U.S. patent application number 13/639853 was filed with the patent office on 2013-03-14 for self-standing container.
This patent application is currently assigned to Petainer Lidkoeping AB. The applicant listed for this patent is Petainer Lidkoeping AB. Invention is credited to Mikael Quasters.
Application Number | 20130062306 13/639853 |
Document ID | / |
Family ID | 42228918 |
Filed Date | 2013-03-14 |
United States Patent
Application |
20130062306 |
Kind Code |
A1 |
Quasters; Mikael |
March 14, 2013 |
Self-Standing Container
Abstract
A petaloid base for a self-standing container has an
approximately hemispherical underlying base contour and a plurality
of ovoid foot formations that interrupt and project from the
underlying base contour to define a corresponding plurality of
feet. Its shape resists stress cracking, maximises capacity
relative to the height of the container and reduces the surface
area of the base and hence material usage in comparison with
equivalent known designs.
Inventors: |
Quasters; Mikael; (Vinninga,
SE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Petainer Lidkoeping AB; |
Lidkoeping |
|
SE |
|
|
Assignee: |
Petainer Lidkoeping AB
Lidkoeping
SE
|
Family ID: |
42228918 |
Appl. No.: |
13/639853 |
Filed: |
October 5, 2012 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP11/55383 |
Apr 6, 2011 |
|
|
|
13639853 |
|
|
|
|
Current U.S.
Class: |
215/375 ;
248/346.03 |
Current CPC
Class: |
B65D 1/16 20130101; B65D
1/0284 20130101; B65D 23/00 20130101 |
Class at
Publication: |
215/375 ;
248/346.03 |
International
Class: |
B65D 23/00 20060101
B65D023/00 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 6, 2010 |
GB |
1005717.2 |
Claims
1. A petaloid base for a self-standing container, the base having a
spheroidal underlying base contour and a plurality of spheroidal
foot formations that interrupt and project from the underlying base
contour to define a corresponding plurality of feet.
2. The base of claim 1, wherein the underlying base contour is an
oblate spheroid whose polar axis coincides with a central axis of
the base.
3. The base of claim 1, wherein the underlying base contour is
substantially hemispherical.
4. The base of claim 1, wherein the foot formations are elongate
ellipsoids.
5. The base of claim 4, wherein the foot formations are prolate
spheroids.
6. The base of claim 4, wherein the foot formations are ovoid, and
wherein the widest part of the cross-section of each foot formation
is offset inwardly toward an inner end of the foot formation.
7. (canceled)
8. The base of claim 4, wherein the foot formations have respective
longitudinal axes, which axes lie in planes extending radially from
a central axis of the base.
9. The base of claim 8, wherein the axes of the foot formations
extend outwardly in conical relation from the central axis of the
base.
10. The base of claim 9, wherein the axes of the foot formations
extend outwardly and upwardly from the central axis of the base,
and wherein the axes of the foot formations meet at the central
axis of the base at a position axially below the base.
11. (canceled)
12. The base of claim 1, wherein each foot formation has an
elliptical intersection with the underlying base contour, the
intersection is ovate and of concave cross section.
13-14. (canceled)
15. The base of claim 1, wherein the foot formations radiate from a
central protrusion.
16. The base of claim 15, wherein the central protrusion has a
radius of curvature that is smaller than the radius of curvature of
the underlying base curve, and wherein the central protrusion
extends to a level beyond the lowermost apex of the underlying base
contour.
17. (canceled)
18. The base of claim 15, wherein a foot formation and the central
protrusion are joined via a smoothly curving transition portion,
wherein the foot formation, the smoothly curving transition portion
and the central protrusion together define a sinuous cross section,
and wherein the transition portion defines a curve whose curvature
is converse to the curvature of at least one of the foot formations
and central protrusion.
19-20. (canceled)
21. The base of claim 15, wherein the central protrusion is
substantially convex with respect to the exterior of the
container.
22. The base of claim 15, wherein the central protrusion defines a
recess with respect to the interior of the container, the recess
being arranged to locate and retain a free end of a fluid delivery
tube within the container.
23. The base of claim 15, wherein the central protrusion is
generally polygonal, with a number of sides corresponding to the
number of foot formations, wherein the foot formations are
separated by valleys, and the valleys radiate from apices of the
polygonal protrusion.
24. The base of claim 1.
25. The base of claim 15.
26. The base of claim 1, wherein the foot formations are separated
by valleys, the valleys widen moving outwardly across the base,
each valley has an inner and an outer section and the walls of the
valley diverge more sharply in the outer section than in the inner
section, and the walls of the valley diverge in both the inner and
the outer sections of the valley.
27-28. (canceled)
29. The base of claim 1, wherein in plan view, each foot formation
has an enlarged central region that tapers inwardly across an inner
portion to an inner end of the foot formation, the inner portions
of the foot formations lie in segmented relation around the base,
and each foot formation tapers from the enlarged central region
outwardly across an outer portion to an outer end of the foot
formation.
30-31. (canceled)
32. A self-standing container having a base as defined in claim
1.
