JP3007820B2 - Core molding equipment for casting - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a casting for forming a hollow casting core using a resin-coated sand (hereinafter referred to as "mold sand") containing a thermosetting resin. The present invention relates to a core molding apparatus.

[0002]

2. Description of the Related Art Heretofore, as an apparatus of this type, the present applicant has disclosed Japanese Utility Model Publication No. Hei 5-30833 or Japanese Patent Laid-Open Publication No. Hei 5-3053.
No. 86 has proposed a technique disclosed therein. The proposed technique includes a mold sand tank portion for filling mold sand, and an air supply / discharge chamber for supplying pressure air to the mold sand tank portion via a wire mesh at a lower portion of the mold sand tank portion or applying suction force to the tank portion. A mold sand pressure feed tank is provided, and the mold sand filled in the mold sand tank portion is supplied by pressure air from the air supply / discharge chamber to a core molding hollow portion formed by an anastomosis of a pair of split molds, Out of the molding sand fed into the hollow portion, the molding sand in contact with the core molding wall is heated and hardened.

After that, by switching the air supply / discharge chamber to air suction, a suction force is applied to the core molding hollow portion via the mold sand filled in the mold sand tank or through a gap between the mold sands. Uncured mold sand near the center of the molding hollow is collected in the same mold sand tank.

[0004] Then, the mold sand in contact with the core molding cavity is heated and hardened by the heated core molding wall of the core molding hollow portion, and the hardened sand remains in the core molding hollow portion, and only the uncured mold sand is discharged. At this time, suction force is applied to the core molding hollow portion, or uncured sand is forcibly discharged to the mold sand tank by a vibration action.

[0005]

As shown in FIG. 10, a hollow core m formed by this conventional apparatus is used as a mold.
When the uncured mold sand is forcibly discharged from the mold sand supply / discharge port 54 and the cured mold sand, that is, the hollow core M is left on the inner wall 53a of the mold 53, the upper wall of the core M is particularly forced by an excessive suction force. As shown in the figure, ma was peeled off or collapsed (this is called "peelback" in the art), and there was a problem that the core M could not be molded with good quality.

When the mold 53 is vibrated without applying suction force or together with the suction force, and the uncured sand in the core molding hollow portion is discharged by the vibrating force, it is necessary to use the arrowhead. The above-described peelback occurs due to the vibration force, and noise pollution occurs due to the vibration effect. Conventionally, it was considered that the generation of this noise was unavoidable in this type of molding plant.

SUMMARY OF THE INVENTION An object of the present invention is to provide an epoch-making proposal which can solve the above-mentioned problems of the conventional device at once.

[0008]

Means for Solving the Problems To achieve the above object, the invention according to claim 1 will be described with reference to the drawings corresponding to the embodiments.
The mold sand S is pressure-fed to the core molding hollow part 2 (FIG. 4) formed by the anastomosis of the cores, and the core molding wall 3 (FIG. 4) of the core molding hollow part 2 is heated by the split molds 1a and 1b. The mold sand Sa in contact is heated and cured, and the uncured mold sand Sb filled near the center of the core molding hollow portion 2 is discharged to form a hollow core M (FIG. 9 (b)). in casting core making device has, outside air introduction hole 44 (FIG. 4, FIG. 7) to the split molds 1a, 1b are pierced, the outer air introduction hole 44, the heating of the core making hollow section 2 The cured mold sand S
a pin tip 45a protruding into the uncured mold sand Sb penetrating through the sealing pin 45 so as to be detachably closed.

In the invention according to claim 2, FIG.
As shown in FIG. 1, a mold sand pressure feeding tank 4 for pumping the mold sand S into the core molding hollow portion 2 is provided corresponding to the core molding hollow portion 2.
A rotary switching valve 7 having a mold sand pressure feed opening 5 for feeding the mold sand to the mold sand pressure feeding tank 4 and a mold sand discharge opening 6 for discharging the uncured mold sand in the core molding hollow portion directly to the outside. It has a configuration according to claim 1.

According to a third aspect of the present invention, as shown in FIG. 6, the mold sand pressure feeding tank 4 includes a mold sand tank portion 4a for filling the mold sand, and a tank portion 4a below the tank portion 4a.
and an air supply chamber 4b for supplying pressurized air to a.

