Metal founding – Process – Including recycling of process material
Reexamination Certificate
2001-07-10
2003-01-14
Lin, Kuang Y. (Department: 1725)
Metal founding
Process
Including recycling of process material
C164S113000
Reexamination Certificate
active
06505670
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for injection molding metallic materials to obtain a product of desired configuration by supplying a metallic material contained in an injection cylinder into a mold cavity.
2. Description of the Related Art
A typical example of known disk brakes for motor vehicles is shown in cross section in
FIG. 32
hereof. As shown in
FIG. 32
, a disk rotor
503
of the example disk brake
502
is mounted to a drive shaft
500
via a hub
501
. A peripheral portion of the disk rotor
503
is placed in a caliper
506
.
A wheel
509
is braked by transmitting an oil pressure from a feed flow path
508
to a cylinder, not shown, of the caliper
506
and pressing brake pads
507
,
507
onto a disk portion
505
of the disk rotor
503
.
Since the brake pads
507
,
507
are pressed hard onto the disk portion
505
of the disk rotor
503
, the disk rotor
503
is required to be formed of a high-strength material.
On the other hand, in order to reduce the total weight of a motor vehicle, the disk rotor
503
is preferably manufactured of a lightweight material.
Metal matrix composite material (MMC) materials are well known for their high strength and lightweight. For example, employing aluminum (Al) alloy as a metal matrix can save the weight, and adding silicon carbide (SiC) to Al alloy matrix can realize increase in strength.
A method for manufacturing the disk rotor
503
from an Al alloy matrix composite material will now be described with reference to
FIG. 34
hereof.
Such a method is carried out in a conventional apparatus for injection molding a metal matrix composite material. An injection cylinder
515
is brought into communication with a cavity
512
defined by a movable die
510
and a stationary die
511
via a gate
513
. A plunger
516
is mounted to the injection cylinder
515
so as to be capable of upward and downward movements, an MMC feeding means
518
is connected to the injection cylinder
515
via a feed path
517
, and a shut-off valve
519
is mounted to an exit side of the feed path
517
.
A shut-off valve
519
is opened and an AL alloy matrix composite material is fed from the MMC feeding means
518
into the injection cylinder
515
as shown by arrow a. The plunger
516
is moved upward as shown by arrow b, and Al alloy matrix composite material is filled into the cavity
512
through the gate
513
. Then, the movable die
510
is moved upward as shown by the arrow c to open the die and the cast product is taken out of the die. The cast product taken out will be described below.
Reference is made next to
FIG. 34
showing a cast product taken out from the die. The cast product
520
is cut into a product portion
521
and a non-product portion
522
.
The product portion
521
is a member formed of Al alloy matrix composite material molded in the cavity
512
and is to be processed to obtain the disk rotor
503
as shown in FIG.
32
.
The non-product portion
522
is a member formed of Al alloy matrix composite material remained at the gate
513
(See FIG.
33
).
The non-product portion
522
remained at the gate
513
is also of Al alloy matrix composite material obtained by adding SiC grains to Al alloy matrix. Therefore, since Al alloy matrix composite material cannot be reused as it is, it is necessary to separate SiC grains from Al alloy matrix in order to reuse it. However, such separation is technically difficult, and if possible, it costs much. Therefore, the non-product portion
522
is put on a shelf in the existing circumstances and this contributes to increase in the cost of the product portion
521
molded by Al alloy matrix composite material (or a metallic material).
On the other hand, there are products that do not require high strength among injection molded articles. Since such products are not required to contain SiC grains for increasing strength, they may be formed of normal aluminum alloy material (or a metallic material) by injection molding. Therefore, there is a tendency that they are considered to be easily reusable because it is not necessary to separate SiC grains as in the case of Al alloy matrix composite material when reusing the non-product remained at the gate.
However, in order to reuse the non-product portion as a molten material in subsequent injection molding, it is necessary to melt the non-product portion, which requires much heat energy for melting the non-product portion. Therefore, in the existing circumstances, the non-product portion is shelved, thereby contributing to increase in cost of the product molded of Al alloy material (metallic material).
FIG. 35
shows a conventional injection molding apparatus. The injection molding apparatus
600
includes an injection apparatus
601
opposed to a die
602
. A molten metallic material
605
is poured into a cavity
604
through a gate
603
. When the molten material
605
is solidified in the cavity
604
, a disk rotor
608
for the disk brake is obtained.
FIG. 36
shows an example disk rotor including casting defects. The disk rotor
608
is a defective apparatus having a defect that is appeared on an opposite side of the gate
603
(See
FIG. 35
) as a boundary of imperfect integrity at the joint due to lowering of the temperature of the molten material, that is, cold shuts
606
and scabs
607
. In other words, referring to
FIG. 35
, when the molten material
605
is injected into the cavity
604
through the gate
603
upwardly at the lower portion and then the molten material
605
collides against the upper portion of the cavity
604
, the cold shuts
606
and scabs
607
are generated.
Referring now to
FIG. 37A
to
FIG. 37C
, a conventional injection apparatus will be described.
In
FIG. 37A
, a molten metal matrix composite material
703
is fed from the molten material feeding apparatus
704
into the injection cylinder
702
of the injecting apparatus
701
.
In
FIG. 37B
, the injection cylinder
702
is connected to the forming die
705
. The molten material
703
is injected into the cavity of the forming die
705
by the plunger
706
moving up and down in the injection cylinder
702
, as shown by the arrow.
In
FIG. 37C
, the plunger
706
moves to the upper limit and injecting operation terminates. After that, when the injected molten material
703
is solidified in the forming die
705
, and the cast product
707
is completed.
However, slugs
708
may enter into the cast product
707
, which is a defect of the cast product. The slug
708
is a residue
709
generated by the oxide of the molten material
703
of metal matrix composite material, and is generated on the surface layer portion
711
of the molten material
703
and may adhere to the inner wall surface
712
of the injection cylinder
702
. The adhered residue
709
causes a defect on the cast product
707
by being mixed in the molten material
703
. When the defect is developed, the cast product has to be disposed, which leads to lowering of manufacturing efficiency.
SUMMARY OF THE INVENTION
It is therefore a first object of the present invention to enable the reuse of the non-product portion remained at the gate to bring down costs for injection-molded articles formed of metallic material.
A second object of the present invention is to provide an injection apparatus for metal matrix composite material that can eliminate defects of cast product caused by residues.
According to a first aspect of the present invention, there is provided a method for injection molding a metallic material in which an injecting material comprised of a half-solidified metallic material or a molten metallic material is injected into a cavity of a die from an injection cylinder through a gate thereof, the method comprising the steps of: taking out a cast product from the die while the cast product is still hot, the cast product having a product portion molded in the cavity and a non-product portion remaining at the gate; separating the non-product portion from the cast product while the non-product portion is in a state o
Echigo Takaharu
Kato Takashi
Nakao Yasuhiro
Shoji Hiroto
Sugaya Kunitoshi
Honda Giken Kogyo Kabushiki Kaisha
Lin Kuang Y.
Merchant & Gould P.C.
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