JPH0645054B2 - Mold structure by vacuum molding method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for injecting a molten metal into a mold obtained by a reduced pressure molding method, in which a coating forming a reduced pressure region in the mold comes into contact with the molten metal. The present invention relates to a template structure capable of effectively preventing a partial decrease in strength of the template due to disappearance.

2. Description of the Related Art Molding methods for producing molds, which are indispensable for casting various cast products, are roughly classified into manual molding using a wooden mold and mechanical molding using a molding machine. For the latter mechanized molding, the Jolt molding method, the squeeze molding method, and the like are known. In addition to these methods, the reduced-pressure molding method is preferably put into practical use as a relatively new molding method. This reduced pressure molding method (also called V process) does not use a binder to bond the mold sand, but tightly bonds the molding sand by utilizing the atmospheric pressure to maintain the strength and strength of the mold as a mold. To secure the.

For example, as shown in FIG. 3 (a), the decompression box 12 is provided with a pattern plate 10 having the same outer contour of unevenness as the half part of the product to be cast and having a large number of pores 10 a. Place it on the opening side of. And the pattern plate 1
0 is covered with a flexible coating 14 such as vinyl chloride, and the air in the decompression box 12 is sucked into the pores 10.
The coating film 14 adheres to the pattern plate 10 via a, corresponding to the uneven shape.

On the pattern plate 10, as shown in FIG. 3 (b), a frame body 18 having a predetermined shape, which defines a decompression chamber 16 inside, is placed. In the frame 18, a plurality of mesh pipes 19 formed by rolling a fine mesh into a cylindrical shape are horizontally arranged, and the pipes 19 are spatially arranged in the decompression chamber 16 at both open ends thereof. It is in communication. In this state, the third
As shown in FIG. (C), when the molding sand 20 such as silica sand is filled into the space defined by the uneven surface of the pattern plate 10 inside the frame 18 and vibration is applied, the molding sand 20
Is on the coating 14 adhered to the pattern plate 10,
It is shaped into the shape of the half of the product to be cast. Then, the upper surface of the molding sand 20 and the upper edge of the frame 18 are covered with another coating 22 in common. The upper part of the illustrated gate 21 is
Make a dent to make a basin 24.

Next, as shown in FIG. 3 (d), while returning air to the normal pressure by returning the air into the decompression box 12 of the pattern plate 10,
The decompression chamber 16 of the frame 18 on the side forming the upper mold 26 is connected to a vacuum source to forcibly sweep air. In this state, the frame 18
When lifted, the pattern plate 10 is released and the mold 26
The atmospheric pressure acts on the coating film 22 located on the back surface side in contact with the atmosphere and on the coating film 14 located on the divided cavity 23 side forming the casting. Therefore, the internal mold 26 is kept in a depressurized state, and the sand grains are firmly adhered to each other to hold the standard mold.

The lower mold 28 is manufactured in the same manner, and as shown in FIG. 3 (e), the upper and lower molds 26, 28 are kept while maintaining the reduced pressure state.
A so-called reduced-pressure molding mold is manufactured by combining the above.

Problems to be Solved by the Invention With the above-described reduced-pressure molding mold, it is possible to easily manufacture the mold without using a binder that easily causes various troubles during casting, and a smooth casting surface is obtained in the casting product. There are advantages such as being obtained.

By the way, the strength of the mold obtained by the reduced pressure molding method depends on the pressure difference between the pressure reduction force (about 300 to 400 mmHg) applied to the mold and the atmospheric pressure. The higher the absolute value between the two pressures, the higher the strength. To be Then, when the high-temperature molten metal is injected into the mold thus held in the depressurized state through the sprue, the molten metal comes into contact with the coating film that defines the cavity and instantaneously disappears it. . Due to this, the pressure difference holding the mold in a fixed form is lowered, and therefore, due to the generated gas pressure or the molten metal pressure from the molten metal or the mold, there is a drawback that it causes deformation in a portion of the mold which is most likely to undergo strength reduction. is there.

Further, even before the disappearance of the coating, since the casting sand has resistance between the sand grains, the greater the distance from the suction surface of the mesh pipe, the weaker the strength of the mold part is pointed out. . In particular, a vacuum source having a relatively small capacity is sufficient as a static condition for holding the mold by the vacuum molding method in a fixed shape, but a large vacuum suction capacity is required after the coating film disappears by casting. In such a case, even if the capacity of the vacuum pump is increased, it is not always effective due to the existence of the above-mentioned inter-grain resistance, and there are drawbacks such as increased equipment cost and running cost.

SUMMARY OF THE INVENTION The present invention has been proposed in order to suitably solve the above-mentioned drawbacks inherent in the mold structure by the reduced pressure molding method, and the strength of the mold is kept substantially uniform. It is an object of the present invention to provide a mold structure capable of effectively preventing the mold strength from rapidly decreasing even when the film is dripped and the coating film disappears due to the injection of the molten metal.

Means for Solving the Problems In order to overcome the above problems and achieve an intended object, the present invention provides a frame body having a decompression chamber connected to a vacuum suction source, and a mesh pipe communicating with the decompression chamber. Each of the mesh pipes is sandwiched between the back side which is in contact with the atmosphere and the dividing surface which defines the cavity, and each is covered with a film, so that the particles of the foundry sand filled inside the frame are brought into close contact with each other by decompressing the decompression chamber Then, in the pressure-reducing molding mold that is configured to hold the required cavity shape on the dividing surface, a pipe having one opening communicating with the atmosphere is inserted into a portion of the mold where deterioration of strength is most likely to occur. It is characterized in that the other opening is configured to be opened in the cavity located at the portion where the strength deterioration easily occurs.

