SK17672002A3 - Impeller for centrifugal crushers with vertical axis and method for making same - Google Patents

Abstract

The invention concerns an impeller for centrifugal crushers with vertical axis. Initially, that is when it is used for the first time, said impeller (1) does not comprise cavities or pockets, but it is provided on its working surface (5) with a reinforcing structure (4), made of a composite material obtained from an alloy based on iron and ceramic grains with high wear resistance and formed on site when the impeller is cast by infiltrating molten metal for forming the part body in a mass of ceramic grains and binder. The wear to which it is subjected in operating automatically causes pockets or cavities to be formed which, when they are filled with crushed material, act as a protection against impacts.

Description

Technical field

The present invention relates to an impactor (also called an ejector or impeller) intended for a shredder called VSI (Vertical Axis Impactor), i. j. Centrifugal crushers with vertical axis equipped with reinforcing structure.

BACKGROUND OF THE INVENTION

Crushers of this type are well known and are widely used for crushing stone, inter alia in quarries and cement plants.

There is evidence of this in WO 99/47264 and also in the other documents cited herein.

These documents indicate that the centrifugal crushers comprise a cylindrical chamber in which a rotatable plate supported by a vertical bearing is located. This plate is equipped with means for rotating it about the main axis of the crusher. The crusher comprises a series of impactors or ejectors mounted on the rotary plate, as well as a series of anvils disposed on the inner vertical wall of the cylindrical chamber around the rotary plate.

The impactor is most often parallelepiped. It is mainly made of alloy and is located on the rotary plate of the crusher. The side of the impactor facing the rotational axis of the plate is called the front of the impactor, while the side opposite the anvils located on the cylindrical chamber forms the outlet side of the impactor.

The area in front of the impactor, the so-called working surface, is that which comes into contact with the material to be crushed and which, in the direction of rotation of the impactor, precedes the rear surface.

This working surface in front of the impactor may comprise one or more cavities that do not pass through the entire structure of the impactor. These cavities form cams that are filled with material while the shredder is rotating to protect the impactor from shocks and wear.

During crushing, the material to be crushed is fed by known means to the center of the turntable. Due to the centrifugal force and the effect of said working surface, the material is thrown in the direction of the anvils on which it crumbles and falls in a crushed form to the crusher bottom from where it is taken. When the shredded material is thrown, the impactors are subjected to a very high load and thus wear rapidly.

The accumulated material in the cams significantly extends the service life of the used cam impactors in certain applications.

In this type of impactor, it is observed that wear occurs preferably at the level of the cam outlet edges, i. j. where the abrasion caused by the particles thrown by the centrifugal force is greatest.

The aforementioned document WO 99/47264, as well as the various documents already mentioned, propose protection or reinforcements to eliminate or reduce wear.

A specific solution is proposed in WO 99/47264, namely the production of an impactor with one or more cams, which will preferably have the shape of a parallelepiped. This solution consists in providing a reinforcing structure of a composite material of iron-based alloy and wear-resistant ceramic grains over the entire circumference of the cam (s) or a portion thereof. This structure, which is formed during casting of the impactor by infiltration of the liquid metal, which serves to form the body of the component by the mass of ceramic grains and binder, has proven particularly effective to ensure the prolongation of the impactor operation.

Despite significant technical progress and important technological advantages associated with this type of production, some limitations or obstacles have emerged.

It should first be noted that in order to obtain effective reinforcement, the substrate formed from ceramic grains and binder must be perfectly infiltrated with metal.

In order to ensure a good infiltration of the ceramic body of the reinforcing structure, it is necessary to ensure both a sufficient metal layer and a sufficient substrate thickness. This leads to the maintenance of the appropriate wall thickness of the component made of composite material and consequently to a limitation of the cam dimensions. For better infiltration, it is also necessary to limit the thickness of the ceramic reinforcement, but this reduces its effectiveness and increases its brittleness.

In addition, the cams are empty and unprotected by the material to be crushed during the first actuation of the impactor, both for single-cam impactors and multi-cam impactors.

