U.S. patent application number 12/595830 was filed with the patent office on 2010-05-13 for pressure container with differential vacuum panels.
Invention is credited to David Murray Melrose.
Application Number | 20100116778 12/595830 |
Document ID | / |
Family ID | 39864137 |
Filed Date | 2010-05-13 |
United States Patent
Application |
20100116778 |
Kind Code |
A1 |
Melrose; David Murray |
May 13, 2010 |
PRESSURE CONTAINER WITH DIFFERENTIAL VACUUM PANELS
Abstract
A plastic container (1) has a first set of flex panels (2) and a
second set of flex panels (3) at least one set being adapted to
react to pressure changes within the container to a different
degree which can be achieved by different curvature and/or size
and/or different distance from a central longitudinal axis of the
container. At least one of the panels has at least two different
extents of curvature. In some embodiments one or more of the panels
may be flat.
Inventors: |
Melrose; David Murray; (
Auckland, NZ) |
Correspondence
Address: |
HENRICKS SLAVIN AND HOLMES LLP;SUITE 200
840 APOLLO STREET
EL SEGUNDO
CA
90245
US
|
Family ID: |
39864137 |
Appl. No.: |
12/595830 |
Filed: |
April 11, 2008 |
PCT Filed: |
April 11, 2008 |
PCT NO: |
PCT/NZ08/00079 |
371 Date: |
October 13, 2009 |
Current U.S.
Class: |
215/381 |
Current CPC
Class: |
B65D 1/40 20130101; B65D
79/005 20130101; B65D 1/0223 20130101 |
Class at
Publication: |
215/381 |
International
Class: |
B65D 1/40 20060101
B65D001/40 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 13, 2007 |
NZ |
554532 |
Claims
1. A plastic container having a body portion including a sidewall
wherein said body portion includes: a first controlled deflection
flex panel on one sidewall portion, and a second controlled
deflection flex panel on a second sidewall portion, at least one of
said controlled deflection flex panels having at least two
different extents of outward curvature, said first and second flex
panels being adapted to react to pressure changes within the
container to a different degree.
2. The plastic container of claim 1 wherein the first controlled
deflection flex panel has a width which is less than the width of
the second controlled deflection flex panel.
3. The plastic container of claim 1 wherein the second controlled
deflection flex panel has one or a plurality of ribs incorporated
within.
4. The plastic container of claim 3 wherein at least one, of said
sidewall portions is symmetrical to an opposing side wall portion
relative to rib and flex panel placement, size and number.
5. The plastic container of claim 4 wherein a, cage structure of
ribs and flex panels cooperate to maintain container shape upon
filling and cooling of the container.
6. The plastic container of claim 1 wherein the first and second
flex panels are adapted to react to pressure changes to a different
degree by being of a different size and/or different distance from
a central longitudinal axis of the container and/or having a
different curvature.
7. The plastic container of claim 1 wherein the container is
hot-fillable.
8. The plastic container of claim 1 including a base which is
rounded.
9. The plastic container of claim 1 including a base which is
non-rounded.
10. The plastic container of claim 1 or 2, wherein there is a pair
of opposite first controlled deflection flex panels and an adjacent
pair of opposite second controlled deflection flex panels.
11. The plastic container of claim 1 wherein the first controlled
deflection flex panel has one or a plurality of ribs incorporated
within.
12. The plastic container of claim 3 or 11 wherein the said ribs
include either an outward or inwardly facing rounded edge, relative
to the interior of the container.
13. The plastic container of claim 12 wherein said ribs are
parallel to each other.
14. The plastic container of claim 1 wherein the first controlled
deflection flex panel has a region of generally outward transverse
curvature.
15. The plastic container of claim 1 wherein the second controlled
deflection flex panel has a region of generally outward transverse
curvature.
16. The plastic container of claim 1 wherein the first controlled
deflection flex panel inverts under vacuum pressure.
17. A container for accommodating volume contraction within the
container after being filled with a heated liquid, having a
sidewall portion including four flex panels spaced apart around the
circumference of a body portion, and arranged as a first pair of of
opposed panels and a second pair of opposed panels, at least one of
said flex panels having at least two different extents of curvature
wherein the panels can deform inwardly to accommodate vacuum
pressure caused by volume contraction of the heated liquid and
wherein the panels are formed so the first pair of panels deforms
inwardly at a different rate than the second pair of panels.
