain the principles of the invention and its
practical application, to
thereby enable others skilled in the art to utilize the invention and various
embodiments with
various modifications as are suited to the particular use contemplated. It is
intended that the
scope of the invention be defined by the claims and their equivalents.
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