Patent Publication Number: US-6706337-B2

Title: Ultrasonic method for applying a coating material onto a substrate and for cleaning the coating material from the substrate

Description:
This application claims the benefit of U.S. Provisional Application No. 60/275,093, filed on Mar. 12, 2001. 
    
    
     FIELD OF THE INVENTION 
     The present invention is in the field of imaging systems. More particularly, the present invention provides a method and apparatus for ultrasonically applying a coating material onto a print substrate mounted on the plate cylinder of a printing press. In addition, the present invention provides a method and apparatus for ultrasonically cleaning the coating material from the surface of the print substrate prior to a reapplication of the coating material. 
     BACKGROUND OF THE INVENTION 
     Lithography is the process of printing from specially prepared surfaces, some areas of which are capable of accepting lithographic ink, whereas other areas, when moistened by an aqueous dampening liquid, will not accept the ink. The image to be printed is provided on a lithographic printing master, such as a printing plate, which is mounted on the plate cylinder of a printing press. The printing master carries an image that is defined by the ink accepting areas of the printing surface. A print is obtained by applying ink and a dampening liquid to the printing surface and then transferring the ink from the ink accepting areas of the printing master, using a blanket cylinder, onto a substrate, typically formed of paper. 
     Many techniques have been used to form an image on a printing master. One common technique, often referred to as “computer-to-film,” transfers the image to be printed onto a supply of film using an imagesetter. After processing, the film is used as a mask for the imaging of a plate precursor, comprising, for example, a print substrate (e.g., an aluminum substrate) that has been coated with a thin layer of a photosensitive material. The imaged plate precursor is subsequently processed to obtain a printing plate that can be used as a printing master on a printing press. 
     Another technique, often called “computer-to-plate” or “direct-to-plate,” eliminates the need for film by transferring the image to be printed directly onto a plate precursor using a platesetter, an on-press imaging system, etc. The imaged plate precursor is then processed to obtain a printing plate that can be used as a printing master on a printing press. Upon completion of a press run, the printing master is removed from the plate cylinder of the printing press and discarded or recycled. A new printing master is then mounted onto the plate cylinder of the printing press in preparation of the next press run. 
     Recently, several computer-to-plate “on-press” imaging techniques have been developed that do not require the printing master to be removed from the plate cylinder of the printing plate upon completion of printing. For example, in one technique, a heat-sensitive coating material, capable of forming a lithographic printing form upon imaging and optional processing, is provided directly on the surface of a reusable hydrophilic print substrate mounted on the plate cylinder of the printing press. (Alternately, the coating material may be provided directly on the surface of the plate cylinder itself.) When the press run is complete, the reusable print substrate (or plate cylinder) is cleaned and recoated with the coating material, at which point it is ready for subsequent imaging and printing. 
     One such computer-to-plate technology, called LiteSpeed™, recently developed by Agfa-Gevaert N.V. of Mortsel, Belgium, uses a polymer-type liquid lithographic coating material, designed to be sprayed or otherwise applied on an anodized aluminum print substrate, to create a lithographic printing form. The lithographic printing form can be imaged using thermal laser technology soon after application, and is then ready for printing. The non-exposed areas are removed from the lithographic printing form during the printing of the first few (e.g., 10) sheets of paper, allowing the press run to begin immediately after imaging without any additional development. At the end of the print run, the print substrate is completely cleaned prior to the next application of LiteSpeed™ and the next concurrent print job. LiteSpeed™ is non-ablative, requires no chemical processing, and each application is equal in performance to a conventional lithographic printing plate, with a run length of approximately 20,000 impressions. 
     On-press computer-to-plate systems, such as those described above, will require some form of cleaning prior to the reapplication of the coating material on the print substrate. LiteSpeed™, and switchable polymer-type applied coating technologies, often require the removal of all of the applied polymer coating material, inks, and other contaminants prior to reapplication. The print substrate must be clean and dry prior to reapplication. One consequence of contamination is a latent or “ghost image” from the previous print run that may appear in the printed output of the next print run. 
