Sensor with cleaning device

Abstract

The invention relates to a sensor with a cleaning device. The sensor (1) comprises: a sensor housing (2) having a housing window (3); a sensor unit (4) arranged in the sensor housing (2) and suitable for transmitting a sensor signal (S) through the housing window (3) and suitable for receiving a detection signal (D) through the housing window (3); a cleaning unit (5) having a cleaning element (6), a bracket (7) and a driver (8), wherein the cleaning element (6) is attached to the bracket (7) in such a way that the cleaning element (6) is suitable for contacting the housing window (3) from the outside, wherein the driver (8) is connected to the bracket (7) in a force-locking manner and is suitable for moving the cleaning element (6) across the housing window (3); and a pressing unit (9) suitable for applying an adjustable contact pressure (F) on the cleaning unit (5) so that the cleaning element (6) is pressed against the housing window (3) with the contact pressure (F).

Description

Technical Field

[0001] The invention relates to a sensor with a cleaning device. Background Art

[0002] In analytical measurement technology, in particular in the field of water management, measured variables such as, for example, the turbidity of the measured medium or separation and transition zones in the measured medium are of particular importance. These measured variables can be detected and monitored, for example, by means of optical sensors or ultrasonic sensors.

[0003] It is essential for process measurement technology that these sensors detect measured values ​​continuously and accurately in order to control and regulate processes with the highest precision. At the same time, the maintenance effort for these sensors should be as low as possible for the operator who installed them. However, in many applications, the sensors are subjected to harsh environmental conditions and are exposed to a high potential for contamination, which increases the maintenance effort for the sensors.

[0004] In the case of optical sensors, precise detection of the measured values ​​can only be guaranteed if the transparent window of the optical sensor and the light path into the measured medium are clean and free of contamination.

[0005] In the case of ultrasonic sensors, contamination can also have a negative impact on the detection of measured values.

[0006] To remove dirt from the window of an optical sensor or from the sensor surface of an ultrasonic sensor, there are different cleaning methods:

[0007] - Mechanical cleaning with the aid of a window wiper;

[0008] - Compressed air or liquid cleaning, where air or cleaning liquid is applied to the sensor's window;

[0009] - Ultrasonic cleaning, where mechanical vibration is used to reduce buildup on the sensor window;

[0010] - Mechanical cleaning of the window with the aid of a hand-held cleaning brush.

[0011] However, depending on the type of soil, e.g. organic soil (such as fat) or inorganic soil (such as pulp deposits), the known cleaning methods have the following disadvantages:

[0012] - For example, in some cases, cleaning the sensor with a wiper may wipe away contaminants deposited on the sensor window across the window surface to be cleaned. Thus, the supposed cleaning may even impair the optical path to the measured medium;

[0013] - In some cases, cleaning with compressed air or cleaning fluids may not be able to satisfactorily prevent the deposition of fouling films. This also applies to ultrasonic cleaning;

[0014] -Handheld cleaning brushes require a lot of work. In addition, if particles are present on the window surface of the sensor and a thorough brush cleaning is performed by hand, these particles can have an abrasive effect that damages the window surface. This damage also results in a compromised light path into the sensor. Summary of the invention

[0015] It is therefore an object of the present invention to specify a sensor with a cleaning unit which enables optimal measuring results to be obtained with minimal effort.

[0016] According to the invention, this object is achieved by a sensor according to claim 1 .

[0017] The sensor according to the present invention comprises:

[0018] a sensor housing having a housing window,

[0019] a sensor unit which is arranged in the sensor housing and which is adapted to transmit sensor signals through the housing window and to receive detection signals through the housing window,

[0020] a cleaning unit having a cleaning element, a carrier and a drive, wherein the cleaning element is attached to the carrier in such a way that the cleaning element is suitable for contacting the housing window from the outside, wherein the drive is non-positively connected to the carrier and is suitable for moving the cleaning element across the housing window,

[0021] A pressing unit adapted to exert an adjustable contact pressure on the cleaning element such that the cleaning element is pressed against the housing window with the contact pressure.

