Note: Descriptions are shown in the official language in which they were submitted.
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A PLASTIC CONTAINER OR A PREFORM
FIELD OF THE INVENTION
[01] The present invention is directed to finishes for plastic containers or
preforms, to preform assemblies for blow molding plastic containers, to
plastic
containers blow molded from such preform assemblies, and to methods of making
such finishes, preform assemblies and containers.
BACKGROUND OF THE INVENTION
[02] In the manufacture of plastic containers, it is conventional to injection
mold or compression mold a container preform having a body and a finish with
one
or more external threads or other closure attachment means. The preform finish
typically is molded to its final geometry, while the body of the preform
subsequently
is blow molded to the desired geometry of the container body. The preform may
be
of monolayer construction, or may be of multilayer construction in which one
or more
intermediate layers in the preform body may or may not extend into the finish
area of
the preform. U.S. Patent Nos. 4,609,516, 4,710,118 and 4,954,376 illustrate
injection molding of multilayer container preforms.
[03] Molding the finish portion of the container as part of the preform
presents a number of problems. For example, when the preforms are formed by
injection molding, the plastic material typically is injected into a mold
cavity at the
closed end of the preform body and must first flow in the area along the sides
of the
preform cavity, to form the relatively thin walled preform body, and then into
the area
in which the finish is molded, to form the substantially thicker finish
portion. Because
it is located at the end of the flow path, it can be difficult to completely
fill the
relatively thicker and more contoured finish portion. Also, the finish
typically requires
more accurate and stable dimensioning than the body of the preform, which can
lengthen the cycle time of the molding process. Furthermore, where the finish
portion of the preform is of the same material as at least the outer layers of
the
preform body, this may limit the ability to obtain more desirable performance
characteristics in the finish. For example, when the preform is of polyester
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construction, such as polyethylene terephthalate (PET), the finish portion of
the
preform can be wholly or partially crystallized to improve the operating
characteristics of the finish area, particularly in higher temperature
container
applications (e.g., hot-fill, pasteurization, refill, etc.). However, the
requirement that
the finish be of the same material as at least the outer layers of the preform
body (in
a multilayer preform) may limit the design, manufacture and/or performance
characteristics of the preform or container.
[04] U.S. Application Serial Nos. 10/351,671, 10/375,376, 10/375,758 and
10/403,415, assigned to the assignee of the present application, disclose
finish
assemblies for preforms and containers in which the preform neck has an
external
flange around its open end, and a separate plastic finish ring is assembled
over the
preform neck in abutment with the external flange. The finish ring has one or
more
external threads or other means for securement of a closure, and can be of a
plastic
construction different from the plastic construction of the preform. The
preform body
and neck may be of relatively thin plastic construction, while the finish ring
(alone or
together with the neck) forms a thickened construction. However, liquid that
spills on
the finish during filling of the container can flow between the finish ring
and the
preform flange, and collect between the finish ring and the preform neck. Such
fluid
is unsightly and can encourage the growth of mold. It would be desirable to
provide
a finish assembly for a plastic preform or container, a method of making a
plastic
preform or container, and a preform assembly that reduce or eliminate the
likelihood
of leakage of fluid between the finish ring and the preform/container neck.
SUMMARY OF THE INVENTION
[05] In accordance with one embodiment of the invention, a method is
provided for making a preform assembly. A plastic preform is provided having a
body with a closed end, and a neck extending from the body, the neck having an
open end and a radially outwardly extending flange surrounding the open end.
The
flange has an open channel proximal to the outer surface of the neck. A finish
ring is
provided having an annular body and an outer surface with an attachment
portion for
securing a closure. An annular lip extends from the body of the finish ring.
The
finish ring and. preform are assembled such that the ring is received over the
outer
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surface of the neck and the annular lip is received in and engages at least a
portion
of the channel.
