Measuring device

Abstract

Measuring device (5) for measuring the moisture content of a material flow, comprising a sensor (6) and a cleaning device (7), characterized in that the cleaning device (7) comprises a movable slide (8) which can be actuated by means of a drive (10) and as a result of its actuation guides a slide lip (9) over the surface of the sensor (6) intended for measurement.

Description

[0001] The invention relates to a measuring device according to the preamble of claim 1 and a screw conveyor unit according to the preamble of claim 7. TECHNICAL BACKGROUND

[0002] When pumping dewatered suspensions or pasty materials, such as sewage sludge, it is often necessary to measure the moisture content remaining in the material stream. Moisture sensors are used for this purpose; these sensors are usually in contact with, or may come into contact with, the material being pumped. The resulting build-up of material on the sensor's surface significantly impairs the measurement accuracy over time. Therefore, to ensure reliable measurement results, the sensors must be cleaned regularly.

[0003] The measuring devices and conveying units known from the prior art are typically designed in such a way that cleaning the sensor is complex and may even require stopping the conveying process. The sensors often have to be cleaned manually. While arrangements are known in which the sensors are shielded to prevent direct contact with the material flow, such arrangements often provide less precise measurement results because the shielding elements generally distort the readings. THE TASK UNDERLYING THE INVENTION

[0004] In view of this, the object of the invention is to enable a precise and reliable measurement of the moisture content of a material stream without having to interrupt the conveying process to clean the moisture meter. INVENTIONAL SOLUTION

[0005] According to the invention, this problem is solved by the features of the main claim relating to the measuring device. Accordingly, the problem is solved by a measuring device for measuring the moisture content of a material flow. The measuring device comprises a sensor and a cleaning device. It is characterized in that the cleaning device includes a slider that is ideally translationally displaceable. The slider can be actuated by means of a drive and, as a result of its actuation, guides a slider lip over the surface of the sensor intended for measurement.

[0006] The sensor measures, preferably continuously, the moisture content of the material flow. Any material that accumulates on the sensor surface and distorts the measurement results is removed by actuating the slider. The slider lip glides across the sensor surface during this process. Regular actuation of the slider, for example every 10 seconds, but ideally at intervals of 2-6 seconds, enables continuous moisture measurement without significant distortion, even with materials that are highly prone to adhesion. Actuation of the slider is automated.

[0007] The sliding lip is preferably a replaceable element that is attached to the slide at the end of the slide furthest from the drive unit by means of a force-fit and / or form-fit connection. The sliding lip is elastic enough that, even when the sliding lip exerts a pressure force on the sensor surface to be cleaned during intended use, the sensor is not damaged when the sliding lip rubs against the sensor.

[0008] The measuring device is designed so that it can be mounted on any conveying system as needed. This is made possible by the measuring device being a pre-assembled module with a bracket that can be attached to the wall of a conveying system, in particular a screw conveyor unit. Attachment can be achieved, for example, via screw, clamp, or flange connections.

[0009] For the purposes of the present application, the term "translatorically displaceable" means a movement of the slide along a substantially straight path, without any significant rotational or pivoting movement of the slide.

[0010] The term "sensor" should not necessarily be understood as referring to a single sensor, but also encompasses a plurality of sensors.

[0011] The term "continuous" should be interpreted to mean that the sensor continuously measures the humidity. Continuous measurement therefore does not simply involve taking individual measurements at regular intervals. However, the term "continuous" does not preclude the possibility that measurements may be interrupted during the period in which the sliding lip is gliding along the sensor surface. ANOTHER PROBLEM UNDERLYING THE INVENTION

[0012] Furthermore, the object of the invention is to enable a device for the continuous conveying of a material flow while simultaneously performing precise and reliable moisture measurement. THE FURTHER INVENTIONAL SOLUTION

[0013] The aforementioned problem is solved by a screw conveyor unit for transporting a material flow. This material flow can, in particular, be dewatered sewage sludge. The screw conveyor unit is characterized by the fact that it includes a measuring device as defined in the invention.

