Solid material comminution or disintegration – Processes – Miscellaneous
Patent
1991-12-13
1993-06-01
Yost, Frank T.
Solid material comminution or disintegration
Processes
Miscellaneous
241 36, B02C 1716
Patent
active
052152634
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a method and a device for regulating the rotational speed of agitator ball mills which have a grinding chamber with grinding balls contained therein, a rotatably mounted agitator body arranged in the grinding chamber and a drive for the agitator body, the rotational speed n of the agitator body being measured.
Agitator ball mills are used, for example, for working powdered solid into liquid media (dispersal) and for the wet grinding of solid materials.
Conventionally, these agitator ball mills run either at a fixed rotational speed or else at a variable rotational speed, this being indicated on a corresponding measuring instrument.
The torque of the agitator shaft is dependent both on the internal parameters of the agitator ball mill and on the nature of the grinding material located in the grinding chamber. In the known agitator ball mills, therefore, changes in the torque of the agitator shaft occur. At high torques, there is the danger that the drive motor for the agitator shaft will be overloaded.
Success of dispersal or comminution during the operation of an agitator ball mill depends on the level of mechanical agitating capacity P. P is determined from the rotational speed n and the torque M of the agitator shaft according to the following equation
In the known agitator ball mills, even when n is constant, the agitating capacity undergoes changes because of the changes in M, and therefore the results of the dispersing or comminuting process are not uniform.
SUMMARY OF THE INVENTION
The object on which the invention is based is to provide a method for regulating the rotational speed of agitator ball mills, which guarantees a better process control.
The object is achieved, according to the invention, in that, in a method of the type mentioned in the introduction, the torque M of the agitator body is measured and the rotational speed n is so regulated that the rotational speed n, the torque M or the mechanical agitating capacity P satisfy desired values predetermined according to the relation
As a result of the method according to the invention, by regulating the rotational speed n either the latter, the torque M or the mechanical agitating capacity P can be kept constant. This permits a process control which is decisively improved in relation to conventional agitator ball mills.
The invention can be used for vertically or horizontally operable agitator ball mills with a continuous or intermittent operating mode. It is advantageous in agitator ball mills both for use in the laboratory and for production.
The rotational speed n can be measured either by known mechanical or inductive methods.
As is likewise known, the torque M can be determined, for example, by strain gages, by the utilization of helical measuring shafts, by eddy-current methods, by determining a reaction torque or else by measuring the current consumption of an electric motor, taking into account the engine characteristic. The last-mentioned method is advantageous especially when a disk-rotor motor is used as a drive for the agitator body.
Although it is already known to record and indicate the current consumption of the drive motor in agitator ball mills, this is nevertheless intended to detect at an early stage an overload of the motor caused by too high a torque on the agitator shaft.
To determine the mechanical agitating capacity from the measured values for the rotational speed n and the torque M, the measurement data n and M are preferably entered in a computing unit. This calculates the value for the mechanical agitating capacity P on the basis of the abovementioned equation. The measured values n, M and P are compared with the predetermined desired value n', M' or P' respectively. The rotational speed of a shaft is then regulated via a regulator unit by means of a control pulse n' dependent on the comparison result.
The measured or calculated values for one or more of the quantities n, M and P and, if appropriate, the predetermined desired value can be stored for documentat
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patent: 4661911 (1987-04-01), Ellery, Sr.
patent: 4709197 (1987-11-01), Goldhammer et al.
Smith Scott A.
Yost Frank T.
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