MXPA99009472A - Improvements to crushers with ring-shaped track and roller - Google Patents

Abstract

The invention concerns a crusher comprising a ring-shaped track with horizontal axis (14), a roller (16) rolling on said track, means for pressing the roller on the track and means (18) for displacing the material from one track edge to the other so that it passes several times under the roller before it is evacuated. In order to improve the efficacy of the roller and the distribution of mechanical stresses in the roller and the track, the track (14) and the roller (16) are so designed that the space between them decreases from the track (14) edge on the side supplying the material to be crushed up to a distance from said edge not less than 80%the track width, and that this space then quickly increases to constitute a decompression zone (19) on the side where the material is evacuated.

Description

IMPROVEMENTS IN MILL WITH TRACK IN RING AND ROLLER FORM The present invention relates to mills consisting of an annular track with a horizontal axis, a roller capable of traveling on the track, means for pressing the roller against the track and means for moving the material from a track. edge of the track towards the other, so that it can pass several times below the roller before being evacuated.

BACKGROUND Dg THE INVENTION In order to improve grinding, when the materials to be ground are grains of heterogeneous size, it is proposed (French Patent No. 91.09788) to provide a profile to the roller and / or the track so that the space between the roller and the track progressively decreases from one edge of the track to the other.

SUMMARY OF THE INVENTION The objective of the present invention is to improve the efficiency of mills of this type and achieve a better distribution of mechanical stresses in the roller and the track. The mill to which the present invention refers is characterized in that in the space between the roller and the track it decreases from the edge of the track located on the side to supply the material to be ground at a distance from the edge at least equal at 80% of the width of the track and then rapidly increases to form a decompression area on the evacuation side of the ground material. According to a preferred form of the embodiment, the track is formed by an integral ring with a drum having a horizontal axis forming a supply chamber on one side of the track and an evacuation chamber on the other side, and it provides an annular barrier at the end of the evacuation chamber opposite to that adjacent to the track, to maintain in the chamber a layer of ground material whose thickness practically touches the edge of the roller in the plane of the adjacent edge of the track. Preferably, the axial limit of the decompression area that counts from the edge of the runway located on the evacuation side of the material is between 2% and 20%, preferably between 5% and 15% of the width of the runway and, in this area the angle formed by the track and the peripheral surface of the roller in the plane containing the axes of the track and the roller is less than 50 °. According to one form of the mill mode, the track is cylindrical and the roller is formed of at least two frustoconical parts, a first part of the diameter, which increases from its end located on the supply side at a distance from its edge at least equal to 80% of the axial length of the roller and a second part of the diameter decreasing located at its other end. Alternatively, the track may have a frustoconical profile with a diameter that decreases from its edge located on the side to supply the material to be ground to the decompression area and a variable or constant angle at the apex; the decompression area, the diameter of the track increases in the direction of progress of the material. With this track, a cylindrical roller whose axis is parallel to the axis of the track or forms an angle less than 5o between them can be used.

