Patent Publication Number: US-2010122638-A1

Title: Flexographic Printing Apparatus And Method

Description:
FIELD OF THE INVENTION 
     This invention relates to flexographic printing, and more particularly to an apparatus and method for mounting and adjusting the positions of a plate roll and an anilox roll in relation to the impression roll of a flexographic printing apparatus. 
     BACKGROUND OF THE INVENTION 
     In a typical flexographic printing apparatus or method, a plate roll and an anilox roll are mounted adjacent to an impression roll of a flexographic printer. The printer includes a printer frame, which typically has a drive side plate and an operator side plate. Generally speaking, the side plates of the printer frame support opposite ends of the impression roll, the plate roll and the anilox roll. For proper operation of the flexographic printing apparatus, it is necessary to have the rolls properly aligned with one another, with their rotational axes generally parallel to one another. It is also necessary for the rolls to be alignable axially to achieve proper registration and operation of the printer. It is further necessary to provide mounting and alignment for associated equipment, such as an ink box, or other inking arrangement for transferring ink to the anilox roll. 
     The impression roll is generally mounted more-or-less fixedly to the printer frame, and the plate roll is mounted in some sort of arrangement which allows the periphery of the plate roll to be positioned substantially in contact with, or moved away from, the periphery of the impression roll. In similar fashion, the anilox roll is typically mounted in some sort of adjustable arrangement so that the periphery of the anilox roll can be brought into contact with, or moved away from, the periphery of the plate roll. An ink box, or other inking arrangement, is typically mounted adjacent the anilox roll, for transferring ink from the inking arrangement to the surface of the anilox roll. The anilox roll, in turn, transfers the ink to a sleeve on the surface of the plate roll which produces an image on the surface of a web of material passing through a nip created between the plate roll and the impression roll, during the printing process. 
     It is also necessary for a flexographic printing apparatus and method to provide for periodic removal and replacement of a sleeve on the surface of the plate roll, in order to change from one printing pattern to another. Typically, it is desirable to leave the plate roll attached and suspended from the drive and side plate, in a cantilevered fashion, and to provide a mechanism for supporting the plate roll with its operator side detached from the operator side frame, while the sleeves are pulled off of, or pushed onto, the outer surface of the plate roll in a direction generally along the rotational axis of the plate roll. In order to free the plate roll from contact with the impression roll and the anilox roll during changeover of the sleeve, it is typically necessary to provide some mechanism for separating the impression, plate and anilox rolls from one another during the process of changing from one sleeve to another, and then bringing the rolls back into proper alignment with one another once the new sleeve has been put in place. 
     Through the years, a number of prior approaches to dealing with one or more of the problems described above have been proposed. None of these approaches has proven to be entirely satisfactory, however, particularly for flexographic printing apparatuses and methods having long rolls which are several feet wide. 
     Accordingly, it is desirable to provide an improved flexographic printing apparatus and method, addressing one or more of the problems described above, or other deficiencies of prior flexographic printing apparatuses and methods as are known to those having skill in the art. It is particularly desirable to provide improvements in flexographic printing apparatuses and methods for use with printers having long rolls. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides an improved flexographic printing apparatus and method through use of a roll mounting apparatus having a support platform configured for attachment to a printer frame, and four bearing support carriages attached to the support platform for operatively supporting opposite ends of a plate roll and an anilox roll. One plate roll carriage and one anilox roll carriage are operatively attached to the support platform along each opposite side of the support platform by a common linear guide arrangement. The plate roll carriages are positioned along the linear guide arrangements by two plate roll linear positioners operatively attached between the support plate and the plate roll carriages. The anilox carriages are positioned along the linear guide arrangements, with respect to the plate roll carriages, by a pair of anilox roll linear positioners operatively attached between the plate roll carriages and the anilox roll carriages. In some forms of the invention, the support platform is also transversely movable with respect to the printer frame for lateral registration. 
     In one form of the invention, a roll mounting apparatus is provided for operatively attaching a plate roll and an anilox roll, adjacent to an impression roll of a flexographic printer having a printer frame supporting the impression roll for rotation about an impression roll axis extending from a drive side of the printer frame to an operator side of the printer frame. The roll mounting apparatus includes a support platform and a pair of roll mounting arrangements. The support platform defines orthogonally intersecting longitudinal and transverse axes thereof, and is adapted for attachment to the machine frame with the transverse axis of the support platform extending substantially parallel to the impression roll axis. The support platform further has a width thereof substantially extending in the transverse direction from a drive side to an operator side of the support platform, corresponding to the drive and operator sides of the printer frame when the support platform is mounted in the printer frame. The pair of roll mounting arrangements are attached to the support platform, with one of the roll mounting arrangements of the pair disposed adjacent the drive side of the support platform, and the other roll mounting arrangement of the pair disposed adjacent the operator side of the support platform. The pair of roll mounting arrangements are adapted for receiving and retaining the plate and anilox rolls. 
