Patent Publication Number: US-7591884-B2

Title: Air cleaner with electrostatic flocked piles

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an air cleaner, and more particularly, to an air cleaner which further improves air cleaning performance through physical filtering and through filtering using an electrostatic force. 
   2. Background of the Related Art 
   An air cleaner is a device that operates to remove particulates such as fine dust, fine contaminants, etc., or remove bad odors or the like. 
   Air cleaners can be divided into electric filtration types, electric dust collection types, anion generation types, mechanical filter types and others, according to a particulate removal mechanism. Air cleaners can also be classified as ozone generation types and carbon adsorption types based on odor removal mechanism. 
   While the electric filtration type and the electric dust collection type have high initial contaminant removal performance, in particular, a high CADR (clean air delivery rate), they have a disadvantage in that their performance is drastically reduced after a sustained period of continuous use. The filters in such devices have to be frequently replaced. The anion generation generally has low maintenance costs, but its filter performance is poor. The mechanical filter type is high in clean air delivery rate, the life span of a filter is long, and its maintenance cost is low, but the filter size is large, which leads to a disadvantage that the volume of the entire system is large and it is difficult to make it compatible with other systems. 
     FIG. 1  schematically illustrates an air cleaner according to a conventional electric dust collection mechanism. An ionization unit  1  uses a high voltage discharge to ionize foreign materials such as dust and the like in the air passing through the ionization unit. The ionized foreign materials are then collected in a dust collection unit  2  by an electrostatic force. The dust collection unit  2  comprises a pair of cathode plates  4   a  and a dust collecting electrode plate  4   b  made of a cathode. The ionization unit  1  comprises a discharge line  3   a  composed of a thin wire made of, for example, tungsten and forming an anode. A pair of opposed discharge electrode plates  3   b  are mounted at upper and lower sides at a predetermined height gap from the discharge line  3   a  and form a cathode. When a high voltage is applied to the discharge line  3   a , current starts to flow due to a high potential difference formed between the discharge line  3   a  and the opposed discharge electrode plate  3   b  and a corona discharge takes place. This discharge ionizes dust in the air flowing in the direction indicated by the arrows. Typically, a plurality of discharge lines  3   a  and opposed discharge electrode plates  3   b  are formed side by side at regular intervals. 
   SUMMARY OF THE INVENTION 
   An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter. 
   An object of the present invention is to provide a novel air cleaning mechanism which can improve air cleaning capability in an air cleaner. 
   Another object of the present invention is to provide a dust collection system which increases the collection area or collectability of foreign materials in an air cleaner. 
   Yet another object of the present invention is to provide an air cleaner which is easy to apply to an air conditioning apparatus or the like. 
   An electrostatic air cleaner embodying the invention includes an ionization unit configured to impart an electrical charge to particles contained in a flow of air entering the air cleaner, and a collection unit configured to remove and collect particles from the flow of air entering the air cleaner, wherein a plurality of flocked piles are disposed on at least one of the ionization unit and the collection unit. The plurality of flocked piles could be disposed on electrodes of the ionization unit, and/or on collection plates of the collection unit. In some embodiments of the invention, a voltage may be applied to the flocked piles on the collection plates of the collection unit. The voltage would serve to electrically polarize the plurality of flocked piles such that the plurality of flocked piles electrically attract particles in the air flowing through collection unit. 