[0014] With this type of screw conveyor unit, the material to be conveyed can be transported continuously. At the same time, its moisture content can be measured precisely and reliably. The conveying process does not need to be interrupted for cleaning the moisture-measuring sensors, nor does the moisture readings become significantly distorted due to persistent sensor contamination. PREFERRED DESIGN OPTIONS

[0015] There are a number of possibilities to design the invention in such a way as to further improve its effectiveness or usability.

[0016] It is therefore particularly advantageous to pause the humidity measurement during sensor cleaning.

[0017] This ensures that the slider lip does not distort the measurement result. The term "pause" can mean both that the measurement process is interrupted and that only the transmission or storage of the measured values ​​is interrupted.

[0018] In another preferred embodiment, the slide of the cleaning device is pneumatically, electrically or hydraulically actuated.

[0019] The pneumatic, electric, or hydraulic actuation of the slide allows the cleaning device to be easily automated and adapted to different operating conditions. This enables reliable cleaning of the sensor surface with minimal maintenance.

[0020] In the case of pneumatic or hydraulic actuation, the slide is coupled to a cylinder-piston system, whereby the slide is either directly part of the piston or connected to it via a piston rod. By applying compressed air or hydraulic fluid to the piston, the slide, along with its lip, is moved along a translational guide track.

[0021] In the case of electric actuation, the slide can be operated via an electric linear drive, for example a spindle drive or a linear motor. Here, too, the movement of the slide lip preferably occurs along a substantially straight path.

[0022] In another preferred embodiment, the sliding lip is made of rubber or plastic.

[0023] By making the sliding lip from an elastic material such as rubber or plastic, the lip can flexibly conform to the sensor surface, thus removing contaminants particularly effectively without damaging the measuring surface. At the same time, this ensures uniform pressure and a long service life for the lip.

[0024] EPDM (ethylene propylene diene monomer rubber) is particularly suitable as a rubber material because it has good resistance to chemical influences while also having sufficient elasticity.

[0025] Due to its high elasticity and high chemical resistance, TPU (thermoplastic polyurethane) is particularly suitable as a plastic material.

[0026] Ideally, the measuring device includes an additional nozzle that allows water or compressed air to be applied to the sensor surface intended for measurement. This additional nozzle enables the sensor surface to be treated with a cleaning fluid both during and after the slider is actuated. This removes even finely adhering particles or residues, resulting in an even more reliable restoration of optimal measuring conditions.

[0027] When using water, the nozzle is preferably activated once the conveying process is complete and no further moisture measurements are being taken. The cleaning nozzle then has the advantage of enabling automated, thorough cleaning of the sensor.

[0028] A compressed air nozzle, on the other hand, is particularly well-suited for use during the conveying process. The term "water" encompasses not only pure water, but also aqueous solutions or mixtures, especially those containing cleaning additives.

[0029] Preferably, the sensor for determining the moisture content of the material flow is based on a capacitive, radar-based, dielectric, ultrasound-based, camera-based or microwave-based measurement technique.

[0030] The moisture content of the material flow can be determined with high accuracy and reproducibility using capacitive, radar-based, dielectric, ultrasound-based, camera-based, or microwave-based measurement techniques. Depending on the measurement principle, non-contact detection is also possible, resulting in less sensor contamination.

[0031] In a further preferred embodiment, the measuring device has a measuring chamber that includes an upper access opening for the material flow to be measured. The measuring chamber is bounded at the bottom by the surface of the sensor intended for measurement.

[0032] When the measuring device is mounted on a conveyor system, the material stream whose moisture content is to be measured flows through the access opening into the measuring chamber. There, the moisture content of the material stream is measured by the moisture sensor.

[0033] Ideally, the measuring chamber is designed so that the material flows not only into the measuring chamber through the access opening but also out of it again. Depending on the design of the measuring device, the slide valve can cause or facilitate the outflow of the material from the measuring chamber. Ideally, the remaining sides of the measuring chamber are formed by the housing or housing components of the measuring device.

[0034] This design ensures that the moisture measurement of the material flow is carried out in an environment where the measurement results are not distorted by a conveying unit, such as a screw conveyor.

[0035] The term "top side" describes the side of the measuring device that points towards the conveying unit when the measuring device is mounted on a conveying unit.

[0036] The term "bottom side" describes the side facing away from the top, where the access opening is located.

