Automatic mill and milling method

Abstract

The invention relates to a mill comprising a feed opening (1) for a product (P) to be milled, at least one milling device (2), a discharge opening (3) for a milled product (M), at least one particle measuring probe (4) for determining the size of particles passing through, a control unit and a device for adjusting the milling device (2). At least one particle measuring probe (4) or a particle suction device connected to the particle measuring probe (4) via a suction device is arranged in the grinding device (2) or between the grinding device (2) and the discharge opening (3). The control unit is used for controlling the device for adjusting the grinding device (2) on the basis of information from the at least one particle measuring probe, in particular on the basis of a size distribution determined by a plurality of measured values.

Description

Technical Field

[0001] The invention relates to an automatic grinding machine and a grinding method for grinding natural products. Background Art

[0002] The purpose of a mill is to grind a coarse material into a fine particle final product, wherein the size of the milled particles is in many cases a decisive quality feature and is therefore a reference size for the milling process. In a mill, the coarse material is usually conveyed between rollers arranged in pairs, wherein the rollers in a pair of rollers are spaced apart by a certain roller gap. The particle size of the milled material formed depends on the width of the roller gap and can be adjusted by moving the rollers together or apart. In addition to the width of the roller gap, the ambient temperature, the temperature of the product to be milled, the pressure in the mill, the humidity, the humidity of the product to be milled, the speed of the rollers, the temperature of the rollers and the vibrations in the mill can also have an impact on the quality of the milled material or provide information about the performance of the mill. In order to ensure the quality stability of the milled material and the performance of the mill, it is known in the prior art that these parameters are measured during the milling process and adjusted to preset target values. In order to monitor and adjust the particle size, a sampling spoon is usually used to extract the milled material from the mill, and then the sample is analyzed in an external device and the mill settings are adjusted according to the measurement results. However, sampling represents a lot of rework and material losses, and the time delay caused by the external measurement does not allow for effective adjustment and control of the mill settings. Therefore, certain mill manufacturers have developed automatic measurement systems to determine and adjust 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, but rather infers that the force is proportional to the degree of grinding (i.e. the particle size). This may be the case for synthetic products, but it is certainly not the case for natural products, which often have very heterogeneous properties. For example, the hardness of coffee beans or wheat particles can vary significantly depending on the plant species, planting location, growing conditions and / or drying process, and the particle size ground by the rollers will also be correspondingly different, even if the force distribution between the rollers is the same. Summary of the invention

[0003] The present invention now sets its technical task to provide a grinding method and an automatic grinding machine, which can automatically, dynamically and finely adjust the particle size of the material to be ground during the grinding process.

[0004] This technical object is achieved by an automatic grinding machine having the features of claim 1 and a grinding method having the features of claim 8. The dependent claims indicate further technical features and embodiments, and their advantages are explained in the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0005] The accompanying drawings show:

[0006] Figure 1a Schematic diagram showing a grinding mill according to the invention in a side sectional view

[0007] Figure 1b a partial view showing a nip of a pair of rollers in side cross-sectional view;

[0008] Figure 1c A partial view of the nip of a pair of rollers is shown in bottom view;

[0009] Figure 2a -b shows a schematic diagram of an embodiment of a mill according to the invention in a side sectional view. DETAILED DESCRIPTION

[0010] The drawings show possible embodiments which will be explained in the following description.

