Abstract:
A sheet and web cleaner has a pair of substantially identical units in facing relation, providing a path for transporting a sheet or web therebetween. Each unit includes a suction hood with an inlet slot. A pair of channels adjacent and parallel thereto have a pressurized air ionizing bar which discharges ionized air at high velocity onto a moving sheet or web. A faceplate covers the channels and the inlet slot and has a tapered central elongate inlet opening which overlies the inlet slot. Elongate air discharge openings overly each of the channels adjacent the inlet opening. A plurality of spaced ridges are disposed on a side of the faceplate proximate the sheet or web oriented relative to a direction of travel of the sheet or web from a travel direction towards respective edges of the sheet or web. Spaces between the ridges communicate with the inlet and discharge openings.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to an apparatus for cleaning particles from moving sheets and webs; and more particularly to a faceplate and ionization air point for such an apparatus.  
         BACKGROUND OF THE INVENTION  
         [0002]    In many industries, sheets and webs of indeterminate length are fed to various processing apparatus, such as printing, gluing, winding, etc. It is important in many instances that these sheets and webs be cleaned of dust and particles.  
           [0003]    A known sheet and web cleaning apparatus is disclosed in U.S. Pat. No. 5,596,783 to Testone, a copy of which is incorporated herein by reference in its entirety. In the Testone &#39;783 patent a sheet or web cleaner comprises a pair of substantially identical facing units, each having a longitudinal suction hood having a generally rectangular inlet slot therein. On either side of and parallel to the inlet slot is a channel containing a pressurized ionizing bar which comprises a hollow tube, a plurality of ionizing points extend from the tube, and small holes adjacent each ionizing point discharge air at high velocity. The sheet or web passes through a pair of opposed units transversely of the longitudinally extending suction hoods, and between respective faceplates on the units.  
           [0004]    Each faceplate is of a smooth, hard material, such as aluminum, steel or a hard plastic material, and has in a face side facing toward the sheet or web a series of spaced, parallel ridges which extend part way through a thickness of the faceplate. The ridges are aligned parallel to each other and are inclined relative to the direction of movement of a sheet or web through the apparatus, and are also inclined to the axis of the suction hood, and to the axes of the ionizing bars. The parallel aligned ridges each have a leading end and a trailing end relative to the direction of travel of the sheet or web, and are aligned obliquely with respect to the direction of travel. In one longitudinal portion of each faceplate the leading ends of the ridges are substantially oriented so as to point away from a co-planar transverse center line through the faceplate in the direction of travel of the web, while the trailing ends are substantially oriented so as to point towards the transverse center line. In another longitudinal portion of each faceplate the leading ends of the ridges are substantially oriented so as to point toward the transverse center line while the trailing ends are substantially oriented so as to point away from the transverse center line.  
           [0005]    The ridges of the faceplate are of generally triangular cross-section, each having an apex facing towards and relatively close to the sheet or web, and facing away from the suction hood. Spaces between the ridges provide a plurality of converging air paths which are in communication with elongate openings in an oppositely facing face side surface of the faceplate, and which extend partly through the faceplate thickness.  
           [0006]    In the oppositely facing face side surface of the faceplate there is a central, elongate inlet opening of tapering width, with the greater width remote from a suction end of the suction hood in order to permit substantially equal volumes of air to flow into the suction hood through its rectangular inlet slot irrespective of a relative position along a longitudinally extending length of the suction hood. There is also an elongate side discharge opening in the faceplate on either side of the central tapered inlet opening, each of which is in registry with a corresponding ionizing bar to permit ionized air discharged from the ionizing bars to flow through the respective discharge openings in the faceplate and through the spaces between the ridges.  
           [0007]    High velocity ionized air currents created by the flow of ionized air from the ionizing bars flows through the respective discharge openings in the faceplate and through the spaces between the ridges. The high velocity ionized air strikes the moving sheet or web neutralizing the static electricity on both the sheet or web material being processed and the contaminant particles dislodging the particulate making the particulate airborne, while an airflow induced by suction draws the air and airborne particles into the suction hood.  
