Vibrating system for protecting a sensor against biological fouling by aquatic microorganisms

Abstract

Vibration system for protecting a sensor against biological fouling by aquatic microorganisms One aspect of the invention relates to a system (10) for combating biological fouling by microorganisms, adapted to cooperate with a measuring device adapted to be immersed in a liquid, the measuring device comprising a fouling surface capable of allowing a measurement, the system (10) being configured to cover the fouling surface and comprising a membrane (11) and an actuator (12) for vibrating the membrane (11). Figure to be published with the abstract: Figure 1

Description

Title of the invention: Vibrating system for protecting a sensor against biological fouling by aquatic microorganisms TECHNICAL FIELD OF THE INVENTION

[0001] The technical field of the invention is that of measuring devices in liquid media which are subject to biological fouling by microorganisms (in English "biofouling").

[0002] In particular, the invention relates to a system for combating biological fouling by microorganisms. TECHNOLOGICAL BACKGROUND OF THE INVENTION

[0003] Equipment used in a liquid environment, in which it is partially or totally immersed, is subject to biological fouling (in English "biofouling") by microorganisms (for example bacteria, algae, molluscs, etc.) due to their deposition and adhesion on the surfaces of said equipment, and this after only a few minutes of immersion.

[0004] When the equipment in question is measuring equipment comprising a sensor, the measurements it takes are disturbed, or even distorted or impossible to carry out, because of the accumulation of these microorganisms and their development, in particular on and around the portion of the sensor used for measurement. This is typically the case for an optical sensor where the emission and capture of the light wave are disturbed by fouling on the window of the sensor through which the light wave propagates.

[0005] It is known to apply to the surface to be protected a coating comprising biocidal chemical agents whose toxicity repels and destroys the micro-organisms which are deposited there. These chemical coatings are however polluting and are not long-lasting, since the quantity of biocides in the coating is not unlimited. Once this quantity is exhausted, the coating becomes ineffective against biological fouling.

[0006] It is also known to use mechanical devices to prevent the deposition of microorganisms, for example, a shutter protecting the measuring surface which only opens when a measurement is to be taken. Mechanisms are also known which remove the deposit of microorganisms from the surface in question, for example a "windshield wiper" type mechanism. However, these solutions are also sensitive to biological fouling and require regular maintenance to remove the deposit of microorganisms.

[0007] It is also known to instrument the sensors with a device designed to vibrate the portion of the sensor used to make the measurement in order to project the microorganisms that settle there. The disadvantage is that this requires adapting the sensor window so that it does not break under the effect of its vibration. Thus, this approach requires modifying the sensor when it already exists, thereby degrading its sealing but also the precision and robustness of the measurement it makes. In addition, repeatedly vibrating the window can cause it to deform, as well as weaken the structure on which the window is fixed.

[0008] There is therefore a need for an anti-biological fouling system that can be fitted to any submerged sensor. Summary of the invention

[0009] The invention provides a solution to the problems mentioned above, by proposing a system for combating biological fouling by microorganisms which is adapted to cooperate with a measuring device without requiring modification of said measuring device.

[0010] One aspect of the invention thus relates to a system for combating biological fouling by microorganisms, adapted to cooperate with a measuring device intended to be immersed in a liquid, the measuring device comprising a fouling surface, the system being configured to cover the fouling surface, the system comprising: • a membrane; • an actuator, positioned on one of the faces of the membrane and capable of setting the membrane into vibration, the actuator forming a pattern comprising an internal contour and an external contour, the internal contour and the external contour being concentric with center C, the internal contour having a minimum distance dj from the center C and the external contour having a minimum distance dj from the center C, the actuator being such that q 9t<0.4-de

[0011] The term “measuring device” means equipment suitable for measuring one or more properties, such as a sensor or a probe. For example, this is an optical sensor (a fluorescence sensor, a camera, a laser, etc.), an oxygen sensor, a turbidity sensor or any other type of sensor whose component used to detect the quantity to be measured is not in contact with the liquid medium, in particular due to the presence of a window between the detection component and the liquid.

[0012] The term "fouling surface" means a portion of the measuring device which, when said measuring device is not assembled with the system according to the invention, is in contact with the liquid. The fouling surface is therefore a surface on which we want to avoid fouling. For example, in the case where the measuring device is an optical sensor, the fouling surface is the sensor window through which the sensor makes its measurement. When this surface is fouled, the measurement by the optical sensor is erroneous.