[0011] In the simplest embodiment of the invention, the automatic mill comprises an inlet 1 for the product P to be milled, at least one milling device 2, an outlet 3 for the milled material M, at least one particle measuring probe 4, a control unit and a device for adjusting the milling device 2 ( Figure 1a -b). At least one particle measuring probe 4 is arranged in the milling device 2 or between the milling device 2 and the discharge port 3, and regularly measures the size of the particles passing through it. The determined size is transmitted to the control unit, which uses these measured values ​​to determine the size distribution. Based on this information, the device for adjusting the milling device 2 is controlled. The device for adjusting the milling device 2 includes, for example, a drive, with which the adjustment of the milling device 2 can be changed. Preferably, a target value or a comparison value for the desired size distribution of particles of the milling material M is stored in the control unit, and the size distribution of the measured particles is compared with the input value. If the determined size distribution does not match the expected value, the settings of the milling device 2 are adjusted accordingly. According to the existing measured values, the information for adjusting the settings is either stored as a preset value, or stored as an empirical value, or the settings are changed using a trial and error method until the desired particle distribution is achieved. The size distribution of the milled particles is determined by the particle measuring probe 4, and the settings of the milling device 2 are preferably adjusted accordingly continuously, automatically and in real time during the milling process. This control can respond immediately to changes in particle size without manual or external intervention to ensure stable output quality.

[0012] In a preferred embodiment of the present invention, the grinding device 2 comprises at least one pair of rollers 21, which are separated by a certain roller gap 22 ( Figure 1b). During the grinding process, these rollers 21 rotate relative to each other so that the product P to be ground is conveyed through the roller gap 22 and ground into smaller particles. The particle measurement probe 4 is located after the roller 21 and determines the size distribution of the particles formed. 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 according to the measured size distribution of the ground particles: if the particles are too large, the rollers 21 move together and the roller gap 22 becomes narrower, if the particles are too small, the rollers 21 move apart and the roller gap 22 becomes wider. The device for adjusting the grinding device 2 is used to move the rollers 21 together and apart, and is controlled by the control unit. In order to control the movement of these rollers 21 relative to each other and the width of the roller gap 22, a measuring unit can be provided, which either directly measures the width of the roller gap 22 or the position of the rotation axis of each roller 21.

[0013] Due to wear or contamination of the rollers, the width of the nip 22 along the rollers 21 may be non-uniform, resulting in non-uniform particle size of the milled material M. Therefore, in an advantageous embodiment of the invention, a plurality of particle measurement probes 4 ( FIG. 1 c ) are arranged along the nip 22. If excessive deviations in particle size are detected by the particle measurement probes 4 along the nip 22, the alignment of the rollers 21 relative to each other can be automatically adjusted by means of the device for adjusting the milling device 2 to correct the non-uniform nip 22.

[0014] Advantageously, if the grinding device 2 has a plurality of pairs of rollers 21, the product P to be ground is ground multiple times by these rollers and ground into increasingly fine particles (FIG. 1a). For example, the plurality of pairs of rollers may be arranged one after the other or one above the other so that the product to be ground is transferred from one pair of rollers to the next pair of rollers. In this case, the mill may be provided with a particle measuring probe 4 after each pair of rollers 21 in order to check the particle size and adjust each pair of rollers 21 individually ( Figure 2a In a simple embodiment of the mill, the single particle measuring probe 4 can also be arranged after the last pair of rollers 21 or in the discharge port 3 or between the milling device 2 and the discharge port 3 ( Figure 2b ). It is expected that the ground final product M has been sufficiently mixed by the pairs of rollers 21 or by a conveyor arranged therebetween, so that the single particle measurement probe 4 can determine a representative measurement value.

[0015] In one possible embodiment, the mill is provided with a suction device which can alternately suck particle samples from the particle suction device at multiple different positions of the mill 2 and deliver them to a single particle measurement probe 4. This enables checking the particle size at multiple positions of the mill 2 and adjusting each pair of rollers 21 without installing multiple particle measurement probes 4 in the mill.

[0016] In addition to the particle size, other parameters relevant to the quality of the milled material M can also be measured and controlled during the milling process:

[0017] Temperature: The temperature of the product P to be ground can be monitored by a temperature probe in the feed opening 1. If necessary, a pretreatment of the product P to be ground can be provided so that it reaches a certain temperature before reaching the grinding device 2. By means of the pretreatment it can be ensured that no quality-related deviations occur in the temperature of the ground material in the grinding device 2. During the grinding process, the temperature of the ground material can also be monitored in the grinding device 2 or in the discharge opening 3. Controlled heating or cooling can be provided in order to keep the temperature of the ground material around a predetermined target value. This of course also applies correspondingly to the ambient temperature, which should also be kept as uniform as possible.

