Abstract:
A corona discharge static neutralizing device includes a wire electrode retained in tension between spaced ends of a resilient support member that is positioned within a flowing air stream. Another electrode aligned with and spaced from the wire electrode promotes a flowing ion stream, when connected to receive an ionizing difference of potential, that flows in skew orientation relative to the flowing air stream. Multiple wire electrodes are supported in tension on a resilient support member along with another electrode disposed on the support member intermediate the wire electrodes and in substantially the same plane therewith.

Description:
FIELD OF THE INVENTION 
   This invention relates to ion generators and more particularly to static neutralizing apparatus for efficiently delivering ions in a flowing stream of air or other gas. 
   BACKGROUND OF THE INVENTION 
   Electrode structure for generating ions of one or other polarity commonly rely upon a point emitter to establish an intense electrical field about the point sufficient to form ions in response to an applied ionizing voltage. However, ions generated in this manner for delivery within a flowing stream of air or other gas are significantly immobilized by the intense electrical field and may be poorly delivered into the flowing stream. 
   Long, thin wire electrodes are known for generating ionizing electric fields over linear dimensions, for example, for delivering ions of one polarity to a closely-spaced charging object such as an imaging drum of an xerographic printing device. However, an ionizing electrode of this type is usually mounted very close to the charging object and in tension over the span of its length to assure reasonably accurate spacing between the wire electrode and imaging drum. 
   SUMMARY OF THE INVENTION 
   In accordance with one embodiment of the present invention, a non-conductive support member retains a thin ion-emitting wire electrode in proximity to a low voltage electrode, all disposed within a flowing air stream. Various configurations of support member are configured to minimize air-flow restrictions in order to improve the efficiency of ion delivery from the ion-emitting wire electrode to the flowing air stream. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1A  is a plan view of one embodiment of the apparatus according to the present invention; 
       FIG. 1B  is a sectional view of a coated electrode wire in accordance with the present invention; 
       FIG. 2  is a multiple-electrode configuration of the apparatus of  FIG. 1 ; 
       FIG. 3  is a plan view of another embodiment of thin-wire electrodes according to the present invention; 
       FIG. 4  is a plan view of another embodiment of a thin-wire electrode according to the present invention. 
       FIG. 5  is a pictorial illustration of one electrode structure within an air-flow delivery system; 
       FIG. 6  is a pictorial illustration of another embodiment of an electrode structure within an air-flow delivery system according to the present invention; 
       FIG. 7  is a pictorial illustration of another embodiment of an electrode structure within an air-flow delivery system according to the present invention; 
       FIG. 8  is a pictorial illustration of another embodiment of an electrode structure within an air-flow delivery system according to the present invention; 
       FIG. 9  is a pictorial sectional view of a delivery system for gas under pressure including an electrode structure according to the present invention; and 
       FIG. 10  is a plan view of an electrode structure according to the present invention for fabrication within a confined slot in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring now to  FIG. 1A , there is shown a plan view of one embodiment of the present invention in which a generally U-shaped support member  4  is formed of non-conductive electrically-insulating resilient material such as printed-circuit substrate, or polycarbonate, or the like. Conductive pads  2  are disposed at upper ends of the U-shaped support member and a low voltage electrode  3  is also disposed in the root or base of the U-shaped support member  4 . A thin wire  1  forms a high-voltage emitter electrode in the span between the upper ends of the support member  4 . In this configuration, the wire electrode  1  may be attached as by soldering, welding, crimping, riveting, or the like to the conductive pads  2  while the support member  4  is slightly flexed inwardly to retain the wire electrode  1  in tension upon return of the support member  4  toward its relaxed shape. The low voltage electrode  3  and the high voltage electrode  1  are thus configured to reside in substantially the same plane, for mounting and connections into electrical circuits  21 , as later described herein. The distance between the low and high voltage electrodes  1 ,  3  may be in the range of about 0.4 to about 0.8 inches, and preferably in the range of about 0.5-0.6 inches for operation of the high voltage wire electrode at voltages in the range from about 3KV to about 10KV. The spacing can be optimized for the associated operating conditions of voltage (and frequency of AC ionizing voltage) and air-flow velocity over the structure. In addition, the thickness and elastic properties of the support member  4  should be greater than such properties of the wire electrode  1 . Specifically, the thickness of the support member  4  should be about 10-20 times greater, and preferably 10-12 times greater than the diameter of the wire electrode  1  to provide desirable aerodynamic properties to the structure, for reasons as later described herein. In addition, the Young&#39;s modulus of elasticity of the support member  4  should be significantly greater than the Young&#39;s modulus of elasticity of the wire electrode  1  to assure reliable tensioning of the wire electrode  1  on the support member  4  over time and temperature of operating conditions. 