[0013] The term “cover” means that the fouling surface is not in contact with the liquid medium when it is covered by the system according to the invention.

[0014] The term "membrane" means a mechanical device capable of being set into vibration via excitation generated by the actuator. This membrane preferably has a thin thickness compared to its other dimensions, in particular its length or its diameter. The membrane may be circular, rectangular, or any other shape suitable for the sensor.

[0015] The term "actuator" means a device whose activation by an electrical signal makes it possible to set the membrane into vibration. This is typically a thermal or piezoelectric actuator.

[0016] The term “pattern” means a geometric shape formed by the actuator, in particular formed on the membrane, in particular on the face of the membrane where the actuator is positioned.

[0017] Thanks to the invention, it is possible to prevent the deposition, adhesion and development of aquatic microorganisms on the membrane as well as on the fouling surface, when the system cooperates with the measuring device. In particular, the vibration of the membrane makes it possible to drive the microorganisms towards the periphery of the membrane in question.

[0018] This protection against biological fouling is, moreover, cleverly implemented with a membrane whose dimensions are determined so as to reduce the damping of the vibration, and therefore to increase the amplitude of the membrane displacement, in order to improve the detachment and projection of the microorganisms which are deposited on it.

[0019] Tests have shown that such a dimensioning of the actuator makes it possible to increase the amplitude of the deformation of the membrane by increasing the transduction coefficient between the actuator and the membrane. In addition, such a dimensioning makes it possible to achieve large amplitudes of deformation of the membrane without risking damaging or causing rupture of the actuator during its actuation, which would typically be the case if the ratio between the minimum distances and was less than 0.2, or even less than 0.3.

[0020] This system is, moreover, compatible with any submerged measuring device technology. It is not necessary to adapt or modify the structure of the measuring device to assemble the system according to the invention with the measuring device.

[0021] In addition to the characteristics which have just been mentioned, the system according to the invention may have one or more complementary characteristics among the following, considered individually or according to all technically possible combinations.

[0022] In one embodiment, the measuring device comprises an optical measuring sensor configured to emit an optical beam, in which the membrane comprises a surface, called the measuring surface, corresponding to a portion of the membrane that the optical beam passes through when the system cooperates with the measuring device, a center of the measuring surface corresponds to the center C of the internal contour and of the external contour of the pattern formed by the actuator, and an interior surface delimited by the internal contour is at least equal to 70% of the measuring surface.

[0023] In one embodiment, the minimum distance of the internal contour is between 1 mm and 20 cm.

[0024] In one embodiment, the minimum distance from the outer contour is between 1.5 mm and 25 cm.

[0025] In one embodiment, the actuator is configured to vibrate the membrane at an excitation frequency between 10 Hz and 1 kHz.

[0026] Vibrating the membrane at such a frequency makes it possible to excite the fundamental mode of the membrane, and therefore to maximize the amplitude of displacement of this membrane, thereby increasing the projection of microorganisms that settle there. Tests have shown that this frequency range is particularly suitable for removing fouling that forms on the membrane.

[0027] Another advantage of exciting the membrane on its fundamental vibration mode is to produce a single vibration antinode, the dimensions of which are the largest compared to the other vibration modes. Consequently, such excitation makes it possible to remove fouling from the same portion of a significant size of the membrane. Advantageously, this portion can be used for the purposes of measurement by the measuring device, in particular to allow the measuring device to carry out the measurement through this portion, which is therefore not or only slightly subject to fouling.

[0028] In one embodiment, the actuator comprises a plurality of disjointed actuation modules.

[0029] The advantage of using several actuation modules, i.e. several independent actuators, allows redundancy of the actuation mechanism and therefore to actuate the membrane even when certain actuation modules are faulty or inoperative.

[0030] In one embodiment, the membrane and the pattern formed by the actuator are of the same shape.

[0031] By "of the same shape" is meant that if the membrane is circular in shape then the pattern is circular in shape, for example annular, or if the membrane is parallelepipedal in shape, for example a rectangle, then the pattern is parallelepipedal in shape, for example a rectangle.

[0032] In one embodiment, the membrane is circular in shape and the outer contour of the pattern formed by the actuator is located at a distance less than a predefined threshold distance from a contour of the membrane.

[0033] The actuator is therefore a “peripheral” actuator which is located on the periphery of the membrane surface. For example, the predefined threshold distance is less than or equal to 10% of the distance between the membrane contour and the center of the membrane.

