Title of Invention

"METAL MOLD FOR RESIN MOLDING."

Abstract There are provided: metal molds (1), (2) formed with a cavity (4) for obtaining moldings of a prescribed shape; an injection port (5) provided in the lower part of the metal molds (1), (2), whereby epoxy resin (3) is injected into the cavity (4); an exhaust port (6) whereby air in the cavity (4) is exhausted, provided in the upper part of the metal molds (1), (2); and a movable valve (7) made of a resilient member that closes the exhaust port (6) when the interior of the cavity (4) is filled with epoxy resin (3).
Full Text TITLE OF THE INVENTION
Metal mold for resin molding
BACKGROUND OF THE INVENTION 1. Field of the Invention
The present invention relates to a metal mold I
|i : i
for resin molding whereby insulation defects loffj ! molded articles can be suppressed, and electricjalj performance and mechanical performance improved. ;
2. Description of the Related Art
Molded products manufactured by injecting insulating material such as epoxy resin into a metal mold for resin molding under vacuum have excellent electrical properties and mechanical properties and are widely used in electrical equipment. However, insulation defects called idids may be formed in the molded product if traces c|f ; air remain in the metal mold for resin molding| |
In order to solve this, as stated in Laid-op^iii Japanese Patent Application No. H. 5-64820, thijj
ji ' :
technique is previously known of providing an !i M exhaust port in the metal mold for resin molding,^ and extruding remaining air from this exhaust ]|drft when injecting the epoxy resin.

As shown in Figure 1, a metal mold for resifn molding of this type is divided into two parts;
l! ' :
shown on the left and on the right in the Figu|t$, \ namely/ a first metal mold 1 and a second meta|L mold 2. Also, an injection port 5 for injectiojh of epoxy resin 3 into the cavity 4 is provided at[ the lower part as shown in this Figure and an exhajagt
i. . •
port 6 is provided at the upper part in this Ffigure.;
: • • •
In this exhaust port 6, a movable valve 7 suchjas
i :
to float on the epoxy resin 3 is provided so ak to be freely movable in the vertical direction as shown in the Figure, The movable valve 7 is freely detachable and is fixed to one or other of the |
i
metal molds 1 (2) by a support fitting 8 such a> to
i. '.
permit free movement thereof in the vertical
direction in the Figure. |
i,
When carrying out molding, the first metal ijnold 1 and second metal mold 2 are closed, and are i arranged in a prescribed vacuum of for example | pressure 150 Pa. At this time point, the movable valve 7 is positioned at the lower part in the
Figure below the exhaust port 6, due to its ownj

weight, the exhaust port 6 being in an opened |
j.
condition and the interior of the cavity 4 b under vacuum. Then, when liquid epoxy resin 3 i injected from the injection port 5, the epoxy

