JPS63126641A - Structure of casting mold by vacuum molding method - Google Patents

Abstract

PURPOSE:To maintain nearly uniform strength of a casting mold and to effectively prevent abrupt degradation in the mold strength by pouring of a molten method by inserting pipes communicating with the atm. into the sections of the mold where the deterioration in the strength of the mold is liable to arise and opening the other end into a cavity. CONSTITUTION:The pipes 30 having apertures communicating whith the atm. are inserted into the sections 26a of a cope 26 where the degradation in the strength of the casting mold formed by a vacuum molding method is most liable to arise. The other apertures of the pipes 30 are opened into a cavity 23 positioned in the sections 26a where the deterioration in the strength is liable to arise. Such cope 26 and a drag 28 are mated with each other and the atm. pressure is introduced through the pipes 30 into the cavity 23. A large relative pressure difference between the degree of the pressure reduction in the mold 26 and the atm. pressure is assured and the degradation in the strength of the mold 26 is minimized by this mechanism. The presence of the pipes 30 itself has the effect of playing the role of reinforcement in the sections where the pipes are disposed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is directed to a process in which, when a molten metal is poured into a mold obtained by a vacuum molding method, a coating defining a vacuum area within the mold comes into contact with the molten metal. The present invention relates to a mold structure that can effectively prevent a partial decrease in strength of the mold due to disappearance.

BACKGROUND TECHNOLOGY Molding methods for producing molds essential for casting various cast products are broadly divided into manual molding, which is performed manually using a wooden mold, and mechanical molding, which uses a molding machine. Jolt molding method and squeeze molding method are known as the latter mechanized molding method, but in addition to these, there are other molding methods that are comparatively more precise.
The reduced pressure molding method has been suitably put into practical use. This vacuum molding method (also known as the V process) does not use a binder to bind the molding sand, and uses atmospheric pressure to tightly bind the molding sand to maintain and strengthen the mold. The purpose is to ensure that

For example, as shown in FIG. 3(a), a pattern plate 10 having the same uneven external contour as the half-dead part of a product to be manufactured and having a large number of pores 10a is placed at a vacuum node 12. Place it on the open side.

After covering the pattern plate 10 with a highly flexible coating 14 such as vinyl chloride, when the air in the vacuum box 12 is sucked, the coating 14 is applied to the pattern plate 1o through the pores 10a. Adheres to uneven shapes.

On this pattern plate 10, as shown in FIG. 3(b), a frame 18 of a desired shape defining a decompression chamber 16 inside
Place. Inside the frame 18, a plurality of mesh pipes 19 formed by rolling a fine wire mesh into a cylindrical shape are arranged horizontally, and the pipes 19 spatially communicate with the decompression chamber 16 at both open ends thereof. are doing. In this state, as shown in FIG. 3(c), the space defined by the uneven surface of the pattern plate 10 inside the frame 18 is filled with molding sand 20 such as silica sand and vibration is applied. , the molding sand 20 is smoothed onto the coating 14 in close contact with the pattern plate 10 into the shape of the semi-dead part of the product to be cast. Next, another coating 22 is commonly applied to the upper surface of the molding sand 20 and the upper edge of the frame body 18 . Note that the upper part of the illustrated sprue 21 is depressed so that a pool 24 can be formed.

Next, as shown in FIG. 3(d), the pattern plate 10
At the same time, the pressure is reduced and the air is returned to normal pressure in the f411i12, and the pressure reduction chamber 16 of the frame 18 on the side constituting the upper mold 26 is connected to a vacuum source to forcibly sweep the air. When the frame 18 is lifted in this state, the pattern plate 10 is detached, and the coating 22 located on the back side of the mold 26 that is in contact with the atmosphere is removed.
Atmospheric pressure acts on the coating 14 located on the side of the divided cavity 23 forming the casting. Therefore, the internal mold 2
6 is kept under reduced pressure, and the sand grains adhere firmly to each other to maintain the fixed shape of the mold.

