Classifying – separating – and assorting solids – Fluid suspension – Gaseous
Reexamination Certificate
1998-12-10
2001-08-14
Walsh, Donald P. (Department: 3653)
Classifying, separating, and assorting solids
Fluid suspension
Gaseous
C209S713000, C209S139100
Reexamination Certificate
active
06273269
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a pneumatic separator having a centrifugal action designed to grade or classify a granular material into a fine fraction and a coarse fraction. The present invention is of the type including a rotor with a vertical axis provided with vanes regularly distributed over its periphery, guide blades disposed about the rotor, along the generating lines of a fictitious cylinder, and capable of imparting to a stream of air or another gas penetrating the fictitious cylinder a movement of rotation about the axis of the cylinder, and a housing in which are enclosed the rotor and the guide blades and which is equipped with one or more inputs for the air and for the material to be graded, with an output orifice disposed above or below the rotor and through which is sucked the stream of air laden with the fine fraction of the material, and with at least one output for the coarse fraction, with the air penetrating the rotor at its periphery, via the channels formed between the vanes, and circulating inside the rotor towards the output orifice.
BACKGROUND ART
In a separator of this type, the material to be graded and the air stream can introduced separately inside the space with an annular section defined by the guide blades and the rotor, or the material to be graded can be placed in suspension in the air stream before the latter is admitted into the space, through the blades. The air stream then penetrates the rotor and is evacuated via the output orifice.
In both cases, the air stream and the material to be graded are subjected to rotation, about the axis of the rotor, in the space with an annular section contained between the rotor and the guide blades. The particles forming the coarse section of the material are projected by the centrifugal force generated by this rotation against the guide blades and drop through the effect of gravity into a collecting hopper provided with an evacuation orifice, while the particles forming the fine fraction are entrained by the air stream through the rotor and the central output orifice.
The fine fraction that is separated contains practically all the particles the size of which is smaller than a first dimension, while the coarse fraction contains practically all the particles the size of which is larger than a second dimension, which is larger than the first one. In addition, the two fractions contain particles the size of which is between the first and second dimensions. This is reflected by a distribution curve comprising two substantially horizontal portions linked by an inclined portion the slope of which characterizes the separator.
The distribution of the particles of intermediate size in one or the other of the fractions characterizes the cut-off precision of the separator. In general, it is attempted to obtain, by construction, a cut-off that is as marked as possible between the two fractions, that is to say to reduce the interval between the first and second dimensions, which is reflected by a distribution curve with a steep slope.
In certain cases, the product that it is sought to be obtain has to have a grain size distribution that differs from that of the fraction, whether fine or coarse, obtained by means of a separator of this type. This applies particularly to cement obtained by compression grinding the clinker. Hitherto, the only solution to this problem was to use two separators placed in series or in parallel and adjusted to the different cut-off dimensions. This represents a costly solution.
The object of the present invention is to perfect separators of the type concerned so that it is possible to adjust the slope of the distribution curve in a simple manner, that is to say to modify the grain size distribution of the particles the size of which is between the first and second dimensions.
SUMMARY OF THE INVENTION
The separator according to the invention is characterized in that the air circulating through the rotor is divided into at least two separate streams, and the rotor is equipped with means for adjusting the speed and/or the flow rate of at least one of the streams.
If the speeds of the two air streams through the channels provided between the vanes of the rotor are adjusted to different values, the drag forces exerted by the two streams upon a particle of a given mass and given dimensions will differ. In the channels through which the air stream flows at a reduced speed, the balance between the drag forces and the centrifugal forces, which corresponds to the theoretical cut-off mesh, will occur for a smaller particle dimension than that for which the balance occurs in the other channels, through which the air speed is higher. Everything will thus take place as if there were two separators in parallel having different cut-off meshes. By adjusting the speeds of the air streams, the cut-off meshes can be adjusted and, consequently, the grain size distribution of the particles in the finished product.
The means for adjusting the speed and/or the flow rate of the air streams can be formed by means for varying the input section of at least some of the channels provided between the vanes of the rotor and/or by means for varying the passage sections of the openings through which the air streams escape from the rotor.
According to a particular form of embodiment, the rotor is divided into sectors by radially disposed vertical partitions, and each sector communicates with the air output orifice via an opening provided with means for adjusting the passage section which can be formed, by pivoting flaps or diaphragms. In this form of embodiment, the radial partitions perform the anti-vortex function of the second set of vanes of the separator
To vary the section of the channels formed between the vanes of the rotor, use can be made of the plates disposed in the channels, each plate being movable, by rotation about an axis parallel to the axis of the rotor, between a first position, wherein it leaves practically all of the section of the respective channel free, and a second position, wherein it closes off the channel practically completely.
It can be chosen, for example, to place at the channel output two plates pivotally mounted on a vertical axis disposed in the median plane of the channel. These plates can be brought, via an appropriate mechanism, from a first position in which they are pressed against one another and disposed practically in the median plane, to a second position, in which their free ends abut the ends of the vanes defining the channel.
Alternatively, some vanes of the rotor can be orientatable about vertical axes so that their ends can come to bear against a neighbouring vane to close off the channel that they define.
Another solution is to produce the vanes in two portions; a fixed part and mobile portion, orientatable by rotation about a vertical axis. For example, one of the faces of the vane can be fixed, and the other mobile and capable of pivoting about a vertical axis located close to the periphery of the rotor so as to come to bear on the adjacent vane to close off the channel that they form. According to another form of embodiment, the radially external portion of the vane can be fixed, and its internal portion rotary. The mobile portions of two adjacent vanes is able to be brought into abutment with one another to close the channel defined by the two vanes.
Further characteristics of the object of the invention will emerge from a study of the following description, which refers to the accompanying drawings, which show, by way of a non-limitative example, several forms of embodiment of the invention.
REFERENCES:
patent: 1746686 (1930-02-01), Sturtevant
patent: 1779993 (1930-10-01), Sturtevant
patent: 1933604 (1933-11-01), Sturtevant
patent: 2030612 (1936-02-01), Sturtevant
patent: 2109477 (1938-03-01), Gray
patent: 2188430 (1940-01-01), Fraser
patent: 3669265 (1972-06-01), Conley
patent: 3770124 (1973-11-01), Frangquist
patent: 4071441 (1978-01-01), Schauer
patent: 4626343 (1986-12-01), Folsberg
patent: 4636302 (1987-01-01), Folsberg
patent: 4689141 (1987-08
Cordonnier Alain
Lemaire Danielle
FCB Societe Anonyme
Harrison & Egbert
Jones David A
Walsh Donald P.
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