Methods and devices for operating a pressure unit

The present invention is directed to methods and devices for operating a printing unit. At least one counter-pressure cylinder and one transfer cylinder constitute a printing position. The cylinders are driven at controlled speeds.

In the course of driving cylinders or groups of cylinders by the use of separate drive mechanisms, for example in satellite printing units, process-related unwinding differences between the pairs of cylinders can occur. These unwinding differences are dependent on the cylinder contact pressure, on the number of active printing positions, on the thickness of the dressings carried by the cylinders, on the type of cylinders, or even on the producer, or source of the dressing itself, whether the friction gear is embodied without or with bearer rings, on the radii of the bearer rings, or on the radius ratios of the friction gear as a whole.

This unwinding difference can result, in part, in considerable and, with changing conditions, in considerably varying output effects between the cylinders, or groups of cylinders. This is undesirable, since it results in asymmetries in the output layout, in different outputs, depending on the conditions and modes of operation, or even in overloads of the motors and regulators.

Cylinders of a rotary printing press with bearing rings are known from DE 195 01 243 A1. The bearing rings of the satellite cylinder are rotatably seated for the purpose of reducing the output transfer.

In WO 00/41887 A1, a compensating friction gear, in the form of bearing rings of reversed radius ratios, is superimposed on a friction gear with cylinders which are in process-related frictional contact. The normal force between the cylinders placed against each other is set in such a way that a value of a difference between the power consumption of the motors driving the cylinders is minimal.

DE 195 27 199 A1 shows a drive mechanism for a printing unit. A forme cylinder can be driven at varying circumferential speeds as a function of a contact of the printing forme with a counter-pressure cylinder. A circumferential speed, which differs from that of the counter-pressure cylinder, occurs in a phase of the cylinder rotation in which there is no printing contact between the forme and the counter-pressure cylinder.

The object of the present invention is directed to providing methods and devices for operating a printing unit.

In accordance with the invention, these objects are attained by driving a printing unit, which includes at least one counter-pressure cylinder and one cooperating transfer cylinder, in a manner such that the speeds of the two cylinders may be different. The counter-pressure cylinder is driven by a drive motor. The speed of the counter-pressure cylinder may be varied as a function of the absorbed output or of the electrical output of that drive motor. A deviation between the speeds of the two cylinders may be sensed [means of the characteristics of claim 1 , 3 , 5 or 12 , and 13 , 14 or 22 ].

The advantages which can be obtained by the invention consist, in particular, in that a sufficiently good unwinding of the printing cylinders takes place, which unwinding is, to a large extent, a function of the contact pressure and/or of the number of the active printing positions, or of the thickness of the dressing and/or the type or the manufacturer of the dressing. With changing configurations of the printing positions and/or the dressings, and in particular with changing configurations of the printing blankets on the transfer cylinders, the print quality is not, or is only slightly, reduced.

In principle, it is possible to determine a suitable defined difference in the cylinder circumferential speeds at different modes of operation and/or for various dressings, which defined differences can be stored in a memory, for example, and, depending on the mode of operation/or dressing, can be forced on and maintained during production.

A minimization of the fluctuation range of the motive or of the generative output of the drive motor takes place in an advantageous manner by the regulation, in accordance with the present invention, of the leading or of the trailing of the rpm, or of the circumferential speed, of at least one of the cylinders with respect to at least one oppositely located cooperating second cylinder as a function of the output of the drive motor, either produced or received, via the friction gear.

The above mentioned regulation can be employed, in particular, in connection with printing units in which several transfer cylinders form printing positions with so-called satellite cylinders. For example, this regulation can be used in 5-cylinder printing units, in 9-cylinder satellite printing units, or in 10-cylinder satellite printing units.