[0037] The fact that the measuring space is "limited" on the bottom side by the surface of the sensor intended for measurement does not preclude the possibility that other surfaces of the sensor and / or the housing of the measuring device also limit the measuring space on the bottom side.

[0038] Ideally, the measuring chamber is dimensioned such that the distance between the sensor surface intended for measurement and the access opening of the measuring chamber is at least five centimeters, preferably at least eight, and ideally at least ten centimeters. Preferably, the distance is a maximum of twenty centimeters.

[0039] The aforementioned dimensions of the measuring chamber ensure sufficient clearance between the sensor's surface intended for measurement and the conveying unit of the conveyor system to which the measuring device is mounted. Consequently, the measurement results are not distorted by structural elements or movements of the conveying unit, such as a screw conveyor. At the same time, the measuring chamber is designed to be compact enough that the material within it can exit after measurement without significantly impairing the material flow.

[0040] In another preferred embodiment, the measuring device for measuring the moisture content of the material flow is mounted on the screw conveyor unit in such a way that the sensor protrudes into the material flow.

[0041] This allows the moisture content to be measured directly within the conveyed material stream, and not just at its edges. This enables a particularly precise determination of the maximum moisture content of the material stream. LIST OF FIGURES Fig. Figure 1 schematically shows a preferred embodiment of a screw conveyor unit according to the invention with a measuring device according to the invention. Fig. Figure 2 shows a measuring device according to the invention in longitudinal section. Fig. 3 shows the measuring device Fig. 2 in top view Fig. 4 shows the measuring device Fig. 2 in cross-section Fig. 5 shows the protective plate of the measuring device Fig. 2 in top view Fig. 6 shows the mudguard made of Fig. 5 in the front view Fig. 7 shows the mudguard made of Fig. 5 in longitudinal section Fig. Figure 8 shows the sliding bearing housing of the measuring device. Fig. 2 in top view Fig. 9 shows the plain bearing housing made of Fig. 8 in the front view Fig. Figure 10 shows the plain bearing housing made of Fig. 8 in longitudinal section Fig. 11 shows the mounting plate made of Fig. 2 in top view Fig. 12 shows the mounting plate made of Fig. 11 in longitudinal section Fig. 13 shows the mounting plate made of Fig. 11 in the front view Fig. 14 shows the slider of the measuring device Fig. 2 Fig. Figure 15 shows the first side housing plate of the measuring device. Fig. 2 Fig. Figure 16 shows the second side housing plate made of Fig. 2 Fig. 17 shows the mounting plate of the measuring device Fig. 2 in top view Fig. 18 shows the mounting plate made of Fig. 17 in the front view PREFERRED EXAMPLES

[0042] The functionality of the invention will be demonstrated by way of example: Fig. 1 explained. Fig. Figure 1 schematically shows a screw conveyor unit 1 equipped with a measuring device 5 according to the invention.

[0043] The material to be conveyed, for example in the form of dewatered sewage sludge, is fed into the conveying trough 2 of the screw conveyor unit 1 via the material feed 4. The screw conveyor 3, rotating about its longitudinal axis in the conveying trough 2, transports the material in the conveying trough 2 towards the free end of the screw conveyor unit 1, which is furthest away from the material feed 4.

[0044] The material flow generated in the conveying trough 2 passes through the measuring device 5 mounted on the underside of the conveying trough 2. The sensor 6 of the measuring device 5 measures the moisture content of the flowing material. To prevent the sensor 6 from delivering distorted readings due to the accumulation of material on its surface, the measuring device 5 is equipped with the cleaning device 7.

[0045] The cleaning device 7 comprises a slide 8 driven by a drive unit 10 in the form of a pneumatic cylinder, and a slide lip 9. The slide lip 9 is mounted at the end of the slide 8 facing away from the drive unit 10. During operation, the drive unit 10 moves the slide 8 in a translational motion along the longitudinal axis of the drive unit 10. This control of the slide 8 is automated.

[0046] The movement of the slider 8 causes the slider lip 9, with its edge facing the sensor 6, to scrape along the surface of the sensor 6 facing in the direction of the material flow. This cleans the surface of the sensor 6 of any material adhering to it.