           [0008]    The above described prior art apparatus has been found to have a deficiency when cleaning relatively lightweight, sensitive web materials such as tissue papers, thin gauge films and/or metal foils. In applications involving thin, lightweight sheets or webs the lightweight sheets or webs have been found to be susceptible to a lateral displacement by the induced air current relative to the direction of travel of the web. When the high velocity air strikes the lightweight sheet or web, the sheet or web material on the one longitudinal side of the apparatus whose leading ends of the ridges are oriented so as to point away from the transverse centerline have been found to track along and follow the path of the ridges from their respective leading ends toward the trailing ends as the sheet or web travels along the direction of travel. The result has been that a lateral side portion of the sheet or web on the one longitudinal side tended to be displaced towards the transverse centerline as the web traveled through the apparatus with the result that the sheet or web material became bunched up and wrinkled along the one longitudinal side. Consequently, the one longitudinal side could not be adequately cleaned, and downstream processes were adversely impacted because the sheet or web was not smooth and wrinkle free. This required that the entire sheet or web feeding and handling apparatus be stopped, and that the web material be straightened and smoothed out. This was time consuming, required labor to remedy the situation, and caused interruption of production.  
           [0009]    It has been further observed that lightweight sheets and webs tend to travel through the cleaning apparatus tangential to the face side of one or the other of the faceplates of the opposed units; and that due to transient variations in, for example, the suction or an amount of tension under which the sheet or web is drawn through the apparatus, the faceplate against which the sheet or web travels tangentially can change, the sheet or web sometimes exhibiting oscillatory behavior wherein the sheet or web flutters between the opposed faceplates.  
           [0010]    Due to the inconsistent and sometimes oscillatory behavior of the sheet or web relative to the faceplate against which the sheet or web aligns itself tangentially, attempts to mitigate the lateral displacement of the sheet or web by using two similarly structured, oppositely aligned faceplates, a first faceplate with a general left-to-right alignment of the ridges, and a second faceplate, identical to the first, but installed in an inverted or opposed orientation relative to the first faceplate and thus having a general right-to-left alignment of the ridges have been unsuccessful.  
         SUMMARY OF THE INVENTION  
         [0011]    In a first preferred embodiment of the present invention there is provided a faceplate for a cleaning apparatus for cleaning from a moving web particles which are adhered to it by static electricity, of the type having a pair of oppositely facing suction hoods each having a pair of ionizing bars providing a source of high velocity ionized air, comprising: a plate having oppositely facing face sides, said plate having in a first face side thereof a central tapered elongate first opening, said first opening being of tapered width a greater width thereof at a first end thereof and a lesser width at a second end thereof; through openings in said plate extended from the opposite face side of said plate to, and in communication with, said central tapered elongate first opening; a pair of elongate longitudinal side openings is said first face side, said side openings in said plate further being in communication with said through openings; a series of spaced, first parallel ridges and second parallel ridges extended on a second face side thereof, portions of spaces between said first parallel ridges and portions of spaces between said second parallel ridges being said through openings; wherein said first and second parallel ridges are disposed bilaterally symmetrically about a transverse central axis of said plate.  
           [0012]    In a second preferred embodiment of the present invention there is provided a faceplate for a cleaning apparatus for cleaning from a moving web particles which are adhered to it by static electricity, of the type having a pair of oppositely facing suction hoods each having a pair of ionizing bars providing a source of high velocity ionized air, comprising: a plate having oppositely facing face sides, said plate having in a first face side thereof a central tapered elongate first opening, said first opening being of tapered width a greater width thereof at a first end thereof and a lesser width at a second end thereof; through openings in said plate extended from the opposite face side of said plate to, and in communication with, said central tapered elongate first opening; a pair of elongate longitudinal side openings is said first face side, said side openings in said plate further being in communication with said through openings; a series of spaced, first parallel ridges and second parallel ridges extended on a second face side thereof, said first and second parallel ridges being disposed bilaterally symmetrically about a transverse central axis of said plate, each of said first and second parallel ridges having a leading end and a trailing end in a direction of travel of said moving web; wherein leading ends of said first parallel ridges on a first side of said transverse central axis are disposed nearer said transverse central axis than trailing ends thereof; and leading ends of said second parallel ridges on a second side of said transverse central axis are disposed nearer said transverse central axis than trailing ends thereof.  
