Note: Descriptions are shown in the official language in which they were submitted.
In conven~ional plastic blow molding ma~hines, the
molten plastic is injected into the cavity of an injection
mold to aPply a parison to a core rod in the cavity. The
plas~lcizer injects the plastic at high pressure and ~hen
main~ains a reduced pressure which supplies plastic to the
- mold to compensate for such shrinkage as occurs from the
înitial cooling of the plastic in the mold cavity.
;~ The plasticizer then draws back plastic to disconnect
the runners from the parison and following this operation,
the plasticizer screw works its way back in the screw barrel
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- to accumulate a charge of plastic for the next injection
operation.
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In some apparatus, new core rods can be brought to the
injection mold more rapidly than the plasticizer can go
through its cycle; and this means that the operation of the
~' plasticizer delays the injection operation and thus limits
what could otherwise be higher production of the molding
machine.
This inventionutilizes two plasticizers which are used
alternately. They are operated so that one of the plasti-
ciæers can prepare itself for the next injection operation
while the other plasticizer is injecting molten material into
the injection mold cavity. In order to make this alternate
operation practical, this invention utilizes a plastic pump
to perform some of the operations of each plasticizer so that
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-~ after an injection of plastic into the injection mold cavity,
the plasticizer wh~ich performs the inljection can start re-
cov~rin~ for the next injection.
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As soon as either ~lasticizer has injected ~lastic
into th~ in,jection mold cavity, valve me~ns shut off that
plasticizer from communication with the in,jection mold. The
plastic oump maintains a pressure on the plastic to compen-
sate for such shrinkage as occurs immediately after injection;
and the plastic pump also draws back the plastic ~o disconnect .. :
the plastic in the runners from the parison in the cavity
both of these functions being ord~narily performed by the
plasticizer. Thus the plastic pump permits the plasticizer :`
to start its re-~overy operat~on immediately following its .
injection of plastic into the injection mold. ~:
The second plasticizer stands ready to inject plas~ic
into the injection mold as soon as the next core ro~ or core
rods are in position and the mold has closed. The plastic
from the second plasticizer is in.jected into the mold and
the second plasticizer is immediately shut off by a valve :~
from communication with the mold so that the plastic pump
. . .. . can again take over and perform the operations of compensating
. ~ for shrinkage and drawing back plastic from the mold runners.
: 20 The same plastic pump can perform the shrinkage com-
pensation and drawback operation for both of the plasticizers
. and in the preferred construction the plastic pump always re-
mains in communication with the mold runners of ~he injection
: molds so that the only valving necessary is that required
for putting the plasticizers alternately in communication
with the injection mold followed by immediate cutoff from
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~ communication with the:injection mold.
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A plastic pump used as a time saver in connection with
a single plasticizer is disclosed in Patenk No. 3,709~644,
issued January 9, 1973.
Other objects, features and advantages of the inven-
. . tion will appear or be poin~ed out as the descrip~ion .,,~,' proceeds.
,~ In the drawing, forming a part ihereof, in which like
; reference characters indicate corresponding parts ~n all
the views: :
... 10 F~gure 1 is a diagrammatic top plan view of a blow
molding machine equipped with two plaatic1zers and a plastic .
.~ pump in accordance with this inventlon; and
' Figure 2 is a fragmentary view~ mostly in section,
showing the injectlon mold, plasticizers and plastic pump
` of Figure 1 on a larger scale. ' , ~ .
~: , Figure 1 shows a four-position blow molding machine
lO which has a frame 12 supporting an injection station 14,
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a parison conditioning station 16, a blowing station lg and
a stripper station 20. An indèxing head 22 rotates about a
:~ 20 center supporting shaft 24 and supports core rods 26 which
extend from the four faces of the i~dexing head 22.
An injection mold 2~ at the injection station 14 has
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~,~ a manifold 30 for supplying molten plastic to the cavities
',~ of the in,jection~mold 2~. At the center of the manifold 30 -~
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there is a recess for receiving an injection nozzle 32 which
is supplied with plastiç material from two separate plas-
ticizers 34 and 36. These two plasticizers are mounted on
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a frame 3~ which is movable toward and from the manifold
20 to bring the nozzle 32 into engagement with the socket
Or the manifold through which plastic is injected into the :~
manifold 30 of the injection mold 2~
The plasticizer 34 has a barrel ~0 which discharges ;
plastic material into a passage 42, and ~here is a shutoff
valve 44 by which the passage 40 can be closed for purposes
which will be explained 1n connection with ~igure 2.
The passage ~2 leads to the nozzle 32. The valve 4
is operated by a handle ~6 which is shown in solid lines
~- in the position which puts the valve 4~ in open position.
The dotted line position of the handle 46 puts the valve. 44
in closed position.
The plasticizer 36 is similarly connected with the ~`
nozzle 32 and parts corresponding to those of the plasticizer
34 are indicated by the same~reference characters for the
pIasticizer 36 but wi~h a prime appended.
