Self-cleaning linear ionizing bar and methods therefor

A self-cleaning linear ionizer with at least one ionizing electrode, at least one electrode-cleaner, and at least two spool assemblies is disclosed. The electrode has opposing ends and defines an axial working length with a surface that produces an ion cloud and develops degradation products with use. Although the working length of the electrode is stationary, the electrode is movable. The electrode-cleaner is also stationary and selectively engages the electrode along its working length. The opposing ends of the electrode are fixed to the opposing spool assemblies which selectively move the ionizing electrode such that the electrode-cleaner removes at least some of the surface degradation products from the electrode during movement. Methods of using the disclosed ionizer have self-cleaning and ionization modes of operation, which may occur cyclically, alternately, or simultaneously, are also disclosed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is directed to self-cleaning linear ionizers and related processes for corona ionizers. The invention is particularly useful in (but not limited to) ionizing bars in which the linear ion emitter is a wire. Accordingly, the general objects of the invention are to provide novel systems, methods and apparatus of such character.

2. Description of the Related Art

Conventional linear ionizing bars are typically composed of: (1) a bar type ionization cell having at least one linear emitter and one or more non-ionizing reference electrode(s); (2) a clean air (or other gas) supply system having a group of jet type nozzles surrounding each ion emitter and connected to a supply manifold; and (3) a control system with an AC or pulsed DC high voltage power supply connected to the ionization cell. Such linear ionizing bars have found applications in a wide variety of manufacturing industries including flat panel displays, general electronics, semiconductors, etc. While some designs/applications may be optimized for ionization/charging, others may, instead, be optimized for charge neutralization. Charge neutralization applications may entail neutralization of large charged objects at relatively close distances and at rapid throughput rates. For example, the front and back of glass panels having a length and a width exceeding 3000 mm may need to be charge-neutralized wherein the distance between an ionizing bar(s) and the display panels usually ranges from 50-100 mm up to 1000 mm or more, and wherein the display panels are transported at high speeds using robotics systems.

Charge neutralizing bars with linear ionizers (ionizing cells comprising long thin wire(s) as emitter(s)/electrode(s)) have been suggested in (1) U.S. Pat. No. 7,339,778, entitled “Corona Discharge Neutralizing Apparatus”; (2) U.S. Pat. No. 8,048,200, entitled “Clean Corona Gas Ionization For Static Charge Neutralization”; and (3) U.S. Pat. No. 8,492,733 entitled “Multi-Sectional Linear Ionizing Bar And Ionization Cell”, all of which patents are hereby incorporated by reference in their entirety. Further, ionizing bars with wire emitters are currently produced by AB Liros Electronic of Malmö, Sweden and/or Liros Electronic of Hamburg, Germany, and Simco-Ion Technology Group of Alameda, Calif. USA.

With joint reference toFIGS. 1 and 2, a conventional multi-sectional linear ionizing bar100comprises four primary elements: a housing/enclosure103, two ionization cells101and102with a stationary linear ion emitter201for establishing an ion plasma region along the length thereof, a manifold (hidden from view within housing103) for receiving gas from a source and for delivering same past linear ion emitter201, and means for applying202an ionizing signal/voltage (from a conventional/suitable power supply) to linear ion emitter201to thereby establish the ion plasma region. The ionization cells101,102also have common reference (non-ionizing) electrodes104and105positioned on both sides of the ion emitter201. The electrodes104,105are conventionally positioned parallel to, on opposite sides of, and equally distant from ion emitter201This particular linear ionizing bar is shown and described in detail in U.S. Pat. No. 8,492,733 entitled “Multi-Sectional Linear Ionizing Bar And Ionization Cell” (incorporated by reference above).

As shown inFIGS. 1 and 2, housing103supports detachable ionization cell modules101and102from one side such that daisy-chaining of multiple cells together is easily accomplished. Enclosure103may house a high voltage power supply and control system within an interior side (bidden from view by the enclosure103).

Each conventional ionization cell101and102may comprise a linear, for example, wire type corona discharge ion emitter/electrode201, a pair of grills205aand205b, and an array (multiplicity/plurality) of gas orifices206positioned behind linear ion emitter201and through plate203for delivering gas steams past linear ion emitter201as shown.

