U.S. patent application number 11/518604 was filed with the patent office on 2008-03-13 for structural ribs for hot fillable containers.
Invention is credited to David Deemer, Chad Keilen, Hassan Mourad.
Application Number | 20080061024 11/518604 |
Document ID | / |
Family ID | 39168516 |
Filed Date | 2008-03-13 |
United States Patent
Application |
20080061024 |
Kind Code |
A1 |
Keilen; Chad ; et
al. |
March 13, 2008 |
Structural ribs for hot fillable containers
Abstract
A plastic container includes an upper portion having a mouth
defining an opening into the container. A shoulder region extends
from the upper portion. A sidewall portion extends from the
shoulder region to a base portion. The base portion closes off an
end of the container. The sidewall portion is defined in part by at
least one arcuately formed rib having a body portion and opposite
ends. The body portion curves from a central portion toward the
base portion at each of the opposite ends.
Inventors: |
Keilen; Chad; (Chelsea,
MI) ; Mourad; Hassan; (Canton, MI) ; Deemer;
David; (Adrian, MI) |
Correspondence
Address: |
HARNESS, DICKEY & PIERCE, P.L.C.
P.O. BOX 828
BLOOMFIELD HILLS
MI
48303
US
|
Family ID: |
39168516 |
Appl. No.: |
11/518604 |
Filed: |
September 8, 2006 |
Current U.S.
Class: |
215/382 |
Current CPC
Class: |
B65D 2501/0018 20130101;
B65D 1/0223 20130101; B65D 79/005 20130101; B65D 2501/0081
20130101 |
Class at
Publication: |
215/382 |
International
Class: |
B65D 90/02 20060101
B65D090/02 |
Claims
1. A plastic container comprising: an upper portion having a mouth
defining an opening into said container; a shoulder region
extending from said upper portion; a sidewall portion extending
from said shoulder region to a base portion, said base portion
closing off an end of said container, said sidewall portion defined
in part by at least one arcuately formed rib having a body portion
and opposite ends; and wherein said body portion of said at least
one arcuately formed rib curves from a central portion toward the
base portion at each of said opposite ends.
2. The plastic container of claim 1 wherein said at least one
arcuately formed rib defines an inboard depression along said
sidewall portion.
3. The plastic container of claim 2 wherein the container defines a
first pair of opposing sidewalls and a second pair of opposing
sidewalls, wherein said first pair of opposing sidewalls are longer
in length than said second pair of opposing sidewalls.
4. The plastic container of claim 3 wherein said at least one
arcuately formed rib defines a series of ribs.
5. The plastic container of claim 4 wherein said series of ribs are
defined on said first pair of opposing sidewalls.
6. The plastic container of claim 5 wherein said series of ribs
each define a length that is about 50% to about 90% of a width of
said first pair of opposing sidewalls.
7. The plastic container of claim 6 wherein said sidewall portion
is defined in part by at least two vacuum panels formed therein,
said vacuum panels being movable to accommodate vacuum forces
generated within the container resulting from heating and cooling
of its contents.
8. The plastic container of claim 7 wherein said series of ribs are
defined on said vacuum panels.
9. The plastic container of claim 8 wherein said sidewall portion
defines a label panel area on an area across said vacuum panels,
said label panel area adapted to accept a label covering said
series of ribs.
10. A plastic container comprising: an upper portion having a mouth
defining an opening into said container; a shoulder region
extending from said upper portion; a sidewall portion extending
from said shoulder region to a base portion, said base portion
closing off an end of said container, said sidewall portion defined
in part by at least one arcuately formed rib having a body portion
and opposite ends, wherein said at least one arcuately formed rib
curves away from said mouth toward each of said opposite ends; and
wherein said sidewall portion is further defined in part by at
least two vacuum panels formed therein, said vacuum panels being
movable to accommodate vacuum forces generated within the container
resulting from heating and cooling of its contents.
11. The plastic container of claim 10 wherein said at least one
arcuately formed rib defines an inboard depression along said
sidewall portion.
12. The plastic container of claim 11 wherein the container defines
a first pair of opposing sidewalls and a second pair of opposing
sidewalls, wherein said first pair of opposing sidewalls are longer
in length than said second pair of opposing sidewalls.