33. The container of claim 32, wherein the foot formations of the
base define respective contact points that together are spaced
around a contact circle whose diameter (x) relates to a side wall
diameter (Dy) of the container as: Dy 0.5 x = k ##EQU00002## where
k is between 3.6 and 5.5.
34. The container of claim 33, wherein k is between 4.0 and
5.3.
35. The container of claim 34, wherein k is between 4.2 and
5.0.
36. The container of claim 32, having an average burst pressure
resistance to material usage ratio of greater than 3 MPa/kg.
37. The container of claim 32, having a capacity to material usage
ratio of greater than 40 litres/kg.
38. The container of claim 32, comprising a fluid delivery tube
aligned with a central longitudinal axis of the container, the tube
extending between the base of the container and an opening of the
container.
Description
[0001] This invention relates to self-standing containers, more
specifically to a petaloid base for such a container. Such
containers may be blow-moulded of plastics material such as
polyethylene terephthalate (PET).
[0002] As will be understood in the art, the generic term `PET`
includes compositions that predominantly contain polyethylene
terephthalate--but may also including other materials. For example,
a suitable composition may comprise approximately 95% polyethylene
terephthalate and 5% nylon. As is known in the art, these materials
may be mixed, or provided in different layers, for example via
multilayer injection moulding and overmoulding.
[0003] Blow-moulded PET containers have long been used as bottles
for beverages. More recently, they have been proposed for use as
kegs for transporting, storing and dispensing beverages such as
beer. An example of such a keg is disclosed in WO 2007/064277.
[0004] The example of WO 2007/064277 is given for background
reference only: the broad concept of this invention is not limited
to any particular use, material or method of manufacture of a
container. However the invention has particular advantages in the
context of thin-walled blow-moulded containers of the type apt to
be manufactured from PET. It is in that context that the invention
will be described in this specification.
[0005] Early PET containers had a plain hemispherical base and were
rendered self-standing by the attachment of a separate base
moulding to the base. Whilst a hemispherical base is simple, light
and strong in isolation, the addition of a separate base moulding
increases material and production costs and may hinder
recycling.
[0006] To make a PET container self-standing without recourse to a
separate base moulding, it is now well known to provide the
container with an integrally-moulded petaloid base. The term
`petaloid` refers to a multi-footed base shape whose feet are
disposed in an angularly-spaced arrangement around the base, the
resulting shape resembling the petals of a flower when viewed from
under the container in use. The container usually has a cylindrical
side wall of circular horizontal cross-section, in which case the
feet typically lie on a contact circle that is concentric with, and
whose diameter is smaller than, the circular cross-section of the
side wall. The feet act together to provide a stable multi-point
support for the container.
[0007] There is continual pressure in the art of containers to
reduce material and production costs and to ease recycling. Not
only has this led to the adoption of one-piece containers with
petaloid bases, but efforts continue to improve the petaloid base
so that containers can be produced more economically while still
performing reliably during storage, transportation and use. It is
particularly desirable to reduce the amount of material necessary
to give the container sufficient integrity and stability for
commercial use. Even a small saving of material per container has a
massive effect on the cost of production when reproduced across
potentially tens to thousands of millions of containers per
annum.
[0008] The correct trade off between the amount of material used
and the integrity of the container is especially important when the
container is to be used as a pressurised vessel. For example, the
container may be used for storing, transporting and dispensing
effervescent beverages such as beer. The beverage itself may be
carbonated, or a propellant gas may be injected into the container
at super-atmospheric pressure to force the beverage out of the
container. Such a container needs to withstand these internal
pressures under a range of environmental conditions. As well as
withstanding internal pressures, the container needs to survive
rough handling during transportation of the container.
[0009] It is against this background that the present invention has
been devised. From one aspect, the invention resides in a petaloid
base for a self-standing container, the base having a spheroidal
underlying base contour and a plurality of spheroidal foot
formations that interrupt and project from the underlying base
contour to define a corresponding plurality of feet.
[0010] As the feet are spheroidal, it will be understood that their
contact with a planar surface on which the base can rest is via a
convex surface. Preferably therefore, contact between a given foot
and that planar surface is via a point on the curved surface of
that foot.
[0011] To maximise the capacity and strength of the container while
minimising material usage, the underlying base contour is
preferably substantially hemispherical. The contour may, for
example, be that of an oblate spheroid whose polar axis coincides
with a central axis of the base. For similar reasons, the foot
formations are suitably elongate, such as partial ellipsoids or
prolate spheroids. In preferred embodiments of the invention, the
foot formations are ovoid (partially egg-shaped), in which case the
contact points of the feet are most conveniently defined by the
widest part of the cross-section of each foot formation being
offset inwardly toward an inner end of the foot formation. In other
words, the foot formations taper to a greater extent at their
radially outer portions than their radially inner portions with
respect to the central axis of the base.
[0012] Preferably, the base comprises formations, such as foot
formations, whose shapes are substantially rotationally symmetrical
about an axis. For example, shapes such as spheroids, ellipsoids
and ovoids that define the foot formations are preferably
substantially rotationally symmetrical about an axis.
