EP0183583A1 - Ultrasonic device - Google Patents

Abstract

An ultrasonic device comprises at least one transducer and a probe having a first active part adapted to be immersed in a medium, an adapter part for matching the impedance of the probe to the medium and an end surface on the adapter part adapted to emit ultrasonic waves longitudinally into the medium. The first active part lies between the end surface on the adapter part, at which is located a peak of the longitudinal ultrasonic waves, and a limiting part at which is located a node of the longitudinal ultrasonic waves. It comprises a second active part adapted to emit ultrasonic waves radially into the medium and at which is located one or more peaks of the radial ultrasonic waves.

Description

The field of the present invention is, in general, that of the ultrasonic treatment of objects, surfaces or organisms, possibly using the phenomenon known as "ultrasonic cavitation".

It is known that, whatever the medium concerned, a field of waves or ultrasonic vibrations is associated with a field of pressure variations which has a mechanical action which may result in the destruction of micro-organisms, the setting in mechanical vibrations particles and / or their resonance, which can fragment or even destroy them.

In the case of a high power ultrasonic field in a liquid medium, we are witnessing the phenomenon known as "cavitation" which results, at the level of microorganisms, at the same time by a destructive mechanical and chemical action. All of these two actions can result, in the case of radioactive particles, in detachment. of the latter and therefore in the decontamination of objects to which these radioactive particles would be attached, after removal of said particles.

In fact, it is known that when a liquid is subjected to an alternating ultrasonic wave field, this causes pressure variations within the liquid and thus creates zones subjected alternately to depressions and to overpressures. In a vacuum area, cavities are created and filled with gas. It is accepted that these cavities arise at the level of microbubbles suspended in the liquid or trapped on the surface of any solid impurity. During the successive phases of overpressure and depression caused by the ultrasonic field, the diameters of these cavities or cavitation bubbles vary.

• Pendant la phase de dépression créée par l'onde ultrasonore, la bulle de cavitation croit jusqu'à un rayon maximum, qui peut atteindre des valeurs de l'ordre de 40 fois le rayon initial. Dans la phase suivante de surpression, elle se comprime et implose brutalement, donnant naissance à de multiples effets parmi lesquels:
  • - formation d'une onde de choc qui se propage à une vitesse qui peut dépasser celle du son dans le liquide, créant dans le voisinage des champs de pression et de température très élevés;
  • - apparition de sonoluminescence;
  • - formation d'ions particulièrement actif (OH et H⁺) avec la libération de molécules d'oxygène et formation d'eau oxygénée.

The so-called vapor cavitation regime occurs as follows:

• During the vacuum phase created by the ultrasonic wave, the cavitation bubble grows up to a maximum radius, which can reach values of the order of 40 times the initial radius. In the next phase of overpressure, it compresses and implodes suddenly, giving rise to multiple effects including:
  • - formation of a shock wave which propagates at a speed which can exceed that of sound in the liquid, creating in the vicinity of very high pressure and temperature fields;
  • - appearance of sonoluminescence;
  • - formation of particularly active ions (OH and H ⁺ ) with the release of oxygen molecules and formation of hydrogen peroxide.

At the place of implosion, gas bubbles are reformed in the next cycle during depression and the process begins again. Generations of bubbles thus vary in volume at the same point at the rate of the ultrasonic wave leading very quickly = to the state of cavitation. This state of cavitation is manifested by a characteristic hiss and a cloud of bubbles.

Due to the formation, at the ultrasonic frequency considered, of turbulence associated with very high pressure and temperature fields, ultrasonic cavitation has a particularly erosive effect on the surfaces arranged in the immediate vicinity of the cavitation zone and is found to be , therefore, be very effective in cleaning these surfaces.

The mechanical and chemical phenomena mentioned above result in the destruction of bacteria that can be found fixed on the surfaces to be cleaned. Thus it is possible to consider ultrasonic cavitation as a means of = cleaning and / or sanitizing surfaces.

The same is true for radioactive messy deposits that can be found on surfaces to be decontaminated, such as those in nuclear pools or inside piping in nuclear power plants. Mechanical and chemical phenomena on contaminated particles necessarily detach them from their support, which, after removal of the particles, is decontaminated.

Within the meaning of the present invention, the concept of cleaning includes that of decontamination. The effectiveness of such a cleaning device is nevertheless linked to the volume of liquid that can be insonified, since the surfaces or objects to be cleaned reach large dimensions. The problem of the quantity of available energy can then arise.

The present invention relates to a head called "insonification" of a solid, liquid or gaseous medium having a particularly high efficiency and energy dispersing capacity. The present invention also relates to cleaning devices and installations using the insonification head.

The Applicant has already developed insonification heads, in particular for liquid media, which comprise at least one ultrasonic transducer which is, in general, a piezoelectric cell, more commonly called "ceramic" and at least one emission member of which a part, called "action" or "cavitation" is immersed in said medium and comprises an impedance adaptation portion to said medium with a terminal face for transmitting longitudinal vibrations. In general, these heads comprise one or more transformer members, namely a "quarter wave" and one or more "sonotrodes". The impedance adapter consists of a set of these sonotrodes, namely elements whose length equals a multiple of half the wavelength at the excitation frequency in the material in which they are made and whose section generally varies according to any hyperbolic function, constant or decreasing in the direction of first wave propagation. The sonotrodes allow, by the ratio between their input and output surfaces, to multiply the amplitude of the vibration by said ratio, at the frequency considered.

The output of such a head of insonification, although satisfactory for certain applications, is quite often insufficient for other applications requiring a great dispersion of energy. Indeed, the energy supplied to the environment is only so from the terminal surface, which, given the characteristic shape of the terminal element of the impedance adapter, usually that of an inverted horn, is relatively small.