3 in the cavity 4 fills the cavity towards
upper direction from below in the Figure, and any
traces of air are extruded from the exhaust port 6.
i
| ' ;
When filling has been effected with the e^qxy
j",
resin 3 as far as the exhaust port 6, the movjable
r
valve 7 is moved upwards as shown in the Figujre to : close the exhaust port 6. Epoxy resin 3 therefore cannot leak to outside the metal molds and 1 jand 2.
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A molding of the desired shape is then obtained by
applying a prescribed pressure of for example! 300
kPa to the epoxy resin 3, thermal hardening/ ^nd
releasing from the mold. !
i
In order to improve productivity, a high-sjpeed molding method is known wherein, as described|in Laid-open Japanese Patent Application. No. 200]H
38774, the first metal mold 1 and second meta^ into Id
|. :
2 are raised to a high temperature of for example
at least 120 °C and epoxy resin 3 is injected i;into the cavity 4 in a short time. Even in this hig^i-speed molding method, traces of air can be extjrtided from the exhaust port 6 as described above, inj order to suppress insulation defects such as vjoids.
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However, conventional metal molds for resirji
|. :
molding as described above are subject to the j following problems.
After closing the exhaust port 6, the $poxijj
\, ;
resin 3 in the cavity 4 is pressurized, but this
j| :
pressurization is abruptly discontinued when ajj
[ ;
prescribed value is reached. Consequently/ as ^
r
by the arrows in Figure I, the direction of fljpw of the epoxy resin 3 in the cavity A changes upst|:$am of the exhaust port 6, so that the flow become^ a
i-
random flow. Thermal hardening is then performed in
\\ .
this condition. In particular, in the high-spe|d molding method, the flow of epoxy resin 3 is f^st,
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so large-scale random flow is generated, producing
i"
thermal hardening. !
Consequently, the air that is extruded to t|ie exhaust port 6 may again be entrained into the j
|,
cavity 4 by this random flow. If air is entrained into the cavity 4, voids, producing insulation!; defects, are formed, adversely affecting electrical properties such as partial discharge of the molding
i[
or mechanical properties such as the bending j:
strength or tensile strength. ji
The present invention was made in order to ^olve the problems described above, its object being | to provide a metal mold for resin molding whereby i
i i;
moldings can be obtained with improved electrical
|,
and mechanical properties by positively ! accumulating the extruded air at the exhaust pcjirt.
SUMMARY OF THE INVENTION
Accordingly, one object of the present inventioh
| ; '.
is to provide a novel metal mold for resin moldingJ A metal mold for resin molding according to the j \ present invention is constructed as follows. Specifically, a metal mold for resin molding comprises:
a metal mold formed with a cavity for obtaining!
a molding of a prescribed shape; ;
an injection port for injecting epoxy resin irjitjo
the cavity, arranged at the lower part of the metjal
: [ i
mold; I ;
an exhaust port for exhausting air within saic cavity, provided in an upper part of the metal mold; and
i ;
a movable valve having a resilient member^ thai ;
closes the exhaust port when an interior of the ! cavity is filled with epoxy resin. I
By arranging to close the exhaust port by meartS of the deformation of a movable valve employing a i
; ! ! !
resilient member provided at the exhaust port of L the metal mold, the change in pressure during | i pressurization and discontinuance of pressurizatjtqrt of the epoxy resin with which the cavity is fillp4 can be made to occur in gradual fashion, so a j ;
I I; molding with improved electrical properties aijid
mechanical properties can be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
More complete appreciation of the present invention and many of the attendant advantage^ >
: | ; ;
thereof will be ready obtained as the same becomes better understood by reference to the following ;
detailed description when considered in connection
j> i with the accompanying drawings, wherein: I
Figure 1 is a cross-sectional view showingi the construction of a conventional metal mold for ;reisin molding;

Figure 2 is a cross-sectional view showing

the

construction of a metal mold for resin molding according to a first embodiment of the presenl| :
j, =
invention; j:
!' :
Figure 3A and Figure 3B are detail cross-section views given in explanation of the operation•of the movable valve of the metal mold for resin molding according to the first embodiment of the present
invention;

Figure 4 is a view given in explanation of

the

change of pressure of the epoxy resin in the ; r
i ;
according to the first embodiment of the present
invention; and

Figure 5 is a detail cross-sectional view

of a

metal mold for resin molding according to a s/ejcond embodiment of the present invention.
Figure 6 is a detail cross-sectional view of a metal mold for resin molding according to a | ; modified example of the present invention.
DETAILED DESCRIPTION OP THE PREFERRED
I
EMBODIMENTS I
Referring now to the drawings, wherein like
reference numerals designate identical or |
: corresponding parts throughout the several views,
and more particularly to Figure 2 to Figure 4
i
thereof, one embodiment of the present inventjiq>n will be described.
An embodiment of the present invention is described below with reference to the drawing^.:
(First embodiment)
First of all, a metal mold for resin
according to a first embodiment of the present !
| i
invention will be described with reference to j Figure 2 to Figure 4 . Figure 2 is a crossrsectfibnal view showing the construction of a metal mold ifpr resin molding according to a first embodiment oif the present invention; Figure 3 shows detail cross-section views given in explanation of the operation

