JP3322382B2 - Core molding method and apparatus - Google Patents

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 gas-hardened molding sand.

[0002]

2. Description of the Related Art Conventionally, gas-hardening molding sand is filled into a core cavity by blowing, and a hardening gas is introduced into the core cavity to harden the core to a predetermined strength. The molding method is known (for example, Japanese Patent Publication No. 48-13804).

However, in the conventional method, since the sand is filled only by blowing, when the number of blow nozzles is increased in a type such as putting many pieces, the blowing performance of each blow nozzle is not improved. Due to the difference, the core was sometimes partially filled. For this reason, it has been necessary to provide a large number of exhaust ports, such as vent plugs for blowing, in the mold in anticipation of the flow of air during blowing from the shape of the core cavity. Also, in order to optimize the number and position of these vent plugs for blowing, the trial of blowing is repeated many times to evaluate the sand filling density and surface roughness of the core product. However, since the mold had to be modified, the production of the mold was time-consuming and expensive.

[0004]

SUMMARY OF THE INVENTION An object of the present invention has been made in view of these problems, and has been made to increase the packing density of a core, reduce the number of vent plugs, and reduce the time and cost for repairing a mold. To provide a core molding method and an apparatus for reducing core.

[0005]

Means for Solving the Problems In order to achieve the above object, the core molding method according to the present invention comprises filling a core cavity with gas-hardening molding sand, and filling the core cavity with 2 to 100 parts.
The pressure was reduced to Torr, and air was pumped from above into the depressurized core cavity at a rate of 50 to 600 kg / cm ^2.
/ Sec to apply a pressing force to the upper surface of the gas-hardened molding sand to increase the packing density, and to introduce a hardening gas into the core cavity to harden the gas-hardened molding sand. The core molding apparatus suitable for the core molding method includes a blow head, a pressure chamber, a pressure reducing unit, a blow valve, an air introduction valve, a curing gas introduction unit, and a curing gas discharge unit. It is characterized by. According to the present invention, the core cavity is filled with gas-hardened molding sand, and the air introduction valve of the air introduction means is operated for the core cavity in a reduced pressure state to rapidly introduce air into the core cavity. Impact pressure acts on the upper surface of the gas-hardening foundry sand,
The gas-hardened molding sand is compressed by the pressure of air, and the packing density is further increased from the packing density of the initial filling alone.

[0006]

Embodiment 1 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view of a core molding apparatus. In FIG. 1, an upper frame F is provided at an upper end of a plurality of columns 2 erected on a base 1. On the upper frame F, a sand hopper 4 having a sand charging gate 3, a blow valve 5, an air introducing valve 6, and an air introducing means having an air tank 7 are fixedly provided. Below the sand hopper 4, a movable blow head 10 having an air inlet 8 for receiving the gas-hardened molding sand S and introducing compressed air is provided at the upper portion, and a blow nozzle 9 having a blow nozzle 9 is provided at a lower portion thereof. Have been.
The air inlet 8 can communicate with the blow valve 5 by moving. Further, a pressure chamber 11 is connected to the blow head 10, and both are integrally provided so as to be movable by a cylinder 12. The pressure chamber 11
The upper part is communicated with the air introduction valve 6, and the lower part is provided so as to be able to adhere to the upper opening of the upper mold 13 a.

On the other hand, an elevating table T is provided below the inside of the plurality of columns 2, and a core cavity 14 is defined above the elevating table T by an upper mold 13a and a lower mold 13b. Has been established. An opening 13c for blowing is provided in the upper part of the upper mold 13a so as to be able to communicate with a blow nozzle 9 provided in a lower part of the blow head 10. Further, a vent hole 1 is provided in the upper mold 13a and the lower mold 13b.
Vent plugs 16, 16 fixed to the cores 5, 15 are provided, and the vent holes 15, 15 reduce the pressure in the core cavity 14 by a vacuum pump P.
It is communicated with 6. One end of the decompression means 18 is connected to the lifting table T and the bottom plate of the pressure chamber 11,
The lower cavity and the upper cavity of the core cavity 14 are communicated with each other, and the other end is provided with a vacuum pump P via a vacuum valve 17. With the operation of the vacuum valve 17, the inside of the core cavity 14 is moved to 2 to 100 Torr by the vacuum pump P.
Can be decompressed to Further, the inside of the pressure chamber 11 and the vent hole 15 of the upper mold 13a are communicated with a hardening gas introducing means 20 for introducing a hardening gas from a gas generator 19 into the core cavity 14, and a lower mold 13b is provided.
The vent hole 15 communicates with the hardening gas discharging means 21 for discharging the hardening gas in the core cavity 14 through valves 22 and 23 in communication with the elevating table T.