In this type of embodiment, there is a lack of energy available for transmission in the form of longitudinal vibrations and, in any event, an insufficient efficiency since only these longitudinal vibrations are used.

Also known, in the prior art, tanks called ultrasonic tanks. These tanks are filled with a liquid, usually water with a detergent added. The objects to be cleaned are then placed there, which are completely submerged. This volume of water is subjected to an ultrasonic field by means of an ultrasonic head, substantially of the same type as that described succinctly above, which is secured to the bottom of the tank. The liquid volume inside the tank enters cavitation.

This type of tank is generally satisfactory but is limited by its own internal dimensions so that certain bulky objects cannot be cleaned by these techniques.

There are also known dental probes that the surgeon holds in his hand. These probes allow the emission of a fairly fine jet of liquid which is subjected to a field of ultrasonic waves. This technology, which is well suited to the problem of dental surgery, can hardly be extrapolated to the cleaning of large industrial objects. In fact, this technique is generally characterized by a particularly low yield. In addition, as mentioned above, industrial objects to be cleaned are often quite large, which makes it difficult to extrapolate and adapt these dentistry probes.

The object of the present invention is to provide a particularly high efficiency insonification head, allowing a great dispersion of energy whatever the medium which is excited with this ultrasonic field.

Another object of the present invention is to provide several cleaning devices and installations allowing in particular the cleaning of industrial objects of particularly bulky size, as well as hollow objects whose interior volume is difficult to access. Another application of the insonification head according to the present invention is a device and an installation for cleaning surfaces such as tunnels, hospital rooms or nuclear pools in power plants.

The present invention relates to a head as defined succinctly above, characterized in that the part .. action extends axially between said end face, seat of a belly of longitudinal vibration mode, and a limit portion, seat'd 'a mode-de-vibrations-longitudinal node, and has a radial action portion seat. at least one belly of radial vibration mode ..

Thanks to these provisions, the present invention achieves its objectives, particularly that of proposing an insonification head, in particular in a liquid medium, the yield and the power dissipation capacity of which are significantly increased compared to the insonification heads. recalled above.

Indeed, in these heads, only the emission surface at the end of the emission member, seat of a belly of _' longitudinal vibrations, constitutes the coupling surface between the head and the medium.

In the head according to the present invention, the coupling surfaces with the medium are multiple and are formed on the one hand by the seat end surface of a belly of longitudinal vibrations, and on the other hand by the seat portion (s) ( s) a belly of radial vibrations formed on said action part.

The present invention also relates to the cleaning and / or decontamination of surfaces and / or industrial objects - by insonification of a volume of liquid and by cavitation consecutive thereto.

The Applicant was faced with the problems of cleaning hollow objects whose interior volume is particularly difficult to access. More specifically, the problem of cleaning the decontamination of the interior surfaces of valves or other piping elements in nuclear power plants has been posed to the Applicant.

Already known from US Patent No. 3,173,034 a process for cleaning the internal combustion chamber of an engine by insonification of a volume of liquid, introduced into this room, by means of a probe emitting a signal ultrasonic, this probe being fixed on a support itself screwed in place of the candle.

This technique can theoretically give satisfaction as soon as it would be suitable for cleaning piping elements such as valves. However, the ultrasonic energies to be used are too great to be able to use the known insonification heads, the structure of which has been mentioned above.

Also an object of the present invention is to provide a device for cleaning hollow objects, such as valves or piping elements by insonification of a volume of liquid confined inside the object, provided in addition with good efficiency and high power transmission capacity.

The cleaning device according to the present invention is intended for hollow objects comprising a main orifice and inside which a volume of liquid is confined, the device comprising a support suitable for closing said main orifice. According to the present invention it is characterized in that the support is adapted to carry at least one insonification head as succinctly defined above, so that the action part of the head is immersed in the liquid volume confined to the interior of the hollow object to be cleaned.

Thanks to this arrangement, and in particular to the use of the insonification head according to the present invention, it is now possible to insonate a large volume of liquid and thereby clean the interior surfaces of objects having a particularly volume important such as valves in the piping of nuclear power plants, for example. In this regard, it is recalled that diameters of the order of several tens of centimeters are commonly used for such valves, the internal volume of these possibly being of the order of m ³ , which gives the measurement of the volume at insonify. The ultrasonic head according to the present invention and the device with which it is associated make it possible to insonate such volumes and thus to clean the internal surfaces of the valves in question.

Another problem that the Applicant has posed is that of cleaning and decontaminating large surfaces, such as, for example, those of swimming pools in nuclear power stations or, in a completely different field, those of railway, road tunnels or even those of hospital rooms.

Is known in particular from patent G.B. No. 1,282,552 a device for cleaning surfaces by confining a volume of liquid coming into contact with the surface and cavitation of this volume.

Here again, and until now, this technique was satisfactory on a theoretical level or when it was applied to relatively small surfaces. Indeed, the insonification heads which can then be envisaged, and in particular those mentioned above, only allowed to insonate a relatively small volume of liquid, thereby reducing the cleaning capacity of devices such as that described. in the GB patent cited above.

Another object of the present invention is therefore to provide a device for cleaning surfaces of high efficiency allowing effective cleaning of particularly large surfaces.

The device according to the present invention, which is of the type comprising an enclosure for confining a volume of liquid with an opening to be directed onto the surface to be cleaned, is in particular characterized in that it comprises at least one insonification head such as briefly described above, the action part of the head being immersed in said volume of liquid.

Thanks to this arrangement, it is now possible to insonify a large volume of liquid, and consequently to propose a cleaning device having a large surface of insonified liquid in contact with the surface to be cleaned.

