JPH10277415A - Production method of sand and sand producing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and its device for producing sand by which the crushed sand stabilized in quantity and having a desired grain size distribution based on an FM value is automatically produced at a low product cost with the inexpensive device. SOLUTION: The raw sand to be supplied from a crushed raw sand line is crushed by a sand producing machine consisting of a cage mill and a part of the crushed product is returned by a fixed ratio to the crushed raw sand feed line as the raw sand of the cage mill. In this case, a sand producing device is composed of the crushed raw sand feed lines 12 and 1, a sand producing machine 2 for crushing the crushed raw sand supplied from the crushed raw sand feed line consisting of a cage mill, a distributor 3 for distributing the crushed product from the sand producing machine 2 by a specified ratio, a product crushed sand producing line including a classifier 5 and connected to one of the distributed side of the distributor 3 and a returning means 4 connected to the other side of the distributed side of the distributor 3 and returning a part of the crushed product by a fixed ratio from the sand producing machine 2 to the sand producing machine 2 side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sand making method capable of crushing and sand making a crushed sand raw material by a predetermined sand making means to produce a crushed sand having a desired coarse particle size distribution such as a single sand and the like. The present invention relates to a sand making device suitable for use in carrying out the method. The single sand refers to sand that can be used as it is as a raw material for concrete or the like without requiring any mixing operation such as mixing with natural sand at a demand destination.

[0002]

2. Description of the Related Art Typical prior art of this type of dry sand making apparatus used in sand making plants and the like is disclosed in Japanese Patent Publication No. 58-900 (first conventional example) and Japanese Utility Model Publication No. 4-909 (No. 2 conventional example) and JP-A-8-173835 (third conventional example).

[0003] In the first prior art, the crushed product of the primary crusher is sieved into coarse aggregate on a sieve and crushed sand passing through a sieve, and the crushed sand passed through the sieve and coarse aggregate having a small particle size are further sized. It is sieved by the following sieves, and those that do not pass through the sieve are crushed by a secondary crusher. Thereafter, a part of the crushed product of the secondary crusher and the crushed sand having a small particle size passing through the sieve surface are supplied to a dry classifier, and the remaining crushed product of the primary crusher and the crushed sand classified by the dry classifier are provided. Is supplied to a humidifying mixer, and a series of treatments of mixing with moisture are performed to produce sand.

[0004] The particle size distribution of the crushed product obtained by crushing general crushed sand raw materials by each type of conventional dry crusher including the first conventional example was examined.
The result as shown in FIG. That is, referring particularly to FIG. 7 in FIGS. 7 and 8, in order to obtain the above-mentioned crushed product that can be used as single sand, FIG.
(B) must have a particle size distribution within the particle size range defined by the Japan Society of Civil Engineers, represented as the area between the two broken lines, but any crushed products obtained by those dry crushers However, those having a sieve nominal size of 0.6 mm to 0.15 mm are insufficient.

[0005] Crushed sand having such a particle size structure is generally used for blending with natural sand, for example, and cannot be used as single sand.
In this regard, in the first conventional example, the FM value (Fineness M
odule: Coarse particle size of product crushed sand) No adjustment or adjustment of particle size distribution has been made, so crushed sand obtained by crushing and classification has a particle size distribution as shown in Fig. 7 (B). As a result, it cannot be used as the single sand targeted by the present invention. However, if a cage mill as a dry crusher is used at a very high rotation speed, the crushing performance may be improved and it may be possible to produce single sand depending on the raw material. Is extremely fast and cannot be used in a short period of time.

On the other hand, the second conventional example is such that a crushed product from a dry crusher is distributed by a distribution chute and a part thereof is returned to the dry crusher. The distribution chute can change the distribution ratio. It has a structure, and the particle size of the crushed product is adjusted by adjusting the distribution ratio. However, in the second conventional example, when the distribution ratio of the distribution chute is changed, the production amount of the crushed product naturally changes accordingly. Therefore, for example, the production amount of the product every month is not stable, There is a problem that it is difficult to make an accurate production plan. In addition, since the supply amount to the dry crusher also changes depending on the distribution ratio, there is a disadvantage that the operation state is likely to be unstable.

In this second conventional example, it is said that the FM value can be adjusted. However, there is no mention of the adjustment of the particle size distribution conforming to the range of the Japan Society of Civil Engineers as shown in FIG. 7 (B). Therefore, even if the FM value is an appropriate value, it is sufficiently considered that the FM value is out of the range of the Japan Society of Civil Engineers. In the second conventional example, too, it is difficult to obtain crushed sand usable as single sand. 1 Same as the conventional example.

