DEVICE FOR CLEANING AN OPTICAL SURFACE

Abstract

The invention relates to a device (5) comprising an optical surface (10) and a cleaning device (15) for cleaning the optical surface comprising: a wave transducer (25) acoustically coupled with the optical surface and configured to synthesize an ultrasound wave (W) propagating within the optical surface, and a spraying unit (20) for dispensing a washing liquid (L) onto the optical surface, the device being shaped so that the ultrasound wave displaces the washing liquid on the optical surface.

Claims

1. A device comprising: an optical surface; and an apparatus for cleaning the optical surface, the device comprising: a wave transducer acoustically coupled to the optical surface and configured to synthesize an ultrasonic wave propagating in the optical surface; and a spraying unit for delivering a washing liquid onto the optical surface, the spraying unit being superposed on the transducer, the device being configured so that the ultrasonic wave displaces the washing liquid on the optical surface.

2. The device as claimed in claim 1, the spraying unit being secured to the optical surface and/or to the transducer.

3. The device as claimed in claim 1, the transducer being arranged between the spraying unit and the optical surface.

4. The device as claimed in claim 1, the spraying unit being configured to deliver the washing liquid onto a zone of the optical surface situated on the propagation path of the ultrasonic wave.

5. The device as claimed claim 1, the spraying unit comprising a channel for supplying washing liquid at least partially superposed on the transducer and distant less than 4 cm from the transducer.

6. The device as claimed in claim 1, the cleaning apparatus comprising a thermal diffusion member, arranged between the transducer and the spraying unit, made from a material having thermal conductivity greater than or equal to 50 W.m.sup.?1.K.sup.?1.

7. The device as claimed in claim 1, the cleaning apparatus being arranged on the periphery of the optical surface.

8. The device as claimed in claim 1, the spraying unit being configured to deliver the washing liquid sequentially.

9. The device as claimed in claim 1, the transducer having a thickness of between 1 ?m and 500 ?m.

10. The device as claimed in claim 1, the optical surface being a glazing element of a motor vehicle.

11. The device as claimed in claim 1, the spraying unit being configured to deliver the washing liquid at a relative pressure of less than 1 bar.

12. A method for cleaning an optical surface, the method comprising: a) supplying a device as claimed in claim 1, b) spraying the optical surface with a washing liquid by the spraying unit, c) synthesizing an ultrasonic wave propagating in the optical surface and suitable for displacing the washing liquid to a body arranged on one face of the support.

13. The method as claimed in claim 12, the electric power supply to the transducer being maintained at least until the body is displaced on the optical surface with the washing liquid.

14. The method as claimed in claim 12, the distance between the zone in which the washing liquid comes into contact with the optical surface and the transducer being less than 1 mm and/or the relative pressure of the washing liquid at the outlet of the spraying unit being less than 1 bar.

15. The method as claimed in claim 12, at least some of the electrical energy powering the electric transducer being converted into the form of heat by the transducer, the heat being sufficient to defrost the washing liquid previously contained in step b) in the spraying unit and/or to heat the washing liquid by more than 10? C. between the inlet and the outlet of the spraying unit.

Description

[0101] FIG. 1a

[0102] FIG. 1b and

[0103] FIG. 1c are schematic transverse cross-sections of a first example of a device according to the invention,

[0104] FIG. 1d is a variant of the first example of a device according to the invention,

[0105] FIG. 1e and

[0106] FIG. 1f are cross-sections along the line (BB) viewed from above and along the line (AA) viewed from the side respectively of another variant of the first example of a device according to the invention,

[0107] FIG. 2 is a perspective view of a second example of a device according to the invention,

[0108] FIG. 3 is another enlarged perspective view of the second example, and

[0109] FIG. 4 is a schematic cross-section viewed perpendicular to the optical surface of the second example illustrated in FIGS. 2 and 3.

[0110] For the sake of clarity, the elements that make up the drawing are not always shown to scale.

[0111] FIGS. 1a to 1c illustrate a first example of a device 5 according to the invention. The device 5 comprises an optical surface 10, in the form of a plate, and a cleaning apparatus 15.

