Patent Document

PRIORITY 
     This application is a continuation of application Ser. No. 12/510,789 filed Jul. 28, 2009, which in turn is a Continuation in Part of U.S. patent application Ser. No. 12/104,110 filed Apr. 16, 2008, which claims the benefit of U.S. Provisional Patent Application 60/925,974 filed Apr. 24, 2007 and U.S. Provisional Patent Application 60/964,870 filed Aug. 15, 2007, and application Ser. No. 12/510,789 also claims the benefit of U.S. Provisional Patent Application 61/084,131 filed Jul. 28, 2008. Each of the foregoing applications is hereby fully incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates generally to the field of flexographic printing and, more particularly, to portable flexographic ink proofing apparatus, systems and methods for providing proofs of ink samples. 
     BACKGROUND 
     In the field of flexographic printing ink samples may be obtained by drawing ink over a substrate using a hand ink proofer or by more sophisticated proofing methods. In hand proofing ink is applied to the substrate by manually rolling the hand proofer across the substrate. Manual ink proofer tools are utilized for proofing ink colors in an effort to accurately predict the results to be obtained by running a selected ink specimen in a printing press. A computer microscope or other instrument is then used to examine the ink smear on the substrate. The computer then indicates to the technician various color components to be added to the ink in order to achieve the desired ink coloration. 
     In a flexographic printing operation, resilient plates are utilized for delivering the ink to the substrate. Substrates generally include the stock or paper to be printed but may also include plastic and many other materials. 
     The shade of a color on a flexographic printing press is dependent on the thickness of the ink film applied to the substrate or stock. The ink film thickness is determined by the speed of the press, the pressure applied between the printing plate and paper (i.e., impression), and the pressure between the rollers on the printing unit. 
     U.S. Pat. No. 6,814,001 describes an ink proofer designed to overcome the problems associated with conventional manual proofer tools by generating consistent and reliable ink draws using a hand-held proofer tool retained in a movable mounting assembly. A variable pressure system is coupled to the mounting assembly to move the proofer tool into a contact position with a cylindrical drum. The transfer roller of the proofer tool then transfers ink to a substrate inserted between the drum and the transfer roller of the proofer tool when a drive motor for the drum is engaged. U.S. Pat. No. 6,814,001 is hereby incorporated by reference. 
     Printing presses generally use an anilox roll to meter ink and a cylinder bearing an engraved plate to transfer the ink from the anilox roll and to deposit it onto the substrate as a printed image. The substrate commonly includes paper but may also include many other materials such as plastic bags or any other material onto which printing may be applied. 
     The engraved plate may be made to include both solid and/or dot patterns depending upon image requirements. For a single color image, typically a plate with a solid or smooth surface may be used. For a multi-color image where more than one color is required a dot pattern is generally used. The superimposition of multiple dot patterns onto a substrate is used to print multi-color images. Typically each dot pattern is printed with a primary color onto the substrate. By putting the substrates through multiple passes in the press, any shade or color may be created by the combination of primary colors. 
     To obtain the desired colors in multi-color materials however, each primary color must print correctly and be of the correct density. Therefore, when adjusting inks for color, it is the primary color in each dot pattern that must be controlled. 
     Current proofing processes only use an anilox in a transfer roll to lay down ink. This process creates a smear of ink that proofs its color and density. The transfer roll duplicates the volume of the ink in the anilox and color, but does not duplicate the dot percentage pattern found in an offset plate. The dot percentage pattern is based on the proportion of the substrate that is covered with ink. Small dots result in a smaller percentage of coverage than large dots. 
     Printing plates can be and often are tested on the printing press but the expense of doing so is high. Modern printing presses are expensive. Any time that is used to test on the press is non productive time and cannot be used for profitable production. A printing press requires considerable time for setup and cleanup in addition to the time that is used in a test run. In addition, modern printing presses operate at high speed and can consume large quantities of ink and substrate quickly adding to the expense of testing. 
     Thus, there is still room for improvement in the preparation of proofing printouts in order to provide the best results in a printing press. While current proofing techniques are helpful in preparing for production printing press runs they are not adequate to predict the performance of the printing press. 
     A standard flexographic printing press has four main components: 
     1. A metering roll. This roll rotates in an ink well, wherein ink adheres to its surface. The ink well is necessarily located below the metering or inking roll because of gravity. As such the metering roll is located below and in contact with the anilox roll. As the metering roll rotates, it contacts the anilox roll and squeezes the ink into the anilox cells. 
     2. The anilox rotates, laden with ink, to the doctor blade. 
     3. The doctor blade is located near the metering roll, and presses against the anilox, and also is positioned with the edge “leading” (or cutting) into the anilox. This position shears the excess ink from the anilox and, usually, returns it to the ink well via gravity. 
     4. The photopolymer plate or other printing plate then receives the ink from the anilox and transfers it to the substrate. 
     A conventional hand proofer has three components: 
     1. An anilox which transfers metered ink from the doctor blade to the transfer roll or photopolymer plate. 
     2. A doctor blade located near the top of the anilox and positioned with its edge trailing (creating wiping action). This wiping action is necessary because ink needs to be forced into the anilox before metering it. So a trailing edge anilox services two purposes, forcing ink into anilox and metering it level to the anilox surface. These two actions compromise each others&#39; ability to perform. The wiping action of the trailing blade tends to lift the doctor blade, allowing non-metered ink to pass. This non-metered amount of ink reduces accuracy of ink application and reduces the quality and consistency of the resulting proof. 
     3. An ink transfer roll that receives ink from the anilox and applies an ink sample to the substrate. 
     SUMMARY 
     The present invention solves many of the above-discussed problems. In one aspect, the invention is a proofing tool including an anilox roll, and a transfer roll. 
