Note: Descriptions are shown in the official language in which they were submitted.
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Conventional in~jection blow molding apparatus operates
through a cycle beginning with the injection of plastic material
into an injection mold containing a core rod. A parison is
formed around the core rod, and the injection mold then opens
and permits the core rod to move to the next performance sta-
tion.
The second station is usually a blowing mold in which
the parison is blown to the desired shape of a finished
article; and when the blown article cools sufficiently, it is
]o removed from the blowing mold and transferred to a stripper
station. At the stripper station the blown article is removed
from the core rod.
One of the limitations on the speed Or a conventional
cycle is the time required to cool the blown article suffi-
ciently to remove it from the blowing mold and to the stripper
station. One of the principal purposes of this invention is
to cool the blo~n article more quickly and thereby reduce
time cycle of the machine and correspondingly increase the
production of the blow molding machine.
2~ This invention includes, in its preferred embodiment,
- an elastic balloon which is attached to a core rod assembly
in position to hug the core rod when the balloon is deflated.
When a parison is formed over the core rod, it is applied
over the outside of the collapsed balloon and over a short
length of the core rod assembly beyond the end of the balloon.
This short length of the parison is the portion which forms
the mouth or neck of the article to be blown and it is a portion
of the parison which is not expanded in the blow mold.
The balloon has two important advantages. One is that it
permits the blown article to be cooled from the ~side. Cooling
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fluid can be circulated through the inside of the balloon
during a blowing operation and immediately after the comple-
tion of the blowing operation. The core rod of this invention
is constructed so that cooling fluid flows from inside the
core rod into the space between the core rod and the expanding
balloon and parison; and this cooling fluid exhausts through
other passages communicating with exhaust openings in the
side of the core rod. If desired, fluid of any temperature
can be circulated for the purpose Or obtaining an orientatlon
temperature of the parison before its final expansion to the
shape of the desired article.
Part of the cons~ruction of this invention relates to
the way in which the balloon is attached to the core rod as-
sembly in such a way that the balloon connection to the core
rod assembly is not subjected to any axial pull when the blown
article is being stripped from the core rod. In the preferred
; construction, a sleeve which has a shoulder on one end, serves
as part of the parison supporting surface of the core rod as-
sembly. The balloon is attached to the core rod assembly in
an undercut cavity at the shoulder of the sleeve and the dia-
meter of the collapsed balloDn is less than that of the sleeve
so that the balloon is protected from axial pull when an article
blown on the core rod assembly is stripped from the core rod
` assembly by a stripper plate bearing against the part of the
'- blown article that is formed on the surface of the sleeve.
The invention also includes several provisions for
admitting air between the blown parison and the outside sur-
face Or the balloon so that the balloon can collapse after
the parison is fully blown to the shape of the desired article.
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Without provision for admitting air between the outside surface
of the balloon and the blown parlson, the balloon would be pre-
vented from collapsing, independently of the blown parison, be-
cause of the existence of vacuum batween the parison and the
balloon.
; One modification of the invention has provision for cir-
culating fluid within the parison to control the temperature
and more specifically to reduce the temperature quickly. This
modification also has provis~on for cooling the parison from
the outside by circulating cooling fluid into contact with
; the outside of the parison in the blowing mold. A special
type of blowing mold can be used in which the article is blown
; within a shroud having a multitude of openings into which
fluid enters to form a fluid cushion, preferably an air cushion,
inside the shroud. The article is blown into contact with
this cushion which increases in pressure as the parison ex-
pands toward the inside surface of the shroud. This blowing
. of the parisOn against an air cushion instead of into contact
with a solid surface is intended especially for use with con-
tainers having rigid mouth or neck portions and flexible and
pliant body portions.
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Other objects, features and advantages of the invention
~J will appear or be pointed out as the description proceeds.
j In the drawing, forming a part hereof, in which like
reference characters indicate correspondin~ rarts in all the
views:
~igure 1 is a diagrammatic sectional view showing a core
' rod support and core rod assembly with a balloon and blown
-parison on the core rod assembly and with provision for admit-
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ting air between the balloon and the blown parison to permit
collapse of the balloon while the blown parison retains its
blown shape;
Figure 2 and 3 are sectional views taken on the lines
2-2 and 3-3, respectively, of Figure l;
Figure 4 is an enlarged sectional view taken on the line
4-4 of Figure l;
Figure S is a fragmentary sectional view taken on the
line 5-5 of Figure l;
Figure 6 is a fragmentary sectional view showing a mo-
dified end construction for the core rod of Figure 1 and a
. connection of an open-ended balloon with the core rod, the
structure being shown within a blowing mold;
Figure 7 is a diagrammatic view of a modified form of
the sleeve shown in Figure 1 with the balloon attached in a
different way;
Figure ~ is a greatly enlarged fragmentary sectional
view showing the connection of the balloon to the sleeve in
Figurel;
Figure 9 is a greatly enlarged sectional view showing
the connection Or the balloon to the sleeve of Figure 7;
Figure 10 is a diagrammatic, sectional view, partly
broken away, showing a core rod assembly, similar to that in
Figure 1, placed in a unique blowing mold in which the parison
is expanded against a fluid cushion instead of into contact
with a solid surface; and
Figure 11 is an enlarged detail view of a portion of the
structure shown in Figure 10.