[06] In accordance with another embodiment of the invention, a finish
assembly is provided for a plastic container or preform. The assembly includes
a
plastic neck having an open end surrounded by an external flange, the flange
having
an open channel proximal to an outer surface of the neck. The assembly further
includes a plastic finish ring having an annular body with an inner surface
positioned
opposite the outer surface of the neck, and an outer surface having an
attachment
portion for securing a closure. An annular lip on the finish ring extends into
and
engages at least a portion of the channel.
[07] In a further embodiment, a preform assembly is provided for blow
molding a plastic container. The assembly includes a plastic preform having a
body
with a closed end which is blow molded to form a container, and a neck
extending
axially from the body and having an open end with a radially outwardly
extending
flange. The flange has an annular undercut forming an open channel on an
underside of the flange. The assembly further includes a finish ring having an
annular body disposed over the neck of the preform, and an outer surface
having at
least one external thread. An annular lip on the ring extends into and engages
at
least a portion of the channel.
(08] In various described embodiments of the invention, the engaging
portions of the lip and channel comprise one or more facing surfaces which
enable
sealing of the finish ring against the flange. The channel, which may be
extracted
from or molded into the underside of the flange, produces a radially-extending
top
flange portion and a downwardly projecting outer flange projection or lip. The
outer
flange lip is generally axially aligned with the channel (and with the preform
neck
central axis). This lip on the flange has at least one facing surface which
matches an
opposed facing surface on the annular lip of the finish ring, to seal the ring
and
flange. The facing surfaces may, for example, form mating conical surfaces.
The
facing surfaces may extend to the outer surfaces of the finish ring and
flange, to
thereby retard or prevent the entrance of any fluid between the preform neck
and
finish ring. The finish ring lip and preform channel may be in complete
abutment, or
there may be a gap between at least a portion of the lip and channel so long
as
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another portion seals the lip and channel. The lip and channel may
alternatively
have stepped facing surfaces.
[09] Generally, each of the finish ring and preform neck are annular bodies
have axially elongated inner and outer annular engaging surfaces,
respectively. The
finish ring thus forms a collar around the preform neck.
[10] The finish ring may be used to provide a substantially thicker finish
portion to the neck of the preform or container, compared to a sidewall of the
container. The finish ring may be of a different plastic material than the
preform or
container neck, thus, providing different performance characteristics. The
finish ring
may be treated (e.g., thermally) either prior to or subsequent to its assembly
with the
neck, to provide different properties (even if made of the same material as
the neck).
The finish ring may be slid over the bottom end and onto the neck of the
preform,
followed by blow molding of the preform body to form a container.
[11] Other various embodiments of the invention can be understood from
the following description and accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[12] FIG. 1 is an elevational view of a preform assembly in accordance with
one embodiment of the invention;
[13] FIG. 2 is an exploded perspective view of the preform assembly
illustrated in FIG. 1;
[14] FIG. 3 is a fragmentary sectional view taken substantially along the line
3-3 in FIG. 1;
[15] FIG. 3A is a fragmentary sectional view on an enlarged scale of the
upper end of the preform neck illustrated in FIG. 3;
[16] FIG. 3B is a fragmentary sectional view on an enlarged scale of the
upper end of the finish ring illustrated in FIG. 3;
[17] FIGS. 4 and 5 are fragmentary sectional views, similar to that of FIG. 3,
but illustrating modified embodiments of the finish ring and preform neck;
[18] FIG. 6 is a perspective view of a preform and finish ring for providing a
preform assembly in accordance with another embodiment;
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[19] FIG. 7 an enlarged fragmentary sectional view of the preform neck and
finish ring taken substantially along the line 7-7 in FIG. 6; and
[20] FIG. 8 is a fragmentary sectional and partially schematic view of a
finish ring and preform neck, similar to the preform assembly shown in FIGS. 6-
7,
and further illustrating a blow molded container portion made from the body
portion
of the preform.
DETAILED DESCRIPTION
[21] FIGS. 1-3B illustrate a preform assembly 10 in accordance with one
embodiment of the invention. The assembly 10 includes a preform 12 and a
finish
ring 14 assembled thereto.
