Abstract
The ultrasonic tubular transducer is activated at the centre thereof by two symmetrical electromechanical converters. The vibration generated by the two electromechanical converters is converted and then transmitted to the tube via a coupler. The ultrasonic transducer can be vibrationally isolated from the interfaces thereof by caps equally suitable for connecting the transducer to a stationary frame, a free end or another similar ultrasonic transducer. A device for pre-stressing electromechanical converters has a hole bored at the centre thereof in order to allow cables from the transducer as well as from adjacent transducers to pass therethrough.
Claims
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2. (canceled)
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4. (canceled)
5. (canceled)
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12. Tubular ultrasonic transducer to propagate acoustic waves in a fluid medium, and comprising: an electromechanical conversion device with active elements associated with at least one metallic tube for transmitting vibrations to the fluid medium, power supply cables of the conversion device, and a pre-stressing device of the active elements of said conversion device, wherein the conversion device is composed of two electromechanical converters arranged axially inside the tube, on each side of a coupler, which is located in the central part of the tube and in contact with the latter, and each end of the tube is equipped with a cap, the assembly forming a submersible symmetrical module with radial vibration.
13. Ultrasonic transducer according to claim 12, wherein the pre-stressing device of the active elements of each module comprises a pass-through axial passage to enable routing of the power supply cables of the adjoined modules and of the opposite converter.
14. Ultrasonic transducer according to claim 12, wherein the two electromechanical converters are supplied by AC voltages, either in phase or in opposite phase, to respectively obtain a first radial vibration mode of the tube or a second axial vibration mode of the tube.
15. Ultrasonic transducer according to claim 12, wherein each electromechanical converter comprises a stack of active elements and a counterweight arranged opposite the common central coupler.
16. Ultrasonic transducer according to claim 15, wherein the pre-stressing device is formed by a hollow rod passing through the two converters and the coupler, and a pair of securing rings for compressing the stacks of active elements and their counterweights.
17. Ultrasonic transducer according to claim 12, wherein the transmission tube of each module is composed of two adjoined symmetrical tubes with interposition of the coupler.
18. Ultrasonic transducer according to claim 12, wherein the cap of each module comprises a decoupling part to isolate the module from its mechanical interfaces in vibratory mode, in particular a connection to a frame, a connection to another juxtaposed module and a connection to a closing cap.
19. Modular assembly of a plurality of transducers according to claim 12, wherein the different modules are supplied by a common electronic circuit configured to reduce the number of cables running through the modules, using a mean resonance frequency for the excitation frequency of the system.
20. Treatment machine comprising a tank in which a set of transducers according to claim 19 are housed, and a surface to be treated by ultrasounds, wherein the surface to be treated is located at a distance from the surface of the tube substantially equal to a half wavelength in the medium of the transducer.
21. Treatment machine according to claim 20, wherein the surface to be treated by ultrasounds is a strip of material, guided around several transducers to increase.
