U.S. patent application number 10/376910 was filed with the patent office on 2003-08-07 for manifold with film heater.
Invention is credited to Belhadjamida, Hakim, Gellert, Jobst U..
Application Number | 20030145973 10/376910 |
Document ID | / |
Family ID | 23959107 |
Filed Date | 2003-08-07 |
United States Patent
Application |
20030145973 |
Kind Code |
A1 |
Gellert, Jobst U. ; et
al. |
August 7, 2003 |
Manifold with film heater
Abstract
The present invention provides improved heated manifolds,
heaters and nozzles for injection molding, having a high strength
metal skeleton infiltrated with a second phase metal having higher
thermal conductivity. Also disclosed is method of forming a
manifold, heater or nozzle preform and infiltrating the preform
with a highly thermally conductive material. The invention also
provides a method of simultaneously infiltrating and brazing
injection molding components of similar or dissimilar materials
together.
Inventors: |
Gellert, Jobst U.; (Glen
Williams, CA) ; Belhadjamida, Hakim; (Toronto,
CA) |
Correspondence
Address: |
BERESKIN AND PARR
SCOTIA PLAZA
40 KING STREET WEST-SUITE 4000 BOX 401
TORONTO
ON
M5H 3Y2
CA
|
Family ID: |
23959107 |
Appl. No.: |
10/376910 |
Filed: |
March 3, 2003 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10376910 |
Mar 3, 2003 |
|
|
|
09493149 |
Jan 28, 2000 |
|
|
|
6405785 |
|
|
|
|
Current U.S.
Class: |
164/98 ;
164/312 |
Current CPC
Class: |
B22F 2998/10 20130101;
B29C 45/2737 20130101; B22F 2999/00 20130101; B22F 2999/00
20130101; B22F 2998/10 20130101; B33Y 80/00 20141201; B22F 2998/10
20130101; B22F 3/22 20130101; B22F 5/007 20130101; B22F 5/007
20130101; B22F 5/007 20130101; B22F 3/26 20130101; B22F 3/225
20130101; B22F 7/08 20130101; B22F 7/06 20130101; B22F 3/22
20130101; B22F 3/22 20130101; B22F 3/26 20130101; B22F 3/26
20130101; B22F 7/08 20130101; B29C 2045/2745 20130101; B22D 11/0405
20130101; B29C 2045/2746 20130101; B22F 7/062 20130101; B22F 3/22
20130101; B22F 3/225 20130101; B22F 3/26 20130101; B22F 7/08
20130101; B22F 2999/00 20130101; C23C 26/00 20130101; B22F 2998/10
20130101; B22F 7/062 20130101; B23P 15/007 20130101; B22F 2998/00
20130101; B29C 45/2738 20130101; B22F 2998/00 20130101 |
Class at
Publication: |
164/98 ;
164/312 |
International
Class: |
B22D 017/08; B22D
019/04 |
Claims
We claim:
7. A hot runner injection molding apparatus, comprising: (a) a melt
conveying system having (i) a melt distribution manifold having at
least one melt passage for transferring melt from a source of
pressurized melt, and (ii) at least one injection nozzle having a
nozzle melt passage therethrough, said nozzle melt passage in fluid
communication with said at least one manifold melt passage; (b) at
least one mold cavity adjacent said at least one injection nozzle,
said mold cavity in fluid communication with said nozzle melt
passage of said at least one injection nozzle, (c) wherein at least
one of said melt distribution manifold and said injection nozzle
comprises a body and a heating element capable of heating at least
a portion of said body; wherein at least a portion of said body is
made of a parent metal, said parent metal being at least partially
infiltrated with a second metal having a different thermal
conductivity than said parent metal.
8. A melt distribution manifold for an injection molding apparatus,
the manifold having at least one melt passage for transferring melt
from a source of pressurized melt to an injection nozzle, and
comprising a body and a heating element capable of heating at least
a portion of said body, wherein at least a portion of said body is
made of a parent metal at least partially infiltrated with a second
metal having a different thermal conductivity than said parent
metal.
9. An injection nozzle for an injection molding apparatus, the
injection nozzle having a melt bore therethrough and comprising a
body and a heating element capable of heating at least a portion of
said body, wherein at least a portion of said body is made of a
parent metal at least partially infiltrated with a second metal
having a different thermal conductivity than said parent metal.
10. A process for fabricating an injection molding component having
an electrical heating element attached thereto, the process
comprising the steps of: (a) contacting said electrical heating
element with a powdered metal preform having at least partial open
porosity, said powdered metal preform being composed of a first
metal; (b) contacting said preform adjacent a region of said open
porosity with a mass of a second metal, said second metal having a
different thermal conductivity than said first metal; (c) heating
said preform, said heating element and said mass so as to cause
said second metal to at least partially infiltrate said open
porosity of said preform and at least partially join said heating
element to said preform when cooled.
11. A process for fabricating a metal part having at least two
components, the process comprising the steps of: (a) making a
powdered preform of a first component, said preform having at least
partial open porosity; (b) contacting a second component with said
preform of said first component; and (c) infiltrating said open
porosity of preform with a second metal wherein said second
component is brazed to said first component by said second metal
substantially contemporaneously with said infiltration step.
12. A process for fabricating a metal part having at least two
components, the process comprising the steps of: (a) making a
powdered preform of a first component, said preform having at least
partial open porosity; (b) contacting a second component with said
preform of said first component to form an assembly thereof; (c)
contacting said preform first component with a mass of a metal
infiltrant; (d) controllably heating said assembly and said metal
infiltrant to melt said metal infiltrant; (e) holding said assembly
and said metal infiltrant at temperature until said open porosity
of said preform of said first component is at least partially
infiltrated by said metal infiltrant and said second component is
at least partially brazed to said first component by said metal
infiltrant; and (f) controllably cooling said assembly to solidify
the metal infiltrant.