     The drive side of the support platform may be adapted for attachment to the drive side of the printer frame, and operator side of the support platform may be adapted for attachment to the operator side of the printer frame. The support platform may be attached to the frame by a transversely oriented linear slide arrangement, in such a manner that the support platform is moveable transversely with respect to the frame, along the transverse axis of the support platform, to adjust lateral registration of the plate roll with respect to either or both of the impression roll and the web of material passing through the nip between the plate roll and the impression roll. 
     A roll mounting apparatus, according the invention, may include a lateral registration positioner, operatively connected between the printer frame and the support platform, for moving the support platform transversely with respect to the frame along the transverse axis of the support platform. The lateral registration positioner may include a linear screw actuator arrangement. In some forms of the invention, the lateral registration positioner may take other appropriate forms including, but not limited to, a linear motor, or a hydraulic servocylinder. 
     In some forms of the invention, the plate roll may include a portion thereof extending outboard of the roll mounting arrangements on the drive side of the support platform. The plate roll may also include a changeable sleeve. The roll positioning apparatus may include a drive side plate roll cantilever support, mounted on the drive side of the printer frame and configured to selectively bear in a substantially downward direction against the portion of the plate roll extending outboard of the roll mounting arrangements on the drive side of the support platform, for generating a cantilever support moment on the plate roll. The roll mounting arrangement on the operator side of the support platform may be configured to be selectively releasable from the plate roll, to thereby allow a sleeve of the plate roll to be changed while the plate roll is being maintained in a cantilevered support condition by action of the drive side plate roll cantilever support. 
     Some forms of the invention may also include a controller for positioning the mounting arrangement in a sleeve-changing configuration, whereat the plate roll and the anilox roll are positioned longitudinally along the support platform with a portion of the plate roll extending outboard of the roll mounting arrangement on the drive side of the support platform being aligned substantially vertically beneath the drive side plate roll cantilever support, and the anilox roll separated from the plate roll. 
     Some forms of the invention may include an inking arrangement mounted on the roll mounting arrangement for applying ink to the anilox roll and movement with the anilox roll. In some embodiments of the invention, an inking arrangement, such as an ink box, may be mounted on one or more anilox roll support carriages, for movement with the anilox roll. 
     In some forms of the invention, at least one of the plate and anilox rolls may have a portion thereof extending outboard of the roll mounting arrangement on the drive side of the support platform. A roll positioning apparatus, according to the invention, may include at least one roll drive motor having a housing and a rotatable drive member. The drive member may be attached to the portion of at least one of the drive and anilox rolls extending outboard of the roll mounting arrangement on the drive side of the support platform. The drive motor housing may be operatively attached to the support platform in such a manner that the drive motor housing is precluded from rotating with respect to the support platform. 
     A roll mounting apparatus, according to the invention, may include the plate roll and the anilox roll, operatively attached to the pair of roll mounting arrangements for rotation respectively about a plate roll axis and an anilox roll axis. Both the plate and anilox roll axes are oriented substantially parallel to the transverse axis of the support platform. 
     In some forms of the invention, each roll mounting arrangement of the pair of roll mounting arrangements has a plate roll bearing carriage and an anilox roll bearing carriage attached to the support platform by a common linear guide arrangement for linear movement in a direction substantially parallel to the longitudinal axis of the support platform. The plate roll carriage is disposed closer to the impression roll axis than the anilox roll, when the roll mounting apparatus is attached to the printer frame. Each roll mounting arrangement of the pair also may have a plate roll linear positioner operatively connected between the support platform and the plate roll carriage for selectively positioning the plate roll carriage along the linear guide arrangement. Each roll mounting arrangement of the pair may further have an anilox roll linear positioner operatively connected between the plate roll carriage and the anilox roll carriage for positioning the anilox roll carriage along the linear guide arrangement with respect to the plate roll. At least one of the linear positioners may include a linear screw actuator arrangement. 
     Some forms of the invention may include a controller which is operatively connected to the plate roll linear positioners and the anilox roll linear positioners, for positioning the plate roll carriages along the common linear guide arrangements, and for positioning the anilox roll carriages along the common linear guide arrangements with respect to the plate roll carriages. 