Advantageously, if these shapes that form the base are rotationally
symmetrical, the material used to form these structures can be
minimised. At the same time the internal capacity of the base, as
well as its strength can be maximised.
[0013] To define feet with minimal usage of material, the elongate
foot formations preferably have respective longitudinal axes, which
axes lie in planes extending radially from a central axis of the
base. Those axes of the foot formations suitably extend outwardly
and upwardly in conical relation from the central axis of the
base.
[0014] Each foot formation may have an elliptical, preferably ovate
intersection with the underlying base contour. To reduce stress
concentration, the intersection is preferably of concave cross
section.
[0015] To strengthen the base, the foot formations preferably
radiate from a central protrusion. That protrusion may be
approximately polygonal, with a number of sides corresponding to
the number of foot formations.
[0016] The foot formations are suitably separated by valleys, that
may for example radiate from apices of the polygonal protrusion. To
minimise material usage, the valleys preferably widen moving
outwardly across the base. Each valley may, for example, have an
inner and an outer section and the walls of the valley may diverge
more sharply in the outer section than in the inner section.
However, the walls of the valley may diverge in both the inner and
the outer sections of the valley.
[0017] In plan view, each foot formation may have an enlarged
central region from which the foot formation tapers inwardly across
an inner portion to an inner end. In that case, the inner portions
of the foot formations suitably lie in segmented relation around
the base. To minimise material usage, it is preferred that in plan
view, each foot formation tapers from the enlarged central region
outwardly across an outer portion to an outer end of the foot
formation.
[0018] The inventive concept extends to a container such as a keg
or a bottle having the base of the invention. Preferably, the
container is constructed by blow-moulding a preform, ideally made
of PET.
[0019] Preferably, where the material used is PET, the container
has an average pressure resistance to material usage ratio of
greater than 3 MPa/kg. More preferably, the average pressure
resistance to material usage ratio is greater than 3.75 MPa/kg.
Also, preferably, the container has a capacity to material usage
ratio of over 40 litres/kg. More preferably, the container has a
capacity to material usage ratio of over 80 litres/kg.
[0020] In order that the invention may be more readily understood,
reference will now be made, by way of example, to the accompanying
drawings in which:
[0021] FIG. 1 is a plan view from underneath a container having a
petaloid base in accordance with the invention;
[0022] FIG. 2 is a side view of the petaloid base of the container
shown in FIG. 1;
[0023] FIG. 3 is a sectional side view through the petaloid base of
the container shown in FIG. 1;
[0024] FIGS. 4(a), 4(b) and 4(c) are, respectively, an underneath
plan view, a side view and a perspective view of a container having
a base as shown in FIGS. 1 to 3, embodied in this example as a
bottle of 0.33 litre capacity;
[0025] FIGS. 5(a), 5(b) and 5(c) are, respectively, an underneath
plan view, a side view and a perspective view of another container
having a base as shown in FIGS. 1 to 3, embodied in this example as
a keg of 20 litres capacity;
[0026] FIGS. 6(a), 6(b) and 6(c) are, respectively, an underneath
plan view, a side view and a perspective view of another container
having a base in accordance with the invention, embodied in this
example as a bottle of 1.5 litres capacity, the base of this
example being a variant having seven feet;
[0027] FIG. 7 is the underneath plan view of the container as shown
in FIG. 1 marked in this instance with section lines referred to in
FIGS. 8 and 9;
[0028] FIG. 8 is an enlarged partial sectional side view through
the petaloid base of the container of FIG. 7, taken along section
line VIII-VIII;
[0029] FIG. 9 is an enlarged partial sectional side view through
the petaloid base of the container of FIG. 7, taken along section
line IX-IX;
[0030] FIG. 10 is a side view of a container having a five-footed
petaloid base as shown in FIGS. 1 to 3, embodied in this example as
a keg having a non-cylindrical side wall, and of 18-litre
capacity;
[0031] FIG. 11 is a side view of a plastics preform for blow
moulding into the 18-litre capacity keg as shown in FIG. 10;
and
[0032] FIG. 12 is an enlarged sectional side view of the container
base as shown in FIG. 3, together with a beverage dispensing tube
within the container.
[0033] Referring firstly to FIGS. 1 and 2 of the drawings, a
container 10 in this example of the invention comprises a hollow
body of blow-moulded PET. The body of the container 10 is of
circular horizontal section, the radius of that circle extending
orthogonally from a central longitudinal axis 12 that extends
centrally through the closed base 14 of the container 10. Above the
base 14, but not shown in FIGS. 1 and 2, is a substantially
cylindrical side wall surmounted by a neck portion. The side wall
is integral with and terminates at its lower end in the base 14; in
turn, the side wall is integral with and terminates at its upper
end in the neck portion at the top of the container 10.
[0034] The fundamental or underlying shape of the base 14 is a
slightly flattened hemisphere, that hemisphere being rotationally
symmetrical about the central longitudinal axis 12 of the container
10. More generally, the underlying shape of the base 14 is an
oblate spheroid, being a rotationally symmetric ellipsoid having a
diameter on its polar axis (coinciding with the central
longitudinal axis 12) that is shorter than the diameter of the
equatorial circle whose plane bisects it. This approximately
hemispherical shape maximises resistance to internal pressure,
reduces stress concentrations to resist cracking, and also
maximises internal volume while minimising material usage.
