Abstract:
An air purifier having an electret module for capturing airborne particles, the electret module including an electret element disposed within a housing and an adhesive layer coupled to the housing to capture airborne particles, whereby the static field of the electret attracts the airborne particles, which subsequently adhere to the adhesive layer.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The field of the present invention is air purifiers, particularly air purifiers that capture airborne particles using electret modules. 
         [0003]    2. Background 
         [0004]    During the course of a day, an average person takes in approximately 500 milliliters of air per breath. For each breath taken, a person can inhale numerous types of airborne particles, including dust, pollen, mold spores, bacteria, etc. These particles consist of particulate matter in the form of microscopic solids and liquid droplets. This matter can potentially carry harmful diseases, causing irritation, allergic reactions, and disease. Types of diseases which are carried by airborne particles include tuberculosis, chickenpox, measles, and influenza. 
         [0005]    The size of airborne particles is related to their potential harm. Smaller particles, for example, those less than 10 micrometers in diameter, are known to cause the greatest harm. These particles can migrate into a person&#39;s lungs and bloodstream, potentially affecting vital organs. 
         [0006]    Conventional methods of preventing the inhalation of airborne particles are often limited by particle size. Mesh filters worn over a person&#39;s mouth, for example, prevent inhalation of large airborne particles. These larger particles, however, are merely irritants and generally will not have a long-term impact on health. While conventional filters can function well for their intended purpose, they generally are not effective in preventing the inhalation of smaller airborne particles. The inhalation of smaller airborne particles, particularly those that are less than 10 microns is, therefore, still a concern. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention is directed toward air purifiers, particularly air purifiers that capture airborne particles, using electret modules. The electret module emits an electret field that allows the purifier to capture airborne particles. 
         [0008]    In a first separate aspect of the invention, an electret module includes an electret element disposed within a housing and an adhesive layer coupled to the housing to capture airborne particles. In general terms, electrets are materials known to emit a quasi-permanent static charge. 
         [0009]    One or more optional configuration features may be incorporated into the air purifier, either singly or in combination. In one optional configuration, the air purifier may include a filter that a user can place over their nose and/or mouth. In another optional configuration, the air purifier may include headgear coupled to the electret module. 
         [0010]    In a second separate aspect of the invention, the surface potential of an electret element may be restored back to its initial level or further increased using a static restorer. The static restorer includes a battery, a high voltage generator, a rectifier and a smoothing filter. Once applied, the surface potential of the electret element should be restored back to its original potential, or even higher. 
         [0011]    Accordingly, an improved air purifier is disclosed. Advantages of the improvements will appear from the drawings and the description of the preferred embodiment. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    In the drawings, wherein like reference numerals refer to similar components: 
           [0013]      FIG. 1  schematically illustrates an air purifier shown as an electret module; 
           [0014]      FIG. 2  schematically illustrates an air purifier; 
           [0015]      FIG. 3  schematically illustrates an air purifier; 
           [0016]      FIG. 4  illustrates a user wearing a air purifier; and 
           [0017]      FIG. 5  illustrates an electret module attached to headgear; 
           [0018]      FIG. 6  illustrates an air purifier incorporated into headgear. 
           [0019]      FIG. 7  schematically illustrates a static restorer; 
           [0020]      FIG. 8  is a graph illustrating the surface potential decay curve of an electret element after exposure to air; and 
           [0021]      FIG. 9  is a graph illustrating the surface potential decay curve after application of the static restorer. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0022]    Turning in detail to the drawings,  FIG. 1  illustrates an air purifier  11  formed from an electret module  13 . The electret module  13  includes an electret element  15  disposed within a housing  17 . 
         [0023]    The electret element  15  may be constructed from synthetic polymers, including fluoropolymers, polyolefins, polyesters, and the like. In one configuration, the electret element  15  is constructed from a non-porous polytetrafluoroethylene (PTFE) film. Other suitable materials may include polypropylene and ethylene terephthalate. Non-porous PTFE is one type of suitable material because of its ability to achieve a high surface potential, using thin film configurations. Non-porous PTFE, however, is known to be affected by its environment, particularly humid conditions and surrounding electric fields. The surface potential of non-porous PTFE may also be unstable and have a faster rate of a surface potential decay, in comparison to other fluoropolymer materials.  FIG. 8 , for example, shows a surface potential decay curve of non-porous PTFE after exposure to air. 
