MXPA00000253A - Tube mill - Google Patents

Abstract

The invention concerns a mill comprising a cylindrical frame (16) lined with an inner armour and designed to receive the material to be crushed and a load of milling machines wherein the shell, which consists of juxtaposed individual armour plate rings, has inner longitudinal lifting sections to lift the load and the material to be crushed when the mill rotates. In order to adapt the lifting section to the mill operating parameters and conditions, each plate has, on its rear surface, viewed in the mill rotating direction, a step (10b, 12b, 14b) radially higher than the front surface and each ring of the plates comprises several types of different plates (10, 12, 14) which are different at least in their step (10b, 12b 14b) radial height and which follow one another, in the circumferential direction, according to a predetermined order.

Description

TUBULAR MILL Description of the invention The present invention is concerned with a rotary mill comprising a cylindrical die provided with an inner shield and intended to contain the material to be ground and a load of grinding projectiles, in which the shield, which is constituted of rings of individual armor plates juxtaposed, presents internal longitudinal undulations to favor the elevation of the load and of the material to be ground during the rotation of the mill. The invention contemplates more in particular the mills used in cement factories and in the mining industry. These mills are constituted by a metallic cylindrical die that revolves around its longitudinal axis and that contains a grinding load consisting of grinding projectiles, in general barrel bullets, but can also be constituted by cylinds, boulders, etc. variable dimensions. The material to be ground is introduced on one side of the mill and, as it moves towards the exit, on the opposite side, it is ground and crushed between the grinding projectiles. During the rotation of the mill, the material to be ground and the grinding load are raised by the shield and from a given moment, they slide, again downwards. It follows then that the mill load is concentrated REF .: 31910 essentially in the fourth trigonometric quadrant if the mill rotates in the trigonometric direction and in the third quadrant if the mill rotates in a clockwise direction and occupies a plane radial, a zone in the form of "bean" as shown in Figure 4A of the Belgian patent application 09301481. The grinding is performed by the cutting and rubbing forces during the movement of the dough. To obtain an efficient grinding and avoid the breaking of the shields and projectiles, it is necessary that the armor has a profile such that it raises the load to a level such that it remains compacted, because a very important lifting causes the projection of the bullets of cannon beyond the foot of the load, that is to say that the cannon balls hit directly the shield, without interposition of the matter to be ground. On the other hand, the load must be raised sufficiently in such a way that there is a good mixture of the dough. It goes without saying that the filling coefficient plays a decisive role in milling efficiency and that the bean-shaped area occupied by the load must have a well-defined shape, position and dimensions for efficient and optimum milling. In order to favor the lifting of the material and the load, the provision is known, in the plates that form the lower shield of the mill, of longitudinal undulations that are adapted to the conditions and operating parameters of the mill. The problem is, however, that if the undulations or profiles of the mill plates are adapted to a particular mill, this can only be done if the conditions change. It is necessary to know, in fact, that the lifting of the load and of the matter depends on numerous factors such as, for example, the size of the mill, its speed of rotation, the size of the grinding projectiles, etc. On the other hand, the armor plates are subjected to intense use in such a way that, even if the lifting conditions are optimal at the beginning, they can be degraded rapidly due to the change of profile of the plates caused by wear or wear. Known armor plates have, on the other hand, the disadvantage of being quite heavy, of the order of 40 to 50 kg, in such a way that their manipulations are laborious and dangerous. The reforms of labor legislation have, on the other hand, the tendency to prohibit the handling of objects where the weight exceeds 25 Kg. Another restriction is the replacement of the plates used and their attachment to the die, particularly when they are bolted. It is necessary to know in fact that the dies have, in view of the fixation of the shield plates, perforations that are arranged according to the standards in general standard but that these standards may vary from one constructor to the other. Any model of the plate that does not satisfy these normalized perforations causes the need to perform a new perforation of the mill, which can not be contemplated because it is a very expensive operation that has as a consequence a weakening of the die and a risk of leakage of ground material increased. DE 1126709 discloses a mill where the armor plates form tiers in the direction of rotation. Different plates of. Different radial depths follow each other in a certain order. The face with the greatest radial depth lies forward, in the direction of rotation. This has the disadvantage that the grinding projectiles are projected, which reduces the milling efficiency and increases the risk of plate breakage. On the other hand, the tiers of a ring are offset in relation to the tiers of an adjacent ring, that is to say that the tiers are not axially aligned. This causes cutting forces that increase the speed of wear of the plates at the edges. WO 86/04267 also describes a mill where the armor plates are arranged in steps to form lifting ramps. In this mill, there is in fact only one type of bleachers. On the other hand, the plates are bolted to the die, in such a way that the arrangement of the plates is limited to the configuration of holes in the die. In the mills with tiered shielding, it is necessary to increase the inclination of the ramps when the diameter of the mill increases. In known mills, this requires an increase in the thickness of all the plates, which increases the total weight of the shield. The object of the present invention is to provide a new type of shielding that allows attenuating the drawbacks described hereinabove and more particularly, a mill where the shielding is formed of shielding plates that allow adapting the lifting profile to the parameters and operating conditions of the mill and that are modified less quickly under the effect of wear or wear. To achieve this objective, the invention proposes a shielding of the kind described in the preamble, which is characterized in that each plate has, on the rear side, seen in the direction of rotation, a tier of a radial height higher than the front face, because each plate ring comprises several types of different plates that differ, at least, by the radial height of its tier and by the nature of its material and that occur in the circumferential direction, according to a certain order. A certain number of one of the types of plates are fixation plates bolted to the die by bolts but held in place by a simple arching effect. Since several types of plates are arranged differently, it is possible, by a judicious choice, based on tests, to combine the different types of plates to form a well-defined lifting profile that allows an optimum lifting adapted to the operating conditions of the mill. According to another aspect of the invention, the different types of plates are also differentiated by the nature of their material. Thus, different types of plates can be combined depending on their risk of wear. It is thus possible to obtain a lifting profile that is less vulnerable to wear, ie to keep the initial lifting profile longer. On the other hand, it is possible to combine plates optimally to have at the same time a good resistance to wear and a good resistance to shocks. The shielding plates, with the exception of the fixing plates, preferably comprise at least one longitudinal rib, respectively a corresponding longitudinal groove or vice versa on their radial faces to be mutually adjusted and held in place by the fixing plates.

