Printing – Work supporting members – Grippers
Reexamination Certificate
2001-01-26
2004-11-02
Nguyen, Anthony H. (Department: 2854)
Printing
Work supporting members
Grippers
C101S246000
Reexamination Certificate
active
06810806
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a printing machine, preferably for printing sheet-type material, which includes at least two printing unit groups having drives which are decoupled from one another and assigned, respectively, to one printing unit group, the printing unit groups having printing units with transfer cylinders and, for transferring the printed sheets, a dynamic control device and compensation elements for compensating for speed differences and positional errors between two printing unit groups. In addition, the invention relates to a method of transferring printed sheets in a printing machine of this type.
A printing machine with a great number of printing units is beset by a problem that the fundamental or inherent mechanical frequency thereof shifts to ever lower values the greater the number of printing units. This fundamental frequency is already excited at the printing speeds which are common nowadays, and contributes to an impairment or deterioration of the printed image.
Approaches for minimizing the influence of these fundamental or inherent frequencies are, for example, active or passive oscillation damping. With regard to active oscillation damping, the oscillations are damped by employing highly dynamic actuators for introducing additional energy for damping, while passive dampers, such as absorber systems, serve merely for absorbing the oscillation energy.
An alternative to these systems is offered by printing machines which are decoupled into two or more printing unit groups, each printing unit group containing its own drive. In this regard, during the transfer of a printed sheet from a preceding printing unit group to a succeeding printing unit group, differences in the speed and the position of the transported printing sheets have to be taken into account. These differences produce a transfer error leading to damage to the printed sheet or to faulty printing results.
In order to reduce this transfer error, the published German Patent Document DE 197 42 461 A1 discloses a device and a method for synchronizing printing unit groups. For this purpose, the device is provided with a transfer station having a separate drive. The separate drive is initially synchronized with the operating parameters of the preceding printing unit group, and the printed sheet is accepted by the transfer station. The drive of the transfer station is then synchronized with the succeeding printing unit group, and the printed sheet is passed on to the latter. A disadvantage of this device is that a transfer station is required for each printing unit group. In addition to a control system, a considerable amount of mechanical equipment is required for realizing this synchronization. In addition, torque fluctuations which are caused by the transfer devices, such as gripper systems, remain unconsidered.
A further possibility for reducing the transfer error is disclosed by the published German Patent Document DE 44 06 740 A1. A device is described therein which has displaceably arranged sheet holders. The sheet holders are movable in the peripheral direction and in the axial direction of the transfer cylinder of the preceding printing unit group. Before the transfer, the speed difference and the positional difference of the printed sheet are determined by computation. This is performed by sensors and a control device for processing the operating parameters. If a speed difference and a positional difference, respectively, are determined, the appropriate sheet holder is displaced by actuators in the conveying direction of the printed sheet and, transversely thereto, into the calculated or computed position and is transferred to the succeeding printing unit group. The actuators are accordingly controlled by the control device.
A disadvantage of this device is that a positional displacement caused by the transfer remains unconsidered by the positional correction. It is also disadvantageous that torque fluctuations caused by transfer equipment, and a speed change induced thereby, such as are produced by gripper systems and dynamic sheet holders, remain unconsidered by the positional correction.
The transfer performed by the devices and methods of the prior art is therefore inadequate and faulty, which results in a lower print quality, and damage to the sheet material.
SUMMARY OF THE INVENTION
Consequently, it is an object of the invention to provide a method and device for compensating for transfer errors in a printing machine which overcome the foregoing disadvantages and permit error-compensated transfer of the printed sheets, with regard to position and speed, between printing unit groups.
With the foregoing and other objects in view, there is provided, in accordance with one aspect of the invention, a printing machine, which includes at least two printing unit groups having drives which are decoupled from one another and assigned, respectively, to one printing unit group, and having printing units with transfer cylinders, comprising compensation elements for compensating for speed differences and positional errors between two printing unit groups, the compensation elements being assigned to a printing unit group which is an accepting printing unit group, in order to compensate for transfer errors.
In accordance with another aspect of the invention, there is provided a printing machine, which includes at least two printing unit groups having drives which are decoupled from one another and assigned, respectively, to one printing unit group, and having printing units with transfer cylinders, comprising compensation elements for compensating for speed differences and positional errors between two printing unit groups, the compensation elements being assigned to a first transfer cylinder of a printing unit group which is an accepting printing unit group, in order to compensate for transfer errors.
In accordance with a further aspect of the invention, there is provided a printing machine for printing sheet material, which includes at least two printing unit groups having drives which are decoupled from one another and assigned, respectively, to one printing unit group, and having printing units with transfer cylinders, comprising, for transferring the printed sheets, a dynamic control device and compensation elements for compensating for speed differences and positional errors between two printing unit groups, the compensation elements being assigned to a first transfer cylinder of a printing unit group which is an accepting printing unit group, in order to compensate for transfer errors.
In accordance with an added aspect of the invention, there is provided a printing machine for printing sheet-type material, which includes at least two printing unit groups having drives which are decoupled from one another and assigned, respectively, to one printing unit group, and having printing units with transfer cylinders, which comprise, for transferring the printed sheets, a dynamic control device and compensation elements for compensating for speed differences and positional errors between two printing unit groups, the compensation elements being assigned to a printing unit group which is an accepting printing unit group, in order to compensate for transfer errors.
In accordance with an additional feature of the invention, the dynamic control device is connected for communicating with the printing unit groups so as to record operating parameters, and is connected for communicating with the compensation elements so as to control the transfer.
In accordance with yet another feature of the invention, the printing machine includes sensors selected from the group consisting at least of charge-coupled switching elements, photosensors, electronic and electromagnetic sensors, and assigned to the printing unit groups, for recording operating parameters of the printing unit groups, and for passing the parameters on to data processing elements of the dynamic control device.
In accordance with yet a further feature of the invention, the printing machine is provided
Faulhammer Holger
Wagensommer Bernhard
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Locher Ralph E.
Nguyen Anthony H.
Stemer Werner H.
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