Metering and / or weighing device for food products

Abstract

According to one aspect of the invention, the metering and / or weighing device (1) comprises a bulk material container (40) having a bulk material inlet (11) and a bulk material transport. The latter is configured to convey the bulk material (20) present in the bulk material container (40) at intervals in a metered and / or controlled manner. The metering and / or weighing device is characterized by a radar sensor (31) which is attached to the upper side of the container and which produces a beam cone (33) directed downward towards the interior of the container in order to determine the filling level of the bulk material (20) present in the container.

Description

Technical Field

[0001] The present invention relates to food processing, and in particular to the processing of cereal products. It particularly relates to a metering or weighing device for bulk materials, which is applied to the processing of cereal products by a machine. Background Art

[0002] Such metering and / or weighing devices exist as components of machines and also as autonomous machines ("stand-alone devices"). Examples of devices that are components of machines are feeders for roller mills or also weighing and metering devices for flour filling plants. Examples of autonomous machines are bulk scales or differential scales.

[0003] GB 2119104 teaches feeding, for example, fibrous material or also cereals to a process and determining its weight and additionally its moisture content and volume.

[0004] The metering and / or weighing devices each comprise a bulk material container from which the bulk material is transported further in a metered manner or in which the bulk material is collected and weighed for metering purposes.

[0005] For metering devices without weighing units, such as feeders of roller mills, it is usually necessary to monitor the filling level of the bulk material container. For this purpose, it has been suggested to use a weight determined by a force transducer, wherein the force transducer is arranged in the bulk material container. However, the force on the weight sensor is only a measure of the filling degree to a limited extent, because in addition to the filling level, it also depends on other parameters, such as the density of the bulk product, and, depending on the arrangement and design, on other characteristics, such as particle size or flow characteristics. In order to take these situations into account, EP3605034 suggests using a capacitive level sensor in addition to a force transducer. The level sensor determines when a certain level has been reached in the bulk material container, and this information can be used for calibration. The disadvantage of this solution is that it is relatively complex. Elsewhere, capacitive rod sensors are used to monitor the filling level. The advantage of these is that they can measure the filling level independently of the density. However, due to the adhesion of the material, they are prone to failure. US 5433391 shows a roller mill with capacitive level measurement.

[0006] It is also known to perform fill level measurement via a plurality of light barriers arranged at different heights. However, light barriers are also susceptible to malfunctions due to the adhesion of dust and material.

[0007] For metering devices with a weighing cell, the weight measurement simultaneously provides information about the fill level in the corresponding container. However, the disadvantage of density dependence also exists in these devices, i.e. the fill level cannot be determined directly from the fill weight. Summary of the invention

[0008] The object of the invention is to provide a metering and / or weighing device which overcomes the disadvantages of the prior art and which in particular enables a reliable and robust estimation of the filling level and which is as simple and inexpensive as possible.

[0009] According to one aspect of the invention, the metering and / or weighing device comprises a bulk material container having a bulk material inlet and a bulk material conveyor. The latter is configured to convey the bulk material present in the bulk material container in a metered and / or controlled manner at intervals. The metering and / or weighing device is characterized by a radar sensor, which is attached to the upper side of the bulk material container and generates a beam cone pointing downwards into the interior of the container in order to determine the fill level of the bulk material present in the container.

[0010] The metering and / or weighing device is configured for metering and / or weighing food products, in particular cereal products. Cereal particles and products resulting from the size reduction of cereal particles, thus flour, meal, semolina, oats, etc., are denoted as cereal products. The particle size (average diameter) of the bulk material can in particular be up to several millimeters, for example up to 5 mm or up to 3 mm. The finest possible particle size is that of flour, thus less than 0.18 mm or less than 0.112 mm, wherein the average particle size can be approximately 0.07-0.1 mm, or also larger or smaller than these values, depending on the type of flour.

[0011] In addition to being used to measure distance, radar sensors themselves are known. A measurement principle can be based on frequency modulation, for example, by continuously changing the frequency. The frequency difference between the emitted radar signal and the signal reflected back by the object is then a measure of the so-called flight time, and therefore also a measure of the distance between the radar sensor and the object. Radar sensors have also been suggested for measuring the filling level of, for example, high silos and large fuel silos. The measurement of the flight time is achieved in this article, especially in the case of using frequency modulation, by transmitting a radio signal in a continuous manner, but with a continuously changing frequency. In this article, the flight time is generated by comparing the frequency of the emitted radio radiation and the received signal. This type of radar measurement has been suggested for measuring the filling level of large silos, which are used as warehouses for products in industrial processes (especially in the chemical industry). CN211033818U and US2021 / 0140811 show corresponding examples. EP3913335 and DE102012109101 discuss the problems of this filling level measurement in terms of measurement technology.