           [0013]    In another preferred embodiment of the present invention there is provided a faceplate for a cleaning apparatus for cleaning from a moving web particles which are adhered to it by static electricity, of the type having a pair of oppositely facing suction hoods each having a pair of ionizing bars providing a source of high velocity ionized air, comprising: a plate having oppositely facing face sides, said plate having in a first face side thereof a central tapered elongate first opening, said first opening being of tapered width a greater width thereof at a first end thereof and a lesser width at a second end thereof; through openings in said plate extended from the opposite face side of said plate to, and in communication with, said central tapered elongate first opening; a pair of elongate longitudinal side openings is said first face side, said side openings in said plate further being in communication with said through openings; a series of spaced, first parallel ridges and second parallel ridges extended on a second face side thereof, said first and second parallel ridges being disposed bilaterally symmetrically about a transverse central axis of said plate and obliquely inclined thereto; a plurality of transverse minor axes parallel to, and disposed longitudinally away from, said transverse central axis; and further comprising: a plurality of lateral ridge sets, each lateral ridge set comprising ones of said series of first parallel ridges and ones of said series of second parallel ridges; wherein each said lateral ridge set is disposed bilaterally symmetrically about a corresponding one of said plurality of transverse minor axes.  
           [0014]    Associated with each preferred embodiment of the present invention, a pair of opposed bilaterally symmetrical faceplates is provided for a sheet and web cleaner having a pair of substantially identical facing units, each having a longitudinal suction hood having a generally rectangular inlet slot therein. On either side of and parallel to the inlet slot is a channel containing a pressurized ionizing bar which comprises a hollow tube, a plurality of ionizing points extending from the tube, and small holes to discharge air at high velocity. In a conventional embodiment of the ionizing bar the small holes are adjacent each ionizing point; while in a particularly preferred embodiment of the ionizing bars of the present invention the ionizing points are hollow, needlelike structures having the small holes therethrough and terminated at tips thereof. The sheet or web passes through a pair of opposed units as above described, transversely of the longitudinally extending suction hoods, and between respective faceplates on the units.  
           [0015]    Each faceplate is of smooth hard material, such as aluminum, steel, or other hard plastic material, and has in the side adjacent the sheet or web a series of spaced, parallel ridges which extend part way through the thickness of the faceplate. The ridges are inclined to the direction of travel of a sheet or web through the apparatus, and are also inclined to the axis of the suction hood, and to the axes of the ionizing bars. The ridges of the faceplate are preferably of generally triangular cross-section, each having an apex relatively close to the sheet and web, and remote from the suction hood, the spaces between the ridges provide a plurality of converging air paths which are in communication with elongate openings in the opposite surface of the faceplate, which also extend partly through the faceplate thickness. There is a central, elongate inlet opening which is of tapering width, with the greater width remote from the suction end of the suction hood in order to permit the flow of equal quantities of air into the suction hood through the rectangular inlet slot of the suction hood. There is also provided an elongate side discharge opening in the faceplate on either side of the central tapered inlet opening, each of which is in registry with an ionizing bar to permit ionized air discharged from the ionizing bar to flow through the discharge openings in the faceplate and through the spaces between the ridges. The high velocity ionized air strikes the moving sheet or web, neutralizing the electrostatic attraction of particles to the sheet or web, the flow induced by suction carrying them into the suction hood.  
           [0016]    In the preferred embodiment of the faceplates, on each longitudinal side of each faceplate leading ends of all ridges are oriented so as to point substantially towards a transverse center line defined by the direction of travel of the sheet or web, while all trailing ends of the ridges are oriented so as to point away from the transverse center line. When the high velocity air strikes the lightweight sheet or web, the sheet or web material on each of the longitudinal sides is induced to track along and follow the path of the ridges from their respective leading ends to the trailing ends as the sheet or web travels along the direction of travel with the result that each of the lateral side portions of the sheet or web tends to be drawn away from the transverse centerline as the web travels through the apparatus with the result that web material remains smooth and flat through the apparatus.  
           [0017]    In an alternative embodiment of the faceplates, one or more transverse minor axes are defined parallel to the transverse centerline. On longitudinal sides of each transverse minor axis leading ends of a set of ridges are oriented so as to point substantially towards the respective transverse minor axis while trailing ends of the set of ridges are oriented so as to point away from the transverse minor axis. As in the preferred embodiment, when the high velocity air strikes the lightweight sheet or web, the sheet or web material on outermost portions of each of the longitudinal sides is induced to track along and follow the path of the ridges from their respective leading ends to the trailing ends as the sheet or web travels along the direction of travel with the result that each of the lateral side portions of the sheet or web tends to be drawn away from the transverse centerline as the web travels through the apparatus with the result that web material remains smooth and flat through the apparatus.  
