Metering and / or weighing device for food

Abstract

According to one aspect of the invention, the metering and / or weighing device (1) has a bulk-material container (40), with a bulk-material feed (11) and a bulk-material discharge. The latter is designed to discharge bulk material (20) contained in the bulk-material container (40) at intervals in a metered and / or controlled manner. The metering and / or weighing device is distinguished by a radar sensor (31), which is attached on the upper side of the bulk-material container and produces a beam cone (33) directed downwards into the interior of the container in order to ascertain the level of the bulk material (20) contained in the container.

Description

[0001] DOSING AND / OR WEIGHING DEVICE FOR

[0002] FOOD

[0003] The invention relates to food processing and specifically to the processing of grain products. It particularly relates to a dosing or weighing device for bulk material, such as is used in the mechanical processing of grain products. Such dosing and / or weighing devices occur both as components of machines and as stand-alone devices. Examples of a device as a component of a machine are the feed of a roller mill or a weighing and dosing device in a flour filling plant. Examples of stand-alone machines are bulk scales or loss-in-weight scales. GB 2 119 104 teaches the feeding of, for example, fibrous material, or grain, to a process, with determination of its weight and, in addition, its moisture content and volume.

[0004] Dosing and / or weighing devices each have a bulk material container from which the bulk material is transported in a metered manner, or in which the bulk material is collected and weighed for dosing. In dosing devices without a weighing unit, for example those feeding a roller mill, there is generally a need to monitor the fill level of this bulk material container. For this purpose, it has been proposed to use a weight determined by a force transducer, with the force transducer being arranged in the bulk material container. However, the force acting on a weight transducer is only a limited measure of the fill level, since it depends not only on the fill level but also on other parameters, such as the density of the bulk material and, depending on the arrangement and design, on other properties such as grain size or flow properties.To address this situation, EP3605034 proposes using a capacitive level sensor in addition to the force sensor. The level sensor detects when a certain level is reached in the bulk material container, and this information can be used for calibration. This solution has the disadvantage of being relatively complicated. Elsewhere, capacitive rod sensors are used for level monitoring. These have the advantage of being able to measure the level regardless of density. However, they are susceptible to malfunctions caused by product adhesion. US Pat. No. 5,433,391 shows a roller mill with capacitive level measurement.

[0005] Another common method is level measurement using a number of light barriers arranged at different heights. However, light barriers are also susceptible to malfunctions caused by dust or product buildup.

[0006] In dosing devices with a weighing unit, the weight measurement also provides information about the fill level in the corresponding container. However, the disadvantage of density dependence also exists in these devices, meaning that the level cannot be directly determined from the fill weight. It is an object of the present invention to provide a dosing and / or weighing device that overcomes the disadvantages of the prior art and, in particular, enables a reliable and robust estimation of the fill level while being as simple and cost-effective as possible.

[0007] According to one aspect of the invention, the dosing and / or weighing device comprises a bulk material container with a bulk material inlet and a bulk material discharge. The latter is configured to discharge bulk material present in the bulk material container in a metered and / or controlled manner at intervals. The dosing and / or weighing device is characterized by a radar sensor, which is mounted on the top of the bulk material container and generates a beam cone directed downwards into the container interior to determine the level of the bulk material present in the container.

[0008] The dosing and / or weighing device is designed for dosing and / or weighing food products, particularly grain products. Grain products are defined as grains and products resulting from the comminution of grains, i.e., flour, flour, semolina, grits, etc. The grain size of the bulk material (the average diameter) can be up to a few millimeters, for example, up to 5 mm or up to 3 mm. The finest possible grain size is that of flour, i.e., less than 0.18 mm or less than 0.112 mm. Depending on the type of flour, the average grain size can be approximately 0.07-0.1 mm, or even more or less than these values.

[0009] Radar sensors are well known for their use, among other things, in measuring distances. One measuring principle can be based on frequency modulation, for example, whereby the frequency is continuously changed. The frequency difference between the emitted radar signal and the one reflected by an object is then a measure of the so-called 'time of flight' and thus of the distance between the radar sensor and the object. Radar sensors have already been proposed, for example, for measuring the fill level of tall silos and large bunkers. The 'time of flight' is measured in particular using frequency modulation, whereby the radio signal is transmitted continuously but at a continuously changing frequency. The time of flight is determined by comparing the frequencies of the emitted radio radiation and the received signal.Radar measurements of this type have also been proposed for measuring the fill level of large silos used to store goods in industrial processes, particularly in the chemical industry. CN211033818U and US 2021 / 0140811 provide examples. EP3913335 and DE10 2012 109 101 address metrological aspects of such fill level measurements.

