U.S. patent application number 11/599873 was filed with the patent office on 2007-03-15 for swage-forming of container threads.
This patent application is currently assigned to Graham Packaging PET Technologies Inc.. Invention is credited to Keith J. Barker, Bassam M. Kalmouni, Brian A. Lynch, Thomas E. Nahill.
Application Number | 20070059462 11/599873 |
Document ID | / |
Family ID | 32594736 |
Filed Date | 2007-03-15 |
United States Patent
Application |
20070059462 |
Kind Code |
A1 |
Nahill; Thomas E. ; et
al. |
March 15, 2007 |
Swage-forming of container threads
Abstract
A method of making a plastic container having a threaded
wide-mouth finish includes providing a preform having at least an
exterior surface of molded polyester construction. The preform is
placed in a mold cavity having a first portion for forming a
container body, a second portion adjacent to the first portion for
forming a cylindrical finish wall without threads, and a third
portion adjacent to the second portion for forming a trim dome or
moil. The preform is expanded within the mold cavity to form a
one-piece intermediate product that includes a body, a cylindrical
wide-mouth finish wall and a moil. After removing the intermediate
product from the cavity, the moil is severed from the end of the
finish wall. At least one thread is then formed on the finish wall
by engaging the finish wall with at least one thread-forming tool,
which may be heated to facilitate the forming operation.
Inventors: |
Nahill; Thomas E.; (Amherst,
NH) ; Barker; Keith J.; (Candia, NH) ; Lynch;
Brian A.; (Merrimack, NH) ; Kalmouni; Bassam M.;
(Pembroke, NH) |
Correspondence
Address: |
RISSMAN JOBSE HENDRICKS & OLIVERIO, LLP
ONE STATE STREET
SUITE 800
BOSTON
MA
02109
US
|
Assignee: |
Graham Packaging PET Technologies
Inc.
York
PA
17402
|
Family ID: |
32594736 |
Appl. No.: |
11/599873 |
Filed: |
November 15, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10329666 |
Dec 24, 2002 |
7138082 |
|
|
11599873 |
Nov 15, 2006 |
|
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|
Current U.S.
Class: |
428/34.1 ;
264/533; 264/534 |
Current CPC
Class: |
Y10T 428/13 20150115;
B29C 2793/009 20130101; B29L 2031/7158 20130101; Y10T 428/1352
20150115; B29C 49/76 20130101; B29C 49/42 20130101; B29C 49/74
20130101; B29L 2031/716 20130101; B29K 2077/00 20130101; B65D 1/023
20130101; B29C 49/06 20130101; B29K 2995/0067 20130101; B29K
2067/00 20130101 |
Class at
Publication: |
428/034.1 ;
264/533; 264/534 |
International
Class: |
B29C 49/00 20060101
B29C049/00; B31B 45/00 20060101 B31B045/00 |
Claims
1-8. (canceled)
9. A wide-mouth blow molded plastic container that includes a
hollow body and a cylindrical wide-mouth finish wall integrally
blow molded with said body, said blow-molded wide-mouth finish wall
having a diameter less than that of the blow molded body, and said
finish wall having at least one thread swage-formed in said finish
wall.
10. The container set forth in claim 9 wherein said at least one
thread comprises at least one external thread, and wherein at least
an exterior surface portion of said finish wall is of PET
construction.
11. The container set forth in claim 10 wherein at least an
exterior surface portion of said finish wall is crystallized.
12. The container set forth in claim 9 wherein said finish wall,
including said at least one thread, is of substantially uniform
wall thickness between radially inner and outer surfaces of said
wall, including said at least one swage-formed thread.
13. The container set forth in claim 9 wherein said finish wall is
of PET construction throughout.
14. The container set forth in claim 9 wherein said at least one
thread is an external thread.
15. The container set forth in claim 9 wherein said finish wall
includes a swage-formed top sealing surface.
16. The container set forth in claim 9 wherein said blow-molded
wide mouth finish wall is strain hardened.
