Note: Descriptions are shown in the official language in which they were submitted.
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VACUUM ABSORBING BASES FOR HOT-FILL CONTAINERS
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to United States Patent
Application No. 15/198,668 filed on June 30, 2016. This application is also a
continuation-in-part of United States Patent Application No. 14/072,377 filed
on November 5, 2013, (now U.S. Patent No. 9,394,072), which is a
continuation in part of United States Patent Application No. 12/847,050 filed
on July 30, 2010 (now U.S. Patent No. 8,616,395), which is a continuation-in-
part of United States Patent Application No. 12/272,400 filed on November
17, 2008 (now U.S. Patent No. 8,276,774), which is a continuation-in-part of
United States Patent Application No. 11/151,676 filed on June 14, 2005 (now
U.S. Patent No. 7,451,886), which is a continuation-in-part of United States
Patent Application No. 11/116,764 filed on April 28, 2005 (now U.S. Patent
No. 7,150,372), which is a continuation of United States Patent Application
No. 10/445,104 filed on May 23, 2003 (now U.S. Patent No. 6,942,116).
United States Patent Application No. 12/847,050 claims the benefit of United
States Provisional Patent Application No. 61/230,144, filed on July 31, 2009
and United States Provisional Patent Application No. 61/369,156 filed July 30,
2010. The entire disclosures of the above applications are incorporated
herein by reference.
[0002] The entire disclosure of the above application is incorporated
herein by reference.
FIELD
[0003] The present disclosure relates to vacuum absorbing bases for
hot-fill containers.
BACKGROUND AND SUMMARY
[0004] This section provides background information related to the
present disclosure, which is not necessarily prior art. This section also
provides a general summary of the disclosure, and is not a comprehensive
disclosure of its full scope or all of its features.
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[0005] As a
result of environmental and other concerns, plastic
containers, more specifically polyester and even more specifically
polyethylene terephthalate (PET) containers, are now being used more than
ever to package numerous commodities previously packaged in glass
containers. Manufacturers and fillers, as well as consumers, have recognized
that PET containers are lightweight, inexpensive, recyclable and
manufacturable in large quantities.
[0006]
Manufacturers currently supply PET containers for various liquid
commodities, such as juice and isotonic beverages. Suppliers often fill these
liquid products into the containers while the liquid product is at an elevated
temperature, typically between 68 C - 96 C (155 F - 205 F) and usually at
approximately 85 C (185 F). When packaged in this manner, the hot
temperature of the liquid commodity sterilizes the container at the time of
filling. The bottling industry refers to this process as hot filling, and
containers
designed to withstand the process as hot-fill or heat-set containers.
[0007] The
hot filling process is acceptable for commodities having a
high acid content, but not generally acceptable for non-high acid content
commodities. Nonetheless, manufacturers and fillers of non-high acid content
commodities desire to supply their commodities in PET containers as well.
[0008] For non-high
acid commodities, pasteurization and retort are the
preferred sterilization process. Pasteurization and retort both present an
enormous challenge for manufactures of PET containers in that heat-set
containers cannot withstand the temperature and time demands required of
pasteurization and retort.
[0009] Pasteurization
and retort are both processes for cooking or
sterilizing the contents of a container after filling. Both processes include
the
heating of the contents of the container to a specified temperature, usually
above approximately 70 C (approximately 155 F), for a specified length of
time (20 - 60 minutes). Retort differs from pasteurization in that retort uses
higher temperatures to sterilize the container and cook its contents. Retort
also applies elevated air pressure externally to the container to counteract
pressure inside the container. The
pressure applied externally to the
container is necessary because a hot water bath is often used and the
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overpressure keeps the water, as well as the liquid in the contents of the
container, in liquid form, above their respective boiling point temperatures.
[0010] PET
is a crystallizable polymer, meaning that it is available in an
amorphous form or a semi-crystalline form. The ability of a PET container to
maintain its material integrity relates to the percentage of the PET container
in
crystalline form, also known as the "crystallinity" of the PET container. The
following equation defines the percentage of crystallinity as a volume
fraction:
% Crystallinity = p¨ Pa X 100
Pc ¨Pa
where p is the density of the PET material; pa is the density of pure
amorphous PET material (1.333 g/cc); and pc is the density of pure crystalline
material (1.455 g/cc).
[0011]
Container manufactures use mechanical processing and thermal
processing to increase the PET polymer crystallinity of a container.
Mechanical processing involves orienting the amorphous material to achieve
strain hardening. This processing commonly involves stretching a PET
preform along a longitudinal axis and expanding the PET preform along a
transverse or radial axis to form a PET container. The combination promotes
what manufacturers define as biaxial orientation of the molecular structure in
the container. Manufacturers of PET containers currently use mechanical
processing to produce PET containers having approximately 20% crystallinity
in the container's sidewall.
[0012] Thermal processing involves heating the material (either
amorphous or semi-crystalline) to promote crystal growth. On amorphous
material, thermal processing of PET material results in a spherulitic
morphology that interferes with the transmission of light. In other words, the
resulting crystalline material is opaque, and thus, generally undesirable.
Used
after mechanical processing, however, thermal processing results in higher
crystallinity and excellent clarity for those portions of the container having
biaxial molecular orientation. The thermal processing of an oriented PET
container, which is known as heat setting, typically includes blow molding a
PET preform against a mold heated to a temperature of approximately 120 C
- 130 C (approximately 248 F - 266 F), and holding the blown container
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against the heated mold for approximately three (3) seconds. Manufacturers
of PET juice bottles, which must be hot-filled at approximately 85 C (185 F),
currently use heat setting to produce PET bottles having an overall
crystallinity in the range of approximately 25 - 35%.
[0013] After being
hot-filled, the heat-set containers are capped and
allowed to reside at generally the filling temperature for approximately five
(5)
minutes at which point the container, along with the product, is then actively
cooled prior to transferring to labeling, packaging, and shipping operations.
The cooling reduces the volume of the liquid in the container. This product
shrinkage phenomenon results in the creation of a vacuum within the
container. Generally, vacuum pressures within the container range from 1-
300 mm Hg less than atmospheric pressure (i.e., 759 mm Hg - 460 mm Hg).
If not controlled or otherwise accommodated, these vacuum pressures result
in deformation of the container, which leads to either an aesthetically
unacceptable container or one that is unstable.
[0014] In
many instances, container weight is correlated to the amount
of the final vacuum present in the container after this fill, cap and cool
down
procedure, that is, the container is made relatively heavy to accommodate
vacuum related forces.
Similarly, reducing container weight, i.e.,
"lightweighting" the container, while providing a significant cost savings
from a
material standpoint, requires a reduction in the amount of the final vacuum.
Typically, the amount of the final vacuum can be reduced through various
processing options such as the use of nitrogen dosing technology, minimize
headspace or reduce fill temperature. One drawback with the use of nitrogen
dosing technology however is that the maximum line speeds achievable with
the current technology is limited to roughly 200 containers per minute. Such
slower line speeds are seldom acceptable. Additionally, the dosing
consistency is not yet at a technological level to achieve efficient
operations.
Minimizing headspace requires more precession during filling, again resulting
in slower line speeds. Reducing fill temperature is equally disadvantageous
as it limits the type of commodity suitable for the container.
[0015] Typically, container manufacturers accommodate vacuum
pressures by incorporating structures in the container sidewall. Container
manufacturers commonly refer to these structures as vacuum panels.
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Traditionally, these paneled areas have been semi-rigid by design, unable to
accommodate the high levels of vacuum pressures currently generated,
particularly in lightweight containers.
[0016]
Development of technology options to achieve an ideal balance
of light-weighting and design flexibility are of great interest. According to
the
principles of the present teachings, an alternative vacuum absorbing
capability is provided within both the container body and base. Traditional
hot-fill containers accommodate nearly all vacuum forces within the body (or
sidewall) of the container through deflection of the vacuum panels. These
containers are typically provided with a rigid base structure that
substantially
prevents deflection thereof and thus tends to be heavier than the rest of the
container.
