U.S. patent application number 10/339545 was filed with the patent office on 2003-05-29 for closure cap with injection molded annular gasket and method of making same.
Invention is credited to Kras, Stephen J., Taber, James.
Application Number | 20030098287 10/339545 |
Document ID | / |
Family ID | 24542743 |
Filed Date | 2003-05-29 |
United States Patent
Application |
20030098287 |
Kind Code |
A1 |
Taber, James ; et
al. |
May 29, 2003 |
Closure cap with injection molded annular gasket and method of
making same
Abstract
A closure cap and method of making the same wherein an annular
or ring-shaped gasket is injection molded onto the inner surface of
a cap shell formed of plastic or metal. The annular or ring-shaped
gasket includes radially extending tabs integrally formed
therewith, one of said tabs being formed at a location wherein the
plastic melt is fed to an annular gasket-forming channel in a mold
core and another of said tabs being formed at the location wherein
plastic melt is discharged from said channel. Preferably, said
other tab includes a cold well formation which communicates with
the annular gasket through a connecting portion of reduced
cross-sectional area with respect to the cross-sectional areas of
both the gasket and the cold well formation.
Inventors: |
Taber, James; (Aurora,
IL) ; Kras, Stephen J.; (Chicago, IL) |
Correspondence
Address: |
COOK, ALEX, MCFARRON, MANZO, CUMMINGS & MEHLER LTD
SUITE 2850
200 WEST ADAMS STREET
CHICAGO
IL
60606
US
|
Family ID: |
24542743 |
Appl. No.: |
10/339545 |
Filed: |
January 9, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10339545 |
Jan 9, 2003 |
|
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|
09634182 |
Aug 9, 2000 |
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Current U.S.
Class: |
215/352 ;
215/349; 264/268 |
Current CPC
Class: |
B29C 45/0025 20130101;
B29C 45/14 20130101; B65D 41/3428 20130101; B29C 2045/0044
20130101; B65D 41/045 20130101; B65D 41/0442 20130101; B29C
2045/14983 20130101; Y10S 425/809 20130101; B29L 2031/26 20130101;
B29C 45/14336 20130101; B29L 2031/565 20130101 |
Class at
Publication: |
215/352 ;
215/349; 264/268 |
International
Class: |
B65D 053/00; B29C
045/14 |
Claims
What is claimed:
1. A closure cap comprising: a shell which includes an end panel
and an integral skirt downwardly extending therefrom, said end
panel having a generally circular inside surface of a given outer
diameter; and, an injection molded annular gasket having a
ring-shaped body which includes an outer edge and an inner edge,
said outer edge having a diameter which is less than the outer
diameter of said end panel inner surface whereby said outer edge of
said gasket body is inwardly spaced from the outer periphery of
said end panel inside surface to define a substantially gasket-free
annular border which surrounds said ring-shaped gasket body, said
gasket having a width sufficient to provide a top seal with an end
finish of a container mouth to which said closure is applied, said
inner edge of said ring-shaped gasket body surrounding a
substantially gasket-free interior portion of said inside surface
of said end panel, said gasket also including a first inwardly
extending tab of generally uniform cross section formed therewith
and a second inwardly extending tab integrally formed therewith,
said second tab including an inner-most and an outer-most portion,
said inner-most portion having a relatively small cross section
with respect to the cross section of said outer-most portion.
2. The closure of claim 1 wherein said first and second tabs extend
radially inwardly from the inner edge of said ring-shaped gasket
body.
3. The closure cap of claim 2 wherein said first and second tabs
are oppositely disposed along the circumference of said ring-shaped
gasket body.
4. The closure cap of claim 1 wherein said ring-shaped gasket body
includes a top seal-forming surface defined by a plurality of
concentric ribs.
5. The closure cap of claim 4 wherein said concentric ribs are
conically shaped.
6. The closure cap of claim 1 wherein said gasket is composed of a
moldable resin which is substantially free of vinyl chloride.
7. The closure cap of claim 1 wherein said gasket is composed of a
thermoplastic elastomer.
