Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a process and apparatus for
molding hollow plastic articles, and more particularly to a
novel core rod, and process and apparatus for the injection blow
molding of hollow plastic articles and/or containers utilizing
such core rod.
Various methods of molding hollow plastic articles
and/or containers are well known in the prior art. Plastic con-
tainers have found substantial increasing applications, however,
dèspite their weight and toughness, théir use is restricted by
the cost and characteristic of the plastic composition,
particularly for storage of products which will deteriorate or
be contaminated, inter alia, by water, carbon dioxide, oxygen
and the like.
Recently, a process has been advanced which produced
a barrier container, i.e. a semi-rigid plastic container pro-
vided with a liner or inner layer of another material or
materials having properties different than the outer layer
thereof. In accordance with such process, a preformed liner
or sleeve (manufactured, for example, by thermoforming techniques)
is positioned over a core rod with a parison or preform being
subsequently formed about the liner in an injection station of
an injection blow molding machine. The lined parison is
expanded in a blow molding station of the machine with the
resulting lined container being removed from the core rod in a
product receiving station. As a result of the creasing tendency
of the liner during the formation of the preform due to orienta-
tion and/or size variations of the thermoformed liner, many
barrier containers are formed which have poorly fitted liners.
An object of the present invention is to provide an
improved process and apparatus for the injection blow molding
of hollow plastic articles which overcome the problems of the
prior art.
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Still another object of the present invention is to
provide an improved process and apparatus for forming a barrier
container whereby creasing of the liner of the barrier container
is substantially eliminated.
Another object of the present invention is to provide
a novel blow core for an injection blow molding process and
apparatus.
A further object of the present invention is to pro-
vide a novel blow core which allows for more uniform tempera-
ture conditioning of the blow core.
An additional object of the present invention is toprovide a novel blow core which allows for more uniform tempera-
ture conditioning and consequently a liner upon placement
thereof in a barrier container process and apparatus.
A still further object of the present invention is to
provide a novel blow core for a barrier container injection blow
molding process and apparatus to insure liner placement and to
prevent liner movement.
Various other objects and advantages of the invention
will become clear from the following detailed description of an
exemplary embodiment thereof and the novel features will be
particularly pointed out in connection with the appended claims.
In accordance with one embodiment of the present
invention, there is provided a core rod formed of a porous
metal and in particular a core rod thereof formed of a porous
metal and including conduit means for passing air through a-
blow slot thereof as well as from and through the porous metal
of the head portion of the core rod as more fully hereinafter
described. Another embodiment of the present invention is
directed to the use of the hereinabove described porous core
rod in a process and apparatus for manufacturing hollow articles,
and in particular, such use in an injection blow molding
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process and apparatus for the manufacture of barrier containers.
Accordingly, a core rod is provided on such an injection blow
molding apparatus to permit the reduction of air pressure below
atmospheric within the core rod during placement of the liner
on the core rod during liner feeder operation thereby to hold
the liner on the core rod against further movement, until at
least the preform injection operation, and preferably through
the preform injection operation. In this manner, the liner is
more evenly temperature conditioned and creasing is minimized
due to liner shrinkage during preform injecting through the
molding operation.
The invention will be more clearly understood by
reference to the following detailed description of an exemplary
embodiment thereof in conjunction with the accompanying drawings
in which:
Figure 1 is a schematic top view, partially in section,
of a four stage rotary injection blow molding machine embodying
one of the principles of the present invention;
Figure 2 is a schematic sectional view of the rotary
injection blow machine of Figure 1 taken along the lines 2-2
thereof; and
Figure 3 is a cross-sectional view of a porous core
rod of the present invention.
