Abstract:
A method of re-registering a press job after disturbing the setup having the steps of recalling phase and compensator positions previously stored for the job; positioning compensators ( 113 - 116 ) to their nominal position; re-phasing the press color cylinders for the job; rerouting a web ( 117 ) through the press for the job; determining new phase offsets by running the press for a minimum of one revolution; and comparing a distance offset between adjacent print operations, thereby confirming the distance is zero and the press is back in register for the job.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The invention is in the field of control systems for printing presses. 
         [0003]    2. Description of the Related Art 
         [0004]    In web offset printing presses, a substrate such as a web of paper is sequentially driven through a series of print cylinders, each cylinder using ink of a different color, which cooperates to imprint a multicolor image on the web. To provide an accurate and clear multicolor image, the rotational and lateral position of each print cylinder must be precisely aligned, i.e., proper color registration of the respective colors must be maintained. 
         [0005]    Most printing presses use three basic subtractive primary colors: yellow, magenta, cyan and black to create a printed image. Special print colors can also be utilized. There are several reasons why the print may not be in register after being disturbed. The most important being that when a new job is run, it is very difficult to accurately replace the print cylinders to exactly the same position they were in when the job was last optimally run. Additionally, during the course of a run, a print cylinder may need to be replaced for defective or print change reasons. Replacing the print cylinders in exactly the same phase as before the press was stopped is very difficult and not practically achieved in the press room. A second job may need to be performed in the middle of a first job. Inks may need to be changed. Mechanical breakdown can occur. It is therefore important to accurately re-register the press as efficiently as possible. 
         [0006]    In practice, the accurate re-engagement of a print cylinder to obtain the exact same phase and therefore minimal register error for a particular web path is very difficult and seldom possible. What results is the generation of substantial amounts of waste as the press is run and brought into register by the operator and/or automatic register control systems. What is needed, therefore, is a re-registration method and apparatus for a mechanical drive press that reduces waste to an absolute minimum. 
       SUMMARY 
       [0007]    The invention is a method and apparatus that satisfies the need to reduces waste from re-registering the press to an absolute minimum. The method of the present invention has the steps of recalling phase and compensator positions previously stored for the job; positioning compensators to their nominal position; re-phasing the press color cylinders for the job; rerouting a web through the press for the job; determining new phase offsets by running the press for a minimum of one revolution; and comparing a distance offset between adjacent print operations, thereby confirming the distance is zero and the press is back in register for the job. 
         [0008]    An apparatus according to the present invention has a press encoder coupled to a drive shaft adapted to provide a pulse train to count position; a color cylinder proximity sensor coupled to each color cylinder to provide a single index pulse per revolution of the cylinder; a compensator position sensor; and a computer operatively coupled to each encoder, sensor, and compensator. These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, drawings, and claims. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a side elevation of a press with associated equipment. 
           [0010]      FIG. 2  is a side elevation of the press of  FIG. 1  in greater detail and without the web. 
           [0011]      FIG. 2A  is a graph displaying encoder and index signals. 
           [0012]      FIG. 3  is a side elevation of the press of  FIG. 1  in greater detail and without the web. 
           [0013]      FIG. 3A  is a graph displaying encoder and index signals. 
           [0014]      FIG. 4  is a side elevation of another embodiment of the present invention. 
           [0015]      FIG. 5  is a side elevation of another embodiment of the present invention. 
           [0016]      FIG. 6  is a side elevation of another embodiment of the present invention. 
           [0017]      FIG. 7  is a side elevation of another embodiment of the present invention. 
           [0018]      FIG. 8  is a side elevation of another embodiment of the present invention. 
           [0019]      FIG. 9  is a side elevation of a compensator between two rollers in three positions. 
           [0020]      FIG. 10  is a process flow chart of the method of the present invention. 
       
