U.S. patent number RE38,265 [Application Number 09/928,230] was granted by the patent office on 2003-10-07 for injection molding apparatus having a cooled core.
This patent grant is currently assigned to Mold-Masters Limited. Invention is credited to Denis L. Babin, Jobst Ulrich Gellert, Hans Guenther.
United States Patent |
RE38,265 |
Gellert , et al. |
October 7, 2003 |
Injection molding apparatus having a cooled core
Abstract
Injection molding hot runner apparatus having a cooled mold core
with an elongated body portion with a front portion or head. A
cooling tube extends centrally in body portion of the mold core. A
cooling fluid circuit extends from the open front end of the
cooling tube outwardly through a number of spaced radial bores.
Each radial bore connects to an L-shaped duct leading back to a
cylindrical space around the cooling tube.
Inventors: |
Gellert; Jobst Ulrich
(Georgetown, CA), Babin; Denis L. (Georgetown,
CA), Guenther; Hans (Georgetown, CA) |
Assignee: |
Mold-Masters Limited
(Georgetown, CA)
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Family
ID: |
28678946 |
Appl.
No.: |
09/928,230 |
Filed: |
August 10, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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802048 |
Feb 18, 1997 |
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Reissue of: |
008995 |
Jan 20, 1998 |
05935621 |
Aug 10, 1999 |
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Foreign Application Priority Data
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Jan 24, 1997 [CA] |
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21959074 |
Dec 19, 1997 [CA] |
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2224796 |
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Current U.S.
Class: |
425/549;
425/552 |
Current CPC
Class: |
B29C
45/7312 (20130101) |
Current International
Class: |
B29C
45/73 (20060101); B29C 045/73 () |
Field of
Search: |
;425/547,548,549,552,568 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Heitbrink; Tim
Attorney, Agent or Firm: Sterne, Kessler, Goldstein &
Fox, P.L.L.C.
Parent Case Text
This application is a Continuation-in-part of application Ser. No.
08/802,048 filed Feb. 8, 1997 now abandoned.
Claims
The embodiments of the invention in which an exclusive property or
privilege is claimed is defined as follows:
1. In an injection molding hot runner apparatus having at least one
heated nozzle seated in a cooled mold to convey melt to a gate
leading to a cavity, and at least one cooled core having an
elongated body portion, a central bore, and a front end to provide
the at least one cooled core with a front portion having an outer
surface forming one side of at least a portion of the cavity
extending around the front portion of the cooled core, the cooled
core having a central cooling tube extending in the central bore of
the cooled core with a first cylindrical space extending between
the cooling tube and the surrounding body portion of the cooled
core, the central cooling tube having an open front end inside the
front portion of the cooled core, whereby a cooling fluid circuit
is provided extending inside the cooling tube and along the first
cylindrical space outside the cooling tube to cool the cooled core,
the improvement wherein: the front portion of the at least one
cooled core has a plurality of spaced openings extending outwardly
therein through which the cooling fluid circuit extends, each
opening having an inner end and an outer end, the inner end of each
opening being located adjacent the open front end of the cooling
tube to receive cooling fluid therefrom, the outer end of each
opening being connected by rearwardly and inwardly extending
cooling fluid flow means to the first cylindrical space extending
rearwardly between the cooling tube and the surrounding body
portion of the cooled core.
2. Injection molding apparatus as claimed in claim 1 wherein the
outwardly extending spaced openings are radially extending
bores.
3. Injection molding apparatus as claimed in claim 2 wherein the
rearwardly and inwardly extending cooling fluid flow means
comprises a plurality of spaced L-shaped ducts, each L-shaped duct
having a rear end and an inner end, the rear end being connected to
the outer end of one of the radially extending bores, the inner end
being connected to the first cylindrical space extending rearwardly
between the cooling tube and the surrounding body portion of the
cooled core.
4. Injection molding apparatus as claimed in claim 3 wherein the
front portion of the at least one cooled core comprises a head
which is substantially larger in diameter than the rest of the
cooled core.
