JPS641004Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a grinding mill ball used for pulverizing coal or the like.

A conventional ball of this kind is shown as 21 in FIG. 1, and has a cavity 23 formed inside a spherical shell 22 made of cast steel, and the shell 22 further has a plurality of transparent holes communicating between the inside and outside. A hole 24 is provided.

When these balls 21 wear out, the grinding efficiency decreases, so in order to prevent this, so-called fill-in balls are replenished, but the wear progresses further and the grinding efficiency decreases. All balls that are worn to an unacceptable level will be replaced with new ones.

The weight ratio of the worn part of the worn ball to the new ball in this way is called the wear ratio, and it is said that the higher the wear ratio, the better, but in the case of the above-mentioned ball, it is about 68%. I couldn't go beyond that.

In order to correct this, if the entire body is made of a metal with excellent toughness, this will have low wear resistance, and if it is made of a metal with high wear resistance, the toughness will decrease and it will be replaced when there is a large amount of remaining metal. This means that the wear rate is low, and none of them could sufficiently correct the above-mentioned problem.

Therefore, in order to correct the above-mentioned problem, the applicant of this application previously proposed an improved ball in U.S. Pat. No. 58-135230. This ball is shown as 31 in FIGS. 2A and 2B, and is coated on the entire outer periphery of a cast steel spherical shell 32.
A plurality of covering pieces 35 made of a material with better abrasion resistance than those of No. 2 were arranged and bonded with a bonding material 36, and this fully met expectations.

The proposed ball was able to eliminate the drawbacks of the conventional ball, but the covering piece 35
When joining the shell 32 to the shell 32, after applying the bonding material 36 on the joining surfaces of both, the covering piece 35 is held in the shell for a predetermined period of time (usually about 30 minutes or more and several hours) with the joining surfaces of both in contact with each other. This results in pressure being applied to the body 22.

On the other hand, in this type of balls, from the viewpoint of reducing vibration of the mill and improving grinding ability, it is strongly required that the balls have high roundness and that the difference in diameter between the balls is small.

By the way, in order to meet these requirements with the proposed ball, the thickness of the bonding material layer to be applied must be uniform on each coated surface, and furthermore, the pressure on each coating piece must be uniformly applied. Since it is impossible to achieve such uniform pressure by pressing all the pieces against the shell at once, it is necessary to wait until the joining of one covering piece is completed before joining the next covering piece. In addition to being difficult to assemble due to the need to move the assembly, it also has the disadvantage of being inefficient.

The purpose of this invention is to provide a ball with high roundness that can eliminate the drawbacks of the previously proposed balls, is easy to assemble, and can be produced efficiently.

In order to achieve the above object, this invention fixes a threaded rod on the surface of the shell opposite to the covering pieces, and the bottom part of each covering piece has a diameter slightly smaller than that of the threaded rod. A stepped hole is provided in which the upper part becomes a small diameter part with a larger diameter and a large diameter part with a larger diameter. It is characterized by being screwed together.

An embodiment of this invention shown in FIG. 3 and subsequent figures will be described.

1 shows the ball according to this invention, and 2 is the shell body, which is made of cast steel with high bending strength, elongation, and impact resistance, and is rich in toughness, and has a minimum thickness of meat that can withstand the load required for crushing. It is made of an integrally cast product with a cavity 3 and a plurality of holes 4, and is heat-treated to improve the above-mentioned properties, and the surface is processed as necessary to achieve the desired roundness and smoothness. It will be done like this.

Reference numeral 5 indicates a plurality of sheathing pieces arranged and bonded to the entire outer circumference of the shell body 2, made of high hardness and wear-resistant material such as high chromium cast iron, cemented carbide, or ceramics, and each sheathing piece 5 having a triangular shape. The adjacent sides are in contact or close to each other.

Reference numeral 6 denotes a bonding layer that bonds the shell 2 and the covering piece 5, and it must be as thin as possible, and the material must be stable even at temperatures exceeding approximately 200°C, which is the temperature during the crushing operation. Commercially available Belzona,
Molecular Metal (registered trademark) and the like are suitable for this purpose.

