Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
1 Field of the Invention
The present invention relates to a method and apparatus
for forming oriented thermoplastic articles, and more particu-
larly to a method and apparatus utilizing moveable blow pins
for transporting blown pre-forms through a thermal conditioning
region prior to the final blowing operation.
2. The Prior Art
In the art of blow molding thermoplastic articles,
the so-called "blow and blow" technique has become widely used
for molecular orientation. In such operations, a blowable
plastic parison is positioned within a first mold cavity and
blown to a pre-form configuration. Next, the pre-form is
positioned within a second mold cavity, where it is blown to a
configuration of the final container. This general overall
process has undergone several refinements, including a sequential
blow, stretch, and blow technique as disclosed in United States
Patent No. 3,781,395.
Even though the overall operation of Patent No.
3,781,395 advanced the art of molecular orientation, this patent
does not disclose a thermal conditioning means between the
pre-form mold and final blow mold. Thus, the blown pre-form
must be maintained in the pre-form mold for a sufficient period
of time to bring the plastic material temperature to within the
range for molecular orientation. Depending upon the material
being used, an unnecessarily long dwell time may be required
for the pre-form in the first mold cavity, thereby prolonging
the overall "blow and blow" operation cycle.
United States Patent No. 3,873,660 proposes that the
temperature of a blown pre-form be adjusted within a thermal
conditioning chamber between the pre-form molding station and
the final molding station. The apparatus disclosed in this
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patent, however, requires pre-fonm h~ling an~ tr~ung mechanism which
can adversely affect the temperature for optimum molecular
orientation.
Applicants here propose to overcome these disadvantages
in the prior art by the use of a plurality of moveable blow pins
from which the blow pre-forms suspend while in a thermal
conditioning chamber in transit to the final blow molding
station. Although moveable blow pins, per se, are disclosed in
United States Patent No. 3,599,280, and pre-form conveying
10systems are disclosed in United States Patent No. 3,324,507,
these patents do not provide the overall advantages, method,
or apparatus of the present invention.
SUMMARY OF THE INVENTION
The present invention provides a method and apparatus
for blowing a plastic parison into a pre-form, thermally
conditioning the pre-form to a temperature conducive to molecular
orientation, and then blowing the thermally conditioned pre-form
to a final article. The method utilizes the pre-forming step to
thermally pre-condition the plastic material by direct mold
contact prior to a secondary thermal conditioning step within a
separate thermal region.
In a first proposed embodiment, a plurality of
independently moveable blow pins are utilized for transporting
the blown pre-forms from a pre-form molding station to the
final molding station, the blow pins being connected to individual
carrier plates that are slideable along guide rails. These
independently moveable blow pins are inserted into an open end
portion of a mold-enclosed parison at the pre-form molding station.
Air under pressure is supplied through the blow pin to inflate
the parison to a pre-form configuration. After molding operation,
the pre-form mold sections are opened, leaving the blown pre-
; form pendently suspended from the moveable blow pin, which is
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then indexed into a thermal conditioning chamber.
In accordance with the invention, the thermal
conditioning chamber adjusts the temperature of the pre-form
to within a range conducive to substantial molecular orientation
in a final molding operation. After the proper thermal treatment,
the moveable blow pins with suspended pre-forms are then moved
to a final molding station where the pre-form is blown to the
final article and the plastic material is molecularly oriented.
In the apparatus of this first embodiment, the pre-form
mold, thermal conditioning chamber, and final blow mold are
arranged on one general horizontal level and the maveable blow
pins are moved from the pre-form blowing station to the final
blowing station along a set of guide rails. After the blow
; pins are used in the final blowing operation, they are lifted
to a position above the final blow mold and then intermittently
moved back to a position generally above the pre-form mold. When
positioned above the pre-form mold, the blow pin carrier plates
are inserted within a descent yoke and lowered to insert the blow
pins in an open ended portion of a mold-enclosed parison.
In a second embodiment, the moveable carriers, or blow
pins, are attached to a chain-type system which progressively and
intermittently moves the blow pins through a thermal conditioning
chamber to a final blow molding station. In this embodiment, a
separate blow nozzle is used at the pre-form molding station for
; inflating the parison to a pre-form configuration. A set of
bracket arms are attached to the pre-form molds for transporting
the blown pre-form from the blowing nozzle to the moveable blow
~; pins. These bracket arms include vertically reciprocal members
which grasp the outer surface of the blown pre-form neck for
telescopically inserting the pre-form neck over the moveable
blow pins. Then, the bracket arms release the pre-form necks,
leaving the pre-form pendently suspended from the moveable blow
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pins for displacement through the thermal conditioning means to
the final blowing station.