[0017] In
contrast, POWERFLEX technology, offered by the assignee
of the present application, utilizes a lightweight base design to accommodate
nearly all vacuum forces. However, in order to accommodate such a large
amount of vacuum, the POWERFLEX base must be designed to invert, which
requires a dramatic snap-through from an outwardly curved initial shape to an
inwardly curved final shape. This typically requires that the sidewall of the
container be sufficiently rigid to allow the base to activate under vacuum,
thus
requiring more weight and/or structure within the container sidewall. Neither
the traditional technology nor POWERFLEX system offers the optimal balance
of a thin light-weight container body and base that is capable of withstanding
the necessary vacuum pressures.
[0018]
Therefore, an object of the present teachings is to achieve the
optimal balance of weight and vacuum performance of both the container
body and base. To achieve this, in some embodiments, a hot-fill container is
provided that comprises a lightweight, flexible base design that is easily
moveable to accommodate vacuum, but does not require a dramatic inversion
or snap-through, thus eliminating the need for a heavy sidewall. The flexible
base design serves to complement vacuum absorbing capabilities within the
container sidewall. Furthermore, an object of the present teachings is to
define theoretical light weighting limits and explore alternative vacuum
absorbing technologies that create additional structure under vacuum.
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[0019] The
container body and base of the present teachings can each
be lightweight structures designed to accommodate vacuum forces either
simultaneously or in sequence. In any event, the goal is for both the
container
body and base to absorb a significant percentage of the vacuum. By utilizing
a lightweight base design to absorb a portion of the vacuum forces enables an
overall light-weighting, design flexibility, and effective utilization of
alternative
vacuum absorbing capabilities on the container sidewall. It is therefore an
object of the present teachings to provide such a container. It should be
understood, however, that in some embodiments some principles of the
present teachings, such as the base configurations, can be used separate
from other principles, such as the sidewall configurations, or vice versa.
[0020] The
present teachings provide for a plastic container including
an upper portion, a base, a plurality of surface features, and a substantially
cylindrical portion. The upper portion has a mouth defining an opening into
the container. The base is movable to accommodate vacuum forces
generated within the container thereby decreasing the volume of the
container. The plurality of surface features are included with the base and
are
configured to accommodate vacuum forces. The substantially cylindrical
portion extends between the upper portion and the base.
[0021] The present
teachings further provide for a plastic container
including an upper portion, a base, a plurality of adjacent equilateral
triangular
features, and a substantially cylindrical portion. The base is movable to
accommodate vacuum forces generated within the container thereby decreasing
the volume of the container. The plurality of adjacent triangular features
protrude from the base and are configured to accommodate vacuum forces.
The substantially cylindrical portion extends between the upper portion and
the
base.
[0022] The
present teachings also provide for a plastic container
including an upper portion, a base, a plurality of adjacent equilateral
triangular
features, and a substantially cylindrical portion. The upper portion has a
mouth defining an opening into the container. The base is movable to
accommodate vacuum forces generated within the container thereby
decreasing the volume of the container. The plurality of adjacent equilateral
triangular features protrude from about 50% of the base and are configured to
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accommodate vacuum forces. The triangular features are spaced apart from
both a central pushup of the base and a wall of the base. The substantially
cylindrical portion extends between the upper portion and the base. The
triangular features are formed from a mold including a plurality of peaks and
troughs corresponding to the equilateral triangular features. The peaks are
aligned along a first plane and the troughs are aligned along a second plane
extending parallel to the first plane.
[0023] The
present teachings further provide for a polymeric container
including an upper portion defining an opening to an interior volume of the
container. A base is movable to accommodate vacuum forces generated within
the container, thereby decreasing the volume of the container. A substantially
cylindrical sidewall extends between the upper portion and the base. A rigid,
central pushup portion of the base is at an axial center of the base. A
central
longitudinal axis of the container extends through a center of the central
pushup
portion. A flexible diaphragm of the base extends outward from the central
pushup portion.
[0024]
Further areas of applicability will become apparent from the
description provided herein. The description and specific examples in this
summary are intended for purposes of illustration only and are not intended to
limit the scope of the present disclosure.
DRAWINGS
[0025] The
drawings described herein are for illustrative purposes only
of selected embodiments and not all possible implementations, and are not
intended to limit the scope of the present disclosure.
[0026] FIG. 1 is an
elevational view of a plastic container according to
the present teachings, the container as molded and empty.
[0027] FIG.
2 is an elevational view of the plastic container according to
the present teachings, the container being filled and sealed.
[0028] FIG.
3 is a bottom perspective view of a portion of the plastic
container of FIG. 1.
[0029] FIG.
4 is a bottom perspective view of a portion of the plastic
container of FIG. 2.
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[0030] FIG. 5 is a cross-sectional view of the plastic container,
taken
generally along line 5-5 of FIG. 3.
[0031] FIG. 6 is a cross-sectional view of the plastic container,
taken
generally along line 6-6 of FIG. 4.
[0032] FIG. 7 is a cross-sectional view of the plastic container, similar
to FIG. 5, according to some embodiments of the present teachings.
[0033] FIG. 8 is a cross-sectional view of the plastic container,
similar
to FIG. 6, according to some embodiments of the present teachings.
[0034] FIG. 9 is a bottom view of an additional embodiment of the
plastic container, the container as molded and empty.
[0035] FIG. 10 is a cross-sectional view of the plastic container,
taken
generally along line 10-10 of FIG. 9.
[0036] FIG. 11 is a bottom view of the embodiment of the plastic
container shown in FIG. 9, the plastic container being filled and sealed.
[0037] FIG. 12 is a cross-sectional view of the plastic container, taken
generally along line 12-12 of FIG. 11.
[0038] FIG. 13 is a cross-sectional view of the plastic container,
similar
to FIGS. 5 and 7, according to some embodiments of the present teachings.
[0039] FIG. 14 is a cross-sectional view of the plastic container,
similar
to FIGS. 6 and 8, according to some embodiments of the present teachings.
[0040] FIG. 15 is a bottom view of the plastic container according to
some embodiments of the present teachings.
[0041] FIG. 16 is a cross-sectional view of the plastic container,
similar
to FIGS. 5 and 7, according to some embodiments of the present teachings.
[0042] FIG. 17 is a cross-sectional view of the plastic container, similar
to FIGS. 6 and 8, according to some embodiments of the present teachings.
[0043] FIG. 18 is a bottom view of the plastic container according to
some embodiments of the present teachings.
[0044] FIG. 19 is a bottom view of the plastic container according to
some embodiments of the present teachings.
[0045] FIG. 20 is a cross-sectional view of the plastic container of
FIG.
19.
[0046] FIG. 21 is a bottom view of the plastic container according to
some embodiments of the present teachings.
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[0047] FIG. 22 is a cross-sectional view of the plastic container of
FIG.
21.
[0048] FIG. 23 is an enlarged bottom view of the plastic container of
FIG. 21.
[0049] FIG. 24 is a bottom view of the plastic container according to
some embodiments of the present teachings.
[0050] FIG. 25 is a cross-sectional view of the plastic container of
FIG.
24.
[0051] FIG. 26 is a bottom view of the plastic container according to
some embodiments of the present teachings.
[0052] FIG. 27 is a cross-sectional view of the plastic container of
FIG.
26.
[0053] FIG. 28 is a graph illustrating the vacuum response versus
displacement for the plastic container of FIG. 19.
[0054] FIG. 29 is a graph illustrating the vacuum response versus
displacement for the plastic container of FIG. 1.
[0055] FIG. 30 is a graph illustrating the vacuum response versus
displacement for the plastic container of FIG. 8.
[0056] FIG. 31 is a cross-sectional view of a plastic container
according
to some embodiments of the present teachings.
[0057] FIG. 32 is a cross-sectional view of a plastic container
according
to some embodiments of the present teachings.
[0058] FIG. 33 is a bottom view of the plastic container according to
some embodiments of the present teachings.
[0059] FIG. 34 is a cross-sectional view of the plastic container of FIG.
33 taken along line PL-PL of FIG. 33.