In the invention according to claim 4, FIG.
As shown in the figure, the switching valve 7 is provided with a molding sand pressure feeding surface 8 for feeding the molding sand S of the molding sand pressure tank 4 to the core molding hollow portion 2 and a molding sand S of the hollow molding hollow portion 2 on the outer peripheral surface thereof. The mold sand closing surface 9 for closing the mold sand pressure feeding tank 4 so as not to leak into the tank 4 is formed.

In the invention according to claim 5, FIG.
Alternatively, as shown in FIG. 5, the switching valve 7 includes a mold sand pressure feeding hose 10 for feeding the mold sand S to the mold sand pressure feeding tank 4,
The structure according to any one of claims 1 to 4, which is connected to a mold sand suction hose 11 for discharging the mold sand S from the core molding hollow portion 2 to the outside.

Further, in the invention according to claim 6, the mold sand S sucked and discharged from the core molding hollow portion 2 to the outside by the mold sand suction hose 11 passes through the filtration device 12 and is again sent by the mold sand pressure feeding hose 10 to the mold sand. The configuration according to any one of claims 1 to 5, which is adapted to be pressure-fed to the pressure-feeding tank (4).

[0014]

1 to 3 show the appearance of a core molding apparatus for casting according to an embodiment of the present invention. Of the pair of split molds 1a and 1b, one mold 1a is a fixed mold supported by a fixed frame, and the other mold 1b is
The movable mold is supported by the movable frame 14 that moves along the guide bar, and moves toward and away from the fixed mold 1a between the chain line and the solid line in FIG.

A mold sand pressure feed tank 4 is arranged immediately below the position where the movable mold 1b is anastomosed with the fixed mold 1a at the position of the dashed line. As shown in FIG. 6, the mold sand pressurizing tank 4 includes a mold sand tank portion 4a for filling the mold sand S, a mesh net 4c under the mesh sand tank portion 4a, which allows air to pass therethrough but prevents the mold sand from passing therethrough. An air supply chamber 4 for supplying pressurized air to the tank portion 4a via the wire mesh 4c.
b. The air supply chamber 4b is connected to an air supply hose 16.

FIG. 1 and FIG.
As shown in FIG. 7, the split mold 1a is mounted on a carriage 17 and lifted by a lifting cylinder 18 and a lifting guide rod 18a.
1b is supported so as to be able to ascend toward the anastomosis portion of the guide rail 1b, and the guide rail 20
, And reciprocate between a solid line position and a chain line position in the figure.

A mold sand input hopper 21 is provided on the movable end side of the mold sand pressure feed tank 4 shown by a chain line in the figure, and the hopper 21 is connected to a sub-tank 23 through an opening / closing gate 22, and the sub-tank 23 is opened and closed. The measuring tank 25 has an air supply pipe 25a at one end and is connected to the mold sand pressure feeding hose 10 at one end. The mold sand pressure feeding hose 10 is connected to a switching valve 7 (FIG. 5) provided in the mold sand pressure feeding tank 4.

As shown in FIG. 1, especially FIG. 5, the switching valve 7 built in the mold sand pressure feeding tank 4 is provided with a valve switching cylinder 26.
And a switching cylinder 27 connected to the switching arm 27. The switching valve 7 is formed of a rotary-type thick cylindrical body that swings in the circumferential direction, and the switching valve 7 penetrates its axis in the longitudinal direction as shown in FIG. A mold sand flow passage 28 is formed, and a hopper-shaped mold sand supply / discharge opening 29 that opens toward the outer peripheral surface in communication with the flow passage 28 is formed in the entire longitudinal direction of the flow passage 28. The mold sand flow passage 28 and the mold sand supply / discharge opening 29 form a mold sand pressure feed opening 5 and a mold sand discharge opening 6 as described later.

As shown in FIG. 6, on the outer peripheral surface of the switching valve 7, a part thereof is cut out in a flat surface 8, and the flat surface 8 is formed in the mold sand supply / discharge hole 30 of the mold sand tank 4a. When the mold sand supply / discharge hole 30 and the flat surface 8
((B) of FIG. 8) is formed, and the mold sand S of the mold sand tank portion 4a is fed into the core molding hollow portion 2 from the mold sand pressure feeding gap 31. Therefore, the flat surface 8 forms the mold sand pressure feeding surface 8. Further, an arc surface 9 is formed on the outer peripheral surface of the switching valve 7 adjacent to the mold sand pressure feeding surface 8, and when the arc surface 9 faces the mold sand supply / discharge hole 30, the supply / discharge hole 30 is closed. The mold sand S of the core molding hollow portion 2 is prevented from leaking from the supply / discharge port 32 (see FIG. 8C) to the mold sand tank portion 4a side. Thus, the arc surface forms a mold sand closing surface 9. In addition, open / close valves 33 and 34 (see FIGS. 3 and 4) are provided at both ends of the switching valve 7.

