U.S. patent application number 10/187634 was filed with the patent office on 2004-01-01 for pressurizable container.
Invention is credited to Kamineni, Satya, Mooney, Michael R..
Application Number | 20040000533 10/187634 |
Document ID | / |
Family ID | 29780055 |
Filed Date | 2004-01-01 |
United States Patent
Application |
20040000533 |
Kind Code |
A1 |
Kamineni, Satya ; et
al. |
January 1, 2004 |
Pressurizable container
Abstract
A container base that is capable of receiving positive internal
pressure, such as that created by introducing liquefied gas during
a hot filling process, includes either ribs that substantially
connect to a standing ring or a draft surface formed on the bottom
of the ribs, or a combination of such features.
Inventors: |
Kamineni, Satya; (Westmont,
IL) ; Mooney, Michael R.; (Frankfort, IL) |
Correspondence
Address: |
WOODCOCK WASHBURN LLP
ONE LIBERTY PLACE, 46TH FLOOR
1650 MARKET STREET
PHILADELPHIA
PA
19103
US
|
Family ID: |
29780055 |
Appl. No.: |
10/187634 |
Filed: |
July 1, 2002 |
Current U.S.
Class: |
215/373 ;
215/384; 220/606 |
Current CPC
Class: |
B65D 79/005 20130101;
B65D 1/0276 20130101 |
Class at
Publication: |
215/373 ;
220/606; 215/384 |
International
Class: |
B65D 008/06; B65D
090/02; B65D 006/28; B65D 008/04 |
Claims
We claim:
1. A heat-set, pressurizable container suitable for filling at an
elevated temperature, said container comprising: a body; an upper
portion extending upwardly from the body and including a finish and
an opening therein; an enclosed base disposed below the body, said
base including: a standing ring on which the container rests; a
recess that extends inwardly and upwardly relative to the standing
ring; and plural ribs extending substantially inwardly from the
recess, each one of the plural ribs including a lower portion that
includes a draft surface extending inwardly and upwardly from the
standing ring; whereby (i) the draft surface deforms substantially
downwardly in response to internal pressurization of the container,
(ii) the container rests on the standing ring even after internal
pressurization of the container, and (iii) the ribs resist eversion
of the recessed base surface such that the container is capable of
withstanding internal positive pressure.
2. The container of claim 1 wherein the container is formed of a
heat-set plastic.
3. The container of claim 1 wherein the internal pressurization is
formed by introducing a liquefied gas into the container prior to
capping.
4. The container of claim 1 wherein the draft surface is
substantially linear, in a first longitudinal cross section that is
coplanar with a longitudinal centerline of the rib, while the
container is in an unpressurized state.
5. The container of claim 4 wherein the draft surface is
substantially planar while the container is in an unpressurized
state.
6. The container of claim 4 wherein the draft surface is curved in
a second longitudinal cross section that is perpendicular to the
first longitudinal cross section.
7. The container of claim 1 wherein the draft surface is directly
connected to the standing ring.
8. The container of claim 1 wherein each one of the plural ribs
include a face surface that extends inwardly from the draft
surface.
9. The container of claim 8 wherein draft surface includes a outer
point proximate the standing ring and an inner point proximate the
rib face, a line between the draft surface outer point and the
draft surface inner point forming a draft angle relative to a
horizontal line that is between approximately 0 degrees and 45
degrees.
10. The container of claim 9 wherein the draft angle is between
about 3 degrees and about 40 degrees.
11. The container of claim 9 wherein the draft angle is between
about 5 degrees and about 30 degrees.
12. The container of claim 9 wherein the draft angle is between
about 5 degrees and about 15 degrees.
13. The container of claim 9 wherein the draft angle is between
about 5 and 25 degrees.
14. The container of claim 9 wherein the draft angle is about 5
degrees.
15. The container of claim 9 wherein the draft surface is directly
coupled to the standing ring proximate the draft surface outer
point and is directly coupled to the rib face proximate the draft
surface inner point, whereby the draft surface couples the standing
ring and the rib face together.
16. The container of claim 9 wherein the standing ring defines a
standing ring diameter and a standing ring land width, and the
draft surface has a radial dimension of no more than approximately
one-third the standing ring diameter minus four times the standing
ring land width.
17. The container of claim 16 wherein the draft surface radial
dimension is no more than approximately 80 percent of one-third the
standing ring diameter minus four times the standing ring land
width.
18. The container of claim 16 wherein the ribs have a depth
measured proximate the draft surface that is at least the draft
surface radial dimension divided by two times cosine of the draft
angle.
