Abstract:
There is described an ultrasonic spraying device, comprised of a body wherein a core which generates piezo-electric vibrations, is arranged, said vibrations being conveyed to a spray nozzle which receives the liquid to be atomized, in which against the free end of said spray nozzle, a diaphragm is mounted which is so designed as to improve the atomizing characteristics of the liquid.

Description:
BACKGROUND OF THE INVENTION 
     This application is a continuation-in-part of prior application Ser. No. 855,968, filed Apr. 23, 1986, now abandoned. 
    
    
     This invention relates to an ultrasonic spraying device comprised of a body wherein a core which generates piezo-electric vibrations, is arranged, said vibrations being conveyed to a spray nozzle which receives the liquid to be atomized. 
     An object of the invention is to provide a device which markedly improves the atomizing features of the sprayed liquid. 
     Another object of this invention is to generate a compact bundle of microscopic moisture droplets in the form of a spray which, for a given vibration frequency, can be moved over a longer distance, and where the moisture particle size is smaller than usual. 
     The concept &#34;compact&#34; implies that the water droplets being spread by the spraying device and conveyed by the air, which form as it were a bundle, do not fall too fast downwards by gravity when leaving the spray nozzle, but should move as long as possible in a cone shape. 
     A device fitted with such a spray nozzle has already been described in Belgian Pat. No. 902,301. In a device as disclosed in said Patent, problems are encountered due to the sprayed liquid moving downwards soon after leaving the spray nozzle, in such a way that the surface area which is reached by the sprayed liquid, is relatively limited. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to obviate said drawbacks and to provide a spraying device which makes it possible to cause the sprayed liquid to reach with a much higher homogeneity, at a relatively long distance, a large surface area. 
     To obtain such a result according to the invention, against the free end of said spray nozzle, a diaphragm is mounted which is so designed as to improve the atomizing characteristics of the liquid. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other details and features of the invention will be apparent from the following description, given by way of non-limitative example and with reference to the accompanying drawings, in which: 
     FIG. 1 is a partial lengthwise section through the spraying device according to the invention. 
     FIG. 2 shows diagrammatically a fluid bundle sprayed from an ultrasonic spraying device which is not fitted with a diaphragm. 
     FIG. 3 shows a fluid bundle sprayed from a spraying device which is provided with a diaphragm according to the invention. 
     FIGS. 4 and 5 show alternate embodiments of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The device as shown in FIG. 1 comprises a body 1 wherein a core 2 is mounted, which comprises the required piezo-electric components to generate the desired ultrasonic vibrations. Reference number 3 refers to conductors which lead to connectors 4. The core 2 is joined to a spray nozzle 5, the free end 6 of which has for example, but not necessarily, an enlarged cross-section. Body 1 is linked to an extension 7, which surrounds completely said spray nozzle 5. 
     The supply of the liquid to be atomized comes from a supply 8 to a center channel provided in said spraying nozzle 5, although the liquid may also flow outwardly along the spray nozzle 5. 
     To improve substantially the atomizing characteristics of the sprayed liquid, according to the invention, a diaphragm 9 is provided in contact with the enlarged part 6 of spray nozzle 5. 
     The presence of said diaphragm 9, which contacts the enlarged part 6 of spray nozzle 5, comprises essentially the essence of the invention. 
     Although the spray nozzle shown by way of example has enlarged part 6, the invention may naturally also be applied to spray nozzles which have a completely different shape. 
     It has indeed been ascertained that atomizing of the liquid in a device fitted with the above-defined means for generating ultrasonic vibrations, occurs under particularly favorable conditions. Indeed, by atomizing the liquid through a diaphragm engaging a spray nozzle of the above-defined type, a bundle of microscopic liquid droplets is generated, and this bundle still has a compact structure at a suitable distance from said spraying device. Such a compact structure, the general appearance of which approximates a cone, is shown diagrammatically in FIG. 3. 