This has the effect of allowing the cleaning of particularly large surfaces with good efficiency.

• la figure 1 représente, en coupe axiale, un mode de réalisation d'une tête d'insonification selon la présente invention ;
• les figures la, lb sont des diagrammes d'amplitude de vibrations longitudinales et radiales respectivement ;
• la figure lc est une vue de détail à grande échelle de l'encart IC de la figure 1;
• la figure 2 est une vue schématique illustrant la distribution du champ de variation de pression dans un milieu liquide insonifié par une tête d'insonification selon la présente invention ;
• la figure 3 est une vue correspondant à la figure 2, mais illustrant la distribution du champ de variation de pression dans le volume de liquide insonifié par une tête d'insonification de l'art antérieur ;
• la figure 4 est une vue schématique d'une installation de nettoyage d'objets creux selon la présente invention ;
• la figure 5 est une vue schématique en coupe partielle, à plus grande échelle, du dispositif de nettoyage de l'installation de la figure 4 ;
• la figure 6 est une vue en coupe sur la ligne VI-VI de la figure 5 du support du dispositif de la figure 5 ; la figure 7 illustre l'emploi du dispositif et de l'installation de nettoyage illustrée aux figures 4 à 6 pour un corps creux autre qu'une vanne ;
• la figure 8 est une vue schématique en section selon la ligne VIII-VIII de la figure 9 d'un dispositif de nettoyage de surfaces selon la présente invention ;
• la figure 9 est une vue schématique en section selon la ligne IX-IX de la figure 8 de ce même dispositif;
• la figure 10 est un schéma synoptique représentant l' interconnexion du dispositif des figures 8 et 9 avec d'autres éléments d'une installation de nettoyage selon la présente invention.

The characteristics and advantages of the invention will become apparent from the description which follows, by way of example, with reference to the appended schematic drawings in which:

• FIG. 1 represents, in axial section, an embodiment of a insonification head according to the present invention;
• Figures la, lb are amplitude diagrams of longitudinal and radial vibrations respectively;
• FIG. 1c is a detail view on a large scale of the insert IC of FIG. 1;
• FIG. 2 is a schematic view illustrating the distribution of the pressure variation field in a liquid medium insonified by an insonification head according to the present invention;
• Figure 3 is a view corresponding to Figure 2, but illustrating the distribution of the pressure variation field in the volume of liquid insonified by an insonification head of the prior art;
• Figure 4 is a schematic view of a hollow object cleaning installation according to the present invention;
• Figure 5 is a schematic view in partial section, on a larger scale, of the device for cleaning the installation of Figure 4;
• Figure 6 is a sectional view on the line VI-VI of Figure 5 of the support of the device of Figure 5; FIG. 7 illustrates the use of the device and of the cleaning installation illustrated in FIGS. 4 to 6 for a hollow body other than a valve;
• Figure 8 is a schematic sectional view along line VIII-VIII of Figure 9 of a surface cleaning device according to the present invention;
• Figure 9 is a schematic sectional view along line IX-IX of Figure 8 of the same device;
• Figure 10 is a block diagram showing the interconnection of the device of Figures 8 and 9 with other elements of a cleaning installation according to the present invention.

According to the embodiment chosen and shown in FIG. 1, an insonification device 10 comprises a soundproofing head 11 mounted in a protective casing 12. In this exemplary embodiment, the insonification head 11 comprises two piezo ceramics 22, 23 electric sandwiched between a mass called "rear" 24 and a "quarter wave" acoustic impedance adapter 25, of axial size equal to a quarter of the ultrasonic wavelength in the material considered.

The set of elements 22, 23, 24, 25 constitutes what will be called an "ultrasonic head" 26.

It will be observed that the rear mass 24 and the quarter wave 25 have, in this embodiment, a sectional constriction, the section decreasing from an upper portion of the parts 24 and 25 to a terminal portion 19 and 30 respectively, the surface of which is in contact with the next part. As for the quarter wave 25, this constriction makes it possible to constitute an amplitude transformer, the amplitude of the vibrations at the level of the output surface 30 being equal to the product of that at the input surface by the ratio between these two surfaces, minus the losses inherent in propagation in the material.

These provisions implement an adaptation of inpedance, optimizing the performance of the whole.

The surface 30 is in contact with a one-piece middle part or "sonotrode" 27, the length of which is equal. at half a wavelength in the material considered. This sonotrode itself comprises two different parts, namely a first cylindrical part 27A whose length is equal to a quarter of the wavelength followed by a second part 27B of the same length, comprising a necking. This sonotrode part 27 serves to increase the amplitude of the vibrations, and participates in the impedance matching function. The sonotrode 27 comes into contact via a common contact surface 35, with an emission member 32.

In general, the emission member 32 includes a so-called "action" part 34 immersed in the medium to be insonified and an internal part 37.

In this example, the medium to be insonified is a liquid, here water added or not with detergent: the action part is then called "cavitator".

The total axial length of the transmitting member 32, between its end surface 33 and its internal contact surface 35, is here of two half-wavelengths. In fact, this length must be such that the total length which separates the end surface 33 and the contact surface 30 is equal to a multiple of the half-wavelength at the frequency considered in the material constituting the head d insonification 11. A part 34B immediately preceding said end surface 33 of the cavitator, also has a quarter wavelength constriction for the amplitude increase and the impedance adaptation to the medium intended to be insonified, here water with or without detergent added. It will be observed that the upper part 34A of the cavitator is cylindrical, as is the internal part 37.

. Before going further in the description of the -: insonification head 11, a brief description will be given of the operation of the structure which has just been described.

