FR2655279A1 - METHOD OF MICRO-SPRAYING AN ULTRA SOUND SOLUTION AND DIFFUSER OF MICRO-DROPLETS IMPLEMENTING SAID DEVICE - Google Patents

Abstract

The invention relates to a method for atomising a liquid solution by ultrasound as well as a micro-droplet diffuser for the vaporisation of a liquid solution intended especially for forming a spray of disinfecting substances for aseptisation of medical premises. According to the invention, the ultrasound (3) is generated within a bath (1) of the liquid solution to be vaporised and the ultrasonic waves (3) are focused in order that they concentrate in a zone (4) of the surface of the bath (1). Thus, a fountain (5) is created in which micro-bubbles (7) burst in order to create a spray (6) of atomised liquid.

Description

The invention relates to a method of micro-spraying a

  ultrasonic liquid solution and a microdroplet diffuser for the vaporization of a liquid solution, intended for example in the medical environment for the emission of vapors of disinfectants, for the aseptic

premises, instruments or other.

  Although the invention has been specially developed in the context of the decontamination of surgery rooms, it can be extended perfectly to applications in which it is necessary to produce a calibrated micro-spray of a

  liquid solution with a relatively large production.

  Currently, the production of liquid micro-droplets, for example a disinfectant product, can be obtained according to three

different principles.

  The first apparatus that can be used comprises a propeller system, the helix of which is surrounded by baffles, and comprises a perforated hub, through which the solution to be sprayed is injected. For this purpose, the hub has lateral orifices through which the liquid escapes. in droplets Due to the strong centrifugal force at this level, the droplets are ejected

  radially with a large force.

  In addition, at the periphery of the propeller is placed a static grid on which the droplets are sprayed into a fog then driven by the main ventilation The unpowdered liquid part is recovered in the bottom of the device o

  a pump reinjects the liquid into the hub of the propeller.

  The advantage of this device is its simplicity, however care must be taken to ensure its proper operation to regularly clean it Its use is to be avoided in an atmosphere

  dusty and, its faults are unfortunately many.

  First of all, the spraying is poorly controlled too, large droplets are driven by ventilation and there is a phenomenon of supersaturation which results in a liquid condensation in the environment close to the apparatus In the case of a disinfectant product it means a strong

  consumption for a non-homogeneous aseptic.

  The second spraying technique uses the nozzle principle, in which the liquid to be sprayed is injected under pressure, and then, at the rear of the nozzle, an outlet nozzle is placed.

  of compressed air that drives the droplets emitted.

  This type of installation has a better efficiency than that described above but requires a pump and a compressor which greatly increases the cost of installation In addition the control of the micro-spraying is not guaranteed and one

  may encounter phenomena of supersaturation.

  The purpose of a diffuser is to vaporize a liquid, it is important that, in the technique used, the spray results in obtaining droplets of the smallest possible size Indeed, in this case, the ratio between the surface and the mass is optimum and the vaporization is easy since it is sufficient to bring the droplet a very small amount of heat for

result in its total vaporization.

  There is also a recent technique by ultrasound used to vaporize the liquids For this, it generates in the bath of liquid to vaporize ultrasonic waves which, on the surface of the liquid, because of the sudden variation of impedance creates a small spray of central water accompanied by a production of drops which, in combination with cavitation phenomena within the same

  liquid, creates a superficial fog.

  The micro-droplets that form this fog can be driven by a stream of air in which the micro-droplets evaporate. This micro-spraying principle offers great advantages, particularly in terms of the powers applied.

  game and micro-droplet dimensions formed.

  However, at present, these devices are unsuitable for the disinfection of premises because they have significant limits in terms of flow generated, which today are around 0.5 liters per hour, whereas such

  disinfection would require flow rates of the order of 2 liters per hour.

  In addition, there is no control over the size of micro-droplets

  formed and it is necessary to deplore at this level a great dispersion.

