Roller mill

Abstract

According to one aspect of the invention, a roller mill for comminuting a cereal product is made available which has at least one pair of milling rollers (2, 3). The roller mill moreover has a measuring device (11) with a plurality of temperature sensors, which are arranged distributed along a length of the first milling roller (2). The temperature sensors are arranged outside the first milling roller (2), i.e. not conjointly rotating therewith, but facing the surface of the milling roller and in immediate proximity thereto, in order to measure the temperature of the surface of the milling roller. The roller mill moreover has an electronic unit which is configured to output the temperatures measured by the sensors, according to the position or identity of the sensor, i.e. per sensor, and / or to control a roller mill process according to the temperatures measured by the sensors.

Description

[0001] ROLLER MILL

[0002] The invention relates to a roller mill.

[0003] Roller mills are used in grain mills or other food processing mills. A roller mill comprises at least one set—often two or four sets—of two grinding rollers each, between which a grinding gap is formed during operation. These rollers rotate—generally at different speeds—to crush the material in the grinding gap.

[0004] Common roller packages have a fixed and a movable bearing body on each side of the grinding rollers. The movable bearing body can be moved relative to the fixed bearing body by means of a disengagement device and an adjusting device to adjust the grinding gap and to engage and disengage the bearings.

[0005] Depending on the desired fineness of the material to be ground, the grinding gap is very small; depending on the situation, it can also be adjusted so that the grinding rollers would touch each other if they were not pushed apart by the material to be ground.

[0006] Since the grinding rollers rotate at different speeds, considerable frictional heat is generated in the grinding gap during operation. If, for example, the feed of the material to be ground is interrupted, the rollers can even rub directly against each other, which very quickly leads to overheating and the risk of fire. It has already been proposed to install one or more temperature sensors as safety elements near one of the two grinding rollers. This would trigger an emergency shutdown and / or immediate disengagement (moving them away from each other) and / or raise an alarm if overheating of the grinding rollers is detected. However, depending on the physical design of the support for such temperature sensors, the problem of deposits on the support can arise. For example, document DE 102 26 411 shows a strip with temperature sensors outside the roller.With such a bar, the problem of deposits arises if the bar is positioned close to the roller surface. There is also the risk that the bar itself acts as a temperature conductor, which can distort measurements.

[0007] DE 1987 19 614 A1 relates to a method for milling grains using a rolling mill. The rolling mill has a plurality of discrete temperature sensors, designed as infrared sensors, which measure the surface temperature of the respective roller at various locations, for example, to regulate the contact pressure. However, an arrangement with discrete temperature sensors is complex to install. Furthermore, infrared sensors, being optical sensors, are susceptible to surface contamination and are therefore unsuitable for safety-relevant applications.

[0008] In WO 2014 / 195309, WO 2018 / 036978, and WO 2021 / 037525, it was proposed to equip the roller with temperature sensors inserted into a bore extending axially into the roller from the end. These sensors allow for comparatively accurate measurement of the temperature in the roller. This allows process data to be obtained, which can be evaluated and, for example, enable optimization of the grinding process. According to WO 2018 / 036978, conclusions can be drawn from the measurements as to whether the grinding rollers are parallel to each other or not. However, the solution with temperature sensors in the roller has the disadvantage that the temperature sensors must communicate without contact and are also dependent on a battery, which is why the temperature sensors are not suitable as a safety element. Furthermore, the solution is complex because a bore must be created in the roller.Replacing the battery also requires removing the entire roller assembly, which entails a downtime. Finally, the presence of a battery in the product chamber also poses a contamination risk and a safety risk due to the potential risk of explosion at high temperatures.

[0009] It is therefore an object of the present invention to provide a roller mill which overcomes disadvantages of the prior art and which offers advantages in terms of process monitoring without having to accept excessive disadvantages in terms of economic efficiency.

[0010] This problem is solved by a roller mill as defined in the patent claims.