Since most of the shielding plates are not bolted to the die but simply maintained by mutual bolting, there is, at the time of the installation of a shielding as such, fewer stresses due to the arrangement of drilling holes in the die. Each of the plates is preferably dimensioned so as not to exceed a weight of 25 kg. This reduced weight facilitates the handling of the plates and is within the limits imposed by the new legislation. In addition, the smaller and stubby plates allow the use of less resilient steels or castings, which allows better use / resistance exchanges to be made for shocks than with conventional armoring. Other features and characteristics will emerge from the description of some advantageous embodiments presented hereinafter, as an illustration, with reference to the accompanying drawings in which: Figure 1 shows a perspective view of a set of three types of plates armor; Figure 2 shows a side view of the plates of Figure 1; Figure 3 shows a part of a shield plate crown constituted of a combination of two types of plates chosen from the three types of Figure 1; Figure 4 shows a side view of the combination of Figure 3; Figure 5 shows a view analogous to that of Figure 3, with another combination of two types of plates; Figure 6 shows a side view of the combination of Figure 5; Figure 7 shows a part of a shield plate ring made up of a combination of three types of plates of Figure 1 and Figure 8 shows a side view of the combination of Figure 7. Figures 1 and 2 show different types of shield plates 10, 10a, 12 and 14 having a slightly curved outer face to correspond to the inside face of the cylindrical mill die indicated schematically by the reference number 16. Seen in the direction of rotation of the mill represented by the arrow A, all the plates have a front face where the height is lower than that of the back face, in order to define a step on the back side of each plate, step comprising a rounding 10b, 12b, 14b, such so that the juxtaposition of the plates creates a wavy profile. The different types of plates differ at least by the height of their rear face, that is to say the height of their tier 10b, 12b and 14b. Thus, the step 14b of the plates 14 is more marked than the step 12b of the plates 12 which, around it, is more marked than the step 10b of the plates 10 or 10a. From the point of view of the contribution to the shape of the inner profile, the plates 10 and 10a are identical since they have the same tier. The plates 10 and 10a can thus be considered of the same type, in such a way that figures 1 and 2 show three different types of plates. However, contrary to the plates 10, the plates 10a are fixing plates and have for this purpose a central opening 18 to be bolted to the die 16 through a perforation of the die 16. All the plates other than the plates 10a do not they are fixed directly to the die 16 but are simply held in place by the effect of mutual dullness. To this end, each plate has, on the rear face, along the entire length, a slot 20 and on the front face, a corresponding rib 22 engageable in the slot 20 of the preceding plate. The slots 20 and the ribs 22 can of course be inverted. The fixing plates 10a do not comprise a rib or a groove. The front and rear faces are smooth and retractable, thus converging towards the die 16. The coining is realized by means of wedges 24 and 26 of triangular section that are interspersed between the fixing plates and the neighboring plates. These wedges 24 and 26 have inclined inner faces complementary to the inclined faces of the fixing plate 10a. The outer faces of the wedges 24 and 26 are straight and provided with a slot 20, respectively, of a rib 22 for bolting in the rib 22, respectively in the slot 20 of the adjacent plates. Thus, the tightening of the fixing plate 10a to the die 16 generates a tangential separation force which is transmitted to the adjacent plates and solidly maintains their mutual bolting. By using wedges of varying thicknesses, the clamping amplitude can be determined, in particular to be able to catch the game in operation. The different types of plates 10, 12 and 14 can be further differentiated by the height of their tier, by the nature of their material or alloy. Thus, the plates most exposed to wear, in particular the plates 12 and 14 with the most marked harrow, can be made of cast iron with good resistance to use and the plates 10 that are less exposed can be made of steel. The overall dimensions of the different plates are preferably such that their weight does not exceed 25 Kg. To alleviate the plates, it is in particular possible that their outer side of the die side has cracks as indicated schematically in dashed lines 28.