[22] Preform 12 includes a body 16 with a closed lower end 18 and an
integrally formed neck 20 with an external flange 22 extending radially
outwardly
from the open end of the neck. Neck 20 is generally of cylindrical
construction, and
flange 22 is circumferentially continuous and substantially perpendicular to
the
central longitudinal axis of the preform neck 20 (shown by line 3-3 in FIG. 1
). An
open channel (or undercut) 24 (FIGS. 3 and 3A) is formed on the undersurface
33 of
flange 22, such as by being molded into the flange or formed in the flange in
a post-
molding operation, thus leaving a top portion 25 above the channel and a
downwardly extending projection or lower lip 23 on the flange 22. As best seen
in
FIG. 3A, channel 24 has a generally radially outwardly facing surface 26 that
preferably is a continuation of the radially outwardly facing surface 28 of
preform
neck 20, an annular undersurface 30 adjacent (and substantially perpendicular)
to
surface 26, and an inclined (at less than 90° with respect to the
central neck axis)
radially inwardly facing surface 32 (see Fig. 3A) extending from the outer
edge of
channel undersurface 30. In this example, the inclined surface 32 is of
conical
construction with respect to the longitudinal neck axis. Conical surface 32
preferably
is at an angle of about 30° to the central axis of the preform neck 20.
The annular
undersurface 30 of channel 24 preferably lies in a plane substantially
perpendicular
to the axis of neck 20. Similarly, the annular undersurface 33 of the outer
flange lip
23 preferably lies in a plane substantially perpendicular to the axis of neck
20.
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[23] Finish ring 14 preferably is of molded plastic construction, and may be
of a different or the same plastic material as preform 12. If the same
material is
used, the molded finish ring may be processed differently than the preform to
provide
different properties. The finish ring 14 has an elongated annular body 34 with
an
integrally formed axially extending upper lip 36. Ring body 34 and lip 36
preferably
are circumferentially continuous. Lip 36 has an inner surface 38 (FIG. 3B)
preferably
formed as an extension of the inner surface 40 of ring body 34, both
preferably being
cylindrical. Lip 36 also has an upper end surface 42, which preferably lies in
a plane
perpendicular to the longitudinal axis of ring 14 (same as the neck axis), and
a
radially outwardly facing conical surface 44 that extends from the outer edge
of
upper surface 42. Conical surface 44 preferably is complementary to conical
surface
32 on preform flange lip 23, preferably at an angle of about 30°, so
that the two
facing surfaces will abut one another in sealing engagement. A second upper
surface 46 on ring 14, which may be parallel to or angled with respect to
uppermost
surface 42, extends from conical surface 44 to the radially outer surface 48
of ring
body 34. Ring body 34 also includes at least one external thread, bead or
other
means 50 for securing a closure to the final container (FIG. 8). In the
exemplary
embodiments illustrated in the drawings, ring body 34 also includes an annular
bead
52 for engagement by tamper-indicating means on the closure, and a support
flange
54 to facilitate subsequent handling of the preform and container.
[24] Preform 12 preferably is formed in a compression or injection molding
operation. Finish ring 14, which preferably is itself formed in a suitable
plastic
molding operation, can be slid over the closed end of the preform so that the
radially
inner surface 40 of finish ring 14 is in close sliding engagement with the
radially outer
surface 28 of preform neck 20. The above-noted pending applications disclose
various techniques for assembling finish ring 14 over neck 20 and securing the
finish
ring to the neck, such as by interference press fit, alone or enhanced by
adhesive
and/or ultra-sonic welding. The assembly of finish ring 14 over preform neck
20
continues until lip 36 on finish ring 14 is received within channel 24 on
preform neck
flange 22 and conical surfaces 44, 32 are brought into abutting facing
engagement.