Hereinafter, the operation of the core molding apparatus thus configured will be described. In FIG. 1, gas-hardened molding sand S previously kneaded at another position (not shown) is stored in a sand hopper 4. By the opening operation of the sand injection gate 3, an amount of sand of one shot or more is injected into the blow head 10. Subsequently, the blow head 10 and the pressure chamber 11 connected to each other are moved by a wheel running (not shown) by a cylinder 12, and the lower part of the blow head 10 is
It moves to the upper part of the lifting table T (FIG. 2), and the upper part communicates with the air inlet 8. Then, the elevating table T on which the lower mold 13b is placed rises, and the upper mold 13a and the lower mold 13b are integrated with the blow nozzle 9 attached to the lower part of the blow head 10 to move upward. The inlet of the mold 13a is communicated and clamped. In this state, the molding sand is blown. By the opening operation of the blow valve 5, the compressed air is supplied from the air tank 7 to the blow head 1 via the blow pipe.
It is blown into 0. The blown air is filled into the core cavity 14 together with the sand from the blow nozzle 9 and the air is discharged by the vent plugs 16 and 16 of the lower mold 13b. In this case, the vent plug 16 of the lower mold 13b may be disposed only in consideration of exhaust, and there is no need to consider the filling density of the gas-hardened molding sand S. Next, the lifting table T is lowered to separate the blow head 10 and the upper mold 13a (as shown in FIG. 2), and the blow head 10 and the pressure chamber 11 connected to each other are returned to their original positions. Return. Subsequently, the lifting table T is raised, and the air supply port of the pressure chamber 11 and the blow port of the upper mold 13a are communicated and clamped. Here, the inside of the core cavity 14 is operated by operating the vacuum valve 17 to 2 to 2.
Reduce the pressure to 100 Torr. Here, vent plug 1
The components 6 and 16 may be arranged in consideration of the pressure reduction of the core cavity 14, and there is no need to consider the filling density of the gas-hardening molding sand S.

Next, the air introducing valve 6 is operated to rapidly introduce air into the core cavity 14 through the pressure chamber 11. This air instantaneously acts on the upper surface of the gas-hardened molding sand S as an impact pressure, and the gas-hardened molding sand S is compressed by the pressing force of the air. Due to the effect of the impact pressure, the filling density of the gas-hardened molding sand S is further increased from that of the blowing alone (FIG. 1).

After that, a curing gas is introduced into the core cavity 14 by the curing gas introduction means 20. By the introduction of the hardening gas, the hardening gas flows into the gas hardening molding sand S, and the hardening gas sand S hardens, and a core having a strength higher than that of the conventional hardening sand is obtained. Thereafter, purging is performed as required, and the lifting table T is lowered to take out the core from the upper and lower dies 13a, 13b. At this time, the core is pushed out by the push-out pin mechanisms 25, 25 as in the prior art.

The gas-curable molding sand S used in the present invention is preferably a gas-curing molding sand using water glass, phenol resin, urethane resin, furan resin or the like as a binder. A curing gas such as carbon dioxide, TEA gas, sulfur dioxide, and methyl formate is selected according to the gas-cured molding sand.

In the first embodiment of the present invention, although the blowing is used as a means for filling the core cavity 14 with the gas-hardening molding sand S, it can be filled by gravity. Further, it can be filled under reduced pressure. In this case, by reducing the pressure in the core cavity 14, the gas-hardening molding sand S is filled due to the pressure difference between the core cavity 14 and the blow head 10. In this state, the blow head 10
The pressure can be applied to the upper surface of the gas hardened molding sand S by introducing air into the inside. Therefore, in this case, the blow head 10 has an apparatus structure also serving as the pressure chamber 11, and the pressure chamber 11 is not required. Also,
Either the blow valve 5 or the air introduction valve 6 may be omitted.

Although the pressure reducing means 18 communicates with the upper and lower portions of the core cavity 14, in another embodiment of the present invention, the communication between the pressure reducing means 18 and the core cavity 14 is performed by the upper and lower molds 13a and 13a.
13b may be left or right instead of up and down.

[0014] The pressure increasing speed by air introduction is 50-600.
Kg / cm ² / sec is preferred. More preferably, it is 200 to 400 Kg / cm ² / sec. The introduced air may be at atmospheric pressure, but the pressure of the pressurized air is preferably up to 10 kg / cm ² . The pressure value is optimized according to the shape and size of the air introduction valve.

In the first embodiment of the present invention, the blow head 10 and the pressure chamber 11, which are connected to each other, are integrally moved by a cylinder 12 by running wheels (not shown). 10 and pressure chamber 11
Need not always be connected, and may be separately movable.

In the first embodiment of the present invention, the sand hopper 4 is used. However, the sand hopper 4 is not an essential component of the present apparatus, and means for supplying an appropriate amount of kneading sand from a conveyor belt or the like is different from the present apparatus. It may be provided separately.

In the first embodiment of the present invention, the mold opening / closing means also serves as the lifting table T, but may be provided separately. In this case, the mold opening and closing means can be opened and closed right and left instead of up and down.

When the hardening gas is introduced, the inside of the core cavity 14 may be depressurized in the same manner as described above, and then the hardening gas may be introduced into the core cavity 14 by the hardening gas introducing means 20. In this case, there is an effect that the introduction amount of the curing gas decreases.