    
    
       [0021]      
         [0000]    
       
         
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 TABLE OF REFERENCES 
               
             
          
           
               
                 Number 
                 Description 
               
               
                   
               
             
          
           
               
                 101 
                 print unit 
               
               
                 102 
                 print unit 
               
               
                 103 
                 print unit 
               
               
                 104 
                 print unit 
               
               
                 105 
                 print cylinder gap for proximity sensor 
               
               
                 106 
                 print cylinder gap for proximity sensor 
               
               
                 107 
                 print cylinder gap for proximity sensor 
               
               
                 108 
                 print cylinder gap for proximity sensor 
               
               
                 109 
                 proximity sensor 
               
               
                 110 
                 proximity sensor 
               
               
                 111 
                 proximity sensor 
               
               
                 112 
                 proximity sensor 
               
               
                 113 
                 web compensator 
               
               
                 114 
                 web compensator 
               
               
                 115 
                 web compensator 
               
               
                 116 
                 web compensator 
               
               
                 117 
                 web, e.g. paper 
               
               
                 118 
                 main drive encoder 
               
               
                 119 
                 folder 
               
               
                 120 
                 proximity sensor 
               
               
                 121 
                 stud for proximity sensor on folder 
               
               
                 122 
                 knife cylinder for folder 
               
               
                 123 
                 main drive shaft 
               
               
                 124 
                 computer 
               
               
                 201 
                 print unit 
               
               
                 202 
                 print unit 
               
               
                 203 
                 print cylinder gap for proximity sensor 
               
               
                 204 
                 print cylinder gap for proximity sensor 
               
               
                 205 
                 proximity sensor 
               
               
                 206 
                 proximity sensor 
               
               
                 207 
                 web compensator 
               
               
                 208 
                 main drive shaft 
               
               
                 209 
                 main drive encoder 
               
               
                 210 
                 count pulse signal on main encoder 
               
               
                 211 
                 index pulse signal on main encoder (folder encoder) 
               
               
                 212 
                 proximity sensor signal from gap on print cylinder 203 and 205 
               
               
                 213 
                 proximity sensor signal from gap on print cylinder 204 and 206 
               
               
                 301 
                 print unit 
               
               
                 302 
                 print unit 
               
               
                 303 
                 print cylinder gap for proximity sensor 
               
               
                 304 
                 print cylinder gap for proximity sensor 
               
               
                 305 
                 proximity sensor 
               
               
                 306 
                 proximity sensor 
               
               
                 307 
                 web compensator 
               
               
                 308 
                 main drive shaft 
               
               
                 309 
                 main drive encoder 
               
               
                 310 
                 count pulse signal on main encoder 
               
               
                 311 
                 index pulse signal on main encoder (folder encoder) 
               
               
                 312 
                 proximity sensor signal from gap on print cylinder 303 and 305 
               
               
                 313 
                 proximity sensor signal from gap on print cylinder 304 and 306 
               