13. The plastic container of claim 12 wherein said at least one
arcuately formed rib defines a series of ribs.
14. The plastic container of claim 13 wherein said series of ribs
are defined on said first pair of opposing sidewalls.
15. The plastic container of claim 14 wherein said sidewall portion
defines a label panel area on an area across said vacuum panels,
said label panel area adapted to accept a label covering said
series of ribs.
16. A method of making a blow-molded PET plastic container, said
method comprising the steps of: disposing a preform into a mold
cavity having a surface defining a shoulder forming region, a
sidewall forming region and a base forming region, the sidewall
forming region defining at least one arcuately formed extension rib
having a body portion and opposite ends, the opposite ends of said
at least one arcuately formed extension rib curves from a central
portion toward the base forming region at each of said opposite
ends; blowing the preform against the mold surface to form a
resultant container having a shoulder, a sidewall and a base, the
sidewall defining at least one arcuate depression rib corresponding
to the at least one arcuately formed extension rib of the mold
cavity; and removing the resultant container from the mold
cavity.
17. The method of claim 16 wherein the sidewall forming region
defines a series of arcuately formed extension ribs each having a
body portion and opposite ends.
18. The method of claim 17 wherein the step of blowing the preform
further includes blowing material comprising the preform around the
series of arcuately formed extension ribs, the material generally
flowing from the body portion of each extension rib at an upstream
area toward the opposite ends of each extension rib at a downstream
area.
19. The method of claim 18 wherein the step of blowing further
includes forming at least two vacuum panels at the sidewall.
20. The method of claim 19 wherein forming at least two vacuum
panels includes forming the at least two vacuum panels along a
surface encompassing the at least one arcuate depression rib.
Description
TECHNICAL FIELD
[0001] This disclosure generally relates to plastic containers for
retaining a commodity, and in particular a liquid or semi solid
commodity. More specifically, this disclosure relates to a plastic
container having a sidewall portion defining arcuate ribs that
promote improved material distribution during container
formation.
BACKGROUND
[0002] The statements in this section merely provide background
information related to the present disclosure and may not
constitute prior art.
[0003] As a result of environmental and other concerns, plastic
containers, more specifically polyester and even more specifically
polyethylene terephthalate (PET) containers are now being used more
than ever to package numerous commodities previously supplied in
glass containers. Manufacturers and fillers, as well as consumers,
have recognized that PET containers are lightweight, inexpensive,
recyclable and manufacturable in large quantities.
[0004] Blow-molded plastic containers have become commonplace in
packaging numerous commodities. PET is a crystallizable polymer,
meaning that it is available in an amorphous form or a
semi-crystalline form. The ability of a PET container to maintain
its material integrity relates to the percentage of the PET
container in crystalline form, also known as the "crystallinity" of
the PET container. The following equation defines the percentage of
crystallinity as a volume fraction:
% Crystallinity = ( .rho. - .rho. a .rho. c - .rho. a ) x 100
##EQU00001##
where .rho. is the density of the PET material; .rho..sub.a is the
density of pure amorphous PET material (1.333 g/cc); and
.rho..sub.c is the density of pure crystalline material (1.455
g/cc).
[0005] Container manufacturers use mechanical processing and
thermal processing to increase the PET polymer crystallinity of a
container. Mechanical processing involves orienting the amorphous
material to achieve strain hardening. This processing commonly
involves stretching an injection molded PET preform along a
longitudinal axis and expanding the PET preform along a transverse
or radial axis to form a PET container. The combination promotes
what manufacturers define as biaxial orientation of the molecular
structure in the container. Manufacturers of PET containers
currently use mechanical processing to produce PET containers
having approximately 20% crystallinity in the container's
sidewall.
[0006] Thermal processing involves heating the material (either
amorphous or semi-crystalline) to promote crystal growth. On
amorphous material, thermal processing of PET material results in a
spherulitic morphology that interferes with the transmission of
light. In other words, the resulting crystalline material is
opaque, and thus, generally undesirable. Used after mechanical
processing, however, thermal processing results in higher
crystallinity and excellent clarity for those portions of the
container having biaxial molecular orientation. The thermal
processing of an oriented PET container, which is known as heat
setting, typically includes blow molding a PET preform against a
mold heated to a temperature of approximately 250.degree.