[0011] According to one aspect of the invention, a grain milling machine, namely a roller mill for comminuting a grain product, is provided, which comprises at least one pair of grinding rollers. The roller mill further comprises a measuring device with a plurality of temperature sensors, which are arranged distributed along a length of at least one of the grinding rollers (hereinafter referred to as the "first grinding roller"). The first grinding roller can be mounted in the roller mill such that its axis (rotational axis) is essentially stationary, or it can also be a movable, disengageable grinding roller, in which case the measuring device follows the movements of the first grinding roller in directions perpendicular to its axis, for example. The temperature sensors are outside the respective grinding roller, i.e.Not rotating with the grinding roller, but pointing toward the surface of the grinding roller and in its immediate vicinity, for contactless measurement of the temperature of the surface of the grinding roller or the boundary layer. The roller mill further comprises an electronic unit configured to output the temperatures measured by the sensors—as a function of the position or identity of the sensor, i.e., per sensor—and / or to control a process of the roller mill depending on the temperatures measured by the sensors.

[0012] Controlling a process means influencing at least one parameter that has a qualitative and / or quantitative influence on the actual grinding process, for example the gap width, the parallelism of the grinding rollers, the speed of the grinding rollers, etc. - and therefore not just switching it on and off.

[0013] The temperatures measured by the sensors can be output visually, for example, via a display, whereby such a display can be part of the roller mill. However, the display can also be provided via an external device that communicates with the roller mill via an interface, e.g., a higher-level system control system (e.g., for an entire mill or a subsection of one), a generic computer, a smartphone with a corresponding app, a tablet, etc. In this case, the temperatures measured by the sensors are output by transmitting these temperatures to the external device via the interface. The roller mill then also includes, for example, appropriate software (e.g., an app) for the external device.

[0014] The roller temperature display can, in particular, include a representation of the temperature as a function of position, e.g., a measurement curve as a function of position, a bar graph (with one bar for each temperature sensor), etc.; colors can also be customized (e.g., with red color components for a measured temperature above a certain value (e.g., above 100°C), which is still below the threshold for emergency shutdown, etc.).

[0015] In any case, the display is designed to allow a user to check the temperature distribution along the roll and compare temperatures along the roll length—not just read a single temperature or check whether overheating is present or not. In particular, the user can use the temperatures to check whether there is an uneven product feed, a skewed gap setting, and / or whether the roll crown is too large or too small, etc. Even if the temperature distribution often does not provide a clear indication of the cause of an unevenness, at least if the asymmetry is sufficiently strong, it clearly indicates that one exists and at least provides clues to the cause.

[0016] It is also possible for the user to deactivate individual sensors as needed.

[0017] The measuring device can, in particular, be part of the roller package to which the pair of grinding rollers belongs. A 'roller package' within the meaning of this text can, in particular, form a unit which can be removed as a whole from a roller mill and inserted into it, thus forming an independent module. Maintenance and, under certain circumstances, certain calibration and testing steps can thus be carried out on the isolated roller package and do not have to be carried out on the machine while it is installed. The electronics unit does not have to be part of the roller package. However, it is also not excluded that the roller package contains the electronics unit or at least parts thereof. In particular, it is possible for the electronics unit or part thereof to comprise a circuit board with electronic components arranged thereon, which forms part of the measuring device and is, for example, integrated in the base body (see the following explanations).

[0018] The procedure using a measuring device that has a plurality of temperature sensors that are arranged outside the grinding roller but distributed along its axial extent and are evaluated individually, solves the tasks described above.

[0019] Firstly, it enables process monitoring by allowing the operator to qualitatively compare and / or quantitatively read the heat distribution along the axial extent of the grinding roller. This allows conclusions to be drawn about the characteristics of the grinding process. If necessary, measures can be initiated to optimize it. It has been shown – quite surprisingly – that good conclusions can be drawn in this regard even when the sensors are arranged outside the grinding roller – especially since a very precise reading of the absolute temperature has proven to be unnecessary. Rather, it is sufficient if the temperatures are approximately known and, moreover, are easily comparable along the axial extent of the grinding roller.