The two piezoelectric ceramics 22, 23 are coupled to an ultrasonic generator, not shown, the frequency of which is here 20,000 Hz. The electrical signal excites these transducing ceramics which thus generate mechanical vibrations at the same frequency, propagating throughout of the head 11. These vibrations are reflected on the one hand by the rear surface 24A of the rear mass 24 and on the other hand, by the end surface 33.

The mechanical vibrations generated by the piezoelectric cell 22, 23 are longitudinal vibrations since the ceramics work in compression in the axial direction.

The multiple reflections at the two aforementioned ends 24A and 33 of the insonification head create a stationary vibratory field: It is thus created along the head of the vibratory modes comprising nodes and bellies.

In figure the amplitude of the longitudinal vibrations has been represented as a function of the distance from the source constituted by the ceramics 22, 23. We thus observe a distribution of nodes -points of amplitude O- and bellies -points relative maximum amplitude - along the ultrasonic head 11 shown from the contact surface 30 between the quarter wave 25 and the central part 27.

It will also be observed that the dimension of the various elements 24, 25, 27 and 32 is such that the end surface 33 is the seat of a belly of longitudinal vibrations.

The Applicant has discovered that the radial vibrations, associated with the longitudinal vibrations make it possible to increase, to a surprising extent, the efficiency of the emission member.

FIG. 1b represents the amplitude of radial vibrations as a function of the distance from the source. We also observe a distribution of nodes and bellies in radial vibration mode.

According to the invention, the action part or cavitator 34 of the emission member 32 extends axially between the end face 33, seat of a belly of longitudinal vibration mode and a limit portion 36, here separating the action part 34 of the internal part 37 of the transmission member 32, this limiting portion 36 being the seat of a longitudinal vibration mode node, and comprises a radial action portion, here the upper part 34A of the cavitator 34, seat of at least one belly of radial vibration mode.

In the embodiment shown, the upper part 34A is the seat of only one belly of radial vibrations. In other embodiments, the radial action portion can have a greater axial length in order to present several bellies of submerged radial vibrations.

Advantageously, this length can be n (λ 2), n being an integer, λ being the wavelength. The length of the action part is then (2n + 1) 4.

The insonification head is here made of titanium, the wavelength in this metal for a frequency of 20k _H z being of the order of 33cm. The size of the head shown in Figure 1 is therefore about 70cm, its diameter being 6cm.

It will be observed that titanium has low internal transmission losses and a high resistance to fatigue caused by the vibrations which pass through it.

We will now describe all of the means for connecting the insonification head 11 inside the casing 12.

According to one aspect of the invention, the means for connecting the insonification head 11 with the casing are arranged to act on at least a portion of the insonification head which is the seat of a longitudinal vibration mode node.

In the embodiment shown, and according to another aspect of the present invention, said connecting means comprise at least one damper seal.

In the example shown in FIG. 1, the emission member 32 is connected to the casing 12 by means of a basic annular damper seal 59, which acts on this member 32 at the limit portion 36, seat of a longitudinal vibration mode node which thus acts as a fixing portion.

The damping seal 59 is clamped between an annular seal holder part 58 comprising a groove intended to partially receive this seal 59, this part being integral with the casing 12, and a closing ring 53 which comes to tighten the seal holder part 58.

The seal piece 58 has tapped bores 54 allowing tightening by means of fixing screws 93, passing through orifices 55 formed in the ring 53. The seal 59 is thus blocked by compression in a position of radial tightening of the emission member 32, and therefore ensures a seal between the liquid medium intended to be insonified and the interior of the casing 12.

₅ According to the embodiment shown, the connecting means comprise an intermediate annular damping seal 64, for action on the central part 27.

According to the present invention, this seal relates to the ₀ junction 7 between the necking 27B and the cylindrical portion 27A, this junction being the seat of a user node of longitudinal vibration, figures 1 and.

For this purpose, the seal 64 has in radial section (Fig.lc a notch 69 of a shape complementary to that of the junction 70 of the parts 27A and 27B, so that the seal 64 participates in the support of the central part 27 and even speaks to that of the whole head 11.

The seal 64 is mounted in an annular support structure generally referenced at 65, which comprises a seal carrier ring 66 on which retaining pins 73 are mounted and a so-called "compression" ring 67.

The seal ring 66 has a set of bores: the tapped bores 76 and the non-tapped bores 96.

The retaining pins 73, which, in this embodiment are four in number, only one having been shown in Figures 1 and lc, have a bore 75 and are fixed to the seal carrier ring 66 by screws 95 screwed into the threads 76.

The lugs 73 penetrate into millings 77 of the central part 27, each of these lugs having a retaining face 78 bearing against a corresponding bearing face 79 of the milling 77. A flat seal 97 of small thickness is interposed between the two faces 78, 79.

The compression ring 67 has tapped bores 81. Screws 97 pass through the bores 96 and are screwed into the tapped bores 81.

According to one aspect of the present invention, the maintenance in the axial direction of the whole of the support structure 65 is ensured by a damping-holding joint 80 compressed between the crowns 66, 67.

The retaining damper joint 80 is here in the form of an O-ring.

A closing plate 91 is mounted by means of screws 92 at the upper end of the casing 12.

The mounting of the insonification head 11 in the casing 12 is done as follows:

We first mount the seal ring 66 with the intermediate damper joint 64 on the junction 70 between the constriction 27B of the cylindrical part 27A of the central part 27. The retaining lugs 73 are then screwed, by interposing the flat seals 97 between the retaining faces 78 of the lug and support 79 milling 77.

The assembly is then positioned in the casing 12 by introducing it through the upper end, so that only the cavitator 34 protrudes outside and thus the limit portion 36 comes opposite the location of the first shock absorber seal 59.

