Abstract:
In a conventional sheet-fed printing machine having a central drive, the dynamic positional deviation with respect to a setpoint value continually increases from printing unit to printing unit due to the elasticity (a vibratory multi-mass system). Thus, the precision is dependent on the number of printing units. A mechanical interconnection of the individual cylinders of the sheet-fed printing machine is partially removed and replaced by individual drives is, therefore, provided. In the multiple motor open-loop drive control described, the fault does not increase because in each printing unit, the torque is supplied separately, and all drives are closed-loop controlled using the same reference variable.

Description:
FIELD OF THE INVENTION 
     The present invention relates to an open-loop drive control for sheet-fed printing machines having a multiplicity of printing units (printing mechanisms). Each printing unit includes cylinders that are mechanically coupled to each other. In particular, a feeder, transfer rollers, printing cylinders and rubber cylinders are coupled to each other as a sheet-travel module. The printing units further include plate cylinders, inking systems, and a delivery assembly, and are driven by an electrical drive. 
     BACKGROUND INFORMATION 
     Sheet-fed printing machines generally include a plurality of printing units, which are mechanically coupled to each other in a roller system. In this context, each printing unit has associated to it an inking system, which acts upon a plate cylinder. Every plate cylinder is mechanically coupled to a rubber cylinder and, via the latter, to a printing cylinder. The printing cylinders of individual printing units are in mechanical contact with each other via so-called transfer rollers. The first printing cylinder for its part is mechanically coupled to a feeder, the last printing cylinder to a delivery assembly. In one conventional sheet-fed printing machine, each printing unit is mechanically coupled to the aforementioned specific cylinders as a so-called sheet-travel module. 
     In one conventional sheet-fed printing machine, all the cylinders—in the form of rollers—that participate in the paper guidance and in the printing are mechanically coupled via a traversing wheel train or a vertical shaft. FIG. 1 shows the design of a sheet-fed printing machine of this type having four printing units  1  through  4 . The system is depicted in a cross-section of individual cylinders. Four printing units  1  through  4  are illustrated, having, respectively, inking system F 1  through F 4 , plate cylinder P 1  through P 4 , rubber cylinder G 1  through G 4 , and printing cylinders D 1  through D 4 , which are connected via transfer rollers T 2  through T 4 . In addition, a feeder AN and a delivery assembly AB are shown. 
     Conventionally, a mechanical interconnection of this type of sheet-fed printing machine is moved by a central electrical drive. However, the cylinders that are coupled in this manner represent a vibratory multiple-mass system. Thus, vibrations can affect the printing precision negatively. As a result, the number of printing towers or printing units that can be included in the mechanical interconnection is limited. 
     In a conventional sheet-fed printing machine having the mechanical interconnection described involving a central drive, the dynamic positional deviation with respect to a setpoint value continually increases from printing unit to printing unit due to the elasticity of the multiple-mass system. Thus, precision is dependent on the number of printing units. In the case of a prescribed mandatory level of precision, it follows that the number of printing units is limited. 
     SUMMARY 
     An object of the present invention is to provide a drive control for a sheet-fed printing machine having a multiplicity of printing units which avoids the problem of the dynamic positional deviation increasing from printing unit to printing unit, delivers a higher level of precision, and in addition makes it possible to realize a greater number of printing units in the mechanical interconnection. A further object is to provide a corresponding method for the drive control. 