Various alternative structures are also disclosed for
use with either of the two primary overall embodiments. First,
S means are disclosed for rotating the blow pins while in the
thermal conditioning chamber to achieve a more uniform peripheral
pre-form temperature. Second, a replaceable blow pin is dis-
closed, as being releaseably maintained in a blow pin carrier
by a snapfit arrangement. Third, means are disclosed for
stretching the blown pre-form prior to the final blowing
operation.
In accordance with the present teachings, an -
improvement is provided in an apparatus for blow molding plastic
containers which includes a sectional blow mold for receiving
successive blowable parisons, the parisons being blown within
a mold cavity of the first sectional blow mold to successive
pre-forms which have a blown plastic body surmounted by a neck,
and a second sectional blow mold for successively receiving the
; blown pre-forms, the pre-forms being blown within the cavity of
the second blow mold to the final containers and a thermal
conditioning chamber interposed between the first and second
molds and including means for adjusting the temperature of the
blown body of the pre-forms to within a range conducive to
molecular orientation. The improvement which is provided
resides in a plurality of laterally moveable blow pins which
pendently convey the blown pre-forms through the thermal
conditioning chamber to the final blown mold, with each blow
pin iAcluding a downwardly directed nozzle portion including
a substantially cylindrical surface for telescopically fitting
within and engaging the neck portion of a pre-form, each of
the blow pins being rotatably supported by a carrier component,
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and means provided for rotating the blow pins with the pendently
supported pre-forms about a generally vertical axis while the
blow pins are positioned within the thermal conditioning chamber,
so that the temperature of the pre-forms are adjusted substan-
tially uniformly around the periphery thereof, means is pro-
vided for intermittentily and successively displacing the blow
pins with pendently suspended pre-forms from the thermal
conditioning chamber to the final blow mold; and means is
provided for injecting air through the blow pins into the pre-
forms at the final mold to form the blown plastic containers.
It is therefore an object of the present invention toprovide a method and apparatus for continuously manufacturing
blown plastic articles, for reducing overall operational cycle
time and for reducing apparatus components.
A further object of the invention is to provide a
molding method and apparatus capable of accurately adjusting the
temperature of a pre-form to within t~e range for substantial
molecular orientation during a final blowing operation.
Still another ob~ect is to provide a method and
apparatus capable of rapidly quenching plastic material from
melt temperature during a pre-form molding operation to create
shape stability and to control crystalline structure.
Other objects of this invention will appear from the
following description and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic elevational view of one
; embodiment proposed by the present invention for thermally
conditioning a blown pre-form while suspended on a moveable
blow pin.
Figure 2 is a top plan view taken along plane 2-2 as
indicated in Figure 1.
Figure 3 is a perspective view of the blow pin carrier
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descent yoke utili~ed in the embodiment of Figure 1.
Figure 4 is a schematic cross-sectional view taken along
plane 4-4 as indicated in Figure 1, illustrating the thermal
conditioning cham~er with a pre-form suspended from a moveable
blow pin.
Figure 5 is a schematic cross-sectional view taken along
plane 5-5 as indicated in Figure 1, illustrating the final blow
mold station.
Figure 6 is a schematic elevational view illustrating
the parison ejection station and blow pin carrier lift mechanism.
Figure 7 is a schematic elevational view of an
alternative mechanism for spinning the suspended pre-forms
while in a thermal conditioning chamber to provide a uniform
peripheral pre-form temperature.
Figure 8 is a cross-section elevation view taken along
plane 8-8 as indicated in Figure 7.
Figure 9 is a schematic top plan view of a second
embodiment for thermally conditioning a blown pre-form as it is
suspended from a moveable blow pin.
Figure 10 is a cross-sectional view taken along plane
10-10 as indicated in Figure 9, illustrating the pre-form mold
and pre-form conveyor arm proposed for this embodiment.
Figure 11 is a view similar to Figure 10, il~ustrating
the manner of inserting a blown pre-form onto a moveable blow
pin.