22. Treatment machine comprising a tank in which a set of transducers according to claim 19 is housed, wherein the tank is of cylindrical shape, the fluid being inlet at one end and outlet at the other end to enable a continuous-flow treatment, and the transducers are arranged in substantially coaxial manner in said tank.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0058] Other advantages and features will become more clearly apparent from the following description of a particular embodiment of the invention, given for non-restrictive example purposes only and represented in the appended drawings, in which:
[0059] FIG. 1A represents a schematic view of a tubular transducer according to the prior art, described in the document U.S. Pat. No. 4,537,511;
[0060] FIGS. 1B and 1C show the vibratory speed amplitude along two tubular transducers according to the prior art;
[0061] FIGS. 2A and 2B represent the vibratory deformation of a modular transducer according to the invention, with its two operating modes, and the respective generated cavitation fields;
[0062] FIG. 2C illustrates the vibratory speed amplitude along the modular transducer of FIG. 2A;
[0063] FIG. 3 represents the modularity and decoupling principle of the modules of the transducer according to the invention, with several examples of configurations;
[0064] FIG. 4 represents a cross-sectional view of an embodiment of the ultrasonic transducer of FIG. 2A, in which the electromechanical conversion is performed by two converters formed by two stacks of symmetrical active elements and a drilled pre-stressing system, the mechanical vibration generated then being transmitted to two tubes for transmitting vibrations to the medium;
[0065] FIG. 5 shows the routing and securing of cables inside a transducer module according to FIG. 4;
[0066] FIG. 6 represents several electronic power supply configurations for modular ultrasonic transducers according to the invention for which the modules can be supplied in series, in parallel or independently;
[0067] FIG. 7 is a schematic cross-sectional view of a configuration of a tank including a part exposed to the ultrasounds generated by the transducer according to the invention;
[0068] FIGS. 8A and 8B represent two arrangements of several modular transducers according to the invention in a medium so as to maximize the acoustic amplitude transmitted to the medium at the surface of a textile strip to be processed;
[0069] FIG. 9 represents a configuration of a coaxial cylindrical tank with the transducer according to the invention.
DESCRIPTION OF PARTICULAR EMBODIMENTS
[0070] FIGS. 2A and 2B represent a symmetrical transducer (8) according to the invention illustrating two different operating modes.
[0071] In a first operating mode (FIG. 2A), called radial mode, the symmetrical transducer (8) is composed of two symmetrical electromechanical converters (9a, 9b), a coupler (10) and a tubular structure (12a, 12b) designed for radial acoustic generation. The two converters are placed along a z-axis, symmetrically on each side of the coupler (10), which is located in the central plane of the tubular structure (12a, 12b), formed by two adjoined tubes (12a, 12b) and aligned on the z-axis.
[0072] The two converters (9a, 9b) are excited in phase, which produces axial expansion vibrations (6c) in compression on the coupler (10). This device will then convert the axial vibration (6c) into radial vibration (6d). This radial vibration (6d) enables the radial vibration mode (4b) of the tubular structure (12a, 12b), designed for radial acoustic generation, to be excited.
[0073] The vibration thus develops according to the radial wavelength of the tube, i.e. a much lower wavelength than the wavelength of longitudinal mode. Typically it is possible to design the tubular structure (12a, 12b) in such a way that the half wavelength of the radial flexion mode is about 1 to 3 cm. This half wavelength is small compared with the length of a tube, typically 30 to 60 cm. This enables more than 10 half wavelengths to be placed on the tube. Co-relatively, this means that numerous radial vibration modes exist. It is therefore not necessary to adjust the length of the tubes to the excitation frequency of the electromechanical converters (9a, 9b), unlike a tubular transducer according to the prior art. There will always be a radial mode close enough in frequency to be excited at the resonance frequency of the vibration mode of the converters.
[0074] The caps (11a, 11b) arranged at the opposite ends of the tubes (12a, 12b) concentrate the vibrations on the cylindrical surface of the transducer and prevent generation of axial ultrasonic waves. As all the vibratory energy is produced on the cylindrical surface, the global efficiency of the transducer is increased for methods requiring acoustic power in an area containing the segment z′ parallel to the z-axis of the transducer placed facing the cylindrical surface of the transducer.
[0075] In a second operating mode (FIG. 2B), called axial mode, the symmetrical transducer (8) according to the invention implements the two symmetrical electro-mechanical converters (9a, 9b) which are excited in opposite phase. This results in a translational vibration (6e), thereby resulting in a movement according to the z-axis of the coupler (10). This device will then transmit this vibration to the transmission tubes (12a, 12b) to the medium in which it is immersed. The vibration thus develops according to a longitudinal mode of the tube (4c), i.e. according to a similar mode to that of the transducer according to the prior art. The advantage of this mode alone is not determinant, however in combination with the previous mode, this double operating mode reduces the number of nodes, or even generates a progressive wave along the transducer, thereby resulting in a large homogenization of the applied treatment.