  The main object of the present invention is to present a method of micro-spraying a liquid solution by ultrasound which offers the advantages of being able to deliver a large flow rate compatible with the capacities required for the disinfection of premises and with which there is has a control of the size of the micro-droplets. The advantages of a stand-alone apparatus, of modest dimensions, are found, with, however, a better yield and a complete absence of risk of oversaturation of the environment. Therefore, the diffuser of the present invention is perfectly compatible with medical applications for disinfecting the environment. local

  o It is very efficient especially in terms of performance.

  Other objects and advantages of the present invention

  will appear in the following description which is not

  however given as an indication.

  According to the invention, the method of micro-spraying a liquid solution by ultrasound, intended in particular to form a disinfectant product mist, to sanitize the medical or other premises, according to which ultrasounds are generated within the body. a bath of liquid solution is characterized in that it focuses

  the ultrasonic waves on the surface of the bath.

  The diffuser of micro-droplets for the vaporization of a liquid solution, intended in particular for the emission of disinfectant product vapors, allowing the implementation of the process of the invention, which comprises a device for producing micro-droplets by ultrasound, placed in an air circulation duct for driving and diffusing the micro-droplets, is characterized in that the device for producing micro-droplets comprises means for concentrating the ultrasound, delivered by a transducer on the surface of the liquid solution. The invention will be better understood on reading the

  following description with accompanying drawings from

  which: FIG. 1 schematizes the principle of operation of the ultrasonic micropainting method according to the invention, FIG. 2 represents a first means for focusing the ultrasonic waves on the surface of the liquid, FIG. an advantageous embodiment of the focussing of the ultrasonic waves on the surface of the liquid, FIG. 4 is a cross-sectional view of the various components of the diffuser according to the present invention, FIG. 5 shows in sectional view the transducer, the Figure 6 shows the radiation pattern of a

apodized transducer.

  The present invention is directed to a method of micro-depigration of a liquid solution by ultrasound as well as a microdroplet diffuser for the vaporization of a liquid solution allowing the implementation of said method It will find particular application in the medical environment for disinfection

  premises by diffusion of a disinfectant product.

  Today, the asepsis of the surgical premises by the aerial is widely used To do this, one vaporizes in the atmosphere of the room a suitable chemical product by means of a diffuser Currently one uses mainly two types of diffusers, which are characterized by their principle of spraying the liquid solution, ie with fan or jet, such

as recalled above.

  Furthermore, it is known the technique of spraying a liquid by ultrasound, used in small power humidifiers that maintains ultrasonic waves in a liquid bath The waves on the surface cause a small spray of water central unit accompanied by a production of drops which, in combination with micro-bubbles created by cavitation generate a fog. In the case of the disinfection of medical rooms by vaporization of a liquid solution, it is imperative to be able to at least dispense two liters per hour of disinfectant In addition, to avoid any phenomenon of supersaturation of the air, it is preferable to limit the size of liquid microdroplets to 0.3 micron Beyond this, the atmosphere can not absorb the liquid element in gaseous form in a reasonable time and there is a risk of

condensation or non-vaporization.

  It is with these objectives of capacity and control of the micropulverisation especially with regard to the homogeneity of

  generated droplets that the present invention has been developed.

  For the application of the micro-spraying process of the invention, as shown diagrammatically in FIG. 1, there is found the bath 1 of liquid solution intended to be micro-sprayed, as well as a source 2 of ultrasound La frequency used for ultra-sound emissions is not imposed; however the range extending from 0.5

  megahertz at 5 megahertz is recommended.

  So far, we exploit the source of ultrasound in a "wild" way, that is to say that we simply

  waves to the surface without further precision.

  According to the process of the present invention, the ultrasonic waves 3 are focused on the surface 4 of the bath 1. Under these conditions, it is nowadays thought that cavitation bubbles are created on the surface of the liquid and that generate significant microdroplet production and

  reduced size, less than 0.3 micron.