Figure 12 is a cross-sectional view taken along plane
12-12 as indicated in Figure 9, illustrating suspended pre-forms
in the thermal conditioning chamber.
Figure 13 is a cross-sectional elevation view illus-
trating an alternative blow pin proposed for use in the embodi-
ment of Figure 9, as it is positioned at a final blowing station.
Figure 14 is a cross-sectional elevation view similar
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to Figure 13, illustrating the pre-form in a stretched condition
prior to final blowing.
Figure 15 is a cross-sectional elevation view similar
to Figures 13 and 14, illustrating the final blown container
within the final blow mold.
Figure 16 is a cross-sectional view taken along plane
16-16 as illustrated in Figure 15.
Figure 17 is a cross-sectional elevational view taken
along plane 17-17 as illustrated in Figure 9.
DETAILED DESCRIPTION OF_THE PREFERRED EMBODIMENTS
The overall method and apparatus of this disclosure
relates to forming a plastic parison, blowing the plastic parison
to a pre-form configuration in a first mold cavity, thermally
conditioning the blown pre-form while suspended from a moveable
blow pin, and then blowing the thermally conditioned pre-form
within a final blow mold. Referring to the drawings, and in
particular to Figures 1 and 2, a first embodiment is illustrated
for carrying out this overall process.
Reference numeral 20 ïndicates an extruder which includes
a downwardly directed annular orifice structure 22 from which a
generally tubular thermoplastic parison 24 issues, either
continuously or intermittently as is well known in the art.
A pre-form mold 25 includes mold sections 26 and 28
which are mounted on tie rods 30 and 32 for transver6e sliding
movement relative to one another by hydraulic cylinders and
pistons 34, 36, 38, and 40, respectively. When closed, as
shown in Figure 2, the pre-form mold sections define a neck or
finish region 41 and a pre-form cavity 42 against which the
parison is expanded to form a blown pre-form.
Figure 1 also illustrates an inclined actuating cylinder
44 having a piston rod 46 that is secured to tie rod 32 for
moving the pre-form molding assemhly 25 from the pre-form mold
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position illustrated in Figures 1 and 2 to a position illustrated
in phantom in Figure 1 for receiving a tubular parison 24.
The sequence of operation for positioning a tubular
parison within a pre-form cavity 42 at the pre-form molding station
is as follows. First, hydraulic cylinders 34 and 38 are actuated
to retract piston rods 36 and 40 to thereby open the pre-form
mold sections 26 and 28. Next, hydraulic cylinder 44 is actuated
to extend piston rod 46 and position the opened pre-form mold
sections on each side of the extruded tubular parison 24. The
pre-form mold sections 26 and 28 are then closed by hydraulic
cylinders 34 and 38 to pinch the parison shut at its bottom end.
A conventional blade 48 then servers the mold enclosed parison
portion from that portion of the parison which is issuing from
the extruder nozzle 22, thereby forming an open-ended parison
portion to receive a blow pin at the pre-form molding station.
Piston rod 46 is then retracted and moves the closed pre-form
mold sections 26 and 28 to the position shown in Figures 1 and 2.
In accordance with the embodiment of Figure 1, a
plurality of independently moveable blow pins, or carriers, 50,
52, 54, 56, 58, 60, 62 and 64 are provided for successive
insertion into the severed, opened ends of blowable plastic
parisons enclosed in the pre-form mold 25. As illustrated, blow
pin 50 is supported within a descent yoke 70 at the pre-form
m~lding station; blow pins 52 and 54 are supported on guide rail
sections 98A and 98B in a thermal conditioning chamber 102;
blow pin 56 is supported on guide rail sections at the final
blowing station; blow pin 58 is supported within a lift mechanism
150; and blow pins 60, 62 and 64 are supported on guide rails
sections 170, prior to placement within the descent yoke assembly
70 for insertion within a blowable parison at the pre-form molding
station.
As best illustrated in Figures 4 and 5, each blow pin
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includes a downwardly directea, dome-shaped terminal nose
portion A, for example 54A and 56A, which is dimensiorLed to fit
within the open end portion of a parison, so that the pre-form
can be suspended therefrom. An enlarged cylindrical shaft portion
B, for example 54B and 56B, surmounts the blow pin nose and is
threadedly recei~ed in a blow pin carrier plate C, for example
54C and 56C. A bore extends through each blow pin carrier
plate and blow pin shaft and nose, as illustrated in Figure 5,
to supply blow air into the parisons and pre-forms during the
molding operations.
