U.S. patent application number 09/953433 was filed with the patent office on 2003-03-20 for devices and methods for melting materials.
Invention is credited to Yamada, Fujio.
Application Number | 20030051851 09/953433 |
Document ID | / |
Family ID | 25493990 |
Filed Date | 2003-03-20 |
United States Patent
Application |
20030051851 |
Kind Code |
A1 |
Yamada, Fujio |
March 20, 2003 |
Devices and methods for melting materials
Abstract
A molten material supply unit includes a heating cylinder. The
heating cylinder may receive and heat the material in a
substantially vacuum condition. A molding apparatus may include a
pressurizing and charging unit in addition to the molten material
supply unit. The pressurizing and charging unit is adapted to
receive the melted material from the molten material supply unit
and to charge the melted material into a die under pressure.
Inventors: |
Yamada, Fujio; (Aichi-ken,
JP) |
Correspondence
Address: |
DENNISON, SCHULTZ & DOUGHERTY
1745 JEFFERSON DAVIS HIGHWAY
ARLINGTON
VA
22202
US
|
Family ID: |
25493990 |
Appl. No.: |
09/953433 |
Filed: |
September 17, 2001 |
Current U.S.
Class: |
164/113 ;
164/312; 264/102; 264/328.17; 425/256; 425/546; 425/547 |
Current CPC
Class: |
B22D 17/007 20130101;
B29C 45/63 20130101; B22D 17/28 20130101; B29C 45/53 20130101; B22D
17/30 20130101; B29C 45/72 20130101; Y10S 164/90 20130101; B29C
45/462 20130101 |
Class at
Publication: |
164/113 ;
264/102; 264/328.17; 425/256; 425/546; 425/547; 164/312 |
International
Class: |
B22D 017/10; B29C
045/00 |
Claims
1. A molten material supply unit comprising a heating cylinder
constructed and arranged for receiving and heating the material in
a substantially vacuum condition.
2. A molten material supply unit as in claim 1, further including a
vacuum device communicating with the heating cylinder and being
arranged and constructed to generate a reduced pressure within the
heating cylinder.
3. A molten metal supply unit as in claim 2, wherein the vacuum
device comprises a vacuum pump that is disposed adjacent to the
heating cylinder in a position near an inlet of the heating
cylinder.
4. A molten material supply unit as in claim 1, the material is
supplied into the heating cylinder in the form of rods that have a
predetermined length.
5. A molten material supply unit as in claim 4, wherein the rods
are made of metal.
6. A molten material supply unit as in claim 4, further including a
pusher device that is adapted to push the rods into the heating
cylinder.
7. A molten material supply unit as in claim 4, further including a
preheating device that is adapted to heat the rods so as to preheat
and soften the rods before the rods are pushed by the pusher
device.
8. A molten material supply unit as in claim 6, further including a
squeezing member disposed at an inlet of the heating cylinder, the
squeezing member having a diameter slightly smaller than the
diameter of the rods.
9. A molten material supply unit as in claim 1, wherein the heating
cylinder has an inner wall that is covered with a protective layer
that does not chemically react with the melted material within the
heating cylinder.
10. A molten material supply unit as in claim 9, wherein the
protective layer is made of at least one material selected from the
group consisting of ceramic, ceramic-metal composite and chromium
oxide.
11. A molding apparatus for molding a material using a die,
comprising: a molten material supply unit having a heating cylinder
that is constructed and arranged to heat and melt the material in a
substantially vacuum condition; and a pressurizing and charging
unit that is adapted to receive the melted material from the molten
material supply unit and to discharge the melted material into the
die under pressure.
12. A molding apparatus as in claim 11, wherein the molten material
supply unit and the pressurizing and charging unit are further
arranged and constructed to discharge the melted material in a
substantially vacuum condition.
13. A molding apparatus as in claim 11, wherein the pressurizing
and charging unit comprises a charging cylinder and a piston that
is movable within the charging cylinder, the piston serving to
pressurize and inject the melted material from the charging
cylinder.
14. A molding apparatus as in claim 13, wherein the heating
cylinder has an inner wall that is covered with a protective layer
that does not chemically react with the melted material within the
charging cylinder.
15. A molding apparatus as in claim 14, wherein the protective
layer comprises one or more materials selected from the group
consisting of ceramic, ceramic-metal composite and chromium
oxide.
16. A molding apparatus as in claim 13, wherein the heating
cylinder communicates with the charging cylinder via an inlet
formed in the charging cylinder, the piston is movable between a
retracted position and an advanced position, which retracted and
advanced positions will respectively open and close the inlet.
17. A molding apparatus as in claim 11, further including a first
hot nozzle communicating with the charging cylinder, the melted
material being charged through the first hot nozzle.
18. A molding apparatus as in claim 17, wherein the first hot
nozzle includes a flow channel for discharging the melted material
and an inner wall of the flow channel is covered with an
electrical-insulation layer that does not chemically react with the
melted material.
19. A molten material supply unit as in claim 18, wherein the
electrical-insulation layer comprises a ceramic material.
20. A molding apparatus as in claim 17, further comprising the die,
wherein the die comprises a plurality of cavities, a runner block,
and a plurality of second hot nozzles, the runner block having a
plurality of branch channels, wherein melted material discharged
from the first hot nozzle is injected into the cavities through the
branch channels and the corresponding second hot nozzles.
21. A molding apparatus as in claim 20, wherein a plurality of
pressurizing and charging units are disposed in parallel with each
other and have respective first hot nozzles communicating with the
branch channels.
22. A molding apparatus for molding a material using a die,
comprising a molten material supply unit having a heating cylinder
that is constructed and arranged to heat and melt the material in a
substantially vacuum condition.
23. A molding apparatus as in claim 22, wherein the material is
supplied into the heating cylinder in the form of a plurality of
rods having a predetermined length.
24. A molding apparatus as in claim 23, wherein the rods are made
of metal.
25. A molding apparatus as in claim 23, further including a pusher
device for pushing the rods into the heating cylinder.
26. A molding apparatus as in claim 25, further including a
preheating device for preheating the rods to a predetermined
temperature prior to the pushing device pushing the rods.
27. A molding apparatus as in claim 26, further including a
squeezing member disposed at or around an inlet of the heating
cylinder, the squeezing member having an inner diameter that is
slightly smaller than the diameter of the rods.
28. A molding apparatus as in claim 22, wherein the heating
cylinder has an inner wall that is covered with a protective layer
that does not chemically react with the melted material disposed
within the heating cylinder.
29. A molding apparatus as in claim 28, wherein the protective
layer comprises one or more materials selected from the group
consisting of ceramic, ceramic-metal composite and chromium
oxide.
30. A molding apparatus as in claim 28, wherein the pushing device
comprises a piston arranged and constructed to contact a rear end
of each rod and to move each rod by a predetermined stroke in order
to push the rods into the heating cylinder, the predetermined
stroke being determined in response to the volume of a cavity
defined within the die.
31. A molding apparatus as in claim 30, further including a stacker
that stores a plurality of rods and supplies the rods one after
another to the pushing device, the pushing device being arranged
and constructed to sequentially push the rods into the heating
cylinder.
32. A molding apparatus as in claim 31, wherein the stacker
includes a heater arranged and constructed to preheat the rods
before the rods are supplied to the pusher device.
33. A method of melting a material, comprising: heating and melting
the material within a heating cylinder in a substantially vacuum
condition; and discharging the melted material from the heating
cylinder.
34. A method as in claim 33, wherein the heating cylinder receives
the material as a plurality of rods having a predetermined
length.
35. A method as in claim 33, further including preheating the rods
before the heating cylinder receives the rods.
36. A method of molding a material using a die, comprising: heating
and melting the material within a heating cylinder in a
substantially vacuum condition and further injecting the melted
material into the die in a substantially vacuum condition.
37. An apparatus adapted to melt a material selected from the group
consisting of a magnesium alloy and an aluminum alloy, comprising:
a heating cylinder having an inlet and outlet, the inlet being
adapted to receive the material to be melted; and a vacuum pump
communicating with the heating cylinder and being arranged and
constructed to generate a reduced pressure within the heating
cylinder.
38. An apparatus as in claim 37, further including a squeezing or
scraping member disposed at the inlet of the heating cylinder, the
squeezing or scraping member having an opening for receiving the
material, which is provided in the form of a rod, supplied into the
inlet, wherein a substantially airtight seal is created between the
squeezing or scraping member and the material rod.
39. An apparatus as in claim 38, wherein a channel is defined
within the squeezing or scraping member, the channel having a first
end that opens towards the opening at a position that is opposite
to the material rod to be supplied, and a second end that
communicates with the vacuum pump.
40. An apparatus as in claim 38, wherein the opening of the
squeezing or scraping member has a diameter slightly smaller than
the diameter of the material rod.