of the movable valve of the metal mold for resin molding according to the first embodiment of ; present invention; and Figure 4 is a view given in explanation of the change of pressure of the epoxy resin in the cavity according to the first embodiment of the present invention. Structural parts that are the same as in the conventional metal mold are given the same reference symbols in the Figures.
As shown in Figure 2, a metal mold for resin molding is divided into two parts shown on the left and on the right in the Figure, namely, a first metal mold 1 and a second metal mold 2. Also, an injection port 5 for injection of epoxy resin 3 into the cavity A is provided at the lower part as shown in this Figure and an exhaust port 6 is provided at the upper part in this Figure. The exhaust port 6 comprises a small-diameter section 6a, a large-diameter intermediate section 6b connected with the cavity 4, and an exhaust section 6c that communicates with the outside. The large-diameter section 6b may be for example of tubular shape, dome shape or pillar shape. Moldings of prescribed shape are obtained using the cavity 4 formed by the metal molds 1 and 2.

A movable valve 7 such as to float on the ejppxy resin 3 is provided in the large-diameter section 6b of the exhaust port 6 so as to be freely movable in the vertical direction as shown in the Figure. The movable valve 7 comprises a floating section 7a and a pin section 7b: the floating section 7a comprises a resilient member having resilience* such as a spring plate or silicone rubber. Also, it may be made of thin plate shape comprising material such as fluorine-based resin, creating resilience, and may be heat resistant. The pin section 7b is freely detachable and is fixed to one or other of the metal molds 1 (2) by a support fitting 8 such as to permit free movement thereof in the axial direction.
The first metal mold 1 is fixed to a first heating plate 10 in the left/right direction irfi the Figure and the second metal mold 2 is fixed to a second heating plate 11. One end of a vacuum enclosure 12 that can be used to evacuate the rtietal molds 1, 2 to vacuum is fixed to the second heating plate 11. A gasket 13 is provided at the other end of the vacuum enclosure 12 and is tightly fixed to the first heating plate 10. A resin injection pipe 14 for injection of epoxy resin 3 is detachably provided in airtight fashion at the injection port

5 in the lower part in the Figure of the vacuujn enclosure 12.
are
Then, when manufacturing a molding, first Of all,
and
the first metal mold 1 and second metal mold 2 firmly closed by a closing device, not shown, heated to for example a temperature of 180 °C,
the interior of the vacuum enclosure 12 is evacuated to a prescribed vacuum of for example pressure 150 Pa. At this time point, the floating section 7a of the movable valve 7 is positioned;at

the lower part in the Figure below the exhaust

port

6, due to its own weight, the exhaust port 6 bfeing
' in an opened condition and the interior of the
cavity 4 being under vacuum.
The resin injection pipe 14 is then connected
f
with the injection port 5 and liquid epoxy res|.n 3
i; • is injected. When this done, the interior of the
j
cavity 4 is filled with epoxy resin 3 from the lower part in the Figure towards the upper part,, residual air being extruded from the exhaust $ort 6.
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Since the diameter of this exhaust port 6 changes from the small-diameter section 6a to a large-diameter section 6b, the speed of the airflow
j- ;
passing through the small-diameter section 6a 1$
i fast, facilitating extrusion of residual air from
within the cavity 4.

When filling with the epoxy resin 3 has bjeen
effected as far as the exhaust port 6, as $h r :
Figure 3A and Figure 3B, the floating sectioiji 7a of
i
the movable valve 7 floats on the epoxy resiif 3 and moves in the upwards direction in the Figure through the large-diameter section 6b. This ; floating section 7a is then pressed onto the exhaust section 6c, so that the exhaust port 6 is thereby closed. After this closure, the epox^r resin 3 is pressurized to a prescribed pressure of for
j
example 300 kPa. The floating section 7a of t|he: movable valve 7 is deformed by this pressurization, being gradually bent into 'a bowl shape about thJe exhaust section 6c.
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The pressure change of the epoxy resin 3 j*/hen '
the floating section 7a is thus bent is described
with reference to Figure 4. j
At the commencement of injection at time tO, the interior of the cavity 4 is at a pressure of PI
r
(for example Pl=150 Pa). When injection of thW i epoxy resin 3 proceeds, at the time tl, the e^xhaust port 6 is closed, and injection is terminatecJ!.
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After this, the interior of the cavity 4 is pressurized to a pressure P2 (for example P2=s30p kPa), and at the time t2 pressurization is discontinued. Since pressurization is effected

