Patent Publication Number: US-8967493-B2

Title: Atomizing device

Description:
FIELD OF APPLICATION AND PRIOR ART 
     This application claims the priority of the German patent application No. 10 2010 024 913.0. The whole disclosure of this prior application is herewith incorporated by reference into this application. 
     The invention relates to an atomizer for atomizing liquids, more particularly pharmaceutical or cosmetic liquids. A generic atomizer comprises a liquid storage receptacle and an atomizing device comprising an atomizing chamber that communicates with the ambient atmosphere by means of a plurality of outlet orifices, and a vibrator, by means of which liquid present in the atomizing chamber can be caused to vibrate for the purpose of atomization. Furthermore, a generic atomizer comprises an intake channel, by means of which the liquid storage receptacle is connected to the atomizing device, and a pumping device that is provided in the intake channel for the purpose of conveying liquid from the liquid storage receptacle to the atomizing chamber. An electronic control device is provided for controlling the pumping device and the vibrator. 
     Generic atomizers are known in the prior art. They are used for atomizing liquids to a fine spray. These liquids are, in particular, pharmaceutical or cosmetic liquids. In the case of pharmaceutical liquids, the purpose of atomization can consist, for example, in the production of a very readily inhalable spray by means of the atomizer. In the case of cosmetic liquids, the purpose of atomization can consist in achieving a very homogeneous discharge by means of the atomizer, for example for the production of a very homogeneous layer of liquid on an area of the skin. 
     The pumping device of generic atomizers can serve the purpose of providing a continuous supply of liquid to the atomizing device. However, it has been found that it is difficult to coordinate the pumping device and the atomizing device in such a way that the pumped volumetric flow rate produced by the pumping device perfectly matches the rate of atomization of the liquid. In the case of an extremely high pumped volumetric flow rate, there is the risk of deterioration of the atomizing characteristics in that the liquid flows through the discharge orifices in a non-atomized state and covers the side of the discharge orifices remote from the atomizing device with a liquid film to obstruct atomization. In the case of an extremely low pumped volumetric flow rate, it is likewise impossible to achieve good quality atomization, since comparatively large amounts of air gather in the atomization chamber and counteract the discharge of liquid in an atomized form. These disadvantages are particularly problematic in an atomizer that is intended for use in different positions. This positional variability can be desirable for various reasons. Thus, for example, in an atomizer used for the inhalation of medicines, it is desirable that the atomizer be usable by the patient in different positions, for example, in a standing or lying position. In the case of an atomizer used for cosmetic products that are to be applied to different areas of the skin, it is difficult to do this when the atomizer is held in a constantly invariable position. The variable orientation of a generic atomizer intensifies the aforementioned problem since it can promote the entry of air into the atomizing chamber. In addition, pressure conditions in the atomizing chamber depend to a major extent on the orientation and movement of the atomizer. 
     In order to deal with the problem of achieving coordination between the pumping device and the atomizing device, it is known in the prior art, for example from DE 10 2004 006 452 A1, to activate the pumping device and the vibrator successively. Initially, the atomizing chamber itself and any capillary channel directly connected thereto are filled with liquid by means of the pumping device. Then the vibrator is activated in order to discharge the amount of liquid introduced into the atomizing chamber and the capillary channel. The disadvantage of such a design is that the amount of liquid discharged is small. It is thus impossible to achieve a continuous atomizing process. This is a considerable disadvantage in the case of some medicines and also in the case of cosmetic liquids. 
     OBJECT AND ITS ACHIEVEMENT 
     It is an object of the invention to develop a generic atomizer by achieving a continuous atomizing process whilst avoiding considerable effort in achieving coordination between the pumping device and the atomizing device. More particularly, it is desired to provide an atomizer that is suitable for use in an atomizing process in which it can be held at different orientations. 