[0076] FIG. 2C illustrates a set of modular transducers (15) according to the invention, composed of several transducers (8) of FIG. 2A or 2B and several caps (11). The vibration amplitude (14c) is symmetrical at the level of each module and the maximal attenuation ratio is low. The generated vibration amplitude profile is more regular than that of the other two configurations and the length is not limited. The acoustic energy, responsible for cavitation, is thus relatively homogeneous along a segment z′ parallel to the z-axis. There is little acoustic energy produced in the z-axis, at the ends of the set of modular transducers (15).
[0077] The twofold symmetrical and modular property of the transducer according to the invention enables a more regular generated vibration amplitude to be obtained over larger treatment widths, which makes it possible to comply with the regularity and dimensional requirements of certain applications, involving ultrasonic treatment of large parts, such as depositions on textile assisted by ultrasounds.
[0078] FIG. 3 presents the configurations A1 to A7 made possible by the modular design of the ultrasonic transducer according to the invention. These configurations enable surface treatment problems to be addressed on very different widths and without any theoretical limitation. The modular transducer (8) is represented in simplified manner by its device for transmitting vibration to the medium (12) and its cap (11). The ends of the sets of transducers are composed by interfaces with a frame (16), a single shrouding (17) sealing the inside of the transducer, or another transducer modular according to the invention.
[0079] The configurations presented are the following: [0080] A1, single module: the transducer module of the type of FIGS. 2A and 2B is fixed to a frame (16) via one end and in contact with the medium via the other end. The module is isolated in vibratory manner from the two ends by vibratory isolation devices integrated in the caps (11). This configuration enables a similar useful vibration generation length to that of a transducer according to the prior art to be obtained. [0081] A2, two modules: this configuration is similar to configuration A1 with the addition of a transducer module in series with the previous module. In this configuration the decoupling device is common to the two modules. This configuration illustrates the modularity principle and enables the useful vibration generation length to be doubled. [0082] A3, n modules: this configuration is similar to configurations A1 and A2 with an integral number [n−2] of modules (15) between the end modules. The interfacing principle between the modules remains identical to configuration A2. This configuration enables a theoretically infinite useful vibration generation length to be obtained. [0083] A4, n modules, double embedding: this configuration is similar to configuration A3 with the two ends connected to a frame (16). This configuration enables the static flexion problem of the complete transducer to be reduced, which enables larger lengths to be achieved. [0084] A5, two transducers with one facing module: this configuration presents two transducers as defined in configuration A1, placed facing one another in order to increase the vibration generation width. In addition, decoupling of the shrouding enables the disturbances generated by the transducers in the longitudinal direction to be reduced, thereby reducing the losses of performance encountered with tubular transducer is according to the prior art. [0085] A6, two transducers with two facing modules: this configuration presents two transducers as defined in configuration A2, placed facing one another in the same way and for the same reasons as in configuration A5. [0086] A7, two transducers with n facing modules: this configuration presents two transducers as defined in configuration A3, placed facing one another in the same way and for the same reasons as in configuration A5. [0087] The nonrestrictive set of configurations permitted by the modularity and by the vibratory isolation of the modular transducer enables a large variety of problems to be addressed with a great flexibility as regards the vibration generation length.
[0088] FIG. 4 presents an embodiment of a modular ultrasonic transducer according to FIGS. 2A and 2B. The transducer (8) is composed of two electromechanical converters (9a, 9b), a central coupler (10), a symmetrical device for transmitting vibration (12a, 12b) to the medium, and a device for performing symmetrical vibrating isolation in the caps (11a, 11b). The transducer is symmetrical with respect to the plane P, orthogonal to the axis of symmetry of revolution z.
[0089] The electromechanical converters (9a, 9b) are each composed of a stack of active elements (18a, 18b), a counterweight (21a, 21b) and a pre-stressing device (22a, 22b). The stacks of active elements are typically composed of successive layers of annular piezoelectric ceramics (19a, 19b, 19c, 19d) converting an electric signal into a mechanical vibration, and of electrodes (20a, 20b, 20c, 20d) performing supply of the active materials (18a, 18b).