[0047] To ensure that sensor 6 consistently delivers accurate measurements, this cleaning process is repeated at regular intervals. The frequency of the cleaning process can vary depending on the material properties and is performed at shorter or longer intervals as needed. In the case of pasty materials that quickly accumulate over a large area on the surface of sensor 6, it is advisable to repeat the cleaning process every three to five seconds.

[0048] In addition to the cleaning device 7, a cleaning nozzle 11 is provided on the measuring device 5. The cleaning nozzle 11 is mounted on the side of the sensor 6 opposite the slide 8 and projects towards the sensor 6 in such a way that it can supply compressed air to the surface of the sensor 6 facing the material flow. For this purpose, the nozzle is connected to a compressed air source and has one or more outlet openings oriented so that the airflow is parallel or at a shallow angle to the sensor surface. The application of compressed air removes loosely adhering particles, fine dust, or residual moisture from the sensor surface, thereby enhancing the effectiveness of the mechanical cleaning by the slide 8.

[0049] In the Fig. Figure 2-18 shows a further embodiment of a measuring device 5 according to the invention. The measuring device 5 from the Fig. 2-18 is attached to the conveyor trough of a [unclear] by means of the mounting plate 31, using the through holes 32 and a corresponding number of threaded screws. Fig. 2-18, not shown, is mounted. Preferably, a flat gasket or liquid gasket is used to seal the gap between the conveying trough and the mounting plate 31.

[0050] The mass conveyed in the conveying trough falls from above through the access opening 34, via a corresponding opening provided in the conveying trough, into the measuring chamber 33 of the measuring device 5. The measuring chamber 33 of the measuring device 5 is bounded by the protective plate 12, the front housing plate 25, and the mounting plate 20, including the sensor 6 projecting in its recess 22, as well as by the side housing plates 23. The sensor 6 then measures the moisture content of the mass located in the measuring chamber 33. The measuring technology of the sensor 6 is based on a dielectric radar measurement method, in which the moisture content of the material is determined via the transit time of electromagnetic pulses. The sensor 6 continuously measures the moisture content of the material located in the measuring chamber 33 down to a penetration depth of 10 cm.

[0051] In order to convey the mass again from the measuring chamber 33 of the measuring device 5 towards the conveying trough and to clean the surface of the sensor 6 which is intended for moisture measurement and which projects into the recess 22 of the mounting plate 20, the slide 8 is actuated.

[0052] The slide 8 is connected via the thread 19 to a drive (not shown) which moves the slide 8 back and forth along its longitudinal axis.

[0053] When the slider 8, together with the EPDM slider lip 9 attached to its end away from the thread 19, is moved in the direction away from the protective plate 12, the slider lip 9 pushes the mass located in front of it towards the front housing plate 25.

[0054] Since the housing plate 25 forms a slope connecting the mounting plate 20 and the mounting sheet 31, the mass is conveyed by the sliding lip 9 towards the conveying trough. The front housing plate 25 therefore serves as a conveying ramp.

[0055] During the subsequent reverse movement of the slide 8 away from the front housing plate 25, the mass located between the splash guard 12 and the slide lip 9 is also conveyed towards the conveying trough. For this purpose, the splash guard 12 also has a corresponding ramp serving as a conveying ramp.

[0056] Furthermore, as a result of this translational movement, the sliding lip 9 glides along the surface of the sensor 6 intended for measurement. For this purpose, the sensor 6 projects into the recess 22 of the mounting plate 20 to such an extent that the surface of the sensor 6 intended for measurement is at the same height – measured in a direction orthogonal to the longitudinal axis of the slider 8 – as the surface of the mounting plate 20 facing the mounting plate 31. As the sliding lip 9 glides along the sensor 6, the sensor 6 is cleaned.

[0057] To clean the area between the protective plate 12 and the slide lip 9, as well as to additionally clean the sensor 6, the cleaning nozzle 11 is mounted in the measuring device 5 by means of a screw that passes through the through-hole 24 of the side housing plate 23. A medium – optionally compressed air, water, or a cleaning agent – ​​can be introduced via the nozzle 11 to remove adhering residues. The nozzle 11 is oriented such that the medium flowing from it covers both the surface of the sensor 6 intended for measurement and – at least when the slide 8 is in a corresponding axial position – the edge of the slide lip 9 facing away from the sensor 6.