[0010] However, such silos lack a bulk material inlet through which bulk material could be fed during operation. For this reason alone, and due to their dimensions, they would be completely unsuitable for applications in, for example, milling. Furthermore, the measurement principles used assume a defined surface of the bulk material. A prerequisite for such measurements to work is that the radio signal is reflected at a defined location.

[0011] However, this requirement is not met in dosing and / or weighing devices for cereal products, for reasons discussed below.

[0012] The present invention is based on the finding that, despite these circumstances, radar sensors are also suitable for level monitoring of bulk containers in weighing and dosing devices for food products, even though these containers are orders of magnitude smaller and the corresponding devices are much more delicate. Furthermore, the dimensions are relatively small compared to the wavelength of the radio radiation used; the distance between the transmitter and the reflecting surface can be significantly less than 1,000 wavelengths. It is also generally difficult to measure distances in narrow containers with radar sensors, as there can be numerous reflections, e.g., from walls; the background (reflections from the container bottom and nearby devices such as screw conveyors, flaps, etc.) also provides non-negligible signal components.In addition, flour-like products are poor reflectors because radio waves can penetrate relatively deeply, meaning reflections do not only occur on the surface. Rather, the reflection behavior is diffuse. A further characteristic of dosing and / or weighing devices for food products in bulk is the presence of a bulk material inlet and a bulk material outlet, through which bulk material is added or removed during operation. The bulk material feed, in particular, is configured so that bulk material can be and is fed in during operation, during which level measurements are also taken. The feed of the bulk material, for example to the dosing device of a roller mill, can be continuous, i.e. there is a constant product flow into the dosing device, which, among other things, also means that there is often a constant layer of dense dust above the product level.Despite all these points, it is clear that good results can be achieved using existing measurement techniques.

[0013] The dosing and / or weighing device is therefore designed to detect the level even while bulk material is being fed through the bulk material inlet.

[0014] Coherent radar systems have proven particularly advantageous. Coherent radar systems have been found to be particularly well-suited for eliminating interference caused by reflections and background noise. Coherent radar systems are pulse radar systems in which the transmitted pulses are coherent, i.e., have a defined phase relationship. According to the state of the art, coherent radar systems are particularly well-known for detecting moving targets (e.g., aircraft).

[0015] In this context, the dosing and / or weighing device can be configured, in particular, to measure the precise phase position of the pulses in an initial measurement and to subtract this from the measurement signal when determining the level for the purpose of background suppression (or to disregard signal components with this phase position). This makes it possible to utilize an advantage of the coherent radar system when permanently installed (such an advantage is present in a device according to the invention): the reflections can be empirically accounted for using such an initial measurement. This also applies if the reflections are attenuated, for example, due to the filling of the container during level determination, and it also applies without requiring an exact model of the container and its interaction with the radio waves. Due to the coherence of the radar, this can be taken into account in every level measurement following the initial measurement.

[0016] The distance between the radar sensor and the bottom of the volume to be monitored in the container is relatively small in devices of the type according to the invention, for example a maximum of approximately 3 m or even a maximum of 1.5 m. The distance can be measured, for example, between the radar sensor on the one hand and the control element on the other. The control element is the element through which the bulk material is discharged, e.g. the feed roller together with a slide valve in a roller mill feed system or the outlet flap or the outlet slide valve in a bulk material scale or a flow rate 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. The radar sensor can be set up to detect minimum distances of up to 0.2 m or even down to 0.1 m or less.The device may be configured to enter an alarm or safety state when the minimum measurable distance or an adjustable minimum distance (corresponding to a maximum fill level) is exceeded.

[0017] The radar sensor comprises, in particular, a radio wave transmitter (transmitter) and a corresponding receiver. The radio wave transmitter and receiver can, in particular, be part of a radar sensor module and, for example, be present on a common circuit board, for example, even integrated into a common integrated circuit. In addition, such a radar module also comprises evaluation means for performing evaluation steps on the received signal. Thus, as mentioned, the radar sensor module can, in particular, be designed to transmit the radio waves in the form of coherent transmission pulses, with the 'time-off' preferably being determined directly in the radar sensor module, in close proximity to the transmitter and receiver.