   In some embodiments of the invention, the electrodes and collection plate could be plate shaped, and in other embodiments, they may be formed of a metal mesh. Some embodiments of the invention may include an auxiliary filter in addition to the collection unit. The auxiliary filter could be disposed between the ionization unit and the collection unit, and a plurality of flocked piles may also be disposed on the auxiliary filter. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements, and wherein: 
       FIG. 1  is a schematic view illustrating an air cleaning mechanism of a conventional air cleaner; 
       FIG. 2  is a schematic view illustrating an air cleaning mechanism of an air cleaner according to the present invention; 
       FIG. 3  is an enlarged view of part A of  FIG. 2 ; 
       FIG. 4  is a schematic view illustrating an electrostatic flocking process; 
       FIG. 5  is a schematic sectional view illustrating a basal plate on which electrostatic flocked piles are bonded; 
       FIG. 6  is a photograph showing a mesh electrode on which electrostatic flocked piles are bonded; 
       FIG. 7  is a graph illustrating discharge current characteristics depending on the length of electrostatic flocked piles; and 
       FIG. 8  is a photograph of an air cleaner actually manufactured for illustration. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   An air cleaner embodying the invention includes an ionization unit which causes a high voltage discharge; and a dust collection unit for collecting foreign materials that have been ionized while passing through the ionization unit. A plurality of electrostatic flocked piles are disposed on either the ionization unit or the dust collection unit, or both. The electrostatic flocked piles perform a dual filtering action by filtering out dust or foreign materials in the air at the ionization unit or the dust collection unit by physical contact, and by an electrostatic force, thereby doubling air cleaning performance. An air cleaner according to the present invention may further comprise an auxiliary filter in addition to the ionization unit and the dust collection unit. It is preferable that this auxiliary filter is formed between the ionization unit and the dust collection unit. However, the auxiliary filter may be mounted next to the dust collection unit to serve as a secondary dust collection unit. Preferably, the electrostatic flocked piles according to the present invention are also disposed on this auxiliary filter. 
   Flocking, or electrostatic flocking, is a finishing technique in which monofilaments, also called flocks or piles, are adhered onto the surface of various types of materials to give a velvet-like appearance. The flocks or piles are obtained by chopping cotton, synthetic fibers, etc. to a length of several mm. In the electrostatic flocking method, an adhesive is coated onto the surface of a material, and then flocks/piles are dispersed onto or adhered onto the surface of the material by using an electrostatic attraction force. Materials for electrostatic flocking are diverse, including wood, paper, textiles, plastics, glass, metal, etc. The piles to be flocked in an air filter embodying the invention include polymer materials such as nylon, rayon, polyester, etc. However, a variety of other fibrous materials can also be utilized. 
   An air filter embodying the present invention includes electrostatic flocked piles or fibrous layers in an ionization unit, and/or in the dust collection unit, and/or in an auxiliary filter. The electrostatic flocking is applied to the parts of the air filter in a manner that is similar to how flocking is conventionally applied to the surface of fabrics, or similar to a color printing technique. The electrostatic flocking further reinforces the filtering function through these piles or fibrous layers. 
