JPH08174155A - Method and device for molding mold - Google Patents

Abstract

PURPOSE: To provide a method and device for molding a mold capable of molding a uniform mold even for a complicate pattern by effectively using the energy of the compressed air in a sand magazine for molding the mold, and eliminating the limit of the compressed air whose pressure has been limited. CONSTITUTION: In a method for molding a mold where the molding sand 4 in a sand magazine 3 which is arranged to the upper part of the mold molding space to be demarcated by a pattern plate 1 and the molding flask 2 is filled in a molding flask 2, an opening part of the mold molding space is closed by the sand magazine 3 having a throwing port 11 which is openable/closable at the bottom. The throwing port 11 is closed, and the molding sand 4 is thrown into the sand magazine 3, and then, the sand magazine 3 is closely sealed. The gas is smoothly introduced into the closely sealed sand magazine 3 to obtain the high pressure mixture with the gas of 4-9kgf/cm<2> . When the pressure in the sand magazine 3 reaches the prescribed value, the throwing port 11 is opened in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for molding foundry sand put in a sand magazine arranged above a molding space defined by a model plate and a casting frame.

[0002]

2. Description of the Related Art Conventionally, casting sand is placed in a sand magazine located above a molding space defined by a model plate and a molding frame, and the sand magazine closes the molding space and the sand magazine is closed. A so-called blow molding method is known in which compressed air is blown into the mold all at once and the molding sand is blown into the molding space through a projection port (for example, Japanese Patent Laid-Open No. 52-20928). However, with this method, the pressure loss in the sand magazine is large near the projection port, and the energy of the compressed air introduced into the sand magazine is lost at the projection port, and as a result, the energy used for mold making is reduced. It was running low. Further, since the compressed air flows to the projection opening in the sand magazine, the molding sand is pushed toward the projection opening, and the density around the projection opening becomes high. Since this molding sand has poor fluidity and has compressibility, it is hung from the shelf near the projection port, and the molding sand does not enter the casting frame through the projection port. This tendency becomes greater as the pressure of the compressed air blown into the foundry sand is increased. Therefore, the pressure of the compressed air is generally as low as ¹ Kgf / cm ² to 3 Kgf / cm ^{2 for} blowing. Therefore, the conventional blow molding method cannot form a mold having a uniform hardness, and is not suitable for molding a mold having a complicated shape or a deep shape. The present invention has been made in view of the above-mentioned drawbacks, and uses the energy of compressed air as effectively as possible for mold making, and eliminates the limitation of compressed air, which has been limited to the pressure so far, in a complicated model. An object of the present invention is to provide a mold making method and an apparatus therefor capable of forming a uniform mold.

[0003]

[Means for Solving the Problems] In order to achieve the above-mentioned object, a molding method according to the present invention comprises casting molding sand in a sand magazine arranged above a molding space defined by a model plate and a molding frame. A method of molding a mold to be filled in a frame, a step of closing an opening part of the mold molding space with a sand magazine having an opening / closing projection opening on the bottom surface, and casting sand in the sand magazine together with closing the projection opening. after turning, high pressure and a step of sealing the interior sand magazine, gently introducing a gas into the sand in the magazine closed with the said sand magazine, and gas from the casting sand and 4 kgf / cm ² of 9 Kgf / cm ² The method is characterized by including a step of obtaining a mixture and a step of opening the projection port in a short time when the pressure in the sand magazine reaches a predetermined height. Further, a mold making apparatus for achieving the object of the present invention is a sand magazine which is arranged above a casting frame and provided with a plurality of projection openings at the bottom, and a gable which is provided at the top of the sand magazine and which can be opened and closed. -A mechanism, an inlet provided in the sand magazine for introducing compressed air, a vent plug provided in the bottom of the sand magazine for discharging only compressed air, and a gate mechanism for opening and closing the projection port. It is characterized by having.

[0004]

According to the present invention, by using the above-mentioned solving means, hanging of a shelf does not occur, and a mold can be molded by a mixture of foundry sand and high-pressure gas.

