Measuring device for process measurement technology and method for its operation

Abstract

The invention discloses a measuring device in process measurement technology for determining one or more physical and / or chemical process variables, comprising a sensor element for measuring the process variable and a cleaning device for cleaning deposits and deposits on an end face of the sensor element, wherein the cleaning device has a plurality of rotatable cleaning arms which are arranged to be rotatable and pivotable about a common axis of rotation; The invention further discloses a method for operating such a device.

Description

The present invention relates to a measuring device of process measurement technology according to the preamble of claim 1 and to a method for operating the same.Sensors, e.g. optical sensors, contaminate the process. Even when measured in liquids using other sensors, formation of algae or else formation of air bubbles, for example in the case of ultrasonic sensors, can occur, for example. There are cleaning options in which the cleaning is carried out by one cleaning element each, such as brushes or wipers. Both cleaning elements wear out and must be replaced at regular intervals. The replacement is time-consuming and thereby interrupts the measurement.Typical examples of such single-armed wiper or brush systems are described in DE 10 2011 078 617 A1, DE 10 2021 133 192 A1, EP 1 816 462 A1 and EP 1 488 211 A2.The single-armed systems are thus established. However, they have high maintenance intervals during bristle or lip replacement. Moreover, there are only systems with wiper lips or bristle on the market as a matter of choice.The problem here is that these systems are usually in permanent contact with the surface to be cleaned. If solid particles come between the wiper and the sensor surface, this can scratch the sensor surface, since the solids are held in a clamping manner. Furthermore, wiper blades can be successively permanently deformed plastically by the contact pressure without the possibility of a return deformation and have to be replaced more frequently.The present invention therefore starts from the aforementioned prior art with the object of reducing the aforementioned disadvantages of the prior art.The present invention achieves this object by providing a measuring device having the features of claim 1 and by a method having the features of claim 13.A measuring device of process measurement technology for determining one or more physical and / or chemical process variables comprises a sensor element for measuring the process variable and a cleaning device for cleaning deposits and deposits on an end face of the sensor element.According to the invention, the cleaning device has a plurality of, but at least two or more, rotatable cleaning arms which are arranged rotatably pivotable about a common axis of rotation.The use of a plurality of cleaning arms enables the maintenance intervals to be extended and is advantageous above all in the case of sensors which are difficult to access. A combination of different cleaning methods can be made possible. The fitting with calibration standard / reference for optical sensors for an arm is conceivable. The mode of operation of the optical sensor can thereby be checked. In addition, the degree of contamination can also be detected indirectly as a result.The present invention achieves extended maintenance intervals, improved cleaning capabilities, and additional calibration capabilities. The maintenance intervals when using two cleaning arms are thereby advantageously even surprisingly more than twice as long as in the case of single-arm cleaning devices.Advantageous embodiments of the invention are the subject matter of the dependent claims.It is advantageous if at least one or all of the cleaning arms are designed as wipers, preferably each comprising an elastomer lip and / or TPE lip as a cleaning element. In this variant, one cleaning arm is in contact with the cleaning surface, while a second cleaning arm can be cleaned or rinsed. Alternatively, the cleaning arm can be erected again due to restoring forces, whereby the elasticity of the cleaning element is regenerated to a degree.It is advantageous if at least one or all of the cleaning arms is or are designed as a brush arm, preferably comprising in each case a bristle track as a cleaning element. Bristles also deform elastically. However, permanent deformations also occur in part during permanent contact. The use of a plurality of cleaning arms counteracts this.It is also possible for at least one or all of the cleaning arms to be designed as a scraper arm, preferably comprising in each case a scraper strip as a cleaning element.The cleaning arms of the cleaning device preferably have different cleaning elements, preferably selected from a group of scraper bar, brush arms and / or wipers. Thus, a first cleaning arm can have a brush arm and a second cleaning arm can have a wiper. It is also possible for both cleaning arms to have brush arms, but with different bristles, e.g. bristle length or bristle thickness. The same applies to wipers, scrapers and / or other cleaning elements.The cleaning device can be arranged interchangeably on the sensor element.The measuring device can advantageously and particularly preferably have a peripheral attachment module for attachment to the sensor element, wherein the cleaning device is formed as a partial component of this attachment module. Thus, the entire cleaning device is arranged on the sensor element