GRINDER, METHOD FOR OPERATION

Abstract

A grinder includes a grinding table rotatable about a first rotational axis and at least two grinding rollers. Each of the at least two grinding rollers is arranged for rotation about a second rotational axis such that ground material can be comminuted between the grinding table and the grinding rollers during operation. A sensor arrangement can detect a change in inclination of the grinding table beyond a given threshold value.

Claims

1.-13. (canceled)

14. A grinder, comprising: a grinding table rotatable about a first rotational axis; at least two grinding rollers, each of the at least two grinding rollers being arranged for rotation about a second rotational axis such that ground material is able of being comminuted between the grinding table and the grinding rollers during operation; and a sensor arrangement configured to detect a change in inclination of the grinding table beyond a given threshold value.

15. The grinder of claim 14, further comprising a central processing unit and a human-machine interface, said central processing unit connected to the human-machine interface and the sensor arrangement and designed to display an alarm by the human-machine interface, as soon as the sensor arrangement detects that the change in inclination of the grinding table exceeds the given threshold value.

16. The grinder of claim 14, further comprising bearings for support of the grinding table.

17. The grinder of claim 16, wherein the bearings are designed as slide bearings.

18. The grinder of claim 14, wherein the sensor arrangement comprises sensors designed as eddy current sensors, tracers, optical sensors or capacitive sensors.

19. The grinder of claim 14, wherein the sensor arrangement comprises at least three path sensors.

20. The grinder of claim 19, wherein the at least three path sensors measure against a bearing tread surface of the grinder table.

21. The grinder of claim 19, wherein the at least three path sensors are arranged so as to describe a triangle.

22. The grinder of claim 16, wherein the bearings are designed as tilting pad bearings.

23. The grinder of claim 15, wherein the central processing unit is designed to determine in response to measurements of the sensor arrangement a tilting angle which indicates an angular deviation of the first rotational axis from a specified orientation of the first rotational axis.

24. The grinder of claim 15, wherein the central processing unit is designed to determine in response to measurements of the sensor arrangement a direction of tilt, and further comprising a display device configured to display a lowest or highest point of a circumferential position due to the tilt.

25. A method for operating a grinder, said method comprising: measuring variables as the grinder is in operation to determine a tilt of a grinding table of the grinder from a specified position; comparing a change in inclination of the grinding table with a given threshold value; and outputting an alarm via a human-machine interface, when the change in inclination of the grinding table has reached, or exceeded, the given threshold value.

26. The method of claim 25, further comprising: determining a tilting angle of the grinding table as the grinding table rotates about a rotational axis to indicate an angular deviation of the rotational axis from a specified orientation; and displaying the tilting angle on a display device of the grinder.

27. The method of claim 25, further comprising: determining a direction of tilt of the grinding table; and displaying a circumferential position of a lowest point due to the tilt on a display device of the grinder.

Description

[0018] A further acceleration of the maintenance work that may be necessary allows an advantageous development of the method, in which the direction of tilt is determined, so that the circumferential position of the lowest point or the highest point on account of the tilt can be displayed on the display device. The invention is described in greater detail below for clarification purposes with the help of a special exemplary embodiment. In the drawings:

[0019] FIG. 1 shows a schematic longitudinal section through a grinder according to the invention,

[0020] FIG. 2 shows a section according to II-II in FIG. 1,

[0021] FIG. 3 shows a perspective schematic representation of the grinding table, the sensor arrangement and the bearing arrangement of the grinding table,

[0022] FIG. 4 shows a schematic representation of the geometric relationships between the grinding table, the tilt and the sensor arrangement,

[0023] FIG. 5 shows a schematic flow chart of the method for operating a grinder according to the invention.

[0024] FIG. 1 shows a schematic representation of a longitudinal section of a detail of a grinder GAR according to the invention. The grinder GAR comprises a grinding table GTL which is rotatable about a first rotational axis RX1 and at least two grinding rollers GRL which are each arranged so as to rotate about a second rotational axis RX2 in each case. The ground material GRM is comminuted between the grinding table GTL and the grinding rollers GRL during operation. The individual second rotational axes RX2 of the individual grinding rollers GRL each form an obtuse angle with the first rotational axis RX1 of the grinding plate GTL, which angle may also be right-angled. In the present case, the grinding rollers GRL are designed with conical grinding surfaces. Accordingly, the second rotational axes RX2 are oriented obliquely to the first rotational axis RX1.

[0025] The grinding table GTL is equipped axially by means of bearings BEA which are designed as slide bearings SBE and in this case as tilting pad bearings TPB. The grinding table GTL is set in rotation about the vertical first rotational axis RX1 by means of a drive which is not shown by means of a drive shaft DRS. The drive shaft DRS in this case is mounted on a stator STA by means of radial bearings RBE, in such a manner that the first rotational axis RX1 is vertically oriented.