5. Injection molding apparatus as claimed in claim 4 wherein the
rearwardly and inwardly extending cooling fluid flow means
comprises a second cylindrical space extending rearwardly to a rear
end from the outer ends of the radially extending bores and a
radially extending space extending inwardly from the rear end of
the second cylindrical space to the first cylindrical space
extending rearwardly between the cooling tube and the surrounding
body portion of the cooled core.
6. Injection molding apparatus as claimed in claim 1 wherein the at
least one cooled core comprises an insert integrally seated in the
elongated body portion to form the front end of the cooled core,
the insert having the plurality of spaced openings extending
outwardly therethrough.
7. Injection molding apparatus as claimed in claim 6 wherein the
outwardly extending spaced openings are radially extending
bores.
8. Injection molding apparatus as claimed in claim 7 wherein the
insert has a generally flat front end and a generally cylindrical
outer surface fitting into a portion of the elongated body portion
having a cylindrical inner wall, and the rearwardly and inwardly
extending cooling fluid flow means comprises a plurality of spaced
L-shaped grooves in the cylindrical outer surface and flat front
end of the insert, each L-shaped groove having a rear end and an
inner end, the rear end being connected to the outer end of one of
the radially extending bores, the inner end being connected to the
first cylindrical space extending rearwardly between the cooling
tube and the surrounding body portion of the cooled core.
9. Injection molding apparatus as claimed in claim 8 wherein the
front portion of the at least one cooled core comprises a head
which is substantially larger in diameter than the rest of the
cooled core..Iadd.
10. An injection molding apparatus, comprising: a melt passage for
conveying hot melt; a mold including a nozzle retainer plate and a
cavity retainer plate; and a cooled core, wherein the nozzle
retainer plate is provided with a heated nozzle in communication
with the melt passage, the cavity retainer plate is provided with a
cavity insert for forming one side of a cavity, and the cooled core
is provided with a head with an outer surface for forming the other
side of the cavity, whereby hot melt is conveyed through the melt
passage, through the heated nozzle, through a gate, and into the
cavity, and wherein the cooled core is provided with a cooling tube
having one end extending into the head, and the head is provided
with a plurality of spaced openings extending from the one end of
the cooling tube, whereby a cooling fluid is circulated through the
cooling tube and the spaced openings in order to cool the head of
the cooled core..Iaddend..Iadd.
11. An injection molding apparatus in accordance with claim 10,
wherein the cooled core comprises an elongated body portion and an
insert, the elongated body portion having a central bore through
which the cooling tube extends, the central bore extending
outwardly at the head to a larger diameter seat to fit around the
insert..Iaddend..Iadd.
12. An injection molding apparatus in accordance with claim 10,
wherein the head is substantially larger in diameter than the rest
of the cooled core in order to provide increased cooling to the
cavity..Iaddend..Iadd.
13. An injection molding apparatus in accordance with claim 11,
wherein the spaced openings are outwardly extending radial
bores..Iaddend..Iadd.
14. An injection molding apparatus in accordance with claim 13,
wherein the radial bores communicate with L-shaped ducts formed
when the insert and the elongated body portion are assembled
together..Iaddend..Iadd.
15. An injection molding apparatus in accordance with claim 11,
wherein the elongated body portion and the insert are brazed
together to form an integral cooled core..Iaddend..Iadd.
16. An injection molding apparatus in accordance with claim 11,
wherein the cooling tube is sufficiently smaller in diameter than
the central bore to provide an elongated cylindrical space between
the cooling tube and the elongated body portion, and wherein the
spaced openings communicate cooling fluid through the head and
between the cooling tube and the elongated cylindrical
space..Iaddend..Iadd.
17. A cooled core for cooling a mold cavity, comprising: an
elongated body portion with a head having an outer surface for
forming one side of the mold cavity; and a cooling tube having one
end extending into the head, the head being provided with a
plurality of spaced openings extending from the one end of the
cooling tube, whereby a cooling fluid is circulated through the
cooling tube and the spaced openings in order to cool the head of
the cooled core..Iaddend..Iadd.