in an exchangeable manner, for example for the purpose of exchanging the cleaning arms or the entire cleaning device.Furthermore, the geometry of the wiper and / or of the peripheral attachment module can advantageously be designed such that the cleaning arms move or are movable from a rest position into a cleaning position during at least partially or fully rotational movement in the course of a revolution, wherein in the cleaning position the lower edge of the wiper blade is flush with the upper edge of the end face, by contact of the wiper blade with the end face, clean the latter, and return to the rest position.It is advantageous if the cleaning device has an electric motor and / or pneumatic drive.Advantageously, each of the cleaning arms can extend parallel to the end face, wherein the distance of several or all of the cleaning arms from the end face is of different sizes. As a result, individual cleaning arms can take over a pre-cleaning of large adhesions at a lower contact pressure, while other cleaning arms remove a more strongly adhering biofilm at a higher contact pressure.The cleaning arms can advantageously be arranged on a rotatably mounted drive shaft in a rotationally fixed manner and wherein the drive shaft extends along the axis of rotation. This allows a good adjustment of the contact pressure to be achieved by axial displacement of the drive shaft. Moreover, the mechanical construction is simple and the exchangeability of the shaft in the event of a defect is comparatively simple.Furthermore, the drive shaft can advantageously be arranged to be linearly movable along the axis of rotation or the drive shaft can be configured telescopically for setting a contact pressure of the cleaning element on the end face.It is furthermore advantageous if the end face has a measurement window, along which measurement signals are emitted and / or received in a medium, and wherein the cleaning arms are arranged in such a way that each of the cleaning arms can be guided over the measurement window by rotation. The term rotation in the sense of the present invention also encompasses a partial rotation in the form of a pivoting movement. The partial rotation can preferably take place at a particularly preferred angle of 20-60°.The cleaning elements can be arranged interchangeably on a support arm of the cleaning arm. In particular, the cleaning elements can be plugged onto the support arm.In a particularly preferred embodiment variant, the support arm can preferably have a guide means, particularly preferably a guide groove or a guide strip for engagement with a complementary guide means of the cleaning element.Preferably, a first of the cleaning arms can abut the end face, while a second of the cleaning arms is not in contact with the end face.This can then be cleaned or it can be erected, whereby in particular elastic cleaning elements regenerate their restoring forces.The measuring device can furthermore comprise a protective cavity, e.g. for mechanically protecting the cleaning arm, wherein the second of the cleaning arms is arranged in the protective cavity.Furthermore, the invention relates to a method for operating a measuring device according to the invention, wherein the cleaning device can be operated in a maintenance interval and in a cleaning interval, wherein a cleaning arm can be moved in the maintenance interval from a position outside the end face into a position in contact with the end face, and wherein the cleaning arm is moved in partial rotation in the cleaning interval in opposite directions above the end face.During the maintenance interval, the cleaning arm can be actively cleaned or simply re-right in a rest position, in order to counteract permanent plastic deformations.The cleaning device can furthermore advantageously guide the first cleaning arm and subsequently the second cleaning arm over the end face during operation, preferably in a continuous rotational movement.On the basis of at least one of the cleaning arms of the cleaning device and / or an additional cleaning element of the attachment module, calibration and / or function testing of the cleaning device and / or of the sensor can take place within the scope of the method according to the invention.Alternatively, a solid-state calibration standard can also check the functionality of a sensor, in particular for the case of an optical sensor. For this purpose, this is inserted into the optical path in order to thus monitor / check the measurement performance and thus also the cleaning performance. A drop in the measurement performance can indicate that a replacement of the cleaning elements is necessary.The subject matter of the invention is explained in more detail below on the basis of an exemplary embodiment and with the aid of the appended figures. The following are shown: FIG. 1 shows a schematic structure of an interface of a measuring device according to the invention; and FIGS. 2 a- 2 c show schematic views of further variants of cleaning device of a measuring device.FIG. 1 shows a measuring device 10 with a sensor element 1, which is preferably sealed liquid-tight. The sensor element 1 has an end face 2 which contacts the measuring medium at the end.The outer housing 3 of the sensor element 1 can be manufactured from stainless steel, for example. Depending on the application, embodiments made of rigid plastic, in particular of PVC, POM or PPS GF 40, are conceivable. The sensor element is preferably designed for permanent retention in liquids, in particular in wastewater, or