           [0018]    These and other objects, features, and advantages of the invention will be better understood by those skilled in the art by reference to the following detailed description taken together with the following drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    [0019]FIG. 1 is a perspective view of a conventional sheet and web cleaner.  
         [0020]    [0020]FIG. 2 is an elevational view with parts removed and broken away of a suction hood and faceplate forming a unit of the conventional sheet and web cleaner of FIG. 1.  
         [0021]    [0021]FIG. 3 is a view taken on line  3 - 3  of FIG. 2, with parts removed and broken away.  
         [0022]    [0022]FIG. 4 is a plan view of one face side of a conventional faceplate, with parts broken away.  
         [0023]    [0023]FIG. 5 is a plan view of an opposite face side of the faceplate of FIG. 4.  
         [0024]    [0024]FIG. 6 is a cross-sectional view taken on the line  6 - 6  of FIG. 1.  
         [0025]    FIGS.  7 A- 7 B show a plan view of a sheet or web moving through the prior art cleaning machine of FIG. 1 equipped with the faceplate of FIG. 4.  
         [0026]    FIGS.  8 A- 8 B are plan and elevational views, respectively, of a first preferred embodiment of a faceplate of the present invention.  
         [0027]    FIGS.  9 A- 9 B are plan views of alternative embodiments of the faceplate of the present invention.  
         [0028]    FIGS.  10 A- 10 B are front and side elevational views, respectively, of needle-like ionizing air points of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0029]    Referring now to the drawings in which like numerals identify like components throughout the several views, there is shown in FIG. 1 a sheet  5  travels in a direction of travel  7  through a conventional sheet and web cleaner  10  to be cleaned. Sheet  5  can be a relatively fragile, easily scratched material such as a coated paper or a plastic film such as acetate and Mylar; can be a relatively heavy weight sheet or web material, or can be a relatively thin material such as tissue paper or a thin metal foil. Typically, sheet  5  can have a travel speed through sheet and web cleaner  10  of approximately 3,000 feet per minute.  
         [0030]    Sheet and web cleaner  10  comprises a pair of substantially identical units  11 , one located on one side or above sheet  5 , and the other located on another side or below sheet  5 . Each unit includes an elongate suction hood  12  having a large end  14 , and being of decreasing cross-section to an opposite, closed end  16 . At end  14 , a duct  18  is connected to each of suction hoods  12 . Ducts  18  are connected to a vacuum fan or other suction device (not shown). A pressurized air conduit  20  provides pressurized air to ionizing bars as described below.  
         [0031]    Sheet and web cleaner  10  is supported on legs  22  and a support frame  24 , to which is attached through mounting plate  26 .  
         [0032]    As shown in FIG. 2, suction hood  12  is of somewhat pyramidal shape, having above it an ionizing bar  30  which is linearly extending from end to end of suction hood  12 . At one end, there is connected to ionizing bar  30  an air conduit  20  which supplies air at relatively high pressure. Adjacent the end of ionizing bar  30  which is remote from the air conduit  20  is an electrical conductor  32  for supplying electrical current to ionizing bar  30  from a suitable source (not shown).  
         [0033]    In the conventional sheet or web cleaner  10 , faceplate  50  extends over the ionizing bars  30 , and comprises a series of spaced ridges  52  each of which, as shown, has a portion  54  of generally triangular cross-sectional shape with an apex  56  to provide a series of contact elements to be engaged by sheet  5  passing through sheet and web cleaner  10 . Other geometric cross-sectional shapes for portions  54  can be used that provide for a line of tangential contact between sheet  5  and ridges  52  such as semi-circular, semi-elliptical, parabolic and hyperbolic cross sections. Ridges  52  extend part way through the thickness of faceplate  50 , and between ridges  52  are spaces  58 . Faceplate  50  is machined from a plate which has opposite sides and is of relatively smooth, hard plastic material, such as aluminum, steel, or other hard plastic material.  
