Printing – Print plate feeding or delivering
Reexamination Certificate
2002-05-23
2003-12-02
Evanisko, Leslie J. (Department: 2854)
Printing
Print plate feeding or delivering
C101S415100
Reexamination Certificate
active
06655283
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for fastening a printing plate onto a plate cylinder of a rotary printing machine, in particular a web-fed rotary offset printing machine. The invention also relates to a device for fastening a printing plate to a plate cylinder of a rotary printing machine, in particular a web-fed rotary offset printing machine. In the heretofore known method and device of these general types, provision is made for the printing plate to have a first end and a second end, which are accomodated in a clamping gap formed in the circumferential surface of the plate cylinder, at least approximately parallel to the axis of rotation of the plate cylinder.
Before the printing plate can be fastened to the plate cylinder, both of the ends of the printing plate are initially bent over with the aid of an edge bending device located outside the printing machine. The bent-over first end is then inserted into the clamping gap and held firmly with the aid of a clamping device. The printing plate is then wound onto the circumferential surface of the plate cylinder until the bent-over second end is located over the clamping gap. Finally, this bent-over second end is likewise inserted into the clamping gap and held firmly with the aid of a second clamping device. Each clamping device includes at least one movable jaw which, in order to hold the bent-over end firmly, can be set against the latter and forces it against a side wall of the clamping gap. The clamping gap, therefore, has to be of sufficient width for accommodating the clamping devices. In addition, the clamping devices increase the construction expense and, therefore, the production and maintenance costs of the plate cylinder. In the case of rotary printing machines, however, it is desired that the clamping gap be as narrow as possible, because the part of the circumferential surface of the plate cylinder which is occupied by the clamping gap is not available for the printing. Primarily, for web-fed rotary printing machines wherein paper is infed in the form of a paper web unwound from a paper reel, the width of the clamping gap is a measure of the paper wastage.
A further disadvantage of the heretofore known method and device is that the edge-bending device has to be procured and operated separate from the actual printing machine. In addition, the printing plates provided with bent-over ends present problems when stored in a magazine for automatic printing-plate changing, because at least two printing plates have to be stored or handled simultaneously in such a magazine, so that damage may possibly occur quite easily to the sensitive printing surface of one printing plate by the bent-over ends of the other printing plate.
Furthermore, the bending over of the edges must be carried out very carefully, because the printing plates cannot be aligned correctly on the plate cylinder if the required angles and radii are not respected when the edges are bent over, and the edge-bending line does not extend perpendicularly to the longitudinal edges of the printing plate. Even a slight shape difference between printing plate and cylinder increases the risk that the printing plate will tear on the cylinder, as a result of which the entire printing machine can be damaged seriously.
The published European Patent Document EP 0 654 349 B2 discloses a sheet-fed rotary printing machine having an automatic plate changing device, wherein the printing plates are fed in flat form at least approximately tangentially to the plate changing device from a magazine and, with the aid of an edge turning or bending bar and a pressure roller, are provided with a bent-over edge on one side immediately before being inserted into the appertaining plate clamping device. In the described device, both the plate leading edge and the plate trailing edge are held in separate clamping devices, which can be operated separately and are spaced at a great circumferential distance from one another, the great spaced distance being usual for sheet-fed printing machines.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a method and a device of the type mentioned at the introduction hereto wherein the plate cylinder is constructed more simply, the clamping gap is narrower and a separate edge-turning or bending device is unnecessary.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a method for fastening a printing plate to a plate cylinder of a rotary printing machine, more particularly a web-fed rotary offset printing machine, the printing plate having a first end and a second end, both of which being accommodatable in a clamping gap formed in the circumferential surface of the plate cylinder at least approximately parallel to the axis of rotation of the plate cylinder, which comprises the following method steps: inserting the first end of the printing plate into the clamping gap; bending over an edge of the printing plate in the region of the first end at an edge of the clamping gap; winding the printing plate onto the circumferential surface of the plate cylinder until the second end of the printing plate comes to lie over the clamping gap; and pressing the second end of the printing plate into the clamping gap, and deforming the printing plate so that the second end blocks the first end of the printing plate in the clamping gap.
In accordance with another mode, the method includes, in order to bend over an edge, setting an edge-bending element against the plate cylinder in the region of the trailing edge of the clamping gap, as viewed in the continuous printing direction, and rotating the plate cylinder in the continuous printing direction relative to the edge-bending element.
In accordance with a further mode, the method includes providing a pressure roller as the edge-bending element.
In accordance with an added mode, the method further includes, in the winding step, setting a pressure element against the printing plate, and rotating the plate cylinder in the continuous printing direction relative to the pressure element.
In accordance with an additional mode, the method further includes providing a pressure roller as the pressure element.
In accordance with yet another mode, the method further includes providing the pressure roller as a single pressure roller serving as both the edge-bending element and a pressure element and, in the winding step, setting the pressure roller against the printing plate, and rotating the plate cylinder in the continuous printing direction relative to the pressure roller.
In accordance with yet a further mode, the method further includes setting a blade against the second end of the printing plate for inwardly pressing the printing plate, and pressing the second end of the printing plate into the clamping gap.
In accordance with yet an added mode, the method further includes providing for the trailing side wall of the clamping gap, as viewed in the continuous printing direction, to extend at an acute angle to the circumferential surface of the plate cylinder.
In accordance with yet an additional mode, the method further includes providing the clamping gap with a cross section having at least approximately the shape of a trapezoid, with the short base thereof forming the opening of the clamping gap.
In accordance with still another mode, the method further includes introducing compressed air into the clamping gap in order to loosen the printing plate from the plate cylinder.
In accordance with still a further mode, the method further includes assigning a blanket cylinder to the plate cylinder, the blanket cylinder bearing a rubber blanket sleeve which is pullable axially off the blanket cylinder.
In accordance with another aspect of the invention, there is provided a device for fastening a printing plate to a plate cylinder of a rotary printing machine, more particularly a web-fed rotary offset printing machine, the printing plate having a first end and a second end, both of which are acc
Deslangle Dominique
Noiret Christophe
Evanisko Leslie J.
Heidelberger Druckmaschinen AG
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