               
                 401 
                 print unit 
               
               
                 402 
                 print unit 
               
               
                 403 
                 print cylinder gap for proximity sensor 
               
               
                 404 
                 print cylinder gap for proximity sensor 
               
               
                 405 
                 proximity sensor 
               
               
                 406 
                 proximity sensor 
               
               
                 407 
                 web compensator 
               
               
                 408 
                 web compensator 
               
               
                 409 
                 main drive shaft 
               
               
                 410 
                 main drive encoder 
               
               
                 411 
                 web 
               
               
                 412 
                 print unit 
               
               
                 413 
                 print cylinder gap for proximity sensor 
               
               
                 414 
                 proximity sensor 
               
               
                 501 
                 print unit 
               
               
                 502 
                 print unit 
               
               
                 503 
                 print cylinder gap for proximity sensor 
               
               
                 504 
                 print cylinder gap for proximity sensor 
               
               
                 505 
                 proximity sensor 
               
               
                 506 
                 proximity sensor 
               
               
                 507 
                 web compensator 
               
               
                 508 
                 web compensator 
               
               
                 509 
                 main drive shaft 
               
               
                 510 
                 main drive encoder 
               
               
                 511 
                 web 
               
               
                 601 
                 print unit 
               
               
                 602 
                 print unit 
               
               
                 603 
                 print cylinder gap for proximity sensor 
               
               
                 604 
                 print cylinder gap for proximity sensor 
               
               
                 605 
                 proximity sensor 
               
               
                 606 
                 proximity sensor 
               
               
                 607 
                 web compensator 
               
               
                 608 
                 web compensator 
               
               
                 609 
                 main drive shaft 
               
               
                 610 
                 main drive encoder 
               
               
                 611 
                 string (from string encoder) 
               
               
                 612 
                 string anchor tie off 
               
               
                 613 
                 string encoder 
               
               
                 701 
                 print unit 
               
               
                 702 
                 print unit 
               
               
                 703 
                 print cylinder gap for proximity sensor 
               
               
                 704 
                 print cylinder gap for proximity sensor 
               
               
                 705 
                 proximity sensor 
               
               
                 706 
                 proximity sensor 
               
               
                 707 
                 web compensator 
               
               
                 708 
                 web compensator 
               
               
                 709 
                 main drive shaft 
               
               
                 710 
                 main drive encoder 
               
               
                 711 
                 string (from string encoder) 
               
               
                 712 
                 string anchor tie off 
               
               
                 713 
                 string encoder 
               
               
                 801 
                 print unit 
               
               
                 802 
                 print unit 
               
               
                 803 
                 print unit 
               
               
                 804 
                 print unit 
               
               
                 805 
                 print cylinder gap for proximity sensor 
               
               
                 806 
                 print cylinder gap for proximity sensor 
               
               
                 807 
                 print cylinder gap for proximity sensor 
               
               
                 808 
                 print cylinder gap for proximity sensor 
               
               
                 809 
                 proximity sensor 
               
               
                 810 
                 proximity sensor 
               
               
                 811 
                 proximity sensor 
               
               
                 812 
                 proximity sensor 
               
               
                 813 
                 web compensator 
               
               
                 814 
                 web compensator 
               
               
                 815 
                 web compensator 
               
               
                 816 
                 web compensator 
               
               
                 817 
                 web, e.g. paper 
               
               
                 818 
                 main drive encoder 
               
               
                 819 
                 folder 
               
               
                 820 
                 proximity sensor 
               
               
                 821 
                 stud for proximity sensor on folder 
               
               
                 822 
                 knife cylinder for folder 
               
               
                 823 
                 main drive shaft 
               
               
                 901 
                 motor/encoder assembly 
               
               
                 902 
                 compensator cylinder in extended position 
               
               
                 903 
                 compensator cylinder in center position 
               
               
                 904 
                 compensator cylinder in retracted position 
               
               
                 905 
                 web support cylinder 
               
               
                 906 
                 web support cylinder 
               
               
                 907 
                 coupler from motor/encoder shaft to threaded screw 
               
               
                 908 
                 threaded screw 
               
               
                 909 
                 web 
               
               
                 1001 
                 modify press 
               
               
                 1003 
                 bring press into register manually 
               
               
                 1005 
                 store press state 
               
               
                 1007 
                 press disturbed 
               
               
                 1009 
                 reset to nominal positions 
               
               
                 1011 
                 rotate one revolution and take measurements 
               
               
                 1013 
                 adjust compensators for distance offset 
               
               
                   
               
             
          
         
       
     
