Sheet feeding or delivering – Feeding – With means to align sheet
Reexamination Certificate
1999-02-04
2001-06-05
Jillions, John M. (Department: 3653)
Sheet feeding or delivering
Feeding
With means to align sheet
C271S277000, C101S409000
Reexamination Certificate
active
06241241
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and a device for eliminating rhythmic register errors in sheet-fed rotary printing machines.
In sheet-fed rotary printing machines with a transport drum of double the conventional printing-unit cylinder size, in particular an impression cylinder of double size, and, as a consequence thereof, having two gripper arrangements, the problem arises that an error in the unwinding of successive sheets in relation to the rubber blanket cylinder, and a consequent print offset occur due to manufacturing or assembly tolerances in the components of the impression cylinder. Two successive sheets, which are therefore transported alternately by different gripper arrangements, consequently have a circumferential offset in relation to one another. The result of this is that the sheets receive their print at a slightly offset location in a two-by-two rhythm. During a single run of a sheet through the printing machine, this small offset influences only the length of the print-free sheet edge, which is virtually of no significance.
A problem arises only when a print order is to have a second print run, for example when a four-color print is to be produced by a two-color machine.
In this case, then, in order to avoid the offset between the print image of the first run and that of the second run, it will be necessary for the impression cylinder gripper arrangement which grasped the sheet during the first print run also to transport the same sheet during the second print run.
It has been possible heretofore to satisfy this requirement only by executing a specimen proof print at the start of the second print run. The print result indicated whether the sequence of the sheets supplied was correct. If this was not so, it was possible for the pressman to correct the sequence by removing a sheet from the sheet pile or feed table. Moreover, after damaged sheets had been removed, this operation possibly had to be repeated during the processing of the order (for example, by stopping at the feeder due to multiple and oblique sheets, respectively, or overshooting), because the correct relationship was lost again due to the random withdrawal or extraction of an odd number of sheets. These measures, however, require a considerable amount of time, and an appreciable quantity of spoilage occurs.
The published German Patent Document DE 196 18 029 A1 can solve the problem described above by gripper arrangements on a sheet transfer cylinder, the gripper arrangements having adjustable closing times.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a device for eliminating rhythmic register errors in sheet-fed rotary printing machines which ensure that sheets, having been once printed, can be printed in-register, irrespective of the sequence thereof, during a second print run through a sheet-fed rotary printing machine.
With the foregoing and other objects in view, there is provided in accordance with one aspect of the invention, a method for eliminating rhythmic register errors in sheet-fed rotary printing machines, the sheets therein being transported by an impression cylinder of double size having two gripper arrangements, which comprises bringing front lays, which have been provided for orienting the sheets at a feed table, out of an end position outside a conveying plane of the sheets and into a first orientation position on the feed table, then bringing the front lays back into the end position, and thereafter bringing the front lays into a second orientation position on the feed table.
In accordance with another mode, the method of the invention includes pivoting the front lays.
In accordance with a further mode, the method of the invention includes transferring the sheets by a pregripper from the feed table to a gripper arrangement of a single-size supply drum.
In accordance with an added mode, the method of the invention includes setting the first orientation position in relation to a first gripper arrangement of the impression cylinder, and the second orientation position in relation to a second is gripper arrangement of the impression cylinder.
In accordance with another aspect of the invention, there is provided a device for eliminating rhythmic register errors in sheet-fed rotary printing machines, wherein sheets are transportable by an impression cylinder of double size having two gripper arrangements, comprising a cyclically driven front lay shaft having a front lay lever, the front lay lever having a stop face that is bringable into contact with a cyclically pivotable stop.
In accordance with a further feature of the invention, the stop face is bringable alternately into contact with a fixed stop and with the cyclically pivotable stop.
In accordance with an added feature of the invention, the front lay shaft is drivable in a single revolution, and the cyclically pivotable stop is drivable in a half revolution.
In accordance with an additional feature of the invention, the single-revolution drive is a first control cam, and the half-revolution drive is a second control cam.
In accordance with yet another feature of the invention, the first orientation position is settable independently of the second orientation position.
In accordance with yet a further feature of the invention, the front lay shaft is mounted in an adjustable lever, and a setting device is included for adjusting the front lay shaft in and opposite to a sheet transport direction.
In accordance with a concomitant feature of the invention, the pivotable stop has an adjustable eccentric, the eccentric being in rolling contact, via a roller lever and a control roller, with a control disk.
In the method according to the invention, it is advantageous that, in particular, the printed sheet to be transported is exactly oriented, as early as at the feed table, in relation to the gripper arrangement which subsequently transports it and which is located on the impression cylinder.
Because to each gripper arrangement on the double-size impression cylinder there is assigned a position of the front lays on the feed table, the pressman does not have to pay attention to the sequence of the printed sheets during the second print run. This avoids spoilage and affords time saving. The quality of the printed product is increased.
The device for performing the method according to the invention advantageously has, in addition to the front lay shaft driven in a single revolution, a control cam driven in a half revolution, for pivoting a stop into two end positions.
The front lay, which is pivotable back and forth, is thereby brought alternately into two different orientation positions on the feed table. Because the end positions can be set independently of one another, each front lay orientation position can be set exactly in relation to the corresponding gripper arrangement on the double-size impression cylinder.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a method and device for eliminating rhythmic register errors in sheet-fed rotary printing machines, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein:
REFERENCES:
patent: 4402266 (1983-09-01), Sugiyama
patent: 4825762 (1989-05-01), Fischer
patent: 5080347 (1992-01-01), Funada
patent: 5125336 (1992-06-01), Germann
patent: 5496023 (1996-03-01), Becker et al.
patent: 5749572 (1998-05-01), Fricke et al.
patent: 5761998 (1998-06-01), Fricke et al.
patent: 5862757 (1999-01-01), Hauck
Fricke Andreas
Hofstetter Rudi
Luxem Heiner
Greenberg Laurence A.
Heidelberger Druckmaschinen AG
Jillions John M.
Lerner Herbert L.
Stemer Werner H.
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