U.S. patent application number 10/522840 was filed with the patent office on 2006-01-05 for method and apparatus for injection foaming molding.
This patent application is currently assigned to KABUSHIKI KAISHA KOBE SEIKO SHO. Invention is credited to Takeshi Muguruma, Seiji Nishi, Tatsuya Tanaka, Kazuo Yamaguchi.
Application Number | 20060000572 10/522840 |
Document ID | / |
Family ID | 31184960 |
Filed Date | 2006-01-05 |
United States Patent
Application |
20060000572 |
Kind Code |
A1 |
Tanaka; Tatsuya ; et
al. |
January 5, 2006 |
Method and apparatus for injection foaming molding
Abstract
A method for the injection foaming molding of a light alloy
wherein a melt(2) of a light alloy containing a thickener and a
blowing agent decomposing at a high temperature to generate a
gaseous component in respectively specified percentages is held at
a temperature lower than the decomposition temperature of the
blowing agent and then is agitated to allow the thickener and the
blowing agent to disperse, a predetermined amount of the melt is
measured for the injection into a mold (24) and then is injected
into the mold (24) to produce a foaming molded article of the light
alloy, characterized in that the temperature of the melt (2) is
adjusted to a temperature higher than the decomposition temperature
of the blowing agent and also the foaming of the melt is inhibited
by pressuring at least immediately before the injection; and an
apparatus for practicing the method.
Inventors: |
Tanaka; Tatsuya; (HYOGO,
JP) ; Yamaguchi; Kazuo; (Hyogo, JP) ;
Muguruma; Takeshi; (Hyogo, JP) ; Nishi; Seiji;
(Hyogo, JP) |
Correspondence
Address: |
OBLON, SPIVAK, MCCLELLAND, MAIER & NEUSTADT, P.C.
1940 DUKE STREET
ALEXANDRIA
VA
22314
US
|
Assignee: |
KABUSHIKI KAISHA KOBE SEIKO
SHO
10-26, WAKINOHAMACHO 2-CHOME, CHUO-KU KOBE-SHI
HYOGO
JP
651-8585
|
Family ID: |
31184960 |
Appl. No.: |
10/522840 |
Filed: |
July 30, 2003 |
PCT Filed: |
July 30, 2003 |
PCT NO: |
PCT/JP03/09698 |
371 Date: |
January 27, 2005 |
Current U.S.
Class: |
164/79 ; 164/113;
164/312 |
Current CPC
Class: |
B22D 25/005 20130101;
B22D 17/2061 20130101; C22C 2001/087 20130101; C22C 1/08
20130101 |
Class at
Publication: |
164/079 ;
164/113; 164/312 |
International
Class: |
B22D 27/00 20060101
B22D027/00; B22D 17/08 20060101 B22D017/08 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 31, 2002 |
JP |
2002-223322 |
Claims
1. A method for injection foaming molding of a light alloy
comprising the steps of holding a melt of a light alloy containing
a thickener and a blowing agent decomposing at a high temperature
to generate a gaseous component in respectively specified
percentages at a temperature lower than the decomposition
temperature of said blowing agent, then agitating said melt to
allow said thickener and said blowing agent to disperse, measuring
a predetermined amount of said melt for the injection into a mold,
and injecting said melt into said mold to produce a foaming molded
article of the light alloy, wherein said melt is
temperature-adjusted to the decomposition temperature of said
blowing agent or higher and also inhibited to foam by pressuring at
least immediately before said injection.
2. A method for injection foaming molding of a light alloy
comprising the steps of holding a melt of a light alloy containing
a thickener and a blowing agent decomposing at a high temperature
to generate a gaseous component in respectively specified
percentages at a temperature lower than the decomposition
temperature of said blowing agent, introducing said melt to an
injection molding device having an agitating function, a measuring
function and an injecting function, agitating said melt to allow
said thickener and said blowing agent to disperse, measuring a
predetermined amount of said melt for the injection into a mold,
and injecting said melt into said mold to produce a foaming molded
article of the light alloy, wherein said melt is
temperature-adjusted to the decomposition temperature of said
blowing agent or higher and inhibited to foam by pressuring at
least immediately before said injection.
3. The method for injection foaming molding of the light alloy
according to claim 1, wherein the temperature of said melt is lower
than the decomposition temperature of said blowing agent at the
time of agitating said melt.
4. The method for injection foaming molding of the light alloy
according to claim 2, wherein the temperature of said melt is lower
than the decomposition temperature of said blowing agent at the
time of agitating said melt.
5. A method for injection foaming molding of a light alloy
comprising the steps of agitating a melt of a light alloy
containing a predetermined amount of a thickener to allow said
thickener to disperse, supplying inert gas as a blowing agent into
said melt in a specified percentage while agitating to allow said
inert gas to disperse, measuring a predetermined amount of said
melt for the injection into a mold, and injecting said melt into
said mold to produce a foaming molded article of the light alloy,
wherein said melt is inhibited to foam by pressuring said melt at
least until said injection is performed after the supply of said
inert gas.
6. The method for injection foaming molding of the light alloy
according to claim 5, wherein said pressuring is performed by a
pressing force caused by said agitation with a screw.
7. The method for injection foaming molding of the light alloy
according to claim 1, wherein said melt is injected in an injection
amount reduced by a foaming portion relative to the inner capacity
of the mold to break said pressuring, whereby said melt is allowed
to foam within said mold to obtain the foaming molded article.
8. The method for injection foaming molding of the light alloy
according to claim 2, wherein said melt is injected in an injection
amount reduced by a foaming portion relative to the inner capacity
of said mold to break said pressuring, whereby said melt is allowed
to foam within said mold to obtain the foaming molded article.
9. The method for injection foaming molding of the light alloy
according to claim 5, wherein said melt is injected in an injection
amount reduced by a foaming portion relative to the inner capacity
of said mold to break said pressuring, whereby said melt is allowed
to foam within said mold to obtain the foaming molded article.
10. The method for injection foaming molding of the light alloy
according to claim 1, wherein said melt is injected in an injection
amount equal to the inner capacity of said mold, and said mold is
opened by the capacity of a foaming portion to break said
pressuring, whereby said melt is allowed to foam to obtain the
foaming molded article.
11. The method for injection foaming molding of the light alloy
according to claim 2, wherein said melt is injected in an injection
amount equal to the inner capacity of said mold, and said mold is
opened by the capacity of a foaming portion to break said
pressuring, whereby said melt is allowed to foam to obtain the
foaming molded article.
12. The method for injection foaming molding of the light alloy
according to claim 5, wherein said melt is injected in an injection
amount equal to the inner capacity of said mold, and said mold is
opened by the capacity of a foaming portion to break said
pressuring, whereby said melt is allowed to foam to obtain the
foaming molded article.
13. A method for injection foaming molding of a light alloy
comprising the steps of adjusting the temperature of a melt of a
light alloy containing a thickener and a blowing agent decomposing
at a high temperature to generate a gaseous component in
respectively specified percentages to a temperature lower than the
decomposition temperature of said blowing agent, supplying said
melt into a barrel having a screw provided to be rotatable,
protrudable and retreatable, agitating said melt by rotating said
screw to allow said thickener and said blowing agent to disperse,
measuring said melt in a measuring part formed at a front portion
of said barrel by retreating said screw with rotation, adjusting
the temperature of said melt to the decomposition temperature of
said blowing agent or higher while inhibiting the foaming of said
melt by pressuring the melt within the measuring part the capacity
of which is made constant by stopping the retreat of said screw at
least immediately before injection, and injecting said melt into
said mold by protruding said screw to obtain a foaming molded
article.
14. A method for injection foaming molding of a light alloy using
an apparatus for injection foaming molding comprising a barrel
containing a screw and a cylinder containing a plunger, a front
portion of said cylinder communicating with the front portion of
the barrel through a communicating passage, comprising: (a) a
supplying process for supplying the melt of the light alloy
containing a thickener and a blowing agent decomposing at a high
temperature to generate a gaseous component in respectively
specified percentages, which is temperature-adjusted and held at a
temperature lower than the decomposition temperature of said
blowing agent, into said barrel; (b) an agitating process for
agitating said melt within said barrel by rotating said screw
within the barrel to allow said thickener and said blowing agent to
disperse; (c) a measuring process for introducing and measuring
said melt from said barrel to a measuring part formed in the front
portion in said cylinder by retreating said plunger through said
communicating passage; (d) a pressuring process for adjusting the
temperature of said melt to the decomposition temperature of said
blowing agent or higher, and pressuring said melt to inhibit the
foaming of said melt by generating the gaseous component within
said measuring part the capacity of which is made constant by
stopping the retreat of said plunger at least immediately before
injection; and (e) an injection foaming process for injecting said
melt inhibited to foam in said pressuring process into a mold
communicating with the inner portion of said cylinder in the front
portion of said cylinder by protruding said plunger.
15. A method for injection foaming molding of a light alloy
comprising the steps of holding a melt of a light alloy containing
a thickener and a blowing agent decomposing at a high temperature
to generate a gaseous component in respectively specified
percentages at a temperature lower than the decomposition
temperature of said blowing agent, agitating said melt to allow
said thickener and said blowing agent to disperse, measuring a
predetermined amount of said melt for the injection into a mold,
and injecting said melt into said mold through an injection nozzle
to produce a foaming molded article of the light alloy, wherein
said melt is heated to the decomposition temperature of said
blowing agent or higher at least immediately before the injection
into said mold.
