JPH0252584B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention melts metal in reduced pressure air, inert gas air, or air by high frequency induction heating, resistance heating, or other heating means,
This relates to a pressure casting device that applies pressure such as inert gas to the mold and casts it into a mold to manufacture small precision parts for dental or industrial use.

As shown in FIG. 1, a convex mold 1 has a crucible 3 in its upper protrusion 2, as shown in FIG. , a mold cavity 5 formed on the lower base 4 by firing by the lost wax method, and a sprue 6 communicating with the crucible 3 are integrally molded using, for example, a phosphate-based investment material 7. The protruding portion 2 is inserted from below into an internal space 9 of a refractory cylindrical body 8 made of quartz glass, etc., and the space 9 serves as a heating and pressurizing chamber in this device, and a high-frequency induction heating coil 10 on its outer periphery serves as a heating and pressurizing chamber. Therefore, the metal M in the crucible 3 is melted, but this melting means is not directly related to the present invention. A prepared mold may also be used. Therefore, the cylindrical space 9 is an airtight chamber, and the horizontal member 11 that engages with the lower end of the airtight chamber 9 is made of a refractory material such as asbestos molded airtightly connected to the cylindrical body 8, and its lower surface is It is formed into a flat surface and is fixed to, for example, an apparatus base. A portion constituted by the horizontal member 11 and the cylindrical member 8 (including the heating coil 10 in this case) is referred to as a cover member 9B. The upper surface 4u of the shoulder portion of the lower base 4 of the convex mold 1 is a ring-shaped heat-resistant packing 1 usually asbestos packing 1 whose plan view is shown in FIG.
2 to the lower surface 9BD of the cover member. 13 is a mold holder at the upper end of the pressure welding lifting mechanism, and 14 is an asbestos ring. Reference numeral 15 denotes a universal joint that supports the pedestal 13, and is connected to the upper part of the piston of an air cylinder (not shown), for example, and applies a pushing force F _u in the direction of the arrow to the asbestos packing 12 to airtightly seal the airtight chamber 9. .

In such a pressure casting apparatus, the molten metal M is poured into the cavity 5 through the sprue 6 at that pressure and continuously pressurized until the metal solidifies.The pressure of an inert gas such as argon gas depends on the size of the cast product, The pressure is usually 2 to 5 kg/cm ² G, although it varies depending on the shape and other conditions.
Requires _PG . The asbestos packing 12, which completely seals this pressure _P For example, if the surface is not completely flat over the entire circumference _,
is 2 Kg/cm ² G, and the area S ₁ of the inner hole d ₁ is 13 cm ² , the force F _D applied to the mold is theoretically about 26 Kg, but for the above-mentioned reason, the force applied to the mold is 12
The push-up force F _u for airtight pressure welding is required to apply a pressure slightly higher than the above P _G to the area occupied by the outer diameter d ₂ of the flat plate part of the seal (S ₂ = π x d ₂ /2), and is approximately 100 kg. It will also happen. Therefore, if the width l is narrowed in order to reduce S ₂ , there is a risk of breakage, and it is difficult to reduce the pressure contact force F _u . By using asbestos packing in this way, the pressure contact force of the pressure contact lifting mechanism must be made strong, which necessitates a large pressure contact mechanism, which impedes miniaturization and simplification of the pressure casting apparatus.

This invention solves the above-mentioned problems of the conventional pressure casting device, completely seals the mold and the pressure chamber with a much lower pressure force than the conventional device, and improves the pressure lifting mechanism. The aim is to simplify the pressure casting equipment and make it smaller and cheaper. Its structure consists of a cylindrical protrusion member made of a metal material that protrudes by about 2 mm, for example, at a position as close as possible to the outside of the lower opening of the airtight chamber on the upper surface of the mold shoulder or to the outer diameter of the molten metal storage part of the mold. For example, 2 to 2 of the above protruding parts of the member
A portion of a flat plate such as a ring-shaped asbestos packing, which is a sealing member, is locally airtightly welded with a wall thickness of about 3 mm.