gases, at least in a terminal partial region which also comprises the end face.The outer housing typically has the shape of a right circular cylinder. The end face 2 is positioned orthogonally to the sensor body longitudinal axis LA. Other embodiments are conceivable, however: It should also be mentioned that the end face 2 can be arranged at an angle not equal to 90° with respect to the sensor body longitudinal axis LA. The end face 2 additionally has a measurement window 11 for transmitting and / or receiving measurement signals. The material of the measurement window can differ from the material of the outer housing 3 and can be a transparent material, for example.In the embodiment in FIG. 1, the measuring device 10 is designed for determining an optical process variable. This can be used, for example, for determining the turbidity, the sludge level or the solids content. Here, impurities may accumulate along the medium-contacting end face 2. For cleaning the end face 2, the measuring device 10 has a cleaning device 4.The cleaning device 4 comprises a drive, not shown, as well as a drive shaft 5 rotatably mounted about a rotation axis R. The longitudinal course of the output shaft 5 extends along the rotation axis R. The drive shaft 5 lies in a rotationally fixed bearing tube 13.In FIG. 1, two cleaning arms 6, 7 extend radially away from the axis of rotation R. Each of the cleaning arms 6, 7 has at least one support arm 8 and at least one cleaning element 9 each, which extends in its longitudinal extension preferably parallel to the support arm 8.The cleaning element 9 is preferably arranged on the support arm 8 in an exchangeable manner. The cleaning element 9 can only be plugged on, for example via a piping which is inserted in a corresponding groove of the support arm 8. Alternatively, a dovetail groove connection can also be provided between support arm 8 and cleaning element. Other plug connections are also conceivable. In the plug connection, a form fit preferably takes place between the support arm 8 and the cleaning element 9 parallel to the axis of rotation R.As can be seen in FIG. 1, a first of the cleaning arms 6 bears on the end face, while the second of the cleaning arms 7 projects in the radial direction with respect to the sensor element 1. As a result, the cleaning arm 7 can be damaged by the medium pressure, entrained solids such as stones or the like or other effects. For mechanical protection, the measuring device 10 has a protective pocket 14, which is fixed to the bearing tube 13 and which defines a protective cavity 15. The protective bag 14 may be made of a metal sheet. The protective pocket can also be formed as a lattice cage or the like. The second cleaning arm 7 is arranged within the protective pocket 14. Despite mechanical protection, the cleaning arm 7 can be flushed with the measurement medium and thus the cleaning element 9 can be cleaned.The cleaning element 9 can preferably be a lip, e.g. a rubber lip, a brush and / or a scraper.It is possible to achieve a cleaning optimisation by means of different cleaning elements.The distance of the cleaning elements 9 from the end face can likewise be different and / or adjustable. As a result, the end face can be cleaned with different contact pressures. For this purpose, the drive shaft can be moved on the axis of rotation and fixed at different positions on this axis of rotation R. Alternatively or additionally, the drive shaft 5 can be designed as a telescopic shaft or the cleaning arms 6 and 7 can be arranged at fixed but mutually different distances from the end face 2.The cleaning device 4 can preferably be driven by electric motor and / or pneumatically. One or more fixing elements can be provided between the cleaning device 4 and the sensor element 1, which fixing elements are particularly preferably designed for the detachable fixing of the two parts of the measuring device.In principle, however, the cleaning device 4 can also be used for cleaning the end face of a sensor body of a measuring device 10 for non-optical process variables.In summary, FIG. 1 shows a multi-wiper unit having a plurality of wiper arms. Also conceivable are 2, 3, 4,... uniformly arranged arms 6, 7, 16, 17 per unit, as shown in FIGS. 2a-c. Each arm can be equipped as desired, for example a mixture of bristles, lips, scrapers or else just one variant, but a plurality thereof.The cleaning can always be carried out with wiper arm 1 for the first maintenance interval and then with wiper arm 2, until the service life is reached here as well.The advantage is a time to change, which is prolonged 2... x times, compared to the known one-arm solution. When using different cleaning attachments, cleaning processes matched to the process are possible, e.g. scrapers, bristle, wiper lip, at individual frequencies, preferably one after the other. Either a back and forth wiping at a wiper arm position is possible or else travel in a circle with all wiper arms.It is also conceivable to attach a solid-state calibration standard for optical sensors to an arm in order to check and / or calibrate the functioning of the sensor and to monitor the cleaning result.List of reference characters1 Sensor element 2 End face 3 Outer housing 4 Cleaning device 5 Drive shaft 6 Cleaning arm 7 Cleaning arm 8 Support arm 9 Cleaning element 10 Measuring device 11 Measuring window 13 Bearing tube 14 Protective pocket 15 Protective cavity 16 Cleaning arm 17 Cleaning arm R Axis of rotationReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2011 078 617 A1