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Figure 1 shows a core rod support 12, such as an indexing
hsad. A core rod assembly 14 is connected to the ~upport by
fastening means such as screws 16.
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The core rod assembly 14 includes a base flange or
spacer block 1~ to which is connected a sleeve 20. This
sleeve 20 has a flange 22 which is attached to the spacer
block 1~ by the screws 16.
The sleeve 20 also has a shoulder 22 and an end face 24.
Within the sleeve there is a core rod 26. In the illus-
trated construction the base flange or spacer block 1~ is an
integral part of the core rod 26 and there is an inner end
portion 2~ of the core rod which fits into a recess 30 in the
core rod support 12. Thus the core rod is attached to the
support 12 by the screws 16.
i
For the portion of the core rod nearest to the support
there is a pipe or tube 32 extending coaxially along the
length of the core rod, and with the outside diameter of the
tube 32 somewhat less in diameter than the hollow interior
~3 34 of the core rod. Near the outer end (right hand in Figure
1) of the tube 32 the interior diameter of the core rod is
reduced at a location 3~. The tube 32 fits tightly into the
core rod at this reduced diameter 36; and beyond the end
of the tube 36, much of which is broken away in Figure 1,
there is a chamber 3~ enclosed by the core rod.
i There are a multitude of openings 40a and 40b. The
openings 40a communicate with the chamber 3~ within the core
rod. The openings 40b communicate with an annular chamber
¦ which comprises the space between the tube 32 and the larger
interior diameter portion 34 of the core rod.
Fluid, either liquid or gas, flows through the tube 32
in the direction indicated by the arrows 42and this fluid
flows out through the openings 40a in directions indicated by
the arrows 42 near the end Or the core rod 26. This circula-
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tin~ fluid which flow out of the core rod 26 through the open-
ings 40a ~lows back into the annular chamber between the tube
32 and the interior larger diameter portion 34 of the core rod
as indicated by the arrows 44. This exhaust flow is indicated
by the arrows 44 along the outside of the tube 32 in Figure 1.
As long as the pressure of the fluid supply to the core
rod is adjusted with respect to the back pressure of the fluid
exhaust so that pressure builds up within the space surrounding
- the core rod, a parison 4~ will be blown and expanded. The
10 core rod structure shown in Figure 1 can be used in several
ways. Fluid can be circulated continuously through the open-
ings 40a and 40b so as to cool the parison 4~ from the inside,
-1 or to bring it to a particular temperature desired for orien-
tation of the parison, or a given quantity of liquid can be
in~ected into the parison from the openings 40a while liquid
in the exhaust passage of the core rod is blocked.
When a given volume of liquid is thus introduced into the
-~ parison from the core rod, while exhaust of liquid from the
passages 40b is blocked, then the parison will be blown to a
predetermined volume depending upon the volume of the liquid.
The shape of the blown article, under such circumstances, can
be determined by a balloon 50 attached to the core rod assembly -
in a manner which will be explained. The thickness and elas-
ticity of the walls of the balloon 50, which can be different
at different locations if desired, determines the shape to
which the balloon expands and thereby determines the shape of
the article blown from the parison 4~, even though the blowing
is not performed in a blowing mold.
The balloon 50 is an elastic balloon which is permanently
co~ected to the core rod assembly and this balloon hugs the
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outside surface of the core rod 26 when the balloon is col-
lapsed.
-- The use of such a balloon is advantageous even when blow-ing the parison in the cavity of a blow mold because it per-
mits the circulation of cooling fluid inside the balloon and
parison at substantial velocities for rapid cooling and such
circulation of cooling fluid could not be used if in direct
contact with the molten parison 4~. Another advantage Or the
' balloon 50 is that it permits the parison to be expanded by
' 10 the use of much higher pressures than are conventional and
.~ the use of such hi~her pressures makes possible the blowing
of the parison at orientation temperatures where the plastic
, material of the parison is beginning to solidify and the
parison cannot be expanded except by the use of much higher
pressures than are used for conventional blow molding. Such
pressures could not be used without the balloon because of the
risk of bursting the wall of the parison at points whlch
were somewhat weaker than other points.