     According to the present invention, in an open-loop drive control for sheet-fed printing machines of the type discussed above, for example, the mechanical coupling of the individual cylinders AN, T 1  . . . T 4 , D . . . D 4 , G 1  . . . G 4 , P 1  . . . P 4 , F 1  . . . F 4 , AB is at least partially removed and provision is made in the de-coupled cylinders for further electrical drives MP 1  . . . MP 4 , MG 1  . . . MG 4 , which, in each case, have an assigned separate closed-loop control R_MP 1  . . . R_MP 4 , R_MG 1  . . . R_MG 4 , all closed-loop controls R_MP 1  . . . R_MP 4 , R_MG 1  . . . R_MG 4  obeying a common reference variable A_Soll. 
     A method is also provided for the open-loop drive control for sheet-fed printing machines in which the mechanical coupling of individual cylinders AN, T 1  . . . T 4 , D 1  . . . D 4 , G 1  . . . G 4 , P 1  . . . P 4 , F 1  . . . F 4 , AB is at least partially removed and the decoupled cylinders are electrically driven independently of each other, there being, in each case, an assigned separate closed-loop control R_MP . . . R_MP 4 , R_MG 1  . . . R_MG 4 , each closed-loop control R_MP 1  . . . R_MP 4 , R_MG 1  . . . R_MG 4  obeying a common reference variable A_Soll. 
     The present invention, which, for example, partially removes the mechanical interconnection of the sheet-travel modules of individual printing units and replace it with individual drives, offers the advantage that as a result of a multi-motor open-loop drive control, the fault does not continue to increase from printing unit to printing unit, since at each printing unit the torque is supplied separately, and all the drives are closed-loop controlled at the same reference variable. 
     In one embodiment of the present invention, the coupling between the rubber cylinders and the plate cylinders is removed and is replaced by individual drives in the rubber cylinders and the plate cylinders. 
     A further advantageous embodiment of the present invention prescribes a common reference variable through a reference variable interpolator, which continually interpolates the reference variable in accordance with the acceleration capacity of the sheet-fed printing machine and with a preselected rotational speed. 
     It is also advantageous if the closed-loop control of each drive is designed in a cascading arrangement made up of a closed-loop control of position, rotational-speed, and power. The highest precision is achieved using an open-loop drive control according to the present invention in accordance with a further specific advantageous embodiment, such that every closed-loop control of a drive has the same delay time constant. 
     The delay times can be reduced and the vibrations dampened in a particularly advantageous manner due to the fact that each closed-loop control of a drive has a rotational-speed and power pilot control (precontrol) for reducing delay times. 
     If set-up, cleaning, or maintenance work is to be carried out on a conventional sheet-fed printing machine having a central drive, then all the cylinders must be moved synchronously, as a result of which such tasks cannot be carried out in parallel, thus impairing machine amortization. 
     This problem can be circumvented by providing a drive control according to the present invention in which the closed-loop control R_MG 1  . . . R_MG 4  of each rubber cylinder G 1  . . . G 4  or closed-loop control R_MP 1  . . . R_MP 4  of each plate cylinder P 1  . . . P 4 , instead of obeying common reference variable A_Soll, obeys a reference variable A_P 1 , A_P 2  of its own, separate from a sheet-travel motion. 
     Further advantages and details of the present invention are provided on the basis of the following description of an exemplary embodiment and in connection with the Figures. In this context, elements having the same functionality are designated using the same reference numerals. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a conventional sheet-fed printing machine having four printing units; in particular, a cross-section of the individual rollers is illustrated. 
     FIG. 2 shows a sheet-fed printing machine according to the present invention having a multiple-motor drive, in a cross-section of the rollers. 
     FIG. 3 shows a circuit diagram of a multiple-motor open-loop drive control of a sheet-fed printing machine according to the present invention. 
     FIG. 4 shows a schematic sketch of an open-loop control and interpolation of the plate cylinders for carrying out cleaning work. 
    