The employment of the regulation is particularly advantageous for printing units with cylinders which roll off one another without the use of bearing rings. The satellite cylinder is operated in a leading or trailing manner, which manner of operation is a function of the power consumption, or of the output, of the drive motor assigned to it, with respect to the transfer cylinder cooperating with it. In the case of cylinders without bearing rings, the output is transferred exclusively by the cylinders themselves rolling off on each other. In case of a change of the configuration of a cylinder, in particular when changing the dressings on the transfer cylinders, for example dressings in the form of printing blankets with different conveying properties, which are so-called negatively, neutrally or positively conveying printing blanket, the required generative or motive output at the satellite cylinder is maintained within narrow limits by use of the regulation. In this way, an excess size of regulation and/or the danger of overloading regulating device and drive motors is reduced.

However, the regulation is also suitable for printing units with bearing rings which roll off on each other. In this case, a slippage between the bearing rings within defined limits, as discussed subsequently, is permitted.

In order to maintain a desired print quality, selectable lower or upper limits of the deviation of the number of revolutions, or of the circumferential speed of the satellite cylinder, from the circumferential speed of the cooperating transfer cylinders, are not downwardly or upwardly exceeded. This occurs simultaneously with the reduction of the generative or motive output at the satellite cylinder. The satellite cylinder is driven within these limits at its minimum absolute output, either generative or motive. These deviation limits can each be variously selected in connection with various materials to be imprinted, with various printing methods and with various demands made on quality. They range, for example for newspaper printing, at a deviation of ±0.01% to ±0.05% from the production, or circumferential speed of the cooperating cylinders.

This speed regulation is advantageous for printing units whose cylinders are driven in groups or which are driven individually by several mechanically unconnected drive motors. Such regulation is advantageous, for example, for 9-or 10-cylinder satellite printing units with one drive motor each per cylinder, for 9-or 10-cylinder satellite printing units with one drive motor for each forme cylinder-transfer cylinder pair and the satellite cylinder(s), and also for 9-or 10-cylinder satellite printing units with one drive motor each for each group of forme cylinder-transfer cylinder pairs.

Preferred embodiments of the present invention are represented in the drawings and will be described in greater detail in what follows.

Shown are in:

FIG. 1, a schematic representation of cooperating cylinders of a rotary printing press in accordance with the present invention, in

FIG. 2, a schematic representation of a 9-cylinder satellite printing unit, and in

FIG. 3, a schematic representation of a 10-cylinder satellite printing unit.

A rotary printing press, as depicted in FIG. 1, has a printing position 01 with two cylinders 03 , 04 , which, in a print-on position, work together through a web 02 , for example a web 02 of material to be imprinted, in particular a paper web 02 . In the printing press depicted in FIG. 1, the cylinders 03 , 04 are embodied without bearing rings and constitute a friction bearing because of their jacket surfaces which roll off on each other. The first cylinder 03 is embodied as a counter-pressure cylinder 03 , for example as a steel cylinder 03 , and during letterpress or flexographic printing counter-pressure cylinder 03 can be driven directly or indirectly by a first drive motor 06 . Counter-pressure cylinder 03 is driven independently of the second cylinder 04 , which is, for example, a transfer cylinder 04 , or a printing block cylinder 04 .

The second cylinder 04 , which is, for example, embodied as a transfer cylinder 04 , can also be driven directly or indirectly, for example via a gear, that is not specifically represented, for example through a gear wheel, a toothed belt or a friction gear, by a second drive motor 07 . The transfer cylinder 04 can be driven individually, or can be driven, together with a third cylinder 08 working together with it, for example a forme cylinder 08 , or an inking or dampening unit, which is not specifically represented. In the printing press shown in FIG. 1, the transfer cylinder 04 can be driven together with the forme cylinder 08 by use of the drive motor 07 , as is depicted schematically in FIG. 1 .

On its jacket, the second cylinder 04 has a dressing 09 , in the form of, for example, a printing blanket 09 , a rubber blanket 09 or a printing block 09 . Dressing 09 is the means by which the ink is applied to the paper web 02 .

In the embodiment of the present invention shown in FIG. 1, the counter-pressure cylinder 03 is embodied with a radius r 03 , and the transfer cylinder 04 with a radius r 04 , with both cylinders 03 , 04 being of a so-called double circumference, i.e. with each having a circumference corresponding to two vertical or to two horizontal printed pages, for example to two horizontal or vertical newspaper pages. In order to counteract a distortion or a displacement of the printed image, which may, for example, be caused by flexing of the dressing 09 , the radius r 03 of the counter-pressure cylinder 03 is designed to be larger by 0.2 to 1 per thousand than the radius r 04 of the transfer cylinder 04 .