19. The container of claim 16 wherein the ribs have a depth
measured proximate the draft surface that is at least 1.2 times the
draft surface radial dimension divided by two times cosine of the
draft angle.
20. The container of claim 1 wherein the standing ring is
substantially continuous and circumferential.
21. The container of claim 1 wherein the standing ring is
circumferentially discontinuous.
22. The container of claim 21 wherein the standing ring is
interrupted by the draft surface of the ribs.
23. The container of claim 1 wherein the standing ring has a width
that is less than approximately 0.100 inches.
24. The container of claim 23 wherein the standing ring width is
less than about 0.060 inches.
25. The container of claim 23 wherein the standing ring width is
less than about 0.050 inches.
26. The container of claim 23 wherein the standing ring width is
less than about 0.025 inches.
27. The container of claim 23 wherein the standing ring width is
about 0.10 inches.
28. The container of claim 18 wherein the standing ring width no
more than approximately four percent of standing ring diameter.
29. The container of claim 18 wherein the standing ring width no
more than approximately three percent of standing ring
diameter.
30. The container of claim 18 wherein the standing ring width no
more than approximately two percent of standing ring diameter.
31. The container of claim 23 wherein the standing ring width is as
small as the blow molding process will allow.
32. The container of claim 1 wherein the base further includes a
heel extending upwardly from the standing ring toward the body.
33. The container of claim 32 wherein the heel is coupled to the
base.
34. The container of claim 1 wherein the upper portion includes a
dome from which the finish extends.
35. The container of claim 34 wherein the upper portion includes an
elongated neck extending from the dome, the finish formed on the
neck.
36. The container of claim 1 wherein the base further includes a
heel that is coupled between the standing ring and the body, the
standing ring defines a standing ring diameter, and the heel has a
radial heel dimension that is no more than approximately 20 percent
of the standing ring diameter.
37. The container of claim 36 wherein the heel radial dimension is
at least approximately 10 percent of the standing ring
diameter.
38. The container of claim 36 wherein the heel radial dimension is
more than approximately 17.5 percent of the standing ring
diameter.
39. The container of claim 38 wherein the heel radial dimension is
at least approximately 15 percent of the standing ring
diameter.
40. The container of claim 1 wherein the standing ring defines a
standing ring diameter that is between approximately 60% and
approximately 80% of a base diameter.
41. The container of claim 40 wherein the standing ring diameter
between approximately 65% and approximately 70% of the base
diameter.
42. The container of claim 1 wherein the internal pressurization is
between approximately 15 and approximately 35 psi at hot fill
temperatures.
43. The container of claim 1 wherein the internal pressurization is
between approximately 0 and approximately 10 psi at ambient
temperatures.
44. The container of claim 1 wherein said container is formed of a
material having an intrinsic viscosity greater than approximately
0.75.
45. A heat-set, pressurizable container suitable for filling at an
elevated temperature, said container comprising: a body; an upper
portion extending upwardly from the body and including a finish and
an opening therein; an enclosed base disposed below the body, said
base including: a standing ring on which the container rests; a
recess that extends inwardly and upwardly relative to the standing
ring; and plural ribs extending substantially inwardly from the
recess, each one of the plural ribs including a lower portion that
includes a draft surface extending inwardly and upwardly from the
standing ring, the draft surface being directly coupled to the
standing ring and forming a draft angle of between approximately 0
degrees and approximately 45 degrees, the draft surface is directly
coupled to the standing ring proximate a draft surface outer point
and is directly coupled to the rib face proximate a draft surface
inner point, whereby the draft surface couples the standing ring
and the rib face together.
46. The container of claim 44 wherein the draft angle is between
about 3 degrees and about 40 degrees.
47. The container of claim 44 wherein the draft angle is between
about 5 degrees and about 30 degrees.
48. The container of claim 44 wherein the draft angle is between
about 5 degrees and about 15 degrees.
49. The container of claim 44 wherein the draft angle is about 5
degrees.
50. The container of claim 44 wherein the standing ring has a width
that is less than approximately 0.100 inches.
51. The container of claim 44 wherein the standing ring width is
less than about 0.075 inches.
52. The container of claim 44 wherein the standing ring width is
less than about 0.050 inches.
53. The container of claim 44 wherein the standing ring width is
less than about 0.025 inches.
54. The container of claim 44 wherein the standing ring width is
less than about 0.10 inches.
