Cleaning unit for contact cleaning of an observation window of an optical sensor

Abstract

The invention relates to a cleaning unit (1) for contact cleaning of an observation window of an optical sensor, comprising: - a support (10) extending along a first axis (X), - a contact unit (20) which is attached to the carrier (10), wherein the contact unit (20) has a wear layer (21) with a wear material and a signal layer (22) with a signal material, wherein the wear layer (21) covers the signal core (22) and is suitable for coming into contact with an observation window (36) of an optical sensor (30), the signal material differs from the wear material, at least in its optical properties.

Description

[0001] The invention relates to a cleaning unit for contact cleaning of an observation window of an optical sensor, a sensor system and a method for checking the condition of a cleaning unit.

[0002] In analytical measurement technology, particularly in water management, environmental analysis, industrial applications such as food technology, biotechnology, and pharmaceuticals, as well as for a wide variety of laboratory applications, measured variables such as pH, conductivity, or the concentration of analytes, such as ions or dissolved gases in a gaseous or liquid medium, are of great importance. These measured variables can be recorded and / or monitored using electrochemical sensors, such as optical, potentiometric, amperometric, voltammetric, or coulometric sensors, or even conductivity sensors.

[0003] Some optical sensors are used in process environments that are prone to deposits on the housing or the observation window of the optical sensor. To ensure maximum measurement accuracy even over extended periods of use of the optical sensor, the observation window must be cleaned regularly. A windshield wiper is usually used for cleaning. However, due to the friction of the windshield wiper on the observation window, the windshield wiper wears out over time. If wear is too great, this in turn affects the cleaning ability of the windshield wiper. The windshield wiper should therefore be replaced when it is worn. However, the wear rate of the windshield wiper depends on the measuring medium, which means it is not possible to predict exactly when the windshield wiper should be replaced.Premature replacement obviously results in unnecessary work, increases operating costs and worsens the sensor's environmental footprint.

[0004] It is therefore an object of the invention to provide a cleaning unit which enables a simple determination of the state of wear of the cleaning unit during the ongoing process.

[0005] This object is achieved according to the invention by a cleaning unit for contact cleaning of an observation window of an optical sensor, according to claim 1.

[0006] The cleaning unit according to the invention comprises: - a support extending along a first axis, - a contact unit attached to the carrier, wherein the contact unit has a wear layer with a wear material and a signal layer with a signal material, wherein the wear layer covers the signal core and is suitable for coming into contact with an observation window of an optical sensor, wherein the signal material differs from the wear material at least in its optical properties.

[0007] The cleaning unit according to the invention makes it possible to reliably determine the wear level of the cleaning unit during operation. This allows for maximum utilization of the cleaning unit's service life. This leads to a minimization of maintenance effort, process downtime, and material costs.

[0008] According to one embodiment of the invention, the signal material has a different color than the wear material.

[0009] According to a further embodiment of the invention, the signal material comprises a luminescent material.

[0010] According to one embodiment of the invention, the wear material comprises an elastomer.

[0011] According to one embodiment of the invention, the wear layer has a contact surface which is suitable for coming into contact with an observation window, wherein the signal layer has a signal surface which extends parallel to the contact surface.

[0012] According to one embodiment of the invention, the contact unit extends along the first axis and has a fastening section and a cleaning section, wherein the contact unit is attached to the carrier by means of the attachment section and the cleaning section faces away from the attachment section, wherein the cleaning section tapers along a second axis which is arranged transversely to the first axis.

[0013] The above object is also achieved by a sensor system according to claim 7.

[0014] The sensor system according to the invention comprises - a cleaning unit according to the invention, - an optical sensor with a housing, a light source, a detector, a motor and a control unit, wherein at least the light source and the detector are arranged in the housing, and the control unit is connected to the motor, the detector and the light source, wherein the housing has an opening with an observation window, wherein the light source is adapted to emit an emission light through the observation window from the housing, and the detector is adapted to detect a detection light incident through the observation window into the housing, wherein the motor is mechanically connected to the cleaning unit and is suitable for moving the cleaning unit in contact with the housing between a rest position and a cleaning position over the observation window, wherein the control unit is adapted to evaluate the detection light in order to determine whether the signal layer is visible.

[0015] According to one embodiment of the invention, the signal material is suitable for emitting a luminescent light and the light source is suitable for emitting an emission light which is suitable for stimulating the signal material to emit the luminescent light and the detector is suitable for detecting the luminescent light.

[0016] According to one embodiment of the invention, the light source is suitable for emitting UV light.

[0017] The above object is also achieved by a method for checking the condition of a cleaning unit according to claim 10.

