Note: Descriptions are shown in the official language in which they were submitted.
CA 02695927 2012-12-13
= A Mold for One-step Injection Blow Molding
Plastic Hollow Container with Single Station and Application thereof
Field of the Invention
The present invention relates to plastic processing, and particularly to a
special mould
for forming a plastic hollow container by injection blow molding once on an
injection
molding machine with a set of molds, mainly applied to ordinary injection
molding
machines.
The present invention also relates to a method for forming a plastic hollow
container by
injection blow molding once on an ordinary injection molding machine by a one-
step
method at a single station, wherein a mold core is fixed, and a blow-molding
core and a
parison do not rotate or translate during blow molding, mainly applied to a
hollow container
mold by injecting and blowing in a two-line and one-step manner at a single
station and
with a fixed mold core of the ordinary injection molding machine.
Background of the Art
A hollow plastic product is formed and processed by blowing chiefly by two
kinds of
processes, namely, "extruding-blowing" process and "injecting-blowing"
process. A
protruding seam appears on a surface of the hollow product produced by the
extruding-blowing process and renders the product surface not pleasant and
smooth.
Furthermore, redundant leftover bits and pieces are caused inevitably, which
increases costs
of the product and cause a waste of raw material. On account of the above, a
method of
forming a hollow plastic product by injecting-blowing in two steps is
advanced, wherein the
method relates to injection molding a parison on the injection molding machine
first, then
turning to a blow molding machine to heat the parison and then blow to swell
to form a
hollow container product. In the two-step processing method, there are many
links of
protection, a large investment for equipment is required, the forming process
is complicated
and pollution to the parison is likely to be caused. Recently to overcome the
above
drawbacks, a method for producing a hollow plastic container (see CN 2244992Y
and CN
2122715U) by "injecting and blowing molding in one step at three stations" is
developed,
wherein "injection molding" and "blow molding" are finished on the same
machine. With
regard to the injection-blow molding machine for forming a hollow container at
three
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stations, the three stations are arranged with an angle of 120 degrees
therebetwen in an
equilateral triangle: the first station is an injection forming station, the
second station is a
blow-mold forming station, and the third station is a bottle removing station.
The three
stations can operate simultaneously and are disadvantageous in the following:
the apparatus
for injection-blow molding the hollow container is a special injection-blow
apparatus which
requires a long period of production and processing, a high cost, a large
investment, a
complicated process, and a great difficulty in processing the mold and
difficulty in
mastering it; since a moveable rotary mold core is utilized, the parison
exhibits an
undesirable centering and forming performance so that quality problem such as
uneven wall
of the product might be caused, and the system requires a high configuration
and exhibits a
poor applicability.
In view of the above drawbacks of the specialized apparatuses for injection-
blow
molding a hollow article a method for forming a hollow plastic container by
"injection and
blow molding in one step at two stations" (see CN 1944033A, CN 100361803C and
CN
200970891Y) is proposed, wherein a set of dies are directly mounted on an
ordinary
injection molding machine, the dies are provided with an injection-blow mold,
wherein a
movable die is configured as a mandrel, and after the mandrel injection molds
the parison, it
is brought by a rotary shaft to rotate 900 or 180 and then form the hollow
article by blow
molding. According to this method, the centering performance of the mandrel is
not good
upon blow-molding positioning, the thickness of the blow-molded hollow
container is
uneven, and the product quality is not easy to ensure. The invention patent
(CN 1269626C)
and utility model patent (CN 2511674Y) are mainly applicable for a horizontal-
type
translation-type mold in one step at two stations. According to the method,
after the
injection mold, finishing injection molding of the blow mold parison, opens,
the mandrel
together with the blow-mold parison translate to a blow-mold die of dies of an
injection
molding machine to blow mold to form the product. In this method, the
production
process is hard to control, the dies are not structurally compact, positioning
and centering
performance is undesireable and the product quality is not easy to ensure.
Summary of the Invention
It is thus desirable to provide a mold for forming a plastic product by
injection blow
molding on an ordinary injection molding machine, to overcome one or more of
the above
drawbacks in the prior art.
It is also desirable to provide a method for forming a plastic hollow
container by
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injection blow molding on an ordinary injection molding machine by one-step
method at a
single station, wherein a mold core is fixed without rotation or translation.