     Many cleaning techniques have been proposed to clean a surface in a printing press. For example, U.S. Pat. No. 5,713,287 issued to Gelbart on Feb. 3, 1998 and U.S. Pat. No. 5,148,746 issued to Fuller et al. on Sep. 22, 1992, incorporated herein by reference, both describe cleaning devices and methods that use abrasive techniques to disengage materials from a surface. The former uses a cloth blanket type washer. The latter uses a type of brush or pad to dislodge materials, and a fan or other means for removal. The difficulty in these and other types of abrasive methods is the deteriorated surface condition left on the hydrophilic print substrate, and circumferential interruptions in the plate cylinder surface. These methods tend to produce a shorter print run length with less lithographic latitude. Some of the blanket washer types have the added disadvantage of requiring a full axial volume adjacent to the plate cylinder. 
     Another cleaning technique uses a stream of high pressure water to remove coating materials from the print substrate. After application of a cleaning solution, the stream of high pressure water is sprayed onto the print substrate. The water, removed coating material, inks, cleaner, and other contaminants are then removed from the print substrate using a vacuum system. The print substrate is then dried prior to the reapplication of the coating material. Great care must be taken when using this method to prevent the water and other substances removed from the print substrate from detrimentally affecting the on-press imaging system and other components/functions of the printing press. Subsequent filtration of large amounts of water having solubolized materials requires specialized equipment. As such, this process is difficult and costly to implement. 
     The coating material is commonly applied to the print substrate using a dedicated system that is independent from the cleaning and imaging systems. For example, the coating material may be applied to the print substrate by a spraying or a rolling system. Unfortunately, since access to the plate cylinder in the printing press is generally very limited, the implementation of separate coating, cleaning, and imaging systems is a complex and costly task. 
     Thus, there is a need for a method and apparatus for applying coating materials onto a print substrate, and for cleaning the coating materials from the print substrate, that avoids these and other problems present in currently available on-press systems. 
     SUMMARY OF THE INVENTION 
     The present invention provides methods and apparatus for applying a coating material onto, and cleaning the coating material from, a surface of a print substrate mounted on the plate cylinder of a printing press using ultrasonic techniques. 
     Generally, the present invention provides a method for applying a coating material onto a print substrate, comprising: 
     delivering a supply of the coating material to a distributive surface of an ultrasonic horn, the distributive surface controlling a flow of the coating material to an active edge of the ultrasonic horn, and atomizing the coating material at the active edge of the ultrasonic horn and directing the atomized coating material onto a surface of the print substrate. 
     The present invention also provides an apparatus for applying a coating material onto a print substrate, comprising: 
     an ultrasonic horn having a distributive surface and an active edge, and a delivery system for delivering a supply of the coating material to the distributive surface, the distributive surface controlling a flow of the coating material to the active edge, the active edge atomizing and directing the coating material onto the surface of the print substrate. 
     The present invention further provides an apparatus, comprising: 
     an ultrasonic horn having an active edge for atomizing and directing a coating material onto a print substrate, and a distributive surface for controlling a flow of the coating material to the active edge. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present invention will best be understood from a detailed description of the invention and embodiments thereof selected for the purpose of illustration and shown in the accompanying drawings in which: 
     FIG. 1 illustrates a printing press having a plate cylinder, an ultrasonic acoustic coating apparatus for applying a coating material onto a surface of a print substrate mounted on the plate cylinder, and an ultrasonic acoustic cleaning apparatus for cleaning the surface of a print substrate, in accordance with an embodiment of the present invention. 
     FIG. 2 is a cross-sectional view of a first embodiment of an ultrasonic acoustic cleaning apparatus in accordance with the present invention. 
     FIG. 3 is a cross-sectional view taken along line  3 — 3  of FIG.  2 . 
     FIG. 4 illustrates an ultrasonic acoustic cleaning apparatus in accordance with another embodiment of the present invention. 