55. A method of filling a container with a flowable product, said
method comprising: providing a container comprising a body and a
base, the base including: a standing ring on which the container
rests; a recess that extends inwardly and upwardly relative to the
standing ring; and plural ribs extending substantially inwardly
from the recess, each one of the plural ribs including a lower
portion that includes a draft surface extending inwardly and
upwardly from the standing ring; introducing hot contents and
liquefied gas into the container; sealing the container before all
of the liquefied gas vaporizes to create a positive internal
pressure within the container; whereby the draft surface deforms
substantially downwardly in response to internal pressurization of
the container, the container rests on the standing ring even after
internal pressurization of the container, and the ribs resist
eversion of the recessed base surface such that the container is
capable of withstanding internal positive pressure.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to plastic containers, and
more particularly to plastic containers capable of receiving
positive internal pressure.
[0002] Consumers and manufacturers often prefer containers to glass
containers for containing comestible products. The safety and
appeal of plastic containers for such products have been enhanced
by the development of hot-filling processes, in which a product is
introduced into the container at an elevated temperature--typically
180 degrees to 190 degrees F.--and sealed.
[0003] Hot filling capabilities have spurred the development of
related technologies to address problems of container thermal
shrinkage and vacuum-induced deformation. To reduce shrinkage of
polyethylene terephthalate ("PET") containers upon exposure to
hot-fill temperatures, for example, PET containers typically
undergo a "head-set" process. Often, a PET container is head-set by
blow molding at an elevated temperature (compared with those for
conventional containers for non-hot-fill applications, such as
carbonated soft drinks) for predetermined times, and held at
predetermined temperatures for predetermined times. Further, heat
set containers are typically formed from a plastic mix having
higher intrinsic viscosity that that for bottles suitable only for
non-hot-fill, PET applications, such as carbonated soft drinks.
[0004] Head-set PET containers are, thus, able to be filled at
conventional hot-fill temperatures with acceptable shrinkage, such
as approximately one percent, as for example taught in U.S. Pat.
No. 4,863,046 (Collette). Further, heat-treating or heat-setting is
taught in a number of patents, including, for example, U.S. Pat.
No. 4,233,022 (Brady), U.S. Pat. No. 4,711,624 (Watson), and U.S.
Pat. No. 4,219,526 (Mehnert). Each of the patents and applications
referred to in the specification is incorporated herein by
reference in its entirety.
[0005] Vacuum deformation of a hot-filled container occurs upon
capping and cooling after filling with contents at an elevated
temperature. Employing vacuum panels or others structure(s) that
flex or deform in response to internal container negative pressure
has been a popular approach to preventing container collapse upon
vacuum deformation. Numerous approaches to vacuum panels in the
container sidewalls have been developed. For example, U.S. Pat.
Nos. 5,178,289, 5,092,475, and 5,054,632 teach stiffening portions
or ribs to increase hoop stiffness and eliminate bulges while
integral vacuum panels collapse inwardly.
[0006] Other containers include a pair of vacuum panels, each of
which has an indentation or grip portion enabling the container to
be gripped between a user's thumb and fingers. For example, U.S.
Pat. No. 5,141,120 teaches a bottle having a hinge continuously
surrounding a vacuum panel, which includes indentations for
gripping. In response to cooling of the container contents, the
hinge enables the entire vacuum panel in collapse inwardly. U.S.
Pat. No. 5,141,121 similarly teaches a bottle having an outward
bulge that inverts in response to cooling of the container
contents. Further, bases for heat-set, hot-fillable containers have
been developed which are capable of withstanding internal negative
pressures common to hot-filling applications. Such bases typically
have a continuous standing ring on which the container rests and a
ribbed recess portion. For example, U.S. Pat. Nos. 5,503,283;
5,642,826; 4,993,567; 4,993,566; 4,598,831; and 4,108,324 disclose
conventional base configurations.
[0007] Often, a continuous standing ring is commercially beneficial
because it enables the plastic bottle to mimic the overall
appearance of a glass bottle. Further, bases for heat-set,
hot-fillable bottles typically have a standing ring that is
substantially flat and horizontal in order to accommodate internal
negative pressure. In order to promote flexing or deformation of
the standing ring, and thereby relieve stress inherent upon vacuum
deformation or diminish the magnitude of the corresponding stress
risers, such standing rings typically are relatively large.
[0008] Because conventional hot-fillable containers are subjected
to negative internal pressure, the ribs of conventional
hot-fillable container bases generally are configured to control
only inwardly directed forces and deformation. In this regard, the
magnitude of inward deformation of a portion of the base typically
is inconsequential or unimportant as long as the base is
sufficiently strong. The ribs of such bases are generally spaced
apart from the standing ring because stiffening proximate the
standing ring is unimportant, and because ribs coupled to the
standing ring may interfere with the beneficial deformation of the
standing ring to compensate for the negative internal pressure.