13. The process of claim 12 further comprising the steps of: (a)
providing said first component by: (i) mixing a metal powder with a
binder to form an admixture; (ii) injection molding said admixture
into a preform; (iii) heating said preform to extract said binder
from said binder, thereby leaving said preform with open porosity;
and (iv) partially sintering said preform to partially reduce said
open porosity.
14. The process of claim 12 wherein said second component is
substantially impermeable to said metal infiltrant.
15. The process of claim 14 wherein said second component is a
resistance heater element.
16. The process of claim 12 wherein said second component is a
green powder preform having at least partial open porosity, such
that said second component is capable of being infiltrated by said
metal infiltrant.
17. The process of claim 16 wherein said first and second
components are matable heater plates for a manifold heater.
18. The process of claim 12 wherein said metal infiltrant is a
material having different thermal conductivity than said
preform.
19. The process of claim 12 wherein said metal infiltrant is
substantially copper.
20. The process of claim 12 wherein said first component is made of
a high strength metal alloy.
21. The process of claim 20 wherein said first component is made of
a tool steel.
22. The process of claim 13 wherein said first component is made of
a tool steel.
23. The process of claim 22 wherein the binder is extracted at a
temperature not exceeding 500.degree. C.
24. The process of claim 22, wherein the preform is partially
sintered at a temperature between 1150.degree. C. and 1260.degree.
C.
25. The process of claim 22, wherein said first component porosity
comprises between 40 to 10% volume of said first component prior to
infiltration.
26. The process of claim 12 wherein said infiltration is localized
over a region of said first component.
27. A process for fabricating an injection molding component, the
process comprising the steps of: (a) mixing a powdered tool steel
with a binder to form an admixture; (b) injecting said admixture
into a preform; (c) debinderizing said preform; (d) partially
sintering said preform to achieve 40% to 10% volume open porosity
therein; (e) contacting said preform with a metal infiltrant, said
metal infiltrant having a different thermal conductivity than said
preform; (f) controllably heating said preform and said metal
infiltrant to at least the melting temperature of said metal
infiltrant; (g) holding said preform and said metal infiltrant at
temperature until said porosity of said first component is at least
partially infiltrated by said metal infiltrant; and (h) cooling
said preform to solidify the metal infiltrant and yield said
injection molding component.
28. The process of claim 27 wherein steps (a)-(d) are repeated
prior to step (e) to form a second preform and wherein said second
preform is contacted with the first preform in step (e) such that
said second preform is at least partially infiltrated by said metal
infiltrant in steps (f)-(h) to yield a second manifold heater
plate.
29. The process of claim 28 wherein said manifold heater plate and
said second manifold heater plate are also brazed together by the
performance of steps (e)-(h).
30. The process of claim 29 wherein step (e) further comprises
providing a heater element and contacting said heater element to
said preform and said second preform.
31. The process of claim 30 wherein said heater element is brazed
to at least said manifold heater plate by the performance of steps
(e)-(h).
Description
FIELD OF THE INVENTION
[0001] The invention relates to injection molding and more
particularly to an improved heating element, having high strength
and high thermal conductivity, for use in an injection molding
apparatus.
BACKGROUND OF THE INVENTION
[0002] As is well known in the art, hot runner injection molding
systems have a manifold to convey the pressurized melt from the
inlet at a molding machine to one or more outlets, each of which
lead to a nozzle which, in turn, extends to a gate to an injection
mold cavity. Manifolds and nozzles have various configurations,
depending upon the number and arrangement of the cavities. It is
known to be desirable to provide a means of heating the manifold
and/or nozzles to maintain a desired temperature distribution
across the manifold and/or nozzle. Various means of heating
manifolds and nozzles are known. For instance, a manifold can have
an electrical heating element integrally cast or brazed into the
manifold, as described respectively in U.S. Pat. Nos. 4,688,622 to
Gellert and 4,648,546 to Gellert, a cartridge heater can be cast in
the manifold, as disclosed in U.S. Pat. No. 4,439,915 to Gellert,
or a plate heater can be positioned adjacent the manifold to
provide heat thereto, as disclosed in pending U.S. application Ser.
No. 09/327,490, filed Jun. 8, 1999 and concurrently owned herewith.
Similarly, a nozzle may have an integral heater element brazed
therein, as shown in U.S. Pat. No. 4,557,685 to Gellert, may have a
heated sleeve disposed around the nozzle, as shown in U.S. Pat.
Nos. 5,411,392 and 5,360,333 to Von Buren and Schmidt,
respectively, or may employ a film heater as shown in U.S. Pat. No.
5,973,296.
[0003] The high pressures and temperatures and numerous cycles
experienced in injection molding systems requires manifold, nozzle
and heater components to be fabricated of high strength materials,
typically high strength tools steels, such as H13. Such materials
also typically have good corrosion resistance properties, which is
beneficial as is well known in the art. Tools steels, however, have
poor thermal conductivity, making exacting control over runner and
gate temperatures difficult. Materials such as copper, however,
though highly thermally conductive, typically have low strength and
hardness in comparison to tool steels. Further, copper and its
alloys also have a very poor corrosion resistance. Though, other
thermally conductive materials are known, such as refractory alloys
like molybdenum and tungsten, these materials can be prohibitively
expensive, not to mention difficult to machine.
