CA1087821A - Injection of plastic in molding machine - Google Patents
Injection of plastic in molding machineInfo
- Publication number
- CA1087821A CA1087821A CA236,965A CA236965A CA1087821A CA 1087821 A CA1087821 A CA 1087821A CA 236965 A CA236965 A CA 236965A CA 1087821 A CA1087821 A CA 1087821A
- Authority
- CA
- Canada
- Prior art keywords
- mold
- injection
- pump means
- plasticizers
- plasticizer
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Landscapes
- Injection Moulding Of Plastics Or The Like (AREA)
- Moulds For Moulding Plastics Or The Like (AREA)
Abstract
INJECTION OF PLASTIC IN MOLDING MACHINE
ABSTRACT OF THE DISCLOSURE
The invention reduces the time that a core rod must remain at an injection station of a plastic blow molding machine. The injection operation is usually performed by a plasticizer, and while the injection operation itself requires very little time, the plasticizer performs other roles that must be complete before the next injection. This invention uses two plasticizers alternately so that one can inject while the other recovers for its next injection opera-tion. A plastic pump is used to relieve the plasticizers of some of the operations that they previously performed.
ABSTRACT OF THE DISCLOSURE
The invention reduces the time that a core rod must remain at an injection station of a plastic blow molding machine. The injection operation is usually performed by a plasticizer, and while the injection operation itself requires very little time, the plasticizer performs other roles that must be complete before the next injection. This invention uses two plasticizers alternately so that one can inject while the other recovers for its next injection opera-tion. A plastic pump is used to relieve the plasticizers of some of the operations that they previously performed.
Description
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 ~ . .
- to accumulate a charge of plastic for the next injection operation.
.~ ' .
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 ..
-~ 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.
., , . , .;
'^ 'C''t ~-'., ' ~`
~1 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 ,,. ~, ~ communication with the:injection mold.
..
i. ; ~
~3~ ,~
, , .
:
,'8~
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, .~ . .
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 :
~,~ a manifold 30 for supplying molten plastic to the cavities ',~ of the in,jection~mold 2~. At the center of the manifold 30 -~
.~ .
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 .
~ " . , . , - -. . . .
~8 ~ 8 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.
-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 S
., , ;.' ' . , ~
., .
.: . . ' !. ' . ' : : , : ' ' :; ' " ' ' .. ' . ' r 8;~
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.
.
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 :
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
;~ 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 ~ . .
- to accumulate a charge of plastic for the next injection operation.
.~ ' .
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 ..
-~ 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.
., , . , .;
'^ 'C''t ~-'., ' ~`
~1 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 ,,. ~, ~ communication with the:injection mold.
..
i. ; ~
~3~ ,~
, , .
:
,'8~
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, .~ . .
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 :
~,~ a manifold 30 for supplying molten plastic to the cavities ',~ of the in,jection~mold 2~. At the center of the manifold 30 -~
.~ .
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 .
~ " . , . , - -. . . .
~8 ~ 8 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.
-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 S
., , ;.' ' . , ~
., .
.: . . ' !. ' . ' : : , : ' ' :; ' " ' ' .. ' . ' r 8;~
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.
.
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 :
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. ~
'~ -6- ::
' :
:, , ;' ' 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.
.~ .
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 :: , 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~ ;
: "., 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 :
come together.
,~, ~igure 2 shows the interior of the barrel ~0 of the .. , ~ .
plasticizer 34. A' plasticizer screw 72, located in the barrel 40, has helical screw threads 74 which advance the ,.~
, pIastic material in the barrel 40 as the screw 72 rotates.
~ .', .
The screw 72 accumulates plastic material in the ,, :,,,, - :
.
~; ~ !
.. . _ . . . : . . .
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.
. .
., . : 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 ,`,', .
_g_ .
~ .
:
, ' . '~.,' ~
.
, . . . ~ .
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'. :; .
. .
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 - .
., full line position shown ~o the dotted line position an~
, ~ this turns the valve 42' from closed position to open po-, 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 ... . .
the valve 42'.
, . 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 ~ :
.. ..
lines indicated by the arrows under the slide valve ~6. The 9~ .
: . , , :
.
' 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 , ........................................................................ .
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 . .
throu~h tubing 112 leadin~ from the controller 94 to the opposite ends of the cylinder on opposite sides of the pis--:, 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~
-10_ ' '.
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 ..
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 .
~harge of plastic material into the manifold 30 and injection ;:`i mold 2~.
.- .
, ~ ~ d 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.
^' ' :: : .- .
: 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.
, ' : ' .,, , ~12-.', .
; ` `' ` ' ,'.' ~ ~
shown in ~igure 1. ~
'~ -6- ::
' :
:, , ;' ' 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.
.~ .
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 :: , 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~ ;
: "., 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 :
come together.
,~, ~igure 2 shows the interior of the barrel ~0 of the .. , ~ .
plasticizer 34. A' plasticizer screw 72, located in the barrel 40, has helical screw threads 74 which advance the ,.~
, pIastic material in the barrel 40 as the screw 72 rotates.
~ .', .
The screw 72 accumulates plastic material in the ,, :,,,, - :
.
~; ~ !
.. . _ . . . : . . .
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.
. .
., . : 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 ,`,', .
_g_ .
~ .
:
, ' . '~.,' ~
.
, . . . ~ .
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'. :; .
. .
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 - .
., full line position shown ~o the dotted line position an~
, ~ this turns the valve 42' from closed position to open po-, 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 ... . .
the valve 42'.
, . 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 ~ :
.. ..
lines indicated by the arrows under the slide valve ~6. The 9~ .
: . , , :
.
' 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 , ........................................................................ .