[0060] FIG. 35 illustrates an exemplary triangular feature of an
inversion ring of the plastic container of FIG. 33.
[0061] FIG. 36 is a cross-sectional view of a mold for forming the
plastic container of FIG. 33.
[0062] FIG. 37 is an exterior plan view of another base according to
the
present teachings for a plastic container, such as the plastic container
illustrated in Figure 1.
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[0063] FIG.
38 is a cross-sectional view of the base of FIG. 37 in an as-
blown position, the cross-sectional view taken along line 38-38 of FIG. 37.
[0064] FIG. 39 is a perspective view of the base of FIG. 37.
[0065] FIG.
40 is an exterior plan view of another base according to the
present teachings for a plastic container, such as the plastic container of
FIG.
1.
[0066] FIG. 41 is a perspective view of the base of FIG. 40.
[0067]
Corresponding reference numerals indicate corresponding parts
throughout the several views of the drawings.
DETAILED DESCRIPTION
[0068]
Example embodiments will now be described more fully with
reference to the accompanying drawings.
Example embodiments are
provided so that this disclosure will be thorough, and will fully convey the
scope to those who are skilled in the art. Numerous specific details are set
forth such as examples of specific components, devices, and methods, to
provide a thorough understanding of embodiments of the present disclosure.
It will be apparent to those skilled in the art that specific details need not
be
employed, that example embodiments may be embodied in many different
forms and that neither should be construed to limit the scope of the
disclosure.
[0069] The
terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be limiting. As
used herein, the singular forms "a", "an" and "the" may be intended to include
the plural forms as well, unless the context clearly indicates otherwise. The
terms "comprises," "comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations,
elements, and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
components, and/or groups thereof. The method steps, processes, and
operations described herein are not to be construed as necessarily requiring
their performance in the particular order discussed or illustrated, unless
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specifically identified as an order of performance. It is also to be
understood
that additional or alternative steps may be employed.
[0070] As discussed above, to accommodate vacuum forces during
cooling of the contents within a heat-set container, containers generally have
a series of vacuum panels or ribs around their sidewall. Traditionally, these
vacuum panels have been semi-rigid and incapable of preventing unwanted
distortion elsewhere in the container, particularly in lightweight containers.
However, in some vacuum panel-less containers, a combination of controlled
deformation (i.e., in the base or closure) and vacuum resistance in the
remainder of the container is required. As discussed herein, each of the
above examples (i.e. traditional vacuum absorbing container having a
lightweight and flexible sidewall with a heavy and rigid base, and
POWERFLEX container having a lightweight and flexible base with a heavy
and rigid sidewall) may not fully optimize a hot-fill container design.
Moreover, the simple combination of the sidewall of the traditional vacuum
absorbing container and the base of the POWERFLEX container would
typically lead to a container having a sidewall that is not sufficiently rigid
to
withstand the snap-through from an outwardly curved initial shape to an
inwardly curved final shape.
[0071] Accordingly,
the present teachings provide a plastic container
which enables its base portion under typical hot-fill process conditions to
deform and move easily while maintaining a rigid structure (i.e., against
internal vacuum) in the remainder of the container. As an example, in a 16 fl.
oz. plastic container, the container typically should accommodate roughly 18-
24 cc of volume displacement. In the present plastic container, the base
portion accommodates a majority of this requirement. The remaining portions
of the plastic container are easily able to accommodate the rest of this
volume
displacement without readily noticeable distortion. More
particularly,
traditional containers utilize a combination of bottle geometry and wall
thickness to create a structure that can resist a portion of the vacuum, and
movable sidewall panels, collapsible ribs, or moveable bases to absorb the
remaining vacuum. This results in two elements of internal vacuum¨residual
and absorbed. The sum of the residual vacuum and the absorbed vacuum
equals the total amount of vacuum that results from the combination of the
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liquid commodity and the headspace contracting during cooling in a rigid
container.
[0072] Although alternative designs are available in the art,
including
those requiring the use of external activation devices on the filling line (as
in
the Graham ATP technology), the present teachings are able to achieve
lighter hot fillable containers, without requiring an external activation
device,
by absorbing a higher percentage of the internal vacuum and/or volume in a
controlled way while simultaneously providing sufficient structural integrity
to
maintain the desired bottle shape.
[0073] In some embodiments, the container according to the present
teachings combines sidewall vacuum and/or volume compensation panels or
collapsible ribs with a flexible base design resulting in a hybrid of previous
technologies that results in a lighter weight container than could be achieved
with either method individually.
[0074] The vacuum and/or volume compensation characteristics could
be defined as:
[0075] X = the percentage of the total vacuum and/or volume that is
absorbed by the sidewall panels, ribs and/or other vacuum and/or volume
compensation features;
[0076] Y = the percentage of the total vacuum and/or volume that is
absorbed by the base movement; and
[0077] Z = the residual vacuum and/or volume remaining in the
container after the compensation achieved by the vacuum and/or volume
compensation features in the sidewall and/or base.
[0078] In the case of the traditional vacuum compensation features (i.e.
sidewall only or base only), the vacuum and/or volume compensation could
be expressed as:
[0079] Z = 10 to 90% of the total vacuum and/or volume; and
[0080] X OR Y = 10 to 90% of the total vacuum and/or volume.
[0081] It should be appreciated from the foregoing that a conventional
container could merely achieve a total of 90% of the total vacuum and/or
volume.
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[0082]
However, according to the present teachings, a hot-fillable
container is provided where the vacuum and/or volume compensation could
be described as:
[0083] Z = 0 to 25% of the total vacuum and/or volume;
[0084] X = 10 to 90% of the total vacuum and/or volume; and
[0085] Y = 10 to 90% of the total vacuum and/or volume.
[0086] As
can be seen, according to these principles, the present
teachings are operable to achieve vacuum absorption in both the base and
the sidewall, thereby permitting, if desired, absorption of the entire
internal
vacuum. It should be appreciated that in some embodiments a slight
remaining vacuum may be desired.
[0087] To
accomplish the lightest possible container weight with
respect to vacuum, the residual vacuum (Z) should be as close as possible to
0% of the total vacuum and the combined movements of the vacuum
absorbing features would be designed to absorb basically 100% of the volume
contraction that occurs inside of the container as the contents cool from the
filling temperature to the point of maximum density under the required service
conditions. At this point external forces such as top load or side load would
result in a pressurization of the container that would help it to resist those
external forces. This would result in a container weight that is dictated by
the
requirements of the handling and distribution system, not by the filling
conditions.
[0088] In some embodiments, the present teachings provide a
significantly round plastic container that does not ovalize below 5% total
vacuum absorption that consists of a movable base and a movable sidewall at
an average wall thickness less than 0.020". However, in some embodiments,
the present teachings can provide a plastic container that comprises a base
that absorbs between 10 and 90% of the total vacuum in conjunction with a
sidewall that absorbs between 90 and 10% of the total vacuum absorbed. In
some embodiments, the base and the sidewall can activate simultaneously.
However, in some embodiments, the base and the sidewall can activate
sequentially.
[0089]
Still further, according to the present teachings, a significantly
round plastic container is provided that provides a movable base and a
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movable sidewall that both activate simultaneously or sequentially at a
vacuum level less than that of 5% of the total vacuum absorption of the
container.
[0090] In a
vacuum panel-less container, a combination of controlled
deformation (i.e., in the base or closure) and vacuum resistance in the
remainder of the container is required. Accordingly, the present teaching
provides for a plastic container which enables its base portion under typical
hot-fill process conditions to deform and move easily while maintaining a
rigid
structure (i.e., against internal vacuum) in the remainder of the container.