[0005]

Embodiment 1 An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 1, a casting frame 2 and a fill frame 2a are placed on the model plate 1 placed on the lifting device T,
A model molding space is defined by the model plate 1, the casting frame 2 and the fill frame 2a. The lower end of a sand magazine 3 is fitted in the open part of the mold making space, the molding sand 4 can be charged into the sand magazine 3, and the upper part of the sand magazine 3 is opened and closed by a gate cylinder 5. 6 is provided. Further, an inlet 7 for compressed air is provided on the upper side surface of the sand magazine 3, and the inlet 7 is connected to a compressed air source 9 through a control valve 8. On the other hand, the bottom portion 10 of the sand magazine 3 is provided with a plurality of projection ports 11 and a vent plug 12 for separating and discharging only compressed air from a mixture of foundry sand and compressed air. The dimensions of the vent plug 12 and the projection port 11 are as shown in FIG. That is, the projection ports 11 having a diameter of 25 mm are arranged in a lattice shape at the vertices of a square having a side of 50 mm, which is obtained by equally dividing the cross-sectional area of the molding flask 2, and the vent plug 12 having a diameter of 30 mm is provided at the center of the square. . The upper part of the projection port 11 can be opened and closed by a slide hole plate 13. The slide hole plate 13 is connected to the shutter cylinder 14 to form a gate mechanism. When the shutter cylinder 14 is operated, the projection aperture 1 is opened.
1 is opened so that the inside of the sand magazine 3 and the inside of the flask 2 are communicated with each other.

The operation of the apparatus configured as described above will be described. First, the elevating device T is actuated to fit the bottom of the sand magazine 3 into the open part of the molding space, resulting in the state shown in FIG. In this state, the projection port 11 of the bottom portion 10 of the sand magazine 3 is closed. Next, the gate cylinder 5 on the sand magazine 3 is operated to open the gate 6, and the casting sand 4 is loaded into the sand magazine 3 by a casting sand 4 feeding device (not shown). Next, use the gate cylinder 5
The gland 6 is closed and the inside of the sand magazine 3 is sealed. Then, the compressed air is introduced from the compressed air inlet 7 provided on the upper side surface of the sand magazine 3. This introduction speed is gently introduced by, for example, a control valve 8 provided between the introduction port 7 and the compressed air source 9. The pressurization rate was 3 kgf / cm ² / sec. Compressed air was introduced until the pressure in the sand magazine 3 reached 7 Kgf / cm ² . A high-pressure mixture of foundry sand and compressed air is formed here. Then, after that, the shutter cylinder 14 was rapidly operated to move the slide hole plate 13 laterally to open the projection opening 11 at a speed of 0.2 seconds. At this time, the molding sand 4 in the sand magazine 3 is filled from the projection port 11 into the molding space together with the compressed air.
Further, the compressed air is separated by the vent plug 12 and exhausted from an exhaust port (not shown). Thereafter, if necessary, the foundry sand filled in the flask 2 is further squeezed by raising the model plate 1 by the lower elevating device T (for example, a hydraulic cylinder). After that, the model plate 1 is lowered to separate the sand magazine 3 and the filling frame 2a, and further, the casting frame 2 and the filling frame 2a are separated, and then the die is removed.

Now, the reason why the molding sand can be filled and the molding sand can be satisfactorily compressed by this method will be described.
The sand slinger method has been used as a conventional method for molding by casting foundry sand. In this sand slinger method, casting sand is lumped with an impeller into lumps having a diameter of about 2 to 5 cm and cast on a model plate to solidify the casting sand. The foundry sand can be compacted in a certain size and thrown from a high place so that it can be compressed at the pattern plate. And, it is known that, in the sand slinger, since no pressure is applied to the casting frame, spring back does not occur and a very good mold can be produced. On the other hand, it has been experienced that casting sand does not harden even if it is thrown one by one. The present invention is based on a completely new idea applying the principle of sand slinger, and as the sand slinger method gives energy to the foundry sand lump by the impeller, the present invention gives energy to the foundry sand by high-pressure gas, It is a method of projecting a mixture of foundry sand and high-pressure gas into the flask with a minimum pressure loss. Then, the mixture of the molding sand and the high-pressure gas is separated into the high-pressure gas and the molding sand by the vent plug in the flask, and only the molding sand is filled.
In the present invention, when the projection distance is within 500 mm, the weight mixing ratio of foundry sand and air is 500 to 1500 and the projection speed is 10 to 10.
It was confirmed that a high hardness was exhibited under the conditions of 20 m / sec and the diameter of the projection opening 11 of 15 to 30 mm. On the other hand, in the conventional blowing apparatus, since the blowing pressure cannot be increased, the raw sand hardness can be only about 70.