[0022] The cleaning unit according to the invention of the sensor makes it possible to optimally clean the sensor even if the sensor is exposed to high levels of dirt. Depending on the dirtiness of the optical sensor, the cleaning unit can in particular minimize the risk of abrasive cleaning and at the same time minimize the cleaning time. Cleaning with the cleaning unit is therefore particularly effective. A further advantage is that the sensor is cleaned in the best possible way and that the cleaning is carried out by the cleaning unit which is as gentle as possible on the material.

[0023] According to an embodiment of the invention, the sensor further comprises a dirt detection unit adapted to detect dirt on the housing window. The dirt detection unit is connected to the pressing unit and adapted to control the contact pressure according to the detected dirt on the housing window.

[0024] According to one embodiment of the present invention, the pressing unit comprises a magnetic module having a magnetic field generator and a magnetic matching part. The magnetic field generator is suitable for generating an adjustable magnetic field, and the magnetic matching part is connected to the cleaning unit, so that the contact pressure of the cleaning element can be adjusted by the adjustable magnetic field.

[0025] According to one embodiment of the invention, the magnetic match is connected to the carrier or is part of the carrier and the magnetic field generator is designed such that the adjustable magnetic field moves the carrier in such a way that the contact pressure acts on the cleaning elements.

[0026] According to one embodiment of the invention, the cleaning element is a circular brush and is adapted to be rotationally driven by the carriage.

[0027] According to one embodiment of the invention, the cleaning element is a wiper. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention will be explained in more detail according to the following description of the accompanying drawings. It is shown as follows:

[0029] - Figure 1 : A schematic diagram of a sensor with a cleaning device according to the present invention;

[0030] - Figure 2 : Figure 1 Alternative embodiments of the sensor having alternative cleaning means;

[0031] - Figure 3 : Figure 1 An alternative embodiment of the sensor having an alternative cleaning device. DETAILED DESCRIPTION

[0032] Figure 1 A sensor 1 according to the invention is shown, which has a sensor housing 2, a sensor unit 4, a cleaning unit 5 and a pressure unit 9. The sensor 1 is, for example, an optical sensor or an ultrasonic sensor.

[0033] The sensor housing 2 has a housing window 3. The housing window 3 is designed so that it is transparent for radiation or sound waves of a certain wavelength. If the sensor 1 is an optical sensor, the housing window 3 is made of, for example, glass or sapphire glass or another optically transparent material. If the sensor 1 is an ultrasonic sensor, the housing window 3 is made of, for example, epoxy resin, another plastic or another ultrasonically transparent material.

[0034] The sensor unit 4 is arranged in the sensor housing 2 and is suitable for transmitting a sensor signal S through the housing window 3. The sensor unit 4 is also suitable for receiving a detection signal D through the housing window 3. If the sensor 1 is an ultrasonic sensor, the sensor signal S is a sound signal in the frequency range of 100kHz to 1300kHz. If the sensor 1 is an optical sensor, the sensor signal S is an electromagnetic wave signal in the wavelength range of 190nm to 10,000nm. In the case of an optical sensor, the sensor unit 4 includes a light source and a light detector (not shown). In the case of an ultrasonic sensor, the sensor unit 4 includes a piezoelectric element (not shown) suitable for transmitting and receiving ultrasonic waves.

[0035] The cleaning unit 5 comprises a cleaning element 6, a bracket 7 and a drive 8. The cleaning element 6 is attached to the bracket 7. The drive 8 is connected to the bracket 7 in a force-locking manner. The drive 8 is arranged in the sensor housing 2. The drive 8 is, for example, an electric motor. The drive 8 and the bracket 7 are suitable for moving the cleaning element 6 across the housing window 3 (see Figure 1 More specifically, the driver 8 and the bracket 7 enable the cleaning element 6 to move between the first position and the second position. The first position and the second position are arranged in a first plane parallel to the housing window 3. In addition, the driver 8 and the bracket 7 enable the cleaning element 6 to move between the first position and the third position (see Figure 1 The first position and the third position are arranged in a second plane different from the first plane. The second plane is preferably perpendicular to the first plane. In other words, the bracket 7 can at least move the cleaning element 6 in three dimensions.