[0091] As shown in
FIGS. 1 and 2, a plastic container 10 of the
invention includes a finish 12, a neck or an elongated neck 14, a shoulder
region 16, a body portion 18, and a base 20. Those skilled in the art know
and understand that the neck 14 can have an extremely short height, that is,
becoming a short extension from the finish 12, or an elongated neck as
illustrated in the figures, extending between the finish 12 and the shoulder
region 16. The plastic container 10 has been designed to retain a commodity
during a thermal process, typically a hot-fill process. For hot-fill bottling
applications, bottlers generally fill the container 10 with a liquid or
product at
an elevated temperature between approximately 155 F to 205 F
(approximately 68 C to 96 C) and seal the container 10 with a closure 28
before cooling. As the sealed container 10 cools, a slight vacuum, or negative
pressure, forms inside causing the container 10, in particular, the base 20 to
change shape. In addition, the plastic container 10 may be suitable for other
high-temperature pasteurization or retort filling processes, or other thermal
processes as well.
[0092] The
plastic container 10 of the present teaching is a blow
molded, biaxially oriented container with a unitary construction from a single
or multi-layer material. A well-known stretch-molding, heat-setting process
for
making the hot-fillable plastic container 10 generally involves the
manufacture
of a preform (not illustrated) of a polyester material, such as polyethylene
terephthalate (PET), having a shape well known to those skilled in the art
similar to a test-tube with a generally cylindrical cross section and a length
typically approximately fifty percent (50%) that of the container height. A
machine (not illustrated) places the preform heated to a temperature between
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approximately 190 F to 250 F (approximately 88 C to 121 C) into a mold
cavity (not illustrated) having a shape similar to the plastic container 10.
The
mold cavity is heated to a temperature between approximately 250 F to 350 F
(approximately 121 C to 177 C). A stretch rod apparatus (not illustrated)
stretches or extends the heated preform within the mold cavity to a length
approximately that of the container thereby molecularly orienting the
polyester
material in an axial direction generally corresponding with a central
longitudinal axis 50. While the stretch rod extends the preform, air having a
pressure between 300 PSI to 600 PSI (2.07 MPa to 4.14 MPa) assists in
extending the preform in the axial direction and in expanding the preform in a
circumferential or hoop direction thereby substantially conforming the
polyester material to the shape of the mold cavity and further molecularly
orienting the polyester material in a direction generally perpendicular to the
axial direction, thus establishing the biaxial molecular orientation of the
polyester material in most of the container. Typically, material within the
finish
12 and a sub-portion of the base 20 are not substantially molecularly
oriented.
The pressurized air holds the mostly biaxial molecularly oriented polyester
material against the mold cavity for a period of approximately two (2) to five
(5) seconds before removal of the container from the mold cavity. To achieve
appropriate material distribution within the base 20, the inventors employ an
additional stretch-molding step substantially as taught by U.S. Patent No.
6,277,321 which is incorporated herein by reference.
[0093] Alternatively, other manufacturing methods using other
conventional materials including, for example, high density polyethylene,
polypropylene, polyethylene naphthalate (PEN), a PET/PEN blend or
copolymer, and various multilayer structures may be suitable for the
manufacture of plastic container 10. Those having ordinary skill in the art
will
readily know and understand plastic container 10 manufacturing method
alternatives.
[0094] The finish 12
of the plastic container 10 includes a portion
defining an aperture or mouth 22, a threaded region 24, and a support ring 26.
The aperture 22 allows the plastic container 10 to receive a commodity while
the threaded region 24 provides a means for attachment of the similarly
threaded closure or cap 28 (shown in FIG. 2). Alternatives may include other
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suitable devices that engage the finish 12 of the plastic container 10.
Accordingly, the closure or cap 28 engages the finish 12 to preferably provide
a hermetical seal of the plastic container 10. The closure or cap 28 is
preferably of a plastic or metal material conventional to the closure industry
and suitable for subsequent thermal processing, including high temperature
pasteurization and retort. The support ring 26 may be used to carry or orient
the preform (the precursor to the plastic container 10) (not shown) through
and at various stages of manufacture. For example, the preform may be
carried by the support ring 26, the support ring 26 may be used to aid in
positioning the preform in the mold, or an end consumer may use the support
ring 26 to carry the plastic container 10 once manufactured.
[0095] The
elongated neck 14 of the plastic container 10 in part
enables the plastic container 10 to accommodate volume requirements.
Integrally formed with the elongated neck 14 and extending downward
therefrom is the shoulder region 16. The shoulder region 16 merges into and
provides a transition between the elongated neck 14 and the body portion 18.
The body portion 18 extends downward from the shoulder region 16 to the
base 20 and includes sidewalls 30. The specific construction of the base 20
of the container 10 allows the sidewalls 30 for the heat-set container 10 to
not
necessarily require additional vacuum panels or pinch grips and therefore,
can be generally smooth and glass-like. However, a significantly lightweight
container will likely include sidewalls having vacuum panels, ribbing, and/or
pinch grips along with the base 20.
[0096] The
base 20 of the plastic container 10, which extends inward
from the body portion 18, can comprise a chime 32, a contact ring 34 and a
central portion 36. In some embodiments, the contact ring 34 is itself that
portion of the base 20 that contacts a support surface 38 that in turn
supports
the container 10. As such, the contact ring 34 may be a flat surface or a line
of contact generally circumscribing, continuously or intermittently, the base
20. The base 20 functions to close off the bottom portion of the plastic
container 10 and, together with the elongated neck 14, the shoulder region
16, and the body portion 18, to retain the commodity.
[0097] In
some embodiments, the plastic container 10 is preferably
heat-set according to the above-mentioned process or other conventional
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heat-set processes. In some embodiments, to accommodate vacuum forces
while allowing for the omission of vacuum panels and pinch grips in the body
portion 18 of the container 10, the base 20 of the present teaching adopts a
novel and innovative construction. Generally, the central portion 36 of the
base 20 can comprise a central pushup 40 and an inversion ring 42. The
inversion ring 42 can include an upper portion 54 and a lower portion 58.
Additionally, the base 20 can include an upstanding circumferential wall or
edge 44 that forms a transition between the inversion ring 42 and the contact
ring 34.
[0098] As shown in
the figures, the central pushup 40, when viewed in
cross section, is generally in the shape of a truncated cone having a top
surface 46 that is generally parallel to the support surface 38. Side surfaces
48, which are generally planar in cross section, slope upward toward the
central longitudinal axis 50 of the container 10. The exact shape of the
central pushup 40 can vary greatly depending on various design criteria.
However, in general, the overall diameter of the central pushup 40 (that is,
the
truncated cone) is at most 30% of generally the overall diameter of the base
20. The central pushup 40 is generally where the preform gate is captured in
the mold. Located within the top surface 46 is the sub-portion of the base 20
which includes polymer material that is not substantially molecularly
oriented.
[0099] In
some embodiments as shown in FIGS. 3, 5, 7, 10, 13 and 16,
when initially formed, the inversion ring 42, having a gradual radius,
completely surrounds and circumscribes the central pushup 40. As formed,
the inversion ring 42 can protrude outwardly, below a plane where the base
20 would lie if it was flat. The transition between the central pushup 40 and
the adjacent inversion ring 42 can be rapid in order to promote as much
orientation as near the central pushup 40 as possible. This serves primarily
to
ensure a minimal wall thickness 66 for the inversion ring 42, in particular at
the lower portion 58 of the base 20. In some embodiments, the wall thickness
66 of the lower portion 58 of the inversion ring 42 is between approximately
0.008 inch (0.20 mm) to approximately 0.025 inch (0.64 mm), and preferably
between approximately 0.010 inch to approximately 0.014 inch (0.25 mm to
0.36 mm) for a container having, for example, an approximately 2.64-inch
(67.06 mm) diameter base. Wall thickness 70 of top surface 46, depending
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on precisely where one takes a measurement, can be 0.060 inch (1.52 mm)
or more; however, wall thickness 70 of the top surface 46 quickly transitions
to
wall thickness 66 of the lower portion 58 of the inversion ring 42. The wall
thickness 66 of the inversion ring 42 must be relatively consistent and thin
enough to allow the inversion ring 42 to be flexible and function properly. At
a
point along its circumventional shape, the inversion ring 42 may alternatively
feature a small indentation, not illustrated but well known in the art,
suitable
for receiving a pawl that facilitates container rotation about the central
longitudinal axis 50 during a labeling operation.