The difference between the conventional blow molding method and the principle of the present invention will be described with reference to the drawings. In FIG.
FIG. 5A shows the conventional blow molding method, and FIG. 5B shows the principle of the present invention. Conventional blow - pressure of the gas used in the molding method was ^{1kgf / cm 2 ~3kgf / cm 2} , pressure of the gas in the principles of the present invention is 4kgf / cm ² ~9kgf / cm ² is available, comparison Therefore, it was set to 5 kgf / cm ² . Regarding the inside of the sand magazine, in the conventional blow method, the pressure loss inside the sand magazine is large near the projection port, and the energy of the compressed air introduced into the sand magazine is lost at the projection port, and as a result, the mold Less energy is used for molding. In the present invention, the pressure loss in the sand magazine is almost non-existent in the vicinity of the projection port, and as a result, the energy used for mold making is large. That is, the total pressure P ₁ that can be used as velocity energy is different as shown by the diagonal lines. Further, the casting sand in the sand magazine has the following differences. In the conventional method, since the compressed air flows to the projection opening in the sand magazine, the molding sand is pushed toward the projection opening and the density around the projection opening becomes high. Since this molding sand has poor fluidity and has compressibility, it is hung from the shelf near the projection port, and the molding sand does not enter the casting frame through the projection port. This tendency becomes greater as the pressure of the compressed air blown into the foundry sand is increased. On the other hand, in the present invention, since pre-compressed air is contained in the sand magazine, the pressure loss is generated only in the nozzle portion below the projection port, so that the hanging in the vicinity of the projection port does not occur. The pressure of the compressed air in the sand magazine 3 when opening the projection port 11 is preferably 4 Kgf / cm ^{2 to} 9 Kgf / cm ² . 4 kgf / cm ² less as a template hardness during molding becomes lower than while the compressed air may foundry sand higher is tightened 10 Kgf / cm ² or more is generally not used for dangerous factory.

In the present invention, it is important that the compressed air initially put in the sand magazine 3 is slowly introduced. This is because when the compressed air is rapidly introduced, the molding sand is compressed by the air pressure in the vicinity of the projection port 11, and thereafter the molding flask cannot be filled. The rate of pressurization in the sand magazine 3 is preferably 10 Kgf / cm ² / sec or less. The projection speed of the foundry sand from the projection opening 11 needs to be projected at a speed of 10 m / sec or more. The reason will be described below. The velocity V of the foundry sand ejected from the projecting port 11, the pressure loss of the projecting port 11 is Pm, the diameter of the projecting port 11 is D, the length of the projecting port 11 is 1, the mixing ratio of the molding sand and the gas is m, and the air is When the specific gravity is γ and the powder fluid ejection coefficient is λ, the projection velocity is calculated as follows from the calculation of air transportation.

[0010]

[Equation 1]

The opening of the projection opening 11 in a short time of 0.2 seconds or less was obtained as follows. Assuming that one projection port 11 is responsible for filling a square with a projection area of 5 cm, the carrier carrier area of the frame is Q, the cross-sectional area of the projection port 11 is A, and the velocity of the foundry sand ejected from the projection port 11 is V. Then, the time T during which the frame having a height of 30 cm can be filled can be calculated as follows.

[0012]

(Equation 2)

Accordingly, the molding sand is filled with the molding sand in 0.09989 seconds. Here, the opening speed of the slide perforation plate 13 should be finished within 1/3 or less of the filling time. If the opening speed of the slide perforation plate 13 is slower than this,
A mixture of foundry sand and high-pressure gas was projected from the inside of the sand magazine when the slide perforation plate 13 was half-opened, and this mixture collided with the slide perforation plate 13, and the slide perforation plate was squeezed. This is because the pressure loss increases and the original principle does not work. As a result of the experiment, preferably, the opening speed of the slide perforation plate 13 is 1 /
It has been found necessary to open between 500 and 1/300 seconds. However, the opening speed of the slide hole plate is 0.2
If it is less than a second, filling may be possible. Therefore, a sufficient filling effect cannot be obtained unless the opening time of the slide perforated plate 13 is 0.2 seconds or less, preferably 2/1000 seconds to 5/1000 seconds.

