Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTIO~
Injection blow molding processes and apparatus are
widely known and widely used in industry. For example,
reference should be had to U.S. Patents 3,183,552 to Farkas,
U.S. Patent 3,819,314 to Marcus, U.S. Patent 3,339,231 to
Piotrowski and Canadian Patent 995,418 to Cannon et al.
It is and has been a long standing objective of art
processes to achieve a high productivity, i.e., to develop a
process with a rapid, efficient and economical operating
cycle. Art processes known heretofore are subject to one or
more significant disadvantages. Frequently, they are
cumbersome and expensive to operate, and characterized by a
relatively slow operating cycle. A shorter operating cycle
is particularly desirable since it is directly translatable
into a larger number of end products produced.
Processes are known with overlapping cycles in order to
reduce overall cycle time, for example, by providing that
while one parison is being molded another is being blown and
still another is being removed. ~owever, even with
processes using overlapping cycles the output still leaves
much to be desired even after improvement in cycle time.
The foregoing difficulties are at times further
compounded by lack of reliability of prior art processes
necessitating interruptions of the operatlon that impair
operating efficiency.
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Stack-molds are fre~uently used for injection molding
of relatively flat articles and also of cup-shaped
articles. The principle of such a mold is to use
back-to-back injection mol~s in order to double the output
of the unit without substantially increasing its size.
Thus, if a stack-mold is used for a two impression mold one
would obtain four impressions consisting of a "stack" of two
times two impressions, back-to-back.
However, difficulties are encountered in using
stack-molds in injection blow molding since doing so affects
other components of the mold set besides the injection
mold. For example, a preferred operation embodied in
copending U.S. Patent Application Serial No. 618,956, for
INJECTION BLOW MOLDING PROCESS AND APPARATUS, By Tommy
Thomas and John W. West, Filed June 11, 1984, assigned to a
common assignee and the disclosure of which is incorporated
herein by reference, shows, in addition to the injection
mold, a blow core, a blow mold, a removal mold and a removal
mandrel. When one stacks this injection mold in this type
of assembly insufficient space is provided for the removal
of finished parts without extraordinary measures and causing
interference of the function of one removal mold with that
of the other.
AccGrdingly, it is a principal object of the present
invention to provide a process and apparatus for injection
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blow molding hollow plastic articles using a stack-mold for
injection, and to provide a mold assembly characterized by a
rapid, efficient and economical operating cycle in which
finished parts removal may be effec~ed without i~terference.
It is a still further object of the present invention
to provide a process and apparatus as aforesaid which is
convenient and easy to use on a commercial scale and may be
reliably used with high productivity.
Further objects and advantages of the present invention
will appear from the following specification.
SUMMARY OF THE INVENTION
In accordance with the present invention, it has now
been found that the foregoing objects and advantages are
obtained. The method and apparatus of the present invention
are for injection blow molding hollow plastic articles. The
method comprises providing back-to-back first and second
injection molds each i.ncluding a respective first and second
mold cavity formed by a respective first and second mold
wall and a respective first and second core, back-to-back
first and second blow molds each` adjacent respective first
and second mold cavities in side-by-side relationship
therewith, back-to-back irst and second ejection stations
in side-by-side relationship with said respective first and
second blow molds, and first and second ejection mandrels
adjacent respective first and second cores, injecting molten
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plastic into said mold cavities to form first and second
parisons on said cores, moving said parisons on said cores
into said blow molds, expanding said parisons on said cores
in said blow molds to form hollow articles, transferring
said hollow articles to said ejection stations and removing
said hollow articles from said ejection stations, wherein
said first and second cores and said first and second
mandrels operate in overlapping cycles whereby said first
core and first mandrel are located at said first injection
mold and first blow mold, respectively while said second
core and second mandrel are located at a position spaced
from said second injection mold and second blow mold,
respecti-ely and preferably at said second blow mold and
second ejection station. In accordance with the preferred
embodiment first and second ejection mandrels are provided
engageable with said first and second ejection stations,
respectively, and including the steps of transferring the
hollow articles from said blow molds to said ejection
stations on said ejection mandrels. Said cores, blow molds
and ejection stations comprise a first set and second set,
respectively: and a corresponding third and fourth set of
cores, mandrels, blow molds and ejection stations are
provided adjacent and in line with the first and second set,
respectively, with the blow molds and ejection stations in
back-to-back relationship with each other and on opposite
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sides of said first and second injection molds. In the
preferred operation one locates said first core and Eirst
ejection mandrel at said first injection mold and first blow
mold, respectively, while said .second core and second
ejection mandrel are at the same time located at said second
blow mol.d and second ejection station, respectively.