  According to the present invention, it is recommended to focus the ultrasonic waves 3 on the surface 4 of the bath with oblique incidence relative to the level to form a homogeneous fountain 5 in the shape of an arc of a circle, as illustrated in FIG. Thus, there is created a fountain 5 which extends along the surface of the liquid and there is a formation of a fog 6 or

  aerosol all along the fountain 5.

  The fountain 5 forms a stream of cylindrical liquid which flows regularly. In general, for a given power, the

  regularity of flow of the fountain 5 is optimum.

  Thanks to the inclination of the fountain 5, the micro-bubbles 7, created inside the fountain 5, explode on the surface and form the aerosol 6 By focusing in a zone 4 of the surface of the liquid, Acoustic waves propagate in the jet of fountain 5 under strong power of o the creation of many

microbubbles 7.

  It is necessary to ensure the homogeneity of the micro-droplets that form the aerosol 6 and in this respect, it is necessary to have a large surface for the fountain 5 so that the micro-bubbles can freely emerge throughout the course of the liquid jet With respect to an almost vertical fountain, the inclined fountain of the invention has an upper surface for a

given energy and flow.

  The power of the ultrasound generally ranges from about 1 to 3 watts For each power, the fountain has a conformation

ideal to look for.

  As an indication, it is desirable to have a sufficient length of fountain as long as possible of the order of 1 to 10 -6 cm for a central elevation above the level of the liquid with a

  diameter of the jet from three to five millimeters.

  If the diameter of the fountain is too small, there is an increase in projections detrimental to the size of the microdroplets. As far as possible, secondary radiations are avoided which constitute energy losses and can disrupt the smooth operation of the production of calibrated micro-droplets. Therefore, we use a directional source 2 and in particular that does not exhibit lobes of

secondary radiation.

  There are several principles for focusing ultrasonic waves on the surface of the bath. The example of FIG. 2 shows the use of a source 2 whose profile concentrates the radiated waves 3 towards a point 4 of the liquid surface. practice, the use of a transducer 2 whose surface would have been dug in a concave profile to direct the waves to a focal point, gives

  some results but not fully satisfactory.

  Certainly, it has created a greater fog but the presence of large unwanted droplets has been recorded This lack of homogeneity in the particles formed is detrimental

  to the full vaporization of the product aerosol.

  On the other hand, better results have been obtained by using a source 2, as illustrated in FIG. 3, whose radiation is focused by reflection on a suitable geometric surface 8. The geometric profile of the surface can be determined.

  by applying the laws of reflection of the waves on a surface.

  FIG. 4 represents a diffuser 9 of micro-droplets for the vaporization of a liquid solution 10 allowing a setting

  process of the previously discussed method.

  The diffuser 9 comprises a device 11 for the production of microdroplets by ultrasound, placed in a vein 12 of air circulation, to entrain and diffuse into the atmosphere the microdroplets produced In the example chosen, the circulation of the air in the vein 12 is provided by means of a motorized propeller 13. The device 11 for producing micro-droplets firstly comprises an ultrasonic source 14 dipped into the bath of solution to be vaporized and means 15 to focus the

  ultrasound 16 at the surface 17 of the liquid solution 10.

  According to the invention, the means for focusing the ultrasonic radiation are in the form of a reflection surface 18 of ultrasound with a geometrical profile adapted to

  concentrate the radiation at a point 17 of the liquid level 10.

  For example, a parabolic metal mirror made of a metallic material such as steel can be used.

  very hard stainless steel and perfectly polished and homogeneous.

  In the example chosen, the reflection surface 18 is formed directly by the wall of the container containing the liquid solution to be sprayed. This container has at its upper part an opening through which the micro-droplets of fog are entrained by the air circulation. set in motion by the

fan 13.

  It is important to work with a constant liquid level so that the adjustment of the focal zone 17 is always perfectly adjusted. In this sense, an overflow orifice and a filling pump are used to maintain the liquid solution.

always at the same level.

