JP3142042B2 - Mold making method and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a mold molding method in which molding sand is poured into a molding space defined by a model plate with a model and a molding frame matched to the model plate, and air pressure acts on the molding sand. A method and an apparatus therefor.

[0002]

2. Description of the Related Art Conventionally, there have been various methods for molding a mold using a jolt, a squeeze, a flow pressurization, a shock wave, and the like. While these methods have been used singly or in combination, these methods have their own drawbacks. In Jolt, vibration and noise are problems.In squeeze, the hardness of the mold near the model surface is often a problem. Noise and cracks occurred in the mold, and the filling condition near the pattern surface was not very good. For this reason, there has been a demand for a filling molding method which does not generate vibration noise during molding and has no cracks in the molded mold and uniformity. The present invention has been made in view of the above-mentioned problems, and has low vibration and noise when pre-compressing or molding molding sand, can reduce the number of vents, and can uniformly form without causing cracks in a molded mold. It is an object of the present invention to provide a method and an apparatus for molding a mold having a high packing density.

[0003]

Means for Solving the Problems In order to achieve the above-mentioned object, a method for molding a mold according to the present invention is directed to a molding space defined by a model plate with a model and a molding frame fitted around the model plate. In a method in which molding sand is charged and air pressure is applied to the molding sand, from above the molding sand, a) the frequency of air is 8 Hz to 20 Hz; b) the maximum amplitude is 0.1 MPa to 0.6 MPa; It is characterized in that a certain air pressure vibration is applied for a vibration time of 0.3 second to 2 seconds.

[0004]

By adopting the above-mentioned solution,
Since the bridge is broken while being compressed by air pressure vibration during the molding of the mold, the vibration and noise are low, and a uniform mold is produced without causing cracks in the molded mold.

[0005]

Embodiment 1 Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In FIG. 1, a cylinder 2 is attached to a central portion of a base 1 so that a piston rod 3 thereof is directed upward. A table 6 having an exhaust hole 5 communicated with 4 is fixed. The table
A model plate 8 on which a model 7 is fixed is fixed on the bull 6. The model plate 8 is provided with a ventilation hole 9 formed so as to penetrate the upper and lower sides, and the ventilation hole 9 has a mesh plug (not shown) having a mesh size enough to allow only gas to pass therethrough.
Is embedded. On the other hand, column members 11 erected on the base 1 are provided at four positions of the base 1, and a plurality of rollers 12 are rotatably mounted at an intermediate portion of the column members 11. A pair of first roller conveyors 13a is extended right and left and laid at predetermined intervals in front and rear so that the table 6 can pass up and down, and the upper part of the first roller conveyor 13a is provided. , A rectangular cast frame 14 is placed movably to the left and right. On an upper surface of a bracket 15 protruding inward from a position slightly above the roller conveyor 13a in the column member 11, a filling frame 16 engaged with a guide pin (not shown) is placed so as to be able to move up and down. ing. A head frame 17 is provided at the upper end of the column member 11, and the bracket 15 and the head frame 17 are provided.
A second roller conveyor 13b is provided between the first and second rollers. On the second roller conveyor 13b, a closing cover 18 whose upper part is sealed is placed so as to be movable left and right, and a squeeze foot 19 is built in the inside of the closing cover 18. Further, the closing cover 18 is connected to a sand charging hopper 20. An air supply hole 21 is opened on one side of the closing cover 18, and the air supply hole 21 is connected to a lower end of an air supply pipe 22. An air pressure vibrator 24 is provided above the head frame 17. The air supply pipe 22 is connected to a supply / discharge pipe 23 of the air pressure vibrator 24. The air pressure vibrator 24 has an opening ratio. Is connected to a compressed air source 26 via an opening / closing valve 25 that can change the pressure. Here, the air pressure vibration device 24 includes a rotary air valve 27 and an inverter 28 for varying the rotation of the rotary air valve 27. The rotary air valve 27 has a rotor 31 rotatable in the casing 30 and an exhaust port 3 having one end of the casing 30 opened.
2 are provided. A louver 33 is provided in the sand charging hopper 20 and is filled with kneaded molding sand 41. Here, the center position of the head frame 17 constitutes a central station 35, and the sand-filling position on the left side of the drawing constitutes a sand-filling station 36.