Similarly, the third and fourth sets are simultaneously in
corresponding positions with injection taking place
simultaneously in two opposed injection molds. It is
particularly advantageous to provide a common platen for the
first and third cores and a common platen for the second and
fourth cores with balanced motive means for both platens in
order to use less force to move the platens.
The apparatus of the present invention compri~ses
back-to-back first and second injection molds each including
a mold wall, opposing first and second cores each engageable
with a respective injection mold to form a mold cavity w.ith
its respective mold wall, means to inject molten plastic
into said mold cavities to form parisons therein,
back-to-back first and second blow molds adjacent respective
injection mold cavities in side-by-side relationship
therewith, back-to-back first and second ejection stations
adjacent respective blow molds in side-by-side relationship
therewith, means to move said parisons from said first and
second injection molds to said first and second blow molds
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and means to expand said parisons in said blow molds to form
hollow articles therein, means to move said hollow articles
from said blow molds to said ejection stations for removal
therefrom, and means to locate said first and second cores
in overlapping cycles wherein said first core is located at
said first injection mold while said second core is located
at a position spaced from said second injection mold and
preferably at said second blow mold.
In accordance with a preferred embodiment first and
second ejection mandrels are provided adjacent and in
side-by-side relationship to said first and second cores,
respectively, engageable with the first and second ejection
stations~ respectively, operative to transfer the hollow
articles from said blow molds to said ejection stations.
The cores, mandrels, blow molds and ejection stations
comprise a first and second set, respectively. Preferably,
a corresponding third and fourth set of cores, mandrels,
blow molds and ejection stations are provided adjacent and
in line with the first and second set, respectively, in
back-to-back relationship with each other and on opposite
sides of said first and second injection molds, wherein the
first and second set are operative to operate in overlapping
cycles with each other and at the same time the third and
fourth sets are operative to operate in over]apping cycles
with each other.
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Thus, it can be readily seen that in accordance with
the process and apparatus of the present invention
stack-mo]ds are provided for injections conveniently and
expeditiously enabling one to produce simultaneously twice
as many parts in the same interval, thereby doubling the
output. The overlapping cycle operation is especially
expeditious and enables the process and apparatus to operate
smoothly and efficiently. Moreover, the operation enables
convenient removal of the hollow articles in overlapping
relationship whereby the articles may be expeditiously
removed or ejected without jamming by first removing an
article from one side of the stack and then from another
side of the stack.
Further advantages of the present invention will appear
from the ensuing discussion.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will be more readily
understandable from a consideration of the drawings which
form a part of the present specification wherein
Figure 1 represents an elevational partly schematic
view showing the apparatus of the present invention in the
open position; and
Figure 2 represents an elevational partly schematic
view showing the apparatus of the present invention in the
closed position.
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DETAILED DESCRIPTION
Referring to the drawing, injection station 10, the
first injection station, is secured in platen 11. First and
third blow stations 12 and 13 are also secured to platen 11
and are situated adjacent injection station 10 and in
side-by-side relationship with respect thereto, with blow
station 12 containing first blow mold 16 which may be split
if desired being on one side of the injection station and
blow station 13 containing third blow mold 17 which may be
split if desired being on the other side. Blow molds 16 and
17 correspond to the shape of the hollow articles to be
made. First and third ejection stations 14 and 15 are also
secured to platen 11 and are situated adjacent the
respective blow stations in side-by-side relationship with
respect thereto, with first ejection station 14 situated
adjacent first blow station 12 and third ejection station 15
situated adjacent third blow station 13.