Thus, conventional ribs are typically spaced apart from the
standing ring to enable the base to deflect inwardly such that the
base may compensate for the negative internal pressure to
supplement the vacuum panels. Moreover, if ribs were to contact the
standing ring under such conditions, the standing ring would
transition quickly from the inner portion that is stiffened by the
ribs to the unstiffened portion, which may result in stress risers
or otherwise be detrimental to the strength or other attribute of
the base.
[0009] U.S. Pat. No. 5,251,424 (ZENGER), which is incorporated
herein by reference in its entirety, discloses another approach to
enabling a container to accommodate negative internal pressure from
a hot-filling application. The '424 patent discloses introducing
liquefied gas into the container upon hot-filling to provide a
positive internal pressure. Thus, the internal positive pressure
counteracts the negative pressure induced by the shrinkage of the
contents upon cooling.
[0010] It is a goal of the present invention to provide a base, and
corresponding container, that is suitable for a heat-set container
that is capable of withstanding positive internal pressure.
SUMMARY
[0011] A base is provided for a heat-set container that is suitable
for withstanding internal pressurization without everting. The base
includes a standing ring on which the container rests, a recess
that extends inwardly and upwardly relative to the standing ring;
and plural ribs extending substantially inwardly from the recess.
Each one of the plural ribs includes a lower portion that includes
a draft surface extending inwardly and upwardly from the standing
ring.
[0012] Preferably, the draft surface is directly connected to the
standing ring such that the draft surface extends down to a
lowermost surface of the container. The angle of the draft surface
preferably is approximately five degrees, although the present
invention encompasses other ranges, as explained more fully herein.
Various geometric relationships are employed to describe the
configuration of bases, and it is understood that an independent
claim may rely on any single one of the geometric relationships
and/or structure described herein, as well as any combination
thereof.
[0013] The draft surface deforms substantially downwardly in
response to internal pressurization of the container, such as that
created upon internal pressurization of the container by
introducing liquefied gas upon filling. The container rests on the
standing ring even after internal pressurization of the container.
The ribs resist eversion of the recessed base surface such that the
container is capable of withstanding internal positive pressure. A
corresponding method is also provided.
BRIEF DESCRIPTION OF THE FIGURES.
[0014] FIG. 1 is an elevation view of a bottle, with the base shown
in phantom, with that illustrates an aspects of the present
invention;
[0015] FIG. 2 is a bottom view of the bottle shown in FIG. 1;
[0016] FIG. 3 is an enlarged view of the base shown in FIG. 1;
[0017] FIG. 4 is an enlarged view of the bottom view shown in FIG.
2;
[0018] FIG. 5 is a cross sectional view of the base taken through
line 5-5 of FIG. 4;
[0019] FIG. 6 is a cross sectional view of the base taken through
line 6-6 of FIG. 4;
[0020] FIG. 7A is a cross sectional view of a portion of the rib
taken through line 7A-7A of FIG. 4;
[0021] FIG. 7B is a cross sectional view of a portion of the rib
taken through line 7B-7B of FIG. 4;
[0022] FIG. 8A is an enlarged diagrammatic view of a portion of the
base shown in FIG. 5;
[0023] FIG. 8B is an enlarged diagrammatic view of the base shown
in FIG. 5 with some geometric features labeled;
[0024] FIG. 9A is an enlarged cross-sectional diagrammatic view of
a portion of the base shown in FIG. 5; and
[0025] FIG. 9B is an enlarged cross-sectional diagrammatic view of
an alternative embodiment to the portion shown in FIG. 9A.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0026] A heat-set container 9 is configured to receive and contain
positive internal pressure. Container 9 includes a base 25, a body
12 extending upwardly from base 25, and an upper portion 14
extending upwardly from body 12. Body 12, as shown in FIGS. 1 and
3, preferably is cylindrical. Because container 9 is intended to
contain positive internal pressure, complex vacuum panels are not
required to collapse or deform in response to negative internal
pressure. Even though vacuum panels are not required, the present
invention encompasses employing a gripping surface or surfaces,
such as finger grips 15, and/or vacuum panels. Thus, the invention
contemplates base 25 as described or claimed herein being employed
with any container type or configuration.
[0027] Container upper portion 14 includes a dome 16, a neck 18
extending upwardly from dome 16, an opening 20 formed in neck 18,
and a finish 22 formed on neck 18 proximate opening 20. Dome 16
yields to body 12 at a lower portion thereof, and smoothly yields
to neck 18 at an upper portion thereof. Finish 22 may be any
configuration for receiving a closure (not shown) of any type.
Preferably, neck 18 is elongated and dome 16 is rounded, although
the present invention is not limited to any particular
configuration of upper portion 14. A shoulder may be disposed
between body 12 and each of base 25 and dome 16, as shown in FIG.