     The invention includes a transfer or transfer roll that includes a printing plate similar to that used on a flexographic printing press. The printing plate may include for example a photopolymer printing plate. 
     The transfer roll and the anilox roll are shiftable relative to each other between an engaged position where the transfer roll is engaged with the anilox roll and a disengaged position where the transfer roll is disengaged from the anilox roll. An anilox support member supports the anilox roll and a transfer support member supports the transfer roll such that the anilox roll and the transfer roll are oriented substantially parallel and separated by a nip distance. The invention may also include a positive rotational linkage between the anilox roll and the transfer roll so that the pitch velocity of the anilox roll and the pitch velocity of the transfer roll are substantially matched. 
     The invention includes a proofing tool, having an anilox roll and a transfer roll. The transfer roll and the anilox roll are shiftable relative to each other between an engaged position where the transfer roll is engaged with the anilox roll and a disengaged position wherein the transfer roll is disengaged from the anilox roll. The invention further includes an anilox support member supporting the anilox roll and a transfer support member supporting the transfer roll such that the anilox roll and the transfer roll are oriented substantially parallel to one another and separated by a nip distance. The invention may also further include a positive stop nip adjustment mechanism operably connected to the anilox roll and the transfer roll which is adjustable so that when the anilox roll and the transfer roll are in the engaged position the positive stop prevents the nip distance from being smaller than a set value. 
     The invention may also further include a positive stop nip adjustment mechanism operably connected to the proofing tool and a proofing machine such that nip between the transfer roll and the drive roller of the proofing machine which is adjustable so that when the transfer roll and the drive roller of the proofing machine are in the engaged position the positive stop prevents the nip distance from being smaller than a set value. 
     In another aspect, the invention includes a gear driven anilox proofing tool with a positive stop adjustment of nip distance the anilox roll and the transfer roll or the transfer roll and the drive roller of the proofing machine. The present invention includes a proofing tool that has a positive rotating connection between the anilox roller and the transfer or transfer roller so that no matter how light the nip pressure is the speed of the rollers remains matched. The positive rotating connection matches the pitch velocity of the anilox roll with the transfer roll whether the anilox roll and the transfer roll are of similar or varying diameters. 
     In addition, the present invention allows the nip of the proofing tool to closely simulate the nip of the printing press so that the shear properties of the ink are not affected significantly differently in the proofing tool than in the printing press, which would lead to variations in color, density and shade between the proof and the printed result. A gear drive between the anilox roll and the transfer roll prevents slipping between the anilox roll and the transfer roll. The gear drive also allows wider variation in pressure ratios without slipping. 
     The proofing tool of the present invention is also adapted for use with a proofing machine that has a drive roll. A typical proofing machine has a drive roll that is formed of rubber. Often, a drive roll is formed of 60 durometer rubber. The drive roll may have a polished metallic surface, a textured surface or a surface of another material. In an embodiment of the invention, the drive roll has a polished metallic surface in a center segment and resilient bands at the edges. For example the resilient bands may be formed or rubber or urethane. Materials of forty to sixty durometer may be suitable. The present invention creates positive or semi-positive drive between the drive roll of the proofing machine and the transfer roll of the hand proofer. For the purposes of this application, a positive drive will be considered a drive that has essentially no slippage between the transfer roller and the drive roller in the case of an automated proofing arrangement and the transfer roller and the surface that supports the substrate in the case of a hand proofing arrangement. In other words a positive drive in accordance with the present invention maintains the pitch velocities of the anilox roll and the transfer roll to be substantially equal. An exemplary positive drive includes a gear tooth engagement between the transfer roll and the drive roller or supporting surface. A semi-positive drive will be considered a drive that has limited slippage between the transfer roller and the drive roller in the case of an automated proofing arrangement and the transfer roller and the surface that supports the substrate in the case of a hand proofing arrangement. An exemplary semi-positive drive includes a high friction engagement between the transfer roll and the drive roller or supporting surface. For example, a gear rolling on a resilient rubber surface creates a semi-positive drive. A positive or semi-positive drive allows lighter nip pressure on the substrate even with high contact pressure between the anilox roll and the transfer roll. 
     This is particularly helpful for film drawdowns. In addition, the positive or semi-positive drive between the drive roll and the transfer roll allows for higher doctor blade pressures. The positive or semi-positive drive between the drive roll and the transfer roll may be accomplished by the gears on either side of the transfer roll engaging with the drive roll instead of the drive roll engaging the paper which then in engages the transfer roll by friction. 
     Another aspect of the present invention is that the nip is adjustable by positive displacement rather then by the application of variable spring pressure. In the present invention the nip is set by displacement adjustable by one or more micrometer thimbles built into the proofing tool. This allows for consistent, repeatable displacement between the anilox roll and the transfer roll and better approximates the nip of the printing press, thus allowing more reliable consistent proofing of the resulting material. 
     The hand proofer of the present invention may be operated manually or may be used with a proofing machine. 
     In another aspect, the present invention lends itself to particularly easy cleaning for removing inks to allow for multiple proofing of multiple color inks without significant delay. 
     Another benefit of the present invention is that it may be adapted to use readily available anilox rolls from multiple suppliers currently in the market. 
     Another aspect of the present invention is that when it is used for proofing, the anilox and transfer rolls are oriented in a vertical position relative to one another. This vertical orientation of the anilox roll above the transfer roll simulates the orientation found in a printing press so that the effect of gravity on ink in the cell structure of the anilox roll is similar to that found in the printing press. This provides for more reliable consistent proofing that is more comparable to the results that will be seen in the printing press when the actual print run is made. 