[0018] Pressure in the milling device 2: The pressure in the milling device 2 may vary depending on the processed product P and may increase during the milling process if discharge of the milled material occurs. The pressure prevailing in the milling device may therefore be monitored and a controlled exhaust system or external air supply may ensure that pressure conditions are kept stable around a predetermined target value.

[0019] Humidity: The humidity of the product P to be milled can be monitored by means of a humidity probe in the inlet 1. If necessary, pretreatment of the product P to be milled can be provided so that it reaches a certain humidity before it reaches the milling device 2. With the pretreatment it can be ensured that no quality-related deviations occur in the humidity of the milled material in the milling device 2. During the milling process, the humidity of the milled material can also be monitored in the milling device 2 or in the outlet 3. Controlled humidifiers or desiccants can be provided in order to keep the humidity of the milled material around a predetermined target value. The humidity inside and outside the mill can also be controlled accordingly and kept as constant as possible.

[0020] In an advantageous embodiment of the mill, parameters providing information about the performance of the mill are also monitored:

[0021] • Power consumption of the roller motor: If the product remains the same and the power consumption of the roller motor changes, it can be inferred that the roller 21 is dirty or worn, because the friction will increase.

[0022] Vibration and roller temperature: If the vibration or roller temperature or roller coolant temperature changes slowly and steadily for the same product, it can be inferred that the product quality is poor or the roller is dirty. Heat is usually caused by poor heat dissipation due to dirt.

[0023] By monitoring one or more of these parameters, defects can be detected at an early stage and necessary maintenance of the grinding device 2 can be planned in good time, or the ideal time for cleaning or replacing the rollers can be calculated.

[0024] Contamination of the rolls can be compensated to a certain extent by adjusting the roll gap. Wear or contamination can cause gradual changes in the target value. The system detects such changes and stores the new target value in the control unit directly after the process is completed.

[0025] 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 roller 21 is detected.

[0026] However, at some point, the rollers must be cleaned or replaced. To do this, the rollers must be removed, cleaned or replaced and reinstalled. The distances between these rollers are then referenced again. Ideally, the reference setting can be based on empirical values ​​after cleaning or replacing the rollers. In certain cases, the rollers must be recalibrated using a test run. After maintenance or cleaning of the system, the original target values ​​are restored.

[0027] According to the invention, it is provided that a recipe is determined before the milling process, in which one or more of the above-mentioned parameters (including at least the desired size distribution of the milled particles) are determined as target values. It is advantageous if, in addition to the target values, tolerances specific to the recipe are defined for each parameter. During the milling process, these parameters are measured and compared with the target values ​​according to the recipe by a control unit. If all measured values ​​are within the expected range, it can be inferred that the milled material M has the desired stable quality. If the measured values ​​do not correspond to the determined target values, the control unit adjusts the settings of the milling device 2 by means of a device for adjusting the milling device 2. During the milling process, the size distribution of the milled particles is preferably determined continuously, automatically and in real time by means of a particle measuring probe 4 and the settings of the milling device 2 are adjusted accordingly.

[0028] In an advantageous embodiment, the mill outputs a signal containing the measured value during the milling process, or triggers an alarm if the measured value does not correspond to the desired target value. The signal can be, for example, a visual signal displayed on a screen. The signal can also be an acoustic signal, in particular when it is used as an alarm. The signal can also be an electrical or electromagnetic signal and is sent to a separate electronic device, such as a central control unit, via a cable or wirelessly. In order to input the parameters to be monitored and the corresponding target values ​​and tolerances, the mill can be provided with a user interface and / or it can receive electrical or electromagnetic signals containing parameters, target values ​​and tolerances from a separate electronic device.