[0018] In addition to the radar sensor module, the radar sensor may also include a housing or other support structure, as well as a lens positioned at a distance of, for example, 1-5 cm from the radio wave transmitter, which focuses the emitted radio waves. Such lenses can be made of plastic, for example.

[0019] It has proven particularly advantageous in many applications if the beam cone emitted by the radar sensor – possibly after appropriate focusing – has an aperture angle of between 5° and 15°. In this range, the results of measuring the bulk material level in the container of the type described here are particularly good and reproducible. At larger aperture angles, effects caused, for example, by reflections on the container wall, as well as averaging over an excessively large surface area, can make the result somewhat blurred, while at smaller aperture angles, the radiation intensity may be too high locally.

[0020] A weighing and / or dosing device of the type described here is used in particular for dosing grain products (or possibly other foodstuffs produced in bulk) during mechanical processing and / or packaging. For this purpose, it comprises a control element through which the bulk material is discharged.

[0021] If the device is a feed system for a roller mill, then this control element is formed, for example, by a feed roller, together with a means for metering the feed rate passed on by the feed roller, in particular one that is automatically controllable. Such a means can, for example, include controlling the drive of the feed roller, which can rotate at different speeds. Additionally or alternatively, a feed gap, through which the feed roller conveys the metered material, can have an adjustable dimension.

[0022] If the device is a bulk material scale, e.g., a bulk material scale or a loss-in-weight scale, the control element is an electrically or pneumatically operated discharge flap or an electrically or pneumatically operated discharge gate. The discharge flap or discharge gate can be configured to fully open and fully close at specific intervals and / or to continuously control the flow cross-section, depending on the desired application. If the device is a scale, i.e., a weighing unit with at least one load cell for determining the weight, it can also be configured to determine a value for the density of the bulk material.This is because the level determined allows an estimation of the bulk material volume in the container, using geometric data about the container and / or previously determined calibration data stored in the control system of the device.

[0023] Regardless of the application, the controller that reads the data from the radar sensor - or even the radar sensor itself - can be configured to communicate with a higher-level controller and / or with other devices, e.g. a mill - for example, to control the supply of bulk material through the bulk material inlet.

[0024] Additionally or alternatively, the control of the dosing and / or weighing device (which can also be part of a higher-level control system) can be set up to regulate the bulk material discharge depending on the data from the radar sensor.

[0025] If the dosing and / or weighing device is a feeding device for a roller mill for food processing, the bulk material discharge, as mentioned above, will comprise, for example, a feed roller, which discharges bulk material present in the container ('collection chamber') into another chamber, where it is crushed between (grinding) rollers or - depending on the processing carried out - simply flattened. The container may also contain a conveying means, e.g., a conveying roller, which distributes the bulk material along the axial extent of the feed roller. In embodiments, the control of the dosing and / or weighing device is configured to adjust a rotational speed of the feed roller and / or a width of the feed gap between the feed roller and a baffle and / or, if applicable, a conveying speed of the conveying means depending on the level determined by the radar sensor.

[0026] In addition to the dosing and / or weighing device, a roller mill is also the subject of the present invention. This comprises, in addition to a processing unit with at least one pair of rollers, between which a grain product is crushed and / or pressed, a dosing and / or weighing device of the type described here, which serves as a feeding device for the roller mill. The dosing and / or weighing device can then in particular comprise a feed roller, wherein the quantity of bulk material that can be discharged by the feed roller per unit of time can be adjusted, e.g. by adjusting the rotational speed of the feed roller and / or possibly also another parameter, e.g. the width of the mentioned feed gap. The control of the dosing and / or weighing device - which can be part of the roller mill control system or part of a higher-level control system, e.g.an entire mill plant - will be designed and configured in embodiments to adjust the quantity of bulk material discharged per unit of time depending on the level determined by the radar sensor.

[0027] The invention also relates to the use of a dosing and / or weighing device of the type described in this text for dosing a grain product in a mill. In particular, the level determined by the radar sensor can be used to adjust the amount of bulk material discharged per unit of time.

[0028] In such a use, in particular, the feed through the bulk material inlet will be continuous, and / or the level will be determined continuously. In particular, the use provides for the level to be detected even while bulk material is being fed through the bulk material inlet.