F.-350.degree. F. (approximately 121.degree. C.-177.degree. C.),
and holding the blown container against the heated mold for
approximately two (2) to five (5) seconds. Manufacturers of PET
juice bottles, which must be hot-filled at approximately
185.degree. F. (85.degree. C.), currently use heat setting to
produce PET bottles having an overall crystallinity in the range of
approximately 25%-35%.
[0007] Food and juice suppliers often fill these products into the
containers while the product is at an elevated temperature,
typically between 155.degree. F.-205.degree. F. (68.degree.
C.-96.degree. C.) and usually at approximately 185.degree. F.
(85.degree. C.). When packaged in this manner, the hot temperature
of the commodity sterilizes the container at the time of filling.
The bottling industry refers to this process as hot filling, and
the containers designed to withstand the process as hot-fill or
heat-set containers.
[0008] One challenge associated with thermal processing of an
oriented PET container is the ability to direct material throughout
the critical areas of the container during formation. One approach
includes preferential heating of the preform to control material
distribution wherein different portions of the preform are heated
to different temperatures to encourage material distribution in
critical areas of the container. However, such as with formation of
some rectangular or oval containers, this approach is costly and
does not always yield satisfactory material distribution throughout
the container. Additionally, in some instances it may be desirable
to incorporate ribs at various locations on the container to
improve structural integrity of the container as a whole. While
such ribs may provide improved durability to the container, the
ribs may make it more difficult to successfully distribute the
material throughout the container during formation. Explained
further, containers incorporating horizontal ribs (i.e., in a
direction generally parallel to a container base), may result in
material being trapped at the ribs thereby inhibiting material
distribution in the heel or base of the container during formation.
Similarly, containers incorporating vertical ribs (i.e. in a
direction generally transverse to a container base), may result in
material being trapped at the ribs thereby causing an uneven
distribution of material throughout the sides of the container
during formation.
[0009] After being hot-filled, the heat-set containers may be
capped and allowed to reside at generally the filling temperature
for approximately five (5) minutes at which point the container,
along with the product, is then actively cooled prior to
transferring to labeling, packaging, and shipping operations. The
cooling reduces the volume of the commodity in the container. This
product shrinkage phenomenon results in the creation of a vacuum
within the container. Generally, vacuum pressures within the
container range from 1-380 mm Hg less than atmospheric pressure
(i.e., 759 mm Hg-380 mm Hg). If not controlled or otherwise
accommodated, these vacuum pressures result in deformation of the
container, which leads to either an aesthetically unacceptable
container or one that is unstable. Hot-fillable plastic containers
must provide sufficient flexure to compensate for the changes of
pressure and temperature, while maintaining structural integrity
and aesthetic appearance. Typically, the industry accommodates
vacuum related pressures with sidewall structures or vacuum panels
formed within the sidewall of the container. Such vacuum panels
generally distort inwardly under vacuum pressures in a controlled
manner to eliminate undesirable deformation.
[0010] While such vacuum panels allow containers to withstand the
rigors of a hot-fill procedure, the panels have limitations and
drawbacks. First, such panels formed within the sidewall of a
container do not create a generally smooth glass-like appearance.
Second, packagers often apply a label to the container over these
panels. The appearance of these labels over the vacuum panels is
such that the label often becomes wrinkled and not smooth.
Additionally, one grasping the container generally feels the vacuum
panels beneath the label and often pushes the label into various
panel crevasses and recesses.
[0011] Thus, there is a need for an improved plastic container,
which allows for improved material distribution during formation
and accommodates the vacuum pressures which result from hot
filling.
SUMMARY
[0012] Accordingly, the present disclosure provides a plastic
container including an upper portion having a mouth defining an
opening into the container. A shoulder region extends from the
upper portion. A sidewall portion extends from the shoulder region
to a base portion. The base portion closes off an end of the
container. The sidewall portion is defined in part by at least one
arcuately formed rib having a body portion and opposite ends. The
body portion curves from a central portion toward the base portion
of the container at each of the opposite ends.
