JPH072265B2 - High frequency casting equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Field of Industrial Use The present invention relates to a mold in which a metal melted by high frequency induction heating in a vacuum atmosphere or an inert gas atmosphere is placed in the same atmosphere. The present invention relates to a high-frequency casting device for manufacturing a dental or industrial small precision casting product by casting.

(2) Conventional technology Among the high-frequency casting equipment used for precision casting of precious metal or non-precious metal in conventional dental prosthesis materials, the so-called high-frequency melting pressure casting equipment that uses the continuous pressure casting method is a separate plate melting method including centrifugal casting. It is widely used as a dental casting device because it has excellent quality compared to casting type devices, such as the crystal grains of the cast product being fine and the surface of the casting surface being smooth.
FIG. 1 is a vertical cross-sectional view showing the structure of a casting part of the conventional high-frequency casting device. Convex mold (1) Crucible (2) and mold cavity formed by lost wax method, namely precision mold
(3) and the sprue (4) are integrally molded, and the crucible (2) of the upper protruding portion is inside the cylindrical body (7) made of quartz glass or ceramics, that is, the heating chamber. The convex mold base (8) is housed inside (7R) and the mold base (8) is
It is supported via an asbestos gasket (10) on top. This mold cradle (9) is a compression spring (1) of the mold lifting mechanism (11).
2) It is pushed up from below by a preset pressure (Pu) by (13) or a pneumatic cylinder piston (not shown),
The mold base (8) is pressed against the heating chamber pedestal (15) made of an asbestos molding material via the asbestos gasket (14). The heating chamber pedestal portion (16) is composed of the pedestal (15) and a metal ring-shaped member (15M) coupled to the peripheral edge of the pedestal (15), and the heating chamber pedestal (17) is hermetically coupled to the pedestal (17). Indoor (7R)
Are airtightly separated from the open air portion (18). However, the quality of the cast body is improved by reducing the pressure around the mold base (8) to, for example, 10 ^-2 to 10 ^-3 Torr and replacing it with an inert gas such as argon at 1 kg / cm ² G. If you want to stabilize it, install the lower housing (19) indicated by the dotted line and attach the gasket (20).
Since the ring-shaped member (15M) is pressure-contacted via the above, and the inside of the lower housing (19R) is independently decompressed and replaced by the vacuum suction pipes / gas introduction / extraction pipes (21) (22) shown by the arrows. is there.
Returning to the tubular body (7) again, a high-frequency heating coil (23) is wound around the outer circumference of the tubular body (7), and a peep window (6R) made of a fire-resistant semitransparent material that seals the upper end of the heating chamber (7R). 24) and the heating chamber (7R) is 10 ^-2 to 10 ^-3 as above.
A vacuum suction pipe (25) for reducing the pressure to the Torr position and a gas introduction pipe (26) for introducing a pressure source such as argon gas having a pressure of about 5 kg / cm ² G are provided, and the heating chamber pedestal (16) and Constitutes a heating chamber (6). The above is the configuration of the casting part of the conventional high-frequency casting apparatus, and the mold lifting mechanism (11) is not directly related to the present invention, and therefore, the illustration and detailed description thereof are omitted.

By the way, the heating chamber (6) of the above-mentioned conventional apparatus is in direct contact with the atmosphere opening part (18) through a cylindrical body (7) such as ceramics, and the upper end of the cylindrical body (7) has an asbestos gasket (30A). It is airtightly connected to the upper base (31) of the equipment via the asbestos gasket (30B) and the lower opening is also the pedestal of the heating chamber.
Airtightly coupled to the pedestal (15) of (16). However, these cylindrical bodies (7), asbestos gaskets (30A) (30B), and pedestals (15) of asbestos molded products, due to their materials, emit a large amount of released gas immediately after they are evacuated from the atmosphere, and therefore leaks are added. Exhaust speed of 20 used in normal casting equipment
In the decompression with a small vacuum pump of about 60 l / min, it takes a considerable time to reach the above-mentioned vacuum pressure of 10 ^-2 Torr, and there is a drawback that the work efficiency is low. It is customary to perform casting in a low vacuum atmosphere of several Torr except when required for Ti alloy casting. On the other hand, the frequency of the current flowing through the high-frequency heating coil, which is the heating source, is several tens of KHz.
At high frequencies in the wireless communication range of ~ 2KHz, and the high-frequency power of this type of device is about 2KW, which is comparable to the output of small-scale broadcasting stations. Therefore, in the conventional device, a method of enclosing the entire device with a so-called electromagnetic shield is adopted in order to prevent radio wave interference that gives noise to various wireless communication devices and televisions and radios by electromagnetic waves radiated in the air by the high frequency heating coil and the high frequency line. It is customary to However, in this envelope electromagnetic shield method, the higher the frequency, the more rigorous the shield is required, and even a small gap or a lead hole for lead wires often causes problems. Therefore, it is difficult to manufacture the envelope part. Not only that, but it also has the drawback of increasing the shielding area and making it expensive.

