Static molds – Including means within surface to confine heat exchange medium
Reexamination Certificate
2002-06-25
2004-12-07
Mackey, James P. (Department: 1722)
Static molds
Including means within surface to confine heat exchange medium
C249S205000, C425S552000, C164S348000
Reexamination Certificate
active
06827323
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a cooling device for molds used in die casting or the like and particularly it relates to a technique for efficiently feeding fluid to a fluid flow passageway for cooling formed in a mold.
As well known, in the case of a mold used for die casting or the like, in order to form a hole in a predetermine place in a cast article, a pin section, such as a core pin, is inserted in a predetermined place in a cavity formed in the mold. It is common practice to attach a cooling device to this kind of mold for cooling said pin section.
Such cooling device comprises a fluid flow passageway formed in a pin section, a pump section for feeding cooling liquid from a liquid source to said fluid flow passageway, and a fluid feeding and discharging circuit for driving said pump section. In this case, the fluid flow passageway of said pin section is constructed such that, as shown in
FIG. 9
, the pin section
91
of a mold
90
is formed with a bottom-closed cooling hole
93
having spherical bottom surface
92
in the front end, positioned in said bottom-closed cooling hole
93
are the respective front end openings in concentrically disposed inner and outer pipes
94
and
95
. The front end opening in the inner pipe
94
is disposed in opposed closely adjacent relationship to said bottom surface
92
than the front end opening in the outer pipe
95
, in opposed relationship thereto, and a fluid flow passageway
91
a
is constructed so that the inner passageway
96
of the inner pipe
94
serves as a forward passageway for the cooling water while a between-pipe passageway
97
between the inner and outer pipes
94
and
95
serves a backward passageway for the cooling water. And, in performing the casting operation, the cooling liquid is fed to the fluid flow passageway
91
a
of the pin section
91
after the completion of the poring of molten metal into the cavity portion
98
, and at the time when the molten metal has solidified and cooled to a suitable degree, the mold is opened to take out the cast article.
In this case, if the cooling liquid remains in the fluid flow passageway
91
a
of the pin section
91
when one lot of cast articles are produced upon the termination of the preceding casting operation, not only troubles occur in performing the subsequent casting operation but also it presents a cause of corrosion occurring in the fluid flow passageway
91
a
. Therefore, upon termination of casting operation for each lot is applied the so-called air purge in which air is fed under pressure to the fluid flow passageway
91
a
for a very short time to discharge the cooling liquid out of the fluid flow passageway
91
a
of the pin section
91
into the outside.
Further, this kind of pump section of the cooling device is of the so-called single-acting type in which the cooling liquid is fed only when the piston reciprocably held in the cylinder chamber moves in one way; therefore, usually the cooling liquid is intermittently fed to the fluid flow passageway
91
a
of the piston portion
91
.
In the method of intermittently feeding the cooling liquid by using a single-acting pump as described above, however, it is difficult to feed a large amount of cooling liquid under uniform pressure continuously to the fluid flow passageway
91
a
of the pin section
91
, so that in cooling the cast article, the quickening of application or stoppage of cooling action is hindered, leading to degradation of response. Further, such method only makes it advantageous to execute batch processing, and effecting batch processing according to this method would produce problems including one of increasing the size of the pump section or the fluid feeding and discharging circuit including the cooling liquid source, thus incurring the soaring of the cooling device costs.
Further, conventionally, to increase the pump performance, the pump section is driven by using oil pressure. Such method, however, requires not only the cooling liquid feeding and discharging circuit for feeding the cooling liquid to the pin section
91
but also an oil pressure feeding and discharging circuit including an oil pressure source for driving the pump section, and an air feeding and discharging circuit including an air source for applying air purge to the fluid flow passageway
91
a
of the pin section
91
, thus incurring an increase in the size of the cooling device and the soaring of its costs.
Further, the temperature control of the outer surface of the pump section
91
(and the inner surface of the hole in a cast article) during molding according to the conventional method, actually, is effected depending on the cooling liquid alone which is fed to the fluid flow passageway of the pin section. And, if the termination temperature of the outer surface of this pin section
91
is too high, a release agent which is to be applied to the outer surface of the pin section
91
so as to execute the subsequent is repelled on the outer surface, making it impossible to apply a suitable amount of release agent. Further, if the termination temperature of the outer surface of this pin section
91
is too low, such release agent will flow down and fails to stick, so that in this case also it becomes impossible to apply a suitable amount of release agent.
Therefore, the termination temperature of the outer surface of the pin section
91
is very important in making high-quality cast articles; however, conventionally, since the temperature control thereof has been dependent on the feeding of the cooling liquid, as described above, it has been considered very difficult to stabilize the outer surface of the pin section
91
at a suitable termination temperature.
On the other hand, the cooling water flowing from the inner passageway
96
of the pipe
94
shown in
FIG. 9
into the bottom-closed cooling hole
93
collides with the bottom surface
92
to change its direction of flow, then passing through a cooling hole inner passageway
99
existing on the outer periphery side of the inner pipe
94
into a between-pipe passageway
97
between the two pipes
94
and
96
, then flowing out of the between-pipe passageway
97
.
In this case, the bottom-closed cooling hole
93
formed in the pin section
91
of the conventional mold
90
, as shown in the same figure, has a central region, with an axis (X) in the bottom surface
92
used as a reference, which forms a spherical surface
92
x
, with the outer peripheral region thereof usually forming a tapered conical surface
92
y.
However, with the central region of the bottom surface
92
thus forming the spherical surface
92
x
, if the cooling water from the inner pipe
94
change its direction of flow as it collides with the spherical surface
92
x
, the cooling water after its change of direction has produced therein a flow component which tends to converge in the vicinity of the center of the spherical surface
92
x
(in the vicinity of the axis (X)), said flow component flowing in the direction opposite to the flow of cooling water from the inner pipe
94
and colliding therewith. Therefore, obstruction to passage of the cooling water takes place in the vicinity of the bottom surface
92
of the bottom-closed cooling hole
93
, thus causing the stagnation of cooling water. As a result, smooth outflow of cooling water is obstructed and since the lack of cooling action causes the mold
90
(core pin
91
) to become heated to high temperature, there occurs an imperfection that a diecast article (for example, aluminum cast article) becomes partly fused to the mold
90
.
Furthermore, the outer peripheral region of the bottom surface
92
being the tapered conical surface
92
y
results in a flow component which tends to converge in the vicinity of the axis (X) being produced in the cooling water which has changed its direction of flow as it collides with said conical surface
92
y
, said flow component flowing in the direction opposite to the flow of the cooling water from the inner pipe
94
to collide with said cooling water; therefore, the o
Heckenberg Donald
J.C. Patents
J.F.T. Co., Ltd.
Mackey James P.
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