First core 20 is provided secured to movable platen 21
engageable with first injection station 10. The injection
station 10 includes mold wall 22. Thus, when core 20 is
engaged with injection station 10 as shown in Figure 2 the
core 20 is spaced from the mold wall 22 to form a first mold
cavity therebetween. Injection means 24 is in communication
with the mold cavity and is connected to a source of hot
flowable plastic (not shown) for forcin~ said hot formable
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plastic under pressure into the first mold cavity to form a
parison therein, as parison 25.
Core 20 is movable into and out of engagement with
injection station 10 by movable platen 21 actuated by the
motive means shown schematically in the drawings and in a
cycle to be described in more detail hereinbelow.
Naturally, the movement of platen 21 may be accomplished by
conventional means, shown only schematically in the
drawings, which are capable of providing a clamping force
between the two platens to keep them from separating during
the injection step and the other steps which will be
described below.
The hot, newly formed parison 25 remains in the mold
cavity until sufficiently cooled to be removed, if desired
using cooling means 26 adjacent mold wall 22, as for
example, by fluid circulation. If desired, such cooling
means may also be provided in core 20. After such cooling
of parison 25 the clamping force is released and platen 21
is moved away from platen 11 carrying with it core 20 and
parison 25 adhered thereto as shown in the drawing. If a
neck mold is used as to form a threaded neck portion the
neck mold is openable by conventional means and remains
closed during the formation of the parison, removal of the
parison from 'he injection station and blowing, which also
aids in retention of the parison on the core. In the
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present embodiment a neck mold is not employed and both the
parison and final article have a cup-shaped configuration as
seen in the drawing. Thus, parison 25 as well as the final
hollow article has a base portion, a curved lip and
outwardly flaring side walls extending from the base to
lip. The curved lip may serve as an undercut to aid in
retention of the parison on the core. Core 20 is provided
with fluid passageway 33 connected to a source of fLuid
pressure for blowing the final article. If desired, a
vacuum may be drawn through passageway 33 to aid in
retentior. of the parison on the core.
Core 20 with parison 25 thereon is then moved to first
blow station 12 in a manner which first separates the
parison from the mold wall 22 by moving the parison on core
20 axially in a straight path away from said mold wall at
least until the parison clears the injection station,
preferably followed by movement in a substantially arcuate
path into axial alignment with first blow station 12 and
~irs~ blow mold 16, preferably followed by moving the
parison on the core axially in a straight path into blow
mold 16. The preerred axial-arcuate-axial movements are
fully disclosed in said copending U.S. Patent Application SN
618,956. Parison 25 is then expanded on core 20 in blow
mold 16 by fluid pressure through passageway 33 to form
hollow article 34. Figure 1 shows core 20 with parison 25
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thereon removed from the injection station on its path
between injection station 10 and blow station 12 and Figure
2 shows core 20 engaged with the injection station.
After the formation of hollow article 34, core 20 is
S removed from blow station 12 leaving hollow article 34
remaining therein and returned to the injection station
along paths corresponding to the path taken by core 20 from
the injection station 10 to the blow mold 16.
Third core 40 having fluid passageway 45 similar to
passageway 33 is provided on movable platen 21 adjacent core
20 in side-by-side relationship with respect thereto. Third
core 40 is engageable with injection station 10 when core 20
engages blow mold 16 to form a second parison in an
overlapping cycle with respect to core 20. Thus, third core
40 engages injection station 10 to form a parison 25 in a
manner similar to the formation of a parison on core 20 in
the injection station 10. The formation of a parison on
core 40 takes place while core 20 is in the blow mold 16
forming the hollow article. Core 40 carrying a parison 25
is then removed from the injection station and transferred
to third blow station 13 and third blow mold 17 in a path
corresponding to the transfer path of core 10 to first blow
station 12 and first blow mold 17 for formation of an
additional hollow article 34 in blow mold 17. The transfer
of core 40 to blow mold 17 takes place simultaneously with
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the return of core 20 to injection station 10.