[0004] For some applications, it is known that high strength and
high thermal conductivity can be achieved through the use of
so-called `metal infiltration` techniques, wherein a porous
skeleton composed of a high strength metal is infiltrated by a
thermally conductive metal to yield a two-phase composite part
having improved characteristics over both component metals. U.S.
Pat. No. 4,710,223 to Matejcezyk discloses an infiltration method
for achieving super erosion and high-temperature resistance in
rocket nozzles and reaction engines by infiltrating a refractory
metal, such as molybdenum or tungsten, with copper or an alloy of
copper. U.S. Pat. No. 5,775,402 to Sachs discloses a process of
so-called `three dimensional printing` whereby a metal
powder/binder mixture is deposited in layers by computer-controlled
machinery to fabricate the complexly-shaped preform layer-by-layer.
The preform is then sintered and infiltrated according to known
techniques to achieve a two-phase material having good strength and
temperature conductivity. Sachs however, requires complex
programming and machinery to achieve the preform.
[0005] There is a need for achieving injection molding manifold,
nozzle and heater components with increased thermal conductivity
without sacrificing strength and, further, there is a need for
achieving such parts through simpler fabrication techniques.
[0006] As noted above, injection molding components can be heated
by an integral heater, such as disclosed in U.S. Pat. No. 4,648,546
to Gellert. Typically, a brazing or bonding step is required to
join the heater element to the component, to obtain good heat
transfer characteristics between the element and the manifold,
nozzle and/or heater. This brazing step, however, requires
additional effort and time in the tooling process.
[0007] Accordingly, there is also a need for a reduction in the
number of manufacturing and tooling operations required in making
high strength and highly thermally conductive manifolds, nozzles
and heaters.
SUMMARY OF THE INVENTION
[0008] In a first embodiment, the present invention provides an
assembly for heating an injection molding component, the assembly
comprising a body and a heating element for controllably heating
the body, the heating element attached to the body, wherein the
body is made of a parent metal, the parent metal being at least
partially infiltrated with a second metal, the second metal having
a higher thermal conductivity than the parent metal.
[0009] In a second embodiment, the present invention provides a hot
runner injection molding apparatus comprising a melt conveying
system, the system having a melt distribution manifold having at
least one melt passage for transferring melt from a source of
pressurized melt, and at least one injection nozzle having a melt
bore therethrough, the melt bore in fluid communication with the at
least one manifold melt passage, at least one mold cavity adjacent
the at least one nozzle, the mold cavity in fluid communication
with the melt bore of the at least one nozzle, a body for heating
at least a portion of the melt conveying system, the body having a
heating element attached thereto, the heating element capable of
heating at least a portion of the body, wherein at least a portion
of the body is made of a parent metal, the parent metal being at
least partially infiltrated with a second metal having a higher
thermal conductivity than the parent metal.
[0010] In a third embodiment, the present invention provides a
process for fabricating an injection molding component having an
electrical heating element attached thereto, the process comprising
the steps of: contacting the electrical heating element with a
powdered metal preform having at least partial open porosity, the
powdered metal preform being composed of a first metal; contacting
the preform adjacent a region of the open porosity with a mass of a
second metal, the second metal having higher thermal conductivity
than the first metal; heating the preform, the heating element and
the mass so as to cause the second metal to at least partially
infiltrate the open porosity of the preform and at least partially
join the heating element to the preform when cooled.
[0011] In a fourth embodiment, the present invention provides a
process for fabricating a metal part having at least two
components, the process comprising the steps of: making a powdered
preform of a first component, the preform having at least partial
open porosity; contacting a second component with the preform of
the first component; and infiltrating the open porosity of preform
with a second metal wherein the second component is brazed to the
first component by the second metal substantially contemporaneously
with the infiltration step.
[0012] In a fifth embodiment, the present invention provides a
process for fabricating a metal part having at least two
components, the process comprising the steps of: making a powdered
preform of a first component, the preform having at least partial
open porosity; contacting a second component with the preform of
the first component to form an assembly thereof; contacting the
preform first component with a mass of a metal infiltrant;
controllably heating the assembly and the metal infiltrant to melt
the metal infiltrant; holding the assembly and the metal infiltrant
at temperature until the open porosity of the preform of the first
component is at least partially infiltrated by the metal infiltrant
and the second component is at least partially brazed to the first
component by the metal infiltrant; and controllably cooling the
assembly to solidify the metal infiltrant.
[0013] In a sixth embodiment, the present invention provides a
process for fabricating an injection molding component, the process
comprising the steps of: mixing a powdered tool steel with a binder
to form an admixture; injecting the admixture into a preform;
debinderizing the preform; partially sintering the preform to
achieve 40% to 10% volume open porosity therein; contacting the
preform with a metal infiltrant, the metal infiltrant having high
thermal conductivity; controllably heating the preform and the
metal infiltrant to at least the melting temperature of the metal
infiltrant; holding the preform and the metal infiltrant at
temperature until the porosity of the first component is at least
partially infiltrated by the metal infiltrant; and cooling the
preform to solidify the metal infiltrant and yield the injection
molding component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] For a better understanding of the present invention, and to
show more clearly how it may be carried into effect, reference will
now be made by way of example to the accompanying drawings. The
drawings show articles made according to preferred embodiments of
the present invention, in which:
[0015] FIG. 1 is a sectional side view of a portion of a typical
injection molding system incorporating an infiltrated heated
manifold in accordance with the present invention;
[0016] FIG. 2 is an exploded isometric view, from the underside, of
the heated manifold assembly of FIG. 1;
[0017] FIG. 3 is a sectional view along the line 3-3 in FIG. 2;
[0018] FIG. 4 is a sectional side view of the heated nozzle of FIG.