         [0034]    As shown in FIG. 3 a pair of substantially identical spaced ionizing bars  30  in parallel relation each has air conduit  20  connected at one end and conductor  32  connected at the other end. Each ionizing bar  30  comprises a hollow, preferably cylindrical, tube  34  having a series of transverse linearly spaced ionizing points  36  extending therefrom (see FIG. 6). On either side of each of ionizing points  36  is an opening  38  for the discharge of pressurized air in a direction substantially parallel to ionizing points  36 . There is thereby discharged from each of ionizing bars  30  a high velocity, low volume stream of air, which contains ions as created by the application of electrical current from conductor  32  to ionizing points  36 .  
         [0035]    Spaced parallel ridges  52  of faceplate  50  are inclined at an oblique angle φ to the axis of the ionizing bars  30  and at an angle θ to direction of travel  7  of sheet  5 . At the ends of faceplate  50 , there are provided sealing strips  59 , to close any gap between faceplate  50  and mounting plate  26 . On the opposite side of faceplate  50  there are elongate openings including a tapered central elongate opening  60  and a pair of side elongate openings  62  and  64 , the openings  62  and  64  being in registry with ionizing bars  30 . Openings  60 ,  62  and  64  extend part way through the thickness of faceplate  50 .  
         [0036]    As shown in FIGS.  4 - 5 , central tapered elongate inlet opening  60  is wider at one end and tapers to a narrow width at another end thereof. Spaces  58  between ridges  52  provide openings which are in communication with openings  60 ,  62  and  64  to permit air to flow from the ionizing bars  30  through the faceplate  50  to strike sheet  5 . Central tapered elongate opening  60  permits air to flow through the spaces  58  of faceplate  50  and into the suction hood  12 . The area of the central tapered elongate inlet opening  60  is substantially equal to the combined areas of the elongate side openings  62  and  64 . Channels  66  between adjacent ones of ridges  52  permit discharged air to travel parallel to ridges  52  from areas adjacent respective discharge openings  62 ,  64  to an area adjacent opening  60 .  
         [0037]    Referring now to FIG. 5, there is shown the opposite face side of faceplate  50  to that shown in FIG. 4, where there may be seen elongate side openings  62  and  64 , and between them central tapered elongate opening  60 . Extending in inclined configuration across the openings  60 ,  62  and  64  are ridges  52  with spaces  58  between them.  
         [0038]    Referring now to FIG. 6, there is shown suction hood  12  in cross-section. Suction hood  12  is of generally square cross-sectional shape, and of modified pyramidal configuration in the longitudinal direction. A wall  70  of suction hood  12  has a rectangular longitudinally extending inlet slot  72 , and on either side of the inlet slot  72  there is mounted a pair of spaced parallel channels  74 , each of the channels  74  comprising a pair of parallel walls  76  and  78 . The walls  76  and  78  of each channel  74  provide an elongate rectangular air discharge opening  80  between them, and between the proximal walls  78  of the channels  74  there is a continuation of the inlet slot  72 .  
         [0039]    Faceplate  50  underlies and is in engagement with channels  74 , with elongate side openings  62  and  64  in registry with openings  80  in each of the channels  74 ; and tapered elongate central opening  60  in registry with an elongate rectangular opening between walls  78  of channels  74  and inlet slot  72  of suction hood  12 .  
         [0040]    In operation, sheet or web  5  is caused to pass through sheet and web cleaner  10 , and more specifically, between, parallel to and transversely of two spaced, parallel faceplates  50  and transversely of said elongate side openings  62  and  64 . Sheet  5  moves at high speed, which may be approximately 3,000 feet per minute. As sheet  5  moves through sheet and web cleaner  10 , ionizing bars  30  generate ions, which are carried therefrom by high velocity air exiting from the openings of holes  38  in tube  34 . The high velocity air carries the ions generated by the ionizing points  36  through the opening  80  in each of the channels  74  and thence through respective openings  62 ,  64  in faceplate  50  and into the spaces  58  between ridges  52 . The ionized air strikes a face of moving sheet  5 , and is drawn through channels  66  between ridges  52  into central tapered elongated central opening  60 , the opening between the walls  78  of the channels  74 , the inlet slot  72 , and into suction hood  12  from which it is remotely filtered and/or exhausted (not shown).  