The reason why the weight mixing ratio of foundry sand and gas in the sand magazine 3 is required to be 500 to 1500 is as follows. If the mixing ratio is too large, the proportion of the foundry sand becomes large, and hanging or the like occurs, making it impossible to project the foundry sand sufficiently. On the other hand, if the mixing ratio is too small, the proportion of the foundry sand will be too small and cannot be projected. When squeezing is performed after the molding by the projection, there is an advantage that the hardness of the mold near the bottom of the sand magazine 3 can be increased.

The effects of the method of the present invention will be described below. In the present invention, since no force is applied to the flask, the springback of the mold becomes minute. Springback is caused by the presence of internal stress, and there is no springback because internal stress does not occur when the molding sand is partially solidified little by little. Further, in the method according to the present invention, since energy loss is small, even a complicated model can be uniformly filled. For example, in the conventional mainstream static pressure molding method, the ratio of the diameter of the mold to the depth was limited to 3: 1. However, in the molding method of the present invention, 5: 1 was sufficient for molding. Furthermore, since there is no hanging of molding sand or no step at the time of molding, no cracks or wrinkles are generated in the mold, and a mold having uniform hardness can be obtained.

In the apparatus according to the present invention, the strength of the flask need not be so high as in the sand slinger method. Therefore, the cost of the molding flask is reduced. Further, similar to the blowing method, there is no need for sanding after molding, and there is an effect that a sand cutter is unnecessary because the upper surface of the mold is flat. Moreover, in this embodiment, the structure of the gate mechanism is simplified.

In this embodiment, the raw sand is described, but the present invention can be applied to various casting sands such as thermosetting sand such as shell sand and self-hardening sand such as cold Bockox sand. Also,
The position of the vent plug 12 does not necessarily have to be on the bottom portion 10 of the sand magazine 3, and the shape of the vent plug 12 is not limited to a circle, but a rectangle, a square, or the like can be used. In addition, the sand magazine 3 is placed in the open part of the mold making space.
The step of fitting the bottom of the device is not necessarily the first step of operating the apparatus, and may be performed simultaneously with the introduction of compressed air.

[0018]

Second Embodiment Another embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 2, as in the first embodiment,
A model molding space is defined by the model plate 1, the casting frame 2 and the fill frame 2a. A lower end portion of a sand magazine 3 is fitted into an open portion of the molding space, and a gate 6 which is opened and closed by a gate cylinder 5 is provided above the sand magazine 3. Further, an inlet 7 for compressed air is provided on the upper side surface of the sand magazine 3, and the inlet 7 is connected to a compressed air source 9 through a control valve 8.
On the other hand, the bottom portion 10 of the sand magazine 3 is provided with a plurality of projection ports 11 and a vent plug 12 for separating and discharging only compressed air from a mixture of foundry sand and compressed air. The projection port 11 is a rotary valve 1.
It can be opened and closed by 5,15. The rotary valves 15 and 15 are connected to the rotary levers 16 and 16, and are configured as a gate mechanism that opens the projection port 11 when the rotary levers 16 and 16 are rotated by the cylinder 16a.

In the apparatus constructed as described above, first, the elevating device T is operated to fit the bottom portion of the sand magazine 3 into the open portion of the mold forming space, and the state shown in FIG. 2 is obtained. In this state, the projection port 11 of the bottom portion 10 of the sand magazine 3 is closed. Next, the gate cylinder 5 on the sand magazine 3 is operated to open the gate 6, and the casting sand 4 is loaded into the sand magazine 3 by a casting sand 4 feeding device (not shown). Next, the gate 6 is closed by the gate cylinder 5, and the inside of the sand magazine 3 is sealed. Then, the compressed air is introduced from the compressed air inlet 7 provided on the upper side surface of the sand magazine 3. This introduction speed is, for example, 7
Is slowly introduced by a control valve 8 provided between the compressed air source 9 and the compressed air source 9. Compressed air is introduced until the pressure in the sand magazine 3 reaches a predetermined pressure of 7 Kgf / cm ² . A mixture of compressed air and foundry sand is obtained here. Then, after that, the rotary lever is rapidly rotated by 90 degrees to open the rotary valve. At this time, the casting sand 4 in the sand magazine 3 is projected into the projection port 1
1 to be filled with compressed air into the molding space of the mold. Further, the compressed air is separated by the vent plug 12 and exhausted from the exhaust port. After that, the mold filled in the casting frame 2 is further squeezed by raising the model plate 1 by the elevating device T (hydraulic cylinder) below. After that, the model plate 1 is lowered to separate the sand magazine 3 and the filling frame 2a, and further, the casting frame 2 and the filling frame 2a are separated, and then the die is removed.