     FIG. 5 illustrates an embodiment of an ultrasonic acoustic coating system in accordance with the present invention. 
     FIG. 6A is a cross-sectional view of the ultrasonic acoustic coating system of FIG. 5 with the ultrasonic horn positioned vertically over a plate cylinder. 
     FIG. 6B is a cross-sectional view of the ultrasonic acoustic coating system of FIG. 5 with the ultrasonic horn positioned horizontally next to a plate cylinder 
     FIG. 7 illustrates several overlapping coating lines produced by the ultrasonic acoustic coating system of the present invention. 
     FIG. 8 illustrates another embodiment of an ultrasonic acoustic coating system in accordance with the present invention. 
     FIGS. 9 and 10 illustrate exemplary distributive surfaces for use in the ultrasonic acoustic coating system of FIG.  8 . 
     FIGS. 11 and 12 illustrate the flow boundaries of the coating material, provided by a capillary tube, on the distributive surfaces of FIGS. 9 and 10, respectively. 
     FIGS. 13 and 14 illustrate an ultrasonic horn configured to produce a plurality of small jets of atomized coating material. 
     FIG. 15 illustrates the use of lined depressions in the distributive surface for controlling the flow boundaries of the coating material. 
     FIGS. 16 and 17 illustrate another method for controlling the flow boundaries of the coating material. 
     FIG. 18 illustrates a multi-purpose ultrasonic acoustic coating/cleaning apparatus in accordance with the present invention. 
     FIG. 19 is an end view of a vacuum nozzle used in the ultrasonic acoustic coating/cleaning apparatus of FIG.  18 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The features of the present invention are illustrated in detail in the accompanying drawings, wherein like reference numerals refer to like elements throughout the drawings. Although the drawings are intended to illustrate the present invention, the drawings are not necessarily drawn to scale. 
     A printing press  10  having an ultrasonic acoustic cleaning apparatus  12  for cleaning a surface  14  of a reusable print substrate  16  in accordance with the present invention, and an ultrasonic acoustic coating system  24  (or  224 , FIG.  8 ), for applying a coating material onto the surface  14  of the print substrate  16  in accordance with the present invention, is illustrated in FIG.  1 . As shown, the reusable print substrate  16  is mounted on a plate cylinder  18  that is configured to rotate about an axis  20  as indicated by directional arrow  22 . The printing press  10  is a conventional “on-press” type of printing press in which a coating material, capable of forming a lithographic printing form upon imaging and optional processing (e.g., LiteSpeed™ or switchable polymer-type coatings), is provided directly on the surface  14  of the reusable print substrate  16 . 
     In the example illustrated in FIG. 1, the ultrasonic acoustic coating system  24  is used to apply the coating material onto the surface  14  of the reusable print substrate  16  prior to imaging and after the cleaning of the surface  14 . A drive system D 1  displaces the ultrasonic acoustic coating system  24  axially along the plate cylinder  18  as indicated by directional arrow  26  during the application of the coating material. As shown in FIG. 7, the coating material is applied in a helical pattern on the surface of the print substrate  16 , with an amount of overlap between adjacent coating lines L 1 , L 2 , L 3 , . . . , as the ultrasonic acoustic coating system  24  is displaced axially along the rotating plate cylinder  18 . 
     An imaging system  28  is provided to form an image on the coating material that has been applied on the surface  14  of the reusable print substrate  16  by the ultrasonic acoustic coating system  24 . The imaging system  28  can comprise any type of system capable of exposing an image on the coating material. For example, the imaging system may comprise means for generating one or more laser beams and for directing the laser beam(s) onto the coating material to form an image thereon. A drive system D 2  is used to displace the imaging system  28  axially along the plate cylinder  18  during imaging (i.e., in a “slow scan” direction) as indicated by directional arrow  30 . 