(3) Purpose The present invention solves the above-mentioned drawbacks of the conventional apparatus, and has a structure in which the heating chamber for heating and melting the metal in the crucible is configured so that a desired high vacuum can be reached in a short time by a small-capacity vacuum pump. Moreover, it is possible to perform casting with an excellent oxygen-free effect, and to shield the electromagnetic waves of the radio frequency emitted from the high-frequency heating coil, that is, both the electric field and the magnetic field, as much as possible from the surroundings of the heating chamber, and to prevent electromagnetic interference to external electronic devices. It is an object of the present invention to provide an apparatus which is inexpensive, inexpensive, has high casting efficiency, and can obtain high-quality cast products.

(4) Configuration The high-frequency casting apparatus according to the present invention is not so different from the conventional apparatus in the casting method and the basic configuration. The structure which is a major difference of the present invention is such that the cylindrical heating chamber which is a hermetically sealed chamber is selectively covered from above by the mold lifting mechanism of the conventional apparatus, and has an inner diameter of at least twice the high-frequency heating coil diameter. The bowl-shaped cover member is made of, for example, an aluminum material having a large electromagnetic shielding effect, and the cover member serves as a bottom for the pedestal portion of the heating chamber to hermetically shield the heating chamber from the atmosphere and to shield the electromagnetic field. A shield chamber is formed, and an exhaust hole and a pressurizing hole that penetrate the cover member and communicate with the inside of the heating chamber are provided to decompress and pressurize the space inside the heating chamber and to electrically insulate the cover member. The high frequency heating coil is energized via the. Further, the cover lid member may be directly provided with an exhaust hole, and a preliminary depressurizing means for preliminarily depressurizing the inside of the airtight shielding chamber may be provided prior to depressurizing the heating chamber.