41. An apparatus as in claim 37, further comprising a die sealingly
coupled to the outlet of the heating cylinder.
42. An apparatus as in claim 41, further including a squeezing or
scraping member disposed at the inlet of the heating cylinder, the
squeezing or scraping member having an opening for receiving the
material, which is provided in the form of a rod, supplied into the
inlet, wherein a substantially airtight seal is created between the
squeezing or scraping member and the material rod.
43. An apparatus as in claim 42, wherein a channel is defined
within the squeezing or scraping member, the channel having a first
end that opens towards the opening at a position that is opposite
to the material rod to be supplied, and a second end that
communicates with the vacuum pump.
44. An apparatus as in claim 42, wherein the opening of the
squeezing or scraping member has a diameter slightly smaller than
the diameter of the metal rod.
45. A method comprising: heating a material into a softened state,
inserting the softened material through an inlet of a melting
chamber, wherein the softened material forms a substantially
airtight seal with the inlet, melting the softened material within
the melting chamber, reducing the pressure inside the melting
chamber and discharging the melted material from the melting
chamber substantially in the absence of air.
46. A method as in claim 45, further comprising: supplying the
melted material discharged from the melting chamber under pressure
to a die, the melted material being supplied to the die
substantially in the absence of air, and molding the melted
material within a cavity of the die substantially in the absence of
air.
47. A method as in claim 45, wherein the melting and pressure
reducing steps are performed substantially simultaneously.
48. A method as in claim 45, further comprising shearing the
softened material after inserting the softened material into the
melting chamber and before substantially melting the softened
material.
49. A method as in claim 45, further comprising cooling melted
material disposed within a discharge outlet of the melting chamber
when the melted material is not being discharged from the melting
chamber, wherein the melted material at least partially solidifies
and substantially seals the outlet.
50. A method as in claim 49, further comprising: shearing the
softened material after inserting the softened material into the
melting chamber and before substantially melting the softened
material, supplying the melted material discharged from the melting
chamber under pressure to a die, the melted material being supplied
to the die substantially in the absence of air, and molding the
melted material within a cavity of the die substantially in the
absence of air, and wherein the melting and pressure reducing steps
are performed substantially simultaneously.
51. An apparatus comprising: first means for heating a material
into a softened state, second means for melting the material into
substantially a liquid state, the second means comprising an inlet
adapted to receive the softened material, third means for inserting
the softened material through the inlet of the second means,
whereby the softened material forms a substantially airtight seal
with the inlet, fourth means for reducing the pressure inside the
second means and fifth means for discharging the melted material
from the second means substantially in the absence of air.
52. An apparatus as in claim 51, further comprising: means for
supplying the melted material discharged from the second means
under pressure to a die, the melted material being supplied to the
die substantially in the absence of air, and means for molding the
melted material within a cavity of the die substantially in the
absence of air.
53. An apparatus as in claim 51, wherein the second means and the
fourth means are arranged and constructed to operate substantially
simultaneously.
54. An apparatus as in claim 51, further comprising means for
shearing the softened material after inserting the softened
material into the second means and before substantially melting the
softened material.
55. An apparatus as in claim 51, further comprising means for
cooling melted material disposed within a discharge outlet of the
second means when the melted material is not being discharged from
the second means, wherein the melted material at least partially
solidifies and substantially seals the outlet of the second
means.
56. An apparatus as in claim 55, further comprising: means for
shearing the softened material after inserting the softened
material into the second means and before substantially melting the
softened material, means for supplying the melted material
discharged from the second means under pressure to a die, the
melted material being supplied to the die substantially in the
absence of air, and molding the melted material within a cavity of
the die substantially in the absence of air, and wherein the second
means and the fourth means are arranged and constructed to operate
substantially simultaneously.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to molten material supply
units, and may be, for example, advantageously utilized to melt
materials, such as metals and/or mixtures of metal and plastic,
that have relatively high melting points. The present invention
also relates to molding apparatus (e.g. molding dies) that include
such molten material supply units.
[0003] 2. Description of the Related Art
[0004] Die-cast molds (machines) are typically used in order to
mold metals into articles of manufacture. Molten metals, such as
molten aluminum alloys and magnesium alloys, are usually melted in
a blast furnace and then transferred to the die while being exposed
to air. Thereafter, the molten metals are injected under pressure
into the die. Generally speaking, die-cast molds utilize a
piston-cylinder mechanism to pressurize the molten metals, so that
the molten metals can be injected into the die under pressure. The
injected molten metal is then cooled and solidified within the die,
thereby forming a metal molded product.
[0005] However, a blast furnace is usually expensive and requires a
costly installation. Further, heated gases generated when the metal
is melted within the blast furnace and exposed to air may create
environmental pollution. Therefore, there is a long-felt need for
apparatus and methods that can inexpensively melt materials,
including but not limited to metals and metal-plastic mixtures, and
preferably minimize environmental pollution.
SUMMARY OF THE INVENTION
[0006] It is, accordingly, an object of the present invention to
teach improved molten material supply units and molding apparatus
having such supply units.
[0007] In one aspect of the present teachings, the molten material
supply units may be utilized to melt solid or semi-solid materials
without using a blast furnace and may preferably reduce (or
substantially eliminate) pollutant gases that are discharged into
the surrounding environment. Herein, the terms "semi-solid,"
"semi-melted" and "softened" are intended to mean a state in which
the material (e.g. a metal, a metal-plastic mixture or a non-metal
organic composition) simultaneously exists in both solid and liquid
phases, or a state in which dendrite (solid particles) is dispersed
or suspended within a liquid material. Thus, a semi-solid material
may be substantially solid, but may be moldable or flexible. In one
aspect of the present teachings, the material may not be normally
moldable or flexible in its purely solid state, but becomes
moldable or flexible in the semi-solid state. Thus, in this aspect
of the present teachings, any material that can transition to or
assume a softened state may be advantageously melted and processed
according to the present teachings.
[0008] According to another aspect of the present teachings, molten
material supply units are taught that can reduce pollutant gases
that are typically generated when the material is melted in the
presence of air. Thus, in one embodiment of the present teachings,
molten material supply units may optionally include a vacuum
heating device. For example, a heating structure may communicate
with a vacuum device, such as a vacuum pump. In this aspect of the
present teachings, the heating structure may have any appropriate
design or configuration, as long as the heating structure is
substantially airtight, other than an inlet and an outlet of the
heating structure. For example, melting chambers, heating
structures and heating cylinders arc described further below in
representative embodiments of the present teachings. One
appropriate class of heaters may, e.g., generate heat by supplying
an electric current through an electrically resistive material.
However, other types of heaters are naturally contemplated
including heaters that generate heat by combusting a fuel source.
Thus, in this aspect of the present teachings, the materials
preferably can melt within the heating structure from a solid state
or a semi-solid state into a molten state (e.g., a purely liquid
state) substantially in the absence of air.
[0009] In another aspect of the present teachings, the materials
may be supplied into the heating structure one after another (e.g.
sequentially) in forms of rods or another convenient configuration,
which configuration is not particularly limited in this aspect of
the present teachings. In one embodiment of the present teachings,
the outer dimension of the material (e.g., a cylinder-shaped rod)
preferably substantially corresponds to an inner dimension of the
inlet to the heating structure. More preferably, the inner
dimension of the inlet is slightly smaller than the outer dimension
of the softened material. Thus, in this aspect, the material is
preferably in a softened or semi-solid state when it is inserted
through an inlet of the heating structure. For example, in another
embodiment, the softened material may be forcibly introduced
through the inlet of the heating structure. In such case, an
airtight seal preferably will be formed at the inlet between the
inner wall of the heating structure and the softened material.
[0010] In another aspect of the present teachings, the materials
may be supplied in the form of a softened cylindrical rod and the
inlet may be a device that squeezes the material as the softened
metal rod is forced through the inlet, thereby ensuring an air
tight seal. The squeezing device may be a ring or any other
appropriate structure than has an inner perimeter or diameter
slightly less than the perimeter or diameter of the rods. The
squeezing device is preferably disposed substantially at or around
the inlet of the heating structure. In this embodiment of the
present teachings, substantially no air preferably contacts the
molten materials within the heating cylinder.
[0011] In another aspect of the present teachings, a device may be
provided to preheat the material that will be melted (e.g., in the
shape of cylinder-shaped rods) before the material is fed into a
melting chamber, which may be, e.g., a vacuum heating device.
Preferably, the preheating device brings the solid material to a
softened or semi-solid state. Thus, the melting process within the
melting chamber can be easily and rapidly performed. In addition,
the preheated (softened) material may be easily squeezed when being
forcibly inserted into the melting chamber.