1;
[0019] FIG. 5 is a sectional side view of the nozzle of FIG. 4,
shown prior to installation of the nozzle heating element;
[0020] FIG. 6 is a representation of a photomicrograph of the
infiltrated heated manifold of the device of FIG. 1;
[0021] FIG. 7 is a sectional side view of a portion of a typical
injection molding system incorporating an infiltrated manifold
heater plate assembly in accordance with an alternate embodiment of
the present invention;
[0022] FIG. 8 is an exploded isometric view of the heater plate
assembly of FIG. 7;
[0023] FIG. 9 is an isometric view of the assembled heater plate
assembly of FIG. 7;
[0024] FIG. 10 is an isometric view of an alternate embodiment of
the heater plate assembly of FIG. 7;
[0025] FIG. 11 is a sectional view along the line 11-11 in FIG.
10;
[0026] FIG. 12 is a sectional side view of a typical injection
molding system incorporating an infiltrated nozzle band heater
assembly in accordance with an alternate embodiment of the present
invention;
[0027] FIG. 13 is an exploded view of a band heater and spring
clamp according to one aspect of the embodiment of FIG. 12;
[0028] FIG. 14 is a sectional side view of a bimetallic band heater
according to a second aspect of the embodiment of FIG. 12;
[0029] FIG. 15 is an isometric view of the green preform assembly
of the heater plate of FIG. 7;
[0030] FIG. 16 is a sectional side view of a manifold heater
wherein one plate is infiltrated and one plate is
uninfiltrated;
[0031] FIG. 17 is a sectional side view of a portion of a typical
injection molding system incorporating a film heater element and
infiltrated components in accordance with the present
invention;
[0032] FIG. 18 is an enlarged partial view of the film heater plate
of the embodiment of FIG. 17;
[0033] FIG. 19 is a plan view of the film heater of FIG. 17;
and
[0034] FIG. 20 is an enlarged sectional view of the band heater of
FIG. 12 employing a film heater element.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0035] An injection molding system according to the present
invention is shown in the Figures generally at M. Reference is
first made to FIG. 1, which shows a portion of molding system M
having one or more steel nozzles 10 (only one is shown in FIG. 1)
to convey pressurized plastic melt through a melt passage 12 to a
gate 14 leading to a cavity 16 in a mold 18. In this particular
configuration, mold 18 includes a cavity plate 20 and a back plate
22 which are removably secured together by bolts 24. It will be
understood that mold 18 may have a greater number of plates
depending on the application, only plates 20, 22 are shown and
described here, for ease of illustration.
[0036] Mold 18 is cooled by pumping cooling water through cooling
conduits 26 extending in cavity plate 20 and back plate 22. An
electrically heated, infiltrated melt distribution manifold 28
(preferably copper-infiltrated steel) is mounted between cavity
plate 20 and back plate 22 by a central locating ring 30,
positioned in a mating hole 30a in manifold 28, and insulative and
resilient spacer members 32. Melt distribution manifold 28 has a
cylindrical inlet portion 34 and is heated by an integral
electrical heating element 36. An insulative air space 38 is
provided between heated manifold 28 and the surrounding cooled
cavity plate 20 and back plate 22. Melt passage 12 extends from a
common inlet 40 in inlet portion 34 of manifold 28 and branches
outward in manifold 28 to each nozzle 10 where it extends through a
central melt bore 42 and then through an aligned central opening 44
in a torpedo 46 to one of gates 14.
[0037] Each nozzle 10 has an outer surface 48, a rear end 50, and a
forward end 52. Nozzle 10 of this particular configuration is also
heated by an integral electrical heating element 54 which has a
spiral portion 56 extending around melt bore 42 and an external
terminal 58 to which electrical leads 60 from a power source are
connected. In other applications, heating element 36 and the melt
itself may supply sufficient heat that a heating element is not
required in nozzle 10. Nozzle 10 is seated in a well 62 in cavity
plate 20 with a cylindrical locating flange 64 extending forwardly
to a circular locating shoulder 66 in well 62. Thus, an insulative
air space 68 is provided between inner surface 70 of well 62 and
outer surface 48 of nozzle 10 to provide thermal separation between
heated nozzle 10 and the surrounding cooled mold cavity 16. In this
embodiment, melt bore 42 has an enlarged portion with a threaded
inner surface 72 to form a threaded seat 74 at its forward end 52.
In this particular configuration, well 62 has a smaller central
portion 76 which extends forwardly past air space 68 and tapers
inwardly to gate 14. A small circular seat 78 extends in mold
cavity 16 around a central portion 76 of well 62. It will be
understood that nozzle 10 may have other configurations for
different gating arrangements, depending on the gating desired for
a particular application.
[0038] Referring to FIGS. 2 and 3, manifold 28 comprises a
substantially planar body 80 having a groove 82 in a face 84 of
body 80 for receiving electrical heater element 36. The
configuration of groove 82 in face 84 is designed to provide
manifold 28 with a desired temperature distribution depending on
the application. Element 36 is brazed (indicated by reference
numeral 86) into groove 82 in face 84. Such brazing may be
performed according to U.S. Pat. No. 4,648,546 to Gellert,
incorporated herein by reference, or by other known brazing
techniques, i.e. as separate and distinct operations after the
infiltration of manifold 28 has been completed, however, according
to an aspect of the present invention such brazing is preferably
achieved simultaneously with the infiltration of manifold 28, as
will be described more fully below. Also, rather than brazing,
element 36 may equally be joined to manifold 28 by other means,
such as other mechanical attachment means, as are known in the art,
such as by pressing element 36 into manifold 28 to create an
interference, friction or deformation fit. Likewise, thermal
spraying techniques may be employed to bond element 36 to manifold
28. The placement of heating element 36 can also be varied to
locate it in an opposite face 88 of body 80, rather than face
84.