     A cross-sectional view of a first embodiment of the ultrasonic acoustic cleaning apparatus  12  in accordance with the present invention is illustrated in FIG. 2. A cross-sectional view of the ultrasonic acoustic cleaning apparatus  12  taken along line  3 — 3  of FIG. 2 is illustrated in FIG.  3 . The ultrasonic acoustic cleaning apparatus  12  includes an ultrasonic system comprising an ultrasonic horn  40  and an ultrasonic transducer  42  for driving the ultrasonic horn  40 . The ultrasonic acoustic cleaning apparatus  12  further includes a spray nozzle  44  for supplying an atomized spray of a cleaning solution. The ultrasonic horn  40 , ultrasonic transducer  42 , and the spray nozzle  44  are all enclosed within a vacuum cannula  46 . As shown in FIG. 2, the ultrasonic acoustic cleaning apparatus  12  is positioned in close proximity to the surface  14  of the print substrate  16 . The particular distance of the ultrasonic acoustic cleaning apparatus  12  from the surface  14  of the print substrate  16  is generally application specific, and may be dependent upon many factors, including the power of the ultrasonic transducer  42 , the configuration of the ultrasonic horn  40 , the type of spray nozzle  44  used, the strength of the vacuum applied within the vacuum cannula  46 , the material properties of the coating material  48  to be removed from the surface  14  of the print substrate  16 , etc. Similarly, the power of the ultrasonic transducer  42  is generally application specific, and may be dependent upon factors including those presented above. For example, the power of the ultrasonic transducer  42  may be in the range of about 1500 to 6000 watts. Other power values are also possible. 
     Referring to FIG. 3, the ultrasonic transducer  42  is supported within a housing  50  along a center of the vacuum cannula  46 . The housing  50  is attached to an inner surface of the vacuum cannula  46  by a plurality of radially extending ribs  52 . Power/control lines  54  of the ultrasonic transducer  42  extend out of the end  56  of the vacuum cannula  46  into a hose  58  through connector  60 . 
     A vacuum is supplied to a vacuum port  62  within the vacuum cannula  46  by a vacuum source (not shown). The vacuum source is coupled to the vacuum port  62  via hose  64  and connector  66 . 
     Cleaning solution is supplied to the spray nozzle  44  through a supply line  68 . The supply line  68  extends through connector  60  into hose  58 . 
     In accordance with the present invention, the ultrasonic acoustic cleaning apparatus  12  is used to clean the surface  14  of the print substrate  16  after a print run and before reapplication of the coating material  48 . In particular, as shown in FIG. 2, a cleaning solution is directed onto the surface  14  of the print substrate  16  through spray nozzle  44  as the plate cylinder  18  rotates as indicated by directional arrow  72  past the vacuum cannula  46 . After passing under the spray nozzle  44 , the surface  14  subsequently rotates under the ultrasonic horn  40 , which operates to remove the coating material  48  from the surface  14 . As rotation of the press-cylinder  18  continues, all debris from the cleaning process is collected and removed through the vacuum port  62 . During the cleaning process, the ultrasonic acoustic cleaning apparatus  12  is displaced by a drive system D 3  axially along the plate cylinder  18  in a “slow-scan” direction as indicated by directional arrow  70  (see FIGS.  1  and  3 ). After cleaning, the print substrate  16  may be “refreshed” if necessary using a water rinse. 
     In previous cleaning systems, a solvent-type cleaning solution was applied on the surface of the print substrate. After waiting some dwell period to allow the solvent to sufficiently soften the bonded polymer of the coating material, the coating material was removed by mechanical means (e.g., scrubbed with a brush or roller). The resultant waste material was then rinsed from the print substrate, and the substrate was dried using hot air. The cleaning solution of the present invention, however, is not only used for its inherent solvent cleaning/softening function, but also as a coupling agent for the ultrasonic horn  40 . In particular, when sprayed as a mist between the ultrasonic horn  40  and the print substrate  16 , the atomized cleaning solution couples and focuses the energy of the ultrasonic horn  40  to the coating material  48  on the surface  14  of the print substrate  16 . The focused energy promotes acoustic cavitation. This cavitation is the result of excitation at the molecular level of the coupling liquid (i.e., the cleaning solution) on and at the coating material  48 . The excitation causes friction and thus turns the acoustic energy to heat. The heat causes the water molecules of the cleaning solution to move apart forming gas or steam which condenses on colder surrounding areas, thereby causing voids to develop. Adjacent molecules fill in the voids, violently sending shock waves through the coating material  48  and initiating a series of subsequent chain reactions and surface implosions. This causes the coating material  48  (e.g., polymer) to be instantly softened and “blasted” from the surface  14  of the print substrate  16 . The softening characteristic of the solvent is so enhanced by cavitation that the cleaning of the surface  14  of the print substrate  16  is immediate and complete so as not to require additional mechanical cleaning. 
