Printing plate mounting system and method employing the same

A system for mounting a flexographic printing plate having a registration mark includes a printing plate support surface having a transparent portion formed therein, a plate cylinder, means operably connected to the plate cylinder for positioning the plate cylinder toward the printing plate support surface in a manner to establish a uniform contact line along one side of the printing plate when positioned on the printing plate support surface, a camera operably disposed adjacent another side of the transparent portion for taking a picture of the registration mark of the printing plate when the same is positioned over one side of the transparent portion and a monitor operably connected to the camera having means for viewing the registration mark and position thereof with respect to the camera in another embodiment which includes a pressure roller and method employing the same.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a printing plate mounting system and 
method for the same. More specifically, the invention relates to a 
printing plate mounting system using cameras and plate mounting aid and 
methods employing the same. 
2. Related Art 
There exist a number of techniques for mounting a flexographic printing 
plate onto a plate cylinder. Techniques commonly employ a method of 
aligning a pair of microdots formed on the plate with a central axis of 
the plate cylinder to place the plate in register, wherein the plate 
cylinder is placed into a printing system such that the plates are 
generally in register to a web's printing run direction. 
The industry trend has been to use a pair of cameras which are positioned 
in parallel over a printing plate mounting surface. Each camera is 
operatively connected to a split screen monitor to display the position of 
the microdots. The microdots, and in turn the printing plate, are manually 
manipulated on the printing plate mounting surface as well as the cameras 
to bring the microdots into a center of the screen to indicate a 
registering of the plate on the surface. Then, a sticky-back cylinder is 
brought in contact with the printing plate, lifted and hand rolled onto 
the cylinder. 
These techniques require a relatively high degree of human intervention in 
judgment of alignment and positioning. Additionally with such systems, the 
mounter's hands and/or the sticky-back cylinder is necessarily interposed 
between the cameras and microdots and consequently interfere with viewing 
the microdots. Accordingly, this increases possible errors in alignment of 
printing plates which can occur in displacing the microdots slight amounts 
each time a centering of the microdots is accomplished. These errors are 
considerably noticed in printing multicolor jobs wherein respective color 
printing plates are positioned on respective plate rollers so that when 
the web passes from one roller to the next, each color will be accordingly 
applied and misalignments result in miscoloring of the end product. 
Likewise, these errors are noticeable in some black and white 
applications. 
There is a need to improve printing plate mounting systems. There is also a 
need to increase the accuracy in which the alignment of printing plates is 
accomplished and accordingly reduce the errors which are introduced during 
the registering process. 
BRIEF SUMMARY OF THE INVENTION 
An object is to improve printing plate mounting systems. 
Another object is to improve the system and method for mounting 
flexographic printing plates. 
Accordingly, the present invention is directed to a system for mounting a 
flexographic printing plate having a registration mark, including a 
printing plate support surface having a transparent portion formed 
therein, a plate cylinder, means operably connected to the cylinder for 
positioning the cylinder toward the printing plate support surface in a 
manner to establish a uniform contact line along one side of the printing 
plate when positioned with its registration marks over transparent 
portion, a camera operably disposed adjacent another side of the 
transparent portion for taking a picture of the registration mark of the 
printing plate and a monitor operably connected to the camera having means 
for viewing the registration mark and position thereof with respect to the 
camera. 
A method for mounting a flexographic printing plate which has a 
registration mark thereon includes the steps of orienting the printing 
plate onto a printing plate support surface having a transparent portion 
in the surface thereof such that the registration mark is positioned over 
one side of the transparent portion, orienting camera means adjacent 
another side of the transparent portion for viewing the registration mark 
when positioned over the transparent portion, manipulating at least one of 
the printing plate and the camera means such that the registration mark is 
substantially centered within the view afforded the camera means, 
contacting a plate cylinder to a first surface of the printing plate along 
a uniform contact line, and adheringly applying to the printing plate to 
said cylinder. The method may further include contacting a rotatable 
pressure roller to a second surface of the printing plate along the 
contact line such that the printing plate is frictionally disposed between 
the plate cylinder and the pressure roller to aid in applying the printing 
plate to the plate cylinder. 
Another aspect of the invention includes in a printing plate mounting 
system for a flexographic printing plate, a plate cylinder, a printing 
plate support surface, means operably connected to the cylinder for 
positioning the cylinder toward the printing plate support surface in a 
manner to establish a uniform contact line on one side of the printing 
plate when positioned on the printing plate support surface, a pressure 
roller and means operably connected to the pressure roller for positioning 
the pressure roller toward the plate cylinder in a manner to dispose the 
pressure roller on another side of the printing plate along the contact 
uniform line such that the printing plate is frictionally disposed between 
the plate cylinder and the pressure roller. 