whilst the floating section la is being deformed and this pressurization is then discontinued, tfhe epoxy resin 3 undergoes pressure change as shown by
L
the continuous line A, in which its pressure I gradually rises to reach the pressure P2. The flow of the epoxy resin 3 therefore does not tend t be made to flow in a fixed direction towards tljie
1
exhaust port 6 as shown in Figure 2. Consequently, entrainment of residual air in the vicinity of the exhaust port 6 into the cavity 4 can be suppressed. When pressurization is discontinued, the ep^xy
i
resin 3 undergoes thermal hardening in the cavjity 4, and, when released from the mold after hardening, a
:
molding in which insulation defects are suppressed
can be obtained. The epoxy resin 3 that harden^ at
the exhaust port 6 and injection port 5 is removed
by mechanical processing after release from th^
mold. I
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It should be noted that, in the conventional
i
I. . ;
method, as shown by the single-dotted chain li|ie B,
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pressurization is discontinued at a time t3 th^t is shorter than the time t2 after completion of I injection at the time tl. Since, with this modb of pressure change, there is an abrupt rise in | pressure, followed by a sudden discontinuance j&t
I
the time t3, the direction of flow of the epojxy
resin 3 easily becomes random. In particular,! in
the high-speed injection method, there is shorter
time between pressurization and discontinuances of
pressurization, so the flow of epoxy resin 3 |can
easily become turbulent. However, since the change
of pressure occurs more gradually whilst the i.
movable valve 7 is being deformed, disturbanc^ of
the direction of flow of the epoxy resin 3 isj
unlikely, which is more suitable for a high-speed
molding method. j
The length of the small-diameter section 6Ja of
the exhaust port 6 is 10 mm to 50 mm. This is
because, if the length of the small-diameter j
section .6a is less than 10 mm, epoxy resin 3, [whose
viscosity has become low, flows into the Iarg0-
diameter section 6b from the cavity 4 in a sho time, so the effect of extruding residual air jis
small; but if the length of the small-diameter]
section 6a is more than 50 mm, the viscosity ojf the
epoxy resin 3 in the small-diameter section 6a|
rises, making it difficult to control the pressure
within the cavity 4. i
With a metal mold for resin molding according to the first embodiment described above, a movabl^ valve 7 that closes this exhaust port 6 while |>eing

bent by the pressurization of the epoxy resin {$ is provided at the exhaust port 6 provided by the first metal mold I and second metal mold 2. Consequently, the change in pressure of pressurization and discontinuance of pressurization of the epoxy resin 3 in the cavity 4 is made gradual, so entrainment of air that was extruded from the cavity 4 back into the cavity 4 can b^
j
suppressed, making it possible to obtain moldijjngs of improved electrical and mechanical properties.
(Second embodiment)
Next, a metal mold for resin molding according to a second embodiment'of the present invention is described with reference to Figure 5. Figure 5 is a detail cross-sectional view of a metal mold fo]f resin molding according to a second embodiment of the present invention.
The point of difference of this second embodiment from the first embodiment lies in the construction of the movable valve. In Figure 5,

parts which are the same in construction as in

the

first embodiment are given the same reference symbols and detailed description thereof is dispensed with.
As shown in Figure 5, the movable valve 7 has a pin 7b and hollow floating section 7c. The floating

