Autonomous mill and milling method

Abstract

The invention relates to a mill comprising an inlet (1) for products (P) to be milled, at least one milling mechanism (2), an outlet (3) for the milled product (M), at least one particle measuring probe (4) for ascertaining the sizes of the particles running past the particle measuring probe, a control unit, and means for adjusting the milling mechanism (2). The at least one particle measuring probe (4) or a particle removing device which is connected to the particle measuring probe (4) via a suction device is arranged in the milling mechanism (2) or between the milling mechanism (2) and the outlet (3). The control unit is suitable for controlling the means for adjusting the milling mechanism (2) on the basis of information from the at least one particle measuring probe, in particular a size distribution ascertained on the basis of multiple measurements.

Description

[0001] Autonomous mill and grinding process

[0002] The present invention relates to an autonomous mill for comminuting natural products and a milling method.

[0003] The purpose of a mill is to reduce coarse material into a fine-grained end product. The size of the ground particles is often the decisive quality characteristic and thus the control variable of the milling process. In the mill, the coarse material is usually conveyed between pairs of rollers, with the rollers of a pair being spaced apart by a certain gap. The particle size of the resulting ground material depends on the width of the gap and can be adjusted by moving the rollers closer together or apart.In addition to the width of the roller gap, the ambient temperature, the temperature of the products to be ground, the pressure prevailing in the mill, the air humidity, the moisture content of the products to be ground, the speed of the rollers, the roller temperature and the vibrations prevailing in the mill can also influence the quality of the ground material or provide information on the performance of the mill. To ensure consistent quality of the ground material and the performance of the mill, it is known in the art to measure these parameters during the grinding process and to adjust them to a predetermined set value. To monitor and adjust the particle size, ground material is typically pulled out of the mill using a sampling scoop. The sample is then analyzed in an external device and the mill settings are then adjusted depending on the measurement result.However, sampling involves considerable repetitive effort and material loss, and the time delay caused by external measurement does not allow for efficient regulation and control of mill settings. Certain mill manufacturers have therefore developed automatic measuring systems for determining and regulating the force distribution between the rollers in order to continuously adjust the particle size during the milling process. However, this method does not directly measure the particle size; rather, it is assumed that the force is proportional to the degree of grinding, i.e., the particle size. This may well be true for synthetic products, but certainly not for natural products, which typically have very inconsistent properties.For example, the hardness of coffee beans or wheat grains can vary greatly depending on the plant variety, cultivation location, growing conditions, and / or drying method. The size of the particles ground by the rollers also varies accordingly, even with identical force distribution between the rollers. The present invention therefore aims to provide a grinding method and an autonomous mill that enables automatic, dynamic, and fine adjustment of the particle size of the ground material during the grinding process.

[0004] This object is achieved by an autonomous mill having the features of patent claim 1 and a grinding method having the features of patent claim 8. Further features and embodiments emerge from the dependent claims, and their advantages are explained in the following description.

[0005] The drawings show:

[0006] Figure la Schematic representation of the mill according to the invention, side view in section

[0007] Figure 1b Detailed view of the roller gap of a

[0008] Pair of rollers, side view in section

[0009] Figure 1c Detailed view of the roller gap of a

[0010] Pair of rollers, view from below

[0011] Figures 2a-b Schematic representations of embodiments of the mill according to the invention, side views in section. The figures represent possible embodiments which are explained in the following description.

[0012] In the simplest embodiment of the invention, the autonomous mill comprises an inlet 1 for products P to be ground, at least one grinder 2, an outlet 3 for the material to be ground M, at least one particle measuring probe 4, a control unit and means for adjusting the grinder 2 (Figures 1a-b). The at least one particle measuring probe 4 is arranged in the grinder 2 or between the grinder 2 and the outlet 3 and regularly measures the sizes of the particles passing by. The determined sizes are forwarded to the control unit, which uses these measured values ​​to determine a size distribution. The means for adjusting the grinder 2 are controlled on the basis of this information. The means for adjusting the grinder 2 comprise, for example, drives with which the settings of the grinder 2 can be changed.Preferably, a target value or comparison value for the desired size distribution of the particles of the material to be ground M is stored in the control unit and the measured size distribution of the particles is compared with this information. If the determined size distribution does not match the desired value, the settings of the grinder 2 are adjusted accordingly. The information for adjusting the settings is stored either as predefined values ​​depending on the available measured values ​​or as empirical values, or the settings are changed using the trial and error method until the desired size distribution of the particles is achieved. The determination of the size distribution of the ground particles by the particle measuring probe 4 and the corresponding adjustment of the settings of the grinder 2 preferably takes place continuously, automatically and in real time during the grinding process.This control enables immediate response to changes in particle size without manual or external intervention in order to ensure consistent output quality at all times.