[0020] Secondly, the solution is significantly less complex to implement than a hole in the grinding roller that accommodates the sensors.

[0021] Thirdly, the arrangement of the sensors outside the grinding roller also enables the sensors to serve as a safety element, as they are not dependent on a battery-based power supply. In particular, it can therefore be provided that the roller mill is set up to trigger an alarm and / or a machine stop and / or an automatic grinding gap enlargement upon detection of excessive temperature. An excessive temperature can, for example, represent an exceeding of a threshold value for one sensor, for at least two sensors, or another criterion (e.g. relating to an average value of sensor measurements for adjacent sensors, etc.). In connection with the non-battery-based power supply, there is also no incentive to restrict functionality, e.g. by using a low sampling rate, in order to save energy and thus extend the battery life.Furthermore, the battery-independent power supply significantly reduces maintenance effort, as there is no longer any need to remove the roller package when changing the battery.

[0022] Finally, the solution with a permanently pre-assembled measuring device installed relative to the roller package also ensures that the assignment of individual sensors to a corresponding roller is always clear.

[0023] The measuring device therefore has, in particular, a conductor-based power supply, meaning it operates (entirely) with electrical energy supplied from outside the measuring device. It is therefore free of batteries and other energy storage devices; however, it cannot be ruled out that it also has energy storage devices, e.g., for non-safety-relevant components.

[0024] The output of the temperatures measured by the sensors can include the absolute values. However, this is not required. In general, it is sufficient if the temperatures recorded by the various sensors are comparable to determine a relative temperature distribution, and if overheating is also detected, e.g., based on a comparison with a threshold value. The electronics unit can be a dedicated roller package control unit, or it can be fully or partially integrated into a control module for the entire roller mill and / or partially integrated into at least one external component – ​​e.g., a universal computer connected via an interface, a mobile device, and / or a higher-level controller for controlling multiple devices in a grain mill.

[0025] The measuring device has in particular a housing which can be installed monolithically and as a whole into the roller mill, in particular the roller package, and which carries the temperature sensors.

[0026] In one group of embodiments, the measuring device has, for example, a base body that extends in the axial direction along the first grinding roller. A plurality of sensor pins, each carrying one of the temperature sensors, extends from the base body to the surface of the grinding roller. The base body and the sensor pins together form, for example, a monolithic housing. The sensor pins are designed in particular as tubes, i.e. as wooden profiles (with a round or non-round cross-section), inside which each temperature sensor is located. The temperature sensors are arranged in particular such that their sensing surface projects towards the surface of the grinding roller at the end. They can be soldered inside their sensor pins, which also ensures optimal temperature transfer between the sensor pin and the temperature sensor.

[0027] The sensor pins can be permanently attached to the base body, for example, pressed, soldered, welded, screwed or otherwise fastened to it. The sensor pins are therefore physically attached to the base body. The base body and the sensor pins together form a monolithic housing. The base body can also be designed as a tube, the interior of which accommodates the cabling to the temperature sensors - and possibly also part of the electronics unit. The lumen of the sensor pins opens into the lumen of the base body, so that power supply and / or signal lines coming from the sensor can run through the base body. Separate or combined power supply and / or signal lines can be present; for example, in the case of temperature sensors based on electrical resistance measurement, the determination of the measured variable (e.g. electrical resistance) can also take place outside of the actual temperature sensors, e.g.in the electronics unit.

[0028] In particular, it can be provided that the base body supports a circuit board. This has the advantage that the power supply and / or signal lines leading to the sensors can be routed to the circuit board. It is not necessary for at least one cable per temperature sensor to be routed out through the base body. Instead, at least one conductor per temperature sensor can be routed from the circuit board to a dedicated connector on one end of the base body. For this purpose, a flexprint element or similar can be assigned to the circuit board to accommodate the orientations of the connector and the circuit board determined by the geometry.