18. The container of claim 17 wherein one said pair of panels has a
different amount of outward curvature to the other said pair of
panels.
19. The container of claim 17 wherein one said pair of panels is
substantially flat.
20. The container of claim 17 wherein one said pair of panels is
substantially concave.
21. The container of claim 17 wherein one said pair of panels has a
variable outward curvature.
22. The container of claim 17 wherein one said pair of panels has a
generally even outward radius of curvature, excluding any ribs or
grip features on said panels.
23. The container of claim 22 wherein one said pair of panels has a
variable outward projection.
24. The container of claim 23 wherein a substantially central
section of said panels projects outward to a greater extent.
25. The container of claim 23 wherein a substantially central
section of said panels projects outward to a lesser extent.
26. (canceled)
27. The container of either of claim 1 or claim 17 wherein said at
least two different extents of curvature comprise varying amounts
of projection from a plane defined by a longitudinal axis of said
at least one panel.
28. The container of claim 27 wherein a substantially constant arc
of curvature is provided along said longitudinal axis of said at
least one panel.
29. The container of claim 27 wherein a variable arc of curvature
is provided along said longitudinal axis of said at least one
panel.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to hot-fillable containers.
More particularly, the present invention relates to hot-fillable
containers having collapse panels.
BACKGROUND OF THE INVENTION
[0002] `Hot-Fill` applications impose significant and complex
mechanical stress on a container structure due to thermal stress,
hydraulic pressure upon filling and immediately after capping, and
vacuum pressure as the fluid cools.
[0003] Thermal stress is applied to the walls of the container upon
introduction of hot fluid. The hot fluid will cause the container
walls to soften and then shrink unevenly, causing distortion of the
container. The polyester must therefore be heat-treated to induce
molecular changes resulting in a container that exhibits thermal
stability.
[0004] Pressure and stress act upon the side walls of a heat
resistant container during the filling process, and for a
significant period of time thereafter. When the container is filled
with hot liquid and sealed, there is an initial hydraulic pressure
and an increased internal pressure is placed upon containers. As
the liquid, and the air headspace under the cap, subsequently cool,
thermal contraction results in partial evacuation of the container.
The vacuum created by this cooling tends to mechanically deform the
container walls.
[0005] Generally speaking, containers incorporating a plurality of
longitudinal flat surfaces accommodate vacuum force more readily.
Agrawal et al, U.S. Pat. No. 4,497,855 discloses a container with a
plurality of recessed collapse panels, separated by land areas,
which allows uniformly inward deformation under vacuum force. The
vacuum effects are controlled without adversely affecting the
appearance of the container. The panels are drawn inwardly to vent
the internal vacuum and so prevent excess force being applied to
the container structure, which would otherwise deform the
inflexible post or land area structures. The amount of `flex`
available in each panel is limited, however, and as the limit is
approached there is an increased amount of force that is
transferred to the side walls.
[0006] To minimise the effect of force being transferred to the
side walls, much prior art has focused on providing stiffened
regions to the container, including the panels, to prevent the
structure yielding to the vacuum force.
[0007] The provision of horizontal or vertical annular sections, or
`ribs`, throughout a container has become common practice in
container construction, and is not only restricted to hot-fill
containers. Such annular sections will strengthen the part they are
deployed upon. Cochran U.S. Pat. No. 4,372,455 discloses annular
rib strengthening in a longitudinal direction, placed in the areas
between the flat surfaces that are subjected to inwardly deforming
hydrostatic forces under vacuum force. Akiho Ota et al U.S. Pat.
No. 4,805,788 discloses longitudinally extending ribs alongside the
panels to add stiffening to the container. Akiho Ota also discloses
the strengthening effect of providing a larger step in the sides of
the land areas. This provides greater dimension and strength to the
rib areas between the panels. Akiho Ota et al, U.S. Pat. No.
5,178,290 discloses indentations to strengthen the panel areas
themselves.
[0008] Akiho Ota et al, U.S. Pat. No. 5,238,129 discloses further
annular rib strengthening, this time horizontally directed in
strips above and below, and outside, the hot-fill panel section of
the bottle.
[0009] In addition to the need for strengthening a container
against both thermal and vacuum stress, there is a need to allow
for an initial hydraulic pressure and increased internal pressure
that is placed upon a container when hot liquid is introduced
followed by capping. This causes stress to be placed on the
container side wall. There is a forced outward movement of the heat
panels, which can result in a barrelling of the container.
