Abstract:
The invention concerns a device comprising a rotary body ( 1 ) made of a fibrous or porous material, means for rotating ( 3, 4 ) said body ( 1 ) and means for inputting liquid ( 10, 11 ) contacting said body ( 1 ), so as to subject said liquid to the dispersing action of forces at the liquid/solid interface, and to rotate the body ( 1 ) so as to subject the comminuted liquid to a centrifugal force.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The present invention relates to a method and device to disperse a liquid which can be used in particular, but not exclusively, for mist propagation i.e. the dispersion of the liquid in droplets of adjustable size, ranging from fine, ultra-fine droplets to a stage very close to vaporization. 
     2. Description of the Prior Art 
     Generally, it is known that to disperse a liquid mass, devices are usually used which have recourse to high pressure pumps feeding spray nozzles, optionally assisted by ultrasound. Another solution consists in using jets of compressed air used to fragment the liquid phase e.g. similar to a paint gun or airbrush. 
     At all events, they are complex devices, delicate to regulate and relatively costly. In addition, they require particularly demanding maintenance (risks of clogging), they are very difficult to adjust and require a relatively high energy supply. 
     OBJECT OF THE INVENTION 
     One particular purpose of the invention therefore is to solve these problems and to reduce these drawbacks so as to obtain simple, efficient dispersion devices which are easy to maintain and yet low cost. 
     SUMMARY OF THE INVENTION 
     For this purpose it proposes a dispersion method consisting of subjecting the liquid both to the dispersing action of forces which develop spontaneously at the interface between a liquid and a solid, such as a capillary force for example, and of causing the solid to rotate so as to subject the fragmented liquid to a centrifugal force causing its extraction and spraying in the surrounding medium in the form of drops, droplets, ultra-fine droplets, vapour. 
     Advantageously the supply of liquid to the solid can be ensured either:
         by aspiration due to centrifugal force;   by capillarity, by means of a material that is porous or fibrous or powdery for example, having the required affinities with the liquid so that the phenomenon of capillarity can develop,   by pumping, using pumping means, or   by gravity e.g. using a drip.       

     Also the above-said solid may be heterogeneous and may comprise a fraction exerting an interactive attraction force on the liquid, and a fraction exerting an interactive repelling force on the liquid. 
     Additionally, having regard to the fact that the solid is caused to rotate, it is possible by means of a particular conformation of the solid and/or of additional elements associated with it, to set up an air stream which, when applied to the fragmented or vaporized liquid, completes the dispersion of the liquid in the surrounding medium. 
     Therefore, fragmentation may be applied to a larger volume of surrounding medium. 
     Evidently, the invention concerns devices to implement the method just described. 
     These devices therefore have recourse to a rotating body in a solid material, rigid or flexible, which may for example be fibrous (micro-fibrous), porous, cellular or micro-cellular, to means for driving said body in rotation and to liquid intake means in contact with said body. 
     Preferably, the body may have symmetrical outer shapes relative to its axis of rotation. 
     The radial faces of the body may be at least partly coated or impregnated with a sealing layer. 
     The body may be rotatably mounted via a hollow drive shaft used to supply it with liquid. In this case, the liquid intake may be obtained by means of the aspiration generated by the centrifugal forces exerted on the liquid inside the body and/or by assistance means using capillarity and/or pumping means. 
     As a variant, the intake of liquid on the body may be made under gravity, by means of a dispenser e.g. of drip type arranged above the body. 
     It has been found that if the rotating body is a porous or fibrous body having orifices on its periphery for the passing of liquid, the size of the droplets generated during rotation is variable in relation to the size and shape of these orifices. 
     Having regard to this finding, the invention provides for the use of a body in compressible material, and for the adjustment of this size and shape:
         either by an adjustable, permanent mechanical action exerted on the body to cause compression or expansion of the body material at least at its periphery,   or by automatic or automated action, such as servo-control by a parameter such as the speed of rotation of the body, in particular so that it is possible to adjust the size of the droplets in relation to this parameter e.g. the rotating speed of the body.       

     Additionally, the device of the invention may comprise means allowing an airflow to be generated so as to channel the fog generated by the body, particularly for an application such as painting or phytosanitary treatment. In this case, deflection means may be provided so that the channelled fog has a circular or rectangular section similar to a conventional brush. 