17. The container set forth in claim 9 wherein said at least one
thread is an internal thread.
18. The container set forth in claim 9 wherein said finish wall
includes multiple layers.
Description
[0001] The present invention is directed to wide-mouth containers,
and more particularly to a method of forming threads on a container
finish of polyester construction, particularly PET.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] In the manufacture of plastic containers, such as monolayer
or multilayer PET containers, it is conventional to mold a
container preform having a body and a finish with one or more
external threads. The finish typically is molded to its final
geometry in the preform, while the body of the preform is
subsequently blow molded to the desired geometry of the container
body. Although this manufacturing technique is satisfactory for
fabrication of containers with narrow-neck finish diameters, the
throughput of the process is greatly reduced when employed for
fabricating preforms and containers of larger finish diameters. For
example, a preform mold cavity block that has ninety-six mold
cavities for preforms with a 28 mm finish diameter would typically
accommodate only forty-eight cavities having a 43 mm finish
diameter for the same overall cavity block size. This throughput is
even further reduced for wide-mouth preforms having a finish
diameter greater than about 2.0 inches or 50 mm.
[0003] To address this manufacturing throughput problem, it has
been proposed to fabricate a wide-mouth container by molding a
narrow-neck preform and then blow molding the preform body within a
cavity that forms the container body, a container finish with
external threads, and a trim dome or moil. The trim moil must be
removed from the container body and finish, along with the preform
finish, after the container is removed from the blow mold. A
problem with this technique is that the external threads on the
container finish are blow molded, and are not as sharply defined
and detailed as desired. Furthermore, this thread definition and
are not as sharply defined and detailed as desired. Furthermore,
this thread definition problem is exacerbated in the case of
containers having at least an external surface of polyester
construction, such as PET, because the polyester material can
strain harden as it expands during blow molding, making it more
difficult to force the finish material into the thread-forming
portions of the blow mold. It is therefore a general object of the
present invention to provide a method of making a plastic
wide-mouth container, and/or a plastic wide-mouth container formed
by such method, in which the container threads are formed in a
post-molding operation so as to possess improved quality and
definition.
[0004] In accordance with one aspect of the present invention, a
method of making a plastic container having a threaded wide-mouth
finish includes providing a preform of molded plastic construction.
The preform is placed in a mold cavity having a first portion for
forming a container body, a second portion adjacent to the first
portion for forming a cylindrical finish wall without threads, and
a third portion adjacent to the second portion for forming a trim
dome or moil. The preform is expanded within the mold cavity to
form a one-piece intermediate container product that includes a
body, a cylindrical wide-mouth finish wall without threads, and a
trim moil. After removing the intermediate product from the cavity,
the moil is severed from the end of the finish wall. At least one
internal or external thread is then formed on the finish wall by
engaging the finish wall with at least one thread-forming tool. In
the preferred method of the invention, the cylindrical finish wall
is exteriorly engaged by at least one first tool having at least
one groove segment. The cylindrical finish wall is simultaneously
interiorly engages by at least one second tool having at least one
rib segment, complimentary to the at least one groove segment, to
force portions of the cylindrical finish wall into the groove
segment and thereby form at least one external thread. One or both
of the first and second tools may be heated to facilitate the
forming operation.
