U.S. patent application number 10/746319 was filed with the patent office on 2005-06-30 for swage-forming of container or preform internal threads.
Invention is credited to Larsen, W. Bruce, Nahill, Thomas E..
Application Number | 20050139569 10/746319 |
Document ID | / |
Family ID | 34700627 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050139569 |
Kind Code |
A1 |
Larsen, W. Bruce ; et
al. |
June 30, 2005 |
Swage-forming of container or preform internal threads
Abstract
A method of making a plastic container having a body and an
internally threaded finish includes providing a preform of molded
plastic construction having a body and an integral neck, and
expanding the body of the preform within a mold cavity to form the
body of the container. Either prior to or subsequent to blow
molding the container body, at least one internal thread is formed
in the neck by engaging an inner surface of the neck with a first
rotary tool having a peripheral channel, engaging an outer surface
of the neck with a second rotary tool having a peripheral bead, and
causing rotation of the neck and tools to swage at least one
internal thread in the neck.
Inventors: |
Larsen, W. Bruce; (Holland,
OH) ; Nahill, Thomas E.; (Amherst, NH) |
Correspondence
Address: |
VENABLE LLP
P.O. BOX 34385
WASHINGTON
DC
20435-9998
US
|
Family ID: |
34700627 |
Appl. No.: |
10/746319 |
Filed: |
December 24, 2003 |
Current U.S.
Class: |
215/44 ; 264/312;
264/318 |
Current CPC
Class: |
B29B 2911/14326
20130101; B29B 2911/14066 20130101; B29B 2911/14333 20130101; B29K
2105/258 20130101; B29B 2911/14226 20130101; B29L 2031/7158
20130101; B29C 2049/021 20130101; B29K 2623/086 20130101; B29B
2911/14126 20130101; B29B 2911/14331 20150501; B29K 2995/0043
20130101; B29B 2911/14153 20130101; B29C 2049/2026 20130101; B29C
2049/2043 20130101; B29B 2911/1446 20130101; B65D 1/0246 20130101;
B29B 2911/1458 20130101; B29C 59/007 20130101; B29K 2067/00
20130101; B29B 2911/14453 20130101; B29B 2911/14337 20150501; B29B
2911/14033 20130101; B29B 2911/14026 20130101; B29B 2911/14106
20130101; B29B 2911/14133 20130101; B29K 2023/06 20130101; B29B
2911/14093 20130101; B29C 49/0073 20130101; B29B 2911/1404
20130101; B29B 2911/14053 20130101; B29B 2911/14606 20130101; B29K
2023/12 20130101; B29C 49/02 20130101; B29B 2911/14328 20150501;
B29B 2911/1442 20130101; B29C 49/22 20130101; B29B 2911/14146
20130101; B29B 2911/14466 20130101; B29B 2911/1402 20130101; B29B
2911/14213 20130101; B29K 2077/00 20130101; B29B 2911/1408
20130101; B29C 57/00 20130101; B29B 2911/1412 20130101; B29C 49/06
20130101; B29C 49/76 20130101; B29B 2911/14233 20130101; B29K
2995/0041 20130101; B29K 2023/086 20130101; B29B 2911/1444
20130101; B29B 2911/14335 20150501 |
Class at
Publication: |
215/044 ;
264/312; 264/318 |
International
Class: |
B65B 007/28 |
Claims
1. A method of making a plastic container having a body and an
internally threaded finish, which includes the steps: (a) providing
a preform of molded plastic construction having a body and an
integral neck, (b) expanding said body of said preform within a
mold cavity to form said body of said container, and (c) either
prior to or subsequent to said step (b), forming at least one
internal thread in said neck by: (c1) engaging an inner surface of
said neck with a first rotary tool having a peripheral channel,
(c2) engaging an outer surface of said neck with a second rotary
tool having a peripheral bead, and (c3) causing rotation of said
neck and said tools to swage at least one internal thread in said
neck.
2. The method set forth in claim 1 wherein said step (c) includes
heating one or both of said tools.
3. The method set forth in claim 1 which includes the step,
following said step (c3), of: (d) placing a finish ring with at
least one external thread over said neck to form a container having
a finish with both internal and external threads.
4. The method set forth in claim 1 wherein said step (a) includes
providing at least one molded external thread on said neck, such
that said neck has at least one external thread and at least one
internal thread following said step (c).