[0012] However, such silos do not include a bulk material inlet through which bulk material can be fed during operation. For this reason, and solely on account of their size, they would not be suitable for applications, for example, in milling facilities. Furthermore, the measurement principle taught assumes a defined surface of the bulk material. A prerequisite for such a measurement to work is in particular that the reflection of the radio signal occurs at a defined position.

[0013] However, this prerequisite is not given in metering and / or weighing devices for cereal products, for reasons that will be explained below.

[0014] The invention is based on the recognition that radar sensors are also suitable for monitoring the filling level of bulk material containers of weighing and metering devices for food products, even though these containers are several orders of magnitude smaller and the corresponding devices are not equally more sophisticated. In addition, the dimensions are relatively small compared to the wavelength of the applied radio radiation; the distance between the transmitter and the reflecting surface can be significantly less than 1000 wavelengths. In addition, it is generally difficult to measure distances with radar sensors in narrow containers, because there can be many reflections (for example on the walls), and the background (reflections on the bottom of the vessel and the equipment in its vicinity, such as conveying screws, baffles, etc.) does not convey a negligible signal component. In addition, flour-like products are poor reflectors, because radio waves can penetrate relatively deeply and reflections can not only occur on the surface. On the contrary, the reflection behavior is diffuse. A further feature of metering and / or weighing devices for food products present as bulk materials is the presence of a bulk material inlet and a bulk material conveyor, through which the bulk material is fed and discharged during operation, respectively. In particular, the bulk material feeder is configured such that bulk material can also be fed and is fed during operation, during which operation a measurement of the filling level is also achieved. The feeding of bulk material to a metering device such as a roller mill can take place continuously, i.e. there is a continuous product flow into the metering device, which has, among other things, the effect that compact dust often persists above the product filling level. Despite all these problems, it has been found that good results can be achieved with existing measuring techniques.

[0015] Therefore, the metering and / or weighing device is configured to detect the fill level even when bulk material is fed through the bulk material inlet.

[0016] Coherent radar systems have been found to be particularly advantageous. Coherent radar systems have been found to be particularly suitable for eliminating interfering signals due to reflections and background. Pulse radar systems in which the transmitted pulses are coherent, i.e. have a defined phase relationship, are denoted as coherent radar systems. Coherent radar systems according to the prior art are known in particular for detecting moving targets (e.g. aircraft).

[0017] In this context, the metering and / or weighing device can in particular be configured to measure the exact phase position of the pulse in an initial measurement and to subtract this phase from the measurement signal when determining the fill level, for the purpose of eliminating the background (that is to say not taking into account signal components with this phase position). In this way, the advantages of a given fixedly installed coherent radar system are utilized, which is present in the device according to the invention: by means of this initial measurement, the reflections can be taken into account empirically. This is also the case when the reflections are attenuated, for example due to the filling of the container during the determination of the fill level, and also in the case where no exact model of the container and its interaction with the radio beam becomes necessary. Due to the coherence of the radar, this can be taken into account in each fill level measurement after the initial measurement.

[0018] The distance between the radar sensor and the bottom of the volume in the container to be monitored is relatively small, for example a maximum of approximately 3 m or even a maximum of 1.5 m, with a device of the type according to the invention. For example, the distance between the radar sensor on the one hand and the control element on the other hand can be measured. The control element is an element by which the conveying of bulk material is achieved, for example a feed roller and a slide for feeding a given roller mill, or an outlet baffle or an outlet slide for a given bulk material scale or a throughput controller. The distance between the radar sensor and the control element can be, for example, between 0.1 m or 0.2 m and 3 m, in particular between 0.3 m and 1.5 m.

[0019] The radar sensor may be configured to detect a minimum distance as low as 0.2 m or even as low as 0.1 m or less. The device may be configured to enter an alarm state or a safe state when the minimum measurable distance or a settable minimum distance (corresponding to a maximum fill level) is insufficient.

[0020] In particular, the radar sensor comprises a radio wave transmitter (transmitter) and a corresponding receiver. The radio wave transmitter and the receiver can in particular be part of a radar sensor module and can, for example, be present on a common circuit board, for example even integrated in a common integrated circuit. In addition, such a radar module also includes an evaluation device for performing an evaluation step of the received signal. Thus, as described, the radar sensor module can in particular be designed to transmit radio waves in the form of coherent transmission pulses, wherein the determination of the flight time preferably takes place directly in the radar sensor module, in the local vicinity of the transmitter and the receiver.