However, cylinders 03 , 04 can be embodied as both with the same, single circumference or, for example, the transfer cylinder 04 can be configured with a single, and the counter-pressure cylinder 03 with double circumference. The width of each of the cylinders 03 , 04 , 08 can be single, double, triple or quadruple.

In customary methods, the drive of the cooperating cylinders 03 , 04 , 08 takes place in such a way that the circumferential speeds u 03 , u 04 of the cylinders 03 , 04 , 08 are almost identical. As a rule, when using several drive motors 07 , 06 , which are not mechanically coupled with each other, this speed control is accomplished by the use of an rpm regulation, and via an “electronic shaft”, i.e. by the use of electrical synchronization.

However, a strong mechanical coupling takes place between the cylinders 03 , 04 , 08 , in particular in connection with cylinders 03 , 04 without bearing rings, which strong mechanical coupling is greatly dependent on the type of the dressings 09 , the properties of these dressings 09 , and on the number of cylinders, such as transfer cylinders 04 which are placed against a counter-pressure cylinder 03 . For example, rubber blankets or dressings 09 of different types or from different producers show very different conveying properties when rolling off on the jacket of the counter-pressure cylinder 03 .

At the same circumferential speed u 04 , u 03 , or motor rpm n 07 , n 08 , so-called negatively conveying rubber blankets 09 on the transfer cylinder 04 have a tendency for braking the counter-pressure cylinder 03 , while so-called positively conveying rubber blankets 09 tend to accelerate the counter-pressure cylinder 03 in Rs direction of rotation. In the first case, the operation of the drive motor 08 for the counter-pressure cylinder 03 requires an increased motor output, and in the second case the drive motor 08 for the counter-pressure cylinder 03 requires an increased generating or braking output.

A regulation of the cylinders, or of the motors to identical circumferential speeds u 03 , u 04 , or to identical motor rpm n 06 , n 07 , or to a fixed relative angle of rotation position, does not solve the problem if these conditions change.

As schematically represented in FIG. 1, the circumferential speeds u 03 , u 04 of the cylinders 03 , 04 , or the rotational speeds or rpm n 06 , n 07 of their drive motors 06 , 07 , are picked up and are provided to a control device 11 . Detection of these speeds can take place through the use of separate angle encoders, of encoders internal to the motor, or in any other way. In addition, at least the output L 06 of the drive motor 06 at the counter-pressure cylinder 03 is picked up and is provided to the control device 11 .

The control device 11 can be embodied in various ways, so that, for example, each one of the drive motors 06 , 07 will have its own drive control 12 , 13 , which is assigned a desired value n 06 -soll, n 07 -soll for a circumferential speed u 03 , u 04 at the cylinders 03 , 04 , or motor rpm n 06 , n 07 corresponding to the cylinder 08 , through the control device 11 . However, the respective drive control for each motor can also be integrated into the control device 11 . The evaluation of the rpm n 06 , n 07 and the assignment of desired values n 06 -soll, n 07 -soll can take place by use of suitable software in a computer, in the control console, or in a module of an SPS by the provision of programming or hardware.

At the start of production of the rotary printing press depicted in FIG. 1, the drive motors 06 , 07 are regulated to desired values n 06 -soll, n 07 -soll of their rotational speeds or rpm by the use of feedback of the actual values of the rotational speeds or rpm n 06 , n 07 as the command variable. This regulation is accomplished in such a way that the circumferential speeds u 03 , u 04 of the cooperating cylinder 03 , 04 are almost identical.