By making a judicious choice between the different types of plates available and alternating them according to a well-determined combination, it is possible to adapt the profile of the raised plates to the parameters and operating conditions of the mill in order that the lifting of the material and of the load is sufficient without projecting the grinding projectiles, that is to say that the dough occupies the ideal form of bean, favorable to an optimum grinding. This possibility of choosing between different types of plates allows a substantial reduction in the weight of the shielding. Thus, a shielding with the combination of plates according to Figure 5 in a mill with a diameter of 5.2 m has a weight / m2 of 525 Kg whereas a classic shielding using plates identical to each other has a weight of 668 Kg / m2 for a mill of the same diameter and for a comparable lifting effect. If the operating conditions of the mill change for one reason or another, it is possible at any time to change the type of plate and / or combination to restore an ideal ripple profile. Figures 3 and 4 show a first example of arrangement of the plates according to which only the two types of plates 10 and 12 are used and according to which, to each plate of a type 10 or 12, two plates of the same are juxtaposed. another type 12 or 10. Figures 5 and 6 illustrate an arrangement analogous to the previous one but here the plates of the type 10 are alternated with those of the type 14. Figures 7 and 8 illustrate an example of an arrangement with a double alternation of the three types of plates 10, 12 and 14. The combination chosen is: 10 - 12 - 10 - 14 - 10 -12 ..., that is to say that there are twice more plates of type 10 than plates of type 12 and plates of the type 14. Of course it is possible to provide other combinations than those mentioned hereinabove as examples. Also, it is possible to provide more than three different types of plates. On the other hand, it is possible that, in the same mill, the grinding conditions are different depending on whether it is on the input side or on the output side, in particular as the progressive grinding continues and the changing granulometry of the material to grind. In order to adapt the profile of lifting plates to these different conditions, different types of plates and / or combinations could be supplied in the same mill, at the entrance, to those of the exit. The invention has thus provided a new mill with a perfectly modular shield and adaptable to varying conditions and parameters.

It is noted that, in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it refers.

Claims (6)

1. CLAIMS Having described the invention as above, it is claimed as property, contained in the following claims: 1. A rotating mill comprising a cylindrical die provided with an internal shield and intended to contain the material to be ground and a load of grinding projectiles in which the shielding, which is constituted by rings of individual armor plates juxtaposed, has internal longitudinal elevating profiles to favor the lifting of the load and of the material to be ground during the rotation of the mill, characterized in that each plate has, in the rear face, seen in the direction of rotation of the mill, a tier of a radial height higher than the front face, because each ring of plates comprises several types of different plates that differ by the radial height of their tier and nature of its material, which occur in the circumferential direction according to a certain order and which are aligned s axially and in which a certain number of one of the types of plates are fixation plates bolted to the die, all other plates are not fixed to the die by bolts but are attached by simple arching effect.
2. 2. The mill according to claim 1, characterized in that the plates with the most marked harrow are made of cast iron and the plates with the less marked harrow are made of steel. The mill according to any of claims 1 or 2, characterized in that all the shielding plates, with the exception of the fixing plates, comprise on their front face and on their rear face, at least one longitudinal rib, respectively a corresponding longitudinal groove or vice versa for mutually bolting and being held in place between the fixing plates. 4. The mill in accordance with the claim 3, characterized in that the rear and front faces of the fixing plates converge towards the die and are separated from the adjacent shielding plates by means of wedges having, on their outer face, a groove, respectively a rib to be bolted on the rib, respectively in the rib of each adjacent plate. 5. The mill in accordance with the claim 4, characterized in that the wedges are of variable thicknesses. The mill according to any of claims 1 to 5, characterized in that each type of plate has a thickness of less than 25 kg.