As illustrated in Figure 1, blow pin carrier plate 50C
is supported within the yoke descent assembly 70, with the blow
pin nose 50A inserted within the open-ended neck portion of a
mold enclosed parison. The yoke assembly 70 is illustrated in
the perspective view of Figure 3 and includes a vertical
abutment plate 72, a top horizontal pressure plate 74, and two
parallel support arms 76 and 78 extending from the vertical
abutment plate 72. Thus, the blow pin carrier plate C fits
between top pressure plate 74 and rests upon the two horizontal
support arms 76 and 78, with the blow pin extending downwardly
between the slot be~ween the two horizontal support arms.
The descent yoke assembly is raised and lowered by a
hydraulic cylinder 80 and piston rod 82, which is rigidly
connected at its lower end to the top horizontal pressure plate
74. Prior to placement within the descent yoke assembly 70,
blow pin 50 was supported on guide rail sections 170 at the
position where blow pin 64 is illustrated in Figure 1. The
descent yoke assembly was raised to the position as illustrated
in phantom in Figure 1, and blow pin 50 was pushed horizontally
into the descent yoke assembly as will be more fully explained
below.
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With the blow pin 50 and descent yoke assembly positioned
as illustrated in Figure 1, the mold-enclosed parison is blown
to the pre-form configuration by injecting air under pressure
through a blow line 84, into a bore 86 which extends through
piston rod 82 and top pressure plate 74, and then through the
bore of the blow pin. The preform may be removed from the pre-
form mold prior to being cooled to room temperature, thus
serving (a) to reduce the energy required for reheating to
orientation temperature and (b) to reduce the time required
within the next adjacent thermal conditioning chamber. After
the pre-form has been blown, conventional tail pullers 88 are
actuated to remove excess plastic material depending from the
pre-form mold cavity.
An indexing mechanism 90 is provided for displacing
blow pin 50 fLom within the descent yoke 70 after the formation
of the pre-form and after the pre-form mold sections have been
opened. The indexing mechanism includes a hydraulic cylinder 92,
a piston rod 94, and a pull plate 96, the hydraulic cylinder
92 being secured to the top of thermal conditioning chamber
102 by suitable means. As illustrated in Figure 2, pull plate
96 is securely mounted to the end of piston rod 94 and extends
laterally therefrom for alignment with at least a portion of the
blow pin carrier plate. Thus, to move blow pin 50 from descent
yoke 70, piston rod 94 is retracted and pull arm 96 displaces
blow pin 50 to the position previously occupied by blow pin 52.
Blow pin 50 in turn pushes blow pin 52 to the position previously
occupied by blow pin 54 an~ so on, so that blow pin 56 is
pushed to a position beneath lift assembly 150 as supported
partially on guide rails sections 98, 99 and lO0. As illustrated
in Figures 4 and 5, the guide rails sections are comprised of
sets of L-shaped members, for example 98A and 98B. Guide rail
sections 98, 99 and lO0 are longitudinally spaced to provide
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clearance for components of the lift assembly 150, as will be
explained in greater detail below.
Reference numeral 102 indicates a thermal conditioning
chamber which has a dual purpose in the present invention.
First, the chamber reduces the cure time for the blown pre-form
within the pre-form mold and therefore reduces the overall
cycle time for the "blow and blow" process. Second, the thermal
conditioning chamber provides the ability to very accurately
adjust the temperature of the pre-forms to within the optimum
range for the most effective molecular orientation of plastic
material in the final blowing operation. As illustrated in the
drawings, the pre-forms are pendently suspended from the
moveable blow pins while in the thermal conditioning chamber so
that the body of the pre-forms are not in communication with
other transporting members which could conduct heat and there-
fore adversely affect the pre-form thermal condition. It
should be noted also that no additional handling means are
necessary for transporting the thermally conditioned pre-forms
from chamber 102 to the final blowing station. That is, the
thermally conditioned pre-forms remain in a suspended position
from the moveable blow pins for placement in the final blowing
position.
