JPH03216258A - Vacuum casting apparatus - Google Patents

Abstract

PURPOSE:To simplify the vacuum casting apparatus and to reduce the equipment cost by tightly covering sand mold with a sand mold cover, arranging molten metal pouring part at position corresponding to a sprue in the sand mold cover, further opening gas exhaust hole at position sufficiently being apart from the sprue and connecting gas exhaust passage. CONSTITUTION:After tightly covering the sand mold 11 with the resin film-made sand mold cover 12, the pressure in the sand mold cover 12 is reduced with a vacuum pump through the gas exhaust passage connected with the gas exhaust holes 12c opened at one or more positions in the sand mold cover 12, and the molten metal 18 is poured into the sand mold 11 through the sprue 11c under reduced pressure condition to execute the reduced pressure. Therefore, a reduced pressure box comes to be unnecessary and the pressure reducing equipment can be simplified and by utilizing the existing casting equipment, the equipment cost is reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a vacuum casting apparatus suitable for use in casting thin-walled castings using a sand mold.

(Prior art) When casting thin-walled castings using a sand mold, vacuum casting is sometimes performed in which molten metal is poured into the sand mold while the inside of the sand mold is depressurized to prevent poor circulation of the casting. To,
Conventionally, as shown in FIG. 3, a sand mold 1 is airtightly covered with a vacuum box 2 that is larger than the sand mold 1, and an exhaust port 2a of the vacuum box 2 is closed.
A vacuum pump (not shown) is connected to the vacuum pump, and the inside of the sand mold 1 is depressurized by evacuating the air as shown by arrow 8 in the figure and decompressing the entire inside of the decompression box 2. When pouring the molten metal 3, since the decompression box 2 is made removable, it is difficult to pour the molten metal from above.
Compressed air is supplied as shown by arrow B in the figure into a melting furnace 4 provided in the floor on which the sand mold 1 is placed, and from the melting furnace 4, the sand mold l is
This was carried out by pumping the molten metal 3 through a sprue 1a that opened on the lower surface of the molten metal.

(Problems to be Solved by the Invention) However, the conventional vacuum casting apparatus described above requires the installation of new large-scale casting equipment, resulting in extremely high equipment costs, and the installation of the sand mold on the floor. It takes time to maintain the airtightness of the decompression box 2, and the volume to be depressurized is large and it takes time to depressurize, resulting in low productivity.Furthermore, the sand mold I has a sprue 1a and a runner arranged differently than usual. Since it has a mold structure, there are problems in that existing mold models cannot be used and the cost of forming the sand mold increases.

The present invention provides a vacuum casting apparatus that advantageously solves these problems.

(Means for Solving the Problems) The vacuum casting apparatus of the present invention airtightly covers the periphery of the sand mold with a sand mold cover made of a resin film, and also has a pouring section of the sand mold cover at a position corresponding to the sprue of the sand mold. The sand mold cover is further provided with an exhaust port at one or more positions sufficiently spaced from the sprue, and an exhaust passage is connected to the exhaust port of the sand mold cover. It is. Further, in the apparatus of the present invention, a filter formed by hardening sand may be inserted between the exhaust port and the exhaust passage so as to cover the exhaust port.

(Function) In such a device, after the sand mold is airtightly covered with a sand mold cover made of resin film, the sand mold is covered with a sand mold cover made of a resin film, and then a vacuum pump is used to run the sand mold through an exhaust passage connected to one or more exhaust ports provided in the sand mold cover. Depressurize the inside of the sand mold cover and therefore the sand mold,
In this reduced pressure state, the pouring section is opened and the molten metal is poured from there into the sand mold through the sprue to perform vacuum casting.

Therefore, this device not only prevents poor water circulation when casting thin-walled castings, but also eliminates the need for a vacuum box because airtightness is achieved simply by covering the sand mold with a sand mold cover made of resin film. Therefore, the decompression equipment can be made extremely simple. Moreover, if the resin film constituting the sand mold cover is made transparent or closely attached to the surface of the sand mold, the sand mold can be used even if it has a normal mold structure with a sprue on the top of the sand mold. Since the pouring part can be placed precisely at the position corresponding to the sprue, there is no need for large-scale pouring equipment that pumps the molten metal from the melting furnace installed in the floor where the sand mold is placed. In addition, equipment costs can be significantly reduced by reusing
This eliminates the need for a decompression box, making it easier to ensure airtightness and pouring, and the time required for depressurization is shortened, making it possible to significantly increase productivity.Furthermore, it is possible to use a regular mold structure. Therefore, existing mold models etc. can be used to form sand molds at low cost.

