EP1279438A1 - Lifting element for rotating grinder and grinder priviude with such elements - Google Patents

Abstract

The lifting element comprises an elastomer or rubber base (18) with a fastening (14) for attaching it to the inner cylindrical surface of the grinder, and wear plates (20) embedded in the base and alternating with layers of the base's material. The plates are trapezoid in shape and positioned to present attack faces (16) that form an acute angle with the grinder's axial plane, the size of the angle being a function of the grinder's operation.

Description

The present invention relates to a composite lifting element intended to form part of the interior shielding of a rotary horizontal mill comprising an elastomer or rubber base provided with means for being fixed on the interior surface of the cylindrical shell of the mill and parts thereof. wear integral with said base. The invention further relates to a rotary mill equipped with such lifting elements.

These lifting elements are used to raise and stir the load of the mill during the rotation of the latter. These shredders can be of the FAG (Full Autogenous Grinding) type in which self-shredding takes place under the effect of impacts and friction between the particles and pieces of material to be shredded. The crushers can also be of the SAG (Semi-Autogenous Grinding) type which contain a crushing load which can consist of steel balls weighing up to about 9 kg and which are used for crushing the material under the effect of shocks and friction. It is also possible to use such lifting elements in conventional tubular mills (tube mills) intended for coarse grinding and using grinding machines of diameter up to 100 mm.

All these grinders are used in particular in wet grinding applications and particularly in the mining industry.

It is obvious that these lifting elements are exposed to enormous stresses of impact and wear by abrasion and friction. However, the resistance properties to these different types of stress cannot be reconciled. The high-alloy cast iron lifters certainly have good abrasion resistance, but cannot be used because they do not withstand the shocks caused by the material to be ground and / or the grinding load. On the other hand, the steel, which is more ductile, generally resists well to breakage caused by shocks, but its rate of wear remains important, because, even hardened, the metallurgical structure contains little or no carbides, as this is the case for chrome irons for example.

The lifting elements made entirely of cast iron or steel have, in addition, the disadvantage of their high weight and that of giving off and transmitting a lot of noise during the grinding operation.

These latter drawbacks are considerably reduced by the lifting elements proposed by US patent 4,402,465 and which are made of rubber. Rubber also has the advantage of offering better resistance to impact and breakage. The parts offered by this document do not, however, solve the problem of wear.

US Patent 3,804,346 tried to find a compromise with a shield consisting of alternating steel bars and rubber bands. However, this type of shield does not solve the problem of wear because it uses rolled steels and not cast iron or high hardness steels.

From the profile point of view, this shield does not allow sudden variations in the height of the elements, but only admits gradual variations, which reduces the lifting capacity and results in a larger bulk of the shield in the grinding chamber, thus reducing the throughput of the mill. Finally, the large dimensions of the bars make them fragile after a little wear, which leads to a risk of deformation and breakage of the plates. This type of shielding has also remained at the testing stage.

US Patent 4,448,681 proposes composite lifting elements comprising an elastomer base or base and the leading face of which is responsible for entraining the material, consists of a wear plate fixed to the elastomer base. Since the entire surface of these plates is exposed to the impact of the balls and the material to be ground and these plates are supported flat on an elastomer block, these plates risk being quickly broken if they are made of cast iron or steel high hardness. In addition, since these plates are only supported by their rear face on an elastomer base, they risk rapidly detaching from their support.

The object of the present invention is to provide a new lifting element with good resistance properties, both to wear and to impact, as well as a crusher equipped with such lifting elements.

To achieve this objective, the present invention provides a lifting element of the kind described in the preamble which is characterized in that that the wearing parts are made up of plates embedded in the material of the base and juxtaposed alternately with interposed layers of the material of the base in a diametrical plane of the mill so that the field side of all the plates defines at least the leading face of the lifting element seen in the direction of rotation of the mill.

The leading face of each lifting element preferably forms an acute angle α with an axial plane of the mill. This angle can be adapted to the working conditions of the mill.

The plates may be in the form of a parallelogram, one longitudinal side of which is on the leading face of the element and one transverse side of which is at the head of the lifting element.