     A support platform, according to the invention, may be attached to the frame by a transversely oriented linear slide arrangement, in such a manner that the support platform is moveable transversely with respect to the frame along the transverse axis of the support platform, to thereby adjust lateral registration of the plate roll with respect to the impression roll and/or the web of material passing between the plate roll and the impression roll. Some forms of the invention may also include a lateral registration positioner, operatively connected between the printer frame and the support platform for moving the support platform transversely with respect to the frame along the transverse axis of the support platform. 
     A controller may be utilized, in some forms of the invention, for operatively connecting the plate roll linear positioners, the anilox roll linear positioners and the lateral registration positioner, for positioning the plate roll carriages along the common linear guide arrangements, the anilox roll carriages along the common linear guide arrangements with respect to the plate roll carriages, and for positioning the support platform transversely along the transverse axis of the support platform with respect to the printer frame. 
     The invention may also be practiced in the form of a method for constructing or operating a flexographic printing apparatus in accordance with the invention. In one form of the invention, a method is provided for operatively attaching a plate roll and an anilox roll adjacent to an impression roll of a flexographic printer having a printer frame supporting the impression roll for rotation about an impression roll axis extending from a drive side of the printer frame to an operator side of the printer frame, with the method including, attaching the plate and anilox rolls to the printer frame with a roll mounting apparatus having a support platform and a pair of roll mounting arrangements in accordance with the invention. 
     The invention may also take the form of a flexographic printing apparatus for operatively positioning a plate roll and an anilox roll adjacent to an impression roll of a flexographic printer having a printer frame supporting the impression roll for rotation about an impression roll axis extending from a drive side of the printer frame to an operator side of the printer frame. The flexographic printing apparatus may include the plate roll, the anilox roll, and a roll mounting apparatus for operatively attaching the plate roll and the anilox roll adjacent to the impression roll. The roll mounting apparatus may have a support platform and a pair of roll mounting arrangements. The support platform may define orthogonally intersecting longitudinal and transverse axes thereof, and be adapted for attachment to the printer frame with the transverse axis extending substantially parallel to the impression roll axis. The support platform may further have a width thereof substantially extending in the transverse direction in the drive side to an operator side of the support platform, corresponding to the drive and operator sides of the printer frame when the support platform is mounted in the printer frame. The pair of roll mounting arrangements may have a drive side roll mounting arrangement disposed adjacent the drive side of the support platform and an operator side mounting arrangement disposed adjacent the operator side of the support platform, with the pair of roll mounting arrangements being adapted for receiving and retaining the plate and anilox rolls on the support platform. 
     A flexographic printing apparatus, according to the invention, may further include the flexographic printer. The flexographic printing apparatus may include the printer frame. 
     A flexographic printing apparatus, according to the invention, may include a support platform mounting arrangement for attaching the support platform to the printer frame. The support platform mounting arrangement may include a transversely oriented linear slide arrangement and a lateral registration positioner. The transversely oriented linear slide arrangement may be configured for operatively attaching the support platform to the printer frame in such a manner that the support platform is moveable transversely with respect to the printer frame along the transverse axis of the support platform, to adjust lateral registration of the plate roll. The lateral registration positioner may be further operatively connected between the printer frame and the support platform for moving the support platform transversely with respect to the frame along the transverse axis of the support platform. 
     Other aspects, objects and advantages of the invention will be apparent from the following detailed description and accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
         FIG. 1  is a perspective illustration of a first exemplary embodiment of the invention, in the form of a flexographic printer. 
         FIG. 2  is a partially exploded perspective illustration, of the exemplary embodiment of the flexographic printer of  FIG. 1 , showing an upper flexographic printing apparatus, according to the invention, removed from the remainder of the printer. 
         FIG. 3  is a partially exploded perspective illustration of the flexographic printing apparatus of  FIG. 2 , with a plate roll, an anilox roll, and an ink box of the printing apparatus of  FIG. 2  removed to better illustrate components of a roll mounting apparatus according to the invention. 
         FIGS. 4 and 5  are perspective illustrations of a drive side roll mounting arrangement, and a linear slide arrangement of the exemplary embodiment of the roll mounting apparatus shown in  FIG. 2 . 
         FIG. 6  is an additional perspective illustration of the drive side roll mounting arrangement of the roll mounting apparatus of  FIG. 2 . 
         FIG. 7  is a perspective illustration of an operator side roll mounting arrangement of the roll mounting apparatus shown in  FIG. 2 . 
         FIGS. 8 and 9  are a drive side view and a front view of the exemplary embodiment of the flexographic printer of  FIG. 1 , showing a drive side plate roll cantilever support, according to the invention, and details of the construction and connection of drive motors for the impression roll, plate roll and anilox roll of the flexographic printer of  FIG. 1 . 
