Abstract:
A printing unit is comprised of at least one counter-pressure cylinder and a transfer cylinder. A printing point is formed between the two cylinders when they are in contact. The counter-pressure cylinder is actuated by one drive motor independently of the transfer cylinder. In a print-on position, the counter-pressure cylinder is adjusted as a guide variable in relation to the power of the motor which drives the cylinder.

Description:
FIELD OF THE INVENTION 
     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. 
     BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     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.