[0039] Referring to FIGS. 4 and 5, outer surface 48 of nozzle 10
has a generally spiralled channel 56 which extends around and along
surface 48 of nozzle 10. A generally helical heating element 54 is
received in the channel 56 and is embedded therein by brazing with
a highly conductive material, such as nickel or copper, as is more
fully described in U.S. Pat. No. 4,557,685 to Gellert and
incorporated herein by reference. As described in the '685 patent,
and as may be seen in the Figures, the pitch of the spiralled
channel 56 is not necessarily uniform, and is generally tighter in
the vicinity of the areas where more heat is required.
[0040] Referring to FIG. 6, manifold 28 comprises a metal skeleton
90 infiltrated by a second phase metal 92, the second phase metal
92 having a higher thermal conductivity than that of metal skeleton
90. Metal skeleton 90 is preferably a tool steel, and more
preferably one of H13, M2 and D2, and most preferably H13. Second
phase metal 92 is any highly thermally conductive metal and
preferably copper, a copper alloy, silver or silver alloy, most
preferably copper. In this application, including the claims
appended hereto, it will be understood that the term "metal" is
used to refer generally to both pure metals and alloys of metal(s).
The process by which infiltration is achieved is described in more
detail below.
[0041] In a second embodiment, nozzle(s) 10 in molding system M is
also infiltrated by a second phase metal, in a manner as just
described for manifold 28, and heater element 54 is also
simultaneously brazed during infiltration into groove 56 by the
second phase metal, as described below. In another aspect of this
embodiment, nozzle 10 is infiltrated and manifold 28 is not.
[0042] In a third embodiment, the melt distribution manifold is
heated externally, such as by a electrical heater plate adjacent
the manifold, as described in U.S. pending application Ser. No.
09/327,490, filed Jun. 8, 1999, which is concurrently owned
herewith and the contents of which are incorporated by reference.
Referring to FIG. 7, in molding system M', a manifold 100 is
mounted between cavity plate 20' and back plate 22' by a central
locating ring 30', and a plurality of insulative spacers 32' are
provided to facilitate maintenance of a temperature differential
between melt distribution manifold 100 and mold 18'. An infiltrated
heater plate 106 (preferably copper-infiltrated steel) according to
the present invention is removably mounted between nozzles 10' and
melt distribution manifold 100 by screws 108 extending through
heater plate 106, through holes 106a, and into manifold 100. A
plurality of locating pins 110 extend from heater plate 106 into
melt distribution manifold 100. Disposed within heater plate 106 is
an electrical heating element 36'. Nozzle 10' is secured to heater
plate 106 and melt distribution manifold 28' by bolts (not shown)
extending through the melt distribution manifold 28' and heater
plate 106.
[0043] Referring to FIGS. 8 and 9, heater plate 106 comprises a
planar body 112 having a front plate 114, having a groove 114a in
an inner face 114b, and a rear plate 116, having a groove 116a in
an inner face 116b. Heating element 36' is positioned intermediate
plates 114 and 116, in a channel 118 formed by grooves 114a and
116a. A central bore 120 is provided in plates 114 and 116 to
permit the passage of pressurized melt from manifold 100 to nozzle
10'. In other embodiments, the heater plate 106 can have a
plurality of melt bores 120 extending therethrough to permit heater
plate 106 to be mounted adjacent a plurality of nozzles 10'.
Heating element 36' has terminal portions 36a extendably positioned
from heater plate 106 for connection to the leads (not shown) of a
controlled power supply (also not shown). The configuration of
channel 118 in heater plate 106 is designed to provide and maintain
the desired temperature distribution across heater plate 106, and
therefore also manifold 100 by conduction from plate 106, for a
given application. Although channel 118 is comprised of cooperating
grooves 114a and 116a in plates 114 and 116, it will be understood
by one skilled in the art that such cooperation is not essential
and that the channel 118 can equally be provided entirely within
plate 114 or 116, as desired.
[0044] Heating element 36' is preferably brazed into channel 118
and plates 114 and 116 are preferably brazed together at faces 114b
to 116b. Such brazing may be performed according to the prior art,
ie. as separate and distinct operations after the infiltration of
plates 114 and 116 has been completed, however, according to an
aspect of the present invention such brazing is preferably achieved
simultaneously with the infiltration of plates 114 and 116, as will
be described more fully below. Alternately to brazing, plates 114
and 116 may be joined, and element 36' bonded therein and thereto,
using any other mechanical or metallurgical means known in the art
as suitable, such as friction fit or thermal spraying, etc.
[0045] It will be understood by one skilled in the art that the
heater plate may be positioned elsewhere in relation to the
manifold, such as the position shown in the FIG. 17 embodiment
described below.
[0046] Referring to FIGS. 10 and 11, it will be understood that
other means of heating the manifold and heater plate are available.
The heater elements 36 and 36' can be replaced by a heating passage
130 through which a heated fluid 132, such as oil, is circulated.
In another embodiment (not shown), the heating element can be one
or more conventional cartridge type resistance heaters or heat
pipes extending into one or more bores in manifold 28 or heater
plate 106, such as is described in U.S. Pat. No. 4,500,279 to
Devellian, incorporated herein by reference.
[0047] In a yet further embodiment, nozzle 10, rather than having
integral heating element 54, has an external band heater, of the
types disclosed in U.S Pat. Nos. 5,411,392 to Von Buren and
5,360,333 to Schmidt, both of which are incorporated herein by
reference. The construction of such band heaters will only briefly
be described herein, though one skilled in the art will understand
that the '392 and '333 patents fully describe the construction and
operation of such heaters.