   Referring to the sectional view of  FIG. 1B , there is shown an insulating coating  5  such as glass or ceramic overlaying the electrode wire  1  for use in ultra-clean environments in which corona discharge and associated electroerosion of particles from the wire electrode  1  is unacceptable. In this configuration, the electrode wire is operable on high ionizing AC applied voltage in the range of about 3KV-10KV (rms) at a frequency of about 50-100,000 Hz. 
   Referring now to  FIG. 2 , there is shown a top view of another embodiment of the present invention in which the support member  4  includes a pair of substantially U-shaped supports disposed in back-to-back configuration substantially as an H-shaped support member  4 . The extreme ends of the H-shaped uprights each includes a conductive pad  2  that supports and connects to a tensioned, thin electrode wire  1 , in the manner as previously described herein. In addition, the root or lateral segment of the H-shaped support member includes a low voltage electrode  3  disposed intermediate the high-voltage emitter electrode wires  1 . 
   Referring now to  FIGS. 3 and 4 , there are shown alternative configurations of the wire electrodes  1  according to the present invention in which the electrode  1  is disposed in a loop attached to a conductive pad  2 . In the embodiment of  FIG. 3 , the loops may be closely spaced apart from each other to establish interactive electrical fields therebetween. Similarly, in the embodiment of  FIG. 4 , a loop electrode  1  is disposed closely adjacent a planar electrode  3  to establish interactive electrical-fields therebetween. Alternatively, each of the individual loops may be associated with a helical winding of a wire electrode having a longitudinal axis disposed substantially normal to the page for delivering ions to a stream  8  of air flowing over the structure. The loop radius may be in the range of about 0.05″ to 2″, and preferably in the range of about 0.1″ to 0.5″. The diameter of the wire forming the loop electrode may be in the range from about 2 to 5 mils, and preferably in about 2.4 to 2.5 mils. 
   Referring now to  FIG. 5 , there is shown a pictorial sectional view of apparatus for delivering ions in a flowing stream  8  of air in accordance with the present invention. A fan  15  moves a stream  8  of air within a surrounding insulative shroud  6  past an electrode structure, for example, as illustrated and described herein with reference to  FIG. 2 . The delivery of ions into the flowing air stream  8  is dependent upon the electrode positions relative to the flowing air stream  8 . Ideally, the ratio of ion-generating area to area obstructing air flow past the electrodes is greater for wire electrode than for emitter point electrode. Air flow is very efficient at moving ions when they are not tightly bound by the electrical field. The electrostatic field intensity is at a maximum at the surface of the wire electrode  1 , where all ions are created. A minimum field intensity occurs on the surface of the low voltage electrode  3 . In a strong electrical field, ions are not free to follow the air flow. For that reason, the electrode arrangements according to the present invention are positioned so that the low-voltage electrode  3  is located upstream and the high-voltage wire electrode  1  is located downstream in the air flow, as shown in  FIG. 8 , to maximize the ion harvest into the air flow  8 . 
   In some applications, the air flow is not uniform. In that case, it is possible to maximize ion harvest by utilizing aerodynamic forces to move the ions most efficiently. In order to accomplish this, the ionizer should have the maximum airflow at the flat low voltage electrode, typically realized near the periphery of an axial fan within a confining shroud  6 . 
