Metal founding – Process – Shaping liquid metal against a forming surface
Reexamination Certificate
2001-10-29
2003-07-22
Elve, M. Alexandra (Department: 1725)
Metal founding
Process
Shaping liquid metal against a forming surface
C164S119000, C164S312000
Reexamination Certificate
active
06595265
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a technology for producing a sirocco and a propeller fan by molding an alloy having a low fusion point, such as a magnesium alloy, in use of, for example, injection molding.
DISCUSSION OF BACKGROUND
A sirocco fan made of a metal is mainly used in cases that noncombustibility is required to avoid a fire in, for example, a kitchen and that an ambient temperature becomes high. Sirocco fans are ordinarily made from a thin steel plate or a thin aluminum plate, a main plate having a rotation shaft, a side plate on an air invent side, and a plurality of vanes. These components are fixed by, for example, a caulked joint. Therefore, in a structure using the thin steel plate, the weights of the components are increased, whereby balancing becomes important. Further, in case of using the thin aluminum plate, a material cost is expanded, and it becomes difficult to weld the caulked portion for reinforcement. In Japanese Utility Model No. 1792736, Japanese Unexamined Utility Model Publication JP-A-62-14199, Japanese Unexamined Patent Publication JP-A-8-42495 disclose that a joint of a caulked portion is reinforced by successively welding after caulking by coating, or by bonding, became the joint is weak.
In Japanese Unexamined Patent Publication JP-9-126189 and Japanese Patent No. 2667748, a technology that a sirocco fan is monolithically molded out of a plastic. In
FIG. 39
, a structure of a fan monolithically molded out of a plastic is shown. In
FIG. 39
, numerical reference
31
designates a centrifugal blower; numerical reference
33
designates an impeller, constructed by main vanes
40
, auxiliary vanes
41
, and a cone-like stiffening plate
37
, which impeller is accommodated in a case
32
and a bottom surface
42
; numerical reference
43
designates a shaft boss, directly connected to a motor
34
, for rotating the impeller; numerical reference
39
designates a stiffening ring for holding the impeller so as to be shaped like a cylinder; and numerical reference
35
and
36
respectively designate an air outlet and an air inlet, which are provided in a case.
Such an impeller is monolithically molded as a final product such that a resin is injected from a resin injecting gate, located apart from the shaft boss, into a cavity of a separated molding die and applied with heat and a temperature. Thus, the main vanes and the auxiliary vanes, both of which are thin, and the stiffening ring are monolithically formed. However, because leaves (lvs) of a metal mold is large, and a molten metal is hard to flow in a method of producing such as an aluminum die-cast, it is difficult to construct thin vanes of 1 through 2 mm.
However, because it is difficult to reuse a material of a plastic, particularly of a strengthen special plastic, in which a glass fiber is mixed like a fan. Therefore, an admixture is changed to a metal in consideration of the global atmosphere preservation. It is desired to utilize a metal having a low melting point in comparison with a combination of dissimilar metals, which are hardly separated, and also a metal requiring a high energy for producing, such as steel plate and an aluminum. In the Nikkei Mechanical Dec. 9, 1996,Vol.495; the Nikkei Mechanical March 1998,Vol.522; the Kogyo Zairyo May 1998, Vol.46, No.5, and the Kogyo Zairyo October 1998, Vol.46, No.10, a thixomolding method, by which a magnesium alloy being a representative metal having a low melting point, is subjected to injection molding, is disclosed. The thixomolding method is a coined word derived from thixotropy and injection molding, wherein the thixomolding method means a semi-molten metal injection molding method developed in U.S.A. Grain-like chips, made of a magnesium alloy ingot(igt) are used as a low material to inject into a metal mold of a product like injection molding of a plastic. Thereafter, a molded object is taken out of the metal mold. The magnesium alloy to be injected is changed depending on a use such that the magnesium alloy is in a liquid phase or contains an arbitrary solid.
FIG. 40
illustrates a structure of a thixomolding device as an injection molding device. Numerical reference
101
designates a hopper for throwing a raw material to a feeder
105
; numerical reference
107
designates an electrical heater, i.e. ceramic band heater, inside which a screw
103
is rotated; numerical reference
102
designates a cylinder heated by the electrical heater; numerical reference
104
designates a back flow prevention ring; numerical reference
106
designates an inactive atmosphere; numerical reference
109
designates a metal mold of a product; numerical reference
112
designates a nozzle for injecting a molten metal accumulated in a reservoir
122
from an injection molding machine by a rapid shot system; and numerical reference
121
designates a rotary drive.
In
FIG. 40
, a pellet-like magnesium alloy is thrown from the hopper
101
, and a part of the magnesium alloy, measured by the feeder
105
, is thrown into the cylinder
102
. An outer peripheral portion of the cylinder is heated by the electric heater
107
, i.e. the ceramic band heater, to make a semi-fusion magnesium alloy, wherein the semi-fusion magnesium alloy is separated from the magnesium alloy in the feeder by the inactive atmosphere
106
. Only an injected amount of the magnesium alloy is measured and supplied from the feeder to appropriately control the amount of the semi-fusion magnesium alloy. However, the injected amount and a supplied amount do not completely match, unlike resin molding. The magnesium alloy thrown into the cylinder
102
is forward conveyed, made to be like slurry, and injected by a rotation of the screw
103
. Thixomolding uses characteristics of thixotropy of a magnesium alloy. A magnesium alloy exists in a condition that dendrites in a solid phase are connected like branches in a solid-liquid coexisting state. Accordingly, a viscosity is high in this state. When a shear force is continuously applied by the rotating screw
103
, the dendrites are cut and minutely powdered, whereby fluidity is enhanced.
FIG. 41
illustrates a structure of a nozzle of the molding machine. Numerical reference
110
designates a coagulate plug, which prevents the semi-fusion magnesium alloy
111
from flowing out of the tip nozzle
112
; and numerical reference
113
designates a gate of the metal mold
109
. The tip nozzle
112
is shaped like a projected hemisphere. An entrance of the gate
113
of the metal mold
109
is shaped like a recessed hemisphere having an inlet a little larger than an outlet of the tip nozzle
112
. The tip nozzle
112
and the inlet of the gate
113
are in contact with each other and combined on their hemispheres. If the contact is not tight, there is a possibility that the semi-fusion magnesium alloy is brown into the atmosphere. Therefore, it is necessary to carefully adjust the contact. At a top of the semi-fusion magnesium alloy
111
, a lump formed by a metal, referred to as the coagulate plug
110
, is located. When the semi-fusion magnesium alloy is injected, the coagulate plug is projected and an injection is finished within a very short time of several dozens of microseconds through several milliseconds.
FIG. 42
illustrates a state that the injection molding machine is separated from the metal mold after completing the injection. A metallic piece chokes the gate portion
113
, and a coagulate plug
110
is left at a separated portion.
Meanwhile, a propeller fan, supplied for an ordinary use, is made of a plastic. When a propeller fan is used where a fire is used as in a kitchen, or where is a high temperature, the propeller fan is made of a metal. A method of producing the propeller fan made of a metal is such that a thin steel plate, a thin aluminum plate, or the like is used; an impeller is formed by monolithical drawing; and a rotation shaft, formed as another component, is joined to and fixed to the fan. Therefore, the impeller formed by monolithically drawing a thin steel plate is abruptly twisted at a hub
Endo Akio
Fukuyama Jiro
Iwamura Yoshimi
Kikuchi Hitoshi
Makino Yasuyoshi
Burns Doane , Swecker, Mathis LLP
Elve M. Alexandra
Tran Len
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