     The proofing tool of the present invention generally includes an anilox support, a transfer support, an anilox roll, a transfer roll and a positive roll drive. The anilox support and the transfer support are substantially parallel in substantially similar yoke shaped structures adapted to support the anilox roll and the transfer roll respectively. The anilox support and the transfer support are connected to one another at an end distal from the anilox roll and the transfer roll. The anilox support and the transfer support can flex relative to one another in a limited, controlled fashion. 
     The anilox roll and the transfer roll are supported in close proximity to one another on independent axles so that they can roll relative to one another. In one aspect of the invention, the anilox roll and the transfer roll are interconnected by an anilox gear and transfer gear. The anilox gear and the transfer gear mesh to provide a positive rotation of the anilox roll related to the transfer roll so that slippage cannot occur and pitch velocity is maintained equal between the two. 
     The anilox support and the transfer support are separated by a short gap and one or two micrometer thimbles are interposed so that the micrometer thimbles can be adjusted to accurately alter the spacing between the transfer support and the anilox support. The micrometer thimbles create a positive stop so that the distance between the anilox roll and the transfer roll, when they are engaged, can be precisely and repeatably set. The positive stop sets a minimum distance that can be achieved between the anilox roll and the transfer roll. Thus, the spacing between the anilox support and the transfer support may be repeatedly and precisely set. 
     In another aspect to the invention there may be a transfer gear located at each end of the transfer roll. Thus, when the proofing tool is used with a mechanical proofer the transfer gears on each side of the transfer roll engage with the drive roll to create a positive or semi-positive drive between the drive roll and the transfer roll. 
     The anilox roll and the transfer roll of the present invention are oriented so that, in use, they are in vertical position with the anilox roll above the transfer roll. This duplicates the arrangement in a printing press such that the effect of gravity on ink transfer between the anilox roll and the transfer roll is similar to that in a printing press producing more reliable and consistent proofs. 
     The present invention and engraved printing plate may be applied to the transfer or transfer roller of the proofer. The engraved plate may be made to include both solid and/or dot patterns depending upon ink and image requirements. For spot colors, those colors used for a single color image, typically a plate with a solid or smooth surface may be used. For process colors, colors that are used in a multiple color image, where more than one color is required, a dot pattern is generally used. The superimposition of multiple dot patterns onto a substrate in a printing press is used to print multi-color images. 
     The printing plate used in the present invention may include a photopolymer printing plate. In one embodiment of the invention, the photopolymer printing plate used on the proofing tool may be made simultaneously with or even as a portion of the same plate as a photopolymer printing plate that is used on the printing press for a particular printing job. The portion of the printing plate for use on the proofer can then be utilized to predict the performance of the printing plate on the printing press at much lower cost than that which would be required to test a printing plate on the printing press. In this way, performance of the plate on the press is highly predictable. It is possible to closely match both color density and dot gain, thereby predicting the performance of the plate on the printing press without the necessity or expense of doing a printing press run. When color density and dot gain are closely matched, for example within five percent, the appearance of the printed result is indistinguishable to all but the most careful and experienced observer. 
     In another embodiment, the present invention includes a method of predicting the performance of a printing plate on a printing press including preparing a printing plate for the printing press simultaneously or in parallel with a printing plate for a proofing device. The proofing plate is mounted on the proofing device. Optimization of performance of the printing plate on the proofing device is achieved by adjusting to achieve minimum ink transfer from the anilox roller to the printing plate and minimum ink transfer from the printing plate to the substrate. A printing proof is prepared and the proof is evaluated for characteristics including dot gain and color density. This information is used to adjust the parameters of the printing plate, if required. An adjusted printing plate is prepared and the process repeated. This allows the printing technician to set up the printing press to optimize the performance of the printing press plate on the printing press while also minimizing printing press downtime and maximizing printing press run time. 
     In another aspect of the invention, the photopolymer plate on the proofing tool is utilized to predict the performance of the ink, the combination of ink, photopolymer and sticky back adhesive that is used to secure the printing plate to the transfer roll. 
     Printing plates can be and commonly are tested on the printing press, but the expense of doing so is very high. A modern printing press can cost upward $300,000.00, and uses large quantities of substrate and ink in a relatively short time. In addition, the time required to clean and adjust the printing press can be substantial. Thus, printers would prefer to have the printing press operating doing production work as much of the time as possible. Any press time that is used in testing plates, ink or combinations of plates, ink and the sticky back adhesive that is used to secure the plates is time that is unavailable for press production activities. 