[0034] In one embodiment, the actuator is configured to vibrate the membrane at an excitation frequency, the system further comprises an electronic circuit configured to determine a vibration frequency of the membrane and to modify the excitation frequency as a function of the determined vibration frequency.

[0035] It is thus possible to retroactively control the excitation produced by the actuator on the membrane in order to correct the vibration frequency of the membrane, typically to make the membrane vibrate at the frequency of its fundamental vibration mode. This feedback makes it possible to ensure that the membrane vibrates at its resonance frequency for which the deformation amplitude will be the strongest, despite the changing constraints of the environment which impact its resonance frequency, such as the movement of the liquid medium (for example swell, storm) or variations in immersion depth (for example due to waves or the tide).

[0036] Another aspect of the invention relates to an assembly comprising a measuring device and a system for combating biological fouling according to the invention, in which the fouling surface and the membrane are opposite each other.

[0037] By "facing" is meant that the fouling surface and the membrane are assembled so as to face each other, that is to say to be opposite each other.

[0038] In one embodiment, the membrane has a maximum displacement amplitude umax relative to a resting position of the membrane in a direction normal to a surface of the membrane, and a distance L between the fouling surface and the membrane is such that L >

[0039] The term “maximum displacement amplitude” means the maximum amplitude that the displacement of the membrane can have under the effect of a vibration in a predefined range of excitation frequencies.

[0040] By "relative to a rest position" is meant that the maximum amplitude of displacement corresponds to the maximum distance of this displacement, in one direction or the other of the direction normal to the surface of the membrane, from the rest position of the membrane, i.e., the position without excitation of the membrane.

[0041] The distance d is thus sufficiently large to ensure that the displacement of the membrane under the effect of excitation by the actuator will not come into contact with the fouling surface. This distance d is also thus sufficiently large to avoid having too high a pressure in the space between the membrane and the fouling surface which would damage the membrane, the actuator and / or the fouling surface.

[0042] In one embodiment, the membrane has two opposite faces, called front face and rear face, the front face is intended to be in contact with the liquid, the assembly comprises a closed cavity delimited at least in part by the rear face of the membrane and by the fouling surface, a pressure variation in the cavity is only caused by the displacement of the membrane under the effect of its vibration.

[0043] In one embodiment, the fouling surface is a surface dedicated to a measurement by the measuring device.

[0044] “Dedicated to measurement” means that the fouling surface does not significantly alter the measurement by the measuring device. That is to say, the fouling surface is the portion of the measuring device via or through which the measurement is carried out, such as a porthole for an optical sensor. In other words, it is the measurement interface of the measuring device with the liquid.

[0045] The invention and its various applications will be better understood upon reading the following description and examining the accompanying Figures. BRIEF DESCRIPTION OF THE FIGURES

[0046] Other characteristics and advantages of the invention will appear on reading the description, which can be read in conjunction with the Figures. These Figures are presented for information purposes only and in no way limit the invention.

[0047] [Fig.l] comprises schematic representations of an anti-biofouling system, according to different embodiments of the invention.

[0048] [Fig.2] is a schematic representation of a membrane of the anti-biological fouling system, according to one embodiment of the invention.

[0049] [Fig. 3] is a schematic representation of a membrane of an antifouling system, according to several embodiments of the invention.

[0050] [Fig.4] is a schematic representation of a measuring device intended to be protected by the anti-fouling system, according to one embodiment of the invention.

[0051] [Fig.5] is a schematic representation of a variant of an actuator of the system according to the invention.

[0052] [Fig.6] is a schematic representation of an assembly comprising the anti-fouling system and the measuring device, according to one embodiment of the invention.

[0053] [Fig.7] is a schematic representation of a displacement of the membrane, according to one embodiment.

[0054] [Fig.8] comprises two schematic representations of alternative embodiments of the assembly of [Fig.7]. DETAILED DESCRIPTION

[0055] Unless otherwise specified, the same element appearing in different figures has a single reference.

[0056] The present invention relates to a system for protecting the fouling surface of a sensor, typically through which the sensor performs its measurements, against biological fouling by aquatic microorganisms. The proposed system is based on the use of a membrane whose vibration drives away the microorganisms that are deposited thereon. The system is also adapted to be assembled with a sensor in order to isolate the fouling surface from the liquid medium, which prevents the deposition of microorganisms on the fouling surface. The membrane is also adapted to allow measurement by the sensor through said membrane.