section 7c comprises a resilient member having resilience being made for example of silicone j rubber, that is capable of free movement within the large-diameter section 6b of the exhaust port |;6.
\-
When the epoxy resin 3 is pressurized after closure
of the exhaust port 6, this hollow section is
deformed into an oval shape. !
(Modified example)
Also, as shown in Figure 6, processing cosjts can be reduced by making the floating section 7d (pome-shaped. Forming an air reservoir 15 between t|ie interior of the dome of the floating section iFd and the resin 3 ensures that buoyancy is not lost.
With the metal mold for resin molding acco|jrding to this second embodiment, even more change o|f pressure can be absorbed^by the hollow floating section 7b, and a similar effect to that of the
j:
first embodiment can be obtained. |
Obviously, numerous additional modifications and variations of the present invention are possible in
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light of the above teachings. It is therefore! to be
j;
j;
understood that within the scope of the appended claims, the present invention may be practiced otherwise than as specifically described herein.












We Claim:
1. A metal mold for resin molding comprising:
a metal mold formed with a cavity for obtaining a molding of a prescribed shape;
an injection port for injecting epoxy resin into said cavity, arranged at a lower part of said metal mold;
an exhaust port for exhausting air within said cavity, provided in an upper part of said metal mold; and
a movable valve having a resilient member that closes said exhaust port when an interior of said cavity is filled with said epoxy resin.
2. The metal mold for resin molding according to claim 1, wherein said movable valve comprises a floating section and a pin, wherein, when said epoxy resin is pressurized after closure of said exhaust port by said floating section, deformation of said floating section causes a change of pressure to occur in gradual fashion.
3. The metal mold for resin molding according to claim 2, wherein, in a deformation of said floating section, a hollow section thereof becomes oval-shaped.
4. The metal mold for resin molding according to claim 2, wherein a shape of said floating section is dome-shaped.
5. The metal mold for resin molding according to claim 1 or claim 2, wherein said exhaust port comprises:
a small-diameter section connected with said cavity;
a large-diameter intermediate section; and
an exhaust section communicating with an outside; and
an floating section of said movable valve is arranged to be freely movable in a
vertical direction in said large-diameter section.
6. The metal mold for resin molding according to claim 4, wherein the length of said
small-diameter section is 10 mm to 50 mm.

Documents:

2371-del-2006-Abstract-(17-11-2009).pdf

2371-del-2006-abstract.pdf

2371-del-2006-Assignment-(17-11-2009).pdf

2371-del-2006-Claims-(17-11-2009).pdf

2371-del-2006-claims.pdf

2371-del-2006-correspondence-other.pdf

2371-del-2006-Correspondence-Others-(17-11-2009).pdf

2371-del-2006-description (complete).pdf

2371-del-2006-drawings.pdf

2371-del-2006-form-1.pdf

2371-del-2006-form-18.pdf

2371-del-2006-form-2.pdf

2371-del-2006-Form-3-(17-11-2009).pdf

2371-del-2006-form-3.pdf

2371-del-2006-form-5.pdf

2371-del-2006-Petition-138-(17-11-2009).pdf


Patent Number 242925
Indian Patent Application Number 2371/DEL/2006
PG Journal Number 39/2010
Publication Date 24-Sep-2010
Grant Date 20-Sep-2010
Date of Filing 31-Oct-2006
Name of Patentee KABUSHIKI KAISHA TOSHIBA
Applicant Address 1-1 SHIBAURA 1-CHOME, MINATO-KU, TOKYO, 105-8001, JAPAN
Inventors:
# Inventor's Name Inventor's Address
1 KOMIYA GEN 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
2 MAXIMA SATOSHI 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
3 SAITO TOSHIHISA 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
4 MATSUOKA MIKA 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
5 KINOSHITA SUSUMU 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
6 SAKAGUCHI OSAMU 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
7 MIYAGAWA MASARU 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
8 SATO JUNICHI 1-1,SHIBAURA 1-CHOME,MINATO-KU,TOKYO,105-8001 ,JAPAN
PCT International Classification Number B29C33/10; B29C33/00
PCT International Application Number N/A
PCT International Filing date
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 P2005-319825 2005-11-02 Japan