         FIGS. 10A-C  and  11 A-E are schematic illustrations of the drive side and the operator side, respectively, of the exemplary embodiment of the invention shown in  FIGS. 1-9 , sequentially illustrating a series of steps in a method for operating the exemplary embodiment of the printer during a process of removing and replacing a sleeve on the outside of the plate roll. 
     
    
    
     While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a first exemplary embodiment of the invention, in the form of a two-color flexographic printer  100 . The exemplary embodiment of the flexographic printer  100  includes a printer frame  102 , supporting upper and lower impression rolls  104 ,  106 , for rotation of the impression rolls  104 ,  106  about upper and lower impression roll axes  108 ,  110  extending from a drive side  112  to an operator side  114  of the printer frame  102 . 
     As shown in  FIGS. 1 and 2 , the printer frame  102  includes a drive side end plate  116  and an operator side end plate  118 , which are joined to one another by one or more cross members  119 . 
     The exemplary embodiment of the flexographic printer  100  also includes an upper flexographic printing apparatus  120  operatively mounted to the printer frame  102  for use with the upper impression roll  104 , and a lower flexographic printing apparatus  122  which is operatively connected to the frame  102  for operation with the lower impression roll  106 . The upper flexographic printing apparatus  120  is shown removed from the flexographic printer  100  in  FIG. 2 , for clarity. The upper and lower flexographic printing apparatuses  120 ,  122  are essentially identical in construction and operation in the exemplary embodiment of the flexographic printer  100 . Therefore, the description below of the construction and operation of the upper flexographic printing apparatus  120  will be understood to be applicable to the lower flexographic printing apparatus  122  as well. 
     As shown in  FIG. 2 , the upper flexographic printing apparatus  120  includes a plate roll  124 , an anilox roll  126  and an inking apparatus, in the form of an ink box  128 , all of which are mounted on a roll mounting apparatus  130 , which operatively attaches the plate roll  124 , anilox roll  126  an ink box  128  adjacent to the upper impression roll  104 . 
       FIG. 3  shows the upper flexographic printing apparatus in a partially exploded view. In the exemplary embodiment  100 , the roll mounting apparatus  130  includes a support platform  132 , a drive side roll mounting arrangement  134 , an operator side roll mounting arrangement  136 , and a support platform mounting arrangement having a transversely oriented linear slide arrangement in the form of four linear bearings  138 ,  140 ,  142 ,  144  and a lateral registration positioner  146 . 
     The support platform  132  defines orthogonally intersecting longitudinal and transverse axes  148 ,  150 . When the flexographic printing apparatus  130  is attached to the printer frame  102 , the transverse axis  150  extends substantially parallel to the axis  108  of the upper impression roll  104 . The support platform  132  also has a width (W) thereof which extends substantially in the transverse direction  150  from a drive side  152  to an operator side  154  of the support platform  132 , which correspond respectively to the drive and operator sides  112 ,  114  of the printer frame  102 , when the support platform  132  is mounted in the printer frame  102 . The drive side  152  of the support platform  132  is adapted for attachment to the drive side  112  of the printer frame  102 , and the operator side  154  of the support platform  132  is adapted for attachment to the operator side  114  of the printer frame  102 . 
     As shown in  FIGS. 4 and 5 , the support platform  132  is operatively attached to the printer frame  102  by the linear slide arrangements  138 ,  140 ,  142 ,  144  and the lateral registration positioner  146 , of the support platform mounting arrangement. Specifically, as shown in  FIGS. 4 and 5 , the linear slide arrangements  138 ,  140  are attached between the bottom side of the support platform  132  and the drive side end plate  116  of the printer frame  102 . The remaining two linear slide arrangements  142 ,  144  (not visible in  FIGS. 4 and 5 ) are attached in similar fashion between the bottom side of the support platform  132  and the operator side end plate  118  (not shown) of the printer frame  102 . As will be understood by those having skill in the art, the linear slide arrangements  138 ,  140 ,  142 ,  144  of the exemplary embodiment  100  are precision linear guides which are attached between the support platform  132  and the printer frame  102  in such a manner that the support platform is moveable transversely with respect to the printer frame  102 , along the transverse axis  150  of the support platform  132 , to thereby provide for adjusting lateral registration of the plate roll  124  with respect to the upper impression roll  104 , and/or with respect to a web of material (not shown) passing between the plate roll  124  and the upper impression roll  104 . Those having skill in the art will recognize that, although four linear slide arrangements  138 ,  140 ,  142 ,  144  are used in the exemplary embodiment described herein, in other embodiments of the invention fewer or more supports may be used for operatively connecting a support platform to a printer frame. It will be further understood that other appropriate types of supports may be used in other embodiments of the invention. 