         [0041]    As shown in FIGS.  7 A- 7 B, a lightweight sheet or web  105  is moved through sheet or web cleaner  10  across faceplates  50  in direction of travel  7  transverse to faceplates  50 . Lightweight sheet or web  105  is of relatively low mass and has negligible structural rigidity in both its direction of travel  7  and transverse to its direction of travel. Sheet or web  105  is drawn through sheet or web cleaner  10  with a controlled tension on both an upstream side  110  and a downstream side  112  of sheet or web cleaner  10 . As sheet or web  105  moves through sheet and web cleaner  10  in direction of travel  7 , high velocity air exits from the openings of holes  38  in tubes  34  and passes through openings  62 ,  64  in each of faceplates  50  and into spaces  58  between ridges  52 . Although lightweight sheet or web  105  has negligible structural rigidity in its direction of travel  7 , since sheet or web  105  is drawn through sheet or web cleaner  10  with controlled tension on both the upstream and downstream sides  110 ,  112 , sheet or web  10  remains relatively unaffected in direction of travel  7  by airstreams induced by the flow of high velocity air from the openings of holes  38  through openings  62 ,  64  in each of faceplates  50  and into spaces  58  between ridges  52 . However, since lightweight sheet or web  105  has negligible structural rigidity along the longitudinal direction of sheet or web cleaner  10 , transverse to direction of travel  7 , and since no controlled tension is maintained transverse to the direction of travel  7 , a lateral edge  114  of sheet or web  105  on a side  116  of faceplate  50  where ridges  52  have respective leading ends  118  oriented further from a transverse center line  120  of faceplate  50  than corresponding trailing ends  122  thereof, has been observed to be susceptible to distortion in direction  124  along a direction of ridges  52  by airstreams induced by the flow of high velocity air from the openings of holes  38  through openings  62 ,  64  and by frictional tracking forces induced by ones of apices  56  in contact with an adjacent surface of sheet or web  105  with the result that sheet or web  105  becomes unacceptably bunched-up and/or wrinkled  126  along edge  114  thereby necessitating that production be shut down so that sheet or web  105  can be smoothed out. In contrast, an opposite lateral edge  128  of sheet or web  105  on a side  130  of faceplate  50  where ridges  52  have respective leading ends  132  oriented closer to transverse central axis  120  of faceplate  50  than corresponding trailing ends  134  thereof, no such distortion by airstreams induced by the flow of high velocity air or by frictional tracking forces has been observed as the combined affect of the airflow and frictional tracking forces on side  130  tends to draw lateral edge  128  away from transverse central axis  120  thereby keeping sheet or web  105  smooth.  
         [0042]    With reference now to FIGS.  8 A- 8 B there is shown a first preferred embodiment of a faceplate  800  of the instant invention. Faceplate  800  is hard and smooth and is preferably made of aluminum, steel or other metal, or a hard plastic material.  
         [0043]    A first side face  801  of faceplate  800  has a centrally disposed transverse axis  802 . On a first side  804  of transverse central axis  802  is a series of first parallel ridges  806 . On a second side  808  of transverse central axis  802  is a series of second parallel ridges  810 . First parallel ridges  806  have openings  812  therebetween similar to openings  58  between ridges  52  in faceplate  50 . Second parallel ridges  810  similarly have openings  814  therebetween. First and second parallel ridges  806 ,  810  are oriented oblique to transverse central axis  802  by an angle a and are arranged bilaterally symmetrical thereabout. When viewed in direction of travel  7  of a web  105 , leading ends  816  of first parallel ridges  806  on first side  804  of transverse central axis  802  are oriented nearer transverse central axis  802  than corresponding trailing ends  818  thereof, and leading ends  820  of second parallel ridges  810  on second side  808  of transverse central axis  802  are oriented nearer transverse central axis  802  than corresponding trailing ends  822  thereof.  
         [0044]    A second face side  823  of faceplate  800  has a tapered central elongate opening  860  and a pair of side elongate openings  862  and  864 , similar to elongate openings  60 ,  62  and  64  of faceplate  50 .  
         [0045]    First and second parallel ridges  806 ,  810  are preferably of generally triangular cross-section having apices  824  remote from second face side  823 . Alternatively ridges  806 ,  810  can be of other geometric cross-sectional configurations such as, but not limited to: semi-circular, semi-elliptical, parabolic, or hyperbolic.  
         [0046]    An area of tapered central elongate opening  860  is substantially the same as the combined areas of elongate side openings  862 ,  864 .  