[0035] In accordance with the invention, the base 14 further
includes integrally-moulded blister-like feet disposed in a
petaloid arrangement around the base, the feet being defined in
this example by five hollow ovoid foot formations 16 that radiate
equiangularly from a relatively shallow generally pentagonal convex
protrusion 18 on the central longitudinal axis 12. More generally,
the foot formations 16 are elongate ellipsoids in the form of
prolate spheroids, a prolate spheroid being a spheroid whose
diameter along its polar axis is greater than its equatorial
diameter.
[0036] The polar axes 20 of the spheroidal foot formations 16
extend outwardly and upwardly in equi-angularly spaced
radially-disposed planes from the central longitudinal axis 12 of
the container 10. Thus, the polar axes 20 of the foot formations 16
(see FIG. 2) lie on a virtual frusto-conical surface surrounding
the central longitudinal axis 12.
[0037] Circumferentially adjacent pairs of foot formations 16 are
separated by valleys 22 that radiate equi-angularly from the apices
24 of the pentagonal central protrusion 18. The valley floors
follow the spheroidal shape of the base 14 and open at their outer
ends to an outer portion of the base 14 that lies radially
outwardly beyond the foot formations 16. Furthermore, each foot
formation 16 and the central protrusion 18 are joined via a
transition portion that curves smoothly without distinct
transitions or discontinuities. Thus, as shown in FIG. 3, a foot
formation 16, the smoothly curving transition portion and the
central protrusion 18 together define a sinuous cross section.
[0038] Also as shown in FIG. 3, the convex central protrusion 18
has a radius of curvature r that is smaller than the general radius
of curvature R of the spheroidal base 14: thus R>r. Moreover,
the convex central protrusion 18 extends to a level beyond--and
thus, in use, below--the lowermost apex of the underlying base
contour. Also, the convex central protrusion 18 extends to a level
within--and thus, in use, above--the extent of the foot formations
16.
[0039] The foot formations 16 bulge outwardly from the underlying
spheroidal contour of the base 14 by virtue of an ovoid convex
wall. The convex wall of each foot formation 16 is surrounded by a
concave transition zone 26 in the shape of an ovate ring. The
transition zone 26 extends smoothly into the spheroidal wall of the
base with a large radius of curvature to reduce stress
concentration and hence to minimise stress cracking. The transition
zones 26 of circumferentially adjacent foot formations 16 partially
define the valley 22 between those foot formations 16.
[0040] Each foot formation 16 is generally elliptical (in this
example, ovate) in underneath plan view, reaching a maximum width
in an enlarged central region 28 between its inner end 30 and its
outer end 32. Thus, each foot formation 16 tapers in opposite
directions from the widest part of the central region 28: along an
inner portion 34 moving inwardly toward the central longitudinal
axis 12 to the inner end 30; and along an outer portion 36 moving
outwardly away from the central longitudinal axis 12 to the outer
end 32.
[0041] In underneath plan view, the inwardly-tapering inner
portions 34 of the foot formations 16 fit closely between their
neighbours around the circular base 14 like segments of an orange.
These inner portions 34 of the foot formations 16 alternate with,
and are separated by, narrow inner sections 38 of the valleys 22,
which may be approximately parallel but, in this example, widen
slightly as they extend outwardly from the pentagonal central
protrusion 18. However where they extend outwardly into their outer
sections 40 beyond the widest part of the foot formations 16, the
valleys 22 widen near-exponentially between the tapering outer
portions 36 of the foot formations 16 until they reach a maximum
width between the outer ends 32 of adjacent foot formations 16.
[0042] Thus, moving along the valleys 22 from the central
longitudinal axis 12 toward the outer diameter of the base 14, the
gap between the foot formations 16 increases. In contrast, in a
previously-known petaloid base such as that disclosed in EP
0671331, this gap decreases.
[0043] Viewed now from the side, the foot formations 16 extend to a
level beyond--and thus, in use, below--the lowermost apex of the
base 14 defined by the central pentagonal protrusion 18. The foot
formations 16 all extend to the same level. Thus, at that level,
each foot formation 16 defines a contact point 42 that will lie
stably upon a flat support surface (not shown) orthogonal to the
central longitudinal axis 12 of the container 10.
[0044] FIG. 3 shows that the foot formations are somewhat
egg-shaped with the widest part of their cross-sections offset
slightly inwardly and downwardly toward their inner ends 30.
[0045] The contact points 42 of the foot formations 16 are
equi-spaced on and around a contact circle centred on the central
longitudinal axis 12 of the container 10. The diameter (x) of the
contact circle relates to the side wall diameter (Dy) of the
container 10 in a ratio as follows:
Dy 0.5 x = k ##EQU00001##
[0046] In accordance with the invention, k is preferably between
3.6 and 5.5, more preferably between 4.0 and 5.3, still more
preferably between 4.2 and 5.0 and typically 4.7. This may be
contrasted with typical PET bottles on the market whose
corresponding ratio k is typically 2.5 to 3.5. The relatively large
value for k in the invention stems from a relatively small value
for x. This is advantageous because a small contact circle creates
a small--and hence inherently stiff--diaphragm between the contact
points 42.
