Patent Publication Number: US-8528355-B2

Title: Atomization unit with negative pressure actuator

Description:
FIELD OF THE INVENTION 
     The presently described technology relates generally to an atomization unit for atomizing a liquid wherein the liquid is atomized through a perforated layer. More specifically, the presently described technology relates to an atomization unit that employs a negative pressure actuator to reduce the fluid pressure acting on the perforated layer to thereby minimize or prevent leakage of the fluid through the perforated layer. The atomization unit is particularly suited for use in a refrigerator to cool and humidify at least a portion of the refrigerator. 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the presently described technology is to provide an atomization unit having a negative pressure actuator that reduces the fluid head pressure acting on the atomizer in order to minimize fluid leakage. The atomization unit comprises a liquid storage unit containing a liquid to be atomized; an atomizer in fluid communication with the liquid contained within the liquid storage unit and comprising a perforated layer through which the liquid is atomized. The atomizer is positioned such that the liquid contained within the storage unit is maintained above the atomizer resulting in a positive fluid pressure acting on the atomizer. The atomization unit further comprises an actuator in sealing relation with the liquid storage unit, wherein when the actuator is activated, the actuator promotes a negative fluid pressure that reduces the fluid pressure acting on the atomizer, thereby minimizing leakage of fluid through the perforated layer. 
     Another aspect of the presently described technology is to provide a method of minimizing liquid leakage through a perforated layer of an atomizer subjected to a positive liquid head pressure. The method of the presently described technology comprises the steps of:
         (a) providing a liquid storage unit containing a liquid to be atomized, the liquid storage unit further comprising an actuator in sealing relation with the liquid storage unit;   (b) providing an atomizer in fluid communication with the liquid contained within the liquid storage unit, the atomizer comprising a perforated layer and positioned within the liquid storage unit such that a column of liquid is maintained above *the atomizer resulting in a positive fluid pressure acting on the atomizer; and   (c) reducing the fluid pressure acting on the atomizer by moving the actuator in a direction that promotes a negative fluid pressure, wherein reduction in the fluid pressure minimizes liquid leakage through the perforated layer.       