[0013] According to additional features, a series of arcuately
formed ribs are defined on the sidewall portion. Each of the ribs
define an inboard depression along the sidewall portion. The
sidewall portion may be defined in part by at least two vacuum
panels formed therein. The vacuum panels are movable to accommodate
vacuum forces generated within the container resulting from heating
and cooling of its contents. The sidewall portion may define a
label panel area on an area across the vacuum panels. The label
panel area may be adapted to accept a label over the series of
ribs.
[0014] A method of making a blow-molded PET plastic container
includes disposing a preform into a mold cavity. The mold cavity
has a surface defining a shoulder forming region, a sidewall
forming region and a base forming region. The sidewall forming
region defines at least one arcuate extension rib having a body
portion and opposite ends. The opposite ends of each extension rib
curve from a central portion toward the base forming region at each
of the opposite ends. The preform is blown against the mold surface
to form a resultant container having a shoulder, a sidewall and a
base. The sidewall defines at least one arcuate depression rib
corresponding to the at least one arcuate extension rib of the mold
cavity.
[0015] The configuration of the arcuate extension ribs in the mold
cavity are consistent with the directional flow of material during
container formation thus facilitating consistent material flow
during formation of the container. Moreover, the arcuate extension
ribs are generally curved from a central portion at an upstream
area to opposite ends at a downstream area. In this way, material
may flow smoothly around the arcuate surfaces without becoming
substantially impeded or trapped at the ribs.
[0016] Additional benefits and advantages of the present disclosure
will become apparent to those skilled in the art to which the
present disclosure relates from the subsequent description and the
appended claims, taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a perspective view of a plastic container
constructed in accordance with the teachings of the present
disclosure;
[0018] FIG. 2 is a front view of the container of FIG. 1;
[0019] FIG. 3 is a side view of the container of FIG. 1;
[0020] FIG. 4 is a cross-sectional view of the plastic container,
taken generally along line 4-4 of FIG. 2; and
[0021] FIG. 5 is a sectional view of an exemplary mold cavity used
during formation of the container of FIG. 1 and shown with a
preform positioned therein.
DETAILED DESCRIPTION
[0022] The following description is merely exemplary in nature, and
is in no way intended to limit the disclosure or its application or
uses.
[0023] FIGS. 1-4 show one example of the present container. In the
figures, reference number 10 designates a plastic, e.g.
polyethylene terephthalate (PET), hot-fillable container. As shown
in FIG. 2, the container 10 has an overall height A of about 8.15
inch (207 mm), and a sidewall and base portion height B of about
4.50 inch (114 mm). The height A may be selected so that the
container 10 fits on the shelves of a supermarket or store. As
shown in the figures, the container 10 is substantially oval in
cross sectional shape including opposing longer sides 14 each
having a width C of about 3.00 inch (76.4 mm), and opposing
shorter, parting line sides 15 (FIG. 3) each having a width D of
about 1.65 inch (42.0 mm). The widths C and D are selected so that
the container 10 can fit within the door shelf of a refrigerator.
As with typical prior art bottles, opposing longer sides 14 of the
container 10 of the present disclosure are oriented at
approximately 90 degree angles to the shorter, parting line sides
15 of the container 10 so as to form a generally oval cross section
as best shown in FIG. 4. As such, the container 10 further includes
a diagonal width G of about 3.04 inch (77.3 mm). In this particular
example, the container 10 has a volume capacity of about 14 fl. oz.
(414 cc). Those of ordinary skill in the art would appreciate that
the following teachings of the present disclosure are applicable to
other containers, such as round, square or rectangular shaped
containers, which may have different dimensions and volume
capacities. It is also contemplated that other modifications can be
made depending on the specific application and environmental
requirements.