8. The closure cap of claim 1 wherein said shell is formed of a
moldable thermoplastic resin.
9. The closure cap of claim 8 wherein said thermoplastic resin is a
polyolefin.
10. The closure cap of claim 9 wherein said thermoplastic resin is
polypropylene.
11. The closure cap of claim 8 wherein said end panel of said shell
includes a layer of an oxygen barrier film.
12. The closure cap os claim 11 wherein said layer of oxygen
barrier film is adhered to the inside race or said end panel.
13. The closure cap of claim 1 wherein said shell is composed of a
metal.
14. A closure cap comprising: a shell which includes an end panel
and an integral skirt downwardly extending therefrom, said end
panel having a generally flat, circular inside surface of a given
outer diameter; and, an injection molded annular gasket having a
ring-shaped body which includes an outer edge and an inner edge,
said outer edge having a diameter which is less than the outer
diameter of the end panel inner surface thereby providing a
substantially gasket-free annular border which surrounds said
ring-shaped gasket body, said gasket body having a width sufficient
to provide a top seal with an end finish of a container mouth to
which said closure is applied, said inner edge of the ring-shaped
gasket body surrounding a substantially gasket-free interior
portion of the inside surface of said end panel inner surface; said
gasket also including first and second tabs extending radially
inwardly from the inner edge of said ring shaped gasket body, said
second tab including an inner-most portion adjacent said inner edge
of said ring-shaped gasket and an outer-most portion,
15. The closure cap of claim 14 wherein said first and second tabs
are oppositely disposed along the circumference of said ring-shaped
gasket body.
16. The closure cap of claim 14 wherein said ring-shaped gasket
body includes a top seal-forming surface defined by a plurality of
concentric ribs.
17. The closure cap of claim 14 wherein said concentric ribs are
conically-shaped.
18. The closure cap of claim 14 wherein said gasket is composed of
a thermoplastic elastomer.
19. The closure cap of claim 14 wherein said shell is formed of a
moldable thermoplastic resin.
20. The closure cap of claim 14 wherein said thermoplastic resin is
a polyolefin.
21. The closure cap of claim 20 wherein said thermoplastic resin is
polypropylene.
22. The closure cap of claim 19 wherein said end panel of said
shell includes a layer of an oxygen barrier film.
23. The closure cap of claim 22 wherein said layer of oxygen
barrier film is adhered to the inside face of said end panel.
24. The closure cap of claim 14 wherein said shell is composed of a
metal.
25. A method of making a closure cap having an injection molded
ring-shaped gasket, said method comprising: providing an injection
mold having first and second mold components which are moveable
with respect to each other between an open position and a closed
position, said first mold component having a cap shell-receiving
portion, said second mold component including a core: positioning
said first and second mold components into an open position;
inserting a preformed cap shell which includes a circular end panel
having a given diameter, a circular inside surface and an integral
skirt in surrounding relation thereto; closing said mold to
position said core within the cap shell, a working surface on said
core being in contact with said inside surface of said cap shell
end panel, said core working surface having a ring-shaped channel
formed therein which is defined by outer and inner peripheral
edges, said channel forming a gasket defining mold cavity with said
inside surface of said cap shell, said core working surface
including peripherally-spaced and inwardly-extending melt inlet and
outlet channels in flow communication with said ring-shaped
channel, said outlet channel including a pressure reducing flow
restriction, said inner and outer peripheral edges of said channel
being sealingly engageable with the inside surface of said cap
shell where said mold is in said closed position to provide
melt-flow shut-off barriers therewith; supplying a melt flow under
pressure into said melt inlet channel to feed melt through said
gasket defining cavity; continuing said supply of pressurized melt
flow until a lead portion of said flow is received in said outlet
channel and a complete gasket is formed in said cavity; and,
opening said mold and removing said closure cap shell with the
injection molded gasket formed therein.
26. The method of claim 25 wherein said outlet channel includes a
cold well which communicates with said ring-shaped channel through
a passageway having a reduced cross-sectional area with respect to
the cross-sectional areas of each of said ring-shaped channel and
said cold well.