For a general understanding of the illustrated four
stage rotary injectio~ blow molding machine in which the inven-
tion may be incorporated, reference is made to Figures 1 and 2
in which various system components of the machine are schemati-
cally illustrated. The rotary injection blow molding machine,
generally indicated as 10, is comprised of a square shaped
indexing platen 12 mounted on a shaft 14 driven by a motor and
timing assembly, generally indicated as 16. The motor and
timing assembly 16 includes the usual instrumentation, timing
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circuits, safety features and the like for automatic and con-
tinuous operation of the machine. The machine 10 is provided
with four (4) operational stations, i.e., a liner feed station
A, a preform injection station B, a blow molding station C, and
a product receiving station D. The platen 12 is provided with
a plurality of core rods 18, fluid conduits, generally indicated
as 20, and intermediate heat transfer conduits (not shown). The
preform injection station B and blow molding station C are
provided with injection molds and blow molds, generally
indicated as 22 and 24, respectively, including intermediate
heat transfer conduits (not shown) as are known to those skilled
in the art.
In operation, the platen 12 is set to rotate inter-
mittently through 90 for a segment of each cycle at a time
interval independent on inject time, blow time, part removal
and the like. At the liner feeder station A, liners 26 from a
liner magazine and feed assembly, generally indicated as 28, are
positioned on the core rods 18. After a predetermined time
interval, the platen 12 is caused to rotate through ninety
degrees (90) ~y the motor and timing assembly 16, it being
understood that concurrent with the initiation of an indexing
step (rotational portion of the cycle), that the preform
injection molds 22 and blow molds 24iare caused to separate and
the piaten 12 caused to move vertically upward a distance
sufficient to permit the platen 12 to rotate through such in-
dexing step. Generally, the lower portion of the molds are
immovably positioned with the upper portions mounted to verti-
cally displaceable platens (not shown). After completion of the
indexing step, the platen 12 is caused to return to an opera-
tional position with the mold halves being caused to closeabout the core rods 18.
At the preform injection station B and after a pre-
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determined time interval, a hot plastic material, generallyindicated as 30, is injected for an inject time period through
injection nozzles 32 about the lined core rods 18 to form compo-
site preforms, generally indicated as 34, between the liner 26
and the cavity surfaces 36 of the injection mold 22. After a
segmental time period, the indexing step is initiated with the
platen 12 being rotated through ninety degrees (90), as
hereinabove discussed, with the composite preforms 34 being
positioned within the blow molds C. A pressurized fluid,
generally compressed air, is introduced into the conduit 20 and
through blow slots of the core rods 18 to cause the composite
preforms 34 to be expanded and assume the shape of cavity sur-
faces 38 of the blow molds 24 thereby forming composite con-
tainers 40.
After completion of a subsequent segmental time
period and an indexing step, the platen 12 is caused to assume
a position at which the thus blown containers 40 are at the
product removal station D and are removed, such as by a
mechanical means, onto a conveyor assembly 42 for subsequent
inspection, filling, packaging and the like (not shown). It
will be readily understood by those skilled in the art that the
above discussed sequence of operation for one set of blow cores
is also being cyclically affected with each of the other sets
of blow cores and that the above discussion is general to the
operation of four stage rotary injection blow molding machine.
Referring now to Figure 3, there is illustrated a
core rod, generally indicated as 50, comprised of a head member
and a body member, generally indicated as 52 and 54, respectively.
The head member 52 is formed of a rod member 56, a disc-shaped
base member 58, a tubularly-shaped core pin me~ber 60 and a core
pin support member 62. The rod member 56 is threaded at one
end 64 and is centrally affixed at the other end 66 to base
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member 58 including orifices 68.
The tubularly-shaped core pin member 60 is formed
with a tapered inner wall surface 70 mounted about the
cylindrical outer wall portion of the base member 58 and extends
axially in a direction opposite from the rod member 56.
The core pin member 60 is comprised of two sections,
i.e. a base portion 72 of a solids material, such as stainless
steel, and a face portion 74 of a porous material, (i.e. having
a multiplicity of discrete passageways formed therein during
fabrication thereof) such as a two (2) micron stainless steel,
with the base portion 72 being mounted about the base member 58.
The core pin support member 62 is generally formed of a material
exhibiting excellent heat transfer properties, such as copper,
and is comprised of a base section 76 centrally juxtaposed to
the base member 58 in a co-axial alignment with the rod member
56; a helically-shaped intermediate section 78; and an end
section 80. The threaded portion of the helically-shaped
intermediate section 78 is formed with a flat crest which is in
intimate contact with the tapered inner wall surface 70 of the
core pin member 60 with the end section 80 of the support member
62 being coterminous with the face portion 74 of the core pin
member 60.