According to another embodiment, the plates can be trapezoid-shaped, the two inclined sides of which respectively define the front face and the rear face of the lifting element, while the small base defines the head of the lifting element. . In this case, the lifting element has a symmetrical shape relative to an axial plane of the mill and allows it to rotate in both directions.

All exposed sides of the wear pads are preferably slightly protruding from the elastomeric material of the support to thereby define grooves which, during operation of the mill, fill with ground material and thereby protect the elastomeric material of the wear base. To promote the self-protection of the rubber or of the elastomer, it is possible to provide, on the lateral faces of the plates, lugs, bosses or ribs of different shapes to slow down the sliding of the ground material between the metal plates and thus to promote the formation of pockets which, when filled with material, will retard the wear of the rubber or the elastomer.

Since the inserts attack the load from their field side and they have a reduced surface to impact stresses, they have a much better resistance to impact and breakage than the inserts laid flat. These plates can therefore be produced without problem in cast iron or high hardness steel (> 50 Rc), which improves their resistance to wear.

This arrangement in a direction perpendicular to the known solutions allows a greater junction surface between the pads and the elastomeric support. This reduces the risk of disconnection of the pads in service and ensures a better distribution of the forces in the elastomer support.

The profile of the lifter, in particular its radial height and the inclination α of its leading face, can be adapted to all grinding requirements, this as well in grinders of the FAG type as those of the SAG type.

In a large diameter shredder, it may be useful, in order not to oversize the lifting element, to provide a double lifting element which has a main lifting part which is followed, seen in the direction of rotation of the grinder, a boss which also consists of an elastomeric material in which are embedded wear pads oriented in the same direction as the pads of the main lifting part.

• la figure 1 est une coupe transversale à travers un premier mode de réalisation d'un élément de relevage selon la présente invention ;
• la figure 1a est une vue plongeante partielle sur l'élément de la figure 1 ;
• la figure 1b est une variante du mode de réalisation de la figure 1 ;
• la figure 2 est une coupe transversale à travers un deuxième mode de réalisation d'un élément de relevage selon la présente invention ;
• la figure 3 est une coupe transversale à travers un troisième mode de réalisation d'un élément de relevage selon la présente invention
• la figure 4 est une autre variante du mode de réalisation de la figure 1.
• les figures 5a et 5b sont respectivement des vues de face et de côté d'un premier mode de réalisation de plaquettes d'usure avec des protubérances latérales pour freiner le glissement de la matière.
• les figures 6a et 6b sont respectivement des vues de face et de côté d'un second mode de réalisation de plaquettes d'usure avec des protubérances latérales pour freiner le glissement de la matière et
• la figure 7 est une vue de face d'un élément de relevage de plaquettes d'usure selon les figures 6a et 6b.

Other particularities and characteristics of the invention will emerge from the detailed description below of several embodiments presented, by way of illustration, with reference to the drawings in which:

• Figure 1 is a cross section through a first embodiment of a lifting element according to the present invention;
• Figure 1a is a partial plunging view of the element of Figure 1;
• Figure 1b is a variant of the embodiment of Figure 1;
• Figure 2 is a cross section through a second embodiment of a lifting element according to the present invention;
• Figure 3 is a cross section through a third embodiment of a lifting element according to the present invention
• FIG. 4 is another variant of the embodiment of FIG. 1.
• Figures 5a and 5b are respectively front and side views of a first embodiment of wear pads with lateral protrusions to slow the sliding of the material.
• FIGS. 6a and 6b are respectively front and side views of a second embodiment of wear pads with lateral protuberances to slow down the sliding of the material and
• Figure 7 is a front view of a wear pad lifting element according to Figures 6a and 6b.

The lifting element shown in Figure 1 generally has a section in the shape of a "shoe" facing front to back with a radial lifting part 10 followed by a foot 12 of shallower depth and forming the transition between the lifting part 10 and the following lifting element. The lifting element comprises known means 14, for example a T-shaped groove, for being fixed on the inner surface of the cylindrical shell of a rotary mill. This lifting element will rotate with the crusher, seen in Figure 1, from right to left, that is to say that the left flank is the leading face 16 which drives and lifts the material during rotation of the crusher.