[0005] A wide-mouth blow molded plastic container in accordance
with a second aspect of the present invention includes a hollow
body and a cylindrical wide-mouth finish integrally blow molded
with the body. The finish has at least one internal or external
thread swage-formed in the finish wall after molding. At least the
exterior surface portion of the finish wall preferably is of PET
construction.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] The invention, together with additional objects, features
and advantages thereof, will be best understood from the following
description, the appended claims and the accompanying drawings in
which:
[0007] FIG. 1 is a sectioned schematic drawing that illustrates a
plastic preform placed in a blow mold in accordance with one aspect
of the present invention;
[0008] FIG. 2 illustrates an intermediate container product blow
molded in the mold of FIG. 1;
[0009] FIG. 3 illustrates an externally threaded wide-mouth
container fabricated in accordance with an exemplary but presently
preferred implementation of the present invention;
[0010] FIG. 4 is a sectional view on an enlarged scale of the
portion of FIG. 3 within the area 4;
[0011] FIG. 5 is a schematic diagram of an apparatus for forming
the container finish external threads in the container of FIGS. 3
and 4; and
[0012] FIG. 6 is a schematic diagram of an alternative apparatus
for forming the finish external threads in the container of FIGS. 3
and 4.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] The terms "narrow-neck" finish and "wide-mouth" finish are
employed in their conventional senses in the present application,
in that a "wide-mouth" finish has an outside diameter (E diameter)
greater than about 2.0 inches or 50 mm, while a "narrow-neck"
finish has an outside diameter equal to or less than about 2.0
inches or 50 mm. A 63 mm finish is a conventional relatively small
wide-mouth finish in the plastic container industry, although the
present invention is by no means limited to wide-mouth finishes of
this particular size. An 83 mm finish is a larger conventional
wide-mouth finish size.
[0014] FIG. 1 illustrates a preform 10 as comprising a body 12 and
an integrally molded upper portion or finish 14. Preform 10
typically is fabricated in an injection molding or compression
molding operation. Preform 10 is positioned in a blow mold 18, with
preform body 12 being disposed within a cavity 20 formed by mold
18. Application of air under pressure to the interior of preform 10
expands preform body 12 to the confines of mold cavity 20. The
resulting intermediate container product 22 is illustrated in FIG.
2 as including a hollow body 24 and an integral cylindrical finish
wall 26 without external threads. A trim dome or moil 28 extends
upwardly from the upper end of finish wall 26, and terminates in
upper portion 14 of preform 10. (It will be appreciated that
directional words such as "upper" and "lower" are employed by way
of description and not limitation with respect to the upright
orientation of the mold, preform, intermediate product and
container illustrated in the drawings. Directional words such as
"radial" and "circumferential" are employed by way of description
and not limitation with respect to the axis of the container
finish.)
[0015] Trim moil 28 and upper preform portion 14 are severed from
finish wall 26 by 20 means of a suitable blade 30 (FIG. 2). One or
more external threads 32 are then formed on cylindrical finish wall
26 to provide the wide-mouth container 34 illustrated in FIG. 3.
Container 34 includes body 24, finish cylindrical wall 26
integrally extending from body 24, and one or more external threads
32 formed in cylindrical wall 26 after the blow molding
operation.
[0016] Cylindrical finish wall 26 has an external diameter in final
container 34 greater than about 2.0 inches or 50 mm--i.e.,
container 34 is a wide-mouth container. FIG. 4 illustrates threads
32 formed on finish wall 26. There are indentations or channels on
the inside surface of finish wall 26 corresponding to the external
geometry of threads 32, and finish wall 26 is generally of uniform
radial thickness throughout its height and circumference.
[0017] FIGS. 5 and 6 illustrate two exemplary techniques for
forming external threads 32 in container finish wall 26 in an
after-molding operation. The apparatus 40 of FIG. 5 includes a pair
of rollers 42, 44 for disposition inside of and outside of finish
wall 26 respectively. Internal roller 42 has one or more external
spiral beads or ribs 46, and external roller 44 has one or more
internal spiral channels or recesses 48. Tooling generally
indicated at 50 brings rollers 42,44 into opposed engagement with
the internal and external surfaces of finish wall 26, and the
rollers are rotated with respect to each other to form external
threads 32 (FIGS. 3 and 4) on wall 26. These threads are formed by
forcing the material of wall 26 radially outwardly into channel 48
on roller 44. Rollers 42, 44 preferably are heated to facilitate
this forming operation. As an alternative, rollers 42, 44 may be at
room temperature, so that the threads on finish wall 46 are cold
formed with the necessary heat being supplied at the molecular
level. Tooling 50 may be caused to orbit around a stationary
container finish 26, or container body 24 alternatively may be
positioned on a rotatable table 52.
