Air ionizer
BACKGROUND OF THE INVENTION 
     Air ionizers are widely used in industry to prevent electrostatic charge build-up and to neutralize existing charges. Ionizers are also used for therapeutic purposes to produce mostly negative ions which have a beneficial effect on respiratory diseases and allergies, perform a tranquilizing function, lower bacteria, and improve reaction time. 
     Known industrial ionizers use radioactive materials or alternating current corona discharge to produce positive and negative air ions. Radioactive ionizers, which are relatively weak, produce equal amounts of positive and negative ions. The alternating current corona discharge ionizers produce more negative than positive ions. The common corona discharge arrangement uses a needle point or a thin wire in close proximity to a grounded surface to produce a strong electric field. Ozone and nitrus oxides are generated as undesirable by-products. 
     U.S. Pat. No. 3,873,835 describes a combination of an electric fan and ion-producing carbon brushes. This device produces a draft and requires a slip ring to supply the high voltage to the rotating fan. U.S. Pat. No. 3,936,698 describes a method for producing the desired ion ratio by using two independent unipolar air ionizers of opposite polarity which are alternately energized for different periods of time. This approach is complicated and requires a fan for ion distribution. 
     For optimum therapeutic application, the amount of unipolar air ions inhaled must be controlled. The amount of bipolar ions is not as important as the ratio of positive to negative ions. The maximum beneficial effect can be achieved by simultaneous application of bipolar air ions having a ratio of less than one and an electric field of +500 to +1000 volts per meter. Both requirements are easily achieved by the present invention. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a plan view of an air ionizer embodying the invention; 
     FIG. 2 is a side elevational view of the apparatus of FIG. 2; 
     FIG. 3 is an elevational view, partly in section, of the apparatus of FIG. 1; 
     FIG. 4 is an elevational view, partly in section, of a modification of the invention; and 
     FIG. 5 is an enlarged sectional view of a portion of the apparatus of FIG. 1 showing a modification therein. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An air ionizer 10 embodying the invention, referring to FIGS. 1-3, comprises a hemispherical shell 20 made of insulating material, and having an outer surface 30 and an inner surface 40. The shell is seated on and secured to an insulating base 44. A conductive layer 50 having several holes 60 is provided on the inner surface 40 of the shell 20, and individual conductive layers or plates 70 are formed on the inner surface 40 within the holes 60 in layer 50. Layers 70 are insulated from layer 50, and they are interconnected by an insulated lead or wire 80. A plurality of conductive discs or plates 90, each carrying a plurality of conductive filamentary elements 100 are attached to the outer surface of the shell 20 aligned with the corresponding layers 70 and thus capacitively coupled thereto. As seen in FIG. 1, the plates 90 and their conductive filaments 100 are spaced apart on the outer surface of the shell. The area of the plates 90 and the filaments 100 may be about one square inch. 
     The ionizer 10 includes a high voltage power supply 110 which is mounted, for safety, inside the shell 30 and on the base 44 and has its electrical line cord 120 running through the base. The line cord provides line voltage and ground for the high voltage power supply which preferably has an alternating current output at terminal 114 of about 4000 volts RMS and a direct current output at terminal 112 of about 5600 volts. A half-wave modifier or signal modifying circuit 120, made up of a diode 132 and a resistor 124 in parallel, is connected between the A.C. output terminal 114 of the power supply and all of the layers 70 so that the A.C. output of the power supply, modified by circuit 120, is coupled to these layers, D.C. terminal 112 is connected to conductive layer 50. 
     In operation of the apparatus 10 of FIG. 3, conductive layers 70, together with the insulating shell 20 and the outer conductive discs 90, represent capacitors, and, with A.C. terminal 114 connected to them, they produce an alternating voltage on the conductive filamentary elements 100. The D.C. output terminal 112 connected to conductive layer 50 causes an external electric field to be generated. Both positive and negative air ions will be generated by corona discharge at the filaments 100, with the ratio of positive to negative ions being controlled by the half-wave modifier 120. Depending on the orientation of the diode 123 and the value of the resistor 124, more or fewer ions of one desired polarity could be produced. The diode 123 passes one unmodified half-wave of alternating current, and the other half-wave goes through the resistor and will experience a voltage drop, as is well known in the art. Those skilled in the art can readily adjust circuit 120 to achieve the desired type and density of ions generated. 
     Optimum generation and spread of ions is achieved by the interaction of the effect of the A.C. output connected through circuit 120 to plates 70 and filaments 100 with the effect of D.C. terminal 112 connected to layer 50 which generates an external electric field outside the ionizer. 
     In a modification of the invention illustrated in FIG. 4, the ionizer 10 includes the same elements as the ionizer shown in FIGS. 1-3 except that conductive layers 70 in the holes in conductive layer 50 are omitted and the conductive plates 90 and filamentary elements 100 are connected through housing 20 (through holes 60 in conductive film 50) to wire 80 and thence to D.C. terminal 112 of the high voltage power supply through a resistor 130 (to prevent shock to the user). The alternating current output at terminal 114 is connected through the half-wave modifier 120 to the conductive inside layer 50. 
     As above, the filaments 100 generate ions, and these fill the space surrounding the ionizer to a favorable distance due to the interaction of the A.C. and D.C. fields. 
     It is noted that the filaments 100 are preferably of carbon to eliminate ozone. 
     The principles of the invention, disclosed above, will permit those skilled in the art to make modifications in the specific structures and circuits described above.