~: The balloon 50 is attached to the core rod assembly
by having a mouth portion 52 of the balloon 50 bear against
: the end face 24 (Figure ~) of the sleeve 20. The end of the
mouth portion of the balloon extends into an undercut recess
54 of the sleeve 20 and as an additional feature for increasing
the strength of this connection there are screw threads 56
-~ as part of the wall of the undercut recess S4. While the
portion of the balloon bulges into the undercut recess 54 is
jammed between the sleeve 20 and the core rod that the sleeve
surrounds, as shown in Figure 1, adhesive is also preferably
¦ used to obtain a tight connection between the balloon 50 and
the sleeve 20,
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In s~ite of the strong connection provided by the con-
struction shown in Figure ~, wear and tear on the balloon is - -further red~ced by having the outside surface 60 of the sleeve
20, which is beyond the shoulder 22, serve as a part of the
parison supporting surface of the core rod assembly. After
the parison is blown to its full size, and the balloon 50 is
collapsed into position hugging the core rod, the outside
diameter of the balloDnis less than the diameter of the sleeve
surface 60 so that the mouth portion of the blown article can
be stripped axially from the core rod assembly without imposing
any axial pull on the collapsed balloon 50.
In order to collapse the balloon 50, after a blowing
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operation, it is essential that provision be made for admitting
air between the outside of the balloon and the inside of the
-~; blown article. Otherwise reduced pressure within the balloon
-. will not collapse the balloon because vacuum will prevent the
! balloon 50 from pulling away from the blown parison ~
, Figures 1, 2 and 3 illustrate means for admitting air
between the balloon and the blown parison, and air supply tube
62 communicates with a passage 64 in the core rod support
12. There is a circumferential groove 66 around the outside of
~ the flange 1~ within the socket 30 Thiscircumferential groove
J communicates through a passage 6~ whichcsmn~nicates with anotherpassage 70 formed by a groove in the outside surface of the
core rod 26. This groove passage 70 leads to another circum-
ferential groove 72 in the outside surface of the core rod 26.
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~. There are angularly spaced openings throu~h the sleeve 20
;~ leading from the annular groove 72 through a part of the out-
side surface of the sleeve 20 over thich the parison ~ extends.
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Small poppet valves 7h in the openings 74 prevent plastic
material from bein~ in~jected into the openings 74 when the
core rod structure is extendin~ into an injection mold.
When pressure is supplied from the tube 62 through the
passages 64, 66, and connecting passages to the radial pas-
sages 72, at the end of a blowing operation, this pressure
moves the poppet valves 76 outwardly far enough to permit air
to enter between the blown parison and the balloon. Channels
7~ in the outside surface 60 Or the sleeve 20 can b~ provided
leading axially from the openings 72; however these channels
;~ are not essential because the air pressure expands the mouth
portion of the parlson, when the blow mold opens, and permits
free flow of air axially to the out~ide surface of the balloon
5Q.
The inner end of the core rod 20 is in axial alignment
`- with a tube ~2 that forms a continuation of the center passage
~'7 through the tube 32. This tube g2 has a splined outer surface
~4 for providing continuation of the annular chamber through
which fluid exhausts along the core rod. The portion of the
tube 32 near the inner end of the core rod is preferably made
~ with a splined surface from the location ~6; this surface
-~ being similar to that shown in Figure 5 and for the purpose
of maintaining the coaxial relation of the tube 32 in the core
rod.
Figure 6 shows a modified construction for introducing
air between the balloon and the blown parison. In Figure 6
~ a balloon 50' is covered by a parison 4~'; and the parison
- 4g' is shown blown to its full size in a blowing mold g6.
7 The end wall of the balloon 50' has an opening ~ at its center.
There is a bead 90 formed on the edge of the openlng ~ of the
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balloon and this bead is held in an undercut slot 92. The under-
cut slot is formed in an end portion of a core rod 94 which may
be similar in construction to the core rod in Figure 1 except
for the open end with a tapered seat 96 against which a poppet
valve 9~ closes.
In the construction illustrated, there is a flange 100 on
the end of the core rod 94 to prevent the portion of the balloon
near the opening from flexing and to provide a surface against
the parison 4g' along which the air flows initally on its way
to the interface between the parison 4~' and the balloon 50'.