5. A method of making an internally threaded finish on a plastic
preform or container, which includes the steps of: (a) providing a
plastic neck on the preform or container without internal threads,
and (b) forming at least one internal thread in said neck by: (b1)
engaging an inner surface of said neck with a first rotary tool
having a peripheral channel, (b2) engaging an outer surface of said
neck with a second rotary tool having a peripheral bead, and (b3)
causing rotation of said neck and said tools to swage at least one
internal thread in said neck.
6. The method set forth in claim 5 wherein said step (c) includes
heating one or both of said tools.
7. The method set forth in claim 5 which includes the step,
following said step (c3), of: (d) placing a finish ring with at
least one external thread over said neck to form a container having
a finish with both internal and external threads.
8. The method set forth in claim 5 wherein said step (a) includes
providing said neck with at least one external thread, such that
said neck has at least one external thread and at least one
internal thread following said step (c)
9. A plastic container made in accordance with the method set forth
in claim 1.
10. A finish on a plastic container or preform made in accordance
with the method set forth in claim 5.
11. A finish on a plastic container or preform made in accordance
with the method set forth in claim 8.
12. A finish on a plastic container or preform, which includes: a
cylindrical neck of substantially uniform wall thickness and having
at least one internal thread, and a finish ring secured over said
neck and having at least one external thread.
13. A finish on a plastic container or preform, which includes: a
cylindrical neck having at least one internal thread and at least
one external thread.
14. The finish set forth in claim 13 wherein said neck is of molded
plastic construction, said at least one external thread is
integrally molded with said neck, and said at least one internal
thread is swage-formed on said neck.
Description
[0001] Reference is made to copending application Ser. No.
10/329,666 filed Dec. 24, 2002.
[0002] The present application is directed to plastic containers
and preforms for blow molding plastic containers, and more
particularly to a method of forming internal threads on the preform
or container finish.
BACKGROUND AND SUMMARY OF THE INVENTION
[0003] In the manufacture of plastic containers, such as monolayer
or multilayer polyethylene terephthalate (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. However, this manufacturing technique is not well
suited for fabrication of preforms or containers having internal
threads because, among other reasons, it is difficult to strip a
preform having molded internal threads from its forming mold. It is
therefore a general object of the present invention to provide a
method of forming internal threads in the finish of a molded
plastic preform or container, and to provide a preform or container
finish manufactured in accordance with such method.
[0004] A method of making a plastic container having a body and an
internally threaded finish, in accordance with one presently
preferred aspect of the invention, includes providing a preform of
molded plastic construction having a body and an integral neck, and
expanding the body of the preform within a mold cavity to form the
body of the container. Either prior to or subsequent to blow
molding the container body, at least one internal thread is formed
in the neck by engaging an inner surface of the neck with a first
rotary tool having a peripheral channel, engaging an outer surface
of the neck with a second rotary tool having a peripheral bead, and
causing rotation of the neck and tools to swage at least one
internal thread in the neck.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] The invention, together with additional objects, features,
advantages and aspects thereof, will be best understood from the
following description, the appended claims and the accompanying
drawings, in which:
[0006] FIG. 1 is a perspective view of a container preform molded
without threads in accordance with one aspect of the present
invention;
[0007] FIG. 2 is a schematic diagram that illustrates swaging
internal threads in the preform of FIG. 1;
[0008] FIG. 3 is a schematic diagram that illustrates swaging
internal threads in a container molded from the preform of FIG.
1;
[0009] FIG. 4 is a sectional view of the portion of FIG. 3 within
the area 4;
[0010] FIG. 5 is an exploded fragmentary perspective view of a
preform or container finish assembly having both internal and
external threads in accordance with another aspect of the present
invention;
[0011] FIG. 6 is a schematic diagram that illustrates swaging
internal threads in a preform having molded external threads;
and
[0012] FIG. 7 is a sectional view of a preform having molded
external threads and swaged internal threads.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0013] FIG. 1 illustrates an exemplary container preform 10 having
a body 12 and an integral neck 14. Neck 14 preferably is
cylindrical in contour, and has no internal or external threads in
this embodiment as molded. The specific preform 10 illustrated in
FIG. 1 is molded with an external stop bead 16 for cooperating with
tamper-indicating structure in a closure secured to the final
container, and a support flange 18 that facilitates handling of the
preform and the container. Bead 16 and flange 18 are optional.