To achieve proper pre-form temperature, a variety of
thermal condition sources may be utilized, depending upon the
particular material being used. For example, Figure 4
illustrates a plurality of heating coils or rods 104 for
supplying heat to the thermal conditioning chamber. These
heating rods could be replaced with hot air sources, or even
alternatively cool air sources. Specifically, heating sources
may be utilized when the blown pre-form is maintained in the
pre-form mold for a significant period of time and becomes
cooled, for example, for transfer stability. In this instance,
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the pre-form would be re-heated to a temperature conducive to
a optimum molecular orientation. As is known in the art, the
most preferable orientation temperature is just above the
glass transition temperature point for the particular plastic
material being used.
In certain instances, the thermal conditioning chamber
may include cool air sources. For example, when thick, heavy
weight polyethylene material is used to form bottles, the
curing time in the pre-form mold may not cool the material to
the optimum temperature for substantial molecular orientation.
In other situations, it may be desirable to adjust
diferent portions of the pre-form to differing temperatures,
so-called differential temperature adjustment. For example,
the heel sections of a blown pre-form may be adjusted to a
temperature cooler than the remaining portions of the pre-form,
since it is known that cool sections expand to a less extent
during final blowing. Therefore, cool air sources could be
positioned in the bottom portion of the thermal conditioning
chamber with warmer air sources being provided for the blown
body portion of the pre-form. Further, as will be discussed
in regard-~o Figures 7 and 8, it may be desirable to rotate
the blown pre-form while in the thermal conditioning chamber
to achieve a more uniform temperature distribution around the
entire pre-form periphery.
Turning now more specifically to Figure 5, the final
blow mold is illustrated as including a pair of sectional
mold halves 106 and 108 which are securely mounted on platens
110 and 112 in any conventional manner. The platens 110 and 112
are slideably transversely toward and away from one another
by power means 113 and 114 (Figure 2) along tie rods 115 and
116. When closed, the blow mold sections 106 and 108 define a
final blow mold cavity 118 which surrounds the pendently
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supported, thermally conditioned pre-form. From Figure 5, it
should be noted that the final blow mold sections 106 and 108
initially contact the pre-~orm substantially only at the
previously formed pre-form neck portion, thus maintaining the
desired pre-form orientation temperature for the body of the
pre-form until the final blowing operation.
The means for supplying blow air to the pre-form for
the final blowing operation comprises an arm 120 which is
pivotally mounted on a hinge pin 122 that extends between
upstanding arms 124 and 126 on platen 110. One end of the arm
120 is pivotally connected by a pin 128 to a piston rod 130
of a hydraulic cylinder arrangement 132 that is suitably
mounted by a bracket 134 to platen 110. A coupling 130 is
threadedly secured within the other end portion of pivotal arm
` 120 and establishes fluid communication between an air supply
line 138 and a bore 140 for accommodating the suppiy of blow
air through the bore in the blow pin for blowing the pre-form
to the configuration of the final article. As illustrated, a
suitable gasket 142 may be secured to the bottom surface of
pivotal arm 120 in alignment with bore 140 so that a fluid-tight
connection will be achieved between the pivotal arm 120 and
the blow pin carrier plate 56C.
The operational sequence at the final blowing station
is as follows. After the pre-form has been blown to the final
blown article, during which blowing operation substantial
molecular orientation is accomplished because the pre-form is
at a temperature conducive to orientation, piston rod 130 is
- retracted to pivot arm 120 about hinge pin 122, thus lifting
gasket 142 away from the top surface of blow pin carrier plate
56C. Next, hydraulic power sources 113 and 114 are actuated
to displace platens 110 and 112 away from each other, leaving
the blown final article pendently suspended from blow pin 56.
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When the indexing mechanism 90 is actuated to pull blow pin 50
from the pre-form molding station to a position within the
thermal conditioning chamber, blow pin 56 is in turn pushed to
a position beneath a lift mechanism 150 and blow pin 54 with a
thermally conditioned pre-form is pushed to a position between
the opened mold sections 106 and 108. Next, the hydraulic
sources 113 and 114 are actuated to displace plates 110 and 112
along tie rods 115 and 116, thereby enclosing the pre-form
on blow pin 54 within mold cavity 118. Piston rod 130 is then
extended to the position shown in Figure 5 so that communication
is established between air supply bore 140 and the bore
extending through blow pin 54. A suitable valving mechanism
~not shown) then supplies blow air through supply line 138, and
another blown article is formed.
While blow pin 56 is positioned at the final blowing
station, blow pin 58 is supported with a suspended final
article 144 on guide rail sections 98, 99 and 100. At this
position, the final blown article is ejected from the blow pin
by any suitable means for position on a conveyor belt 146.
