FR2580198A1 - DEVICE FOR CLEANING ULTRASOUND MECHANICAL PARTS - Google Patents

Abstract

The device comprises a tank (1) receiving a cleaning agent in which a part (P) to be cleaned is immersed. The tank (1) is equipped with electroacoustic transducers (2) capable of generating powerful ultrasonic mechanical waves in the cleaning agent. Means (3) for generating periodic electric signals make it possible to supply the transducers (2). Means for regulating the frequency and the power of the ultrasonic wave (4, 5) are provided in order to adjust the abovementioned parameters. Furthermore, means (6) make it possible to focus the beam resulting from the ultrasonic wave emitted by the transducers (2). The focusing and/or the deflecting of the resulting beam towards the part to be cleaned permits an illumination of a selective treatment of this part. Application to the cleaning of mechanical parts in industrial part-treatment processes such as, for example, chromium plating.

Description

258,198

  The present invention relates to a device and a method for cleaning parts

mechanical ultrasound.

  In the current technique of cleaning ultrasonic mechanical parts the parts to be cleaned are placed in a tank containing a bath or cleaning agent in which is generated an ultrasonic wave intended to cause in the bath mechanical disturbances. These mechanical disturbances reaching the part or parts to be cleaned, cause in connection with the cleaning agent a

  stripping the free surface of the parts by detaching

  superficial particles of the material constituting the part, or traces of

  for machining, greases, glues or the like.

  The devices currently used

  certainly make it possible to obtain good results.

  However, it is necessary, in most cases, depending on the cleaning agents used such as water plus detergent, trichlorethylene, freon or the like, to use relatively large emission powers of the sound wave throughout the volume of the bath so that to obtain, at the

  of the only piece to be cleaned, a density of

  enough to obtain a proper cleaning effect. The electroacoustic transducers used must therefore be supplied with high level electrical energy for the duration of the cleaning treatment, which leads to high electrical power levels due to

  of the average efficiency, of the order of 66%, of the

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  cookers feeding transducers when these

  ci, according to the classical technique, are excited direc-

  from a sinusoidal alternating signal.

  The object of the present invention is to remedy the aforementioned drawbacks by the implementation of a device and a method in which the level of electric power necessary for the excitation of

  emitting transducers is significantly reduced by

  port to the devices of the prior art for a level

  of similar power in the vicinity of the part to be cleaned.

  Another object of the present invention is the implementation of a device and an ultrasonic cleaning method with a significantly improved efficiency. Another object of the present invention is the implementation of a device and a method of

  ultrasonic cleaning in which, due to the

  calibration of the ultrasonic wave beam, great flexibility of use of the device or the process

  is obtained, the cleaning of the parts can be

  taggedly programmed into cleaning sequences by

  determined areas of the room to be cleaned.

  The mechanical parts cleaning device

  ultrasound, object of the invention, comprises a tank for receiving a cleaning agent in which is immersed a piece P to be cleaned,

  the tank being provided with electronic transducers

  acoustic transmitters capable of generating ultrasonic power waves within the cleaning agent. The device of the invention is

  remarkable in that it includes general means

  periodic power signals for powering the transducers and means for regulating power and

  frequency of the ultrasonic wave emitted by the trans-

  transmitters. Means for focusing the beam resulting from the ultrasonic wave emitted by the emitting transducers allow focusing and / or deflection of the resulting beam towards the workpiece

to clean.

  The invention finds application in all parts machining processes prior to

  steps such as chromium plating or the like.

  It will be better understood when reading

  the description and the observation of the drawings

  FIG. 1 represents a general block diagram of an arrangement of emitter transducers, constituted in a two-dimensional plane array, on which the various geometrical parameters of FIG. definition

  the resulting beam and the focus or de-

  bending of it are represented and defined.

  Figures 3a and 3b show in

  longitudinal section of the tank, a detail of

  invention relating to the transducers emitting

tors,

  Figure 4 shows a schematic diagram

  more complete electronic circuits in accordance with the block diagram in Figure 1, 30. Figure 5 shows an example of

  particular realization of a phase-shifter or delay

  programmable transmitter according to the diagram of Figure 4, -4-

  Figure 6 shows the arrangement

  of a complete device controlled by a micro-

  computer allowing the establishment of sequences of

  determined in particular with regard to

  geometric meters or topology of the part to be cleaned. In the drawings, the different elements bear the same references, but however were not represented according to their relative rates and proportions so as not to impair their clarity and

their understanding.