     If after proofing a plate on the proofing device it is necessary to make adjustments in the plate, adjustments in the plate can be made and the new adjusted plate proofed on the proofing device without the expense of set-up and clean-up and other necessary expenses involved in proofing the plate on the printing press. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a plan view of an embodiment of a proofing tool in accordance with the invention with some structures shown in phantom and some parts removed for clarity; 
         FIG. 1B  is an elevational view of an embodiment of a proofing tool in accordance with the invention with some structures shown in phantom and some parts removed for clarity; 
         FIG. 2  is a partial exploded view of an embodiment of a proofing tool in accordance with the invention; 
         FIG. 3  is a plan view of an embodiment of a of a proofing tool in accordance with the invention; 
         FIG. 4  is an elevational view of an embodiment of a of a proofing tool in accordance with the invention; 
         FIG. 5  is an elevational view of an embodiment of a proofing tool in accordance with the invention with some structures shown in phantom; 
         FIG. 6  is an elevational view of the proofing tool of  FIG. 5  with some structures shown in phantom and some structures removed for clarity; 
         FIG. 7  is a detailed view taken from  FIG. 6  with some structures shown in phantom; 
         FIG. 8  is a sectional plan view of a proofing tool in accordance with the invention with some structures shown in phantom; 
         FIG. 9  is an elevational view of a proofing tool in accordance with the invention including a leading edge doctor blade with some structures shown in phantom; 
         FIG. 10  is an elevational view of a proofing tool in accordance with the invention including a trailing edge doctor blade with some structures shown in phantom; 
         FIG. 11  depicts an example pattern for an engraved printing plate in accordance with the invention; 
         FIGS. 12A and 12B  schematically depict a printing plate having a proofing portion and a printing press portion in accordance with the invention joined and separated respectively; and 
         FIG. 13  is an elevational view of an embodiment of a proofing tool depicted in contact with a proofing machine and positive stops in accordance with the invention; 
         FIG. 14  is a cross sectional view of an embodiment of a proofing tool in accordance with the invention; 
         FIG. 15  is a plan view of an embodiment of a proofing tool in accordance with the invention; 
         FIG. 16  is a cross sectional view of an embodiment of a proofing tool taken along section line  16 - 16  in accordance with the invention; 
         FIG. 17  is schematic view of a relationship of a leading edge doctor blade and an anilox roll in an ink proofer in accordance with the invention; 
         FIG. 18  is an example graph comparing measured ink color density at various locations on a proof; and 
         FIG. 19  is a table listing the density measurements recorded for each ink color density measurement in  FIG. 18  along with standard deviation calculations. 
         FIG. 20  is a top view of a drive roll in accordance certain embodiments of the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIGS. 1-4  proofing tool  100  generally includes anilox support  102 , transfer support  104 , anilox roll  106 , transfer roll  108  and positive roll drive  110 . Anilox support  102  and transfer support  104  are similar but not identical structures. Proofing tool  100  includes a doctor blade that is not shown in  FIGS. 1-3  for clarity. An exemplary doctor blade and pressure bar are depicted in  FIGS. 4, 5-7 and 9-10 . 
     Anilox support  102  generally includes yoke  112  and extended portion  114 . Yoke  112  supports anilox roll  106  between two arms  116 . Likewise, transfer support  104  includes yoke  122  and extended portion  124 . Anilox roll  106  and transfer roll  108  are supported between the arms of yoke  112  and yoke  122  respectively. Anilox support  102  and transfer support  104  are connected only at distal end  125  of extended portions  120  and  124 . Otherwise, anilox support  102  and transfer support  104  are oriented substantially parallel with a small gap between them. Transfer support  104  is capable of some flexing movement from a disengaged position to an engaged position such that transfer roll  108  is held slightly more separated from anilox roll  106  when no force is applied to transfer roll  108  than when transfer roll is in contact with a printing substrate. 
     Positive roll drive  110  generally includes anilox gear  126  and transfer gear  128 . As best seen in  FIGS. 3 and 4 , anilox gear  126  and transfer gear  128  mesh together to synchronize the motion of anilox roll  106  and transfer roll  108 . In one embodiment of the invention, there is a single set of anilox gear  126  and transfer gear  128 . Another embodiment of the invention includes one anilox gear  126  and two transfer gears  128 . If one anilox gears  126  and two transfer gears  128  are present, one anilox gear  126  is located on one end of anilox roll  106  and two transfer gears  128  are located on each end of transfer roll  108  respectively. 
     Proofing tool  100  also includes one or more micrometer thimbles  130 . Two micrometer thimbles  130  may be used to allow independent adjustment to ensure equal nip spacing across the width of anilox roll  106  and transfer roll  108 . Micrometer thimbles  130  are positioned so that the measuring surfaces of spindles (not shown) contact transfer support  104  to determine a minimum nip spacing between anilox roll  106  and transfer roll  108 . Gear teeth  131  of transfer gear  128  extend beyond transfer roll  108 , in part, so that if the proofing tool  100  is set down on a flat surface there will be a standoff created and transfer roll  108  will not touch the surface. 
     Anilox gear  126  and transfer gear  128  may be formed with fine pitch gear teeth to prevent gear chatter. In one aspect of the invention, the gear teeth mesh such that the gears are separated by slightly more than a true pitch diameter to allow for adjustment of nip without the need to change gears. 
     Optionally, proofing tool  100  may include a separation device (not shown) which can be utilized to force anilox support  102  apart from transfer support  104  a slight distance to ensure separation between anilox roll  106  and transfer roll  108  when not in use. 
     Proofing tool  100  may be formed substantially from aluminum alloy or from other materials known to the art. 
     Referring to  FIGS. 5-8  proofing tool  100  includes pressure bar  134 , doctor blade holder  136  and doctor blade  138 . Pressure bar  134  is located at the end of yoke  122 . Doctor blade holder  136  is pivotably secured to the arms of yoke  122 . Doctor blade holder  136  secures doctor blade  138  by clamping or another technique known to the art. Doctor blade holder  136  has a relief cut into it, to allow positioning of the doctor blade  138  precisely parallel to anilox roll  136 . Adjusting screw  140  passes through pressure bar  134  to bear on doctor blade holder  136 . Adjusting screw  140  adjust the pressure of doctor blade  138  on anilox roll  106 . Doctor blade holder  136  is pivotably attached to arms  116  of yoke  118 . 
     In one embodiment of the invention, doctor blade  138  meets anilox roller  106  at approximately a 30 degree pressure angle. If the diameter of the anilox roll  106  is changed it may be necessary to change doctor blade holder  136  or to relocate the pivotable mounting of doctor blade holder  136 . Alternately, the position of anilox roll  106  may be changed, for example by the use of a bushing having an eccentrically located hole therein. 
