This application is the United States national phase under 35 U.S.C. §371 of International Application No. PCT/EP2007/056769, filed on Jul. 4, 2007. The entirety of International Application No. PCT/EP2007/056769 is incorporated by reference herein.
1. Field of the Invention
The present invention relates to a roller mill for grinding particulate material such as cement raw materials, cement clinker, coal and similar materials, said roller mill comprising a substantially horizontal grinding table and a set of rollers rotating about a vertical shaft, said set of rollers comprising a number of rollers rotatable about separate roller axes and being connected via a roller bearing and a roller shaft to the vertical shaft, and said set of rollers being configured for interactive operation with the grinding table for application of pressure to the particulate material.
2. Background of the Art
A roller mill of the aforementioned kind is known, for example, from the UK patent No. 601,299. This known mill is designed so that the set of rollers rotate in one direction and so that the grinding table rotates in the opposite direction so as to increase the capacity of the mill. According to the above-mentioned patent publication, the rollers are connected to the vertical shaft via a crank-like connection where each roller is supported by a stationary crank which protrudes centrally into the roller. In the publication there is no detailed mention about how the roller is supported on the crank, but based on previous knowledge of roller mills this is most likely achieved either by means of a slide bearing or a rolling bearing provided in the roller itself. With reference to
It is the object of the present invention to provide a roller mill by means of which the aforementioned disadvantage is reduced.
This is obtained by means of a roller mill of the kind mentioned in the introduction and being characterized in that each roller bearing across its entire axial extent is axially located radially towards the vertical shaft inwardly of the location of the resulting force from the grinding zone imposed upon the respective roller, in use.
As a result, the load incurred by the entire bearing and in particular by the innermost part hereof will be reduced since the reaction forces from the gyro moment and the grinding force will have a partial and mutually neutralizing effect across the entire axial extent of the bearing.
In principle, the roller bearing may be constituted by any suitable bearing and in a simple embodiment it may be constituted by a slide bearing which for example is formed as a bearing housing with a circular-cylindrical bearing shell in which the roller shaft is turning. However, it is preferred that the roller bearing is formed as a bearing housing comprising at least two rolling bearings. It is further preferred that the roller bearing comprises an axial bearing.
Each roller shaft is preferably connected to the vertical shaft via a hinged connection with a centre of rotation allowing a free arcuate movement in upward and downward direction in a plane comprising the centreline of the roller shaft. This will cause the gyro moment to contribute to the grinding force acting upon the particulate material. The plane in which the roller moves does not necessarily include the centreline of the vertical shaft. To obtain a minor sliding or shearing effect in the grinding zone the roller is sometimes or quite often slightly angled, meaning that its centreline does not always pass through the centreline of the vertical shaft. As is the case in previously known roller mills, the roller shaft itself may be stationary but in order to ensure maximum contribution to the grinding force from the gyro moment, it is preferred that the roller shaft is fixedly attached to the roller.
It is further preferred that the centre of rotation of the hinged connection in a vertical plane is located under the horizontal plane which comprises the centre of mass of the roller, roller shaft and the hinge part connected thereto so that the centrifugal force acting upon these machine parts during the operation of the mill will generate a turning moment about the hinge and hence a force which is directed downward against the grinding table.
In principle, the roller mill may be formed with inclined roller shafts, e.g. with an inclination between 0° and 45° to the horizontal level, so that, in accordance with the aforementioned, the centrifugal force acting upon each roller will positively contribute towards the grinding pressure when the centre of rotation of the hinged connection is located under the horizontal plane which comprises the centre of mass of the roller, the roller shaft and the hinge part connected thereto. However, the drawback associated with inclined roller shafts is that the force contributed by the gyroscopic effect is reduced. It is therefore preferred that the roller shaft for each roller is substantially horizontal.
The invention will now be explained in further details with reference to the drawing, being diagrammatical, and where
In
In the roller mill shown in
According to the invention, across its entire axial extent each roller bearing 16 is axially located within the resulting force Fg acting upon the roller 4 from the grinding zone, thereby decreasing the load incurred by the entire bearing 16 and particularly the innermost part hereof since the forces of reaction from the gyro moment and the grinding force will have a partial and mutually neutralizing effect across the entire axial extent of the bearing in the manner shown in the
In the embodiment shown in
In the embodiment shown in
While certain present preferred embodiments of a roller mill and methods of making and using the same have been shown and described above, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP2007/056769 | 7/4/2007 | WO | 00 | 12/18/2009 |
Publishing Document | Publishing Date | Country | Kind |
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WO2009/003527 | 1/8/2009 | WO | A |
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601299 | May 1948 | GB |
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Number | Date | Country | |
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20100181401 A1 | Jul 2010 | US |