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 . .
throu~h tubing 112 leadin~ from the controller 94 to the opposite ends of the cylinder on opposite sides of the pis--:, 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~
-10_ ' '.
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 ..
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 .
~harge of plastic material into the manifold 30 and injection ;:`i mold 2~.
.- .
, ~ ~ d 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.
^' ' :: : .- .
: 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.
, ' : ' .,, , ~12-.', .
; ` `' ` ' ,'.' ~ ~
Claims (11)
1. Injection molding apparatus including an injection mold, two plasticizers for injecting hot plas-tic material into the mold, passages through which the plasticizers communicate with the mold, and value means for selectively shutting off the communication of each of the plasticizers with the mold, characterized by pump means that draw back plastic material from the mold at the conclusion of each injection operation, and a passage through which the pump means communicates with the mold at a location on the mold side of the valve means.
2. The injection molding apparatus described in claim 1 characterized by the pump means communicating with the mold downstream of the valve means and being operable independently of the shutting off of the com-munication of either plasticizer with the mold whereby said pump means can draw back from the mold material injected by either of the plasticizers.
3. The injection molding apparatus described in claim 2 characterized by the valve means including two separate valves, a different one of which shuts off the communication between each of the plasticizers and the mold, the pump means communicating with the mold on the mold side of each of the valves.
4. The injection molding apparatus described in claim 1 characterized by controls that actuate the pump means in timed relation with the valves that shut off communication of the plasticizers with the mold.
5. The injection molding apparatus described in claim 4 characterized by the controls being timed to start the pump means in a direction to feed molten plastic material to the mold to compensate for cooling shrinkage when a valve in the plasticizer passage shuts off flow from the plasticizer to the mold.
6. The injection molding apparatus described in claim 4 wherein the mold includes a core rod adapted to have a parison formed thereon and characterized by the controls including a timer that reverses the direction of operation of the pump means to suck back molten plastic from mold runners and sever the runner material from the parison prior to the opening of the mold to transfer the core rod, with the parison thereon.
7. The injection molding apparatus described in claim 5 characterized by the pump means having an actuator that moves the pump means in a direction to discharge some of the sucked back material into the passage leading to the mold before completion of the next injection cycle of the apparatus, a control that stops such movement of the pump means actuator while the pump means still has enough stroke to compensate for cooling shrinkage at the end of the next injection cycle, the control means being operable to again start the actuator for the pump means when the supply of molten plastic material from an active plasticizer is discontinued by closing of the valve for that plasticizer.
8. The injection molding apparatus described in claim 1 characterized by the passages from the two plasticizers including a nozzle that connects with the mold at the entrance of a runner passage of the mold, said passages including a single passage through the nozzle and branch passages from said single passage to each of the plasticizers, the valve means being in said branch passage.
9. The injection molding apparatus described in claim 8 characterized by the pump means being connected directly with the single passage.
10. The injection molding apparatus described in claim 9 characterized by the injection mold including a plurality of cavities for receiving a number of separate core rods, a manifold in the injection mold with runners extending to the individual cavities, and a single en-trance passage to the manifold for receiving molten ma-terial from a nozzle that communicates with both of the plasticizers.
11. The injection molding apparatus described in claim 10 characterized by the pump means communicating with the manifold for sucking back material to sever the runner plastic from parisons formed in the respective cavi-ties.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA236,965A CA1087821A (en) | 1975-10-03 | 1975-10-03 | Injection of plastic in molding machine |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA236,965A CA1087821A (en) | 1975-10-03 | 1975-10-03 | Injection of plastic in molding machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1087821A true CA1087821A (en) | 1980-10-21 |
Family
ID=4104193
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA236,965A Expired CA1087821A (en) | 1975-10-03 | 1975-10-03 | Injection of plastic in molding machine |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1087821A (en) |
-
1975
- 1975-10-03 CA CA236,965A patent/CA1087821A/en not_active Expired
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| US4279582A (en) | Method and apparatus for individual control of injection mold shut-off bushings | |
| US4070142A (en) | Injection of plastic in molding machine | |
| US3709644A (en) | Time saver plastic draw-back valve assembly | |
| US3482284A (en) | Dual injection-molding machine | |
| US4722679A (en) | Injection molding machine | |
| US5454995A (en) | Method for reducing cycle time in an injection molding machine | |
| EP0205710A2 (en) | Multi-cylinder type injection molding apparatus | |
| US3940223A (en) | Injection of plastic in molding machine | |
| CA2373421C (en) | Injection nozzle and method for injection molding | |
| JP4244485B2 (en) | Core control method and apparatus for molding machine | |
| US4749536A (en) | Injection molding method for filling mold and maintaining pressure | |
| USRE28721E (en) | Time saver plastic draw-back valve assembly | |
| US2465889A (en) | Injection molding apparatus | |
| CA1087821A (en) | Injection of plastic in molding machine | |
| JPH11114990A (en) | Preplasticating type injecting apparatus and method for injection molding by using it | |
| US3436443A (en) | Molding apparatus and method | |
| US2608826A (en) | Compound hydraulic motor with telescoping pistons | |
| US4464327A (en) | Injection molding of thermoplastics in sandwich mold employing desynchronized injection periods | |
| US4592713A (en) | Mold closing unit of an injection molding machine | |
| US3370324A (en) | Mold injection unit | |
| US2274800A (en) | Pressure casting machine nozzle shut-off | |
| CN206201351U (en) | A kind of injection mold of automatic shaping | |
| JP2659778B2 (en) | Mold clamping device of injection molding machine | |
| JPS5848114Y2 (en) | Injection molding machine | |
| US3480994A (en) | Parison-type bottle blowing machine |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry |