Abstract:
A rotary-style coating machine of the type capable of applying coatings to various web substrates in the commercial offset web and/or digital web printing industry. The coating machine includes a coating cylinder and a plate cylinder that are rotatably mounted within the machine. The coating cylinder includes a coating sleeve removably mounted on a mandrel, and the plate cylinder includes a plate sleeve removably mounted on another mandrel. The machine further includes a unit for depositing a coating material on the coating sleeve as the coating cylinder is rotated. The plate cylinder is operative to receive the coating material from the coating sleeve. An impression cylinder supports a web substrate that receives the coating material from the plate sleeve.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 61/358,587, filed Jun. 25, 2010, the contents of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention generally relates to equipment and processes used in the commercial printing industry. More particularly, this invention relates to a web coating apparatus and method suitable for use in inline and offline web-fed finishing systems used in the commercial web printing industry. 
     Various types of coating (printing) machines are known and used in the commercial offset web industry. A particular type of coating machine is adapted to transfer a liquid coating to a pre-printed substrate, referred to as a web, formed of a suitable material, for example, paper. The coating process often uses a rotary-style coating machine that includes a coating cylinder (for example, an anilox roller) having a cylindrical outer surface to which a coating is applied as the coating cylinder rotates. A doctor blade assembly is typically used with an anilox roller to remove excess coating from the surface of the coating cylinder, to ensure that the coating cylinder carries a relatively uniform layer of coating on its cylindrical surface. The coating may be applied to the coating cylinder through contact with a second cylinder that is partially submerged in the coating within a reservoir, or directly applied by partially submerging the coating cylinder in the coating. Another alternative is to apply the coating using an enclosed coating chamber that incorporates the doctor blade assembly. The coating cylinder transfers the coating to a rotating fixed repeat-sized plate cylinder (roller), which in turn carries the coating to the web. The plate cylinder carries a raised pattern such that the coating transferred to the plate cylinder will form the desired coating on the web, for example, a gloss or mat finish. The transfer of coating from the plate cylinder to the web occurs at a printing nip between the plate cylinder and a rotating impression cylinder (roller). Once the printed web has traveled away from the printing nip, the coating on the web is cured, for example, using an ultraviolet (UV) curing lamp system. One or more optional “chill rolls” may be placed at the exit of the curing system to help remove excess temperature from the web and control the tension in the web downstream of the curing process. 
     Rotary-style coating machines of the type described above have been historically limited to applying a very narrow range of coatings, such as “gloss coatings,” to substrates. The narrow range of coatings is inherently due to the coating cylinder having a fixed anilox construction. While certain coating machines are described as having a removable and/or changeable coating cylinder, the process requires the removal of the complete coating cylinder from the machine, resulting in an extensive process of uncoupling the drive train and unbolting and lifting heavy cylinders. This process is typically very costly, time consuming and potentially unsafe, with the result that many in the printing industry do not remove and replace coating cylinders. 
     Rotary-style coating machines are also typically dedicated to a plate cylinder having a certain circumference size (referred to as fixed press repeat), with all cylinders of the machine, with the exception of any optional chill rolls, driven together by a single motor or mechanical drive train. A drawback of all cylinders being driven together is the inability to change the repeat (circumference size) of the plate cylinder without making gearing changes. The result is that typical coating machines are dedicated to a fixed size printing press application matching a single image repeat. 
     BRIEF DESCRIPTION OF THE INVENTION 
     The present invention provides a rotary-style coating machine (apparatus) of the type capable of applying coatings to various woven or nonwoven web substrates in the commercial offset web, digital, flexographic, or rotogravure web-fed printing industries. 
     According to a first aspect of the invention, the coating machine includes a coating cylinder and a plate cylinder that are rotatably mounted within the machine, and individual means for rotating the coating cylinder and plate cylinder about their respective axes. The coating cylinder comprises a coating cylinder mandrel and at least a first coating sleeve removably mounted on the coating cylinder mandrel. The machine further includes means for depositing a coating material on the first coating sleeve as the coating cylinder is rotated. The plate cylinder comprises a plate cylinder mandrel and a plate sleeve removably mounted on the plate cylinder mandrel, and the plate cylinder is operatively positioned within the machine to receive the coating material from the first coating sleeve. An impression cylinder is operatively positioned within the machine to support a web substrate as it receives the coating material from the plate sleeve. Means is also provided for moving the plate cylinder and the impression cylinder relative to the coating cylinder in directions transverse to the axis of the coating cylinder. 
     According to a second aspect of the invention, a method is provided for operating the coating machine to print different coatings on multiple web substrates. The method entails depositing the coating material on the first coating sleeve as the coating cylinder is rotated by the rotating means associated therewith, transferring the coating material on the first coating sleeve to the plate sleeve of the plate cylinder as the plate cylinder is rotated by the rotating means associated therewith, transferring the coating material on the plate sleeve to the web substrate to form a first coating on the web substrate, moving the plate cylinder and the impression cylinder relative to the coating cylinder in directions transverse to and away from the coating cylinder, removing the first coating sleeve from the coating cylinder mandrel and installing a second coating sleeve on the coating cylinder mandrel, depositing a second coating material on the second coating sleeve as the coating cylinder is rotated by the rotating means by the rotating means associated therewith, transferring the second coating material on the second coating sleeve to the plate sleeve of the plate cylinder as the plate cylinder is rotated by the rotating means associated therewith, and transferring the second coating material on the plate sleeve to a second web substrate to form a second coating on the second substrate. 
     In view of the above, it can be seen that a significant advantage of this invention is that the coating machine provides a “quick change” capability with respect to the coating and plate cylinders, allowing for the use of coating sleeves having different coating material transfer characteristics and the use of plate sleeves having different thicknesses, which in combination can achieve a vast range of value-added coating possibilities at essentially any repeat (plate cylinder circumference). 
     Other aspects and advantages of this invention will be better appreciated from the following detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  represent a rotary-style coating machine in accordance with an embodiment of this invention, and shows the ability of the coating machine to accommodate plate cylinders of different circumference size (repeat). 
         FIG. 3  represents the coating or plate cylinder of the coating machine of  FIGS. 1 and 2  in a typical run position during operation of the coating machine. 
         FIG. 4  represents a manner in which the circumference size of the coating and/or plate cylinders of  FIG. 3  can be changed in accordance with an embodiment of this invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 1 and 2  represent a rotary-style coating machine  10  of a type suitable for illustrating preferred aspects of the invention. The coating machine  10  is adapted to provide the operator of the machine  10  with a “quick change” capability through the inclusion of a coating cylinder  12  and plate cylinder  14  that are each configured to have changeable sleeves  16  and  18 , respectively, that can be mounted to what will be referred to as a coating mandrel  20  and a plate mandrel  22 , respectively. As will be discussed below, the sleeves  16  and  18  of the coating and plate cylinders  12  and  14  can have different radial thicknesses and other characteristics that enable a wide range of coating processes and repeats (plate cylinder circumferences). To schematically illustrate, the plate cylinder  14  of  FIG. 2  is represented as having a plate sleeve  18  having a different diameter than the plate sleeve  18  of  FIG. 1 . Though cylinder sleeve removal and changing has been practiced in the past, such use has been primarily with printing presses in the flexographic printing industry, for example, of the type widely used in the packaging industry, as well as blanket changes on web offset printing presses. 
     The coating machine  10  is schematically represented as comprising an enclosure or framework  24  that contains the coating and plate cylinders  14  and  16 . The framework  24  further comprises an enclosed doctor blade chamber  26  with which coating can be uniformly applied to the coating cylinder  12 , an impression cylinder  28 , and rollers  30  arranged to transport a web substrate  32  through the framework  24  and a printing nip  34  defined between the plate and impression cylinders  14  and  28 . The doctor blade chamber  26 , impression cylinder  28  and rollers  30  can be of any suitable type, and therefore will not be discussed here in any details here. As an alternative to the doctor blade chamber  26 , it is foreseeable that a pan roll system could be used to apply coatings to the coating cylinder  12 . 
     The coating cylinder  12  is preferably an anilox cylinder, in which case the sleeve  16  of the coating cylinder  12  will be referred to as an anilox sleeve  16 . As known in the art, a conventional anilox cylinder typically comprises a hard metal cylindrical core on which a ceramic layer has been formed. The surface of the ceramic layer contains numerous very small laser-engraved cells, whose characteristics determine the amount of coating that can carried by an anilox cylinder and, therefore, can be transferred from the anilox cylinder to a plate cylinder. Details regarding the use of certain materials, cell characteristics, etc., to achieve desired coating transfer and printing capabilities are generally understood in the art, and therefore will not be discussed in any detail here. The mandrel  20  of the coating cylinder  12  can be an air mandrel that enables the coating sleeve  16  to be released with air pressure, as known in the art. In particular, the mandrel  20  can be fabricated as a hollow cylinder with pinholes in its outer cylindrical wall so that air introduced into the interior of the mandrel  20  is able to force a sleeve  16  installed on the mandrel  20  in a radially outward direction from the mandrel  20 , allowing the sleeve  16  to be installed and removed from the mandrel  20  with relative ease. A suitable sleeve construction for this purpose includes fabricating the coating sleeve  16  to have a relatively rigid tubular support structure, for example, an aluminum tube, on whose interior surface a compressible membrane is provided and on whose exterior surface the ceramic anilox layer is provided. The compressible membrane is sized to create an interference fit with the mandrel  20 , but can be compressed by air flowing through the pinholes of the mandrel  20  to eliminate the interference fit or otherwise permit the sleeve  16  to be installed and removed from the mandrel  20 . 
     Of significant here is the ability to change the anilox sleeve  16  of the coating cylinder  12 , which allows for the use of different configurations of anilox cells to achieve different coating transfer characteristics, as well as allow the use of different types of coatings, including but are not limited to gloss varnishes, matte varnishes, silicone release coatings, scratch-off coatings, glitter, pearl effect and glow-in-the-dark coatings, pseudo “emboss” coatings, pseudo “sheet magnet” coatings, thermo chromatic coatings, and magnetic strips for embedded card information. Such coatings may be curable with the use of ultra-violet (UV) radiation, infrared (IR) radiation, heat, and other known means. This wide range of coatings is possible and practical due to the quick-change capability of the anilox sleeve  16 , which allows for the selection and installation of a sleeve  16  having a desired anilox cell size and count that can be tailored to achieve certain coating characteristics. With this capability, an operator of the machine  10  has the ability to work directly with a coating supplier to tailor the anilox cell pattern of a particular anilox sleeve  16  to optimize the lay down (print) for a specific coating weight, viscosity, thickness, texture, etc., for a particular type of web substrate  32 . This capability also allows for the fabrication of an anilox sleeve  16  that is partitioned to have longitudinal regions located around the circumference of the sleeve  16  that have different cell sizes and/or counts to enable the application of multiple different coatings of different characteristics across the web substrate  32 . Such an anilox sleeve  16  would be used in combination with a doctor blade chamber  26  that is partitioned to be capable of depositing different amounts or types of coating on different regions of the anilox sleeve  16 . 
     As noted above, the plate cylinder  14  of the machine  10  is also configured to have a changeable sleeve  18 , which enables the operator of the machine  10  to change the repeat (circumference size) of the plate cylinder  14 . In addition, the ability to change the anilox sleeve  16  of the coating cylinder  12  to have a variety of different coating transfer characteristics and allow the use of different types of coatings may require, under some circumstances, that plate cylinder sleeves  18  used with the machine  10  to also be adapted to carry a range of different coating volumes to the web substrate  32  to achieve different final coating thicknesses, overprint sequences, screen patterns, intricacies, etc. The sleeve  18  of the plate cylinder  14  can be secured to its mandrel  22  in a manner similar to that described for the coating cylinder  12 , namely, by configuring the mandrel  22  as an air mandrel. For this purpose, the construction of the plate sleeve  18  can comprise a tube formed of plastic or another suitable material, and a compressible membrane on the interior surface of the tube for creating an interference fit with the mandrel  22 . The exterior surface of the tube can be provided with a photopolymer plate or any other suitable layer or material that, depending on the particular requirements of the coating processes and the web substrate  32 , is capable of suitably transferring the coating material from the coating cylinder  12  to the web substrate  32 . 
     Existing technology for plate cylinder sleeves can be used to produce sleeves  18  for use with the invention that are capable of high quality photo-polymer construction, including endless photo-polymer sleeves that can be installed on a reusable support sleeve  36 , which is in turn installed on the plate cylinder mandrel  22 . The operator of the machine  10  can have the option of using an electronic file of the image to be printed to produce the plate cylinder sleeve  18  directly on the reusable support sleeve  36 , which can reduce the “make-ready” for the machine, reduce the risk of operator error of image registration, and increase quality coating performance due to the elimination of seams ordinarily present in plate cylinders of the prior art. 
     In view of the ability to vary the repeat (circumference) size (and, therefore, the diameter) of the plate cylinder  14  through the selection and installation of different plate sleeves  18 , the coating, plate and impression cylinders  12 ,  14  and  28  are all preferably individually driven, for example, with separate motors (not shown). As a result of the plate cylinder  14  being driven by a separate motor, plate sleeves  18  of various thicknesses can be used in a range of repeat (circumference) sizes to match virtually any print repeat length. This aspect of the invention allows the operator of the machine  10  to coat any preprinted web substrate  32  of any repeat length simply by changing the plate sleeve  18  to match the desired circumference. Particularly suitable mechanisms for independently driving the coating, plate and impression cylinders  12 ,  14  and  28  include servo or vector-type motors (represented as a motor  46  in  FIGS. 3 and 4 ), though it is foreseeable that other mechanisms could be used for this purpose. 
     Independent drives for each of the coating and plate cylinders  12  and  14  allow the diameter/circumference of the plate cylinder  14  to change for immediate adaptation to a wide range of repeat print lengths/presses by enabling the matching of repeat and surface speed. This aspect of the invention also allows the operator to print to either surface (the “top side” or “bottom side”) of the web substrate  32  by simply reversing the drive rotational directions of the cylinders  12 ,  14  and  28 . This aspect of the invention also allows two of the machines  10  to be combined in tandem for “perfecting” applications, in other words, to coat in sequence both surfaces (sides) of the web substrate  32 . 