16. The method for injection foaming molding of the light alloy
according to claim 15, wherein the temperature of said melt is
raised to the decomposition temperature of said blowing agent or
higher at the time of passing through said nozzle.
17. An apparatus for injection foaming molding of a light alloy
comprising: a cylindrical member for receiving a melt of a light
alloy containing a thickener and a blowing agent decomposing at a
high temperature to generate a gaseous component, wherein said melt
is agitated by an agitating means provided rotatably in the inner
portion to allow said thickener and said blowing agent to disperse;
a movable member provided to be protrudable and retreatable within
said cylindrical member, said movable member forming a measuring
part for measuring said melt in cooperation with said cylindrical
member at the tip of said cylindrical member by retreating and
injecting said melt with the gaseous component generated therein
into a mold communicating with said measuring part by protruding;
and a position retaining means for retaining the position of said
movable member against an increase in internal pressure of said
cylindrical member in the generation of said gaseous component so
that said melt after the completion of the measurement can be
retained in the pressured state to inhibit the foaming thereof.
18. The apparatus for injection foaming molding of the light alloy
according to claim 17, wherein said position retaining means is a
solenoid valve provided in a hydraulic circuit of a hydraulic
cylinder for protruding and retreating said movable member so as to
be capable of interrupting the incoming and outgoing of oil to the
hydraulic cylinder.
19. The apparatus for injection foaming molding of the light alloy
according to claim 17, wherein said movable member is composed of a
rotatable agitating screw.
20. The apparatus for injection foaming molding of the light alloy
according to claim 17, wherein said cylindrical member comprises a
barrel for agitating said melt and a cylinder connected thereto to
introduce and measure said agitated melt, and said movable member
is a plunger provided within said cylinder.
21. An apparatus for injection foaming molding of a light alloy
comprising: a barrel for receiving a melt of the light alloy
containing a thickener and a blowing agent decomposing at a high
temperature to generate a gaseous component, said barrel comprising
a temperature adjusting means capable of adjusting the temperature
of said melt from a temperature lower than the decomposition
temperature of said blowing agent to the decomposition temperature
or higher, in which the gaseous component can be generated by
adjusting the temperature of said melt to the decomposition
temperature of said blowing agent or higher by said temperature
adjusting means; a screw provided within said barrel to be
rotatable, protrudable and retreatable and adapted to agitate said
melt by rotating to allow said thickener and said blowing agent to
disperse, to form a measuring part in cooperation with said barrel
at the tip of said barrel by retreating, and to inject the measured
melt from said barrel into a mold by protruding; and a position
retaining means for retaining the position of said screw against an
increase in internal pressure of said barrel in the generation of
said gaseous component so that said melt after the completion of
the measurement can be retained in the pressured state to inhibit
the foaming thereof.
22. An apparatus for injection foaming molding of a light alloy
comprising: a barrel for receiving a melt of a light alloy
containing a thickener and a blowing agent decomposing at a high
temperature to generate a gaseous component, said barrel having a
first temperature adjusting means capable of adjusting the
temperature of said melt to a temperature lower than the
decomposition temperature of said blowing agent, in which said melt
is agitated by a screw provided rotatably in the inner portion to
allow said thickener and said blowing agent to disperse; a cylinder
connected to said barrel and having a second temperature adjusting
means capable of adjusting the temperature of said melt to the
decomposition temperature of said blowing agent or higher; a
plunger provided within said cylinder to be protrudable and
retreatable, said plunger forming a measuring part for measuring
said melt in cooperation with said cylinder at the tip of said
cylinder by retreating, and injecting the measured melt from said
cylinder into a mold by protruding; and a position retaining means
for retaining the position of said plunger against an increase in
internal pressure of said cylinder in the generation of said
gaseous component, so that said melt after the completion of the
measurement can be retained in the pressured state to inhibit the
foaming thereof.
23. An apparatus for injection foaming molding of a light alloy
comprising: a cylindrical member for receiving a melt of the light
alloy containing a thickener and a blowing agent decomposing at a
high temperature to generate a gaseous component, in which said
melt is agitated by an agitating means provided rotatably in the
inner portion to allow said thickener and said blowing agent to
disperse; a movable member provided within said cylindrical member
to be protrudable and retreatable, said member forming a measuring
part for measuring said melt in cooperation with said cylindrical
member at the tip of said cylindrical member by retreating and
injecting said melt into a mold communicating with said measuring
part through an injection nozzle by protruding; and a nozzle
heating means capable of heating said melt to the decomposition
temperature of said blowing agent or higher at the time of passing
said melt through said nozzle.
Description
TECHNICAL FIELD
[0001] The present invention relates to a method and apparatus for
injection foaming molding for foaming a melt of a light alloy to
form a foaming molded product.
BACKGROUND ART
[0002] For the conventional production of a foam metal, the
following methods are known: in a method disclosed in Japanese
Patent Publication No. Hei 1-51528 (Technique 1), a thickener and a
blowing agent are added to a melted metal followed by agitating,
the whole mold is heated to the melting point of the foamed metal
or higher, the agitation is terminated to start a foaming process,
in which the air within the mold is released by expanding a number
of bubbles generated by thermal decomposition of the blowing agent
to allow a foam metal to fill the inner portion of the mold
entirely, thereby blocking the mold in a sealed state to form an
uniform cell structure under equilibration of the pressure by the
rise of internal pressure by the bubbles, and the resulting foam
metal is cooled and coagulated in the mold.
[0003] In a method disclosed in U.S. Pat. No. 2,983,597 (Technique
2), a hydrogenated metal is mixed to a melted metal and decomposed,
and the metal is foamed by generation of hydrogen gas. Further, a
second alloyed melted metal is supplied from a halfway screw while
extruding a mixture of a melted metal and a hydrogenated metal by a
first screw at a gas decomposition temperature or lower to perform
a continuous foaming molding by generation of decomposed gas.
[0004] In a method disclosed in Japanese Patent Publication No.
2002-511526 (Technique 3), a molded product is obtained by
compressing a blowing agent and a metal powder, heating the
resulting semi-finished material within a mold to a melting
temperature range to allow the material to foam followed by
cooling.
[0005] In a method disclosed in Japanese Patent Laid-Open No. Hei
9-241780 (Technique 4), as a solution of the problems of a method
for adding a blowing agent to a melted metal to generate hydrogen,
thereby foaming the metal, and a method for mixing a blowing agent
to a metal powder followed by compression molding and then foaming
the metal in a mold by heating, a foam metal is obtained by adding
0.1-5%, based on weight, of titanium hydroxide to a metal having a
melting point of 420.degree. C. or higher, uniformly dispersing it
by agitation, then injecting the melt to a mold, reheating the melt
in the mold to 630.degree. C. or higher to allow the melt to foam
followed by cooling and coagulation.
[0006] However, the methods for producing a foam metal of
Techniques 1-4 have the following problems. Technique 1 needs much
time for the heating since the melted metal is heated and agitated
in the mold, and has a problem with the productivity since the same
mold is also used for the cooling after foaming. Further, a large
mold is needed to form a large molded product. In case of a large
mold, since the heating and cooling depends on only the heat
conductive electric heating from the wall surface, and a metal
having a physical property of excellent heat insulating property is
formed as the foamed body at the time of cooling, further much time
is needed as a result.
[0007] In Technique 2, although a metal body can be continuously
formed by foaming with hydrogen gas similarly to Technique 1, a
molded product of a desired three-dimensional shape or a molded
product of a complicated shape cannot be formed since a function of
injecting into a mold is not provided. Since the control for
holding constant mixing ratio of the melted metal to the blowing
agent such as titanium hydride or magnesium hydride can be
performed only by the screw rotating speed with instability, the
feed rate of the blowing agent cannot be kept constant, nor is the
foaming ratio stabilized. Accordingly, the dispersion of product
quality (foaming state) is increased.
[0008] In Technique 3, it is needed to uniformly mix the powder for
obtaining a uniform foamed body, and this requires much time and an
increased cost. Although a three-dimensional shaped product can be
obtained, the control of temperature and time in the foaming by gas
decomposition and the melting of the metal powder is difficult,
therefore it is difficult to obtain a foaming molded product having
uniform cells.
[0009] In Technique 4, although a three-dimensional shape can be
molded, much time is needed to reheat the melt to 630.degree. C. or
higher in the mold similar to the problem of Technique 1, and there
is a problem with the production efficiency. Since there is a need
for increasing a temperature of the mold to 630.degree. C. or
higher, cost for the mold is high. In case of a large mold, the
temperature control of the melt in the mold is difficult to
increase the dispersion of quality.
[0010] The present invention thus has an object to provide a method
and apparatus for injection foaming molding of a light alloy, which
can minimize the difference in foaming state between batches with
good productivity.