18. A cooled core in accordance with claim 17, wherein the head is
substantially larger in diameter than the rest of the cooled core
in order to provide increased cooling for the mold
cavity..Iaddend..Iadd.
19. A cooled core in accordance with claim 17, wherein the cooled
core comprises an elongated body portion and an insert, the
elongated body portion having a central bore through which the
cooling tube extends, the central bore extending outwardly at the
head to a larger diameter seat to fit around the
insert..Iaddend..Iadd.
20. A cooled core in accordance with claim 19, wherein the spaced
openings are outwardly extending radial bores..Iaddend..Iadd.
21. A cooled core in accordance with claim 20, wherein the radial
bores communicate with L-shaped ducts formed when the insert and
the elongated body portion are assembled
together..Iaddend..Iadd.
22. A cooled core in accordance with claim 19, wherein the cooling
tube is sufficiently smaller in diameter than the central bore to
provide an elongated cylindrical space between the cooling tube and
the elongated body portion, and wherein the cooling fluid flows
through the cooling tube, outward along the head, back in, and
along the cylindrical space around the cooling tube..Iaddend.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to injection molding and more
particularly to hot runner apparatus having improved cooling
provided by the circulation of cooling fluid through spaced
openings in a front portion of an elongated core.
The cycle time of hot runner injection molding systems can be
reduced by providing increased cooling to the cavity. Reducing
cycle time by even a fraction of a second is very important in
large volume applications such as making closures with millions or
even billions of moldings. As seen in U.S. Pat. No. 5,094,603 to
Gellert which issued Mar. 10, 1992, it is well known to provide the
mold with a cooled core by circulating cooling water through a
central cooling tube in the core. While this is satisfactory for
many applications, there is still a considerable delay in the
molding cycle before the mold is opened for ejection waiting for
the melt to solidify. As the front portion of the cooled core forms
part of the cavity, improved cooling must be achieved without
unduly reducing the structural strength of this front portion of
the cooled core.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to at least
partially overcome the disadvantages of the prior art by providing
a cooled core with spaced openings in a front portion through which
cooling fluid is circulated to improve cooling to the cavity.
To this end, in one of its aspects, the invention provides an
injection molding hot runner apparatus having one or more heated
nozzles seated in a cooled mold to convey melt to a gate leading to
a cavity. The mold has one or more cooled cores having an elongated
body portion, a central bore, and a front end. The cooled core has
a front portion having an outer surface forming one side of the
cavity extending around the front portion of the cooled core. The
cooled core has a central cooling tube extending in its central
bore with a first cylindrical space extending between the cooling
tube and the surrounding body portion. The central cooling tube has
an open front end inside the front portion of the cooled core,
whereby a cooling fluid circuit is provided extending inside the
cooling tube and along the first cylindrical space outside the
cooling tube to cool the cooled core. The improvement comprises the
front portion of the at least one cooled core having a number of
spaced openings extending outwardly therein through which the
cooling fluid circuit extends. Each opening has an inner end and an
outer end. The inner end of each opening is located adjacent the
open front end of the cooling tube to receive cooling fluid
therefrom. The outer end of each opening is connected by rearwardly
and inwardly extending cooling fluid flow means to the first
cylindrical space extending rearwardly between the cooling tube and
the surrounding body portion of the cooled core.
Further objects and advantages of the invention will appears from
the following description taken together with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional view showing a portion of a multi-cavity
injection molding system showing a cooled core according to one
embodiment of the invention,
FIG. 2 is a larger sectional view of the cooled core seen in FIG.
1,
FIG. 3 is a sectional view taken along line 3--3 in FIG. 2,
FIG. 4 is a partially cut-away isometric view showing the insert in
position for mounting in the body portion of the cooled core,
FIG. 5 is a sectional view of them assembled together for
brazing,
FIG. 6 is an isometric view similar to FIG. 4 showing the insert
and body portion of a cooled core according to a second embodiment
of the invention,
FIG. 7 is a similar isometric view of a further embodiment of the
invention,
FIG. 8 is a sectional view of the cooled core according to this
further embodiment, and
FIG. 9 is a sectional view taken along line 9--9 in FIG. 8.