With print-on, i.e. when the two cylinders 03 , 04 are in printing contact with each other, the circumferential speed u 03 of the counter-pressure cylinder 03 is varied in such a way that the size of the output L 06 of the drive motor 06 becomes less and, in the ideal case, assumes a minimum value. A change of the relative circumferential speeds u 03 , 04 , or changes in the relative angular position, are intentionally permitted. This is independent of the passage of a printed image through the nip location. Instead, it generally takes place during printing contact. Now the output L 06 is used as the command variable for regulating the circumferential speed u 03 , or the rpm n 06 . Based on the use of the output L 06 as the command variable, a changed desired value of the circumferential speed u 03 -soll, or of the rpm n 06 -soll, for example, can be established and assigned.

In principle, it is also possible to store suitable differences of the circumferential speeds u 03 , u 04 for various operational situations and/or for different dressings 09 , which are then maintained by the use of drive motors 06 , 07 , which are angle-or rpm-controlled.

The variation of the rotational speed or rpm n 06 of the first drive motor 06 takes place under the condition that the circumferential speed u 03 of the counter-pressure cylinder lies maximally below, or is trailing the circumferential speed u 04 of the cooperatively acting cylinder 04 , or of the production speed u p ,by a deviation Δ u 1 , for example Δ u 1 =−0.01% to −0.05%, or is above, or leading the circumferential speed u 04 of the cooperatively acting cylinder 04 , or the production speed up, by maximally Δ u 2 , for example Δ u 2 =+0.01 to +0.05%. For this reason, monitoring of the rpm n 06 , or the circumferential speed u 03 , is continued and compared with the rpm n 07 , or the circumferential speed u 04 of the second cylinder 04 . This is monitored to determine whether the relative deviation Δ u of the circumferential speed u 03 from the circumferential speed 04 still lies within the above mentioned interval.

The following applies regarding the regulation during production and/or in the print-on position:  L06  ( Δ     u )  ′ = Min local     for     all     { Δ     u | Δ     u1 ≤ Δ     u u04 ≤ Δ     u2 }

wherein Δ u=(u 03 -u 04 ).

Thus the regulation of the drive motor 06 to obtain identical, constant rpm n 06 or n 07 , or identical circumferential speeds u 03 and u 04 does not primarily take place. Regulation follows an rpm n 06 along a drop in the output L 06 as a function of the deviation Δ u between the resulting circumferential speed u 03 and the circumferential speed u 04 , or of the production speed u p (for 04 =u p ) of the cooperatively acting cylinder 04 .

A relative minimum for the generative or motive output L 06 can lie in the rpm range permitted for the variation, which corresponds to the interval Δ u 1 , Δ u 2 for the permissible relative deviation from the circumferential speeds u 03 , u 04 . But possibly there can also only be a monotone dropping or rising dependency in the permitted interval Δ u 1 , Δ u 2 between the output L 06 and the deviation from the circumferential speed u 03 , u 04 , so that the rpm n 06 , and therefore the circumferential speed u 06 in the respective operational state takes on the maximally permissible upward or downward deviation Δ u. In this way the generative, or motive output L 06 in the permitted interval is minimized for the deviation Δ u in this case, too. When the limit value Δ u 1 , Δ u 2 has been reached, regulation of the drive of the first cylinder 03 in this case takes place by use of the rpm n 06 , or of the circumferential speed u 03 as the command variable. The rpm n 06 is maintained at this limit value Δ u 1 , Δ u 2 as long as it is not possible to leave the limit value Δ u 1 , Δ u 2 in the permitted direction because of new conditions, for example in the dependency of the output L 06 .

If, for example, the transfer cylinder 04 has a dressing 09 which is negatively conveying, so that it “brakes” the counter-pressure cylinder 03 , the motive output L 06 at the drive motor 06 is increased after reaching the circumferential speed u 03 , u 04 , or of the production speed u p of the cylinders 03 , 04 , and the print-on position. Now the rpm n 06 , or the circumferential speed u 03 of the counter-pressure cylinder 03 is reduced until either a local minimum or the lower limit value Δ u 1 for the deviation Δ u from the circumferential speed u 04 of the second cylinder 04 , or of the production speed u p , has been reached. In this case, an increase of the rpm n 06 would lead to an increased absorption of motive output L 06 .