     FIG. 2  schematically illustrates parts of an air cleaner according to one embodiment of the present invention. An ionization unit  10  is located at the front part of the air cleaner and ionizes foreign materials  40  such as dust or the like in the air flowing into the air cleaner. The structure of the ionization unit may be similar to that shown in  FIG. 1 . However, other arrangements could also be used and there are no special restrictions on its shape or size. To enlarge the ionization area, one electrode may be formed in a wire shape and the other electrode may be formed as a plate or mesh. Alternatively, both of the electrodes may be formed in a wire shape. A high voltage from a power supply unit  30  is applied to the ionization unit  10 . Electrostatic flocked piles may also be disposed on the electrodes of the ionization unit. In this case, the flocked piles may provide their filtering action during the process of ionizing the foreign materials. 
   In addition, an auxiliary filter  21  may be mounted next to the ionization unit. The auxiliary filter may include a mesh-shaped electrode which preferably has electrostatic flocked piles bonded to its surface. An auxiliary filter having electrostatic flocked piles bonded thereto is able to electrostatically filter out dust using the electrostatic flocked piles. A high voltage would be applied to the flocked piles on the auxiliary filter, which would cause ionized particles in the air flow to be attracted to the flocked piles. 
   The dust collection unit  20  includes at least one electrode  22 , and the electrode  22  preferably has electrostatic flocked piles  23  bonded thereto. When a high voltage is applied to the dust collection unit  20 , dust  41  or the like ionized while passing through the ionization unit  10  is attracted to the electrostatic flocked piles  23  by an electrostatic force. The electrostatic flocked piles  23  increase the filtering effect by physically adsorbing the foreign materials  40 , as well as by adsorbing the foreign materials by an electrostatic force. 
   The electrode  22  of the dust collection unit is preferably a mesh shaped electrode. The mesh-shaped electrode makes it easier to form electrostatic flocked piles on the electrode, and it allows the flow of air from which dust or the like has been removed to easily pass through the filter. 
     FIG. 3  is an enlarged view of part ‘A’ of  FIG. 2 , which schematically illustrates the electrostatic flocked piles  23  which are bonded onto the surface of the mesh electrode  22 . The dust particles  41  are adsorbed to the electrostatic flocked piles  23 . Such dust filtering is caused by the polarization orientation property of the electrostatic flocked piles. The polarization orientation of the electrostatic flocked piles is described below with reference to  FIG. 4 . 
     FIG. 4  schematically illustrates an electrostatic flocking process. Piles  53  to be flocked are disposed between two electrodes  51  and  52 . The polarization orientation of the piles occurs when a voltage is applied to the electrodes, and the polarized piles  54  move towards a substrate  60 . An adhesive layer  61  is formed in advance on the surface of the substrate  60  and the piles  55  are secured to the substrate  60  by the adhesive  61 . 
     FIG. 5  schematically shows the electrostatic flocked piles  55  secured to the substrate  60  by the adhesive layer  61 . Since the electrostatic flocked piles  55  bonded to the substrate are polarized and oriented, the polarized state can be continuously maintained by the application of an electric power. The polarized state of the piles  55  enables them to electrostatically adsorb ionized particles such as dust.  FIG. 6  shows the electrostatic flocked piles actually being uniformly disposed on the surface of the mesh electrode. 
   In an air cleaner according to the present invention, it is important to control the shape of the electrostatic flocked piles because they filter out dust or the like by physical contact, as well by an electrostatic attraction. If the electrostatic flocked piles are thick or long, the physical contact can be increased. Further, discharge current properties may differ according to the length of the electrostatic flocked piles, as shown in Table 1. 
   