[0100] The
circumferential wall or edge 44, defining the transition
between the contact ring 34 and the inversion ring 42 can be, in cross
section,
an upstanding substantially straight wall approximately 0.030 inch (0.76 mm)
to approximately 0.325 inch (8.26 mm) in length. Preferably, for a 2.64-inch
(67.06 mm) diameter base container, the circumferential wall 44 can measure
between approximately 0.140 inch to approximately 0.145 inch (3.56 mm to
3.68 mm) in length. For a 5-inch (127 mm) diameter base container, the
circumferential wall 44 could be as large as 0.325 inch (8.26 mm) in length.
The circumferential wall or edge 44 can be generally at an angle 64 relative
to
the central longitudinal axis 50 of between approximately zero degree and
approximately 20 degrees, and preferably approximately 15 degrees.
Accordingly, the circumferential wall or edge 44 need not be exactly parallel
to
the central longitudinal axis 50. The circumferential wall or edge 44 is a
distinctly identifiable structure between the contact ring 34 and the
inversion
ring 42. The circumferential wall or edge 44 provides strength to the
transition
between the contact ring 34 and the inversion ring 42. In some embodiments,
this transition must be abrupt in order to maximize the local strength as well
as to form a geometrically rigid structure. The resulting localized strength
increases the resistance to creasing in the base 20. The contact ring 34, for
a
2.64-inch (67.06 mm) diameter base container, can have a wall thickness 68
of approximately 0.010 inch to approximately 0.016 inch (0.25 mm to 0.41
mm). In some embodiments, the wall thickness 68 is at least equal to, and
more preferably is approximately ten percent, or more, than that of the wall
thickness 66 of the lower portion 58 of the inversion ring 42.
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[0101] When
initially formed, the central pushup 40 and the inversion
ring 42 remain as described above and shown in FIGS. 1, 3, 5, 7, 10, 13 and
16. Accordingly, as molded, a dimension 52 measured between the upper
portion 54 of the inversion ring 42 and the support surface 38 is greater than
or equal to a dimension 56 measured between the lower portion 58 of the
inversion ring 42 and the support surface 38. Upon filling, the central
portion
36 of the base 20 and the inversion ring 42 will slightly sag or deflect
downward toward the support surface 38 under the temperature and weight of
the product. As a result, the dimension 56 becomes almost zero, that is, the
lower portion 58 of the inversion ring 42 is practically in contact with the
support surface 38. Upon
filling, capping, sealing, and cooling of the
container 10, as shown in FIGS. 2, 4, 6, 8, 12, 14 and 17, vacuum related
forces cause the central pushup 40 and the inversion ring 42 to rise or push
upward thereby displacing volume. In this position, the central pushup 40
generally retains its truncated cone shape in cross section with the top
surface 46 of the central pushup 40 remaining substantially parallel to the
support surface 38. The inversion ring 42 is incorporated into the central
portion 36 of the base 20 and virtually disappears, becoming more conical in
shape (see FIGS. 8, 14 and 17). Accordingly, upon capping, sealing, and
cooling of the container 10, the central portion 36 of the base 20 exhibits a
substantially conical shape having surfaces 60 in cross section that are
generally planar and slope upward toward the central longitudinal axis 50 of
the container 10, as shown in FIGS. 6, 8, 14 and 17. This conical shape and
the generally planar surfaces 60 are defined in part by an angle 62 of
approximately 7 to approximately 23 , and more typically between
approximately 10 and approximately 17 , relative to a horizontal plane or the
support surface 38. As the value of dimension 52 increases and the value of
dimension 56 decreases, the potential displacement of volume within
container 10 increases. Moreover, while planar surfaces 60 are substantially
straight (particularly as illustrated in FIGS. 8 and 14), those skilled in the
art
will realize that planar surfaces 60 will often have a somewhat rippled
appearance. A typical 2.64-inch (67.06 mm) diameter base container,
container 10 with base 20, has an as molded base clearance dimension 72,
measured from the top surface 46 to the support surface 38, with a value of
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approximately 0.500 inch (12.70 mm) to approximately 0.600 inch (15.24 mm)
(see FIGS. 7, 13 and 16). When responding to vacuum related forces, base
20 has an as filled base clearance dimension 74, measured from the top
surface 46 to the support surface 38, with a value of approximately 0.650 inch
(16.51 mm) to approximately 0.900 inch (22.86 mm) (see FIGS. 8, 14 and 17).
For smaller or larger containers, the value of the as molded base clearance
dimension 72 and the value of the as filled base clearance dimension 74 may
be proportionally different.
[0102] As
set forth above, the difference in wall thickness between the
base 20 and the body portion 18 of the container 10 is also of importance.
The wall thickness of the body portion 18 must be large enough to allow the
inversion ring 42 to flex properly. Depending on the geometry of the base 20
and the amount of force required to allow the inversion ring 42 to flex
properly,
that is, the ease of movement, the wall thickness of the body portion 18 must
be at least 15%, on average, greater than the wall thickness of the base 20.
Preferably, the wall thickness of the body portion 18 is between two (2) to
three (3) times greater than the wall thickness 66 of the lower portion 58 of
inversion ring 42. A greater difference is required if the container must
withstand higher forces either from the force required to initially cause the
inversion ring 42 to flex or to accommodate additional applied forces once the
base 20 movement has been completed.
[0103] In
some embodiments, the above-described alternative hinges
or hinge points may take the form of a series of indents, dimples, or other
features that are operable to improve the response profile of the base 20 of
the container 10. Specifically, as illustrated in FIGS. 28-30, in some
embodiments the vacuum response profile of base 20 may define abrupt
flexural responses that produce a segmented, non-continuous vacuum curve
(see FIG. 29) defining a pair of vertical sections 302, 304, indicative of
abruptly reduced internal vacuum pressure. Although this response may be
suitable for some embodiments, in other embodiments a more gradual and
smooth vacuum curve may be desired (see FIGS. 28 and 30 which will be
discussed herein). In this way, a gradual and smooth vacuum curve profile
may provide opportunity to redesign the sidewall profile and/or vacuum panels
to reduces the need for vacuum panels and/or reduce material wall thickness
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along the sidewall. Such arrangement can provide reduced container weight
and improved design possibilities.
[0104] That
is, as illustrated in FIGS. 16-27 and 33-36, the inversion
ring 42 may include a series of indents, dimples, or other features 102 formed
therein and throughout. As shown (see FIGS. 16-20), in some embodiments,
the series of features 102 are generally circular in shape. However, it should
be appreciated that features 102 can define any one of a number of shapes,
configurations, arrangements, distributions, and profiles
[0105] With
particular reference to FIGS. 16-27 and 33-36, in some
embodiments, the features 102 are generally spaced equidistantly apart from
one another and arranged in a series of rows and columns that completely
cover the inversion ring 42. Similarly, the series of features 102 can
generally
and completely surround and circumscribe the central pushup 40 (see FIG.
18). It is equally contemplated that the series of rows and columns of
features
102 may be continuous or intermittent. The features 102, when viewed in
cross section, can be in the shape of a truncated or rounded cone having a
lower most surface or point and side surfaces 104. Side surfaces 104 are
generally planar and slope inward toward the central longitudinal axis 50 of
the container 10. The exact shape of the features 102 can vary greatly
depending on various design criteria. While the above-described geometry of
the features 102 is preferred, it will be readily understood by a person of
ordinary skill in the art that other geometrical arrangements are similarly
contemplated.
[0106] With
particular reference to FIGS. 19 and 20, the features 102
are illustrated as a similarly shaped series of dimples spaced equidistantly
apart from one another as a plurality of radial row or columns extending from
the central pushup 40 on inversion ring 42. Although illustrated as being
inwardly directed within container 10, it should be appreciated that features
102 can be outwardly directed in some embodiments. It should also be
understood that the particular size, shape, and distribution of dimples can
vary
depending upon the vacuum curve performance desired and provides control
over base flexibility and movement under vacuum providing smooth actuation.
As particularly illustrated in FIG. 28, it can be seen that under vacuum
pressure load, base 20 and container 10, employing the base of FIGS. 19 and
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20, produce a generally smooth and consistent vacuum curve defining a
generally constant slope.