[0010] Thus, Hayashi et al, U.S. Pat. No. 4,877,141, discloses a
panel configuration that accommodates an initial, and natural,
outward flexing caused by internal hydraulic pressure and
temperature, followed by inward flexing caused by the vacuum
formation during cooling. Importantly, the panel is kept relatively
flat in profile, but with a central portion displaced slightly to
add strength to the panel but without preventing its radial
movement in and out. With the panel being generally flat, however,
the amount of movement is limited in both directions. By necessity,
panel ribs are not included for extra resilience, as this would
prohibit outward and inward return movement of the panel as a
whole.
[0011] As stated, the use of blow molded plastic containers for
packaging "hot-fill" beverages is well known. However, a container
that is used for hot-fill applications is subject to additional
mechanical stresses on the container that result in the container
being more likely to fail during storage or handling. For example,
it has been found that the thin sidewalls of the container deform
or collapse as the container is being filled with hot fluids. In
addition, the rigidity of the container decreases immediately after
the hot-fill liquid is introduced into the container. As the liquid
cools, the liquid shrinks in volume which, in turn, produces a
negative pressure or vacuum in the container. The container must be
able to withstand such changes in pressure without failure.
[0012] Hot-fill containers typically comprise substantially
rectangular vacuum panels that are designed to collapse inwardly
after the container has been filled with hot liquid. However, the
inward flexing of the panels caused by the hot-fill vacuum creates
high stress points at the top and bottom edges of the vacuum
panels, especially at the upper and lower corners of the panels.
These stress points weaken the portions of the sidewall near the
edges of the panels, allowing the sidewall to collapse inwardly
during handling of the container or when containers are stacked
together. See U.S. Pat. No. 5,337,909.
[0013] The presence of annular reinforcement ribs that extend
continuously around the circumference of the container sidewall are
shown in U.S. Pat. No. 5,337,909. These ribs are indicated as
supporting the vacuum panels at their upper and lower edges. This
holds the edges fixed, while permitting the center portions of the
vacuum panels to flex inwardly while the bottle is being filled.
These ribs also resist the deformation of the vacuum panels. The
reinforcement ribs can merge with the edges of the vacuum panels at
the edge of the label upper and lower mounting panels.
[0014] Another hot-fill container having reinforcement ribs is
disclosed in WO 97/34808. The container comprises a label mounting
area having an upper and lower series of peripherally spaced,
short, horizontal ribs separated endwise by label mount areas. It
is stated that each upper and lower rib is located within the label
mount section and is centered above or below, respectively, one of
the lands. The container further comprises several rectangular
vacuum panels that also experience high stress point at the corners
of the collapse panels. These ribs stiffen the container adjacent
lower corners of the collapse panels.
[0015] Stretch blow molded containers such as hot-filled PET juice
or sport drink containers, must be able to maintain their function,
shape and labelability on cool down to room temperature or
refrigeration. In the case of non-round containers, this is more
challenging due to the fact that the level of orientation and,
therefore, crystallinity is inherently lower in the front and back
than on the narrower sides. Since the front and back are normally
where vacuum panels are located, these areas must be made thicker
to compensate for their relatively lower strength.
[0016] In discussing the above prior art the applicant does not
acknowledge that it forms part of common general knowledge in New
Zealand or in any other country or region.
SUMMARY OF THE INVENTION
[0017] The present invention provides according to one aspect a
plastic container, having a body portion including a sidewall,
wherein said body portion includes; a first controlled deflection
flex panel on one sidewall portion and a second controlled
deflection flex panel on a second sidewall portion, at least one of
said controlled deflection flex panels having at least two
different extents of outward curvature, said first and second flex
panels being adapted to react to pressure changes within the
container to a different degree. By way of example, a container
having four controlled deflection flex panels may be disposed in
two pairs on symmetrically opposing sidewalls, whereby one pair of
controlled deflection flex panels responds to vacuum force at a
different rate to an alternately positioned pair. The pairs of
controlled deflection flex panels may be positioned an equidistance
from the central longitudinal axis of the container, or may be
positioned at differing distances from the centerline of the
container. In addition the design allows for a more controlled
overall response to vacuum pressure and improved dent resistance
and resistance to torsion displacement of post or land areas
between the panels. Further, improved reduction in container weight
is achieved, along with potential for development of squeezable
container designs.
