Abstract:
The present invention provides a printing press. The printing press includes a frame, a plate cylinder, a plate cylinder support supporting the plate cylinder, a blanket cylinder for receiving an image from the plate cylinder, a blanket cylinder support supporting the blanket cylinder, an impression cylinder for supporting a printing substrate between the blanket cylinder and the impression cylinder, an actuator connected to and controlling a position of the plate cylinder support or the blanket cylinder support and a controller providing the actuator with a position setpoint, the actuator receiving position feedback signals to maintain the position setpoint during a printing operation. The present invention also provides a method for operating a printing press.

Description:
[0001]    The present invention relates generally to printing presses, and more particularly to a printing press with a method for positioning the cylinders therein. 
       BACKGROUND INFORMATION 
       [0002]    U.S. Pat. No. 5,868,071 discloses a variable cutoff printing press with blanket cylinders mounted on linear slide assemblies to accommodate blanket sleeves of different thicknesses. 
         [0003]    U.S. Pat. No. 6,694,877 purports to disclose a device for use in an offset press, for permitting and positioning of at least a format-dependent printing cylinder individually exchangeable therein. A system with bearing arms positions the cylinders by rotation. 
         [0004]    U.S. Pat. No. 5,806,427 discloses a rotary offset printing press having a pair of interchangeable plate cylinders mounted on a carriage. 
         [0005]    U.S. Pat. No. 5,813,336 discloses a printing unit with a rotatable print cylinder and a rotatable blanket cylinder. A tubular printing blanket is removably mounted on the blanket cylinder. The printing unit may have an imaging unit mounted therein. A printing member, which is mountable on the print cylinder, is imaged by the imaging unit inside the printing unit. The printing member has a continuous surface and may be removed axially from the print cylinder. The printing unit may be configured as a cantilever printing unit, or, alternatively, may be configured with both a gear side frame and a work side frame for supporting the print and blanket cylinders. In order to provide a variable-cutoff capability, a plurality of print cylinder saddles may be provided. Each print cylinder saddle has the same inner diameter for mounting on the print cylinders. However, in order to provide a variable cut-off, the print cylinder saddles may have a variety of outer diameters. 
         [0006]    U.S. Pat. Nos. 5,813,336, 5,806,427, 6,694,877 and 5,868,071 are hereby incorporated by reference herein. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention provides a printing press. The printing press includes a frame, a plate cylinder, a plate cylinder support supporting the plate cylinder, a blanket cylinder for receiving an image from the plate cylinder, a blanket cylinder support supporting the blanket cylinder, an impression cylinder for supporting a printing substrate between the blanket cylinder and the impression cylinder, an actuator connected to and controlling a position of the plate cylinder support or the blanket cylinder support and a controller providing the actuator with a position setpoint, the actuator receiving position feedback signals to maintain the position setpoint during a printing operation. 
         [0008]    The present invention also provides a variable format printing press that includes a frame, a plate cylinder, a plate cylinder support supporting the plate cylinder, a blanket cylinder for receiving an image from the plate cylinder, a blanket cylinder actuator connected to the blanket cylinder support, an impression cylinder for supporting a printing substrate between the blanket cylinder and the impression cylinder, an actuator connected to and controlling a position of the plate cylinder support or the blanket cylinder support and a controller providing the actuator with a first position setpoint corresponding to a first plate cylinder diameter and a second position setpoint corresponding to a second plate cylinder diameter, the actuator receiving feedback signals to maintain either the first setpoint position or the second setpoint position during a printing operation. 