[0012] In another aspect of the present teachings, molding
apparatus are taught that can mold the materials while generally
reducing or preventing the generation of pollutant gases. The
molding apparatus may include a pressurizing and charging unit that
may receive the molten materials from the molten material supply
unit and may serve to charge the molten materials into a die under
pressure. Similar to the molten material supply unit, the
pressurizing and charging unit may serve to charge the molten
materials into the die in a substantially vacuum condition.
[0013] In a further aspect of the present teachings, methods of
supplying materials are taught that enable the materials to be
molded while generally reducing or preventing the generation of
pollutant gases. Representative methods may include heating the
materials within a heating structure in a substantially vacuum
condition and pushing the materials out from the heating structure.
The precise pressure state utilized for the substantially vacuum
condition of the present teachings will naturally be determined in
accordance with the particular material that will be melted and
processed. However, preferably the pressure within the heating
structure is less than about 100 mm Hg, more preferably less than
about 50 mm Hg and most preferably, less than about 10 mm Hg.
Herein, the terms "melting chamber," "heating structure" and
"heating cylinder" may generally encompass the same or similar
structures.
[0014] In a further aspect of the present teachings, methods for
molding materials using a die are taught and may include charging
the molten (e.g. substantially or purely liquid) materials into the
die through a pressurizing and charging cylinder also in a
substantially vacuum condition. The above-noted steps may naturally
be combined with these steps to provide additional embodiments of
the present teachings.
[0015] Other objects, features and advantage of the present
invention will be readily understood after reading the following
detailed description together with the accompanying drawings and
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 shows a vertical cross-sectional view of a material
supply unit of a first representative metal molding apparatus;
[0017] FIG. 2 shows a vertical cross-sectional view of a material
charging unit and a part of a die of the first representative metal
molding apparatus;
[0018] FIG. 3 is an explanatory cross-sectional view showing a
representative operation of a pushing cylinder of a representative
preheating unit, in which one metal rod drops into two open
cylinder halves of the pushing cylinder;
[0019] FIG. 4 is a front view of a screen disk that may be disposed
within a representative heating cylinder;
[0020] FIG. 5 is a cross-sectional view of the representative
heating cylinder and shows a representative operation for charging
a semi-melted metal rod into the heating cylinder;
[0021] FIG. 6 is an enlarged cross-sectional view of a part of the
material charging unit and shows the melted material being supplied
into a charging cylinder;
[0022] FIG. 7 is an enlarged cross-sectional view similar to FIG.
6, in which a piston has pushed the molten material toward the end
of the charging cylinder;
[0023] FIG. 8 is an enlarged cross-sectional view similar to FIG.
6, in which the piston has moved to its furthest rightward position
in order to charge the molten material into a cavity of the
die;
[0024] FIG. 9 is a cross-sectional view of a second representative
material supply unit;
[0025] FIG. 10 is a cross-sectional view of a part of a charging
unit and a die of a second representative molding apparatus;
[0026] FIG. 11 is a cross-sectional view of parts of a pair of
charging units and a die of a third representative molding
apparatus; and
[0027] FIG. 12 shows a vertical cross-sectional view of a material
supply unit of a further metal molding apparatus according to the
present teachings.
DETAILED DESCRIPTION OF THE INVENTION
[0028] In one aspect of the present teachings, a vacuum-generating
device (e.g., any appropriate device that can generate a reduced
pressure) is preferably in communication with the interior of the
heating structure. Therefore, during the melting operation, a
substantial vacuum condition can be created within heating
structure. Preferably, the vacuum-generating device (e.g., vacuum
pump) may be coupled to the heating structure (e.g. a heating
cylinder) at a position that is substantially adjacent to the inlet
of the heating structure.
[0029] In other representative embodiment of the present teachings,
the heating structure may have a substantially cylindrical shape
(i.e., a heating cylinder) and the materials may be supplied into
the heating cylinder in forms of rods that have a predetermined
length. The rods may be sequentially pushed into the heating
cylinder and the rods will melt as they move along the length of
the heating cylinder.
[0030] A squeezing device or member, such as a ring, may be
disposed at the inlet of the heating cylinder. The ring may have an
inner diameter that is slightly smaller than the diameter of the
rods, so that an airtight seal (or at least a substantially
airtight seal) will be formed between the ring and the outer
surface of the rod when each rod enters the heating cylinder. For
example, the rods may be in a softened or semi-solid state and may
be forcibly inserted through the inlet and the squeezing device
(e.g. a ring). Therefore, the interior of the heating cylinder can
be reliably maintained in a substantially vacuum condition, because
an airtight seal is formed between the inlet and the inserted
material. In another embodiment of the present teachings, a
preheating device may heat the rods to a predetermined temperature,
which may be a temperature at which the rods become soft.
Therefore, the means for squeezing the softened material (e.g. a
ring) can effectively maintain an airtight seal between the inlet
of the heating structure and the softened material.
[0031] In another aspect of the present teachings, a protective
layer may cover the inner wall of the heating cylinder and the
protective layer preferably does not chemically react with the
molten materials disposed within the heating cylinder. If for
example the molten materials comprise one or more metals, the
protective layer may preferably comprise a ceramic material,
ceramic-metal composite and/or chromium oxide. In such case, the
protective layer will prevent the molten materials from reacting
with the heating cylinder, if it is e.g., formed from a metal, such
as iron or steel. As a result, metal by-products (side-products)
are not generated, which by-products could stain the molten
materials and any resulting molded product.
[0032] In another aspect of the present teachings, molding
apparatus for molding materials using a die are also taught that
may include a pressurizing and charging unit in addition to the
molten material supply unit. The pressurizing and charging unit may
be arranged and constructed to receive the molten materials from
the molten material supply unit and to charge the molten materials
into the die under pressure.
[0033] In another embodiment of the present teachings, the
pressurizing and charging unit may include a charging cylinder and
a piston. The charging cylinder may define a space that
communicates with the interior of the heating cylinder, so that the
space within the charging cylinder also may be brought into a
substantially vacuum condition. Therefore, the die can produce
molded products while minimizing or eliminating pollutant and/or
harmful gases. Naturally, the inner wall of the charging cylinder
also may be covered with a protective layer that does not
chemically react with the molten materials.
[0034] In another embodiment of the present teachings, the heating
cylinder may communicate with the charging cylinder via an inlet
formed in the charging cylinder. In this case, the piston can move
between a retracted position and an advanced position, by which the
inlet is respectively opened and closed by the piston.
[0035] In a preferred representative embodiment, a hot nozzle may
be connected to the charging cylinder, so that the molten materials
are charged through a flow channel formed in the hot nozzle. The
temperature of the hot nozzle may be appropriately controlled in
response to the molding cycle. In particular, the temperature of
the hot nozzle may be controlled such that the molten materials
only flow out of the charging cylinder during an operation for
discharging the molten material from the charging cylinder.
Therefore, the molding process can be effectively performed
Preferably, the flow channel of the hot nozzle may be covered with
an electrical-insulation layer, which layer may be formed of a
ceramic material that does not chemically react with the molten
materials.
[0036] In another embodiment of the present teachings, the die may
include a plurality of cavities, a runner block, and a plurality of
second hot nozzles. The runner block may have a plurality of branch
channels, so that the molten materials discharged from the first
hot nozzle are charged into the cavities through the branch
channels and the corresponding second hot nozzles. Therefore, a
plurality of products can be molded at one time. described in
detail with reference to the attached drawings. This detailed
description is merely intended to teach a person of skill in the
art further details for practicing preferred aspects of the present
teachings and is not intended to limit the scope of the invention.
Only the claims define the scope of the claimed invention.
Therefore, combinations of features and steps disclosed in the
following detail description may not be necessary to practice the
invention in the broadest sense, and are instead taught merely to
particularly describe a representative example of the invention.
Moreover, various features of the representative example and the
dependent claims may be combined in ways that are not specifically
enumerated in order to provide additional useful embodiments of the
present teachings.
[0037] A first representative metal molding apparatus is generally
shown in FIGS. 1-8. The first representative metal molding
apparatus may include, for example, a molten metal supply unit 1,
as shown in FIG. 1, and a pressurizing and charging unit 2, as
shown in FIG. 2.
[0038] Referring to FIG. 1, the molten metal supply unit 1 may
include a preheating section 3 and a vacuum heating section 4.
Preferably, the preheating section 3 may include a material stacker
5 and a hydraulic cylinder device 6. A space may be defined within
the material stacker 5 to receive cylindrical metal rods R in a
vertically stacked row. For example, the metal rods R may be cut
from a single long rod to have a predetermined (e.g., constant or
uniform) length. Preferably, the length of the metal rods R is
determined such that the volume of each metal rod R is
substantially equal to the volume of a cavity C of a die M, as will
be further explained below. The hydraulic cylinder device 6 may be
utilized to push the metal rods R into the vacuum heating section 3
one after another.