[0107] With
particular reference to FIGS. 21-23, the features 102 are
illustrated as a similarly shaped series of triangularly intersecting dimples
spaced equidistantly apart from one another as a plurality of row or columns
extending from the central pushup 40 on ring 42. Features 102 of the present
embodiment are inwardly directed and define common boundaries with
adjacent features 102 along edges of the inverted triangle. It should also be
understood that the particular size, shape, and distribution of dimples can
vary
depending upon the vacuum curve performance desired and provides control
over base flexibility and movement under vacuum providing smooth actuation.
[0108] With
particular reference to FIGS. 24 and 25, the features 102
are illustrated as a spider web of radially extending creases 400 spaced
equidistantly apart from one another extending from the central pushup 40 on
ring 42. Creases 400 can be joined by a series of interconnecting creases
402, such as arcuate creases, extending between adjacent creases 400
forming a series of concentrically spaced circumferential rings extending
about pushup 40. It should also be understood that the particular size, shape,
and distribution of creases 400 and interconnecting creases 402 can vary
depending upon the vacuum curve performance desired and provides control
over base flexibility and movement under vacuum providing smooth actuation.
[0109] With
particular reference to FIGS. 26 and 27, the features 102
are illustrated as a similarly shaped series of circumferentially-extending
creases 500 being spaced equidistantly apart from one another extending
from the central pushup 40 on inversion ring 42. Circumferential creases 500
can be joined by a series of radially-extending, interconnecting creases 502
extending between adjacent circumferential creases 500. Circumferential
creases 500 and radially-extending, interconnecting creases 502 together
form a rotated brick design. It should be noted that radially-extending,
interconnecting creases 502 can extending continuously from pushup 40 each
as a single continuous crease or can be staggered to form the brick design. It
should also be understood that the particular size, shape, and distribution of
creases 500 and 502 can vary depending upon the vacuum curve
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performance desired and provides control over base flexibility and movement
under vacuum providing smooth actuation.
[0110] With
reference to FIGS. 33-36, the features 102 can be a series
of triangular features, which may be equilateral in which all sides 112
thereof
have the same length J, isosceles in which only two sides 112 have the same
length J, or scalene in which none of the sides 112 have the same length J.
The triangular features 102 can be arranged in any suitable manner, such as
in a plurality of rows and/or columns. Neighboring triangular features 102 can
be adjacent to one another, such that they share sidewalls or boundaries as
illustrated. The triangular features 102 can be configured such that centers
110 thereof protrude outward from the base 20, as generally illustrated. The
triangular features 102 are offset from both the wall 44 and the central
pushup
40 of the base 20. Any suitable offset can be provided. For example and as
illustrated in Figure 33, an outermost edge 106 of the triangular features 102
can have a diameter of 67.78mm or about 67.78mm, and an innermost edge
108 of the triangular features 102 can occupy a diameter of 23.55mm or about
23.55mm as measured through the central longitudinal axis 50. The base 20
can have an outermost diameter of 87.5mm or about 87.5mm, as measured
through the central longitudinal axis 50. The triangular features 102 can
occupy any suitable portion of the surface area of the base 20, such as from
about 30% to about 70%, about 50%, or 50% of the surface area of the base
20. For example, the triangular features 102 can occupy or cover a surface
area of the base 20 of 3,172mm2, or about 3,172mm2, out of a total surface
area of 6,013mm2 or about 6,013mm2 of the base 20. The triangular features
102 can be present on any suitable portion of the base 20, such as at any
suitable portion of the inversion ring 42 between the wall 44 and the side
surfaces 48 of the central push up 40, for example.
[0111] With
reference to Figure 34 for example, which illustrates the
base 20 prior to the plastic container 10 being hot-filled, the inversion ring
42
including the triangular features 102 present thereon between the wall 44 and
the side surfaces 48 of the central push up 40 can have a radius R of between
about lOmm and about 30mm, such as about 20mm, or 20.6mm. The wall 44
can be angled inward towards the central longitudinal axis 50 at an angle D of
9.5 , or about 9.5 , relative to the sidewall 30. The top surface 46 of the
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pushup 40 can have a diameter E as measured through the central
longitudinal axis 50 of 10.13mm or about 10.13mm. The top surface 46 can
be spaced apart from the support surface 38 to provide a base clearance F of
15.5mm or about 15.5mm. The inversion ring 42 can be spaced apart from
the support surface 38 at a minimum distance G of 2.27mm or about 2.27mm.
In other words, at a portion of the inversion ring 42 closest to the support
surface 38 prior to the plastic container 10 being hot-filled, the inversion
ring
42 is spaced apart from the support surface 38 at a distance of 2.27mm or
about 2.27mm. As measured through the central longitudinal axis 50, the
contact ring 34 includes a diameter H of 67.41mm or about 67.41mm, which
can decrease to 66.41 mm or about 66.41 mm after the plastic container 10 is
hot-filled.
[0112] With
reference to Figure 35 for example, when the triangular
features 102 are equilateral triangles each triangular feature 102 can have a
height I of 3mm or about 3mm, each side 112 can have a suitable
corresponding length J, and each triangular feature 102 can define a depth
within the inversion ring 42 between the triangular features 102 at sides 112
of 1mm or up to about 1mm as measured from an outer surface of the
inversion ring 42. However, the triangular features 102 can each have any
suitable height I and define any suitable depth, and the sides 112 can have
any suitable length J. The height I, depth, and/or length J of each one of the
triangular features 102 can be the same or different. The particular size,
shape, number, and distribution of each one of the triangular features 102 can
vary depending on the vacuum curve performance desired, and to provide
control over flexibility of the base 20 and movement under vacuum to provide
smooth actuation of the base 20.
[0113] The
triangular features 102 can be formed in any suitable
manner, such as with mold 150 of Figure 36. The mold 150 includes a
plurality of peaks 152 and troughs 154 formed therein to define triangular
recesses that are configured to provide the base 20 with the triangular
features 102. Thus, neighboring peaks 152 can be spaced apart at a distance
K of 3mm or about 3mm to provide the triangular features 102 with the height
I of 3mm or about 3mm. The troughs 154 can be recessed within the mold
150 at a distance L from the peaks 152 of 1mm or about 1mm, thereby
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providing a blow mold ratio of 3:1 or about 3:1 width (or height) to depth of
the
triangular features 102, which can be optimal in some applications. Each of
the peaks 152 can be aligned along a first plane P1, and each of the troughs
154 can be aligned along a second plane P2. The first and second planes P1
and P2 can extend parallel to one another.
[0114] To
form the plastic container 10 including the triangular features
102, the portion of the base 20 to become the inversion ring 42 can be
positioned against the mold 150, such that the base 20 extends generally
parallel to each of the first and second planes P1 and P2. When heated, the
PET material from which the plastic container 10 may be formed extends
towards the troughs 154. The triangular recesses defined by the peaks 152
and troughs 154 project the triangular features 102 onto and into the
inversion
ring 42, which is formed as a curved surface. The triangular features 102 can
be formed in any other suitable manner as well.
[0115] As such, the
above-described base designs cause initiation of
movement and activation of the inversion ring 42 more easily by at least
increasing the surface area of the base 20 and, in some embodiments,
decreasing the material thickness in these areas. Additionally, the
alternative
hinges or hinge points also cause the inversion ring 42 to rise or push upward
more easily, thereby displacing more volume. Accordingly, the alternative
hinges or hinge points retain and improve the initiation and degree of
response ease of the inversion ring 42 while optimizing the degree of volume
displacement. The alternate hinges or hinge points provide for significant
volume displacement while minimizing the amount of vacuum related forces
necessary to cause movement of the inversion ring 42. Accordingly, when
container 10 includes the above-described alternative hinges or hinge points,
and is under vacuum related forces, the inversion ring 42 initiates movement
more easily and planar surfaces 60 can often achieve a generally larger angle
62 than what otherwise is likely, thereby displacing a greater amount of
volume.