27. The method of claim 25 wherein said ring-shaped channel has a
bottom surface defined by a plurality of concentric rings to
provide the molded gasket formed therein with a top seal-forming
surface defined by a plurality of sharply-defined concentric
ribs.
28. The method of claim 27 wherein said concentric rings have a
V-shaped cross-section which produce a conically-shaped cross
section on the corresponding concentric ribs in the seal-forming
surface of the molded gasket.
29. The method of claim 25 wherein at least one of said mold
components includes a stand-off post which contacts the other of
said mold components when said first and second mold components are
in a closed position to precisely control the position of said core
in said cap shell.
30. The method of claim 29 wherein said second mold component
includes said stand-off post.
31. The method of claim 25 wherein said inlet and outlet channels
are oppositely disposed with respect to each other along the inner
circumference of said ring-shaped channel.
32. The method of claim 25 wherein said cap shell is composed of a
moldable thermoplastic resin and said inner and outer peripheral
edges of said channel penetrate said inside surface of said cap
shell to produce said melt-flow shut-off barriers.
33. A method of making a closure cap having an injection molded
ring-shaped gasket, said method comprising: providing an injection
mold having first and second mold components which are moveable
with respect to each other between an open position and a closed
position, said first mold component having a cap shell-receiving
portion, said second mold component including a core; positioning
said first and second mold components into an open position;
inserting a preformed shell composed of a moldable thermoplastic
resin which includes a circular end panel having a given diameter,
a circular inside surface and an integral skirt in surrounding
relation thereto; closing said mold to position said core within
the cap shell, a working surface on said core being in contact with
said inside surface of said cap shell end panel, said core working
surface having a ring-shaped channel formed therein which is
defined by outer and inner peripheral edges, said channel forming a
gasket defining mold cavity with said inside surface of said cap
shell, said core working surface including peripherally-spaced and
inwardly-extending melt inlet and outlet channels in flow
communication with said ring-shaped channel, said outlet channel
including a cold well which communicates with said ring-shaped
channel through a passageway having a reduced cross-sectional area
with respect to the cross-sectional areas of each of said
ring-shaped channel and said cold well, said inner and outer
peripheral edges of said channel penetrating the inside surface of
said cap shell when said mold is in said closed position to provide
melt-flow shut-off barriers therewith; supplying a melt flow under
pressure into said melt inlet channel to feed melt through said
gasket defining cavity; continuing said supply of pressurized melt
flow until a lead portion of said flow is received in said outlet
channel and a complete gasket is formed in said cavity; and,
opening said mold and removing said closure cap shell with the
injection molded gasket formed therein.
34. The method of claim 33 wherein said ring-shaped channel has a
bottom surface defined by a plurality of concentric rings to
provide the molded gasket formed therein with a top seal-forming
surface defined by a plurality of sharply-defined concentric
ribs.
35. The method of claim 34 wherein said concentric rings have a
V-shaped cross-section which produce a conically-shaped cross
section on the corresponding concentric ribs in the seal-forming
surface of the molded gasket.
36. The method of claim 33 wherein at least one of said mold
components includes a stand-off post which contacts the other of
said mold components when said first and second mold components are
in a closed position to precisely control the position of said core
in said cap shell.
37. The method of claim 36 wherein said second mold component
includes said stand-off post.
38. The method of claim 33 wherein said inlet and outlet channels
are oppositely disposed with respect to each other along the inner
circumference of said ring-shaped channel.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention generally relates to new and useful
improvements in closure caps for glass and plastic containers and,
more particularly, to a closure cap having an improved injection
molded annular gasket and method of making the same. In this
regard, an important aspect of the present invention is directed to
a closure cap having a one-piece or unitary cap shell formed of a
polyolefin such as, for example, polypropylene, in which an annular
or ring-shaped gasket characterized by improved uniformity,
definition and consistency which is composed of a moldable resin
such as, for example, a thermoplastic elastomer, is injection
molded onto the inner surface of the closure cap shell via an
insert molding procedure.