[0018] According to another aspect of the invention a container for
accommodating volume contraction within the container after being
filled with a heated liquid has a side wall portion having four
flex panels spaced apart around the circumference of a body portion
and arranged as a first pair of opposed panels and a second pair of
opposed panels, at least one of said flex panels having at least
two different extents of curvature wherein the panels can deform
inwardly to accommodate vacuum pressure caused by volume
contraction of the heated liquid and wherein the panels are formed
so the first pair of panels deforms inwardly at a different rate
than the second pair of panels. Preferably each flex panel may have
a generally variable outward curvature with respect to the
centerline of the container. The first pair of panels may be
positioned whereby one panel in the first pair is disposed opposite
the other, and the first pair of panels has a geometry and surface
area that is distinct from the alternately positioned second pair
of panels. The second pair of panels may be similarly positioned
whereby the panels in the second pair are disposed in opposition to
each other. The containers are suitable for a variety of uses
including hot-fill applications.
[0019] In hot-fill applications, the plastic container is filled
with a liquid that is above room temperature and then sealed so
that the cooling of the liquid creates a reduced volume in the
container. In this preferred embodiment, the first pair of opposing
controlled deflection flex panels, having the least total surface
area between them, have a generally rectangular shape, wider at the
base than at the top. These panels may be symmetrical to each other
in size and shape. These controlled deflection flex panels have a
substantially outwardly curved, transverse profile and an initiator
portion toward the central region that is less outwardly curved
than in the upper and lower regions. Alternatively, the amount of
outward curvature could vary evenly from top to bottom, bottom to
top, or any other suitable arrangement. Alternatively, the entire
panel may have a relatively even outward curvature but vary in
extent of transverse circumferential amount, such that one portion
of the panel begins deflection inwardly before another portion of
the panel. Alternatively, one pair of panels may be substantially
flat or concave while the opposing pair of panels comprise
controlled deflection flex panels having a variable outward
curvature. Alternatively again, one pair of panels may be
substantially evenly outwardly curved, while the opposing pair of
panels comprise controlled deflection flex panels having a variable
outward curvature. This first pair of controlled deflection flex
panels may in addition contain one or more ribs located above or
below the panels. These optional ribs may also be symmetric to
ribs, in size, shape and number to ribs on the opposing sidewalls
containing the second set of controlled deflection flex panels. The
ribs on the second set of controlled deflection flex panels may
have a rounded edge which may point inward or outward relative to
the interior of the container. In a first preferred form of the
invention, whereby the first pair of controlled deflection flex
panels is preferentially reactive to vacuum forces to a much
greater extent initially than the second pair of controlled
deflection flex panels, it is preferred to not have ribs
incorporated within the first pair of panels, in order to allow
easier movement of the panels.
[0020] The vacuum panels should be selected so that they are highly
efficient. See, for example, PCT application NO. PCT/NZ00/00019
(David Melrose) where panels with vacuum panel geometry are shown.
`Prior art` vacuum panels are generally flat or concave. The
controlled deflection flex panel of Melrose of PCT/NZ00/00019 and
the present invention is outwardly curved and can extract greater
amounts of pressure. Each flex panel has at least 2 regions of
differing outward curvature. The region that is less outwardly
curved, the initiator region, reacts to changing pressure at a
lower threshold than the region that is more outwardly curved. By
providing an initiator portion, the control portion (the region
that is more outwardly curved) reacts to pressure more readily than
would normally happen. Vacuum pressure is thus reduced to a greater
degree than prior art causing less stress to be applied to the
container sidewalls. This increased venting of vacuum pressure
allows for many design options: different panel shapes, especially
outward curves; lighter weight containers; less failure under load;
less panel area needed; different shape container bodies.
[0021] The controlled deflection flex panel can be shaped in many
different ways and can be used on inventive structures that are not
standard and can yield improved structures in a container.
[0022] All sidewalls containing the controlled deflection flex
panels may have one or more ribs located within them. The ribs can
have either an outer or inner edge relative to the inside of the
container. These ribs may occur as a series of parallel ribs. These
ribs are parallel to each other and the base. The number of ribs
within the series can be either an odd or even. The number, size
and shape of ribs are symmetric to those in the opposing sidewall.