[0112] The cleaning apparatus 15 comprises a spraying unit 20 and a wave transducer 25 in contact with the optical surface 10. The transducer 25 is covered on each of its opposite faces 30a, 30b by the spraying unit 20 and by the optical surface 10, which protect it by sandwiching it.

[0113] The cleaning apparatus 15 can be arranged on the periphery of the optical surface 10.

[0114] The transducer 25 can be electrically connected to a current generator, not shown. When it is supplied with electric power, the transducer generates an ultrasonic wave W that propagates in the optical surface 10. The ultrasonic wave can be a Lamb wave or an ultrasonic surface wave that preferably propagates on the face 35 of the optical surface in contact with the transducer.

[0115] A supply channel 40 is made in the spraying unit 20 in order to convey, as indicated by the arrow C, a washing liquid L from a tank to a distribution orifice 45 that emerges onto the optical surface.

[0116] The device can comprise a pump 50 in order to transport the washing liquid L to the distribution orifice 45.

[0117] The supply channel 40 can be superposed on the transducer 25 and be at a distance of less than 30 mm. The washing liquid L contained in the supply channel 40 can thus be heated by the heat dissipated by Joule heating by the transducer. For optimum heating of the washing liquid, the spraying unit is preferably in contact with the transducer or with a thermal diffusion member 55 that is in contact with the transducer 25. The device in the example illustrated comprises such a thermal diffusion member 55, for example made from aluminum, which covers the transducer, in order to efficiently diffuse the heat produced by the transducer to the supply channel.

[0118] To clean the optical surface, a predetermined volume of a washing liquid is conveyed, for example by transport by means of the pump 50, to the distribution orifice 45, through which it flows. It reaches the face 35 of the optical surface to which the cleaning apparatus is secured. The transducer generates an ultrasonic surface wave that propagates in the optical surface of the transducer towards an opposite edge 60 of the optical surface, along a propagation path that passes through the zone Z of the optical surface covered by the washing liquid.

[0119] The washing liquid is then moved away from the transducer, as indicated by the arrow D, under the action of the ultrasonic wave on the optical surface. The washing liquid can thus meet a body 65, such as dust or a greasy particle, adhering to the optical surface. The body can then be dissolved in the washing liquid, as illustrated in FIG. 1c, and driven off the optical surface via the edge 60.

[0120] Advantageously, the entire volume of washing liquid deposited by the spraying unit onto the optical surface can be evacuated under the effect of the propagation of the ultrasonic wave W. This thus avoids the formation of a residual film resulting from the evaporation of the washing liquid not evacuated from the optical surface.

[0121] The optical surface of the device illustrated in FIGS. 1a to 1c is shown horizontally, but it can obviously be oblique or vertical without affecting the operating efficiency of the device.

[0122] In a variant embodiment illustrated in FIG. 1d, a slot 61 can be made between the transducer 25 and the thermal diffusion member 55 in order to separate the transducer from the thermal diffusion member. This exemplary embodiment is preferred when the thickness of the transducer is less than the wavelength of the ultrasonic wave generated by the transducer, for example when the thickness of the transducer is less than 50 ?m. The thermal diffusion member of the transducer can be secured, for example bonded, to an acoustically insulating element 62, for example made from a thermoplastic, secured to the optical surface 10 and thicker than the transducer.

[0123] FIGS. 1e and 1f illustrate another example of a device according to the invention, which differs in particular from the device illustrated in FIG. 1d in that the transducer comprises a piezoelectric substrate 71 and two electrodes with opposite polarity in contact with the substrate. The electrodes are each in the form of a comb 72 comprising a connector 73 and fingers 74 that extend perpendicularly from the connector. The fingers of the combs are interconnected. When the electrodes are supplied with electric power, the difference in polarity thus generates the vibration of the piezoelectric substrate 71 in the portion Pa of the substrate delimited by the peripheral combs, which results in the generation of the ultrasonic wave. The piezoelectric substrate is extended outside the assembly delimited by the peripheral fingers of the combs, and thus defines an inactive portion Pi of the transducer, in which no wave is directly generated by supplying electric power to the electrodes. As illustrated in FIGS. 1e and 1f, the thermal diffusion member is secured to the inactive portion Pi of the piezoelectric substrate and a slot is made between the transducer and the spraying unit, by means of the thermal diffusion member, which is sufficiently thick to space apart the combs of the spraying unit. The heat produced by the heating of the transducer can thus be transferred efficiently by conduction through the thermal diffusion member to the washing liquid circulating in the spraying unit. Preferably, in order to avoid the formation of a short circuit when the electrodes are supplied with electric power, the thermal diffusion member is separated from the combs by a distance greater than the wavelength of the ultrasonic wave.

