JPH0976047A - Method and device for molding core - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fill the casting sand at a uniform and high density even in a core of complicate shape by splitting the casting sand for molding the core into two parts, and rapidly introducing air a several times both from the top of the casting sand which is first charged and of the top of the casting sand to be charged next. SOLUTION: The total weight of the casting sand 2 necessary for molding a core mold at least into two parts by setting the time, and the first amount to be charged and the second amount to be charged are set respectively. In the case of a large core or a core of complicate shape, the number of split is increased. The first amount to be charged is directly dropped into a core cavity 7 by a belt feeder 3, and a gate 5 is closed and the air is evacuated until the desired degree of vacuum is obtained in the core cavity 7. Then, the compressed air is introduced into the core cavity 7 in the evacuated condition at the prescribed pressure increasing speed. The second amount to be charged is successively charged to achieve the similar evacuation and pressurization, and the core mold is made and taken out. The casting sand can be filled at the uniform and high density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for molding a core using air pressure.

[0002]

2. Description of the Related Art Conventionally, there have been proposed a number of methods such as blowing and suction filling for molding a core by filling a molding cavity with molding sand.

[0003]

However, many cores have complicated shapes, and a method for efficiently molding the cores by filling foundry cavities with molding sand is desired.

[0004]

[Object] It is an object of the present invention to propose a method and apparatus for efficiently molding a core by filling the core cavity with molding sand even if the core has a complicated shape.

[0005]

In order to achieve the above object, a core molding method according to the present invention is a core molding method in which a molding sand for molding a core mold is filled in a core cavity to mold the core. In, the step of measuring the first amount of the casting sand obtained by dividing the total weight of the casting sand necessary for molding the core mold into at least two and feeding it into the core cavity 7,
Air is boosted multiple times from above the input casting sand 30 to 50
The step of rapidly introducing at 0 kg / cm ² / sec;
The balance of the molding sand of the second charging amount is additionally charged into the core cavity, and air is boosted several times from above the core cavity.
It is characterized in that the step of rapidly introducing at kg / cm ² / sec is repeated once or more.

The present invention has been made by intensively examining the process of filling foundry sand with air. First, the reason why the molding sand is divided and put into the core cavity and then air is introduced a plurality of times will be described. The first dose is charged into the core cavity. At this time, the foundry sand closes the space between the air inlet and the core cavity. Then, the first rapid introduction of air into the molding sand causes the sand to move laterally to release the closure between the air introduction port and the core cavity. FIG.
[Fig. 3] is a schematic view showing a state at this time. In FIG. 1, the cast molding sand is moved laterally or upward into the cavity depression by the air introduced from above (see arrow). Most of the air introduced from above the foundry sand flows in that direction in proportion to the size of the cavity volume (cross-sectional area). Then, by introducing air, the molding sand is compressed toward the direction in which the volume of the core cavity is large. Therefore, the surface shape of the foundry sand is almost perpendicular to the air flow, and the entire surface has a curved surface as shown in FIG. Then, air is introduced again. By the second rapid introduction of air, the energy of the air acts on the molding sand, and the molding sand is filled and moved to the side and above the core cavity. Therefore, in the case of the present invention, the filling and moving movement of the molding sand in the lateral direction and the upward direction becomes possible.

The filling process of the present invention can be explained as follows. In FIG. 2, as shown by, a first charging amount is charged into the core cavity. At this time, the foundry sand closes the space between the air inlet and the core cavity. The foundry sand is moved laterally by the rapid introduction of air as shown in FIG. Then, air is introduced again to make the packing dense. Then,
As shown in (3), the molding sand is charged again to close the space between the air inlet and the core cavity. The molding sand is filled by moving the molding sand to the side and above the core cavity by rapid air introduction as shown in FIG. Further, air is introduced again to make the packing dense. The casting sand is put in as shown in to introduce air, and the filling is completed as a whole in.

The reason why the molding sand used for core molding is divided into the core cavities will be described. A casting sand hanging phenomenon occurs in a complicated portion of the core cavity, and this phenomenon is more likely to occur as more casting sand is charged at one time and the height of the casting sand is higher. Therefore, the amount of foundry sand is reduced.