         [0047]    Unlike the prior art faceplate of FIGS.  1 - 7 , on both side  804  and  808  of faceplate  800  respective first ridges  806  and second ridges  810  are each oriented so that leading ends  816 ,  820  thereof are all oriented closer to the transverse central axis  802  of faceplate  800  than corresponding trailing ends  818 ,  822  thereof. Consequently, the combined affect of airstreams induced by the flow of high velocity air from the openings of holes, such as holes  38  (shown in FIG. 3) or holes  1138  (discussed below with respect to FIGS.  10 A- 10 B), through openings  862 ,  864  and frictional tracking forces induced when apices  824  contact an adjacent surface of sheet or web  105  tends to draw each of lateral edges  114  and  128  away from transverse central axis  820  thereby keeping sheet or web  105  uniformly smooth across its entire width.  
         [0048]    With reference now to FIG. 9A, there is shown an alternative embodiment of faceplate  900  of the present invention having two sets of ridges, each set comprising a corresponding series of first parallel ridges and a series of second parallel ridges wherein each set is disposed bilaterally symmetrical about a respective transverse minor axis, and the faceplate is bilaterally symmetrical about a transverse central axis. Faceplate  900  is similarly of a hard and smooth material such as aluminum, steel or other metal, or a hard plastic material.  
         [0049]    A first side face  901  of faceplate  900  has a centrally disposed transverse central axis  902 . On a first side  904  of transverse central axis  902  is a first series of first parallel ridges  906  and a first series of second parallel ridges  907 . On a second side  908  of transverse central axis  902  is a second series of first parallel ridges  910  and a second series of second parallel ridges  911 . First and second series of first parallel ridges  906  and  910  have openings  912  therebetween similar to openings  58  between ridges  52  in faceplate  50 . First and second series of second parallel ridges  907 ,  911  similarly have openings  914  therebetween. On first side  904  of transverse central axis  902  is a first transverse minor axis  915 . First series of first parallel ridges  906  and second parallel ridges  907  are oriented oblique to transverse minor axis  915  at an angle β and are arranged bilaterally symmetrical thereabout. On second side  908  of transverse central axis  902  is a second transverse minor axis  916 . Second series of first parallel ridges  910  and second parallel ridges  911  are oriented oblique to second transverse minor axis  916  at an angle β and are arranged bilaterally symmetrical thereabout. Preferably first series of first and second parallel ridges  906 ,  907  and second series of first and second parallel ridges  910 ,  911  are arranged mutually bilaterally symmetrical about transverse central axis  902 . When viewed in direction of travel  7  of a web  105 , leading ends  917  of first series of first parallel ridges  906  and leading ends  918  of first series of second parallel ridges  907  are oriented nearer transverse minor axis  915  than corresponding trailing ends  919 ,  920  thereof. Similarly, leading ends  921  of second series of first parallel ridges  910  and leading ends  922  of second series of second parallel ridges  911  are likewise oriented nearer transverse minor axis  916  than corresponding trailing ends  923 ,  924  thereof.  
         [0050]    A second face side  924  of faceplate  900 , opposite face side  901 , has a tapered central elongate opening  960  and a pair of side elongate openings  962  and  964 , similar to elongate openings  60 ,  62  and  64  of faceplate  50 ; and an area of tapered central elongate opening  960  is substantially the same as the combined areas of elongate side openings  962 ,  964 .  
         [0051]    As in prior embodiments, the respective series of first and second parallel ridges are preferably of generally triangular cross-section having apices remote from the second face side; and, as before, the ridges can alternatively be of other geometric cross-sectional configurations such as, but not limited to: semicircular, semi-elliptical, parabolic, or hyperbolic.  
         [0052]    [0052]FIG. 9B shown a further alternative embodiment of the present invention having three sets of corresponding series of first and second ridges, a first and a second set each disposed bilaterally symmetrically about a transverse minor axis and a third set centered on the transverse central axis.  