The body member 54 is comprised of a cylindrically-
shaped stem portion 82 and a cylindrically-shaped sleeve portion
84, and is formed with a centrally disposed cylindrical passage-
way 86. An end section of the stem portion 82 opposite the
sleeve portion 84 is provided with counterbored orifices 88 and
90. The sleeve portion 84 is formed with a cylindrical chamber
92 and a countersunk shouldered surface 94. The rod 56 of the
head member 52 is positioned within the passageway 86 biasedly
held by a spring 96 against the shouldered surface 94 of the
body member 54 by a nut 98 rotatably mounted on the thread
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portion 64 of the rod member 56, and is spaced apart from the
inner wall surface of the counterbored orifice 90. The spacial
relationship between the rod 56, and the orifices 90 and 88 with
the passageway 56 together with the spacial relationship
between the outer surface of the base portion 72 of the core
pin member 60 and the inner surface forming the chamber 92
provides a passageway for the fluid expanding medium.
The head member 52 is caused to move from the body
member 54 in the direction illustrated by the arrow A in Figure
3 by a mechanical force (not shown) associated with the platen
12 andllurged against the nut 98, and to assume thereby the
position illustrated by the dotted lines and permit the concen-
tric passage of a compression fluid between such head and body
members. Removal of the mechanical force causes the head
member 52 to resume a static position by the compressive force
of the spring 96 against the nut 98 threadably mounted on rod
member 56. Additionally, as a result of the orifices (not
shown) in the porous metal of the face portion 74 of the head
member 52, a gaseous medium may be passed through such porous
face portion 74, as more fully hereinafter described.
In operation, a plurality of core rods 50 of Figure 3
are mounted (as the core rods 18) about the platen 12 of the
apparatus of Figures 1 and 2 in a manner known to those skilled
in the art, and after a warm-up period, operational cycling of
the machine is initiated upon completion of an indexing step by
placing liners 26 on the core pins 18 by the liner magazine
and feeder assembly 28. The conduit 20 of the platen 12 at the
liner feed station A is placed in fluid communication by line
100 with the suction side of a pump 102 to reduce the pressure
within the core rods 18 at such station, thereby to cause the
liners to contact intimately the surface of the core pins 18
and to be held in such position by the below atmospheric
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pressure by a check valve 104 at the initiation of an indexing
step. It will be understood that the conduit 20 when placed in
fluid communication with the line 100 may be subjected to low
pressures via the suction side of the pump 104 operating con-
tinuously or with an accumulator vessel (not shown) held at low
pressures by an intermittently operated pump including
associated pressure switches and the like.
At the completion of a segment of a cycle, the platen
12 is caused to index to the next station, i.e. injection
station B. At injection station B, hot molten plastic 30 is
introduced through injection nozzles 32 over the liners 26 and
between the contoured cavity surface 36 of the injection molds
22 to form composite preforms 34. Generally, the liners 26 are
permitted to be temperature conditioned for a given time period
prior to injecting the hot plastic. It is understood that
simultaneous with the operation at injection station B, that
liners 26 will have been positioned on the core rods 18 at
liner feed station A. Operation through another segment of
the cycle causes the composite preforms 34 to be positioned
within the blow molds 24 of the blow station C now at an overall
temperature sufficient for expansion. As the conduit 20 is
placed in fluid communication by line 106 with the discharge
side of a pump 108, a disabling means (not shown) disengages
the check valve 104 from its closed position. Compressed air
is permitted to flow through the passageway 58 and exit between
the head member 52 and body member 54, as hereinabove discussed
with reference to Figure 3, thereby permitting the composite
preforms 34 to expand to the contoured cavity surfaces 38 of
the blow mold 24 and form the containers 40.