In the reverse situation , when using a positively conveying dressing 09 , the drive motor 06 is provided with an additional torque via the frictional gearing of the cylinders 03 , 04 following the placement of the cylinders into the print-on position, and in case of a regulation to identical constant circumferential speeds u 03 , u 04 , the drive motor 06 would need an increased generative output L 06 . Now the rpm n 06 , or the circumferential speed u 03 of the counter-pressure cylinder is increased until either a local minimum or the upper limit value Δ u 2 for the deviation Δ u from the circumferential speed u 04 of the second cylinder 04 , or of the production speed u p , has been reached. In this case a decrease of the rpm n 06 would lead to a further increased absorption of generative output L 06 .

Such a regulation in respect to the minimal motive, or generative output L 06 can be embodied so it is preset manually or, in an advantageous embodiment, is self-adaptive. The limit values Δ u 1 , Δ u 2 are a function of the printing press, the material to be imprinted, the demands made on the printing result and the configuration of the printing press, and can be preset in the form of programs which are fixedly stored in the control device 11 and which are possibly selectable, or via an input arrangement.

With newspaper printing on appropriate paper, the lower, or trailing limit value Δ u 1 , as well as the upper, or leading limit value Δ u 2 , lie advantageously at±0.01 to ±0.03%, and in particular are at ±0.02%, so that the following applies:  L06  ( Δ     u )  ′ = Min local     for     all     { Δ     u | Δ     u1 ≤ Δ     u u04 ≤ Δ     u2 }

wherein: Δ u=(u 03 -u 04 ).

In actual operations, the determination and regulation toward defined motor rotational speeds or rpm n 06 , n 07 , or cylinder circumferential speeds u 03 , u 04 , also takes place by determination of angular positions of the cylinders 03 , 04 , or of the drive motors 06 , 07 , and/or their chronological changes. In what was discussed before and what will be discussed, as follows, the determination and the regulation of the rpm n 06 , n 07 , or of the circumferential speeds u 03 , u 04 , should also be understood in the sense of determining the angular positions and a regulation in respect to the angular positions and/or their chronological changes or in their angular velocities.

A regulation in respect to identical circumferential speeds u 03 , u 04 of two cooperating cylinders 03 , 04 then corresponds, in the case of cylinders 03 , 04 of equal circumference, to the correspondingly identical changes in the angular positions of the cylinders 03 , 04 and/or possibly of the drive motors 06 , 07 . For different radii r 03 , r 04 of the cylinders 03 , 04 , it is necessary in the course of the regulation, to take into consideration the chronological changes of the angular positions, or of the angular positions themselves, in respect to the radius conditions.

For a regulation wherein a relative deviation Δ u from the circumferential speeds u 03 , u 04 of the cylinders 03 , 04 is permissible, or is intentionally caused, in this mode of operation the regulation to identical angular positions and/or to their chronological changes is suspended, at least for the drive mechanism of one of the cylinders 03 , 04 . The other cylinder 03 , 04 , however, can be synchronized with respect to other cylinders, to printing units and/or units of the printing press, i.e. regulated to identical circumferential speeds u 03 , u 04 , or to corresponding angular positions, to maintaining a defined relative angular position, and/or identical chronological changes in the angular positions.

A 9-cylinder satellite printing unit 14 with four possible printing positions 01 , in accordance with the present invention, is represented in FIG. 2. A paper web can be imprinted in a print-on position, it being understood that the printing positions 01 and the paper web 02 , as well as dressings 09 , are not specifically represented in FIGS. 2 and 3. In contrast to FIG. 1, four transfer cylinders 04 can be placed against a counter-pressure cylinder 03 , which is embodied as a satellite cylinder 03 . The transfer cylinders 04 and their cooperating forme cylinders 08 can each be driven in pairs by use of the respective drive motors 07 . In contrast to FIG. 1, no motor drive controls 12 , 13 have been represented as being situated between the drive motors 06 , 07 and the control device 11 .

Depending on the number of transfer cylinders 04 in contact with satellite cylinder 03 , on the type of the dressings 09 ; i.e. positively, negatively, neutrally conveying on each transfer cylinder 03 , and the conveying behavior of the paper type used in the paper web 02 , and with the satellite cylinder 03 set to a constant circumferential speed u 03 , or motor rotational speed or rpm n 06 , the generative or motive output L 06 at the drive motor 06 can again fluctuate considerably.