The other end of the switching valve 7 is connected to a mold sand suction hose 11, and the hose 11 is connected via a relay chamber 35 and a relay hose 36 to a suction device 37 (suction pump).
It is connected to. The suction device 37 is provided with an inverter 38 (see FIG. 4) for adjusting the suction pressure. As shown in FIG. 3, a bag-shaped filter 39 is interposed in the relay chamber 35 so that the collected mold sand S does not enter the suction device 37. The mold sand S collected in the relay chamber 35 passes through the on-off valve 41 and is applied to the filtration device 12.

The filtering device 12 is vibrated by a vibration (shaking action), and a wire mesh for allowing the mold sand S having a certain grain size or less to pass downward but preventing the mold sand S having a larger grain size from passing therethrough, and a lower receiving plate. Significantly, the mold sand S having a certain grain size or more on the wire mesh is discharged to the outside by the vibration action of the vibration, and the mold sand S having the small grain size on the receiving plate is also caused by the vibration action of the vibration, as shown in FIG. It is being sent to. The mold sand S thus reused is filtered.

The root portion of the sand blasting machine 40 is
At the same time, it is connected to a hopper 52 for supplying new mold sand S as shown in FIGS. And the hopper 5
2 and the uncured mold sand S collected via the filtration device 12 are sent upward together by the sand sanding machine 40, and the mold sand introduction hopper 21 through the mold sand introduction pipe 42 from the upper end thereof. It is to be thrown into.

The configuration of the present invention is as follows.
As shown in FIG. 7, an outside air introduction hole 4 penetrating in and out of, for example, a parting surface 43 (anastomosis surface) of the pair of split molds 1a and 1b.
4 is established. As shown in FIGS. 7 (a) and 7 (c), the introduction hole 44 is formed on the upper surface side of both split molds 1a and 1b. In FIGS. 7 (b) and 7 (d), both split molds 1a and 1b are opened. The introduction holes 44 are formed on both side surfaces of 1b. The outside air introduction hole 44 is detachably fitted by a closing pin 45 so that the introduction hole 44 is closed, and when the closing pin 45 is fitted into the outside air introduction hole 45 and closed. The tip 45a of the pin 45 slightly projects into the core molding hollow portion 2.

As shown in FIGS. 1 and 2, and more specifically, FIG. 4, the closing pins 45, 45 on the upper surface side and both side surfaces of the split molds 1 a, 1 b are connected to the support frame 4 extending from the machine frame 46.
The outside air introduction holes 44 are detachably closed up and down or left and right by a pin moving cylinder 48 attached to 7. When unnecessary, it can be rotated back to the position shown by the dashed line in FIG.

The operation sequence of the present invention will be described.
As shown in the figure, the mold sand pressure feeding tank 4 is moved by the bogie 17 to the mold sand charging hopper 21 as shown by a chain line in the figure, and at this position, the mold sand supply / discharge hole 30 of the mold sand tank portion 4a of the mold sand pressure feeding tank 4 is sealed. The plate 49 is closed with a plate 49 (see FIGS. 1 and 8 (a)) and, as shown in FIG. 8 (a), the mold sand supply / discharge opening 29 of the switching valve 7 is swung so as to be in the horizontal direction. The mold sand supply / discharge hole 30 is closed by a certain mold sand closing surface 9. In this state, the opening / closing gate 22 is opened from the mold sand charging hopper 21 and the opening / closing gate 22 is opened, and the opening / closing valve 24 is further opened, and the opening / closing valve 24 is opened and the mold sand S is injected into the measuring tank 25. Air weighing tank 2
5, a certain amount of mold sand S in the measuring tank 25 is supplied to the switching valve 7 from the sand supply hole 50 (FIG. 5) at one end of the switching valve 7 through the molding sand pressure feeding hose 10, and the switching is performed. The mold sand S is filled into the mold sand tank 4a through the mold sand flow passage 28 of the valve 7 and the hopper-shaped mold sand supply / discharge opening 29 to the mold sand tank 4a of the mold sand pressurizing tank 4. Therefore, the mold sand flow passage and the mold sand supply / discharge opening of the switching valve 7 form the mold sand pressure supply opening 5 for the mold sand pressure supply tank 4.