[0021] In addition to the radar sensor module, the radar sensor may also include a housing or another carrier structure and a lens, which is arranged at a distance of about 1-5 cm from the radio wave transmitter and focuses the emitted radio waves. Such a lens may be composed of plastic, for example.

[0022] In many application cases, it has been found to be particularly advantageous if the opening angle of the beam cone from the radar sensor (possibly after appropriate focusing) has an opening angle of between 5° and 15°. Within this range, the measurement results of the bulk material level in a container of the type described here are particularly good and reproducible. Given a larger opening angle, effects caused, for example, by reflections on the vessel wall and averaging over too large a surface area can blur the result somewhat, while given a smaller opening angle, the radiation intensity can be locally too high.

[0023] The metering and / or weighing device of the type described here is particularly used for metering cereal products (or other foods that may appear as bulk materials) in processing and / or packaging by machines. For this purpose, it comprises a control element, by which the conveying of bulk materials is realized.

[0024] If the device is a feeder for a roller mill, the control element is formed, for example, by a feed roller together with a device for metering the delivery amount transmitted by the feed roller, in particular in an automatically controllable manner. Such a device can include, for example, a drive for controlling the feed roller that can rotate at different speeds. In addition or alternatively, the feed gap through which the feed roller transports the material delivered in a metered manner can have an adjustable size.

[0025] If the device is a scale for bulk materials, such as a bulk scale or a differential scale, the control element is formed by an electrically or pneumatically operated outlet damper or an electrically or pneumatically operated outlet slide. The outlet damper or outlet slide can be configured for complete opening and complete closing during corresponding intervals and / or for continuous control of the flow cross section - depending on the desired application.

[0026] If the device is a scale and therefore comprises a weighing unit with at least one load cell for determining weight, it can also be configured to determine the density value of the bulk material. This is because the determined fill level allows estimating the bulk material volume in the container while utilizing geometrical data on the container and / or pre-determined calibration data stored in the control of the device.

[0027] Independently of the use, the control reading the data of the radar sensor - or also the radar sensor itself - can be configured to communicate with a superordinate control and / or other equipment (e.g. a mill), for example for the purpose of closed-loop control of the feeding of bulk material through a bulk material inlet.

[0028] Additionally or alternatively, the control of the metering and / or weighing device (which can also be part of a superordinate control) can be configured for closed-loop control of the bulk material transport in a manner that depends on the data of the radar sensor.

[0029] If the metering and / or weighing device is a feeder for a roller mill for processing foods, then, as described above, the bulk material transport will include, for example, feed rollers which bring the bulk material present in the container ("collection space") into a further space where it is reduced in size between the (grinding) rollers or - depending on the processing carried out - is simply flattened. There may also be conveying devices in the container, such as conveying rollers, which distribute the bulk material along the axial extension of the feed rollers. In an embodiment, the control of the metering and / or weighing device is configured to set the rotation speed of the feed rollers and / or the width of the feed gap between the feed rollers and the aperture and / or the conveying speed of the possible conveying device, depending on the material level determined by the radar sensor.

[0030] In addition to the metering and / or weighing device, a roller mill is also a subject of the present invention. In addition to a processing unit having at least one pair of rollers, between which the cereal product is reduced in size and / or squeezed, the processing unit also includes a metering and / or weighing device, which serves as a feeder for the roller mill and is of the type described herein. In particular, the metering and / or weighing device can then include a feed roller, wherein the amount of bulk material that can be purchased each time by the feed roller can be adjusted, for example by adjusting the rotation speed of the feed roller and / or possibly another parameter (for example the width of the feed gap). In an embodiment, the control of the metering and / or weighing device - which can be part of the roller mill control, or can also be part of a superior control (for example the entire grinding facility) - is designed and configured to adjust the amount of bulk material brought out per unit time depending on the material level determined by the radar sensor.

[0031] The use of a metering and / or weighing device of the type described herein to meter cereal products in a mill is likewise a subject of the invention. In this context, in particular, the fill level determined by a radar sensor can be used in order to regulate the amount of bulk material brought out per unit time.

[0032] With regard to this use, in particular the feeding through the bulk material inlet takes place continuously and / or the filling level determination takes place continuously.

[0033] In particular, the use envisages also detecting the fill level when bulk material is fed through the bulk material inlet.