[0029] It is also possible for at least one element of the electronics unit to be located directly on the circuit board in the base body, so that each of the sensors can be read individually without the need for a conductor to be routed to the outside for each sensor. In this case, only a thin cable, for example, for transmitting a digital signal, leads from the base body, particularly via a plug connection. Such a cable can connect the element of the electronics unit to other units of the electronics unit – or to higher-level machine electronics. The interior of the sensor pins and / or the base body can be encapsulated in a hardened compound that surrounds the cabling, possibly including the circuit board, and possibly also at least partially the temperature sensors. Welded end points can provide additional protection for the external, exposed measuring points.

[0030] Apart from the sensor pins and, if necessary, such a potting compound, the temperature sensors can operate without additional sheathing, which optimizes the response behavior.

[0031] It is also possible for elements of the electronic unit, in particular an evaluation unit which evaluates the physical measurement signals and, for example, transmits digital measurement data, to be arranged in the base body itself.

[0032] The design with a base body and sensor pins projecting towards the surface of the first grinding roller has the following advantage: To ensure sufficiently precise measurements, the temperature sensors must be positioned close to the surface of the first grinding roller, at a distance of, for example, no more than 1-5 mm. However, in the area surrounding the grinding rollers, an air flow containing flour dust is entrained due to their rotation. This would lead to a tendency for deposits in a rod-shaped measuring device located in the immediate vicinity of the grinding roller. In addition to hygiene problems, heavy product adhesion can lead to fires or damage the roller surface if inadequately cleaned. The design with the sensor pins, which can be comparatively thin and offer little surface area for the air flow to attack, effectively prevents this tendency.The design with a base body and sensor pins thus results in very compact measuring points with sufficient clearance between the measuring points, the roller surface, and the machine casing. This design is therefore particularly advantageous with regard to safety and hygiene requirements.

[0033] The measuring device is mounted, for example, on the side walls of the roller package.

[0034] The measuring device can be movable as a whole relative to the first grinding roller to move the measuring pins away from the surface. It can be pivotable, for example, by rotating the base body through a certain angle around its axis to pivot the measuring pins away from the roller surface and then position them back against the roller surface. This design is particularly advantageous and stable in terms of the shape of the measuring device with the base body and sensor pins. Alternatively, the measuring device can also be linearly displaceable.

[0035] The sensor pins can run radially with respect to the axis of the measuring device.

[0036] The rollers of the roller pack can be between 0.8 m and 1.8 m long, for example, and can have lengths of 1000 mm, 1250 mm, or 1500 mm (corresponding to common roller lengths). They can be smooth or have a ridge, for example, a fine ridge (with at least approximately one ridge per mm of circumferential length). The diameter of the grinding rollers can also be a common diameter, for example, between 238 mm and 252 mm.

[0037] The temperature sensors can be commercially available temperature sensors with a measuring range of, for example, at least between 0°C and 150°C, or a measuring range of between a value lower than 0°C and at least 250°C. For example, platinum resistance sensors or other resistance sensors can be used, e.g. Pt1000 sensors. In general, a requirement for the temperature sensors is that they enable quantitative measurements in the specified temperature range (particularly between room temperature and 150°C) and not just a comparison with a threshold value - like bimetallic switches, for example. The requirements for the absolute accuracy of the temperature measurements are, as mentioned, not extremely high, since valuable information can be obtained through comparison even with less precise measurements.An accuracy of plus or minus 10°C may be sufficient, whereby the greatest, but still acceptable, uncertainty does not come from the accuracy of the sensors, but from the fact that the non-contact measurement actually measures the temperature of the boundary layer in the immediate vicinity of the grinding roller and not directly the surface temperature.

[0038] The number of temperature sensors can depend on the roller length and can be, for example, between 5 and 25, in particular between 10 and 15. The sensors can, for example, be placed in a row, at intervals of between 50 mm and 200 mm, in particular between 80 mm and 150 mm, for example, approximately 100 mm. The outermost sensors in the row can, for example, be arranged at a distance of approximately 50 mm from the edge of the first grinding roller.

[0039] It may also be provided that, if necessary, a further temperature sensor is present on those parts of the electronic unit (e.g. the aforementioned evaluation unit) which are installed as part of the measuring device.

