U.S. patent application number 11/675939 was filed with the patent office on 2007-07-05 for compression molding container preforms.
This patent application is currently assigned to Graham Packaging PET Technologies Inc.. Invention is credited to W. Bruce Larsen.
Application Number | 20070154586 11/675939 |
Document ID | / |
Family ID | 37744886 |
Filed Date | 2007-07-05 |
United States Patent
Application |
20070154586 |
Kind Code |
A1 |
Larsen; W. Bruce |
July 5, 2007 |
COMPRESSION MOLDING CONTAINER PREFORMS
Abstract
An apparatus for supplying a mold charge for a mold cavity in
accordance with one aspect of the present invention includes a mold
charge chamber having a longitudinal dimension and at least two
lateral inlets for supplying resin materials to the chamber such
that the materials are stratified longitudinally of the chamber. A
plunger is movable longitudinally into the chamber to force the
stratified materials out of the chamber and thereby provide a
stratified mold charge for a mold cavity. The at last two lateral
inlets to the chamber preferably are spaced from each other
lengthwise of the chamber. In one embodiment, the plunger has a
contoured end for imparting a contour to the mold charge as the
mold charge is forced from the chamber. A gate preferably is
positioned at an end of the chamber remote from the plunger for
selectively closing the chamber for filling and opening the chamber
for discharge of the mold charge.
Inventors: |
Larsen; W. Bruce; (Holland,
OH) |
Correspondence
Address: |
RISSMAN JOBSE HENDRICKS & OLIVERIO, LLP
ONE STATE STREET
SUITE 800
BOSTON
MA
02109
US
|
Assignee: |
Graham Packaging PET Technologies
Inc.
York
PA
|
Family ID: |
37744886 |
Appl. No.: |
11/675939 |
Filed: |
February 16, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10746404 |
Dec 24, 2003 |
7179071 |
|
|
11675939 |
Feb 16, 2007 |
|
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Current U.S.
Class: |
425/130 ;
425/412 |
Current CPC
Class: |
B29K 2105/251 20130101;
B29C 43/203 20130101; B29B 11/12 20130101; B29B 11/14 20130101;
B29C 31/10 20130101 |
Class at
Publication: |
425/130 ;
425/412 |
International
Class: |
B29C 43/20 20060101
B29C043/20 |
Claims
1-16. (canceled)
17. A method of supplying a mold charge to a mold cavity for
compression molding a plastic container preform, which includes the
steps of: (a) providing a mold charge chamber having a longitudinal
dimension and a lateral dimension that is uniform longitudinally of
said chamber and having at least two lateral inlets to said chamber
that are disposed between longitudinally spaced ends of said
chamber and are spaced from each other longitudinally of said
chamber, (b) filling said chamber through said inlets with at least
first and second resin materials that are stratified longitudinally
of said chamber, (c) discharging a stratified mold charge from said
chamber into a preform mold cavity, and then (d) compression
molding a container preform from said mold charge in said
cavity.
18. The method set forth in claim 17 wherein said step (a) includes
providing a plunger that is movable between a first position that
closes an upper end of a chamber and a second position that
substantially fills said chamber, and a gate that selectively
closes an end of said chamber opposite said plunger, wherein said
step (b) is carried out with said plunger in said first position
and said gate closed, and wherein said step (c) is carried out by
opening said gate and moving said plunger from said first position
to said second position.
19. The method set forth in claim 18 wherein said step (a) includes
contouring an end of said plunger to impart a contour to said mold
charge during said step (c).
20. The apparatus set forth in claim 18 further comprising an
actuator coupled to said plunger for moving said plunger from said
first position to said second position.
21. The apparatus set forth in claim 21 wherein said actuator is
selected from the group consisting of an electrical servo actuator
and a fluid actuator.
Description
[0001] The present invention relates to compression molding
preforms for subsequent blow molding as plastic containers, and
more particularly to an apparatus and method for feeding a plastic
resin mold charge into a mold cavity for compression molding a
container preform.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] In compression molding a preform for subsequent blow molding
as a plastic container, a mold charge is fed to a female
compression mold cavity and a male mold core is inserted into the
cavity to form the mold charge into a preform. This preform is
subsequently blow molded to form a plastic container. The mold
charge typically is fed to the mold cavity using a transfer wheel
or the like that obtains a mold charge from the outlet of an
extruder or other melt-phase transfer mechanism, and then releases
the mold charge to fall by gravity into the female mold cavity.