1, or body 12 may smoothly merge into base 25 and dome 16.
[0028] Base 25 includes a heel 30, a standing ring 32, a recess 34,
and plural ribs 36. Heel 30 extends downwardly from the lower
shoulder and smoothly merges into standing ring 32. Standing ring
32 preferably is substantially continuous. Preferably, standing
ring 32 forms a planar surface that is the lowermost point of
container 9 either while container 9 is in an unpressurized state
or in a pressurized state.
[0029] Recess 34 extends inwardly and upwardly to enclose the
underside of container 9. Recess 34 may be substantially
frustoconical, have an elliptical, parabolic, or other arcuate
shape (in longitudinal cross section, not shown in the figures), or
another suitable shape. Plural ribs 36 extend relatively,
substantially radially inwardly from recess 34 and stiffen base 25,
especially to prevent recess 34 from everting (that is, a
structural failure in which at least a portion of recess 34
outwardly collapses or bulges). A recess surface 44, which is
disposed between ribs 36, terminates at a top portion or dome
46.
[0030] FIGS. 2 and 4 illustrate base 25 by showing four ribs 36,
although the present invention may employ any plural number of
ribs. The quantity of ribs will depend upon container base
diameter, base thickness, the magnitude of internal pressure, and
like parameters, as will be understood by persons familiar with
conventional container design and technology in view of the present
disclosure. Further, the present invention encompasses employing
one or more ribs, as described herein, in combination with
conventional ribs (not shown in the Figures). The present invention
is described by employing radial ribs, and the present invention
encompasses non-radial ribs, such as (but not limited to, those
forming a spiral configuration.
[0031] Each one of ribs 36 includes a draft surface 38 and rib face
40, each of which merges with a pair of opposing rib sides 42.
Also, a rib upper face 41 may be disposed such that it extends
upwardly from rib face 40 so as to merge with recess surface 44
and/or dome 46, as shown in the Figures. Alternatively, rib face 40
may extend upwardly without rib upper face such that rib face 40
thereby forms a substantially continuous angle, radius of
curvature, or arc. Employing rib upper face 41, in some
configurations, may provide a benefit to plastic flow during the
blow molding process as the preform (not shown) expands outwardly
and downwardly over an interior of base 25. Further, rib upper face
41 may also provide a larger top portion 46 (compared with the
configuration in which rib face 40 extends to and merges directly
into top portion 46), which in some configurations may enhance
contact with the blow pin (not shown) or with the distal tip of the
preform (not shown) during the blow molding process. Portions of
surfaces 38, 40, and 41 may be substantially perpendicular to
portions of rib sides 42. Rib sides 42 merge with recess surface 44
to fully enclose base 25.
[0032] As best shown in FIGS. 5 through 8, draft surface 38 extends
directly from standing ring 32 at its lower end and merges into rib
face 40 at its upper end. A draft surface inner point 50 is defined
on draft surface 38 proximate rib face 40, and a draft surface
outer point 52 is defined on draft surface 38 proximate standing
ring 32. Preferably, a line between the draft surface outer point
and the draft surface inner point forms a draft angle .theta.
(theta) therebetween relative to a horizontal line, as best shown
in FIG. 8A. Draft angle .theta. (theta) is measured in the
container's as-molded state or in the mold, as distinguished from
the container's hot or pressurized state, as explained more fully
below.
[0033] It is preferred that draft surface 38 be substantially
rectilinear--that is, a majority or all of draft surface 38 forms a
straight line between draft surface inner point 50 and outer point
52 in longitudinal cross section (that is, in a first plane that is
co-planar with a longitudinal centerline CL of container 9 and
substantially bisects the subject rib 36) as shown in FIGS. 58A,
and 8B. Such a shape generally provides good plastic flow
conditions during blow molding and a predictable deformation upon
pressurization. Further, draft surface 38 may be either
substantially rectilinear or curved in a second cross section that
is substantially longitudinal and parallel to the longitudinal
centerline CL and perpendicular to the first longitudinal
centerline, as shown in FIG. 7. In the embodiment in which draft
surface 38 is substantially rectilinear in the second cross
section, opposing edges of draft surface 38 may be radiused to
smoothly merge into rib sides 42. The present invention is not
limited to any particular shape of draft surface, but rather
encompasses any shape, including encompassing curves, waves, steps,
and the like, as well as encompassing draft surfaces that are not
radial.
[0034] The present invention encompasses any draft angle .theta.