     Advantageously:
         Said above body may be arranged between two disks variably spaced apart, the adjustment of the spacing possibly being obtained by screwing a screw on the rotating shaft of the body;   The means to adjust the size and shape of the body orifices may exert a mechanical action in relation to the speed of rotation, for example by means of weights arranged in said body so that, in the peripheral region of said body, they exert a pressure that is proportional to the speed of rotation of the solid,    For this purpose, the body may be arranged between two cups whose peripheral edges converge towards each other;   The said above weights may be arranged in an annular region of the body and be linked together by a coaxial elastic ring;   The drive shaft of the body may pass through a chamber delimiting an annular recipient intended to contain the liquid to be sprayed and whose bottom part is provided with liquid dispensing means able to supply a controlled flow of liquid to the body.       

    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the device according to the invention are described below as non-limiting examples with reference to the appended drawings in which: 
         FIG. 1  is a schematic cross-sectional view of a first embodiment of the invention; 
         FIG. 2  is a schematic cross-section of a variant of embodiment of the device in  FIG. 1 ; 
         FIG. 3  is an overhead view of the disk used in the devices illustrated  FIGS. 1 and 2 ; 
         FIG. 4  is a schematic axial section of a dispersion device comprising mechanical adjustment means of droplet size; 
         FIG. 5  is an axial section of the rotor of a dispersion device with self servo-control for adjustment of droplet size. 
     
    
    
     In the example shown  FIG. 1 , the device of the invention has recourse to a horizontal rotor  1  comprising a disk  2  in porous material, for example fibrous, micro-fibrous, alveolar optionally having antiseptic, viricide and/or catalytic properties. 
     This disk  2  is driven in rotation by an electric motor  3  positioned underneath the disk  2 , by means of a coaxial drive shaft  4  and coaxial circular plate  5 . 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In this example the lower face of disk  1  is coated with a sealing layer  6  impervious to liquids and gases. 
     The fixing of disk  2  on the plate  5  is achieved by gluing. 
     The upper face of the disk  2  is partly coated with a ring-shaped sealing layer  7  which, in its centre, delimits an exposed area  8  used for the intake of liquid. 
     This liquid is delivered in the form of a succession of drops  9  supplied by an adjustable drip  10  fed from a liquid recipient  11 , the assembly being positioned above the disk  2 . 
     Optionally, the liquid intake zone  8  is edged with a feed chute  12  here shown in the form of a tubular sleeve to prevent the drops delivered by the drip from being carried away by the air stream resulting from rotation of the disk  2 . 
     Optionally, the upper face of the disk  2 , at the sealing layer  7 , is equipped with blades or vanes  13  used to generate a radial air stream on the periphery of the disk. 
     For a similar purpose, the lower face of the disk may be equipped with similar blades or, as illustrated by the dashed line, with a ring  14  in porous material, e.g. fibrous or alveolar, with open cells. 
     Optionally, the recipient  11  equipped with the drip  10  may be connected to the motor structure via U-bars  15  or similar. 
     The functioning of the above-described device is therefore as follows: 
     The disk  2  is driven in rotation by the motor  3  at a speed in the order of 5000 to 15000 rpm for example (in relation to the diameter of the disk). 
     In parallel, the drip  10 , at an adjustable flow rate, delivers a succession of drops which fall on the intake area  8  of the disk  2 . 
     Each drop  9  is absorbed by a central part of the disk  2  and is distributed therein three-dimensionally under gravity but chiefly by capillarity. In this region, the centrifugal force applied to the liquid is relatively low: it is essentially the capillary forces which fragment the liquid in the thickness and towards the periphery of the disk  2 . 
     The more liquid approaches the periphery of the disk  2 , the greater the centrifugal force becomes relaying the capillarity forces and thereby accelerating the radial displacement of the fragmented liquid which nevertheless follows a pathway imposed by the capillary forces. 
     At the periphery of the disk  2 , the centrifugal force exerted by the fragmented liquid is greater than the interaction forces between the liquid and the solid material in rotation. On this account, the fragmented liquid is expelled in the form of fine or very fine droplets which are carried away radially by the airflow generated by the blades  13  and/or ring  14  in porous material. 
     To facilitate impregnation of the central part of the disk  2  and to increase the fragmenting of the liquid at this level, it is possible to make provision in this central part for a cavity  16  leading to the outside in its upper part at the falling point of the drops  9  delivered by the drip  10 . 