[0018] FIG. 6 illustrates an alternative exemplary thread forming
apparatus 60. External arcuate formers 62 have recessed thread
portions or channels 64, and an internal plug 66 has one or more
external beads or ribs 68. Plug 66 is positioned by an actuator 70
or the like within finish wall 26, and external formers 62 are
moved radially inwardly against the outside surface of wall 26.
Formers 62 shrink finish wall 26 onto plug 68 so that external
finish threads 32 (FIGS. 3 and 4) are formed in the finish wall.
External formers 62 are then expanded radially outwardly and
internal plug 70 is withdrawn from the finish, either axially as
illustrated in FIG. 6 or by unthreading the plug from the inside of
the finish wall. Formers 62 and plug 66 preferably are heated, as
in the embodiment of FIG. 5, although cold forming may also be
employed.
[0019] It is preferred to heat finish wall 26 during the thread
forming operation. This heating preferably is carried out by
conduction from rollers 42, 44 in FIG. 5, or formers 62 and plug 66
in FIG. 6. The finish wall preferably is heated to a level above
room temperature, such as in the range of 50.degree. C. to
100.degree. C. for PET finishes. The temperature of the finish wall
should not exceed the glass transition temperature Tg of the finish
wall material by more than about 40 to 50.degree. C. For example,
finish wall heating to a level of 120.degree. C. or above can cause
distortion and warping in a PET finish wall. Five seconds of
contact time is ample for thread formation when cylindrical wall 26
has a thickness of 0.5 to 1 mm (0.019 to 0.039 inch). A lesser
contact time, such as on the order of one second, is generally not
adequate unless the finish wall is very thin, which is not
desirable. Thus, one or more external threads are swage formed on
the E wall of container finish 26.
[0020] As noted above, the present invention finds particular
utility in connection with containers in which at least the outer
surface portion of the finish wall is of polyester construction,
particularly polyethylene terephthalate (PET). This is because
radial expansion of finish wall 26 during blow molding can strain
harden the PET material, and makes it more difficult to obtain
desired thread sharpness and definition during the blow molding
operation in the prior art. Preform 12 and container 34 may be of
monolayer or multilayer construction. A typical preform 10 may have
multiple layers, including internal and external layers of PET
construction, and one or more intermediate layers of barrier
material such as ethylene vinyl alcohol (EVOH) or polyamide (such
as nylon). The intermediate layer or layers are disposed in preform
body 12 (FIG. 1), and may or may not extend into preform upper
portion 14. It is preferable that the intermediate layer or layers
not extend into dome 28 in intermediate product 22, so that the
intermediate layer or layers are not exposed at the end of finish
wall 26 by severing moil 28 with blade 30. Finish wall 26 may be of
PET construction throughout, with the intermediate barrier layer or
layers being disposed in container body 24. At least the exterior
surface of finish wall 26 may be crystallized before or during
formation of threads 32 to prevent shrinkage or distortion. The
finish alternatively could be through-crystallized. This would be
particularly desirable in hot-fill applications, where the
temperature of the material placed in the container might otherwise
cause shrinkage or distortion of the container finish.
Crystallization of the container finish may extend throughout the
radial depth and axial length of the finish, if desired.
[0021] There have thus been disclosed a container and method of
manufacture that fully satisfy all of the objects and aims
previously set forth. The container and method of manufacture have
been disclosed in conjunction with several embodiments thereof, and
a number of modifications and variations have been discussed. Other
modifications and variations will readily suggest themselves to
persons of ordinary skill in the art. For example, tooling could be
provided on rollers 42, 44, or on external former 62 and plug 66,
to swage-form the top sealing surface at the axially upper edge of
the finish wall. Trim moil 28 may be of any convenient geometry,
and preform finish 14 may be with or without threads as convenient.
The invention has been discussed in conjunction with formation of
external threads; however, internal threads alternatively can be
formed on the container finish employing the same techniques. The
invention is intended to embrace all such modifications and
variations as fall within the spirit and broad scope of the
appended claims.
* * * * *