The third prior art is a technique relating to a method for producing crushed sand using a rod mill as a crushing means, and is capable of producing crushed sand having a desired particle size distribution. Since it is a treatment method, there is a problem that turbid water treatment requires a long time and high cost, and therefore, it is a method significantly different from the dry crushing intended by the present invention.

[0009]

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems of the prior arts.
Another object of the present invention is to provide a sand making method and a sand making method capable of automatically producing crushed sand having a desired particle size distribution on the basis of an FM value, and capable of producing the sand at low equipment cost and low product cost.

[0010]

The present invention has the following configuration to achieve the above object. That is, in the present invention, the invention according to claim 1 crushes a crushed sand raw material supplied from a crushed sand raw material supply line by a sand maker comprising a cage mill, and supplies a part of the crushed product as a cage mill raw material by a fixed ratio to supply the crushed sand raw material. A sand making method characterized by returning to a line.

[0011] According to the present invention, in the state where the properties (rock quality, size, etc.) of the crushed sand material are small and substantially stable, the crushed product can be obtained by a fixed crushed sand distribution ratio adapted to the crushed sand material. By returning to the crushed sand raw material supply line, the particle size distribution of the crushed sand raw material can be made finer, and crushed sand that is likely to be insufficient in the size range of the sieve nominal size of 0.6 mm to 0.15 mm is replenished, and the desired Crushed sand with particle size distribution,
For example, it is possible to always produce single sand in a stable amount. The cage mill is an impact-type pulverizer,
The advantage is that high quality crushed sand can be obtained at low running cost.

Further, according to the invention of claim 2, the crushed sand raw material supplied from the crushed sand raw material supply line is crushed by a sand maker comprising a cage mill, and the crushed product is passed through a classifier to be classified into product crushed sand and fine powder. On the other hand, one of the crushed product and the product crushed sand is periodically and automatically sampled and its particle size distribution is automatically measured, and the rotation speed of the cage mill is controlled so that the measurement result meets predetermined setting conditions. It is a sand making method characterized by performing.

According to the present invention, even when the properties of the raw material for crushed sand change or when the crushing performance of the sand maker changes, crushed sand having a constant particle size can always be produced.

According to a third aspect of the present invention, the crushed sand raw material supplied from the crushed sand raw material supply line is crushed by a sand maker comprising a cage mill, and the crushed product is passed through a classifier to be classified into product crushed sand and fine powder. On the other hand, a part of the crushed product from the cage mill is returned to the crushed sand raw material supply line as a cage mill raw material by a certain ratio, and one of the crushed product and the product crushed sand is periodically and automatically sampled to determine its particle size distribution. The sand making method is characterized in that automatic measurement is performed and the rotation speed of the cage mill is controlled so that the measurement result meets predetermined conditions.

According to the present invention as described above,
These characteristics are also exhibited, and it is possible to produce qualitatively and quantitatively stable high-quality crushed product sand.

Further, the invention of claim 4 provides a sand making machine comprising a crushed sand raw material supply line including a conveying device, a cage mill for crushing the crushed sand raw material supplied from the crushed sand raw material supply line, A distributor for distributing the crushed product at a predetermined distribution ratio, a product crushed sand production line including a classifier and connected to one distributed side of the distributor, and the distributor connected to the other distributed side of the distributor. A sand making device is constituted by a return means for returning a part of the crushed product from the sand making machine to the above-mentioned crushed sand raw material supply line by a fixed ratio.

According to the present invention, crushed sand having a desired particle size distribution, for example, single sand, can always be produced in a stable amount with low equipment cost and low running cost.

Further, the invention of claim 5 provides a sand making machine comprising a crushed sand raw material supply line including a conveying device, a cage mill for crushing the crushed sand raw material supplied from the crushed sand raw material supply line, and a classifier. Product crushed sand production line connected to the crushed product take-out part of the machine, and periodically or automatically sample one of the crushed product and product crushed sand in the product crushed sand production line, and automatically measure the particle size distribution. The sand maker is constituted by a distribution measuring means and a rotation control means for controlling the rotation speed of the cage mill so that the measurement result of the particle size distribution measuring means meets predetermined setting conditions.

According to the present invention, it is possible to always produce crushed sand having a constant particle size even when the properties of the crushed sand raw material change or when the crushing performance of the sand maker changes.
Moreover, it has the feature that the apparatus cost and running cost can be kept low.