     In the exemplary embodiment  100 , the lateral registration positioner  146  includes a ball screw arrangement  145  driven by an electric motor  147 . The lateral registration positioner  146  is operatively connected between the printer frame  102  and the support platform  132  for moving the support platform  132  transversely with respect to the frame  102  along the transverse axis  150  of the support platform  132 . It will be understood, however, by those having skill in the art, that in other embodiments of the invention the support platform mounting arrangement, linear slide arrangement, and lateral positioner may take any other appropriate form. 
       FIGS. 6 and 7  illustrate the construction and operation of the drive side and operator side roll mounting arrangements  134 ,  136 . As shown in  FIG. 6 , the drive side roll mounting arrangement  134  includes a drive side plate roll bearing carriage  156  and a drive side anilox roll bearing carriage  158  attached to the support platform  132  by a common drive side linear guide arrangement, having a pair of longitudinally extending drive rails  159 ,  160 , in such a manner that the plate roll and anilox roll bearing carriages  156 ,  158  are constrained for linear movement in a direction substantially parallel to the longitudinal axis  148  of the support platform  132 . The drive side plate roll bearing carriage  156  is disposed closer to the axis  108  of the upper impression roll  104  than the drive side anilox roll bearing carriage  158 , when the roll mounting apparatus  120  is attached to the printer frame  102 . 
     The drive side roll mounting arrangement  134  also includes a plate roll linear positioner  161 , in the form of a precision drive screw apparatus  162 , driven by an electric motor  164 . A threaded screw portion of the drive screw  162  is mounted for rotation in a pair of bearing blocks  166 ,  168 , which are fixedly attached to the support frame  132 . The bearing blocks  166 ,  168  and the drive screw  162  are configured such that as the drive screw  162  is selectively rotated by the motor  164 , the drive screw  162  does not move longitudinally with respect to the support frame  132 . A traveling nut portion  170  of the drive end plate roll linear positioner  160  is fixedly attached to an extension of the drive end plate roll bearing carriage  156 , in such a manner that rotation of the drive screw  162  by the drive end plate roll motor  164  causes the drive side plate roll bearing carriage  156  to move in the longitudinal direction along the drive side plate roll tracks  159 ,  160 , for selectively positioning the plate roll carriage  156  along the tracks  159 ,  160 . 
     As further shown in  FIG. 6 , the drive side roll mounting arrangement also includes an anilox roll linear positioner  172 , operatively connected between the plate roll carriage  156  and the anilox roll carriage  158 , for positioning the anilox roll carriage  158  along the tracks  159 ,  160  of the linear guide arrangement with respect to the plate roll carriage  156 . The drive side anilox roll linear positioner includes an anilox roll drive screw  174  and an anilox roll carriage positioner motor  176 , for rotating the drive screw  174  in a bearing block  177  which is attached to an extension of the drive side anilox roll bearing carriage  158 , in such a manner that the drive screw  174  and motor  176  travel with the drive side anilox roll bearing carriage  158  along the tracks  159 ,  160 . The drive side anilox roll linear positioner  172  also includes a nut portion  178 , which is fixedly attached to the drive side plate roll bearing carriage  156 . 
     By virtue of the above-described arrangement, the position of the drive side anilox roll bearing carriage  158  can be adjusted longitudinally with respect to the drive side plate roll bearing carriage  156  by operating the drive side anilox carriage positioning motor  176  to thereby rotate the drive screw  174 , which in turn causes the drive side anilox roll bearing carriage  158  to be drawn closer to, or moved away, from the drive side plate roll bearing carriage  156 , dependent upon the direction of rotation of the motor  176 , through action of the nut  178  and the drive screw  174 . In this manner, the drive side of the anilox roll  126  can be moved into and out of contact with the plate roll  124 . 
     Also, by virtue of the above-described relationship, rotation of the drive screw  162  of the drive side plate roll linear positioner  161  by the drive side plate roll positioning motor  164 , without rotation of the anilox roll drive screw  174 , will cause both the drive side plate and anilox roll bearing carriages  156 ,  158  to move together in a longitudinal direction along the tracks  159 ,  160 . 
     As shown in  FIG. 7 , the operator side roll mounting arrangement  136  includes an operator side plate roll bearing carriage  180  and an operator side anilox roll bearing carriage  182  attached to the support platform  132  by a common operator side linear guide arrangement, having a pair of longitudinally extending drive rails  184 ,  186 , in such a manner that the operator side plate roll and anilox roll bearing carriages  180 ,  182  are constrained for linear movement in a direction substantially parallel to the longitudinal axis  148  of the support platform  132 . The operator side plate roll bearing carriage  180  is disposed closer to the axis  108  of the upper impression roll  104  than the operator side anilox roll bearing carriage  182 , when the roll mounting apparatus  120  is attached to the printer frame  102 . 