     According to the invention, this object is achieved by the provision of a return channel, which is distinct from the intake channel and serves to drain liquid from the atomizing chamber into the liquid storage receptacle. Thus a channel leading from the atomizing chamber to the liquid storage receptacle is provided in such a design in addition to the intake channel through which the liquid is conveyed by the pumping device from the liquid storage receptacle to the atomizing chamber of the atomizing device. It is the primary task of this return channel to recirculate excess liquid from the atomizing chamber to the liquid storage receptacle. This allows the atomizing chamber to be fed at a volumetric flow rate of liquid that is significantly greater than the discharged volumetric flow rate as can be atomized by means of the atomizing device. The excess amount of liquid is not discharged through the outlet orifices, but instead it flows through the return channel back into the liquid storage receptacle. The return channel can be dimensioned appropriately for this purpose. This structure ensures continuous atomization of liquid, during which sufficient liquid is always available for the purpose of atomization in that a volumetric flow rate of liquid that is clearly greater than the atomized volumetric flow rate is fed continuously to the atomizing chamber. Furthermore, even if air enters the atomizing chamber through the outlet orifices, the return channel enables this air to be removed from the atomizing chamber and to flow together with the excess liquid into the liquid storage receptacle. Thus the atomizer of the invention ensures a very reproducible and constant atomizing process. 
     The atomizing device of an atomizer of the invention is similar to atomizing devices known in the prior art. The liquid present in the atomizing chamber is caused to vibrate by the vibrator, which is preferably in the form of a piezoelectric vibrator, such that a reproducible discharge of liquid through the plurality of very small outlet orifices is achieved under substantially constant pressure conditions in the atomizing chamber. The liquid discharged is replaced, by means of the pumping device, with liquid from the liquid storage receptacle. For this purpose, the pumping device is preferably in the form of a micropump. Such a micropump can have, for example, a pump chamber which is provided with an inlet valve and an outlet valve and which is cyclically enlarged and reduced in volume by means of one or more piezoelectric actuators. 
     For the purpose of achieving a homogeneous discharging behavior, the pumped volumetric flow rate of the liquid fed by the pumping device to the atomizing chamber is greater than the discharged volumetric flow rate of liquid passing through the outlet orifices. The discharged volumetric flow rate depends significantly on the design of the atomizing device and on the activation of the vibrator by means of the control device. The pumped volumetric flow rate depends on the design of the pumping device itself and its activation by the control device and the design of the channels conveying the liquid. The desired pumped volumetric flow rate that is greater than the discharged volumetric flow rate can be achieved by means of an appropriate design of the atomizing device, the pumping device, and the channels, and particularly by means of the activation thereof by the control device. 
     It is of particular advantage when the pumped volumetric flow rate is greater than the discharged volumetric flow rate by at least 20% during the atomizing process. It is more advantageous when the pumped volumetric flow rate is greater than the discharged volumetric flow rate to an even greater extent. It is even more advantageous when the pumped volumetric flow rate is greater than the discharged volumetric flow rate by 40% or more. The homogeneity of the atomizing process is ensured very effectively when the amount of liquid delivered by the pumping device is significantly greater than the amount of liquid atomized by the atomizing device. 
     In principle, it is feasible for the control device to be configured so as to start the pumping device and the vibrator simultaneously in response to a start signal, for example in response to actuation by a user. However, it is regarded as being advantageous when the control device is configured so as to activate the pumping device first in a preparatory phase before the atomizing process commences and to additionally activate the vibrator on termination of the preparatory phase. The preparatory phase, which preferably lasts at least 0.3 seconds and more preferably at least 0.8 seconds, ensures that the atomizing chamber is completely filled with liquid prior to activation of the vibrator and that a positive pressure ensues in the atomizing chamber due to the activity of the device. These are ideal set-up conditions for subsequent activation of the vibrator and thus for triggering the atomizing process. 
     Particularly to prevent liquid from being discharged through the outlet orifices of the atomizing device under the pressure generated by the pumping device during the preparatory phase, it is advantageous for the pumping device to be configured and/or to be activated by the control device and for the outlet orifices of the atomizing device to be configured such that the pressure ensuing in the atomizing chamber in the preparatory phase is not sufficient to force the liquid through the outlet orifices. This can be achieved by the use of small outlet orifices, by selecting a suitable shape of the outlet orifices, and/or by establishing a low pressure in the atomizing chamber. The pressure must be adjusted such that it suffices only in combination with the vibrations produced by the vibrator to force the liquid through the outlet orifices. A comparatively low pressure can be produced in the atomizing chamber by means of appropriate adjustment of the pumping device. However, a throttle that is distinct from the pumping device is advantageous for this purpose. 
