Note: Descriptions are shown in the official language in which they were submitted.
CA 02271099 1999-OS-OS
HEATPIPE MOLD
This is a regular United States patent application filed pursuant to 35 USC ~
111
(a) and claims the benefit under the provisions of 35 USC ~ 119 (e) (1) of the
priority of
United States provisional patent application SN 60/064,066 filed October 17,
1997.
S Field of the Invention
This invention relates to molding apparatus and methods, more particularly to
method and apparatus for cooling and/or heating the mold-cavity-defining
surfaces of a
mold.
Background of the Invention
l0 The technology associated with the production of electroformed inserts for
molds
is well known. See, for example, U. S. patent 4, 338, 968. This electroform
processing
technology is described hereinafter in order to highlight the difficulty
associated with
heating or cooling the electroform while it is in place in a mold.
As diagrammatically illustrated in Fig. l, electroformed mold inserts are
usually
15 produced by depositing nickel or some other elemental metal onto a machined
pattern
form 20 through an electroplating process. i he pattern form 20 has been
machine shaped
to satisfy the geometry that is the reverse (mirror) of a desired molding
surface. The
electroplating process is stopped when the nickel deposit 22 on the machined
form has
achieved sufficient thickness. The nickel deposit 22 is then removed from the
pattern
20 form 20. The surface 24 of the deposited nickel that has been in contact
with the
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CA 02271099 1999-OS-OS
machined form 20 has now assumed the shape, thickness and dimension of the
machined
mating surface 26 of form 20 such that it can now be used as a molding
surface, as
diagrammatically indicated in Fig. 2, Due to the nature of the deposition
process, this
electroform 22 has a generally constant cross sectional thickness.
As shown diagrammatically in Fig. 3, and as taught conventionally in the prior
art,
electroform 22 is typically bedded on and welded at 28 to a metal (or
otherwise affixed to
a non-metal) backing or bedding block 30 to enable the electroform to operate
in the high
pressure environment of the molding process. Bedding block 30 is either cooled
or
heated to provide the correct temperature to the electroformed molding face 24
during the
molding process. As best seen in Fig. 3A, due to the random as-manufactured
tolerance
variance irregularities in spacing between the electroformed non-molding
surface 32 and
the electroform mounting surface 34 of the bedding block, significant air gaps
36 occur.
These air gaps create random thermal breaks between surfaces 32 and 34 which
act as
insulators that restrict the transfer of heat energy between the electroform
22 and the
bedding block 30 and therefore cause electroform 22 to be heated or cooled in
an
inappropriately slow and non-uniform fashion.
As shown diagrammatically in Fig. 4, heatpipe technology is also well known
and
consists of introducing a charge fluid liquid phase 40 into an evacuated
chamber 42
having inert elemental metal, chamber-defining, interior boundary surfaces
(not shown)
lined with a wick structure 42 to transport the liquid phase of the charge
fluid. The
atmospheric pressure within the evacuated chamber 42 is made low enough to
permit
phase change of the charge fluid when very small temperature changes occur at
any
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random evaporation locations 44 and 46 on the interior surface of chamber 42.
This
localized increase in temperature causes the charge fluid at sites 44 and 46
to change state
from liquid 40 to vapor 50 due to the low vapor pressure in the chamber. This
phase
change causes the vapor to absorb the energy associated with the latent heat
of
evaporation of the liquid phase of the fluid. The phase change in turn
produces a
localized positive pressure which causes the vapor to migrate, as indicated by
arrows 48,
within chamber 42 to a lower pressure area. As the vapor 50 contacts a
condensation
location 52, 54 that is marginally lower in temperature than the vapor, the
vapor changes
phase back to a liquid and all the latent heat of condensation residing in the
vapor is
yielded to the chamber wall at that condensing site. Wick structure 42
installed along the
boundary surface in the chamber assists, by capillary action, return of the
liquid to the
evaporation site 44, 46 to assure that fluid is available to continue the
phase change
reaction. In this way, large amounts of thermal energy can be transferred
uniformly at a
high rate throughout the chamber.
Qbiects of the Invention
Accordingly, among the objects of the present invention are to provide a new
and
improved method and apparatus for utilizing the nickel electroplated deposit
that forms
the thin mold face piece or equivalent mold surface structure normally used to
define the
cavity-side surface of the mold in an improved heatpipe mold construction and
method
that insures uniform heating andlor cooling of the mold-cavity-side surface of
the
molding surface during the molding cycle, and which eliminates the
aforementioned
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randomized thermal breaks so that the heating and cooling can occur rapidly
and in a
uniform fashion.