     The operator side roll mounting arrangement  136  also includes an operator side plate roll linear positioner  188 , in the form of a precision drive screw apparatus  190 , driven by an electric motor  192 . A threaded screw portion of the drive screw  190  is mounted for rotation in a pair of bearing blocks  194 ,  196 , which are fixedly attached to the support frame  132 . The bearing blocks  194 ,  196  and the drive screw  190  are configured such that as the drive screw  190  is selectively rotated by the motor  192 , the drive screw  190  does not move longitudinally with respect to the support frame  132 . A traveling nut portion  198  of the operator end plate roll linear positioner  188  is fixedly attached to an extension of the operator end plate roll bearing carriage  180 , in such a manner that rotation of the drive screw  190  by the operator end plate roll motor  192  causes the operator side plate roll bearing carriage  180  to move in the longitudinal direction along the drive side plate roll tracks  184 ,  186 , for selectively positioning the operator side plate roll carriage  180  along the tracks  184 ,  186 . 
     As further shown in  FIG. 7 , the drive side roll mounting arrangement  136  also includes an operator side anilox roll linear positioner  200 , operatively connected between the plate roll carriage  180  and the anilox roll carriage  182 , for positioning the operator side anilox roll carriage  182  along the tracks  184 ,  186  of the linear guide arrangement with respect to the operator side plate roll carriage  180 . The operator side anilox roll linear positioner  200  includes an anilox roll drive screw  202  and an operator side anilox roll carriage positioner motor  204 , for rotating the drive screw  202  in a bearing block  208  which is attached to an extension of the operator side anilox roll bearing carriage  182 , in such a manner that the drive screw  202  and motor  204  travel with the operator side anilox roll bearing carriage  182  along the tracks  184 ,  186 . The operator side anilox roll linear positioner  200  also includes a nut portion  206 , which is fixedly attached to the operator side plate roll bearing carriage  182 . 
     By virtue of the above-described arrangement, the position of the operator side anilox roll bearing carriage  182  can be adjusted longitudinally with respect to the operator side plate roll bearing carriage  180  by operating the operator side anilox carriage positioning motor  204  to thereby rotate the drive screw  202 , which in turn causes the operator side anilox roll bearing carriage  182  to be drawn closer to, or moved away, from the operator side plate roll bearing carriage  180 , dependent upon the direction of rotation of the motor  204 , through action of the nut  206  and the drive screw  202 . In this manner, the operator side of the anilox roll  126  can be moved into and out of contact with the plate roll  124 . 
     Also, by virtue of the above-described relationship, rotation of the drive screw  202  of the operator side plate roll linear positioner  188  by the operator side plate roll positioning motor  192 , without rotation of the operator side anilox roll drive screw  202 , will cause both the operator side plate and anilox roll bearing carriages  180 ,  182  to move together in a longitudinal direction along the tracks  184 ,  186 . 
     As shown in  FIGS. 6 and 7 , the drive side and operator side anilox roll bearing carriages  158 ,  182  both include respective bolting pads  210 ,  212  for attachment thereto of the ink box  128 , so that the ink box  128  moves together with the anilox roll  126 . Adjustment of the operative contact between the ink box  128  and the anilox roll  126  is accomplished in any applicable manner known in the art. 
     As shown in  FIGS. 8 and 9 , in the exemplary embodiment of the flexographic printing apparatus  120 , the plate roll  124  includes a portion  212  thereof extending outboard of the roll mounting arrangements  130  on the drive side  134  of the support platform  132 . The plate roll  124  also includes an outer surface thereof in the form of a changeable sleeve  213  carrying printing plates (not shown) on an outer periphery thereof, as is known in the art. 
     The drive side roll mounting arrangement  134  also includes a drive side plate roll cantilever support  214 , mounted on the drive side end plate  116  of the printer frame  102 . As best seen in  FIG. 8 , in the exemplary embodiment  100 , the drive side plate roll cantilever support  214  takes form of a hydraulic cylinder having a moveable piston  216 . A shoe  218  at a distal end of the piston  216  is configured to bear in a substantially downward direction against the portion  212  (see  FIG. 9 ) of the plate roll  124  extending outboard of the roll mounting arrangements  130  on the drive side  134  of the support platform  132 , for generating a cantilever support moment on the plate roll  124  to thereby facilitate removal and replacement of the changeable sleeve  213  in a manner described in more detail below with reference to  FIGS. 10A-C  and  11 A-E. Although the drive side plate roll cantilever support  214  takes the form of a hydraulic cylinder in the exemplary embodiment  100  of the invention, it will be understood that in other embodiments of the invention the drive side plate roll cantilever support may take any other appropriate form. 