[0024] As shown in FIGS. 1-3, the plastic container 10 of the
invention includes a finish 12, a shoulder region 16, a sidewall
portion 18 and a base 20. Those skilled in the art know and
understand that a neck may also be included having an extremely
short height, that is, becoming a short extension from the finish
12, or an elongated height, extending between the finish 12 and the
shoulder region 16. The plastic container 10 has been designed to
retain a commodity during a thermal process, typically a hot-fill
process. For hot-fill bottling applications, bottlers generally
fill the container 10 with a liquid or product at an elevated
temperature between approximately 155.degree. F. to 205.degree. F.
(approximately 68.degree. C. to 96.degree. C.) and seal the
container 10 with a closure (not illustrated) before cooling. As
the sealed container 10 cools, a slight vacuum, or negative
pressure, forms inside causing the container 10, in particular, the
sidewall portion 18, as will be described, to change shape. In
addition, the plastic container 10 may be suitable for other
high-temperature pasteurization or retort filling processes, or
other thermal processes as well.
[0025] The finish 12 of the plastic container 10 includes a portion
defining an aperture or mouth 22, a threaded region 24 having
threads 25, and a support ring 26. The aperture 22 allows the
plastic container 10 to receive a commodity while the threaded
region 24 provides a means for attachment of a similarly threaded
closure or cap (not illustrated). Alternatives may include other
suitable devices that engage the finish 12 of the plastic container
10. Accordingly, the closure or cap (not illustrated) engages the
finish 12 to preferably provide a hermetical seal of the plastic
container 10. The closure or cap (not illustrated) is preferably of
a plastic or metal material conventional to the closure industry
and suitable for subsequent thermal processing, including high
temperature pasteurization and retort. The support ring 26 may be
used to carry or orient a preform 28 (the precursor to the plastic
container 10, shown in FIG. 5) through and at various stages of
manufacture. For example, the preform 28 may be carried by the
support ring 26, the support ring 26 may be used to aid in
positioning the preform 28 in the mold, or an end consumer may use
the support ring 26 to carry the plastic container 10 once
manufactured.
[0026] Integrally formed with the finish 12 and extending downward
therefrom is the shoulder region 16. The shoulder region 16 merges
into and provides a transition between the finish 12 and the
sidewall portion 18. The sidewall portion 18 extends downward from
the shoulder region 16 to the base 20. The specific construction of
the sidewall portion 18 of the heat-set container 10 allows the
shoulder region 16 and the base 20 to not necessarily require
additional vacuum panels and therefore, the shoulder region 16 and
the base 20 are capable of providing increased rigidity and
structural support to the container 10. The base 20 functions to
close off the bottom portion of the plastic container 10 and,
together with the finish 12, the shoulder region 16, and the
sidewall portion 18, to retain the commodity.
[0027] The plastic container 10 is preferably heat-set according to
the above-mentioned process or other conventional heat-set
processes. To accommodate vacuum forces, the sidewall portion 18
may include vacuum panels 30 formed therein. As illustrated in the
figures, vacuum panels 30 may be generally rectangular in shape and
are formed in the opposing longer sides 14 of the container 10. It
is appreciated that the vacuum panels 30 may define other
geometrical configurations. Accordingly, the container 10
illustrated in the figures has two (2) vacuum panels 30. The
inventors however equally contemplate that more than two (2) vacuum
panels 30, such as four (4), can be provided. That is, that vacuum
panels 30 can also be formed in opposing shorter, parting line
sides 15 of the container 10 as well. Vacuum panels 30 may also
include an underlying surface 34. Surrounding vacuum panels 30 is
land 32. Land 32 provides structural support and rigidity to the
sidewall portion 18 of the container 10.
[0028] The plastic container 10 according to the present teachings
provides a series of arcuately formed ribs 40. The ribs 40
generally define a body 42 having opposite ends 44 curved in a
direction away from the finish 12. As best illustrated in FIG. 3,
the ribs 40 define inboard depressions on the sidewall portion 18.
As will become more appreciated from the following description, the
ribs 40 facilitate an even distribution of material during
formation of the container 10. In the example shown, three ribs 40
are formed on the sidewall portion 18 on each of the vacuum panels
30. As shown, the ribs 40 generally define a consistent radius. It
is appreciated however, that the ribs 40 may alternatively define
an increasing radius or a decreasing radius from a central portion.
