Abstract:
A replacement reservoir assembly ( 30 ) for an atomizing device ( 20 ), which uses a vibratable orifice plate ( 37 ) for atomizing liquid, includes a container ( 31 ), which contains a liquid to be atomized, and an elongated wick ( 56 ) having a lower end which is immersed in the liquid within the container ( 31 ) and an upper end located above the container ( 31 ). The wick ( 56 ) includes a dimensionally stable material having capillary passages for drawing liquid out of the container ( 31 ) to the upper end of the wick ( 56 ), which is outside the container ( 31 ). The upper end of the wick ( 56 ) has at least one surface that is configured to provide an unobstructed passage to the atmosphere from a region between a top surface of the wick ( 56 ) and a facing surface of the vibratable orifice plate ( 37 ) when the replacement reservoir is positioned in the atomizing device ( 20 ). A wick ( 56 ) for use in a replaceable reservoir assembly ( 30  ) that contains liquid to be atomized by a vibratory orifice plate ( 37 ) and a method of positioning an upper end of a solid, dimensionally stable wick ( 56 ) are also disclosed.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Field of the Invention  
           [0002]    This invention relates to the atomization of liquids and more particularly it concerns novel methods and apparatus for supplying liquid to be atomized to a surface of an orifice plate which, upon vibration, atomizes the liquid and ejects minute droplets of the liquid from its opposite surface.  
           [0003]    2. Description of the Related Art  
           [0004]    Atomizers of the type to which the present invention relates use a vibration orifice plate or membrane to atomize liquid which is brought to one side of the plate by a pliant wick which presses against the plate. An example of such an atomizer is shown in U.S. Pat. No. 6,450,419.  
           [0005]    Atomizing devices that use wicks or conduits of various types to deliver liquids to a vibratory atomizing element are disclosed in U.S. Pat. Nos. 6,467,476, 6,085,740, 5,529,055, 4,790,479, 4,753,579, 4,334,531 and U.S. Pat. No. 4,301,093 and published European Patent Application EP 0 897 755 A2. U.S. Pat. Nos. 4,582,654 and 4,474,326 describe the use of tubes or needles to deliver a liquid to be atomized. U.S. Pat. Nos. 5,863,196 and 5,124,200 describe wicks.  
           [0006]    Our invention solves a problem which occurs when a solid, dimensionally stable wick is used to convey the liquid to be atomized to the orifice plate. An example of an atomizing device which uses a solid, dimensionally stable wick is shown and described in U.S. patent application Ser. No. 10/154,509, filed May 24, 2002, assigned to the assignee of this invention and incorporated herein by reference. Such wicks are generally made of plastic and contain interstices or capillary passages, which extend therethrough from one end to the other to draw liquids up through the wick from one end of the wick to its other end. It has been found that when the wick of a replacement reservoir is positioned against an orifice plate that is still wet from the wick of a previous reservoir, it is often difficult to restart the atomizing operation. It may take hours or even days for the atomizing operation to restart, which adversely affects the use of the atomizer.  
           [0007]    Accordingly, we found a need in the art for an atomization device that is “self priming,” meaning that the wick included in the atomization device reliably and instantaneously delivers fluid to a piezoelectric pump.  
         SUMMARY OF THE INVENTION  
         [0008]    Our invention improves the delivery of fluid to a vibrating-orifice-plate atomizer when a replacement reservoir containing a new, dimensionally stable wick is mounted in the atomizer.  
           [0009]    According to one aspect, our invention provides a method of positioning an upper end of a solid, dimensionally stable wick having liquid-filled interstices against a surface of a vibratable orifice plate, which has a plurality of minute orifices formed therethrough and is configured to dispense the liquid filling the interstices of the wick as the orifice plate vibrates. The method comprises the step of moving the wick toward the vibratable orifice plate while maintaining a liquid-free passage that extends to the atmosphere from a space between the upper end of the wick and the surface of the orifice plate as the wick is positioned with a portion of the upper end contacting the orifice plate.  
           [0010]    According to another aspect, our invention provides a wick for use in a replaceable reservoir assembly that contains liquid to be atomized by a vibratory orifice plate, which has a plurality of minute orifices formed therethrough and is configured to dispense the liquid in the reservoir assembly. The wick comprises a dimensionally stable material having capillary passages for drawing a liquid from a lower end to an upper end. The wick has different levels at the upper end that are configured to provide an unobstructed passage to the atmosphere from a region between a top surface of the wick and a facing surface of the vibratory orifice plate.  