Summary of The Invention
In general, and by way of summary description and not by way of limitation,
the
invention achieves the foregoing as well as other objects indicated
hereinafter by
providing a heatpipe construction arranged, constructed and configured to
function as a
mold half with the entire electroformed mold piece serving as one end of the
mold
heatpipe chamber.
Brief Description of the Drawings
The foregoing, as well as other objects, features and advantages of the
present
invention will become apparent from the fohowing detailed description of the
best mode
presently known by the inventor for making and using the invention, from the
appended
claims and from the accompanying drawings wherein:
Fig. 1 is a diagrammatic illustration of making a mold-cavity-defining-surface
piece made by electroplating nickel onto the cavity-forming complemental
surface of a
machined pattern form in accordance with conventional prior art practice.
Fig. 2 is a diagrammatic illustration of the electroform part after completion
thereof and removal from the machined pattern form, and inverted for assembly
to a
lower mold half bedding block in accordance with prior art practice.
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Fig. 3 is a diagrammatic view of the electroform superimposed on, and fastened
by
peripheral edge welding to, a mold bedding block so as to be supported by the
electroform mounting surface of the bedding block and therefore provide a sub-
assembly
to be used as a lower mold half of a typical two-piece openable and closable
mold
assembly.
Fig. 3A is a fragmentary view of the portion encircled by the circle 3A in
Fig. 3
and greatly enlarged thereover.
Fig. 4 is a diagrammatic illustration of the structure and made of operation
of a
typical heatpipe of the prior art.
Fig. 5 is a diagrammatic view of a lower mold half part defining a negative or
cavity molding face surface and constructed as a heatpipe mold in accordance
with the
invention.
Fig. SA is a diagrammatic view illustrating the lower mold half of Fig. 5 in
operative juxtaposition to another, upper mold half part defining a positive
or core
molding face surface and likewise constructed in accordance with the invention
as a
heatpipe mold.
Fig. 6 is a diagrammatic view illustrating a second embodiment of the mold
half
part of Fig. 4 modified by being equipped with associated exterior cooling
tubes to
thereby adapt the same for use in a thermoplastic molding application in which
the
molding surface is to be cooled to cause solidification of the molding
material before
removal from the mold.
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Fig. 7 is a view similar to Fig. 6 illustrating a third embodiment of the mold
half of
Fig. 4 modified by associated exterior heating elements being provided to
adapt the mold
half for use in molding of thermosetting plastic material that must be heat
cured within
the mold to cause solidification before the mold can be opened.
Fig. 8 is a diagrammatic view of a fourth embodiment modification of the third
embodiment of Fig. 6 in which the cooling tubes are replaced with coolant
passages in a
thicker section shell wall of the heatpipe lower mold half.
Fig. 9 is a diagrammatic view of fifth embodiment of a mold half of the type
shown in Fig. 5 in which a series of inert metal support pillars are installed
in the mold
heatpipe chamber to transmit molding pressure applied to the mold cavity
surface through
the chamber to the mold frame.
Fig. 9A is a sixth embodiment of the mold half similar to that of Fig. 9, but
wherein the support pillars are constructed of hollow or solid sintered
materials.
Fig. 9B is seventh embodiment of a mold half similar to that of the
embodiments
of Figs. 9 and 9A in which the support pillars are constructed as perforated
tubes.
Fig. 9C is a greatly enlarged fragmentary view of the portion encompassed by
the
ellipse 9C in Fig. 9B.
Fig. 10 is a diagrammatic view of an eighth embodiment of the mold half
similar
to the embodiment of Fig. 6 but in which the charge fluid is augmented by an
external
pumping circuit for use in instances where the molding operational thermal
demands
exceed the ability of the interior wick to replace the charge fluid at the
evaporator site or
sites.
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Fig. l0A is a diagrammatic view of a ninth embodiment of the mold half part
combining the external pumping circuit of the eighth embodiment of Fig. 10
with the
perforated support pillars of the sixth and seventh embodiments of Figs. 9B
and 9C in
which the pillars act as dispersion nozzles for the external pumping circuit.
Fig. lOB is a tenth embodiment of the mold half similar to the embodiment of
Figs. 9B and 9C but wherein the perforated support pillars act as evacuation
outlets for
outgoing charge or working fluid circulation into external pumping circuit
(not shown).