[0009] As described above, the casting sand is not charged in a large amount at one time, but the thickness of the casting sand layer is set to 2 to 10 c for small articles.
In the case of m and large ones, the filling property is improved by putting them in layers of 5 to 30 cm and compressing them. This kind of idea can be compared to casting molding sand little by little and molding with an air hammer.

[0010]

Embodiment 1 of the present invention will be described in detail below with reference to the drawings. In FIG. 3, the upper hopper-1 is provided with a belt feeder 3 which also functions as a molding sand measuring means 3a for measuring the molding sand 2 and a molding sand charging means 3b, and the first charging amount by setting the time. The first input amount and the second input amount that is the second input amount can be set. Below the running end 3c of the belt feeder 3,
A casting sand feeding port 4 is provided, an openable gate 5 is provided at the casting sand feeding port 4, and an introducing pipe 6 and the introducing pipe 6 which are provided in communication with a lower portion of the casting sand feeding port 4 It is possible to seal the core cavity 7 that is communicated via the. Also,
The core cavity 7 is defined by a core box 8, which is mounted on a vertically movable table 9. Further, an air suction pipe 10 is provided in the middle of the introduction pipe 6,
The air suction pipe 10 communicates with a vacuum pump 12 via an air suction valve 11. On the other hand, an air introducing pipe 13 is provided in the middle of the introducing pipe 6, and the air introducing pipe 13 communicates with a compressed air tank 15 via an air introducing valve 14. That is, the introduction pipe 6 serves as a common inlet for sand feeding and air introduction.

The operation of the core molding apparatus having the above structure will be described below. In FIG. 3, depending on the set time,
The total weight of the molding sand 2 required for molding the core mold is divided into at least two parts, and the first and second amounts of the molding sand 2 are set. Divide into 2-3 for small items core and 3-1 for large items
Divide the foundry sand into 0 times. In addition, the number of divisions in the core with a complicated shape is increased as compared with the simple one. Next, after the gate 5 is opened, the first charging amount measured by the belt feeder 3 is transferred to the core cavity 7 from the belt feeder 3 through the sand charging port 4 and the introducing pipe 6 by gravity. Drop directly. At this time, the core cavity 7 and the outlet of the air introduction pipe 13 are closed. After the first injection of the molding sand 2, the gate 5 is closed and the air suction valve 11 is closed.
Is opened and the air in the core cavity 7 is sucked from the vacuum pump 12. The pressure of the core cavity 7 is 100-vacuum degree.
When the pressure reaches 3 Torr, the air intake valve 11 is closed. Next, the air introduction valve 14 is opened, and the compressed air for the first time is introduced from the compressed air tank at a pressure rising rate of 30 to 500 kg / cm ² / sec. The introduction of air releases the closure. At this time, it is preferable to introduce the compressed air twice or three times. That is, compressed compressed air is introduced into the core cavity 7 in a reduced pressure state in which the molding sand 2 is charged. Then, the air introduction valve 14 is closed and the gate 5 is opened again. Then, the second amount of casting sand 2 is charged from the belt feeder 3 into the core cavity 7, the gate 5 is closed, the air in the core cavity 7 is sucked, and the second amount is input. For compressed air, pressurization speed is 3
It is introduced at 0 to 500 kg / cm ² / sec. These steps are continuously performed until the divided doses are completed, the core cavity 7 is filled, and the core is molded. afterwards,
The table 9 descends and the core is demolded.

[0012]

Second Embodiment Another embodiment of the present invention will be described below in detail with reference to the drawings. In FIG. 4, it is the same as the first embodiment except for the introduction of air and the gassing plate 17 communicating with the gas generator 16. The introduction of air in this embodiment is characterized in that an air introduction pipe 13 is provided in the middle of the introduction pipe 6, and the air introduction pipe 13 is communicated with the atmosphere via an air introduction valve 14. That is, atmospheric pressure air is introduced into the core cavity 7 in a depressurized state in which the molding sand 2 is charged.