Such abutting facing engagement of surfaces 44, 32 helps prevent any flow of
liquid
between the opposing surfaces of the finish ring and the preform neck. The
axial
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dimension (depth) of channel 24 may be less than the axial dimension (height)
of the
finish lip 36 so that there is a gap 56 (FIG. 3) between preform flange 22 and
finish
ring surface 46 when assembled, which helps ensure that conical facing
surfaces 44,
32 are in seating engagement. In FIG. 3, the gap 56 is between the lower lip
23 (see
FIG. 3A) of flange 22 and upper surface 46 (see FIG. 3B) of finish ring 14.
[25] FIGS. 4 and 5 illustrate other preform assemblies 60, 62 in accordance
with respective modified embodiments of the invention. Reference numerals in
FIGS. 4 and 5 that are identical to those in FIGS. 1-3B indicate identical or
related
components. The primary difference between preform assembly 60 in FIG. 4 and
preform assembly 10 in FIGS. 1-3 is that preform flange 22a and/or finish ring
lip 36a
is/are dimensioned so that there is abutting engagement for both of lower
surfaces
30, 33 (FIG. 3A) on flange 22a and upper surfaces 42, 46 (FIG. 3B),
respectively, on
finish ring 14a. In other words, the channel flange and the finish ring lip
are
dimensioned to eliminate gap 56 in FIG. 3. As a further alternative, there can
be a
gap provided between surfaces 30, 42 (FIGS. 3A and 3B) in the embodiment of
FIG.
4. In FIG. 5, neck flange 22b has a channel in which conical surface 32b
extends to
the outer edge of the flange, and conical surface 44b on finish ring lip 36b
extends to
the outer surface of the finish ring, which is to say that engaging surfaces
33 (FIG.
3A) and 46 (FIG. 3B) are eliminated.
[26] FIGS. 6-8 illustrate a further embodiment wherein the assembled
preform and neck finish are used to form a blow molded container 64. FIG. 6
illustrates a finish ring 14c, shown separately below, and assembled with a
preform
12c in the upper portion of the figure. FIG. 7 is an enlarged fragmentary
sectional
view of the assembled preform neck 20c and finish ring 14c of FIG. 6. FIG. 8
shows
the assembly of FIGS. 6-7 after blow molding of the preform body 16c to form a
container body 60c. The resulting container 64 thus includes the unexpanded
preform neck 20c integral with container body 60c, and finish ring 14c
positioned
over neck 20c.
[27] Preforms may be of any suitable plastic construction, such as
monolayer PET or multilayer construction of PET layers alternating with layers
of
barrier resin such as ethylene vinyl alcohol (EVOH) or nylon. Preforms may be
injection molded or compression molded. Likewise, finish rings may be of
injection
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or compression molded plastic construction. By providing finish rings separate
from
preforms, the finish rings may be of any desired material construction, either
the
same as.or more preferably different from the material construction of the
preform.
For example, the finish ring can be of PET, post consumer resin (PCR), process
regrind (REG), polypropylene (PP), polyethylene (PE) or polyethylene
naphthalate
(PEN) construction. Where the finish ring is of polyester construction (e.g.,
PET,
PEN or process regrind), the finish ring may be wholly or partially
crystallized as
molded. This may be accomplished by employing fast-crystallizing materials, or
suitably setting process conditions for manufacture of the finish ring, such
as high
mold temperature, slow mold cooling, heated areas in the mold cavity, etc. The
finish ring alternatively may be wholly or partially crystallized in a post-
molding
operation. In other words, the material and conditions of fabrication of the
finish ring
may be selected separately from the material and manufacturing conditions of
the
preform to achieve desired operating characteristics at the finish area of the
preform
and the final container. Furthermore, the preform can be molded with thin wall
sections without having to accommodate flow of material into a thicker finish
area,
which reduces material cost and mold cycle time. The finish ring is secured to
the
neck of the preform by interference fit (e.g., press fit or shrink fit),
adhesive or
welding. The finish ring and/or the preform neck can be provided with suitable
means for preventing rotation of the ring on the neck.
[28] Other embodiments of the invention will be apparent to those skilled in
the art from consideration of the specification and practice of the invention
disclosed
herein. It is intended that the specification and examples be considered as
exemplary only, with a true scope of the invention being indicated by the
following
claims.
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