In the thus constructed apparatus, the model plate 8 is raised by operating the cylinder 2 in FIG. 1, and the model plate 8, the casting frame 14, and the filling frame 16 are temporarily stopped. Thus, a molding space defined by the model plate 8, the casting frame 14, and the filling frame 16 is formed. Next, the sand hopper 20 is moved to the central station 35, and the louver 33 is opened to perform sand pitting (FIG. 2). As a result, the molding sand 41 is moved into the molding space defined by the model plate 8, the casting frame 14, and the filling frame 16,
Can be put loosely. Thereafter, the sand hopper 20 returns to the sand hopper station 36 on the left side, and the cover 18 is closed.
Enters the central station 35 and the model plate 8 rises again, and the upper surface of the model plate 8 and the lower surface of the casting flask 14, the upper surface of the casting frame 14 and the lower surface of the filling frame 16, the upper surface of the filling frame 16 and the closing cover 18 are formed. , The upper surface of the closing cover 18 and the head frame 17 are connected. Thereby, the supply / discharge pipe 23 of the rotary air valve 27
Is communicated with the upper end of the air supply pipe 22 and through the air supply hole 21 to the closing cover 18. Thereafter, as shown in FIG. 3, the opening / closing valve 25 is slightly opened and the rotary air valve 27 is rotated, so that air is blown from the upper surface of the molding sand 41. At this time, the air pressure is alternately increased (FIG. 3A) and depressurized (FIG. 3B) in accordance with the rotation of the rotary air valve 27, and the air is supplied to the supply / discharge pipe 23, the supply air pipe 22, and the molding space 3.
Vibrates up and down at 7. Subsequently, the opening / closing valve 25 is further opened to gradually increase the amount of air. In FIG. 3A, since the molding sand 41 has compressibility as a whole, when the molding space is pressurized by air pressure, the molding sand 41 in the molding space is compressed.
Move downward and are compressed by the airflow. When the rotary air valve is in the state shown in FIG. 3B, the molding sand 41 is returned slightly upward due to the effect that the air pressure in the molding space is reduced (depressurized) and a part of the high-pressure air from above is reflected by the model plate 8. . Thereby, the molding sand 41 is fluidized, and the bridge due to the resistance between the molding sands 41 is broken, so that the molding sand 41 is made uniform. Then, it is pressurized again by the next air pressure. By this repetition, the level of the upper surface of the molding sand 41 gradually decreases, and the filling rate of the molding sand 41 gradually increases. Here, if the air pressure is strong (high pressure) from the initial stage of filling, the casting sand 41 separates, that is, cracks occur in the mold. When the casting sand 41 is separated, the speed of pressurization and decompression may be changed. By performing the pressurization at a high speed (increase in pressure or increasing the pressurization speed) and reducing the pressure slowly (decrease or decrease the pressure), separation of the molding sand 41 does not occur. Thus, the molding sand 41 is gradually compressed. The excess air at this time is intermittently exhausted from the exhaust port 32. When the compression by the air pressure vibration is completed, the squeeze foot 19 is lowered by, for example, a hydraulic drive, and the molding sand 41 is further mechanically compressed (FIG. 4). Thereafter, the cylinder 2 is moved down to close the cover 18 and the filling frame 1.
6. The casting flask 14 is lowered to the original position to perform the die cutting. In this embodiment, since the molding sand 41 is compressed using the vibration of the air pressure, the molding can be performed without vibrating the casting frame itself like a jolt. Noise, which is a problem in the case of an impact, can also be reduced. Further, as the vibration of the air pressure is repeated, impurities having a low specific gravity move to the upper surface of the mold and uniform sand particles move to the mold surface, so that the mold near the model plate is cleaned. Therefore,
Vibration and noise are low when molding a mold, and a mold having a uniform density can be molded without causing cracks in the molded mold. In the present embodiment, mechanical compression is performed after preliminary compression. However, mechanical compression is not always necessary, and squeezing can be omitted depending on the type of molding sand 41, the amplitude of air pressure vibration, and the amount of air. In this embodiment, the vent plug is used, but the vent plug is not essential because it is compressed by vibration of air pressure.