  The device for cleaning mechanical parts

  sonic ultrasound shown in Figure 1, object of the invention comprises a tank 1 for receiving a cleaning agent in which is immergéeune part P to clean. The cleaning agents that can be used are those already mentioned earlier in the

  description. The tank 1 is provided with transducers

  electro-acoustic transmitters capable of generating ultrasonic power mechanical waves within the cleaning agent. In Figure 1, the

  transmitter transmitters referenced Ti are represented

  are arranged in a particular arrangement on a wall of the tank, the wall 10 constituting the bottom thereof. As an indication, the necessary power of the ultrasonic waves to obtain a satisfactory cleaning effect depending on the cleaning agent chosen as mentioned above must be between 1 and 5 Watts / cm of the surface of

the room to clean.

  According to the invention, the device further comprises periodic electrical signal generating means 3 for supplying the emitting transducers and means for regulating the power of the ultrasonic wave emitted by the emitters and regulating means 4 the frequency of the emission of the ultrasonic wave. All of the aforementioned means allows a fine regulation of the ultrasonic power or the ultrasonic power density emitted or

  to which the part to be cleaned is actually

put during treatment.

  Means 6 for focusing the beam

  resulting from the ultrasonic wave emitted by the trans-

  Electroacoustic conductors are furthermore provided for focusing and / or deflecting the resulting beam to the part P to be cleaned. It will be understood that the focus and / or flexion of the

  resulting beam ultimately allows localization

  sation of the ultrasonic energy emitted in an area defined substantially by a solid angle in a determined direction. The localization of the emission energy consequently makes it possible to reduce the electrical energy required to supply the transducers in order to obtain an energy density in the localized emission zone sufficient to obtain satisfactory cleaning compared to known devices of the prior art. On the

  figure 1, the stages of attack power of trans-

  ductors are not represented. A particular configuration of the emitter transducer network 2

  will now be described in connection with Figure 2.

  By way of nonlimiting example, the network 2 of emitting transducers may consist of a set of transducers distributed in a plane according to a rectangular mesh network comprising

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  -6- M columns of transducers aligned parallel to a first reference direction Ox and N lines

  transducers arranged parallel to one

  x direction Oy perpendicular to the first direction Ox. The network 2 thus comprises M × N transmitter transmitters, the center of the network substantially corresponding to a transducer is denoted 0 and the order of a line is denoted m, m between 1 and M, the order of a column being denoted n, n being between 1 and N. The emitting transducers Ti are spaced according to the directions Ox and Oy, the distance

  between each consecutive transducer in these guidelines

  tions that can be identical. This distance is noted d. In Figure 2, the direction perpendicular to the plane Ox, Oy containing the transducers is denoted Oz. Any point F of the space exposed to the radiation of the grating will thus be spherically co-ordinated by the parameters O0, 0F, Oz and *, angle of Ox with the projection of 0 on the plane

Ox, Oy containing the network 2.

  A theoretical calculation, conducted in the case o as previously described where the transmitters or sources are equidistant in the directions Ox and Oy and / or, in addition, these same transmitters are powered by signals of the same amplitude and are therefore subject to identical operating conditions

  causing the emission of sensitive ultrasonic waves

  of the same amplitude, the supply of each of the emitters being furthermore subjected to a phase shift of a constant value with respect to the neighboring emitters for the directions Ox, Oy, makes it possible to define the interference field parameters. set of sources at point F. For a phase difference between two consecutive sources taken equal to 1t x in the direction Ox and equal to qy in the direction Oy, the interference field of all sources at point F is given by the relation I below: + M / 2 + N / 2 j 2iLl (sinecos + txX> + n (sin6sin +) 7 = úE Ae X 2d 2d - d

-M -N

  2 2 in which A represents the emission amplitude of a transmitting transducer X the ultrasonic emission wavelength in the propagation medium

consisting of the cleaning agent.