     With reference to  FIGS. 10A-C  and  11 A-E, an exemplary method for operating the flexographic printer  100  and upper flexographic printing apparatus  20  will be illustrated, with regard to manipulation of the various components of the exemplary embodiment  100 , during change-over of the changeable sleeve  213  of the plate roll  124 . 
       FIGS. 10A and 11A  are partially schematic views of the drive end and the operator end, respectively, of the upper flexographic printing apparatus  120  with the plate roll  124 , the anilox roll  126  and the ink box  128  operatively positioned by the drive and operator side carriages  156 ,  158 ,  180 ,  182 , with respect to the impression roll  104 , for printing a web of material fed through the nip  220  between the impression roll  104  and the printing plates (not shown) mounted on the changeable sleeve  213  of the plate roll  124 . 
       FIGS. 10B and 11B  show the first step in the exemplary embodiment of a method for exchanging the sleeve  213 . Specifically, in transitioning between the position of the components as illustrated in  FIGS. 10A and 11A  to the position illustrated in  FIGS. 10B and 11B , the plate roll positioning motors  164 ,  192  at the drive and operator sides of the roll mounting apparatus  130  have been simultaneously driven, and the anilox roll positioning motors  176 ,  204  at the drive and operator ends of the roll mounting apparatus  130  have not been driven, so that the plate roll  124 , the anilox roll  126  and the ink box  128  move as a unit longitudinally on the frame  132 , to a longitudinal position, as best shown in  FIG. 10B , whereat the shoe  218  on the piston  216  of the drive side plate roll cantilever support can be brought to bear on the portion  212  of the plate roll  124  extending outboard of the drive side end plate  116 . 
     As shown in  FIGS. 10C and 11C , in the next step of the exemplary embodiment of the sleeve changing process, the anilox roll positioning motors  176 ,  204 , at the drive and operator sides  152 ,  154  of the platform  132  are operated in unison, while the plate roll positioning motors  164 ,  192  are left stationary, in order to separate the anilox roll  126  and ink box  128  attached to the anilox roll carriage  182  from the plate roll  124 . 
     As shown in  FIG. 11D , once the relative positioning described above with regard to  FIGS. 10C and 11C  is achieved, a hinged portion  222  of the operator side plate roll bearing carriage  180  is opened, and the anilox roll positioning motors  164 ,  204  are operated, with the plate roll positioning motors  176 , and  204  left stationary, so that the operator side plate roll bearing carriage  180  is moved longitudinally along the support platform  132  away from the plate roll  124  far enough (as shown in  FIG. 11E ) so that the sleeve  213  and the printing plates mounted on the sleeve  213  can be pulled off of the plate roll  124 . It will also be understood, that as the operator side plate roll bearing carriage  180  is pulled away from the plate roll  124 , the plate roll  124  remains supported in a cantilevered manner by virtue of the pressure being exerted in a downward direction by the shoe  218  of the drive side plate roll cantilever support  214  on the portion  212  of the plate roll  124  extending outboard of the drive side end plate  116  of the printer frame  102 . It will be further understood that during this operation the operator side plate roll positioning motor  204  may move the operator side plate roll carriage  180  longitudinally farther than the drive side plate roll positioning motor  176  moves the drive side plate roll carriage  156 , so that the anilox roll  126  remains substantially transversely aligned as the operator side plate roll bearing carriage  180  is pulled away from the plate roll  124 . 
     Once the operator side plate roll bearing carriage has been moved away from the plate roll  124  in the manner described above and shown in  FIG. 11E , the changeable sleeve  213  may be readily pulled off of the remainder of the plate roll  124  and be serviced or replaced by another sleeve. The steps described above in relation to  FIGS. 10A-C  and  11 A-E are then reversed to place the printer  100  back in the state shown in  FIGS. 10A and 11A  for printing on a web of material fed through the nip  220  between the impression roll  104  and the plate roll  124 . 
     As illustrated schematically in  FIG. 3 , in the exemplary embodiment  100 , one or more of the roll positioning motors  164 ,  176 ,  192 ,  204 , the lateral registration positioning motor  146  and the drive side plate roll cantilever support  214  may be operatively connected to a controller  224  to facilitate coordinated movement of the various components of the roll mounting apparatus  130  for performing operations such as cylinder changing, or adjustment in the relative positions of the plate roll  124  and the anilox roll  126  with respect to the impression roll  104 . 