     When no use is made of a diaphragm according to the invention, the bundle generated by the spraying device occurs substantially according to the profile shown in FIG. 2. 
     In FIG. 2 it may indeed be noticed that the sprayed liquid droplets fall downwards directly after leaving the spray nozzle. This means also that the area which is reached by the sprayed liquid droplets is limited and is only a short a distance from the spray nozzle. 
     Such drawbacks are obviated with the spraying device according to the invention, whereby a cone-shaped bundle 10 is generated in a manner which allows the spray to reach longer distances, and to cover a larger surface area, in a more homogenous manner. 
     Diaphragm 9 may be made of a variety of materials. The diaphragm may be comprised of a fabric made from natural, synthetic, glass or carbon fibers, and the diaphragm may also be formed by a perforated material or a moisture-pervious non-woven material. 
     Remarkable results have been obtained with fibers which are manufactured by the Dupont de Nemours company under the trade name &#34;KEVLAR&#34;. 
     A requirement lies in the diaphragm 9 engaging said spray nozzle 5. It is assumed that the vibrations being imparted to the diaphragm accelerates the liquid particles which flow through the diaphragm. It has also been determined that the air dynamics are changed by the use of such a diaphragm, and that there is a strong air displacement of the liquid particles which contributes to the displacement over the required distance. 
     This explains why the bundle fluid or water droplets which appear thereby, acts as shown in FIG. 3, together with the acceleration of the surrounding air. 
     When the sprayed liquid, particularly those droplets which compose the spray, is not sufficiently accelerated, the result is a profile such as shown in 11 in FIG. 2, with all the drawbacks connected thereto. 
     With the embodiment illustrated in FIG. 1, extension 7 includes an inside surface 12 that extends around outlet 6 of nozzle 5, and this surface defines an inside, circumferentially extending groove 14. A ring is secured in the groove, and diaphragm 9 is held between this ring and nozzle 5 to atomize the liquid discharged from the nozzle outlet. Further, with this embodiment, extension 7 includes a first cylindrical member 7a connected to and extending forward from body 1, and a second cylindrical member 7b releasably connected to and extending forward form the first cylindrical member 7a. Preferably, second member 7a defines the above-mentioned circumferentially extending groove 14. 
     FIGS. 4 and 5 disclose alternate spraying devices also in accordance with this invention. These alternate devices include many elements, such as body 1, core 2, leads 3, connectors 4, spray nozzle 5 and diaphragm 9, that are either identical to or very similar to the corresponding element of the spraying device shown in FIG. 1, and it is not necessary to describe these elements of FIGS. 4 and 5 further. 
     The principle difference between the embodiment of FIG. 1 and the embodiments of FIGS. 4 and 5 relate to the construction of extension 7. With each of the embodiments shown in FIGS. 4 and 5, the first member 7a of extension 7 is releasably connected to body 1, the second member 7b of extension 7 is captured between part 7a and body 1, and diaphragm 9 is capturec between members 7a and 7b. Preferably, first member 7a includes a radially inwardly extending ring portion 16, and second member 7b is axially captured between the ring portion and a radial flange 1a of body 1. 
     This arrangement is of utility for several reasons. First, it helps to assemble the ultrasonic spraying device; and, in particular, facilitates locating diaphragm 9 in place, and, if necessary, replacing the diaphragm. Second, preferably member 7a may be moved forward and rearward at least slightly relative to the body of the spraying device, and this allows the pressure with whcih diaphragm 9 is held against nozzle 5 to be varied. Adjusting this pressure modifies within large ranges the characteristics of the nebulized liquid discharged from the spraying device. 
     With the arrangement shown in FIG. 4, outer member 7a is in a tight pressure fit with a forward cylindrical portion 1b of body 1, and a seal 18 may be located between outer member 7a and body portion 1b to prevent liquid from leaking through the interface between these two parts. Alternately, as shown in FIG. 5, outer member 7a may be threaded onto forward cylindrical portion 1b of body 1.