The lower mold 28 is manufactured in the same manner, and as shown in FIG. 3(e), both the upper and lower molds 26.2 are
By combining 8, a so-called vacuum molding mold is manufactured.

Problems to be Solved by the Invention With the vacuum molding mold described above, the mold can be easily manufactured without using a binder that tends to cause various troubles during casting, and the cast product has a smooth casting surface. There are advantages such as:

By the way, the strength of a mold obtained by vacuum molding is determined by the reduced pressure (approximately 300 to 400 mmHg) applied to the mold.
It depends on the pressure difference between the pressure and the atmospheric pressure, and the larger the absolute value between the two pressures, the higher the strength can be obtained. When high-temperature molten metal is injected into the mold, which is kept under reduced pressure, through the sprue, it comes into contact with the coating that defines the cavity, causing it to disappear instantly. . As a result, the pressure difference that holds the mold in its regular shape decreases, and this has the disadvantage of causing deformation in the parts of the mold that are most likely to lose strength due to the gas pressure and hot water pressure generated from the molten metal and the mold. be.

It has also been pointed out that even before the coating disappears, the foundry sand has intergranular resistance, so the greater the distance from the suction surface of the mesh pipe, the lower the strength of the mold part. In particular, a vacuum source with a relatively small capacity is sufficient as static conditions for holding a mold in a fixed shape in a vacuum molding method.

After the coating disappears due to casting, a large vacuum suction capacity is required. In such a case, even if the capacity of the vacuum pump is increased unnecessarily, it is not necessarily effective due to the presence of the resistance between the sand grains, and there are drawbacks such as increased equipment costs and running costs.

Purpose of the Invention The present invention has been proposed in order to suitably solve the above-mentioned drawbacks inherent in the mold structure produced by the vacuum molding method. It is an object of the present invention to provide a mold structure that can effectively prevent mold strength from rapidly decreasing due to dripping and, moreover, the disappearance of a coating due to pouring of molten metal.

Means for Solving the Problems In order to overcome the above-mentioned problems and achieve the intended purpose, the present invention provides a frame body provided with a decompression chamber connected to a vacuum suction source, and a mesh pipe communicating with the decompression chamber. The mesh pipe is sandwiched between the mesh pipe and the back side in contact with the atmosphere and the dividing surface defining the cavity are respectively covered with a film, and the molding sand particles filled inside the frame are brought into close contact with each other by the reduced pressure of the reduced pressure chamber, In the vacuum molding mold in which the dividing surface maintains the required cavity shape, a pipe whose one opening communicates with the atmosphere is inserted into the part of the mold where strength deterioration is most likely to occur, and the other opening of this pipe is The present invention is characterized in that the opening is configured to open into a cavity located at a portion where strength deterioration is likely to occur.

Example Next, regarding the mold structure by the reduced pressure molding method according to the present invention,
Preferred embodiments will be described below with reference to the accompanying drawings. Note that the same members disclosed in the mold structure of FIG. 3 are indicated by the same reference numerals, and detailed explanation thereof will be omitted.

As shown in FIG. 1, in the mold structure according to this embodiment, the strength of the mold 26 is most likely to deteriorate at a portion 26a (usually the portion furthest from the mesh pipe 19 or the portion having a complicated shape and becoming thinner). ), a pipe 30 whose one opening communicates with the atmosphere is inserted, and the other opening of this pipe 30 is opened into the cavity 23 located in the area where strength deterioration is likely to occur. . This pipe 30 is made of a metal that can withstand high temperatures during pouring of molten metal, and the number of pipes provided is appropriately determined depending on the number of parts where strength is likely to deteriorate.