The invention of claim 6 provides a sand making machine comprising a crushed sand raw material supply line including a conveying device, a cage mill for crushing the crushed sand raw material supplied from the crushed sand raw material supply line, A distributor for distributing the crushed product at a predetermined distribution ratio, a product crushed sand production line including a classifier and connected to one distributed side of the distributor, and the distributor connected to the other distributed side of the distributor. A return means for returning a part of the crushed product from the sand maker to the crushed sand raw material supply line by a fixed ratio, and periodically and automatically sampling any one of the crushed product and the product crushed sand in the product crushed sand production line And, a particle size distribution measuring means for automatically measuring the particle size distribution, and a rotation control means for controlling the rotation speed of the cage mill so that the measurement result of the particle size distribution measuring means matches a predetermined setting condition Thus it is obtained by constituting the manufacturing sand device.

According to the present invention as described above,
By combining these features, it is possible to produce qualitatively and quantitatively stable high-quality crushed sand at low equipment costs and low running costs.

According to a seventh aspect of the present invention, in the sand making apparatus according to the fourth, fifth or sixth aspect, the cone crusher for crushing a raw stone having a size that cannot be supplied to a cage mill is provided in the crushed sand raw material supply line. And a sieve for sieving the crushed material from the crusher are provided in series.

According to the present invention, it is possible to produce a product crushed sand having a desired particle size distribution such as a single sand from a large sized rough, and to simultaneously use the product crushed sand and the crushed stone having a coarse sieve size. A feature that can be efficiently produced is further added to the invention of claims 4, 5 and 6. In addition, even if the raw material of the crushed sand is a large ore, the whole amount can be crushed sand by the present invention.

According to an eighth aspect of the present invention, in the sand making device according to the fifth or sixth aspect, the predetermined setting condition is that the rotation speed of the sand maker and an FM value corresponding to the rotation speed are different. It is based on a database determined by the relationship.

According to the present invention, there is further provided a feature that crushed sand having a desired particle size can be stably and automatically produced based on the setting conditions written in the database. Can be

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. FIGS. 1 and 2 schematically show the configuration of the first and second embodiments of the present invention. The sand maker according to the first embodiment shown in FIG. 1 includes a crushed sand material supply line formed including a crushed sand material bin 12 and a supply device 1, a sand maker 2 including a cage mill, a distribution device 3, and a return machine. A means 4, a product crushed sand production line formed including a classifier 5 and a humidifier kneader 8, and a control means 6 for controlling the operation of the sand maker 2 are provided.
The sand making device according to the present invention comprises a sand making machine 2 and a distribution device 3.
And a sieve device (not shown) may be interposed between them. The classifier 5 may be either a dry type or a wet type. You may not use it.

The crushed sand raw material is supplied from a crushed sand raw material bin 12 to a sand making machine (hereinafter referred to as a cage mill) 2 through a supply device 1. As the supply device 1, for example, a fixed-quantity cutting device including an electromagnetic feeder is used. The cage mill 2 performs crushing operation by rotating a rotor at an appropriate speed in a range of a peripheral speed of 20 to 50 m / s. The raw material is returned to the cage mill 2 by returning it to the crushed sand raw material supply line through the return means 4 consisting of At that time, the ratio returned by the return means 4 is determined in accordance with the type and size of the crushed sand raw material within the range of 50 to 0%, and is fixed unless there is a change in this property.

The remaining crushed products distributed and taken out by the distribution device 3 are sent to a classifier, for example, a dry classifier 5, where they are classified, and then humidified and kneaded by the humidifier and kneader 8, and the product crushed sand 20 is obtained.
Produced as The fine powder 21 classified by the dry classifier 5 is stored separately from the product crushed sand 20.

As described above, the FM value, which is a value indicating the property of the product crushed sand 20 produced by the embodiment of the present invention that performs crushing and classification with partial return, is as follows:
As shown in FIG. 3 and FIG. 4 with reference to a comparative example, as shown in FIG. 3, a raw material having a particle size of 5 to 2.5 mm was used and the FM value was in the range of 2.6 to 2.8. When producing product crushed sand, in the case of hard sandstone, only FM values 2.71 to 3.14 can be adjusted without return.
If the desired performance is not achieved, the FM value can be adjusted to 2.6 to 2.8 by setting the return to 25%.
With diorite this can be achieved without a return. For andesite, without return, FM value 2.75-3.30
The desired performance cannot be achieved because it can only be adjusted. On the other hand, the FM value is set to 2.6 to 2.
Eight adjustments are possible.