Accordingly, a first aspect of the present invention provides a mold for
injection blow
molding a plastic hollow container in one step at a single station, the mold
comprising an
injection mould assembly comprising a movable die and a fixed die arranged
horizontally,
the moveable die being controlled by a first driving mechanism to move
horizontally
relative to the fixed die for opening and closing the injection mould
assembly, wherein
parison-cavities are provided on the fixed die and mandrels are mounted on the
movable die,
each one of the mandrels having a blow opening aligned with a respective one
of the
parison-cavities on the fixed die; and a blow mould assembly for the mandrels,
comprising
first and second injection mold forming modules located respectively on
opposite sides of
the mandrels, wherein an inner side of each one of the first and second
injection mold
forming modules has mold cavities each aligned with a corresponding one of the
mandrels;
and wherein the first and second injection mold forming modules are controlled
by a second
driving mechanism to open and close.
The mold may be directly installed on an ordinary injection molding machine,
wherein
after the injection mold finishes injection molding of the blow mold blank,
the injection
mold opens, then the blow mold closes and blows for formation.
The fixed die may comprise a sprue bush, a hot runner and a parison-cavity
plate,
wherein the hot runner may be an equipartition open type runner. The at least
one column of
parison-cavities may be provided on the parison-cavity plate, and a runner
injection molding
port may be provided at a bottom of the parision cavities.
A push plate moveable in the horizontal direction may be provided on an inner
side of
the moveable die, where the mandrels pass through the push plate. A blow mold
die may be
supported on an outer side of the push plate, and the movement of the push
plate may be
controlled by a third driving mechanism.
Each one of the mandrels may have an interior cavity. A bottom portion of the
interior
cavity may be in communication with an air cylinder on an air intake plate,
and a top
portion of the interior cavity may have an air outlet. A mold core rod
abutting a spring may
be provided inside the interior cavity to control the opening and closing of
the air outlet.
There is also disclosed a method for forming a product of a plastic hollow
container by
injecting and blowing molding once on an ordinary injection molding machine by
one-step
method at a single station, mainly applied to a hollow container mold by
injecting and
blowing in a multi-line and one-step manner at a single station and with a
fixed mold 'core
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of the ordinary injection molding machine.
By this method, a mold for directly injection and blow molding the product of
the
hollow plastic container is mounted on the ordinary injection molding machine,
the method
comprising an injection mold processing stage and a blow mold processing
stage, wherein
the injection mold stage comprises: closing of the mold, injection molding and
opening of
the mold, and the blow mold stage comprises: closing of a blow mold module,
blow
molding, opening of the blow mold module and ejection of the finished hollow
container,
characterized in that during the injection mold stage and the blow mold stage,
after the
opening of the mold, a mandrel is fixed in a moveable die all the while and
not driven by a
power mechanism to rotate or translate; an injection-formed blank is adhered
to the mandrel,
after the mold is completely opened blow mold modules on both sides of a
parison close
under the action of a push rod, after the blow mold modules completely close,
blowing is
carried out in the interior of the mandrel and blow mold formation of the
hollow container is
finished.
The injection mold stage is between injection and the mold opening. During
this stage,
only formation of the injection blank is required, and pressure maintenance
and cooling
setting are not required, and the injection molding machine is in a mold
closing state.
During the blow mold state, the closing of the blow mold module, blowing to
form and
opening the mold to push out the finished product are all finished on the same
mold.
The opening of the mold means that the mandrel constantly follows the opening
and
movement of moveable die without any change of position, and the parison blank
is adhered
to the mandrel. The mandrel does not require a power mechanism to drive to
rotate or
translate.
The closing of the blow mold module means that the blow mold modules are
provided
on both sides of the mandrel, the push rod is driven directly by the third
driving mechanism
such as an oil cylinder or other driving means to allow the blow mold modules
to open and
close, and a center of the blow mold module is coaxial with the mandrel with
the parison.
In a mold exemplary of an embodiment of the present invention, the mandrels
can be
arranged in a single row or multiple rows, and blow molding of the hollow
container can be
carried out by one mold in multiple cavities.
The blow mold parison and the blow mold may be integral with the moveable die.
The
blow mold modules may be installed on both sides of the moveable die core.
After the
injection mold finishes injection molding of the blow mold parison, the
moveable die and
the blow mold parison of the injection mold and the blow mold may together
withdraw and
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open. The parison and the blow mold parison may be fixed on the moveable die
all the
time and may not require a power mechanism to drive to rotate or translate.