It will be appreciated that the contact/tensioning springs202are preferably positioned at and affixed to each end of wire electrode201and to stationary cell103. Springs202also receive high voltage ionizing signals and apply them to electrode201. When such AC ionizing signals (typically, high voltage AC, but DC in certain applications) is applied to linear electrode201, corona discharge occurs (between the electrodes201and104,105) to thereby yield copious amounts of both polarity ions. As a result, emitter201is surrounded by dense, high-concentration bipolar ion cloud of positive and negative ions.

Despite the advantages of conventional linear ionizing bars of the type discussed above, they still suffer from at least one deficiency common among corona discharge ionizers: emitter corrosion/contamination/degradation which may significantly reduce ionizing bar performance by causing an undesirable ion balance offset, longer discharge times, and the spread of contamination to the ambient environment and the target workpiece(s). Therefore, manual and regular emitter cleaning is a mandatory maintenance requirement for linear ionizing bars of the type discussed above. In this design, wire emitter is elevated above base plate203by the spring arrangement to facilitate manual removal of corrosion, debris, dust, etc. that accumulates on wire electrode201.

Manual cleaning is undesirable for a number of reasons. For example, the manual cleaning process requires turning off the flow of air/gas and the high voltage ionizing signals and inserting some type of wire cleaning implement between two grills/rails205aand205b. This cleaning implement may be a brush, a wet/dry wipe, or a foam block that physically contacts emitter wire201as it is rubbed back and forth along emitter201. The cleaning implement may be connected to a stick to reach emitter wire201from a relatively long distance because it is often difficult to reach the ion emitter wire for manual cleaning especially for ionizing bars installed in large semiconductor tools. For this reason, manual cleaning may damage the wires, spring contacts, and shorten lifetime of the detachable ionization cells. Last but not least, the frequency with which cleaning cycles must occur depends on the ambient air conditions/cleanness (such as airborne particulate concentration or airborne molecular contamination (AMC)) of rooms/production floors in which the ionizing bars are used. Such cleaning cycles may be time-consuming and may be required daily or weekly in certain critical field-applications.

SUMMARY OF THE INVENTION

The currently disclosed invention suggests new approaches for linear ionizer designs that are capable of solving the above-mentioned problems and, thus, are naturally beneficial for FPD industrial, semiconductor, and other applications.

In one apparatus form, the present invention satisfies the above-stated needs and overcomes the above-stated and other deficiencies of the related art by providing a self-cleaning linear ionizer having at least one ionizing electrode with opposing ends, at least one electrode-cleaner, and at least two spool assemblies. The electrode defines an axial working length that establishes a linear ion cloud when an ionizing voltage is applied thereto and a surface that develops degradation products with use. Such degradation products may (or may not) be due to the accumulation of contaminant byproducts as a result of interaction between the electrode surface and the ambient environment during corona discharge. For example, degradation products may be due to wire erosion/corrosion rather than any attraction of undesirable particles. As used herein the working length of the electrode is the linear portion of the electrode that discharges charge carriers in response to the application of an ionizing voltage, whether or not the electrode is moving. Although the working length of the electrode is stationary, the electrode may be axially movable along the stationary and linear working length. The electrode-cleaner may selectively engage the electrode along its working length and, optionally, may be stationary, or vibrate. The opposing ends of the electrode may be fixed to the opposing spool assemblies which selectively move the ionizing electrode such that the electrode-cleaner removes at least some of the surface degradation products from the electrode during movement. A constant-force spring motor tensions the electrode such that a substantially constant tensional force is maintained on the electrode.

One method form of the invention may comprise a method of using an ionizer of the type having a movable ionizing electrode with opposing ends and a linear and axis-defining working length that is equal to or less than the length of the electrode, a stationary or movable electrode-cleaner that may selectively engage the electrode, opposing spool assemblies to which the electrode ends are affixed such that the linear working length of electrode is disposed between the opposing spool assemblies, and a constant force spring assembly tensioning the electrode on the opposing spool assemblies such that a substantially constant tensional force is maintained on the electrode. One step of the inventive methods of using may comprise applying an ionizing signal to the electrode, during an ionization/working mode of operation, to thereby establish a linear ion cloud along the linear working length thereof whereby the electrode surface develops degradation products with use. Another step of the inventive methods of using may comprise rotating the spool assemblies, during a cleaning mode of operation, to move and tension the ionizing electrode in a first axial direction such that the electrode-cleaner removes surface degradation products from the electrode during movement.