     Still referring particularly to  FIG. 5 , ball ends  142  may be used to removably secure proofing tool  100  to an automated proofing machine (not shown.) If ball ends  142  are utilized, proofing tool  100  includes ball sockets  144  to receive ball ends  142  therein. Proofing tool  100  may also include one or more slide lockpins  146  located in an aperture in proofing tool  100  to secure proofing tool  100  to one or more ball ends  142  at ball sockets  144 . 
     The orientation of the doctor blade  138  in the present invention is reversed from that in known conventional prior art proofing tools. Orientation reversal allows the optional introduction of a felt dam  147  adjacent to the doctor blade  138 . The application of a felt dam  147  allows for the maintenance of a larger volume of ink in the well adjacent the doctor blade  138  which is useful, particularly, in long draw downs. 
     Referring to  FIGS. 5, 6 and 8 , note that extended portion  115  and extended portion  120  of anilox support  102  and transfer support  104  may be milled to thin them. The level of milling can be altered to adjust the flexibility of anilox support  102  relative to transfer support  104  allowing for adjustment of the relative flexion of anilox support  102  relative to transfer support  104 . 
     Anilox roll  106  and transfer roll  108  may be supported in anilox support  102  by precision ball bearings, sleeve bearings or bushings. Anilox roll  106  or transfer roll  108  may be supported at a one end by fixed bearing  148  and at a second end by moveable bearing  150 . One or both of anilox roll  106  or transfer roll  108  may be supported at both ends by fixed bearing  148  or by moveable bearing  150 . Fixed bearing  148  and moveable bearing  150  may be, for example, Delrin bearings. Moveable bearing  150  may be adjustable so as to be loosened to remove transfer roll  108  and tightened to secure transfer roll  108  in place for use. 
     In another embodiment of the invention, the drive roll of a proofing machine (not shown) may include a drive roll gear  152  such that transfer gear  128  engages the drive roll gear  152  so that the drive roll gear drives transfer gear  128  which in turn drives anilox gear  126  providing a positive drive engagement between a drive roll (not shown), transfer roll  108  and anilox roll  106 . 
     In another embodiment of the invention, proofing tool  100  may incorporate an auxiliary ink reservoir (not shown). Auxiliary ink reservoir may include a drip line and a valve to allow the institution of a steady drip supply to replenish a well of ink at doctor blade  138 . 
     Referring to  FIGS. 9 and 10 , doctor blade  138  may include trailing edge doctor blade as depicted in  FIG. 10  or leading edge doctor blade as depicted in  FIG. 9 . Trailing edge doctor blade  154  tends to force ink into anilox roll  106  while leading edge doctor blade  156  tends to meter the amount of ink by shearing off excess ink from the anilox roll  106 . Another embodiment of proofing tool  100  may include both a trailing edge doctor blade  154  and a leading edge doctor blade  156  acting on a single anilox roll  106 . This embodiment may be especially advantageous when proofing tool  100  is used with highly viscous inks. Highly viscous inks may tend to overwhelm the force of a trailing edge doctor blade  154  toward the anilox roll  106  and “hydroplane” the trailing edge doctor blade. 
     In an embodiment of the invention like that depicted in  FIGS. 1A, 1B and 2 , transfer roll  108  is replaced with cylinder  158  that is typically of larger diameter than transfer roll  108 . An engraved offset printing plate  160  is attached to the cylinder, for example, by double-sided tape also known to those skilled in the art as sticky back or sticky back tape. Printing plate  160  may be formed, for example, of rubber, vinyl or metal. 
     Printing plate  160  may include, for example, a plate made from a photopolymer via a photopolymer printing process. Photopolymers are used in a plate making process in which a sheet of photopolymer plastic is exposed, generally with a positive image transparency via an enlargement or contact printing process. The photopolymer is then “developed” with chemicals that etch the surface of the photopolymer to make it take ink in varying degrees. The resulting printing plate  160  is then fixed with other chemicals and dried to prepare if for use in the printing process. The photopolymer plate is then used in the printing process to provide images that allow for tonal gradations when printed. Photopolymer plates can also be prepared using a laser process. 
     Another aspect of the present invention is that positive roll drive  110  may be used to maintain rotational integrity during proofing as in other embodiments described herein. The meshing anilox gear  126  and transfer gear  128  match the pitch velocity of anilox roll  106  with cylinder  158  bearing printing plate  160  which is also may be matched with the pitch velocity of a drum (not shown) that transports the substrate. 
     Cylinder  158  bearing the engraved printing plate  160  will typically be of larger diameter than transfer roll  108  described in some embodiments. For example, cylinder  158  may have a diameter of approximately 2 inches. In order to accommodate the larger diameter of cylinder  158  bearing engraved printing plate  160 , spacer  162  may be used as depicted in  FIGS. 1A, 1B and 2 , to space anilox support  102  and transfer support  104  apart from one another. Other size cylinders may of course be used. 
     The larger diameter of the cylinder  158  bearing the engraved printing plate  160  provides more surface area for producing larger useable images. 
     Printing plate  160  may have similar engraved characteristics as an engraved offset plate that will be run on a printing press. Alternately, a standard printing plate  160  may be used that includes, for example, dot patterns ranging from five to one hundred percent density as well as solid patterns. An example printing plate  160  pattern is depicted in  FIG. 11 . 