Preferably, the ribs 40 define a length L (FIG. 2) that is about
50% to 90% of the width of opposing longer sides 14, and more
preferably 60% to 80%. The present disclosure is especially
effective for producing containers that are substantially
rectangular, oblong or oval in shape such as containers wherein the
width of opposing longer sides 14 is 1.5 to 2.5 times greater than
the width of opposing parting line sides 15. It is appreciated that
fewer or more ribs 40 may be incorporated on the container 10.
Furthermore, it is appreciated that the ribs 40 may define
alternate configurations and/or be located elsewhere on the
container 10.
[0029] The specific height and resulting radius of curvature of the
ribs 40 is dependent on container design aspects that affect the
amount of stretching the material undergoes during blow molding of
the container 10 from the preform 28. The preferred range of a
height H (FIG. 2), for a given length L of the ribs 40, is defined
by the following equations:
H.sub.MIN=[(L/C).times.(SPL-FPL)].times.(C/D);
and
H.sub.MAX=[(L/C).times.(CPL-FPL)].times.(G/D)
where CPL (FIG. 1) represents the corner profile length which is
the length of a vertical profile of the container 10 measured from
the shoulder region 16 to the base 20 at a corner or an
intersection of an opposing parting line side 15 and an opposing
longer side 14, SPL (FIG. 2) represents the side profile length
which is the length of a vertical profile of the container 10
measured from the shoulder region 16 to the base 20 at a midpoint
of the opposing parting line sides 15, and FPL (FIG. 3) represents
the front profile length which is the length of a vertical profile
of the container 10 measured from the shoulder region 16 to the
base 20 at a midpoint of the opposing longer sides 14.
[0030] Accordingly, by way of example, the container 10, may have a
length L of the ribs 40 measuring approximately 2.18 inch (55.3
mm), representing about 72.4% of the width C, measuring
approximately 3.00 inch (76.4 mm). Similarly, the container 10 may
also include a width D measuring approximately 1.65 inch (42.0 mm),
a diagonal width G measuring approximately 3.04 inch (77.3 mm), a
corner profile length CPL measuring approximately 9.52 inch (241.73
mm), a side profile length SPL measuring approximately 9.37 inch
(237.90 mm), and a front profile length FPL measuring approximately
9.00 inch (228.74 mm). Thus, by way of example, using the
above-described equations and dimensions, the preferred range of
the height H for the ribs 40 generally may be approximately 0.49
inch (12.06 mm) (H.sub.MIN) to 0.70 inch (17.31 mm) (H.sub.MAX).
The above and previously mentioned dimensions were taken from a
typical 14 fl. oz. (414 cc) container. It is contemplated that
comparable dimensions are attainable for containers of varying
shapes and sizes.
[0031] A label panel area 50 is defined at the sidewall portion 18.
The label panel area 50 may generally overlay the vacuum panels 30.
As is commonly known and understood by container manufacturers
skilled in the art, a label may be applied to the sidewall portion
18 at the label panel area 50 using methods that are well known to
those skilled in the art, including shrink-wrap labeling and
adhesive methods. As applied, the label may extend around the
entire body or be limited to a single side of the sidewall portion
18.
[0032] Upon filling, capping, sealing and cooling, as illustrated
in FIG. 4 in phantom, the underlying surface 34 of vacuum panels 30
is pulled radially inward, toward a central longitudinal axis 46 of
the container 10, displacing volume, as a result of vacuum forces.
In this position, the underlying surface 34 of vacuum panels 30, in
cross section, illustrated in FIG. 4 in phantom, forms an
underlying surface 34'. The greater the inward radial movement
between underlying surfaces 34 and 34', the greater the achievable
displacement of volume. The configuration of the sidewall portion
18, vacuum panels 30 and ribs 40 allow the vacuum reaction to be
absorbed in a controlled manner. Furthermore, the container 10
maintains its outwardly curved cross-sectional shape during vacuum
absorption providing a desirable surface for applying a label.