[0039] In one representative embodiment, the metal rods R may
comprise an aluminum alloy and/or a magnesium alloy, which alloy
can be suitably molded with the die M shown in FIG. 2, although
naturally other metal alloys (as well as metal-plastic mixtures and
non-metal materials) are contemplated by the present teachings. In
one preferable, but not limiting example, the aluminum alloy may be
ADC 12 (Al--Si--Cu family, JIS H 5302) containing about 11% of Si
and about 2.5% of Cu, although naturally a variety of other
aluminum alloys may be used with the present teachings. In another
preferable, but not limiting example, the magnesium alloy may be
MD1D (AZ-91 family) containing 8.3 to 9.7% of Al, 0.35 to 1.0% of
Zn, greater than 0.15% of Mn, less than 0.10 of Si and small
amounts of Cu, Ni and Fe, although again a variety of other
magnesium alloys may be used with the present teachings. The
hydraulic cylinder device 6 may include a supply cylinder 7 that
serves to receive the cylindrical metal rods R that may be gravity
fed one by one from the stacker 5 into the supply cylinder 7. The
hydraulic cylinder device 6 also may include a pushing piston 8
that serves to push the metal rods R into the vacuum heating
section 4.
[0040] One or more heaters 9 may be mounted on the outside of the
stacker 5 and may serve to preheat the metal rods R to an
appropriate temperature, which may be e.g., a temperature that will
bring the metal rod R into a softened state. For example, the metal
rods R may be heated to a softened state before the metal rods R
are supplied to the vacuum heating section 4. Although not shown in
the drawings, an upper inlet opening may be defined within the
stacker 5 and the metal rods R may be inserted through the upper
inlet opening in order to be received within the stacker 5. The
capacity of the stacker 5 or the number of metal rods R that can be
received within the stacker 5 is not particularly limited and may
be suitably determined, e.g., with consideration to the capacity of
the pressurizing and charging unit 2. Preferably, a stop 10 may be
disposed at the bottom of the stacker 5. An actuator (not shown)
may be utilized to horizontally move (i.e. substantially
perpendicular to the longitudinal axis of stacker 5) the stop 10,
thereby extending the stop 10 into the stacker 5 and withdrawing
the stop 5 from the stacker 5. Thus, the stop 10 can be utilized to
selectively load or insert the metal rods R into the supply
cylinder 7.
[0041] A cross-sectional view of a representative, but not
limiting, supply cylinder 7 is shown in FIG. 3. This supply
cylinder 7 may be positioned directly below the stacker 5 and may
include, e.g., a pair of cylinder halves 7A. A hinge (not shown)
may pivotably attach the bottom edges of the cylinder halves 7A and
the actuator (not shown) may open and close the cylinder halves.
Thus, the cylinder halves 7A may open to receive the metal rods R
when the metal rods R are inserted or dropped by withdrawing the
stop 10 from the stacker 5. The cylinder halves 7A may then close
to allow the pushing piston 8 to push the metal rod R towards the
vacuum heating section 4. Preferably, the actuator of the cylinder
halves 7A and the actuator of the stop 10 may function together
with the hydraulic cylinder device 6, so that the metal rods R are
sequentially placed into the supply cylinder 7 and then pushed by
the pushing piston 8.
[0042] The representative vacuum heating section 4 will now be
described in further detail with reference to FIGS. 1 and 5. The
vacuum heating section 4 may include a heating cylinder 11 that
serves to receive the preheated metal rods R from the supply
cylinder 7. In addition, the heating cylinder 11 preferably
furthers heats the metal rods R. As a result, the metal rods R may
be heated to a higher temperature, thereby completely melting the
softened metal rods R into molten metal. Thereafter, the molten
metal is supplied to the die M (shown in FIG. 2) for molding. In
order to further heat the metal rods R, heaters 12 may be attached
to the outer side of the heating cylinder 11.
[0043] In another preferable, but optional, embodiment, a
protective tube 13 may be inserted into the heating cylinder 11, so
that the heating cylinder 11 does not directly contact the molten
materials. Preferably, the protective tube 13 may comprise one or
more materials that are heat-resistant and that do not chemically
react with the molten materials, while providing suitable
mechanical strength and a small coefficient of thermal expansion.
In one preferable, but not limiting example, ceramics and
ceramic-metal composites may be utilized in the protective tube 13.
For example, suitable ceramics include Si.sub.3N.sub.4 and
Sialon.TM. (HCN-10), which is distributed by Hitachi Metals, Ltd.
of Tokyo, Japan. Further, suitable ceramic-metal composites include
HFA50, which is also distributed by Hitachi Metals, Ltd.
[0044] Although external heaters 12 are illustrated in the first
representative embodiment, the particular type of heater that may
be used as heaters 12 is not particular limited. For example,
internal heaters may be embedded within the heating cylinder 11. In
addition, the length of the heating cylinder 11 may be suitably
determined by considering the heating capability of the heaters 12
and the melting point of the material that will be melted.
[0045] Still referring to FIGS. 1 and 5, an inlet ring 14 may be
positioned at the rear end of the heating cylinder 11, so that the
ring 14 opposes the front end of the supply cylinder 7 of the
preheating section 3. Preferably, the ring 14 may have a relatively
high melting point and high mechanical strength, so that the ring
14 can squeeze or to scrape the outer surface of the semi-melted
metal rods R. For example, ultra-hard alloys may be utilized to
form ring 14. Further, the inner diameter of ring 14 is preferably
slightly smaller than the outer diameter of the metal rods R. For
example, if the rods R have a diameter of 50 mm, the ring 14 may
have an inner diameter of about 49.5 to 49.8 mm.
[0046] The inner diameter of the ring 14 may be uniform along the
axial (longitudinal) direction of the vacuum heating section 4 or
may gradually decrease along the axial (longitudinal) direction. In
addition, an annular recess 15 may be formed within the inner
peripheral surface of the ring 14 and may communicate with a vacuum
pump 17 via a communication port 16. Thus, in a preferred aspect of
the present teachings, the inner space of the heating cylinder 11
may be brought into a substantially vacuum condition when the metal
rods R are completely melted, as will be further explained
below.
[0047] In addition, a screen disk 18 may be mounted within the
heating cylinder 11 at a position displaced from the ring 14 by a
predetermined distance. For example, the distance between the
screen disk 18 and the ring may be less than the length of the
metal rods R. A representative screen disk 18 is shown in FIG. 4 in
greater detail and may have, for example, a plurality of through
holes 18a.
[0048] Referring back to FIGS. 1 and 5, projections 8A may be
formed on the front end surface of the pushing piston 8 of the
hydraulic cylinder device 6 and may serve to engage the rear end of
the metal rods R. Although not shown in the drawings, a drive
device for rotating the pushing piston 8 about the longitudinal
axis of the pushing piston 8 may optionally be provided In that
case, the metal rods R will rotate with the pushing piston 8 by
engaging by the projections 8A.
[0049] The first representative pressuring and charging unit 2 will
now be described with reference to FIG. 2. The pressuring and
charging unit 2 may be constructed as a die-cast machine and may
include a hydraulic cylinder device 19. The hydraulic cylinder
device 19 may include a piston member 20A that is connected to a
front end of a piston rod 20. The pressurizing and charging unit 2
also may include a charging cylinder 21 that can slidably and
movably receive the piston member 20A. A hot nozzle 22 may be
attached to a front portion 21a of the charging cylinder 21.
[0050] Similar to the heating cylinder 11 of the vacuum heating
section 4, a protective tube 23 may be inserted into the charging
cylinder 21. The protective tube 23 may be made of the same
material as the protective tube 13, although naturally other
materials may be utilized. A material charging port 24 may be
defined within a side wall of the charging cylinder 21, for
example, at a position that is slightly rearward of the middle of
the charging cylinder 21 along its longitudinal axis. The charging
port 24 preferably communicates with the heating cylinder 11 of the
vacuum-heating unit 4, so that the molten materials may be supplied
into the charging cylinder 21.
[0051] The inner wall of front portion 21a of the charging cylinder
21 preferably becomes narrower toward the front end of the front
portion 21a. Further, the front portion 21a preferably communicates
with a flow channel 25 defined within the hot nozzle 22.
Preferably, heaters 26 may be attached to the outer periphery of
the charging cylinder 21, so that the temperature of the molten
materials supplied into the cylinder 21 can be suitably
maintained.
[0052] A front end 20B of the piston member 20A may have a
substantially conical configuration so as to substantially conform
to the configuration of the inner space of the front portion 21a of
the charging cylinder 21. Piston rings 28 may be fitted around the
outer periphery of the piston member 20A and may be spaced from
each other by an appropriate distance in order to provide a
suitable seal between the piston member 20A and the charging
cylinder 11. The piston ring 28 may be, for example, made of a
material that is the same or similar to the material utilized to
form the protective tube 13 or 23, although the piston rings 28 may
naturally be constructed from a variety of materials. Moreover, the
number of piston rings 28 is not particular limited, and other
sealing means may be utilized instead of piston rings 28.