[0002] Closure caps having full disks formed by compression or
injection molding the same in a closure shell are known. For
example, U.S. Pat. No. 4,398,874 describes a molding tool for
forming a full disk liner in a closure shell which includes a
central punch or molding member and a shell positioning sleeve
disposed externally of the molding member that is received within a
cap shell. Liner material deposited within the shell is contacted
by the punch and forms a full disk liner with the cap shell.
Correspondingly, U.S. Pat. No. 4,803,031 describes a closure cap
and method wherein an injection molded full disk gasket is formed
followed by injection molding the closure cap shell around the thus
formed gasket. These full disk closure caps while providing
generally satisfactory sealing on containers are characterized by
higher manufacturing costs associated with using greater amounts of
gasket-forming resin and also by the disadvantages of having the
entire inside surface of the cap shell fully covered thereby
increasing the possible migration of gasket components into product
(particularly food products) in the container sealed therewith and
also making the inner surface of the cap shell unavailable for
displaying labels or other message-conveying indicia.
[0003] U.S. Pat. No. 5,685,443 describes a composite closure cap
where an annular gasket providing a top and side seal is injection
molded onto a metal disk followed by injection molding a plastic
skirt around the disk in surrounding and capturing relation
therewith. This composite closure while utilizing an injection
molded annular gasket requires the presence of a separate disk
which adds to the cost of the closure and to the complexity of
manufacturing the same.
SUMMARY OF THE INVENTION
[0004] The present invention overcomes the foregoing disadvantages
of these prior art closures by providing a novel closure utilizing
a plastic or metal cap shell and an injection molded annular or
ring-shaped gasket wherein the central portion of the inner surface
of the cap shell is free of gasket material.
[0005] In accordance with an important aspect of the present
invention, an improved closure cap is provided which includes a
unitary or one-piece plastic or metal shell and an annular
ring-shaped gasket having inwardly radially extending tabs
integrally formed therewith, one of said tabs being formed at the
location wherein plastic melt is fed to an annular gasket-forming
channel in a mold core and the other of said tabs being formed at
the location wherein plastic melt is discharged from said channel.
The latter of said tabs, in accordance with a preferred embodiment
of the present invention, includes a cold well which communicates
with the annular gasket forming channel through a passageway of
reduced cross-sectional area with respect to the cross-sectional
areas of both the gasket forming channel and the cold well.
[0006] It is, therefore, an object of the present invention to
provide an improved closure cap having a novel injection molded
annular gasket and method of making the same.
[0007] Another object of the present invention is to provide a
closure cap having a one-piece plastic or metal shell and an
injection molded top seal annular gasket which utilizes a
cost-effective amount of moldable, gasket-forming material and
which provides an efficient seal with the end finish of a container
to which the closure cap is applied.
[0008] Another object of the present invention is to provide an
injection molded annular gasket formed by insert molding the same
in a one-piece closure cap shell wherein the uniformity and
consistency of the gasket is enhanced which gasket is characterized
by integral radially extending tabs at locations along the
periphery of the gasket corresponding to the locations wherein the
melt is supplied to and from a gasket defining channel.
[0009] These and other objects of the present invention will be
apparent from the following detailed description taken in
conjunction with the accompanying drawings wherein like reference
numerals refer to like parts and in which:
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a perspective view, partially broken away, of a
closure cap embodying the present invention and a portion of a
container on which the closure is fitted;
[0011] FIG. 2 is a bottom plan view of the closure cap shown in
FIG. 1;
[0012] FIG. 3 is a sectional view of the closure cap shown in FIGS.
1 and 2 taken along the line 3-3 of FIG. 2;
[0013] FIG. 4 is a sectional view of the closure cap shown in FIGS.