         [0009]    The present invention also provides a method for operating a printing press. The method includes setting a position of a plate cylinder or a blanket cylinder in a printing press via an actuator to a cylinder position setpoint, receiving position feedback information and actively controlling the actuator during a printing operation to maintain the cylinder position setpoint. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    The present invention will be described with respect to preferred embodiments, in which: 
           [0011]      FIG. 1  shows schematically a variable-format printing press of a first embodiment using servo-hydraulic actuators to position the cylinders of the printing press; 
           [0012]      FIG. 2  shows schematically the printing press of  FIG. 1  with larger diameter plate and blanket cylinders; 
           [0013]      FIG. 3  shows a second embodiment of the printing press of the present invention; 
           [0014]      FIG. 4  shows a third embodiment of the printing press of the present invention; and 
           [0015]      FIG. 5  shows a fourth embodiment of the printing press of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0016]    Previous printing presses, such as prior art variable format printing presses, have allowed for positioning of cylinders using actuators. However, these actuators generally have been passive, in that they are set to a specific position for example for a certain format size and thereafter are not changed. They thus do not react or correct to compensate for variations induced by many factors. These factors may include mechanical vibrations, temperature and humidity fluctuations, and wear over time from normal operations. In particular, the printing press described in U.S. Pat. No. 6,694,877 describes a mechanical ball screw actuator that may not perform well when the screw carries a load in a fixed position for an extended period of time. 
         [0017]    The present invention can provide for active control of the cylinders in the printing press during operation via position feedback. Proper squeeze settings and positioning can be ensured, even as conditions change during printing. Moreover, the present invention has particular advantages with respect to variable format printing presses, in that the position changes required for the variable format cylinders can be easily and quickly achieved. No size-specific components other than replaceable sleeves or cylinders are required. 
         [0018]      FIG. 1  shows schematically a variable-format printing press  10  having a plate cylinder  20 , a blanket cylinder  30  and an impression cylinder  40 . Plate cylinder  20  is supported by a plate cylinder support  22  fixed at one end  24  via a pivot  26  to a frame  50  of the printing press  10 , shown schematically. Plate cylinder support  22  at another end  27  is fixed via a pivot  28  to a plate cylinder actuator  120 . 
         [0019]    Blanket cylinder  30  is supported by a blanket cylinder support  32  fixed at one end  34  via a pivot  36  to frame  50 . Blanket cylinder support  32  at another end  37  is fixed via a pivot  38  to a blanket cylinder actuator  130 . 
         [0020]    While, the impression cylinder  40  may be fixed to rotate in frame  50 , in the preferred embodiment, impression cylinder  40  is also supported by an impression cylinder support  42  fixed at one end  44  via a pivot  46  to frame  50 . Impression cylinder support  42  at another end  47  is fixed via a pivot  48  to an impression cylinder actuator  140 . Similarly, it is possible to provide plate cylinder  20  in a fixed rotational support and to have only blanket cylinder support  32  and impression cylinder support  42  movable by actuators  130 ,  140 . 
         [0021]    Advantageously, actuators  120 ,  130 ,  140  may be servoactuators, and have integral linear position feedback. Thus actuators  120 ,  130 ,  140 , unlike the prior art U.S. Pat. No. 6,694,877 actuators, have integral feedback capabilities, and can respond to a setpoint signal sent for example by a controller  100  via a communications line  110 , for example an Ethernet, SERCOS or PROFIBUS link, to each servoactuator  120 ,  130 ,  140 . Actuators  120 ,  130 ,  140  may be for example hydraulic servoactuators and may include respective hydraulic cylindrical rods  121 ,  131 ,  141  movable within respective housings  124 ,  134 ,  144 . Feedback advantageously thus occurs directly within the servoactuator in respective housings  124 ,  134 ,  144  and may be based on direct measurement of the respective hydraulic cylinder rod  121 ,  131 ,  141 . Mechanical ball screw actuators on the other hand infer position from a pitch of the screw and contains any error associated with the screw. 
         [0022]    Controller  100  may be for example a microcomputer or ASIC, and may include a memory device for storing different setpoints for various sized cylinders and printing substrate materials. Controller  100  can send the setpoint once to the servoactuators  120 ,  130 ,  140  during an initalization, or can send the setpoint continually during the printing operation. Adjustment of the setpoints, for example based on predetermined tables or operator inputs, thus can occur during printing. For example, as a temperature in the press area during printing changes, automatic setpoint adjust could occur based on predetermined tables that indicate, for example, that the plate and blanket cylinders should be slightly moved apart a specific distance given a temperature rise that slightly expands the cylinder diameter. A temperature sensor  116  feeding an input to the controller  100  is thus provided, for example. In addition or alternative to adjusting the setpoints based on temperature, the setpoints for example may also be adjusted based on mechanical vibrations, wear of printing press components and/or humidity fluctuations measured by corresponding sensors within the press area. 