DISCLOSURE OF THE INVENTION
[0011] The present invention involves a method for injection
foaming molding of a light alloy comprising the steps of; holding a
melt of a light alloy containing a thickener and a blowing agent
decomposing at a high temperature to generate a gaseous component
in respectively specified percentages at a temperature lower than
the decomposition temperature of the blowing agent; agitating the
melt to allow the thickener and the blowing agent to disperse;
measuring a predetermined amount of the melt for the injection into
a mold; and then injecting the melt into the mold to produce a
foaming molded article of the light alloy, in which the melt is
temperature-adjusted to a temperature higher than the decomposition
temperature of the blowing agent and also inhibited to foam by
pressuring at least immediately before the injection.
[0012] Since the thickener and the blowing agent are preliminarily
added to the melt in the specified percentages, the difference in
foaming state between batches is minimized. Although the
decomposition of the blowing agent is caused immediately before the
injection, the foaming of the melt is inhibited since the inner
capacity of a measuring part is made constant, and the melt is laid
in the pressured state. Therefore, since the melt releases the
pressure at once within the mold immediately after the injection
and foams to spread into every corner of the mold, the transfer
property of the mold is enhanced to enable the formation of a
foaming molded article of a complicated shape. Since the heating of
the mold to the decomposition temperature of the blowing agent or
higher is dispensed, the productivity is improved.
[0013] The present invention further involves a method for
injection foaming molding of a light alloy comprising the steps of;
holding a melt of a light alloy containing a thickener and a
blowing agent decomposing at a high temperature to generate a
gaseous component in respectively specified percentages at a
temperature lower than the decomposition temperature of the blowing
agent; introducing the melt to an injection molding device having
an agitating function, a measuring function and an injecting
function; agitating the melt to allow the thickener and the blowing
agent to disperse; measuring a predetermined amount of the melt for
the injection into a mold; and injecting the melt into the mold to
produce a foaming molded article of the light alloy, wherein the
melt is temperature-adjusted to the decomposition temperature of
the blowing agent or higher and also inhibited to foam by
pressuring at least immediately before the injection.
[0014] Since the melt containing the thickener and the blowing
agent in the specified percentages are held at a temperature lower
than the decomposition temperature of the blowing agent, then
introduced into the injection molding device, and agitated within
the injection molding device, the thickener and the blowing agent
are dispersed to minimize the difference in foaming state between
batches. Although the decomposition of the blowing agent is caused
immediately before the injection, the foaming of the melt is
inhibited since the inner capacity of a measuring part is made
constant, and the melt is laid in the pressured state. Therefore,
since the melt releases the pressure at once within the mold
immediately after the injection and foams to spread into every
corner of the mold, the transfer property of the mold is enhanced
to enable the formation of a foaming molded article of a
complicated shape. Further, since the heating of the mold to the
decomposition temperature of the blowing agent or higher is
dispensed, the productivity is improved.
[0015] The method for injection foaming molding of the light alloy
of the present invention is characterized in that the temperature
of the melt is lower than the decomposition temperature of the
blowing agent at the time of agitating the melt.
[0016] The blowing agent can be uniformly dispersed without
decomposition in the melt by holding the temperature of the melt at
a temperature lower than the decomposition temperature of the
blowing agent at the time of agitating the melt.
[0017] The present invention involves a method for injection
foaming molding of a light alloy comprising the steps of; agitating
a melt of a light alloy containing a predetermined amount of a
thickener to allow the thickener to disperse; supplying an inert
gas as a blowing agent into the melt in a specified percentage
while agitating to allow the inert gas to disperse; measuring a
predetermined amount of the melt for the injection into a mold; and
then injecting the melt to the mold to produce a foaming molded
article of the light alloy, wherein the melt is inhibited to foam
by pressuring the melt at least until the injection is performed
after the supply of the inert gas.
[0018] The melt containing the thickener is agitated to allow the
thickener to disperse, and a predetermined amount of the inert gas
is supplied into the melt and evenly dispersed by agitation with a
screw, whereby a foaming molded article having a substantially
uniform cell structure can be formed. Since the measuring part is
laid in the pressured state before the injection, the foaming of
the inert gas in the melt is inhibited. Therefore, since the melt
releases the pressure at once in the mold immediately after the
injection and foams to spread into every corner of the mold, the
transfer property of the mold is enhanced to enable the formation
of a foaming molded article of a complicated shape. Since the
heating of the mold to the decomposition temperature of the blowing
agent or higher is dispensed, the productivity is improved.
[0019] The method for injection foaming molding of the light alloy
of the present invention is characterized in that the pressuring is
performed by a pressing force caused by the agitation with the
screw.
[0020] The predetermined amounts of the thickener and the blowing
agent added to the melt can be dispersed by agitation, and the
measuring part can be laid in the pressured state by the pressuring
force by the screw for feeding the melt to the front part of a
barrel. Therefore, the foaming of the blowing agent in the melt can
be inhibited.
[0021] The method for injection foaming molding of the light alloy
of the present invention is also characterized in that the melt is
injected in an injection amount reduced by a foaming portion
relative to the inner capacity of the mold to break the pressuring,
whereby the melt is allowed to foam within the mold to obtain the
foaming molded article.
[0022] The melt is injected into the mold in an injection amount
reduced by the foaming portion relative to the inner capacity of
the mold, whereby the mold opening at the foaming is dispensed, and
the size and shape of the foaming molded article can be precisely
controlled.
[0023] The method for injection foaming molding of the light alloy
of the present invention is characterized in that the melt is
injected in an injection amount equal to the inner capacity of the
mold, and the mold is opened by the capacity of a foaming portion
to break the pressuring, whereby the melt is allowed to foam to
obtain the foaming molded article.
[0024] Since the pressure is suddenly released by opening the mold
substantially simultaneously with the injection or after the
injection, the melt sufficiently spreads into minute parts in the
mold, and a foaming molded article of a complicated shape can be
formed.
[0025] The present invention further involves a method for
injection foaming molding of a light alloy comprising the steps of;
adjusting the temperature of a melt of a light alloy containing a
thickener and a blowing agent decomposing at a high temperature to
generate a gaseous component in respectively specified percentages
to a temperature lower than the decomposition temperature of the
blowing agent; supplying the melt into a barrel having a screw
provided to be rotatable, protrudable and retreatable; agitating
the melt by rotating the screw to allow the thickener and the
blowing agent to disperse; measuring the melt in a measuring part
formed in a front portion of the barrel by retreating the screw
with rotation; and adjusting the temperature of the melt to the
decomposition temperature of the blowing agent or higher while
inhibiting the foaming of the melt by pressuring the melt in the
measuring part the capacity of which is made constant by stopping
the retreat of the screw at least immediately before the injection;
and injecting the melt into a mold by protruding the screw to
obtain a foaming molded article.
[0026] Since the melt of the light alloy to be supplied into the
barrel contains the thickener and the blowing agent in the
specified percentages, the thickener and the blowing agent are
uniformly dispersed in a kneading part in the barrel. Since the
melt is injected after measuring, the difference in foaming state
between batches is minimized. Although the decomposition of the
blowing agent is caused immediately before the injection, the
capacity is made constant state by stopping the screw, and the
foaming of the melt is inhibited while laying the melt in the
pressured state. Therefore, since the melt releases the pressure at
once within the mold immediately after the injection and foams to
spread into every corner of the mold, the transfer property of the
mold is enhanced to enable the formation of a foaming molded
article of a complicated shape. Since the heating of the mold to
the decomposition temperature of the blowing agent or higher is
dispensed, the productivity is improved.
[0027] The present invention also involves a method for injection
foaming molding of a light alloy using an apparatus for injection
foaming molding having a barrel containing a screw and a cylinder
communicating with a front portion within the barrel through a
communicating passage and containing a plunger, the method
comprising; (a) a supplying process for supplying the melt of the
light alloy containing a thickener and a blowing agent decomposing
at a high temperature to generate a gaseous component in
respectively specified percentages, which is temperature-adjusted
and held at a temperature lower than the decomposition temperature
of the blowing agent, into the barrel; (b) an agitating process for
agitating the melt by rotating the screw within the barrel to allow
the thickener and the blowing agent to disperse; (c) a measuring
process for introducing and measuring the melt from the barrel to a
measuring part formed in the front portion within the cylinder by
retreating the plunger through the communicating passage; (d) a
pressuring process for adjusting the temperature of the melt to the
decomposition temperature of the blowing agent or higher and
pressuring the melt by generating the gaseous component in the
measuring part the capacity of which is made constant by stopping
the retreat of the plunger to inhibit the foaming of the melt at
least immediately before injection; and (e) an injection foaming
process for injecting the melt inhibited to foam in the pressuring
process into a mold communicating with the inner portion of the
cylinder in the front portion of the cylinder by protruding the
plunger to foam the melt.
[0028] Since the melt containing the thickener and the blowing
agent in the specified percentages is held at a temperature lower
than the decomposition temperature of the blowing agent, then
introduced into the injection molding device, and agitated within
the injection molding device, the thickener and the blowing agent
are dispersed to minimize the difference in foaming state between
batches. Although the decomposition of the blowing agent is caused
immediately before the injection, the capacity is made constant by
stopping the plunger to inhibit the foaming of the melt while
laying the melt in the pressured state. Therefore, since the melt
releases the pressure at once within the mold immediately after the
injection and foams to spread into every corner of the mold, the
transfer property of the mold is enhanced to enable the formation
of a foaming molded article of a complicated shape. Since the
heating of the mold to the decomposition temperature of the blowing
agent or higher is dispensed, the productivity is improved.