DETAILED DESCRIPTION OF THE INVENTION
Reference is first made to FIG. 1 which shows a portion of a
multi-cavity hot runner injection molding system or apparatus
wherein a melt passage 10 branches in a melt distribution manifold
12 to convey hot melt through each heated nozzle 14 to a gate 16
leading to a cavity 18. While the configuration of the mold 20
depends upon the application, in this case the melt distribution
manifold 12 which interconnects the nozzles 14 is mounted between
the nozzle retainer plate 22 and the back plate 24 by a central
locating ring 26 and insulating and resilient spacer members 28. As
can be seen, this provides an insulative air space 30 between the
melt distribution manifold 12 which is heated by an integral
electrical heating element 32 and the surrounding nozzle retainer
plate 22 and back plate 24 which are cooled by pumping cooling
water through cooling conduits 34. Each nozzle 14 extends through
an opening 36 in the nozzle plate 22 with its rear end 38 abutting
against the front surface 40 of the melt distribution manifold 12.
It is heated by an electrical heating element 42 which extends
around a central bore 44 through which the melt passage 10 extends.
The nozzle 14 has a forwardly extending flange portion 46 which
sits on a circular seat 48 in the nozzle retainer plate 22 to
locate the nozzle 12 with an insulative air space 50 between it and
the surrounding mold 20. In this case, a two-piece nozzle seal 52
is mounted in the front end 54 of each nozzle 14 leading to the
aligned gate 16.
As also seen in FIG. 1, the mold 20 also includes a cavity retainer
plate 56 through which holes 58 extend to receive a cavity insert
60 aligned with each nozzle 14. As described in U.S. Pat. No.
5,443,381 to Gellert which issued Aug. 22, 1995, the cavity insert
60 has a front surface 62 which is shaped to form one side of the
cavity 18. Cooling is provided to each cavity insert 60 by cooling
water from an inlet 64 flowing through tortuous passages 66 to an
outlet 68.
The other side of the cavity 18 is formed by the outer surface 70
of the front portion or head 72 of a cooled core 74 according to
the invention. The cooled core 74 has an elongated body portion 76
which in this embodiment has the front portion or head 72 which is
substantially larger in diameter than the rest of the cooled core
74. In the configuration shown, a thin portion 77 of the cavity 18
extends between a cavity ring 78 and a stripper ring 80. The cavity
ring 78 is held in place by a core guide 82 which extends around
the body portion 76 of the core 74. The stripper ring 80 is
received in an opening 84 in a stripper plate 86.
Referring now to FIGS. 2 and 3, it can be seen that the elongated
body portion 76 of the cooled core 74 has a central bore 88
extending into the head 72. A cooling tube 90 extends through the
central bore 88 in the elongated body portion 76 to an open front
end 92 in the head 72. The front end 92 of the cooling tube 90 is
threaded screws into the threaded portion 94 of the central bore 88
in the front portion or head 72. The cooling tube 90 is
sufficiently smaller in diameter than central bore 88 to provide an
elongated cylindrical space 98 between the cooling tube 90 and the
surrounding body portion 76 of the cooled core 74. The front
portion or head 72 of the elongated body portion 76 of the cooled
core 74 has a number of outwardly extending radial bores 100
equally spaced around it. Each radial bore 100 has an outer end 102
and an inner end 104 extending from the central bore 88 adjacent
the open front end 92 of the cooling tube 90. In the embodiment
shown, the head 72 has eight embodiments. The head 72 of the cooled
core 74 also has an equal number of forwardly extending L-shaped
ducts 106, each having a rear end 108 and an inner end 110. The
rear end 108 of each L-shaped duct 106 connects with the outer end
102 of one of the radial bores 100 and the inner end 110 of each
L-shaped duct 106 connects with the cylindrical space 98 between
the cooling tube 90 and the surrounding body portion 76 of the
cooled core 74. Thus, as shown by the arrows in FIG. 2, the core 74
has a circuit 112 for a suitable cooling fluid such as water
flowing through the cooling tube 90, radially outward through the
radial bores 100, along the head 72 and back in through the
L-shaped ducts 106, and along the cylindrical space 98 around the
cooling tube 90. Of course, in other embodiments, the direction of
flow through the circuit can be the opposite.