  The maximum field, that is to say the maximum density of ultrasound energy at the point F is obtained when the parameters 80 and 0 satisfy the relation II below: 2S0Tin 80o = -OCosao {S 80 cs2ird Sin 80 sin 0 = Coseo This new relation II then makes it possible to define the direction, defined by the directional parameters O0, 0 in which the radiated resultant field is maximum, this direction being analyzed as the intersection of a first cone of axis Ox of half -angle

  at the top "o and a second cone of axis Oy, half

  angle at the top eo, these cones being defined by the

relation II above.

  The phase shifts tx and t y needed to ob-

  tion of a maximum field at a point F located in -8- no direction direction direction 80, e0 are given for the directions Ox and Oy of the network by the relation III below: î x = - 2_d Sin 0 0. Cos 0 At t * y = 2rd Sin 00. Sin m0 In relation III the sign - indicates that the maximum field direction is inclined towards the negative phases, that is to say the delays with respect to the phase of the center O of the network . The value of the maximum resultant field obtained is equal to M x N x A o M x N is the total number of sources or emitters and A the amplitude radiated by an emitter. We will call

  focusing or deflecting the concentration or loca-

  of radiated ultrasonic energy in the direction

  60, 0 above. In addition, the distance d between the transmitters of the network may be chosen so as to eliminate the focus of the second order that can be obtained. In this case, the distance d satisfies the relation IV: d <1 + cos 6m m in which 6m represents the maximum admissible value for the half-angles at the apex of the cones defining the direction of the maximum field relative to

Ox and Oy axes already mentioned.

Ox and Oy axes already mentioned.

  In fact, it will be understood that, in addition to the efficiency increase already mentioned, the device of the invention, because of the focusing of the ultrasonic energy in a preferred direction, makes it possible to carry out a concentration of this energy. ultrasound in the above-mentioned localized area. This focusing has the effect of causing in particular in the vicinity of the part to be cleaned a series of overpressures and depressions in the propagation medium consisting of the cleaning agent, which have the effect in connection with this cleaning agent, to perform a stripping from the surface of the room. The phenomenon of stripping is actually obtained by a phenomenon analogous to a phenomenon

  cavitation due to overpressure and depression

  which causes turbulence around the resulting beam in the vicinity of the impact on the

  the room, causes the cleaning of it. The pro-

  pagation of ultrasound in the propagation fluid or cleaning agent causes the formation of bubbles that implode under the action of ultrasonic sound pressure. This implosion generates a very shock wave

  important. This phenomenon known as

  vitation originates in certain areas, functions

  parameters such as, frequency of emission,

  temperature, temperature. By way of non-limiting example, the emission frequency of ultrasonic waves is

  taken at 20 kHz or higher.

  In conventional methods, soils detached from the wall to be cleaned are suspended in the liquid, some of which can be deposited again on the part, the entire volume of the cleaning bath being subjected to ultrasound. In the case of focusing the ultrasound beam on the contrary,

  on the one hand, the local power density is sup-

  but an area of turbulence surrounds this area. The filtering of suspended particles in suspension is then more effective if it

  is performed on the course of turbulence.

  A detailed description of a mode of

  advantageous realization of the network structure 2 will now be given in connection with the

Figures 3a and 3b.

  According to the above figures, the trans-

  Ti ductors are attached to the wall 10 of the tank

protruding from it.

  In the devices of the prior art, the transducers consisting essentially of a piezoelectric ceramic sandwich and vibrating metal masses were fixed on a diaphragm secured to the wall of the tank at one end of the metal masses. However, in such

  devices, and in particular when using

  In the case of such transducers, the mechanical vibration of the vibrating masses is maximum at the free ends of the vibrating masses and minimum or zero at the center, that is to say at the junction

  two pellets of piezoelectric ceramic.

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  These types of transducers are perfectly

  known from the state of the art.

  necessary from the free end of a vibrating mass.

  to the diaphragm is normally performed by gluing, brazing or soldering. However, this technique has the disadvantage that the connection of the transducer to the diaphragm is located at the location of greater amplitude of vibration. This necessarily leads to fatigue of the mechanical connection

  diaphragm transducers and, in the long run, a function-

  faulty part of the whole. In addition,

  necessary powers to obtain the effect of net-

  in the absence of focus of the resulting beam most often require the presence

  several transducers on the same diaphragm.