[0124] FIGS. 2 to 4 show a second exemplary embodiment of the device according to the invention.

[0125] The device 15 differs in particular from the device illustrated in FIG. 1a in that the optical surface 10 comprises two portions 70, 75 stacked one on top of the other and having faces in contact with each other having complementary shapes.

[0126] The first portion 70 is acoustically conductive and is intended to propagate an ultrasonic wave W. This first portion 70 is attached to a second portion 75 with a larger area, which is for example a windshield of a motor vehicle.

[0127] The second portion 75 can be acoustically insulating as it is not intended to propagate the ultrasonic wave generated by the transducer.

[0128] The first portion 70 can be removably secured to the second portion 75, for example by means of a layer of heat-sensitive adhesive. If one or other of these two portions breaks, it is thus easy to replace the damaged portion.

[0129] In addition, the device illustrated in FIGS. 2 to 4 also differs from the device illustrated in FIGS. 1a to 1c in that the sprayer unit comprises a structure 80 and a sprinkler nozzle 85 housed in the structure.

[0130] The structure 80 comprises an arm 90 that extends, like the sprinkler nozzle, along the entire width 1 of the first portion 70. The arm comprises a straight groove 95 with an axis X and the transverse cross-section of which has an arc-shaped contour. The structure can further comprise a foot 97, in contact with the second portion 75, which extends from the arm, perpendicular thereto.

[0131] In the example illustrated in FIG. 4, the device comprises one or more transducers 25 for generating ultrasonic waves that are in contact with the first acoustically conductive portion 70 and entirely covered by the arm 90.

[0132] The sprinkler nozzle 85 is housed in the groove 95. It is rotatable about the axis X in the groove relative to the structure. It can be held by the structure so that it is translatably fixed along the axis X relative to the structure.

[0133] The sprinkler nozzle 85 can be a cylindrical tube with an axis of rotation X comprising a wall 100 the shape of the radially outer face of which complements the shape of the groove. The tube can be closed at its opposite ends 105, 110 along the axis X.

[0134] In addition, the structure 80 and the sprinkler nozzle 85 are in fluid communication in order to convey the washing liquid L from a tank to the optical surface 10.

[0135] The structure can comprise a slot 115 made in the foot 97 that emerges into the groove 95 at one of its ends and into a hole 120 passing through the thickness of the second portion at another of its ends. The washing liquid can be introduced into the structure by means of the hole 120.

[0136] The sprinkler nozzle 85 can comprise a hollow inner space 125, an opening 130 made in the wall that emerges onto the slot 115 and one or more distribution orifices 45 made in the wall that emerge onto the optical surface 10. The inner space 125 is preferably superposed on the transducers 25, shown in dashed lines.

[0137] The slot 115 and the inner space 125 placed in fluid communication by the opening 130 thus define a channel for supplying washing liquid.

[0138] As indicated by the arrows C in FIG. 4, the washing liquid L thus flows from the hole 120 into the supply channel, where it is heated by the heat emitted by the transducers 25. It is then distributed onto the optical surface through the distribution orifices 45.

[0139] The washing liquid is then displaced by the ultrasonic wave generated by the transducer on the optical surface in order to clean it, as illustrated previously in FIGS. 1a to 1c.

[0140] In addition, the spraying unit can comprise a motor for arranging the sprinkler nozzle 85 in a specific angular position about the axis X.

[0141] The structure can comprise one or more ducts 140 in which electric cables can be housed, in order to electrically connect the transducer(s) and/or the motor to an electricity generator.

[0142] Advantageously, the device illustrated in the second example makes it possible to efficiently clean the face 145 of the first portion, for example in order to make it possible for an apparatus 150, as illustrated in FIG. 2, to emit and/or receive radiation through this first portion.

[0143] Of course, the invention is not limited to the exemplary embodiments of the invention given by way of non-limiting illustration.