As is apparent from the above description, the present invention provides a step of closing a mold half by a mold opening / closing means to define a core cavity, and filling the core cavity with gas-hardened molding sand. Filling step, and 2 to 1 in the core cavity.
Depressurizing to 00 Torr, and pressurizing air from above into the depressurized core cavity at a rate of 50 to 600
a step of applying a pressing force to the upper surface of the gas-hardening molding sand to increase the packing density by introducing the gas-hardening molding sand at a rate of kg / cm ² / sec; Process, so that it is possible to easily improve the sand filling density and core strength of the core, reduce the number of vent plugs, and reduce the time and cost of mold repair and prototype production. Can be. Further, cleaning work may be reduced. As described above, the effect of the present invention on the industry is remarkable.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a state after sand filling.

FIG. 2 is a schematic diagram showing a state before sand filling.

[Explanation of symbols]

 2 Column 4 Sand hopper 5 Blow valve 6 Air inlet valve 8 Air inlet 9 Blow nozzle 10 Blow head 11 Pressure chamber 13 Mold 14 Core cavity 15 Pressure chamber 18 Pressure reducing means 20 Curing gas introducing means 21 Curing gas discharging means P Vacuum pump T Elevating table S Gas-cured molding sand F Upper frame

Continuation of front page (56) References JP-A-62-197243 (JP, A) JP-A-55-156640 (JP, A) JP-A-59-197340 (JP, A) (58) Fields investigated (Int) .Cl. ⁷ , DB name) B22C 9/12 B22C 9/10

Claims (10)

(57) [Claims] 1. A half mold 13 by a mold opening / closing means.
a, a step of defining the core cavity 14 by closing the core 13b, a step of filling the core cavity 14 with the gas-hardening molding sand S, and a step of filling the core cavity 14 with 2 to 100 Torr.
r, and reducing the pressure of the core cavity 14
Air is pumped up from above at a rate of 50-600kg / c
m ² / sec to increase the packing density by applying a pressing force to the upper surface of the gas-hardening molding sand S, and introducing a hardening gas into the core cavity 14 to introduce the gas-hardening molding sand S
And a step of curing the core. 2. The core molding method according to claim 1, wherein the filling of the core cavity 14 with the gas-hardening molding sand S is performed by blowing. 3. The method for molding a core according to claim 1, wherein the filling of the core cavity 14 with the gas-hardening molding sand S is performed under reduced pressure. 4. The core molding method according to claim 1, wherein the pressure of the air introduced into the core cavity is reduced to the atmospheric pressure. . 5. The method according to claim 1, wherein the introduced air is pressurized air. 6. The gas-hardened molding sand S by the introduction of air.
The pressure in the core cavity 14 is reduced again after the filling density of the core is increased, and a hardening gas is introduced into the core cavity 14 to harden the gas-hardened molding sand S. The core molding method according to claim 5. 7. Half of upper and lower molds 1 by mold opening and closing means.
This is a core molding apparatus for molding a core by charging gas-hardening molding sand S into a core cavity 14 defined by closing 3a and 13b. The core molding apparatus has an air inlet 8 in the upper part and a blower in the lower part. A blow head 10 having a nozzle 9 for receiving gas-hardening molding sand S and supplying the gas-hardening molding sand S to the core cavity 14, and a pressure chamber 11 provided to be movable and adhered to an upper opening of an upper mold 13a. Pressure reducing means 18 for reducing the air in the core cavity 14 by a vacuum pump P; a blow valve 5 for introducing air to the blow head 10; and an air introducing valve for introducing air to the pressure chamber 11. 6, a hardening gas introducing means 20 for introducing a hardening gas into the core cavity 14, a hardening gas discharging means 21 for discharging a hardening gas from the core cavity 14, Lifting Te raising and lowering the lower mold - Bull T
And a core molding apparatus comprising: 8. The core molding apparatus according to claim 7, wherein the blow head 10 and the pressure chamber 11 are connected to each other. 9. A lifting table provided inside a plurality of columns 2.
Half the upper and lower molds 13 by the mold opening / closing means also serving as the bull T
A core molding apparatus for molding a core by charging a gas-hardening molding sand S into a core cavity 14 defined by closing a and 13b, wherein an upper frame F provided on the plurality of columns 2 is provided. Can be positioned beneath the sand hopper 4 by moving below, and has an air inlet 8 at the upper part and a blow nozzle 9 at the lower part to receive the gas-hardened molding sand S and gas-harden the core cavity 14. A blow head 10 for supplying molding sand S, and the upper frame F
And the air inlet 8 is provided to the blow head 10.
A blow valve 5 for introducing air through the core, pressure reducing means for reducing the air in the core cavity 14 by a vacuum pump 18, and curing gas introducing means 20 for introducing a curing gas into the core cavity 14. And a hardening gas discharging means 21 for discharging a hardening gas from the core cavity 14. 10. A pressure chamber 11 connected to the blow head 10 and provided in close contact with the upper opening of the upper mold 13a, and air supplied to the pressure chamber 11 provided in the upper frame F. The core molding apparatus according to claim 9, further comprising an air introduction valve (6) for introducing.