     In another aspect of the invention, depicted in  FIG. 13 , positive stop  164  mounted on a proofing machine (schematically depicted in part) may be added. Positive stop  164  provides a mechanism to adjust nip or printing pressure between cylinder  158  bearing the printing plate  160  and a substrate to which printing plate  160  will be applied. When proofing tool  100  is lowered during proofing, substrate micrometer  166  engages to positive stop  164  to mechanically position proofing tool  100 . Micrometers  166  may be incorporated into the structure of proofing tool  100  or the proofing machine to allow precise repeatable measurement of nip between cylinder  158  supporting printing plate  160  and drive roll  168  of the proofing machine (not shown). Substrate micrometers  166  may be adjusted. Adjustment of micrometers  166  upward will lower printing pressure by widening the nip. Adjusting micrometers  166  lower, will increase the nip pressure by narrowing the nip distance. Positive stop  164  is beneficial to control nip as the surface area of printing plate  160  changes. Without controlling the nip, the control of pressure only may cause the cylinder  158  bearing the printing plate  160  to “hump” with variations in the thickness of printing plate  160 . Printing plate  160  tends to drop into low spots in the engraving where there is a reduced image offset area and create an abrupt thump when a higher portion of the offset image is encountered. 
     An example embodiment of a drive roll  168  according to one example embodiment is shown in  FIG. 20 . The drive roll includes a polished metallic center segment surface  169  disposed between and resilient band surface segments  171  adjacent each end of the metallic center portion  169 . The resilient bands may be formed of rubber, urethane or other similar material. Materials having a forty to sixty durometer measurement may be used according to one example embodiment. 
     A semi-positive drive is formed by the contact of the resilient band segments  171  of the drive roll  168  with the teeth of the impression roll  108  or the cylinder  158  having the plate  160  secured thereto, such as is shown in  FIG. 13 . Thus, there will be little or no slippage between the impression roller and the drive roller  168 . This configuration allows for the use of lighter nip pressure on the plate compared to configurations where the plate must provide the traction against the drive roll in order to operate the proofing apparatus. 
     The present invention also includes a method of predicting the performance of a printing press for a printing job. The method includes preparing a first printing plate  160  then securing the printing plate  160  to a proofing tool  100 . The proofing tool  100  is then adjusted to optimize ink transfer from anilox roll  106  to printing plate  160  and further adjusted to optimize ink transfer from printing plate  160  to a substrate. Optimization of ink transfer generally is achieved by adjusting the nip until minimum ink transfer without skipping of the image occurs across the width of the printed image. Once ink transfer is optimized an operator prepares a printing proof on a substrate and then evaluates the printing proof to predict the performance of a second printing plate  160  which is adapted for use on the printing press. This evaluation allows prediction of the performance of the second printing plate  160  on the printing press. 
     When the operator is evaluating printing performance the operator may measure dot gain and/or color density as well as other factors related to the printing proof. Instruments for making these measurements are known. In some embodiments of the invention, the first printing plate  160  and second printing plate  160  are prepared as a single printing plate having a first portion and a second portion that are then separated to create the first printing plate  160  and the second printing plate  160 . Optionally the printing plates may be prepared separately but simultaneously or prepared to similar or identical standards to allow prediction of the performance of the printing plate  160  on the printing press. 
     The proofs prepared with the first printing plate  160  on proofing tool  100  may also be evaluated for the performance of sticky back adhesive which is applied between the printing plate  160  and cylinder  158  of proofing tool  100 . A skilled operator can observe the results on the proof and determine whether the sticky back adhesive is too thick, too thin, too hard or too soft, too stiff or too flexible. 
     Referring to  FIG. 11 , the method may also include designing the first printing plate  160  to include a first portion that has dot images including a range that may extend from 0 to 100% dot density. The method may include designing the printing plate  160  as depicted in an example pattern in  FIG. 11  to include some smaller portion of the range form 0 to 100% dot density. The invention further includes designing printing plate  160  to include a portion for testing print density. Determining print density is a way of measuring the thickness of an ink layer laid down on substrate by printing plate  160 . 
     Based on the evaluation of the sample proof prepared with printing plate  160  it may be desired to adjust the characteristics of printing plate  160 . An additional adjusted printing plate  160  may be prepared in which the adjusted printing plate  160  is adjusted relative to the first printing plate to alter dot density or print density or other characteristics. For example, the adjusted printing plate  160  may be adjusted to compensate for an undesirable dot gain by increasing or decreasing the dot density on the plate. 
     The present invention also includes a method of supplying a kit for predicting the performance of a printing press for a printing job. The method includes supplying or providing a proofing device including a proofing tool  100  to which a first printing plate  160  is securable and providing instructions to perform the method as outlined above. 
     Referring to  FIGS. 11 and 12 , an embodiment of the invention also includes a method of preparing a printing press for a press run including creating a printing plate  160  having a printing press portion  170  that is dimensioned to be secured to a printing press and a proofing portion  172  that is dimensioned to be secured to a proofing tool. The method may also include separating the printing press portion  170  from the proofing portion  172  and applying the proofing portion  172  to the proofing tool. An operator then prepares a proof with the proofing tool and the proofing portion  172  and then uses the proof to calibrate the printing press or the ink to be used with the printing press to predict the performance of the printing press with the portion of the plate that is intended for the printing press. Some embodiments the present invention also include modifying the thickness and/or hardness of printing plate  160  as well as the thickness and/or hardness and/or flexibility of the sticky back mounting adhesive used to mount the printing plate  160 . 
     In another embodiment of the invention the method is used to test the ink and compatibility of the ink with a particular photo polymer printing plate  160  and substrate. 
     In another embodiment of the invention the invention may be utilized to validate the ink photopolymer and sticky back combination for use on the printing plate to run a printing job which has previously been run. The present invention may also include a printing plate  160  for printing that includes a printing press portion  170  that is dimensioned to be secure to a printing press as well as a proofing portion  172  that is dimensioned to be secure to a proofing tool  100 . The printing press portion  170  and the proofing portion  172  are separable so that the printing press portion  170  can be secured to the printing press and the proofing portion  172  can be secured to the proofing tool  100 . 