The above is the same as shown in FIGS. 2A and 2B,
Similarly, the covering piece 5 may have various shapes other than those described above.

By the way, this embodiment has the following structure other than the above.

Several recesses 7 are provided on the outer peripheral surface of the shell 2,
The inner surface of the covering piece 5 facing the recess 7 is provided with a protrusion 8 that has approximately the same shape and fits therein, and a minute gap 9 is formed between adjacent edges of each covering piece 5. It's becoming like that.

At the centroid of the plan view of the covering piece 5, the bottom part is the small diameter part 1.
0, and a stepped hole with a larger diameter portion 11 is provided at the top (FIG. 5). Note that this stepped hole may be provided at a location other than the centroid, or a plurality of stepped holes may be provided.

A threaded rod 12 having a diameter slightly smaller than the diameter of the small diameter portion 10 is fixed at a position corresponding to the stepped hole of the shell 2, and this fixation is done by an appropriate means such as welding or screwing. It is carried out with

When joining the covering piece 5 to such a shell 2, the joining material 6 is applied to the opposing surfaces of both shells 5 and 5.
is brought into contact with the surface of the shell 2 by inserting a threaded rod 12 into the small diameter portion 10 of the stepped hole, and a nut 13 is attached to the portion of the threaded rod 12 located within the large diameter portion 11.
are screwed together, and the covering piece 5 is firmly crimped onto the shell 2 by means of the nut 13. In this way, all the covering pieces 5 are attached to the shell 2, and the gap 9 is also filled with the bonding material 6, and after a certain period of time, the bonding with the bonding material 6 is completed and the ball 1 is obtained.

Although it is possible to obtain a product with a fairly high degree of roundness through such operations, if it is still considered insufficient, the covering piece 5 is attached to the shell 2 before applying the bonding material.
Temporarily install it in the same way as above, measure the roundness, diameter, etc. of such a thing, and if you can't get a satisfactory value, adjust the necessary parts to get the desired value. After that, a bonding material is applied, and the assembly work is performed in the same manner as described above.

This idea is as described above, and the outer peripheral surface of the cast steel spherical shell is coated with a covering piece made of a material with excellent wear resistance.As with the previously proposed ball, the wear unit is low, and the wear resistance is reduced. In addition to having the effect of increasing the ratio, the positioning of the covering piece relative to the shell can be determined by simply inserting a threaded rod fixed to the shell into the stepped hole provided in the covering piece. By threading a nut onto the threaded rod, the sheathing piece is held in place relative to the shell for the time necessary to complete the bonding with the bonding material. This prevents the covering pieces from moving unnecessarily and causing fluctuations in their position relative to the shell, and therefore allows the work of attaching a large number of covering pieces to the shell without waiting for the joining of previous covering pieces to be completed. The process can be carried out continuously, the overall working time can be greatly shortened, the process can be efficiently manufactured, and the resulting balls have a high degree of roundness.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional front view of a conventionally known ball, FIG. 2A is a front view of an improvement over the well-known ball previously proposed by the applicant of this application, and FIG. 2B is a longitudinal sectional front view of the same as above. FIG. 3 is a front view of an embodiment of this invention, FIG. 4 is an enlarged longitudinal sectional front view of the same, and FIG. 5 is an enlarged view of portion A in FIG. 4. DESCRIPTION OF SYMBOLS 1...Ball, 2...Shell, 5...Coating piece, 6...Joining material, 10...Small diameter part, 11...Large diameter part, 12...Threaded rod, 13...Nut.

Claims (1)

[Scope of utility model registration request] A ball for a grinding mill in which a plurality of covering pieces made of a material with better wear resistance than the shell are arranged and bonded to the entire outer circumference of a spherical shell made of cast steel, and a screw is installed on the surface of the shell opposite to the covering pieces. A rod is fixedly installed, and the bottom portion is a small diameter portion having a diameter slightly larger than the diameter of the threaded rod at a position corresponding to the threaded rod of each covering piece,
The upper part thereof is provided with a stepped hole having a larger diameter than the large diameter part, and the threaded rod is fitted into the stepped hole and screwed with a nut inserted into the large diameter part. Balls for grinding mills.