At this point, particularly thin walls are exposed to the impact of the largest particles and foreign bodies (pieces of steel, shovel tips, etc.)

This can lead to rupture of the most fragile reinforced walls, which seriously damages the part, and often requires very rapid replacement after first use.

In vertical shredders, we also observe that the wear profile is usually not controllable because the operating conditions depend on different parameters that change over time. From these parameters we can mention the grain size of the supplied material, the abrasion of the material particles.

According to the solution proposed in WO 99/47264, changing the shape of the cams requires an overall modification of the casting models and core cores, but without estimating the result.

These operations are some of the most expensive and cause considerable time losses.

If we want to change the profile of the cams, we are also limited by the shape chosen, which is related to the above infiltration difficulties,

Impactor wear in VSI crushers remains ultimately despite all major problems, since wear and impact stresses are very severe, and therefore experts are constantly striving to extend the lifetime of impactors.

SUMMARY OF THE INVENTION

The present invention seeks to solve these problems and in particular to improve the performance of the impactors, taking advantage of the associated advantages of the impactor manufacturing technology described in WO 99/47264.

The invention proposes a vertical axis centrifugal impactor which, unlike the prior art, intentionally initially (i.e. during the first use) does not contain cavities or cams, but which is provided on its work surface with a reinforcing structure made of a composite material obtained from base of iron and ceramic grains very resistant to wear. This structure is formed in its place when the impactor is cast through the penetration of the liquid metal forming the body of the component through a mass consisting of ceramic grains and a binder.

The geometrical arrangement of said reinforcing structure should be such that the metal layer reaches at certain points (ie in areas without reinforcing structure) up to the level of the work surface so that wear in use automatically induces the formation of cams or cavities which will protect when crushed against impact, while maintaining the reinforcement at the upper edge of the cams thus formed (ie on the work surface).

Such an impactor makes it possible to solve these problems completely.

With respect to the difficulties associated with infiltration, in the case of the invention, all the metal that forms part instead of the metal that forms only a simple wall can be used to infiltrate the substrate. In addition, we can apply reinforcement in places where we consider it necessary, because the larger amount of liquid metal available creates better conditions for infiltration.

The fact that the cams do not arise at the very first use of the impactor eliminates the risk of the existence of thin walls, since sufficiently thick walls can be realized.

If we want to change the shape of the cams, only the reinforcement profile has to be modified according to the version proposed in the invention, which greatly reduces costs and offers a better solution of the shapes and concept. In addition, it is possible to cast the component without using one or more sand cores that serve to form the cam (s), which also significantly reduces manufacturing costs.

Finally, the technology according to the invention makes it possible to considerably extend the service life, since as soon as the cams begin to form, self-protection is already achieved by the material retained in the formed cams. The cam formation process is thereby slowed and the lifetime is prolonged for the entire time required to fully form the cams.

It can simply be said that the invention encompasses the specific advantages of a reinforcing structure made of a composite material obtained by infiltrating a liquid metal with a ceramic mass, described in WO 99/47264, as well as the advantages and advantages of manufacturing a cam or cam-free component.

The method used is particularly simple in its implementation, since it is sufficient to fasten to the bottom of the mold by suitable means (glue, mechanical fastening, nails, screws, fastening rod or other) armature made of wear-resistant technical ceramics whose geometrical arrangement is later there could be a cam-like cam. In particular, this construction has the shape of a mass composed of ceramic grains based on alumina and zirconia and a binder. The metal mass is then poured to form the impactor body. By infiltrating the ceramic, the metal ensures a perfect connection with the molded part during cooling of the part. It is then sufficient to remove the part from the mold and after the possible finishing (eg cleaning) the impactor can be used directly.

DETAILED DESCRIPTION OF THE INVENTION 1

Other features and advantages of the invention will appear upon reading the following description with reference to the accompanying drawings.

The attached drawings show:

Figure 1: a perspective view of an impactor with metal infiltrated ceramic reinforcement cams according to the prior art;

figure 2: perspective view of an impactor according to the present invention with the same type of reinforcement and without cams;

Figure 3: a longitudinal section through the impactor of Figure 2 with an evolutionary representation of the profile of the cams during their formation.