     As shown in  FIGS. 8 and 9 , in the exemplary embodiment of the flexographic printer  100 , the drive motors  226 ,  228 ,  230  for the plate roll  124 , the anilox roll  126 , and the impression roll  104  are all operatively attached to their respective rolls at a point outboard of the drive side end plate  116  of the frame  102 . Specifically, each of the roll drive motors  226 ,  228 ,  230  has a drive shaft (not shown) thereof directly coupled to its respective roll  124 ,  126 ,  104 , and a housing which is operatively attached through a respective torque arm  232 ,  234 ,  236 , to either the platform  232  or the printer frame  102  in such a manner that the housings of the motors  226 ,  228 ,  230  are precluded from rotating with their respective rolls  124 ,  126 ,  104 . 
     The torque arm  236  of the impression roll drive motor  230  is operatively attached directly to the printer frame  102 , as illustrated in  FIG. 8 . 
     Best seen as in  FIG. 8 , the torque arm  232  of the plate roll drive motor  226  is operatively attached to the drive end plate roll carriage  156  to move longitudinally along tracks  159 ,  160  with the drive end plate roll carriage  156 , and also can move transversely with the platform  132  during operation of the lateral registration positioning motor  146 . In similar fashion, the torque arm  234  of the anilox roll drive motor  228  is operatively attached to the drive end anilox roll carriage  158 , to thereby allow the anilox roll drive motor  228  to move longitudinally along the tracks  159 ,  160  with the drive end anilox roll carriage  158 , and to also allow the anilox roll drive motor  228  to move transversely with the support frame  132  during operation of the lateral registration positioning motor  146 . 
     It will be understood, by those having skill in the art, that various embodiments of a flexographic printing apparatus, according to the invention, may include the printer frame  102  or even the entire flexographic printer  100 . It will be further understood that in other embodiments of the invention, more or fewer than two printing apparatuses, such as the upper and lower flexographic printing apparatuses  120 ,  122  described herein with regard to the exemplary embodiment  100 , may be used in practicing the invention. For example, in a single color printing arrangement, it may be desirable to use only a single printing apparatus, of the type described above with regard to the embodiments identified herein as the printing apparatus  120  or  122 , whereas in a multicolor process, it may be desirable to have three or more of such printing apparatuses. 
     It will further be understood, that, although the exemplary embodiment  100  included a separate impression roll  104 ,  106  for use with the flexographic printing apparatuses  120 ,  122 , the apparatuses  120 ,  122  could be used in embodiments of the invention having only a single impression roll in combination with multiple printing apparatuses operatively disposed about the single impression roll in a “common impression roll” arrangement as is known in the art. It will also be understood that, although only a stacked arrangement of the exemplary embodiment of the flexographic printing apparatuses  120 ,  122  is expressly described herein, with the support platforms  132  of the printing apparatuses  120 ,  122  extending substantially horizontally, the invention may also be practiced in other forms. For example, it is contemplated that one or more printing apparatuses according to the invention may be disposed in a linear manner along a horizontally extending material web path, with support platforms of the printing apparatuses being oriented substantially vertically. 
     It will also be recognized, by those having skill in the art, that in various embodiments of the invention, the controller  224  may be provided as a single central unit, or split into a number of smaller controllers, or even include some manual adjustments. An apparatus or method, according to the invention, may also utilize a number of sensors (not shown) of various appropriate types operatively connected to the controller. 
     It will be further recognized, that in some embodiments of the invention, it may be desirable to utilize arrangements for operatively attaching the anilox roll carriages and the plate roll carriages to the support platform in an appropriate manner which differs from the screw driven arrangements described herein with respect to the exemplary embodiment. For example, it may be desirable to use a different form of linear servo actuator, and/or linear guide arrangement, disposed between one or more of the roll mounting carriages and the support platform. 
     Those having skill in the art will readily recognize, from the description given above in conjunction with the accompanying drawings that the invention provides significant improvements over the prior art in flexographic printing apparatuses and methods. Such advantages include more efficient and effective alignment of the plate and anilox rolls with the impression roll, facilitation of maintenance and changeover of sleeves on the plate roll, and improved maintainability and reliability through a reduction in the number of components and adjustments that need to be made in comparison to prior printing apparatuses and methods. A further advantage is provided by mounting all of the roll drive motors and positioning mechanisms at outboard edges of the printer frame to thereby facilitate clean-up operations of the apparatus required during printing operations. Mounting the rolls on the support platform, according to the invention, also provides enhanced stiffness and improved support which is particularly advantageous and flexographic printing apparatuses and methods having rolls which may be several feet wide. 
     The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
     Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.