  This last feature has the drawback of inevitable mechanical coupling between transducers located on the same diaphragm, any phase shift applied to one of the transducers being necessarily coupled to neighboring transducers. Therefore, there can be no independent transmission or definitive order

separated from the transducers.

  The particular embodiment shown by means of Figures 3a and 3b overcomes the aforementioned drawbacks. The transducers Ti, according to the invention, are attached to the wall iodine the tank in the vicinity of their middle part substantially. It will thus be understood that the transducers may be attached to the wall by brazing at the end of the

  not free of a vibrating mass, that is to say the

  mite of the vibrating mass directly in contact with one of the piezoelectric pellets constituting the transducer. This embodiment of course allows a better service life of the transducer connection wall of the tank since the connecting element used, such as a solder or a weld or the like, is subjected to a vibration of substantially zero amplitude or very weak. In addition, it will be understood that the absence or almost no vibration at the same link has the effect of virtually eliminating the coupling between the

  transducers, the wall 10 not transmitting

  no more vibration to neighboring transducers.

  Separate independent control of the transducers can therefore be envisaged with maximum efficiency

  the focus of the resulting beam.

  By way of non-limiting example, the transducers Ti consist of piezoelectric ceramics 103, 104, the vibrating masses 101, 102, the vibrating mass 101 being fixed to the wall 10 in the vicinity of the ceramic pellet.

  piezoelectric 103. The excitation of each trans-

  The conductor is obtained from an excitation wire 106 connected to an electrode 105 ensuring the junction

  piezoelectric pellets 103, 104. The trans-

  ductors can be attached to a removable portion of the vessel 1, the removable portion itself being able to constitute a wall of a sealed housing enclosing

  electronic control and power circuits

  tation of the transmitting transducers.

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  In addition, as shown in FIG. 3b, the arrangement of emitter transducers is constituted by a plate 100 in one piece on which are distributed pads 1011 or mechanical masses in a network configuration. Each pad 1011 is in fact intended to constitute the vibrating mass located in the tank of each transducer. The active part of each transducer is attached to each stud on the opposite face of the plate 100. In FIG. 3b, the same references 103, 104, 105, 106,

  represent the same elements as in Figure 3a.

  When the transducers are mounted on a removable plate in the case of Figures 3a or 3b, a seal 110 may further be provided to ensure a repetitive assembly / disassembly of the removable plate

  for cleaning purposes for example. The mode of realization

  3b, also has certain advantages from the point of view of ease of use, the plate 100, in one piece, can be machined under conditions of mechanical tolerance quite satisfactory, which allow a good

  focus accuracy of the resulting beam.

  A more complete description of the circuits

  electronic devices of the entire device of the invention will now be given by means of the

Figures 4 to 6.

  As shown in FIG. 4 and 1 in particular,

  means for regulating the power and the frequency

  The emission of the ultrasonic wave comprises a receiver transducer 7 disposed in the tank and preferably placed in the vicinity of the location intended for the part P to be cleaned. As represented in a way -14-

  non-limiting in FIG. 1, the transducer

  7 may be removably mounted relative to the part P in a direction of translation noted for example

  X parallel to the network 2 and in the vertical direction

  Z. The receiving transducer 7 thus allows a survey of the ultrasonic power received by the part to be cleaned P in different localized areas of the surface thereof. The transducer 7 can be mounted on a movable carriage, which will not be

  described as well known for the state of the art

  Picnic. The transducer 7 delivers an electrical signal representative of the frequency and the transmission power of the ultrasonic wave emitted by the emitting transducers to a first detection circuit 4 capable of generating a signal proportional to the frequency of the electrical signal delivered by the receiving transducer 7. The signal delivered by the receiving transducer 7 being substantially sinusoidal, the detection circuit 4 may consist of a commercially available zero cross detection circuit or a frequency discriminator. The signal delivered by the receiver bansducer 7 is also also delivered to a second detection circuit 5 capable of generating a signal proportional to the level of the electrical signal delivered by the receiving transducer 7. The second detection circuit 5 may be constituted by a

  simple double-wave rectification circuit

  then producing a signal representative of the power of the signal generated by the receiver transducer 7 and therefore of the power of the ultrasonic wave emitted by the emitting transducers 2 or of the ultrasonic power received by the localized zone of the part subjected to the beam impact. The signals delivered by the detectors 4 and 5 then make it possible to control

  the generator means 3 of periodic electrical signals

  diques for feeding the transducers. The assumption of the transmission frequency of the ultrasonic wave and the transmission power can thus be implemented with respect to respective reference values of

  frequency and / or transmission power.