Fig. 11 is a diagrammatic view of an eleventh embodiment similar to the view
of
Fig. 5 but wherein the mold-cavity-defining end cap of the heatpipe is
machined from a
suitable heat conductive metallic material and its chamber-facing surface
plated with an
elemental metal to prevent contamination of the charge fluid in the heatpipe
chamber.
Fig. 1 lA is a greatly enlarged fragmentary view of the portion encompassed by
the
circle 11A in Fig. 11.
Fig. 12 is a diagrammatic view of a twelfth embodiment of the invention
utilizing
the two mold halves of Fig. SA, the heating or cooling tubes of Figs. 6 or 7
and
incorporating the same into. complemental mold nests in upper and lower
platens of a
compression mold assembly for use in compression molding of plastic material.
Fig. 13 is a diagrammatic view of a thirteenth embodiment of the invention
wherein pre-formed individual heatpipes are nested and incorporated integrally
with
electroform encapsulating material that defines the end cap of the massed
heatpipe mold
part during the plating process.
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Fig. 13A is a fourteenth embodiment of the invention similar to the embodiment
of
Fig. 13, but illustrating the massed array of nested heatpipes extending
beyond the bottom
face of the electroform body.
Detailed Description of the Preferred Embodiments of the Invention
In accordance with the present invention, and referring to Fig. 5, a
significant
improvement in the energy transfer rate and surface temperature uniformity of
the
electroformed molding surface 24 can be achieved if the electroform 22 is
attached by a
circumferentially continuous weld 52 to the upper edge of a mold half shell 60
made of
electroformed nickel and constructed and arranged in a three-dimensional
configuration,
e.g., a five-sided box open at the top, and then capped by electroform 22,
thereby creating
a sealed chamber 64. A wick material 66 is installed in the chamber as an
interior
capillary transport covering over preferably all interior facing surfaces that
define
chamber 64. The chamber is then evacuated, after which charge fluid 40/50 is
injected
into the chamber. The chamber therefore has all the components associated with
a
heatpipe and is operable to function as a unitary heatpipe. This heatpipe
assembly then
can be utilized as a lower mold half 70 providing the negative or cavity
molding surface
24 when used in conjunction with a suitable mating upper mold half 72, as
shown
diagrammatically in Fig. SA. Mold half 72 is constructed in the manner of mold
half 70
but with its electroform end cap 74 configured as the inverse of the end cap
electroform
22 of mold half 70 to thereby provide for example, a positive or core molding
surface 76
complemental to surface 24.
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Fig. 6 illustrates a second embodiment of the invention wherein the
electroform/shell heatpipe mold assembly is constructed for use in a
thermoplastic
molding application. In such applications the molding material is applied to
the molding
surface 24 in a heated condition and must be cooled to cause solidification
before
removal from the mold. Hence, thermal energy from the molding material being
formed
by the lower and upper molding surfaces 24 and 76 of the mold cavity is at a
positive
temperature with respect to these molding surfaces. This energy is rapidly
conducted
through such electroform to the associated shell surface via the evaporation
and
condensation occurring within the associated chamber. Each shell can then be
cooled
through the use of fins (not shown) or cooling tubes 80 bonded to, or integral
with, the
shell exterior surfaces.
It is to be noted that, in accordance with one of the principal features of
the
invention, these exterior shell surfaces can be many times larger in exposed
heat transfer
area than the electroformed molding surface 22/76. Therefore, the heat energy
applied to
or removed from the electroform surfaces 24, 76 will be transferred thereto or
dissipated
therefrom at rates that are a function of the ratio of the surface areas of
each electroform
and the associated shell. Thus, an electroform having a mold-cavity-defining
surface
area, for example, of 4 square inches that is welded as a heatpipe end cap to
a heatpipe
shell having an exposed exterior surface area of 20 square inches, and then
the mold
heatpipe chamber sealed, evacuated and fluid charged to function as a heatpipe
mold, will
transfer energy to or from the electrofolm surface at a rate approximately
five times faster
than an electroform bearing directly on a conventional bedding block 30,
provided that
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CA 02271099 1999-OS-OS
the shell and the bedding block are heated or cooled at the same rate per unit
time.