     Similar to the peripheral edge of the disk, the edge of this cavity can assume most varied shapes. 
     For example,  FIG. 3  illustrates polylobate peripheral shapes both for the peripheral surface  17  of the disk and that  19  of the cavity  16 . 
     These shapes allow the intake and outlet surface of the liquid to be considerably increased. Regarding the peripheral surface  17  of the disk  2 , this enables the outlet flow rate to be increased and allows eddy currents to be generated which contribute towards increasing the fragmentation of the extracted liquid. 
     In the variant of embodiment illustrated  FIG. 2 , the disk  2 ′ is mounted on a coaxial, hollow rotating shaft  20  driven in rotation in its upper part by an electric motor  21 . 
     This hollow shaft  20  is closed in its upper part, and its lower part is immersed in a liquid contained in a recipient  22 . 
     At the point where it passes through the disk  2 ′, the tubular shaft  20  is provided with at least one side through-hole  23  leading onto the porous material of the disk  2 ′. 
     The upper and lower faces of the disk are coated with a layer sealed against liquids  24 ,  25  and gases. These faces may be provided with means allowing a radial air stream to be generated as in the preceding example (blades or ring in porous material). 
     The functioning of this device is similar to the preceding device. However, in this case, the rotation of the disk  2 ′, by centrifugal effect, generates a negative pressure inside the hollow shaft  20  and hence aspiration of the liquid contained in the recipient  22 . The aspirated flow rate is related to the speed of rotation of the disk  2 ′. It may be adjusted by calibrating the through-holes  23 . 
     Priming of the rise of liquid can be facilitated through the use of a wick in a material which absorbs the liquid to be sprayed. This wick may be arranged inside or outside the tubular shaft  20 . 
     In both cases, this wick must be in close contact with the rotating material of the disk  2 . 
     Therefore, when stationary, the liquid rises in the wick and comes to impregnate the absorbent material  26  of the disk  2 . Owing to the presence of this liquid, when the device is set in operation, this liquid already present in the absorbent material  26  is ejected under the effect of the centrifugal force and, by causing a negative pressure inside the tubular shaft  20  (much greater than that caused by ejection of the gas contained in the disk) ensures priming of the device. 
     In the example illustrated  FIG. 2 , the dashed line represents a tubular wick  27  surrounding the tubular shaft  20  and which crosses through layer  25  to reach the absorbent material  26  of the disk  2 ′. 
     If the wick occupies the entirety of the inner volume of the hollow shaft, the constituent material of the wick may be chosen so as to conduct separation between liquids of different types. For example, a hydrophilic wick will not allow fatty substances to rise. 
     As mentioned previously, the constituent material of disk  2 ′ may be heterogeneous and comprise several materials having different physicochemical properties with respect to the liquid to be sprayed. 
     In the example illustrated  FIG. 2 , the disk  2 ′ comprises a peripheral region  28  in which the porous or fibrous material has repellent properties with respect to the liquid to be sprayed. 
     By means of this provision in region  21 , the fragmented liquid driven by the centrifugal force will also be subjected to the repelling forces of this material and will undergo additional dispersion (instead of collecting on the surface of the material, it is released from it and is exploded). 
     Evidently, the invention is not limited to the embodiment just described. 
     For example, the disk  2 ,  2 ′ may be replaced by a rotating body of varied shapes, such as propeller blades designed to generate an airflow. 
     In the example illustrated  FIG. 4 , the dispersion device comprises a rotor  30  having two coaxial disks  31 ,  32  between which a lining  33  is arranged in porous or fibrous material that is elastically deformable. 
     These disks  31 ,  32 , each comprise, on their periphery, two rings  34 ,  35  that are axially offset and connected to the disk by a circular inset. 
     These two rings  34 ,  35  are oriented so that come to grip the lining  33  on its periphery. 
     The securing of the disks  31 ,  32  on the rotating drive shaft  36  is designed to allow adjustment of the space between the two disks  31 ,  32 . 
     For example, the disk  31  may be fixedly mounted on the shaft  36 , whilst the disk  32  is slidingly mounted on this same shaft  36 . The axial maintaining of the disk  32  can then be ensured by means of a screw  37  which screws onto the threaded lower end of the shaft  36 , a washer  38  possibly being inserted between them. 
     The disk  31  comprises a coaxial circular orifice  39  interrupted by radial linking elements. 