[0048] Referring to FIG. 12, molding system M" is substantially
identical to molding system M, except as will now be described.
Nozzle 10" comprises a simple injection molding nozzle having a
smooth outer surface 48". A band heater 200 is positioned snugly
around nozzle 10". In operation, band heater 200 is connected to
electrical leads 60" and provides heat by conduction to nozzle
10".
[0049] In one aspect of the embodiment of FIG. 12, band heater 200
may comprise a heater of the type disclosed in U.S. Pat. No.
5,411,392. Referring to FIG. 13, in this aspect heater 200
comprises an annular heater 202 and an annular spring 204. Spring
204 is formed to be spring-like and to exert continuous pressure on
heater 202 to urge heater 202 towards nozzle 10". Spring 204 is
preferably formed into a diameter smaller than heater 202 so as to
exert continuous tension therearound and to apply a preload to
heater 202 for a secure assembly. Spring 204 preferably exerts
continuous pressure and contact on heater 202 along the heaters
entire length, however other configurations may be preferable for a
given molding application. Ends 206 and 208 of spring 204 are
spaced from each other to leave, a gap 210 therebetween which
permits leads 60" from heater 202 to exit, however, other
configurations may be used, and spring 204 may completely surround
heater 202 and overlap itself. Either or both of heater 202 and
spring 204 can be comprised of a two-phase infiltrated metal, as
shown in FIG. 6 and described in further detail below, to enhance
the strength and thermal conductivity of heater 200.
[0050] In a second aspect of this embodiment, band heater 200 may
comprise a bi-metallic clamping system of the type described in
U.S. Pat. No. 5,360,333. Such a system provides a construction
which holds heater 200 firmly on and around nozzle 10" without the
need for additional clamping means. Referring to FIG. 14, heater
200 is bi-metallic, formed by a cylindrical body or heater sheath
220 comprising a coaxial tube assembly with a cylindrical inner
sleeve 222, a cylindrical outer sleeve 224 and a heater coil 226
positioned therebetween. Heater coil is electrically connected to
leads 60" (not shown). As described in the '333 patent, inner
sleeve 222 is formed from a material having a higher thermal
expansion than outer sleeve 224. As will be understood by one
skilled in the art, one or both of sleeves 222 and 224 can be
fabricated of a two-phase infiltrated metal according to the
present invention, and thus achieve the benefits disclosed herein,
with the only stipulation being that inner sleeve 222 have an
overall resulting thermal conductivity which is higher than that of
outer sleeve 224.
[0051] Referring to FIGS. 17-19, in a further embodiment of the
current invention, a film heater element is used to heat a manifold
heater plate. Film heaters are known and have been used in many
applications outside the injection molding process. Film heaters
have been recently introduced in conjunction with hot runner
injection nozzles and hot runner manifolds. Reference is made in
this regard to European Patent Application No. EP 0963829 to Husky
Injection Molding Systems Ltd. and U.S. Pat. No. 5,973,296 to
Juliano et al., both incorporated herein by reference. FIG. 17
shows a portion of a molding system M'" having an infiltrated
manifold 28'" heated on one side by an element 36'" and heated on
the other side by an infiltrated manifold heater 50'". A melt
channel 12'" though manifold 28'" carries pressurized melt from the
molding machine to an infiltrated nozzle 10'". Referring. to FIG.
18, manifold heater 50'" has a heater unit 300 attached thereto,
the heater unit 300 comprising a film heater element 302 disposed
between a dielectric layer 304 (which can also be a film layer) and
an insulation layer 306. Referring to FIG. 19, film heater element
302 is sheetlike having a heater element 308 and thermocouple
element 310 therein. When activated, heater unit 300 provides heat
to heater plate 50'" which, in turn, heats manifold 28'". The film
heater shown in FIG. 18 and FIG. 19 can be manufactured using any
known technology mentioned in EP 0963829 or U.S. Pat. No.
5,973,296, and the references cited in both patents. It will be
understood by one skilled in the art that heater 50'" could equally
be positioned between manifold 28'" and nozzle 10'", in a similar
manner as shown in the embodiment of FIG. 7, so as to perhaps
remove the need for element 36'".
[0052] Film heater technology can equally be used to provide an
infiltrated band nozzle heater of the present invention (ie. of the
type depicted in FIG. 12). Referring to FIG. 20, a film heater 320
is provided which comprises a film heater layer 322 between a
dielectric layer 324 and an insulation layer 326, as described in
U.S. Pat. No. 5,973,296, and incorporated by reference. This heater
provides heat to the infiltrated band heater 50'
[0053] Depending on a particular application, it may be desirable
to employ a manifold, manifold heater plate and nozzle system in
which some components are infiltrated and others are not. It is to
be understood that the present invention includes all embodiments
wherein at least one of said components is infiltrated.
[0054] In use, injection molding system M is assembled as shown in
FIG. 1. While only a single cavity 16 has been shown in FIG. 1 for
ease of illustration, it will be appreciated that melt distribution
manifold 28, depending on the application, typically may have many
melt passage branches extending to numerous cavities 16. Electrical
power is applied to heating element 36 in manifold 28, and to
heating elements 54 in the nozzles 10, to heat them to a
predetermined operating temperature. Heating elements 36 in
manifold 28 can be connected in series or in parallel.