     In accordance with one embodiment of the present invention, the cleaning solution is an aqueous-based solvent-type cleaning solution that is specifically formulated to soften the coating material  48  on the surface  14  of the print substrate  16 . As detailed above, this type of cleaning solution, when sprayed onto the coating material, also serves to focus the energy of the ultrasonic horn  40  onto the coating material  48  to initiate and sustain acoustic cavitation. In general, however, any suitable type of atomized aqueous spray, including plain water, may be used to couple and focus the energy of the ultrasonic horn  40  onto the coating material  48  on the surface  14 . Of course, the choice of cleaning solution is dependent on many different factors, including, for example, the desired processing time, the material characteristics of the coating material  48 , the power of the ultrasonic transducer  42 , etc. 
     During and after the cleaning process a vacuum is drawn within the vacuum port  62  of the vacuum cannula  46 . The vacuum removes any excess cleaning solution and all of the debris resulting from the cleaning process from the surface  14  of the print substrate  16 . This leaves the surface  14  clean and dry. The removed materials are subsequently transferred through the hose  64  to entrainment separators (not shown) for collection and disposal. 
     The ultrasonic acoustic cleaning apparatus  12  of the present may be used as a stand-alone device as shown in FIG. 1, or may be coupled to other components of the printing press  10 . For example, the ultrasonic acoustic cleaning apparatus  12  may be coupled to the imaging system  28 . As such, a separate drive system for the ultrasonic acoustic cleaning apparatus  12  is not required; displacement of the ultrasonic acoustic cleaning apparatus  12  is provided by the drive system D 2  of the imaging system  28  (or vice-versa). This configuration may be useful, for example, when access to the plate cylinder  18  in the printing press  10  is limited. It should be apparent that the ultrasonic acoustic cleaning apparatus  12  could also be coupled to the ultrasonic acoustic coating system  24 . In this case, displacement of the ultrasonic acoustic cleaning apparatus  12  is provided by the drive system D 1  of the ultrasonic acoustic coating system  24  (or vice-versa). 
     Another embodiment of an ultrasonic acoustic cleaning apparatus  80  is illustrated in FIG.  4 . In this embodiment, the vacuum port  62  and the spray nozzle  44  are incorporated within the body of the ultrasonic horn  40 . This provides a more compact system. With the ultrasonic horn  40  excited, cleaning solution is introduced by the spray nozzle  44  at the leading end  82  of the ultrasonic horn  40  where cavitation begins. As the plate cylinder  18  continues to rotate, the coating material  48  is loosened and removed from the surface  14  of the print substrate  16  by the cavitation process. Any remaining cleaning solution and debris from the cleaning process is sucked from the surface  14  into the vacuum port  62  as the surface  14  passes under the trailing end  84  of the ultrasonic horn  40 . 