[0047] The result is a central area within the contact circle
between the contact points 42 of the foot formations 16 that is
quite rigid and hence resistant to movement during internal
pressure, up to burst pressure. The rigidity of the area within the
contact circle is enhanced by the undulating wall section defined
by the inner portions 34 of the foot formations 16, the valleys 22
between them, and the central protrusion 18.
[0048] Stiffness within the contact circle is important not just
for a high burst pressure but also for stability. This is because
the lowest point on the central longitudinal axis (the lowermost
apex of the base 14 defined by the central pentagonal protrusion
18) will tend to be pushed down under internal pressure. If that
lowest point moves so far as to contact a supporting surface in
use, the container cannot rest stably on the contact points 42 of
the foot formations 16. The stiffness of the base shape of the
invention means that compared to previously known designs, the
distance from the central apex of the base to a supporting surface
is relatively small, to the benefit of stability and capacity
relative to the height of the container.
[0049] Viewing any one foot formation 16 end-on (i.e. from the side
of the container 10 looking inwardly towards the central
longitudinal axis 12), the contour of that foot formation 16
describes a substantially constant convex radius between the
concave radii of the transition zones 26 to each side. A
conventional petaloid base typically has flatter surfaces defining
a V-shaped valley between the feet, to the detriment of material
usage and stress concentration. Stress concentrations create areas
of a container that are particularly vulnerable to rupture under
high internal pressure.
[0050] The arrangement of the base 14 of the present invention is
particularly suited to containers for dispensing liquids under
pressure. In particular, the increased value for k makes the base
stiffer and hence better suited for retaining stability whilst the
container is subject to high internal pressure. Furthermore, by
increasing the value of k, it is possible to have the convex
central protrusion 18 positioned axially lower than would otherwise
be possible for a container that is subject to high internal
pressure. This can maximise the quantity of beverage that can be
practically dispensed from the container 10. This advantage is
discussed with reference to FIG. 12 in which is shown the same
sectional side view of the container base 14 of FIG. 3, together
with a beverage dispensing tube 120.
[0051] In this context, the container is used as a beer keg 10 that
is provided with a closure assembly that is sealed on to the
tubular neck of the keg 10 in a push-fit arrangement. The tube 120
is coupled to the closure assembly (not shown) and extends from it
along the central longitudinal axis 12 into the base of the keg 10.
The axially lower end of the tube 120 extends into the central
protrusion 18. The end of the tube 120 sits within the central
protrusion 18 and hangs just inside the apex of the central
protrusion 18, thereby providing an annular gap through which a
beverage can pass from the keg 10 into the tube 120 or visa-versa.
The shape of the central protrusion 18 also enables the axially
lower end of the tube 120 to be correctly located and retained
within the central protrusion during fitting and use.
[0052] In use, when dispensing a beverage, the keg 10 is maintained
in an upright position. The closure assembly allows a pressurised
gas to be introduced into the headspace of the keg 10 to force the
beverage out through the tube 120. As the axially lowermost end of
the tube 120 is located within the central protrusion 18, and the
central protrusion 18 is disposed at a relatively low axial
position within the keg 10, this ensures that almost all of the
beverage within the keg 10 can be extracted from it.
[0053] It may be possible to further increase the amount of
beverage that can be practically extracted from the keg 10 by
extending the tube 120 into one of the foot formations 16. In such
an arrangement, the tube 120 would need to bend away from the
central longitudinal axis 12 at its lower end. Although this may
marginally increase the amount of beverage that can be dispensed
from the keg 10, this can complicate process of fitting the closure
assembly and tube 120 to the keg 10. In particular, inserting a
bent tube 120 into the keg 10 can require a complicated automated
fitting process. Furthermore, the bending of the tube 120 away from
the central longitudinal axis 12 can subject the closure assembly
to which the tube 120 is attached at its axially upper end to
uneven forces. This can reduce the reliability of the closure
assembly, which is of particular concern when the keg 10 is subject
to high internal pressure.
[0054] The petaloid base of the invention may be applied to a wide
range of containers such as bottles and kegs. FIGS. 4(a), 4(b) and
4(c) and FIGS. 5(a), 5(b) and 5(c) show a five-footed base of the
invention applied, respectively, to a bottle 44 of 0.33 litre
capacity, which may typically be used for carbonated soft drinks,
and a keg 46 of 20 litres capacity, which may typically be used for
beer. These drawings show features omitted from FIGS. 1 and 2,
namely a substantially cylindrical side wall 48 surmounted by a
neck portion 50. The side wall 48 is integral with and terminates
at its lower end in the base 14; in turn, the side wall 48 is
integral with and terminates at its upper end in the neck portion
50 at the top of the container.
