Device for replacing printing plates in rotary printing presses

The present invention relates to a device for replacing printing plates in rotary printing presses. The printing presses include plate cylinders with a gap for receiving both ends of a printing plate while the surface of the printing plate is wound around the plate cylinder. The device includes a ramp for receiving a printing plate on the plate cylinder after the plate has been released by the clamping mechanism of the plate cylinder, and a ramp for feeding a new printing plate to the plate cylinder. The invention is characterized by horizontally movable holding elements provided close to the outer cylindrical surface of the plate cylinder. The holding elements hold the front edge of a printing plate to be fed, until pivotable holding devices, grip the front edge of the printing plate to be fed to bring it in contact with the outer cylindrical surface of the plate cylinder.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a device for replacing printing plates in 
rotary printing presses having plate cylinders. The plate cylinders 
receive both ends of a printing plate in the cylinder gap while the 
surface of the printing plate is wound around the plate cylinder. The 
device has a facility for taking a printing plate from the plate cylinder 
after it has been released by the clamping devices of the plate cylinder 
and a facility for feeding a new printing plate to the plate cylinder. 
2. Description of the Related Art 
European Patent Application No. 0 433 798 discloses a method and a device 
for automatic feeding and/or removing of printing plates. This device is 
provided with a storage section for receiving a printing plate to be 
removed from a plate cylinder before a new printing plate is clamped on 
the plate cylinder. In close vicinity to the plate cylinder receiving the 
printing plates there are provided transport and pressure rollers in order 
to ensure exact feeding of the printing plate front edge. However, the 
newly supplied printing plate as well as the printing plate to be removed 
from the plate cylinder, for the greater part of their transport path, are 
moved over resting surfaces, so that scratching of the highly sensitive 
surfaces of the supplied and removed printing plates can still occur. 
European Patent Application No. 0 432 660 also discloses a method and 
device for automatic replacement of a printing plate. The device for 
implementing the method includes a number of transport rollers disposed 
between the storage sections for the printing plates. Between the 
transport rollers and the surface of the plate cylinder or the wide 
cylinder gap there are arranged a movable discharge finger and a guide 
plate. This construction has an elaborate, costly mechanism which also 
impairs access to the printing units of a rotary printing press. 
The European Patent Application No. 0 570 702 shows a device for supplying 
printing plates to the plate cylinder of printing presses, particularly 
sheet-fed offset presses. This device includes an angular sheet-metal 
plate which is operable by a pneumatic cylinder, whereby the plate profile 
is pressed against brushes. Through the space formed between the 
sheet-metal plate profile and the brushes, a new printing plate can be fed 
directly into the clamping bar of a plate cylinder. There is no mention 
made about the handling of a printing plate to be removed from the plate 
cylinder before a new printing plate is fed to the plate cylinder in that 
application. The teachings of this prior art document are concentrated on 
the simplification of the feed of the printing plate front edge. 
European Patent Application No. 0 431 715 a shows further plate-changing 
device for printing presses. This device relates to sheet-fed rotary 
printing presses and includes a storage section for a new printing plate 
to be fed as well as for the printing plate released form the plate 
cylinder. This device is defined by a cassette which holds multiple 
printing plates, the cassette being pivotally mounted between the 
serially-arranged printing units of a sheet-fed rotary press. In the 
cassette there are multiple L-shaped hooks with which the individual 
printing plates can be fastened in the cassette, so that considerable 
mechanical expenditure has to be made for the storage of printing plates 
in a pivotable cassette. 
SUMMARY OF THE INVENTION 
In view of prior an mentioned herein above, it is the object of present 
invention to provide for reliable, low-cost feeding and removal of 
printing plates to and from a plate cylinder. 
According to the present invention, it is the solution to this object that 
pivotable holding devices which temporarily hold a region of a printing 
plate to be fed will elastically deform this region in such a way that one 
end of the printing plate will be in contact with the outer cylindrical 
surface of the plate cylinder. 