     A first embodiment of an ultrasonic acoustic coating system  24  in accordance with the present invention is illustrated in FIGS.  5  and  6 A- 6 B. The ultrasonic acoustic coating system  24  includes an ultrasonic system comprising an ultrasonic horn  100  and an ultrasonic transducer  102  for driving the ultrasonic horn  100 . A metered amount of the coating material  48 , provided via a supply line  106 , is delivered to a surface  108  of the ultrasonic horn  100  using a nozzle  110 . The nozzle may comprise a wide, flat nozzle as shown in FIG. 5, or an array of smaller nozzles arranged adjacent to one another. Other configurations of the nozzle  110  are also possible. After passing out of a fluid delivery exit  112  of the nozzle  110  onto the surface  108 , a flow of the coating material  48  passes over the surface  108  toward an active edge  114  of the active surface  116  of the ultrasonic horn  100 . The active surface  116  has a curvature corresponding to the curvature of the plate cylinder  18 . Alternately, the active surface  116  may be flat or may have any other suitable surface profile. 
     As shown in FIG. 6A, the ultrasonic horn  100  of the ultrasonic acoustic coating system  24  may be positioned vertically over the plate cylinder  18 . This ensures that the coating material  48  supplied by the nozzle  110  will flow downward over the surface  108  toward the active edge  114  of the ultrasonic horn  100 . The active edge  114  atomizes the coating material  48  and directs the atomized coating material  48  onto the surface  14  of the plate cylinder  16  in a predetermined atomization pattern. As the ultrasonic acoustic coating system  24  is moved axially along the rotating plate cylinder  18  by drive system D 1  (FIG.  1 ), the atomized coating material  48  is applied in a helical pattern of interlaced, overlapping, coating lines L (FIG. 7) on the surface  14  of the print substrate  16  as the plate cylinder  18  rotates in direction  104 . 
     In many printing presses, vertical access to the plate cylinder  18  is generally not available. Often, however, the plate cylinder  18  may be accessed from one or both sides. Such a case is illustrated in FIG. 6B, wherein the ultrasonic horn  100  of the ultrasonic acoustic coating system  24  is oriented horizontally next to a side of the plate cylinder  18 . Unfortunately, when the ultrasonic horn  100  of the ultrasonic acoustic coating system  24  is oriented horizontally, or along a partially horizontal vector, some of all of the coating material  48  will fall by gravity off of the surface  108  of the ultrasonic horn  100  before reaching the active edge  114 . 
     Another embodiment of an ultrasonic acoustic coating system  224 , which solves the gravity fall off problem detailed above, is illustrated in FIG.  8 . The ultrasonic acoustic coating system  224  includes a distributive surface  122  on the ultrasonic horn  100  for controlling the flow boundaries of the coating material  48 . The distributive surface  122  allows the ultrasonic horn  100  of the ultrasonic acoustic coating system  224  to be positioned horizontally, or along a partially horizontal vector, relative to the plate cylinder  18 . 
     In this embodiment, as shown in FIG. 8, a capillary tube  120  is placed and pointed to produce a desired flow pattern of the coating material  48  on the distributive surface  122 . In particular, the coating material  48  is delivered by the capillary tube  120  at a prescribed pressure and delivery angle incident on the distributive surface  122  of the ultrasonic horn  100 . When constrained only by the surface curvature/shape of the distributive surface  122 , the flow of coating material  48  thins and spreads outwardly from the line pressure. When the flow momentum slows from the decreasing pressure, surface tension and molecular cohesion begin to make the flow recede. The distributive surface  122  is designed such that this “energy boundary” occurs at the active edge  124  of the active surface  126  of the ultrasonic horn  100 . Exemplary distributive surfaces  122 , active edges  124 , and active surfaces  126  for circular and square-shaped ultrasonic horns  100  are illustrated in FIGS. 9 and 10, respectively. 