In various alternative method embodiments the ionization and cleaning modes of operation may occur simultaneously, alternately, and/or selectively repeated in desired patterns/cycles. For example, the cleaning mode of operation may be repeated at least twice in a row before each time the ionization mode of operation is repeated.

Naturally, the above-described methods of the invention are particularly well adapted for use with the above-described apparatus of the invention. Similarly, the apparatus of the invention are well suited to perform the inventive methods described above.

Numerous other advantages and features of the present invention will become apparent to those of ordinary skill in the art from the following detailed description of the preferred embodiments, from the claims and from the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

With joint reference toFIGS. 3 through 5B, a first preferred self-cleaning linear ionizer300is first schematically represented inFIG. 3. As discussed herein, ionizer300ofFIGS. 3-5Bis physically and operationally the same as prior art ionizer100except as shown in the accompanying drawings and as discussed in this specification. According to this preferred embodiment ofFIG. 3, the preferred invention may include:1. An ionization cell305including at least one flexible wire electrode301and reference electrodes (items104and105inFIGS. 1 and 2but hidden inFIG. 3);2. An electrode-moving/driving spool assembly302with servo gear motor314;3. A constant-force ionizing electrode moving and tensioning system/assembly303;4. An electrode cleaning mechanism315which can be combined with an electrode contact arrangement318(means for applying) to improve the effectiveness of cleaning mechanism315and, optionally, to apply an ionizing signal a high voltage power supply319to wire electrode301;5. High and low voltage (either AC or DC, as selected based on design considerations and the exercise of ordinary skill in the art) power supplies319and320, respectively, with an associated control system321;6. An optional debris collection and evacuation system312,316, and317; and7. An optional support element304for supporting the linear ion electrode301.

In this embodiment, a single linear ion emitter301is preferably a flexible wire electrode that is resiliently biased between a wire-driving spool assembly302and a wire-tensioning and wire-movement spool assembly303. Spool assembly303preferably includes a passive coiled power spring motor which is able to store and release rotational energy in a form of torque so that electrode301is stretched taut between spool assemblies302and303(Means for moving) with a tension Tw. Spool assembly302and spool assembly303are also referred to herein as the first and second spool assemblies and, inter alia, opposing ends of electrode301may be affixed thereto such that the working length of electrode301may be tautly disposed therebetween. The first spool assembly302may comprise a servo gear motor314and a first spool313. The second spool assembly303may comprise a constant-force spring motor310and a second spool307. In the embodiment ofFIG. 3, the electrode301is coiled around the first electrode spool313as the drive motor314pulls the electrode301in a first axial direction along the working length thereof whereby at least some of the contaminant byproducts are abraded off of the surface of the wire electrode301by the electrode-cleaner315. Also, the electrode301is coiled around the second spool307as the constant-force spring motor assembly pulls electrode301in the opposite axial direction along the working length thereof whereby at least some of the contaminant byproducts are abraded off of the surface of wire electrode301by the electrode-cleaner.

For long ionizers (about 1.0 meter or longer), wire electrode301may also be supported by plural intermediate support elements304such that rotation of the means for moving (first and second spool assemblies) causes axial movement of the wire electrode through the support elements304. These supports304can be positioned on the air/gas supplying manifold305or on the bar enclosure (not shown in this Figure). More details of a physical implementation of this embodiment are presented with respect toFIG. 4et seq.

The wire-tensioning and wire-movement spool assembly mechanism303preferably comprises a guide roll (or, alternatively, a pigtail guide)306and a spool/bobbin307resiliently biased by a spring motor310(means for tensioning). In use, flexible wire electrode301may be wound/coiled on spool307and the resulting wire electrode coil will have a diameter D1. As an option, spool307may hold a minimum of several wraps at all times and these end-wraps may be from the same or different material than emitter wire301. Splicing a “tail” of different material onto an end of an expensive tungsten wire for such end wraps is an inexpensive way of secure the electrode to a spool rather than maintaining extra wraps of tungsten electrode that will never be deployed to produce charge carriers. The length of wire electrode301that can be coiled on spool307preferably should be greater than (at least equal to) the working length (the linear portion) of electrode301residing within ionization bar300(for example 1500 mm).