     
       
         
             
           
             
               TABLE 1 
             
           
          
             
                 
             
             
               Discharge Current Properties depending on the Length of 
             
             
               Electrostatic Flocked Piles 
             
          
         
         
             
             
          
             
                 
               Discharge 
             
             
                 
               Current (μA) 
             
          
         
         
             
             
             
             
             
          
             
                 
               Applied 
               No Electrostatic 
               0.4 mm 
               0.7 
             
             
                 
               Voltage (kV) 
               Flocking Done 
               Pile 
               mm Pile 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
          
             
                 
               4 
               0 
               0 
               0 
             
             
                 
               4.5 
               0 
               4 
               9 
             
             
                 
               4.6 
               4 
               17 
               24 
             
             
                 
               4.8 
               30 
               50 
               55 
             
             
                 
               5 
               50 
               90 
               95 
             
             
                 
               5.5 
               170 
               210 
               220 
             
             
                 
               6 
               300 
               370 
               380 
             
             
                 
                 
             
          
         
       
     
   
   As shown in Table 1, it is clear that discharge currents for the same applied voltage are larger when electrostatic flocked piles are included as compared to when no electrostatic flocking is done. Also, the discharge currents are larger when the electrostatic flocked piles are 0.7 mm in length as compared to when they are 0.4 mm in length. These results indicate that the filtering effect caused by an electrostatic force can be acquired by forming electrostatic flocked piles on components of the air cleaner, and that the longer the electrostatic flocked piles, the larger the filtering effect caused by an electrostatic force. 
   The result of Table 1 can also be understood by observing changes in discharge current depending on changes in voltage as shown in  FIG. 7 . 
     FIG. 8  is a photograph showing an example of an air cleaner embodying the invention. The air cleaner may be provided in a device that is configured to be attached to an air conditioning apparatus, as well as being an independent product. The technical construction of the air cleaner mounted to an air conditioning apparatus is well known to those skilled in the art, thus a detailed description will be omitted. 
   The air cleaning performance of an air cleaner embodying the present invention was tested. In the ionization unit, one discharge electrode was formed of a metal wire, and the opposed electrode was made of a metal plate material or a metal plate material whose surface was electrostatically flocked. As the auxiliary filter, an Al mesh electrode or a mesh electrode containing piles electrostatically flocked thereon was used. As the dust collection unit, a metal plate material or a mesh electrode containing electrostatic flocked piles is used. A high voltage was applied to the ionization unit. The auxiliary filter and the dust collection unit were grounded, or at least no voltage was applied. The result of an air cleaning performance test on this filter is as shown in Table 2. It can be seen that if the electrodes contain electrostatic flocked piles, the air cleaning performance is excellent on the whole. The clean air delivery rate can be improved significantly by about 20% compared to an air cleaner of a comparative configuration which does not have the electrostatic flocking. 
   
     
       
         
             
             
             
             
           
             
                 
               TABLE 2 
             
           
          
             
                 
                 
             
             
                 
               Ionization Unit 
                 
               Dust Collection unit 
             
          
         
         
             
             
             
             
             
             
             
          
             
                 
               Clean air delivery 
               Discharge 
                 
                 
                 
               Application of 
             
             
                 
               rate (CADR) 
               Electrode 
               Opposed Electrode 
               Auxiliary Filter 
               Shape 
               Electric Field 
             
             
                 
                 
             
          
         
         
             
             
             
             
             
             
             
          
             
               Comparative 
               43 
               Wire 
               Plate Material 
               Al Mesh 
               Plate Material 
               ◯ 
             
             
               Example 
             
             
               Example 1 
               50 
               Wire 
               Electrostatic 
               Al Mesh 
               Plate Material 
               ◯ 
             
             
                 
                 
                 
               Flocked Plate 
             
             
                 
                 
                 
               Material 
             
             
               Example 2 
               65 
               Wire 
               Plate Material 
               Electrostatic Flocked 
               Plate Material 
               ◯ 
             
             
                 
                 
                 
                 
               Mesh 
             
             
               Example 3 
               21 
               Wire 
               Plate Material 
               Electrostatic Flocked 
               Electrostatic Flocked 
               X 
             
             
                 
                 
                 
                 
               Mesh 
               Mesh 
             
             
               Example 4 
               60 
               Wire 
               Electrostatic 
               Al Mesh 
               Plate Material 
               ◯ 
             
             
                 
                 
                 
               Flocked Plate 
             
             
                 
                 
                 
               Material 
             
             
               Example 5 
               64 
               Wire 
               Electrostatic 
               Electrostatic Flocked 
               Plate Material 
               ◯ 
             
             
                 
                 
                 
               Flocked Plate 
               Mesh 
             
             
                 
                 
                 
               Material 
             
             
               Example 6 
               53 
               Wire 
               Plate Material 
               Al Mesh 
               Electrostatic Flocked 
               ◯ 
             
             
                 
                 
                 
                 
                 
               Mesh 
             
             
               Example 7 
               49 
               Wire 
               Plate Material 
               Electrostatic Flocked 
               Electrostatic Flocked 
               ◯ 
             
             
                 
                 
                 
                 
               Mesh (earthed) 
               Mesh 
             
             
               Example 8 
               50 
               Wire 
               Plate Material 
               Electrostatic Flocked 
               Electrostatic Flocked 
               ◯ 
             
             
                 
                 
                 
                 
               Mesh 
               Mesh 
             
             
                 
             
          
         
       
     
   
   As described above, an air cleaner according to the present invention can further improve the performance of air cleaners by including electrostatic flocked piles. Moreover, the air cleaning performance can be changed according to size, length, etc. of the electrostatic flocked piles. The air cleaner of the present invention may be mounted to an air conditioning apparatus or the like to auxiliary perform air cleaning operations. 
   The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.