[0057] One aspect of the invention therefore relates to a system 10 for combating biological fouling by microorganisms, also called an anti-fouling system 10, as illustrated in the diagrams of [Fig.l].

[0058] The system 10 comprises a membrane 11 which can be set into vibration by mechanical excitation generated by an actuator 12.

[0059] The membrane 11 can be connected to a support 13, typically by embedding at the perimeter of the membrane 11. That is to say that the membrane 11 is held by embedding its periphery on the support 13.

[0060] As illustrated in [Fig.2], the membrane 11 may comprise two opposite faces: a front face 11-1 and a rear face 11-2. The front face 11-1 faces the liquid medium with which it is intended to be in contact. The rear face 11-2 faces the inside of the system 10. When this system 10 is assembled with a measuring device, for example a sensor, this rear face 11-2 faces the measuring device.

[0061] “Facing towards” means that the face in question faces the object towards which it is facing, i.e. the face is oriented towards said object.

[0062] The membrane has a thickness which is smaller than its other dimensions, in particular compared to its length. Typically, the membrane is circular in shape, i.e. the membrane is a disc, with a thickness of between 50 μm and 5 mm, typically between 50 μm and 500 μm, and a diameter of between 1 cm and 25 cm. Alternatively, the membrane is parallelepipedal in shape, typically a rectangle, with a thickness of between 5 μm and 5 mm, for example between 50 μm and 500 μm, and its length and / or width is at least greater than 1 cm, for example its length and / or width is between 1 cm and 25 cm.

[0063] The membrane 11 is made of a waterproof material capable of withstanding pressures in a liquid medium of up to 2 bar.

[0064] In one embodiment, the membrane 11 comprises a surface, called the measuring surface 11-3, through which the measuring device can perform a measurement. For example, in the case where the measuring device comprises an optical sensor, the optical beam emitted by the optical sensor passes through the measuring surface when the system cooperates with the measuring device. The measuring surface therefore corresponds to the portion of the membrane through which the optical beam passes when the system cooperates with the measuring device.

[0065] The measuring surface 11-3 of the membrane 11 therefore does not significantly alter the measurement by the measuring device. That is to say, the material of the measuring surface 11-3 is such that the measuring surface 11-3 is transparent for the measurement by the measuring device. By “transparent” is meant that the presence of the membrane has a negligible influence on the measurement carried out by the measuring device. Typically, the measurement error induced by the presence of the membrane is less than or equal to 5% compared to a measurement carried out in the absence of the system 10. For example, in the case of an optical sensor, the membrane lets through at least 70% of the optical beam, or even at least 90%, at the emission and / or reception wavelength of said sensor.

[0066] The measuring surface 11-3 may correspond to all or part of the surface of the membrane 11. For example, the measuring surface 11-3 corresponds to at least 50%, at least 60%, at least 70%, or even at least 80%, or even at least 90% of the surface of the membrane 11.

[0067] In the example proposed here, the membrane 11 is made of polycarbonate and is 250 μm thick and 2 cm in diameter. Alternatively, the membrane 11 may be made of polyethylene naphthalate or polyethylene terephthalate, or any other transparent polymer.

[0068] The system 10 also comprises the actuator 12 used to set the membrane 11 into vibration. The actuator 12 is positioned on one of the faces of the membrane 11. It is understood that the actuator 12 may be a single actuator, or a set of separate actuators (as in the example of [Fig.5]).

[0069] In the example of [Fig.l] (a), the actuator 12 is on the rear face 11-2. In the example of [Fig.l] (b), the actuator 12 is on the front face 11-1. In the example of [Fig.l] (c), the system 10 comprises an actuator 12 on the rear face 11-2 and an actuator on the front face 11-1. When the actuator is on the front face, it is preferable to make it passive, that is to say to isolate it from the liquid medium, for example by adding an insulating layer on the actuator or via any other known technology, in particular to isolate its electrodes from the liquid.

[0070] In an alternative embodiment, the actuator 12 may have the same shape as that of the membrane. That is to say that if the membrane 11 is circular in shape, then the actuator 12 may also be circular or annular in shape. Alternatively, when the membrane 11 is parallelepipedal in shape, then the actuator 12 may also be parallelepipedal in shape, for example each may be rectangular in shape.