Such symmetry enhances stability of the container.
[0023] Preferably, the ribs on the side containing the second pair
of controlled deflection panels and having the largest surface area
of panel, are substantially identical to each other in size and
shape. The individual ribs can extend across the length or width of
the container. The actual length, width and depth of the rib may
vary depending on container use, plastic material employed and the
demands of the manufacturing process. Each rib is spaced apart
relative to the others to optimize its and the overall
stabilization function as an inward or outward rib. The ribs are
parallel to one another and preferably, also to the container
base.
[0024] The advanced highly efficient design of the controlled
deflection panels of the first pair of panels more than compensates
for the fact that they offer less surface area than the larger
front and back panels. By providing for the first pair of panels to
respond to lower thresholds of pressure, these panels may begin the
function of vacuum compensation before the second larger panel set,
despite being positioned further from the centerline. The second
larger panel set may be constructed to move only minimally, and
relatively evenly in response to vacuum pressure, as even a small
movement of these panels provides adequate vacuum compensation due
to the increased surface area. The first set of controlled
deflection flex panels may be constructed to invert and provide
much of the vacuum compensation required by the package in order to
prevent the larger set of panels from entering an inverted
position. Employment of a thin walled super light weight preform
ensures that a high level of orientation and crystallinity are
imparted to the entire package. This increased level of strength
together with the rib structure and highly efficient vacuum panels
provide the container with the ability to maintain function and
shape on cool down, while at the same time utilizing minimum gram
weight.
[0025] The arrangement of ribs and vacuum panels on adjacent sides
within the area defined by upper and lower container bumpers allows
the package to be further light weighted without loss of structural
strength. The ribs are placed on the larger, non-inverting panels
and the smaller inverting panels may be generally free of rib
indentations and so are more suitable for embossing or debossing of
Brand logos or name. This configuration optimizes geometric
orientation of squeeze bottle arrangements, whereby the sides of
the container are partially drawn inwardly' as the main larger
panels contract toward each other. Generally speaking, in prior art
as the front and back panels are drawn inwardly under vacuum the
sides are forced outwardly. In the present invention the side
panels invert toward the centre and maintain this position without
being forced outwardly beyond the post structures between the
panels. Further, this configuration of ribs and vacuum panel
represents a departure from tradition.
[0026] These and various other advantages and features of novelty
which characterize the invention are pointed out with particularity
in the claims annexed hereto and forming a part hereof. However,
for a better understanding of the invention, its advantages, and
the objects obtained by its use, reference should be made to the
drawings which form a further part hereof, and to the accompanying
descriptive matter, in which there are illustrated and described
preferred embodiments of the invention.
DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 shows a side view of the container showing the
embodiment having a series of symmetrical ribs on the larger
controlled deflection flex panels.
[0028] FIG. 2 shows a front view of the container shown in FIG.
1
[0029] FIGS. 3a-c show rendered side, front, and perspective solid
views of the container shown in FIGS. 1 and 2.
[0030] FIG. 4a shows a Finite Element Analysis view of the
container shown in FIG. 1 under vacuum pressure Step One
[0031] FIG. 4b shows a Finite Element Analysis view of the
container shown in FIG. 2 under vacuum pressure Step One
[0032] FIG. 5a shows a Finite Element Analysis view of the
container shown in FIG. 1 under vacuum pressure Step Two
[0033] FIG. 5b shows a Finite Element Analysis view of the
container shown in FIG. 2 under vacuum pressure Step Two
[0034] FIGS. 6a-e show Finite Element Analysis cross-sectional
views through line B-B of the container shown in FIG. 1 under
vacuum pressure Step One to Five.
[0035] FIGS. 7 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
having variable curvatures.
[0036] FIGS. 8 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
having variable projecting curvatures
[0037] FIGS. 9 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
having variable curvatures.
[0038] FIGS. 10 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
with one set having an even outward curvature and one set having a
variable outward curvature.
[0039] FIGS. 11 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
with one set of panels having variable outward curvatures and one
set being substantially flat.
[0040] FIGS. 12 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
with one set of panels having variable projecting curvatures and
one set being substantially flat.
[0041] FIGS. 13 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
with one set of panels having variable outward curvatures and one
set of panels being substantially concave.