[0029] The present invention involves a method for injection
foaming molding of a light alloy comprising the steps of; holding a
melt of the light alloy containing a thickener and a blowing agent
decomposing at a high temperature to generate a gaseous component
in respectively specified percentages at a temperature lower than
the decomposition temperature of the blowing agent; agitating the
melt to allow the thickener and the blowing agent to disperse;
measuring a predetermined amount of the melt for the injection into
a mold; and injecting the melt into the mold through an injection
nozzle to produce a foaming molded article of the light alloy,
wherein the temperature of the melt is raised to the decomposition
temperature of the blowing agent or higher at least immediately
before the injection into the mold.
[0030] Since the thickener and the blowing agent are preliminarily
added to the melt in the specified percentages, the difference in
foaming state between batches is minimized. Since the temperature
of the melt to be injected is raised to the decomposition
temperature of the blowing agent or higher at least immediately
before the injection into the mold, the reheating of the mold to
the decomposition temperature of the blowing agent or higher is
dispensed, the cooling time of the mold is also shortened, and the
productivity is thus improved.
[0031] The method for injection foaming molding of the light alloy
of the present invention is characterized in that the temperature
of the melt is raised to the decomposition temperature of the
blowing agent or higher at the time of passing through the
nozzle.
[0032] Since the thickener and the blowing agent are preliminarily
added to the melt in the specified percentages, the difference in
foaming state between batches is minimized. Since the temperature
of the melt to be injected is raised to the decomposition
temperature of the blowing agent or higher at the time of passing
through the nozzle, the reheating of the mold to the decomposition
temperature of the blowing agent or higher is dispensed, the
cooling time of the mold is also shortened, and the productivity is
thus improved.
[0033] The present invention involves an apparatus for injection
foaming molding of a light alloy comprising; a cylindrical member
for receiving a melt of a light alloy containing a thickener and a
blowing agent decomposing at a high temperature to generate a
gaseous component, wherein the melt is agitated by an agitating
means provided rotatably in the inner portion to allow the
thickener and the blowing agent to disperse; a movable member
provided to be protrudable and retreatable within the cylindrical
member, the movable member forming a measuring part for measuring
the melt in cooperation with the cylindrical member at the tip of
the cylindrical member by retreating, and injecting the melt with
the gaseous component generated therein into a mold communicating
with the measuring part by protruding; and a position retaining
means for retaining the position of the movable member against an
increase in internal pressure of the cylindrical member in the
generation of the gaseous component, so that the melt after the
completion of the measurement can be retained in the pressured
state to inhibit the foaming thereof.
[0034] According to such a structure, since the melt including the
thickener and the foaming agent preliminarily added in specified
percentages can be supplied to the cylindrical member, the
difference in foaming state between batches is minimized. Since the
position of the movable member can be retained by the position
retaining means to keep constant capacity of the measuring part in
the cylindrical member although the decomposition of the blowing
agent is caused immediately before the injection, the melt can be
laid in the pressured state while inhibiting the foaming of the
melt. Therefore, since the melt releases the pressure at once
within the mold immediately after the injection and foams to spread
into every corner of the mold, the transfer property of the mold is
enhanced to enable the formation of a foaming molded article of a
complicated shape. Since the heating of the mold to the
decomposition temperature of the blowing agent or higher is
dispensed, the productivity is improved.
[0035] The apparatus for injection foaming molding of the light
alloy of the present invention is characterized in that the
position retaining means is a solenoid valve provided in a
hydraulic circuit of a hydraulic cylinder for protruding and
retreating the movable member so as to be capable of interrupting
the incoming and outgoing of oil to a hydraulic cylinder.
[0036] According to such a structure, the protruding and retreating
of the movable member can be easily controlled. Therefore, the
position of the movable member can be controlled according to the
foaming state of the blowing agent, and the melt can be easily held
in the pressured state.
[0037] The apparatus for injection foaming molding of the light
alloy of the present invention is characterized in that the movable
member is composed of a rotatable agitating screw.
[0038] According to such a structure, the thickener and the blowing
agent in the melt supplied into the cylindrical member can be
evenly dispersed.
[0039] The apparatus for injection foaming molding of a light alloy
of the present invention is characterized in that the cylindrical
member comprises a barrel for agitating the melt and a cylinder
connected thereto to introduce and measure the agitated melt, and
the movable member is a plunger provided within the cylinder.
[0040] According to such a structure, since the melt containing the
thickener and the blowing agent in specified percentages can be
supplied to the cylindrical member, the difference in foaming state
between batches is minimized.
[0041] The present invention further involves an apparatus for
injection foaming molding of a light alloy comprising; a barrel for
receiving the melt of the light alloy containing a thickener and a
blowing agent decomposing at a high temperature to generate a
gaseous component, the barrel comprising a temperature adjusting
means capable of adjusting the temperature of the melt from a
temperature lower than the decomposition temperature of the blowing
agent to the decomposition temperature or higher, in which the
gaseous component can be generated by adjusting the temperature of
the melt to the decomposition temperature of the blowing agent or
higher by the temperature adjusting means; a screw provided within
the barrel to be rotatable, protrudable and retreatable and adapted
to agitate the melt by rotating to allow the thickener and the
blowing agent to disperse, to form a measuring part in cooperation
with the barrel at the tip of the barrel by retreating, and to
inject the measured melt from the barrel into a mold by protruding;
and a position retaining means for retaining the position of the
screw against an increase in internal pressure of the barrel in the
generation of the gaseous component so that the melt after the
completion of the measurement can be retained in the pressured
state to inhibit the foaming thereof.
[0042] According to such a structure, since the melt containing the
thickener and the blowing agent preliminarily added thereto can be
supplied into the barrel and surely dispersed, the difference in
foaming state of every injection is minimized. The temperature of
the melt in the barrel can be easily adjusted to control the state
of the blowing agent in the melt, and the difference in foaming
state between batches can be further minimized. Further, since the
temperature can be adjusted so as to cause the decomposition of the
blowing agent immediately before the injection and the capacity of
the measuring part within the barrel can be kept constant by the
position retaining means for the screw, the foaming of the melt can
be inhibited to lay the melt in the pressured state. Therefore,
since the melt releases the pressure at once in a mold immediately
after the injection and foams to spread into every corner of the
mold, the transfer property of the mold is enhanced to enable the
formation of a foaming molded article of a complicated shape. Since
the heating of the mold to the decomposition temperature of the
blowing agent or higher is dispensed, the productivity is
improved.
[0043] The present invention involves an apparatus for injection
foaming molding of a light alloy comprising; a barrel for receiving
a melt of a light alloy containing a thickener and a blowing agent
decomposing at a high temperature to generate a gaseous component,
the barrel having a first temperature adjusting means capable of
adjusting the temperature of the melt to a temperature lower than
the decomposition temperature of the blowing agent, in which the
melt is agitated with a screw provided rotatably in the inner
portion to allow the thickener and the blowing agent to disperse; a
cylinder connected to the barrel and having a second temperature
adjusting means capable of adjusting the temperature of the melt to
the decomposition temperature of the blowing agent or higher; a
plunger provided within the cylinder to be protrudable and
retreatable and adapted to form a measuring part for measuring the
melt in cooperation with the cylinder at the tip of the cylinder by
retreating and to inject the measured melt from the cylinder to a
mold by protruding; and a position retaining means for retaining
the position of the plunger against an increase in internal
pressure of the cylinder in the generation of the gaseous component
so that the melt after the completion of the measurement can be
retained in the pressured state to inhibit the foaming thereof.
[0044] According to such a structure, since the melt containing the
thickener and the blowing agent preliminarily added thereto can be
supplied into the barrel and surely dispersed, the difference in
foaming state in every injection is minimized. Since the position
of the movable member can be retained by the position retaining
means to keep constant capacity of the measuring part in the
cylindrical member although the decomposition of the blowing agent
is caused immediately before the injection, the foaming of the melt
can be inhibited while laying the melt in the pressured state.
Therefore, since the melt releases the pressure at once within the
mold immediately after the injection an d foams to spread into
every corner of the mold, the transfer property of the mold is
enhanced to enable the formation of a foaming molded article of a
complicated shape. Since the heating of the mold to the
decomposition temperature of the blowing agent or higher is
dispensed, the productivity is improved. The cylinder enables a
precise measurement of the melt. Therefore, since the difference of
melt injection amounts between batches for injection molding is
minimized, a molded product is precisely produced.
[0045] The present invention involves an apparatus for injection
foaming molding of a light alloy comprising; a cylindrical member
for receiving the melt of the light alloy containing a thickener
and a blowing agent decomposing at a high temperature to generate a
gaseous component, in which the melt is agitated by an agitating
means provided rotatably in the inner portion to allow the
thickener and the blowing agent to disperse; a movable member
provided to be protrudable and retreatable within the cylindrical
member, which forms a measuring part for measuring the melt in
cooperation with the cylindrical member at the tip of the
cylindrical member by retreating and injects the melt to a mold
communicating with the measuring part through an injection nozzle
by protruding; and a nozzle heating means capable of heating the
melt to the decomposition temperature of the blowing agent or
higher at the time of passing the melt through the nozzle.