(theta), although some angles provide particular advantages. For
example, a draft angle.theta. (theta) approximately equal to zero
provides a substantially horizontal surface that may enhance
plastic flow during blow molding and that is pushed downwardly
relative to standing ring 32 to form small feet. To enable standing
ring 32 to remain the lowermost point of the container, draft angle
.theta. (theta) preferably is at least slightly greater than zero.
For a preferred embodiment, it has been found that draft angle
.theta. (theta) is at least three degrees, and most preferably five
degrees.
[0035] It has also been determined that draft angle .theta. (theta)
preferably is less than 45 degrees to facilitate plastic flow
during blow molding. Further, angles of 40 degrees, 30 degrees, and
15 degrees have also been determined to be beneficial in this
regard. The width of standing ring 32 preferably is small, which
provides the benefits of stiffening the ring and diminishing the
transition from stiffened to unstiffened portions. Further, in some
circumstances, a wide standing ring may deform outwardly upon
internal positive pressurization and destabilize the standing
surface. Thus, it has been found that the land dimension or width W
(FIGS. 5, 6, 8A, and 8B) of standing ring 32 is less than
approximately 0.100 inches. For hot fill beverage bottles of about
a 64-ounce size, width W preferably is less than approximately
0.060 inches, and more preferably less than approximately 0.050
inches. In theory, width W could be zero and provide the advantages
referred to herein, but a practical lower limit is applied because
of blow-molding considerations. As stated herein, the present
invention is not limited to such dimensions.
[0036] The magnitude of the variables provided herein may apply to
a container of any size, and especially to a container having a
base that is consistent with a single serving container, such as
about 10 to 16 ounces. Because base 10 may be applied to any size
container, some geometric relationships are provided to aid in
describing its features. In this regard, referring to FIG. 8B, base
10 may have an overall base diameter A, and a standing ring
diameter C, which is defined as the outside rim of standing ring
32. Preferably, standing ring diameter C is between 60% and 80% of
base diameter A, and more preferably between 65% and 70% of base
diameter A. Thus, it is beneficial, although not strictly
necessary, for the heel to have a narrow profile, such as having a
heel dimension H no more than approximately 20 percent of base
diameter A, and more preferably no more than approximately 10
percent of base diameter A.
[0037] The relationship of diameters A and C is helpful, among
other things, to indicate a beneficial geometry of heel 30.
Further, standing ring land width W preferably is no more than
about four percent of standing ring diameter C, and more preferably
no more than about three percent of standing ring diameter C, and
even more preferably no more than about two percent of standing
ring diameter C.
[0038] A point E is defined at the juncture between draft surface
38 and rib face 40. For the configurations in which draft surface
38 and rib surface 40 are substantially straight (in longitudinal
cross section, as shown in FIG. 8B), point E is defined at the
intersection between the lines formed by the surfaces. For a
configuration in which the juncture between surfaces 38 and 40 is
rounded, E may be defined as the midpoint on the surface of the rib
between surface 38 and 40. The present invention encompasses
configurations in which either or both of draft surface 38 and rib
face 40 are curved in transverse cross section. In such a
configuration, point E may be defined as the point proximate the
junction between surfaces 38 and 40 having the highest rate of
change of slope. Draft surface width D is defined as the distance
between standing ring 32 and point E. Preferably, draft surface
dimension D is no more than approximately one-third A minus four
times standing ring land width W (that is, ((A/3)-(4W))). Even more
preferably, draft surface dimension D is no more than approximately
80 percent of one-third A minus four times standing ring land width
W (that is, 0.80((A/3)-(4W))).
[0039] The depth of rib 36 should be sufficient to resist internal
container pressure, as described more fully herein. In this regard,
a depth F (measured perpendicular to recess surface 44) of rib 36
near point E preferably is at least D divided by two times cosine
theta (that is, (D/(2 cos .theta.)). Even more preferably, the
depth F or rib 36 is at least 1.2 times D divided by two times
cosine theta (that is, (1.2 D/(2 cos .theta.)).
[0040] FIG. 9A diagrammatically shows a cross section of rib 36
taken proximate point E and approximately along line 9A-9A in FIG.
8B. Origin O is defined through the longitudinal centerline CL
(FIGS. 1, 5, and 6) of the container 9. Point B.sub.1 is defined as
the juncture between rib face 40 and rib side 42,and an angle
.beta..sub.1 is formed between a radial line RL--which intersects
point B.sub.1 and origin O--and a centerline line RCL of rib 36.
Rib sidewall 42 preferably is substantially collinear with line RL
and substantially radial.