[0007]

[Embodiment 2] In the above embodiment, the rotary air valve 27 is used as the air pressure vibrating device 24. However, as shown in FIG. In FIG. 5, the cylinder 52 is communicated with an electromagnetic valve 55 via operation supply / exhaust pipes 53 and 54.
The port of the solenoid valve 55 includes a pressure source 56 and an exhaust hole 57.
The tip of the rod 58 of the cylinder 52 is connected to the bellows 51. This bellows 51
Contains air 59, and the tip of the bellows 51 is connected to the flask 14 through the air supply pipe 22. With this configuration, by switching the solenoid valve 55,
The operating air operates the cylinder 52 through the operating air supply tubes 53 and 54, and the rod 58 of the cylinder 52 vibrates up and down. When the rod 58 is lowered by this vibration, the air in the bellows 51 is compressed and sent to the molding space,
Compress 1 Then, as the air expands, the cylinder 52 is forcibly lifted to increase the volume and reduce the pressure of the air in the molding space. This continues to generate air pressure oscillations. The molding sand 41 is formed by the vibration of the air pressure. In this case, there is an advantage that the consumption of the air amount can be reduced because a large amount of compressed air is not required.

[0008]

Embodiment 3 FIGS. 6 and 7 show another embodiment. The configuration is the same as that of the first embodiment, except for the pneumatic vibration device 61. The configuration other than the pneumatic vibration device 61 is schematically shown. 6, the air pressure vibration device 61 includes a rotary air valve 62, air sources 63 and 64, and a supply / discharge pipe 65. Here, the air sources 63 and 64 are air sources 63 at atmospheric pressure or higher.
And a vacuum air source 64. Here, when the rotating air valve 62 is rotated by the motor 62, the rotation causes air in the supply / discharge pipe 65 to vibrate at a pressure higher than the atmospheric pressure and at a pressure lower than the atmospheric pressure. Thereby, the vibration of the air pressure is applied in the flask. In this case, there is an advantage that the amplitude of the vibration of the air pressure can be obtained even if the pressure of the air source 63 is not too high.

[0009]

Embodiment 4 Referring to FIG.
Can be opened and closed by a cylinder 71 and a cylinder 72. Open end 71A of valve A is connected to a high-pressure air source, and open end 72B of valve B is connected to a low-pressure air source. Here, the high pressure source is 0.30MP
a, The low pressure source is connected to 0.14 MPa. Further, the cylinders 71 and 72 are connected to air pipes 73A and 73A.
The solenoid valve 74 is connected to the solenoid valve 74 via B, and the solenoid valve 74 is connected to the air source 75. In this configuration, air is supplied from an air source 75 to the air pipes 73A and 73B alternately by controlling the solenoid valve 74, and the cylinders 71 and 72 are operated alternately. When the cylinder 72 is at the forward end, the cylinder 71 operates at the return end, the valve A is opened, air flows in from the high-pressure air source, and high-pressure air flows into the flask. After a predetermined time, valve A is closed, instead cylinder 72 is actuated to the return end and valve B is opened, air flows out of the flask into the low pressure air source, and the low pressure air source Pressure close to
This is repeated by operating the solenoid valve 74, and the air alternately pressurizes and depressurizes. FIGS. 8 and 9 schematically show how the air pressure changes in this case. FIG.
In the graph, the vertical axis indicates the operation of the valves A and B, and the horizontal axis indicates the energization time. In FIG. 9, the vertical axis indicates the absolute pressure of air, and the horizontal axis indicates time. When the solenoid valve 74 is energized as shown in FIG. 8, the air pressure generated by the air pressure vibration device and mixed with the high-pressure air source and the low-pressure air source fluctuates as shown in FIG. In this case, in addition to the effect of the vibration of the air pressure, the vibration of the molding sand 41 is good because the vibration is higher than the atmospheric pressure.

