Method and device for controlling a crusher, and a pointer instrument for indication of load on a crusher

1. A method for controlling a crusher which includes first and second crusher elements spaced apart to form a gap into which material to be crushed is introduced, the method comprising the steps of:

A. measuring an instantaneous load multiple times during each of a plurality of time periods to obtain multiple load measurement values in each time period, and forming a sequence of data from the highest loads in the respective time periods,

B. calculating a mean value from the sequence of data from the highest loads in the respective time periods,

C. comparing the mean value to a reference value, and

D. controlling the load on the crusher in accordance with such comparison.

2. The method according to claim 1 wherein the periods of time follow immediately after one another.

3. The method according to claim 1 wherein step A comprises processing the load measurement values continuously during a crushing operation for forming a plurality of sequences of data.

4. The method according to claim 3 wherein upon calculation of a representative value of a current sequence, at least one data is utilized concerning highest load already utilized in an immediately preceding sequence.

5. The method according to claim 1 wherein at least the highest value of data included in the sequence concerning highest load is excluded upon calculation of said representative value of such sequence.

6. The method according to claim 1 , wherein at least the lowest value of the data included in the sequence concerning highest load is excluded upon calculation of said representative value of such sequence.

7. The method according to claim 1 , wherein at least the highest as well at least the two lowest values of the data included in the sequence concerning highest load are excluded upon calculation of said representative value of said sequence, more of the lowest than of the highest values being excluded.

8. Method according to claim 1 , wherein the width of the gap is adjusted by a hydraulic adjusting device, and wherein in step A the load is measured as a function of hydraulic fluid pressure in said adjusting device.

9. Method according to claim 1 , wherein in step A the load is measured as a function of the power of the driving device.

10. The method according to claim 1 , wherein in step A the load is measured as a function of mechanical stress on the crusher.

11. The method according to claim 1 , wherein in step A the load is measured as a function of at least two of the parameters comprised of:

hydraulic fluid pressure in a hydraulic adjusting device, the power of the crusher driving device, and a mechanical stress in the crusher, wherein the one of those parameters which is highest in relation to the reference value is utilized in step C.

12. The method according to claim 1 , wherein in step C the load is controlled by at least one of the following steps:

changing the width of the gap,

changing the supply of material to the gap,

adjusting the rpm of a crusher driving device, and

adjusting the relative movements of the crusher elements.

13. A control system for controlling the load on a crusher which includes first and second crusher elements spaced apart to form a gap into which material to be crushed is introduced, the system comprising:

a measuring device arranged to measure an instantaneous load on the crusher multiple times during each of a plurality of time periods to obtain multiple load measurement values in each time period,

a calculation device arranged to form a sequence of data from the highest loads in the respective time periods, and calculate a mean value of such data,

a control device arranged to compare said mean value with a desired value and to control the load on the crusher depending on said comparison.