           [0011]    According to a still further aspect, our invention provides a replacement reservoir assembly for an atomizing device, which uses a vibratable orifice plate for atomizing liquid. The replacement reservoir assembly comprises a container, which contains a liquid to be atomized, and an elongated wick having a lower end which is immersed in the liquid within the container and an upper end located above the container. The wick comprises a dimensionally stable material having capillary passages for drawing liquid out of the container to the upper end of the wick, which is outside the container. The upper end of the wick has at least one surface that is configured to provide an unobstructed passage to the atmosphere from a region between a top surface of the wick and a facing surface of the vibratable orifice plate when the replacement reservoir is positioned in the atomizing device.  
           [0012]    According to yet another aspect, our invention provides a wick for use in a replaceable reservoir that contains liquid to be atomized by a vibratory orifice plate. The orifice plate has a plurality of minute orifices formed therethrough and is configured to dispense the liquid in the reservoir. The wick comprises a dimensionally stable material having capillary passages for drawing a liquid from a lower end to an upper end, and a cutout having side surfaces depending from the top surface of the wick and a bottom surface being disposed below the top surface of the wick such that the bottom surface does not contact the vibratory orifice plate, with the cutout composing the unobstructed passage. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is an elevational cross section of an atomizer device embodying the invention;  
         [0014]    [0014]FIG. 2 is an enlarged fragmentary cross section, taken in elevation, of the upper portion of a replacement reservoir together with a vibratory-orifice-plate atomizing arrangement used in the atomizing device of FIG. 1;  
         [0015]    [0015]FIG. 3 is a perspective view of the upper portion of a wick that forms part of the replacement reservoir of FIG. 2;  
         [0016]    [0016]FIG. 4 is an enlarged elevational view of the upper portion of the wick of FIG. 3;  
         [0017]    [0017]FIG. 5 is a top view of the upper end of the wick of FIG. 3;  
         [0018]    [0018]FIGS. 6 and 7 are enlarged elevational views showing the upper end of the wick in cross section as it is being placed in position and after it is in its final position, respectively;  
         [0019]    FIGS.  8  to  11  are perspective views of the top ends of wicks forming other embodiments of the invention; and  
         [0020]    [0020]FIG. 12 is an exploded view of components of the atomization device.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0021]    An atomization device  20  according to our invention generally comprises an atomizer assembly  34 , which includes an orifice plate  37 , and a replaceble reservoir assembly  30 . The reservoir assembly  30  includes a reservoir  31  containing fluid and a wick  56 . When one reservoir assembly  30  is removed by a user and replaced with another reservoir assembly, the wick  56  instantaneously delivers fluid to the orifice plate  37 , thus greatly improving the atomization device  20 .  
         [0022]    As shown in FIG. 1, the piezoelectrically actuated atomization device  20  according to a preferred embodiment of our invention comprises a housing  22  formed as a hollow plastic shell and closed by a flat bottom wall  24 . A horizontal platform  25  extends across the interior of the housing  22 . A battery  26  is supported by means of support prongs  25   a  which extend down from the underside of the platform  25  inside the housing  22 . In addition, a printed circuit board  28  is supported on support elements  25   b  which extend upwardly from the platform  25 . A liquid reservoir assembly  30  is replaceably mounted to the underside of a dome-like formation  25   c  on the platform  25 .  
         [0023]    The liquid reservoir assembly  30  comprises a liquid container  31  for holding a liquid to be atomized, a plug  33 , which closes the top of the container, and the wick  56 , which extends from within the liquid container  31  through the plug  33 , to a location above the liquid container  31 . The plug  33  is constructed to allow removal and replacement of the complete liquid reservoir assembly  30  from the underside of the dome-like formation  25   c  on the platform  25 . Preferably, the plug  33  and the platform are formed with a bayonet attachment (not shown) for this purpose. When the replaceable liquid reservoir assembly  30  is mounted on the platform  25 , the wick  56  extends up through a center opening in the dome-like formation  25   c.  The wick  56 , which is described in greater detail hereinafter, operates by capillary action to deliver liquid from within the liquid container  31  to a location just above the dome-like formation  25   c  on the platform  25 .  