The drive motors 07 of the transfer cylinders 04 which are in the print-on position, are regulated to a motor rotational speed or an rpm n 07 -soll through the output supply by use of the actual value of the motor rotational speed or rpm n 07 as the command variable, which corresponds, for example, to the selected production speed up, or to the circumferential speed u 04 -soll of the transfer cylinders 04 .

The drive motor 06 of the satellite cylinder 03 is initially, and in particular prior to the print-on position, regulated to the same circumferential speed u 03 =u 04 , for example the production speed u p , by use of the preset desired value n 06 -soll.

After one or several transfer cylinders 04 are in the print-on position, the supply of the output L 06 is no longer regulated in respect to a rpm n 06 -soll corresponding to the circumferential speed u 04 , or to the circumferential speed u 03 -soll, but in a reverse manner the rpm n 06 , or the circumferential speed u 03 is regulated by use of the output L 06 as the command variable in respect to a minimal motive or generative output L 06 of the drive motor 06 . The desired value u 03 -soll at the satellite cylinder 03 is changed, for example, by a relative deviation Δ u. The marginal condition must again be met, that the deviation Δ u of the circumferential speed u 03 of the satellite cylinder 03 from the circumferential speed u 04 , or the production speed u p , is not permitted to downwardly or upwardly exceed a lower, or trailing limit value Δ u 1 and an upper, or leading limit value Δ u 2 , for example ±0.02% of the production speed u p .

If, as represented in FIG. 3, the two satellite cylinders 03 of a 10-cylinder satellite printing unit 16 are each driven by their own drive motors 06 , the regulation regarding the minimum of the output L 06 of each drive motor 06 can take place individually.

The regulation can also be used for larger printing units, or printing unit systems, for example for two stacked 9-cylinder satellite printing units 14 , or also for two stacked 10-cylinder satellite printing units 16 . With such arrangements, and with other similar arrangements the paper web 02 can be printed in four colors on both sides or, for example, in two colors on both sides with full imprinter functionality.

If the cooperating transfer and forme cylinders 04 , 08 are not driven in pairs, but each one is driven by its own drive motor 07 , the regulation of the drive motors 07 for the forme cylinders 08 and for the transfer cylinders 04 , in respect to their circumferential speeds u 04 -soll, u 08 -soll, or the regulation of the rpm n 07 -soll for the drive motor 07 , is performed in accordance with the above-described preferred embodiments for the drive motors 07 .

The regulation of a drive motor 06 , 07 of the cylinders 03 , 04 by the use of the output L 06 as the command variable is not limited to the counter-pressure or satellite cylinder 03 represented in the preferred embodiments. It is also possible, in the reverse way during production, to perform a regulation of the satellite cylinders 03 by use of the actual value of the rpm n 06 , or of the circumferential speed u 03 , as the command variable to a constant rpm n 06 -soll, or a constant circumferential speed u 03 -soll, while the cooperating transfer cylinder or cylinders 04 is or are regulated to a minimum output in the respective interval by the use of an output, which is not specifically represented, as the command variable.

In the case of individually driven cylinders 03 , 04 , 08 , the regulation of the drive motor 06 for each cylinder takes place in a way wherein the drive motor 06 substantially absorbs the same output L 06 as the drive motor 07 of the cylinder 04 , which, in this case, is individually driven. For this purpose, a deviation of the circumferential speed u 03 , u 04 within the stated limits is intentionally accepted.

A high generative output L 06 , in particular, is avoided by use of the described regulation, without the quality of the product lying outside a tolerable range. This applies to the use of differently conveying rubber blankets 09 .

While preferred embodiments of methods and devices for operating a printing unit in accordance with the present invention have been set forth fully and completely hereinabove, it will be apparent to one of skill in the art that various changes in, for example, the specific sizes of the cylinders, the types of drive motors used, the type of web being printed, and the like could be made without departing from the true spirit and scope of the present invention which is accordingly to be limited only by the following claims.