This transfer wheel and gravity drop technique is not sufficiently
fast for high-speed production of preforms and containers, and does
not consistently result in the desired placement and orientation of
the mold charge within the mold cavity. It is a general object of
the present invention to provide an apparatus and a method that
reduce mold charge transfer time as compared with the prior art,
and increase the accuracy of placement and orientation of the mold
charge within the mold cavity.
[0003] An apparatus for supplying a mold charge for a mold cavity
in accordance with one aspect of the present invention includes a
mold charge chamber having a longitudinal dimension and at least
two lateral inlets for supplying resin materials to the chamber
such that the materials are stratified longitudinally of the
chamber. A plunger is movable longitudinally into the chamber to
force the stratified materials out of the chamber and thereby
provide a stratified mold charge for a mold cavity. The at last two
lateral inlets to the chamber preferably are spaced from each other
lengthwise of the chamber. In one embodiment, the plunger has a
contoured end for imparting a contour to the mold charge as the
mold charge is forced from the chamber. A gate preferably is
positioned at an end of the chamber remote from the plunger for
selectively closing the chamber for filling and opening the chamber
for discharge of the mold charge.
[0004] Apparatus for compression molding preforms for blow molding
plastic containers in accordance with another aspect of the present
invention includes a mold charge chamber having a longitudinal
dimension and a lateral dimension that is uniform throughout the
length of the chamber. At least one lateral input to the chamber is
connected to a source of resin material to fill the chamber. A
plunger has a lateral dimension substantially equal to the lateral
dimension of the chamber, and is movable between a first position
that closes an upper end of the chamber and a second position in
which the plunger substantially fills the chamber. A gate is
positioned at an end of the chamber remote from the plunger for
selectively closing the chamber for filling and opening the chamber
for discharge of a mold charge as the plunger moves toward the
second position. A preform mold cavity is disposed to receive a
mold charge discharged from the mold chamber, and a mold core is
positioned to enter the mold cavity and compression mold a
container preform. In one preferred embodiment of the invention,
the at least one lateral inlet to the chamber includes at least two
lateral inlets that are spaced from each other longitudinally of
the chamber. The at least two inlets are connected to associated
sources of plastic resin material for supplying resin to the
chamber in such a way that the materials are stratified
longitudinally of the chamber. The mold charge supplied to the mold
cavity is thus stratified longitudinally of the mold charge, and is
adapted for compression molding preforms having layers of material
corresponding to the material stratification in the mold
charge.
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. 1A is a schematic diagram of an apparatus for supplying
a mold charge to a mold cavity in accordance with one exemplary
embodiment of the invention;
[0007] FIGS. 1B and 1C are schematic diagrams that illustrate
sequential stages of operation of the apparatus following the stage
of in FIG. 1A;
[0008] FIG. 2 is en elevational view of an exemplary preform made
with the apparatus of FIGS. 1A-1C;
[0009] FIG. 2A is a fragmentary sectional view of the portion of
the preform within the area 2A in FIG. 2;
[0010] FIG. 3 is a schematic diagram that shows a modification to
the apparatus of FIG. 1A; and
[0011] FIG. 4 is a sectional view that is similar to that of FIG.
2A but illustrates the layered construction of a preform obtained
when employing the modification of FIG. 3.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0012] FIGS. 1A-1C illustrate an apparatus 10 in accordance with
one exemplary embodiment of the invention. A housing or block 12
has an internal cavity that forms a mold charge chamber 14. Chamber
14 has a longitudinal dimension, and has a lateral dimension that
is uniform throughout the length of the chamber. Chamber 14 may be
of cylindrical geometry, for example. A gate 16 is positioned at
the lower end of block 12, and is movable under control of a gate
control 18 between the position illustrated in FIG. 1A in which
gate 16 closes the lower end of chamber 14 and a second position in
which the gate opens the lower end of the chamber. A plunger 20 is
disposed within chamber 14. Plunger 20 is movable by a servo
control 22 between a first position illustrated in FIG. 1A in which
plunger 20 closes the upper end of chamber 14, and a second
position in which plunger 20 is moved through the chamber to the
lower end of the chamber so as substantially to fill the chamber.