[0041] Alternatively, the sidewall of rib 36 may be formed by an
angle that is not substantially radial. Such alternative
configurations are indicated by sidewalls 42' and 42", each of
which is shown in dashed lines. First embodiment sidewall 42' forms
an angle .phi..sub.1 (measured substantially clockwise--that is,
inwardly toward the rib centerline RCL--as oriented in FIG. 9A)
from the radial line RL that preferably is no more than
approximately angle .beta..sub.1 plus 5 degrees. Thus, rib 36 may
be narrower at its outer potion than at its inner portion. As
another alternative, second embodiment rib sidewall 42" may form an
angle .phi..sub.2 (measured substantially counterclockwise that is,
outwardly away from the rib centerline RCL--as oriented in FIG. 9A)
from the radial line RL that preferably is no more than
approximately two times angle .beta..sub.1.
[0042] The present invention is not limited to employing ribs
having straight sidewalls. For illustration, FIG. 9B shows a cross
section of a rib 36' that has an arcuate cross section. An angle
.beta..sub.2 is formed between a rib center line RCL and a line
between origin O and a point B.sub.2, which is a point on the outer
surface of sidewall 36'. Angle .beta..sub.2 and point B.sub.2 are
formed such that angle .beta..sub.2 is the largest angle at which
line RL contacts rib 36', and point B.sub.2 is the point of
contact. Angles .phi..sub.1 and .phi..sub.2 are formed between line
RL and the tangent of the curve formed by the sidewall at point
B.sub.2. Thus, the angle formed between the line RL and the tangent
taken at point B.sub.2 preferably is within the range of magnitudes
of angles .phi..sub.1 and .phi..sub.2, as described above.
[0043] The present invention is not limited to bases with ribs
having the angle ranges disclosed herein, but rather encompasses
ribs of any configuration. The geometry of the ribs 36 and 36' is
recited to provide guidance to optimize base performance under some
circumstances, but is not intended to limit the scope of the
invention unless expressly recited in the claim. Further, the
description above employs diameters and a container of circular
transverse cross section to describe base 10. The present invention
is not limited to containers having such circular cross section,
but rather encompasses any cross sectional shape. Thus, for
example, diameters A and C may be measured along major or minor
axes of an elliptical or oval base, or along the major or minor
lengths of a container having substantially flat sides (in
transverse cross section).
[0044] Container 9 having base 10 as described herein is intended
to be filled at an elevated temperature, and base 10 is configured
to receive contents at up to approximately 212 degrees F. without
failure, although such temperature is not a limit to the scope of
the invention. In this regard, a plastic resin having an intrinsic
viscosity of over 0.75 may be employed, and most preferably an
intrinsic viscosity of approximately 0.84 may be employed. The
present invention is not limited to such viscosities, which are
provided only for guidance.
[0045] Upon introduction of the contents into container 9, a
predetermined quantity of liquefied gas is introduced therein. The
liquefied gas, which preferably is liquefied nitrogen, quickly
vaporizes. After capping, such vaporization increases the internal
pressure within container 9. Preferably, the internal pressure
range is 15 to 35 psi at hot-fill temperature, and 0 to 10 psi upon
cooling to ambient temperature (that is, approximately 72 degrees).
The pressure ranges are provided to be exemplary, and the scope of
the present invention is not limited to such pressure ranges.
[0046] Co-pending U.S. patent application Ser. No. ______ (Attorney
Docket Number CC-3412), entitled "Method For Diminishing
Delamination Of A Multilayer Plastic Container," and co-pending
U.S. patent application Ser. No. ______ (Attorney Docket Number
CC-3449), entitled "Method For Extending The Effective Life Of An
Oxygen Scavenger In A Container Wall," describe nitrogen dosing
techniques with which the container according to any aspect of the
present invention may be employed. Further, U.S. Pat. Nos.
5,955,527; 5,639,815; 5,049,624; and/or 5,021,515 disclose an
oxygen scavenging material that is suitable for use in bottles in
hot-fillable and other containers, and that may be employed in
container 9. Each of the applications and patents referred to
herein is incorporated herein by reference in its entirety.
[0047] Techniques for introducing liquefied gas into container 9
are well known, especially by persons familiar with such technology
for introducing liquefied nitrogen into metal cans. Such nitrogen
dosing systems are commercially available and nearly exhaustively
described in the literature. The present invention is not limited
to a particular means for introducing liquefied gas, but rather
encompasses any introduction technology. The magnitude of the dose
of liquefied gas introduced into the container may be determined
according to such parameters as contents temperature, headspace
volume, characteristics of the container (including its elasticity
or relationship between volume change and pressure), order of
introduction of the product and nitrogen dose (that is, whether the
nitrogen dose is introducing into the container before,
concurrently with, or after the contents), and the time period
between introducing the nitrogen dose and capping or sealing.