         [0024]    An atomizer assembly  34  is supported on the platform  25  in cantilever fashion by means of a resilient, elongated wire-like support  27 . As is described more fully in copending U.S. patent application Ser. No. 10/304,215, filed Nov. 26, 2002, assigned to the assignee of this invention and incorporated herein by reference, in the preferred embodiment, the wire-like support  27  is attached at its ends  27   a,    27   b,  shown in FIG. 12, to posts, which protrude upward from the platform  25 . As shown in FIGS. 1, 2 and  12 , the support  27  is shaped such that it resiliently supports the lower surface of the orifice plate  37  and a spring housing  39 , while a spring  43  resiliently presses on the upper surface of the orifice plate  37 . (Rather than press on the orifice plate  37  itself, the spring  43  may alternatively or additionally press on a member, such as an actuator element  35 , discussed below, which is connected to the orifice plate  37 .) Together, the support  27  and the spring  43  hold the orifice plate  37  in place in a manner that allows the orifice plate  37  to move up and down against the resilient bias of the wire-like support  27 .  
         [0025]    Other ways of supporting the atomizer assembly  34 , in addition to the foregoing, are possible, and another such way is disclosed in U.S. patent application Ser. No. 10/154,509, filed May 24, 2002, noted above.  
         [0026]    The atomizer assembly  34  comprises an annularly shaped piezoelectric actuator element  35  and the circular orifice plate  37 , which extends across and is soldered or otherwise affixed to the actuator element  35 . A construction of a vibrator type atomizer assembly is per se well known and is described, for example, in U.S. Pat. No. 6,296,196, which is incorporated herein by reference. Accordingly, the atomizer assembly  34  will not be described in detail except to say that when alternating voltages are applied to the opposite upper and lower sides of the actuator element  35  these voltages produce electrical fields across the actuator element and cause it to expand and contract in radial directions. This expansion and contraction is communicated to the orifice plate  37  causing it to flex so that a center region thereof vibrates up and down. The center region of the orifice plate  37  is domed slightly upward to provide stiffness and to enhance atomization. The center region is also formed with a plurality of minute orifices which extend through the orifice plate  37  from the lower or under surface of the orifice plate  37  to its upper surface. A flange is provided around the center region of the dome.  
         [0027]    In operation, the battery  26  supplies electrical power to circuits on the printed circuit board  28  and these circuits convert this power to high frequency alternating voltages. A suitable circuit for producing these voltages is shown and described in U.S. Pat. No. 6,296,196 noted above. As described in that patent, the device may be operated during successive on and off times. The relative durations of these on and off times can be adjusted by an external switch actuator  40  on the outside of the housing  22  and coupled to a switch element  42  on the printed circuit board  28 .  
         [0028]    When the atomizer assembly  34  is supported by the support member  27 , the flange of the orifice plate  37  is positioned in contact with the upper end of the wick  56 . The atomizer assembly  34  is thereby supported above the liquid reservoir assembly  30  such that the upper end of the wick  56  touches the underside of the orifice plate  37 , as shown in FIG. 2. Thus, the wick  56  delivers liquid from within the liquid reservoir  31  by capillary action to the underside of the orifice plate  37 , which upon vibration, causes the liquid to pass through its orifices and be ejected from its opposite side (i.e., the upper surface) in the form of very small droplets.  
         [0029]    It will be appreciated from the foregoing that the horizontal platform  25  serves as a common structural support for both the liquid reservoir assembly  30  and the atomizer assembly  34 . Thus, the horizontal platform maintains the liquid reservoir assembly  30 , and particularly, the upper end of the wick  56 , in alignment with the orifice plate  37  of the atomizer assembly  34 . Moreover, because the atomizer assembly  34  and the orifice plate  37  are resiliently mounted, the upper end of the wick  56  will always press against the under surface of the orifice plate  37  and/or the actuator element  35  irrespective of dimensional variations which may occur due to manufacturing tolerances when one liquid reservoir is replaced by another. This is because if wick  56  of the replacement liquid reservoir assembly  30  is higher or lower than the wick  56  of the original liquid reservoir assembly  30 , the action of the spring  43  will allow the orifice plate  37  to move up and down according to the location of the wick  56  in the replacement reservoir assembly  30 , so that the wick  56  will always press against the underside of the orifice plate  37  and/or the actuator element  35 . It will be appreciated that the wick  56  should be of a solid, dimensionally stable material so that it will not become deformed when pressed against the underside of the resiliently supported orifice plate  37 . Examples of such solid, dimensionally stable wicks  56  are described below.  