[0029] Additionally or alternatively, the quantity of bulk material introduced through the bulk material inlet per unit of time can also be adjusted, for example by controlling a corresponding control device (e.g. a slide valve) or an upstream machine, e.g. a plansifter.

[0030] Embodiments of the invention are described below with reference to the drawings. In the drawings, like reference numerals designate like or similar elements. The drawings are all schematic. They show partially corresponding elements in different sizes from figure to figure. They show:

[0031] - Fig. 1 is a view of a roller mill;

[0032] - Fig. 2 a cross-section through a feed of a roller mill;

[0033] - Fig. 3 a radar sensor;

[0034] - Fig. 4 a cross-section through a bulk weigher; and

[0035] - Fig. 5 a cross-section through a differential scale.

[0036] Figure 1 shows a roller mill 1 as used in grain mills. The roller mill has at least one housing in which at least one pair, often several pairs, of rollers is / are arranged. The grain product introduced from above is crushed and / or pressed between the rollers of the roller pair. For the purpose of supplying a metered amount of the grain product, the roller mill has a feed 3, which is designed as a device according to the invention.

[0037] The feed system 3, shown schematically in cross-section in Figure 2 (section plane perpendicular to the image plane of Figure 1), comprises a bulk material container 40 with a bulk material inlet 11 and a bulk material discharge. The latter is formed by a feed roller 41 and a feed slide 43 movable relative to the feed roller by means of a suitable mechanism 44. Between the feed slides, a feed gap 42 is formed through which the bulk material 20 is transported further for processing by the at least one pair of rollers. Figure 1 illustrates the possibility of the interior of an upper part of the container 40 being visible from the outside through a viewing window 49.

[0038] The radar sensor 31, a pulsed coherent radar sensor, is mounted on top of the container 40. It generates a beam cone 33 of radio wave radiation directed downwards toward the (free) surface 21 of the bulk material 20 and detects radiation reflected from the surface 21. By measuring the reflected radiation, the time of flight of the radio wave radiation to the surface and back to the sensor can be determined. The time of flight directly yields twice the distance between the radar sensor 31 and the surface 21 and thus the level 22, i.e., the fill level.

[0039] The radio wave radiation used can have a comparatively short wavelength, corresponding to a frequency of, for example, over 50 GHz, for example, approximately 60 GHz. In particular, the radio waves are therefore microwaves, as is characteristic of radar technology. In radar technology, the microwaves used are sometimes also called "radar waves." Within the possible spectrum of radar waves, relatively short-wave radar waves with frequencies above 20 GHz, especially above 50 GHz, and, for example, as mentioned, approximately 60 GHz, are of interest in this context.

[0040] The measured value for the fill level (level 22) determined by the radar sensor 31 is transferred to a control module 45. This control module 45 can form the control of the entire roller mill 1 or be a standalone control module of the feed system 3. In particular, it can communicate directly or indirectly with other units of a system to which the roller mill belongs, for example, to influence the supply of the grain product to the roller mill. The feed slide 43, the feed roller 41, and / or other elements of the feed system not shown in Fig. 2, e.g., a conveyor screw for horizontally distributing the grain product, can also be controlled by the control module 45.

[0041] The radar sensor 31, also shown in Figure 3, has a radar sensor module 32 with one or more integrated circuits, for example, on a circuit board. The radar sensor module includes, possibly integrated, a transmitter and a receiver, as well as evaluation electronics. Furthermore, the radar sensor 31 includes a support structure with a lens holder 34 and a convergent lens 35 for focusing the emitted radio radiation. The lens can be made of a plastic, for example, and can possibly be custom-made using an additive manufacturing process ("3D printing").

[0042] The lens 35 - or more generally a focusing optics of the radar sensor - can in particular be designed such that the opening angle (of the beam cone) is between 5° and 15°, in particular between 6° and 12°, for example approximately 8°. It can be seen that opening angles in this range result in an optimized effect for the applications described in this text. On the one hand, with larger opening angles, the scattering effect of the vessel walls would be significant, and the signal would be averaged over too large an area of ​​the surface 21 and therefore blurred. On the other hand, with smaller opening angles, the radio power would have to be reduced too much in order to avoid locally excessive, potentially harmful radiation power. However, a reduction in the radio power would also have a negative effect on the signal quality.