Choosing the magnitude of the dose of liquefied gas for a
particular application will be straightforward for persons familiar
with liquefied gas dosing technology, such as, for example, as used
in the metal can industry, in light of the present disclosure and
the above parameters.
[0048] The internal positive pressure within container 9 acts on
all surfaces of base 10. Thus, pressure urges top portion or dome
46 substantially downwardly, urges against the interior surfaces of
recess 34 and ribs 36 substantially downwardly and substantially
inwardly, urges against the interior surface of standing ring 32
substantially downwardly, and urges against the interior of heel 30
substantially outwardly and somewhat downwardly. Each of the
downward components of the pressure vectors, as well as most of the
other components of the pressure vectors, urges base 10 toward
eversion. The term "substantially downwardly" as used herein refers
generally to the downward direction when the container is upright,
and nay also include a lateral component.
[0049] Conventional bases often fail under such conditions either
by complete eversion, which is a complete failure mode in which
much of recess 34 is pushed fully out the bottom of base 10 to
break the plane defined by standing ring 32, or by partial
eversion, in which a portion of standing ring 32 (most often at a
single circumferential location) is pushed downwardly relative to
the plane defined by the as-molded standing ring. Even a partial
eversion of small magnitude might destroy or inhibit the
container's ability of the container to solidly rest on a flat
surface or its ability to stand.
[0050] Standing ring 32 is stiffened by ribs 36, thereby
diminishing downward deflection of standing ring 32, upon
pressurization of base 10, compared with an unstiffened
configuration. Draft surface 38 being directly connected to
standing ring 32 enhances such stiffening. Also, because standing
ringland dimension or width W, as described above, is small
(compared, for example, to configurations common to hot-fill
bottles that are subject to internal negative pressure), the total
force and moments acting on standing ring 32 (about, for example,
the interface between heel 30 and standing ring 32) contributes to
keeping the deformation of standing ring 32 small.
[0051] Thus, the stiffening of standing ring 32 by ribs 36 and the
standing ring's small dimension W each enhance the stability of
container 9 when standing upright on standing ring 32 and
inhibiting partial or localized eversion. Each of such features may
be employed independently of the other such that the present
invention is not limited to employing both features. Rather, the
present invention encompasses a base employing a standing ring
having the dimensions provided herein in combination with ribs that
are spaced apart therefrom. As well, the present invention
encompasses a base employing ribs that extend from the standing
ring in combination with a standing ring having a dimension W that
is outside that described herein.
[0052] Upon pressurization of container 9, draft surface 38 deforms
downwardly such that, for the embodiment in which draft surface 38
is flat in its as molded state, draft surface 38 forms a convex bow
(relative to a plane) in draft surface 38 when viewed from below
base 10. Further, the draft angle .theta. (theta) decreases upon
such pressurization. The magnitude of the bow may be small, such as
a few thousandths of an inch for containers in the 48 to 64 ounce
container size. Alternatively, if draft surface 38 is sufficiently
stiff, by, for example, the stiffening effect of rib sides 42 on
draft surface 38, draft surface may deflect downwardly by a few
thousands in such a way that no bow if formed. Thus, the present
invention encompasses any deflection or deformation of draft
surface 38.
[0053] Preferably, draft surface 38 in its fully deformed or
deflected state (that is, upon pressurization of container 9 as
described herein), does not interfere with standing ring 32 such
that standing ring 32 remains circumferentially continuous. in this
regard, draft surface 38 does not extend downwardly below standing
ring 32 even in its deformed or deflected state such that
substantially all of standing ring 32 is substantially planar.
However, the present invention encompasses any configuration in
which draft surface 38 deflects downwardly in response to internal
pressurization, as described above.
[0054] Persons familiar with preform and blow molding processes and
technology in light of the present disclosure will be enabled to
configure a container that employs the present invention(s), such
as a container base in which its draft surface deforms as described
above.
[0055] Further, a method is provided in which hot-fillable
container base 10 is provided that is capable of receiving positive
internal pressure. Upon introducing hot product contents and
introducing liquefied gas and subsequent sealing or capping, draft
surface 38 flexes downwardly about its junction with standing ring
28 or about a draft surface outer point 52 proximate standing ring
28, and may otherwise perform as described above with respect to
the description of the structural aspects of base 10.
[0056] The geometry of draft surface 38 and the width of standing
ring 28 each contribute to the capability of base 10 to receive
internal positive pressure as described above. The present
invention, however, is not limited to simultaneously employing both
(or any other) features described herein, but rather each feature
may be employed alone or with any other feature to provide the
positive pressure capabilities.
* * * * *