[0010] Fig. 10 and Fig. 11 show examples of the vibration of the air pressure above the molding sand in the molding flask which defines the molding space in this case. This pressure depends on the size of the flask, the frequency, and the pressure of the air source. Here, the vertical axis is the absolute pressure,
The horizontal axis indicates time. FIG. 10 shows a temporal change of the air pressure in the molding space when the air pressure vibration of only the pressurizing vibration is used. In FIG. 10, before the pressurizing vibration, the pressure in the molding space is atmospheric pressure. Here, for example, the pneumatic vibration device described above with reference to FIG. 3 is operated to increase the opening ratio of the opening / closing valve 25 to gradually increase the amplitude. Thus, the absolute pressure in the molding space gradually increases while vibrating. Further, since the air gradually accumulates in the molding space, the minimum pressure of the air pressure vibration also gradually increases. Next, when the amplitude of the pressurized vibration that is gradually increased is set to a constant value, the pressure in the molding space is also in an equilibrium state accordingly, and the minimum pressure is kept constant and the amplitude is increased. Then, the opening / closing valve is gradually closed to gradually reduce the amplitude of the pressurized vibration to make the aperture ratio zero. Along with this, the pressure in the molding space gradually decreases and returns to the atmospheric pressure.

FIG. 11 shows the change over time of the pressure in the molding space when the air pressure vibration of the pressurized and depressurized vibration using the compressed air source and the vacuum source is used. In FIG. 11, before the pressurized and depressurized vibration, the pressure in the molding space is at the atmospheric pressure.
Here, in FIG. 6, open / close valves (not shown) are provided for the high-pressure source and the low-pressure source, the pneumatic vibration device is operated, and the aperture ratios on the high-pressure source side and the low-pressure source side are increased to gradually increase the absolute value of the amplitude. Make it bigger. Thereby, the air pressure vibration gradually increases in the molding space. Next, when the absolute value of the amplitude of the pressurized vibration, which is gradually increased while keeping the opening ratio constant, is set to a constant value, the pressure in the molding space is in an equilibrium state, and the amplitude is maintained while the maximum and minimum pressures are kept constant. Thereafter, the opening ratio of the on-off valve is reduced to zero. Along with this,
The pressure in the molding space also gradually decreases in amplitude and returns to atmospheric pressure.

FIG. 12 shows an experimental result in the case of molding using the above-described air pressure vibration device. The pressure of the air source is 0.
3 MPa was used. This is a case where a cylindrical type having a diameter of 105 mm × 400 mm is formed by using the same experimental apparatus as in Example 1. There is a limit on the frequency. If the frequency changes from pressurized to depressurized when the frequency is increased too much,
Since the next pressurization starts before the pressure inside the flask is sufficiently reduced, the effect of the vibration of the air pressure is not obtained. 20H frequency
This tendency was observed at the time of z or more. On the other hand, when the frequency is 8 Hz
If it is made smaller, the effect of bridge collapse due to vibration will not be obtained. The amplitude is determined by the pressure of the air pressurization source and the opening ratio of the on-off valve, but the pressure is not theoretically limited. However, it is advantageous to use compressed air normally used in factories from the viewpoint of ease of handling compressed air and cost reduction. On the other hand, in the case of the pressurized vibration, it was confirmed that the above-described effects could be obtained if the absolute value of the amplitude was 0.1 MPa or more. The vibration time depends on the particle size of the foundry sand and the binder, and is limited from an economic viewpoint. In other words, the one shorter than 0.3 seconds has a small frequency,
No effect of air pressure vibration. On the other hand, if the vibration time is longer than 2 seconds, for example, 3 seconds, the hardness of the mold does not increase so much even if the vibration time is increased. There is a correlation between the frequency and the pressure (pressure of the pressure source). When the specific gravity of the molding sand is large and as the particle diameter of the molding sand is large, high pressure vibration is required.
As the pressure in the flask is rapidly reduced, the air in the flask is more likely to be reflected. In order to increase the pressure reduction speed in the flask, the amplitude of the vibration of the air pressure is increased. To loosen, a throttle is attached to the exhaust port 32. As described above, the vibration frequency of the air pressure is 8 Hz to 20 Hz and the amplitude is 0.1 MPa from above the molding sand.
A high quality mold can be formed by applying an air pressure vibration of ~ 0.6 MPa to a vibration time of 0.3 seconds to 2 seconds, and within a predetermined range, the hardness becomes 80 or more, and it can be used as a mold. did it. FIG. 1 shows one waveform example of the air pressure vibration waveform.
3. For example, when a pressurizing source is used, the air pressure vibration is composed of waves during pressurizing and depressurizing, but the pressurizing speed during pressurizing is equal to or higher than the depressurizing speed during depressurizing It turned out to be favorable. If the rate of pressure reduction is too high, cracks will occur in the mold.