The spool307is preferably axially aligned with and fixedly attached to (or integrally formed with) a pulley/bobbin308with diameter D2. As shown, one end of a cord/cable322may be wound/coiled on pulley308and the other may be resiliently-biased with a constant tension force Fs to spring motor assembly310. Spring motor assembly310may be a reel/retriever/spool/bobbin and is preferably rated for a retracting load/force of 100-300 grams. Those of ordinary skill in the art may calculate the resulting tension Tw on wire electrode301from the condition of equal torques for spools307and pulley308as follows:
Tw=Fs×D2/D1

Wire electrode301is preferably a small diameter tungsten or titanium wire. However, electrode301may, alternatively, also be any other type of conventional (prior art) corona discharge wire. Control of the electrode-tension Tw is important during normal ionization mode (a static mode of operation) to reduce breakage as well as movement/vibration during ionization (since such movement/vibration may shorten the useful life of electrode301). Similarly, control of the electrode-tension Tw is important during cleaning mode (a dynamic/moving mode of operation) to reduce breakage as well as to provide adequate contact between electrode301and cleaning mechanism3151/(318). Therefore, it is important that the means for tensioning (spring-motor assembly310) provide a substantially constant and stable electrode-tension during both static and dynamic modes of operation. As used herein, the tensional force is considered to be substantially constant if it is within 20 percent (plus or minus) of the predetermined desired tensional force. The spring motor/retriever assembly310may include a coil-spring rotation sensor310′ to monitor the number turns of pulley308(or spool307if307and308are stationary relative to one another) during the wire-cleaning mode for control of the wire-movement. The diameter D2of pulley308is preferably less than that of spool307and, therefore, the tensional force on the cord is less than that on the wire electrode. Spool307and pulley308may be positioned inside a plastic (or other electrically isolative) enclosure311which may be in fluid communication with a pneumatic line and/or vacuum port312to support the high cleanliness of the wire moving and wire-tensioning assembly of ionizer300.

Electrode-driving assembly302preferably comprises an electrically-isolating spool313(made of a conventional electrically isolative material such as common plastics) directly connected to a reversible servo gear motor314. As an alternative to the arrangement shown inFIG. 3, spool313may instead be connected to a motor by a pulley/cord-based transmission (in other words, indirectly connected) for better electrical isolation of spool313. A portion of this pulley/cord-based transmission arrangement preferably used in this alternative is shown inFIG. 5Abelow.

Wire-cleaning mechanism315may comprise one or more of the following abrading/cleaning elements: a brush, a wiper, a wire scraper, a closed or open cell foam block and/or other ablation means/electrode-cleaning means or other functional equivalent known in the art. Electrode-cleaner315may selectively engage electrode301and is preferably connected to a vacuum line312comprising an eductor316and an aerosol filter317for collecting contaminant byproducts/debris cleaned/abraded off of wire electrode301. This means for evacuating enables the evacuation from the electrode-cleaner of at least some of the contaminant byproducts abraded off of the surface of the electrode.

Self-cleaning ionizing bar300may, optionally, include a wire-electrode-supporting/contacting device318to (1) selectively provide a consistent/reliable physical contact between cleaning mechanism315and electrode301(to urge them toward one another) during cleaning operation mode; and (2) apply a high voltage ionizing signal from HVPS319to electrode301during normal operation mode (means for applying). Supporting/contacting device318may comprise any one or more of the following: a simple metal spring contact, a spring-loaded brush or any other known equivalent to deliver ionizing electrical signals to electrode301. Alternatively, spool307may be made from a conductive material such as metal and fixed on central conductive shaft309bwhich is in electrical communication with high voltage power supply319through spring motor310(means for applying). In this way, ionizing signals may be applied to wire electrode301from HVPS319through the conductive shaft and spool to power wire emitter301in the normal ionization mode of operation. Regardless of how ionizing signals are applied to electrode301, both of the low voltage320and high voltage319power supplies are preferably controlled by a microprocessor-based control system321to produce an ion cloud along electrode301in accordance with known techniques/methods/signals/operation.

FIG. 4Ais a partial, perspective, and exploded view of a simplified assembly of an ionization cell400. Those of ordinary skill will see the similarities between this embodiment of the invention and the prior art linear ionizers shown inFIGS. 1 and 2(meaning bar100formed of ionization cells101and102). Significantly, however, the embodiment ofFIGS. 4A-4Dsimplifies construction, increases reliability, and lowers the cost of the inventive ionization bars by avoiding a number of spring assemblies and electrical contacts on each ionization cell.