The valve 9~ is operated by a valve stem 102 leading back into
Y the support for the core rod and to actuating mechanism that
opens the valve in response to the control means for the cycle
j of the machine.
l Figure 7 shows a sleeve 20' which ls similar to the sleeve
20 shown in Figure 1. Other structure in Figure 7, which cor-
responds to that in Figure 1, is indicated by the same reference
character with a prime appended. The sleeve 20' is shown with-
i out any core rod in it; but a balloon 50l is secured to an end
, 20 face 24' shown in greater detail in Figure 9. The connection
of the balloon 50' to the sleeve 20' is a simpler construction
than that shown in Figure B. The face 24' is formed with a Vee
depression which increases the surface area of the end face 24'.
The mouth of the balloon, which contacts with the face 24', is
thicker than the rest of the balloon 50' and is shaped to fit
into the Vee groove in the face 24'. This provides a large sur-
face area for an adhesive connection of the balloon 50' to the
end face 24'.
The construction shown in Figure 9 is not as strong a
connection as that shown in Figure ~; but for many purposes it
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is more than adequate and it is easier to construct.
Figure 10 shows diagrammatically the core rod assembly
14 of Figure 1 used with a parison 4~a from a different injec-
tion mold than that used for the parison 4~ of Figure 1.
Figure 10 also shows a blowing mold indicated generally by
the reference character 106. An upper mold part 10~ separates
from a lower mold part 110 along a plane 112 in order to open
the mold.
' The mold 106 encloses a cavity 112 which contains a shroud
114 of circular cross section at right angles to the longi-
tudlnal axis of the core rod 26. The shroud 114 is made in
two parts, one of which is attached to the upper mold sec-
- tion 10~ and the other to the lower mold section 110. The
parts of the shroud 114 separate along the plane 112 in the
same manner as the upper and lower sections of the mold 106.
Air or other gas is introduced into the cavity 112
through a supply pipe 11~ in the direction irdicated by the
arrow 120. This air enters the cavity 112 around the outside
-' of the shroud 114 which is smaller than the cavity 112 in
~? 20 both its vertical and horizontal extent. There is clearance
around the shroud 114 both behind and in front Or the shroud
as viewed in Figure 10 so that the air circulates freely and
the pressure is substantially the same in both the upper and
i lower parts of the cavity 112.
Figure 11 shows a portion of the shroud 114 on a larger
scale. There are a multitude of small openings 124 through
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the shroud 114 over substantially the entire area of the
shroud. These openings 124 are not shown in Figure 10 be-
cause the scale of Figure 10 is too small.
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Figure 11 shows the way in which air entering the inside
of the shroud 114 impinges on the surface of the parison 4~a.
The air flow is indicated by arrows 126; and the jets of air
flowing into the inside of the shroud 114 through the openings
124 are strong enou~h to build up an air cushion in the shroud
114. The parison 4ga is expanded by the balloon 50 against this
cushion of air.
The pressure of the cushion of air within the shroud 114
increases as the parison 4~a is expanded until the pressure
-~ 10 approaches the upstream pressure of the air at the upstream
- sides of the openings 124.
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~ The temperature of the air introduced into the chamber
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112 can be at the orientation temperature of the material of
.`r:' the parison 4~a so that the parison is blown at its orienta-
.
-~ tion temperature to produce a stronger container wall. Cold
air can be introduced into the chamber 112 toward the end of the
~,j; blowing period to cool the parison 4~a quickly to a temperature
below its melting point so as to facilitate collapse of the
c,;; balloon 50 and removal of the core rod assembly, balloon and
~- 20 parison from the blowin~ mold.
~t' ~ Air is withdrawn from the inside of the shroud 114 through
~- an exhaust pipe 130 at a controlled rate which depends upon
, the pressure buildup desired within the shroud 114.
The operation illustrated in Figures 10 and 11, in which
the parison is blown against an air cushion instead of being
~` blown into contact with a solid wall of a blow mold cavity is
intended primarily for making containers which have thin
- walls that are pliant and flexible in the finished container.
~; Such containers are made with a thick- and rigid neck or mouth
,,~ 30 portion 134 as illustrated in Figure 10. This mouth portion
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134 as illustrated in Figure 10. This mouth portion 134 is,
however, made of the same material as the rest of the parison
and is therefore of one-piece construction with the flexible
walls of the container. Such a construction is obtained by
having an injection mold with more space for parison material
in the region of the neck than in the portion that will form
the side wall of the container, or by designating the apparatus
so as to expand the wall portion substantially more than with
theusual blown plastic container.
,
. 10 The preferred embodiments of the invention have been illus-
trated and described, but changes and modifications can be made
and some features can be used in different combinations without
departing from the invention as defined in the claims.
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