[0013] In the preferred embodiment of the invention, the grinding mechanism 2 comprises at least one pair of rollers 21, which are spaced apart by a certain roller gap 22 (Figure 1b). During the grinding process, the rollers 21 rotate relative to one another, so that the product P to be ground is conveyed through the roller gap 22 and ground into smaller particles. The particle measuring probe 4 is arranged downstream of the pair of rollers 21 and determines the size distribution of the resulting particles. Since the size of the particles is an increasing function of the width of the roller gap 22, the width of the roller gap 22 is dynamically adjusted by the control unit depending on the measured size distribution of the ground particles: If the particles are too large, the rollers 21 are moved together and the roller gap 22 becomes narrower - if the particles are too small, the rollers 21 are moved apart and the roller gap 22 becomes wider.The means for adjusting the grinding mechanism 2 serve to move the rollers 21 closer together and further apart and are controlled by the control unit. To control the movement of the rollers 21 relative to one another and the width of the roller gap 22, a measuring unit can be provided that either directly measures the width of the roller gap 22 or the position of the rotational axis of each roller 21.

[0014] Due to wear or contamination of the rollers, the width of the roller gap 22 along the rollers 21 may become uneven, resulting in a non-uniform particle size of the ground material M. In an advantageous embodiment of the invention, several particle measuring probes 4 are therefore arranged along the roller gap 22 (Figure 1c). If excessive deviations in the particle size are detected by the particle measuring probes 4 along the roller gap 22, the alignment of the rollers 21 relative to one another can be automatically adjusted using the means for adjusting the grinding mechanism 2 in order to correct the uneven roller gap 22.

[0015] It is advantageous if the grinding mechanism 2 has a plurality of pairs of rollers 21, by means of which the product P to be ground is ground several times into increasingly finer particles (Figure 1a). The plurality of roller pairs can, for example, be arranged one after the other or one above the other, so that the product to be ground passes from one pair of rollers to the next. In this case, the mill can be provided with a particle measuring probe 4 after each pair of rollers 21, for checking the particle size and adjusting each individual pair of rollers 21 (Figure 2a). In a simple embodiment of the mill, a single particle measuring probe 4 can also be arranged after the last pair of rollers 21 or in the outlet 3 or between the grinding mechanism 2 and the outlet 3 (Figure 2b).It is to be expected that the ground final product M is already sufficiently mixed by the various pairs of rollers 21 or by conveyors arranged between them, so that this single particle measuring probe 4 can determine representative measurements.

[0016] In one possible embodiment, the mill is equipped with a suction device that can alternately take particle samples from several different locations on the mill 2 using particle sampling devices and transport them to a single particle measuring probe 4. This enables the particle size to be monitored at several locations on the mill 2 and the adjustment of each roller pair 21 without having to install multiple particle measuring probes 4 in the mill.

[0017] In addition to the particle size, other parameters relevant to the quality of the ground material M can also be measured and controlled during the grinding process:

[0018] • Temperature: The temperature of the products P to be ground can be monitored by means of a temperature probe in the inlet 1. If necessary, pre-conditioning of the products P to be ground can be provided in order to bring them to a certain temperature before they reach the grinder 2. This pre-conditioning ensures that there are no quality-relevant deviations in the temperature of the material to be ground in the grinder 2. The temperature of the material to be ground can also be monitored during the grinding process in the grinder 2 or in the outlet 3. Controlled heating or cooling devices can be provided in order to keep the temperature of the material to be ground around a predetermined setpoint. The same naturally applies to the ambient temperature, which should also be kept as uniform as possible.