Alternatively, each heating element 36 or one or more groups of the
heating elements 36 can be connected to a separately controlled
power source (not shown) to individually adjust its temperature. In
order to maintain the whole melt passage 12 at a uniform
temperature it may be necessary to provide more heat to some
manifolds 28 than to others. For instance, less heat is usually
required for a manifold 28 in the centre of the mold 18 than for
those around the periphery. Pressurized melt from a molding machine
(not shown) is then injected into melt passage 12 through common
inlet 40 according to a predetermined cycle in a conventional
manner. The pressurized melt flows through melt bore 42 of each
nozzle 10, past torpedo 46 and through gate 14 to fill cavity 16.
After cavities 16 are filled, injection pressure is held
momentarily, to pack the part, and then released. After a
predetermined cooling period, the mold is opened to eject the
molded products. After ejection, the mold is closed and injection
pressure is reapplied to refill cavities 16. This cycle is
continuously repeated with a frequency dependent on the size and
shape of cavities 16 and the type of material being molded.
[0055] As will be apparent to one skilled in the art, molding
system M', as depicted in FIGS. 4 and 5, M", as depicted in FIG.
12, and M'" as depicted in FIG. 17, operate substantially as just
described, with the obvious exceptions. In the case of system M',
heating elements 36', when activated, provide heat to heater plate
106 which, in turn heats manifold 28'. In the case of system M",
heater 200 heats nozzle 10".
[0056] Due to the improved thermal conductivity characteristics of
the infiltrated components according to the present invention, heat
transferred from the heating element is more quickly and
efficiently distributed through the infiltrated component by reason
of the interconnected network of second phase metal 92 infiltrating
the skeleton parent metal 90.
[0057] Thus, according to the present invention, by providing an
injection molding component, such as manifold 28, heater plate 106,
nozzle 10" or band heater 200, comprising a high-strength parent
metal infiltrated by a second phase metal having high thermal
conductivity, an injection molding component is achieved having
high hardness, for withstanding high operation pressures and
numerous operation cycles, and good thermal conductivity to
effectively transfer heat throughout the structure. The result is
improved temperature control of the pressurized melt within the
manifold runner system, which can thereby beneficially affect cycle
time, part quality and system efficiency.
[0058] According to the method of the present invention, manifold
28, front plate 114, rear plate 116, film heater plate 50'", nozzle
10" and/or band heater 200 can be formed using metal infiltration
techniques to yield a two phase metal part having high hardness and
enhanced thermal properties. The following description relates to
the practice of the method to form plates 114 and 116, but it will
be understood that such description applies equally to the
fabrication of manifold 28, heater 50'", nozzle 10" and band heater
200, which contain modifications which will be evident to one
skilled in the art.
[0059] A parent metal, typically a tool steel such as H13, is mixed
in powder form with a plastic binder and prepared for metal
injection molding into a preform having the near-net shape of a
heater plate 114 or 116. It will be understood by one skilled in
the art that the powder loading in the metal+binder admixture will
be such that the green part will have shape retention when the part
is debinderized. The admixture is then injection molded, using
techniques well-known in the art, to yield a green part having a
desired net or near-net shape.
[0060] The green part is next heated in a vacuum or inert gas
environment to a temperature below the melting point of the parent
metal but above the melting point of the binder, to debinderize the
preform and leave a green preform comprising a skeleton having
interconnected open porosity. The porous preform is then partially
sintered to decrease the porosity of the part, and create a
sintered porous preform. As will be understood by the skilled
artisan, an increase in sintering temperature correspondingly
decrease the amount of porosity in the preform. Thus, as
preservation of the interconnected porosity throughout the sintered
preform is desired, the sintering temperature should not exceed the
temperature at which pore closure is initiated. Preferably, the
sintered preform will have a porosity of between 40% to 10% volume
and, more preferably between 30% and 15%.
[0061] Referring to FIG. 15, the porous preforms 114" and 116" of a
front heater plate 114 and a rear heater plate 116, respectively,
are then aligned and positioned with mating inner surfaces 114b and
116b adjacent one another, and with electrical heater element 36'
positioned in channel 118 therebetween, to form a preform assembly
140. Terminals 36a of element 36 are left suitably exposed from
preforms 114" and 116" for ultimate connection to a controlled
power supply (not shown). The preform assembly 140 is then
subjected to an infiltration of a second phase metal to
substantially fill the porosity of the parent metal of heater plate
preforms 114" and 116", as will now be described. A mass (not
shown) of a thermally conductive metal, such as plate, sheet or
ingot, is placed in contact with preforms 114" or 116", or both, of
preform assembly 140 and then placed in a vacuum or inert gas
furnace and heated to an infiltration temperature. The infiltrant
mass need not contact both preforms 114" and 116", but need only
contact one. In a particular application, however, a plurality on
infiltrant masses may be desirable. The infiltration temperature of
the furnace need only be slightly higher than the melting
temperature of the metal infiltrant, and the infiltration
temperature and time should generally be kept as low as possible to
minimize any interaction or solubility between the parent metal and
the infiltrant metal. At the infiltration temperature, the metal
infiltrant melts over time and is absorbed by capillary action into
the porous preform to fill the void spaces of the interconnected
porosity therein. As will be apparent to one skilled in the art,
sufficient infiltrant metal should be provided to substantially
fill the interconnected porosity of the parent metal preform.
[0062] Advantageously, it has been found that as the second phase
metal infiltrates into the interconnected porosity of the parent
metal preform, the infiltrant also acts to braze faces 114b and
116b together. The infiltrant also simultaneously brazes electrical
heating element 36' to channel 82. Thus, simultaneously with
infiltration, an integral and metallurgically-bonded heater
assembly 106 is achieved, thereby yielding good strength and
thermal characteristics. Preferably, electrical heater element 36'
is not infiltrated and the infiltration process does not otherwise
affect the functionality of heater element 36.
