JPH0357218Y2 - - Google Patents

Description

[Detailed explanation of the invention] (1) Purpose of the invention (a) Industrial application field This invention is used in precision casting for dental purposes, etc. to apply pressure or negative pressure to the melted metal in a crucible using heating means. The present invention relates to a pressure casting device that pours metal into a cavity in a mold using pressure, and particularly to a crucible and mold suitable for casting noble metal alloys such as gold and silver alloys.

(b) Prior art and its problems Among dental casting equipment, so-called pressure casting equipment, which applies an external force to molten metal to be cast and pours it into a mold, is widely used. All are made using the lost wax method. The above-mentioned mold is usually made by integrally molding a convex mold 1 as shown in FIG. 1 with an investment material 2. In the figure, 3 is a crucible, 4 is a cavity formed by the lost wax method, and 5 is a runner. The metal to be cast is placed in the crucible 3 and melted by heating means such as high-frequency induction heating, and the molten metal 6 is pressurized. Or by applying an external force in the direction of arrow a using negative pressure,
The molten metal is poured into the cavity 4 through the molten metal. However, an investment material 2 suitable for integrally molding a complex-shaped convex mold 1 having a crucible 3 with a thin crucible peripheral wall 3W and a deep depth 3D as shown in FIG. It is a large phosphate-based investment material. However, when processing the cast product after casting, the investment material attached to the cast product cannot be removed without using a dental chisel or a metal brush. The use of phosphate-based investment materials is limited to high-melting non-noble metal alloys such as alloys, and practically cannot be used for casting low-melting noble metal alloys such as gold and silver alloys, which have low hardness. In the casting of these noble metal alloys, gypsum-based investment materials, that is, cristoblast investment materials or quartz investment materials, which can be easily removed by brushing in running water after casting, have been used exclusively. However, while this investment material has the above-mentioned features, when molded into a mold, the bonding strength during curing is extremely low, making the molded product brittle and easy to collapse.
It was difficult to mold the crucible 3 shown in FIG. 1 to any desired capacity. In order to solve this problem, the authors devised two convex molds suitable for casting noble metal alloys, which have already been applied for. ” and Japanese Utility Model Application No. 173476/1988 “High-frequency casting device.” The former is a composite convex mold in which a mold is provided with a crucible bottom formed on the top using various investment materials, such as the above-mentioned gypsum-based investment material, and a short tubular member made of a highly heat-resistant refractory material is placed on top of the mold as the side wall of the crucible. It is a shaped mold,
This configuration not only facilitates the casting of precious metal alloys, but also allows the capacity of the crucible to be increased arbitrarily.
Furthermore, by repeatedly using the side walls of the crucible, casting costs were reduced. However, this composite mold simply places a short tubular member in a predetermined position on the mold, and does not require any connecting means or molten metal leakage sealing means.
During the melting and pressurized pouring process in the heating chamber, the molten metal does not leak and there is no problem, but when setting the mold in the casting machine during the preparation stage for casting, it is necessary to place a short tubular crucible in the heating chamber with a narrow opening. When inserting the crucible, the crucible that comes into contact with the opening often falls off, so the crucible must be carefully set, resulting in a time-consuming problem.

In addition, in the latter convex mold, the mold forming the cavity is made of gypsum-based investment material, and a large diameter brim and a crucible positioning protrusion or recess are formed at the engagement part with the mold using a highly heat-resistant refractory material. This is a composite convex mold consisting of a crucible portion. With this structure, the former problem is solved, the capacity of the crucible can be increased arbitrarily, and post-treatment can be done by washing with water, making casting of noble metal alloys extremely easy. However, when casting expensive metals such as gold alloys using this composite mold, it is necessary to maintain an especially appropriate increase ratio of the amount of alloy melted in the crucible to the amount of alloy in the main body of the casting, and if the amount of melted metal is too large, If,
After pouring, molten metal remains in the runners of the crucible and at the bottom of the crucible, resulting in a casting loss of expensive alloy. Further, even if the amount of melting is appropriate, there is a problem that the molten metal remains as a thin film attached to the bottom of the crucible and the runners, resulting in irrecoverable loss. Furthermore, there is a risk that air from the sprue of the mold located between the crucible and the mold may be drawn into the molten metal during pouring.