[0018] The method according to the invention comprises: - Providing a sensor system according to the invention, - Moving the cleaning unit into the rest position or the cleaning position so that the light source is suitable for emitting an emission light to the contact unit and the detector is suitable for detecting a detection light and / or a signal light, - Emitting an emission light by the light source, - Detecting a detection light by the detector, - Evaluation of the detection light by the control unit. Output of an indication of a change of the cleaning unit, depending on the evaluation of the detection light.

[0019] According to one embodiment of the invention, the emission light is a UV light.

[0020] The invention is explained in more detail with reference to the following description of the figures. They show: - Fig. 1: a schematic representation of a sensor system according to the invention, - Fig. 2: another view of the Fig. 1 shown sensor system, - Fig. 3: an alternative embodiment of a cleaning unit, - Fig. 4: another alternative embodiment of a cleaning unit.

[0021] Fig. 1 shows a sensor system 100 with a cleaning unit 1 and an optical sensor 30.

[0022] The cleaning unit 1 comprises a carrier 10 and a contact unit 20.

[0023] The support 10 extends along a first axis X. For example, the support 10 is made of metal or plastic. The support 10 is, for example, a retaining bracket.

[0024] The contact unit 20 is attached to the carrier 10. The contact unit 20 has a wear layer 21 made of a wear material and a signal layer 22 made of a signal material. The wear layer 21 covers the signal core 22 and is designed to come into contact with an observation window 36 of the optical sensor 30. The signal material differs from the wear material at least in its optical properties.

[0025] The wear layer 21 has a contact surface 23 which is suitable for at least partially contacting an observation window 36. The signal core 22 has a signal surface 24 which preferably extends parallel to the contact surface 23.

[0026] The contact unit 20 extends along the first axis X and has a fastening section 25 and a cleaning section 26. The contact unit 20 is fastened to the carrier 10 by the fastening section 25, and the cleaning section 26 faces away from the fastening section 25. The cleaning section 26 preferably tapers along a second axis Z, which is arranged transversely to the first axis X. The contact unit 20 preferably has a triangular cross-section relative to the first axis X (see Fig. 1). According to the Fig. 3 and Fig. In the alternative embodiments illustrated in Figure 4, the contact unit 20 has a trapezoidal cross-section relative to the first axis X. Of course, it is also possible to choose other shapes for the contact unit 20.

[0027] Fig. 3 shows a first variant in which the signal layer 22 has a signal surface 24 which is parallel to all contact surfaces 23 of the wear layer 21. Fig. Figure 4, however, shows an alternative variant in which the signal layer 22 is arranged only in the cleaning section 26 of the contact unit 20. This alternative variant has the advantage that little signal material is required.

[0028] The wear material preferably comprises an elastomer, for example a rubber.

[0029] According to a first embodiment, the signal material has a different color than the wear material. The signal material is, for example, white, and the wear material is, for example, black. For example, the colors used are complementary colors to maximize contrast between the colors and thus reliably detect an emerging wear layer.

[0030] According to a second embodiment, the signal material comprises a luminescent material. According to this embodiment, the signal material is suitable for emitting luminescent light. The luminescent light is preferably fluorescent light.

[0031] The optical sensor 30 comprises a housing 31, a light source 32, a detector 33, a motor 34 and a control unit 35 (see Fig. 1).

[0032] The light source 32 and the detector 33 are arranged at least in the housing 31. The Fig. The embodiment illustrated in Figure 1 also shows the motor 34 and the control unit 35 arranged within the housing 31. Of course, alternative arrangements for the motor 34 and the control unit 35, for example, outside the housing 31, are also possible. The control unit 35 is connected to the motor 34, the detector 33, and the light source 32. The light source 32 is, for example, capable of emitting UV light or light of a predetermined wavelength. For example, the light is capable of stimulating a luminophore arranged in the wear layer.

[0033] The housing 31 has an opening with the observation window 36. The observation window 36 is made, for example, of glass or another material transparent to radiation emitted by the light source 32.

[0034] The light source 32 is suitable for emitting an emission light EL through the observation window 36 from the housing 31. For this purpose, the light source 32 is aligned such that the emission light EL strikes the contact unit 20 when the cleaning unit 1 is in a cleaning position CP (see Fig. 2). According to a Fig. In the embodiment shown in Figure 2, the light source 32 is aligned such that the emission light EL also hits the contact unit 20 when the cleaning unit 1 is in a rest position RP.

[0035] The detector 33 is suitable for detecting a detection light DL incident on the housing 31 through the observation window 36. The detection light DL is, for example, a light reflected by the contact unit 20 or a luminescent light emitted by the signal layer 22. The detector 33 is preferably suitable for detecting a detection light DL with a light spectrum in the range of 200 to 800 nm. The detector 33 is, for example, a photodiode, which is preferably optimized for a single wavelength, and / or a spectrometer suitable for recording a broadband spectrum.