The operation of the core molding apparatus having the above structure will be described below. The operation is similar to that of the first embodiment. However, when the first time the casting sand is added, the
Closed, the air intake valve 11 is opened, and the vacuum pump 1
The air in the core cavity 7 is sucked in from 2. When the pressure in the core cavity 7 reaches a vacuum degree of 100 to 3 Torr, the air suction valve 11 is closed. Next, air introduction valve 1
The only difference is that 4 is opened and the atmosphere is introduced.
Then, the second molding sand is introduced and air is rapidly introduced a plurality of times from above. Incidentally, the molding sand was put into the flask, the molding space was evacuated to about 0.2 bar, and then,
It is known that a high-pressure air is made to act rapidly to mold a mold (Japanese Patent Publication No. 58-500474).

[0014]

Third Embodiment of the Invention The third embodiment of the present invention is
It can be realized by the same device as that of the first embodiment shown in FIG.
However, the difference is that after the first time the casting of the molding sand 2 is finished, the air in the core cavity 7 is not sucked and the air introduction valve 14 is immediately opened to introduce compressed air a plurality of times. That is, the compressed air is introduced into the core cavity 7 in which the molding sand 2 is charged and at the atmospheric pressure.

[0015]

Fourth Embodiment of the Invention A fourth embodiment of the present invention is
It can be realized by almost the same device as that of the first embodiment shown in FIG. However, it is different in that the upper part of the core cavity 7 communicates with a gas generator 16 for hardening the molding sand 2 via a gassing plate 17. Moreover, as the casting sand 2,
The molding sand for cold boxes, which is one type of gas-hardening molding sand, is used. Further, after the filling is completed, a gassing plate 17 is inserted in the upper part of the core cavity 7 and a hardening gas is passed through the foundry sand 2 to cure the core.

In the present invention, the term "core mold" refers to a mold in which the cavity space of a box-shaped core box is filled with molding sand, and its actual name may be a core, a main mold or the like. . For example, the H process master mold can be molded according to the present invention.

In the first embodiment of the present invention, a predetermined amount of foundry sand 2 was dropped into the core cavity 7 as the first input amount, but a metering device (not shown) was installed in the introduction pipe 6. ) May be provided, and the amount of casting sand may be measured while feeding the sand.

The higher the boosting speed in the present invention, the better.
30 to 500 kg / cm ² / sec is preferable. More preferably, 100 kg / cm ² / sec to 400 kg / cm ² / se
c, more preferably 300 kg / cm ² / sec to 400 k
g / cm ² / sec is good. If it is larger than 400 kg / cm ² / sec, the air introduction valve becomes large, which is not economical.
On the other hand, the vacuum state of the core cavity is 100 to 3 Torr.
Is preferable, and even in this range, the higher the vacuum is, the more preferable. When compressed air is used for introducing air, the pressure is preferably ² to 9 kg / cm ² , and more preferably 4
It is up to 9 kg / cm ² , and even within this range, the higher the pressure generally available in the factory, the better. The effect of filling the molding sand with the introduced air is that the core cavity 7
The same applies to the case where compressed air is introduced into the core cavity 7 and the case where atmospheric pressure air is introduced into the core cavity 7 in a vacuum reduced pressure state. However, since the compression ratio of air in a vacuum state is larger than the compression ratio of pressurization that applies compressed air to atmospheric pressure, it has the effect of moving the molding sand to every corner of the concave portion of the model and inserting air after vacuum. In this case, the core can be molded more efficiently.

In the present invention, as the casting sand 2, self-hardening casting sand using an organic or inorganic binder, gas hardening casting sand, and raw sand containing bentonite as a binder are used. it can. Here, the method of the introduced air can be changed depending on the type of the molding sand 2 used. For example, in the case of foundry sand 2 using an organic binder, it is more efficient to introduce air after depressurization. Furthermore, it is preferable that the air is introduced a plurality of times. This is because the molding sand is filled with the energy of air as the number of times increases.

In the fourth embodiment of the present invention, a molding sand for a cold box using a urethane resin, which is one kind of gas-hardening molding sand, as a binder is used as the molding sand, but other water is used. There is no limitation on the type of gas-hardened foundry sand such as glass. A hardening gas is selected for such a gas hardening foundry sand.