(c) Technical issues This invention is a casting device in which the metal to be cast, particularly the precious metal alloy, melted in a crucible via a heating means is poured into a cavity in a mold by applying pressure or negative pressure. , the bottom of a crucible and a mold having a cavity communicating therewith are integrally molded into a convex shape using an investment material suitable for casting noble metal alloys,
By using this investment material molded body, we aim to perform casting without casting loss by using an integral mold part that combines the outer shell of the crucible made of a highly heat-resistant refractory material and the casting ring that is in contact with the lower part of the crucible shell. It is something.

(2) Structure of the invention (technical means) The technical means taken to solve the above problems are as follows.

(b) Made of highly heat-resistant refractory material with through holes;
A crucible outer shell is provided with a large-diameter collar for sealing a heating chamber and a mold at the lower end of a thin-walled cylindrical body forming a peripheral wall of the crucible; (c) An investment material compatible with the metal to be cast is placed inside the engaging body to integrally connect the bottom of the crucible and the mold having a cavity communicating therewith. The method is to provide a mold section formed by molding.

(3) Effects of technical measures Refractory materials with high heat resistance, ie refractory porcelain, can be robustly molded and sintered into any shape. Therefore, the peripheral wall of the crucible can be molded to any thickness using this porcelain, and it is also possible to mold the peripheral wall of the crucible to any desired thickness. Instead of the mold shoulder 7 of the shaped mold 1, a crucible outer shell can be formed having an appropriate thickness to maintain the strength of the large-diameter brim that seals the heating chamber via a gasket. This crucible outer shell is the above-mentioned peripheral wall 3
It is a cylindrical body that penetrates the inner cavity of W, and is usually a cylindrical body. The inner cavity has a slight slope in its downward expansion to facilitate separation of the investment material after casting. The outer shell of the crucible made of fire-resistant porcelain is supported by a pre-prepared wax pattern with a spool wire, and then formed into a truncated cone shaped like the bottom of the crucible, and then molded into a rubber mold integrated with the truncated cone. Insert with the brim facing up. The position of the truncated cone in the lumen of the cylinder therefore determines the depth of the crucible. Next, a so-called casting ring, which has an asbestos lining on the inner surface of the metal ring, is placed in contact with the brim of the outer shell of the crucible, and a gypsum-based investment material suitable for casting precious metal alloys is poured into the casting ring to fill it with an appropriate amount. By curing depending on temperature and time, a crucible and a mold can be integrally molded using the investment material. By providing a ring-shaped protrusion on the lower surface of the outer shell of the crucible, the shear stress of the mold part connected by the investment material can be strengthened. Note that since the alloy to be cast is a low melting point metal, there is no need to apply a high temperature heat resistant agent to the bottom of the crucible of the gypsum-based investment material to reinforce the heat resistance of the investment material.

(4) Effects of the invention This invention is structured as described above, so
When casting precious metal alloys, a crucible bottom part and a mold having a hollow part are integrally molded using a gypsum-based investment material that is easy to post-process, and a crucible outer part made of a refractory material and a metal casting ring are used together, This completely solves the problem of low bonding strength of the investment materials mentioned above. Therefore, the integrated mold part of the device according to this invention allows for easy and quick preparation work such as determining the amount of alloy to be cast into the crucible and setting it in the casting machine during casting, and also allows for easy and quick preparation work such as determining the amount of alloy to be cast into the crucible and setting it in the casting machine. It is possible to cast high-quality cast products with no entrainment of pressurized gas, etc., and almost no other casting defects, and the subsequent processing is easy, there is no casting loss of precious metal alloys, and the outer shell of the crucible is repeatable. can be used to reduce casting costs.