The side grills/rails405aand405bare shown as exploded from base plate203for clarity. Electrode support elements406aand406bcan be mounted on opposite ends of base plates203and204(only partially shown) to support ionizing wire301. Those of skill in the art will appreciate that wire electrode301defines an axis along the length thereof and support elements406aand406brestrain movement of electrode301in all directions except along the axis defined by electrode301.

With joint reference now toFIGS. 4B, 4C, and 4D, a preferred pigtail support/guide element406a/406bis shown in a top view inFIG. 4B. The same pigtail support is shown in orthogonal side elevation views inFIGS. 4C and 4D. Naturally, the threaded end of the pigtail support is intended to affix the support to the ionization cell400through base plates203,204. The opposing free end preferably takes the form of a helical pigtail guide407which permits axial movement of electrode301therethrough. Further, electrode301may be inserted into helical guide/support301in a direction other than in the direction of the electrode axis during assembly of the inventive ionizer or during replacement of an old/spent/used electrode. While elements406a/406bare preferably fabricated from conductive (or semi conductive materials) such as thick stainless steel wire that are bent into shape and threaded, they must be electrically isolated from each other as well as from ground. One simple way to ensure this is to ensure that base plates203and204are formed of electrically insulating material. In this preferred embodiment, pigtail supports can be mounted, for example, on each ionization cell400(instead of using the springs employed by prior art devices) in spaced relation to prevent wire301from sagging and/or vibrating between the support elements.

It will be appreciated that, inFIG. 4A, ion emitter301is positioned in spaced relation to cell base plates203,204(over a manifold having air jet nozzles). Further, emitter301is at least generally centrally located as in the known linear bars. In this preferred embodiment, emitter301is also preferably supported by group of pigtail guides (406a,406band so on).

Simplified side cutaway views of an inventive self-cleaning ionizing bar are shown inFIGS. 5A and 5B. They show a first spool assembly cross-section300aand a second spool assembly cross-section300bof an ionizer300, respectively, both positioned within a linear ionization bar housing. This housing is the same in all important respects to conventional housing103. In the embodiment ofFIG. 5A, a spool313carries coiled emitter wire301and a pulley314ais connected to servo motor (not shown) by a belt505a. Both pulley314aand belt505amay be made of an electrically isolative material such as conventional polymers or plastics or equivalents known in the art. Further, spool313and pulley314aare shown as being fixedly attached to (or integrally formed with) one another and are disposed on and for rotation about axle309a. Those of skill in the art will appreciate that the pulley/belt arrangement discussed with respect toFIG. 5Arepresents an alternative to the servo gear motor arrangement shown inFIG. 3. One benefit of the arrangement ofFIG. 5Acompared to that ofFIG. 3is a decrease in any possible leakage current from the high voltage applied to wire301and to low voltage servo motor.

As shown inFIG. 5B, spool307carries emitter wire301coiled thereon and pulley308carries a cord322coiled thereon. Cord322connects pulley308with spring-motor or retriever assembly (not shown here but see sensor310′ and motor310ofFIG. 3). As shown inFIG. 5B, a cross-section300bof ionizer300reveals that the second spool assembly is preferably positioned inside of an elongated bar enclosure of the same general type as enclosure103of prior art ionizer100. In particular, spool307and pulley308are shown as being fixedly attached to (or integrally formed with) one another and are disposed on and for rotation about axle309b. Axle309band cord322may, optionally, be made of a conventional electrically isolative material such as various plastics known in the art. Alternatively, spool307and axle309bmay be made of a conventional conductive material (such as various metals known in the art) and in electrical communication with HVPS319(although not shown inFIG. 3, such electrical communication could be provided through spring motor310or other arrangement as a mere matter of design choice). Further, in accordance with various preferred embodiments of the invention shown herein, the wire emitter, the gas-supplying manifold, and emitter-support elements can all be positioned between the two opposing spool assemblies.

Returning toFIG. 3, preferred methods of using inventive linear ionizer in accordance with the invention will now be discussed with particular emphasis on methods of self-cleaning (the cleaning mode of operation) a flexible wire electrode used in the invention. The self-cleaning mode is preferably initiated with microprocessor-based control system321.

Control system321may monitor the ion current of the ionization cell (using a conventional HVPS current sensor, not shown), the ion balance of the ionized gas flow delivered to the target workpiece (using a conventional ion balance sensor, not shown) or both. If the ion current and/or the ion balance is/are determined to be outside of predetermined limits, control system321may either (1) inform relevant personal that electrode cleaning is warranted, and/or (2) initiate automatic electrode cleaning by initiating a cleaning mode of operation. In either case, ionizer300will enter an electrode cleaning mode of operation to restore ionizing performance within the predetermined current and/or balance limits.