Fig. 7 illustrates a third embodiment application involving the molding of
thermosetting plastic wherein the molding material is presented to the molding
surfaces in
a relatively cool form and must be heat cured within the mold cavity to cause
solidification before the mold can be opened. The molding material, being
formed by the
molding surfaces, in such application is at a negative or lower temperature
with respect to
the molding surfaces. In this instance it would be necessary to provide
thermal energy to
the molding surfaces in order to cure the molding material. Accordingly, in
this
embodiment a suitable form of energy is supplied to an array of heating
elements 82
bonded to or otherwise mounted in the shell wall or on the exterior shell
surface. The
heat thus generated by heating elements 82 is then transferred to the molding
surface 24
through evaporation and condensation of the charge fluid 40/50 occurring
within the
evacuated chamber 64. The wick 66 returns condensate to the evaporator site as
in the
first instance above. The same thermodynamic reaction takes place as in the
cooling
instance, but the evaporator and condenser surfaces are reversed.
In both of the above applications the cooling or heating introduced to the
shell can
be in the form of heaters or cooling tubes bonded to the shell exterior
surfaces.
Alternatively, as diagrammatically illustrated in the fourth embodiment of
Fig. 8, if the
walls of shell 60 are of sufficient thickness, the cooling tubes 80 can be
replaced with
coolant passages 84 in these shell walls, or in the case of heating elements,
holes can be
drilled in the shell walls to accommodate the heaters.
CA 02271099 1999-OS-OS
From the foregoing it now will be seen that, pursuant to another principal
feature
of the invention, in either the cooling or heating applications the
electroform, shell, wick
structure, and charge fluid form one integral heatpipe half mold unit that can
be installed
in a mold frame or fixture and removed therefrom, simply, without disassembly
of the
unit or constituent chamber components.
Fig. 9 illustrates a fifth embodiment modification that is preferred in those
instances where the electroform heatpipe end cap structure, due to the molding
pressures
and the geometry of the molding surface, is insufficient to support typically
applied
molding pressures. In such instances, a series of inert metal pillars 86 and
88 are
l0 installed in chamber 64 of modified mold half 87 to support electroform 22
against
molding pressure deformation forces and transmit the same from electroform 22
through
chamber 64 to the mold frame, shell 60.
Alternatively, as diagrammatically illustrated in Fig. 9A by the modified
sixth
embodiment of mold half 89, a plurality of support pillars 90 and 92 are
constructed of
hollow or solid sintered materials having porosity of a suitable nature so
that they also
function as a supplementary wick to help replace the charge fluid at the
evaporator of
condenser site.
Figs. 9B and 9C illustrate a seventh embodiment mold half 94 having support
pillars 95 and 98 constructed from perforated tubes so as to permit the
incursion of charge
vapor into those regions inside the support tubes. Additional wicking
materials 100 may
be placed along the tube LD. to transfer the charge fluid to the evaporator or
condenser
sites.
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The eighth embodiment mold half 104 of Fig. 10 may be provided in those
instances where the molding operational thermal demands on the assembly exceed
the
ability of the wick to replace the charge fluid at the evaporator site. To
alleviate this
condition the charge fluid is positively pumped to the evaporator site using
an external
bellows pump 106 and associated liquid suction lines 108 and 110 and liquid
feed lines
112-120 organized as a liquid phase positive pressure feeding circuit as
diagrammed in
Fig. 10 to supplement capillary wicking action.
In orientations and applications that require both the use of a charge fluid
pump
106 and support pillars 96, 98, these perforated support pillars may be
provided to act as
dispersion nozzles and/or evacuation outlets for incoming and/or outgoing
charge or
working fluids, as shown diagrammatically in ninth and tenth embodiment
modified
mold halves 130 and 140 of Figs. l0A and lOB respectively (chamber fluid
return lines
and pump not being shown in Fig. lOB).
Figs. 11 and 11A show another eleventh embodiment variation of the method and
apparatus of the invention for producing a heatpipe mold half 150 having a
modified
fabricated heatpipe end cap 22 made by using any high strength metal or alloy
material
that can be machined to satisfy the conditions of a molding surface and made
to a
reasonably constant cross sectional thickness. The metal or alloy molding
surface end
cap 22" is then attached to a shell 60 of suitable size and provided with an
evacuated
chamber 64, charge fluid 40/50 and appropriate wick material 66. If the
molding surface
end cap 22" (and also, if desired, shell 60) are made of alloy steel or other
metallic
material that will cause incompatibility with the charge fluid, i.e., possibly
cause non-
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condensable gases to develop in chamber 64, then the interior surfaces of the
evacuated
chamber 64 must be plated with an inert elemental metal 152, such as nickel or
copper,
prior to the evacuation of chamber 64 and the introduction of the charge
fluid.