In order to stably arrange this pipe 30 in an upright state within the mold 26, for example, the means shown in FIG. 2 is suitably employed. That is, the through holes 32 are bored in the valley portions of the pattern plate 10 and in the portions of the mold where strength deterioration is most likely to occur when the mold is filled with molding sand and manufactured by vacuum molding. The coating 1 is inserted into this through hole 32.
4, and a long bolt 34 is inserted from below. The pipe 30 is inserted into the bolt 34, the upper end of the bolt 34 extends upward from the upper end opening of the pipe 30, and the bolt 34 is tightened with a nut 36, so that the pipe 30 is attached to the pattern plate. 1
o is securely fixed upright. In this state, the frame 18
After filling the internal space defined by the pattern plate 10 with molding sand and performing vacuum molding, the nut 36 is
When the bolts 34 are loosened and removed, the bolts 34 are separated from the pipe 30, and only the pipe 3o remains in the mold 26. At this time, the upper coating 22 is torn at a portion corresponding to the upper end opening of the pipe 3o, so that the pipe 30 communicates with the atmosphere.

The upper mold 26 and lower mold 28 obtained in this way are
When matched as shown in FIG. 1, atmospheric pressure is introduced into the cavity 23 through the pipe 30. In another embodiment, for example, a Y-shaped branch pipe is used as the pipe 30 that communicates with atmospheric pressure, and this branch pipe is placed at a plurality of locations where the strength of the mold 26 is likely to deteriorate, and each pipe end is connected to the cavity 23. It may be made to open inside.

According to this embodiment, even if the coating starts to disappear due to pouring of the molten metal, the pipe 30 communicating with the atmosphere is connected to the cavity 23 at the location 26a where the strength of the mold is likely to deteriorate.
Since the mold 26 is opened to introduce atmospheric pressure into the mold 26, a large relative pressure difference between the degree of depressurization inside the mold 26 and the atmospheric pressure can be ensured, and therefore, a decrease in the strength of the mold 26 can be minimized. Can be suppressed. In addition, the existence of pipe 3o itself
It also serves as reinforcement at the location where it is installed.

As described in detail, according to the present invention, the pipe that communicates with atmospheric pressure faces the part of the mold where the strength is most likely to deteriorate and is opened into the cavity, so that the degree of depressurization at this part can be reduced. It is possible to maintain a sufficiently large pressure difference with atmospheric pressure, and f
) Static strength of the mold is maintained, and even if the coating disappears at the start of casting, no sudden pressure drop occurs at that location. Furthermore, the pipe also functions as a reinforcing member, and there is no need to select a vacuum source with a large capacity to connect to the decompression chamber, which has the advantage of economically suppressing running costs.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing a preferred embodiment of the mold structure by the vacuum molding method according to the present invention, and Fig. 2 is a cross-sectional view showing a preferred embodiment of the mold structure by the vacuum molding method according to the present invention. FIGS. 3(a) to 3(e) are cross-sectional views showing means for stably arranging the mold in this state, and FIGS. 3(a) to 3(e) are explanatory diagrams showing the chronological steps in manufacturing a mold by the vacuum molding method. 10... Pattern plate 12... Decompression box 14...
・Coating 16... Decompression chamber 18... Frame
19...Mesh pipe 20...Casting sand 21...Gate 22...Coating
23...Divided cavity 24...Hot water pool
26... Upper mold 28... Lower mold 30...
・Pipe 32...Through hole 34...Bolt 36...Nut patent applicant Daido Steel Co., Ltd. FIG,
1 IG 2 '10 FIG, 3 (No rear drawing)

Claims (1)

[Scope of Claims] A mesh pipe communicating with the decompression chamber is provided on a frame body that includes a decompression chamber connected to a vacuum suction source, and a split surface that defines a cavity with the back side that is in contact with the atmosphere with the mesh pipe interposed therebetween. and are each covered with a film, and particles of molding sand filled inside the frame are brought into close contact with each other by the reduced pressure of the reduced pressure chamber, so that the divided surface maintains a desired cavity shape. A pipe with one opening communicating with the atmosphere is inserted into the part of the mold where strength deterioration is most likely to occur, and the other opening of this pipe is opened into a cavity located at the part where strength deterioration is most likely to occur. A mold structure made by a vacuum molding method, characterized by being configured as follows.