Next, as shown in FIG. 1, the mold sand pressure feeding tank 4 is moved by the bogie 17 to a position immediately below the anastomosis position of the split molds 1a and 1b as shown by a solid line.
As shown in (b), the switching valve 7 is swung by the valve switching cylinder 26 and the switching arm 27, and the mold sand pressure feeding surface 8 which is a flat surface of the switching valve 7 is changed to the mold sand supply / discharge hole 30 of the mold sand tank portion.
Face to face. As a result, a mold sand pressure feeding gap 31 is formed between the mold sand supply / discharge hole 30 and the mold sand pressure sending surface 8.

Thereafter, as shown in FIG. 6, by supplying pressure air from an air supply hose 16 to an air supply chamber 4b below the mold sand tank 4a, the air passes through a wire netting 4c and the mold sand tank 4a. The mold sand S in the mold sand tank 4a is supplied to the pair of split molds 1a, 1b by the air pressure of the pressurized air.
Is sent into the core molding hollow part 2 formed by the above.

When a certain amount of the molding sand S is fed into the core forming hollow portion 2, the switching valve 7 is further swung as shown in FIG. The mold sand closing surface 9 faces the mold sand supply / discharge hole 30 of the mold sand tank portion 4a.
To prevent the mold sand S in the core molding hollow portion 2 from leaking from the supply / discharge port 32 to the mold sand tank portion 4a side. In this state, the mold sand S fed to the core molding hollow portion 2 is For about 60 seconds, the core molding wall 3 is heated by the core molding wall 3 at 250 ° to 300 °, and the mold sand Sa in contact with the core molding wall 3 is heated and hardened.

As described above, the outside air introduction hole 44 penetrating through the pair of split molds 1a and 1b forming the core mold hollow portion 2 is closed by the closing pin 45, and the tip 45a is heated. It is necessary to penetrate the cured mold sand Sa and protrude into the uncured mold sand Sb (FIGS. 7A and 7B).
And (a) of FIG. 9).
When (b) in FIG. 9 is formed, the outside air introduction hole 44 formed by the closing pin 45 in the core M is also formed in the core M itself. M
Is preferably formed in a portion that does not hinder the casting operation used thereafter, for example, in a portion of the baseboard 51 for supporting the core M in the casting mold.

Next, the switching valve 7 is further swung as shown in FIG. 8D so that the mold sand supply / discharge opening of the switching valve 7 faces the supply / discharge port 32 of the core molding hollow portion 2. And connect them. As a result, as shown in FIG.
And the mold sand suction hose 1 connected to the switching valve 7 and the switching valve 7
1 is connected.

In this state, the closing pins 45 on the upper surface and the closing pins 45 on both sides closing the outside air introduction hole 44 of both split molds 1a and 1b are connected as shown in FIGS. More specifically, as shown in FIGS. 7 (c) and 7 (d), the pin is moved out of the outside air introducing hole 44 by driving the pin moving cylinder 48.
The suction device 37 of the mold sand suction hose 11 is operated. The order of removing the closing pins 45 is such that the pins 45 on the upper surface side or both side surfaces are simultaneously or in accordance with the shape of the core molding hollow portion 2. Or from one side.

As described above, the closing pin 45 is connected to both split molds 1.
By operating the suction device 37 of the mold sand suction hose 11 while extracting the core from the core molding hollow portion 2,
The uncured mold sand Sb inside is sucked and discharged to the outside directly from the mold sand suction hose 11 through the mold sand supply / discharge opening 29 of the switching valve 7 and the mold sand flow passage 28. Therefore, the switching valve 7
The mold sand supply / discharge opening 29 and the mold sand flow passage 28 form the mold sand discharge opening 6 for sucking and ejecting the mold sand Sb to the outside.

According to this embodiment, the inside surrounded by the core molding hollow portion 2 and the hardening sand Sa which has been heated and cured in contact with the core molding wall 3 passes through the outside air introduction hole 44 to introduce outside air. As a result, the uncured mold sand Sb filled therein can be discharged to the outside very well, and the suction force of the suction device 37 related to the mold sand suction hose 11 can be improved. Need not be raised more than necessary.