  In order to ensure servocontrol

  and in the aforementioned transmission power, the general means

  In this embodiment, the emitters 3 preferably deliver to the emitting transducers 2 electrical signals formed by adjustable rectangular frequency pulses of recurrence frequency. Of course, the frequency of recurrence of the signals is controlled from the signal delivered by the detection circuit 4. Similarly, the generator means 3 deliver to the transmitting transducers electrical signals with an adjustable duty cycle, thereby enabling the regulation of the power. of the ultrasonic wave emitted by the emitting transducers. Of course, the control of the value of the duty cycle signals delivered by the means

  generators 3 is carried out from the deli-

checked by the detector 5.

  The power supply of the emitting transducers by means of rectangular pulses therefore allows precise control of the transmission parameters, which are the frequency and the transmission power. This type of power supply of the emitting transducers also makes it possible to improve the efficiency of the electrical circuits, as well as to reduce the width to

  6 dB beams emitted by the transducers.

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  The generating means 3 can be

  stored by a frequency generator of recurrence frequency and duty cycle adjustable and for example by an integrated circuit MC 3420 distributed by MOTOROLA.

  In accordance with the embodiment

  4, the generator 3 controlled by the detectors 4 and 5 delivers the rectangular pulses to focusing means 6 of the beam resulting from the emitted ultrasonic wave constituted by programmable delaying means. The programmable delay means 6 comprise a control input denoted C and a plurality of outputs denoted S each connected to a transducer Ti of the network 2. In FIG.

  the connection between an output S of the means of

  6 and a Ti transducer has been shown by means of power circuits capable of generating

  impulses that may excite the transduc-

  T.sub.rms, of course keeping the phase relationships or delays between pulses in accordance with the phase laws as previously given by means of the relation III. In Figure 4, as a non-standard example

  limiting, power circuits have been

  as consisting of two circuits mounted in

  parallel 41, 43, 46; 42, 44, 47 allowing the application

  cation of a power voltage pulse to an isolating transformer 48. By way of non-limiting example, the circuits 41, 42 may be

  optoelectronic coupling circuits

  galvanic isolation of all

  control circuits of the power control part

  ciency. These circuits are normally available commercially. The circuits 43 and 44 are logic circuits of control and control, allowing the corresponding control of power switching transistors constituting the circuits 46 and 47. It will be noted that the switching transistors constituting the circuits 46 and 47 mentioned above, are connected in in series with the primary winding of the isolation transformer 48 so as to apply thereto a DC voltage of a + rated power supply on the circuit 46. The control logic circuits 43 and 44 will not be a

  detailed description because their function is limited

  the restitution of the pulses transmitted by the opto-electronic coupling circuits 41 and 42 with possibly, if necessary, additional functions capable of ensuring the safety of the switching generated by the switching transistors of the circuits 46 and 47. The winding

  secondary isolation transformer 48 is-

  tres] .ied to the transmitting transducers Ti through

  For example, a compensation circuit 49 makes it possible, for example, to obtain calibrated pulses of the same level for each transducer. It will of course be understood that each of the outputs S means

  6 is connected to the transducers emitting

  corresponding Ti by a power circuit

  identical to that shown in FIG.

  Focusing means 6 will now be

  The focusing means 6 are constituted by delay circuits able to deliver the pulse each.

  or the impulses delivered by the general means

  3 with a delay determined by the address and

  the position of the corresponding transmitter transmitter Ti.