[0043] Figure 4 shows an example of another dosing and / or weighing device, namely a bulk scale 61 for grain products and other food products present in bulk. The bulk scale also has 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 has at least one load cell 64, which either measures the weight of the entire container 40 including its contents, from which, taking calibration data into account, the weight of the bulk material 20 can be determined, or which can alternatively measure the weight force acting on an element inside the container, for example, on an outlet flap 63.

[0044] As is known for bulk material scales, the bulk material is introduced in portions through the bulk material inlet 11. For this reason, an inlet flap (not shown in Fig. 4) may be present, for example, which can open and close the bulk material inlet controlled by a control module 45. The weight measurement takes place when no bulk material is being added and the outlet flap 63 is closed. Following the measurement, the outlet flap 63 is opened, thus emptying the container, with the bulk material entering an outlet area 65, from which it can continuously flow out.

[0045] Similar to the feed 3 for a roller mill 1 described above, the radar sensor 31 is used to determine the distance to the surface 21 of the bulk material and thus to determine the fill level. The fill level information thus obtained can, firstly, be used generally for process control. For example, it can be used to ensure that the container is never overfilled, which could falsify measurements and possibly clog elements.

[0046] Secondly, it can be provided in particular that the control module 45 causes a measurement to be taken by the radar sensor (even if or only if) when no bulk material is being fed in and the outlet flap 63 is closed. The fill level is then a measure of the volume of the bulk material whose weight is being measured. From this, the density of the bulk material can be approximately determined. Although volume measurement is generally significantly less precise than weight measurement, since the exact shape of the surface 21 is not taken into account and cannot even be determined with a single radar sensor. However, even an approximate determination of the bulk material density is still valuable, as it can be used to control the amount of bulk material fed to the scale. A density value can also represent valuable information for other devices in a system to which the determined value can be made available.Compared to the state of the art, this can eliminate the need for inspection runs and manual adjustments by an operator, for example when switching between different types of processed bulk material (e.g. between grains, flour, semolina, different types of grain, etc.).

[0047] Figure 5 shows another bulk material scale, namely a differential scale 71. In contrast to the bulk material scale 61 in Fig. 4, the bulk material is not discharged intermittently at intervals, but rather through an outlet flap 73 with a controllable throughput. This scale also measures the weight in the container, and also determines the weight flowing out of the container 40 per unit of time, particularly when no bulk material is being added. This can be used to regulate the throughput through the outlet flap 73. The function of the radar sensor 31 is analogous to the bulk material scale 61 shown in Fig. 4.

Claims

PATENT CLAIMS Dosing and / or weighing device (3, 61, 71) for food products in bulk, comprising a container (40), a bulk material inlet (11) for feeding the bulk material into the container, and a bulk material discharge configured to dose and / or control the dispensing of bulk material (20) present in the container (40) at intervals, characterized by a radar sensor (40), which is mounted on the top of the container and generates a downward-directed beam cone (33) into the interior of the container in order to determine a level (22) of the bulk material (20) present in the container. Dosing and / or weighing device according to claim 1, wherein the radar sensor (31) comprises a radar sensor module (32) with a radio wave transmitter and a a radio wave receiver and a convergent lens (35), wherein the lens is arranged at a distance from the radar sensor module (32) in order to focus radio waves emitted by the radio wave transmitter. A metering and / or weighing device according to claim 1 or 2, wherein the opening angle (<|)) of the beam cone (33) is between 5° and 15°. A metering and / or weighing device according to any one of the preceding claims, wherein the bulk material discharge has a control element that includes a feed roller. (41) or has an electrically or pneumatically actuated shut-off device (63, 73). 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 discharge point is between 0.1 m and 3 m. A metering and / or weighing device according to any one of the preceding claims, which is a feeder for a roller mill and comprises a feed roller (41) through which a meterable quantity of a grain product can be discharged to a downstream grain product processing unit of the roller mill. A metering and / or weighing device according to any one of the preceding claims, further comprising a weighing unit with a load cell (64) for determining the weight of the bulk material (20) contained in the container (40). A metering and / or weighing device according to claim 7, which is configured to determine the density of the bulk material from the determined level and the determined weight. Dosing and / or weighing device according to claim 7 or 8, which is a bulk scale or a differential scale for bulk material.Roller mill comprising a processing unit with at least one pair of rollers between which a grain product is crushed and / or pressed, and a metering and / or weighing device according to claim 6 for metering a supply of the grain product to the processing unit.

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

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