Injection molding apparatus

Abstract

An apparatus provided is capable of performing injection molding of a high-melting point metal. The injection molding apparatus comprises a mold, a sleeve disposed so as to be movable forward and backward toward a pouring gate of the mold, a plunger slidably disposed in the sleeve, a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of the sleeve and the plunger mentioned above, and a raw material lump supplying means for supplying the raw material lump to the above-mentioned raw material accommodating part from above. For the purpose of ensuring that a melt of a metal which has been heated and melted hardly flows into a gap between the plunger and the sleeve, the above-mentioned plunger and / or sleeve is equipped with a cooling means.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This is a continuation of Application PCT / JP2005 / 000377, filed Jan. 14, 2005, which was published under PCT Article 21(2).BACKGROUND OF THE INVENTION [0002] 1. Field of the Invention [0003] This invention relates to an injection molding apparatus, and more particularly to an apparatus which is suitable for the vacuum injection molding of a high-melting point metal, particularly an active metal such as an amorphous alloy, and capable of carrying out the high-speed injection molding of a melt of the active metal while maintaining a clean state thereof. [0004] 2. Description of the Prior Art [0005] Recently, as an injection molding method capable of casting a molded article having no void with an active metal, a molding method which uses a sleeve movable toward a mold and is carried out by supplying a raw material lump into a raw material accommodating part formed by an inside wall of a sleeve and the upper end face of a plunger slidably d...

AI Technical Summary

Benefits of technology

[0011] The present invention has been made in view of the prior art described above and its fundamental object is to provide an apparatus capable of producing a high-quality molded article, in which a melt of a metal which has been heated and melted hardly flows into a gap between a plunger and a sleeve, the sliding movement of the plunger can be smoothly performed in the sleeve, and consequently the injection can be performed stably, even in the injection molding of a high-melting point metal having a melting point of about 1200° C. or more.

[0012] A further object of the present invention is to provide an apparatus which, even in the case of an active metal such as an amorphous alloy, can perform injection molding of the active metal continuously with one raw material loading, without releasing the vacuum state in the space of a heating-melting section, and can carry out mass production of the injection-molded article of high quality at a low cost.

[0016] In accordance with another preferred embodiment, different materials are used for the plunger and the sleeve. When the plunger and the sleeve are constituted so as to have different thermal expansion coefficients, it is effective in preventing formation of a gap therebetween. For example, the above-mentioned plunger is formed from a metal or alloy having a melting point of not less than 800° C., such as Fe, Ni, Co, Mo, W, Ta, and Nb, or part or all of the above-mentioned plunger is formed from ceramic. On the other hand, the above-mentioned sleeve is formed from ceramic.

[0018] As described above, in the injection molding apparatus of the present invention comprising a mold, a sleeve disposed so as to be movable forward and backward toward a pouring gate of the mold, a plunger slidably disposed in the sleeve, and a heating means for heating and melting a raw material lump supplied into a raw material accommodating part formed by an inside wall of the sleeve and the plunger mentioned above, since the plunger and / or sleeve mentioned above is equipped with a cooling means, a melt of a metal which has been heated and melted hardly flows into a gap between the plunger and the sleeve. Particularly, when the plunger has an internal space formed therein and extending along its axial direction and a cooling medium supply pipe disposed in the internal space so as to leave a space portion around its circumference, i.e. its leading end portion in the vicinity of a plunger head part and the circumference of the pipe wall, so that a cooling medium supplied through the above-mentioned cooling medium supply pipe may flow through the internal space of the above-mentioned plunger from its leading end, the fluid as the cooling medium is supplied in the state suffering little influence by heating in the upper part, and the upper part of the plunger can be cooled efficiently. Further, by using different materials for the plunger and the sleeve so that they have different thermal expansion coefficients, it is possible to effectively prevent formation of a gap therebetween. Consequently, since the sliding movement of the plunger in the sleeve may be smooth, injection can be done without any problem in sliding movement of the plunger, and it is possible to produce a high-quality casting article stably.

[0019] Further, by combining the injection mechanism with the raw material lump supplying means mentioned above, even in the case of an active metal such as an amorphous alloy, it is possible to perform injection molding of the active metal continuously with one raw material loading, without releasing the vacuum state in the space of the heating-melting section, and to carry out mass production of the injection-molded article of high quality at a low cost.

Problems solved by technology

However, since in the conventional vacuum injection molding machine cooling of the plunger or sleeve is not performed, there is a high possibility that molten metal will flow into a small gap between the inner surface of the sleeve and the side of the plunger (piston) during injection and solidify therein.

Consequently, the frictional resistance increases, and at the worst the plunger will become the immovable state within the sleeve and cannot effect injection.

When ceramic is used for the sleeve which requires heat resistance, there is a possibility that the sleeve itself may be destroyed due to the resistance of the solidified metal when the plunger is operated and the molten metal may spout out of the sleeve into a vacuum chamber.

Further, it has been thought that if the sleeve and the plunger of the above-mentioned vacuum injection molding machine are provided with a cooling mechanism, the temperature of the molten metal will not be increased and the injection can not be performed.

Therefore, the conventional vacuum injection molding machine has been caught in such a dilemma that the plunger and the sleeve are not cooled and, as a result, the problems described above are apt to be produced conversely.

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