According to the invention, the lifting element consists of a base 18 made of elastomeric material or rubber and a series of wear pads 20 which define the attack surface 16 and the head 22 of the lifting element. These plates are arranged in the field in the base 18 and the majority of their surface is secured to the mass of the base 18.

The leading face 16 forms an angle α with an axial plane of the mill or with the vertical on the drawing board. This angle can vary depending on the type of mill and determines the degree of lifting. The smaller the angle α, the greater the lifting. As a general rule, this angle can be between -10 ° (attack surface tilted forward) and around 45 °.

As a result of this angle, the plates 20 have a shape of parallelogram, one longitudinal side of which is in the leading face 16 and one lateral side in the head 22 of the lifting element.

As can be seen from Figure 1, each plate 20 emerges slightly from the base 18 to define, on the attack surface 16 and the head 22, grooves between the adjacent plates. During the operation of the mill, these grooves are filled with material to thus ensure self-protection of the elastomer against wear. Due to the faster wear of the rubber, these grooves are maintained throughout the service life of the lifting element. The composite lifting elements according to the invention make it possible to provide wear pads 20 made of a much harder alloy, therefore more resistant to wear, without risk of breakage in service. These are in particular alloys of the martensitic type treated with a hardness of 50 to 53 RC or alloys of the cast iron type with high chromium treated with a hardness of 60 to 66 RC. These last two types of alloys have wear resistance characteristics significantly superior to those of the low alloy alloy commonly used for this kind of applications.

We will now describe some concrete examples of implementation:

Example 1

Shield for a SAG type crusher rotating at 70% of the critical speed, that is to say the speed at which centrifugation of the load of the crusher occurs. In such a mill, the lifting of the material to be ground and the grinding balls, although important, does not reach a critical level at which a projection occurs. We can use for example plates with a thickness of about 15 to 30 mm made of high chrome cast iron and having a hardness of maximum 66 RC. These plates will be separated by rubber strips of equal thickness between them and a hardness of 60 shores. The lifting is not critical, we can improve the grinding efficiency by choosing a low angle α of 10 ° without fear of dangerous projections of the material or balls on the shielding.

If, on the other hand, we want to favor resistance to wear, we can adopt a higher height of the lifting elements to have more material to use and a greater angle α to reduce lifting and avoid the risk of violent shocks on the shield.

Compared to a conventional 350 HB steel shield commonly used, this composite shield will have a lifespan on the order of two to three times greater than conventional shielding.

Example 2

In a mill of the SAG type rotating at 80% of the critical speed, the lifting of the material and the balls is important and we will adopt plates made of an alloy of the martensitic type treated with a hardness of about 50 RC which is more resilient than the alloy at 66 RC. In addition, we can increase the angle α to about 40 ° to reduce the lift. In such a case, we can hope for a lifetime of the composite armor on the order of twice that of a conventional steel armor.

FIG. 1b shows a variant of the embodiment of FIG. 1. According to this variant the plates 20b have the shape of a trapezoid by example a regular trapezoid where the inclined sides respectively define the attack face 16 and the rear face of the lifting element. The plates 20b therefore extending across the entire thickness of the base.

Figure 2 shows a lifting element suitable for a crusher that can rotate in both directions. This lifting element is, in fact, double that shown in FIG. 1. It has a median plane of symmetry and an elastomer base 28 with a radial central lifting part 30 and two lateral feet, 32, 34. Next the direction of rotation of the mill is either the left flank or the right flank of the lifting part 30 which forms the attack surface.

In this embodiment, the central part 30 has a trapezoidal section and consists of a juxtaposition of trapezoidal wear plates 36 and layers of elastomeric material of the base 28. The inclined sides of the plates define the attack surface of the lift, while the small bases define the head of the lift element. The advantages achieved by the diametrical arrangement (relative to the grinder) of the wear pads 36 alternating with layers of elastomer of the base 28 are the same as those achieved with the embodiment of FIG. 1.

Figure 3 shows an embodiment of a lifting element suitable for a large diameter grinder, greater than 10 meters for example. In such a crusher, a lifting element like that of Figure 1, would become too bulky and lose its advantages in terms of weight.