[0040] The signal and data transmission between the sensors and the electronic unit - and if necessary between subunits of the electronic unit, e.g. the aforementioned evaluation unit and a central module of the electronic unit - can be analogue or digital, e.g. by means of a bus system.

[0041] Embodiments of the invention are described below with reference to drawings. In the drawings, like reference numerals designate like or similar elements. The drawings are partly schematic and not to scale. They show partly corresponding elements in different sizes from figure to figure. They show:

[0042] Fig. 1 : A view of a roller package for the roller mill;

[0043] Fig. 2 shows a schematic cross-section through the roller package and elements of the roller mill;

[0044] Fig. 3 a view of the measuring device;

[0045] Fig. 4 is a diagram of the measuring device together with the electronic unit and an output unit; and

[0046] Fig. 5 shows a schematic view of the roller mill.

[0047] Figure 1 shows a view of a roller package 1, and Figure 2 shows schematically a section - perpendicular to the axis of the grinding rollers - through the roller package as well as element of the cladding which the roller mill forms around the first grinding roller shown on the left in Fig. 1.

[0048] The roller assembly comprises a first grinding roller 2 and a second grinding roller 3. The first and second grinding rollers each have a roller stub 21, 31 on either side, which is rotatably mounted by a corresponding bearing. A roller assembly frame 7 forms a supporting structure and can be attached to a roller mill frame or forms part of the same. A first bearing body with the bearing for the first grinding roller and a second bearing body with the bearing for the second grinding roller, movable relative to the first bearing body perpendicular to the axes of the grinding rollers 2, 3, are provided or mounted on the roller assembly frame 7.

[0049] The bearings of the first and second grinding rollers as well as the mechanisms for adjusting the grinding gap and disengaging - with an adjusting and disengaging device 6 on each side - are designed as described in the Swiss patent application CH 000 148 / 2023, to which reference is made here.

[0050] The present invention is not dependent on the mechanisms for adjusting the grinding gap and disengaging and is also applicable to roller mills with completely differently designed roller packages.

[0051] In Fig. 1 and Fig. 2, the measuring device 11 can also be seen, which is also shown in Fig. 3. The measuring device has a base body in the form of a rod 12, which extends in the axial direction along one of the grinding rollers - in the example shown, along the first grinding roller 2. A plurality of sensor pins 13 are attached to the base body, which project away from the base body towards the surface of the first grinding roller 2. At the front ends of the sensor pins 13, i.e. the ends towards the first grinding roller 2, each has a temperature sensor. An end cap 15 is arranged on each axial end side of the rod 12. At least one of the end caps 15 allows the passage of cables for supplying power to the sensors and for retrieving and / or reading out the signals generated by them. Due to the arrangement and orientation of the sensor pins 13, the distance a sof the sensors from the surface of the first grinding roller 2 is significantly smaller than the distance t of the base body (i.e. the rod 12). Since the sensor pins 13 can be comparatively thin, this means that the sensors in the sensor pins 13 can be close to the surface of the first grinding roller 2 in order to reliably measure the temperature at the surface, without the process air, which is drawn along by the rotation of the grinding roller (see the block arrow in Fig. 2), being impeded in its flow by the measuring device 11, and without deposits of flour dust or similar forming on the surface of the measuring device 11. Fig. 2 shows that the cladding 14, which the roller mill forms in the vicinity of the first grinding roller, is arranged at a distance from its surface so that a circumferential flow space 10 for the process air can be formed, which is not interrupted by the measuring device.

[0052] As schematically illustrated in Figure 4, the sensors 51 can be read individually by the electronics unit 52. For example, it can be provided that a separate physical connection for power supply and readout exists between each of the sensors 51 and the electronics unit 52 – i.e., a cable leads from each of the sensors to the electronics unit. The cables are then bundled and routed through the rod 12. However, it is also possible that, using a bus system and sensor electronics present in each sensor, each of the sensors can be read individually, without each sensor requiring its own cable.