(5) Example A specific example of the device according to this invention will be explained below with reference to the drawings. FIG. 2 is a longitudinal sectional view of the main part of the casting section 10 of the pressure casting apparatus according to this invention, in which the heating means is, for example, high-frequency induction heating. This casting section is the same as the conventional device except for the integrated mold section 11 according to this invention, so a brief explanation will be provided. Heating chamber 1 made of a refractory cylindrical body such as quartz
2 is sealed at its upper end with a viewing window 13, and has a high frequency induction heating coil 14 wound around its outer periphery. The lower end of the heating chamber 12 engages with a heating chamber pedestal 15 made of asbestos molding material to form a heating chamber opening 16. The mold part 11 is placed on a mold pedestal 17 via an asbestos gasket 18, and the mold pedestal 17 is raised and lowered by a mold lifting mechanism 19 composed of a pneumatic cylinder and its piston (not shown). The mold section 11 is brought into pressure contact with the heating chamber opening 16 via the gasket 20 by a preset pressure P during rising, and the inside of the heating chamber 12 is hermetically sealed from the atmosphere opening section 22. The side wall section 23 at the top of the heating chamber has a section inside the heating chamber.
A vacuum suction pipe 24 for reducing the pressure to about 10 ^-2 to 10 ^-3 Torr and an inlet/outlet pipe 25 for pressurizing argon gas or the like having a pressure of about 5 kg/cm ² G are provided.
5 simply indicates the position. The configuration of the conventional device has been described above, and now we will describe the integrated mold section 11, which is the main part of this invention. The mold section 11 consists of a crucible outer shell 26 that integrates a crucible peripheral wall and a large-diameter collar, a casting ring 27, and a convex mold 28 formed inside these. The crucible outer shell 26 is sintered and molded from a highly heat-resistant refractory material such as alumina oxide or cordierite, and the cylindrical body 26P forming the crucible peripheral wall is formed to have an arbitrary wall thickness t, and an inner cavity passing through it. A sloped portion 26T is provided to facilitate removal of the convex mold 28 after casting, and a large-diameter collar 26G is integrally formed. Alternatively, the cylindrical body 26P may be made to protrude below the brim 26G to form a ring-shaped protrusion 26R to strengthen the shear stress of the convex mold 28. The cast ring 27 is conventionally used, and is generally made of stainless steel, and has an asbestos lining 27A applied to its inner surface. The bottom part 30B of the crucible 30, the runner 32, and the cavity part 3 are provided with a gypsum-based investment material 29, that is, a cristoblast investment material or a quartz investment material, inside the abutment engagement body of the crucible outer shell 26 and the casting ring 27.
The convex mold 28 is formed by integrally molding and hardening 3.
By the hardening, the crucible outer shell 26 and the casting ring 27 are joined and integrated. With this configuration, when the molten metal 6 of the noble metal alloy in the crucible 30 is poured into the cavity 33 by pressurizing with an inert gas, the molten metal 6 completely fills the cavity, and then flows into the runner 32.
Of course, even if molten metal remains on the crucible bottom 30B, the investment material 29 can be completely and easily removed, so that it is all recovered and no loss occurs.

Although the above is one embodiment of this invention, this invention is not limited to the drawings and description. For example, cast rings are not necessarily circular in cross section;
It may be oval or other shapes, and the engagement of the cast ring with the collar is not limited to concentricity.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view of a convex mold used in a conventional pressure casting apparatus, and FIG. 2 is a vertical cross-sectional view of the main part of the casting part of a pressure casting apparatus according to an embodiment of the present invention. DESCRIPTION OF SYMBOLS 10... Casting part of pressure casting apparatus, 11... Mold part, 12... Cylindrical heating chamber, 14... High frequency induction heating coil, 16... Heating chamber opening, 19... Mold lifting mechanism, 22 ... Atmosphere opening part, 25 ... Pressurized gas introduction and exit pipe, 26 ... Crucible outer shell part of the above 11, 27 ... Casting ring of the above 11, 28 ... Convex mold, 26P ... Thin wall of the above 26 Cylindrical body, 2
6G...Large-diameter brim of the above 26, 26R...Ring-shaped protrusion of the above 26, 29...An investment material suitable for casting the metal to be cast (in this case, a gypsum-based investment material),
30... Crucible, 32... Yudou, 33... Cavity.

Claims (1)

[Claims for Utility Model Registration] 1. A cylindrical heating chamber having heating means and means for pressurizing and depressurizing the interior thereof and having an open bottom, a crucible housed inside the heating chamber, and a mold part disposed at the lower part of the mold and having a cavity communicating with the crucible inside; a mold lifting mechanism that presses the mold part into contact with the opening of the heating chamber and seals the inside of the heating chamber from the atmosphere; In this apparatus, the metal to be cast melted in the crucible is poured into the mold cavity under pressure or negative pressure. A crucible outer shell is formed by forming a cylindrical body, passing through the inner cavity thereof, and providing a large-diameter collar at the lower end of the cylindrical body to seal the heating chamber and the mold. A casting ring made of a metal material is brought into engagement, and a mold part is provided inside this engaging body, which integrally forms a crucible and a mold using an investment material suitable for casting the metal to be cast. A pressure casting device characterized by: 2. The pressure casting apparatus according to claim 1, wherein the crucible outer shell of the mold portion has a ring-shaped protrusion formed on its lower surface. 3. The pressure casting apparatus according to claim 1 or 2, wherein the metal to be cast is a low melting point noble metal.