As described above, since it is not necessary to increase the suction force of the suction device 37 more than necessary, it is possible to prevent the hardened mold sand Sa from collapsing due to the suction action as in the prior art, as shown in FIG. As shown, a high quality core M can be formed.

Further, since it is not necessary to apply the vibration effect to the mold, noise pollution can be eliminated from the work site.

Further, according to this embodiment, as shown in FIG. 4, the suction device 37 is provided with the inverter 38 capable of accurately adjusting the suction force, so that the core M formed is formed. Inverter 3 according to shape and thickness
8, the suction force of the suction device 37 can be adjusted, so that the hardening sand Sa can be collapsed by the suction force when the uncured sand Sb is sucked and discharged from the core molding hollow portion 2. Can be prevented.

After the uncured sand Sb in the core molding hollow part 2 is discharged, the hollow core M (FIG. 9)
(See (b)), the anastomotic state of the two split molds 1a and 1b is released, and the hollow core M may be taken out from the interior. Then, the hollow core M is taken out and the split molds 1a and 1b are again anastomosed, and the closing pin 45 is closed.
Is fitted into the outside air introduction hole 44 and is closed.

The uncured sand Sb sucked and discharged by the mold sand suction hose 11 is collected in the relay chamber 35, and the inside of the relay chamber 35 is formed in a bag shape so that the collected sand S is not mixed into the suction device 37. The fact that the filter 39 is interposed is as described above.

The molding sand Sb collected in the relay room 35 is passed through the filtration device 12, and the molding sand having a certain particle size or more is discharged to the outside by vibrating action. Along with the new sand S introduced into the hopper 52 to be supplied,
, And is fed into the above-mentioned sand hopper 21 by a sand inlet pipe 42 from the upper end thereof.

[0040]

According to the first aspect of the present invention, the outside air is introduced through the outside air introduction hole into the core molding hollow portion and the inside surrounded by the hardening sand which is heated and cured in contact with the core molding wall. As a result, the uncured mold sand Sb filled therein can be discharged to the outside very well, which requires the suction force of the suction device relating to the mold sand suction hose. There is no need to raise it.

As described above, since it is not necessary to increase the suction force of the suction device more than necessary, it is possible to prevent the hardened mold sand from collapsing due to the suction action as in the related art, and to mold a good quality core. it can. Furthermore, since it is not necessary to apply the vibration action to the mold, noise pollution can be removed from the work site.

According to the second aspect of the present invention, when the mold sand is pressure-fed from the mold sand tank portion of the mold sand pressure feed tank to the core molding hollow portion and the mold sand is heated and hardened in the hollow portion, no air is blown. It is not necessary to always supply the pressurized air in the supply / exhaust chamber to the core molding hollow part, and the operation is easy accordingly.

According to the second aspect of the present invention, when the uncured sand in the hollow part is recovered in the mold sand tank after being heated and hardened in the core molding hollow part, it is directly removed by the suction means. Since the hardened mold sand is sucked, it is possible to quickly collect the mold sand. For this reason, there is little need to discharge the mold sand from the core molding hollow part by vibrating action, and the cause of noise pollution can be eliminated.

According to the second aspect of the present invention,
When collecting the uncured sand, the mold sand is collected through a different path from the path for pumping the core into the core molding hollow part, whereby semi-cured or hardened mold sand is collected in the core molding hollow part. Since it is configured not to be fed into the hollow part, the mold sand collected from the core molding hollow part can be effectively reused as the core forming mold sand.

According to the third aspect of the present invention, the mold sand pressure feeding tank includes a mold sand tank portion for filling the mold sand, and an air supply chamber below the tank portion and supplying pressurized air to the tank portion. Therefore, the mold sand in the mold sand tank can be reliably fed to the core molding hollow portion by the pressurized air from the air supply chamber.

According to the fourth aspect of the present invention, the molding sand pressure feeding surface for pressing the molding sand of the molding sand pressure feeding tank to the core molding hollow portion on the outer peripheral surface thereof and the molding sand of the hollow molding hollow portion leak into the molding sand pressure feeding tank. The feeding of the molding sand can be controlled by a switching valve having a simple structure in which a molding sand closing surface for closing the molding sand pressure-feeding tank is formed so as to prevent the molding sand from being fed. The mold sand can be closed, and the operation can be performed very easily.