After removal of core 20 from blow station 12 hollow
article 34 remains in blow mold 16. Hollow article 34
corresponds in shape generally ,to parison 25 with an
expanded configuration caused by the blowing step. The
blown article 34 cools in contact with the walls of the blow
mold which may contain cooling means 44, as for example for
cooling by fluid circulation in a conventional manner, and
may be retained in the blow mold after removal of the core
lQ therefrom. First ejection mandrel 50 and third ejection
mandrel 51 are provided on movable platen 21 adjacent and in
side-by-side relationship to cores 40 and 20, with first
ejection mandrel 50 alongside core 20 and third ejection
mandrel 51 alongside second core 40. Thus, when cores 20
and 40 leave their respective blow molds 16 and 17 for
return to the injection station with the hollow articles
remaining therein, ejection mandrels 50 and 51 move into
engagement with said hollow articles in the blow molds along
paths corresponding to the paths of cores 20 and 40.
~andrels 50 and 51 then disengage from the blow molds
removing hollow articles 34 with them and move from the blow
stations to the ejection stations along paths corresponding
to the paths of cores 20 and 40. Removal of hollow article
34 onto the ejection mandrels may be assisted by a pusher
means operatively associated with the blow molds for
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positively pushing article 34 away from the blow molds.
Also, ejection mandrels 50 and 51 may be provided with fluid
passageways connected to a source of fluid pressure (not
shown) wh~ch may be used to draw a vacuum and aid in removal
of hollow article 34 from the respective blow molds. The
final hollow article is then transferred to the respective
ejection station, which may incorporate any suitable
ejection means as a chute, suction tube or other
conventional means to convey pla~tic articles. Removal of
article 34 ~rom the ejection mandrels 50 and 51 at ejection
stations 14 and 15 may be assisted by fluid pressure from
the ejection mandrels and also by a stripper means
associated with the ejection mandrels. After removal of the
hollow article 34 at the ejection stations the cycle is
repeated.
The first cores and mandrels together with the first
blow station and the first ejection station comprises the
first set and the third cores and mandrels together with the
third blow station and the third ejection station comprises
the third set. Corresponding to the first and third sets
there are a second and fourth set with blow stations and
ejection stations in back-to-back relationship therewith
which function in the same way as the first and third sets
in overlapping relationship therewith.
Thus, a second injection station 110 is provided in
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back-to-back relationship with the first injection station
10. In side-by-side relationship with the second in~ection
station is the second blow station 112 and in side-by-side
relationship with the second blow station is the second
ejection station 114, both of these elements being in
back-to-back relationship with their counterparts in the
first set. Fourth blow station 113 and the fourth ej0ction
station 115 are provided situated back-to-back with their
corresponding elements in the third set. Second injection
station 110 functions serially with the second and fourth
sets similar to first injection station 10. The second and
fourth sets are carried by fixed platen 111 which may be
joined to platen 11 if convenient. The second in~ection
station may include heating or cooling elements 126 and
includes mold wall 122. Similarly, the second and fourth
blow stations includes a second blow mold 116 and a fourth
blow mold 117 similar to their corresponding elements in the
first and third sets together with heating or cooling means
144.
In a manner similar to the first and third sets, second
core 120 cooperates with the second injection mold and
second blow mold and fourth core 140 cooperates with the
second injection station and fourth blow mold. The second
and fourth cores are carried by movable platen 121 actuated
by motive means shown schematically in a manner similar to
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platen 21. Molten plastic is fed to second injection
station by the same injection means 24 which feeds the first
injection station. The second core includes core passageway
133 and the third core includes core passageway 145.