[0046] According to such a structure, since the melt containing the
thickener and the blowing agent preliminarily added thereto can be
supplied into the barrel and surely dispersed, the difference in
foaming state in every injection is minimized. Since the melt is
injected through the injection nozzle, the injection pressure can
be increased. The temperature of the melt is raised to the
decomposition temperature of the blowing agent or higher when the
melt is passed through the nozzle, or immediately before the
injection into the mold, whereby the blowing agent is decomposed to
generate the gaseous component. Accordingly, since the melt foams
at once within the mold immediately after the injection, the
heating of the mold to the decomposition temperature of the blowing
agent or higher is dispensed and the productivity is improved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0047] FIG. 1 is a general illustrative view showing one embodiment
according to an apparatus for injection foaming molding of a light
alloy of the present invention;
[0048] FIG. 2 is a general illustrative view showing another
embodiment of the apparatus for injection foaming molding of a
light alloy of the present invention;
[0049] FIG. 3 is a view showing an essential part of the embodiment
of the apparatus for injection foaming molding of a light alloy of
the present invention, which illustrates a molding process;
[0050] FIG. 4 is a view showing an essential part of the embodiment
of the apparatus for injection foaming molding of a light alloy of
the present invention, which illustrates the molding process;
and
[0051] FIG. 5 is a view showing an essential part of the other
embodiment of the apparatus for injection foaming molding of a
light alloy of the present invention, which illustrates the molding
process.
BEST MODE FOR CARRYING OUT THE INVENTION
[0052] Preferred embodiments of the present invention will be
described based on the drawings. FIG. 1 shows one embodiment of the
present invention. An apparatus for injection foaming molding 1
according to this embodiment is composed of an injection molding
device 3 and a mold clamping device 17 as shown in FIG. 1.
[0053] The injection molding device 3 comprises; a feed port 8 for
supplying a melt of a light alloy containing a thickener and a
blowing agent decomposing at a high temperature to generate a
gaseous component; a cylindrical member A for agitating the melt
supplied from the feed port 8 by an agitating means 4 provided
rotatably to allow the thickener and the blowing agent to disperse;
a movable member B provided to be protrudable and retreatable
within the cylindrical member A, which forms a measuring part 6 for
measuring the melt in cooperation with the cylindrical member A at
the tip of the cylindrical member A by retreating and injects the
melt with the gaseous component generated therein into a mold 24
communicating with the measuring part 6 by protruding; and a
position retaining means C for retaining the position of the
movable member B against an increase in internal pressure of the
cylindrical member A in the generation of the gaseous component so
that the melt after the completion of the measurement can be held
in the pressured state to inhibit the foaming thereof. A barrel 7
that is the cylindrical member A for agitating the melt comprises a
temperature adjusting means 10 for adjusting the temperature of the
melt 2 of the light alloy supplied and the melt 2 of the light
alloy supplied to an injection part 9. The injection part 9 for
injecting the melt 2 measured by the measuring part 6 into the mold
24 is provided at the tip of the barrel 7.
[0054] Since the barrel 7 is substantially vertical as shown in
FIG. 1, the melt 2 of the light alloy supplied surely moves to the
lower portion within a kneading part 5 by its own weight.
[0055] The injection part 9 has an L-shaped passage 11, wherein the
passage of the melt 2 of the light alloy is vertical in kneading
and agitating and horizontal in injection. Accordingly, even in the
case, as shown in FIG. 1, where the injection molding device 3 is
connected to the mold clamping device 17, the setting area of the
apparatus for injection foaming molding 1 can be minimized as much
as possible.
[0056] In this apparatus for injection foaming molding 1, a nozzle
part 13 having a valve means 12 is provided at the tip of the
L-shaped passage 11 provided at the lower end of the barrel 7. This
tip part is allowed to abut on the mold 24 which horizontally
slides to open and close by the mold clamping device 17.
[0057] Of the components of the apparatus for injection foaming
molding 1, the lower end opening part of a hopper 14 for receiving
the melt of the light alloy melted in a melting furnace (not shown)
and storing it in the melted state is connected to the feed port 8
in the upper portion of the barrel 7. The hopper 14 comprises a
temperature control means such as a heating heater. By this
temperature control means, the melt 2 in the hopper 14 can be
controlled, for example, to a constant temperature equal to or
higher than a liquid phase temperature and lower than the foaming
temperature of the blowing agent, or equal to or higher than the
decomposition temperature of the blowing agent.
[0058] The hopper 14 further comprises a feeder for quantitatively
supplying the thickener and the blowing agent to be added to the
melt 2 of the light alloy. The powdery thickener and the blowing
agent can be quantitatively supplied by this feeder to minimize the
difference in foaming state between batches. The melt of the light
alloy containing predetermined amounts of the thickener and the
blowing agent may be supplied directly to the hopper 14.
[0059] As the thickener to be added to the melt 2 of the light
alloy, a known one such as calcium can be used. As the blowing
agent, a known metallic hydroxide including titanium hydroxide can
be applied. Titanium hydroxide causes gas decomposition at about
640.degree. C. In the use of an AL alloy as a light alloy, the
liquid phase line temperature is 630.degree. C., and the liquid
phase line temperature or higher described later means a
temperature of 630.degree. C. or higher, and the titanium hydroxide
can be dispersed by agitation without causing any decomposition by
holding the melt temperature, for example, at 630.degree. C. by the
temperature adjusting means 10 of the barrel.
[0060] The hopper 14 is filled with an inert gas 18 such as Ar
supplied by an inert gas feeding unit 16 to seal the level of the
melt 2 of the light alloy with the inert gas 18. The position
retaining means C is provided at the upper end of the barrel 7 that
is the cylindrical member A. The position retaining means C
comprises a drive motor 19 and a screw hydraulic cylinder 21
connected to the drive motor 19.
[0061] A through spline hole is provided in the drive shaft of the
drive motor 19, and a spline shaft provided at the upper portion of
the screw 4 rotatably inserted into the barrel 7 is inserted
through to permit the transmission of a rotational driving force
and the axial movement of the screw 4.
[0062] The screw hydraulic cylinder 21 having a vertically
protruding and retreating cylinder rod 2 is connected to the upper
portion of the drive motor 19. The screw 4 is connected to the
cylinder rod 20 of the screw hydraulic cylinder 21, and arranged in
a cantilever form so that the lower end is free within the barrel
7. Therefore, a stirring blade of the screw 4 is protruded (moved
downward) through the drive motor 19 by downwardly protruding the
cylinder rod 20 of the screw hydraulic cylinder 21, whereby the
melt 2 of the light alloy collected in the lower end part within
the barrel 7 can be passed to the L-shaped passage 11 and injected
into the mold 24 through the nozzle part 13.
[0063] When the screw hydraulic cylinder 21 is operated to move the
screw 4 that is the movable member B upward in the axial direction,
the measuring part 6 is formed in a lower portion within the barrel
7. The measuring part 6 can be properly set by the retreating
quantity of the screw hydraulic cylinder 21 so as to provide a
capacity necessary for obtaining a molded product. A valve means 12
of the nozzle part 13 is closed except the time of injection. As
the valve means 12, similar ones as those described later can be
applied.
[0064] The circumferential surface of the barrel 7 and the
injection part 9 is covered with the temperature adjusting means
10. The temperature adjusting means 10 is composed of a plurality
of vertically separated heating heaters. The temperature of the
melt of the light alloy in the barrel 7 can be adjusted at least in
two systems by these heating heaters. Accordingly, the temperature
control can be performed separately in the upper portion and lower
portion of the barrel 7 to control the decomposition of the blowing
agent in the melt 2.
[0065] The mold clamping device 17 comprises a link housing 26
raised on a base 25, a fixed board 28 fixed to the housing 26
through a horizontal tie bar 27, a fixed mold 24b fixed to the
fixed board 28, a movable board 29 sidably inserted and supported
relative to the tie bar 27, and a movable mold 24a fixed to the
movable board 29 so as to be openable and closable by sliding
horizontally relative to the fixed mold 24b. A mold clamping
cylinder 30 is fixed to the outer surface center of the link
housing 26, and the tip of the cylinder rod 31 of the mold clamping
cylinder 30 is connected to the center part of the movable board
29. The link housing 26 is connected to the movable board 29
through a plurality of links 32 which are folded when the both are
mutually approached, and substantially linearly arranged in the
horizontal direction when the both are separated.
[0066] An extrusion cylinder 33 is provided on the side surface of
the movable board 29 on the link housing 26 side, and an extrusion
rod 34 of the extrusion cylinder 33 is connected to a product
protruding mechanism of the movable mold 24a through the movable
board 29. Accordingly, in this mold clamping device 17, the
cylinder rod 31 of the mold clamping cylinder 30 is protruded to
extend the links 32 linearly into a stretched state, whereby the
movable mold 24a can be strongly pressed to the fixed mold 24b. The
release of a product is performed by protruding the extrusion rod
34 of the extrusion cylinder 33 to operate the product protruding
mechanism.
[0067] Since the melt 2 of the light alloy is allowed to foam at
once within the mold 24 after the injection by the apparatus for
injection foaming molding 1 described above, the melt 2 spreads
into every corner of the mold 24. Accordingly, the transfer
property to the mold 24 is enhanced to enable the formation of a
foaming molded article of a complicated shape. Further, since the
heating of the mold to the decomposition temperature of the blowing
agent or higher is dispensed, the productivity is improved.