The advantage of this inventive idea lies in the fact that the elasticity 
of thin printing plates is utilized to feed the respective printing plate 
from edge into the narrow gap in plate cylinders. Then, after the removal 
of the printing plate from the circumference of the plate cylinder, a 
reversal of the direction of rotation of the plate cylinder is performed, 
which is necessary for the feeding of the new printing plate, and the 
front edge of the new printing plate can dip into the plate cylinder gap. 
The force required for the printing plate front edge to dip into the plate 
cylinder gap is generated by the pivotable holding device which can be 
positioned so as to effect the contact of the printing plate from edge 
with the plate cylinder surface. The holding device allows a continuous 
feed of the printing plate while keeping it away from the from part of an 
infeed ramp, so that damage to the printing plate is avoided. The 
continuous pressure-loading of the holding device during the feeding 
movement of the new printing plate is ensured. 
According to other characteristic feature of the present invention, the 
holding devices are disposed on a support plane which is pivotable around 
a pivot axis, whereby the holding devices rest equally distributed on one 
region of the printing plate. The support plane is movable through 
controllable actuating units, for example, through actuating cylinders 
loaded with a pressure medium. The pivotable support plane on which the 
holding devices are arranged is situated above the infeed ramp. The 
holding devices, for example, are designed for application of vacuum, 
since vacuum can be easily and uniformly supplied, a there already exists 
a pneumatic system at the printing units. 
The device for feeding a printing plate as well as the device for receiving 
the printing plate to be removed are designed as ramps. The conveying 
planes for the printing plates on these inclined ramps are formed by the 
circumferential surface of rotatably mounted rotary bodies. It has been 
proven to be very advantageous that the printing plate to be fed can be 
brought onto the infeed ramp in an essentially upright position. 
According to a further characteristic feature of the present invention, 
horizontally movable holding devices are arranged below the infeed ramp, 
adjacent to the outer cylindrical surface of the plate cylinder. These 
movable holding elements temporarily hold the front edge of a printing 
plate to be fed, i.e., until a region of the printing plate to be fed is 
gripped by the holding devices which are disposed on a pivotable support 
plane. The horizontally movable holding devices are provided with 
actuating units which effect the horizontal movement. 
Furthermore, below the removal ramp there is provided a holding device 
which grips the printing plate to be removed and moves it to a final 
removal position. There, the printing plate can be very easily be removed 
by an operator. In order to secure this final removal position of the 
printing plates, there is provided at least one holding bracket below the 
removal ramp.

DETAILED DESCRIPTION OF THE INVENTION 
A plate cylinder 1 is associated with an infeed ramp 2 and with a removal 
ramp 3. The infeed ramp 2 as well as the removal ramp 3 are formed by a 
plurality of loosely rotatable rollers disposed in one plane, so that the 
printing plates A and B deposited thereon can be conveyed almost without 
friction. Above the infeed ramp 2 there is shown a pair of actuating 
cylinders 4, 5 which pivot holding device 9 around an axis 8. For the 
drive of these actuating cylinders 4, 5 there can be provided a driving 
mechanism of compact design which may be controlled electromagnetically, 
electrically, hydraulically or even pneumatically, in order to feed the 
printing plate into the cylinder gap 11 exactly at the moment when the 
cylinder gap 11 is positioned opposite the angled end of the printing 
plate front edge. Also, a support 7 is mounted so as to be pivotable 
around the axis 8. On the infeed ramp 2 there is placed a new printing 
plate B to be fed, having a front edge 28' and a rear edge 29', as shown 
in FIG. 1. Below the removal ramp 3 there is arranged an actuating 
cylinder 6 which moves a holding device 10 into various positions within 
the removal ramp 3. In the front region of the removal ramp 3 there is 
arranged a holding bracket 16 on which a printing plate A to be removed 
from the plate cylinder 1 can be deposited. 
The plate cylinder 1 shown in FIG. 1 carries a printing plate A to be 
exchanged, rear edge 29 of which is clamped in the plate cylinder gap 11. 