Parisons 125 are formed on the second and fourth cores in a
manner similar to that described hereinabove. Second
ejection mandrel 150 cooperates with the second blow mold
and second ejection station and fourth ejection mandrel 151
cooperates with the fourth blow mold and fourth ejection
station. Hollow articles 134 are serially ejected via the
second and fourth ejection stations.
Alternatively, either platen 21 or platen 121 may be
movable only in a lateral direction relative to platens 11
and 111 and fixed only in the axial direction of the cores'
while platens 11 and 111 are movable in the axial direction
of said cores and while fixed in the perpendicular direction
thereto. In such an instance hot molten plastic is injected
in a direction perpendicular to platens 11 and 111 by means
arranged between the cores and injection molds, as is
customary in injection molding using stack molds.
Thus, in accordance with the process and apparatus of
the present invention the operation is as follows. First
core 20 cooperates with the first injection mold to form a
parison thereon. The parison is removed from the Eirst
injection mold on core 20 and transferred on core 20 to
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first blow mold 16 where a hollow article is formed
therein. At the same time third core 40 is situated in
injection station 10 to form an additional parison thereon.
The hollow article formed on core 20 is left in the first
blow mold, core 20 removed therefrom and first ejection
mandrel 50 engaged therewith and transferred thereon to
first ejection station 14 for removal therefrom. First core
20 is then resituated in first injection mold for repeat of
the cycle. Third core 40 and third ejection mandrel 51
repeats the cycle in overlapping relationship with the first
core and first ejection mandrel. Thus, for the irst and
third sets while first ejection mandrel 50 is situated in
first ejection station i4 and first core 20 in first blow
mold 16, third ejection mandrel 51 is siutated in third blow
mold 17 and third core 40 in the injection mold.
Simultaneously with the operation of the first and
third cores the second and fourth cores perform the
identical functions except that fourth mandrel 151 is
situated in fourth ejection station 115 while third mandrel
51 is siutated in third blow mold 17. Similarly, first
ejection mandrel 50 is situated in first ejection station 14
while second ejection mandrel 150 is situated in second blow
mold 116.
This procedure enables one to conveniently and
expeditiously utilize the back-to-back ejection stations
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630~
serially in an overlapping cycle. Gate means 60 are
provided in each ejection station to enable the articles to
be ejected from the respective ejection stations. Thus, the
overlapping cycles provide a cooperative relationship
between all cores and molds and ejection stations and enable
the performance of a plurality of functions in overlapping
relationship without interference from one to the other.
An additional advantage of the process and device of
the present invention resides in the use of a coordinated
motive means to move platens 21 and 121 with resultant
conservation of energy. For example one may conveniently
use mech~snical means such as pulleys where the platens are
in balance and only a slight force is necessary to move said
platens. Alternatively, a common fluid pressure source may
be associated with each platen all in a known manner.
While the present invention has been discussed with a
preferred embodiment, it can be readily understood that
numerous variations may be conveniently employed based on
requirements. For example, if desired one may utilize
conventional hot runners associated with both injection
molds communicating with a distributor member by means of
telescoping channels and gating means. Thus, for example,
one may provide that the melt runner system extend through a
movable center platen to reach the cavities. Alternatively,
if desired one may conveniently use only two sets, for
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example only the first and second set may be employed in an
overlapping relationship. Still further, if desired one may
leave either platen 21 or 121 stationary and move the other
platens in cooperative relationship therewith. Naturally,
other variations may be readily apparent to one skilled in
the art.
This invention may be embodied in other forms or
carried out in other ways without departing from the spirit
or essential characteristics thereof. The present
embodiment is therefore to be considered as in all respects
illustrative and not restrictive, the scope of the invention
being indicated by the appended claims, and all changes
which come within the meaning and range of equivalency are
intended to be embraced therein.
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