JPH02180743A - Production of sand - Google Patents

Abstract

PURPOSE:To obtain sands nearly free from acute edges causing the concentration of an electric field or stress in a high yield by successively subjecting a sand base to extrusion molding into a noodle shape, drying, crushing to granules, screening and calcining. CONSTITUTION:A sand base is prepd. and dehydrated with a filter press to form a cake having a proper water content. This cake is put in a kneader, kneaded and extruded from a perforated plate having many through holes of about 1.8-2.0mm diameter to obtain noodle-shaped molded bodies. The diameter of the molded bodies is made equal to or slightly larger than the max. diameter of objective sands. The molded bodies are dried, crushed and screened with a crusher and a disintegrating screening machine to obtain granules whose diameter is nearly equal to that of the molded bodies. The granules are sorted with a screen, packed into a shearth and calcined. This calcined product is broken into granules again with a breaking sieve to produce sands.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention produces in a high yield ceramic sand which is bonded in advance to the surface of an insulator in order to increase the bonding strength when bonding metal fittings to the insulator. The present invention relates to a method for producing sand.

(Prior art) The sand used for the above purpose has a particle size of 0.7 to 1.7.
Ceramic particles are approximately W in size. Conventionally, a sand base material is extruded into a block shape using a clay kneading machine, which is fired and then crushed using a crusher, and the crushed product is then sized within a certain particle size range using a size regulating machine. It was manufactured using a grinding method. However, in such conventional methods, the proportion of particles falling within the particle size range suitable for use as sand for crushing block-shaped fired bodies was low, and the particle size yield was at a low level of about 25%. In addition, many of the sands obtained by conventional methods have sharp edges, and when they are incorporated into an insulator, the electric field concentrates on the edges and becomes the starting point for current penetration when steep waves such as lightning impulses act. Not only is this easy, but it is also a factor that reduces the strength of the insulator due to stress concentration.

(Problems to be Solved by the Invention) The present invention solves the above-mentioned conventional problems and manufactures sand with a high yield with few sharp edges that cause electric field concentration and stress concentration. It was completed with the aim of creating a method for producing sand.

(Means for Solving the Problems) The present invention, which was made to achieve the above-mentioned problems, involves extruding a sand base material into a noodle shape using a clay kneading machine, and after drying it into granules having approximately the same diameter as the noodle. It is characterized by being crushed, sized, and then fired.

The present invention will be explained in detail below with reference to the flow sheet shown in FIG.

First, a sand base is prepared in the same way as before, and then dehydrated using a filter press to form a cake containing an appropriate amount of moisture.

Put this cake into a clay kneader and knead until the pore diameter is 1.8-2.
．． A noodle-shaped molded product is obtained by extruding it through a perforated plate having a large number of through holes of about 0 m in diameter, and the diameter of the noodle is set to be the same as or slightly thicker than the maximum particle diameter of the target sand. Next, this is dried and pulverized and sized into granules having approximately the same diameter as the noodles using a coarse crusher and a de-sinter granulator. The de-sinter grading machine is a device that performs pulverization and grading while rotating a drum equipped with a large number of through holes.The diameter of the holes provided in the drum is approximately 1.6 to 1. It is preferable to operate at a rotational speed of about 200 rpm, which is much lower than in normal cases.The granules thus obtained have an upper mesh of 1.68 rpm, a lower mesh of 0.
It is passed through a sieve of 84 to 1.0 mm to be sorted, then packed in pods and fired. The baked product is then passed through a sieve to loosen it and become a sandwich product.

When the sand obtained in this way is compared with the sand obtained by the conventional manufacturing method, the coefficient of thermal expansion is 18.5
10-5/”C (600°C) and 18
．． 6X10-'/'C, the amount of crystals such as cordierite, mullite, and quartz is 24.9% and 16.
1%, 1.4% compared to 25.1%, 15.5% of the conventional product
%, which remained almost unchanged at 2.1%. Furthermore, the closed porosity was 9.3%, which was exactly the same as that of the conventional product.

As described above, the physical properties of the sand obtained by the production method of the present invention and the conventional sand are almost the same, but their shapes and yields are significantly different. That is, since the sand obtained by the manufacturing method of the present invention is crushed and sized to a predetermined particle size in the step before firing, it has almost no sharp edges. This sand was adhered to the head of a suspension insulator according to a conventional method, and the cap metal fitting and pin metal fitting were bonded with cement, and the tensile strength was measured. The tensile strength was improved by about 1.0 mm on average. This is thought to be the result of the stress concentration at the edge of the sand being relaxed. In addition, each of these 10 insulators has a voltage of 6000 KV/μs.
We conducted a test to apply a steep wave of When the sand of the present invention was used, no cracks originating from the sand occurred at all. This is considered to be the result of the electric field concentration at the edge of the sand being relaxed.

Moreover, according to the present invention, the yield is extremely high because the noodle-shaped extruded body is crushed, and conventionally, for example, the amount of sand finally obtained for 23 tons of input soil was 5.5 tons.
ton and the yield was 24%.
According to the present invention, 10.9) tons of sand was obtained for the same amount of input soil, and the yield was able to be improved approximately twice to 48%. For reference, FIG. 2 shows the cumulative particle size distribution of the sand produced by the method of the present invention and the sand produced by the conventional method, and FIG. 3 shows an example of the representative particle size distribution of both.

(Effects of the Invention) As explained above, the present invention makes it possible to produce sand with fewer sharp edges that cause electric field concentration and stress concentration at a much higher yield than conventional methods. Therefore, as a method of manufacturing sand that eliminates the drawbacks of conventional methods,
The contribution it makes to the development of industry is extremely large.

[Brief explanation of the drawing]

FIG. 1 is a flow sheet showing an example of the present invention, FIG. 2 is a cumulative particle size distribution diagram of sand, and FIG. 3 is a representative particle size distribution diagram of sand. Patent applicant Nippon Insulator Co., Ltd.
Director name: Akira Shima
Immediate question: Kan Wata
release
[Yama Rei Fumi Fu] Figure C7 =] Finished figure Shinomi opening CP)

Claims (1)

[Claims] The sand base is extruded into a noodle shape using a clay kneading machine, and after drying, it is crushed into granules with approximately the same diameter as the noodle.
A method for producing sand, which is characterized by sizing and firing.