     Basically any form of liquid reservoir can be used as the liquid storage receptacle. In the simplest case, the liquid storage receptacle can be, for example, a dimensionally stable liquid reservoir, into which a riser pipe connected to the pumping device extends. Particularly with regard to the functional efficiency of the atomizer in various orientations, it is considered to be advantageous when the liquid storage receptacle is in the form of a dimensionally flexible liquid-containing bladder that can adapt itself in terms of its internal volume to the amount of liquid present therein. Such a dimensionally flexible liquid-containing bladder does not require any aeration since, irrespective of the remaining volume, the pressure of the liquid in the liquid-containing bladder does not vary significantly, but instead is always equal to the ambient pressure. Such a liquid storage receptacle is filled exclusively with liquid except for the gaseous residues mentioned below, so that the pumping device will always draw in liquid. In the case of the present invention, the liquid storage receptacle has two openings, one of which is connected to the intake channel and the other to the return channel. The use of a liquid-containing bladder is additionally advantageous due to the very low risk of contamination associated therewith. 
     It is advantageous to provide a debubbling device since, inter alia, even the use of such a liquid-containing bladder cannot completely exclude the possibility of gas entering the liquid-containing bladder when the latter is being filled with liquid and the further possibility of air that has passed through the outlet orifices into the atomizing chamber of likewise entering the liquid storage receptacle by way of the return channel. The debubbling device is preferably provided in the intake channel and more preferably between the pumping device and the atomizing chamber. 
     This debubbling device ensures that the liquid fed to the atomizing chamber is free from gas bubbles, at least to a significant extent. Positioning of the debubbling device between the pumping device and the atomizing chamber additionally assists the removal of gas bubbles from the liquid in the debubbling device due to the pressure produced on the pump output side. Preferably, the debubbling device comprises a duct, through which the liquid flows on its way to the atomizing chamber and which is delimited, in part, by a filter surface. This filter surface allows the gas to escape at the pressure produced by the pumping device, while the pressure on the output side of the pump is not sufficient to force the liquid through the filter surface. Preferably, the filter surface is hydrophobic, in order to reduce contact with the liquid as far as possible, so that any gas bubbles will be adsorbed on the filter surface. 
     In a particularly advantageous design of the debubbling device, the aforementioned duct is formed by a groove that is located in a base component and is closed by the flat porous filter surface applied to this base component. This is a structurally very simple solution. The base component can be preferably provided in the form of a plastics component, in which the groove is formed during manufacture of the component, through which groove the liquid will flow on its way to the atomizing chamber. On its open side, this groove is closed by the porous filter surface that can be of flat design for this purpose and can therefore be produced very cost-effectively. The base component and the filter surface, which is preferably in the form of a membrane, can be joined together by gluing or welding. 
     It is regarded as being particularly advantageous when the aforementioned duct of the debubbling device comprises at least one curved or bent portion. Here, it is important that the porous filter surface be provided along this portion also. It has been found that such a curved portion promotes the escape of gas through the porous filter surface, presumably because most of the gas bubbles gather in the region of the inside bend of the curves and are conveyed at a reduced speed in this region. Preferably, several curved or bent portions are provided that are variably oriented relatively to each other so that the removal of the gas bubbles is possible at different orientations of the atomizer. Furthermore, the duct including curved portions that preferably interconnect linear portions produces a long path of flow for the liquid even in the case of a comparatively small component, so that gas bubbles can leave the intake channel through the porous filter surface over a comparatively long period of time. 
     As mentioned above, it is particularly advantageous when the liquid present in the liquid storage receptacle contains an active pharmaceutical ingredient and/or is a cosmetic product, more particularly a self-tanning lotion. 
     An atomizer of the invention can comprise flow meters both in the intake channel and in the return channel, in order to make it possible to precisely determine the amount of liquid that is atomized during a discharge process by taking the difference. 