As illustrated in Figure 1, ejection of article 144
has been accomplished and blow pin 58 is supported within a
lift mechanism 150. As illustrated in Figures 1 and 6, the
lift mechanism includes four lift arms 152 having inwardly
directed flanges 153 for supporting and lifting the blow pin
carrier plates. The lift ~ 152 are each pivotally mounted to tab
~ers 154 by pins 156, the tahs extendin~ from a central lift kody 158 which
israised and lowered by a piston rod 160 of a hydraulic cylinder 162.
Hydrauli(~Cylinders 164 and piston rods 166 are pivotally mounted at
respective ends to each set of lift arms 152 by pins 168 and 170.
As illustrated in Figure 1, lift mechanism 150 is in
the process of raising blow pin 58 from the lower guide rails
sections. The assent of the lifting mechanism will continue
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until blow pin carrier plate 58C is in horizontal alignment
with the blow pin carrier plates of blow pins 60, 62 and 64,
as supported on guide rail sections 170 which are similar in
shape and configuration with guide rail sections 98, 99 and
100. At this position, blow pin carrier plate 58C will also
be in horizontal alignment with a push rod 172, which in
essence is a piston rod of a hydraulic cylinder 174. To remove
blow pin 58 from the lift assembly 150, push rod 172 is
extended to engage the end surface of blow pin carrier plate
58C and then to show the blow pin onto the guide rail surfaces
170. At this same time, the descent yoke assembly 70 will be
positioned as illustrated by the phantom lines in Figure 1.
When blow pin 58 is pushed onto guide rail 170 it will engage
blow pin 60 and therefore push blow pins 60, 62 and 64 to the
left as viewed in Figure 1, with blow pin 64 being pushed into
the descent yoke assembly 70 for displacement to the pre-form
blowing station.
Hydraulic cvlinders 164 are then activated to pivot
arms 152 outwardly about hinge pins 156. Piston rod 160 is then
lowered, and the outwardly pivoted flange surfaces 153 clear
a blow pin carrier plate positioned on guide rail surfaces
98, 99, and 100. When the lift mechanism 150 is positioned in
its lowermost descent, pivot arms 152 fit between the spaces
between guide rail sections 98, 99, and 100. At this position,
hydraulic cylinders 164 are activated to inwardly pivot flange
support surfaces 153 for engaging the bottom surface of a blow
pin carrier plate. Next, hydraulic cylinder 162 is activated
and piston rod 162 raises the lift mechanism.
Turning now to Figures 7 and 8, an alternative
embodiment is provided for spinning the pendently suspended
pre-forms while in the thermal conditioning chamber to achieve
a more uniform peripheral temperature. This embodiment is
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especially useful when heating coils or bands are used, since
these elements concentrate their effect on the most adjacent
pre-form surface.
For illustrative purposes, two blow pins 200 and 202
are shown, these blow pins being similar to those of Figures
1-6 in the sense of having a cylindrical shaft portion 204
surmounting a dome-shaped nose portion 206 for insertion
within a parison and pre-form. In this embodiment, however,
the blow pin carrier plate 208 includes a circular opening
209 within which a cylindrical, rotatable shaft 210 is
maintained. A circular supporting plate 212 is secured to
the top of the shaft 210 and rests upon the top surface of the
blow pin carrier plate 208. Blow pin shaft 204 is threadedly
secured to the bottom portion of shaft 210, with an annular
collar 214 fitting on member 204 in close proximity to the
lower surface of blow pin carrier plate 208. Thus, the blow
pin assembly, including components 204, 206, 210, 212 and 214,
are rotatable with respect to the blow pin carrier plates.
The mechanism for rotating the blow pins includes
a support ledge 214 having a pair of shafts 216 and 218
rotatably maintained within respective circular openings,
one such opening being indicated by xeference numeral 220 in
Figure 8. Each rotatable shaft has a respective driven
wheel 222, 224 secured to the top thereof, and an annular
cap 226, 228 threadedly secured to the bottom thereof. Each
annular cap secures an expansible member 230, 232 in position
for engaging and imparting rotary motion to the respective
circular support plates of the blow pin arrangement.
A rotary drive motor is suitably mounted on ledge 214
and has an output shaft 236 connected to a drive wheel 238.