Example Next, regarding the mold structure by the reduced pressure molding method according to the present invention,
A preferred embodiment will be described below with reference to the accompanying drawings. The same members disclosed in the mold structure of FIG. 3 are designated by the same reference numerals, and detailed description thereof will be omitted.

As shown in FIG. 1, in the mold structure according to the present embodiment, the part 26a of the mold 26 where the strength is most likely to deteriorate (the part that is most distant from the normal mesh pipe 19 or the part that becomes thin in a complicated shape is In the above, the pipe 30 having one opening communicating with the atmosphere is inserted, and the other opening of the pipe 30 is opened into the cavity 23 located in the portion where the strength deterioration easily occurs. . The pipe 30 is made of a metal that withstands a high temperature when the molten metal is cast, and the number of the pipes 30 to be provided is appropriately determined according to the number of sites where the strength is likely to decrease.

In order to stably arrange the pipe 30 in the mold 26 in an upright state, as an example, the means shown in FIG. 2 is preferably adopted. That is, a through hole 32 is formed in a portion which becomes a valley portion of the pattern plate 10 and which is a portion which is most likely to be deteriorated in strength when a casting sand is filled and a casting mold is manufactured by vacuum molding. The coating 1 is provided in the through hole 32.
4, the long-sized bolt 34 is inserted from below. The pipe 30 is inserted through the bolt 34, the upper end portion of the bolt 34 is extended upward from the upper end opening portion of the pipe 30, and the bolt 34 is tightened by a nut 36. 1
It is securely fixed upright to zero. In this state, the frame 18
After the casting sand is filled in the internal space defined by the pattern plate 10 and the pressure reduction molding, the nut 36 is removed.
When the bolt is loosened and removed, the bolt 34 is detached from the pipe 30, and only the pipe 30 remains in the mold 26. At this time, the upper coating film 22 is torn at the portion corresponding to the upper end opening of the pipe 30, so that the pipe 30 communicates with the atmosphere.

The upper mold 26 and the lower mold 28 thus obtained are
If they are matched as shown in FIG. 1, atmospheric pressure is introduced into the cavity 23 through the pipe 30. As another embodiment, for example, a Y-shaped branch pipe is used as the pipe 30 communicating with the atmospheric pressure, and the pipe is located at a plurality of locations where the strength deterioration of the mold 26 is likely to occur, and the respective pipe ends are formed in the cavity 23. You may make it open inside.

According to the present embodiment, even if the coating film begins to disappear due to the casting of the molten metal, the pipe 30 communicating with the atmosphere described above is provided in the cavity 23 at the portion 26a where the strength of the mold is likely to deteriorate.
Since the atmospheric pressure is introduced into the mold 26 by opening the inside, it is possible to secure a large relative pressure difference between the degree of pressure reduction in the mold 26 and the atmospheric pressure, and thus to minimize the strength decrease of the mold 26. Can be suppressed. Also, the existence of the pipe 30 itself
It also plays a role of reinforcement at the installation site.

EFFECTS OF THE INVENTION As described above, according to the present invention, since the pipe communicating with the atmospheric pressure is made to face the portion of the mold where the strength is most likely to decrease and the pipe is opened in the cavity, the degree of pressure reduction at this portion is Can maintain a sufficiently large pressure difference from atmospheric pressure,
The static strength of the mold is maintained, and even if the coating film disappears due to the start of casting, a rapid pressure drop does not occur at that site. Further, the pipe also functions as a reinforcing member, and it is not necessary to select a vacuum source having a large capacity as the vacuum source connected to the decompression chamber, and there is an advantage that the running cost can be economically suppressed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a preferred embodiment of a mold structure by the vacuum molding method according to the present invention, and FIG. 2 is a state in which a pipe is erected in the mold when carrying out the mold structure by the vacuum molding method according to the present invention. 3 is a cross-sectional view showing a means for stably arranging at
(a)-(e) is explanatory drawing which shows the process over time at the time of manufacturing a casting_mold | template by a pressure reduction molding method. 10 ... Pattern plate, 12 ... Decompression box 14 ... Coating, 16 ... Decompression chamber 18 ... Frame, 19 ... Mesh pipe 20 ... Moulding sand, 21 ... Gate 22 ... Coating, 23 ... Divided cavities 24 …… Mold pool, 26 …… Upper mold 28 …… Lower mold, 30 …… Pipe 32 …… Through hole, 34 …… Bolt 36 …… Nut

Claims (1)

[Claims] 1. A frame provided with a decompression chamber connected to a vacuum suction source is provided with a mesh pipe communicating with the decompression chamber, and a back face side which is in contact with the atmosphere with the mesh pipe interposed therebetween and a dividing surface which defines a cavity. In a reduced pressure molding mold in which the particles of the foundry sand filled in the inside of the frame are brought into close contact with each other by decompression of the decompression chamber so as to maintain the required cavity shape on the divided surfaces, The pipe whose one opening communicates with the atmosphere is inserted into the part where the strength deterioration is most likely to occur, and the other opening part of this pipe is opened in the cavity located in the part where the strength deterioration is likely to occur. A mold structure by a reduced pressure molding method characterized by being configured.