1 and 2 taken along the line 4-4 of FIG. 2;
[0014] FIG. 5 is a schematic side elevation view of a mold
apparatus which can be used to manufacture the closure cap of the
present invention;
[0015] FIG. 6 is a schematic perspective view of a portion of the
moving platen of the mold apparatus shown in FIG. 5 which is
separated from a core plate of the stationary platen;
[0016] FIG. 7 is a schematic perspective view of the moving platen
of the bold apparatus of the present invention with the stripper
plate thereof removed;
[0017] FIG. 8 is a partial top plan view of the mold core of the
present invention;
[0018] FIG. 9 is a sectional view taken along the line 9-9 of FIG.
8;
[0019] FIG. 10 is a schematic sectional view of the core head of
the mold apparatus shown in FIGS. 8 and 9;
[0020] FIG. 11 is an enlarged sectional view of the melt discharge
side of the core head shown in FIG. 10;
[0021] FIG. 12 is an enlarged sectional view of the melt inlet side
of the core head shown in FIG. 10;
[0022] FIG. 13 is a fragmentary perspective view, partially broken
away, of the closure cap of another embodiment of the present
invention and a portion of a container on which the closure cap is
fitted; and,
[0023] FIGS. 14-18 are schematic views of a mold apparatus for
manufacturing the closure cap shown in FIG. 13 with each of the
views showing successive phases of the closure shell manufacturing
process.
DETAILED DESCRIPTION OF THE INVENTION
[0024] Referring to the drawings and with particular reference to
FIGS. 1-4, a closure cap embodying the present invention is
generally designated by the reference numeral 20. As shown, closure
cap 20 is applied to a container 21 and includes an end panel 22
having an inner or bottom surface 23, a skirt 24 which terminates
in an enlarged axially extending cylindrical section 25.
[0025] As best shown in FIGS. 1, 3 and 4, bottom cylindrical
section 25 is, in the illustrated embodiment, connected to a tamper
indicating band 26 by a plurality of frangible bridges which
includes an upper band portion 27 and a lower band portion 28 which
are connected by a flexible hinge 29. Closure cap 20 is provided
with a spiral thread 31 on the interior surface of skirt 24,
however, it will be appreciated that other container-engaging
securement systems such as, for example, conventional lugs and the
like may be used without departing from the present invention.
Correspondingly, the closure cap can be made with other forms of
tamper indicating bands or, if desired, without any such band.
[0026] In accordance with an important aspect of the present
invention, closure cap 20 includes an injection molded annular or
ring-shaped gasket 32 positioned around the outer periphery of the
inner or bottom surface 23 for top-seal engagement with an end
finish or top edge 33 of container 21 which defines an open mouth
34 of the container. As shown in FIG. 1, container 21 includes a
spiral thread 35 sized to matingly engage thread 31 on closure cap
20 and also includes a retainer bead 36 for engagement with the
bottom edge of lower tamper indicating band portion 26 in a manner
which is well known in the art.
[0027] Annular or ring-shaped injection molded gasket 32 is
provided with an integral radially inwardly extending tab 37
corresponding to the location at which inlet melt feed is supplied
to the mold cavity during the injection molding process and a cold
well tab 38 and connector portion 39 which also are integral with
the gasket 32 and which correspond to the location at which melt is
discharged from the mold cavity defining the gasket. The precise
manner in which these respective tabs are formed will be more fully
described in connection with the mold apparatus.
[0028] In accordance with another aspect of the described
embodiment of the present invention, the top surface 40 of gasket
32 is provided with a plurality of V-shaped ribs that provide
improved seal-forming contact with the closure finish. It is
important to note that the formation of these V-shaped ribs via
injection molding gives them significantly better definition than
that attainable by other manufacturing procedures, such as, for
example, compression molding. In this regard, however, it will be
appreciated that, if desired, the top surface 40 of gasket 32 can
be flat or of other configurations.
[0029] Closure cap 20, in accordance with the present invention, is
made of suitable moldable polyolefin such as, for example,
polypropylene and homopolymers and copolymers thereof. In this
regard, however, it will be appreciated that other suitable
moldable plastic resins may be used in forming the closure cap.
Alternatively, if desired, the injection molded annular gasket of
the present invention may also be incorporated in metal
closures.