(5) Example Hereinafter, a high-frequency casting apparatus according to an example of the present invention will be described with reference to the drawings. FIG. 2 is a plan view of the casting part provided with the airtight shielding chamber (35) which is the main part of the present invention, and FIG. 3 is its II.
FIG. 4 is a side view including the I-III ′ cross section, and FIG. 4 is a side view also including the IV-IV ′ cross section, showing the convex mold (1) by means of a mold lifting mechanism (11) (not shown) and a chain line (1) ′. It is a figure when it is made to descend to the position of. In each figure, those having the same symbols as those in FIG. 1 have the same function, and therefore detailed description thereof will be omitted. Airtight Shielding Room (35)
Is a bowl-shaped cover member that has a through hole in the center of the upper part and is a molded product of, for example, an aluminum material with excellent electromagnetic shielding effect.
(36), the heating chamber pedestal (16), and the holding tube (37) of the observation window (24) coupled to the opening of the heating chamber tubular body (7) (one of the cover member (36) And the gasket that forms the part) (38)
(39) is airtightly connected and configured. The peep window holding cylinder (37) is screwed with a peep window cap (40) (which also forms a part of the cover member (36)) on the upper portion, and the peep window is fitted with gaskets (38A) (41). A ring nut (4) that is airtightly pressed against (24) and screwed into the upper opening of the cover member (36).
The upper and lower gaskets (30A) and (30B) of the tubular body (7) are pressure-welded by tightening 2) through the small recesses (43) to give sufficient airtightness to the heating chamber (7R). . If the inner diameter (d ₂ ) of the cover member (36) is not less than about 2 times the high frequency heating coil diameter (d ₁ ) (about 3 times in this example), the inductance of the heating coil (23) will be significantly reduced, and the circuit The constant changes. The airtight shielding chamber (35) configured as described above is provided with a high frequency heating coil (2
An eddy current is generated in the cover member (36) due to the penetration of the high-frequency magnetic flux generated by the high-frequency current flowing in 3), which generates a magnetic flux in a direction that cancels the magnetic flux, and the eddy current is generated in the external environment (atmosphere open to the atmosphere (1
(8)) suppresses the generation of high-frequency magnetic flux, and the cover member (3
By grounding (E) 6), the effect of an electrostatic shield can be provided, and the lines of electric force can be prevented from going outside. This is the electromagnetic shielding effect. However, some magnetic flux leaking from the peep window (24) which is not an electric conductor and the pedestal (15) of the asbestos molding material at the bottom is electromagnetically shielded by an envelope not shown. The leakage magnetic flux from the through hole (59) of the insulating terminal board mounting portion, which will be described later, is not a problem because the copper plate shield cover (55) electromagnetically shields it.
The above is the electromagnetic shielding effect of the airtight shielding chamber, which is the main part of the present invention. Returning to FIG. 3, (44) is a vacuum suction hole that penetrates, for example, the upper wall of the cover member (36) and communicates with the heating chamber space (7R), and (25) is an exhaust connected to a vacuum pump. It is a tube. (46) is a vacuum suction hole for preliminary decompression that preliminarily decompresses the airtight shielding room space (47) to a vacuum of, for example, 10 ^-2 Torr, and (48) is an exhaust pipe connected to it. Now, for example, the exhaust system of a direct-coupled oil rotary vacuum pump (P) with an exhaust speed of 20 l / min is branched into two series of valves (49) and (50), the valve (50) is opened and the valve (49) is opened before casting. When operated as closed, the airtight shielding chamber (47) has a gasket (30A) (30B) pedestal (1
5) Suction all the gas released from the sealing member and reach a vacuum pressure of, for example, 10 ^-2 . Next, when the valve (50) is closed and the valve (49) is opened, there is no released gas as described above, and even if there is a slight leakage from the gaskets (30A) and (30B), the airtight shielding chamber is already in the interior. Since it is a high vacuum atmosphere, the heating chamber (7R) with a small capacity reaches a vacuum pressure of 10 ^-2 or 10 ^{-3 in} a very short time. This is the airtightness of the airtight shielding chamber, which is the main part of the present invention. When the metal (M) in the crucible is melted, an inert gas such as argon gas is introduced at about 5 kg / cm ² G through the gas introduction pipe (26). As in the conventional device, the heating chamber (7R) is pressurized. Next, the energizing portion of the high frequency heating coil (23) will be described with reference to FIGS. 2 and 4. The shield cover (55) made of, for example, a copper plate having a good electromagnetic shielding effect, which is tightly coupled to the flat surface portion (54) formed on a part of the peripheral edge of the cover member (36), is an insulating terminal board (56) and, for example, a copper strip high-frequency line. It completely encloses (57) to the outside world and is grounded (E) together with the cover member (36). The insulating terminal board (56) is made of a heat-resistant synthetic resin laminated material and has a gasket (60) so as to seal the penetrating part (59) cut in the flat part (54) of the cover member (36).
The terminal board (56) is airtightly attached to the terminal board (56) by a gasket (62), which is a pair of terminals (61) made of a good conductor. The pair of terminals (61) connect the copper strip line (57) and the heating coil core wire (63),
A flexible tube (64) made of an electrically insulating and heat resistant synthetic resin covering the core wire (63) and a cooling water circulation introducing pipe / extracting pipes (65) (66) are communicatively coupled to each other.