In addition, when air is released from the exhaust port provided in a part of the sand mold cover, if the exhaust port is covered with a filter formed by solidifying sand and the air is exhausted from the gap between the sand in the filter,
Even if the molten metal leaks from the sand mold part near the exhaust port, for example, the gap between the mold dividing surfaces, the molten metal can be stopped by the filter, effectively preventing disasters caused by leakage, so you can remove the sand mold from any position. The internal pressure can be reduced, further increasing the effect of preventing poor water circulation.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a longitudinal sectional view showing one embodiment of the vacuum casting apparatus of the present invention, in which 11 is a sand mold, 12 is a sand mold cover, and l
3 represents a table, 14 represents a sprue, and 15 represents an exhaust adapter.

The sand mold 11 here is for casting an exhaust manifold for an automobile engine, which is a thin-walled product, and has a cavity 11b defined in the same shape as the exhaust manifold using a core 11a, and a mold. It has a sprue 11c for hot water, a runner lid that communicates them, and a gas vent lie.

Here, the periphery of the sand mold 1l is airtightly covered with a sand mold cover 12 as shown in FIG.

That is, as shown in FIG. 2(a), first, in this embodiment, a resin film, which is transparent vinyl, is pulled out from a resin film roll I7, spread on a table L3, and cut to an appropriate length. Then, as shown by solid lines and imaginary lines in FIG. 2(b), the sand mold 11 that has been conveyed above the table 13 is lowered as shown by the arrow and placed on the lower cover 12a. , then Fig. 2 (c
), the lower cover 12a is made of the same material as the lower cover 12a, which is previously formed into a box shape with an outer peripheral flange portion to fit into the sand mold 11, and is transported above the table 13 with an exhaust port 12c opened at one place. The upper cover 12b made of transparent vinyl resin film is lowered as shown by the arrow, and fitted into the sand mold 11 in such a direction that the exhaust port 12c is sufficiently spaced from the sprue 11c. As shown in the figure, the sandwich plate 13b heated by the heater 13a in the table l3 is raised by the cylinder 13c in the table 13, and the sandwich plate 13b and the presser plate 13d fixed above the table l3 are lowered. cover 1
The sand mold cover 12 that airtightly covers the sand mold 11 is formed by supporting the peripheral portion of the sand mold 2a and the outer peripheral flange portion of the upper cover 12b and fusing these parts to each other.

After that, as shown in FIG. 2(e), the sand mold cover 12
A sprue 14 as a pouring part is attached to a position corresponding to the sprue 11c of the sand mold 11, and an exhaust adapter 15 is attached to the position of the exhaust port 12c of the sand mold cover 12.

Here, the sprue l4 is attached by arranging its hot water supply port 14a in alignment with the sprue port 11c visible through the sand mold cover 12, as shown in FIG.
This is done by gluing the sprue l4 to the sand mold cover 12. Thereby, displacement of the sprue 14 can be reliably prevented.

At this stage, the hole is still open in the portion of the sand mold cover 12 between the hot water inlet 14a and the sprue 11c, so that the inside of the sand mold cover 12 can be easily evacuated.

On the other hand, the exhaust adapter 15 includes a filter 15a, a filter receiver 15b that fits and covers the filter 15a, and a filter receiver 15b, as shown in FIG.
The filter 15a consists of an exhaust tube 15c serving as an exhaust passage, one end of which communicates with the inside of the filter 15b. Receiver 15b and exhaust tube 15
c is integrally formed of flexible resin, and the exhaust adapter 15 is attached to the sand mold cover 1.
A filter 15a arranged to cover the exhaust port 12c of No. 2
After adhering to the sand mold cover 12 with adhesive 16, the other end of the exhaust tube 15c is connected to a vacuum pump (not shown), and the vacuum pump reduces the pressure inside the exhaust tube 15c and, in turn, the filter receiver 15b.
This is done by fitting the filter 15a into the filter 15a.

By installing the exhaust adapter 15 above, the sand mold cover 1
The inside of the sand mold 11 is also evacuated and the pressure is reduced through the filter 15a, and the pressure inside the sand mold 11 is also reduced. Here, since the exhaust port 12c is sufficiently spaced from the sprue 11c, the degree of pressure reduction is high at the end of the cavity 11b, which is close to the gas vent lie and far from the runner lid.

Thereafter, the hot water supply port 14a of the sprue 14 is closed with the stopper 17, and molten metal, such as cast steel, is supplied into the sprue 14. When the molten metal reaches a predetermined amount as shown by the imaginary line in FIG. 1, the stopper 17 is closed. Remove, sand mold cover 12, hot water supply port 1
By melting the part between the sprue 4a and the sprue 11c with the heat of the molten metal and forming a hole 12d there, the molten metal 18 is poured from the sprue 14 into the sand mold 11 as shown by the solid line in FIG. Then, pass the sprue 11c and the runner lid into the cavity 1.
1b.