[0068] The operation of the apparatus for injection foaming molding
1 of this embodiment and a method for injection foaming molding of
a light alloy by this apparatus will be described.
[0069] The melt 2 of the light alloy is fed mechanically or by a
means such as an electromagnetic pump from a melting furnace (not
shown) into the hopper 14. As the melting furnace, a high frequency
induction furnace, an electromagnetic induction heating furnace, or
the like can be used regardless of the kind. The melt 2 of the
light alloy in the hopper 14 is temperature-adjusted to a
temperature of the liquid phase line temperature or higher and
lower than the decomposition temperature of the blowing agent, and
held at an uniform temperature by a temperature control means such
as heating heaters or the like provided on the hopper 14. The
thickener and the blowing agent are quantitatively supplied to the
melt 2 of the light alloy by the feeder (not shown) provided on the
hopper 14. According to this, the difference in foaming state
between batches can be minimized. As occasion demands, an agitating
means for agitating the melt 2 of the light alloy in the hopper 14
may be provided to impart an agitating effect. By providing the
above-mentioned inert gas feeding unit 16 on the hopper 14, the
oxidation of the melt can be prevented.
[0070] The melt 2 of the light alloy put in the hopper 14 is
supplied to the upper portion of the barrel 7 while gas-sealing it,
the melt 2 of the light alloy is temperature-adjusted to and held
at a temperature of the liquid phase line temperature or higher and
lower than the decomposition temperature of the blowing agent by
the heating heater, and the melt 2 of the light alloy is agitated
by rotating the screw 4 in the kneading part 5 within the barrel 7
to allow the thickener and the blowing agent to disperse.
Accordingly, by keeping the blowing agent at a temperature lower
than the foaming temperature at the time of agitation, whereby the
blowing agent can be uniformly dispersed because it is powdery.
[0071] When the melt 2 containing only the thickener is supplied
into the barrel 7, an inert gas quantitative feeding unit (not
shown) is provided on the barrel 7 corresponding to the kneading
part 5, whereby inert gas that is the blowing agent can be supplied
to the melt in a specified percentage when the thickener is allowed
to disperse by agitation, and the inert gas is evenly dispersed
into the melt 2.
[0072] When the melt 2 is agitated in the kneading part 5, the melt
2 of the light alloy is pushed downwardly within the barrel 7 by a
pushing force accompanying the rotation of the screw 4; a load is
applied to the axially upper portion of the screw 4. On the other
hand, a fixed back pressure is set on the screw hydraulic cylinder
21 constituting the position retaining means, and when an internal
pressure overcoming the back pressure is generated in the barrel 7,
the screw 4 is moved axially upward and retreated to a
predetermined position set according to a molded product volume.
The melt 2 of the light alloy is measured in the measuring part 6
between the screw 4 and the L-shaped passage 11. In this
embodiment, although the screw 4 is retreated with rotation by the
rise of the internal pressure of the barrel 7 caused by the
rotation, the screw 4 may be retreated without rotation by the
screw hydraulic cylinder 21, or retreated with rotation by the
screw hydraulic cylinder 21. A backflow preventive means such as a
check ring is preferably provided at the tip of the screw 4, and by
providing it, the melt 2 of the light alloy can be smoothly carried
down, at the time of retreating, and measured in the measuring part
6 according to the molded product volume. At the measurement, the
nozzle part 13 of the L-shaped passage 11 is closed by the valve
means 12.
[0073] After the measurement is completed, the melt 2 is laid in
the pressured state at least immediately before the injection to
inhibit the foaming by temperature-adjusting so as to be heated to
the decomposition temperature of the blowing agent within the
measuring part 6 by the heating heaters, and promoting the
decomposition of the blowing agent within the measuring part 6 the
capacity of which is made constant by stopping the retreat of the
screw 4. Since the measuring part 6 can be laid in the pressured
state also by the pushing force of the melt 2 by the rotation of
the screw 4, the foaming of the blowing agent raised in temperature
to the decomposition temperature of the blowing agent can be
inhibited.
[0074] The melt 2 is then injected into the mold 24 by opening the
valve means 12 of the nozzle part 13 and protruding the screw 4,
and the melt 2 inhibited to foam is allow to rapidly foam within
the mold 24 lower in pressure than in the barrel 7, whereby the
formation of a molded article is performed.
[0075] At the injection into the mold 24, when the melt 2 of the
light alloy is injected into the mold 24 in an injection amount
equal to the inner capacity of the mold 24, the pressure of the
gaseous component is released at once by sliding and opening the
movable mold 24a by the volume of a foaming portion after the
injection to allow the melt 2 of the light alloy to foam in the
sliding direction, whereby a foaming molded article in which foamed
cells are uniformly dispersed can be obtained. When the melt 2 of
the light alloy is injected to the mold 24, a skin layer is formed
on the surface where the melt 2 comes in contact with the mold
24.
[0076] Since the pressure of the gaseous component restricted to
expand in the melt 2 of the light alloy is suddenly released by
injecting the melt 2 of the light alloy into the mold 24 and
opening the mold 24 substantially simultaneously with the injection
or after the injection, the foamed melt 2 of the light alloy
sufficiently spreads into minute parts in the mold 24, and a
foaming molded article of a complicated shape can be formed.
[0077] When the melt 2 of the light alloy is injected into the mold
24 in an injection amount reduced by a foaming portion relative to
the inner capacity of the mold (the molded product capacity), the
pressure of the gaseous component is released at once in the mold
24 after the injection to allow the melt 2 of the light alloy to
foam, and a foaming molded article in which foamed cells are
uniformly dispersed can be obtained.
[0078] By reducing the injection amount of the melt 2 of the light
alloy to be injected into the mold 24 by the foaming portion in
this way, the size and shape of a foaming molded article can be
precisely controlled without being influenced by the stopping
precision in opening the mold, the parallel degree of the mold, or
the like.
[0079] According to the method for injection foaming molding using
the apparatus for injection foaming molding 1 as described above,
since the thickener and the blowing agent are preliminarily added
to the melt 2 of the light alloy to be supplied into the barrel 7
in respectively specified percentages, the variations of the
resulting molded product between injections can be minimized. Since
the thickener and the blowing agent are uniformly dispersed in the
kneading part 5 within the barrel 7, a molded product with
uniformly dispersed foamed cells can be obtained. Further,
according to such an injection, the difference in foaming state
between batches is minimized.
[0080] Although the gaseous component is generated by decomposition
of the blowing agent immediately before the injection, the capacity
of the measuring part 6 is made constant by stopping the screw 4 to
inhibit the foaming of the melt (the expansion of the gaseous
component). Therefore, the melt 2 of the light alloy is made to
release the pressure at once within the mold 24 immediately after
the injection to foam, whereby the melt can be filled into every
corner of the mold 24. Accordingly, the transfer property to the
mold 24 is enhanced, the productivity is improved, and the
formation of a foaming molded article of a complicated shape can be
performed. The mold is depressurized by a pressure reducing means
such as a vacuum pump, whereby the transfer property and the
moldability of a foaming molded article of complicated shape can be
further improved Another embodiment according to the apparatus for
injection foaming molding of the present invention will be further
described in reference to FIG. 2. As shown in FIG. 2, an apparatus
for injection foaming molding 40 of this embodiment comprises two
members of a horizontal plunger type injection part 9 different
from that of the apparatus for injection foaming molding 1 and the
same vertical barrel 7 as that of the apparatus 1.
[0081] FIG. 2 is a general illustrative view showing the apparatus
for injection foaming molding 40 of a light alloy of this
embodiment. The apparatus for injection foaming molding 40 has
substantially the same structure for the barrel 7 and the mold
clamping device 17 as the apparatus for injection foaming molding 1
except the horizontal plunger type injection part 9. As a melt of a
light alloy, a thickener and a blowing agent, those described above
are applicable.
[0082] This apparatus for injection foaming molding 40 of a light
alloy comprises an injection molding device 43, and a mold clamping
device 17. The injection molding device 43 comprises a barrel 47
having an agitating function, the barrel being composed of a
kneading part 45 having a feed port 58 for supplying a melt 2
containing a thickener and a blowing agent decomposing at a high
temperature to generate a gaseous component in respectively
specified percentages at an upper portion and a screw 44 provided
in the inner portion to be rotatable, protrudable and retreatable,
in which the melt 2 is agitated by the screw 44 to allow the
thickener and the blowing agent to disperse, and a storage part 46
formed by retreating the screw 44; and a plunger injection machine
50 having a measuring function and an injecting function, the
machine comprising a cylinder 42 a front portion of which is
connected to the lower end of the barrel 47 through a communicating
passage 41 provided at the lower end of the cylinder 42, and a
plunger 48 protrudable and retreatable along the axis of the
cylinder 42 within the cylinder 42, in which a measuring part 49 is
formed at the inner front portion of the cylinder 42 by retreating
the plunger 48, and the melt 2 of the light alloy is injected by
protruding the plunger 48. The mold clamping device 17 comprises a
mold 24 for allowing the melt 2 injected from the plunger injection
machine 50 to foam. The apparatus also comprises a temperature
adjusting means 51 for adjusting the temperature of the melt 2 of
the light alloy supplied from the feed port 58 to the barrel 47 and
the melt 2 of the light alloy supplied to the plunger injection
machine 50
[0083] A nozzle part 52 having a valve means 12 is provided at the
tip of the plunger injection machine 50 of the apparatus for
injection foaming molding 40. The tip part abuts on the mold 24
which is horizontally slid to open and close by the mold clamping
device 17.