[0053] A bracket 31 and bolts 30 may be, for example, utilized to
fix the hot nozzle 22 to the front portion 21a of the charging
cylinder 21, although other fixing means may be utilized. A front
end of the flow channel 25 of the hot nozzle 22 (right side as
shown in FIG. 2) may directly open into the cavity C of the die M
and the inner diameter may decrease towards the cavity C. A variety
of known dies M may be utilized with the present teachings and the
construction of the die M is not particularly limited. In the first
representative embodiment, a die M is shown that includes a movable
die part M1 and a fixed die part M2. A cavity C is defined between
the movable die part M1 and the fixed die part M2.
[0054] The hot nozzle 22 may preferably be constructed according to
the teachings of U.S. Pat. No. 4,648,833, the teachings of which
are hereby incorporated by reference herein in their entirety.
Therefore, the construction of the hot nozzle 22 will be briefly
described herein and the reader is referred to U.S. Pat. No.
4,648,833 for further teachings, if necessary. The construction of
the hot nozzle 22 is not particularly limited and may be made of
metal, such as iron, that is electrically conductive but has an
appropriate electrical resistance.
[0055] For example, the hot nozzle 22 may have a pair of slots 34
(only one slot 34 is shown in FIG. 2) that extend from a base
portion 33 toward a front end portion 32 by a predetermined
distance along the longitudinal direction of the hot nozzle 22.
Thus, the slots 34 preferably do not extend past the front end
portion 32. AC or DC power may be applied across two parts of the
base portion 33 that are separated by the slots 34. As a result,
the hot nozzle 22 will internally heat primarily at the front end
portion 32.
[0056] Although not shown in the drawings, an insulation layer may
cover the outer surface of the hot nozzle 22 and the inner surface
of the flow channel 25 and the insulation layer preferably may be
made of one or more ceramic materials. Ceramic is particularly
preferable as the material of the inner layer, because this
material may also serve to protect the inner wall of the hot nozzle
22 against the molten metals, which was described above in
connection with the protective tube 13 of the heating cylinder 11.
By using this arrangement, the temperature of the hot nozzle 22,
and in particular the temperature at the front end portion 32, can
be reliably and quickly controlled in response to a molding
cycle.
[0057] A representative molding process will now be described with
reference to the above representative embodiment.
[0058] (1) First, the metal rods R are sequentially charged into
the stacker 5 of the preheating section 3 and the heaters 9 heat
the metal rods R to a predetermined temperature, which is
preferably about 300.degree. C. for ADC12 (aluminum alloy) and MD1D
(magnesium alloy). Therefore, the metal rods R are softened within
the stacker 5.
[0059] (2) The cylinder halves 7A of the cylinder 7 then open as
shown in FIG. 3. The stop 10 moves from a support position, which
is directly below the stack of the metal rods R as indicated by
solid lines in FIG. 3, to a release position, which is shown in
dotted lines in FIG. 3. As a result, the lowermost metal rod R will
drop or fall into the open cylinder halves 7A due to gravity. As
soon as the lowermost metal rod R (hereinafter also called the
"first metal rod R") is released from the stacker 5, the stop 10
returns to the support position so as to prevent the next lowermost
metal rod R from dropping into the open cylinder halves 7A. At this
time, the cylinder halves 7A preferably close.
[0060] (3) The pushing piston 8 of the hydraulic cylinder device 6
moves forward (rightward as shown in FIGS. 1 and 5) in order to
push the first metal rod R though the ring 14, which is positioned
on the rear side of the heating cylinder 11, by a predetermined
distance. Therefore, the front end of the first metal rod R is
positioned rearward (leftward as shown in FIGS. 1 and 5) of the
annular recess 15 of the ring 14 by a small distance. Because the
inner diameter of the ring 14 is slightly smaller than the diameter
of the metal rods R, the first metal rod R will be squeezed by the
edge of the rear opening of the ring 14. As a result, an air-tight
seal is formed between the inner surface of the ring 14 and the
outer surface of a part of the first metal rod R that has been
moved into the ring 14. Thus, no gaps exist between the ring 14 and
the first metal rod R, which gaps could permit air to be introduced
into the heating cylinder 11. Consequently, the inner space of the
heating cylinder 11 will be substantially sealed from the outside
environment by forcing the first metal rod R through ring 14, which
has a slightly smaller diameter that metal rod R.
[0061] (4) When the metal rod R is disposed within the heating
cylinder 11, the vacuum pump 17 is preferably driven so as to
create a substantially vacuum condition (preferably less than about
10 mm Hg in this representative embodiment) within the heating
cylinder 11. At the same time, as shown in FIG. 2, the front end
20B of the piston member 20A of the hydraulic cylinder device 19 is
positioned so as not to close the port 24 of the charging cylinder
21 that communicates with the interior of the heating cylinder 11.
Therefore, a space F is defined within the charging cylinder 21 and
space F communicates with the heating cylinder 11. Space F may
further communicate with the cavity C of the die M via the flow
channel 25 of the hot nozzle 22. As a result, a substantially
vacuum condition also may be created within space F, the flow
channel 25 and the cavity C when the vacuum pump 17 is
operated.
[0062] (5) Then, the pushing piston 8 moves further towards the
ring 14 and also rotates about its longitudinal axis. Because the
projections 8A are formed at the front end of the piston 8, the
projections 8A may preferably engage the rear end of the first
metal rod R, because it is in a softened state. Therefore, the
rotational movement of the pushing piston 8 can be effectively
transmitted to the first metal rod R. The rotation and the forward
movement of the pushing piston 8 may be stopped when the rear end
of the first metal rod R reaches a position immediately before the
ring 14. Thereafter, the piston 8 may return to the original
(resting) position, which is shown in FIG. 1.
[0063] (6) The next metal rod R may then be supplied from the
stacker 5 into the cylinder 7 in the same manner as described in
the above-described Step (2). Thereafter, the next metal rod R may
be pushed into the heating cylinder 11 through the ring 14 by means
of the pushing piston 8 until the rear end of the metal rod R
reaches the position immediately before the ring 14. Therefore, the
first metal rod R may be pushed further into the heating cylinder
11 by the next metal rod R. The same operation may be repeatedly
performed for the remaining metal rods R in the stacker 5.
[0064] As noted above, the screen disk 18 is positioned on the
downstream side of the ring 14. Therefore, when the softened metal
rods R are pushed into the heating cylinder 11, the screen disk 18
causes the softened metal rods R is split into a plurality of
strands by passing through the holes 18a In addition, because the
softened metal rods R are rotated while passing through the screen
disk 18, the strands of the softened metal rods R become sheared
and chopped up into short strands. As a result, the flowability
(thixotoropy) of the molten material and the following molding
process using the pressurizing and charging unit 2 can be improved.
In particular, the productivity of the dies and the size tolerances
of the molded products may be improved.
[0065] Because the pushing piston 8 does not move beyond the ring
14 that is positioned rearward of the screen disk 18, the metal
rods R cannot be completely sheared and chopped up by one stroke of
the pushing piston 8. However, each metal rod R is pushed forwardly
(leftward in FIGS. 1 and 5) by the next metal rod R and may rotate
together with the next metal rod R, due to frictional force and
heat of these rods R. Therefore, the screen disk 18 will also shear
and chop up the remaining portion of the metal rods R into short
strands.
[0066] Thus, the metal rods R are supplied into the heating
cylinder 11 one after another and may be sequentially brought from
a semi-solid state into a completely melted state by the heating
operation of the heaters 12. For example, ADC12 (aluminum alloy)
and MD1D (magnesium alloy) may be completely melted at about 580 to
600.degree. C.
[0067] (7) After the heating cylinder 11 has become filled with
molten material, the pushing operation by the pushing piston 8 may
be temporarily stopped. At this stage, the rear portion of the last
metal rod R is positioned rearwardly adjacent to the front end of
the ring 14.
[0068] (8) The piston 8 may then move forward and rotate again to
push the last metal rod R by a distance that preferably corresponds
to a volume V, which may be, for example, a sum of the volume of
the cavity C and the volume of the flow channel 25 of the hot
nozzle 22. In this representative embodiment, the volume of each of
the metal rods R is preferably selected to be equal to the volume
of the cavity C and may be less than the volume V. Therefore, an
additional metal rod R may be supplied to push the last metal rod
R, as shown in FIG. 5. As a result, molten metal having a mass Rm
may be charged into the space F defined within the charging
cylinder 21 of the pressurizing and charging unit 2, as shown in
FIG. 6.