[0036] If the detector 33 is a photodiode, the photodiode is not necessarily sensitive to luminescence. Rather, the photodiode is suitable for evaluating a shift in a reference light signal, which is detectable by a change in color and / or brightness when viewed through the wiper's detector 33. For this purpose, the wiper is positioned at a predetermined position on the window so that the photodiode detects the wiper's presence.

[0037] If the detector 33 is a spectrometer, it can detect and evaluate color and / or brightness changes as well as luminescence signals. This detection is characterized, for example, by the detection of signal peaks in the spectrum of the luminescence signals outside the expected spectrum, in which signals from the process are located. These luminescence signals have a higher wavelength range than the excitation wavelength. The luminescence signals are preferably phosphorescence signals.

[0038] The motor 34 is mechanically connected to the cleaning unit 1 and is suitable for moving the cleaning unit 1 in contact with the housing 31 between the rest position RP and the cleaning position CP via the observation window 36 (see Fig. 2). This makes it possible to clean the observation window 36 from deposits from the process medium, or to prevent deposits from forming. The motor 34 is directly or indirectly connected to the cleaning unit 1 by a force-locking connection. In the case of a direct force-lock connection, the cleaning unit 1 sits, for example, on the armature of the motor 34. In the case of an indirect force-lock connection, a gear is interposed between the motor 34 and the cleaning unit 1. Fig. In Figure 1, the frictional connection between motor 34 and cleaning unit 1 is only schematically represented by a line connection. The two horizontal arrows symbolize the movement of cleaning unit 1 possible due to the frictional connection. If cleaning unit 1 is a wiper, for example, the wiper is moved in a circular motion across observation window 36.

[0039] The control unit 35 is designed to evaluate the detection light DL to determine whether the signal layer 22 is visible. The evaluation for detecting existing wear will be discussed in detail later.

[0040] The following describes a procedure for checking the condition of cleaning unit 1.

[0041] First, the sensor system 100 described above is provided. This means that the sensor system 100 is functional and exposed to a process medium.

[0042] Then, the cleaning unit 1 is moved into the rest position RP, so that the light source 32 is suitable for emitting an emission light EL to the contact unit 20 and the detector 33 is suitable for detecting the detection light DL (see Fig. 2, radiation paths shown in dotted lines).

[0043] In an alternative embodiment of the method, the cleaning unit 1 is moved into the cleaning position CP, preferably into the center of the observation window 36, so that the contact unit 20 is arranged directly in front of or directly between the light source 32 and the detector 33 (see Fig. 2, radiation paths shown in dashed lines). This embodiment has the advantage that very little possible radiation from the process is detectable by the detector 33, since the cleaning unit 1 obscures a large part of the observation window 36. This simplifies the evaluation of the detected signals.

[0044] Then, an emission light EL is emitted by the light source 32. The emission light EL is, for example, UV light. In an alternative embodiment, the emission light EL is light of a predetermined wavelength suitable for stimulating the luminescent material of the signal layer 22.

[0045] Subsequently, a detection light DL is detected by the detector 33. The detection light DL comprises a luminescent light if the signal layer 22 comprises a luminescent material and the wear layer 21 is worn, so that the signal layer 22 is exposed and the luminescent material was stimulated by the emission light EL. If the signal layer 22 does not comprise a luminescent material, but, for example, only differs in color from the wear layer 21, the color, intensity, and / or spectrum of the detection light DL is recorded by the detector 33.

[0046] Next, the detection light DL is evaluated by the control unit 35. During the evaluation, a reference signal recorded during a process measurement is used, for example. During a process measurement, the contact unit 20 is in the rest position RP. The reference signal is, for example, an average of the light intensities determined over a predetermined period of time. If the detector 33 is suitable for recording a light spectrum, the reference signal represents, for example, an average light spectrum. During the evaluation, the control unit 35 preferably compares a currently measured measurement signal, which is generated by the detector 33 based on the received detection light DL, with the stored reference signal. The measurement signal therefore represents the detection light DL. For the sake of simplicity, these terms are used synonymously below.If the detection light DL deviates from the reference signal by more than a predetermined tolerance, wear of the wear layer 21 is assumed. The control unit 35 then issues a warning message. Such a comparison with the reference signal is particularly advantageous when the signal material of the signal layer 22 has a different color, particularly white, than the wear layer 21. Due to the white color of the signal layer 22, significantly more of the emission light EL is reflected to the detector 33 when the wear layer 21 wears.

[0047] An alternative variant of the evaluation by the control unit 35 is carried out, for example, by moving the cleaning unit 1 into its cleaning position CP, i.e., directly above the observation window 36, preferably into the center of the observation window 36. Subsequently, the contact unit 20 is irradiated by the emission light EL of the light source 32. Next, the detection light DL is received by the detector 33 and compared with a reference signal as described above. The reference signal is recorded by the user, for example, after the installation of the cleaning unit 1. At the time of installation of the cleaning unit 1, it can be assumed that the contact unit 20 shows no wear.