       DETAILED DESCRIPTION 
     I. Overview 
       [0022]    A press with single drive shaft performs operations on a continuous moving web at multiple points. Each operation at each point must be in phase or register with all other operations taking place in the overall process. Described herein is a method and apparatus for putting all the operations in phase with a maximum of one revolution on the operation with the slowest period relative to the drive shaft. 
         [0023]    For the purposes of this specification, this method and apparatus of re-registration will be illustrated using the example of a simple newspaper web printing press, although it is applicable to any multi-color web press.  FIG. 1  shows a simplified overall view of a four-color perfecting press with folder  119  and drive shaft  123 . All color print cylinders are mechanically linked to the drive shaft  123  and are adjusted by means of motorized web compensators  113 ,  114 ,  115 ,  116  or circumferential adjustment motors to control their relative phase to the other print cylinders. The overall phase of the print to the fold is controlled by a motorized compensator that adds or subtracts from the total web lead going into the folder  119 . 
         [0024]    In steady state, in-register operation, the phase of each print cylinder relative to the drive shaft  123  will be constant. If one or more of the color cylinders are disengaged or removed from the drive shaft  123  to change the print work and then reinstalled such that the phase between the disengaged/removed cylinder and the drive shaft  123  changes, the final print work will no longer be in register. Additionally, normal operation of the newspaper press entails routing the paper  117  (web) in different paths and disengaging and re-engaging the print cylinders to a new phase relationship to the drive shaft  123  depending on the type of job being run. 
       II. Phase Restoration of Color Print Cylinders Relative to the Drive Shaft 
       [0025]    To accurately re-phase each of the color cylinders to the drive shaft for a particular web path, the printing press must have the following modifications made: 
         [0026]    1) An encoder  118  is attached to the drive shaft  123  providing a nominal resolution of 4096 pulses per revolution  210  of the drive shaft  123 ,  208  and an index pulse  211  providing one pulse per revolution as shown in  FIGS. 1 and 2 . 
         [0027]    2) A proximity sensor  205 ,  206 ,  305 ,  306  or equivalent device that is known to those having skill in the art providing one pulse per revolution  211 ,  311  is attached to each of the color cylinders as shown in  FIGS. 2 and 3 . 
         [0028]    3) Each compensator  207 ,  307  (detail  FIG. 9 ) is profiled using a string encoder and computerized measurement system to provide an accurate compensator position vs. linear distance to the next color cylinder (FIGS.  6 , 7 ). This may require the installation of an encoder or timing mechanism of some sort to provide an accurate indication of compensator position. 
         [0029]    4) A computer  124  and associated interface hardware provide a means of calculating and storing the correct phase relationships of each of the color cylinders to the drive shaft  123 . 
         [0030]    Next the press is brought into register manually. When in register the phase relationships of the color cylinders to the drive shaft  123  are calculated and stored along with the compensator positions. The phase relationships of the color cylinders to the drive shaft are determined in the following manner: the encoder count position on the drive shaft is memorized at the instant of the pulse from each proximity sensor on the color cylinders (shown as pulse train S 1   312  on  FIG. 3A ). The encoder count on the drive shaft (shown and pulse train A  310  in  FIG. 3A ) is periodic and absolute using the index pulse from the encoder (shown and pulse train Z  311  in  FIG. 3A ). Additional accuracy is obtained by inter-encoder pulse timing so that the position of a proximity sensor pulse can be accurately measured on an encoder sub-pulse level. As a result of this phase and compensator position measurement operation, the web distances between adjacent color print cylinders is known for the press being in register for a particular print job. 
         [0031]    After a web path change for a previously stored in-register job, it is only necessary to turn the press over one revolution so that new phase measurements can be made on all color proximity sensor inputs. Web path changes may be due web breakage, ink change, malfunction, the need to run an intervening job, and the like. Such changes will be called ‘disturbances’ in this specification. Using the compensator profile curves to change the web distance between adjacent colors and the folder, the relative phase differences and therefore the web distances between color cylinders and folder are duplicated resulting in an in-register job. 
       III. Detailed Description of Hardware 
       [0032]    Turning to the embodiment shown in  FIGS. 4 and 5 , the following press interfaces must be added:
   1. a) Press Encoder—shown in  FIGS. 4 and 5  as  410 ,  510  the press encoder must be mounted to the drive shaft  409 ,  509  to provide a pulse train to count position. In addition, an index pulse must be mounted to provide a one pulse per revolution of the base operation—in the case of the newspaper example above—a proximity sensor  414  mounted on the folder would provide the required index pulse. This encoder/index pulse addition would provide a count per repeat that would provide an accurate count position within the periodic operation. If the linear distance of the periodic operation is known (in this case the repeat length of the print operation) then the count will provide an accurate distance position within the printed repeat.   1. b) Color Cylinder proximity sensors—each color cylinder must have a proximity sensor  405 ,  406 ,  505 ,  506  mounted to it so as to provide a single index pulse per revolution of the cylinder. As the color cylinder is necessarily periodic with the overall base operation (the folder in this newspaper example) the relative position of each color cylinder index pulse will fall in the same position of the press encoder/index count.   1. c) Compensator position sensor—all compensators  407 ,  408 ,  507 ,  508  must be outfitted with some means to determine their position.  FIG. 9  illustrates a web compenstor in 3 different positions  902 ,  903 ,  904  with web supporting cylinders  905 ,  906 , mounted to a motor driven screw  908  with encoder  901 .   1. d) A personal computer  124  with interface hardware (not shown) must be added to accurately measure and store (on a job basis) the relative phase relationships between all color cylinders and the base operation and compensator positions. In the case of the above newspaper press example, the PC interface hardware must be capable of handling inputs of one standard encoder with index for the press encoder, four proximity sensor inputs for the four color cylinders (in the perfecting example we are using, top and bottom color cylinders are geared together for the purposes of this specification), and four encoder inputs with index for each of the four compensators to measure compensator position.   
 
