FEED LEVEL CONTROL SYSTEM AND METHOD

Abstract

The present invention is related to an inlet arrangement for a grinding machine, preferably a roller mill, comprising a main sensor, preferably a force sensor, and an additional sensor, preferably a level sensor, that extends into the storage container to a level that corresponds to the level where the main sensor is provided, and a control unit which is configured to generate, from the values determined by the main sensor and the additional sensor and from a setpoint value, an output signal to control the flow of the milling material out of the storage container. The present invention is further more related to said control unit, a grinding machine, preferably a roller mill, comprising said inlet arrangement, and to a method for determining and controlling the level of milling material in a storage container for milling material of a grinding machine, preferably a roller mill, involving the above inlet arrangement.

Claims

1. An inlet arrangement for a grinding machine, preferably a roller mill, comprising: a storage container with at least one milling materi-al inlet and at least one milling material outlet; at least one metering device arranged in the storage container for metering milling material into a milling gap of the grinding machine, preferably roller mill, through the milling material outlet; a main sensor, preferably a force sensor, provided at the storage container at a level for determining a weight force exerted by the milling material; an additional sensor, preferably a level sensor, provided at the storage container for determining a milling material level in the storage container; and, a control unit which is connected or connectable to the main sensor and the additional sensor; wherein: the additional sensor extends into the storage container to a level that corresponds to the level where the main sensor is provided; and, the control unit is configured to generate, from the values determined by the main sensor and the additional sensor and from a setpoint value, an out-put signal to control the flow of the milling material out of the storage container.

2. The inlet arrangement according to claim 1, wherein the control unit is configured to generate said output signal based on a comparison of a value, calculated from the values derived from the main sensor and the additional sensor, with said setpoint value.

3. The inlet arrangement according to claim 1, wherein the additional sensor is a level sensor, preferably a capacitive sensor.

4. The inlet arrangement according to claim 1, wherein more than one sensor is provided as an additional sensor, preferably 1 to 6, more preferably 1 to 4 level sensors.

5. The inlet arrangement according to claim 1, wherein the main sensor is a force sensor which comprises an extension arm that protrudes into the storage container, wherein said extension arm is provided at a level that corresponds to the level where on end of the additional sensor in the storage container is located.

6. The inlet arrangement according to claim 1, wherein the main sensor is arranged in a lower region, preferably a lower third, of the storage container.

7. The inlet arrangement according to claim 1, wherein the inlet arrangement further comprises a machine control element.

8. A control unit for an inlet arrangement with a stor-age container of a grinding machine, preferably roller mill, in particular an inlet arrangement according to claim 1 wherein the control unit is connected or can be connected to a main sensor, preferably force sensor, provided at the storage container for determining a weight force exerted by a milling material in the storage container, and to an additional sensor, preferably level sensor, provided at the storage container, for determining a milling material level in the storage container, wherein the control unit is configured to generate, from the values determined by the main sensor and the additional sensor and from a setpoint value, an output signal to control the flow of the milling material out of the storage container.

9. The control element according to claim 8, wherein the control element comprises means for enabling an operator to input a setpoint value.

10. The control element according to claim 8, wherein the control element comprises: optionally one or more A/D converters; optionally one or more processing units for performing an operation selected from the group consisting of scaling, offset and filtering, and combinations there-of; a calculation unit for determining a sensor value for the main sensor in dependence from the values detected by the additional sensor; and, a regulation unit for generating the output signal by comparing the signal value obtained from the calculation unit with the setpoint value.

11. A grinding machine, preferably a roller mill comprising at least two rollers defining a gap between them, wherein the grinding machine, preferably roller mill, further comprises an inlet arrangement according to claim 1.