Cylindrical neck 14 is of generally uniform radial wall thickness.
Preform 10 can be injection molded or compression molded of
monolayer plastic construction such as PET, or of multilayer
plastic construction having matrix or structural layers of PET, for
example, and one or more intermediate layers of barrier material
such as ethylene vinyl alcohol (EVOH) or nylon. The barrier layers
may or may not extend into preform neck 14.
[0014] In accordance with one aspect of the present invention,
internal threads are swage-formed in neck 14 either prior to or
subsequent to blow molding preform body 12. As illustrated in FIG.
2, one or more internal threads 20 are swaged in preform neck 14
prior to blow molding preform body 12. These threads 20 are swaged
into the preform neck by means of a first rotary tool 22 that
engages the inner surface of neck 14, and a second rotary tool 24
that engages the outer surface of neck 14. Inner tool 22 includes a
disk 26 with a peripheral channel 28. Outer tool 24 includes a disk
30 having a peripheral bead or rib 32. With tool 22 in engagement
with the internal surface of neck 14 and tool 24 engaged with the
external surface of neck 14, the tools (and preform) are rotated so
that bead 32 deforms or swages the plastic material of neck 14 into
channel 28 on tool 22. This deformation can be assisted and
promoted, if desired, by heating one or both of the tools 22, 24.
After the internal threads 20 are formed in neck 14, preform 10 is
placed in a suitable blow mold, and preform body 12 is blow molded
to form the body 12a (FIG. 3) of a container.
[0015] FIG. 3 illustrates an alternative technique for swaging
internal threads 20 in preform neck 14 after blow molding container
body 12a. Reference numerals in FIG. 3 that are identical to those
in FIGS. 1-2 indicate identical parts. Whether the internal threads
are swaged in the preform neck prior to or subsequent to blow
molding the preform body, the neck 14 remains of substantially
uniform radial thickness as illustrated in FIG. 4.
[0016] FIG. 5 illustrates a method of forming a preform or
container having both internal and external threads in the preform
or container finish. After swaging one or more internal threads 20
into the neck 14 of the preform or container (FIG. 2 or FIG. 3), a
separately made finish ring 34 is secured over the external surface
of neck 14. Finish ring 34 has one or more external threads 36
preformed therein. As a modification to FIG. 5, stop bead 16 and/or
support flange 18 may be formed in ring 34 rather than in the
preform. Thus, the final container in accordance with the
embodiment of FIG. 5 includes both internal and external threads,
with the internal threads being swaged into the container neck and
the external threads being formed on a separate finish ring.
[0017] FIGS. 6 and 7 illustrate another method of making a preform
having both internal and external threads. In this preform 40, the
preform is molded with external threads 42 on the preform neck 44.
After molding, and either prior to or subsequent to blow molding
the preform body, swage tools 22, 24 are used to form internal
threads 46 on neck 44.
[0018] It may be desirable to heat neck 14 during the thread
forming operation. This heating preferably is carried out by
conduction from tools 22, 24. The neck 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
neck preferably should not exceed the glass transition temperature
Tg of the neck material by more than about 40 to 50.degree. C. For
example, finish neck heating to a level of 120.degree. C. or above
can cause distortion and warping of the neck. Five seconds of
contact time is ample for thread formation when neck 14 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, may not be adequate
unless the finish neck is very thin, which would not be desirable
in the embodiments of FIGS. 1-4 but could be accommodated in the
embodiment of FIG. 5.
[0019] Thus, one or more internal threads are swage formed on the E
wall of preform and container neck 14. All or a portion of the
preform or container neck can be crystallized before or during
formation of internal threads 20 to prevent shrinkage or
distortion. This would be particularly desirable in hot-fill
applications, where the temperature of the material placed in the
container otherwise might cause shrinkage or distortion of the
container finish. Crystallization of the container finish can
extend throughout the radial thickness and the axial length of the
neck, including stop bead 16 and/or support flange 18 where
provided, if desired.
[0020] There have thus been disclosed a preform, a container and a
method of manufacture that fully satisfy all of the objects and
aims previously set forth. The preform, container and method of
manufacture have been disclosed in conjunction with several
presently preferred 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 can be
provided on rotary tools 22, 24 to swage-form the top sealing
surface at the axially upper edge of neck 14. The invention is
intended to embrace all such modifications and variations as fall
within the spirit and broad scope of the appended claims.
* * * * *