[0116]
While not always necessary, in some embodiments base 20 can
comprise three grooves 80 substantially parallel to side surfaces 48. As
illustrated in FIGS. 9 and 10, grooves 80 are equally spaced about central
pushup 40. Grooves 80 have a substantially semicircular configuration, in
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cross section, with surfaces that smoothly blend with adjacent side surfaces
48. Generally, for container 10 having a 2.64-inch (67.06 mm) diameter base,
grooves 80 have a depth 82, relative to side surfaces 48, of approximately
0.118 inch (3.00 mm), typical for containers having a nominal capacity
between 16 fl. oz and 20 fl. oz. The inventors anticipate, as an alternative
to
more traditional approaches, that the central pushup 40 having grooves 80
may be suitable for engaging a retractable spindle (not illustrated) for
rotating
container 10 about central longitudinal axis 50 during a label attachment
process. While three (3) grooves 80 are shown, and is the preferred
configuration, those skilled in the art will know and understand that some
other number of grooves 80, i.e., 2, 4, 5, or 6, may be appropriate for some
container configurations.
[0117] As
base 20, with a relative wall thickness relationship as
described above, responds to vacuum related forces, grooves 80 may help
facilitate a progressive and uniform movement of the inversion ring 42.
Without grooves 80, particularly if the wall thickness 66 is not uniform or
consistent about the central longitudinal axis 50, the inversion ring 42,
responding to vacuum related forces, may not move uniformly or may move in
an inconsistent, twisted, or lopsided manner. Accordingly, with grooves 80,
radial portions 84 form (at least initially during movement) within the
inversion
ring 42 and extend generally adjacent to each groove 80 in a radial direction
from the central longitudinal axis 50 (see FIG. 11) becoming, in cross
section,
a substantially straight surface having angle 62 (see FIG. 12). Said
differently, when one views base 20 as illustrated in FIG. 11, the formation
of
radial portions 84 appear as valley-like indentations within the inversion
ring
42. Consequently, a second portion 86 of the inversion ring 42 between any
two adjacent radial portions 84 retains (at least initially during movement) a
somewhat rounded partially inverted shape (see FIG. 12). In practice, the
preferred embodiment illustrated in FIGS. 9 and 10 often assumes the shape
configuration illustrated in FIGS. 11 and 12 as its final shape configuration.
However, with additional vacuum related forces applied, the second portion
86 eventually straightens forming the generally conical shape having planar
surfaces 60 sloping toward the central longitudinal axis 50 at angle 62
similar
to that illustrated in FIG. 8. Again, those skilled in the art know and
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understand that the planar surfaces 60 will likely become somewhat rippled in
appearance. The exact nature of the planar surfaces 60 will depend on a
number of other variables, for example, specific wall thickness relationships
within the base 20 and the sidewalls 30, specific container 10 proportions
(i.e.,
diameter, height, capacity), specific hot-fill process conditions and others.
[0118] The
plastic container 10 may include one or more horizontal ribs
602. As shown in FIG. 31, horizontal ribs 602 further include an upper wall
604 and a lower wall 606 separated by an inner curved wall 608. Inner
curved wall 608 is in part defined by a relatively sharp innermost radius r1.
In
some embodiments, sharp innermost radius r1 lies within the range of about
0.01 inches to about 0.03 inches. The relatively sharp innermost radius r1 of
inner curved wall 608 facilitates improved material flow during blow molding
of
the plastic container 10 thus enabling the formation of relatively deep
horizontal ribs 602.
[0119] Horizontal
ribs 602 each further include an upper outer radius r2
and a lower outer radius r3. Preferably both the upper outer radius r2 and the
lower outer radius r3 each lie within the range of about 0.07 inches to about
0.14 inches. The upper outer radius r2 and the lower outer radius r3 may be
equal to each other or differ from one another. Preferably the sum of the
upper outer radius r2 and the lower outer radius r3 will be equal to or
greater
than about 0.14 inches and less than about 0.28 inches.
[0120] As
shown in FIG. 31, horizontal ribs 602 further include an upper
inner radius r4 and a lower inner radius r5. The upper inner radius r4 and the
lower inner radius r5 each lie within the range of about 0.08 inches to about
0.11 inches. The upper inner radius r4 and the lower inner radius r5 may be
equal to each other or differ from one another. Preferably the sum of the
upper inner radius r4 and the lower inner radius r5 will be equal to or
greater
than about 0.16 inches and less than about 0.22 inches.
[0121]
Horizontal ribs 602 have a rib depth RD of about 0.12 inches
and a rib width RW of about 0.22 inches as measured from the upper extent
of the upper outer radius r2 and the lower extent of the lower outer radius
r3.
As such, horizontal ribs 602 each have a rib width RW to rib depth RD ratio.
The rib width RW to rib depth RD ratio is, in some embodiments, in the range
of about 1.6 to about 2Ø
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[0122] Horizontal ribs 602 are designed to achieve optimal
performance with regard to vacuum absorption, top load strength and dent
resistance. Horizontal ribs 602 are designed to compress slightly in a
vertical
direction to accommodate for and absorb vacuum forces resulting from hot-
filling, capping and cooling of the container contents. Horizontal ribs 602
are
designed to compress further when the filled container is exposed to
excessive top load forces.
[0123] As
shown in FIG. 31, the above-described horizontal rib 602
radii, walls, depth and width in combination form a rib angle A. The rib angle
A of an unfilled plastic container 10 may be about 58 degrees. After hot-
filling, capping and cooling of the container contents, the resultant vacuum
forces cause the rib angle A to reduce to about 55 degrees. This represents a
reduction of the rib angle A of about 3 degrees as a result of vacuum forces
present within the plastic container 10 representing a reduction in the rib
angle A of about 5%. Preferably, the rib angle A will be reduced by at least
about 3% and no more than about 8% as a result of vacuum forces.
[0124]
After filling, it is common for the plastic container 10 to be bulk
packed on pallets. Pallets are then stacked atop one another resulting in top
load forces being applied to the plastic container 10 during storage and
distribution. Thus, horizontal ribs 602 are designed so that the rib angle A
may be further reduced to absorb top load forces. However, horizontal ribs
602 are designed so that the upper wall 604 and the lower wall 606 never
come into contact with each other as a result of vacuum or top load forces.
Instead horizontal ribs 602 are designed to allow the plastic container 10 to
reach a state wherein the plastic container 10 is supported in part by the
product inside when exposed to excessive top load forces thereby preventing
permanent distortion of the plastic container 10. In addition, this enables
horizontal ribs 602 to rebound and return substantially to the same shape as
before the top load forces were applied, once such top load forces are
removed.
[0125]
Horizontal lands 610 are generally flat in vertical cross-section
as molded. When the plastic container 10 is subjected to vacuum and/or top
load forces, horizontal lands 610 are designed to bulge slightly outward in
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vertical cross-section to aid the plastic container 10 in absorbing these
forces
in a uniform way.
[0126] It
should be appreciated that ribs 602 may not be parallel to the
base 20, as illustrated in FIG. 32. Stated differently, the ribs 602 may be
arcuate in one or more directions about the periphery of the container 10 and
the sidewall 30 of the container 10. More specifically, the ribs 602 may be
arced such that a center of the ribs 602 is arced upward toward the neck 18.
Such may be the case for all of the ribs 602 in the container 10 when viewed
from the same side of the container 10. However, the ribs 602 may be arched
in a different, opposite, downward direction, such as toward a bottom of the
container 10. More specifically, a center of the ribs 602 may be closer to the
base 20 than either of sides. In rotating the container 10 and following the
ribs 602 for 360 degrees around the container 10, the ribs 602 may have two
(2) equally high, highest points, and two (2) equally low, lowest points.
[0127] With
additional reference to FIGS. 37-39, the present teachings
include additional vacuum absorbing bases for polymeric hot-fill containers,
such as but not limited to, the container 10. An exemplary vacuum absorbing
base for the container 10 is illustrated in FIGS. 37-39 at reference numeral
20.