` A time saver or plastic pump 50 is located bet~een the
pa~sages ~2 and 42' and has a passage 52 communicating with
the nozzle 32.
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In the operation of the apparatus shown in Figure 1,one or the other of ~he plasticizers 34 or 36 discharges a
supply of molten plastic material into the manifold 30 to
fill the cavities of the injection mold 2g and thereby coat
each of the core rods, in the differsnt moId cavities, with
a parison. When the injection mold 2g opens, the shaft 24
lifts the indexing head 22, and the core rods 26 which the
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indexing head carries, high enough to clear the fixed lowe~
sec~ion of the mold 2~; and the indexlng head turns 90 to
carry the core rods 26 and their parison~ to a conditioning
station 16. Other core rods which were at the stripping
station 20 move into position at the injection station and
are lowered into position as the support 24 lowers the in-
dexing head.
The injection mold 2~ again closes and a supply of
molten plastic material is supplied to the injection mold
cavities from the.other plasticizer 36. The function of
the plastic pump 50 will be described in connection with ~ .
Figure 2,
After the parisons have been applied to the new group
of core rods 26, the injection mold 2~ again opens, the
indexing head rises, and the core rods advanced one station
as the indexing head rotates through another angle of 90.
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This carries the indexing heads at the conditioning station
16 to the blow mold at the blow station 1~ and carries the
.~, new group of core rods frorn the injection station 14 to
.. 20 the conditioning station 16.
: This type of plastic blow molding machine is well known
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and no additional illustration or description of it is
necessary for a complete understanding of this invention.
The novelty of the present invention is in the apparatus for
supplying the molten plastic material to the injection mold
2~:in combination with a blow molding machine of the type:.
shown in ~igure 1. ~
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Figure 2 shows the manifold 30 with runners 56 leading
to seven different cavities of the mold 2g. The center run-
ner 56 of the manifold 30 i~ sho~n communicating ~ith a run~
ner 60 of' the in~ection mold 2~, and this runner 60 leads in~
to a cavity 62 into which a core rod 26 extends. The cavit~
62 is shown filled with a plastic material 64 which comprises
the parison that is coated over the portion of the core rod
26 which pro~gcts into the cav~y 62. In Figur~ 2 the cavity
62 is shown very much shortened by~the fact that much of the
mold 2~ is broken away in order to increase the scale of the
drawing.
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Only one cavity 62 is shown, but it wi~l be understood
that all of the runners $6 of the manifold 30 communicate
with other runners and mold cavities similar to the runner
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60 and mold cavity 62 but which are merely indicaté~ in
Figure 2 by the broken lines 66 which are the center lines ~ -
~ of sùch 1njection mold cavities and mold runners. ~;: ~" . ':
, Figure 2 shows the nozzle 32 located in the socket 6~ ;
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of the manifold 20 and held in the socket with suf~icient
force to resist the pressure of the material discharged from
, a passage junction 70 where the passages 42, 42' and 52
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come together.
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~igure 2 shows the interior of the barrel ~0 of the
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plasticizer 34. A' plasticizer screw 72, located in the
barrel 40, has helical screw threads 74 which advance the
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, pIastic material in the barrel 40 as the screw 72 rotates.
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The screw 72 accumulates plastic material in the
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inside of the barrel ~0 ahead of the scrèw and the screw
forces itself back, toward the right in Figure 2, as more
plastic material is accumulated beyond the forward end of
the screw.
When enough material has been accumulated ahead of
the screw 72, the rotation of the screw stops; and when this
material is to be fed forward through the passage ~2 and into
the iniection mold, the s~rew 72 i~ ~ushed ~orward like a
~iston ~o force the material from ~he interior of the barrel
40 without any rotation of the screw. It will ~e understood
- ~hat in the opera~ion of the plasticizer 34 the passage 42
and the manifold 30 will already contain plastic material
from previous cycles of the machine so tha~ the piston stroke
of the screw 72 need disnlace only as much plastic as i8
necessary to fill all of the cavities of the injection mold;
that is, to replace the plastic material that was carried
away on the core rods at the previous injection operation.
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. : This operation of the plasticiæer 3~ is conventional
and the apparatus for rotating the screw 72 for one ope~a-
tion and advancing it as a piston without rotation for another
operation are well understood in the art and no description
of thi~ apparatus is necessary for a complete understanding
of the present invention.
The plasticizer 36 operates in the same way as the
plasticizer 34 but these plasticizers alternate in supplying
plastic ma~erial to the manifold in the injection mold. In
Figure 2 the screw 72 of the plasticizer 34 may be considered
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as advancing as a pis~on since the valve 44 is open for com-
munication with the mani`old 30 and plastic forced through
the passage ~2 by the screw 72 is advanced through the mani-
:~ fold 30, manifold 30 and plastic forced through the passage
42 by the screw 72 is advanced through the manifold 30,
: manifold runners 56 and mold runners 60 into the injection
cavities 62 of the mold 2g. The plasticizer 36 may be con- :;
sidered as accumulatlng material for the next charge since ~
its valve 42' is closed and material advanced beyond the : ~:
. 10 end of the screw ?2', as this screw rotates, is accumulated
. ahead of the screw while the screw 72 moves back away from
the passage 42'. :; .