The above is one embodiment of the present invention, but the present invention is not limited to the drawings and the description. For example, the bowl-shaped cover member is not limited to a single metal with high electrical conductivity such as aluminum or copper, but a high-permeability material is placed inside and a material with high electrical conductivity is placed outside, and the outside is grounded. It may be a composite member. Further, even with a device that does not depressurize the inside of the airtight shielding chamber, depressurization of the heating chamber takes some time, but high vacuum can be achieved. The small vacuum pump is not limited to the evacuation speed of 20 l / min, and may be arbitrarily selected and used according to the desired vacuum pressure. Further, the valves (49) and (50) in FIG. 3 are not limited to manual valves, but may be electrically operated valves and incorporated into the sequence automatic control of the casting process. Furthermore, it is not impossible to construct the pedestal part (16) with an electromagnetic shielding material, and if a casting device that does not require a peep window appears, a complete electromagnetic shielding airtight chamber can be created.

(6) Effects Since the present invention is configured as described above, the drawbacks of the conventional high frequency melting / pressurizing type high frequency casting apparatus are eliminated. In other words, the space inside the airtight heating chamber of the cylindrical body with the high-frequency heating coil wound around the outer circumference can be made to a desired high vacuum in a short time by a small-capacity vacuum pump, and casting with excellent anoxic effect can be enhanced. In addition to being efficient, most of the radio frequency electromagnetic waves radiated by the high frequency heating coil are electromagnetically shielded around the heating chamber, and only a small part is electromagnetically shielded in the device surroundings, so that electromagnetic wave-induced noise interference to various external electronic devices, so-called It was possible to provide a device that has no radio interference, is inexpensive, and can cast high quality products.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a vertical sectional view of a casting part of a conventional high frequency casting device, FIG. 2 is a plan view of the casting part of the high frequency casting device according to the present invention, and FIG. 3 is a plan view of FIG. FIG. 4 is a side view including the III-III 'cross section, and FIG. 4 is a side view including the IV-IV' cross section in FIG. (1) …… Convex mold, (2) …… Crucible (M) …… Cast metal, (3) …… Mold cavity (6) …… Heating chamber, (7) …… Cylindrical body (7R) …… Inside the heating chamber, (8) …… Mold base (11) …… Mold lifting mechanism, (16) …… Heating chamber pedestal (18) …… Atmosphere opening part, (23) …… High frequency heating coil ( 25) …… Vacuum suction pipe, (26) …… Pressurized gas inlet pipe (30A) (30B) …… Asbestos gasket (35) …… Airtight shielding chamber, (36) …… Cover cover member (37) …… Peep window holding cylinder (part of cover member) (40) …… Peep window cap (part of cover member) (44) …… Vacuum suction hole inside heating chamber provided in cover member (46) …… For cover member The vacuum suction hole provided inside the airtight shielding chamber, (47) ... the space inside the airtight shielding chamber (48) ... the vacuum suction pipe of (47) above, (49) ... the valve (50) of (25) above …… Valve of (48) above, (P) …… Vacuum pump (55) …… Shield cover, (56) …… Electrically insulated terminal board (57) …… High frequency circuit

Claims (2)

[Claims] 1. A crucible is provided on an upper projecting portion, a convex mold having a mold cavity communicating with the crucible is formed on a base, and the crucible of the projecting portion is housed therein, and a high frequency heating coil is wound around the outer periphery. The rotating body has a rotated tubular body, and the lower end opening portion of the tubular body is airtightly engaged with a pedestal portion having a through hole corresponding to the tubular body. A heating chamber provided with a pressurizing means for introducing a pressure source such as an inert gas, and a mold lifting mechanism for selectively and airtightly pressing the base upper surface of the convex mold to the heating chamber pedestal lower surface, In a device for pouring molten metal in a crucible into a mold cavity, a bowl-shaped cover member made of a material having a large electromagnetic shielding effect and having an inner diameter at least twice the diameter of the high-frequency heating coil is used. With the pedestal part as the bottom, the heating chamber In addition to forming an airtight shielding chamber for airtightly shielding against air and electromagnetic shielding, a pressure reducing and pressurizing means for the space inside the airtight heating chamber is provided via the cover member, and further an electrical insulation provided on the cover member. A high-frequency casting device characterized in that a high-frequency heating coil is energized via a terminal board. 2. The high-frequency casting apparatus according to claim 1, further comprising preliminary depressurizing means for depressurizing the internal space of the airtight shielding chamber formed by the cover member in advance.