[0034] Additionally or alternatively, the amount of bulk material introduced per unit time via the bulk material inlet can be regulated, for example by controlling a corresponding control element (for example a slide) or a machine (for example a flat screen arranged upstream). BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The following is a description of an embodiment of the present invention by means of the accompanying drawings. In the accompanying drawings, the same reference numerals represent equivalent or similar elements. These drawings are schematic. To the extent that they show elements that partially correspond to each other, the sizes of these elements vary from figure to figure. Among them:

[0036] - Figure 1 A view of a roller mill is shown;

[0037] - Figure 2 A cross section of a feeder of a roller mill is shown;

[0038] - Figure 3 A radar sensor is shown;

[0039] - Figure 4 shows a cross section through a bulk scale; and

[0040] - Figure 5 A cross section through a differential scale is shown. DETAILED DESCRIPTION

[0041] Figure 1 A roller mill 1 for use in a grain mill is shown. The roller mill comprises at least one housing in which at least one pair (usually several pairs) of rollers are arranged. The cereal product introduced from above is reduced in size and / or squeezed between the rollers of the roller pairs. For the purpose of feeding a metered amount of cereal product, the roller mill comprises a feeder 3 designed as an apparatus according to the invention.

[0042] exist Figure 2 The middle section (perpendicular to Figure 1 The feeder 3, schematically shown in section in the plane of the drawing, comprises a bulk material container 40 having a bulk material inlet 11 and a bulk material conveyor. The latter is formed by a feed roller 41 and a feed slide 43, which can be moved relative to the feed roller by a suitable mechanism 44 and between which a feed gap 42 is formed, through which the bulk material 20 is transported forward by at least one roller pair for processing purposes. Figure 1 4 shows the possibility of being able to observe the upper inner side of the container 40 from the outside through the observation window 49.

[0043] A radar sensor 31, in particular a pulse coherent radar sensor, is mounted on the upper side of the container 40. It generates a beam cone 33 of radio wave radiation, which is directed downward onto the (free) surface 21 of the bulk material 20 and detects the radiation reflected by the surface 21. The flight time of the radio wave radiation to the surface and back to the sensor can be determined by measuring the reflected radiation. The distance between the radar sensor 31 and the surface 21 and thereby the fill level 22 is doubled, so that the filling level is directly derived from the flight time.

[0044] The applied radio wave radiation can have a relatively short wavelength, which corresponds to a frequency, for example, above 50 GHz, for example about 60 GHz. In particular, the radio waves are therefore microwaves, which are characteristic of radar technology. In radar technology, the applied microwaves are sometimes also referred to as "radar waves". Within the possible spectrum of radar waves, in the present context, relatively short-wave radar waves with a frequency above 20 GHZ, in particular above 50 GHz, and, for example, about 60 GHz as mentioned, are of interest.

[0045] The measured value of the filling level (level 22) determined by the radar sensor 31 is transmitted to a control module 45. This control module 45 can form the control of the entire roller mill 1 or can be a separate control module for the feeder 3. In particular, it can communicate directly or indirectly with other units of the facility to which the roller mill belongs, in order to influence, for example, the feeding of cereal products into the roller mill. Figure 2 Further elements not shown in the figure, such as a conveying screw for horizontal distribution of the cereal product, can also be controlled by the control module 45 .

[0046] Also in Figure 3 The radar sensor 31 shown in FIG. 3 comprises a radar sensor module 32 having one or more integrated circuits, for example on a circuit board. The radar sensor module comprises in some cases a transmitter and a receiver as well as evaluation electronics in an integrated manner. Furthermore, the radar sensor 31 comprises a carrier structure having a lens holder 34 as well as a converging lens 35 for converging the emitted radio radiation. The lens can be made, for example, of plastic and in some cases can be created in a customized manner using methods of additive manufacturing technology (“3D printing”).

[0047] The lens 35 - or very generally the beam-forming optics of the radar sensor - can in particular be designed such that the opening angle φ of the beam cone is between 5° and 15°, in particular between 6° and 12°, for example about 8°. It has been found that the effect produced by the opening angle in this range is optimized for the application described herein. On the one hand, given a larger opening angle, the scattering effect of the vessel wall will be significant, and the signal will be averaged over too large an area of ​​the surface 21 and will therefore be blurred. On the other hand, given a smaller opening angle, the radio power will have to be greatly reduced so as not to result in an excessively high, potentially harmful radiated power. However, the reduction in radio power can have a negative effect on the signal quality.

[0048] Figure 4An example of another metering and / or weighing device, in particular a bulk scale 61 for cereal products and other food products present as bulk material, is shown. The bulk scale likewise comprises a container 40 and a bulk material inlet 11. Furthermore, it is equipped to measure the weight of the bulk material present inside the container. For this purpose, it comprises at least one load cell 64, which measures the weight of the entire container 40 with the contents, from which the weight of the bulk material 20 can be determined taking into account the calibration data, or the at least one load cell can alternatively also measure the weight force acting on an element inside the container, for example on an outlet baffle 63.

