Printing – Processes – Transfer or offset
Reexamination Certificate
1998-10-23
2001-03-27
Asher, Kimberly (Department: 2854)
Printing
Processes
Transfer or offset
C101S177000, C101S217000, C101S182000, C101S184000, C101S185000, C101S218000
Reexamination Certificate
active
06205926
ABSTRACT:
FIELD OF THE INVENTION
The present invention is related to a printing unit in a lithographic web fed rotary printing press for performing on the run changes of the printing plates mounted to the plate cylinders of the unit. Moreover, the present invention is related to a method for deactivating the printing operation in a printing unit of a web fed rotary printing press.
BACKGROUND OF THE INVENTION
In web fed rotary printing presses, which are e.g. used for printing commercials or for printing newspapers, it is often desired to change one or more printing plates mounted to the plate cylinders of the press, without interrupting the printing operation. An exchange of the printing plates may for instance be desirable, if during a running newspaper production, the latest news have to be actualized and printed on the front page of the current editions or if different editions of the same newspaper are distributed in different areas under different names, so that the title of the newspaper has to be changed during the production run.
U.S. Pat. No. 5,063,844 describes a lithographic rotary printing press having a blanket-to-blanket printing unit, in which two plate cylinders can be alternatingly engaged and disengaged with one of the blanket cylinders, in order to carry out a flying plate exchange, while the printing press is in operation. During the flying plate exchange, both blanket cylinders of the printing unit are driven and are in rolling contact with the running paper web, while the plate cylinder which has been disengaged from the blanket cylinder is disconnected from the common drive motor, decelerated to a stop and re-accelerated after the printing plates have been changed.
German Patent DE 44 05 658 C2 describes a printing unit of a lithographic web fed rotary printing press for carrying out an on the run exchange of printing plates. The printing unit comprises two blanket cylinders and associated plate cylinders respectively, which are alternately engaged and disengaged with an impression cylinder over which the running web is passed. Each of the blanket cylinders is driven by its own separate motor and drives the associated plate cylinder via a gear train. The impression cylinder is driven by a further separate motor.
GB 2 309 668 discloses a blanket-to-blanket printing unit for carrying out a flying plate exchange in which the plate cylinders remain in rolling contact with the running web, while the blanket cylinders of the unit are alternately engaged and disengaged with their associated blanket cylinder. The blanket cylinders are constantly coupled to each other via meshing pinion gears and are driven by the main drive motor of the press via a line shaft. The blanket cylinders, however, are coupled to the pinion gears of the blanket cylinders via clutches and associated further pinion gears respectively. For exchanging the printing plates of one of the plate cylinders, while the press is in operation, the drive connection to the plate cylinder is interrupted by activating the respective clutch and the plate cylinder is decelerated by an auxiliary motor. After exchanging the printing plates, the auxiliary motor re-accelerates the plate cylinder up to press speed, before it is reengaged with its associated blanket cylinder. Hence, at least two auxiliary motors are required for performing a flying plate exchange. The document further describes the arrangement of two flying imprinter printing units on top of each other, wherein the engagement and disengagement of the plate cylinders and blanket cylinders is performed crosswise, in order to provide for a continuous printing operation.
OBJECT TO THE INVENTION
It is an object of the present invention to provide for a printing unit of a lithographic web fed rotary printing press, which is simple in design and which allows to carry out a flying exchange of the printing plates or maintenance work at the plate cylinders without employing auxiliary drive motors for decelerating and re-accelerating the plate cylinders.
According to a first object of the present invention, a method for deactivating the printing operation in a printing unit of a web fed rotary printing press, in which a blanket cylinder and an associated plate cylinder are driven by a first drive motor and the blanket cylinder is under impression with an associated impression cylinder which is driven by a second drive motor comprises the steps of interrupting the drive connection between the first drive motor and the blanket cylinder, so that the blanket cylinder is friction driven by the web and separating the plate cylinder from the blanket cylinder for carrying out an exchange of the printing plate or the printing plates on the plate cylinder. After separating or disengaging the plate cylinder from the blanket cylinder, the plate cylinder is decelerated by reducing the speed of the first drive motor, while the other drive motor for driving the impression cylinder is driven with web speed. The impression cylinder is preferably the second blanket cylinder in a blanket-to-blanket printing unit.
According to a further object of the present invention, a printing unit in a lithographic web fed rotary printing press comprises a plate cylinder and an associated blanket cylinder which are mechanically coupled via gears. A first drive motor drives the plate cylinder and the blanket cylinder. An impression cylinder is in rolling contact with the blanket cylinder and is driven by a second drive motor, via a clutch, which allows interrupting the drive connection between the first drive motor and the blanket cylinder, while the blanket cylinder is under impression with the impression cylinder. When the clutch is separated, the blanket cylinder is friction-driven with web speed by the running web and a throw-off mechanism for separating the plate cylinder from the blanket cylinder is operated while the blanket cylinder is in rolling contact with the impression cylinder.
According to a further object of the present invention, the blanket cylinder, the plate cylinder and an inker roller associated with the plate cylinder are mechanically coupled via a gear train. The gear train may include pinion gears and the clutch is preferably located between the pinion gear for driving the blanket cylinder and the blanket cylinder body.
According to a further embodiment of the present invention, the impression cylinder is a further blanket cylinder of a blanket-to-blanket printing unit.
According to yet another exemplary embodiment of the present invention, the second blanket cylinder and its associated plate cylinder form a print couple which is designed in the same way as the print couple formed by the first blanket cylinder and its associated first plate cylinder for carrying out a flying plate exchange.
According to a further embodiment of the present invention, two or more of the printing units for carrying out a flying plate exchange may be arranged on top of each other or side by side, whereby the exchange of the printing plates may be carried out crosswise, so that a continuous operation of the printing press is obtained.
According to another embodiment of the present invention, the printing blankets mounted to the blanket cylinders are sleeve-shaped endless printing blankets which can be axially moved onto the cantilevered blanket cylinder body e.g. by means of compressed air, when the press is stopped. This has the advantage, that even a slight migration of the friction driven blanket cylinder does not result in a dislocation of the cylinder-gap relative to the printed image, as it may occur in case of conventional printing blankets.
It is an advantage of the present invention that the power transmission path from the drive motors to the cylinders avoids unloaded components and minimizes undesirable torsional movements of the plate and blanket cylinders, because the inker unit which is in contact with the plate cylinder loads the plate cylinder and the plate cylinder in turn loads the blanket cylinder and the drive motor. As a result, even a certain amount of backlash between the
Asher Kimberly
Heidelberger Druckmaschinen AG
Kenyon & Kenyon
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