The apparatus according to the present embodiment has the effect that there is no shadow portion and the molding sand in the sand magazine enters more uniformly.

[0021]

Third Embodiment Another embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 3, similar to the first embodiment, the model plate 1, the molding frame 2 and the fill frame 2a define a mold molding space. A lower end portion of a sand magazine 3 is fitted into an open portion of the molding space, and a gate 6 which is opened and closed by a gate cylinder 5 is provided above the sand magazine 3. Further, an inlet 7 for compressed air is provided on the upper side surface of the sand magazine 3, and the inlet 7 is connected to a compressed air source 9 through a control valve 8. On the other hand, the bottom portion 10 of the sand magazine 3 is provided with a plurality of projection ports 11 and a vent plug 12 for separating and discharging only compressed air from a mixture of foundry sand and compressed air. The projection port 11 is a valve plug 17
Can be opened and closed. This valve plug is connected to the frame 18, and is configured as a gate mechanism in which when the frame 18 is raised by the actuator 19, the projection ports 11 are opened all at once.

In the apparatus constructed as described above, first, the elevating device T is operated to fit the bottom portion of the sand magazine 3 into the open portion of the molding space, and the state shown in FIG. 3 is obtained. In this state, the projection port 11 of the bottom portion 10 of the sand magazine 3 is closed. Next, the gate cylinder 5 on the sand magazine 3 is operated to open the gate 6, and the molding sand 4 is charged into the sand magazine 3 by a molding sand 4 charging device (not shown). Then, the gate 6 is closed by the gate cylinder 5, and the inside of the sand magazine 3 is sealed. In this state, an inlet 7 for compressed air provided on the upper side surface of the sand magazine 3
Compressed air is introduced from. This rate of introduction is, for example,
Control valve 8 provided between the inlet 7 and the compressed air source 9
Will be introduced slowly by. Compressed air was introduced until the pressure in the sand magazine 3 reached 9 Kgf / cm ² . Then, thereafter, the actuator 19 is rapidly operated to raise the valve plug 17. At this time, the molding sand 4 in the sand magazine 3 is filled from the projection port 11 into the molding space together with the compressed air. Further, the compressed air is separated by the vent plug 12 and exhausted from the exhaust port. After that, the mold filled in the flask 2 is further squeezed by raising the model plate with the hydraulic cylinder at the lower part. After that, the model plate 1 is lowered to separate the sand magazine 3 and the filling frame 2a, and the casting frame 2 and the filling frame 2a are further separated.
After separating, die-cut. The device according to the present embodiment has effects such as a simple structure of the valve plug 17.

It should be noted that, as common to each embodiment, the cross-sectional area of the projection port 11 is 15% to 30% of the frame area, the area of the vent plug 12 is 20 to 75% of the frame area, and the aperture ratio of the vent plug 12 is 10 to 10. A very good template was obtained at 30%. This is because the larger the projection opening 11, the projection opening 11
This is because the resistance of the mold is tight and the mold is tightly closed. Also, the larger the number of the projection ports 11 is, the less the shadow of the gate mechanism is, and the unevenness in hardness between the area directly under the projection ports 11 and the vicinity thereof can be reduced. For example, it is desirable that the pitch between the projection openings 11 and the projection openings 11 is 30 mm to 60 mm.