Furthermore, a pressure roll 17 as well as a transfer cylinder 40, 
arranged therebelow and not shown in detail, cooperate with the outer 
cylindrical surface of the plate cylinder 1. The plate cylinder 1 and the 
transfer cylinder 40 cooperating with one another form, for example, an 
upper printing unit in a rotary printing press, which is arranged above a 
material web to be processed. 
It is to be noted that schematically illustrated holding elements 82 and 
83, which are movable perpendicularly to the drawing plane as described 
below, limit the lower end of the infeed ramp 2. 
FIG. 2 shows a front view of the device of the present invention. The plate 
cylinder 1 and transfer cylinder 40 are rotatably mounted in the 
schematically shown side walls of a rotary printing press. Also, a 
pressure roller 17 is associated with the plate cylinder 1. 
A pair of actuating cylinders 4, 5, which are mounted in one of the side 
walls, pivot a support 7 around an axis 8, with holding devices 9 being 
disposed on the support 7. Furthermore, the holding elements 82 and 83 are 
mounted in the schematically illustrated side walls. The holding element 
82 has a lateral stop 81. As indicated in FIG. 2, the holding element 82 
and 83 are horizontally movable through respective adjustment units 80 and 
84. These adjustment units 80 and 84 can be electromagnetically operated 
units or pneumatic cylinders connectable to the pressurized air supply of 
the rotary printing press. When the holding elements 82, 83 are in their 
extended position, as indicated by a broken line, the front end of the end 
of the printing plate B to be clamped on the plate cylinder 1 rests on the 
plate cylinder 1 in correct lateral alignment through the stop 81. 
As also shown in FIG. 2, actuating cylinders 6 for actuation of the holding 
devices 10 are arranged below the removal ramp 3 and have rod-like 
extensions on which the holding devices 10 are arranged. As mentioned 
hereinbefore, the printing plate A to be removed can be completely removed 
from the printing unit by these holding devices 10 and be disposed on the 
holding bracket 16 forming the lower end of the removal ramp 3. The infeed 
ramp 2 is schematically indicated above the removal ramp 3. The support 7 
bearing the holding devices 9 is pivotable about the axis 8. The holding 
devices 9 are connected with one another through a central vacuum supply 
system ensuring simultaneous and uniform loading of said holding devices 9 
during the infeed of a new printing plate B. In printing presses having a 
plate cylinder which receives multiple printing plates side by side, 
multiple printing plate replacement devices according to the invention can 
be arranged side by side. 
FIG. 3 is an enlarged illustration of the holding device for the new 
printing plate B to be mounted. The holding elements 82, 83 are in the 
shape of angular pieces and can be moved by a cylinder adjustment unit 84. 
One holding element, in this case the holding element 82, has lateral stop 
81, in order to laterally align the printing plate B to be newly supplied 
correctly before its infeed into the printing unit. 
FIG. 4 shows how the printing plate A to be replaced moves from the plate 
cylinder 1 and enters the removal ramp 3. The rear edge 29 rests on roller 
17 in front of the holding bracket 16. Continuing rotation of the plate 
cylinder 1 in the direction of the arrow causes the printing plate A to 
move from the plate cylinder 1 and to proceed onto the rollers defining 
the removal ramp 3. The removal of the printing plate A from the outer 
circumference of the plate cylinder 1 is supported by the pressure roller 
17. The removal motion of the printing plate A to be replaced is performed 
exclusively by the rotation of the plate cylinder 1. There is no need for 
further support for transporting the printing plate A to be replaced. 
As also shown in FIG. 4, the new printing plate B on the infeed ramp 2 
rests on the holding elements 82 and 83. The pair of actuating cylinders 
4, 5 hold the holding devices 9 in a disengaged position. 
In FIG. 5 the printing plate A moving from the plate cylinder 1 is shown 
transported further onto the removal ramp 3 but is not gripped yet by the 
holding device 10 actuated through an actuating cylinder 6. As already 
explained with respect to FIG. 4, the printing plate A, with its printing 
surface, rests on a roller 16a while moving away from he plate cylinder 1, 
so as to be protected against scratches which could be caused by the 
holding bracket 16. 