         [0053]    Faceplate  1000  has a first side face  1001  with a centrally disposed transverse central axis  1002 . On a first side  1004  of transverse central axis  1002  is a first transverse minor axis  1005 . A series of first parallel ridges  1006  and a first series of second parallel ridges  1007  are disposed bilaterally symmetrically about first transverse minor axis  1005  and are inclined obliquely thereto. On a second side  1008  of transverse central axis  1002  is a second transverse minor axis  1009 . A second series of first parallel ridges  1010  and a second series of second parallel ridges  1011  are disposed bilaterally symmetrically about second transverse minor axis  1009  and are inclined obliquely thereto. A third series of first parallel ridges  1012  and a third series of second parallel ridges  1012  are disposed bilaterally symmetrically about transverse central axis  1002  and are inclined obliquely thereto. Each of first, second and third series of first parallel ridges  1006 ,  1010 , and  1012  has openings  1014  therebetween similar to openings  58  between ridges  52  in faceplate  50 . Similarly, each of first, second, and third series of second parallel ridges  1007 ,  1011 , and  1013  similarly have openings  1015  therebetween. Preferably respective series of first and second parallel ridge are collectively arranged mutually bilaterally symmetrical about transverse central axis  1002 . When viewed in direction of travel  7  of a web  105 , leading ends  1016  of first series of first parallel ridges  1006  and leading ends  1018  of first series of second parallel ridges  1007  are oriented nearer transverse minor axis  1005  than corresponding trailing ends  1019 ,  1020  thereof. Similarly, leading ends  1021  of second series of first parallel ridges  1010  and leading ends  1022  of second series of second parallel ridges  1011  are likewise oriented nearer transverse minor axis  1009  than corresponding trailing ends  1023 ,  1024  thereof; and further similarly leading ends  1025  of third series of first parallel ridges  1012  and leading ends  1026  of third series of second parallel ridges  1013  are likewise oriented nearer transverse central axis  1002  than corresponding trailing ends  1027 ,  1028  thereof.  
         [0054]    A second face side  1030  of faceplate  1000 , opposite face side  1001 , has a tapered central elongate opening  1060  and a pair of side elongate openings  1062  and  1064 , similar to elongate openings  60 ,  62  and  64  of faceplate  50 ; and an area of tapered central elongate opening  1060  is substantially the same as the combined areas of elongate side openings  1062 ,  1064 .  
         [0055]    Further alternative embodiments having other numbers of sets of symmetrically disposed corresponding series of first and second ridges are also possible and would be obvious to persons skilled in the art. Asymmetric configurations are also possible provided that a longitudinally disposed outermost series of first and second parallel ridges on respective outermost longitudinal ends of the faceplate have a sufficient number of parallel ridges oriented with respective leading ends thereof oriented closer to a transverse central axis than corresponding trailing ends thereof so that the combined affect of tracking forces in the longitudinal direction induced by contact between a surface of the sheet or web against apices of the ridges and lateral distortion imparted by the high velocity air impacting on the moving sheet or web tends to draw each lateral edge of sheet or web away from the transverse central axis.  
         [0056]    Referring now to FIGS.  10 A- 10 B, a particularly preferred embodiment of ionizing points  1100  is shown. Unlike conventional ionizing points  36  which require holes  38  in ionizing bar  30  adjacent thereto, ionizing points  1100  are hollow, needle-like ionizing points which combine the function of ionizing points  36  with those of holes  38 .  
         [0057]    Ionizing points  1100  have a base portion  1102  with a proximal opening  1104  therein that connects to an opening (not shown) in ionizing bar  30  in a conventional manner such as welding, brazing, a threaded connection, a friction fit, a twist-lock connection, or other conventional manner. Each ionizing point  1100  comprises a hollow tubular structure  1106  having a tubular wall portion  1108  surrounding a hollow passage  1110 . For simplicity of manufacture tubular structure  1106  is preferably of right-circular cross-section; however, other cross-sectional geometries are possible. Tubular structure  1106  extends from its base portion  1102  to a distal end  1112 . At distal end  1112  a distal hole  1138  communicates with proximal opening  1104  through hollow passage  1110 .  
         [0058]    In a particularly preferred embodiment of the present invention, distal end  1112  is beveled on two sides thereof at an obtuse angle  1114  relative to a longitudinal axis  1116  of ionizing point  1100 ; and is preferably beveled at an angle thereto of approximately 160 degrees. Alternatively, distal end  1112  can be beveled relative to longitudinal axis  1116  around its entire circumference in the nature of a conic section.  
         [0059]    High velocity air from ionizing bar is discharged by ionizing points  1100  through holes  1138  in a conventional manner and is ionized thereby.  
         [0060]    The present invention has now been described with respect to preferred selected embodiments thereof. However, other embodiments would be obvious to those skilled in the art without departing from the spirit and scope of the appended claims.