[0013]

As is apparent from the above description, the present invention makes it possible to form a uniform mold free of cracks by filling molding sand with fluidization or breakage of bridges by air pressure vibration. . Since the molding sand is compressed by the vibration of the air pressure, it is not always necessary to use a vent, and the number of vents can be reduced. Putter
The surface filling becomes better, and deeper shapes can be made. Further, since the flask is not vibrated, the effect on the industrial world is remarkable, such as no vibration and no large noise.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention before sand is charged.

FIG. 2 is a schematic sectional view showing an embodiment of the present invention before sand is introduced.

FIG. 3 is a schematic cross-sectional view showing an embodiment of the present invention when air pressure vibration is applied after sand is charged.

FIG. 3a is a schematic cross-sectional view showing an embodiment of the present invention during pressurization by air pressure vibration after sand is introduced.

FIG. 3b is a schematic cross-sectional view showing an embodiment of the present invention during depressurization by air pressure vibration after sand is introduced.

FIG. 4 is a schematic cross-sectional view illustrating mechanical compression after sand compression according to an embodiment of the present invention.

FIG. 5 is a schematic diagram of a pneumatic vibration device according to a second embodiment.

FIG. 6 is a schematic diagram of a pneumatic vibration device according to a third embodiment.

FIG. 7 is a schematic view of a pneumatic vibration device according to a fourth embodiment.

FIG. 8 is a graph illustrating air pressure vibration according to the third embodiment.

FIG. 9 is a graph showing air pressure vibration according to the fourth embodiment.

FIG. 10 is a graph showing an example of air pressure vibration (pressure vibration) used in Example 1-4.

FIG. 11 is a graph showing an example of air pressure vibration (pressurized and depressurized vibration) used in Example 1-4.

FIG. 12 is a graph showing mold hardness in an experimental example.

FIG. 13 is a graph showing a waveform example (for one cycle) of air pressure vibration.

[Explanation of symbols]

 7 Model 8 Model plate 14 Cast frame 19 Squeeze foot 24 Air vibrator 32 Exhaust port 37 Molding space

Claims (3)

(57) [Claims] 1. A method for introducing molding sand into a molding space defined by a model plate with a model and a molding frame fitted around the model plate, and applying air pressure to the molding sand. From above the foundry sand, a) air frequency vibration of 8 Hz to 20 Hz; b) maximum pressure of 0.1 MPa to 0.6 MPa; air pressure vibration of 0.3 seconds to 2 seconds is applied. Mold making method 2. The molding method according to claim 1, wherein the molding sand is mechanically pressurized after the action of the air pressure vibration. Above wherein pattern plate 8, closable to result co an upper opening in airtight flasks 14 to be placed on the該模template 8
A closing cover 18 having a built- in squeeze foot 19 is disposed therein, and the closing cover 18 communicates with an air supply pipe 22 for supplying air into a space defined by the casting frame 14. 22 is an air pressure vibration device 24 for generating air pressure vibration
The air pressure vibration device 24
Characterized in that the mold is connected to an air source 26.