[0063] Once infiltration is complete, the thermally conductive
metal infiltrant fills the former interconnected porosity of the
parent metal (see FIG. 6). As a result, the manifold 28 and/or
heater plate 106 has high hardness, for withstanding high operation
pressures and numerous operation cycles, and good thermal
conductivity to effectively transfer heat throughout the structure.
The present invention also causes the thermally conductive metal
infiltrant to set around electrical heating element 36', thereby
integrating the element into heater plate 106 and thereby
increasing the heat transfer efficiency of heater plate 106. The
simultaneous nature of such brazing step beneficially reduces the
number of steps required in tooling the molding system.
[0064] The present invention may be used advantageously with any
parent metal having good strength characteristics, such as tool
steels such as H13, M2, D2 or carbide steels. Regardless of parent
metal chosen, the sintering conditions are used to control the
amount of porosity in the green part, as one skilled in the art
understands that overall porosity decreases with increased
sintering temperature and/or time. Since the parent metal green
preform must have connected open porosity, sintering must be
carefully controlled to ensure that pore closure is avoided and the
green part is permeable to the liquid metal infiltrant.
[0065] Any suitable metal infiltrant having high thermal
conductivity may be successfully employed with the present
invention. Copper and alloys of copper are most preferred,
however.
[0066] It will be understood that binders suitable for use with the
process of the present invention are those which melt or soften at
low temperatures, such that the metal/binder admixture exhibits
good flow properties during injection molding. However, the binder
must also provide the green molded article with enough strength to
prevent collapsing or deformation during handling. Preferably, the
plastic binder chosen will degrade at a relatively low temperature
to facilitate debinderization of the green part.
[0067] It will be apparent to one skilled in the art that the
preform processing according to the present invention can be
achieved through any powder processing method, and need not be
limited to metal injection molding of the parent metal preform. For
example, conventional powder pressing may be utilized, wherein the
parent metal powder is first mixed with a lubricant, as is known in
the art, and then pressed into the preform shape. The green preform
is then delubed, and the porous preform is then sintered as
described above. Alternatively, three-dimensional printing or other
powder forming techniques as are known in the art may be employed.
The present invention is not limited to a particular method of
forming the parent metal preform and any method which yields a
preform having interconnected open porosity may be employed.
[0068] The method of the present invention may be used to
infiltrate and bond similar parent metals, for example such as in
the joining of a heater plate 114 to a heater plate 116 as
described above, or dissimilar metals, for example such as in the
case of joining a heater element 36 to a heater plate 114 or 116,
as described above, or both, as in the joining of heater plates 114
and 116 to heater element 36 as described above. The method may
also be employed to create infiltrated injection nozzles, having.
integral heater elements simultaneously brazed therein during
infiltration of the nozzle preform, as mentioned above. Similarly,
other integrally heated. components such as sprue bushings and the
like may also be made according to the present method. Thus, the
present invention may be employed with any number of porous
preforms and any number of non-porous parts to be integrated
therewith during infiltration.
[0069] Further, it will be understood by one skilled in that art
that certain benefits may be achieved, depending upon the
particular application, by using the teachings herein to fabricate
a heater plate 106 according to the present invention in which only
one of plates 114 and 116 is infiltrated according to the present
invention and the other is uninfiltrated (see FIG. 16, wherein
plate 114 is uninfiltrated). Further, though advantageous, the
simultaneous infiltration and brazing of plates 114 and 116 is not
required to achieve benefit according to the present invention. It
may also be desirable, in a particular application, to provide the
FIG. 7 embodiment with an infiltrated melt distribution manifold
100, in addition to or in place of, an infiltrated manifold heater.
It will also be understood that it is not necessary that the
infiltration within a particular part be uniformly distributed
throughout the part, but rather may be localized in a region of the
part. Likewise, it will be understood that plates 114 and 116 need
not be composed of the same parent metals nor be infiltrated with
the same second phase metals.
[0070] The following example is offered to aid understanding of the
present invention and is not to be construed as limiting the scope
of the invention as defined in the attached claims.
[0071] Example
[0072] A powder of H13 tool steel is mixed with a polymer binder.
The admixture is then injection molded into a green part having the
shape of front heater plate 114. The binder is thermally removed in
a furnace, preferably at a temperature not exceeding 500.degree.
C., to yield a green preform having open and interconnected
porosity. The green porous preform is then partially sintered in
the range of 1150.degree. C. to 1260.degree. C. until a final
porosity of the sintered part of between 40% to 10% by volume is
achieved. Simultaneously or successively, an H13 porous preform for
rear heater plate 116 is also created using this described
technique.
[0073] The front and rear heater preforms are fitted with a heater
element 36' in recesses 114a and 116a and the preforms are then
mated to yield a green heater assembly 140. The green assembly is
then placed in a vacuum or inert gas furnace. A copper sheet is
then placed on top of the green heater assembly, and the furnace is
heated to 1120.degree. C., slightly above the melting point of
copper. The infiltrated and brazed integral part is then cooled and
final machining, if any, is performed.
[0074] Thus it will be apparent to one skilled in the art the
present invention provides an improved melt distribution manifold
having improved strength and thermal characteristics over the prior
art. Also, the method of the present invention provides
simultaneous means of infiltrating and brazing a heated manifold
assembly with heating element therein.
[0075] While the above description constitutes the preferred
embodiments, it will be appreciated that the present invention is
susceptible to modification and change without parting from the
fair meaning of the proper scope of the accompanying claims.
* * * * *