         [0030]    As can be seen in FIG. 1, the wick  56  extends from inside the liquid reservoir  31  up through the plug  33  in the top of the reservoir  31  to contact the orifice plate  37  and/or the actuator element  35  from near the bottom of the liquid reservoir  31 . The wick  56  has longitudinally extending capillary passages which draw liquid up from within the container  31  to the upper end of the wick  56 .  
         [0031]    The wick  56  is preferably composed of solid, dimensionally stable material, such as a solid, porous plastic material. In a preferred embodiment the solid, porous plastic material is sold by MicroPore Plastics, Inc. of Stone Mountain, Ga. or the Porex Corporation of Fairburn, Ga. This plastic material is preferably high molecular weight polyethylene, although other materials may be suitable. For other aspects of the invention, wherein the liquid delivery system does not have to be dimensionally stable, pliant wick components, such as wick components made of fabric, yarn, etc., may be used, as will be discussed in more detail below.  
         [0032]    The wick  56  preferably includes an integrally formed attachment assembly for securing the wick  56  to the plug  33 . Of course, the attachment assembly may be a separate piece affixed to the wick  56 . The attachment assembly includes a collar  102  having a lower segment  104  of a relatively large diameter and an upper segment  106  of a relatively small diameter. The top of the lower segment  104  contacts the plug  33  to prevent the wick  56  from moving out of the container  31 . The upper segment  106  frictionally fits into the aperture in the plug  33 .  
         [0033]    As can be seen in FIG. 2, the upper end of the wick  56  enters into an opening in the bottom of the spring housing  39  to supply liquid to a location just below or on the bottom surface of the orifice plate  37 . The wick  56  is substantially in contact with a flange portion on the periphery of the domed portion of the orifice plate  37 . The wick  56  may also be in contact with the actuator element  35 . However, the wick  56  includes a top surface having different levels so that a portion of the wick  56  is not in contact with the orifice plate  37  or the actuator element  35 . This portion provides unobstructed passage to the atmosphere.  
         [0034]    As shown in FIG. 3, in one embodiment, the unobstructed passage is provided by way of the top end of the wick  56  including a pie-shaped cutout  100 . As seen in FIGS. 4 and 5, the width of the pie-shaped cutout  100  at the periphery of the wick  56  is preferably equal to the depth of the cutout  100 . We believe the cutout  100  should preferably be sized so that the volume removed by the cutout  100  is large enough to prevent liquid drawn up by the wick  56  from filling the volume and thereby contacting the orifice plate  37 . In other words, the cutout  100  is large enough to form a liquid-free passage.  
         [0035]    We have found that an appropriate size for the cutout  100  is achieved when the cutout  100  has a constant depth and defines an angle a (alpha) that is about 10 degrees to about 50 degrees, preferably about 15 degrees to about 30 degrees. Other ranges for the angle a (alpha) include an angle of about 20 degrees to about 40 degrees, or about 23 degrees to about 37 degrees, or about 25 degrees to about 30 degrees. In general, we have found that a smaller angle generates a more constant rate of fluid flow to the orifice plate  37  over time.  
         [0036]    The apparent effect of the cutout  100  is best illustrated with reference to FIGS. 6 and 7. FIG. 6 shows the wick  56  as it is being positioned in the atomization device  20 . As the wick  56  moves closer to the orifice plate  37 , we believe that there is the potential for air to be trapped between the wet orifice plate  37  and the top surface of the wick  56 , which is saturated with fluid from the container  31 . However, as shown in FIG. 7, the cutout  100  prevents an air bubble from being trapped, because the air can exit to the atmosphere through the cutout  100  as shown by the arrow.  
         [0037]    Other embodiments may have a similar effect. For example, as shown in FIG. 8, the top of the wick  56  can be positioned at an angle so that a portion of the top of the wick  56  contacts the orifice plate  37  and a remainder of the top angles away from the orifice plate  37 . Alternatively, the atomizer assembly  34  or at least the orifice plate  37  can be tilted with respect to a wick  56  having a horizontal top to obtain the same effect. The top surface of the wick  56  (or the orifice plate  37 ) should be canted at a sufficient angle so that at least a portion of the space between the top surface of the wick  56  and the orifice plate  37  forms a liquid-free passage. In this embodiment, a portion of the top surface is spaced from the orifice plate  37  in order to form an unobstructed passage for air to escape to the atmosphere.  
