JPH06285583A - Method for regenerating molding sand - Google Patents

Abstract

PURPOSE:To provide a method for regenerating molding sand in good efficience and at a low cost. CONSTITUTION:A hollow drum 12 arranged with a charging hole 15 and a discharging hole 17 is rotated centering a rotary shaft 8 and a disk 14 having an eccentric rotary shaft 9 to the rotary shaft 8 of the drum 12 is supported so as to be freely rotated in the drum 12. The molding sand is supplied in the drum 12 from the charging hole 15, and based on the mutual action of the drum 12 and the disk 14, the molding sand is friction-polished and binder is removed from the molding sand.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recycling foundry sand.

[0002]

2. Description of the Related Art A mold used in a casting process is a molding sand such as silica sand having fire resistance, which is fixed by adding a binder such as furan, phenol, water glass or bentonite. Foundry sand that was used for casting once as a mold is
Since the binder adheres to the surface, it is necessary to remove the binder adhered to each surface of the sand particles when reusing. If the binder is not removed sufficiently, the strength of the sand mold made will be insufficient, resulting in the inconvenience of frequent defective products.

[0003] Conventionally, as a method for reclaiming foundry sand, a method of throwing sand into a drum rotating at high speed to cause particles to collide with each other or a method of retaining sand in the drum and applying a centrifugal force to the sand and providing it to the drum are provided. A method of rubbing sand against each other on a sloped surface is known.

[0004]

However, in the former method, a large frictional force cannot be obtained because the contact force between the sands is weak and the contact surface is point-like. Further, in the latter method, friction was generated only on the retained surface, so that the frictional force was also small. Therefore, in any of the methods, the binder removal efficiency is poor, and even a soft binder requires a long-time regeneration treatment, resulting in a high cost. Further, it has been more difficult to remove hard binders such as phenol and water glass by the conventional method.

By the way, in recent years, hard type binders are often used for quality improvement, so that it is becoming more difficult to regenerate foundry sand by the conventional method.

On the other hand, even when the casting sand is discarded without being regenerated, it cannot be easily disposed due to recent industrial waste problems and pollution problems, resulting in high disposal costs.

It is an object of the present invention to solve the above-mentioned problems of the prior art and to provide a method for reclaiming foundry sand which is capable of fully responding to hard type binders and at low cost. I am trying.

[0008]

According to the present invention, a charging port 15 is provided.
The hollow drum 12 provided with the discharge port 17 is rotated about the rotation shaft 8, and the disk 14 having the rotation shaft 9 eccentric to the rotation shaft 8 of the drum 12 is rotatably supported in the drum 12. Regeneration of molding sand, characterized in that the molding sand is supplied into the drum 12 from the charging port 15 and the molding sand is friction-polished based on the interaction between the drum 12 and the disk 14, thereby removing the binder from the molding sand. The method is the gist.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view showing a foundry sand reclamation apparatus 10 for carrying out the method of the present invention.

The reproducing apparatus 10 has a hollow drum 12 which is forcibly rotatable about a drum shaft 11, and a disc 14 which is supported in the drum 12 so as to be freely rotatable about a disc shaft 13.

The drum 12 has a cylindrical shape as a whole, and an inlet 15 is formed on the left side wall 12a in FIG.
On the inner side of the right side wall 12b, a circular ring-shaped plate 1
6 is fixed inside the drum peripheral wall 12c. A plurality of outlets 17 are formed at equal intervals in the circumferential direction between the divider plate 16 and the right side wall 12b. Drum shaft 11
Can be forcedly rotated by a high-speed motor (not shown).

The disc shaft 13 is fixed to an apparatus main body (not shown) so that its central axis 9 is eccentric downwardly from the central axis 8 of the drum shaft 11 by a predetermined distance D. The eccentric distance D is 8.2 to 13.
Set to 7%, more preferably 11.0 to 12.3%
Set to. The rotating body 1 is provided outside the disc shaft 13.
8 is provided via a bearing 19 so as to be freely rotatable. A disk body 20 is detachably fixed to the rotating body 18. The disk body 20 is made of a wear resistant material and has a double structure on the outer circumference.

Next, a method for reclaiming foundry sand using the reclaiming device 10 will be described. Used casting sand is charged into the drum 12 from the charging port 15 (see arrow A). At this time, it is advisable to guide the molding sand with a charging chute (not shown). The sand introduced into the drum 12 which is rotating at a high speed receives a large centrifugal force and is pressed against the inner surface of the drum 12 and adheres in a layered manner.

Since the disk 14 is eccentric to the drum 12 by the distance D, the space inside the drum is slightly narrowed in the lower region. That is, the gap between the inner surface of the drum 12 and the tip of the disk 14 is narrowed in the lower region inside the drum.

For this reason, the disk 14 is impulsively press-fitted into the sand layer, which is adhered to the inner surface of the drum at a high pressure, to rotate.
The sand layer flows due to this impact and pressure, a large frictional force acts between the sand particles, and the sand particles are ground together.
By this polishing, the binder attached to the sand particles is removed.