[0042] FIGS. 14 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
with one set of panels having even outward curvatures and one set
of panels having variable inward curvatures.
DETAILED DESCRIPTION OF THE INVENTION
[0043] A thin-walled container in accordance with the present
invention is intended to be filled with a liquid at a temperature
above room temperature. According to the invention, a container may
be formed from a plastic material such as polyethylene terephthlate
(PET) or polyester. Preferably, the container is blow molded. The
container can be filled by automated, high speed, hot-fill
equipment known in the art.
[0044] Referring now to the drawings, a preferred embodiment of the
container of this invention is indicated generally in FIG. 1, as
generally having many of the well known features of hot-fill
bottles. The container (1), which is generally round or oval in
shape, has a longitudinal axis (C) when the container is standing
upright on its base. The container comprises a threaded neck (5)
for filling and dispensing fluid. Neck (5) also is sealable with a
cap (not shown). The preferred container further comprises a
substantially circular base (8) and a bell (4) located below neck
(5) and above base (8). The container of the present invention also
has a body (9) defined by substantially round sides containing a
pair of narrower controlled deflection flex panels (2) and a pair
of wider controlled deflection flex panels (3) that connect bell
(4) and base (8). A label or labels can easily be applied to the
bell area using methods that are well known to those skilled in the
art, including shrink wrap labeling and adhesive methods. As
applied, the label extends either around the entire bell of the
container or extends over a portion of the label mounting area.
[0045] Generally, the substantially rectangular flex panels (3)
containing one or more ribs (6) are those with a width greater than
the pair of flex panels adjacent (2) in the body area (9). The
placement of the controlled deflection flex panel (3) and the ribs
(6) are such that the opposing sides are symmetrical. These flex
panels (3) have rounded edges. The vacuum panels (3) permit the
bottle to flex inwardly upon filling with the hot fluid, sealing,
and subsequent cooling. The ribs (6) can have a rounded outer or
inner edge, relative to the space defined by the sides of the
container. The ribs typically extend most of the width of the side
and are parallel with each other and the base. The width of these
ribs is selected consistent with achieving the rib function. The
number of ribs on either adjacent side can vary depending on
container size, rib number, plastic composition, bottle filling
conditions and expected contents. The placement of ribs on a side
can also vary so long as the desired goal(s) associated with the
interfunctioning of the ribbed flex panels and the non-ribbed flex
panels is not lost. The ribs are also spaced apart from the upper
and lower edges of the vacuum panels, respectively, and are placed
to maximize their function. The ribs of each series are
noncontinuous, i.e., they do not touch each other. Nor do they
touch a panel edge.
[0046] The number of vacuum panels is variable. However, two
symmetrical panels, each on the opposite sides of the container,
are preferred. The controlled deflection flex panel (3) is
substantially rectangular in shape and has a rounded upper edge
(10) and a rounded lower edge (11).
[0047] As shown in FIG. 1, the narrower side contains the
controlled deflection flex panel (2) that does not have rib
strengthening. Of course, the panel (2) may also incorporate a
number of ribs of varying length and configuration. It is also
preferred that any ribs positioned on this side correspond in
positioning and size to their counterparts on the opposite side of
the container.
[0048] Each controlled deflection flex panel (2) is generally
outwardly curved in cross-section. Further, the amount of outward
curvature varies along the longitudinal length of the flex panel,
such that response to vacuum pressure varies in different regions
of the flex panel. FIG. 6a shows the outward curvature in
cross-section through Line B-B of FIG. 1. A cross-section higher
through the flex panel region, i.e. closer to the bell, would
reveal the outward curvature to be less than through Line B-B, and
a cross-section through the flex panel relatively low on the body
and closer to the junction with the base of the container would
reveal a greater outward curvature than through Line B-B.
[0049] Each controlled deflection flex panel (3) is also generally
outwardly curved in cross-section. Similarly, the amount of outward
curvature varies along the longitudinal length of the flex panel,
such that response to vacuum pressure varies in different regions
of the flex panel. FIG. 6a shows the outward curvature in
cross-section through Line B-B of FIG. 1. A cross-section higher
through the flex panel region, i.e. closer to the bell, would
reveal the outward curvature to be less than through Line B-B, and
a cross-section through the flex panel relatively low on the body
and closer to the junction with the base of the container would
reveal a greater outward curvature than through Line B-B.