Then the blow
mold module may directly close, and blow molding may be carried out. Such a
mold may
form a plastic hollow container by injection blow molding on an ordinary
injection molding
machine. Since the mold core and the injection mold parison can remain at a
constant
position on the moveable die, the mold core may have good centering
performance, the
mold may be structurally compact, easy to install and simple to operate and
maintain, the
product may be finished in one step from the parision, there are not
protruding seams on the
product surface, and the production quality is easier to ensure.
As compared with the prior art, an embodiment of the present invention may
provide one
or more of the following advantages: 1) an ordinary injection molding machine
is directly
used and the drawbacks of production process of the two-step method and the
two-station
method such as too many links and a large investment in equipment are
overcome; 2)
automation degree and production efficiency are substantially improved; 3) the
mold is
structurally compact, easy to install and simple to operate and maintain, 4)
the article is
finished in one step from the parision, the centering performance is good,
there are not
protruding seams on the product surface, and the product quality is easier to
ensure.
Brief Description of the Accompanying Drawings
Fig.1 is a schematic view showing the mounting of the present invention on an
ordinary
injection molding machine;
Fig.2 is a top view of Fig.1;
Fig.2A is a view showing the structure of a mold according to an embodiment of
the
present invention;
Fig.2B is a top view of Fig.2A;
Fig.2C is a partial enlarged view of Fig.2B;
Fig.3A is a schematic view of the mold according to an embodiment of the
present
invention after a first closing of the mold;
Fig.3B is a top view of Fig.3A;
Fig.4A is a schematic view of the mold according to an embodiment of the
present
invention after a first opening of the mold;
Fig.4B is a top view of Fig.4A;
Fig.5A is a schematic view of the mold according to an embodiment of the
present
invention after a second closing of the mold;
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Fig.5B is a top view of Fig.5A;
Fig.6A is a schematic view of blow mold forming;
Fig.6B is a top view of Fig.6A;
Fig.7A is a schematic view of the mold according to an embodiment of the
present
invention after a second opening of the mold;
Fig.7B is a top view of Fig.7A;
Fig.8A is a schematic view illustrating an action state of a push plate of an
embodiment
of the present invention; and
Fig.8B is a top view of Fig.8A.
Embodiments of the present invention are further described below with
reference to the
drawings.
Detailed Description of Preferred Embodiments
As shown in Figs. 1 and 2, an embodiment of the present invention comprises an
injection mold assembly and a blow mold assembly.
The injection mold assembly comprises a moveable die 1 and a fixed die 2
arranged in
the horizontal direction. The moveable die 1 is controlled by a set of driving
mechanisms
to move left and right in a horizontal direction so as to open and close
relative to the fixed
die 2.
The fixed die 2 comprises a sprue bush 203, a hot runner 204 and a parison-
cavity plate
205. The hot runner 204 is an equipartition open type runner. A column of
vertically
arranged parison cavities 201 are provided on each protruding parison cavity
plate 202
disposed on the fixed die 2, and a runner injection molding port is provided
at the bottom of
the parision cavity 201. The fixed die is fixedly connected to a fixed
injection mold end
302 of an ordinary injection molding machine. The parison cavity plate is
convex shaped
so that when the die is closed, a blow molding module on the moveable die is
embedded at
both sides of the parision cavity plate.
On the movable die 1 are fixed two rows of mandrels 101 with blow openings
corresponding to the parison-cavities 201 of the fixed die 2. The moveable die
1
comprises an air intake plate assembly, a base plate 103 and a push plate 102,
wherein the
push plate 102 is provided on one side of the base plate 103 opposite to the
fixed die and
controlled by a second group of driving mechanism to translate left and right
in a horizontal
direction relative to the base plate 103 to push the finished product out, and
the mandrel 101
is provided on the base plate 103 and passes through the push plate 102. In
the interior of
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the mandrel 101 a cavity 1011, is provided, a bottom portion of which is in
communication
with an air inlet 1011 on an air intake plate 6, and a top portion of which is
provided with an
air outlet 1013. Besides, in the interior of the cavity 1011 a mold core rod
1014 with a
spring 1015 to control the opening and closing of the air outlet 1013.
A blow mold assembly is fixed on the outer side of the push rod 102, i.e., on
the side
opposite to the fixed die. Each line of mandrels is provided with a blow mold
assembly 4
which comprises two blow molding modules 401, 402 respectively located on the
left and
right sides of each column of mandrels 101 on the moveable die 1. The two blow
mold
modules are controlled by a third group of hydraulic driving mechanisms 5 to
move forward
and backward in the horizontal direction (i.e., perpendicular to the direction
in which the
moveable die moves left and right in the horizontal direction), thereby
realizing the opening
and closing of the two modules 401, 402. In the present embodiment, since
there are two
columns of mandrels 101, two sets of blow mold assemblies are provided
correspondingly.