[0055] FIG. 10 shows a further five-footed base of the invention
applied to a keg 104 of 18-litre capacity with a non-cylindrical
side wall 108. In this example, the side wall 108 is convex,
rotationally symmetrical about the central longitudinal axis of the
keg 104 and so generally follows the shape of an ovoid. At its
axially lower end portion, the side wall curves smoothly into the
spheroidal underlying contour of the base of the present invention.
At its axially upper end portion, which tapers to a greater extent
than the axially lower end portion, the side wall curves smoothly
into the concave neck of the keg 104. The convex side wall 108 is
shaped in this way to maximise internal pressure resistance,
maximise the internal capacity of the keg 104 and minimise material
usage. FIG. 11 is an enlarged side view of a plastics preform for
blow moulding into the container as shown in FIG. 10.
[0056] Other variations of the invention are possible without
departing from the inventive concept. For example, a variant of the
base of the invention shown in FIGS. 6(a), 6(b) and 6(c) is applied
to a bottle 52 of 1.5 litres capacity. This variant has seven foot
formations 54 instead of five, with a generally heptagonal central
protrusion 56 between them. Like the five-footed base variant,
seven-footed base variants can be applied to any size of container,
such as bottles of 0.33 litres, 0.5 litres, 1 litre, 1.5 litres or
larger, and kegs of 20 litres or other capacities.
[0057] An odd number of feet is preferred for optimum stability,
there being at least three feet (in which case the central
protrusion is generally triangular) but preferably not more than
seven feet; five or seven feet are considered optimal.
[0058] To put the invention into context but without limiting its
broadest scope as defined in the claims, various dimensional
characteristics will now be given by way of example.
[0059] Firstly, the table below sets out a volume comparison
between a conventional base and a base in accordance with the
invention, assuming in this instance that the base defines five
feet. Volumes in the table are expressed in millilitres (ml). The
volume refers to the internal volume of the base, defined as the
portion of the container below the cylindrical side wall of the
container. It will be noted that the base of the invention has a
volume approximately five times greater than the volume of a
conventional petaloid container base, to the benefit of compactness
and material usage for a given container capacity.
TABLE-US-00001 Container with five feet Conventional base Base of
the invention 20 litre keg, dia 235 mm 128 (20%) 634 0.33 litre
bottle, dia 60 mm 2.7 (18%) 15 0.5 litre bottle, dia 65 mm 3.5
(18%) 19 1.0 litre bottle, dia 80 mm 6.5 (18%) 36 1.5 litre bottle,
dia 95 mm 11 (20%) 55
[0060] Secondly, the following dimensions help to define the base
shape for each of the above capacities of container:
TABLE-US-00002 Radius Radius of transition from of underlying
underlying base contour Container with five feet base contour to
side wall 20 litre keg, dia 235 mm 135.0 mm 49.6 mm 0.33 litre
bottle, dia 60 mm 34.5 mm 19.1 mm 0.5 litre bottle, dia 65 mm 37.4
mm 20.7 mm 1.0 litre bottle, dia 80 mm 46.0 mm 25.4 mm 1.5 litre
bottle, dia 95 mm 54.6 mm 30.2 mm
TABLE-US-00003 Radial projection of foot Diameter formations beyond
radius of of contact Container with five feet underlying base
contour circle 20 litre keg, dia 235 mm 18.1 mm 99.9 mm 0.33 litre
bottle, dia 60 mm 5.3 mm 28.6 mm 0.5 litre bottle, dia 65 mm 5.5 mm
31.0 mm 1.0 litre bottle, dia 80 mm 7.1 mm 38.1 mm 1.5 litre
bottle, dia 95 mm 8.4 mm 45.3 mm
TABLE-US-00004 Width of foot formations Length of foot formations
across Container with five feet along polar axis* polar axis* 20
litre keg, dia 235 mm 80.2 mm 59.5 mm 0.33 litre bottle, dia 60 mm
22.9 mm 15.6 mm 0.5 litre bottle, dia 65 mm 24.8 mm 16.9 mm 1.0
litre bottle, dia 80 mm 30.6 mm 20.8 mm 1.5 litre bottle, dia 95 mm
36.3 mm 24.7 mm *Including transition zone
TABLE-US-00005 Radius Radius of transition from of underlying
underlying base contour Container with seven feet base contour to
side wall 20 litre keg, dia 235 mm 135.0 mm 49.6 mm 0.33 litre
bottle, dia 60 mm 34.2 mm 18.9 mm 0.5 litre bottle, dia 65 mm 37.3
mm 20.7 mm 1.0 litre bottle, dia 80 mm 46.2 mm 25.6 mm 1.5 litre
bottle, dia 95 mm 54.6 mm 30.2 mm
TABLE-US-00006 Radial projection of foot Diameter formations beyond
radius of of contact Container with seven feet underlying base
contour circle 20 litre keg, dia 235 mm 18.1 mm 99.9 mm 0.33 litre
bottle, dia 60 mm 5.3 mm 28.5 mm 0.5 litre bottle, dia 65 mm 5.8 mm
31.0 mm 1.0 litre bottle, dia 80 mm 7.2 mm 38.5 mm 1.5 litre
bottle, dia 95 mm 8.4 mm 45.4 mm
TABLE-US-00007 Width of foot formations Length of foot formations
across Container with seven feet along polar axis* polar axis* 20
litre keg, dia 235 mm 78.9 mm 54.8 mm 0.33 litre bottle, dia 60 mm
22.4 mm 14.0 mm 0.5 litre bottle, dia 65 mm 24.4 mm 15.3 mm 1.0
litre bottle, dia 80 mm 30.3 mm 19.0 mm 1.5 litre bottle, dia 95 mm
35.7 mm 22.4 mm *Including transition zone
TABLE-US-00008 Radius of transition zone Radius of transition zone
(five feet) (seven feet) 20 litre keg, dia 235 mm 12.0 mm 8.0 mm
0.33 litre bottle, dia 60 mm 3.15 mm 1.88 mm 0.5 litre bottle, dia
65 mm 3.44 mm 2.05 mm 1.0 litre bottle, dia 80 mm 4.26 mm 2.54 mm
1.5 litre bottle, dia 95 mm 5.0 mm 3.0 mm
[0061] FIGS. 7 to 9 provide additional dimensional information
relating to a 20-litre keg having a five-footed base 14. FIGS. 10
and 11 respectively show dimensional information relating to an
18-litre keg 104 having a five-footed base and its preform 106.