     To accommodate different cylinder circumferences, the plate cylinder  14  and impression cylinder  28  must also be able to move relatively to each other and to the coating cylinder  12  in directions transverse to their axes. As a nonlimiting example, horizontal movements of the cylinders  14  and  28  are represented by two horizontal arrows in  FIGS. 1 and 2 , to adjust for different repeat sizes of the plate cylinder  14 . This movement of the plate and impression cylinders  14  and  28  also allows the cylinders  14  and  28  to be moved relative to the coating cylinder  12  so that the coating sleeve  16  and plate sleeve  18  can be changed. Particularly suitable mechanisms for enabling the relative movement of the coating, plate and impression cylinders  12 ,  14  and  28  include precision profile linear bearing rail systems  58  associated with the plate and impression cylinders  14  and  28 , though it is foreseeable that other mechanisms could be used for this purpose. 
     In combination, the independently-driven coating, plate and impression cylinders  12 ,  14  and  28  and the ability to move the plate and impression cylinders  14  and  28  relative to each other and relative to the coating cylinder  12  enables very precise cylinder-to-cylinder impression settings, which further enable registered deposition of coatings capable of achieving intricate print patterns and registration features. Such precise movements of the cylinders  14  and  28  provide much greater accuracy and stability than current eccentric side frame impression designs commonly used in the art. 
       FIGS. 3 and 4  schematically represent views of the coating or plate cylinder  12  or  14 , and the manner in which the cylinder  12 / 14  can be manipulated to enable sleeves  16 / 18  to be removed and installed.  FIG. 3  shows a side view (perpendicular to the axis of the cylinder  12 / 14 ) and an end view of the cylinder  12 / 14 , representing an axle  40  at one end of the cylinder  12 / 14  as rotatably secured with a bearing unit  42  to a section  44 A of the framework  24  of the machine  10 . An independent drive motor  46  (i.e., the drive motors  46  of the cylinders  12  and  14  are independently operable at different speeds) is coupled to an axle  48  at the opposite end of the cylinder  12 / 14 , and mounted to another section  44 B of the framework  24  with a housing  50  that includes a pivot joint  52 . The bearing unit  42  is adapted to allow the axle  40  of the cylinder  12 / 14  to be released, after which a pneumatic (or hydraulic) cylinder  54  coupled to the housing  50  can be operated to pivot the axle  40  of the cylinder  12 / 14  out of engagement with the bearing unit  42 , as represented in  FIG. 4 . The existing sleeve  16  and  18  can then be removed and replaced with a second sleeve  16 / 18 . 
     Downstream of the impression cylinder  28 , the machine  10  can optionally comprise a curing unit  38 , for example, a UV, infrared (IR), heater, or other type of curing device suitable for curing the particular coating being applied by the machine  10 . Further downstream from the curing unit  38 , the machine  10  may include one or more chill rolls (not shown) to remove excess heat from the web substrate  32  and control the tension in the web substrate  32  downstream of the curing process. The incorporation of the curing unit  38  and chill rolls within the machine  10  can be advantageous in view of the pattern repeat intricacy of the machine  10  resulting from its changeable coating and plate sleeves  16  and  18  and the positioning capability of the plate and impression cylinders  14  and  28  relative to the coating cylinder  12 . In particular, the ability to stabilize the tension in the web substrate  32  facilitates higher quality registration by enhancing the circumferential register control aspect of the machine  10 . 
     In view of the above, the operator of the machine  10  has the ability to select a repeat size by selecting and installing an appropriate plate sleeve  18 . According to a preferred aspect of the invention, the selection of the plate sleeve  18  can be used as inputs to an automated control system  56  capable of automatically positioning the plate and impression cylinders  14  and  28  to their proper positions relative to the coating cylinder  12  based on the selected repeat size. In this manner, the control system  56  can automatically adjust the speed of the individual drive motor  46  of the plate cylinder  14  for the intended repeat (circumference) change, while the rotational speeds of the drive motor  46  for the coating cylinder  12  (and, presumably, the drive motor (not shown) of the impression cylinder  28 ) can be adjusted or maintained to achieve surface speeds that match the existing or desired speed of the web substrate  32 . 
     While the invention has been described in terms of a specific embodiment, it is apparent that other forms could be adopted by one skilled in the art. For example, the machine  10  could differ in appearance and construction from what is schematically represented in the Figures, and the functions of various components of the machine  10  could be performed by components of different construction but capable of a similar (though not necessarily equivalent) function. Therefore, the scope of the invention is to be limited only by the following claims.