[0071] As shown in [Fig. 3], the actuator 12 forms a pattern, that is to say it forms a geometric shape on the membrane 11, in particular on the face on which it is positioned. This geometric shape formed by the actuator 12 is delimited by an internal contour and an external contour. The pattern therefore comprises the internal contour and the external contour. The pattern is, for example, a continuous and / or regular geometric shape.

[0072] The pattern is, for example, a ring, as illustrated in [Fig.3] a), or a parallelepiped, such as a rectangle, as illustrated in [Fig.3] b).

[0073] The internal contour and the external contour are concentric with center C.

[0074] In an alternative embodiment, the center C coincides with the center of the surface measuring surface 11-3. That is, the center of the measuring surface corresponds to the center C of the inner contour and the outer contour of the pattern formed by the actuator.

[0075] The internal contour of the actuator 12 has a minimum distance dt from the center C. This distance therefore corresponds to the radius of the internal perimeter of the actuator when the latter is annular, or to the smallest distance from the center C to the internal contour of the actuator when the latter is parallelepipedal.

[0076] In an alternative embodiment, the measuring surface 11-3 is entirely contained within the surface delimited by the internal contour. This advantageously makes it possible not to disturb the measurement carried out by the measuring device by the presence of the actuator 12.

[0077] The external contour of the actuator 12 has a minimum distance of from the center C. This distance therefore corresponds to a radius, typically the smallest radius, of the external perimeter of the actuator when the latter is annular (for example circular or elliptical), or at the smallest distance from the center C to the external contour of the actuator when it is parallelepiped.

[0078] The actuator 12 is such that g 2 < ii. typically of the order of _ g 3. ​

[0079] The difference between the minimum distance of the external contour and the minimum distance di of the internal contour is noted la and is such that la = dt-dh The difference la therefore corresponds to the distance between the inner and outer perimeters of the pattern formed by the actuator 12.

[0080] In other words, the actuator 12 is such that nod, n A, for example such that u'z ~ d,^ < q?25< < 0.35' typically of the order of, _ g

[0081] In one embodiment, the minimum distance d from the internal contour may be between 1 mm and 20 cm, for example between 1 mm and 2 cm, or even between 4 mm and 1 cm. The minimum distance d from the external contour may be between 1.5 mm and 25 cm, for example between 1.5 mm and 4.5 cm, or even between 6.5 mm and 2 cm.

[0082] In one embodiment, the gap 1a may be between 0.5 mm and 5 cm, or even between 2.5 mm and 2 cm.

[0083] In one embodiment, a maximum distance between an edge of the actuator, for example the edge corresponding to the external contour, and an edge of the membrane may be less than 5 mm or even 0.1 mm.

[0084] In an alternative embodiment, the edge corresponding to the external contour is located beyond the portion of the membrane which is embedded on the system 10, in particular embedded on the support 13.

[0085] The actuator 12 is a thermal, or piezoelectric, actuator. For example, the actuator may be made of piezoelectric ceramic made of lead zirconate titanoates, also called PZT.

[0086] In one embodiment, the material of the actuator 12 may be Polyvinylidene fluoride.

[0087] The system 10 is adapted to cooperate with the measuring device, typically a sensor or a probe. That is to say, the system 10 can be assembled with a measuring device. In particular, the support 13 of the system 10 is adapted to assemble with the measuring device 20.

[0088] Any fastening means may be used to assemble the system 10 with the measuring device 20. For example, it may be a fastening by interlocking, screw-nut, nailing, gluing, welding, etc. It may be necessary to add sealing systems made of Teflon, silicone or any other waterproof material known to those skilled in the art.

[0089] A schematic representation of the measuring device 20 is provided in [Fig.4]. The measuring device 20 comprises a fouling surface 21, which is in contact with the liquid when the measuring device 20 is not assembled with the system 10, i.e. when the measuring device 20 and the system 10 do not cooperate.

[0090] The fouling surface 21 can be used to carry out the measurement, i.e., the fouling surface can be a surface dedicated to measurement by the measuring device 20. For example, when the measuring device 20 is an optical sensor, the fouling surface 21 is a transparent window so that the sensor can emit and capture light waves through this fouling surface 21. In other words, the fouling surface 21 serves as an interface with the surrounding environment for the measuring device 20.

[0091] The fouling surface 21 may also be the detection surface of the measuring device 20, that is to say it is sensitive to the physical quantity measured. For example, in the case where the measuring device is an optical sensor 20 such as a camera, the fouling surface 21 may comprise one or more photosensitive cells in order to capture the light coming from the surrounding environment.