The O-ring 80 is then placed, which is compressed by means of the compression ring 67 by tightening the screws 97.

The axial compression of the damping O-ring 80 causes radial compression of this gasket 80 against the internal wall of the casing 12 and already provides frictionally maintaining the axial length of the assembly of the insonification head 11 and of the annular structure 65 in the housing 12.

The base damper seal 59 is then placed in the groove of the seal holder part 58 and this seal 59 is compressed by means of the screws 93.

Here, too, the axial compression of this damper seal 59 causes the latter to expand radially, resulting in radial pressure against the seal holder part 58 and against the limit portion 36 of the emission member 32.

It will be observed that this arrangement employing several shock-absorbing seals makes it possible to ensure the axial maintenance of the insonification head, in particular by virtue of the radial expansion of the O-ring 80 and of the base shock-absorbing seal 59, while filtering, thanks to the resilience of these joints, mechanized vibrations, the frequency of which, in this example, 20 kHz, is clearly beyond the cutoff frequency of the elastic materials commonly used to make such joints.

It will also be observed that the positioning of the base 59 and intermediate 64 damper seals on portions of the insonification head, seats of a longitudinal vibration mode node (FIGS. 1 and 1a), allows these joints to work only in radial compression-expansion thus allowing a good grip by friction of the insonification head while avoiding axial displacements which could lead, in the long run, to wear by shearing effect. Conversely, the radial vibrations hardly present any disadvantages since the joints work in the direction of their natural resilience.

This is particularly so in this embodiment, with regard to the base seal 59 which has a dual function: axial retention of the head 11 and sealing. By avoiding premature wear by shearing effect, the desired tightness is ensured over time.

In Figure 2, there is shown the variation of the pressure field in a beaker 400 filled with water after introduction and implementation of the insonification device 10 according to the present invention.

In this regard, it should be recalled that the activation of an ultrasonic generator with a frequency of 20 kHz, not shown in the figures, connected to the piezoelectric ceramics of the insonification device 10, subjects the liquid, in particular through the cavitator 34, to an alternating ultrasonic field causing pressure variations within the liquid: as soon as the power used is sufficient, in this example of the order of 300 W effective, there is a phenomenon of cavitation in said regime of steam cavitation of the type succinctly described above.

It should be noted that in general, the erosive quality of an insonified medium depends on the average value of the pressure field: the higher the latter, the higher the insonified medium has a high erosive quality, and therefore, the better is the cleaning of objects in contact with this environment.

The values indicated in the circles shown in FIG. 2 represent the values of the pressure recorded at various points related to the initial average pressure of the liquid before the implementation of the insonification device 10.

It will be observed that the average value of the pressure field is particularly high since many measured points have a value equal to or greater than two and a half times the initial pressure.

Such pressure values have been obtained in particular Thanks to the radial action portion 34A, seat of a radial vibration mode belly. Indeed, the surface of this radial action portion 34A is large, which promotes the emission of radial vibrations.

By way of comparison, the Applicant has carried out tests in a cylindrical beaker of diameter identical to that of the preceding one of an insonification head 401 having a structure identical to that of the insonification device 10, with regard to the mass rear, piezoelectric, quarter wave and middle piece ceramics. Only, the transmission member 32 has been changed and replaced by a transmission member 402 whose neck 402B is identical to the neck 34B of the cavitator 34 according to the present invention. On the other hand, the transmitting member 402 does not have a radial action portion. This organ 402 is thus representative of the resignation organs previously developed by the Applicant.

The insonification head 401 has been arranged so that the end face 433 of the emission member 402 is at the same distance h from the bottom of the beaker as the end face 33 of the emission member 32, in FIG. 2. The same "useful" volume of liquid is thus insonified in both cases: that between the end faces and the bottom of the beaker.

Pressure field values were thus measured under the same conditions as in the case of FIG. 2 and reported in FIG. 3.

It can be seen that below the end face 433 of the transmitting member 4 ₀ 2, the measured field values are quite similar to those measured, in FIG. 2, below the end face 33.

In both cases, it is a pressure variation field induced by the longitudinal vibrations emitted by the end face 33 or 433. As, in the context of this comparison, the powers of play are the same, it is normal that the pressure field induced by the longitudinal vibration mode has in both cases, substantially the same values.

On the other hand, in the rest of the volume of liquid, insonified by the device 402, the value of the mean pressure field remains close to the initial pressure before cavitation since many values equal to one are observed.

Thus, the presence in the cavitator 34, according to the invention, of a portion of radial action 34A, irradiating radial vibrations, therefore ensures a decisive advantage compared to the emission member 402, representative of the organs of emission of the prior art since the average value of the induced pressure field is notably higher, all other things being equal.

We will now describe with the support of Figures 4 to 7 an application of a soundproofing head according to the invention for cleaning hollow objects.

FIGS. 4 to 6 illustrate more particularly the application of an insonification head to cleaning the interior of the body of a valve 114.

According to this aspect of the present invention, a volume of cleaning liquid is confined inside the valve body by sealing the various conduits accessing it beforehand, here the pipes 117; 117 'and leaving only a single orifice which is then said to be "main" available for the insonification device. Generally speaking, in the case of valves, and in particular those used in nuclear power plants, it is possible to access the interior of the "body" of the valve in place after having dismantled the part of the valve. so-called "castle" comprising in particular the shutter: a main orifice 120 is thus released by which one introduces on the one hand said means for closing the inlet and outlet orifices of the valve, these means of shutter being described more away, and on the other hand, an insonification head according to the present invention.