         [0023]      FIG. 2  shows the printing press  10  with a larger diameter plate cylinder  230  and a larger diameter blanket cylinder  240  replacing plate cylinder  30  and blanket cylinder  40 , respectively. Such variable format cylinders can be provided in any known manner, such as replacement of the entire cylinder, or via a variable sized shell on a core of the cylinders. 
         [0024]    Servoactuators  120 ,  130  are thus provided with different setpoints that are a function of the increased diameter of blanket cylinder  240  and plate cylinder  230  and adjust plate cylinder support  22  and blanket cylinder support  32  accordingly. 
         [0025]      FIG. 3  shows an alternate embodiment printing press  310  with a hydraulic servoactuator  320  between the plate cylinder support  22  and the blanket cylinder support  32 , and a further servoactuator  330  between the blanket cylinder support  32  and the impression cylinder support  42 . A further optional servoactuator  340  may be provided to move all supports  22 ,  32 ,  42  together. Servoactuators include respective hydraulic cylindrical rods  321 ,  331 ,  341  movable within respective housings  324 ,  334 ,  344 . In this embodiment, rod  321  is coupled to plate cylinder support  22  while housing  324  is coupled to blanket cylinder support  32 . Similarly, rod  331  is coupled to blanket cylinder support  32  while housing  334  is coupled to impression cylinder support  42 . Rod  341  of actuator  340  is coupled to impression cylinder support  42  and housing  344  is coupled to frame  50 . In this embodiment, a single actuator may control squeeze between two cylinders, for example servoactuator  320  may control the squeeze between cylinders  20 ,  30  and servoactuator may control the squeeze between cylinders  30 ,  40 . Controller  100  via communications line  110  for example send the setpoint signals for servoactuators  320 ,  330 ,  340 . Servoactuators  320 ,  330 ,  340  may be for example hydraulic servoactuators. 
         [0026]      FIG. 4  shows a further alternate embodiment printing press  400 , with a carriage rail  450  fixed to the frame  50 . Individual linear servomotors  420 ,  430 ,  440  provide independent positioning of a plate cylinder support  422 , a blanket cylinder support  432  and, optionally, an impression cylinder support  442 . Each of the supports  422 ,  432 ,  442  may have a respective slot  424 ,  434 ,  444  at one end interacting with a pin  423 ,  433 ,  443 , respectively, fixed to individual linear servomotors  420 ,  430 ,  440 , respectively. Linear servomotors  420 ,  430 ,  440  may for example have a carriage riding on rail  450  with position feedback being a direct result of the position of the respective motor  420 ,  430 ,  440  on rail  450 , which may be measured within the respective motor  420 ,  430 ,  440 . Controller  100  via communications line  110  for example send the setpoint signals for the servomotors  420 ,  430 ,  440 . Servomotors  420 ,  430 ,  440  may be for example linear servomotors. 
         [0027]      FIG. 5  shows yet a further embodiment printing press  500  in which linear servomotors  520 ,  521  support plate cylinder support  522  via rails  550 ,  551  fixed to frame  50 . Likewise, servomotors  530 ,  531  support blanket cylinder support  532 , and servomotors  540 ,  541  impression cylinder support  542 . Controller  100  via communications line  110  for example send the setpoint signals for the servomotors  520 ,  521 ,  530 ,  531 ,  540 ,  541 . Servomotors  520 ,  521 ,  530 ,  531 ,  540 ,  541  may be for example linear servomotors. 
         [0028]    While one of the movable supports for the three cylinders is optional (for example the impression cylinder support as described above with respect to certain embodiments), such as the impression cylinder support, preferably all three supports are movable and controllable by a servomotor during operation for more accurate control. 
         [0029]    It is also noted that double sided print units may also be provided in which the impression cylinder is a blanket cylinder, and a further lower plate cylinder is provided. 
         [0030]    The present invention permits easy and quick movement of cylinders, while permitting proper control during actual printing operations. In addition to integrated position feedback control at the servomotors, it is also possible to provide velocity and acceleration controls if more accurate control is desired. 
         [0031]    In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.