[0029] It is very advantageous if certain or all measured values ​​during the milling process are stored in a database and made available for further processing. Based on the collected data, the process can be analyzed retrospectively at any time or in real time. This enables seamless process monitoring and control as well as more precise determination of target values.

[0030] It is advantageous if the product P to be ground is pre-weighed and dosed, or an online quantity measuring device can be provided at the inlet 1 .

[0031] In summary, a new mill and a new milling method are provided, which have significant advantages over the prior art:

[0032] The mill can operate with little human intervention;

[0033] All quality-related process parameter deviations will be immediately identified and directly corrected or reported;

[0034] Particle size measurement in a closed system without the loss or risk of unnecessary sampling;

[0035] In the event of deviations from determined target values, the mill ensures consistent quality due to immediate correction of quality-relevant parameters. This means that even natural products can be ground in a controlled and stable manner;

[0036] Virtually eliminate downtime during the process due to numerous monitoring systems and data points;

[0037] Mills can be provided with artificial intelligence that predicts maintenance needs based on measured parameters through machine learning and can be scheduled at the ideal time.

Claims

1. A mill, comprising an inlet (1) for a product (P) to be milled, at least one milling device (2), an outlet (3) for the milled material (M), at least one particle measuring probe (4) for determining the size of particles passing through, a control unit, and a device for adjusting the milling device (2), wherein at least one particle measuring probe (4) or a particle suction device connected to the particle measuring probe (4) via a suction device is arranged in the milling device (2) or between the milling device (2) and the outlet (3), The control unit is suitable for controlling the device for regulating the grinding device (2) based on information from the at least one particle measurement probe, in particular based on a size distribution determined from a plurality of measured values.

2. The grinding mill according to claim 1, characterized in that A target value for a desired size distribution of the particles of the grinding material (M) is stored in the control unit and the control unit is adapted to compare the measured size distribution of the particles with the target value.

3. The grinding mill according to claim 1, characterized in that The grinding device (2) comprises at least one pair of rollers (21) separated by a roller gap (22).

4. The grinding mill according to claim 3, characterized in that A plurality of particle measurement probes (4) are arranged along the roll gap (22).

5. The grinding mill according to claim 3, characterized in that The grinding device (2) has a plurality of pairs of rollers (21).

6. The grinding 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 discharge opening (3) or between the milling device (2) and the discharge opening (3).

7. The grinding mill according to claim 1, characterized in that The mill has a plurality of particle suction devices at a plurality of locations of the milling device (2), wherein particle samples can be sucked away alternately by the suction devices at a plurality of locations of the milling device (2) and can be delivered to a single particle measuring probe (4).

8. A grinding method using the grinding mill according to claim 1, characterized in that: The method comprises the following steps: Firstly, a recipe is determined, wherein at least the desired size distribution of the particles of the milling material (M) is determined as a target value; During the grinding process, the size distribution of the particles of the grinding material (M) is measured and compared by the control unit with a target value determined according to the recipe; If the measured size distribution of the particles of the material to be ground (M) does not correspond to a determined target value, the control unit regulates the grinding device (2) by means of the device for regulating the grinding device (2).

9. The grinding method according to claim 8, characterized in that: In addition to the target value for the size distribution of the particles, the recipe also contains target values ​​for one or more of the following parameters: ambient temperature; temperature of the product to be milled (P); temperature of the milling material (M); humidity of the product to be milled (P); humidity of the milling material (M); humidity; pressure in the milling device (2); power consumption of the roller motor; vibration of the milling device (2); temperature of the roller (21); During the milling process, one or more of these parameters are measured and compared by the control unit with target values ​​determined according to the recipe.

10. The grinding method according to claim 9, characterized in that Contamination or defects in the grinding device (2) are detected by monitoring the power consumption of the roller motor and / or the vibration of the grinding device (2) and / or the temperature of the roller (21).

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