The cleaning mode begins with the step of checking the status of high voltage power supply (HVPS)319and (if not already in a “Standby” mode) switching it to a “Standby” mode. Control system321will also stop the flow of CDA/gas to the manifold and restore the CDA pressure to eductor316at the connection to fab/tool vacuum line312. Then, control system321turns-on the low voltage DC power supply320(LVPS) that is connected to servo motor314. Since servo motor314has a large big reduction gear (not shown) it starts slow rotation of spool313. This begins to wind/coil corona wire301from spool307, and axially pull it through support elements304and cleaner315, and onto spool313. Since spool/bobbin313is preferably connected to a servo motor314made from a conventional highly electrically isolative material (such as an ABS plastic or other equivalents known in the art) the possibility of current leakage from emitter wire301to motor314is reduced/eliminated when ionizer300operates in the normal/ionization mode (when ionizing signals are applied to electrode301). Electrical isolation can be further enhanced if both spool313and pulley314aare also made from a conventional highly electrically isolative material (such as an ABS plastic or other equivalents known in the art).

In this cleaning mode of operation the amount of current applied from LVPS320to servo motor314depends on the tension Tw of wire electrode301. Information about this current can be used by control system321to monitor wire electrode tension and/or the status of other wire parameters (such as the degree of wire contamination or wire breakage). For this reason, motor current signals provided by LVPS320are preferably monitored by control system321during the wire cleaning mode of operation.

Further in this embodiment, one end of corona wire electrode301is affixed to spool313and the opposite end is affixed to spool307. Wire tension Tw is substantially constant and balanced by a conventional constant-force spring-motor assembly such as a coiled spring, a retriever, a reel, and/or any other equivalent constant-force spring known in the art. Examples of constant-force spring motor assemblies of the type preferably used in the present invention include those made and offered by Spring John Evans' Sons, Inc. of 1 Spring Ave., Lonsdale, Pa. 19446 with the following product names/descriptions: Enclosed Reels ER04, ER06, ER08; Retreiver 3827-B; and/or Miniature enclosed reel MER-04-SP. Examples of other equivalent spring motor assemblies will readily occur to those of ordinary skill in the art.

The tension force experienced by wire electrode301during cleaning may be equal to or greater than that typically experienced by wire electrode301during the normal ionization mode. During this period, spring motor310will store/accumulate rotational energy. In the cleaning mode, wire301is drawn or pulled onto/wound around spool313and also passes through upstream cleaning mechanism315. When this occurs, cleaning mechanism315preferably abrades off and also traps contaminant particles/debris abraded from the surface of the electrode. Restated, rotational movement of the first and second spool assemblies causes axial movement of the wire electrode along the working length thereof whereby at least some of the contaminant byproducts are abraded off of the surface of the wire electrode by the electrode-cleaner. Particularly desirable cleaning mechanisms for use in the invention include brushes, springs, closed or open cell foam blocks, felt pads, and/or other wire cleaning/polishing means known in the art.

As a first stage of cleaning, cleaning mechanism315(and servo motor314, if desired) may be continuously evacuated by a vacuum (or low pressure) air stream created by eductor316so that contaminant byproducts/debris/particles (removed from the surface of wire301) will also be removed from cleaner315. In particular, the inlet of educator316may be connected to a clean dry air (CDA) line and the outlet of the eductor316can be connected to a filter317to thereby draw the degradation products away from cleaner315and remain trapped in filter317.

After the full working length (for example 1,500 mm) of emitter wire301is wound around spool313, the wire movement preferably stops. For control system purposes, a stop-signal may be generated by sensor310′ or, alternatively, by counting the number of rotations of spool313or of spool307. In response thereto, control system321will turn off servo motor314and reverse the polarity of the voltage applied to motor314by LVPS320so that motor314reverses direction and spool313starts unwinding corona wire301. Since the tension on emitter301is counterbalanced by spring-motor/retriever assembly310, the opposite end of wire301will start to wind back onto spool307as spring motor assembly310releases the previously stored rotational energy. As this happens, cleaning mechanism315begins a second stage of cleaning/polishing/abrading that enhances wire clearness before ionization cell300enters into the ionization mode of operation again. If desired, multiple cleaning/polishing cycles/rounds may occur before cell300enters into the ionization mode of operation again. At the end of the cleaning mode spring motor310again keeps wire tension on constant preselected level Tw during normal operating mode of the linear bar.