[0069] (9) Subsequently, the hydraulic cylinder device 19 may be
driven, so that the piston rod 20 moves forwardly (rightward as
shown in FIG. 2). Because space F is in a substantially vacuum
condition, the movement of the piston rod 20 will cause the mass Rm
of molten metal to fill up space F without the inclusion of air, as
shown in FIG. 7. When the piston rod 20 reaches the forward stroke
end, the molten material may be charged into the flow channel 25 of
the hot nozzle 22 and further into the cavity C of the die M. Thus,
the cavity C may become completely filled, as shown in FIG. 8.
[0070] (10) The die M is then cooled to solidify the molten
material within the die M. Thereafter, the movable die half M1 may
be separated from the fixed die half M2, so that the solidified
material can be taken out of the die M as a molded product.
Further, while the die M is cooling, the hot nozzle 22, and in
particular the front end portion 32, may be maintained at an
appropriate temperature so as to keep the material within the die M
in a semi-solid state. Therefore, the molded product can be easily
removed from the die M. In addition, the temperature of the nozzle
22 can be adjusted so that the material only flows out of the
nozzle 22 during a die charging operation. For example, the nozzle
22 may be maintained at a relatively high temperature during the
die charging operation and a relatively low temperature at other
times. Therefore, at times other than a die charging operation, the
material within the nozzle 22 may re-solidify and thereby provide
an airtight seal within the flow channel 25.
[0071] (11) After the molded product has been removed from the die
M, the movable mold half M1 may return to the original position so
as to close the die M. Then, the piston rod 20 or the piston body
20A of the hydraulic cylinder device 18 may also return to the
original position, which is shown in FIG. 6. Because a portion of
the mass Rm of the now solid or semi-solid material still remains
in the hot nozzle 22, the space F within the cylinder 21 returns to
the substantially vacuum condition after the piston rod 20 has
returned to the original position.
[0072] (12) The stacker 5 may then supply the metal rods R for a
next molded product into the supply cylinder 7 and the piston 8 may
move by one stroke that corresponds to the length of the metal rod
R. Again, the stroke length of the piston 8 preferably displaces a
volume that is substantially equal to the volume of the cavity C of
the die M. As a result, molten material having a volume that
corresponds to the volume of the cavity C can be charged into the
cylinder 21.
[0073] (13) Either before or after Step (12), power may be supplied
to the hot nozzle 22, so that the hot nozzle 22 is heated to
completely melt the semi-solid material within the flow channel 25.
That is, as noted above, the temperature of hot nozzle 22 can be
reduced when hot nozzle 22 is not charging melted material into die
M. Therefore, space F can be maintained in a substantially airtight
condition, due to solidification (partial or complete) of the
molten material disposed within hot nozzle 22.
[0074] (14) The piston member 20A of the hydraulic cylinder unit 19
may then move forwardly to charge the molten material into the
cavity C. This operation may be performed in the same manner as
explained in connection with the first molded product and with
reference to FIGS. 6 to 8, except that the material is already
charged into the flow channel 25 of the hot nozzle 22. Thereafter,
the die M is cooled and the molded product is taken out of the die
M in the same manner as in the above-described Step (10).
[0075] (15) Naturally, steps (11) to (15) may be repeatedly
performed so as to mold additional products.
[0076] In this representative embodiment, the molten metal supply
unit 1 includes the vacuum pump 17, which communicates with heating
cylinder 11 and serves to reduce the pressure within the heating
cylinder 11. Therefore, the semi-melted metal rods R can be heated
substantially in the absence of air or oxygen. As a result, it is
not necessary to use a special blast furnace with the present
teachings. In addition, little or no heated gas vapor may be
produced during the melting step. Further, the vacuum pump 17 may
draw out any vapors that may be produced and these vapors can then
be properly handled in order to limit or avoid environmental
pollution. Furthermore, because the heating process within the
cylinder 11 can be performed in a substantially vacuum condition,
little or no air will be included within the molten materials. As a
result, the molten metal supply unit 1 can be advantageously used
as a material supply unit for the pressuring and charging unit 2
that is used with the die M for molding products.
[0077] More specifically, when the piston member 20A returns from
the most advanced position to the most retracted position, a
reduced pressure or a vacuum may be created within the space F.
Because the vacuum pump 17 is connected to the heating cylinder 11,
the reduced pressure within the space F will balance or equalize
with the reduced pressure generated by the vacuum pump 17. As a
result, the molten materials within the heating cylinder 11
generally do not flow into the space F. Therefore, after the piston
member 20A moves to the most retracted position, the molten
materials may be supplied into the space F by the molten metal
supply unit 1 in an amount that precisely conforms to the volume of
cavity C (i.e., an amount that is required to mold one product
within the die M). The molten materials may then be charged into
the cavity C of the die M through the hot nozzle 22 by an amount
that is substantially equal to the amount that has been supplied
from the molten metal supply unit 1 into the charging cylinder
21.
[0078] Because the space F is maintained in a substantially vacuum
condition, the material within the heating cylinder 11 generally
does not receive any pressure that would push the material back
into the heating cylinder 11, even when the piston member 20A
retracts. Thus, the materials can be reliably supplied from the
heating cylinder 11 in a fixed (i.e. constant) amount without being
influenced by the retracting movement of the piston member 20A.
Therefore, the molding process can be smoothly and reliably
performed. In addition, a valve or valve means is not required at
the outlet of the heating cylinder 11 in order to interrupt the
communication between the space F and the interior of the heating
cylinder 11 during the movement of the piston member 20A.
[0079] Further, because the space F, as well as the interior of the
cylinder 11, can be maintained in a substantially vacuum condition,
the molten materials can be charged into the die M without
including any air in the molten materials. Therefore, the quality
and the yield of the molded products may be improved. Further, this
aspect of the present teachings makes the present representative
method particularly advantageous, even for materials that are not
required to be melted under reduced pressure conditions in order to
minimize pollutant gases. Therefore, this aspect of the present
teachings can be effectively utilized with a wide variety of
materials that will be melted from a solid state and discharged to
another tool or machine for further manipulation of the liquid
material.
[0080] In particular, because the vacuum pump 17 is connected to
the ring 14 at the inlet of the heating cylinder 11, the outer
periphery of the metal rod R may be absorbed toward the inner
periphery of the ring 14 due to the reduced pressure. As a result,
the reduced pressure also may serve to hold the metal rods R within
the ring 14 and to hold the upstream side of the melting metal rods
R within the heating cylinder 11.
[0081] In addition, the metal rods R may be sequentially pushed
into the heating cylinder 11 by the hydraulic cylinder device 6 and
the volume of the metal rod R may be determined to be equal to the
volume of the cavity C of the die M. Therefore, the molten
materials may be supplied into the cylinder 21 of the pressuring
and charging unit 2 by an amount that is necessary for one product
while the metal rod R is pushed into the heating cylinder 11 by a
distance corresponding to the length of the metal rods. Therefore,
the amount of the molten material supplied into the charging
cylinder 21 can be easily controlled.
[0082] Further, because the metal rods R may be preheated by the
preheating unit 3 before they are supplied into the heating
cylinder 11, the metal rods R may be easily quickly melted within
the heating cylinder 11. In addition, because the metal rods R may
be squeezed or scraped by the ring 14 at the inlet of the heating
cylinder 11, no gaps exist between the ring 14 and the metal rods
at the inlet of the heating cylinder 11. Therefore, air can be
reliably prevented from entering the heating cylinder 11, so that
the interior of the heating cylinder 11 can be reliably maintained
in a substantially vacuum condition.
[0083] Furthermore, because the protective tube 13 can be inserted
into the heating cylinder 11, the heating cylinder 11 preferably
does not directly contact the molten materials. In particular,
because the protective tube 13 may be made of materials, such as
ceramic, that do not chemically react with the molten metals, such
as aluminum alloy, the formation of metal by-products may be
prevented. Therefore, the heating cylinder 11 may be protected from
being damaged by the creation of such metal by-products. As a
result, the heating cylinder 11 may have a long lifetime and may be
made of materials, such as steel or iron, which are commonly and
economically used for mechanical parts.
[0084] In addition, the inner wall of the charging cylinder 21 of
the pressurizing and charging unit 2 may be protected by the
protective tube 23. Further, the inner wall of the flow channel 25
of the hot nozzle 22 also may be protected by a protective layer,
which may serve as an insulating layer and also may serve to
protect the hot nozzle 22 from the molten materials in the same
manner as the protective tubes 13 and 23. Therefore, the formation
of metal by-products can be prevented throughout the flow path from
the heating cylinder 11 to the cavity C. As a result, the useable
lifetime of the heating cylinder 11, the cylinder 23 and the hot
nozzle 22 may be increased and the quality and yield of the molded
products may be improved.