[0090] The pre-stressing device is composed of a hollow pre-stressing rod (23a, 23b) which supports the pre-stressing and will enable electric wires to pass. Pre-stressing securing rings (24a, 24b) perform compression of the stacks of active elements (18a, 18b).
[0091] The active stacks (18a, 18b) are supplied by an AC electric voltage chosen to set the electromechanical converters (9a, 9b) in mechanical resonance with the central part (25). Two vibration modes are able to be used. Either the excitations are such that the deformations of the stacks (18a, 18b) are in mechanical phase to cause axial expansion-compression vibrations of the central part (25), or the excitations are such that the deformations of the stacks (18a, 18b) are in mechanical phase opposition to cause vibrations in axial movement of the central part (25).
[0092] With reference to FIG. 4, the coupler (10) comprises the central conversion part (25), a joining rim (26) and a transmission part (27). The joining rim (26) is in the form of a solid ring or of an apertured ring with regularly spaced holes along the z-axis. The symmetrical device for transmitting vibration (12) to the medium is composed of two identical tubes (12a, 12b) arranged in symmetrical manner around the coupler.
[0093] The central conversion part (25) converts the axial vibration generated by the electromechanical converters (18a, 18b) into radial vibration. This radial vibration is transmitted to the tubes (12a, 12b) via the joining rim (26) and transmission part (27).
[0094] According to an alternative embodiment, the symmetrical device for transmitting vibration (12) can be composed of a single tube containing the coupler (10) which acts via the inside of the tube in the plane of symmetry perpendicular to the z-axis.
[0095] In FIG. 4, the caps form a symmetrical vibratory isolation device of the transducer, composed of two identical decoupling parts (29a, 29b) arranged in symmetrical manner with respect to the plane P. These decoupling parts enable the transducer to be isolated in vibratory manner from its mechanical interfaces (30), in particular the connection to a frame (16), the connection to another transducer module or the connection to a single shrouding (17) at the end of the set of modular transducers. This vibratory isolation makes it possible not to dissipate a large amount of energy to set the frame in motion unnecessarily, not to disturb the performances of the transducers adjacent to the transducer concerned, and not to generate a large axial vibration at the end of the transducer. This vibratory isolation device is composed of two cylindrical parts forming a swelling of the tube in order to prevent the creation of cavities and risks of premature wear of the system on account of the cavitation generated by the mechanical waves in the fluid medium.
[0096] FIG. 5 presents a detailed view of the central part of the ultrasonic transducer of FIG. 4. It illustrates all the arrangements made to manage securing and routing of the power supply cables (31). The two electromechanical converters (9a, 9b) are separated by the vibration conversion part (25). Each electromechanical converter is composed of the pre-stressing device (22a, 22b) which securedly maintains the counterweight (21a, 21b) and the stack of active elements (18a, 18b), successively composed of electrodes (20a, 20b, 20c, 20d) and of active materials (19a, 19b, 19c, 19d), under mechanical tension with the central part (25).
[0097] The cables coming from the electrodes are secured (32a, 32b, 32c, 32d) at the level of the edges of the counterweights and of the edges of the pre-stressing devices, for example by means of a spot of glue. In the areas situated between the securing points at the level of the edges of the pre-stressing devices (33), the mechanical tension of the cables is voluntarily very low (“slack loop”) in order to limit the mechanical tension in the cables during operation of the transducer. An isolation cylinder (34), which can be electrically conducting in order to prevent short-circuiting, is located between the electrodes and the pre-stressing device. This cylinder can be formed by an insulating material such as Teflon (registered trademark).
[0098] The cable sheath (35) exiting from a transducer according to the invention is composed of the cable sheath coming from the transducer located upline (36), from the neutral cable of converter 9a (37), from the phase cable of converter 9a (38), from the neutral cable of converter 9b (39) and from the phase cable of converter 9b (40).