Further, as shown in FIG.
In the case of producing product crushed sand having an FM value in the range of 2.6 to 2.8 using the raw material of the above, in the case of quartz rough rock, only the FM value of 2.85 to 3.07 can be adjusted without return,
If the desired performance is not reached, the FM value can be adjusted to 2.6 to 2.8 by setting a 35% return.
For sandstone, FM value 2.98-3.5 without return
7 can be adjusted, so that the desired performance is not achieved. On the other hand, by setting the return to 50%, the FM value of 2.6 to
An adjustment of 2.8 is possible. In the case of hard sandstone, only the FM value of 2.77 to 3.33 can be adjusted without a return, so that the desired performance is not achieved. On the other hand, by setting the return to 35%, the FM value of 2.6 to 2.3. Eight adjustments are possible.

By setting the return-side distribution ratio to a predetermined ratio within the range of 0 to 50% in accordance with the properties of the raw material, it is possible to stably produce a crushed product having a predetermined FM value. It is possible.

On the other hand, regarding the properties of the product crushed sand 20 when the rotation speed of the cage mill 2 is controlled, the FM value of the product crushed sand can be adjusted irrespective of the presence or absence of return, as is apparent from FIGS. That is, the FM value decreases by increasing the peripheral speed, and the FM value increases by decreasing the peripheral speed. Regarding the mode when this rotation speed control is performed, FIG. 6 (A) further shows a product particle size distribution table expressed by a relationship between a sieve nominal size and a weight percentage.
Also, as shown in the product particle size distribution diagram in FIG. 6 (B), according to the illustrated example, the cage mill 2 peripheral speed:
35m / s, return side distribution ratio 0%, cage mill 2 peripheral speed: 35
m / s, return side distribution ratio 25%, cage mill 2 peripheral speed: 40m /
As can be seen from the comparison results of the three examples with the return side distribution ratio of 25%, the particle size distribution can be adjusted by changing the peripheral speed of the cage mill 2 at the return side distribution ratio of 25%. (B) indicates that the particles can fall within the grain size range of the Japan Society of Civil Engineers indicated by the range between the two broken lines. That is, it is possible to produce the product crushed sand 20 that can be used as single sand.

Next, the control means 6 for controlling the operation of the cage mill 2 will be described with reference to FIG. The control means 6 includes a sampling device 9, a particle size distribution measuring device 10 realized by an automatic particle size measuring device, and a rotation control device comprising a controller for controlling the number of rotations of a motor (not shown) for driving the cage mill 2. 11. The sampling device 9 is interposed in the crushed material line from the dry classifier 5 to the humidifying kneader 8 so that a part of the crushed material at the outlet of the dry classifier 5 can be periodically sampled. In addition,
The sampling device 9 may be provided so as to be able to sample the crushed product from the cage mill 2 to the dry classifier 5. The particle size distribution measuring means 10 measures the particle size distribution of the crushed material sampled by the sampling device 9, records the measurement result, and stores the measurement result in a memory as particle size information. Rotation control means 11
Is configured to compare the measurement result (FM value) of the particle size distribution measuring means 10 with a preset target FM value, and to control the rotation speed of the motor so that both values match.

The mode of operation control by the control means 6 is as shown in the control flow of steps S1 to S5 in FIG. 5, and the particle size information obtained by the particle size distribution measuring means 10 is fed back to the cage mill 2. ,
The product crushed sand 20 which always maintains a stable particle size can be produced. In addition, the cycle of the automatic particle size measurement is 30 to 60 mi.
It shall be set to an appropriate value in the range of n.

With respect to the control means 6, a database 27 is created as shown in FIG. 5 as setting conditions predetermined as targets for the product crushed sand 20, and is managed in association with the particle size distribution measuring means 10 and the rotation control means 11. It is a preferable means to keep it as information. In the database 27, the relationship between the rotation speed of the cage mill 2 and the corresponding FM value is obtained by experiment in advance for each type of the crushed sand material, and is used as data. If an arbitrary FM value is input to the control means 6 as setting information based on the database 27, the cage mill 2 can be automatically controlled at an appropriate rotation speed, and the desired granularity (F
M) The product crushed sand 20 can be stably produced.

FIG. 2 shows a sand making apparatus according to a second embodiment of the present invention. This sand-making apparatus has a configuration similar to that of the first embodiment. Corresponding members have the same reference characters allotted, and detailed description thereof will not be repeated here. The configuration of the sand making apparatus is characterized in that a cone crusher 13 and a sieve for sieving the crushed material from the crusher 13 are serially connected to a crushed sand material supply line between the supply device 1 and the cage mill 2. It is interposed.