     The coating material  48  is atomized at the active edge  124  of the ultrasonic horn  100 . The ultrasonic horn  100  may be located very near to the surface  14  of the print substrate  16  since no mixing or shaping distance is required for air atomization. The atomized coating material  48  is directed by the active edge  124  onto the surface  14  of the plate cylinder  16  in a predetermined atomization pattern. As the ultrasonic acoustic coating system  224  is moved axially along the rotating plate cylinder  18  by drive system D 1  (FIG.  1 ), the atomized coating material  48  is applied in a helical pattern of interlaced coating lines L 1 , L 2 , L 3 , . . . , on the surface  14  of the print substrate  16 . To ensure complete coverage on the surface  14 , the coating lines L 1 , L 2 , L 3 , are applied in an overlapping manner as shown, for example, in FIG.  7 . The amount of overlap is dependent upon many factors, including the properties of the coating material, the range of acceptable thickness variations of the coating material  48  on the surface  14  of the print substrate  16 , etc. At this point, the print substrate  16  is ready for imaging and printing as detailed above with regard to printing press  10  (FIG.  1 ). 
     In many cases, it may be desirable to selectively control the thickness profile of the pattern of atomized coating material  48  that is applied on the surface  14  of the print substrate  16 . For example, it may be useful to reduce or “feather” the thickness of the pattern in the overlapping areas of the coating lines to maintain a substantially uniform thickness of the coating material across the surface  14  of the print substrate  16 . An exemplary overlapping technique places sixty-six percent of the volume of the coating material  48  over a particular dimension (e.g., X in FIG.  7 ), while the remaining thirty-three percent of the volume of the coating material  48  is divided between the regions of overlap (e.g., Y), thereby resulting in a uniform fill volume. This may be accomplished by regulating the flow volume of the coating material  48  reaching selective regions on the active edge  114  of the ultrasonic horn  100 . 
     FIG. 11 illustrates the flow boundaries  130  of the coating material  48  on the distributive surface  122  of the ultrasonic horn  100  of FIG.  9 . As shown, the flow volume of the coating material  48  is the highest in the center section of the distributive surface  122  immediately below the exit opening  132  of the capillary tube  120 , where it is pushed out under pressure. The flow volume gradually decreases away from the center section of the distributive surface  122  as the coating material  48  spreads out toward the sides of the distributive surface  122 . Thus, the flow volume of the coating material  48  reaching the active edge  124  is not uniform. This results in a feathered pattern being produced on the surface  14  of the print substrate  16 . 
     FIG. 12 illustrates the flow boundaries  134  of the coating material  48  on the distributive surface  122  of the ultrasonic horn  100  of FIG.  10 . As shown, the flow volume of the coating material  48  is the highest in the center section of the distributive surface  122  immediately below the exit openings  136  of the capillary tube  120 , where it is pushed out under pressure. The flow volume gradually decreases away from the center section of the distributive surface  122  as the coating material  48  spreads out toward the sides of the distributive surface  122 . Thus, the flow volume of the coating material  48  reaching the active edge  124  is not uniform. Again, this results in a feathered pattern being produced on the surface  14  of the print substrate  16 . 
     FIGS. 13 and 14 illustrate an ultrasonic horn  100  configured to produce and direct a plurality of small jets of atomized coating material  48  toward the surface  14  of the print substrate  16 . As shown, an array of openings  140  or the like (e.g., holes, grooves, etc.) are formed on or in the distributive surface  122  at the active edge  124  of the ultrasonic horn  100 . In this embodiment, the coating material  48  flows down the distributive surface  122  into the openings  140  at the active edge  124  where it is atomized and directed toward the surface  14  of the print substrate  16 . The array of openings  140  may all have the same size and configuration to produce uniform jets of atomized coating material  48 , or may be selectively configured and arranged to produce non-uniform jets of atomized coating material to form a specific pattern of the coating material on the surface  14  of the print substrate  16 . For example, by making the openings  140  larger in the center portion of the active edge  124 , and smaller near the sides of the active edge  124 , a feathered pattern of the coating material  48  can be produced on the surface  14  of the print substrate  16 . 
     As shown in FIG. 15, a series of lined depressions  150 , formed (e.g., etched) in the distributive surface  122  and emanating from a delivery exit  152  of a capillary tube  120 , may be used to control the flow boundaries of the coating material  48  reaching the active edge  124 , thereby controlling the resultant pattern boundary dimension of the pattern formed on the surface  14  of the print substrate  16 . The depth of the lined depressions  150  may be varied to control the features of the pattern formed on the surface  14  of the print substrate  16 . For example, a feathered pattern may be produced by forming deeper lined depressions  150  in the center portion of the distributive surface  122  and shallower lined depressions  150  toward the sides of the distributive surface  122 . An exemplary pattern overlap dimension for such a feathered pattern is shown in FIG.  15 . 