The evacuated shell heatpipe half mold technology of the invention thus
envisions
a core or cavity face of a mold half as a complete mold face which is also one
face of the
heatpipe that encompasses all or substantially all of the total molding
surface or wetted
surface or working surface of the mold. In the case of molds having both male
and
female molding faces (also referred to respectively as cavity and core molding
surfaces as
in Fig. SA) one face of a unitary heatpipe construction makes up the total
male or core
face of the mold and one face of another unitary heatpipe construction makes
up the
female or cavity face of the mold. Fig. 12 illustrates this principle applied
to a
compression mold assembly 160 with separable mold nests 162 and 164 carrying
heatpipe mold halves 70 and 72 respectively.
In two further variations illustrated in thirteenth and fourteenth embodiment
mold
halves 170 and 180 of Figs. 13 and 13A respectively, the electrofolin may be
produced in
such a way that it functions as an integrated heatpipe end structure and
heatpipe shell
structure. To accomplish this end result, a plurality of conventional pre-made
copper or
nickel heatpipes 172 are used in mold half 170, and likewise such heatpipes
182 in mold
half 180, and are incorporated as a mutually bonded array integrally with the
electroform
material during the plating process. The array of heatpipes is positioned such
that the
heatpipes may reside entirely within the electrofolm structure (Fig. 13) or
such that their
ends remote from the molding surface extend beyond the bottom surface of the
structure
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(Fig. 13A).
The individual heatpipes 172, 182 are closely nested in their respective
integrated
array in such mold half so as to occupy the maximum possible volume of the
electroform
geometry. Preferably the heatpipes longitudinal axes are mutually parallel and
perpendicular to the general plane of the molding surface and/or mold parting
line plane.
The heatpipe array is preferably also substantially co-extensive in projected
area with all
or alinost all of the area of mold surface 24'. The amount of plating material
required to
encapsulate the heatpipes is thereby reduced while the closely nested array
functions to
maximize heat transfer uniformity at the molding surface to the fullest extent
possible
when using such discrete heatpipe elements encapsulated in this embodiment of
an
electroform heatpipe mold half of the invention. In some applications the
material
encapsulating the plurality of nested heatpipes may be heat conductive ceramic
or
composite materials, the overall heat transfer coefficient thereof being
greatly enhanced
by the encapsulated heatpipe nest.
A further variation in the construction of the heatpipe chamber mold half of
the
invention is to utilize non-metallic heat conducting materials such as heat-
conductive-
type ceramics or composites to form the molding surface end cap, and also for
forming
the half mold shell, and to electroplate the interior chamber-defining
surfaces of these
components with a material such as elemental nickel that is inert to the
reactions
occurring in a heatpipe. When joined together with the wick structure and
sealed, a
charge fluid can be installed, and the chamber evacuated; thus creating
another form of a
heatpipe half mold unit of the invention.
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This same evacuated shell heatpipe mold technology may be used to heat or cool
molding surfaces in slush molds, reaction injection molds, resin transfer
molds, pot molds
and in all other forms of molds and tools where a liquid or semi-solid molding
material is
introduced into a void created by a number of solid metallic or non-metallic
mold blocks
or shapes having molding surfaces that contain the impression of a part. The
liquid or
semi-solid molding material is injected or otherwise introduced into the void
in sufficient
volume and there it is either heated, cured or cooled so as to produce a
finished molded
part with a shape and configuration that fills the void and has outside
dimensions and
geometry that are the exact reverse of the heatpipe molding surfaces described
above. In
accordance with the invention, such molds in whole or in part preferably
utilize
electroforms or fabricated molding surface parts having a generally constant
cross-
sectional thickness to provide both the molding surface and heatpipe chamber
end wall.
It should be also be understood that the heatpipe chamber can be of irregular
shape. Further, the protruding ends of the heatpipe array of FIG. 13A can all
be disposed
in another heatpipe chamber encompassing all of such protruding ends. It
should be
further understood that a common heatpipe chamber will selectively cool or
heat that
portion of the mold cavity surface that exhibits the highest 0 T between the
mold charge
and heat chamber.