     In another embodiment the invention includes a proofing tool  100  including an anilox roll  106  and cylinder  158  as well as a proofing printing plate  160  that is secured to cylinder  158  and which includes a portion of a printing plate  160  that includes a printing press portion  170  and a proofing portion  172  wherein the printing press portion  170  will be used to print materials that have been proofed with the proofing printing plate. 
       FIGS. 14-17  depict another example embodiment in accordance with the invention. Referring to  FIGS. 14-16  proofing tool  200  generally includes anilox support  202 , transfer support  204 , anilox roll  206 , transfer roll  208 , positive roll drive (not shown), photopolymer plate  210 , metering roll  201 , and doctor blade  205 . Anilox support  202  and transfer support  204  are similar but not identical structures. 
     Anilox support  202  generally includes yoke  212  and extended portion  214 . Yoke  212  supports anilox roll  206  between two arms  216 . Likewise, transfer support  204  includes yoke  222  and extended portion  224 . Anilox roll  206  and transfer roll  208  are supported between the arms of yoke  212  and yoke  222  respectively. In this example embodiment, anilox support  202  and transfer support  204  are connected only at distal end  225  of extended portions  220  and  224 . Otherwise, anilox support  202  and transfer support  204  are oriented substantially parallel with spacer  162  and a small gap between them. In other embodiments, anilox support  202  and transfer support  204  are connected at a location closer to anilox roll  206  and transfer roll  208 . Transfer support  204  is capable of some flexing movement from a disengaged position to an engaged position such that transfer roll  208  is held, for example slightly more separated from anilox roll  206  when no force is applied to transfer roll  208  than when transfer roll is in contact with a printing substrate. Transfer support  204  can also hold transfer roll  208  in contact with anilox roll  206 . 
     Positive roll drive  210  generally includes anilox gear  226  and transfer gear  228 . Anilox gear  226  and transfer gear  228  mesh together to synchronize the motion of anilox roll  206  and transfer roll  208 . In an example embodiment of the invention, there is a single set of anilox gear  226  and transfer gear  228 . Another example embodiment of the invention includes one anilox gear  226  and two transfer gears  228 . If one anilox gear  226  and two transfer gears  228  are present, one anilox gear  226  is located on one end of anilox roll  206  and two transfer gears  228  are located on each end of transfer roll  208  respectively. In another example embodiment, proofing tool  200  may utilize a semi positive drive in which anilox gear  226  engages a resilient surface of transfer roll  208  in a substantially non slip relationship. 
     Metering roll  201  is positioned adjacent anilox roll  206  and can be forced against anilox roll  206  under spring tension for example by threaded arrangement  203 . Threaded arrangement  203  may be tightened or loosened as desired to control the force with which metering roll  201  contacts anilox roll  206  to adjust metering pressure. Metering roll  201  can rotate against and in contact with anilox roll  206 , which forces ink into anilox roll  206  cells. A generally wedge shaped space between the metering roll  201  and anilox roll  206  forms a reservoir with adequate volume to contain sufficient ink for proofing an ink sample. Metering roll  201 , in an example embodiment, has a resilient surface such as rubber or another polymer. Metering roll  201  is located above anilox roll  206  in contrast to the prior art. 
     Proofing tool  200  also includes doctor blade  205 . In an example embodiment, doctor blade  205  is designed to have a leading edge that shears the excess ink from the anilox roll  206 . That is, doctor blade  205  is a leading edge doctor blade.  FIG. 17  illustrates the interaction between the anilox roll  206  and the leading edge doctor blade  205 , whereby the anilox roll  206  turns counterclockwise and the doctor blade  205  is positioned with its distal end against the surface of the anilox roll  206  to enable ink shearing. In some example embodiments, doctor blade  205  may also utilize a trailing edge configuration. 
     Proofing tool  200  also includes one or more micrometer thimbles  230 . Two micrometer thimbles  230  may be used to allow independent adjustment to achieve equal nip spacing across the width of anilox roll  206  and transfer roll  208 . In an example embodiment, micrometer thimbles  230  are positioned so that the measuring surfaces of spindles (not shown) contact transfer support  204  to determine a minimum nip spacing between anilox roll  206  and transfer roll  208 . In an example embodiment, gear teeth  131  of transfer gear  228 , as previously described, extend beyond transfer roll  208 , in part, so that if the proofing tool  200  is set down on a flat surface there will be a standoff created and transfer roll  208  will not touch the surface. 
     Anilox gear  226  and transfer gear  228  may be formed with fine pitch gear teeth to prevent gear chatter. In one aspect of the invention, gear teeth  131  mesh such that Anilox gear  226  and transfer gear  228  are separated by slightly more than a true pitch diameter to allow for adjustment of nip without the need to change gears. 
     Optionally, proofing tool  200  may include a separation device (not shown) which can be utilized to force anilox support  202  apart from transfer support  204  a slight distance to ensure separation between anilox roll  206  and transfer roll  208  when not in use. 
     Proofing tool  200  may be formed substantially from aluminum alloy or from other materials known to the art. 
     In operation, referring to  FIGS. 1 through 10 , proofing tool  100  is used to prepare ink proofs for flexographic printing processes. An operator sets a nip distance between anilox roll  106  and transfer roll  108  by adjusting micrometer thimbles  130 . After micrometer thimbles  130  are adjusted to a desired nip distance ink is applied between doctor blade  138  and anilox roll  106 . If present, felt dam  147  is saturated with ink. 