A drive belt 240 fits over drive wheel 238 and imparts rotary
motion to driven wheels 222 and 224.
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The support ledge 214 also includes a longitudinal
bore 242 which is in communication with an air supply line 244
that is connected to the ledge 214 by a threaded coupling 246.
Secondary transverse bores 248 extend from the longitudinal
bore 242 and commu~icate with an annular groove 250 in each
peripheral surface of rotary shafts 216 and 218. A transverse
bore 252 extends radially from the annular groove 250 to
communicate with an axial, longitudinal bore 254, thus
establishing communication between supply line 244 and a
collapsible chamber 256 defined between the lower surface of
the rotatable shafts 216, 218 and the expansible members 230
and 232.
As illustrated in Figures 7 and 8, air under pressure
is being supplied from line 244 to the inflatable, resilient
members 230 and 232. Simultaneously, rotary drive motor 234
is imparting rotary motion to rotatable shafts 216 and 218.
With the inflatable, resilient pads 230 and 232 being in
engagement with the circular supporting plates 212, the blown
pre-forms are rotated about their longitudinal axes while
suspended from the blow pins.
Just prior to the blow pin carrier plates being
indexed to the next position in operational sequence, a negative
pressure may be pulled by line 244, thus collapsing the
expansible members 230 and 232. When blow pin 202 is indexed
to the previous position of blow pin 200, a positive pressure
is re-supplied by line 244, thus expanding pad 230 into contact
with the circular support plate of blow pin 202 to continue
the pre-form spinning operation.
Turning now to Figures 9-17, a second overall embodiment
is illustrated for thermally conditioning pendently supported
pre-forms to a temperature conducive to substantial molecular
orientation. As illustrated in Figure 9, this embodiment
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includes an extruder 300, a pre-form mold 310, a thermal
conditioning chamber 312, a moveable blow pin conveyor system
314, a final mold assembly 316, and a conveyor system 318.
The extruder 300 is conventionally designed and includes a
downwardly directed annular orifice structure 302. The
thermal conditioning chamber 312 may include heating means,
cooling means, or combinations thereo as more fully discussed
in relationship to thermal conditioning chamber 102 of Figure
1. The moveable blow pin conveyor system may be comprised of
conventional chain links, to which separate moveable blow pins
are connected.
As illustrated in Figures 9, 10 and 11, the pre-form
blow mold asse~bly 310 lncludes a pair of blow mold sections 320 and
322 which are moveable transversely toward and away from one
another along tie rods 324 and 326 by piston rods 328 and 330
of hydraulic c~linders 332 and 334. When closed, the blow
mold halves 320 and 322 define a pre-form mold cavity 33~ and
a neck or finished region 338. A piston rod 340 of hydraulic
cylinder 342 is connected to tie rod 326 for moving the pre-
form mold assembly 310 from the pre-form molding position shown
in Figure 10 to a position beneath extruder 300.
A neck bracket assembly 344 is also connected to the
pre-form mold 310 for transporting a blown pre-form from the
pre-form molding station for placement on a moveable blow pin.
The neck bracket assembly includes bracket arms 346 and 348
slideably connected to respective blow mold halves 320 and 322,
the bracket arms having semi-circular recesses 350 and 352 for
gripping the neck portion of a blown pre-form. The bracket
arms are maintained in suitable guideways, (not shown) and are
raised and lowered by respective piston rods 352 of hydraulic
cylinders 354.
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As illustrated in Figure 10, a freshly extruded
tubular parison 304 depends from extruder nozzle 302, a tubular
parison 306 is enclosed within mold cavity 336 in preparation
for the pre-form blowing operation, and a just-blown pre-form
308 is supported by the neck bracket assembly 344 for place-
ment on a terminal nose portion 361 of a moveable blow pin
assembly 362. Further, a vertically reciprocal blow nozzle
356 has been inserted into the open end of the mold-enclosed
parison 306 by a hydraulic cylinder 358.
With the molding assembly positioned as shown in
Figure 10, blow air under pressure is supplied through a
longitudinal bore 360 in blow nozzle 356 for expanding the
mold-enclosed parison 306 to a pre-form configuration.
Substantially simultaneously, hydraulic cylinders 354 are
actuated to extend piston rods 352 to raise bracket arms 346
and 348 for inserting the neck portion of pre-form 308 onto
the blow pin nose 361, as illustrated in Figure 11.