[0084] Of the components of the apparatus for injection foaming
molding 40, a hopper 53 has the same structure as the hopper 14
described above, and comprises a feeder and a temperature control
means such as a heating heater.
[0085] The barrel 47 also has the same structure as in the
apparatus for injection foaming molding 1 of the above-mentioned
embodiment. As shown in FIG. 2, a screw hydraulic cylinder 56
having a vertically protruding and retreating cylinder rod 55 is
connected to the upper portion of a drive motor 54, and the screw
44 is connected to the cylinder rod 55 of the screw hydraulic
cylinder 56 through the drive motor 54. Therefore, the cylinder rod
55 of the screw hydraulic cylinder 56 is protruded down to protrude
(move down) the stirring blade of the screw 44 through the drive
motor 54, whereby the melt 2 of the light alloy collected in the
lower end within the barrel 47 is supplied into the cylinder 42 of
the plunger injection machine 50 through the communicating passage
41.
[0086] The screw hydraulic cylinder 56 is adapted so that a storage
part 46 can be formed at a lower portion within the barrel 47 when
it is moved axially upward. Further, this cylinder has a sufficient
stroke to move the plunger from the position for forming the
storage part 46 to the position capable of closing the
communicating passage 41.
[0087] As shown in FIG. 2, the circumferential surface of the
barrel 47 and the cylinder 42 of the plunger injection machine 50
is covered with the temperature adjusting means 51. The temperature
adjusting means 51 is composed of a plurality of separated heating
heaters. By controlling the heating heaters, at least the melt 2 of
the light alloy in the barrel 47 can be adjusted to a temperature
lower than the decomposition temperature of the blowing agent added
thereto, and at least the melt 2 of the light alloy in the cylinder
42 can be adjusted to a temperature allowing the blowing agent
added thereto to decompose to generate the gaseous component or
higher.
[0088] The plunger injection machine 50 is connected to the barrel
47 through the communicating passage 41 formed at the lower end of
the barrel 47. The plunger injection machine 50 comprises the
cylinder 42 having the nozzle part 52 with the valve means 12 in
the front portion and the plunger 48 protrudable and retreatable
within the cylinder 42. The plunger 48 is driven by the hydraulic
pressure of the plunger hydraulic cylinder 57. When the plunger 48
is retreated, a measuring part 49 is formed in the front portion of
the cylinder 42. The capacity of the measuring part 49 can be
properly set by the retreating quantity of the plunger 48 to attain
a capacity necessary for providing a molded product. The plunger
hydraulic cylinder 57 has a sufficient stroke to move the plunger
48 from the position for forming the measuring part 49 to the
position capable of closing the connection passage 41 connected to
the vicinity of the tip of the cylinder 42 by protruding. The
plunger 48 is provided so as to close the communicating passage 41
when the injection is completed. Accordingly, the melt 2 of the
light alloy for the next molding injection can be supplied into the
barrel 47 immediately after the injection. The valve means 12 of
the nozzle part 52 is laid in a closed state except the time of
injection. As the valve means 12, a one adapted to block the nozzle
by a mechanical or spring type shut-off valve provided at the tip
of the nozzle can be used.
[0089] According to the apparatus for injection foaming molding 40
as described above, the melt 2 can be inhibited to foam in the
state where the gaseous component is generated within the melt 2 at
least immediately before the injection, and made to foam at once
into the mold 24 after the injection. Therefore, the melt 2 spreads
into every corner of the mold 24, whereby the transfer property to
the mold 24 is enhanced, and the productivity is improved. Further,
the formation of a foaming molded article of a complicated shape
can be performed. The maintenance and management of the apparatus
can be facilitated by constituting the barrel 47 and the injection
part from two separate members.
[0090] The operation of the apparatus for injection foaming molding
40 of this embodiment and a method for injection foaming molding
using this apparatus will be described.
[0091] The melt 2 of a light alloy is put into a hopper 53 from the
melting furnace described above in the same manner. A thickener and
a blowing agent decomposing at a high temperature to generate a
foaming gas are added to the melt 2 in respectively specified
percentages, and the resulting melt is temperature-adjusted to a
liquid phase line temperature or higher and a temperature lower
than the decomposition temperature of the blowing agent by a
temperature control means of the hopper 53. In this way, a
supplying process for supplying the temperature-adjusted melt 2 of
the light alloy into the barrel 47 is performed. The thickener and
the blowing agent to be added to the melt 2 may be put into the
hopper 53 by providing a feeder on the hopper 53, or the melt 2
containing predetermined amounts of the thickener and the blowing
agent may be put into the hopper 53.
[0092] The melt 2 is then supplied to the upper portion of the
barrel 47, adjusted to and held at the liquid phase line
temperature or higher and a temperature lower than the
decomposition temperature of the blowing agent, and the thickener
and the blowing agent are uniformly dispersed in an agitating
process for agitating the melt 2 by rotating the screw 44 in the
kneading part 45 within the barrel 47. When the melt 2 containing
only the thickener is supplied into the barrel 47, an inert gas
quantitative feeding unit (not shown) is provided to the barrel 47
corresponding to the kneading part 45, whereby inert gas that is
the blowing agent can be supplied to the melt 2 in a specified
percentage at the time of dispersing the thickener by agitation,
and uniformly dispersed into the melt 2.
[0093] At this time, the plunger 48 of the plunger injection
machine 50 is protruded to the position for closing the
communicating passage 41 as shown in FIG. 3. The screw 44 in the
barrel 47 is retreated with rotation, whereby the storage part 46
is formed between the screw 44 and the communicating passage 41
instead of the above-mentioned measuring part 6, and a primary
measurement is performed in this storage part 46. The storage part
46 is adjusted by the retreating quantity of the screw 44 so as to
have a capacity larger than the amount of the melt to be injected.
The screw 44 may be retreated without rotation, or retreated with
rotation. The backflow preventive means described above can be
provided at the tip of the screw 44.
[0094] Then, a measuring process for introducing the melt 2 from
the barrel 47 to the measuring part 49 formed at the front portion
within the cylinder 42 through the communicating passage 41 by
opening the communicating passage 41 to retreat the plunger 48 of
the plunger injection machine 50 is performed. In this measuring
process, the screw 44 within the barrel 47 is protruded (moved
down) simultaneously with the retreat of the plunger 48 as shown in
FIG. 4. A pressuring force by the screw 44 is worked to press the
melt 2 of the light alloy into the measuring part 49 formed at the
front portion of the cylinder 42 with a positive pressure while the
plunger 48 retreats to a predetermined position set according to
the molded product volume, whereby the melt is secondarily
measured.
[0095] Since the melt 2 including the thickener and the blowing
agent preliminarily added in the specified percentages is held at a
temperature lower than the decomposition temperature of the blowing
agent, and then introduced to and agitated in an injection molding
device 43, the thickener and the blowing agent are uniformly
dispersed to minimize the difference in foaming state in every
injection.
[0096] When the measuring by pressing is completed, the
communicating passage 41 is closed by the screw 44, as shown in
FIG. 5, to prevent the backflow of the melt 2 of the light alloy
from the measuring part 49. At the time of measurement, the nozzle
part 52 at the tip of the cylinder 542 of the plunger injection
machine 50 is closed by the valve means 12.
[0097] After the secondary measurement is thus completed, the melt
2 is temperature-adjusted to the decomposition temperature of the
blowing agent or higher at least immediately before the injection
by each temperature adjusting means 51, and the decomposition
within the measuring part 49 the capacity of which is made constant
by stopping the retreat of the plunger 48 is promoted, whereby a
pressuring process for laying the melt in the pressured state to
inhibit the foaming thereof is performed. Namely, although the
blowing agent gradually starts the decomposition to generate the
gaseous component as the melt 2 of the light alloy is heated to the
decomposition temperature of the blowing agent within the measuring
part 49 by the temperature adjusting means 51, the foaming of the
melt 2 is inhibited by pressuring since the increase in capacity is
suppressed by the back pressure of the plunger 48.
[0098] Then, an injection foaming process for injecting the melt 2
inhibited to foam in the pressurizing process into the mold 24
communicating with the front portion within the cylinder 42
followed by foaming by protruding the plunger 48 is performed to
form a molded article.
[0099] At the injection to the mold 24, a method for injecting the
melt 2 of the light alloy in an injection amount equal to the inner
capacity of the mold 24 into the mold 24 and opening the mold by a
foaming portion to obtain the foaming molded article similarly to
the above-mentioned method, and a method for injecting the melt 2
of the light alloy into the mold 24 in an amount reduced by the
foaming portion to obtain the foaming molded article within the
mold with a constant capacity can be applied.