  FIG. 5 shows in detail the embodiment of the ultrasound source 14. This is only an exemplary embodiment and other implementations could of course be adopted. The transducer employed is a patch 19 of piezoelectric material such as an aged ceramic. The front face of the patch 19 is supported on a metal cup 20, for example made of stainless steel, which comprises an electrical connection lug. The patch 19 and the cup 20 are placed in a box 22 made of

  preferably in an elastic or rubberized material.

  A second cup 23 rests on the back of the pellet 19 by means of tabs 24 which provide electrical contact. The cup 23 also has an electrical connection lug 25. It is necessary to avoid welding and cooling of

  the pellet is on the liquid side.

  By adjusting the thickness of the wafer 19, the resonance frequency of the ultrasound source is adjusted. The diameter of the wafer must preferably remain of reduced size, in particular of the order of twenty millimeters for a frequency of two megahertz,

  this to limit the appearance of secondary radiation lobes.

  Of course, the use of several sources in

  parallel ultrasounds can be perfectly considered.

  Figure 6 shows the desired radiation pattern

  for a source of ultrasound in the context of the present invention.

  The pellet of the transducer comprises two metallized surfaces respectively 26 and 27 of different surfaces With such asymmetry, the lobe 28 of radiation is unique, the traditional secondary lobes are completely eliminated The use of a

  Apodized pellet 19 is recommended.

  In the case of disinfection of premises, the vaporization of about two liters per hour of liquid solution is envisaged using a fan of about one thousand cubic meters per hour of flow and several sources of independent ultrasound and

  essentially different frequencies.

  This would make it possible to implement a disinfecting solution with micro-droplets of different sizes and

  to improve the efficiency of the product.

  Other implementations of the present invention within the reach of those skilled in the art could also be envisaged without

  however, to leave the framework of this one.

Claims (8)

  A method of micro-spraying a liquid solution by ultrasound, intended in particular to form a fog of disinfectants, for sanitizing medical premises or other, according to which ultrasound is generated (3> within a bath (1) of liquid solution (4) characterized in that the waves are focused   (3) ultrasonic sound on the surface of the bath (1>.   2 method for micro-spraying a liquid solution by ultrasound according to claim 1, characterized in that the ultrasonic waves (3) are focused on the surface (4) of the bath (1> with an incidence oblique to form a homogeneous fountain (5) in arc.   3 A method of micro-spraying an ultrasonic liquid solution according to claim 2, characterized in that the power and / or the frequency of the ultrasonic waves (3) are adjusted to obtain a fountain (5> about one to ten centimeters long   with a diameter of about three to five millimeters.   4 A method of micro-spraying a liquid solution by ultrasound according to claim 1, characterized in that one concentrates all of the ultrasonic waves (3> in a zone (4) of the surface of the bath (1).   Method for micro-spraying a liquid solution by ultrasound according to Claim 1, characterized in that the ultrasonic waves (3) emitted by a transducer (2) are focused   by reflection on an appropriate geometric surface (8).   6 Microdroplet dispenser for the vaporization of a liquid solution (10) intended in particular for the emission of steam from disinfectants, allowing the implementation of the method of claim 1, which comprises a production device (11> ultrasonic microdroplets, placed in a vein (12) for circulating air to entrain and diffuse the micro-droplets characterized in that the device (11) for producing micro-droplets comprises means for concentrating the ultrasound delivered by a transducer (14) to the surface (17) of the solution liquid (10).   7 micro-droplet diffuser according to claim 6, characterized in that the means are in the form of a reflection surface (15) of ultrasound (16) profile geometrically appropriate.   8 microdroplet diffuser according to claim 6, characterized in that the reflection surface (151 is formed by the wall of the container containing the liquid solution (10) to be vaporized 9. Microdroplet dispenser according to claim 8, characterized in that the reflection surface is formed of a perfectly polished parabolic metal mirror and very homogeneous.   Microparticle diffuser according to claim 6,   characterized in that the transducer (14) is apodized.