The insonification head generally referenced at 11 in FIGS. 4 and 5 is mounted in a casing generally referenced at La in these figures. These two elements as well as the means of linking them together are similar to those which have been described in the context of Figures 1 and 2, bear the same references in FIGS. 4 and 5 and are not described again.

The casing 12 of the insonification head 11 is mounted on a support 143 having a cylindrical crown 160 in which the casing 12 is forcibly mounted.

This annular support 143 has a diameter similar to that of the head of the valve 114 having the main orifice 120 and is: adapted, by means of a seal 147, to close off this: main orifice 120. The support 143 presents four axial pins, not shown in FIGS. 4 and 5, by which it is centered in the orifice 120.

It will be observed in FIG. 5, that the support assembly 143-casing 12 is arranged such that the cavitator 34 of the insonification head 11 is immersed inside the body of the valve 114.

We will now describe the means for closing secondary orifices which, in this aspect of the present invention, are associated with the insonification head 11.

In this embodiment, these sealing means comprise pneumatic buffers 150, 150 ′ made of balloons introduced into the pipe elements 117, 117 ′ beyond the orifices l16, 116 ′ of the valve l14 on which these elements of piping 117, 117 'are connected. The balloons 150, 150 ′ are inflated by an air circuit shown diagrammatically in FIG. 4 by the conduits 151, 151 ′ connected to a source of compressed air supply shown diagrammatically by the arrow 152.

In FIG. 5, the duct 151 has been shown in solid line, while the duct 151 ′, disposed in front of the cutting plane is shown in phantom.

In the embodiment chosen and shown in these figures, the cleaning device, consisting of the insonification head 11, the casing 12, the support 143 and the shutter means 150, 150 ', 151, 151', comprises a cleaning liquid inlet pipe 153 and a cleaning liquid starting pipe 154, respectively connected to pipes 163, 164 of a cleaning liquid circuit 165, FIG. 4.

The cleaning liquid circuit 165 here comprises a cleaning solution separation filter 170 connected to the liquid starting line 164 coming from the cleaning device. Downstream, the filter is connected to a centrifuge 171 allowing the solid particles to be separated from the rest of the solution. The liquid outlet of this centrifuge is connected to a tank of cleaning solution 172 which is itself connected to a mixer 173. The filter 170 has a water outlet connected to a line 174 which is itself connected to a water tank 175. The outlet of this water tank 175 is connected to the inlet of the mixer 173, the outlet of which is connected to a pump 176 discharging into the pipe 163 for supplying liquid to the cleaning device.

In another embodiment, the filter 170 may include a second water outlet which is directly connected to the mixer 173, this connection being shown diagrammatically at 177 by a line in dashed lines.

It will be noted that an ultrasonic generator-amplifier 180 is connected to the ultrasonic head 26. More particularly, a "+" terminal is connected to the piezoelectric ceramics 22, 23, while a "-" ground terminal is connected to the quarter wave 25. This generator works at a frequency of 20 kHz.

The operation of the cleaning device shown in Figures 4 and 5 will now be described.

As in this example, the hollow object to be cleaned is the body of the valve 114, comprising two secondary orifices 116 and 116 ', connected to the pipes 117, 117', the first operation consists in introducing the pneumatic buffers 150, 1 ₅₀ 'in said body. The support 143 is then brought back with the insonification head 11 on the orifice 120. The latter is thus closed.

The pipes 151, 151 ′ are then connected on the one hand to the source of compressed air 152 and on the other hand, the pipes for the arrival and departure of cleaning liquid 153,154 to the corresponding pipes 163, 164 of the cleaning 165.

The balloons 150, 150 'are then inflated. When the latter are partially swollen, cleaning liquid is then introduced into the interior of the volume of the valve 114. The pressure of this cleaning liquid on the balloons 150, 150 ′ then participates in the installation of the latter in the pipes 117, 117 ′ beyond the secondary orifices 116, 116 ′ of the valve 114. It is then possible to complete the inflation of these balloons so that the interior volume of the valve 114 is hermetically closed.

The ultrasonic head 2 ₆ can then be excited by an ultrasonic wave from the generator-amplifier 180. A ultrasonic field is then established within the valve 114, causing a vapor cavitation phenomenon characterized by the creation and implosion of bubbles to the rhythm of the ultrasonic field.

These bubbles fill most of the interior volume of the body of the valve 114. The implosion of the bubbles coming into contact with the interior surface of said body makes it possible to tear off patches of soiled deposit. The multiplication of these implosions, at the rate of the ultrasonic field means that, fairly quickly, the internal surface of the body of the valve 114 is cleaned.

In the example chosen and shown, the current of liquid used by the pump 176 makes it possible to evacuate through the circuit 165, the soiled deposition portions torn off. The installation shown in Figure 1 works in a closed circuit. The filter 170 makes it possible, downstream of the outlet pipe 154, to separate the cleaning solution from the cleaning water as much as possible. The cleaning solution, laden with dirty particles, is then admitted into the centrifuge 171, which has the function of separating the dirty particles by centrifugation, a relatively pure solution is recovered in the centrifuge and admitted into the solution tank. The outlet of the solution tank and that of the water tank 175 converge towards a mixer 173. The liquid, at the outlet of the mixer, is returned to the inlet circuit 163 by means of the pump 176.

It has already been noted that the axial size of the insonification head is a function of the length of the wave in the metal. Recall that the head 11 is made of titanium and intended to work at 20 kHz, its axial size therefore being approximately 70 cm. Such an insonification head, moreover having a diameter of 6 cm, is particularly well suited for cleaning valves having orifices of more than 15 cm in diameter, such as those shown in FIG. 4.

On the other hand, for valves having holes with a smaller diameter, it is advisable to reduce the size of the head 11, and consequently to work at a higher frequency. In particular for valves having holes less than 15 cm in diameter , we can advantageously use a head about 35cm high and 4 cm in diameter working at 40 kHz.