[0019] Pressure in grinder 2 : The pressure in grinder 2 can vary depending on the product P being processed and during

[0020] The pressure during the grinding process can increase if the material being ground emits gas. The pressure prevailing in the grinder 2 can therefore be monitored, and a controlled air extraction system or an external air supply can ensure consistent pressure conditions around a predetermined target value.

[0021] • Humidity: The moisture content of the products P to be ground can be monitored using a moisture probe in the inlet 1. If necessary, preconditioning of the products P to be ground can be provided in order to bring them to a specific moisture content before they reach the grinder 2. This preconditioning ensures that no quality-relevant deviations in the moisture content of the ground product occur in the grinder 2. The moisture content of the ground product can also be monitored during the grinding process in the grinder 2 or in the outlet 3. Controlled humidification or drying agents can be provided to maintain the moisture content of the ground product around a predetermined setpoint. The air humidity inside the mill, as well as outside, can also be controlled accordingly and kept as stable as possible. In advantageous design variants of the mill, parameters that provide information about the mill's performance are also monitored:

[0022] • Power consumption of the roller motors: If the power consumption of a roller motor changes while the product remains the same, it can be assumed that the roller 21 is dirty or worn because the friction force increases.

[0023] • Vibrations and roller temperature: If the vibrations or the temperature of the rollers or the temperature of the roller coolant fluid change slowly and steadily for the same product, this may indicate poor product quality or dirty rollers. Heating is usually due to poor heat dissipation due to dirt.

[0024] By monitoring one or more of these parameters, defects can be detected at an early stage and the necessary repair of the grinding mechanism 2 can be planned in a timely manner or the ideal time for roller cleaning or replacement can be calculated.

[0025] Contamination of the rollers can be compensated to a certain extent by adjusting the roller gap.

[0026] Due to wear or contamination, the setpoint may gradually change.

[0027] Such changes are recognized by the system and recorded as new

[0028] Setpoints directly after the end of the process in the

[0029] Control unit stored.

[0030] In one embodiment of the invention, the mill is provided with an automatic roller cleaning system which is automatically activated and controlled by the control unit when contamination of the rollers 21 is detected.

[0031] However, at certain times, a thorough roller cleaning or roller replacement is necessary. For this purpose, the rollers must be removed, cleaned or replaced, and reinstalled. The roller spacing is then re-referenced. Ideally, an empirical value after cleaning or replacing the rollers can be used for the reference setting. In certain cases, the rollers must be recalibrated with a test run. After maintenance or cleaning of the system has been carried out, the original target values ​​are restored.

[0032] According to the invention, a recipe is compiled before the grinding process, in which one or more of the above-mentioned parameters, including at least the desired size distribution of the ground particles, are specified as a target value. It is advantageous if, in addition to the target value, recipe-specific tolerances are also defined for each parameter. During the grinding process, these parameters are measured and compared by the control unit with the specified target value according to the recipe. If all measured values ​​are within the desired range, it can be assumed that the ground material M is produced with the desired and constant quality. If the measured values ​​do not correspond to the specified target values, the settings of the grinder 2 are adjusted by the control unit using the means for adjusting the grinder 2.The determination of the size distribution of the ground particles by the particle measuring probe 4 and the corresponding adjustment of the settings of the grinder 2 preferably takes place continuously, automatically and in real time during the grinding process.

[0033] In an advantageous embodiment, the mill emits a signal during the milling process which contains the measured values ​​or triggers an alarm if the measured values ​​do not correspond to the desired setpoints. This signal can, for example, be a visual signal displayed on a screen. This signal can also be acoustic, particularly if it serves as an alarm. The signal can also be electrical or electromagnetic and sent by means of a cable or wirelessly to a separate electronic device, for example a central control unit. In order to enter the parameters to be monitored and the corresponding setpoints and tolerances, the mill can be provided with a user interface and / or it can receive an electrical or electromagnetic signal from a separate electronic device containing the parameters, setpoints and tolerances.