[0085] Preferably, the materials of the protective tubes 13 and 23
and the inner layer of the flow channel 25 of the hot nozzle 22 may
be selected to prevent the creation of metal by-products with the
variety of alloys, which may include aluminum alloys and magnesium
alloys, that are melted in heating cylinder 13. In particular,
ceramics, ceramic-metal composites and chromium oxide coatings may
provide a satisfactory result for this purpose.
[0086] In addition, the front end portion 32 of the hot nozzle 22
may contact the fixed die half M3. In that case, the molten
materials within the front end portion 32 of the hot nozzle 22 may
be cooled rapidly as the fixed die half M3 is cooled in order to
solidify the molten material within the cavity C. Therefore, the
remaining (solid or semi-solid) material within the hot nozzle 22
may serve to interrupt communication between the cavity C and the
space F of the cylinder 23. As a result, a valve means is not
required in order to seal the space F from the outside. In addition
or in the alternative, a valve means is not required to maintain
the space F in the substantially vacuum condition when the piston
member 20A has retracted and the cavity C has been opened in order
to take the molded product out from the die M.
[0087] Further, the use of the hot nozzle 22 in association with
the pressuring and charging unit 2 may enable the production of
molded products that do not have unnecessary appendages, such as
runners, spools, biscuits and overflows, that typically accompany
products that are molded using known die-casting apparatus. Because
appendages are not formed, manufacturing costs of the molded
products may be reduced and the molding cycle may be shortened. In
addition, if it is not necessary to remove appendages from the
molded products, manufacturing costs naturally will be further
reduced. In general, the appendages that are removed from the
molded products of known die-casting apparatus are usually melted
again and are mixed with fresh metal materials so as to be used
again (recycled) in the molding process. However, according to this
representative embodiment, it is not necessary to melt such
appendages, because such appendages are generally not produced in
the first place. In addition, the molded products are stable in
quality, because the molding process can be always performed using
fresh materials.
[0088] A second representative embodiment of a material supply unit
will now be described with reference to FIG. 9. A material supply
unit 51 of this representative embodiment may include, for example,
a preheating unit 53 and a vacuum heating unit 54, which may
substantially correspond to the preheating unit 3 and the vacuum
heating unit 4 of the first representative embodiment. Therefore,
in FIG. 9, similar structures, which were described in further
detail with respect to the first representative embodiment, are
given the same reference numerals.
[0089] The preheating unit 53 may include a stacker 55 and a
hydraulic cylinder device 56. Similar to the stacker 5 of the first
representative embodiment, the stacker 55 may serve to receive or
hold metal rods R in a vertical row or stack. However, the stacker
55 may differ from the stacker 5 in that the stacker 55 does not
store the metal rods R in a position directly above the cylinder
halves 7A of the cylinder 7. Instead, the metal rods R may be
stored in a position rearward (leftward as viewed in FIG. 9) of the
cylinder halves 7A. In addition, the stacker 55 may include a fixed
bottom plate 55A that supports the row or stack of the metal rods R
from the lower side. Further, openings 55B may be formed on both
front and rear sides of the stacker 55 and adjacent to the bottom
plate 55A. Preferably the openings 55B may have a height that is
slightly greater than the diameter of the metal rods R. A
piston-cylinder device 55D may be mounted on the rear side of the
stacker 55 by means of a bracket 55C. In this case, the lowermost
metal rod R within the stacker 55 may be pushed out of the stacker
55 via the front opening 55B by means of a piston rod 55E of the
piston-cylinder device 55D. Therefore, the lowermost metal rod R
may drop into the open cylinder halves 7A due to gravity.
Similarly, the remaining metal rods R within the stacker 55 may
also drop due to gravity until the next lowermost rod R drops onto
the bottom plate 55A. The operation of the cylinder halves 7A may
be substantially the same as the operation described in connection
with the first representative embodiment. Thus, upon receiving the
metal rod R, the cylinder halves 7A may close and the pushing
piston 8 of the hydraulic cylinder device 56 may then move to push
the metal rod R into a vacuum heating section 54.
[0090] By arranging the stacker 55 in this manner, a movable member
is not required to support the weight of the stack of the metal
rods R, as opposed to the stop 10 of the first representative
embodiment. Therefore, the durability of parts of the stacker 55
may be improved and the stacker 55 may reliably operate to supply
the metal rods R into the supply cylinder 7.
[0091] The construction of the vacuum heating section 54 may be
substantially the same as the vacuum heating section 4 of the first
representative embodiment. However, the internal construction of
the heating cylinder 11 may be altered. For example, within the
heating cylinder 11 of the second representative embodiment, the
screen disk 18 may be positioned slightly forward of the position
of the screen disk 18 in the first representative embodiment. In
addition, a plurality of parallel spiral projections 57 may be
formed on the inner wall of the protective tube 13 in a position
forwardly adjacent the screen disk 18.
[0092] With this arrangement, the semi-melted metal rods R, which
are pushed into the heating cylinder 11 by the pushing piston 8,
may be deformed by rotating along the spiral projections 57 before
reaching the screen disk 18. As a result, the metal rods R may be
formed into strands and may be sheared into short strands as they
pass through the screen disk 18. Therefore, the material may have
an improved flowability or thixotoropy in the same manner as the
first representative embodiment.
[0093] Thus, according to this second representative embodiment,
the metal rods R can be rotated without having to rotate the
pushing piston 8 of the hydraulic cylinder device 56. Therefore,
the hydraulic cylinder device 56 may have a relatively simple
construction. In addition, the projections 8A at the front end of
the pushing piston 8, which were utilized in the first
representative embodiment, can be omitted in the second
representative embodiment.
[0094] Although the pressuring and charging unit 2 of the first
representative embodiment is used in combination with the die M
that has a single cavity C, the same pressuring and charging unit 2
can also be used in combination with a die that has a plurality of
cavities.
[0095] Therefore, a second representative embodiment of a metal
molding apparatus will now be described with reference to FIG. 10.
In FIG. 10, similar structures, which were described in further
detail with respect to the first representative embodiment, are
given the same reference numerals.
[0096] A pressurizing and charging unit 2 is shown partially in
FIG. 10 and may have substantially the same construction as the
pressuring and charging unit 2 of the first representative
embodiment. A die MW may include a movable die half MW1 and a fixed
die half MW2 that define a pair of cavities CW therebetween. A
runner block B may be fixed to the fixed die half MW2 and may be
spaced from the fixed die half MW2 by means of a spacer S.
[0097] In this representative embodiment, a pair of additional hot
nozzles 22A may be incorporated in order to charge the molten
materials into the respective cavities CW. The hot nozzles 22A may
be secured to the front surface of the runner block B by means of
bolts 30A. The front surface of the runner block B may oppose the
fixed mold half MW2. Each of the hot nozzles 22A may have the same
construction as the hot nozzle 22 and may have a flow channel 25
formed therein. The flow channel 25 of each hot nozzle 22A may have
a front end that directly opens into the corresponding cavity CW
and that has a diameter that decreases toward the corresponding
cavity CW.
[0098] An inlet port B1 and a pair of branch channels B2 may be
formed in the runner block B. The inlet port B1 may open at the
rear surface of the runner block B and may communicate with the
flow channel 25 of the hot nozzle 22 mounted on the front end 21a
of the charging cylinder 21 of the pressurizing and charging unit
2. One end of each of the branch channels B2 may communicate with
the inlet port B1. The other end of each of the branch channels B2
may open at the front surface of the runner block B and may
communicate with the flow channel 25 of the corresponding hot
nozzle 22A.
[0099] Thus, in this representative embodiment, the hot nozzle 22
at the front end of the cylinder 21 does not serve to directly
charge the molten materials into the cavities CW, but instead
serves to supply the molten materials into the inlet port B1 of the
runner block B. Therefore, during the molding process, the
temperature of the hot nozzle 22 is not required to be controlled
in response to the molding cycle as in the first representative
embodiment. Instead, the temperature of the hot nozzle 22 may be
controlled so as to normally maintain the material in an
appropriate melted state that is suitable for charging into the
mold MW.
[0100] A representative method for using this representative
embodiment will now be explained. In the same manner as described
in connection with the first representative embodiment, the piston
member 20A of the hydraulic cylinder device 19 (not shown in FIG.
10) may be driven to push the mass Rm of the molten material that
has been supplied into the space F. Therefore, the mass Rm may flow
into the inlet port B1 of the runner block B via the flow channel
25 of the hot nozzle 22. The mass Rm may then flow into the flow
channels 15 of the hot nozzles 25A via the branch channels B2 of
the runner block B and may further flow into the cavities CW. The
temperature of the hot nozzles 22A may be controlled in the same
manner as described in connection with the hot nozzle 22 of the
first representative embodiment. As a result, a pair of products
may be molded at the same time in the respective cavities CW.