    
     DETAILED DESCRIPTION 
     FIG. 1 was discussed above in connection with the description of a conventional sheet-fed printing machine. A sheet-fed printing machine having four printing units  1  through  4  is shown, the printing units, in each case, being mechanically coupled as a sheet-travel module. Each printing unit has an inking system F 1  through F 4 , a plate cylinder P 1  through P 4 , a rubber cylinder G 1  through G 4 , and a printing cylinder D 1  through D 4 . Individual printing units or printing cylinders D 1  through D 4  are mechanically coupled to each other by transfer rollers T 2  through T 4 . First printing unit  1  has, at printing cylinder D 1 , a feeder AN, and final printing unit  4  has at printing cylinder D 4  a delivery assembly AB. 
     FIG. 2 shows a sheet-fed printing machine having a multiple-motor drive according to an example embodiment of the present invention. As shown in FIG. 2, the coupling between rubber cylinders G 1  through G 4  and plate cylinders P 1  through P 4  is removed and replaced by individual drives MG 1  through MG 4  for the rubber cylinders and MP 1  through MP 4  for the plate cylinders. 
     As a result of the fact that the mechanical coupling between the rubber cylinders and the plate cylinders is removed, the central drive is dispensed with and is replaced by individual drives MG 1  through MG 4  on the rubber cylinders and MP 1  through the MP 4  on the plate cylinders. Feeder AN, transfer rollers T 2  through T 4 , printing cylinders D 1  through D 4 , and rubber cylinders G 1  through G 4  continue to be mechanically coupled as a so-called sheet-travel module BLM, just as, in each case, is printing unit  1  through  4 , plate cylinder P 1  through P 4 , and inking system F 1  through F 4 . 
     In the printing operation, the drives are controlled using a common reference variable A_Soll on a reference variable interpolator for sheet-travel module BLM. 
     For this purpose, FIG. 3 depicts a circuit diagram of a multiple motor open-loop drive control for a sheet-fed printing machine according to the invention, which makes possible an open-loop control of the drives in the printing operation using a common reference variable A_Soll. All drives MG 1  through MG 4  and MP 1  through MP 4  are closed-loop controlled individually via a cascaded closed-loop control R_MG 1  through R_MG 4  and R_MP 1  through R_MP 4 , composed of position control R 1 , rotational speed control Rv, and power control Ri. In the representation according to FIG. 3, for example, the corresponding closed-loop controls for drives MG 1 , MG 2 , and MP 1 , MP 2  are depicted. All closed-loop controls have the same cascaded design and are acted upon by reference variable interpolator LIP having the aforementioned common reference variable A_Soll. Each drive MG 1  through MG 4  and MP 1  through MP 4  thus obeys reference variable A_Soll within the parameters of its control precision. This reference variable is constantly interpolated by an open-loop control S in accordance with the acceleration capacity of the sheet-fed printing machine and the desired rotational speed. 
     Each closed-loop control R_MG 1  through R_MG 4  and R_MP 1  through R_MP 4 , in this context, may be adjusted so that the delay time constants are low and all closed-loop control circuits are the same. Delay times are advantageously also reduced by a rotational-speed pilot control Vv and a power pilot control Vi. In the block diagram according to FIG. 3, this can be seen in the fact that-each cascaded closed-loop control composed of position, rotational speed, and power closed-loop control has a power actual value that is fed back by drive MG 1  through MG 4  and MP 1  through MP 4 , in each case, to power controller Ri, and a rotational actual value that is fed back to input rotational speed controller Rv. 
     Each axle moves with respect to reference variable A_Soll in the same fault tolerance range. This fault tolerance directly determines the register precision in the paper travel direction of the sheet-fed printing machine. For this purpose, the fault that is aimed at must be smaller than the desired register precision. 
     Using an open-loop drive control according to the present invention, it is also possible, for set up, servicing, and cleaning work on the sheet-fed printing machine, to separate the motion of individual printing towers  1  through  4 , composed of plate cylinders P 1  through P 4  and inking systems F 1  through F 4 , from the motion of sheet-travel module BLM, composed of rubber cylinders G 1  through G 4  and printing cylinders D 1  through D 4  and of other printing towers  1  through  4 . Thus, it is possible for the other printing towers to move at a different speed or even to be motionless. 
     FIG. 4 shows a block diagram of an open loop control and an interpolation of the plate cylinders, which builds on the representation depicted in FIG. 3, and making possible a separation of the plate cylinders and inking systems from the motion of sheet-travel module BLM and other printing towers. By way of example, the closed-loop control of the electrical drives of rubber cylinders MG 1  and MG 2  as well as of plate cylinders MP 1  and MP 2  is shown. The broken lines of the output of reference variable interpolator LIP having common reference variable A_Soll show that the closed-loop controls of the other electrical drives are carried out in the same manner. Each electrical drive MG 1 , MG 2 , and MP 1 , MP 2  has an associated closed-loop control R_MG 1 , R_MG 2  and R_MP 1 , R_MP 2 , which has the design depicted in the representation according to FIG.  3 . During printing operation, each of these closed-loop controls is acted upon by reference variable interpolator LIP having common reference variable A_Soll. 
     In addition, further reference variable interpolators LIP 1  and LIP 2  may be provided, which are assigned, respectively, to closed-loop controls R_MP 1  and R_MP 2 . Using an open-loop control module S, it is possible, for set-up, servicing, or cleaning work, to carry out a switchover of the input of closed-loop controls R_MP 1  and R_MP 2  to reference variable interpolator LIP 1  or LIP 2 , respectively, and accordingly to have closed-loop control R_MP 1  acted upon by its own reference variable A_P 1  and further closed-loop control R_MP 2  acted upon by its own reference variable A_P 2 . In this way, it is possible to move the electrical drives of individual plate cylinders MP 1  and MP 2  at different speeds from the drives of corresponding rubber cylinders MG 1  and MG 2 , or even to stop electrical drives MP 1  and MP 2 . As a result of this design of an open-loop drive control for a sheet-fed printing machine, depicted in the block diagram of FIG. 4, individual plate cylinder drives MP 1  and MP 2  can be interpolated separately from the sheet-travel motion in accordance with a prescribed instruction. For this purpose, the individual interpolators LIP 1  and LIP 2  are made available to the printing units. Of course, it is also possible to assign the separate reference variable interpolators LIP 1  and LIP 2 , not to closed-loop controls R_MP 1  and R_MP 2  for the plate cylinders, but rather to the corresponding closed-loop controls R_MG 1  and R_MG 2  for the rubber cylinders. 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 Reference Numeral List 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 1,2,3,4 
                 Printing unit 
               