[0062] FIG. 8 shows a partial sectional side view through the
petaloid base of the 20-litre keg of FIG. 7, taken along section
line VIII-VIII. The resulting section plane intersects a foot
formation 16 at its contact point 42, and is parallel to and is
radially-spaced at a distance of 50 mm from the central
longitudinal axis 12 of the keg 10. At this section of the foot
formation 16, its contour is a substantially constant convex radius
of 23.0 mm between the concave radii of 12.0 mm of the transition
zones 26 to each side.
[0063] FIG. 9 is a partial sectional side view through the petaloid
base of the 20-litre keg of FIG. 7, taken along section line IX-IX.
The resulting section plane is aligned with the central
longitudinal axis 12 of the keg 10, and intersects the same foot
formation 16 as shown in FIG. 8 at its contact point 42. The view
shown in FIG. 9 corresponds to the view shown in FIG. 3, but
provides the following additional dimensional information relating
to the 20-litre keg:
TABLE-US-00009 RADIUS DATA Radius of underlying base contour 135.0
mm Radius of convex central protrusion 35.0 mm Radius of concave
transition zone between the convex 12.0 mm central protrusion and
the radially inner end of a foot formation Radius of a foot
formation at a position on the inner portion 35.0 mm adjacent the
radially inner end Radius of a foot formation at a position on the
inner portion 43.0 mm between the radially inner end and the
central region of the foot formation Radius of a foot formation at
a position on the central 50.0 mm region between the contact circle
and the inner portion Radius of a foot formation at a position on
the central 20.5 mm region that is radially inner of and adjacent
to the contact circle Radius of a foot formation at a position on
the central 24.0 mm region that is radially outer of and adjacent
to the contact circle Radius of a foot formation at a position on
the central 32.0 mm region between the contact circle and the outer
portion Radius of a foot formation at a position on the outer
portion 27.75 mm between the radially outer end and the central
region of the foot formation Radius of a foot formation at a
position on the outer portion 120.0 mm adjacent the radially outer
end of the foot formation Radius of concave transition zone between
underlying base 12.0 mm contour and radially outer end of a foot
formation Radius of transition from underlying base contour to side
49.6 mm wall
[0064] These radius measurements are also applicable to points on
other foot formations 16 of the container 10. These points
typically lie within any one of the planes aligned with both the
central longitudinal axis 12 of the container and a polar axis of a
given foot formation 16.
TABLE-US-00010 DISTANCE DATA Distance along central longitudal axis
between convex 3.0 mm central protrusion and plane containing the
contact circle Axial depth of convex central protrusion along
central 4.5 mm longitudinal axis Distance along central
longitudinal axis from underlying 8.0 mm base contour to plane
containing the contact circle Distance along axis aligned with
central longitudinal axis 7.5 mm from transition zone (between
central protrusion and a foot formation) to plane containing the
contact circle Axial depth of the base portion (i.e. axial distance
from 91.2 mm plane containing the contact circle to axially lower
end of cylindrical side wall) Radial length from central
longitudinal axis to transition 84.66 mm between base contour and
foot formation
[0065] In addition to dimensional data, the following data derives
from pressure tests indicating the typical burst pressure of the
20-litre keg 10 having a five footed petaloid base 14 according to
the present invention. By way of comparison, pressure tests were
also carried out on a conventional petaloid base under similar
conditions. The values represent the burst pressure in bar.