Embodiments of the present invention will be described below with reference to the drawings. FIG. 3 is a partial vertical cross-sectional view showing the construction of the casting section of a pressure casting apparatus in which the heating melting means is of a high-frequency induction type as an embodiment of the present invention, and parts with the same symbols as in FIG. 1 are shown in detail. Omit. The press-contact lifting mechanism 16 is the first
It consists of a mold holder 13, an outer air cylinder 17 of a universal joint 15, a piston rod 18, etc. shown in the figure. Further, in the upper part of the airtight chamber 9, the housing 19, which is airtightly connected to the cylindrical body 8, is engaged with the device base like the horizontal member 11, and the upper surface of the housing 19 is sealed with, for example, quartz glass. There is a peephole 20. The arrow 21 indicates a vacuum suction tube for reducing the pressure inside the airtight chamber 9, and the arrow 22 indicates a vacuum suction tube for press-fitting the molten metal M from the crucible 3 or the metal container such as the saucer into the mold cavity 5. An inlet/outlet tube for argon gas or air with a pressure of cm ² G. The above configuration is the same as that of the conventional device, but the mold 23 of the present invention has a relatively large outer diameter D ₂ , but the upper shoulder 4u is positioned opposite to the airtight chamber lower opening 9H as possible, i.e. As shown in the figure, a ring-shaped protrusion member 24 is embedded in the periphery of, for example, approximately 1.5 times the airtight chamber inner diameter _D1 . This member 20 is made of a metal material, such as iron or stainless steel, and has a wall thickness t of approximately 2 mm, and a protruding length h of the length L of 2 to 3 mm. The protruding portion 24u of this member 24 locally and strongly presses the flat plate portion of the ring-shaped asbestos packing 12 having a thickness g as shown in FIG. 2 over its entire circumference against the lower surface 9BD of the cover member. In this way, since the pressure receiving area of the mold, that is, the area corresponding to the inner diameter d ₁ of the member 24, is reliably limited, the pushing up force of this device, that is, the pressing force Fu' is applied to the mold by the pressurized gas pressure P _G from above. It suffices if the force slightly exceeds the force F _D that 23 receives. For example, for the F _D of 26 kg mentioned above, Fu′ is 27 ~
28kg is enough. This is because the airtight welding part is not a flat plate but a thin protruding part 24u, and the pushing up force is
This is to avoid expanding Fu′. Therefore, conventional pressure casting is possible with a pressure welding mechanism that has a pressure contact force that is about 1/4 of that of conventional equipment.
Note that there is a metal ring 2 on the outer periphery of the mold indicated by a dashed line.
6' is obtained by omitting the protrusion 26u of the mold outer ring 26 explained in FIG. 4, and its effect will be described later. Further, although not shown, depending on the type of investment material forming the mold, a structure may be added to prevent the ring-shaped protrusion member 24 from falling off or sinking into it.

FIG. 4 is a longitudinal sectional view of a convex mold according to another embodiment of the present invention, and parts with the same symbols as those in FIG. 1 will not be described in detail. The convex mold 25 has a mold cavity 5 of a relatively small size, so that the diameter D ₂ of the mold base 4 is small.
is, for example, about 1.5 times the inner diameter _D1 of the pressurizing chamber 9, which is explained in FIG. 3 and not shown here.
Therefore, the ring member 26 made of a metal material that protrudes from the upper surface 4u of the mold shoulder portion described above has a protruding portion 26u of h≈2 mm at its upper end, as described above, and its lower end is made to coincide with the mold bottom surface 4D. Alternatively, by setting the dimension L' to be slightly longer than that, the peripheral wall of the mold outer periphery 4R is formed. With this configuration, the protrusion 26u can be attached to the lower surface 9 of the cover member.
As described above, the asbestos packing 12 is strongly pressed against the entire circumference of the BD to maintain airtightness. Therefore, when keeping the mold and airtight chamber airtight with asbestos packing in a conventional pressure casting mold, extreme care must be taken to ensure that the upper surface of the mold (the upper surface of the shoulder 4u in the figure) is smooth. However, by protruding the metal ring 24 by 2 to 3 mm, it does not require as much care as in the past, leading to a significant improvement in work. In addition, if the mold investment material has a low compressive strength after curing, or if it takes a high temperature or time to completely harden, the metal ring surrounding wall mentioned above will facilitate the molding and reduce the brittleness after molding. Prevent destruction and loss.