BRIEF DESCRIPTION OF THE DRAWINGS The following description refers to the accompanying drawings which show, by way of non-limiting examples, some forms of the embodiment of the invention and in which: Figure 1 is a vertical section of a mill made of according to the invention; Figure 2 is a section, through the plane perpendicular to the axis of the mill of Figure 1; and Figures 3 and 4 illustrate two other forms of the embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION The mill shown in the drawings is formed by a drum 10 with a horizontal axis, which is supported on shoes or runners 12 that allow it to rotate about its axis; These shoes can be replaced by sleeves or rollers. The drum is driven for rotation by conventional means, not shown, for example by a motor and an output shaft reducer which supports a pinion coupled with a sprocket fixed to the drum. The drum is formed by a shell internally coated with wear plates, which form in the central portion an annular grinding track 14, with a cylindrical surface. The interior of the drum in this way is divided into a supply area 11, a grinding area 13 and an evacuation area 15. The annular edges 17 provided at the two ends of the shell form barriers that allow a layer of material to be maintained in the evacuation and supply areas. The drum is closed at both ends with metal sheets mounted on a fixed support and at the end of which a supply channel is connected and at the other end a discharge channel and a suction duct for pneumatically evacuating the fine particles. A roller 16 is mounted inside the drum and is able to travel on the track 14 when the drum is activated to rotate. More precisely, when the mill is working, the roller travels over the layer of material covering the track. The roller is provided with two arrow ends mounted on the fixed supports to two levers located outside the drum, on either side thereof. The springs or hydropneumatic jacks acting on the supports or on the levers allow the roller to be pressed against the grinding track with a predetermined, adjustable force. Roller 16 is composed of three frustoconical portions of different conicity. The two main parts, la and 16b, extend about 80% of the length of the roller; its diameter increases in the direction of progress of the material on the track (direction of the arrow in Figure 1) and the apex angle of the part lßa, which is closest to the supply area, is greater than that of the part 16b. Part 16c, located on the side of the evacuation area, has a diameter that decreases in the direction of progress of the material and its angle at the apex is markedly greater than that of the other two parts, but less than 100 °; the axial length of this part represents between 2% and 20%, preferably between 5% and 15% of the useful length of the roller. A decompression area 19 that follows from the area to place the material under pressure between the roller and the track is delimited with the track. This decompression area and the layer of material 20 formed in the evacuation area oppose the sudden ejection of the compressed material between the track and the roller near the edge of the roller (edge effect). This makes it easier to control the crushing area in the area adjacent to the decompression area. In addition, the decompression area makes it possible to ensure a better distribution of the mechanical stresses in the roller near its side face. The thickness of the layer of material 20 formed in the evacuation area 15 is such that it practically touches the edge of the roller in the plane of the edge of the track adjacent to this area. A device designed to ensure the direct feeding and step by step of the material, is located in the upper half of the drum from one end of the latter towards the other, in the descending portion of the circular path of the materials. This device is schematically represented in Figure 1 by a series of inclined strips 18 that detach from the wall of the drum and the track of material that is normally held there by the centrifugal force. The detached material slides on the strips 18 and due to its inclination, moves from the entrance to the exit of the mill. By adjusting the inclination of the strips 18, the speed of the front supply of the material is regulated; Different speeds can be selected for the supply, grinding and evacuation areas. Alternatively, the device for direct feeding of the material can be of the type described in French Patent No. 91.09788, mentioned above. In Figure 3, another form of the track and roller mode are represented schematically. Instead of being cylindrical, the track is formed by three frustoconical surfaces 14a, 14b and 14c joined so that their diameter decreases in the direction of the material advance indicated by the arrow, over most of its width, and then decreases sharply in its final portion. The apex angle of the surface 14a is greater than that of the surface 14b. The surface 14c of the track and the roller define the decompression area. In the plane of the figure, which contains the axes of the roller and the track, the angle α formed by this portion of the track and the roller is less than 50 °. The surface of the roller 18 is cylindrical and its axis is parallel to that of the track. In the form of the embodiment shown in Figure 4, the track consists of a first frusto-conical portion, the diameter of which decreases in the direction of material progress (arrow) and a second cylindrical portion. The roller is cylindrical and its axis is inclined in relation to the track axis by an angle ß less than 5o. It consists of a frustoconical portion, at its end adjacent to the evacuation area, which together with the track defines a decompression area. Other track and roller shapes can be selected to obtain a space that decreases, in the direction of material advance, between the track and the roller, over most of the track width and to provide a decompression area in the track. side of the evacuation area. It should be mentioned that all these forms are within the scope of the invention. Furthermore, it is clear that the invention is also applied in mills consisting of several rollers in one and the same track or several tracks.

Claims (5)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following CLAIMS is claimed as property; A mill including at least one annular track with a horizontal axis, at least one roller capable of traveling on the track, means for pressing the roller against the track and means for moving the material from one edge of the track to the other, in such a way that it passes several times below the roller before being unloaded, the space between the roller and the track decreases in the direction of advance of the material to be ground, characterized in that the space between the roller and the track decreases from the edge of the track located on the supply side of the material to be ground at a distance from this edge at least equal to 80% of the width of the track, and because this space increases rapidly to form a decompression area in the side of discharge of the crushed material, and because the track is formed by an integral ring with a coaxial drum that forms a discharge chamber on the side of the track and an annular barrier is provided at the end of the discharge chamber away from the track to maintain, in the chamber, a layer of crushed material whose thickness is such that it practically reaches the edge of the roller in the plane of the adjacent edge of the track.
2. 2. A mill according to claim 1, characterized in that in the plane containing the axis of the roller and the track, the angle (a) formed between the track and the roller in the decompression area is less than 50 °. A mill according to claim 1 or 2, characterized in that the track is cylindrical and the roller is formed by at least two frustoconical parts, a first part whose diameter increases from its end located on the supply side at a distance from this end at least equal to 80% of the axial length of the roller and a second part of decreasing diameter, located at its other end. A mill according to claim 1, 2 or 3, characterized in that the track is formed from at least two frusto-conical surfaces, a first surface whose diameter decreases from its edge located on the supply side up to a distance from this edge at least equal to 80% of the width of the track and a second surface of decreasing diameter adjacent to its other edge. A mill according to claim 1, 2, 3 or 4, characterized in that the axis of the roller is inclined with respect to the axis of the track by an angle (ß) of less than 5 °.