Another method for mounting a flexographic printing plate comprises the 
steps of orienting the printing plate onto a printing plate support 
surface, contacting a rotatable plate cylinder to a first surface of the 
printing plate along a uniform contact line, moving the plate cylinder 
away from the printing plate support surface with the printing plate fixed 
in relative position thereto along the contact line, contacting a 
rotatable pressure roller to a second surface of the printing plate along 
the contact line such that the printing plate is frictionally disposed 
between the plate cylinder and pressure roller, and rotating one of the 
plate cylinder and pressure roller in an adheringly manner to cause the 
printing plate to generally uniformly adhere to the plate cylinder. 
Other objects and advantages will be more apparent from reading the 
following drawings and description hereto.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, a printing plate mounting system is 
generally referred to by the numeral 10. The mounting device 10 shown in 
FIGS. 1-14, includes legs 12, a printing plate support surface 14 
connected to the legs 12, a pair of arms 16 removably hingedly connected 
at one end 18 to an extension 20 of the printing plate support surface 14. 
Rotatably removably connected at the other end 22 of the arms 16 is a 
plate cylinder 24 onto which a flexographic printing plate 26 (as seen in 
FIG. 3, for example) having a microdot thereon is to be mounted. Commonly, 
the plate cylinder 24 will include a sticky back 28 for affixing the 
printing plate 26 to the plate cylinder, but other means of accomplishing 
this will be apparent to those skilled in the art. 
One end 30 of the printing plate support surface 14 includes a transparent 
plate 32 which is disposed in a manner such that as the cylinder 24 is 
positioned adjacent the printing plate support surface 14, a central axis 
of the plate cylinder 24 will extend generally along a central axis 33 of 
the transparent plate 32. The central axis 33 is preferably marked in a 
visible manner on the transparent plant 32 to aid in the registration of 
the printing plate 26 as later discussed herein. The transparent plate 32 
is seated between recessed surfaces 34 and 36 of the printing plate 
support surface 14. 
As shown in FIG. 2, the printing plate support surface may include a grid 
which is useful in registering the printing plate. The grid may be either 
integrally formed onto the printing plate support surface 14 or as an 
overlay to be laid over the printing plate support surface. 
Extending beneath and movably connected to the printing plate support 
surface 14 adjacent the transparent plate 32 is a track 40. Reciprocally 
slidably lockably connected to the track 40 and actuatably positionable 
are cameras 42 which have their lens 44 predisposed to focus on the 
central axis 33 of the transparent plate 32 as each moves back and forth 
along the track 40. The cameras 42 are operably connected to a split 
screen monitor 46 which is, in this case, disposed on the extension 20 for 
ease of viewing while working, but may be disposed at any desired 
location. The track 40, cameras 42 and monitor screen 46 are of the type 
known to the art. The cameras 42 and monitor screen 46 are, for example, 
equipped to show 30.times. magnification and have a centering circle to 
show viewed, i.e., a registration mark or microdot. 
A pair of arms 48 are pivotally mounted at one end 50 to the end 30. At the 
arms 48 other end 52 is a rotatably mounted pressure roller 54. 
The plate 26 may be formed form, for example, a photopolymer of the type 
from: Dupont Cyrel, B.A.S.F./NAPP Nylo-flex, Hercules pourable polymers, 
W. R. Grace Flexlite or Supratech Flexceed; or a rubber of the type from: 
Uniroyal, Good-Year, B. F. Goodrich, Mosstype or Graphic-Arts Rubber. Such 
materials can typically be obtained in sizes up to 60".times.120". 
The flexographic printing plate 26 is produced in a conventional manner 
known to the art and as described in Flexography--Principles and 
Practices--Published by Flexographic Technical Association--Library of 
Congress Catalog Card No. 80-69506, Chapter VI, Engraving and Printing 
Pates, pages 149-183, incorporated herein by reference. For the materials 
listed above, the photopolymer is exposed to an ultraviolet light on one 
side for a predetermined period to harden and cure the photopolymer to a 
predetermined depth of a relief to be formed on the other side for the 
etching process. The other side of the plate is then covered with a 
photographic negative and exposed to the ultraviolet right to harden the 
printing surface through to the pre-hardened depth. The photographic 
negative is removed from the printing plate and the printing plate is 
washed with a polymer solvent to remove the unhardened material thus 
providing a printing surface 56, as seen best in FIGS. 15 and 16. The 
plate 26 may be more fully hardened if desired. 
In recent years, the photographic negative has been generated using the aid 
of a computer. This has enabled the formation highly accurate graphic 
artwork. Particularly, the artwork can be easily positioned at any desired 
x and y coordinates. This positioning ability precipitated the invention 
of microdots 58, as shown in FIGS. 15 and 16, for example, a pair of small 
dots formed in the plate 26, which have been widely used in the industry 
as a registering aid, i.e., a registration mark is created useful in 
orienting the plate. The microdots are uniformly formed along an x and/or 
y coordinate (via creating a small transparent circle in the photographic 
negative adjacent the art design) in the plate 26 and have been used 
principally in the registering process by attempting to align these 
microdots with a common x/y coordinate of another surface (e.g., the 
printing plate support surface) to permit the plate 26 to be mounted in 
register to the plate cylinder 24. Other registering configurations are 
contemplated in the present invention and are accordingly to be included 
within the scope of the present invention. 