According to the fifth aspect of the present invention, the switching valve includes a mold sand pressure feeding hose for feeding the mold sand to the mold sand pressure feeding tank, and a mold sand suction for discharging the mold sand from the core molding hollow portion to the outside. Since it is connected to a hose, it is easy to send the mold sand to the mold sand pumping tank and to discharge the mold sand from the core molding hollow part of the mold sand.

According to the sixth aspect of the present invention, the mold sand sucked and discharged from the core molding hollow portion to the outside by the mold sand suction hose is again fed to the mold sand pressure feeding tank by the mold sand pressure feeding hose via the filtration device. As a result, even if semi-cured or hardened mold sand is discharged from the core molding hollow part, these mold sands can be removed by the filtration device, so that good quality mold sand can be reused. .

[Brief description of the drawings]

FIG. 1 is a front view of a core molding apparatus for casting showing one embodiment of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is a side view of the same.

FIG. 4 is a vertical sectional front view of the essential part.

FIG. 5 is a perspective view of the main part.

FIG. 6 is a vertical sectional front view of another essential part of the same.

FIG. 7 is an explanatory longitudinal sectional view showing an operation state of another main part.

FIG. 8 is an explanatory longitudinal sectional view showing an operation state of another main part.

FIG. 9 is a longitudinal sectional view showing a molding state of a core molded according to the present invention.

FIG. 10 is a longitudinal sectional view showing a molding state of a core molded by a conventional technique.

[Explanation of symbols]

 Reference Signs List 1a split mold 1b split mold 2 core molding hollow part 3 core molding wall M core 4 type sand pressure feed tank 4a type sand tank part 4b type sand supply room 5 type sand pressure opening 6 type sand discharge opening 7 switching valve 8 type sand pressure feeding surface 9 Mold sand closing surface 10 Mold sand pressure feeding hose 11 Mold sand suction hose 12 Filtration device 44 Outside air introduction hole 45 Closing pin

Claims (6)

(57) [Claims] 1. A mold sand is pressure-fed to a core molding hollow portion formed by an anastomosis of a pair of split molds, and the mold sand in contact with a core molding wall of the core molding hollow portion is heated and cured by a heating action of the split mold. In the casting core molding apparatus in which the uncured mold sand filled in and near the center of the core molding hollow portion is discharged and the hollow core is molded, the split mold is exposed to the outside air. An introduction hole is penetrated , and the outside air introduction hole penetrates through the heat-cured mold sand of the core molding hollow portion and is uncured.
A core molding apparatus for casting, which is detachably closed by a closing pin having a pin tip projecting into the mold sand . 2. A mold sand pressure feeding tank for pumping mold sand into the core molding hollow portion is provided corresponding to the core molding hollow portion,
Inside the mold sand pressure feed tank, a rotary provided with a mold sand pressure feed open path in which the mold sand is pumped from the outside to the mold sand pressure feed tank and a mold sand discharge open path in which the uncured mold sand in the core molding hollow portion is directly discharged to the outside. 2. A switching valve according to claim 1.
The core molding apparatus for casting according to the above. 3. The mold sand pressure feeding tank according to claim 1, wherein the mold sand pressure feeding tank comprises a mold sand tank portion for filling the mold sand, and an air supply chamber below the tank portion and supplying pressurized air to the tank portion. Core molding equipment for casting. 4. The switching valve has a mold sand pressure feeding surface for sending the mold sand of the mold sand pressure feeding tank to the core molding hollow portion on the outer peripheral surface thereof and a mold sand pressure of the hollow molding hollow portion so as not to leak into the mold sand pressure feeding tank. The core molding apparatus for casting according to any one of claims 1 to 3, wherein a mold sand closing surface for closing the mold sand pressure feeding tank is formed. 5. The switching valve is connected to a mold sand pressure feeding hose for feeding the mold sand to the mold sand pressure feeding tank, and a mold sand suction hose for discharging the mold sand from the core molding hollow portion to the outside. The core molding apparatus for casting according to any one of claims 1 to 4. 6. The mold sand sucked and discharged from the core molding hollow portion to the outside by the mold sand suction hose is again fed to the mold sand pumping tank by the mold sand feeding hose via the filtering device. 6. The core molding apparatus for casting according to any one of the above items 5.