  The excitation delay of each transducer, obtained by the corresponding delay of the pulses applied to the excitation electrode 106 of the transducers, makes it possible to apply the phase shifts qx 'fy to each transmitter transducer of the network 2 as a function of the address. m, n of this to obtain a focus of the beam in a given direction

  80, 0 according to the relation III already mentioned by way of non-limiting example, the circuits or the delaying means,

  as shown in FIG., comprise a plurality of type D flip-flops connected in cascade. In FIG. 5, the flip-flops have been denoted 1 to R. Each flip-flop receives a synchronization clock signal denoted H and the Q output of a smaller order flip-flop R is connected to the flip-flop input. next. The entrance to the

  first toggle receives the pulse signal

  gules delivered by the pulse generator 3.

  Thus, for a clock signal H constituted by pulses whose recurrence period is AT, not a minimum of phase shift, the output Q of any k-order latch delivers a delayed pulse relative to

  the impulse delivered at the entrance of the first bas-

  1st order by the 3 delayed generator of k x AT.

  The output of each of the D-type flip-flops is furthermore connected to the power stage of the emitting transducers via a selector circuit

  of channels noted 61 in FIG.

  The channels 61 may be constituted by channel selector circuits programmable on 8, 12,

  16 bits, depending on the number of channels, normally available

  in the trade. Each channel selector circuit61 is

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  Further connected to a control BUS 62 constituting in fact the control input denoted C shown previously in FIG. 4. The circuits or means

  retarders as shown in FIG.

  thus put to apply a quantized phase shift value on a determined number of levels of elementary values to the pulses feeding each

  transducers according to a program likely to

  tible to take into account, of course, the direction in which it is necessary to focus the ultrasonic energy into the resulting beam, but also

  other parameters such as shape and dimensions

  the room to be cleaned, the opening angle of the beam, the level of ultrasonic energy to apply

  per piece according to the cleaning agent constitut-

  killing the propagation medium, all the aforementioned parameters can be organized to constitute any optimal sequence of cleaning the room based on the past treatment or treatments

or later applied.

  A particularly advantageous example of

  complete assembly organized around a device according to the invention will now be described in connection with

with Figure 6.

  According to the representation of this figure-

  the device of the invention comprises a micro-

  computer rated MO and a visualization monitor noted CV. The microcomputer is of course equipped with peripherals such as magnetic disk mass memories, for example. The MO microcomputer and the CV display monitor are connected

2 58 0198

  A logic processing system denoted L. The processing logic system denoted L is itself connected by means of the BUS 62 to the focusing means 6, that is to say to all the selectors 61 as shown in FIG. 6. A management program for the entire installation such as

  shown in Figure 6 allows the conduct of the

  above cleaning of a part P placed in the tank, following the following operations: - the geometric parameters of the part P are first introduced by means of the keyboard of the microcomputer MO or a digitizing table as data or parameters definition of cleaning sequences. Other parameters such as in particular the solid angle under which the part is seen with respect to the phase center O of the network 2, opening angle of the resulting ultrasonic wave beam are also introduced by this same means. The management program generally stored in the central memory of the microcomputer, a program of the "menu" type, furthermore makes it possible, upon display prompting on the display monitor in particular, to introduce any driving parameter of the cleaning process such as, for example coded information regarding the cleaning agent used, the level of energy required in view of the agent

* cleaner used, the duration of treatment.

  in the case of the cleaning of very large pieces (several meters) and / or of parts comprising parts of different types of materials, the aforementioned management program also provides for the introduction of geometrical parameters such as as coordinates of the center of the different parts constituting the part, nature of the different constituent materials and corresponding processing time. In the case where the part or parts are of very large dimensions relative to the useful section of the resulting beam, a sub-program also makes it possible to carry out a periodic scanning of the surface of the part or of a part according to a path or pre-established sequence to ensure homogeneous cleaning of the part or

of the aforementioned piece.