[0033] The amount of volume which vacuum panels 30 of the sidewall
portion 18 displaces is also dependant on the projected surface
area of vacuum panels 30 of the sidewall portion 18 as compared to
the projected total surface area of the sidewall portion 18. The
generally rectangular configuration of the container 10 creates a
large surface area on opposing longer sides 14 of the sidewall
portion 18, thereby promoting the use of large vacuum panels. This
large surface area promotes the placing of large vacuum panels 30
in this area. Accordingly, as illustrated in FIG. 2, this results
in vacuum panels 30 having a width E and a height F. In one
example, for the container 10 having a nominal capacity of
approximately 14 fl. oz. (414 cc), the width E is about 2.8 inch
(71.12 mm) while the height F is about 3.74 inch (95.00 mm).
[0034] Turning now to FIG. 5, the preform 28 used to mold the
exemplary container 10 in a mold cavity 60 is shown. The plastic
container 10 of the present invention is a blow molded, biaxially
oriented container with a unitary construction from a single or
multi-layer material. A well-known stretch-molding, heat-setting
process for making the hot-fillable plastic container 10 generally
involves the manufacture of the preform 28 of a polyester material,
such as polyethylene terephthalate (PET), having a shape well known
to those skilled in the art similar to a test-tube with a generally
cylindrical cross section and a length typically approximately
fifty percent (50%) that of the resultant container height. A
machine (not illustrated) places the preform 28 heated to a
temperature between approximately 190.degree. F. to 250.degree. F.
(approximately 88.degree. C. to 121.degree. C.) into the mold
cavity 60 having a shape similar to the plastic container 10.
[0035] The mold cavity 60 generally defines a shoulder forming
region 62, a sidewall forming region 64 and a base forming region
66. The sidewall forming region 64 includes arcuate extension ribs
70 thereon corresponding to the ribs 40 formed on the resultant
container 10. The arcuate extension ribs 70 slope generally from a
central portion 80 downward and away to ends (not specifically
shown in FIG. 5) corresponding to the ends 44 of the ribs 40. The
arcuate nature of the extension ribs 70 facilitate material flow
from an area generally upstream (central portion 80) to an area
generally downstream toward and beyond the ends of the ribs 70. In
this way, material is discouraged from being impeded or trapped at
the ribs 70 during formation of the container 10. As a result, an
even material distribution is realized throughout the container
10.
[0036] During formation, the mold cavity 60 may be heated to a
temperature between approximately 250.degree. F. to 350.degree. F.
(approximately 121.degree. C. to 177.degree. C.). A stretch rod
apparatus (not illustrated) stretches or extends the heated preform
28 within the mold cavity 60 to a length approximately that of the
container 10 thereby molecularly orienting the polyester material
in an axial direction generally corresponding with the central
longitudinal axis 46 (FIGS. 2 and 3) of the container 10.
[0037] While the stretch rod extends the preform 28, air having a
pressure between 300 PSI to 600 PSI (2.07 MPa to 4.14 MPa) assists
in extending the preform 28 in the axial direction and in expanding
the preform 28 in a circumferential or hoop direction thereby
substantially conforming the polyester material to the shape of the
mold cavity 60 and further molecularly orienting the polyester
material in a direction generally perpendicular to the axial
direction, thus establishing the biaxial molecular orientation of
the polyester material in most of the container 10. Typically,
material within the finish 12 and a sub-portion of the base 20 are
not substantially molecularly oriented. The pressurized air holds
the mostly biaxial molecularly oriented polyester material against
the mold cavity 60 for a period of approximately two (2) to five
(5) seconds before removal of the container 10 from the mold cavity
60. This process is known as heat setting and results in a
heat-resistant container suitable for filling with a product at
high temperatures.
[0038] Alternatively, other manufacturing methods, such as for
example, extrusion blow molding, one step injection stretch blow
molding and injection blow molding, using other conventional
materials including, for example, high density polyethylene,
polypropylene, polyethylene naphthalate (PEN), a PET/PEN blend or
copolymer, and various multilayer structures may be suitable for
the manufacture of plastic container 10. Those having ordinary
skill in the art will readily know and understand plastic container
manufacturing method alternatives.
[0039] While the above description constitutes the present
disclosure, it will be appreciated that the disclosure is
susceptible to modification, variation and change without departing
from the proper scope and fair meaning of the accompanying
claims.
* * * * *