[0021]

As is apparent from the above description, the present invention measures the total amount of the molding sand required for molding the core mold into at least two parts, and measures the first amount of the molding sand to be charged. The step of introducing into the cavity, the step of rapidly introducing air from above the injected molding sand a plurality of times, and the additional addition of the remaining amount of molding sand from the amount of the first time charging into the core cavity and the air from above Since the step of rapidly introducing a plurality of times is repeated once or more, the effect of the present invention on the industry is significant because the molding sand can be efficiently and uniformly filled in the core cavity even with a complicated core. Is.

[Brief description of drawings]

FIG. 1 is a schematic view showing a state of movement of foundry sand in the present invention.

FIG. 2 is a schematic diagram showing a process of filling foundry sand in the present invention.

FIG. 3 is a cross-sectional view of the core molding apparatus showing the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a core molding apparatus showing a fourth embodiment of the present invention.

[Explanation of symbols]

 2 Foundry sand 3a Foundry sand charging means 3b Foundry sand measuring means 4 Foundry sand inlet 5 Gate 6 Introducing pipe 7 Core cavity 8 Core box 9 Table 10 Air suction pipe 11 Air suction valve 12 Vacuum pump 13 Air Introducing pipe 14 Air introducing valve 15 Compressed air tank

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[Procedure amendment]

[Submission date] December 8, 1995

[Procedure amendment 1]

[Document name to be amended] Drawing

[Correction target item name] All figures

[Correction method] Change

[Correction contents]

FIG.

[Fig. 2]

[Figure 3]

FIG. 4

Claims (8)

[Claims] 1. A core molding method for molding a core by filling a core cavity with molding sand for molding a core mold, wherein the total weight of the molding sand required for molding the core mold is divided into at least two parts. The step of measuring the first amount of the foundry sand that has been introduced and introducing it into the core cavity, and raising the air from the above-mentioned foundry sand a plurality of times at a rate of 30 to 500 kg / cm ² / se.
a step of rapidly introducing it in step c, and additionally adding the remaining amount of the molding sand of the first charging amount to the core cavity, and air from above the pressurizing speed 30 times.
A core molding method, characterized in that the step of rapidly introducing at ~ 500 kg / cm ² / sec is repeated one or more times. 2. The core molding method according to claim 1, wherein the amount of the molding sand charged is different for each charging time. 3. The core molding method according to claim 1, wherein the core cavity is evacuated before the rapid introduction of the air. 4. The core molding method according to claim 1, wherein the air is compressed air. 5. The molding sand is a gas-hardening molding sand, and the molding sand hardening gas is passed through the filling molding sand after the last rapid introduction of air. Child molding method. 6. A core molding method in which molding sand for molding a core mold is introduced into a core cavity to mold the core by introducing air, and the total volume of the molding sand required for molding the core mold. A step of charging a smaller amount of molding sand to close the space between the core cavity and the outlet of the air introduction pipe; and a step of boosting air from above the charging molding sand a plurality of times 30 to 500 kg / cm ² / sec. Rapidly adding the first casting amount of the remaining molding sand to the core cavity to close the cavity and the outlet of the air introducing pipe. Pressurize the air multiple times from the top of the cast molding sand 30 to 50
A core molding method characterized by rapid introduction at 0 kg / cm ² / sec. 7. A core molding device for molding a core by charging the molding sand 2 into a core cavity 7 provided below the molding sand charging means 3a for measuring and charging the molding sand 2. And a molding sand metering means 3b for metering the molding sand to the amount of the molding sand, a molding sand metering means 3a for charging the metered molding sand 2 into the core cavity 7, and a lower part of the molding sand metering means 3a. A gate that can be opened and closed
A casting sand charging port 4 having a port 5, an introducing pipe 6 communicating with a lower portion of the casting sand charging port 4, and a core box 8 press-communicating with the introducing pipe 6 and the casting. A table 9 provided so as to be relatively close to or away from the sand feeding means 3a, and an air suction pipe 10 provided in the middle of the introduction pipe 6 and communicating with a vacuum pump 12 via an air suction valve 11. The core molding apparatus, further comprising: an air introduction pipe 13 provided in the middle of the introduction pipe 6 and communicating with an air introduction valve 14. 8. The core molding apparatus according to claim 7, wherein the air introduction pipe 13 communicates with a compressed air tank 15.