               
                   
                 F1 through F4 
                 Inking system 
               
               
                   
                 P1 through P4 
                 Plate cylinder 
               
               
                   
                 G1 through G4 
                 Rubber cylinder 
               
               
                   
                 D1 through D4 
                 Printing cylinder 
               
               
                   
                 T2 through T4 
                 Transfer roller 
               
               
                   
                 AN 
                 Feeder 
               
               
                   
                 AB 
                 Delivery assembly 
               
               
                   
                 MP1 through MP4 
                 Drive for the plate cylinder 
               
               
                   
                 MG1 through MG4 
                 Drive for the rubber cylinder 
               
               
                   
                 S 
                 Open-loop control module 
               
               
                   
                 LIP 
                 Reference variable interpolator 
               
               
                   
                 LIP1, LIP2 
                 further reference variable interpolators 
               
               
                   
                 A_Soll 
                 Common reference variable 
               
               
                   
                 A_P1, A_P2 
                 Separate reference variables 
               
               
                   
                 R_MG1, R_MG2 
                 Closed-loop control for the drive of the 
               
               
                   
                   
                 rubber cylinders 
               
               
                   
                 R_MP1, R_MP2 
                 Closed-loop control for the drive of the 
               
               
                   
                   
                 plate cylinders 
               
               
                   
                 R1 
                 Position closed-loop controller 
               
               
                   
                 Ri 
                 Rotational speed closed-loop controller 
               
               
                   
                 Vv 
                 Rotational speed pilot control 
               
               
                   
                 Vi 
                 Power pilot control