[0026] Located in the region of the axially effective bearing BEA are sensors DS1, DS2, DS3 of a sensor arrangement SNA which determines a tilt of the grinding table GTL on a central processing unit CPU connected to the sensor arrangement SNA. As is also shown schematically in FIGS. 2, 3 and 4, sensors DS1, DS2, DS3 are preferably located close to the axially effective bearing arrangement BEA, so that the sensors DS1-DS3 can measure against the bearing surface of the grinding table GTL. The sensors are designed as path sensors in the example, so that a change in distance between the stator STA and the grinding table GTL is detected by the sensors. Insofar as the sensors DS1-DS3 measure different distances, it can be assumed that the first rotational axis RX1 deviates from the original specified position in the manner of a change in inclination of the grinding table GTL.

[0027] FIG. 4 shows the method for determining the tilting angle of the grinding table Θ and the azimuth angle ϕ of the tilt by means of the central processing unit CPU. The central processing unit CPU initially determines the coordinates of the points detected by the sensor arrangement SNA on the circumferential slide bearing tread surface SBS of the grinding table GTL. Based on the example of three sensors DS1, DS2, DS3, the following results from FIG. 4:

[00001]$\stackrel{.fwdarw.}{A}(t=\left(\begin{array}{c}{x}_{0,A}\\ y_{0,A}\\ s_1\left(t\right)\end{array}\right);\stackrel{.fwdarw.}{B}(t=\left(\begin{array}{c}{x}_{0,B}\\ y_{0,B}\\ s_2\left(t\right)\end{array}\right);\stackrel{.fwdarw.}{C}(t=\left(\begin{array}{c}{x}_{0,C}\\ y_{0,C}\\ s_3(t\end{array}\right)$

[0028] The coordinates x.sub.0,A,B,C, Y.sub.0,A,B,C, in this case denote the structurally fixed position of the sensor in a fixed Cartesian coordinate system of arbitrary origin, the z-axis of which coincides with the first rotational axis RX1 or the grinding table GTL in the non-tilted state. The coordinates si(t) correspond to the measurements of the path sensors DS1, DS2, DS3. The tilting of the grinding table GTL is calculated by means of the normal vector of the plane, which corresponds to the rotating tread surface of the slide bearing. The normal vector of this plane is determined through the formation of the cross product between the connection vectors AB and A:

[00002]$\stackrel{.fwdarw.}{n}(t=\frac{\stackrel{.fwdarw.}{\mathrm{AB}}(t\times \stackrel{.fwdarw.}{\mathrm{AC}}(t}{.Math.\stackrel{.fwdarw.}{\mathrm{AB}}(t\times \stackrel{.fwdarw.}{\mathrm{AC}}(t.Math.}$

[0029] The tilting angle of the grinding plate over time Θ(t results over the scalar product of the normal vector {right arrow over (n)}(t):

[00003]$\Theta \left(t\right)=\arccos \left(\frac{\stackrel{.fwdarw.}{n}\left(t\right).Math.\stackrel{.fwdarw.}{e_z}}{.Math.\stackrel{.fwdarw.}{n}\left(t\right).Math..Math..Math.\stackrel{.fwdarw.}{e_z}.Math.}\right)=\arccos \left(\stackrel{.fwdarw.}{n}\left(t\right).Math.\stackrel{.fwdarw.}{e_z}\right)$

where {right arrow over (e.sub.z )} denotes the unit vector in the z-coordinate direction. The direction in which the grinding table GTL tilts can be described via the azimuth angle ϕ, which describes the angle to the x-axis in the XY plane. This can be determined via

[00004]$\varphi \left(t\right)=\{\begin{array}{cc}\arctan \left(\frac{y}{x}\right)& y>0\\ \arctan \left(\frac{y}{x}\right)& y<0\\ 0& y=0,x>0\\ 90°& y=0,x<0\end{array}$

where the angle ϕ can adopt values of [0, 2π].

[0030] An orbit plot can be used for the graphic visualization of the two characteristic values. For this purpose, the normal vector of the plane projects onto the XY plane. The tilt of the grinding table can thereby be visualized for diagnostic purposes.

[0031] FIG. 5 shows a schematic flow chart of the method for operating a grinder according to the invention. Initially, the grinder GAR is put into service (1) and the measurement of variables (2) begins subsequently or simultaneously, said variables allowing a tilt of the grinding plate GTL to be determined from a specified position. Based on these measurements (2)), a comparison (3)) is made between a change in inclination of the grinding table GTL and a given threshold value TRS. Particularty preferably, the central processing unit CPU determines a tilting angle θ for this purpose from the measurements of the sensor arrangement SNA, the sensors of which DS1, DS2 and DS3 each deliver distances between the stator STA and the grinding table GTL. If the change in inclination θ of the grinding plate GTL exceeds the given threshold value TRS, the output of an alarm ALR (4)) by means of a human-machine interface HMI takes place, to the effect that the change in inclination θ of the grinding plate GTL has reached, or exceeded, the given threshold value TRS. The alarm can be output on an optical display device DSP or on an acoustic display device ACA as an alarm ALR. Insofar as the grinder is not switched off, the cycle of comparison 3 based on the measurements of the sensor arrangement SNA and the evaluation of the central processing unit CPU is repeated and the output of an alarm ALR is repeated where necessary. It is particularly preferable for the tilting angle θ to be displayed on the display device DSP of the grinder GAR. An advantageous development also involves determining the direction of the tilt Φ, so that the circumferential position of the lowest point or the highest position due to the tilt can be displayed on the display device DSP.