For such a crusher, there is therefore provided a lifting element, such as that of FIG. 3, which is a double element. It comprises a main front lifting part 40 which is similar to the lifting element of FIG. 1 with an elastomer base and wear pads juxtaposed in a diametrical plane. On the other hand, the elastomer base is extended rearwards by a longer foot 42. This foot 42 is provided, on its surface, with a boss 44 anchored in the mass of the foot 42 and constituted, like the teaching of the present invention, of alternating wear pads and elastomer layers juxtaposed in the diametrical direction.

FIG. 4 shows another variant of the embodiment of FIG. 1 in which the base 18 has on the rear face, that is to say the face opposite to the leading face 16, a longitudinal notch 46. In fact, the base made of elastomer 18 is subjected to a rearward bending when it enters the grinding load, which causes a risk of rupture by fatigue at the base of the rear face of the lifting element due to the lack of compressibility rubber or possibly elastomer.

To limit this drawback, it is therefore possible to provide a recess of any shape such as the notch 46, the bottom of which ends in a rounding which reduces the compressive stress at this location.

FIGS. 5 to 7 illustrate two embodiments of wear pads with protuberances or lateral projections intended to favor the filling of the pockets which are formed between the pads with crushed material to thereby ensure self-protection of the base.

FIGS. 5a and 5b show plates 20a, the two lateral faces of which are provided with bosses 52.

In the embodiment of FIGS. 6a and 6b the plates 54 comprise, on each side, at least one projecting rib 56 respectively 58 which extend over the entire width of the plates 54. When these plates are juxtaposed in a lifting element as As shown in Figure 7, the ribs 56 and 58 define baffles which brake the ground material.

The different embodiments described with reference to FIGS. 1 to 4 can all be fitted with protuberance plates as shown in FIGS. 5 and 6.

Claims (11)

Composite lifting element intended to form part of the interior shielding of a rotary horizontal mill comprising a base (18) made of elastomer or rubber provided with means (14) for being fixed on the interior surface of the cylindrical shell of the mill and parts thereof wear integral with said base, characterized in that the wear parts consist of plates (20) embedded in the material of the base (18) and juxtaposed alternately with interposed layers of the material of the base (28) in a plane diametral of the crusher so that the field side of the set of plates (20) defines at least the leading face (16) of the lifting element seen in the direction of rotation of the crusher. Lifting element according to claim 1, characterized in that the leading face (16) of each lifting element forms an acute angle (α) with an axial plane of the mill, the size of this angle being a function of the working conditions of the crusher. Lifting element according to one of Claims 1 or 2, characterized in that the plates (20) are in the form of a parallelogram, one longitudinal side of which is on the leading face (16) of the lifting element and of which a transverse side is located at the head (22) of the mill. Lifting element according to either of Claims 1 and 2, characterized in that the plates (20b) are trapezoid-shaped, the inclined sides of which respectively define the leading face (16) and the rear face of the lifting element. . Lifting element according to one of claims 1 to 3 characterized in that the base (18) has on its rear face a longitudinal notch (46). Lifting element according to claim 1, characterized in that it has a shape symmetrical with respect to an axial plane of the mill and comprises a central lifting part (30) and two lateral legs (32) and (34) extending laterally thereof and in that the plates (36) are arranged diametrically in the central part (30) and are in the form of a trapezium whose two inclined sides define respectively the front face and the rear face of the lifting part, while the small base defines the head of the lifting element. Lifting element according to claim 1, characterized in that it comprises a main lifting part (40) which is followed, seen in the direction of rotation of the mill, by a boss (44) which is made of a material elastomer in which are embedded wear pads oriented in the direction of rotation of the mill. Lifting element according to any one of Claims 1 to 7, characterized in that all the exposed sides of the plates (20, 36) project from the elastomeric material of the support to define grooves which, during the operation of the crusher, fill with crushed material. Lifting element according to any one of Claims 1 to 8, characterized in that the plates (20) (50) (54) have protuberances on their lateral faces. Lifting element according to claim 9, characterized in that the protrusions are in the form of at least two ribs (56) (58) extending over the entire width of the two lateral faces of each plate (20) (54) . Rotary crusher comprising a cylindrical shell with an inner shield consisting of risers and, optionally, shielding plates, characterized in that the risers are lifting elements according to any one of Claims 1 to 8.

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