[0092] The measuring device 20 is adapted to be immersed in a liquid. As such, it is waterproof.

[0093] Since the system 10 serves to isolate the fouling surface 21 from the surrounding medium, here the liquid, the system 10 is adapted to cover said fouling surface 21. In other words, the system 10 is designed to be assembled with the measuring device 20 so as to cover the fouling surface 21. The system 10 is therefore adapted so that the covering of the fouling surface 21 is sealed.

[0094] Fastening means of the nut and clamping screw type may be used to fix the system 10 with the measuring device 20, thus making it possible to close and seal this assembly. These fastening means may also serve to maintain a seal disposed between the system 10 and the measuring device 20.

[0095] In one embodiment, the internal contour of the pattern formed by the actuator 12 delimits an internal surface, which is therefore circumscribed by the internal contour. This internal surface corresponds to a recess in said actuator 12. In other words, the actuator 12 is hollowed out in its internal part, which corresponds to the surface delimited by the internal contour of the pattern formed by the actuator 12.

[0096] In this embodiment, the inner surface delimited by the internal contour of the pattern formed by the actuator 12 is at least equal to 70%, for example at least equal to 80%, or even at least equal to 90%, of the measuring surface 11-3. That is to say that the area of ​​this surface circumscribed by the internal contour is at least equal to 70%, for example at least equal to 80%, or even at least equal to 90%, of the area of ​​the measuring surface 11-3.

[0097] In other words, the minimum distance d{ from the internal contour is greater than or equal to a predefined distance 7). The predefined distance as illustrated in Figures 3 c) and d), is such that, when the minimum distance dt is equal to the predefined distance Æ, the surface delimited by the internal contour corresponds to at least 70%, for example at least 80% or even at least 90% of the measurement surface 11-3.

[0098] In other words, when the minimum distance d^ is equal to the predefined distance, the recess of the actuator 12 allows the measuring device to carry out a measurement at least through 70%, for example 80% or even 90%, of the measuring surface 11-3.

[0099] In other words, when the measuring device comprises an optical sensor, which is configured to emit an optical beam, the actuator 12 is dimensioned so as to allow at least 70%, for example 80% or even 90%, of the optical beam emitted by the optical sensor passing through the measuring surface, in particular at one or more wavelengths considered for the measurement. In this case, the measuring surface is transparent to the optical beam and is crossed by said optical beam when the system cooperates with the measuring device.

[0100] In an alternative embodiment, the actuator 12 can produce a vibration of the membrane 11 at an excitation frequency of between 10 Hz and 1 kHz. The advantage is thus to excite only the fundamental deformation mode of the membrane.

[0101] In the proposed example, the polycarbonate membrane 250 μm thick and 2 cm in diameter has its fundamental deformation mode which has a resonance frequency equal to 595 Hz at a depth of 50 cm below the liquid level, in this case water.

[0102] Thus, the vibration of the membrane drives out the microorganisms which are deposited on a large portion of the membrane, at least in a portion of the membrane whose displacement amplitude is at least greater than 20% of the maximum displacement amplitude of the membrane relative to its resting position.

[0103] In an alternative embodiment, as illustrated in [Fig. 5], the actuator 12 may be a set of actuators 12-1 to 12-4. These actuators 12-1 to 12-4 are disjoint, i.e., they are not in contact with each other. The set of actuators comprises at least two actuators.

[0104] The actuators 12-1 to 12-4 are arranged so that their arrangement forms a pattern on the membrane, such as a ring as illustrated in [Fig.5] a) or a parallelepiped, such as a rectangle illustrated in [Fig.5] b. In other words, the arrangement of the actuators 12-1 to 12-4 on the membrane 11 forms a fractional pattern on said membrane 11.