TABLE-US-00011 Conventional Base burst pressure Base of the
invention burst Test (bar) pressure (bar) 1 9.29 9.55 2 7.68 9.04 3
9.09 8.59 4 8.92 9.57 5 8.8 9.29 6 5.99 7.78 7 5.96 8.69 8 6.25
8.08 9 9.14 9.31 10 8.82 8.33 AVG 7.99 8.82 MAX 9.29 9.57 MIN 5.96
7.78 DIFF 3.33 1.79
[0066] Thus, it can be seen that the average burst pressure of the
20-litre keg having a five-footed base is approximately 8.8 bar=880
kPa. Furthermore, the material usage of the litre keg corresponds
to 0.234 kg of PET. Accordingly, ratios directed to the pressure
resistance, capacity and material usage can be derived for this
20-litre keg: [0067] Average pressure resistance to material usage
ratio=3.76 MPa/kg [0068] Capacity to material usage ratio=85
litres/kg
[0069] It will be understood that similar ratios can be
extrapolated for containers of different shapes and sizes, but also
incorporating the base 14 according to the present invention.
[0070] FIG. 10 provides additional dimensional data corresponding
to the 18 litre keg 104:
TABLE-US-00012 Convex radius of underlying base contour 135.0 mm
Diameter of body at widest point 287.0 mm Convex radius of body
contour 352.0 mm Convex radius of contour between body and neck
185.0 mm Concave radius of neck contour 65.0 mm Diameter of neck
65.0 mm Total axial length 490.0 mm Axial length from base to neck
collar 472.0 mm Axial length from keg opening, to beverage fill
point (FP) 112.5 mm mark - denoting an 18 litre fill from a level
base
[0071] FIG. 11 provides additional dimension data corresponding to
the preform 106 of the 18 litre keg 104 of FIG. 10:
TABLE-US-00013 Total axial length 195.0 mm Axial length from base
to neck collar 177.0 mm Axial thickness of base 6.0 mm Thickness of
each cylindrical side wall 11.0 mm Axial length of cylindrical neck
portion below neck collar 15.0 mm Axial length of neck portion from
below neck collar to 57.3 mm cylindrical side wall (including
cylindrical neck portion and frustoconical neck portion) Diameter
of cylindrical neck portion 64.2 mm Diameter of cylindrical side
wall 77.0 mm Internal bore diameter of the preform 55.0 mm Diameter
of the neck collar 81.0 mm
[0072] The approximate burst pressure of this 18-litre keg having a
five-footed base is approximately 14 bar=1400 kPa. The material
usage of the 18-litre keg corresponds to 0.468 kg of PET.
Accordingly, ratios directed to the pressure resistance, capacity
and material usage can be derived for this 18-litre keg: [0073]
Average pressure resistance to material usage ratio=.about.3
MPa/kg. [0074] Capacity to material usage ratio=41 litres/kg.
[0075] For a base with five feet, the following ratios apply in
these examples: [0076] For 20-litre keg: [0077] Length of foot
formations along polar axis/width of foot formations across polar
axis=1.35 [0078] Diameter of contact circle/width of foot
formations across polar axis=1.68 [0079] Radius of underlying base
contour/diameter of side wall=0.57 [0080] Radius of underlying base
contour/radius of transition from underlying base contour to side
wall=2.72 [0081] Radial projection of foot formations beyond radius
of underlying base contour/radius of underlying base contour=1.13
[0082] For bottles of various capacities: [0083] Length of foot
formations along polar axis/width of foot formations across polar
axis=1.47 [0084] Diameter of contact circle/width of foot
formations across polar axis=1.83 [0085] Radius of underlying base
contour/diameter of side wall=0.58 [0086] Radius of underlying base
contour/radius of transition from underlying base contour to side
wall=1.81 [0087] Radial projection of foot formations beyond radius
of underlying base contour/radius of underlying base
contour=1.15
[0088] Similarly, for a base with seven feet, the following ratios
apply in these examples: [0089] For 20-litre keg: [0090] Length of
foot formations along polar axis/width of foot formations across
polar axis=1.44 [0091] Diameter of contact circle/width of foot
formations across polar axis=1.82 [0092] Radius of underlying base
contour/diameter of side wall=0.57 [0093] Radius of underlying base
contour/radius of transition from underlying base contour to side
wall=2.72 [0094] Radial projection of foot formations beyond radius
of underlying base contour/radius of underlying base contour=1.13
[0095] For bottles of various capacities: [0096] Length of foot
formations along polar axis/width of foot formations across polar
axis=1.59 [0097] Diameter of contact circle/width of foot
formations across polar axis=2.03 [0098] Radius of underlying base
contour/diameter of side wall=0.57 [0099] Radius of underlying base
contour/radius of transition from underlying base contour to side
wall=1.8 [0100] Radial projection of foot formations beyond radius
of underlying base contour/radius of underlying base
contour=1.15
[0101] It will be apparent from the foregoing description that the
improved petaloid base shape of the invention has various
additional advantages. Its softly-curving shape with an absence of
sharp radii is beneficial to resist stress cracking. Also,
importantly, its surface area is less than equivalent known
designs. Thus, for a given amount of resin, the invention allows a
thicker wall and hence a stronger base. Alternatively it is
possible to reduce weight and material usage while maintaining the
strength of the base. A strong base is particularly important in
applications where the containers are subjected to elevated
internal pressure and/or elevated temperature, such as carbonated
soft drinks, beer and hot-fill or pasteurised liquids.
* * * * *