[0101] The molding process may be substantially performed according
to the same Steps (1) to (15) as described in the first
representative embodiment, except for the following changes in
these steps:
[0102] (a) The volume of each of the metal rods R is preferably
selected to be equal to the sum of the volumes of the two cavities
CW.
[0103] (b) In the initial Step (5) for pushing the first lowermost
metal rod R, the stroke of the pushing piston 8 is determined to
correspond to the sum of the volume of the two cavities CW, the
volume of the flow channels 25 of the hot nozzle 22 and the hot
nozzles 22A, and the volume of the inlet port B1 and the branch
channels B2.
[0104] In addition, in this representative embodiment, the hot
nozzle 22 can be mounted on the front portion 21a of the cylinder
21 even though the hot nozzles 22A directly open into the
corresponding cavities CW. This arrangement is advantageous when
the die MW, which includes the runner block B, is replaced with
another die for molding a different product. Thus, the die MW can
be easily removed from the pressurizing and charging unit 2 and the
material within the hot nozzle 22 does not flow out of the front
end. Thus, the temperature of the front end of the hot nozzle 22
may be set to a temperature that will bring the metal material into
a semi-melted or solid state in order to seal the hot nozzle
22.
[0105] In addition, in order to restart the molding process, the
hot nozzle 22 may be quickly heated to melt the material within the
hot nozzle 22 after the new die for the different product has been
coupled to the hot nozzle 22. Although not shown in the drawings,
the combination of the pressurizing and charging unit 2 and the
mold ME of this representative embodiment can also be used in
combination with the material supply unit 51 that was described
above with reference to FIG. 9. Of course, the die MW may have
three or more cavities CW and three or more hot nozzles 22A may be
incorporated in order to correspond to the number of cavities
CW.
[0106] In the above representative embodiments, one pressurizing
and charging unit 2 and one material supply unit 1 (or 51) are used
for the die MW, which has a plurality of cavities CW. However, in
some cases, the pressurizing and charging unit 2 (or the
pressurizing ability) can not adequately charge the molten
materials into a plurality of cavities. In such a case, increased
force may be generated by replacing the hydraulic cylinder unit 19
with a more powerful cylinder unit and/or by increasing the
diameter of the cylinder 21. More preferably, as shown in FIG. 11,
a plurality of pressurizing and charging units 2 (two units 2 are
shown in FIG. 11) may be disposed in parallel with each other. In
this connection, two inlet ports B1 may be formed in the runner
block B and may be connected to the branch channels B2. In
addition, two material supply units 1 or 51 (not shown) may be
associated with the respective pressurizing and charging units 2.
In FIG. 11, similar structures are given the same reference
numerals as FIG. 10.
[0107] Thus, if each of the pressurizing and charging units 2 can
generate an injection force of 350,000 kgf, an injection force of
700,000 kgf will be available for the die MW. The number of
pressurizing and charging units 2 may be appropriately determined
according to a maximum possible injecting force required for the
die.
[0108] With this arrangement, parts of the pressurizing and
charging units 2 can be commonly used, so that the administration
of parts and the maintenance work can be simplified. In addition,
comprehensive control of maintenance work can be performed
according to an operation manual, so that the molding process can
be reliably performed. Furthermore, if the die MW is replaced with
another die that requires a relatively lower injection pressure,
the injection pressure generated by the combination of pressuring
and charging units 2 may be too high for the replacement die. In
such a case, the operation of one or more of the pressurizing and
charging units 2 may stopped. Therefore, the arrangement of this
representative embodiment can rapidly and easily cope with changes
in the necessary injection pressure.
[0109] In the above representative embodiments, the material supply
unit 1 or 51 is used in combination with the pressurizing and
charging unit 2 of a piston-cylinder type. However, the metal
supply unit of these representative embodiments may also be used in
combination with a variety of pressurizing and charging units other
than piston-cylinder type units. In addition, the metal supply
units also may naturally be used for purposes other than a molding
process.
[0110] In addition, in the above representative embodiments, the
pressuring and charging unit 2 having the hydraulic cylinder device
19 is provided separately from the vacuum-heating section 4.
However, the pressuring and charging unit 2 may be integrated with
the vacuum-heating section 4 so as to eliminate a separate charging
cylinder 21 and a hydraulic cylinder device 19. Such an alternative
embodiment will now be described with reference to FIG. 12.
[0111] Referring to FIG. 12, a molten metal supply unit 101 is
shown that generally comprises a preheating section 103 and a
vacuum heating section 104. Similar to the first representative
embodiment, the preheating section 103 may include a material
stacker 105 and a hydraulic cylinder device 106. The material
stacker 105 and the hydraulic cylinder device 106 can be similar in
construction to the respective material stacker 5 and the hydraulic
cylinder device 106 of the first embodiment. The vacuum heating
section 104 preferably includes a heating cylinder 111 and a
protective tube 113 that may respectively correspond to the heating
cylinder 11 and the protective tube 13 of the first representative
embodiment. The vacuum heating section 104 differs from the vacuum
heating section 104 of the first representative embodiment in that
a hot nozzle 122, which may be similar to the hot nozzle 22 of the
charging cylinder 21 of the first representative embodiment, is
attached to the front end of the heating cylinder 111. In addition,
the inner wall of the front end of the heating cylinder 111, as
well as that of the protective tube 113, is tapered in the
direction towards the hot nozzle 122 in the same manner as the
front end of the charging cylinder 21 of the first representative
embodiment. In other respects, this embodiment can provide
substantially the same results as the first representative
embodiment. Therefore, in FIG. 12, similar structures are given the
same reference numerals as utilized in FIGS. 1 to 8.
[0112] According to this representative embodiment, the hydraulic
cylinder device 106 of the preheating section 103 may also serve to
charge the molten material into the cavity C of the die M through
the hot nozzle 122. Thus, before the molding cycle is started, the
preheated metal rods R are sequentially charged into the heating
cylinder 111 by the piston 8 of the hydraulic cylinder device 106.
At the same time, the heating cylinder 111 is heated, so that the
heating cylinder 111 becomes filled with the molten material. Then,
the molding cycle is started and the piston 8 of the hydraulic
cylinder device 106 moves forward to push the rearmost preheated
rod R into the heating cylinder 111 by a distance that corresponds
to the volume of the cavity C. Consequently, the cavity C will be
filled with the molten material.
[0113] Thus, in this representative embodiment, the rods R are
completely melted within the heating cylinder 111. As a result, the
heating cylinder 111 may have a length that is greater than the
length of the heating cylinder 11 of the first representative
embodiment so as to provide a relatively long heating area. In the
alternative, additional heaters (not shown) may be mounted on or
may be embedded within the heating cylinder 111, so as to increase
the heating capability. The molten material is then cooled and
taken out from the die M as an article of manufacture in the same
manner as described in connection with the first representative
embodiment. The molding cycle naturally can be repeated to
sequentially mold a plurality of articles. Of course, during the
molding cycle, the ring 14 preferably seals the inlet of the
heating cylinder 111. Thus, the molten material within the heating
cylinder 111 is prevented from being exposed to the outside
environment, due to the reduced pressure generated by the vacuum
pump 17.
[0114] One advantageous feature of this representative embodiment
is the pressuring and charging unit 2, and in particular the
hydraulic cylinder device 19, is not required. Of course, the
arrangements shown in FIGS. 10 and 11 also may be adapted to and
utilized with this representative embodiment.
[0115] Although the hot nozzles 22, 22A and 122 are self-heating in
the above representative embodiments, any type of hot nozzle may be
used, such as hot nozzles having a separate external or internal
heater.
[0116] In addition, although the metal rods R of the above
representative embodiments have a circular sectional configuration,
the metal rods R may have a variety of other cross-sectional
configurations, such as polygon shapes, elliptical shapes, etc.
Preferably, the ring 14 is formed to have an inner surface that
substantially conforms to the configuration of the rods R and thus,
the particular configuration of the ring 14 and the rods R is not
important, as long as the configurations substantially correspond.
Moreover, although the representative embodiments have been
described in terms of metal rods R, such rods R may be any type of
material that may be melted and then further processed or
manipulated in a liquid state. For example, metal-plastic mixtures
and other non-metal polymer compositions are also expressly
contemplated by the present teachings.
[0117] Moreover, the means for shearing or shredding the softened
material within the melting chamber (e.g., heating cylinder) is not
limited to the screen disk 18 and rotation of the softened material
(e.g., by parallel spiral projections 57) according the
above-representative embodiments. Various other mechanical devices
can be utilized the shear or cut up the softened material into
smaller pieces in order to aid the melting process. Further, such
shredding means are optional and may not be included in devices and
methods prepared according to the present teachings.
* * * * *