         [0024]    Before being placed into the housing, the electret element  15  is charged. One method for charging the electret element is the corona discharge method. Any effective charging method, however, may be used. In optional configurations, after charging, the surface potential of the electret element can range from 2 KV to 5 KV. This range allows for the electret module to capture small airborne particles. Airborne particles contemplated and their approximate size ranges, in microns, include: 
         [0025]    Pollens: 10-1000 
         [0026]    Bacteria: 0.300-60 
         [0027]    Smoke: 0.010-4 
         [0028]    Viruses: 0.005-0.300 
         [0029]    Because air is known to carry ionic particles and liquid droplets that may affect the surface potential of some types of electret elements, the electret element  15  is contained within a housing  17 . Materials with low attenuation factors, like polyvinylchloride, are preferred as housing materials. These types of housing materials are used to prevent moisture and ionic particles from contacting the electret element  15 . 
         [0030]    An adhesive layer  19  is disposed on the housing. In one configuration, the adhesive layer is made from a synthetic polymer like polyvinylchloride (PVC) sheet material. Preferably, this layer is detachable. The layer  19  uses an adhesive  20  that is suitable for capturing small airborne particles of the size ranges indicated above. The layer  19  is also attached to the housing  17  using an adhesive or other suitable method. 
         [0031]    As shown, the electret module  13  includes a ground layer  21  made from metal, such as a metal foil, or another conductive material, This ground layer is an optional layer, and may be omitted from the electret module depending upon design considerations. 
         [0032]    In one optional configuration, as shown in  FIGS. 2-4 , the air purifier includes a filter  23  and a static chamber  25 . The filter is made from any suitable mesh material that allows for sufficient filtration of larger airborne particles, i.e. those larger than  10  microns. In  FIG. 2 , an air purifier  11  having a mask  27 , a static chamber  25 , and a filter  23  is shown. In this configuration, the static chamber  25  is adjacent to the filter  23  and disposed within the mask  27 . The mask may be made from plastic or other soft materials that allow for comfortable placement over a user&#39;s mouth and/or nose. 
         [0033]    In  FIG. 3 , an electret module is shown disposed within the static chamber  25  along an air flow path  26 . In this configuration, the filter  23  is adjacent to the electret element and in line with the air flow path  26 .  FIG. 4  illustrates a user wearing a mask  27  that incorporates the static chamber  25  and the filter  23 . In this configuration, at least one strap  28  is used to hold the mask  27  securely over a user&#39;s mouth and/or nose. The strap is attached to the mask, using a pin  24  or other suitable method of attachment. The strap may be made from plastic or other soft materials that allow for comfortable placement on a user&#39;s mouth and/or nose. Optionally, the strap  28  is elastic and adapted to extend over a user&#39;s head, ears, and/or neck. 
         [0034]    As shown in  FIGS. 5 and 6 , in other optional configurations, the air purifier includes an electret module coupled to headgear  29 . Although shown as a cap, the electret module may be coupled to any type of headgear or other gear that is close enough to a person&#39;s eyes, mouth and/or nose to capture airborne particles. In  FIG. 5 , a module area  14  where an electret module may be coupled to a cap brim  30  is shown. In this configuration, the electret module can generate a static field (not shown) towards the face of a person. 
         [0035]      FIG. 7  shows a block diagram, illustrating a static restorer  31 . The static restorer  31  increases the surface potential of an electret element. The static restorer  31  uses a high voltage field potential to force the internal molecular dipole to realign with the applied field. After realignment of the C—F bond by the external field, the internal molecular polarities increase the surface potential of the electret element. 
         [0036]    The static restorer  31  includes a high voltage generator  33 , also referred to in the art as an extra high tension (EHT) generator. The static restorer also includes an AC to DC rectifier  35 , a smoothing filter  37 , a battery  39 , and a switch  41 . The high voltage generator  33  is made using a low frequency oscillator and a voltage step-up transformer (not shown). Optionally, the high voltage generator includes a timer  43  to control the duration of EHT output. 
         [0037]    Without the application of the static restorer, the surface potential of an electret element can decay, as shown in  FIG. 8 . In one example, a sample electret element was made from non-porous PTFE. The electret element initially had a surface potential of 11.5 KV. The electret element was then exposed to air for 6.5 hours. After this exposure, the surface potential was measured at 5.5 KV. 
         [0038]    Using this same sample electret element, a static restorer having a 20 KV output was applied for 5 minutes. After this application, the surface potential increased to 10.5 KV. The sample electret element was then exposed to air for 5.6 hours. Afterwards, the surface potential decreased to 4.3 KV. A graphical representation of this decay is shown in  FIG. 9 . 
         [0039]    Accordingly, air purifiers having electret modules and a static restorer are disclosed. While aspects of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein. The invention, therefore, is not to be restricted except in the spirit of the following claims.