The cone crusher 13 is a crusher adapted to crush large crushed sand raw material, for example, 20 mm or more, which cannot be crushed by the cage mill 2, and crushes the crushed sand raw material supplied from the supply device 1. , Provided on the rear side of the supply device 1. On the other hand, the sieve provided on the subsequent stage side with respect to the cone crusher 13 is the first sieve 1
4, the second sieve 15 is provided in two stages, the first sieve 14
A sieve nominal size of 20 mm or 13 mm is used.
The sieve 15 has a sieve nominal size of 5 mm. Further, in connection with the first sieve 14 and the second sieve 15, the transport device 1
6 and a damper 17 are provided. The transport device 16
Feeding device 1 for crushed sand having a large particle size that does not pass through first sieve 14
The damper 17 is used to return the crushed sand that passes through the first sieve 14 and does not pass through the second sieve 15 to the crushed stone storage location or the cage mill 2 on the subsequent stage in an adjustable amount. Distribution device.

In the dry sand making apparatus according to the second embodiment, a rough stone that cannot be supplied to the cage mill 2 is crushed by the cone crusher 13 and blocked by the first sieve 14.
For crushed stones of 0mm or more or 13mm or more, use cone crusher 1.
3 and crushed again, the crushed sand of 5 mm or less passed through the first sieve 14 and the second sieve 15 and a part of the crushed sand of 5 mm or more distributed by the damper 17 were passed through the cage mill 2 and the dry classifier 5, The product crushed sand 20 and the fine powder 21 are stored separately, while the crushed stone 22 of the designation 2005 or 6 blocked by the second sieve 15 can be stored in another storage location. The product crushed sand 2 having a desired particle size from such a large raw material 2
0 can be produced, and further, the product crushed sand 20 and the crushed stone 22 of, for example, 2005 (crushed stone No. 6) can be simultaneously produced at a desired ratio. If all the crushed sand that has passed through the first sieve 14 is sent to the cage mill 2 without providing the second sieve 15 and the damper 17, the entire amount of the crushed sand raw material can be used as the product crushed sand 20.

[0039]

The present invention is embodied in the form described above and has the following effects. According to the inventions of claims 1 and 4, by returning a part of the crushed product of the cage mill as a raw material of the cage mill by a certain ratio, the particle size distribution of the product crushed sand can be reduced to a small fluctuation state. 0.6-
Crushed sand with a particle size range of 0.15 mm is replenished, enabling the production of single sand. In addition, the production amount can be kept constant with a small amount of fluctuation and always stable.

According to the second and fifth aspects of the present invention, it is possible to always produce crushed sand having a constant particle size even when the crushed sand raw material conditions fluctuate or when the crushing performance of the cage mill is reduced due to wear. is there.

According to the third and sixth aspects of the present invention, qualitatively and qualitatively stable high-quality crushed sand can be produced at low equipment cost.
It can be produced at low running cost.

According to the seventh aspect of the present invention, it is possible to stably produce a crushed product having a desired particle size distribution from a raw material having a large sieve size, and combine the crushed product with the product crushed sand (2005 to 20).
5 mm) or 6 (13-5 mm) etc. can be produced simultaneously in a single sand making line, which is very efficient.

Further, according to the invention of claim 8, it is possible to automatically and stably produce the crushed sand having a desired particle size (FM).

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a first embodiment of the present invention.

FIG. 2 is a schematic configuration diagram of a second embodiment of the present invention.

FIG. 3A is a graph showing the relationship between the peripheral speed of a cage mill and the FM value for each type of crushed sand and return rate of crushed product manufactured from a raw material having a particle size of 5 to 2.5 mm according to the embodiment of the present invention and a comparative example. The table shown, (B), is also a diagram.

FIG. 4 (A) shows the relationship between the FM rate and the cage mill peripheral speed with respect to the rock quality and the return ratio of the crushed product manufactured from the raw material having a particle size of 13 to 5 mm according to the embodiment of the present invention and the comparative example. Table (B) is also a diagram.

FIG. 5 is a flow chart of cage mill rotation control according to the embodiment of the present invention.

FIG. 6 (A) is a product particle size distribution table expressed by a relationship between a sieve nominal size and a weight percentage of the product crushed sand manufactured according to the embodiment of the present invention, and (B) is a product particle size distribution diagram similarly. It is.