The sand that has been polished flows past the end plate 16 (arrow B) and is discharged to the outside from the discharge port 17 (arrow C). A cover for collecting sand discharged by centrifugal force is provided around the drum 12, and a discharge chute is connected to the lower part of the cover to send the sand to a collection container (neither is shown).

By constantly charging sand from the charging chute, almost the same amount of reclaimed sand is constantly discharged.
The binder removed along with the sand is also discharged, but both can be easily separated by utilizing the difference in specific gravity.

The results of the actual reproduction test will be described below.

Example 1 An attempt was made to regenerate sand under the conditions shown in the margins of Table 1. The results are shown in Table 1 and FIG. It should be noted that the number of passes means the number of times processing is performed by the playback device. Further, the loss on ignition means a method in which an organic binder is heated and vaporized and the amount of the loss is quantitatively measured. With the burning loss, the regenerating effect is shown with each pass, and 31.9% of the original sand with 3 passes.
And a remarkable extinction rate was obtained. The compressive strength also improved with each increase in the number of passes, and with the reclaimed sand of 3 passes or more, the strength value after 24 hours was about 80% higher than that of fresh sand. In addition, the power consumption was significantly reduced.

In the same manner as in Example 2 , a sand regeneration experiment was tried under the conditions shown in the margins of Table 2. The results are shown in Table 2 and FIG. In the water glass process, which has hitherto been considered to be the most difficult to regenerate, the disappearance rate of residual alkali content was 61.5% in three passes, which was an astonishing figure. Compressive strength is 22.5 kgf / cm ^{2 in} 2 passes
The repeated use of the reclaimed sand was demonstrated in two passes.

Example 3 Process: Raw sand, test sand: Same as under the condition of imported sand (sand that is repeatedly used by mixing raw sand with shell sand, alkaline resole sand, cold box sand, etc.) The reproduction experiment was performed. The results are shown in FIGS. Although the burning loss and the extinction value of all clay in the raw sand are shown, extremely remarkable extinction rate was obtained in all cases. Repeated use of reclaimed sand was demonstrated in two passes.

Summarizing the results of the above-mentioned casting sand regeneration experiment, it has been proved that an excellent regeneration effect can be obtained in any process such as organic self-hardening, inorganic self-hardening, and green mold, and the casting sand can be produced at low cost. It became clear that it can be regenerated.

The centrifugal force of the drum will now be described. Generally, it depends on the strength and grain shape of the sand, but it depends on the silica sand,
It is said that a commonly used sand such as zircon sand and glass beads requires a centrifugal force of 15 G to 40 G, but the experiments conducted by the present inventor have revealed the following.

That is, in silica sand and zircon sand, the centrifugal force is preferably set to 30 G to 40 G, more preferably 35 G to 40 G. The optimum value is 38G. For glass beads, it is preferably set to 5G to 20G, and more preferably set to 15G to 20G.
The optimum value is 17G. Since the glass beads have a round particle shape, they can be sufficiently regenerated even with a small centrifugal force.

The depth at which the disc penetrates into the layered sand on the inner surface of the drum is effectively 30 to 50 mm when the layer thickness of the sand is 50 to 60 mm, and the optimum value is 40.
It was also found to be ~ 45 mm. In other words, the layer thickness of sand is 6
0 to 83% is desirable, and more desirably 67 to
Set to 75%.

[0026]

INDUSTRIAL APPLICABILITY The method for reclaiming foundry sand of the present invention uses the charging port 15
The hollow drum 12 provided with the discharge port 17 is rotated about the rotation shaft 8, and the disk 14 having the rotation shaft 9 eccentric to the rotation shaft 8 of the drum 12 is rotatably supported in the drum 12. The molding sand is supplied from the charging port 15 into the drum 12, and the molding sand is friction-polished based on the interaction between the drum 12 and the eccentric disk 14, thereby removing the binder from the molding sand, so that the molding sand is efficiently and inexpensively manufactured. Foundry sand can be regenerated. Therefore, power consumption can be significantly saved.

The invention is not limited to the embodiments described above. For example, the shape of the disk is not limited to a circular shape, but may be an elliptical shape or a polygonal shape close to a circle. The drum shape is similar.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a main part of a reproducing apparatus for carrying out the method of the present invention.

FIG. 2 is a graph showing the results of Example 1.

FIG. 3 is a graph showing the results of Example 2.

FIG. 4 is a graph showing the results of Example 3.

FIG. 5 is a graph showing the results of Example 3.

[Explanation of symbols]

 10 Playback Device 11 Drum Shaft 12 Drum 13 Disc Shaft 14 Disc 15 Input Port 16 Cutout Plate 17 Ejection Port

[Table 1]

[Table 2]

Claims (1)

[Claims] 1. A hollow drum (12) provided with an inlet (15) and an outlet (17) is rotated about a rotating shaft (8), and the drum (12) is rotated with respect to the rotating shaft (8). A drum (12) is provided with a disc (14) having an eccentric rotation axis (9).
It is rotatably supported inside and the drum (1
2) Regeneration of molding sand, characterized in that the molding sand is fed into the inside, and the molding sand is friction-polished based on the interaction between the drum (12) and the disk (14), thereby removing the binder from the molding sand. Method.