Identical whether similar basic elements have the same reference numerals in the figures.

The conventional cam impactor according to FIG. 1 comprises one or more cams, for example two cams 2 and 2 'formed by casting prior to the use of the impactor L. This impactor 1 is preferably provided with filter ceramics reinforcements 4. The front part 6 of the impactor and the rear part 7 of the impactor, which in principle are also very stressed, can be additionally reinforced (e.g. reinforcement 8 in Figure I).

In the embodiment shown in Figure 2, the impactor I is in the form of a full cam-free component on the work surface 5, but cast cast reinforcements 4 are placed thereon. If two cams are to be formed during operation of the impactor, in Figure 2, the appearance and layout of the reinforcements in Figure 1.

Figure 3 shows the evolution of the cam formation profile (progression I, II and III) during use resulting from the presence of stiffeners 4 prior to component use.

Figure 1 shows a transitional reinforcement that separates cams 2 and 2 / and is common to them. The corresponding intermediate reinforcement is also shown in Figure 2 (and in Figure 3) and has the same thickness. However, in the case of the embodiment of Figure 1, the thickness is limited because in this case it is particularly strenuous to completely infiltrate the entire mass of the ceramic substance with the metal, whereas this problem does not occur in the case of Figure 2 due to the "fullness" of the cast part.

The invention thus provides a simple solution to the various technical problems of the impactor design, in particular the great freedom of design. Moreover, implementation according to the recommended technology is not expensive. The cost of an additionally used alloy is strongly balanced by the increased length of operation, the ease of construction, and also the fact that we do not need to use specific means to form the cams during casting of the component.

The presence of additional stiffeners on the front and outlet portions of the impactor, shown by 8 in FIG. 1, can also be envisaged in the embodiment of the invention shown in particular in FIGS. 2 and 3. They are not shown there for clarity only.

Industrial usability

The impactor manufactured by the method according to the invention is intended on a crusher with a vertical axis. The advantages of this type of impactor are better infiltration conditions due to the greater amount of metal available, better cam-shape design, longer impactor lifetime and lower manufacturing costs.

Claims (7)

PATENT CLAIMS An impactor intended for a centrifugal crusher with a vertical axis, characterized in that it initially (ie during its first use) is intentionally free of cavities or cams, but is provided with a reinforcing structure (4) made of composite material on its work surface (5). obtained from an alloy based on iron and ceramic grains, very resistant to wear, which arise in place during casting of the impactor by infiltration of the liquid metal to form the body of the component by a mass composed of ceramic grains and a binder. Impactor according to claim 1, characterized in that the position of said reinforcing structure (4) is envisaged on the work surface (5) according to a geometrical arrangement such that the metal reaches at certain points (ie in areas without reinforcing structure) up to a level of of the work surface so that wear in use automatically induces the formation of cams or cavities which, when filled with crushed material, protects against impact while maintaining reinforcement at the upper edge of the cams formed in this way (ie on the work surface). Impactor according to claim 2, characterized in that it comprises a reinforcing structure (4) whose tire and arrangement make it possible to induce the formation of at least one cam during wear during use. Impactor according to claim 2, characterized in that it comprises a reinforcing structure (4) whose shape and arrangement make it possible to induce at least two cams during wear during use. Impactor according to one of Claims 1 to 4, characterized in that the ceramic grains are based on alumina and zirconia. Method of manufacturing an impactor according to one of Claims 1 to 5, characterized in that an armature made of a wear-resistant ceramic is fastened to the bottom of the mold (according to the geometric disposition required for the later formation of one or more cams due to wear) and infiltrating the molten metal and then casting the metal mass to form the impactor body so that the metal reaches the work surface in the non-reinforced areas and that after the infiltration of the ceramic fitting with the metal mass, which is removed during cooling, forms the component that forms the impactor. Use of impactors according to one of claims 1 to 5 or impactors obtained by the production method according to claim 6 in vertical-axis centrifugal grinders, during which the cams are gradually formed on the impactor working surface by the action of the material not protected by the reinforcement.