With particular reference to FIG. 38, the base 20 includes rigid, central
pushup portion 40 arranged at a center of the base 20 such that the
longitudinal axis 50 of the container 10 extends through a center of the
rigid,
central pushup portion 40. An inversion ring/flexible outer diaphragm 42 is
arranged between the rigid, central pushup portion 40 and sidewall 30 of the
container 10.
[0128] The central
pushup portion 40 includes a top surface 46, which
is furthest from contact ring 34 of the base 20, which is configured to
support
the container 10 upright on any suitable support surface, such as support
surface 38. At a center of the top surface 46 is a gate portion 46' through
which the longitudinal axis 50 extends. Extending outward from the top
surface 46, away from the longitudinal axis 50, is a side surface 48 of the
central pushup portion 40. The side surface 48 completely surrounds the
longitudinal axis 50. The side surface 48 extends to the flexible outer
diaphragm 42.
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[0129] The
flexible outer diaphragm 42 includes an upper portion 54
and a lower portion 58 at opposite ends thereof. The upper portion 54 is the
portion of the flexible outer diaphragm 42 that is furthest from the contact
ring
34 and the support surface 38 that the container 10 is seated on. The lower
portion 58 is the portion of the flexible outer diaphragm 42 that is closest
to
the contact ring 34 and the support surface 38. The flexible outer diaphragm
42 transitions to the side surface 48 of the central pushup portion 40 at the
lower portion 58, and thus the lower portion 58 also serves as a transition
point between the central pushup portion 40 and the flexible outer diaphragm
42. Between the upper portion 54 and the lower portion 58, the flexible outer
diaphragm 42 is curved so as to be convex relative to an exterior of the base
in the as-blown position of FIG. 38. The flexible outer diaphragm 42 can
also be straight, concave, s-shaped, or have any other suitable shape. The
flexible outer diaphragm 42 is connected to the contact ring 34 by an
15 .. upstanding circumferential wall/edge 44.
[0130] FIG.
38 illustrates the base 20 in an as-blown position, prior to
the container 10 being filled with a hot-fill product. After the container 10
is
filled and capped, the base 20 moves inward into the container 10 as the
product cools in a manner similar to that described above with respect to the
20 other vacuum absorbing bases according to the present teachings.
Specifically, the rigid central pushup portion 40 moves upward along the
longitudinal axis 50 towards the aperture or mouth 22 of the container 10.
The central pushup portion 40 is rigid, and thus neither the top surface 46
nor
the side surface 48 flexes as the central pushup portion 40 moves into the
container 10. The flexible outer diaphragm 42 is flexible at the upper portion
54, at the lower portion 58, and between the upper and lower portions 54 and
58. Thus as the base 20 moves inward in response to vacuum within the
container 10, the flexible outer diaphragm 42 flexes to accommodate
movement of the base 20 into the container 10.
[0131] To facilitate
movement of the base 20 into the container 10, the
flexible outer diaphragm 42 may include a plurality of surface features 102.
The surface features 102 are generally arranged in columns extending along
the flexible outer diaphragm 42 between the upper portion 54 and the lower
portion 58. Some of the features 102 can also be arranged at a portion of the
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side surface 48 proximate to the lower portion 58. The features 102 may be
any suitable surface features configured to facilitate flexion of the base 20.
For example and as illustrated in FIGS. 37-39, the features 102 can be
circular "dimples" or triangles extending either into or out of the container
10.
The base 20 may further include a plurality of base ribs 120 extending along
the flexible outer diaphragm 42 between the upper and lower portions 54 and
58. The base ribs 120 may extend into, or protrude from, the base 20. The
base ribs 120 can be arranged in any suitable manner, such as with one base
rib 120 arranged between neighboring features 120.
[0132] The base 20
may further include surface features in the form of
outer ribs 122 arranged along the upstanding circumferential wall 44. The
outer ribs 122 can be arranged to protrude outward from the wall 44 towards
the central longitudinal axis 50 as illustrated, or can be arranged to extend
into the wall 44 away from the central longitudinal axis 50. As illustrated in
FIGS. 37 and 39, the base 20 may further include center ribs 124. The center
ribs 124 are arranged at the side surface 48 of the central pushup portion 40,
and may protrude into, or extend from, the side surface 48. Figures 40 and
41 illustrate the base 20 without ribs 124, ribs 122, ribs 120, and/or dimples
102, which are thus optional.
[0133] The base 20 of
Figures 37-41 is particularly configured and
dimensioned to provide numerous advantages. With reference to FIG. 38 for
example, the side surface 48 is angled outward from the longitudinal axis 50
at a draft angle M of 30 -35 . For example, the draft angle M can be 33 , or
about 33 . Draft angle N measured through the longitudinal axis 50 between
opposing portions of the side surface 48 is 60 -70 , such as about 66 . The
draft angles M and N provide numerous advantages, such as improved mold
release during manufacture of the base 20, which permits higher base mold
temperatures as compared to conventional vacuum absorbing bases. For
example, angles M and N permit base mold temperatures of 170 F-200 F,
which is 20 F-40 F higher than conventional vacuum absorbing bases.
Higher base mold temperatures advantageously provide enhanced base
crystallinity and thermal stability (which increases strength and definition
of
the base 20), and improved forming definition. Increasing the strength of the
base 20 advantageously allows less material to be used in the base 20,
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reduces thickness of the base 20, and reduces the weight of the base 20.
The increased strength of the base 20 allows the base 20 to better resist any
deformations caused by fill pressure, which improves base retention and
minimizes rollout, and absorbs internal vacuum caused by hot filling and
subsequent cooling.
[0134] In
one exemplary embodiment, the base 20 has a maximum
outer diameter 0 of 2.7 inches, or about 2.7 inches. The central pushup
portion 40 has a diameter P measured across the longitudinal axis 50
between opposing lower portions 58 of 1.4 inches, or about 1.4 inches.
Diameter Q measured across the longitudinal axis 50 between opposing
upper portions 54 is 2.3 inches, or about 2.3 inches. As explained above, the
lower portion 58 is the transition point between the central pushup portion 40
and the flexible outer diaphragm 42. The lower portion/transition point 58 is
arranged generally halfway between the longitudinal axis 50 and the sidewall
30 of the container 10. The lower portion/transition point 58 is the portion
of
the flexible outer diaphragm 42 closest to the support surface 38.
[0135] The
rigid central pushup portion 40 advantageously resists
downward movement and deformation of the base 20 under hot-fill pressures,
which improves base clearance of the base 20. In the as-blown position of
FIG. 39, the top surface 46 is spaced apart from the support surface 38, which
extends across the contact ring 34 when the base 20 is seated on the support
surface 38, at a distance R measured from the gate 46' of 0.5 inches, or about
0.5 inches. The upper portion 54 is spaced apart from the support surface 38
at a distance S of 0.24 inches, or about 0.24 inches. The lower portion 58 is
spaced apart from the support surface 38 at a distance T, which is 0.07
inches to 0.09 inches, such as 0.08 inches or about 0.08 inches.
[0136] The
central pushup portion 40 has an actual surface area of
18.5 cm2, or about 18.5 cm2. The flexible outer diaphragm 42 has an actual
surface area of 22.7 cm2, or about 22.7 cm2. Thus the surface area of the
flexible outer diaphragm 42 is about 20%-25%, such as 23%, greater than the
surface area of the central pushup portion 40.
[0137] As
illustrated in Figure 38, the base 20 can have a width, as
measured along a line "W" extending from upper portion 54 to top surface 46,
of about 0.96 inches. The base 20 can have a depth of about 0.31 inches, as
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measured along line "D" extending between the line "W" and lower portion 58.
The ratio of the width to the depth is in a range of 0.28 to 0.36, or about
0.32.
This width to depth ratio enables improved control over the uniformity and
thickness of material at the flexible diaphragm 42 during blow molding.
[0138] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not intended to
be
exhaustive or to limit the invention. Individual elements or features of a
particular embodiment are generally not limited to that particular embodiment,
but, where applicable, are interchangeable and can be used in a selected
embodiment, even if not specifically shown or described. The same may also
be varied in many ways. Such variations are not to be regarded as a
departure from the invention, and all such modifications are intended to be
included within the scope of the invention.
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