Reference is now made to FIGS. 4 and 5 in describing how the cooled
core 74 according to the invention is made. Firstly, an insert 114
and the elongated body portion 76 are machined of a suitable
material such as H13 tool steel. In other embodiments, the insert
114 can be made of a more thermally conductive material such as
beryllium copper alloy to further improve cooling. As can be seen,
in this embodiment the insert 114 is made with an upwardly
extending stem portion 118 and a cylindrical portion 120 extending
forwardly from a larger diameter circular flange portion 122. The
cylindrical portion 120 has the radial bores 100 extending
outwardly adjacent the threaded portion 94 of the central bore 88
in the head 72 which receives the open end 92 of the cooling tube
90. The body portion 76 is made with the central bore 88 extending
to a first seat 124 which extends outwardly and upwardly to a
larger diameter second seat 126. L-shaped grooves 128 are machined
in the first seat 124 to form the L-shaped ducts 106 when the
insert 114 and body portion 76 are assembled together. The first
seat 124 is made to fit around the cylindrical portion 120 of the
insert 114. Similarly, the second seat 126 is made to fit around
the flange portion 122 of the insert 114. The body portion 76 is
mounted in an upright position and the insert 114 is lowered into
the position shown in FIG. 4 with the cylindrical portion 120
resting on the first seat 124 and the circular flange portion 122
resting on the second seat 126. The body portion 76 has a pin 132
extending upwardly from the first seat 124 which fits in a matching
hole 134 in the cylindrical portion 120 of the insert 114 to ensure
that the radial bores 100 in the insert 114 are aligned with the
L-shaped grooves 128 in the body portion 76. A quantity of a
suitable material such as powdered nickel alloy 130 is poured
around the flange portion 122 of the insert 114 which has a
bevelled rear surface 136 to direct the powder 130 into place. The
insert and body portion 76 are then loaded into a vacuum furnace
and gradually heated to a temperature of approximately 1925.degree.
F. which is above the melting temperature of the nickel alloy. As
the furnace is heated, it is evacuated to a relatively high vacuum
to remove substantially all of the oxygen and then partially
backfilled with an inert gas such as argon or nitrogen. When the
melting point of the nickel alloy is reached, the nickel alloy 130
melts and flows downwardly around the flange portion 122 and
between the contacting surfaces of the insert 114 and the body
portion 76. The nickel alloy 130 spreads between them by capillary
action to integrally braze the insert 114 and body portion 76
together to form an integral core 74. The cooled core 74 has a
center 131 which is used to machine grind threads on the outer
surface 70 of the head 72 of the cooled core 74. The cooled core 74
is then machined to remove the stem portion 118 and to reduce the
distance of the outer surface 70 of the head 72 is from the cooling
fluid circuit 112 and the cooling tube 90 is screwed into place in
the central bore 88 of the core 74. While this configuration with
the L-shaped grooves 128 being machined in the body portion 76
provides an optimum combination of structural strength and cooling
provided by the proximity of the cooling fluid circuit 112 to the
outer surfaces 70 of the head 72, in an alternate embodiment, the
L-shaped ducts 106 can be made by machining L-shaped grooves in the
insert 114 rather than in the body portion 76. In the embodiment
shown, as seen in FIG. 2, the cooled core 74 is only one part 138
which is joined to another overlapping conventional part 140 to
form an elongated cooled core 74. In this case, the one part 138 is
made by the manufacturer and shipped to the mold maker to be brazed
or welded to the other part 140. Of course, in another embodiment,
the entire cooled core can be made by one party without requiring
two parts.