[0048] If the detector 33 is suitable for recording a light spectrum, in addition to or alternatively to the above-described variants of evaluating the detection light DL by the control unit 35, the spectrum of the detection light DL is evaluated using the control unit 35. In particular, if the contact unit 20 has a signal core 22 comprising a luminescent material, a signal deflection becomes visible by evaluating the detection light DL in the range of the wavelength of the luminescent light when wear of the wear layer 21 is present. During the step of evaluating the detection light DL, it is thus immediately apparent whether the signal core 22 has already appeared. A comparison with a reference measurement is not absolutely necessary here, but can be performed optionally to ensure that potential interference radiation from the environment does not lead to incorrect detection of wear.

[0049] Subsequently, an indication for replacing the cleaning unit 1 is output if the control unit 35 has evaluated a detection light DL from the signal core 22. In other words, an indication for replacing the cleaning unit 1 is output if it has either been determined that the emission light EL was reflected by the signal layer 22, for example, because the signal layer 22 has a different color than the wear layer 21, or because the luminescent material of the signal layer 22 has emitted luminescent light that was detected by the detector 33. List of reference symbols 1 cleaning unit 10 carriers 20 contact unit 21 Wear layer 22 Signal core 23 Contact surface 24 Signal surface 25 fastening section 26 Cleaning section 30 optical sensor 31 housings 32 light source 33 Detector 34 Engine 35 Control unit 36 observation windows EL emission light DL detection light X first axis Z second axis

Claims

[1] Cleaning unit (1) for contact cleaning an observation window of an optical sensor, comprising: - a support (10) extending along a first axis (X), - a contact unit (20) which is attached to the carrier (10), wherein the contact unit (20) has a wear layer (21) with a wear material and a signal layer (22) with a signal material, wherein the wear layer (21) covers the signal core (22) and is suitable for coming into contact with an observation window (36) of an optical sensor (30), The signal material differs from the wear material at least in its optical properties. [2] Cleaning unit (1) according to claim 1, wherein the signal material has a different color from the wear material. [3] Cleaning unit (1) according to claim 1 or 2, wherein the signal material comprises a luminescent material. [4] Cleaning unit (1) according to one of the preceding claims, wherein the wear material comprises an elastomer. [5] Cleaning unit (1) according to one of the preceding claims, wherein the wear layer (21) has a contact surface (23) which is suitable for coming into contact with an observation window (36), wherein the signal layer (22) has a signal surface (24) which extends parallel to the contact surface (23). [6] Cleaning unit (1) according to one of the preceding claims, wherein the contact unit (20) extends along the first axis (X) and has a fastening section (25) and a cleaning section (26), wherein the contact unit (20) is fastened to the carrier (10) by means of the fastening section (25) and the cleaning section (26) faces away from the fastening section (25), wherein the cleaning section (26) tapers along a second axis (Z) which is arranged transversely to the first axis (X). [7] Sensor system (100) comprising, - a cleaning unit (1) according to one of the preceding claims, - an optical sensor (30) with a housing (31), a light source (32), a detector (33), a motor (34) and a control unit (35), wherein at least the light source (32) and the detector (33) are arranged in the housing (31), and the control unit (35) is connected to the motor (34), the detector (33) and the light source (32), wherein the housing (31) has an opening with an observation window (36), wherein the light source (32) is adapted to emit an emission light (EL) through the observation window (36) from the housing (31), and the detector (33) is adapted to detect a detection light (DL) incident through the observation window (36) into the housing (31), wherein the motor (34) is mechanically connected to the cleaning unit (1) and is suitable for moving the cleaning unit (1) in contact with the housing (31) between a rest position (RP) and a cleaning position (CP) over the observation window (36), wherein the control unit (35) is adapted to evaluate the detection light (DL) in order to detect whether the signal layer (22) is visible. [8] Sensor system (100) according to claim 7, wherein the signal material is adapted to emit a luminescent light and the light source (32) is adapted to emit an emission light (EL) adapted to stimulate the signal material to emit the luminescent light and the detector (33) is adapted to detect the luminescent light. [9] Sensor system (100) according to claim 7 or 8, wherein the light source (32) is adapted to emit UV light. [10] Method for checking the condition of a cleaning unit (1), comprising: - Providing a sensor system (100) according to one of claims 7 to 9, - moving the cleaning unit (1) into the rest position (RP) or the cleaning position (CP) so that the light source (32) is suitable for emitting an emission light (EL) to the contact unit (20) and the detector (33) is suitable for detecting a detection light (DL) and / or a signal light, - Emitting an emission light (EL) by the light source (32), - detecting a detection light (DL) by the detector (33), - Evaluation of the detection light (DL) by the control unit (35) - Output of an indication of a change of the cleaning unit (1), depending on the evaluation of the detection light (DL).

Images