     This circular orifice  39  is bordered by a circular collar  40  which extends radially and slightly outwardly oblique fashion to form a kind of funnel. 
     The motor  41  used to drive the shaft  36  is secured to the upper part  42  of a chamber  43  which extends into the space lying between the motor  41  and the rotor  30 . 
     For this purpose, the upper  42  and lower  44  faces of the chamber  43  are provided with two respective central, coaxial bore holes O 1 , O 2 , through which the shaft  36  passes. 
     The lower face  44  is provided with a coaxial tubular sleeve  45  opening into orifice O 2 . The function between the sleeve  45  and the lower face  44  is a sealing junction so that the sleeve  45 , the peripheral wall  46  of the chamber  43  and the lower face  44  delimit an annular recipient  47  intended to contain a liquid to be sprayed. 
     Right above the circular orifice  39 , the lower face  44  is provided with at least one bore hole equipped with a drip  48  which may optionally be closable. 
     The functioning of this device is similar to those previously described. 
     Its structure allows it to be hung, by a ring  49  for example, which may be provided on the upper face of the motor casing  41 . 
     Nonetheless, the essential advantage of this apparatus lies in the possible adjustment of the size of the droplets generated by the rotor  30 . 
     For this purpose, all that is required is to vary the spacing between the two disks  31 ,  32  by screwing or unscrewing the screw  37  depending on the desired result. 
     This screwing or unscrewing causes a compression or expansion of a peripheral zone of the lining  33 , and consequently varies (narrowing/expansion) the orifices through which the fluid passes in said zone. 
     This variation causes a corresponding variation in the size of the droplets, independently of the speed of rotation of the rotor  30 . 
     In the example illustrated  FIG. 5 , the rotor R comprises two coaxial cups  50 ,  51  delimiting between them a space which encloses a lining G in an elastically deformable material. 
     The two cups  50 ,  51  each comprise a flanged peripheral zone  52 ,  53  for example of substantially truncated cone shape, and are arranged so that their concavities face one another. 
     The two cups  50 ,  51  are mounted fixedly on a drive shaft in coaxial rotation  54 . 
     The two cups delimit a space which becomes increasingly narrower at the flanged peripheral zones. 
     As in the example previously described, the upper cup  50  comprises a circular orifice  55  intended to receive drops of the liquid to be sprayed, this circular orifice  55  being edged by a circular collar  56  similar to collar  40 . 
     Also, inside the lining G two series of weights M 1 , M 2  are arranged each in an annular region located in the vicinity of the flanged peripheral zones  52 ,  53 . 
     The weights M 1 , M 2  of each of the series are connected together by an elastic coaxial ring  56 ,  57 . 
     The functioning of this device is as follows: 
     When the rotor R is driven in rotation at constant speed, the centrifugal force exerted on the weights M 1 , M 2  causes their displacement and consequently a compressive action of the lining G between the flanged zones  52 ,  53 . 
     On this account, in this zone the liquid passage orifices have smaller sections than when the rotor R was stationary. 
     An increase in the speed of rotation of the rotor R will cause a reduction in the section of the passage orifices and hence a reduction in the size of the droplets generated by the rotor. In parallel, the flow rate of the sprayed liquid (which undergoes a twofold phenomenon of accelerated liquid flow rate owing to the increased rotation speed, and slowing due to the increased load loss when passing through the compressed zone of the lining) will be maintained substantially constant, and may even decrease slightly. 
     On the contrary, a reduction in the rotation speed of the rotor R will cause an increase in the section of the above-said orifices and hence a reduction in the liquid flow rate. Here too the flow rate of the liquid remains substantially constant, with a widened droplet section. 
     In this example, the rotor R is arranged in a spray nozzle B that is funnel-shaped on whose walls an air stream is injected derived from generation means such as a fan or turbine, here indicated by blocks  60 ,  61 . 
     Therefore the fog generated by the rotor R is driven into the nozzle B without touching its walls. 
     It is then ejected from the nozzle B to be applied to a wall P. The outlet section of the nozzle B may be of any shape (e.g. circular, square, rectangular, oblong, etc. . . . ) as appropriate for the desired application. 
     Said solution may be suitable for numerous utilisations such as painting (an alternative to a paint gun), plant treatment, etc. . . . Evidently the type of liquid must be adapted to the type of treatment. 
     Evidently, the air stream generation means may consist of a turbine or turbine blades associated with the rotor.