         [0038]    We also conceived other embodiments for the wick  56 . As shown in FIG. 9, the wick  56  may have an open-cell, flexible foam  200  embedded therein. Such foam material may comprise polyurethane foam, although other materials may also be used provided the materials are chemically inert with respect to the liquid in the liquid container  31 . The foam  200  may be placed substantially concentrically with the wick  56 , or it may be offset. Also, the foam  200  may take up the majority of the cross-sectional area of the wick  56 , as shown, or it may form only a minor part of such area. The foam  200  may provide a way for air to be absorbed or any liquid remaining on the bottom surface of the orifice plate  37 , which may remain after replacement of the reservoir assembly  30 , to be broken up, absorbed, or passed through the orifices in the orifice plate  37 . This may, therefore, prevent air bubbles from being trapped.  
         [0039]    As a further embodiment, shown in FIG. 10, the top of the wick  56  may include an embedded, fibrous material  300 . Such fibrous material  300  may comprise nylon, polypropylene, or cotton. Other materials may also be used, provided the materials are chemically inert with respect to the liquid in the liquid container  31 . The fibrous material  300  may provide a way for air to be absorbed or any liquid remaining on the bottom surface of the orifice plate  37 , which may remain after replacement of the reservoir assembly  30 , to be broken up, absorbed, or passed through the orifices in the orifice plate  37 . This may, therefore, prevent air bubbles from being trapped.  
         [0040]    In yet a further embodiment, shown in FIG. 11, the top of the dimensionally stable wick  56  includes a raised dome  400 , which is also dimensionally stable. The raised dome  400  may have a cross-sectional area that is substantially smaller than the cross-sectional area of the top of the wick  56 , as shown. Alternatively, the raised dome may comprise a larger share of the cross-sectional area of the wick  56 . Regardless, portions of the raised dome  400  and/or the wick  56  itself are/is not in contact with the orifice plate  37 . For example, the raised dome  400  may contact the flange of the orifice plate  37 , thus maintaining the top surface of the wick out of contact with the facing surface of the orifice plate  37 . The raised dome  400  may be tall enough to create a liquid-free passage between at least a portion of the top surface of the wick  56  and the orifice plate  37 . That is to say, liquid will not travel from at least a part of the top surface of the wick  56  to the orifice plate  37 .  
         [0041]    The above-described wicks assure an instantaneous and continuous liquid interface, by way of surface tension contact, between the wick  56  and the lower surface of the orifice plate  37 . We have found that the cutout  100  is particularly effective.  
         [0042]    We believe the wicks  56  according to the preferred embodiments prevent a problem that sometimes occurs when a depleted liquid reservoir assembly  30 , which is replaceable as previously mentioned, is discarded and a new liquid reservoir assembly  30  is inserted. At this time, the orifice plate  37  may still be wet from a previous use. Furthermore, an air bubble may be formed as the replacement liquid reservoir assembly  30  is brought into position in the atomization device  20 . We believe this air bubble may be rendered impassable by liquid because of the wet orifice plate  37  and the contact of the upper end of the wick  56  with the orifice plate  37 , which combine to trap the air bubble. The liquid from the top end of the new wick  56  apparently cannot penetrate through this air bubble.  
         [0043]    We believe that if the clear air passage is provided to vent this air bubble, then the entire space between the top of the wick  56  and the underside of the orifice plate  62  can be provided with liquid and the liquid could readily be pumped through the atomization device  20 .  
         [0044]    Notwithstanding the foregoing, the wicks according to our preferred embodiments may actually operate differently from the operation described above. Nevertheless, we have found that the wicks  56  consistently provide instantaneous flow of liquid, when a replacement reservoir assembly  30  is inserted into the atomizer  20 .  
         [0045]    Many different embodiments of our invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that our invention is not limited to the specific embodiments described in this specification. To the contrary, our invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention as hereafter claimed. The scope of the claims is to be accorded the broadest interpretation so as to encompass all such modifications, equivalent structures and functions.  
       Industrial Applicability  
       [0046]    The embodiments described herein provide consistent start up for an atomizer device, so that a liquid stored in a container can be reliably atomized even after the container has been removed and replaced by another.