   It has been determined that optimum delivery of generated ions into air stream  8  from wire electrode  1  occurs where the ion stream flows perpendicular to, or in opposite direction to, air flow. Thus, as illustrated in  FIG. 5 , an H-shaped structure as shown in  FIG. 2  is disposed perpendicular to the air flow  8  and orients the low-voltage electrode  3  and the high-voltage, ion-emitting thin-wire electrodes  1  across the air flow. This establishes ion streams  7  flowing normal to the air flow  8  established by the fan  15  that is positioned downstream of the ion-generating structure. In this configuration, the fan should ideally be formed of non-conductive material, or include non-conductive surface coating on conductive fan components. Alternatively, as illustrated in  FIG. 6 , the fan  15  may be disposed upstream of the ion-generating structure including an H-shaped support member  4 , as illustrated in  FIG. 2 . 
   Referring now to  FIGS. 7 and 8 , there are shown other embodiments in which the ion-generating structures including U-shaped support members  4 , as illustrated in  FIG. 1 , are oriented within a flowing air stream  8  to form an ion stream  7  in opposite direction to the air flow stream  8 . In these embodiments, the fan  15  may be disposed either upstream of the ion-generating structure, as illustrated in  FIG. 7 , or downstream of the ion-generating structure, as illustrated in  FIG. 8 . 
   Referring now to the sectional view of an elongated corona-generating structure as illustrated in  FIG. 9 , there is shown a housing  14  including an upper chamber for containing electrical components, and a lower chamber  10  for containing air (or other gas) under pressure. A lower shroud  17  of electrically non-conductive material forms a shield about the ion-generating structure including low voltage electrode  3  and high voltage wire electrode  3  (shown with a coating  5 , as illustrated and described with reference to  FIG. 1B ) on support member  4  in a configuration as illustrated in  FIG. 1A . This ion-generating structure produces an ion stream  7  flowing in a direction opposite to the direction of air (or other gas) flowing  8  under pressure from chamber  10  through aperture  11 . These oppositely-directed flows of the ion stream  7  and air stream  8  are found to promote more efficient delivery of the generated ions into the air stream  8  away from the influence of associated electrical fields. 
   In operation, the wire electrode  1  in each of the illustrated embodiments is connected to receive a high ionizing voltage of either polarity or of alternating polarity from an associated power supply  21 . The low-voltage electrode  3  may be connected to a reference potential  23  such as ground, or may be connected as a balance-sensing electrode in a circuit  25  of conventional design for controlling in known manner at least one or other of the polarized voltages to alter the quantities of ions of one or other polarity delivered within the air stream  8 . Of course, a wire electrode  1  may be alternately switched between sources of high ionizing voltages of opposite polarities, or may be pulsed intermittently with DC of one polarity, or may be connected (e.g., capacitively) to an AC source of high ionizing voltage or directly connected to a DC source of high ionizing voltage of one polarity. 
   Referring now to  FIG. 10 , there is shown one embodiment of an ion-generating structure according to the present invention for fabrication within a slot or elongated recess  18  within a fixture  12 . In this embodiment, a resilient, flexible support member  4  includes conductive end pieces  2  to which the wire electrode  1  is attached while the support member  4  is flexed by spacers  13  positioned between the support member  4  and walls of the groove in fixture  12 . After firmly attaching the wire electrode  1  to the end pieces  2 , the spacers  13  may be removed. The support member  4  resiliently returns toward its normal shape, thereby tensioning the wire electrode  1  in a composite structure suitable for operation in the manner as illustrated and described herein. Such fabricated structure may be mounted and distributed for operation and replacement in a larger structure as a disposable cartridge. As illustrated and described herein circuitry connected to the non-wire electrode  3  may be either a source of reference potential such as ground, or a source of low voltage, or a circuit  25  for sensing ions in the vicinity of such electrode in order to control one or more sources of high ionizing voltage in known manner to achieve a selected balance or unbalanced condition of ions flowing in an air stream  8 . 
   Therefore, the ion-generating structures in accordance with the present invention establish ion streams that can be oriented in directions normal to, or in opposition to, the directions of flowing streams of air or other gas. This promotes more effective delivery of generated ions within the flowing stream.