[0034] It is advantageous if certain or all measured values ​​during the milling process are stored in a database and made available for further processing. Using the collected data, processes can be analyzed at any time, either retrospectively or live. This enables seamless process tracking and control, as well as more precise definition of target values.

[0035] It is advantageous if the products P to be ground are either pre-weighed and dosed or the inlet 1 can be provided with an inline quantity measurement.

[0036] In summary, a new mill and a new grinding process are presented which have considerable advantages over the state of the art:

[0037] The mill functions practically without human intervention;

[0038] • All deviations in quality-relevant process parameters are immediately detected and either rectified or reported; • Particle size is measured in a closed system, without losses or risks due to unnecessary sampling;

[0039] • The mill ensures consistent quality thanks to immediate correction of the quality-relevant parameters in the event of deviations from the specified target value.

[0040] This means that even natural products can be ground in a controlled and consistent manner;

[0041] • Downtimes during the process are virtually eliminated thanks to the numerous monitoring and data points;

[0042] • The mill can be equipped with artificial intelligence that uses machine learning to anticipate maintenance needs based on the measured parameters and plan them at the ideal time.

Claims

Patent claims 1. Mill comprising an inlet (1) for products to be ground (P), at least one grinding mechanism (2), and an outlet. (3) for the material being ground (M) , at least one particle measuring probe (4) for determining the sizes of the particles passing by, a control unit and means for adjusting the grinding mechanism (2), wherein the at least one particle measuring probe (4) or a particle extraction device which is connected to the particle measuring probe (4) via a suction device is arranged in the grinding mechanism (2) or between the grinding mechanism (2) and the outlet (3), and the control unit is suitable for controlling the means for adjusting the grinding mechanism (2) based on information from the at least one particle measuring probe, in particular a size distribution determined on the basis of several measurements.

2. Mill according to claim 1 characterized in that a setpoint for the desired particle size distribution of the milled material (M) is stored in the control unit and the control unit is suitable for comparing the measured particle size distribution with this setpoint.

3. Mill according to claim 1 characterized in that the grinding mechanism (2) comprises at least one pair of rollers (21) spaced apart by a roller gap (22).

4. Mill according to claim 3 characterized in that several particle measuring probes (4) are arranged along the roller gap (22).

5. Mill according to claim 3 characterized in that the grinding mechanism (2) has several pairs of rollers (21).

6. Mill according to claim 5 characterized in that the mill has a single particle measuring probe (4) which is arranged after the last pair of rollers (21) or in the outlet (3) or between the grinding mechanism (2) and the outlet (3).

7. Mill according to claim 1 characterized in that the mill has several particle extraction devices at several locations of the mill (2), wherein particle samples can be alternately extracted from these several locations of the mill (2) by means of the extraction device and can be conveyed to a single particle measuring probe 4.

8. Grinding process with the mill according to claim 1, characterized by the following process steps: • First, a recipe is compiled in which at least the desired particle size distribution of the milled material (M) is defined as a target value; • During the grinding process, the particle size distribution of the material being ground (M) is measured and compared by the control unit with the specified target value according to the recipe; • If the measured particle size distribution of the ground material (M) does not correspond to the specified target value, the settings of the grinding unit 2 are adjusted by the control unit using the means for adjusting the grinding unit 2.

9. Grinding method according to claim 8, characterized in that: • the recipe contains, in addition to a target value for the particle size distribution, also target values ​​for one or more of the following parameters: ambient temperature; temperature of the products to be ground (P); temperature of the ground material (M); Moisture of the products to be ground ( P ) ; Moisture content of the milled material (M); humidity; Pressure in the mill (2); power consumption of the roller motors; vibrations of the mill (2); temperature of the rollers (21); • during the milling process one or more of these Parameters are measured and compared by the control unit with the specified target value according to the recipe.

10. Grinding method according to claim 9, characterized in that contamination or a defect of the grinding machine (2) is detected by monitoring the power consumption of the roller motors and / or the vibrations of the grinding machine (2) and / or the temperature of the rollers (21).

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