The actuating mechanisms for the new printing plate B, which is located on 
the infeed ramp 2, are still at rest in FIG. 5. 
In the state shown in FIG. 6 the printing plate A to be removed has left 
the outer cylindrical surface of the plate cylinder 1. The front edge 28 
rests on the pressure roller 17. The printing plate A is further protected 
against scratching by the roller 16a arranged in front of the holding 
bracket 16. The rear edge 29 of the printing plate A to be removed has 
already left the rollers defining the removal ramp 3. In this position the 
printing side of the printing plate A to be removed is gripped by a 
pneumatic holding device 10, since the printing plate A is not transported 
any further against gravity on the removal ramp 3 through rotation of the 
plate cylinder, because there is no contact any more between the printing 
plate A and plate cylinder 1. 
As illustrated in FIG. 7, the printing plate A to be removed is moved on 
the removal ramp 3 by the holding device 10 which moves itself into a 
deflected position 10', until the front edge 28 of the printing plate A to 
be removed snaps into the holding bracket 16 and is supported thereon. In 
this position the printing plate A to be removed is secured against damage 
and against falling off, and the vacuum in the holding device 10 can be 
switched off and printing plate A may be removed by the operator. In this 
state, the devices moving the new printing plate B are still at rest. 
In the state shown in FIG. 8, the pneumatic holding devices 9, which are 
disposed on the support 7 pivoting around the axis 8, are brought in 
contact with the back side of the new printing plate B through the pair of 
actuating cylinders 4, 5. The pivotal motion of the support 7 with holding 
devices 9 around the axis 8 has the effect that the support 7 takes an 
upright position, thereby defining an infeed funnel. Next, the plate 
cylinder 1 is rotated at creeping speed (e.g., 1-2 revolutions per minute) 
in the direction of the arrow and opposite to the direction of rotation 
illustrated in all previous figures. The holding elements 82 and 83 are 
retracted by their adjustment units and release the front edge 2 of the 
new printing plate B. The printing plate B is solely held by the holding 
devices 9 on the support 7 pivoting around the axis 8. Through the suction 
produced by the holding devices 9 the front region of new printing plate B 
comes into contact with the outer cylindrical surface of the plate 
cylinder 1. As a result front edge 28' of the new printing plate B is 
clamped in the gap 11 of the plate cylinder 1 and the infeed of the new 
printing plate B has begun (see FIG. 9). As the holding devices 9 on the 
support 7 pivoting around the axis 8 are continuously supplied with a 
vacuum, the new printing plate B can be held in a position which 
facilitates this infeed movement. The respective region of the new 
printing plate B not yet positioned on the plate cylinder is held solely 
by the holding mechanisms for the actuating cylinders 4, 5 to move the 
holding devices 9, thereby permitting feeding the printing plate front 
edge 28 into the plate cylinder gap 11 at the moment when the cylinder gap 
11 is situated below the printing plate front edge 28'. 
In the state illustrated in FIG. 10 the feed of the new printing plate B 
onto the outer surface of the plate cylinder 1 is almost completed. The 
front edge 28' of the new printing plate B has been fed into the gap 11 
while the rear edge 29' of the printing plate B still is held by the 
holding devices 9 above the infeed ramp 2. An imperfect seal is created 
between the holding devices 9 and the new printing plate B, such that the 
lateral force on the printing plate B caused by wrapping the printing 
plate B around the plate cylinder 1 is greater than the lateral force on 
the printing plate B caused by the holding devices 9, while the vertical 
force on the printing plate B continues to hold the printing plate B 
against the holding devices 9. The imperfect seal is created by either 
having a rough contact surface on the holding devices 9, or a hole of 
small diameter in the holding devices 9. By switching off the vacuum at 
this time, the rear edge 29' of the new printing plate B is released, and 
with the support of the pressure roller 17 the new printing plate B is 
pressed onto the outer cylindrical surface of the plate cylinder 1, and 
after the pressure roller 17 has passed, the rear edge 29' of the printing 
plate B dips into the gap 11 of the plate cylinder 1.