Those of ordinary skill in the art will appreciate that spools313and307may be sized and shaped to accommodate lengths of corona wire301far longer than that of bar300. If so, multiple ionization operations can occur before even one cleaning operation (with two phases) is completed since electrode301may be advanced as appropriate to present new/fresh sections for each ionization operation. In this case, the initial phase of cleaning will occur as the wire is advanced past cleaner315, but the second cleaning phase (reversal of wire direction and rewinding of the entire length of wire301) will not begin until the desired number of ionization operations occurs. Thus, a variety of operational mode combinations may be executed as desired if spools313and307are sized and shaped to accommodate lengths of corona wire301longer than that of bar300.

In sum, according to the embodiment ofFIGS. 3 through 5B, the emitter wire tensioning system preferably includes a combination of active and passive motors with plastic/isolative spools. Further, spools307and313(as well as the spring-motor310) can (optionally) be placed in highly electrically isolative enclosures such as enclosure311(in the case of spool307). Moreover, the wire cleaning/tensioning system may also provide an efficient and effective means to power ionizing emitter301and it may do so in a way that prevents leakage current from the emitter wire301during normal ionization operations.

Turning now toFIG. 6, there is shown a simplified electrical circuit model600showing the parasitic/stray capacitances inherently embodied in the inventive self-cleaning linear ionization bar ofFIGS. 3 through 5B. As shown, the spool with coiled emitter wire601on the schematically-represented driving-end-section602presents a stray capacitance Cd, a group conductive wire guides603present stray capacitance Cg1-Cg4and the schematically represented spool and spring-motor-assembly604present a stray capacitance C5. All capacitors representing the various stray capacitances terminate on a grounded reference electrode605. The model600ofFIG. 6shows that high voltage power supply606primarily sources currents into parasitic capacitance and corona ionization. Naturally, operational efficiency can be improved through the minimization of parasitic/leakage current conditions and this may be achieved in the following ways:

affixation of wire guides into dielectric materials of ionization cells, manifolds and/or enclosures;

the use of plastic/electrically-isolative spools, plastic pulleys, and rubber belts in drive units; and/or

the use of passive mechanical (spring motor) parts, non-conductive spools, cording, and/or enclosures in the electrode tensioning system(s).

In some cases its preferable to have a linear bar comprising a system of easily exchangeable linear ionization cells (such as those previously discussed with respect toFIGS. 1, and 2). The constant force spring mechanisms and/or spring retrievers taught herein with respect to the embodiment ofFIGS. 3-5Bcan also be used in other embodiments of the inventive ionization bars.

FIG. 7Aillustrates an another preferred embodiment of an inventive linear ionizing bar700. This embodiment is preferably equipped with an alternative electrode-cleaning mechanism/means that may include one or more electrically isolative filaments positioned in proximity with and parallel to the ionizing electrode701axis wire and an electrode-cleaning shuttle705that may move with the filament (along axis parallel to the electrode axis) and slide along the length of the electrode from one end of the ionizer to another. The filaments may be made of one of the many conventional electrically isolative materials such as polymers or plastics. The shuttle705may be additionally supported and guided by both rails706aand706b. In this way the shuttle may selectively abrade at least some of the contaminant byproducts off of the surface of the ionizing electrode. The filament(s) is/are preferably in tensioned and stretched between opposing and counter-balanced spool assemblies (of the type discussed above with respect toFIGS. 3-5B) of the cleaning system to permit the shuttle to ride thereon.

In this embodiment the cleaning mechanism most preferably comprises, for example, two filaments702aand702bin which one end of each filament is connected to a driving section703that may include a spool connected to small servo gear motor (not shown). Driving section703is functionally similar to that previously discussed with respect toFIGS. 3 and 5ain all important respects. Further, the opposite end of each of filaments702aand703bis connected to spring/retriever section704which includes a spool linked to constant-force spring mechanism or spring retriever (not shown). Sections703and704may comprise the means for moving the cleaning mechanism discussed herein with respect to this embodiment. Section704is functionally similar to that previously discussed with respect toFIGS. 3 and 5bin all important respects. Finally, filaments702aand702bare preferably fixedly attached to and therefore carry cleaning “platform” or “shuttle”705.