[0105]

[0106]

[0107]

[0108]

[0109]

[0110] [YES]

[0112]

[0113]

[0114] In other words, the actuators are positioned on this same pattern, which respects the constraints imposed on the actuator 12 mentioned above. In particular, this pattern formed by the actuation modules has an internal contour and an external contour, such that the internal contour has a minimum distance d^ from the center C and such that the external contour has a minimum distance d from the center C. Actuators 12-1 to 12-4 are such that qp < q 4, for example such that 0 05 < < 0 35, typically of the order of, 4. _ g 3. In other words, the pattern formed by the actuation modules has a gap la between the minimum distance d from the external contour and the minimum distance d{ from the external contour such that no 4, - for example such that n 4, typically of u'4 U,ZD S df¥7Jg SU,JD the order of, d, _ n In this variant, the ranges of values ​​of the minimum distances d, and de and of the width la are the same as those indicated above. In the example of [Fig.5] a), each of the actuators 12-1 to 12-4 has a circular arc geometry, while in the example of [Fig.5] b) each of the actuators 12-1 to 12-4 has a rectilinear geometry. In an alternative embodiment, the inner surface delimited by the inner contour is at least equal to 70%, for example at least equal to 80%, or even at least equal to 90%, of the measuring surface 11-3. In other words, the minimum distance di from the inner contour of the pattern is greater than or equal to the predefined distance defined above. In a variant, the center C of the pattern is coincident with the center of the measuring surface 11-3. In an alternative embodiment, the system 10 may also comprise an electronic circuit configured to determine the vibration frequency of the membrane 11 by a method known per se, for example via a measurement of the impedance of the actuator 12. The electronic circuit then makes it possible, via a feedback loop, to modify the excitation generated by the actuator 12, in particular to modify the excitation frequency. The electronic circuit thus serves to modify the frequency at which the membrane 11 vibrates in order to maximize its displacement amplitude, in particular by correcting said vibration frequency so that it corresponds to the frequency of the fundamental mode of deformation of the membrane 11. The electronic circuit therefore serves to control the frequency of the actuation signal delivered to the actuator 12 and used to actuate the membrane 11, i.e., the excitation frequency, as a function of the determined vibration frequency.

[0115] This electronic circuit may comprise a processor, a microcontroller, a programmable electronic chip such as an FPGA chip (for “Field-Programmable Gate Array” in English), or any other electronic module capable of determining the vibration frequency and modifying the excitation frequency as a function of said vibration frequency.

[0116] Another aspect of the invention, as illustrated in [Fig. 6], relates to an assembly 30 comprising the system 10 and the measuring device 20, described above.

[0117] The actuator 12 is here positioned on the front face 11-1 for reasons of clarity of the diagram of [Fig.6]. The actuator 12 can, in fact, be positioned indifferently on one and / or the other of the faces of the membrane 11.

[0118] The assembly 30 is such that the fouling surface 21 and the membrane 11 are opposite each other. In other words, the measuring device 20 and the system 10 are assembled so that the fouling surface 21 and the membrane 11 are positioned opposite each other.

[0119] In an alternative embodiment, as illustrated in Figure 7, the membrane can have a maximum displacement amplitude Umax, relative to its resting position, in a direction normal X to one of its faces.

[0120] The normal direction X corresponds to the direction of deformation of the membrane 11 under the effect of excitation by the actuator 12.

[0121] The term “resting position” means the position of the membrane when it is not set into vibration by the excitation produced by the actuator. The maximum displacement amplitude umax thus corresponds to the maximum difference in position reached by the membrane when it is set into vibration by the actuator, relative to its resting position.

[0122] The displacement of the membrane 11 is illustrated by the dotted circular arcs on either side of the membrane 11.

[0123] Referring again to Figure 6, the system 10 and the measuring device 20 are assembled in the assembly 30 such that a non-zero distance L exists between the fouling surface 21 and the membrane 11. The distance L may, alternatively, correspond to the distance between the fouling surface 21 and the rear face 11-2.

[0124] In this variant embodiment, the assembly 30, that is to say the assembly of the system 10 and the measuring device 20, typically via the support 13, can be such that the distance L satisfies the relationship L > 2umax.

[0125] For example, in the case where the membrane has a maximum vibration amplitude of 50 pm, then the distance L is greater than or equal to 100 pm.

[0126] In an alternative embodiment, illustrated in [Fig.6], the assembly 30 may comprise a cavity 31 closed between the membrane 11 and the fouling surface 21.

[0127] The cavity 31 is therefore delimited, at least in part, by the rear face 11-2 of the membrane 11 and by the fouling surface 21.

[0128] In this variant embodiment, the pressure of the fluid contained in the cavity 31 can only be modified by the displacement of the membrane 11 when the latter is set into vibration by the actuator 12. In other words, a variation in pressure in the closed cavity 31 is only caused by the displacement of the membrane 11 under the effect of its vibration.

[0129] In an alternative embodiment, illustrated in [Fig.8] (a) and 8 (b), the assembly 30 may comprise a base 32, for example included in the system 10, typically, the base 32 is integral with the support 13.