     The atomizer of the invention is preferably in the form of a mobile device. For this purpose, it preferably comprises a battery or an accumulator. In one particular embodiment, the device comprises a user-exchangeable pack of consumables not requiring special tools and including at least the liquid-containing bladder. This pack of consumables can additionally include the battery. The comparatively expensive components such as the electronic control device, the pumping device, the debubbling device, and the atomizing device and optionally the accumulator can be components of a base unit, to which the outer pack of consumables can be coupled. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Additional aspects and advantages of the invention are revealed in the claims and the following description of a preferred exemplary embodiment of the invention, which is explained with reference to the figures, in which: 
         FIG. 1  is an overall view of an atomizer of the invention, 
         FIG. 2  shows the atomizer shown in  FIG. 1  after removal of a housing shell, 
         FIG. 3  is a partially exploded view of the atomizer shown in  FIGS. 1 and 2 , and 
         FIG. 4  shows the atomizing device of the atomizer shown in  FIGS. 1 to 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENT 
       FIG. 1  is an overall view of an hand-held atomizer  10  of the invention. The atomizer  10  comprises a housing  12  that is approximately of the size of a cellular phone and that comprises two housing shells  14 ,  16 . A recess  14   a,  behind which there is disposed an atomizing device  20  (explained in more detail below), is provided in the top housing shell  14 . Furthermore, a control switch  18 , by means of which the atomizer  10  can be activated, is provided at the front of the atomizer formed by the housing shell  14 . 
       FIGS. 2 and 3  show the atomizer  10  in an open state, that is, after removal of the top housing shell  14 .  FIG. 3  shows some components in a position removed from the housing  12  to make it possible to identify all significant components. 
     Two distinct regions  12   a,    12   b  are provided inside the housing  12 . The region  12   a  contains a liquid storage receptacle  30  in the form of a liquid-containing bladder  30 . Two openings (hidden in the figures), on each of which a coupling device  32 ,  34  is provided for connection to a flexible tube, are provided on the liquid-containing bladder  30 . 
     The aforementioned control switch  18  and the aforementioned atomizing device  20  are disposed in the region  12   b  of the housing  12 , Furthermore, a control device  40  and an accumulator (not shown) as an energy storage device are provided in this region. The region  12   b  additionally includes a piezoelectric pumping device  50  and a debubbling device  60 . 
     The liquid-containing bladder  30  is connected to the atomizing device  20  in the following manner. The coupling device  32  is connected to the input side  50   a  of the pumping device  50  by means of a flexible tube  70 . An additional flexible tube  72  connected to an inlet  60   a  of the debubbling device  60  is provided on the output side  50   b  of the pumping device  50 . This inlet  60   a  adjoins a debubbling channel  66  that has been formed as a groove in a base component  62  of the debubbling device  60 . As shown in  FIG. 2 , the base component  62  is closed in a liquid-tight manner in the assembled state of the atomizer  10  by means of a membrane  64 , more particularly an acrylic copolymer-based membrane that has a hydrophobic top coating and that can be glued or welded to the base component  62  in the marginal regions of the groove. This membrane  64  is in the form of a porous membrane and serves the purpose of allowing gas bubbles to escape from the liquid flowing through the channel  66 . At the opposite end of the channel  66 , there is provided a throttle in the form of a bottle-neck region  68 , the cross-sectional area of which is substantially smaller than that of the channel portion  66  upstream thereof. This bottle-neck region  68  adjoins an outlet orifice  60   b  of the debubbling device  60 . The atomizing device  20  (shown on an enlarged scale in  FIG. 4 ) is provided directly at this outlet  60   b  of the debubbling device  60 , and through-holes  64   a  are provided in the membrane  64  to make this direct connection possible. 
     The atomizing device  20  comprises an atomizing chamber  22  located between a liquid inlet  20   a  and a liquid outlet  20   b.  On its side near the opening  14   a  of the top housing shell  14 , this atomizing chamber  22  is delimited by a perforated plate  24  comprising a plurality of outlet orifices  24   a.  On its side remote from the perforated plate  24 , the atomizing chamber  22  is provided with a wall  26 , to which a piezoelectric vibrator  28  is attached, which is connected to the control device  40  by means of a cable (shown as a detail). Through-holes are provided in the base component  62  and in the membrane  64  for accommodating and wiring the piezoelectric vibrator  28 . 
     The liquid outlet  20   b  is provided for the excess liquid flowing from the atomizing chamber  22 . In the assembled state of the atomizer, this liquid outlet  20   b  communicates with the inlet  80   a  of a liquid channel  80  that passes through the base component  62  of the debubbling device  60  up to its outlet  80   b  without a debubbling function being assigned to this channel portion  80 . A flexible tube  82  leading to the aforementioned second coupling device  34  of the liquid-containing bladder  30  is connected to the outlet  80   b.    