A line of mold cavities 403 are provided on an inner side of each of the
modules 401, 402 of
the blow mold assembly and correspond to each mandrel 101.
A left portion of the moveable die 1 is connected to the air intake plate
assembly 6.
A processing method comprises an injection mold processing stage and a blow
mold
processing stage. The injection mold stage is comprised of the following
processes: die
closing of the injection molding machine, injection molding of the parision
and opening of
the die; the blow mold stage comprises the following stages: the closing of
the blow mold,
blowing, opening of the blow mold, preplastification and ejection of the
product.
Upon completion of the die closing of the injection parision, the moveable die
moves
and brings the mandrel to move together, the mandrel is fixed on the moveable
die all the
while, injection molding blank is adhered to the mandrel; after complete
opening of the die,
a blow mold forming module is pushed by an oil cylinder, and the push rod
enables the
blow mold module to close; after the blow mold module completely closes, the
interior of
the mandrel is pushed by an air cylinder and meanwhile blowing is started so
that the blow
mold module finishes blow mold formation of the hollow container. Upon
completion of
the blow molding, the push plate pushes out the finished product, and then the
injection
molding machine starts another injection mold-blow mold cycle. The process is
that in the
injection mold stage, the die closes and a parison is injection molded. After
the die is
opened, the process goes to the blow mold stage, whereupon the blow mold
forming module
closes and blows to form the hollow container, then the blow mold module is
opened and
the finished hollow container is pushed out. The process is characterized in
that in the
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_
injection mold stage and the blow injection stage, after the die is opened,
the forming
mandrel is fixed in the moveable die all the while without movement, and
injection mold
blank is adhered to the mandrel; on completion of the opening of the die, the
blow mold
forming module starts to operate; after the complete closing of the blow mold
module, in
the interior of the mandrel the stretching and blowing is carried out to
finish the blow mold
formation of the hollow container. The injection mold stage is between
injection and the
die opening; formation of the injection blank is only required and pressure
maintenance and
cooling setting are not required, whereupon the injection molding machine is
in a die
closing state. During the blow mold state, the closing of the blow mold
forming module,
blowing to form and opening the die to push out the finishes product are all
finished on the
same mold.
Specific procedure is as follows:
As shown in Figs.3A and 3B, the injection mold stage comprises: closing the
injection
mold, wherein the moveable die 1 advances from left to right towards the fixed
die 2, the
mandrel 101 is inserted into the parison-cavity 201, the parison-cavity
injection molds a
blank 7 to an outer surface of the mandrel; opening the mold after completion
of the
injection molding, wherein as shown in Figs.4A and 413, the moveable die 1
moves left in
the horizontal direction away from the fixed die 2, thereby finishing the
injection molding.
As shown in Figs.5A and 5B, in the blow mold stage, driven by the third
driving
mechanism 5 (a hydraulic mechanism), the two blow mold forming modules 401,
402 of the
blow mold close, mold cavities 403 of the molds on the front and rear sides
close up,
thereby enclosing each mandrel 101 at the center.
As shown in Figs.6A and 6B, the air intake plate assembly 6 blows towards the
interior
of the mandrel 101 so that the blank 7 on the outer surface thereof expands to
fill the space
enclosed by the left and right mold cavities 403, thereby forming a finished
article 8.
As shown in Figs.7A and 7B, on completion of blow molding, the two blow mold
forming modules 401, 402 separate to expose the finished article 8.
As shown in Figs.8A and 8B, the push plate 102 translate right to push out the
finished
article 8 which falls from a gap between the moveable die 1 and the fixed die
2 and is then
collected.
As such, a production cycle is finished at this time, and then the injection
molding
machine start another injection mold-blow mold cycle.
The mold according to the present invention can overcome the drawbacks of
production
process of the two-step method and the two-station method such as too many
links and a
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large investment in equipment, the mold is structurally compact, easy to
install and simple
to operate and maintain, the article is finished in one step from the parison,
the centering
performance is good, there are not protruding seams on the product surface,
the product
quality is easier to ensure and automation degree and production efficiency
are substantially
improved.
8a