[0130] The base 32 serves to circumscribe the cavity 31 between the membrane 11 and the fouling surface 21. The closed cavity 31 is therefore delimited by the membrane 11, the fouling surface 21 and the base 32. The base 32 is therefore adapted to cooperate with the measuring device 20 in order to close the cavity 31.

[0131] The base 32 can be fixed on the support 13 so that the cavity 31 extends, at a minimum, over the entire length of the rear face 11-2 of the membrane 11.

[0132] The actuator 12 is here positioned on the front face 11-1 for reasons of clarity of the diagrams of [Fig.8]. It is noted that the actuator 12 can be indifferently positioned on one and / or the other of the faces of the membrane 11.

[0133] The positioning of the base 32 on the support 13 and relative to the measuring device 20 depends on the application in question and the geometric characteristics of said measuring device 20. For example, the base 32 may be close to the membrane 11 and the fouling surface 21, as illustrated in [Fig.8] (a), or be distant from the membrane 11 and the fouling surface 21, as in [Fig.8] (b). The positioning of the base 32 makes it possible to obtain a cavity 31 whose volume is more or less large, depending on the application in question.

Claims

Claims

1. System (10) for combating biological fouling by microorganisms, adapted to cooperate with a measuring device (20) intended to be immersed in a liquid, the measuring device (20) comprising a fouling surface (21), the system (10) being configured to cover the fouling surface (21), the system (10) comprising: - a membrane (11); - an actuator (12) positioned on one face of the membrane (11) and capable of vibrating the membrane (11), the actuator (12) forming a pattern comprising an internal contour and an external contour, the internal contour and the external contour being concentric with center C, the internal contour having a minimum distance di from the center C and the external contour having a minimum distance de from the center C, the actuator (12) being such that q 9 < < g q.

2. System (10) according to claim 1, wherein the measuring device (20) comprises an optical measuring sensor configured to emit an optical beam, wherein the membrane (11) comprises a surface, called the measuring surface (11-3), corresponding to a portion of the membrane through which the optical beam passes when the system (10) cooperates with the measuring device (20), wherein a center of the measuring surface (11-3) corresponds to the center C of the internal contour and of the external contour of the pattern formed by the actuator (12), and wherein an interior surface delimited by the internal contour is at least equal to 70% of the measuring surface (11-3).

3. System (10) according to one of the preceding claims, in which the minimum distance d; from the internal contour to the center C is between 1 mm and 20 cm.

4. System (10) according to one of the preceding claims, in which the minimum distance from the external contour to the center C is between 1.5 mm and 25 cm.

5. System (10) according to one of the preceding claims, in which the actuator (12) is configured to vibrate the membrane (11) at an excitation frequency between 10 Hz and 1 kHz.

6. System (10) according to one of the preceding claims, wherein the actuator (12) comprises a plurality of disjointed actuation modules (12-1, 12-2, 12-3, 12-4).

7. System (10) according to one of the preceding claims, in which the membrane (11) and the pattern formed by the actuator (12) are of the same shape.

8. System (10) according to one of the preceding claims, wherein the actuator (12) is configured to vibrate the membrane (11) at an excitation frequency, the system (10) further comprising an electronic circuit configured to determine a vibration frequency of the membrane (10) and to modify the excitation frequency as a function of the determined vibration frequency.

9. An assembly (30) comprising a measuring device (20) and a system (10) for combating biofouling according to any one of claims 1 to 8, wherein the fouling surface (21) and the membrane (11) are opposite each other.

10. An assembly (20) according to claim 9, wherein the membrane (11) has a maximum amplitude of displacement umax relative to a resting position of the membrane (11) in a direction normal to a surface of the membrane (11), and wherein a distance L between the fouling surface (21) and the membrane (11) is such that L > 2umax.

11. Assembly (30) according to one of claims 9 or 10, the membrane (11) having two opposite faces, called front face (11-1) and rear face (11-2), the front face (11-1) being intended to be in contact with the liquid, the assembly (30) comprising a closed cavity (31) delimited at least in part by the rear face (11-2) of the membrane (11) and by the fouling surface (21), in which a pressure variation in the cavity (31) is caused solely by the displacement of the membrane (11) under the effect of its vibration.

12. Assembly according to one of claims 9 to 11, in which the fouling surface is a surface dedicated to a measurement by the measuring device.

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