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Operating mechanism for the handle 46' is shown as a ~
cylinder-and-piston motor 7~ having a piston rod ~0 with a ~ ;
pin ~2 that~extends through a slot ~4 in the handle 46'.
Reciprocating movement of the motor 7~ causes the handle
46' to move through an angle of approximately 90 from the
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., full line position shown ~o the dotted line position an~
, ~ this turns the valve 42' from closed position to open po-
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20 . sition. It will be understood that this operating mechanism ;
is merely diagrammatic and simplified for clearer illustra-
. tion. It represents an actua~or for opening and closing
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the valve 42'.
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. Apparatus for supplying working fluid to the motor 7g
includes a slide valve ~6 with piping ~ leading to oppo-
site ends of the cylinder of the motor 7~. This slide valve
6 has a center supply iine for working fluid and two exhaust ~ :
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lines indicated by the arrows under the slide valve ~6. The
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slide valve is moved toward the left by a spring 90 whenever
a solenoid 92 is deenergized. Energizing of the solenoid 92
moves the slide valve ~6 into the position indicated by dotted
lines in Figure 2 and this supplies working fluid to the right
hand end of the motor 7~ to move the piston rod ~0 toward the
left so that the valve 42 is moved from closed ~o open posi-
tion.
Power leads of the solenoid 92 lead to a controller
9~ including a timer 96 with power lines 9~ leading to the
solenoid 92.
The plastic pump 50 includes a cylinder-and-piston
mo~or having a piston 100 secured to a piston rod 102 which
~extends into the passage 52 and which carries a small working
piston 104 at the crank end of the piston rod 102.
Adjustable collars 106 on a part of the piston rod 102
beyond the head end of the motor 50 operate limit switches
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lOg and 110 for stopping the movement of the piston rod 102 - `
and the piston 104 at the desired limits of its stroke.
; Working fluid for the motor of the pump 50 is supplied
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throu~h tubing 112 leadin~ from the controller 94 to the
opposite ends of the cylinder on opposite sides of the pis-
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ton 100. The limit switches 10~ and 110 operate the con-
troller to shut off the supply of working fluid to the motor.
It will be understood that the controller 9~ is tied in with
the controls for the plasticizers 34 and 3Ç.
The working piston 10~ is actually the portion of the
plastic pump 50 that contacts with the molten plastic~
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As soon as the plasticizer 34 has completed a stroke in-
jecting plastic material into the manifold 30 and the cavi-
ties of the injection ~old 2~, the control mechanism operates
: a motor 7~a which is identical with the motor 7~ already des~
cribed; and this operation pulls the handle 46 from the full
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line position to the dotted line and thereby closes the valve
~ ~. The controller 94 then supplies working fluid to move
:............ the piston 100 toward the left in Figure 2. This pressure .
on the piston 100 applies pressure to the plastic material ;~
~`: 10 in ~he manifolds 30 and mold 2~ so as to move additional ma- :
terial into the manifold and injection mold as necessary to
compensate for shrinkage of thé plastic during the initial
!;, cooling which follows an injection step.
.~ The controller then reverses the flow of working fluid
ko the piston 100 and urges the piston 100 to move toward
the right so that the working piston 104 draws back molten . ~
plastic material from the runners in the manifold 30 and : .
he injection mold 2~. ~uring this time both o.~ the valves
~ 44 and 44' are closed, and the plasticizer 34 which made 20 the last injection into the manifold 30 and mold 2~ can
be recovering, for the next injection it will make, since
. the plastic pump 50 has relieved the plasticizer 3~ from the
usual plasticizer function of compensating for shrinkage
and drawing back the plastic in the mold runners.
~ As the injection mold 2~ closes for the next group of
;~ core rods, the motor 7~ is actuated.by the timer 9~ to open ~ :~
the valve 44' so that the plasticizer 36 can inject a new
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~harge of plastic material into the manifold 30 and injection
;:`i mold 2~.
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As soon as the p]asticizer 36 has completed its in- :~
: jection of the necessary amount of plastic to fill the in~
jection mold cavities, the motor 7~ closes ~he valve ~4'
and the plastic pump 50 again operates to compensate for
shrinkage and to draw back plastic from the mold runners as
; already described in connection with the operation Or the
plasticizer 34.
The operation of the valve ~4 is under the control of
the controller 94 in the same way as the valve 4~' and as
already described in connection with the valve 4~'. It will
be apparent from the foregoing description that the plastic
pump 50 can operate to relieve both of the plasticizers 34
and 36 from the usual plasticizer operations of compensation
; for shrinkage and drawback of runners; and this combined with
the fact that each plasticizer need operate only every other
cycle greatly shortens the injection period o~ t~e molding ::
;; machine.
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: The preferred embodiment of the invention has be0n il-
. lustrated and described, but chan~es and modifications can
20 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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