[0058] The slide 9 is supported by a linear sliding bearing 16, which is supported in the sliding bearing housing 17. In the radial direction, the sliding bearing housing 17 is supported by the bearing seat 28 and in the axial direction by the shoulder 26. The sliding bearing housing 17 is, in turn, screwed to the mounting plate 20. For this purpose, the mounting plate 20 has corresponding through holes 21 and the sliding bearing housing 17 has corresponding threaded holes 27.

[0059] The slide 8 protrudes through the through-hole 30 in the protective plate. The protective plate 12, which is also mounted on the mounting plate 20 using the threaded holes 29 and the through-holes 21, protects the sliding bearing housing 17 from coarse dirt. To prevent fine dirt particles from entering the linear sliding bearing 16, a wiper 13 is also provided on the sliding bearing housing 17. A radial shaft seal 15, also mounted in the sliding bearing housing 17, ensures a seal between the drive unit and the measuring area of ​​the measuring device 5.

[0060] The sealing between the housing of the sensor 6 and the mounting plate 20 is achieved via the flat gasket 14. REFERENCE MARK LIST 1 screw conveyor unit 2 Conveyor trough 3 auger 4 Material supply 5 Measuring device 6 Sensor 7 Cleaning device 8 sliders 9 sliding lip 10 Drive unit 11 Cleaning nozzle 12 Mudguard against “coarse soiling” 13 wipers against “fine soiling” 14 Flat gasket 15 Radial shaft seal 16 linear slide bearings 17 plain bearing housings 18 not assigned 19 threads on the slide 20 Mounting plate 21 through holes 22 recess 23 side housing plates 24 Through holes in side housing plate 25 Front housing plate Paragraph 26 for linear plain bearings 27 Threaded hole for fastening the sliding bearing housing 28 bearing seat 29 threaded holes for attaching the mudguard 12 30 through holes 31 Mounting plate for attaching the measuring device to the conveyor trough 32 through holes in the mounting plate 33 Measuring room 34 Access opening

Claims

[1] Measuring device (5) for measuring the moisture content of a material stream, comprising a sensor (6) and a cleaning device (7), characterized by , that the cleaning device (7) comprises a movable slide (8) which can be actuated by means of a drive (10) and as a result of its actuation guides a slide lip (9) over the surface of the sensor (6) intended for measurement. [2] Measuring device (5) according to claim 1, characterized by , that the measuring device is designed such that the moisture measurement is paused during the cleaning of the sensor (6). [3] Measuring device (5) according to at least one of the preceding claims, characterized by , that the slide (8) of the cleaning device (7) is pneumatically, electrically or hydraulically actuated. [4] Measuring device (5) according to at least one of the preceding claims, characterized by , that the sliding lip (9) is made of rubber or plastic. [5] Measuring device (5) according to at least one of the preceding claims, characterized by , that the measuring device (5) includes an additional nozzle (11) by means of which the surface of the sensor (6) intended for measurement can be supplied with water or compressed air. [6] Measuring device (5) according to at least one of the preceding claims, characterized by , that the sensor (6) for determining the moisture content of the material flow is based on a capacitive, radar-based, dielectric, ultrasound-based, camera-based or microwave-based measurement technique. [7] Measuring device (5) according to at least one of the preceding claims, characterized by , that the measuring device (5) has a measuring chamber (33) which includes an upper access opening (34) for the material flow to be measured and which is bounded on the bottom side by the surface of the sensor (6) intended for measurement. [8] Measuring device (5) according to the immediately preceding claim, characterized by , that the measuring chamber (33) is dimensioned such that the distance between the surface of the sensor (6) intended for measurement and the access opening (34) of the measuring chamber (33) is at least five, better at least eight and ideally at least ten centimeters and preferably a maximum of twenty centimeters. [9] Screw conveyor unit (1) for transporting a material flow, in particular in the form of dewatered sewage sludge, characterized by that the screw conveyor unit (1) comprises a measuring device (5) according to one or more of the preceding claims. [10] Screw conveyor unit (1) according to the immediately preceding claim, characterized by , that the measuring device (5) for measuring the moisture content of the material flow is mounted such that the sensor (6) protrudes into the material flow.

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