According to the embodiment ofFIGS. 7A and 7Beach filament may be made from plastic polymers such as nylon, polyethylene, polyamide, Teflon and/or other highly flexible and electrically isolative materials. Preferred filaments are round in cross-section with a diameter in the range of about 0.05 mm to about 2 mm (functional, but not preferred, filaments may have a larger diameter), have a smooth surface, and have low adhesion/highly hydrophobic properties. Preferred filament diameters are about equal to that of the ion emitter but may be up to about 2-3 times larger than that of the ion emitter. As a result, filament tension can be significantly higher than wire electrode tension. It should be noted that for installations with a downward facing ionizer, filament tension should be increased sufficiently to oppose the force of gravity to thereby ensure that the filament does not sag downwardly. This increased filament tension might require the selection of a larger filament diameter.

Filaments702aand702bmay perform several different functions simultaneously. One of these functions is to carry (support) cleaning platform705. Another is to serve as a mechanical protection grid for ion emitting wire701. Moreover, the high electrical resistivity of the filaments means that they also serve as a grid that enhances ion balance of the air/gas stream produced by linear ionizing bars in accordance with this invention.

According to a related embodiment, the cleaning mechanism may comprise plural filaments in which at least one filament702acan be made from a flexible conductive material (such as stainless steel) and in which other filaments702bcan be made from electrically isolative materials. In this embodiment, the conductive filament702acan be grounded (or electrically biased) and, therefore, inherently serve as a non-ionizing reference electrode. Further, the electrode cleaner may comprise at least one guide that engages at least one ionizer rail, and the electrode cleaner may be connected to at least one filament that is a non-ionizing reference electrode.

Turning now toFIG. 7Bnow, this Figure illustrates a simplified cleaning platform or cleaning shuttle705of the type shown inFIG. 7A. As shown, shuttle705bis preferably fixedly attached to filaments702aand702band may include one or more of a variety of different wire cleaners708. These may include a simple brush cleaner, a wiper, a wire scraper, a closed or open cell foam block, and/or any other equivalent means for cleaning, material or arrangement known in the art. Although primarily intended to clean a wire electrode701, shuttle705may also carry side cleaners/brushes (not shown) to clean rails706aand706b. The shuttle705also may have additional support from the top side of rails706. If so, shuttle guides709may slide on or in rails706a,706b. Preferably, shuttle705will be “parked” inside driving section703when not in use, for example, after a cleaning operation.

A wire cleaning operation in accordance with the embodiment ofFIGS. 7A and 7Bis initiated by the microprocessor of a control system707. The system707will check the status of the high voltage power supply (seeFIG. 3) and, if is on, switch it to “Standby” mode for the duration of the corona wire cleaning operation. At the start, cleaning shuttle705will be in its parking place and the filament(s) will be coiled on the spool in the same driving section703. Then, the control system707turns “ON” low voltage DC power supply (LVPS) and a servo motor (seeFIG. 3). The motor starts to rotate the spool and to unwind filament(s)702aand702b.

Filament(s)702aand702bmove (are pulled) under tension created/defined by the spring motor or retainer704during unwinding. As the result, cleaning shuttle705moves along the bar and cleans emitter wire701(and, optionally, the springs and grills of the ionization cell if the shuttle is equipped with the optional side cleaners/brushes). As soon as shuttle705reaches the spring section704, control system707stops it and reverses the rotational direction of the driving motor in section703and the shuttle is pulled in the opposite direction. The cleaning mode finally terminates when the shuttle705reaches its original parking place in section703once again.

In some cases, it may be possible to have number of wire cleaning/polishing cycles/runs. The spring motor704keeps the tension of all of the filament(s) at a constant/preselected level during ionization and cleaning operating modes of the linear ionizer.

The time table for corona wire cleaning can be daily, weekly, or monthly or any other schedule depending on environmental conditions in the field. Relatively long self cleaning linear bars can be the most economical solution (long bars take more time to clean and ratio of the cost of the auto-cleaner function to the cost of the bar itself is smaller).

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to encompass the various modifications and equivalent arrangements included within the spirit and scope of the appended claims. With respect to the above description, for example, it is to be realized that the optimum dimensional relationships for the parts of the invention, including variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the appended claims. Therefore, the foregoing is considered to be an illustrative, not exhaustive, description of the principles of the present invention.