12. A method for determining and controlling the level of milling material in a storage container for milling material of a grinding machine, preferably a roller mill, the storage container comprising at least one milling material inlet, at least one milling material outlet and at least one metering device for metering milling material into a milling gap of the grinding machine, preferably roller mill, through the milling material outlet, the method comprising the following steps: determining a first parameter, preferably a weight force, exerted by the milling material with a main sensor, preferably force sensor, provided at the storage container at a level; determining a milling material level in the storage container with an additional sensor, preferably level sensor, provided at the storage container such that the additional sensor extends into the storage container to a level that corresponds to the level where the main sensor is provided; optionally processing signals generated by the main sensor and the additional sensor; providing a setpoint value, preferably by an operator; and, generating, from the values derived from the main sensor and the additional sensor and from the setpoint value, an output signal to control the flow of the milling material out of the storage container.

13. The method according to claim 12, wherein said output signal is generated based on a comparison of a value, calculated from the values derived from the main sensor and the additional sensor, with said setpoint value.

14. The method according to claim 12, wherein said comparison of the value, calculated from the values derived from the main sensor and the additional sensor, with said setpoint value, involves a regulation procedure.

15. The method according to any of claim 12, wherein said output signal is transmitted to a machine control element which controls an element of the inlet arrangement or the roller mill.

Description

[0076] The present invention is described below in more detail with reference to a preferred embodiment in conjunction with the figures. It is shown:

[0077] FIG. 1 a schematic sectional view of an inlet arrangement according to the present invention; and

[0078] FIG. 2 a schematic illustration of the components of a control unit and signal processing by said control unit according to the present invention.

[0079] FIG. 1 schematically shows an inlet arrangement 1 of a grinding machine, e.g. roller mill. The inlet arrangement 1 comprises a storage container 2 with a milling material inlet 3 and a milling material outlet 4. A metering device 5 is also arranged at the milling material outlet 4, which is designed as a throttle valve. A gap width of the milling material outlet 4 can be changed by swiveling the throttle valve.

[0080] A force sensor 6 is provided at the storage container 2, which comprises an extension arm 9 that projects into the storage container 2 and can be designed, for example, as a bending beam. When filling the storage container 2 with milling material, a cone of milling material is formed, which is shown schematically by the arched line in FIG. 1. As soon as the cone of milling material has reached the extension arm 9, the latter is loaded with a weight force FG. The control unit 8, which is connected to the force sensor 6 via a connection line (shown schematically by the dashed line), thus detects that a first fill level has been reached in the storage container 2.

[0081] When the storage container 2 is filled with further material, the cone of milling material and thus the fill level in the storage 2 container increases in the direction of the y arrow in FIG. 1. The increase in the fill level in the storage container 2 is detected by the control unit 8 by an increase in the weight force FG determined by the force sensor 6.

[0082] In addition, a level sensor 7 is provided that extends from the top of the storage container 2 to a level in the storage container 2 corresponding to the level of the extension arm 9 of the force sensor 6. Said level sensor 7 continuously detects the fill level in the storage container 2 (i.e. the surface of the cone of milling material shown schematically by the arched line) and transmits a signal to the control unit 8 via a connection line (shown schematically by the dashed line), which signals that a specific fill level has been reached.

[0083] FIG. 2 shows a flow chart of the operation of the control unit 8 of the inlet arrangement of the present invention.

[0084] The force sensor 6 and the level sensor 7 transmit signals to the control unit 8. The signals are typically converted by A/D converters 10, 11 and further processed in processing units 12, 13. Said processing may comprise an operation selected from the group consisting of scaling, offset and filtering, and combinations thereof.

[0085] The processed signals are transmitted to a calculation unit 14. In said calculation unit 14, a sensor value for the force sensor 6 is determined in dependence from the values detected by the level sensor 7. Said calculation may involve a calibration of the signals provided by the force sensor 6 on the basis of the signals provided by the level sensor 7.

[0086] The thus obtained signal value is transmitted into a regulation unit 15, where the obtained signal value is compared with a setpoint level S that may be provided by an operator, for example via an input signal or a computer interface. If as a result of the comparison of the obtained signal value with the setpoint level a deviation of the two values is identified, the obtained signal value is adjusted to the setpoint value, as described above. Therewith, an output signal is generated that is transmitted, preferably via a D/A converter 16, to a machine control element 17. Said machine control element 17 may accordingly be caused to influence the flow of the material out of the storage container 2, for example by operating the metering device 5.