[0100] According to the method for injection foaming molding using
the apparatus for injection foaming molding 40, since the foaming
of the melt 2 (the expansion of the gaseous component) is inhibited
in a state where the capacity is made constant by stopping the
plunger 48 although the blowing agent is decomposed to generate the
gaseous component immediately before the injection, the pressure is
released at once in the mold 24 immediately after the injection to
allow the melt to foam, whereby the melt 2 can spread into every
corner of the mold 24. Accordingly, the transfer property to the
mold 24 is enhanced to enable the formation of a foaming molded
article of a complicated shape. The transfer property and the
moldability of a foaming molded article of a complicated shape can
be further improved by depressurizing the mold by a pressure
reducing means similarly to the above-mentioned embodiment.
[0101] When inert gas is supplied to the melt 2 in a specified
percentage as a blowing agent by an inert gas quantitative feeding
unit (not shown) by use of the apparatuses for injection foaming
molding 1 and 40 as described above, the inert gas is also
dispersed by agitation in the kneading parts 5 and 45 of the
barrels 7 and 47, and a predetermined amount of the melt 2 is
measured for the injection into the mold 24, and then the melt is
injected into the mold 24. When the temperature is raised by the
temperature adjusting means 10 and 51 before the injection to the
mold 24, the expansion of the gaseous component is promoted. At
that time, the increase in capacity is suppressed by stopping the
retreat of the screw 4 in the apparatus for injection foaming
molding 1 and by stopping the retreat of the plunger 48 in the
apparatus for injection foaming molding 40, and in such a pressured
state, the foaming of the melt 2 (the expansion of the gaseous
component) is inhibited. The screw 4 and the plunger 48 are
protruded while opening the valve means 12 of the nozzle parts 13
and 52 to inject the melt 2 of the light alloy into the mold 24,
whereby the pressuring force acting on the melt 2 is released at
once to allow the melt to foam, whereby the formation of a molded
article is performed.
[0102] Since the inert gas is supplied in the specified percentage
and uniformly dispersed into the melt 2 even in the use of the
inert gas as the blowing agent, a foaming molded article having a
substantially uniform cell structure can be formed while minimizing
the difference in foaming state between injections.
[0103] The supply of Ar gas as a blowing agent from the barrel in
the apparatus for injection foaming. molding 40 with the above
inert gas quantitative feeding unit provided on the barrel will be
further described.
[0104] A predetermined amount of the thickener is added to the melt
2 of the light alloy supplied from the melting furnace to the
hopper 53 similarly to the above. At this time, the temperature is
adjusted to the liquid phase line temperature or higher by the
temperature control means of the hopper 53.
[0105] The temperature-adjusted melt 2 is supplied into the barrel
47, and agitated in the kneading part 45 while adjusting the
temperature to the liquid phase line temperature or higher to
thereby disperse the thickener. At this time, a high-temperature Ar
gas is supplied from the inert gas quantitative feeding unit (not
shown) to the melt 2, whereby the Ar gas is also dispersed into the
melt 2. The melt 2 is then fed to the storage part 46 in the lower
portion of the barrel 47.
[0106] When the addition amount of the thickener to be added to the
melt 2 fed to the storage part 46 is small, no pressure overcoming
the back pressure of the screw 44 is generated because the pressure
of the melt 2 generated by the rotation of the screw 44 in the
barrel 47 is small. In such a case, the screw 44 of the kneading
part 45 is retreated by driving the screw hydraulic cylinder 56 in
the axial direction to feed the melt 2 to the storage part 46 by
its own weight of the melt 2, a pressure for feeding the melt 2 to
the measuring part 49 of the plunger injection machine 50 is
generated by protruding (moving down) the screw 44 to feed the melt
2 to the measuring part 49 by a positive pressure. As a matter of
course, when the addition amount of the thickener is large and the
pressure overcoming the screw back pressure is generated in the
melt 2 by the rotation of the screw 44, the drive by the cylinder
is not necessarily required for the feed of the melt 2 to the
storage part.
[0107] The measured melt 2 is raised in temperature by the
temperature adjusting means 51 within the measuring part 49 before
the injection to promote the expansion of the Ar gas included
therein. However, since the capacity is made constant by stopping
the plunger 48 to inhibit the foaming, and the pressure is released
at once in the mold 24 immediately after the injection to allow the
melt to foam, the melt spreads into every corner of the mold 24 and
a foaming molded article with foamed cells uniformly dispersed
therein can be thus obtained.
[0108] Another embodiment according to the apparatus for injection
foaming molding of the present invention will be described. An
apparatus for injection foaming molding of this embodiment has the
same device structure as the above-mentioned apparatus for
injection foaming molding 1 or the apparatus for injection foaming
molding 40 except the points described below. Accordingly, only the
different points will be described, omitting the description for
the similar points.
[0109] This apparatus for injection foaming molding is adapted to
disperse, measure and then inject a melt of a light alloy
containing a thickener and a blowing agent decomposing at a high
temperature to generate a gaseous component into a mold through an
injection nozzle, and comprises a nozzle heating means capable of
raising the temperature of the melt to the decomposition
temperature of the blowing agent or higher when passing the melt
through the nozzle in the injection. As the nozzle heating means, a
known heating means such as a resistance heating heater or
induction heating heater provided on the circumference of the
injection nozzle can be used, and the induction heating heater
capable of shortening the temperature rising time is more
preferably used.
[0110] According a method for injection foaming molding using this
apparatus for injection foaming molding, since the melt including
the thickener and the blowing agent preliminarily added thereto in
respectively specified percentages is prepared similarly to the
above embodiments, and agitated to allow the thickener and the
blowing agent to uniformly disperse, the difference in foaming
state in every injection is minimized.
[0111] The temperature of the melt is adjusted to a temperature
lower than the decomposition temperature of the blowing agent to
inhibit the foaming at the time of measuring, and raised to the
decomposition temperature of the blowing agent or higher at the
time of the passage to the injection nozzle or immediately before
the injection into the mold to allow the melt to rapidly foam in
the mold after the injection by the gaseous component generated by
the decomposition of the blowing agent at the time of the passage
to the injection nozzle (immediately before the injection into the
mold). Therefore, the reheating of the mold to the decomposition
temperature of the blowing agent or higher is dispensed, and the
productivity is enhanced.
[0112] Although the present invention is described with the
preferred embodiments, the present invention is not limited to
these embodiments, and various changes are possible within the
technical range of the present invention.
[0113] For example, a shutter member may be provided in the hopper
and the feed port part of the barrel connected thereto to
intermittently supply the melt from the hopper to the barrel.
According to this, the addition of the thickener and the blowing
agent in the specified percentages to the melt stored in the hopper
can be facilitated.
[0114] In the method for injection foaming molding using the
apparatus for injection foaming molding 40 according to the
embodiment, the primary measurement is performed in the storage
part 46 formed in the front portion of the barrel 47 by retreating
the screw 44, and the melt 2 is introduced to and measured in the
measuring part 49, which is formed in the front portion within the
cylinder 42 by retreating the plunger 48, from the barrel 47
through the communicating passage 41 by protruding the screw 44.
However, the melt 2 may be introduced to and measured in the
measuring part 49, which is formed by retreating the plunger 48
while rotating the screw 44 without retreating successively to the
agitation by the screw 44. According to this, the screw hydraulic
cylinder 56 can be dispensed to simplify the device structure, and
the primary measuring operation can be omitted.
[0115] A pressure detection means such as a pressure gauge or
pressure sensor may provided in the hydraulic circuit of the screw
hydraulic cylinders 21 and 56 and the plunger hydraulic cylinder 57
to detect the back pressure generated in the screw or plunger 48 at
the time of raising the temperature of the melt to the
decomposition temperature of the blowing agent or higher. According
to this, the temperature rising state of the melt 2 or the
decomposition degree of the blowing agent can be estimated from the
change in the back pressure accompanied by the temperature rise of
the melt 2.
[0116] By detecting the change in the back pressure, the pressure
of the hydraulic cylinder can be controlled by use of the detection
value as a control parameter to control the foaming state of the
melt 2. Namely, when the melt 2 is controlled in such a manner that
the melt 2 is partially foamed before injection, the partially
foamed melt 2 is pressured to inhibit the further foaming, and the
resulting melt 2 is injected into the mold 24, whereby the unfoamed
part is suddenly foamed in the mold 24, the melt 2 before the
injection (at the time of measuring) can be controlled to a desired
foaming state. The partial foaming of the melt 2 may be performed
not by the pressure control of the hydraulic cylinder but by the
position control of the hydraulic cylinder.
[0117] Although the present invention is described in the above
preferred embodiments, the present invention is not restrictive to
these embodiments. The present invention will be understood to
include various other embodiments without departing from the spirit
and scope of the present invention.
INDUSTRIAL APPLICABILITY
[0118] According to the method for injection foaming molding and
apparatus for injection foaming molding of the present invention,
since the melt is adjusted to the decomposition temperature of the
blowing agent or higher and inhibited to foam by pressuring at
least immediately before injection, the difference in foaming state
between batches is minimized. Since the capacity in the measuring
part is made constant although the decomposition of the blowing
agent is caused immediately before the injection, the melt is
inhibited to foam in the pressured state. Therefore, since the melt
releases the pressure at once in the mold immediately after the
injection to foam, the melt spreads into every corner of the mold.
Accordingly, the transfer property to the mold is enhanced to
enable the formation of a foaming molded article of a complicated
shape. Since the heating of the mold to the decomposition
temperature of the blowing agent or higher is dispensed, the
productivity is improved.
* * * * *