[0099] FIG. 6 presents different possible configurations for performing power supply to a set of three transducer modules (8) according to the invention by means of a specific power supply (41). Configurations B1 to B3 presented are applicable to a number of different transducers: [0100] B1, series power supply: In this configuration, the transducers are connected in series on a single power supply (41). As the stacks of active elements behave as capacitors, the necessary voltage is greatly increased, but the current on the other hand does not change.
[0101] Power supply (41) is formed by a frequency and voltage generator, for example 500V and 25 kHz. [0102] B2, parallel power supply: In this configuration, the transducers are connected in parallel on a single power supply (41). The capacitive behaviour of the stacks of active elements results in an increase of the required current without any increase of the voltage. [0103] B3, independent power supplies: In this configuration, each transducer is provided with its own power supply (41). In this way, the supply frequency can be tuned to the resonance frequency of each transducer and the current and voltage requirements do not change according to the number of modules. The number of power supplies does on the other hand have to be adjusted.
[0104] FIG. 7 presents a preferential configuration of implementation of an ultrasonic transducer housed in a tank (43) filled with a fluid (44) and designed to perform a sonochemical treatment such as cleaning of a part by ultrasounds. The distance (45) between the part (42) and transducer (8a, 8b, 8c, 8d) is chosen as a half wavelength in the generated wave medium. The objective is to maximize the pressure amplitude in the medium at the location where the surface to be treated is passed. The cavitation (7) is thus maximal on the surface to be treated in order to maximize the efficiency of the sonochemical treatment. This configuration is suitable both for batch treatment and for continuous treatment. In the case of a part (42) that is long along the y-axis, the part can be moved along this y-axis to be treated in the direction of its length in the z direction.
[0105] FIGS. 8A and 8B present other configurations for ultrasonic transducers (8a, 8b, 8c, 8d, 8e) or a set of transducer modules in any medium, designed to treat a strip of material (42a, 42b) by sonochemistry. The material can for example be textile or aluminum. The strip of material is unwound continuously in front of the transducers, at a suitable speed for sonochemical treatment. The surfaces of the strips of material (42a, 42b) to be treated by ultrasounds are unwound around the transducers in order to maximize the efficiency of their use. In the embodiment where the transducers are supplied in phase, the transducers (8a, 8b) are separated by a distance (49a, 49b, 49c, 49d) equal to a wavelength in the generated wave medium in order to maximize the pressure amplitude in the medium at the location where the surface to be treated is passed. The objective is to ensure that the acoustic energy, and the cavitation if applicable, are maximal on the surface to be treated in order to maximise the efficiency of the sonochemical treatment.
[0106] In a particular embodiment, several transducers are present in a tank (43) and the distance (49a, 49b, 49c and 49d) between each set of transducers (8a, 8b, 8c, 8d and 8e) is equal to the wavelength in the medium. This configuration enables the pressures to be maximized at a distance of a half wavelength. It is at this distance from the transducers that it is recommended to place the surface to be treated in order to maximise the efficiency of the sonochemical treatment. To treat a textile strip, it will therefore be advantageous to make it follow a trajectory placing it at half of the distance (49a, 49b, 49c and 49d) between each transducer. The configuration with 3 transducers makes it possible to double the exposure surface of the surface while only increasing the number of transducers by 50%.
[0107] FIG. 9 presents another preferential configuration of implementation of a modular ultrasonic transducer (8) in a tank (43) designed to perform a continuous-flow fluid treatment (47). The tank (43) is of cylindrical shape with a fluid inlet (46) and a fluid outlet (48) at each end. The transducer is placed in coaxial manner with the tank (43) in order to maximize its efficiency on the fluid (44). This configuration enables a uniform ultrasonic treatment of the fluid the exposure time of which depends on the fluid flowrate and on the number n of transducer modules (15) used.