[0050] Importantly, the amount of arc curvature contained within
controlled deflection flex panel (2) is different to that contained
within controlled deflection flex panel (3). This provides greater
control over the movement of the larger flex panels (3) than would
be the case if the panels (2) were not present or replaced by
strengthened regions, or land areas or posts for example. By
separating a pair of flex panels (3), which are disposed opposite
each other, by a pair of flex panels (2), the amount of vacuum
force generated against flex panels (3) during product contraction
can be manipulated. In this way undue distortion of the major
panels may be avoided.
[0051] In this preferred embodiment, the flex panels 2 provide for
earlier response to vacuum pressure, thus removing pressure
response necessity from flex panels 3. FIGS. 6a to 6e show gradual
increases in vacuum pressure within the container. Flex panels (2)
respond earlier and more aggressively than flex panels (3), despite
the larger size of flex panels (3) which would normally provide
most of the vacuum compensation within the container. Controlled
deflection flex panels (2) invert and remain inverted as vacuum
pressure increases. This results in full vacuum accommodation being
achieved well before full potential is realized from the larger
flex panels (3). Controlled deflection flex panels (3) may continue
to be drawn inwardly should increased vacuum be experienced under
aggressive conditions, such as greatly decreased temperature (deep
refrigeration) or if the product is aged leading to increased
migration of oxygen and other gases through the plastic sidewalls,
also causing increased vacuum force.
[0052] The improved arrangement of the present invention provides
for a greater potential for response to vacuum pressure than prior
art. The container may be squeezed to expel contents as the larger
panels (3) are squeezed toward each other, or even if the smaller
panels (2) are squeezed toward each other. Release of squeeze
pressure results in the container immediately returning to its
intended shape rather than remain buckled or distorted. This is a
result of having the opposing set of panels having a different
response to vacuum pressure levels. In this way, one set of panels
will always set the configuration for the container as a whole and
not allow any redistribution of panel set that might normally occur
otherwise.
[0053] Vacuum response is spread circumferentially throughout the
container, but allows for efficient contraction of the sidewalls
such that each pair of panels may be drawn toward each other
without undue force being applied to the posts (7) separating each
panel. This overall setup leads to less container distortion at all
levels of vacuum pressure than prior art, and less sideways
distortion as the larger panels are brought together. Further, a
higher level of vacuum compensation is obtained through the
employment of smaller vacuum panels set between the larger ones,
than would otherwise be obtained by the larger ones alone. Without
the smaller panels undue force would be applied to the posts by the
contracting larger panels, which would take a less favourable
orientation at higher vacuum levels.
[0054] The above is offered by way of example only, and the size,
shape, and number of the panels (2) and the size, shape, and number
of the panels (3), and the size, shape, and number of reinforcement
ribs is related to the functional requirements of the size of the
container, and could be increased or decreased from the values
given.
[0055] FIGS. 7 a-e, show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels,
the primary panels (2) having variable curvatures whereby their
middle portion is relatively flat, or has a lesser amount of
curvature than the portions in the upper or lower regions of the
panel. The secondary panels (3) also have variable curvatures
whereby the middle portion has a greater amount of curvature than
the regions above and below. This middle region also projects
outwardly to a lesser extent or degree than the region of the panel
above or below. By providing a central portion having a greater
amount of curvature, or a lesser radius of curvature, the central
portion is somewhat strengthened against flexure compared to the
regions having lesser amounts of curvature, or a greater radius of
curvature.
[0056] By providing such variable curvatures within a panel, a
great degree of control can be exhibited over the panel and how
flexure occurs under vacuum pressure. A certain rate of flexure can
be obtained with a high degree of accuracy.
[0057] Additionally, by providing for the secondary panel to have a
lesser projecting region in the middle portion, the amount of
resistance introduced already by the increased amount of curvature
can be further modified. The lesser projection causes a degree of
lesser resistance to vacuum pressure and ensures the central
portion flexes at the correct rate.
[0058] The primary panels (2) have a lesser outwardly projecting
portion in the centre, and this region also has a lesser amount of
curve, or larger radius of curvature than the regions above and
below. Therefore, the combined effect is to control the overall
flexure of the four panels under vacuum pressure, such that the
primary panels flex readily despite having a smaller surface area
and being further displaced from the centerline than the secondary
panels.