FIG. 7 (A) is a product particle size distribution table expressed by a relationship between a sieve nominal size and a weight percentage of product crushed sand crushed by various conventional dry crushers, and (B) is a product particle size distribution diagram similarly. .

FIG. 8 (A) is a product particle size distribution table showing the relationship between the sieve nominal size and the percentage of passage of product crushed sand crushed by various conventional dry crushers, and FIG. 8 (B) is also a product particle size distribution diagram. .

[Explanation of symbols]

1 ... fixed-quantity feeding device, 2 ... sand maker, 3
... Distributor, 4 ... Return means, 5 ... Classifier,
6 ... control means, 7 ... distribution control means, 8
... humidifying kneader, 9 ... sampling device, 10 ...
Particle size distribution measuring means, 11: rotation control means, 12: crushed sand raw material bottle, 13: cone crusher, 14: first sieve,
15: second sieve, 16: transport device, 1
7 ... Damper, 20 ... Crushed product, 21 ... Fine powder,
22 ... crushed stone, 27 ... database,

Claims (8)

[Claims] 1. A crushed sand raw material supplied from a crushed sand raw material supply line is crushed by a sand maker comprising a cage mill, and a part of the crushed product is returned to the crushed sand raw material supply line as a cage mill raw material by a predetermined ratio. A sand making method characterized by the fact that: 2. A crushed sand raw material supplied from a crushed sand raw material supply line is crushed by a sand maker comprising a cage mill, and the crushed product is passed through a classifier to be classified into product crushed sand and fine powder. One of the crushed sand is periodically and automatically sampled and its particle size distribution is automatically measured,
A sand making method, wherein the rotational speed of the cage mill is controlled so that the measurement result meets predetermined conditions. 3. A crushed sand raw material supplied from a crushed sand raw material supply line is crushed by a sand maker comprising a cage mill, and the crushed product is classified into product crushed sand and fine powder through a classifier, while crushing from a cage mill. A certain percentage of the product is returned to the crushed sand raw material supply line as a cage mill raw material, and one of the crushed product and the product crushed sand is periodically and automatically sampled, and the particle size distribution is automatically measured and measured. A sand-making method, wherein the rotational speed of the cage mill is controlled so that the result meets preset conditions. 4. A crushed sand raw material supply line including a conveying device,
A sand mill comprising a cage mill for crushing the crushed sand raw material supplied from the crushed sand raw material supply line, a distributor for distributing the crushed product from the sand maker at a predetermined distribution ratio, and a classifier including the classifier. A product crushed sand production line connected to one of the distributing sides, and a part of the crushed product from the sand maker connected to the other distributing side of the distributing device is returned to the crushed sand raw material supply line by a fixed ratio. A sand-making apparatus comprising: 5. A crushed sand raw material supply line including a conveying device,
A sand crusher comprising a cage mill for crushing the crushed sand raw material supplied from the crushed sand raw material supply line, and a product crushed sand production line connected to a crushed product take-out part of the sand maker including a classifier,
Particle size distribution measuring means for periodically and automatically sampling one of the crushed product and product crushed sand in the product crushed sand production line and automatically measuring the particle size distribution thereof, and the measurement result of the particle size distribution measuring means is predetermined. And a rotation control means for controlling the number of rotations of the cage mill so as to meet a predetermined setting condition. 6. A crushed sand raw material supply line including a transport device,
A sand mill comprising a cage mill for crushing the crushed sand raw material supplied from the crushed sand raw material supply line, a distributor for distributing the crushed product from the sand maker at a predetermined distribution ratio, and a classifier including the classifier. A product crushed sand production line connected to one of the distributing sides, and a part of the crushed product from the sand maker connected to the other distributing side of the distributing device is returned to the crushed sand raw material supply line by a fixed ratio. Return means, and periodically and automatically sample one of the crushed product and product crushed sand in the product crushed sand production line, particle size distribution measuring means for automatically measuring the particle size distribution, and the particle size distribution measuring means A sand control device for controlling the rotation speed of the cage mill so that the measurement result meets predetermined conditions. 7. A crushed sand raw material supply line is provided with a cone crusher for crushing a raw stone having a size that cannot be supplied to a cage mill and a sieve for sieving the crushed material from the crusher in series. The sand-making apparatus according to 4, 5 or 6. 8. The predetermined setting condition is based on a database determined by a relationship between a rotation speed of a sand maker and an FM value corresponding to the rotation speed.
3. The sand-making apparatus according to 1.