In operation, the plate 26 is placed face down on the printing plate 
support surface 14 for mounting, as seen in FIG. 4. The microdots 58 are 
first positioned along the central axis 33 of the transparent plate 32 as 
seen in FIGS. 4 and 6. The cameras 42 are actuated along the track 40 to 
locate the microdots 58 substantially in the centering circles of the 
screen 46 and are then locked in position as depicted in FIGS. 3 and 5. 
It is not uncommon that the plate cylinder 24 will vary up to several 
thousandths of an inch in diameter from one end to the other. 
Consequently, the printing plate 26 will have to be slightly canted to 
adjust for the variation in diameter size. This can be achieved by 
orienting the registration marks on opposite sides of the central axis 33, 
for example, and then adjusting the track 40 and cameras 42 to center the 
marks prior to fixing the cameras 42 for subsequent registration of other 
plates. 
The arms 16 are actuated to a point wherein the sticky back 28 of the plate 
cylinder 24 is brought into contact with a back surface 60 of the plate 16 
along a uniform line. The arms 16 are then actuated in opposite direction 
such that the plate cylinder 24 is sufficiently disposed away from the 
printing plate support surface 14 with the printing plate 10 adhered 
thereto to permit the plate 26 to be rolled into position on the plate 
cylinder 24, as seen in FIG. 8. To aid in this regard, the arms 48 are 
actuated toward the plate cylinder 24 to a point such that the pressure 
roller 54 is positioned against a front surface 62 as seen in FIGS. 9-11. 
The plate 26 is then rolled onto the sticky back plate cylinder 24 in a 
uniform manner by virtue of the frictional nip between the plate cylinder 
24 and pressure roller 54 when one of the plate cylinder 24 and the 
pressure roller 54 is rotated. The arms 48 are then actuated in an 
opposite direction to remove the pressure roller 54 away from the plate 
cylinder 24 as seen in FIG. 12. The plate cylinder 24 with the printing 
plate 26 thereon can then be removed from the arms 16 for use in a desired 
application. 
Alternatively, as seen in FIGS. 13-14, the mounting device 10 is employable 
for use in mounting varying size plate cylinders. The mounting device 10 
in this embodiment differs in that it includes support members 64 fixedly 
connected in a predetermined alignment relationship to the support surface 
14, bored surfaces 66, threaded shafts 68 and means 70 for reciprocating 
the threaded shafts 68. One of the shafts 68 extends through one of the 
bore surfaces 66 and has fixed to one end a bearing member 72 connected 
thereto which slidably fits between the support members 64. A plate 
cylinder 24 having a shaft 74 is disposed between the support members 64a 
and 64b such that the shaft 64 bears upon the bearing member 72. The shaft 
74 is preferably of a diameter slightly less than the distance between 
support members 64a and 64b to keep the plate cylinder 24 in a 
predetermined alignment with respect to the transparent plate 32. 
The reciprocating means 70 includes a crank 76 and operably connected arms 
78 and threaded wheels 80. The wheels 80 are operably connected to the 
threaded shafts 68 such that when the crank 76 is turned, the wheels 80 
rotate to cause the shafts 68 to uniformly move between the support 
members 64 thus moving the plate cylinder 24 toward or away from the 
printing plate support surface 14 depending upon the direction the crank 
76 is turned. It is recognized that other mechanisms may be employed to 
accomplish this result, such as a hydraulic mechanism. 
The mounting process for this embodiment is essentially the same as 
previously described, wherein a difference exists in how the plate 
cylinder 24 is brought into contact with the printing plate 26. It is 
believed this embodiment provides an additional feature of being able to 
easily mount in register plates of varying sizes onto complimentary sized 
plate cylinders by virtue the shaft 74 remaining uniformly positioned and 
centered over the central axis 33 regardless of the plate cylinder 24 
size. 
As previously discussed, some of the plate materials described above are 
limited in their size in which they can be formed. In other cases, it is 
desirous to prepare different strips of printed art work which can be 
ganged together for a run. In either case, the invention works in 
principle the same way. 
By so providing the present invention, there has been created a novel and 
improved printing plate mounting system which substantially reduces human 
error in aligning and registering the flexographic printing plates onto a 
plate cylinder. The present invention has also substantially reduced the 
ease in which the flexographic printing plate mounting process is 
accomplished. 
There will be many modifications and variations to the present invention 
which will be readily apparent to those skilled in the art and the 
embodiments set forth above are put forth by way of example for flexible 
printing plate mounting systems but will have application to other 
techniques, such as letter press, for example. Accordingly, such 
modifications and variations should be within the scope of the claims 
appended hereto.