Solid material comminution or disintegration – Apparatus – With separation or classification of material
Patent
1997-06-10
1998-11-03
Rosenbaum, Mark
Solid material comminution or disintegration
Apparatus
With separation or classification of material
241301, B02C 1718
Patent
active
058296930
DESCRIPTION:
BRIEF SUMMARY
SUBJECT OF THE INVENTION
The present invention relates to tube mills with grinding balls or similar grinding bodies.
These tube mills work either in dry process or in wet process and are used, for instance, for the grinding of cement.
The subject of the present invention relates, more particularly, to a device for holding grates in cast steel on existing partitions frames of partitions.
STATE OF THE ART
In a tube mill, a partition fulfils one of the following aims: either it separates two chambers of the mill by keeping the ball load in the chamber upwards while making possible for the material and the air of ventilation to go through it from the chamber upwards towards the chamber downwards, or it creates a free space between the ball load of the grinding chamber upwards and the outlet trunnion, space through which the ground material and the air could pass in order to reach the outlet trunion and then leave the tube mill.
The outlet partition also protects the outlet bottom from the wear and the impacts caused by the movements of the material and the ball load.
The construction of a partition is characterised by a frame that supports grates and, possibly, backside plates.
The frame is made of a structure--in cast steel or in mechanically joined and/or welded rolled steel--which stands perpendicularly to the mill axis and which, in the case of an outlet partition, rests on the mill bottom. Lifters made of radial blades are welded on that structure. Through the rotation of the mill, they lift the material that is within the lower part of the free space. The lifted material will then fall on a discharge cone or any other mechanical construction able to divert the said material either towards another mill chamber or towards the mill trunnion through which the material leaves the mill. These lifting blades contribute to hold the grates and in the case of an intermediate partition, the backside plates.
Through bolts link the frame to the mill shell.
Grates rest on the frame and are attached to it through bolts. Patent FR-A-2 345 213 (Polysius AG) is an example of such a system: the two "carrying discs" are parts of the frame as their name "carrying" indicates. The grates (plaques a fente) and the backside plates are directly attached to the said discs.
Similarly, in patent WO-A-94 09906 (Slegten s.a.), the grates are directly attached to the frame (framework elements).
Tightening the grates peripheral rings is always unproblematic since one keeps access to the bolts through the centre of the partition. If the centre of the partition remains open, tightening the grates central ring is also easy: the bolt nuts remain accessible as long as the discharge cone is not installed, something that can be done afterwards. On the contrary, if the centre of the partition is closed, the grates central ring must be held with through bolts. This is the only way to tighten easily the bolts by making possible to work simultaneously downwards and upwards. In the case of outlet partitions, through bolts--going from the chamber upwards up to the exterior of the outlet bottom--are a frequent solution.
The problem of non accessibility of the bolt nuts is frequent. It requires the use of through bolts, an expensive solution, for instance in the case of outlet bottoms.
Another possibility is offered by the patent EP-A-O 380 952 (CHR. Pfeiffer Maschinenfabrik GMBH). The bolt nut is blocked within a hexagonal hole as indicated in FIGS. 3 and 4 of the said patent.
The grates are located upwards--the direction of the flow of material being taken as reference. They carry openings, called slots, in order to enable the ground material and the air, if any, either to go from one chamber to the next one, or to leave the mill.
In order to accentuate the purpose of sieving, patent FR-A-2 122 251 (F. L. Smidth & CO.) develops the solution of a double sieve. The first one--thicker--is there to prevent the balls from leaving the chamber upwards while the second one--thinner and having smaller openings--screens the material. This second sieve can
REFERENCES:
patent: 5016826 (1991-05-01), Michelsen et al.
Bekaert Ghislain
Hermans Thierry
Schenk Albert
Rosenbaum Mark
Slegten Societe Anonyme
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