     If a proof is to be hand pulled, an operator grasps proofing tool  100  by extended portion  114  and extended portion  120  and orients proofing tool  100  so that anilox roll  106  is substantially vertically above transfer roll  108 . Transfer roll  108  is then brought into contact with a substrate and proofing tool  100  is drawn along the substrate. Ink is then transferred from anilox roll  106  to transfer roll  108  with the amount of ink being transferred being controlled by doctor blade  138  and the qualities of anilox roll  106 . Ink from transfer roll  108  is transferred to the substrate creating an ink proof. 
     If proofing tool  100  is used with an ink proofing machine (not shown) proofing tool  100  is prepared for proofing in a process similar to that described above. Proofing tool  100  is then attached to proofing machine (not shown) by connecting ball sockets  144  to ball ends  142 . 
     A substrate is inserted between transfer roll  108  or proofing tool  100  and a drive roll (not shown) of ink proofing machine (not shown). 
     If positive roll drive  110  is present, in one embodiment, transfer gear  128  may be engaged to a drive roll gear  152  so that as drive roll  168  rotates the drive roll gear  152  it meshes with transfer gear  128  and rotates transfer roll  106 . Transfer gear  128  engages with anilox gear  126  and rotates anilox roll  106 , thus preventing slippage between the drive roll (not shown), transfer roll  108 , and anilox roll  106 . 
     When proofing tool  100  is released from contact with the substrate, anilox roll  106  and transfer roll  108  may be separated by the resiliency of extended portion  120  and extended portion  124 . 
     In operation, referring to  FIGS. 14-17 , proofing tool  200  is used to prepare ink proofs for flexographic printing processes. An operator sets a nip distance between anilox roll  206  and transfer roll  208  covered by photopolymer plate  210  by adjusting micrometer thimbles  230 . An operator also sets metering tension by adjusting threaded arrangement  203 , which increases or reduces force, as desired, against metering roll  201 . After micrometer thimbles  230  and threaded arrangement  203  are adjusted, ink is applied at the juncture between metering roll  201  and anilox roll  206 . 
     If a proof is to be hand pulled, an operator grasps proofing tool  200  by extended portion  214  and extended portion  220  and orients proofing tool  200  so that anilox roll  206  is substantially vertically above transfer roll  208  and metering roll  201  is above anilox roll  206 . 
     Transfer roll  208  is then brought into contact with a substrate and proofing tool  200  is drawn along the substrate. Ink is pressed into cells of anilox roll  206  by metering roll  201 . Ink is then transferred from anilox roll  206  to transfer roll  208  with the amount of ink being transferred being controlled by doctor blade  205  which shears off excess ink from anilox roll  206  and the qualities of anilox roll  206 . Ink from transfer roll  208  is transferred from photopolymer plate  210  to the substrate creating an ink proof. 
     This operation is substantially different than that of a press. In proofing tool  200 , metering roll  201  is gravitationally above anilox roll  206  and ink is held in the nip between metering roll  201  and anilox roll  206  by the inherent viscosity and surface tension of the ink. In a press, the metering roll is gravitationally below the anilox roll, where the metering roll rotates in an ink bath and lifts ink upward to the anilox roll. It follows then, that doctor blade  205  in proofing tool  200  is functionally different as well. In proofing tool  200 , leading edge doctor blade  205  shears excess ink away from anilox roll  206  at a location above the center of rotation of anilox roll  206 . 
     Trailing edge doctor blades  154  act to both force ink into the anilox roll cells, and to remove excess ink. Because of its trailing edge positioning and dual role, over time, ink particulates can build up on the back of trailing edge doctor blade  154 . This results in a less efficient metering of ink and less accurate prediction of ink and plate performance on the press. It has been observed that when a sufficient quantity of ink particulate accumulate behind trailing edge doctor blade  154  the force with which trailing edge doctor blade  154  is against anilox roll  206  is overcome and an undesired excess quantity of ink is released. The excess quantity of ink is transferred to transfer roll  108  or photopolymer plate  210  and an area of increased color density is created on the substrate. 
     EXAMPLE 
       FIG. 18  illustrates the results of an experiment that tested several kinds of proofers, including those with both trailing and leading edge doctor blades, and measured the density of ink left on a substrate measured at twenty locations. The line depicted with a diamonds, labeled “Vignette Without IR,” is a proofer with a leading edge doctor blade and no metering or ink roll. The line depicted with a squares, labeled “Vignette With IR,” is the proofer identified herein as proofer  200 ; a proofer with a leading edge doctor blade and an ink roll as described herein. The line depicted with a triangle, labeled “DR-100,” is a conventional proofing tool implementing a trailing edge doctor blade. Even a casual glance at the chart evidences the fact that the leading edge doctor blade with ink roll, the embodiment described in proofer  200 , has fewer and less extreme peaks and valleys than either of the other proofers, thus demonstrating its improved consistency. 
       FIG. 19  is a table of the density measurements and standard deviation calculations for the three proofers described above, as well as the printing press “Dot Pattern Mark Andy Press,” an industry standard flexographic printing press. Specifically, the table shows the inputs into the standard deviation calculation; the twenty inking measurements tested and graphed in  FIG. 18 . In this case, standard deviation of ink density can be thought of as a reflection of inking consistency or ink density over the length of a proof drawdown on a substrate. The chart shows that an embodiment of proofer  200 , with a standard deviation of 0.013168943, is not only more consistent than conventional proofers (0.016026294 and 0.023502519 standard deviations, respectively), but also more consistent than an industry standard printing press (0.015652476 standard deviation). 
     The present invention may be embodied in other specific forms without departing from the spirit of any of the essential attributes thereof; therefore, the illustrated embodiments should be considered in all respects as illustrative and not restrictive, reference being made to the appended claims rather than to the foregoing description to indicate the scope of the invention.

Technology Category: 7