[0049] As is known per se for bulk scales, the bulk material enters in portions through the bulk material inlet 11, which is why, for example, an inlet baffle ( Figure 4 The container is not shown in the figure and can open and close the bulk material inlet in a controlled manner by the control module 45. The weight measurement takes place when no bulk material is fed in and the outlet damper 63 is closed. The outlet damper 63 is opened after the measurement and the container is thus emptied by the bulk material entering the outlet area 65 from which the bulk material can flow out continuously.

[0050] Similar to the feeder 3 for the roller mill 1 described above, the radar sensor 31 is used to determine the distance to the surface 21 of the bulk material and thereby to determine the filling level. The information about the filling level determined in this way can firstly be used very generally for process control. For example, it can be ensured that the container is not overfilled at any point in time, which could corrupt the measurement and perhaps block the element.

[0051] Secondly, it is in particular conceivable that the control module 45 implements a measurement performed by a radar sensor if (and therefore when or only when) no bulk material is fed and the outlet damper 63 is closed. The filling level is then a measurement of the volume of bulk material whose weight is measured. As a result, the density of the bulk material can be determined in an approximate manner. Although volume measurements are generally significantly less accurate than weight measurements, since the exact orientation of the surface 21 is not taken into account and cannot even be determined with a single radar sensor, even an approximate assessment of the density of the bulk material is valuable, and this can nevertheless also be used to control the amount of bulk material fed to the scales, respectively. The value of the density can also represent valuable information for other devices of the facility, to which the determined value can be provided. In this way, compared to the prior art, for example, if a change is made between different types of processed bulk materials (for example between granules, flour, semolina, coarsely ground meal, different types of grains, etc.), manual adjustments of the control program and the operator can be omitted, for example.

[0052] Figure 5 Another bulk material scale is shown, specifically a differential scale 71. Figure 4 Compared to the bulk scale 61 of FIG. 6 , the removal of bulk material is not carried out at intervals in an intermittent manner, but rather via an outlet damper 73 with a controlled throughput. With this scale, the weight in the container is also measured, and the weight flowing out of the container 40 per unit time is also determined, in particular during periods when no bulk material is being fed. This can be used for closed-loop control of the throughput via the outlet damper 73. The function of the radar sensor 31 is similar to that according to Figure 4 Bulk scale 61.

Claims

1. A metering and / or weighing device (3, 61, 71) for food products present as bulk material, comprising a container (40) having a bulk material inlet (11) for feeding bulk material into the container and having a bulk material conveyor, the bulk material conveyor being configured to convey the bulk material (20) present in the container (40) in a metered and / or controlled manner at intervals, characterized in that A radar sensor (31) is attached to the upper side of the container and generates a beam cone (33) pointing downwards into the interior of the container in order to determine the fill level (22) of the bulk material (20) present in the container.

2. The metering and / or weighing device according to claim 1, wherein: The radar sensor (31) comprises a radar sensor module (32) having a radio wave transmitter and a radio wave receiver and a converging lens (35), wherein the lens is arranged at a distance from the radar sensor module (32) in order to concentrate the radio radiation emitted by the radio wave transmitter.

3. The metering and / or weighing device according to claim 1 or 2, wherein: The beam cone (33) has an opening angle (φ) between 5° and 15°.

4. A metering and / or weighing device according to any one of the preceding claims, wherein: The bulk material conveyor comprises a control element which comprises a feed roller (41) or an electrically or pneumatically actuatable closing element (63, 73).

5. A metering and / or weighing device according to any one of the preceding claims, wherein: The distance between the radar sensor (31) and the bulk material conveyor is between 0.1 m and 3 m.

6. The metering and / or weighing device according to any one of the preceding claims is a feeder for a roller mill and comprises a feed roller (41), through which a measurable amount of cereal product can be conveyed to a cereal product processing unit of the roller mill arranged downstream.

7. The metering and / or weighing device according to any of the preceding claims, further comprising a weighing unit having a weighing sensor (64) for determining the weight of the bulk material (20) contained in the container (40).

8. The metering and / or weighing device according to claim 7, which is configured to determine the density of the bulk material from the determined filling level and the determined weight.

9. The metering and / or weighing device according to claim 7 or 8, which is a bulk scale or a differential scale for bulk materials.

10. A roller mill comprising: a processing unit having at least one pair of rollers between which the cereal product is reduced in size and / or pressed; and a metering and / or weighing device according to claim 6 for metering the feed of the cereal product to the processing unit.

11. Use of a metering and / or weighing device according to any one of the preceding claims for metering cereal products in a mill.

Images