[0030] Annular or ring-shaped gasket 32 may likewise be formed of
any resilient or elastomeric materials which provide the desired
seal with a container finish, however, vinyl chloride-free resins
or non-PVC materials are preferred. If desired, suitable additives
such as those providing improved oxygen barrier and/or oxygen
scavenger properties, as well as those which facilitate torque
release may be incorporated into the gasket composition.
[0031] These non-PVC materials include rubbery block copolymers
dispersed in a matrix of polyolefin as the continuous phase, with a
moldable thermoplastic elastomer being especially preferred since
they possess a number of processing advantages. Gasket compositions
which can be effectively used include those composed of a
thermoplastic elastomeric material selected from a
moldable-saturated ABA-type block copolymer based on styrene and
butadiene such as styrene-ethylene-butylene styrene (SEBS) type
block copolymers containing from about 20% to about 40% styrene and
about 60% to 80% ethylene-butylene co-monomers such as Kraton.RTM.
G-2705, available from Shell Chemical Corporation. Preferred
thermoplastic elastomers also include the EPDM
(ethylene-propylene-dicycl- opentadiene) elastomers such as those
commercially available under the trade name Santropene.RTM. from
Monsanto Company. Other suitable thermoplastic elastomers are those
which are available from Advanced Elastomer Systems, L. P. of
Akron, Ohio.
[0032] A suitable apparatus for manufacture of the closures of the
present invention is generally depicted in FIGS. 5-12. FIGS. 5-9
schematically depict a mold apparatus having a feed system for
supplying preformed closure cap shells to the molding station
wherein the injection molded gasket is formed via insert molding
procedures. It will be appreciated that while a specific transport
mechanism is described herein for supplying closure cap shells to
the mold apparatus and for transportation of such closure caps
through and from that apparatus, other transport feeding systems
such as, for example, belt and/or robotic closure cap
transportation arrangements, could be used if desired. A common
feature of all molding systems which is important to the present
invention, however, concerns the precise insert molding arrangement
by which annular or ring-shaped gaskets are formed with exceptional
preciseness in their configuration and without air entrapment.
[0033] As generally shown in FIG. 5, the molding apparatus includes
a moving platen 45, and a stationary platen 46 which comprises a
core section 47. Moving platen 45 includes a transfer drive 48, a
transfer dial 49, a stripper plate 50 and feed chute 51 which will
be more fully described in conjunction with FIGS. 6 and 7.
Correspondingly, the core section 47 schematically shown in FIG. 5
includes individual mold cores 52 and 53. Melt is supplied to the
core section 47 from an injection unit 54 which feeds melt to a
manifold section 56 that, in turn, supplies pressurized melt feed
via line 57 and 58.
[0034] As best shown in FIG. 7, moving platen 45 includes a
rotatable star wheel transfer mechanism generally depicted by the
reference numeral 60 which has ten cap-receiving pockets, each of
which is generally designated by the reference numeral 61. As
shown, caps are supplied from feed chute 51 into each of the
individual pockets 61 until the star wheel is fully loaded.
Individual mold cores on mold core section 47 are respectively
received within each of the cap shells. After the gasket-forming
operation is completed, the mold is opened and the completed
closure caps discharge from the moving platen via discharge chute
63. If desired, pressurized air may be used to facilitate loading
and removal of the cap shells in the star wheel transfer mechanism.
In this regard, it will be appreciated that the number of
cap-receiving pockets located in the star wheel can be varied. For
example, in the arrangement illustratively depicted in FIG. 7, ten
cap-receiving pockets are shown, while eight such pockets are shown
in FIG. 6.
[0035] Referring to FIG. 6, it will be observed that a core plate
64 is depicted in space-away relationship to the moving platen 46.
As will be apparent from the description of FIGS. 8 and 9, the
portion of core plate 64 facing moving platen 45 includes a
plurality of standoff posts (shown in FIG. 8 and designated by
reference numeral 65) which control the depth of penetration of the
individual mold cores into each of the closure cap shells.