[0024]

As is apparent from the above description, the molding method according to the present invention introduces compressed air in advance into the sand magazine 3 and uses the energy of the compressed air as effectively as possible for molding. At the same time, since the restriction of compressed air, which has a limit to the pressure so far, is eliminated, a mold having a complicated shape, which could not be achieved in the past, can be molded with energy efficiency. As is clear from the above description, the mold making apparatus according to the present invention does not require the strength of the flask to be so high, which leads to cost reduction of the flask. Also, there is no need for sanding after molding,
Since the upper surface of the mold is flat, there is an effect that a sand cutter becomes unnecessary. As described above, the effect of the present invention on the industrial world is remarkable.

[Brief description of drawings]

FIG. 1 is a schematic partial cross-sectional view showing a state before molding a mold showing an embodiment of the present invention.

FIG. 2 is a schematic partial cross-sectional view showing a state before molding a mold showing another embodiment of the present invention.

FIG. 3 is a schematic partial cross-sectional view showing a state before molding a mold showing still another embodiment of the present invention.

FIG. 4 is a bottom view of the sand magazine showing a positional relationship between a projection port and a vent plug and an opening area and a state thereof.

FIG. 5 is a schematic view showing the principle of a conventional blow molding method and the mold molding method of the present invention.

[Explanation of symbols]

 1 Model Plate 2 Mold Frame 3 Sand Magazine 4 Foundry Sand 5 Gate Cylinder 6 Gate 7 Introduction Port 10 Bottom 11 Projection Port 12 Vent Plug 13 Slide Hole Plate 15 Rotating Valve 17 Valve Plug

Claims (12)

[Claims] 1. A mold molding method for filling a molding sand 2 with a molding sand 4 in a sand magazine 3 arranged above a molding space defined by a model plate 1 and a molding frame 2 on a bottom surface. Closing the opening of the mold making space with a sand magazine 3 having a projecting opening 11 that can be opened and closed; and closing the projecting opening 11 and simultaneously molding sand 4 in the sand magazine 3.
, And the process of hermetically sealing the inside of the sand magazine 3, and slowly introducing gas into the hermetically sealed sand magazine 3 to cause the molding sand 4 and 4 Kgf / cm
^A step of obtaining a high-pressure mixture with a gas of ² to 9 Kgf / cm ² and a step of opening the projection port 11 in a short time when the pressure in the sand magazine 3 reaches a predetermined height. Characteristic mold making method. 2. The mold making method according to claim 1, wherein the speed of increasing the pressure in the sand magazine 3 is 10 kgf / cm ² / sec or less. 3. The casting method according to claim 1, wherein the casting sand 4 is projected from the projection opening 11 at a speed of 10 m / sec or more. 4. The mold making method according to claim 1, wherein the projection port 11 is opened in a short time of 0.2 seconds or less. 5. A molding sand 4 in the sand magazine 3.
The molding method according to claim 1, wherein the mixing ratio of the weight and the gas weight is 500 to 1500. 6. A method of molding a mold, characterized by performing squeezing after molding the mold according to claim 1. 7. A sand magazine 3 which is arranged above the casting frame 2 and has a plurality of projection ports 11 at the bottom thereof, a gate 6 which is provided above the sand magazine 3 and which can be opened and closed, and the sand. An inlet 7 provided in the magazine 3 for introducing compressed air, a vent plug 12 provided in the bottom portion 10 of the sand magazine 3 for discharging only high-pressure gas, and the projection port 11
And a gate mechanism that opens and closes the mold. 8. The casting mold making apparatus according to claim 7, wherein the projection ports 11 are arranged in a lattice shape at the vertices of a square obtained by equally dividing the cross-sectional area of the flask 2. 9. The cross-sectional area of the projection port 11 is 15% of the frame area or more.
30%, vent plug 12 area is 20 to 75 of the frame area
%, The opening ratio of the vent plug 12 is 10 to 30%, and the mold making apparatus according to claim 7, 10. The slide punching plate 13 is a gate mechanism for opening and closing the projection opening 11.
Described mold making machine 11. The mold making apparatus according to claim 7, wherein the gate mechanism for opening and closing the projection port 11 comprises a rotary valve 15 connected to a rotary lever 16. 12. The mold making apparatus according to claim 7, wherein a gate mechanism for opening and closing the projection port 11 is composed of a valve plug 17 which is connected to a frame 18 which can be moved up and down and which moves up and down.