[0059] Importantly, the rate of flexure can be controlled between
the 2 sets of panels to create a better balance and allowing the
container to avoid uncontrolled collapse, and to provide for
greater vacuum absorption.
[0060] As shown in FIGS. 8 a-e, 2 sets of panels having variable
projecting curvatures whereby the primary panels (2) have a similar
construction to the primary panels in FIGS. 7 a-e, but the
secondary panels are constructed to respond at a slightly lower
vacuum threshold than the secondary panels in FIGS. 7 a-e. This is
achieved by having the secondary panels in this instance have the
same radius of curvature through the middle portion rather than the
smaller radius of curvature in FIGS. 7 a-e.
[0061] FIGS. 9 a-e show an alternative embodiment of the container
again, having 2 sets of panels having variable curvatures. In this
example the secondary panels (3) have a middle region that is
further weakened against vacuum pressure by having a lesser amount
of arc, or increased radius of curvature, than the regions above or
below. Thus, the four panels are constructed in a similar manner to
those in FIGS. 8 a-e, but the secondary panels will respond to
vacuum pressures earlier by comparison.
[0062] FIGS. 10 a-e show an alternative embodiment of the container
having 2 sets of panels with one set having an even outward
curvature and one set having a variable outward curvature. By
comparison to the previous example in FIGS. 9 a-e, the secondary
panels (3) are somewhat more resistant to vacuum pressure as the
middle portion shares a common radius of curvature, and a common
projection with the regions above and beyond. This creates a panel
that is stiffer and slower to respond to vacuum pressure.
Subsequently, the primary panels (2) respond significantly faster
than the secondary panels, but overall response within the
container is different to all the previous examples.
[0063] FIGS. 11 a-e show a further alternative embodiment of the
container having 2 sets of panels with one set of panels (3) having
variable outward curvatures and one set of panels (2) being
substantially flat. In this example the primary panels (2) will not
have the same total volume extraction available as in the previous
examples and will respond initially at a similar rate, but then
slow in extraction and cause the secondary panels to in fact speed
up in response to vacuum after the initial volume compensation is
achieved.
[0064] FIGS. 12 a-e show another alternative embodiment of the
container having 2 sets of panels with one set of panels having
variable projecting curvatures and one set being substantially
flat. Again, the combination provides for alternative speed
responses between the panels.
[0065] FIGS. 13 a-e show front, side and cross-section views of an
alternative embodiment of the container having 2 sets of panels
with one set of panels having variable outward curvatures and one
set of panels being substantially concave. In this embodiment, the
primary panels react earlier to vacuum pressure due to being
concave, particularly in the middle regions, but overall extraction
from the primary panels is limited due to the lack of any outward
curvature. This causes the secondary panels (3) to need to provide
for a greater amount of the extraction required, whereby the panels
are drawn closer to the centerline and therefore closer together,
under vacuum pressure.
[0066] FIGS. 14 a-e show an alternative embodiment of the container
having 2 sets of panels with one set of panels having even outward
curvatures and one set of panels having variable inward curvatures.
The primary panels (2) are particularly predisposed to reacting in
the initial stages in this embodiment. The concavity is more
pronounced in the middle portion, wherein the inward radius of
curvature is smaller, such that this region reacts more quickly.
The secondary panels are further configured to encourage this as
they are more stiffly constructed, having a more even outward
curvature. Thus, the secondary panels resist the early vacuum
pressures at the same time the primary panels more readily respond
to vacuum. This creates a greater difference in response at early
stages of vacuum pressure between the panels.
[0067] It is to be understood, however, that even though numerous
characteristics and advantages of the present invention have been
set forth in the foregoing description, together with details of
the structure and function of the invention, the disclosure is
illustrative only, and changes may be made in detail, especially in
matters of shape, size and arrangement of parts within the
principles of the invention to the full extent indicated by the
broad general meaning of the terms in which the appended claims are
expressed.
[0068] All references cited in this specification are hereby
incorporated by reference. The discussion of the references herein
is intended merely to summarize the assertions made by their
authors and no admission is made that any reference constitutes
prior art relevant to patentability and the applicant reserves the
right to challenge the accuracy and pertinency of the cited
references.
[0069] Although this invention has been described by way of example
and with reference to possible embodiments thereof, it is to be
understood that modifications or improvements may be made thereto
without departing from the scope of the invention as defined in the
appended claims.
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