The above is one or two embodiments of the present invention, but the present invention is not limited to the illustrations and explanations.
For example, if the casting device is a pressure type, a separate dish melting device such as a drop type may be used, and the heating and melting means is not limited to high frequency induction heating, but any method can be used. Moreover, the apparatus may be of a type in which the cover member moves up and down, instead of being of a fixed type. Furthermore, the same effect can be achieved even in a convex mold in which the side wall of the crucible is separable with a refractory material. Further, the pressure source of the mold pressure welding mechanism is not limited to air pressure, and may be of any type.

Since this invention is constructed as described above, it solves the problems of conventional pressure casting equipment, improves the sealing function of the conventional heat-resistant sealing member that hermetically presses the mold into the airtight chamber, and allows By completely sealing with a significantly lower pressure welding force against the pressurized gas pressure of It is possible to improve casting efficiency by increasing the gas pressure for hot water, and it is also possible to mold standard molds with a relatively small outer diameter using investment materials with low hardness, making it easier to remove the product after casting. This provides a convenient device that makes it easy to use.

[Brief explanation of drawings]

Fig. 1 is a partial vertical sectional view showing the configuration of the casting section of a conventional pressure casting device, Fig. 2 is a plan view (semicircular portion) of the heat-resistant sealing member of the above-mentioned device, and Fig. 3 is the invention according to the present invention. FIG. 4 is a partial vertical cross-sectional view showing a mold and its surroundings of a pressure casting apparatus according to an embodiment of the present invention, and FIG. 4 is a vertical cross-sectional view of a mold according to another embodiment used in the apparatus of the present invention. 1, 23, 25...Mold, 3...Metal storage part (crucible in this example), 4u...Mold shoulder upper surface, M
... Molten metal, 5 ... Mold cavity, 8 ... Cylindrical body,
9...Airtight chamber, 9H...Airtight chamber lower opening, 9B
...Covering member, 12... Sealing member, 16... Pressure-contact lifting mechanism, 24... Ring-shaped protrusion member, 26...
Mold outer peripheral wall, 26u...ring-shaped protrusion member.

Claims (1)

[Scope of Claims] 1. A mold having a metal accommodating portion for accommodating molten metal in the upper part of the mold, and a mold cavity formed inside communicating with the metal accommodating portion, and a conduit from an inert gas or air pressure source. It has a cover member to which a depressurizing conduit is connected as necessary and has a through hole in the lower part thereof, and a pressure lifting mechanism that brings the mold and the cover member into airtight pressure contact, and by this airtight pressure contact, the mold and a cover member, and during casting, pressurizes the upper surface of the molten metal in the metal storage section with the inert gas or air and pours the metal into the mold cavity. At the engaging portion where the mold and the cover member are brought into airtight pressure contact, the metal housing portion of the mold or the opening of the lower through-hole of the cover member, whichever has a larger diameter, is located at a position close to the outside. A pressure casting device characterized in that a ring-shaped projection member made of a metal member is provided on the upper surface or shoulder surface of the corresponding mold. 2. The pressure casting apparatus according to claim 1, wherein the ring-shaped projection member is integrated with a ring forming the outer periphery of the mold. 3. The pressure casting apparatus according to claim 1, wherein a ring-shaped projection member is provided inside the outer ring separately from the outer ring forming the outer periphery of the mold. 4. The pressure casting apparatus according to any one of the first, second, and third items, wherein the ring-shaped protrusion member is provided with a means for preventing it from coming off from the mold.