With such pouring, vacuum casting can be performed in the sand mold 1L.

Therefore, according to the vacuum casting apparatus of this embodiment, it is possible not only to prevent poor water circulation when casting a thin-walled exhaust manifold, but also to prevent the sand mold 11 from being caused by the sand mold cover made of resin film.
2, airtightness is obtained by simply covering the sand mold cover 12, so there is no need to provide a decompression box like in conventional equipment, and the decompression equipment can be made extremely simple. Since the is made transparent, even if a sand mold 11 with a normal mold structure in which a sprue is provided on the top surface of the sand mold is used, the sprue 14 can be provided accurately at the position corresponding to the sprue 11c of the sand mold 1l, so that it is possible to install the sprue 14 precisely at the position corresponding to the sprue 11c of the sand mold 1l. It is no longer necessary to install large-scale pouring equipment to pump molten metal from a melting furnace installed in the floor where the sand mold is placed, and existing casting equipment can be used to significantly reduce equipment costs. This eliminates the need for a decompression box, making it easier to ensure airtightness and pouring, and the time required for depressurization is shortened, greatly increasing productivity.
Since the sand mold 11 having a normal mold structure can be used, an existing mold model etc. can be used and the sand mold can be formed at low cost.

In this embodiment, when exhausting air from the exhaust port 12c provided in a part of the sand mold cover 12, the exhaust port 12c is covered with a filter 15a formed by solidifying sand, and the exhaust is exhausted from the gap between the sand of the filter 15a. Therefore, even if molten metal leaks from the part of the sand mold 11 near the exhaust port 12c, the molten metal can be stopped by the filter 15a, and disasters caused by molten metal leakage can be effectively prevented.
The pressure inside the sand mold 11 can be reduced from a position close to the gas vent hole 11e, and the effect of preventing poor water circulation can be further enhanced.

Although the above description has been made based on the illustrated example, the present invention is not limited to the above-mentioned example. For example, the exhaust port may be provided at multiple locations on the sand mold cover, and the resin film constituting the sand mold cover may be It may be bag-shaped or simply flat instead of box-shaped.

Furthermore, the resin film may be used as a film of other types of thermoplastic resin used in the molding process, etc. In this case, even if the resin film is opaque, the sand mold cover is exposed to the surface of the sand mold by the reduced pressure inside the sand mold cover. Since they are in close contact, the pouring part can be easily installed. Further, the pouring part may be provided by forming a recess around the sprue of the sand mold to serve as a pool, and recessing the resin film of the sand mold cover to follow the recess, instead of attaching a sprue.

(Effects of the Invention) Thus, according to the vacuum casting apparatus of the present invention, a vacuum box is not required and the vacuum equipment can be made extremely simple.Moreover, the molten metal can be removed from the melting furnace provided in the floor where the sand mold is placed. This eliminates the need for large-scale pouring equipment to pump out molten metal, making it possible to reuse existing casting equipment and significantly reducing equipment costs.In addition, it eliminates the need for a decompression box, making it easier to ensure airtightness. Since the pouring work becomes easier and the time required for depressurization is shortened, productivity can be greatly increased.Furthermore, since the mold structure can be made into a normal mold structure, existing mold models can be used, resulting in lower costs. Sand molds can also be formed at a cost.

In addition, when exhausting air from the exhaust port provided in a part of the sand mold cover, if you cover the exhaust port with a filter formed by solidifying sand and exhaust the air from the gap between the sand in the filter,
Since the occurrence of disasters due to hot water leakage can be effectively prevented, the pressure inside the sand mold can be reduced from any position, and the effect of preventing poor hot water circulation can be further enhanced.

[Brief explanation of drawings]

Fig. 1 is a longitudinal sectional view showing an embodiment of the vacuum casting apparatus of the present invention, Figs. 2(a) to (e) are explanatory diagrams showing the manufacturing process of the apparatus of the above embodiment, and Fig. 3 is a conventional apparatus. FIG. 11 Sand mold 11c - Sprue 12 - Sand mold cover 12c - Exhaust port 14 - Sprue 15
a- Filter 15c - Exhaust tube Figure 2 (a)

Claims (1)

[Claims] 1. The sand mold (11) is airtightly covered with a sand mold cover (12) made of resin film, and a pouring part is provided in the sand mold cover at a position corresponding to the sprue (11c) of the sand mold. (14
), and exhaust ports (12
c) and insert an exhaust passage (
15c) is connected to the vacuum casting device. 2. The vacuum casting apparatus according to claim 1, wherein a filter (15a) formed by hardening sand is inserted between the exhaust port and the exhaust passage so as to cover the exhaust port. .