(Directional words such as "upper" and "lower" are employed by way
of description and not limitation with respect to the upright
orientations of the components illustrated in the drawings.) At
least one lateral material inlet extends from chamber 14 through
block 12. In the exemplary preferred embodiment of the invention
illustrated in FIG. 1A, at least two and preferably three lateral
inlets 24, 26, 28 extend from chamber 14 and are longitudinally
spaced from each other lengthwise of chamber 14. Each inlet 24, 26,
28 is connected to an associated source 30, 32, 34 of resin
materials A, B and C. Sources 30-34 preferably are connected to
inlets 24-28 through associated valves 36, 38, 40 or the like for
preventing back-flow of material from chamber 14. With actuator 20
lifted or retracted to the upper or first position illustrated in
FIG. 1, and with gate 16 closed, materials A, B and C are injected
into cavity 14, preferably substantially simultaneously. In this
way, the materials A, B and C are stratified longitudinally of
chamber 14, as illustrated in FIG. 1A.
[0013] With chamber 14 so filled, gate 16 is opened and plunger 20
is moved downwardly into the chamber to discharge the stratified
mold charge 42 (FIG. 1B) into the female preform mold 44. This
downward motion of plunger 20 preferably is very rapid, so that
mold charge 42 is "shot" into cavity 44. The resin layers of mold
charge 42 are soft, so mold charge conforms to and fills the lower
end of the mold cavity. Cavity 44 is then positioned in alignment
with a male mold core 46 (or mold core 46 is moved into alignment
with cavity 44) and core 46 is moved into cavity 44 (FIG. 1C) to
compression mold mold charge 42 into a compression molded preform
48. As shown in FIGS. 2 and 2A, this compression molded preform 48
has a layered wall construction in which the stratified materials
A, B and C of the mold charge 42 form the inner, intermediate and
outer layers of the preform. Materials A, B and C may be selected
to achieve the desired preform material construction. For example,
materials A and C may be virgin polyethylene terephthalate (PET),
while material B may be a suitable barrier resin such as nylon or
ethylene vinyl alcohol (EVOH). In an alternative implementation,
materials A and C may be different materials, such as virgin PET
and post consumer resin (PCR), for example.
[0014] FIGS. 3 and 4 illustrate another exemplary embodiment of the
invention in which materials A and B are fed from sources 30, 32
through a layer multiplication device 50. Exemplary layer
multiplication devices are disclosed in U.S. Pat. Nos. 5,094,793,
5,202,074, 5,380,479 and 5,628,950. Device 50 forms a stream of
resin material in which the two materials A and B are in multiple
alternate layers. Additional materials may also be employed for
additional layers, such as layers of adhesive between the alternate
layers of materials A and B. The output of layer multiplier 50 is
fed to the inlet 24 of chamber 14. FIG. 3 also illustrates a
modification in which the plunger 52 is coupled to a fluid actuator
54, which may comprise a suitable pneumatic or hydraulic fluid
actuation device. The lower end 56 of plunger 52 is contoured in
this embodiment to impart a contour to the mold charge as it is
ejected from chamber 14, which can be of assistance in maintaining
the layered construction during the compression molding operation.
FIG. 4 illustrates the sidewall construction of a preform 58
produced from the mold charge 60 in FIG. 3, in which there are
multiple layers of material A alternating with multiple layers of
material B. Material A may comprise PET and material B may comprise
barrier resin such as EVOH or nylon. Where adhesive material is
desired between the alternate layers, the adhesive material may be
blended with the barrier resin B, or may be provided as additional
layers as previously discussed.
[0015] There have thus been disclosed an apparatus and method for
supplying a mold charge for compression molding container preforms
that fully satisfy all of the objects and aims previously set
forth. The invention has been disclosed in conjunction with two
exemplary presently preferred embodiment 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. The invention is intended to
embrace all such modifications and variations as fall within the
spirit and broad scope of the appended claims.
* * * * *