[0053] In Fig. 4, in addition to the electronics unit 52, an output unit 54 is also schematically shown. This unit displays the measured temperature T as a function of the sensor position P on a display panel, allowing a temperature profile 56 to be read along the length of the first grinding roller. From this, the operator can draw conclusions, for example, about the parallelism of the grinding rollers and the regularity of the product feed, and adjust the corresponding parameters as needed.

[0054] It is also possible that, in addition to displaying the temperature on an output unit—or instead of such a display—the measured temperatures are used by the machine control system itself, formed by the electronic unit, to automatically adjust parameters—e.g., gap parallelism or gap width. Additionally or alternatively, the measured temperatures can also be transmitted to a higher-level control system in order to influence—also—the operating parameters of other components of the system to which the roller mill belongs. For example, it can be provided that the quantity of product fed per unit of time is adjusted if the measured temperatures are too high or rise too rapidly.

[0055] Fig. 4 also schematically illustrates that an alarm can be triggered (alarm unit 39) and / or an immediate shutdown can be triggered if a corresponding condition is met. Such a condition can, for example, be the exceeding of a threshold value 57 at at least one position.

[0056] Figure 5 shows a very schematic view of the entire roller mill 101 with at least one roller package. A handwheel 102 serves as an electronically readable physical control element. Further input and output options may be available, which are indicated in Fig. 5 by a schematic display panel 103—which may be touch-sensitive—, an input panel 104, and an interface to a mobile phone 105. The output unit 54 shown in Fig. 4 can, for example, be formed by the display panel 103 or the interface and the mobile phone 105 (and / or a tablet and / or a laptop or another computer; a central system control system is also possible); other implementations are also conceivable.

Claims

PATENT CLAIMS 1. A roller mill for comminuting a grain product, comprising at least one pair of first and second grinding rollers (2, 3) and a measuring device (11) with a plurality of temperature sensors (51) arranged distributed along a length of at least the first grinding roller, characterized in that the temperature sensors (51) are arranged outside the first grinding roller (2) for sensing a temperature of the surface of the first grinding roller (2), and in that the roller mill further comprises an electronic unit (52) which is configured to output the temperatures measured by the sensors and / or to control a process of the roller mill depending on the temperatures measured by the sensors.

2. Roller mill according to claim 1, wherein the electronic unit (52) is configured to automatically stop a drive of the first and second grinding rollers and / or to move the grinding rollers away from each other if the measurement of the temperatures shows that overheating is present.

3. Roller mill according to claim 1 or 2, which is arranged and programmed to display the temperature of the first grinding roller (2) as a function of an axial position.

4. Roller mill according to one of the preceding claims, wherein the temperature sensors are supplied with power via electrical conductors from outside the measuring device.

5. Roller mill according to one of the preceding claims, wherein the measuring device (11) has a base body (12) and a plurality of sensor pins (13) extending from the base body to the surface of the first grinding roller.

6. Roller mill according to claim 5, wherein the sensor pins (13) form tubes, in the interior of each of which one of the sensors (51) is arranged.

7. Roller mill according to claim 5 or 6, wherein the base body (12) forms a tube through which power supply and / or signal lines run between the electronics unit and the sensors.

8. Roller mill according to claim 7, wherein the power supply and / or signal lines are cast in a hardened mass.

9. Roller mill according to one of claims 5-8, wherein the measuring device (11) is tiltable about an axis parallel to the axes of the first and second grinding rollers (2, 3) in order to change a distance of the temperature sensors from the surface of the first grinding roller.

10. Roller mill according to one of claims 5-9, wherein the sensors are encapsulated within the sensor pins.

11. Roller mill according to one of claims 5-10, comprising a circuit board with connecting contacts to the temperature sensors, wherein the circuit board is integrated in the base body.

12. Roller mill according to one of the preceding claims, wherein the sensors are measuring resistance sensors which enable a determination of the temperature based on a measured electrical resistance.

13. Roller mill according to one of the preceding claims, wherein the measuring device (11) has a housing which can be mounted as a whole and carries the temperature sensors.

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