In FIG. 7, the application of the cleaning device according to the present invention is illustrated for a hollow object, other than a valve.

In this figure, the hollow object to be cleaned is a tank 300 comprising a part 301 of overall cylindrical shape and a part 302, constituting the bottom of the tank, of overall hemispherical shape. The tank has a certain number of lateral orifices 303, which can be closed off by valves 304. It has, at its upper end, a main orifice 305. In the example shown, the interior of the tank 300 is divided into two chambers separated by an intermediate partition 306 extending along an axial plane.

The cleaning device 311 comprises a support 320 adapted to close off the orifice 305 and to carry, in this example, two insonification heads 321 and 321 '.

These insonification heads 321 and 321 ′ have a structure similar to that of the head 11 described in support of FIG. 1, and also work at a frequency of 20 kHz. The heads 321, 321 'are here also protected by a casing 308, 308' secured to the support 320.

A set of cleaning liquid inlet pipes 353 and a set of cleaning liquid starting pipes 354 are associated with the support 320, only one of the pipes 353 and 354 having been shown in FIG. 7.

In this example, the support 320 is adapted to be fixed to the tank 300 by an annular flange 310 having bores 313 regularly distributed around its periphery, a set of screws 312 ensuring the fixing of said support 320 on the tank 300.

The operation of the device 311 is similar to that of the device described in support of FIGS. 4 to 6. After closing the valves 304 and fixing the support 320 above the orifice 305, the tank 300 is filled with liquid of cleaning by connecting the pipes 353 and 354 to a cleaning liquid circuit such as that of FIG. 4. The transducers 321 and 321 ′ are then excited by a generator, not shown in FIG. 7, and cleaning from the inside of the tank is operated in a steam cavitation regime.

We will now describe in support of FIGS. 8 and 9 another aspect of the present invention, namely a device for cleaning and decontaminating surfaces comprising one or more insonation heads such as that described in support of figure 1.

According to the embodiment described and shown in Figures 8 and 9, this cleaning device 410 comprises a first enclosure 251 called "confinement" of a volume of liquid of generally parallelepipedal shape, and a second enclosure 261, called enclosure " protection ", also of generally parallelepiped shape, in which the confinement enclosure 251 is disposed.

Two insonification heads 211, mounted in their casing 212, are arranged inside the confinement enclosure 251. The heads 211 and casing 212 are similar to the head 11 and to the casing 12 described above. However, in these examples, the cavitators 234 have an axial size of five quarters of wavelength (5 λ 4) and thus have a portion of radial action 234A, seat of two bellies of radial vibration mode.

The housings 212 are mounted on the upper wall 270 of the confinement enclosure 251, so that the insonification heads 211 are arranged head to tail.

The confinement enclosure 251 is connected to a cleaning liquid circuit, the conduit for the arrival of this liquid in the enclosure 251 being referenced 253, while the outlet conduit is referenced 254. These conduits pass through the upper walls of the enclosures 251, 261 to open into the interior volume 255 of the confinement enclosure 251.

The containment 251 has, opposite the upper face 270, an opening 230 intended to be directed towards the surface to be cleaned, the surface 231 in FIG. 9. The opening ₂ thus occupies the entire surface opposite to the upper surface 270. This opening 230 is provided with a seal 256 arranged around this periphery. In this embodiment, the seal 256 is of the so-called "lip seal" type.

The confinement enclosure 251 is secured to the protective enclosure 261 by means of U-shaped legs 235 which are fixed to the walls of the two enclosures in an appropriate manner. These legs 235 carry rollers 252 facilitating the movement of the device 410 on the surface to be cleaned 231. A lip seal 256 ′ is also disposed around the periphery of an opening 232 of the protective enclosure 261 formed substantially in the same plane as the opening 230 of the confinement enclosure 251 and directed, in operation, onto the surface to be cleaned 231.

A means for suctioning the leaks shown diagrammatically in FIG. 8 by tubes 258, and arrows 259, is arranged in the walls of the protective enclosure 261 having a normal extension relative to the surface to be cleaned 231, the walls 243 , 243 ', 244, 244' in Figures 8 and 9.

FIG. 10 illustrates an embodiment of an installation implementing the device 410. The latter is connected to an ultrasonic generator GUS which supplies the insonification devices 211.

Other elements of the electrical installation such as, for example, a power supply, etc., have not been shown in the diagram in FIG. 10. The other connections in FIG. 5, which are shown diagrammatically with a double line , represent the cleaning fluid circulation circuit. The installation comprises a pump PO for circulation of this liquid, a liquid reservoir RE, a filtration installation FI, a main suction device ASP and a suction device for ASF leaks.

The operation of the cleaning device and that of the example installation using this device will now be described.

The device is first of all brought into contact with the surface 231 to be cleaned, the latter thus closing off the openings 230, 232, of the two enclosures. Consequently, a double confinement volume is created: on the one hand the internal volume of the confinement enclosure 251 which can then be filled with cleaning liquid, a certain seal being obtained by the seal 256 and on the other hand, the internal volume of the protective enclosure 261, the lip seal 256 ′ sealing the joint between the enclosure 261 and the surface to be cleaned 231.

Under the action of the PO pump, a circulation of liquid is established inside the confinement enclosure 251. This cleaning liquid is drawn from the tank RE and returned to this tank by the main suction system ASP after filtering in the filter device F _I.

The insonification devices 211 create, under the action of the ultrasonic generator GUS, an ultrasonic field the frequency of which is here around 20 kHz, the frequency of the generator possibly being variable in order to adjust the excitation of the ceramics of said insonification devices taking into account, for example, the liquid medium.