In use, after the system has been assembled as shown in FIG. 1,
electrical power is applied to the heating elements 32, 42 to heat
the manifold 12 and the nozzles 14 to a predetermined operating
temperature. Cooling water is also circulated by pumps (not shown)
through the cooling conduits 34, the cooling passages 66 in the
cavity inserts 60, and the cooling fluid circuits 112 in the mold
cores 74 to cool the mold 20. Pressurized melt from a molding
machine (not shown) is then introduced according to a predetermined
cycle into the central inlet 142 of the melt passage 10 of the
manifold 12, from where it flows through the melt bore 44 of each
nozzle 14 to fill the cavities 18. After the cavities 18 are full,
injection pressure is held momentarily to pack and then released.
After a short cooling period, the mold 20 is opened to eject the
product. After ejection, the mold 20 is closed the injection
pressure is reapplied to refill the cavities 18. This cycle is
repeated in a continuous cycle with a frequency dependent on the
size and shape of the cavities 18 and the type of material being
molded. Providing the radial bores 100 for the cooling fluid to
flow out into the head 72 of the mold core 74 improves cooling and
reduces injection cycle time by the close proximity of the cooling
circuit 112 to the cavity 18. Providing the L-shaped ducts 106
allows maximum surface contact between the insert 114 and body
portion 76 and gives the integral mold core 74 the necessary
structural strength to withstand injection pressures. The
combination of the radial bores 100 and L-shaped ducts 106 ensures
turbulent flow of the cooling water through the circuit 112 which
further improves cooling efficiency.
Reference is now made to FIG. 6 to describe another embodiment of
the invention. This embodiment is the same as that described above
except that the radial bores 100 extend out to a single L-shaped
space 144 extending continuously around between the cylindrical
portion 120 of the insert 114 and the first seat 124 of the body
portion 76. While this embodiment of the cooled core does not have
as much structural strength as the embodiment described above, it
is sufficient for some applications.
Reference is now made to FIGS. 7-9 to describe a further embodiment
of the invention. In this embodiment, the shape of the elongated
body portion 76 is somewhat different, but it has the first and
second seats 124, 126 extending from the central bore 88 similar to
those shown in FIG. 6. The portion 144 of the elongated body
portion 76 forming the first seat 124 has a generally cylindrical
outer surface 148 extending from the flange portion 122 to a
generally flat front end 150. The cylindrical outer surface 148 of
the insert 114 fits within the cylindrical inner wall 146 of the
elongated body portion 76. The insert 114 again has a number of
spaced bores 100 extending radially therethrough from the outer
cylindrical surface 148 adjacent the threaded portion 94 of the
central bore 88. In this embodiment, the insert 114 has a number of
spaced L-shaped grooves 152 extending in the generally cylindrical
outer surface 148 and generally flat front end 150. The rear end
154 of each L-shaped groove 152 connects with the outer end 150 of
one of the radial bores 100 and the inner end 156 of each L-shaped
groove 152 connects with the cylindrical space 98 between the
cooling tube 90 and the surrounding elongated body portion 76 of
the cooled core 74. Thus, as shown by the arrows in FIG. 8, the
cooled core 74 has a circuit 112 for a suitable cooling fluid such
as water flowing through the cooling tube 90, radially outward
through the radial bores 100, back through the L-shaped grooves
152, and along the cylindrical space 98 around the cooling tube 90.
Of course, in other embodiments, the direction of flow through the
circuit can be reversed. In addition to providing improved cooling
by turbulent flow and increased structural strength, the L-shaped
grooves 152 being entirely in the insert 114 provides the advantage
that the insert 114 does not have to be accurately oriented when
mounted in the body portion 76.
While the description of the cooled mold core 74 with the cooling
fluid circuit 112 extending outwardly in its front portion of head
72 has been given with respect to preferred embodiments, it will be
evident that various other modifications are possible without
departing from the scope of the invention as understood by those
skilled in the art and as provided in the following claims.
* * * * *