     Thus the liquid-containing bladder  30  is connected to the atomizing device  20  by means of the channel portions  70 ,  72 ,  66 . This is the intake channel. The return channel is formed by the channel portions  80  and  82 . 
     The operation of the atomizer  10  is explained below. 
     For the purpose of discharging liquid from the liquid storage receptacle  30 , the user activates the control switch  18 . This activation of the control switch is registered by the electronic control device  40 . In order to effect preparatory measures for a subsequent atomizing process, the electronic control device  40  activates the piezoelectrically operated micropump  50 , initially alone. As a result, liquid is drawn in from the liquid storage receptacle  30  through the flexible tube  70  and is further transported through the flexible tube  72  to the debubbling device  60 . Here, the liquid flows into the channel portion  66 . Due to the pumping pressure built up at the output  50   b  of the pumping device  50  together with the throttling effect of the bottle-neck region  68 , a comparatively high pressure builds up inside the channel portion  66 . The positive pressure in the channel portion  66  relative to the environment preferably ranges from 100 mbar to 500 mbar. This positive pressure is sufficient to dispel gas bubbles through the porous membrane  64  from the liquid drawn in, and the gas can then escape through gaps in the housing  12 . The liquid delivered by the micropump  50  cannot escape through the porous membrane  64  at the aforementioned positive pressure. Thus the liquid entering the bottle-neck region  68  is largely free from gas bubbles. The W-shaped configuration of the channel portion  66 , more particularly the three curves  66   a,    66   b,    66   c,  promote the process of removing bubbles, since the bubbles gather at the inside bend in the region of these curves  66   a,    66   b,    66   c  and are further conveyed comparatively slowly in this region. This gives sufficient time for the gas bubbles to escape through the porous membrane  64 . The bottle-neck region  68  connected directly upstream of the atomizing device  20  leads to a significant reduction in the pressure of the liquid. The liquid largely free from gas bubbles therefore flows at a reduced pressure into the atomizing chamber  22 . Since the vibrator  28  has not yet been activated at this point, the liquid flows from the inlet side  20   a  of the atomizing device  20  directly to the outlet side  20   b  of the atomizing device  20 . The liquid pressure that is reduced by the bottle-neck region  68  to a positive pressure ranging from 0 mbar to 30 mbar and preferably from 2 mbar to 10 mbar, is initially not sufficient to force the liquid into the environment by way of the outlet orifices  24   a.  The outlet orifices  24   a  are thus not wetted. Instead, all the liquid delivered flows back into the liquid storage receptacle in the preparatory phase due to the low flow resistance in the channel portions  80 ,  82 . In the preparatory phase, in which only the pumping device  50  but not the vibrator  28  is activated, the entire pumped volume of liquid is thus recirculated. Air that may still be present in the atomizing chamber  22  prior to activation of the control switch  18  is either forced out of the atomizing chamber  22  through the outlet orifices  24   a  when liquid flows into the atomizing chamber or forced through the channel portions  80 ,  82  into the liquid-containing bladder  30  to be removed from the liquid in the debubbling device  60  when the liquid is subsequently drawn in. 
     On termination of the preparatory phase, preferably after approximately one second, the vibrator  28  is also activated by the control device  40 . As a result, the liquid present in the atomizing chamber  22  is caused to vibrate, which results in a discharge of liquid through the outlet orifices  24   a  in the form of extremely small droplets. Thus a fine liquid spray is dispensed through the orifice  14   a  in the top housing shell  14 , and this liquid spray can be inhaled, for example as a medicine, or dispensed onto the skin in the form of a cosmetic deposit, when the appropriate liquid is used. 
     Once the vibrator  28  has been switched into operation, a portion, preferably half or a major portion of the pumped volume of liquid delivered by the pumping device  50  to the atomizing device  20  is dispensed through the outlet orifices  24   a.  There still remains a significant portion of the liquid delivered by the pumping device  50 , which portion is recirculated to the liquid-containing bladder  30  through the channel portions  80 ,  82 . This ensures that any air that may have inadvertently entered the atomizing chamber  22  is reliably removed therefrom. At the same time, the fact that the pumped volumetric flow rate is greater than the discharged volumetric flow rate reliably ensures that a sufficient amount of liquid is present in the atomizing chamber  22  at all times.