Cavities are formed and implode to the rhythm of the ultrasonic wave, those which implode in the vicinity of the surface to be cleaned 231 then detaching plots of dirty deposits attached to this surface. The cleaning liquid polluted by these dirty deposits is evacuated to the filtering device FI, reinjected after filtering the dirty particles in the filtering device F _I. In cases where the surface to be cleaned 231 is not particularly dirty, it is possible to directly re-inject part of the polluted liquid directly into the tank RE, this possibility being illustrated by a connection in dotted lines between the suction device ASP and the RE tank.

According to one aspect of the invention, the leaks occurring towards the outside of the confinement enclosure 251, in spite of the sealing device, here the lip seal 256, are sucked up by the means of suction of the leaks schematized by the conduits 258 and the arrows 259 in FIGS. 8 and 9, by the ASF device in FIG. 10. Thanks to this arrangement, it is possible, on the one hand, to recover cleaning liquid, and on the other hand, to prevent excessive leakage. significant amounts of liquid can take place outside the device 410.

This arrangement thus makes it possible to clean fairly irregular surfaces, such as, for example, tiles, for which it is very difficult to avoid having leaks by means of conventional seals such as the lip seal 256. Most of these leaks are thus sucked in by the device 258, 259 before reaching the second lip seal 256 '.

Thus, such an installation can be used, with success in cleaning surfaces which may have a vertical orientation and which have irregularities such as, for example, the surfaces of tunnels, buildings or even the surfaces of swimming pools.

It will be noted in this regard that the implosion of the cavities makes it possible to decontaminate these surfaces, which makes the device according to the present invention, illustrated in FIGS. 8 and 9, particularly advantageous for cleaning nuclear pools in nuclear power plants.

It will also be noted that the implosion of the cavities makes it possible to destroy any form of life on the surface 231, which is particularly advantageous when cleaning floors contaminated with living organisms, such as for example, hospital floors.

Of course, the invention is not limited to the embodiments described and shown, but encompasses all variant embodiments and / or embodiments.

Claims (17)

1.- Head of insonification of a medium of the kind comprising at least one ultrasonic transducer and at least one emission member of which at least one part called "of action" is immersed in said medium and comprises a section intended for l adaptation of said transmission member to said medium having an end face for transmitting longitudinal vibrations, characterized in that the action part (34) extends axially between said end face (33), seat of a longitudinal vibration mode belly, and a limit portion (36), seat of a longitudinal vibration mode node and has a radial operating range (34A), seat of at least one radial vibration mode belly . 2.- insonification head according to claim 1, characterized in that the limit portion (36) acts as a fixing portion of said head (11). 3.- insonification head according to any one of claims 1, 2, characterized in that the axial dimension of said action part (34) is an odd multiple of the quarter wavelength of the vibrations emanating from the transducer ultrasonic, this odd number being greater than or equal to three. 4.- insonification head according to any one of claims 1 to 3, the head being fixed in a protective casing, characterized in that the connecting means (64, 65, 80, 97, 59, 58) between the head (11) and the casing (12) comprise damping seals (59, 64, 80, 97). 5.- insonification head according to any one of claims 1 to 4, characterized in that connecting means between the head (11) and a housing (12) are arranged to act on a portion of the head of insonification seat of a longitudinal vibration mode node. 6.- insonification head according to any one of claims 1 to 5, characterized in that the maintenance of the head (11) in a protective casing (12) is ensured by a damping support seal (80) associated to means (66, 67, 97) imposing on this joint a radial extension in so that it is compressed against the internal wall of said casing (12). 7.- insonification head according to claim 6, characterized in that the holding damping seal (80) is an O-ring compressed between two crowns (66 and 67). 8.- insonification head according to any one of claims 1 to 7, characterized in that the connection means between the insonification head (11) and a protective casing (12) comprise an associated basic damping seal to means (58, 55 and 93) acting on this joint so that it has a radial expansion resulting in a radial pressure against said limit portion (36) of the emission member (32). 9.- Cleaning device intended for hollow objects, comprising a main orifice, inside which a volume of liquid can be confined, characterized in that it comprises a support (143) adapted to carry at least one head d insonification (11) according to any one of claims 1 to 8, so that the action part (34) of said head is immersed in the liquid volume confined inside the hollow object to be cleaned. 10.- Device according to claim 9, characterized in that it further comprises liquid circulation means (153, 154) adapted to renew the liquid inside the hollow object to be cleaned. 11.- Device according to any one of claims 9, 10, characterized in that it further comprises means for closing secondary orifices (116, 116 ') that has the hollow object. 12.- Device according to claim 11 intended for cleaning hollow objects whose secondary orifices (116, 116 ') are connected to pipes (117, 117') characterized in that the sealing means comprise pneumatic buffers ( 15C, 150 ') made of balloons connected to an air circuit (151, 151'). 13.- Device for cleaning surfaces of the type comprising a containment enclosure (251) of a volume of liquid with an opening (230) to be directed onto the surface (231) to be cleaned, characterized in that it comprises at least one insonification head (211) according to any one of claims 1 to 8, the action part (234) of the head being immersed in said volume liquid. 14.- Device according to claim 13, characterized in that it comprises two insonification heads (211) mounted head to tail inside said confinement enclosure (251). 15.- Device according to any one of claims 13, 14, characterized in that said containment enclosure (251) is mounted inside a protective enclosure (261). 16.- Device according to claim 15, characterized in that it comprises a leakage suction device (258, 259) associated with said protective enclosure (261). 17.- A cleaning installation characterized in that it comprises a cleaning device according to any one of claims 9 to 16.

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