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Claims (15)

  1. Device for cleaning mechanical parts   ultrasound devices comprising a tank (1) for receiving a cleaning agent in which a part (P) to be cleaned is immersed, the tank (1) being provided with emitting electro-acoustic transducers (2) capable of   to generate ultrasonic mechanical waves of   in the cleaning agent, characterized in that said device further comprises: - generator means (3) periodic electrical signals for supplying said transducers, - means (5) for regulating the power of the ultrasonic wave emitted by said transducers, means (4) for regulating the emission frequency of the ultrasonic wave, means (6) for focusing the beam resulting from the ultrasonic wave emitted by said electroacoustic transducers said focusing means for focusing and / or deflecting the resulting beam to the workpiece to be cleaned. 2. Device according to claim 1, characterized in that said means (3) generators deliver to the transducers electrical signals formed by rectangular frequency pulses. adjustable recurrence.   3. Device according to one of the claims   1 or 2, characterized in that said general means   transmitters to the transducers   controllable duty cycles, thereby enabling regulation of the power of the wave   ultrasound emitted by the transducers. -23-   4. Device according to one of the claims   preceding, characterized in that said transducers   electro-acoustic transmitters (Ti) are arranged   on a wall of the tank according to a specific arrangement   said transducers being protruded by relative to the wall of the tank.   5. Device according to claim 4, characterized in that said transducers (Ti) are fixed to the wall (10) of the vessel in the vicinity of their middle part substantially.   6. Device according to claim 5, characterized in that said transducers are attached to a removable portion of the wall of the vessel, said removable portion itself being able to constitute a wall of a sealed casing enclosing the circuits   control electronics and power supply for trans- transmitters.   7. Device according to one of the claims   or 6, characterized in that the arrangement of transmitter transmitters is constituted by a plate in one piece, on which are distributed pins or mechanical masses distributed in a network, the part   of each transducer being reported   to each stud on the opposite side of the plate.   8. Device according to one of the claims   prior art, characterized in that the control means   tion of the power and the frequency of emission, the ultrasonic wave comprise: a receiving transducer (7) disposed in the tank and preferably located in the vicinity of the location intended for the part (P) to be cleaned; said transducer (7) delivering an electrical signal representative of the frequency and the transmission power of the ultrasonic wave of the transmitting transducers; a first detection circuit (4) capable of generating a signal proportional to the   frequency of the electrical signal delivered by the   receiving conductor, - a second detection circuit (5) capable of generating a signal proportional to the level of the   electrical signal delivered by the receiving transducer   representative of the power of the wave   ultrasound emitted by the transducers.   9. Device according to one of the claims   1 and 7, characterized in that said generating means (3) consist of a pulse generator to   recurrence frequency and adjustable duty cycle.   10. Device according to one of the claims   previous, characterized in that said means (6) for focusing the beam resulting from the ultrasonic wave emitted by said emitting transducers   are constituted by program delaying means   connected between the output of the said general means   transmitters and transmitters, each   delaying means being able to deliver the pulse   delivered by the generating means (3) with a delay determined according to the address and the position of the   corresponding transmitter transducer.   11. Device according to claim 10,   characterized in that the delay means comprise   a plurality of D-type flip-flops connected in cascade, each flip-flop receiving a synchronization clock signal (H) and the output (Q) of a flip-flop of smaller order than R being connected to the input of the next rocker, the input of the first rocker 258O198   Receiving the rectangular pulse signal delivered by the pulse generator, the output of each of the latches being connected to the power stage of the transmitting transducers via a programmable channel selector circuit. Device according to claim 11, characterized in that said channel selectors   programmable are controlled by means of a micro-   computer, said microcomputer being connected to   channel selectors constituting the phase shifters   mables via a control logic.   13. A method of cleaning mechanical parts by ultrasound characterized in that it consists: - to place said piece (P) in a tank (1) containing a cleaning agent and comprising electro-acoustic transducers emtteurs (2)   capable of generating ultra-mechanical   sound power within the cleaning agent, - focusing and directing to said part (P) the resulting beam of the ultrasonic wave emitted by said electro-acoustic transducers, so as to cause ultrasonic radiation power density capable of generating, in the cleaning agent, in the vicinity of the room, zones of turbulence and cavitation causing cleaning it.   14. The method of claim 13, characterized in that it further comprises ensuring at the turbulence zones, filtering particles detached in suspension in the cleaning agent.   15. Method according to one of the claims   13 or 14, characterized in that it is conducted sequentially   tially by means of a microcomputer, said sequences being established according to the topology of the part (P) to be cleaned.