[0036] The cleaning element 6 is, for example, a wiper or a brush, preferably a round brush. As a result of the rotation, the cleaning brush itself has a greater cleaning effect than the wiper. The bristles of the cleaning brush are preferably made of plastic. The cleaning brush rotates about the first rotation axis R1, as shown in FIG. Figure 1 and Figure 2 As shown by the circular arrow in .

[0037] The cleaning element 6 is attached to the bracket 7 such that the cleaning element 6 is adapted to contact the housing window 3 from the outside. Figure 1 and Figure 2 In the embodiment of the sensor 1 shown, the cleaning element 6 is a brush. Figure 3 In the embodiment shown, the cleaning element 6 is a wiper.

[0038] The pressing unit 9 is suitable for exerting an adjustable contact pressure F on the cleaning unit 5, so that the cleaning element 6 is pressed onto the housing window 3 with the contact pressure F (see Figures 1 to 3 Arrow F in the figure).

[0039] The contact pressure F is generated, for example, using a magnetic module 11. The magnetic module 11 has a magnetic field generator 12 and a magnetic matching part 13. The magnetic field generator 12 is, for example, an electric coil. The current flowing through the electric coil generates a magnetic field B depending on the current. The magnetic matching part 13 is, for example, a shaft to which the brush is attached (see Figure 1 ).

[0040] exist Figure 1 In the embodiment, the magnetic matching part 13 is connected to the bracket 7 or the magnetic matching part 13 is a part of the bracket 7. In this case, the design of the magnetic field generator 12 should be such that the adjustable magnetic field B moves the bracket 7 so that the contact pressure F acts on the cleaning element 6.

[0041] If the cleaning element 6 is a round brush, it is rotatably driven by the carrier 7. For this purpose, the carrier 7 has, for example, an articulated connection for force transmission.

[0042] In order to adjust the contact pressure F by the pressing unit 9, the pressing unit 9 monitors, for example, the current consumption of the driver 8. When in contact with the sensor surface, a contact pressure F is generated which is exerted by the cleaning unit 5 on the housing window 3. This contact pressure F can be detected indirectly via the increased current consumption of the driver 8. By limiting or selectively adjusting the current consumption of the driver 8, the contact pressure F can therefore be adjusted.

[0043] By means of the adjustable current intensity, the magnetic field B and thus the contact pressure F of the cleaning element 6 on the housing window 3 can be varied by the magnetic field generator 12 .

[0044] If the cleaning unit 5 is a circular brush, the rotation speed of the circular brush can be adjusted by adjusting the current consumption of the drive. In this case, the cleaning unit 5 preferably has a rotation speed sensor (not shown). By adjusting the rotation speed, the housing window 3 can be cleaned according to the application, that is, according to the existing local use conditions.

[0045] Due to the increasing contact pressure and the higher rotational speed, lightly adhering dirt is first gradually removed and, as the cleaning brush approaches the housing window 3 , even more strongly adhering dirt is removed as the pressure increases.

[0046] exist Figure 2 and Figure 3 In the embodiment, the magnetic field generator 12 and the magnetic matching part 13 are arranged inside the sensor housing 2 and are configured similarly to a magnetic switch, for example. In this case, the magnetic matching part 13 is attached to the shaft 14 carrying the cleaning element 6. Thus, by using the magnetic module 11, the shaft 14 and the cleaning element 6 can be axially moved along the second rotation axis R2 so that the cleaning element 6 is pressed against the housing window 3 with a contact pressure F (see Figure 2 and 3The drive 8 is connected to the shaft 14 so that the shaft 14 is suitable for rotating about the second rotation axis R2 to move the cleaning element 6 across the housing window 3 (see around Figure 2 Circular arrow indicating the second rotation axis R2 of the shaft 14 in FIG.