[0036] Referring now to FIGS. 8-12, each of the mold cores
(designated by reference numeral 52) is sized to be received within
the closure cap shell for direct contact with the inner or bottom
surface 23 of end panel 22 of a given closure cap. Melt supplied
from manifold 56 and melt feed line 57 is discharged through a gate
66 into an inlet melt feed line 68 and from there into an annular
channel 67 which, together with the inner or bottom surface 23 of
the closure cap forms a gasket-defining mold cavity. Typically,
with plastic enclosure cap shells, the mold cores will penetrate
the end panel surface to a limited and controlled extent, while
with metal closure cap shells no such penetration is needed in
order to achieve effective melt flow shut-off for containment of
the melt within the gasket-defining mold cavity. The melt flow from
inlet 68 passes in clockwise and counterclockwise directions
through the annular channel 67 and is discharged into a cold well
portion 73 of the core via a connecting passage 74. In accordance
of an important aspect of the present invention, the connecting
passage 74 has a reduced cross-sectional configuration to ensure
that the meeting melt streams will knit at that location and,
additionally, eliminates or at least greatly minimize the trapping
of any air in the gasket itself. This reduced size passageway
results in a lower pressure on the inside portion of the cold well
than is present in the annular gasket-defining portion 67 causing
any air present in the melt to be readily discharged into the cold
well.
[0037] As shown, a vent line 71 can be provided to draw a vacuum on
the system to further facilitate air removal during the feed of
melt. Also, as shown, an air line 72 can be provided to facilitate
removal of the finished closure after the injection molding of the
gasket has been accomplished and the mold opened. If desired, vent
line 71 and air line 72 can be coupled to further facilitate
removal of the finished closure when the molding operation is
complete.
[0038] Heat built up during the injection molding process can be
dissipated through the use of water cooling, which can be
accomplished by an outlet water line 70 which is in flow
communication with an inlet water line (not shown).
[0039] As best shown in FIGS. 11 and 12, the bottom surface 75 of
annular channel 67 is provided with a plurality of V-shaped grooves
which form a plurality of concentric V-shaped ribs that impart
improve seal-forming contact with the closure finish. As previously
noted, the formation of these V-shaped ribs by injection molding
process gives them significantly better definition than is
achievable by other molding procedures.
[0040] FIG. 13 generally designates a further embodiment of the
present invention in the form of a modified closure cap 80 having a
layer of metallic foil or other suitable material bonded to the
inner surface 23 of end panel 22 and to which the annular or
ring-shaped injection molded gasket is bonded. This construction is
particularly suitable for applications wherein improved oxygen
barrier properties are required and/or where it is desirable to
provide a visible display on the interior of the closure cap. As
such, the annular injection molded gasket is particularly suitable
for such applications, since it leaves the central portion of the
panel exposed, enabling use of such area for the display of printed
matter and the like.
[0041] FIGS. 14-18 illustrate one procedure for manufacturing this
closure shell. As shown in FIG. 14, a mold apparatus is provided
which includes an upper mold component 83 having a melt feed line
84 and gate 85, a lower mold component 86 and a core 87. A sheet or
strip of foil or other suitable material which is to be laminated
to the interior surface 23 of the closure cap shell is positioned
between upper and lower mold components 83, 86. As shown in FIG.
15, these mold components are closed, thereby trapping and securely
holding the strip 82 in place.
[0042] Core 87 is then positioned within lower mold component 86 in
direct contact with the strip 82 and defines a mold cavity 88 which
corresponds to the configuration of the closure cap to be formed
therewith. A supply of melt 89 is then fed into the cavity which,
as shown in FIG. 17, forms closure portion 90 and, at the same
time, due to the high pressure of the melt feed, breaks the
marginal portions of the foil strip and continues to flow as shown
in FIG. 18 to form the finished closure shell. The mold portions
are then opened and the formed closure cap shell removed
therefrom.
[0043] While the present invention has been described in connection
with the context of various embodiments, it will be apparent to
those skilled in this art that modifications and variations may be
made therefrom without departing from the sprit and scope of this
invention. Accordingly, this invention is to be construed and
limited only by the scope of the appended claims.
* * * * *