     The atomization unit described herein is particularly suitable for use in a refrigerator to cool and humidify at least a portion of the refrigerator. It is therefore a further aspect of the presently described technology to provide an atomization unit for a refrigerator for cooling and humidifying at least a portion of the refrigerator, wherein the atomization unit comprises a negative pressure actuator that promotes a negative fluid pressure that reduces the fluid pressure acting on the atomizer, to thereby minimize leakage of fluid through the perforated layer of the atomizer. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a diagrammatical representation of an atomization unit showing the negative pressure actuator in an unactivated position; 
         FIG. 2  is a diagrammatical representation of an atomization unit showing the negative pressure actuator in an activated position; and 
         FIG. 3  illustrates a refrigerator provided with an atomization unit of the present technology. 
       The foregoing summary, as well as the following detailed description of certain embodiments of the presently described technology, will be better understood when read in conjunction wit the appended drawings. For the purpose of illustrating the invention, certain embodiments are shown in the drawings. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present technology relates to an atomization unit that employs a negative pressure actuator to reduce the fluid pressure acting on the atomizer in order to minimize or prevent leakage of fluid from the atomizer. Methods of minimizing or preventing fluid leakage from an atomizer are also described. 
     Piezoelectric atomizers can be found in a wide variety of applications, such as domestic humidifiers, aroma dispensers, and medical nebulizers. Piezoelectric atomization technology relies on vibrations created by a piezoelectric cell when an AC power with a low ultrasonic frequency (around 0.01 to 2 MHz) is applied. Fluid passes over the vibrating surface and the vibration energy causes the fluid to break into droplets. 
     In the presently described technology, low wattage ultrasonic water atomizers are enabled by the use of annular piezo elements mounted on a perforated nickel diaphragm. In this way, water can be made available at the external surface of the diaphragm where atomization takes place. One feature of a low wattage ultrasonic atomizer is the ability to change mist direction. However, in certain orientations, pressure promoted by a water column acting on the piezo element can lead to a siphoning effect through the diaphragm perforations. This siphoning effect can lead to water leaks that can delay the start up of the atomizer feature. The atomizer has two operation states—“misting” and “off.” Each of these operation states has a different water head limit. After the atomizer mists for a few minutes and then stops, water drops seep through the perforations in the diaphragm. Also the atomizer takes some time to absorb the water drops and start misting again. In the “misting” operation state, the water head limit is about three inches. Therefore, a water column of about three inches acting on the piezo element can lead to water leaks through the perforations in the diaphragm. 
     Another consideration for the atomizer is the need to continuously maintain a water layer on top of the piezo cell in order for it to mist. Also, fluid flow to the piezo cell needs to be maintained for proper functioning of the piezo cell. Because the water column above the piezo cell cannot exceed three inches, due to the possibility of water leakage, maintaining a constant water availability can result in frequent refillings and/or monitoring, which can be inconvenient. It would, therefore, be desirable to provide an atomization unit that can minimize or prevent leakage through a perforated diaphragm or layer, even in the presence of a water column that is three inches or greater. 
     Referring generally to  FIGS. 1 and 2 , an atomization unit  10  of the presently described technology is shown. The atomization unit  10  includes a storage unit or tank  12  adapted for storing the liquid to be atomized. Typically, the liquid will be water, but other liquids are also contemplated. The storage tank should be constructed to be water tight, especially around its sides and bottom to prevent leakage. 
     The storage tank  12  can be of various sizes and shapes depending upon the end use for the atomization unit. The storage tank  12  is sized and shaped to accommodate a water column above the atomizer that is at least three inches in height. A storage tank of such a size will provide a sufficient liquid supply to the atomizer to maintain proper functioning of the atomizer without the need for frequent refillings that would be required with smaller storage tanks. In one embodiment, the storage tank  12  includes a removable tank cover  14  to allow convenient filling of the storage tank. Optionally, the tank cover  14  can be provided with a cap  16 . 
     The atomization unit  10  includes an atomizer  20  in fluid communication with the storage tank  12 . Typically, the atomizer  20  is located at the bottom of the storage tank and liquid flows to the atomizer through an opening (not shown) in the base of the storage tank. The atomizer  20  is positioned relative to the storage tank  10  such that the liquid in the storage tank promotes a fluid head pressure acting on the atomizer. 
     The atomizer  20  comprises a piezo cell that includes a perforated diaphragm or layer that vibrates when stimulated whereby fluid from a top surface of the piezo cell is drawn through the perforations and distributed in an atomized spray from a bottom surface of the piezo cell. The diaphragm is a perforated diaphragm with perforations that are about 8 to about 12 microns. One side of the diaphragm is in contact with the liquid in the storage tank, while the other side of the diaphragm is exposed to the atmosphere. The piezo cell is fitted within an enclosed casing, and top and bottom seals on either side of the piezo cell allow vibration but maintain a water-tight seal between the piezo cell and the casing. The sealing force of the seals on the piezo cell should not exceed 0.145 pounds. 
     The atomizer is a low wattage atomizer and operation of the atomizer requires electrical input of 110 kHz, up to 200 mA at 5 volts. 
     The atomization unit  10  includes a negative pressure actuator which functions to reduce the fluid head pressure acting on the atomizer to thereby minimize or prevent liquid from leaking through the perforations in the atomizer diaphragm. The negative pressure actuator comprises a sealable member that forms a seal with an opening in the storage tank and is movable relative to the storage tank. Typically, the negative pressure actuator is mounted to the storage tank lid and seals an opening in the lid. However, the negative pressure actuator can be mounted to a sidewall of the storage tank, provided that the negative pressure actuator is mounted at a position that is above the level of the liquid in the storage tank. 
     The sealable member of the negative pressure actuator can take a variety of forms as long as it forms a seal with the storage tank and is moveable relative thereto. For example, the sealable member can be a disk similar to a suction cup, or a moveable plug. The sealable member is preferably formed from rubber, silicone or an elastomeric material. 
     In one embodiment, illustrated in  FIGS. 1 and 2 , the negative pressure actuator is a piston  30  that has a sealable head  32  and a stem  34  connected to the piston. The piston  30  is moveable within the cap  16  located on the cover  14  of the storage tank  12  and forms a seal with the cap  16 . As shown in  FIG. 1 , in its unactivated position, the sealable head  32  is at the same level as the storage tank cover  14 . In this position, the fluid head pressure acting on the liquid in the storage tank  12  is equivalent to the ambient air pressure and the atomizer  20  is subject to leakage. 
     The piston  30  is activated by moving the piston stem  34  in a direction away from the storage tank  12 , which, in the  FIG. 2  embodiment is in the upward direction indicated by the arrow  40 . Activation of the piston  30  creates a vacuum or negative pressure effect that reduces the fluid pressure acting on the atomizer  20  to less than atmospheric pressure. Reduction in the fluid pressure minimizes or prevents leakage of the fluid through the perforations in the diaphragm. 
     Method of Operation 
     To operate the atomization unit  10 , the storage tank  12  is filled with liquid to a desired level, leaving at least some head room between the liquid level and the tank cover  14 , and the tank cover  14  is closed. The filled storage tank  12  results in a positive fluid pressure acting on the atomizer  20  located at the base of the storage tank. After the storage tank  12  is filled, the negative pressure actuator is activated by moving the actuator in a direction that promotes a negative fluid pressure. In the embodiment shown in  FIGS. 1 and 2 , the negative pressure actuator is a piston that is moved upwardly in the direction of the arrow  40  to create a negative pressure acting on the liquid in the storage tank. Once the negative pressure actuator is activated, the atomizer is turned on to begin the misting cycle. Because the negative pressure actuator acts to reduce the fluid pressure acting on the atomizer, liquid leakage through the perforated diaphragm is minimized or prevented. 
     Uses for the Atomization Unit 
     The atomization unit  10  employing a negative pressure actuator as described herein can be used in a variety of applications that employ atomizers subjected to a positive fluid head pressure. One useful application is in a refrigerator that utilizes an atomization unit to cool and humidify a compartment of the refrigerator. For example, an atomization unit  10  as described herein is particularly useful for applying atomized liquid to fruits and vegetables stored within the crisper compartment of a refrigerator. Illustrated in  FIG. 3  is one embodiment of a refrigerator  50  showing the atomization unit  10  of the presently described technology installed to provide atomized liquid to the crisper compartment of the refrigerator  50 . Preferably, the atomization unit  10  is a modular design that is configured and adapted to be added to or removed from a refrigerator as a unit. 
     The invention is now described in such full, clear, concise and exact terms as to enable any person skilled in the art to which it pertains, to practice the same. It is to be understood that the foregoing describes preferred embodiments of the invention and that modifications may be made therein without departing from the spirit or scope of the invention as set forth in the appended claims.