[0047] The sensor 1 further comprises a dirt detection unit 10. The dirt detection unit 10 is adapted to detect dirt of the housing window 3. The dirt detection unit 10 is connected to the pressing unit 9 and is adapted to control the contact pressure F depending on the detected dirt of the housing window 3. The dirt detection unit 10 is, for example, part of the sensor unit 4 or is the sensor unit 4. In the case of an optical sensor, for example, this means that the radiation reflected on the housing window 3 is used to infer the degree of dirt of the housing window 3. If the housing window 3 is clean, hardly any radiation is reflected from the housing window 3 to the sensor unit 4. If the housing window 3 is dirty, radiation is increasingly reflected from the housing window 3 to the sensor unit 4. The same principle can be applied in the case of an ultrasonic sensor.

[0048] By means of the dirt detection unit 10 it is also possible to identify permanent dirt which cannot be removed by the cleaning element 6 , for example by comparing the reflection signal from the housing window 3 with a reference reflection signal.

[0049] The dirt detection unit 10 enables automatic and intensity-adapted cleaning of the sensor 1 , which ensures operability and reduces repair and maintenance costs.

[0050] Reference numerals list

[0051] 1 Sensor

[0052] 2 Sensor housing

[0053] 3 Shell window

[0054] 4 Sensor unit

[0055] 5 Cleaning unit

[0056] 6 Cleaning components

[0057] 7 Bracket

[0058] 8 Driver

[0059] 9 Pressing unit

[0060] 10 Dirt detection unit

[0061] 11 Magnetic Module

[0062] 12 Magnetic Field Generator

[0063] 13 Magnetic matching section

[0064] 14 Axis

[0065] S Sensor signal

[0066] D Detection signal

[0067] F Contact pressure

[0068] B Magnetic Field

[0069] R1 First axis of rotation

[0070] R2 Second axis of rotation

Claims

1. A sensor (1), comprising: - a sensor housing (2), said sensor housing (2) defining an interior and comprising a housing window (3), a sensor unit (4) arranged in the sensor housing (2) and configured to transmit a sensor signal (S) through the housing window (3) and adapted to receive a detection signal (D) through the housing window (3), a cleaning unit (5), said cleaning unit (5) comprising a cleaning element (6), a shaft (14) and a drive (8), wherein the cleaning element (6) is attached to the shaft (14) so ​​that the cleaning element (6) selectively contacts the housing window (3) from an external direction, wherein the shaft (14) extends through the wall of the sensor housing (2), is connected to the cleaning element (6) outside the sensor housing (2) and to the drive (8) inside the housing, and wherein the shaft (14) is operable to rotate about the axis of the shaft (14) and to translate within the sensor housing (2), and wherein the drive (8) is connected to the shaft (14) and is configured to rotate the shaft (14) about the axis and move the cleaning element (6) across the housing window (3), a pressing unit (9) configured to exert an adjustable contact pressure (F) on the cleaning element (6) so that the cleaning element (6) is pressed against the housing window (3) with the contact pressure (F), The pressing unit (9) comprises a magnetic module (11), which is arranged in the sensor housing (2) and comprises a magnetic field generator (12) and a magnetic matching part (13), wherein the magnetic field generator (12) is configured to generate an adjustable magnetic field, and wherein the magnetic field generator (12) or the magnetic matching part (13) is connected to the shaft (14) of the cleaning unit (5) and moves with the shaft (14), so that the contact pressure (F) of the cleaning element (6) can be adjusted by the adjustable magnetic field acting on the magnetic matching part (13).

2. The sensor (1) according to claim 1, wherein: The sensor (1) further comprises a dirt detection unit (10) configured to detect dirt on the housing window (3), wherein the dirt detection unit (10) is connected to the pressing unit (9) so as to enable the contact pressure (F) to be controlled according to the detected dirt on the housing window (3).

3. The sensor (1) according to claim 1 or 2, wherein: The cleaning element (6) is a circular brush.

4. The sensor (1) according to claim 1 or 2, wherein: The cleaning element (6) is a wiper.

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