[0003] DE 10 2021 133 192 A1

[0003] EP 1 816 462 A1

[0003] EP 1 488 211 A2

[0003]

Claims

Measuring device of process measurement technology for determining one or more physical and / or chemical process variables, comprising a sensor element for measuring the process variable and a cleaning device for cleaning deposits and deposits on an end face of the sensor element, characterized in that the cleaning device has a plurality of rotatable cleaning arms which are arranged rotatably pivotable about a common axis of rotation.Measuring device according to claim 1, characterised in that at least one or all of the cleaning arms is or are designed as wipers, preferably each comprising an elastomer lip and / or TPE lip as a cleaning element, and / or that at least one or all of the cleaning arms is or are designed as a brush arm, preferably each comprising a bristle track as a cleaning element, and / or that at least one or all of the cleaning arms is or are designed as a scraper arm, preferably each comprising a scraper strip as a cleaning element.Measuring device according to claim 1 or 2, characterised in that at least one of the cleaning arms has a solid state calibration standard for calibrating and / or checking the cleaning device and / or the sensor element.Measuring device according to one of the preceding claims, characterized in that the measuring device has a peripheral attachment module (7) for attachment to the sensor element, wherein the cleaning device (3) is formed as a part component of this attachment module (7).Measuring device according to one of the preceding claims, characterized in that the geometries of the wiper (3) and / or of the peripheral attachment module (7) are designed such that, in the case of at least partially or fully rotational movement, the cleaning arms (3) move from a rest position into a cleaning position in the course of a revolution, wherein, in the cleaning position, the lower edge of the wiper blade (4) is flush with the upper edge of the end face of the sensor element, by contact of the wiper blade (4) the end face cleanes the latter, and returns to the rest position.Measuring device according to one of the preceding claims, characterized in that the cleaning device has different cleaning elements on the cleaning arms.Measuring device according to one of the preceding claims, characterized in that each of the cleaning arms extends parallel to the end face, wherein the distance of the cleaning arms from the end face is of different sizes.Measuring device according to one of the preceding claims, characterized in that the cleaning arms are arranged on a rotatably mounted drive shaft in a rotationally fixed manner, and wherein the drive shaft extends along the axis of rotation, the drive shaft is arranged particularly preferably linearly movable along the axis of rotation, or in that the drive shaft is particularly preferably configured telescopically, for setting a contact pressure of the cleaning element on the end face.Measuring device according to one of the preceding claims, characterized in that the cleaning elements are arranged interchangeably on a support arm of the cleaning arm, wherein the cleaning element is particularly preferably plugged onto the support arm.Measuring device according to claim 9, characterised in that the support arm preferably has a guide means, particularly preferably a guide groove or a guide strip for engagement with a complementary guide means of the cleaning element.Measuring device according to one of the preceding claims, characterized in that a first of the cleaning arms abuts the end face, while a second of the cleaning arms is not in contact with the end face.Measuring device according to one of the preceding claims, characterized in that the measuring device has a protective cavity, wherein the second of the cleaning arms is arranged in the protective cavity.Method for operating a measuring device according to one of the preceding claims, characterized in that the cleaning device can be operated in a maintenance interval and in a cleaning interval, wherein a cleaning arm can be moved in the maintenance interval from a position outside the end face into a position in contact with the end face, and wherein the cleaning arm is moved in partial rotation in the cleaning interval in opposite directions above the end face.Method according to claim 13, characterised in that during operation, preferably in a continuous rotational movement, the cleaning device initially guides the first cleaning arm and subsequently the second cleaning arm over the end face.Method according to claim 13 or 14, characterised in that on the basis of at least one of the cleaning arms of the cleaning device and / or an additional cleaning element of the attachment module is effected for calibrating and / or functionally checking the cleaning device and / or the sensor.

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