After completion of a segment of the cycle, the platen
12 is caused to raise and lower index whereby the thus formed
containers 40 are brought to the product discharge or removal
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station D whereat the containers 40 are ejected, such as by a
mechanical means, onto the conveyor 42 for subsequent process-
ing operation (not shown), e.g. inspection, filling and
packaging. It is to be understood that each side of the platen
12 is sequentially subjected to the hereinabove described
steps, in that after one cycle of operation, each set of core
rods of the platen is in one functional operational step of a
cycle.
As hereinabove discussed, use of the porous core rod
of the present invention permits the application of a vacuum
within the core rod during liner placement prior to and
preferably continuing through the injection stage of an
injection cycle to prevent liner movement and thereby substan-
tially eliminate liner creasing. Additionally, liner to core
rod fit is less critical as well as the reduction of liner
tolerances in the production of liners.
The internal configuration of the core rod allows
for the introduction and passage of a conditioning fluid
therethrough, e.g. hot air, during start-up of the injection
blow molding assembly, as well as the introduction and passage
of a conditioning fluid, e.g. ambient air, between product
removal and liner placement during the production cycle. The
uniform passage of a conditioning fluid through the porous
face portion 74 of the core pin member 72 is enhanced by the
helically-formed threads including flat crests on the inter-
mediate section 78 of the support member 62. Such a condition-
ing fluid will evenly exit through the surface of the face
portion 74 as a result of the nature of the porous metal. It
will be understood that while a helically-formed intermediate
section 78 is described that the intermediate section 78 of
the support member 62 may take other shapes, e.g. a star-shaped
support member in an axial alignment with the core pin member
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having flat axially and radially extending flat crests which
contact the inner wall surface 70 of the core pin member 60. A
flat crest of the threaded intermediate portion 78 is preferred
to provide sufficient area contact to provide substantial
support for the core pin member 60 as well as to enhance con-
ductive heat transfers from the tip section of the core pin
member 60 to the interior portion of the core pin support
member 62.
As hereinabove discussed, the support member 62 is,
preferably formed of a heat conductive material~such as copper,
to provide for the removal of heat, especially from the end
portion 80 of the core pins 18, since the tip or end portion 80
thereof is normally subjected to higher temperatures as a result
of the positioning of the hot plastic injection nozzles 32,
i.e. generally opposite such end portion during the inject phase
of a cycle. Consequently, in a preferred configuration, porous
metal is not formed over the tip of the end portion 80. As
hereinabove discussed, the core pin assembly is disposed within
the platen 12 provided wi~h suitable conduits for the passage
of cooled intermediate heat transfer medium therethrough to
maintain temperature levels of the core rods together with
other potential conditioning requirements.
As will be appreciated by one skilled in the art, the
base portion 72 of the core pin member 60 is formed of stainless
steel to provide for a stronger contacting surface between the
core pin member 52 of the body member 54 at the surface 94
thereby substantially lengthening the usuable life span of such
a core rod S0 as distinguished from the use of a core pin mem-
ber 60 formed entirely of such porous metal. It will be under-
stood by those skilled in the art that the relative positioningof the blow slot will vary depending on the plastic composition
of the composite preforms, e.g. for polystyrene the blow slot
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is generally positioned as illustrated in Figure 3, whereas for
polyolefin, the blow slot is generally located near the tip of
the blow core. Additionally, while the novel blow core and
process and apparatus of utilizing same has been disclosed with
reference to a rotary injection blow molding apparatus having a
plurality of blow cores disposed on each side of the platen
thereof, it is understood, that the novel blow core may be used
in any process and apparatus for injection blow molding of
articles, e.g. a liner transfer apparatus utilizing a single
blow core, etc. Still further, it is contemplated that a core
rod fabricated of a porous metal may be used as the male member
of a molding dye in a vacuum thermoforming process and apparatus
to form the liner to be subsequently used in the hereinabove
discussed process and apparatus for forming barrier containers.
While the invention has been described in connection
with an exemplary embodiment thereof, it will be understood that
many modifications will be apparent to those of ordinary skill
in the art and that this application is intended to cover any
adaptations or variations thereof. Therefore, it is manifestly
intended that this invention be only limited by the claims and
the equivalents thereof.