     In another embodiment of the present invention, as shown in FIGS. 16 and 17, flow control of the coating material  48  can be provided using a non-uniform channel  160  and a shallow weir  162  formed at the active edge  124 . The non-uniform channel  160  may have a variable depth such that the channel  160  is deeper in the middle than at the edges. In this configuration, the weir  162  helps to ensure uniformity across the flow front to provide uniform atomization of the coating material  48 . 
     The operation of the ultrasonic acoustic coating apparatus  224  and the ultrasonic acoustic cleaning apparatus  12  of the present invention may be combined to produce a multi-purpose ultrasonic acoustic coating/cleaning system  200 . An example of such a multi-purpose ultrasonic acoustic coating/cleaning system  200  is illustrated in FIG.  18 . The ultrasonic coating/cleaning system  200  incorporates an ultrasonic horn  100 , such as that shown in FIG.  8 . Other embodiments of the ultrasonic horn  100  may also be used in the ultrasonic coating/cleaning system  200 . 
     During a coating operation, the plate cylinder  18  is rotated in direction  104 . As detailed above with regard to FIG. 8, a supply of the coating material  48  is delivered by a capillary tube  120  to a distributive surface  122 . The coating material  48  flows across the distributive surface  122  to the active edge  124  of the active surface  126  of the ultrasonic horn  100 , where it is atomized and directed onto the surface  14  of the print substrate  16  in a predetermined pattern. As the ultrasonic coating/cleaning apparatus  200  is moved axially along the rotating plate cylinder  18  by a drive system (e.g., D 1  or D 3 , FIG.  1 ), the atomized coating material  48  is applied in a helical pattern of interlaced, overlapping, coating lines L (FIG. 7) on the surface  14  of the print substrate  16 . 
     After the thus applied coating material has been imaged, and subsequently used for printing on a printing press, the ultrasonic coating/cleaning apparatus  200  can be employed to completely clean the surface  14  of the print substrate  16  in a manner similar to that described with reference to the ultrasonic acoustic cleaning apparatus  12  shown in FIG.  2 . In particular, while rotating the plate cylinder  18  in direction  118  (i.e., in a direction opposite to direction  104 ), a supply of a cleaning solution is delivered via the capillary tube  120  to the distributive surface  122 . The cleaning solution flows across the distributive surface  122  to the active edge  124  of the active surface  126  of the ultrasonic horn  100 , where it is atomized and directed toward and onto the surface  14  of the print substrate. After passing under the active edge  124 , the surface  14  subsequently rotates under the active surface  126  of the ultrasonic horn  100 , where the coating material  48  is removed from the surface  14  by the above-described cavitation process. As rotation of the press-cylinder  18  continues, all debris from the cleaning process is collected and removed through the vacuum port  202  of a vacuum nozzle  204 . As shown in FIG. 19, the vacuum nozzle  204  comprises a semi-circular evacuation portion  206  that covers the lower hemisphere of the ultrasonic horn  100 , and a hose portion  208 . The semi-circular evacuation portion  206  is used to collect the cleaning solution and debris from the cleaning process. The hose portion  208  transfers the collected material to a collection and disposal system. 
     The foregoing description of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and many modifications and variations are possible in light of the above teaching. For example, the ultrasonic acoustic coating apparatus of the present invention may be used to apply a coating material onto many different types of surfaces, including the surface of a plate cylinder. Moreover, the ultrasonic acoustic cleaning apparatus may be used to clean a coating material from many types of surfaces, including the surface of a plate cylinder. Such modifications and variations that may be apparent to a person skilled in the art are intended to be included within the scope of this invention.