CH314061A - Cylindrical ball mill - Google Patents

Description

The subject of the present invention is a cylindrical ball mill, in which the material to be treated enters at one end and leaves at the opposite end, comprising an internal lining furnished with projections capable of hooking this material and to enter it with the balls by the rotation of the mill.

These mills, as well as cylindrical mills with a smooth corrugated or ribbed interior coating, have no classification effect on the mass of the grinding bodies or balls which they contain.

It is known that in order to reduce the consumption of driving force necessary for grinding as well as the wear of the balls, it is advantageous to maintain larger balls close to the entrance of the mill, the other balls having progressively larger dimensions. decreasing as they are located closer to the exit.

To this end, it has already been proposed to divide the mill into several chambers separated from each other by partitions perpendicular to the axis of the mill and to pour into each chamber a mixture of pebbles with an average diameter of as much larger as the considered chamber is nearer to the inlet end of the mill. These partitions allow the material to pass from the inlet end to the outlet end when it is sufficiently reduced, but they prevent the balls from doing the same thing and from migrating from one chamber into the other. another one.

This solution has the drawback of making the mill heavier and of periodically requiring, after wear of the balls, the removal and sorting of the latter in order to be able to constitute again the mixtures best suited to the various chambers.

Ort has also proposed, with a view to obtaining an automatic classification of grinding balls, to replace the smooth cylindrical lining of a mill with a single grinding chamber by a lining made up of frustoconical rings whose large bases are on the side of the mill. the entrance to the chamber, the small bases being on the side of the exit from it. These frustoconical coatings may be slightly corrugated transversely so as to increase somewhat the lift of the material produced by the rotation of the mill.

With a frustoconical ring mill, an automatically obtains a decrease in the size of the balls from the entrance to the chamber towards the exit of the latter but, unfortunately, a large number of more or less large pieces of material RTI ID ="0001.0269" WI="2" HE="4" LX="1546" LY="2066"> to be ground are also sent to the exit where they are no longer subjected to the shock of balls large enough to fragment them. The unground pieces therefore accumulate towards the outlet and there cause padding, that is to say an obstruction, at least partially, forcing the mill to be stopped, so that the use of the device is not possible. industrially practical unless the material is introduced in an already very fine state, for example in the form of sand. Consequently, the use of such a mill requires the commissioning of a mill or other coarsening device in which the material is reduced sufficiently to be able to be introduced without inconvenience into the ring mill. smooth truncated cones.

The present invention aims to remedy the aforementioned drawbacks. To this end, the cylindrical mill according to the invention is characterized in that the aforesaid projections have their heads ä. different distances of Faxe from the mill and are grouped in such a way that, in a longitudinal section of the mill, the said heads appear along a line in successive steps such that, in each of these, the heads farthest from Faxe of rotation are located closer to the entrance of the mill than the heads closer to this axis.

The attached drawing represents, schematically and by way of example, one form of execution of the ball mill according to the invention.

fig. 1 schematically represents a longitudinal section of the mill constituting this form of execution.

fig. 2 is a development of part of the interior lining of which only a few projections have been shown.

fig. 3 is, on a larger scale, a longitudinal section through a plate of the interior lining represented in FIGS. 1 and 2.

fig. 4 represents, analogously to FIG. 3, a variant of the cover plate.

In these various figures, the same reference notations designate identical elements.

In fig. 1 shows a ball mill, generally cylindrical in shape, comprising a single grinding chamber into which the material to be treated is poured into 2 at one end and comes out in 3 at the opposite end. This mill comprises an outer casing 4 surrounding frustoconical rings 5 juxtaposed. In longitudinal section, the set of rings therefore appears as a succession of inclined steps in the form of saw teeth.

The rings 5 are formed by the juxtaposition of plates each comprising a sole 8 (fig. 2) lined with projections 9 (figs. 1 and 3). In fig. 3, sole 8 is hollow. This representation is not possible at the RTI ID="0002.0276" WI="5" HE="4" LX="1759" LY="763"> fig. 1 because it is drawn at too small a scale. In order not to unnecessarily confuse Figs. 1 and 3, only the cut parts of the flanges 8 and the projections 9 have been shown. For the same reason, an has not represented the grinding bodies or balls or the material being processed.

The sole 8 of FIG. 3 forms a certain angle with the bearing surface of the plate, which angle is open against the cylindrical wall of the mill. The projections 9 have a constant length from the inner face 11 of the corresponding sole. The heads 12 of these projections are therefore grouped in such a way that, in the longitudinal section of the mill, a line which is flush with them forms a succession of inclined steps in the same way as the inner faces 11 of the soles B.

It is also seen in fig. 1 that in each of the sloping steps, the distance between the head 12 of the projections 9 and the end of the mill decreases when one passes from one projection to the next, from the entrance to the exit of the mill.

It is also seen in fig. 1 that the projections 9 are arranged so that, in a group of steps located near the exit, their heads are farther from the axis of rotation than in a median group and that, in the latter, they are also further away from Faxe only in another group of bleachers located near the entrance.

In fig. 4, year represented a variant of the cover plate. This plate has a cylindrical sole 8' lined towards the inside with projections 9' whose heights increase progressively from one transverse edge to the other. When these plates are placed in the mill, the heads 12' of their projections are also found, in longitudinal section, in an inclined alignment whose end furthest from the axis of the mill is located closer to the entrance than the end closest to this axis.

Whatever the form of execution adopted for the plates, the distance between the projections can obviously decrease, gradually or discontinuously, from the entrance to the exit of the mill, as in mills with a cylindrical internal coating. lined with protrusions.

Claims (4)

CLAIM Cylindrical mill with balls, in which the material to be treated enters at one end and leaves at the opposite end, comprising an internal lining furnished with projections capable of hooking this material and entraining it with the balls by the rotation of the mill, characterized in that the aforesaid projections have their heads at different distances from the mill and are grouped in such a way that, in a longitudinal section of the mill, the said heads appear along a line in successive inclined steps such that, in each of these, the heads furthest from the axis of rotation are located nearer to the entrance of the mill than the heads closer to this axis. SUB-CLAIMS 1. Cylindrical mill according to the claim, characterized in that the internal lining comprises plates which present projections grouped so that, in a longitudinal section, their heads are more and more distant from the surface. intended to bear against the cylindrical wall of the mill when considering the projections from one end to the other of this cut. 2. Cylindrical mill according to claim, characterized in that the projections are arranged so that, in a group of steps located near the outlet, their heads are farther from the axis of rotation than in a median group and that, in this one, they are also further away from this axis than in another group of steps located near the entrance. 3. Cylindrical mill according to sub-claim 1, characterized in that each plate has a sole which is parallel to the part. LY="1221"> king of the mill and which is furnished with projections adopts the height increases from one transverse edge to the other. 4. Cylindrical mill according to sub-claim 1, characterized in that each plate has a flange which forms, in longitudinal section, an angle with the bearing surface which is open against the cylindrical wall of the mill. , sole which is provided with projections having the same height measured from the inner surface of the sole.