Next, hydraulic cylinders 332 and 334 are actuated
to open the mold halves 320 and 322, thus leaving the freshly
blown pre-form suspended on blow nozzle 356 and pre-form 308
suspended on blow pin assembly 362. Then, hydraulic cylinder
342 retracts piston rod 340 to position mold halves 320 and
322 on each side of parison 304 and neck bracket arms on each
side of the freshly blown pre-form on blow nozzle 356.
Hydraulic cylinders 332 and 334 are then actuated to close the
pre-form mold halves on parison 304, pinching the bottom
portion of the tubular parison shut. At the same time, neck
support bracket arms 346 moved together, with semi-circular
surfaces 350 and 352 closing upon the neck portion of the
previously blown pre-form. While the pre-form mold assembly
is in this position, the moveable blow pin conveyor system 314
is indexed to advance the blow pins. Then hydraulic cylinder
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358 raises blow nozzle 356, hydraulic cylinders 354 lower the
neck bracket assembly, and hydraulic cylinder 342 extends
piston rod 340 to position the pre-form mold assembly as shown
in Figure 10.
Figure 12 simply shows moveable blow pin assemblies
364 and 366 with pendently suspended pre-forms 368 and 370
in thermal conditioning chamber 312. As previously discussed,
the temperature of the suspended pre-forms is adjusted in the
thermal conditioning chamber 312 to within the range most
conducive to substantial thermal orientation during the final
blowing operation.
As shown in Figures 13-15, the final blow mold assembly
316 includes mold halves 372 and 374 which are transversely
mo~eable toward and away from each other by piston rods 376
and 378 of fixed hydraulic cylinders 380 and 382. When closed,
the mold halves 372 and 374 define a final blow molding cavity
384 and a finish or neck region 385. It should be noted from
Figure 14 that the pre-form is contacted by the final blow
mold halves substantially only at the neck portion prior to
the final blowing, thus maintaining the blown pre-form body
substantially at the optimum orientation temperature.
The moveable blow pin assemblies of this embodiment
include a carrier frame 386 which has a central bore 388. A
cylindrical blow pin, or carrier, 390 is maintained within the
central bore 388, with a nose portion of the blow pin 390
extending below the carrier frame 386 for insertion within the
neck of a blown pre-form. The carrier frame 386 includes a
transverse bore 3g2 within which a biasing spring 394 is
maintained by a threaded plug 396, the spring urging a retention
30 ball 398 into an annular groove 400 of blow pin 390. This
arrangement releaseably maintains the blow pin 390 in the
carrier frame assembly 386 to enable quick ejection of the
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blow pins or blow pin substitution.
A hydraulic cylinder 404 is positioned above the final
blow mold assembly 316 and includes a vertically moveable
blow nozzle 406. Figure 13 illustxates the pendently supported
pre-form in position prior to closure of the blow mold halves,
with blow nozzle 406 in alignment with the central bore 402 of
blow pin 390. Figure 14 illustrates that blow nozzle 406 may
be advanced completely through the blow pin 390 to axially
stretch the pre-form to establish an axial orientation of
the thermoplastic material. After the stretching operation,
air under pressure is injected through the blow pin or carrier
390 into the stretched pre-form by supplying air through an
axial bore 408 in the blow nozzle to radial ports 410 or
expanding the pre-form to the configuration shown in Figure 15,
thus bi-axially orienting the molecular structure of the
thermoplastic material.
After the blowing operation hydraulic cylinders 380
` and 382 are actuated to retract blow mold halves 372 and 374,
leaving the blown article pendently suspended from the terminal
nose portion of blow pin 390. The moveable blow pin conveyor
system then indexes the moveable blow pin to a position as
illustrated in Figure 17 above a conveyor 318 where the blown
article can be ejected in any suitable manner.
-~ The foregoing disclosure, therefore, relates to two
primary embodiments for utilizing moveable blow pins for
continuously forming molecularly oriented thermoplastic
containers. It is to be understood that many facets of the
invention which were discussed in regard to one embodiment
could be employed equally as well with the other embodiment.
For example, the rotation means of Figures 7 and 8 may easily
be adapted for use with the moveable blow pin conveyor system
- illustrated in the embodiment of Figure 9. Further, the pre-
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form stretching mechanism disclosed in Figures 13-15 may
likewise be used in conjunction with the final blow mold
assembly shown in Figure 5.
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