       IV. Detailed Description of Setup 
       [0037]    The one operation that must be performed prior to operation is compensator position profiling. Web compensators  407 ,  408 ,  507 ,  508  work by increasing or decreasing the web path between adjacent print operations. Compensator profiling results in a curve of compensator position versus web length between print operations. Additionally, compensators can be inserted (webbed) between print operations in different ways depending on the type of operation to be performed. How a compensator is inserted between its adjacent print operations directly affects the compensator profile curve. Thus a profile curve must be generated for each compensator and each possible way that compensator can be inserted between its adjacent print operations. 
         [0038]    In the example of the newspaper press, compensator profiling entails using a string encoder and measuring the distances between adjacent print operations through the intervening compensator while the compensator is run from one extreme of its travel to the other. This procedure can be automated and must be performed for every different instance of compensator insertion between adjacent print operations. 
         [0039]    This is illustrated in  FIGS. 6 and 7  where the string encoder is routed through the color unit in different ways to reflect two different web paths. In  FIG. 6 , only the lower print cylinders are being used (printing both sides of the web—known as perfecting). In  FIG. 7  the color unit is printing two colors on each side of the web, thus the web is routed through both print cylinder pairs. 
         [0040]    The results of compensator profiling are a table of compensator position versus distance between adjacent print operations for each instance of compensator insertion between the print operations. 
         [0041]    Turning to  FIG. 9 , details of how compensator position  902 ,  903 ,  904  mounted on a screw  908  changes the alignment of the web  909 . 
       V. Detailed Description of Operation 
       [0042]    Turning to  FIG. 10 , the process starts by providing a press having the apparatus described above  1001 . Then, the press must be brought into manual register  1003  at which time the phase positions of all color cylinders and compensator positions are stored. This press state is stored for this particular job  1005 . For some reason, the press setup becomes disturbed  1007 . 
         [0043]    At some later date when this job is run again, the phase and compensator positions are recalled. From the phase angle difference between the adjacent print operations a distance offset is calculated. From the compensator profile curve for this recalled job and stored compensator position, the linear distance between adjacent print operations is calculated. This value is combined with the distance offset from the phase angle difference calculation to provide an overall distance value between the adjacent print operations. Next, the press is setup to run the new job by positioning compensators to their nominal position  1009 , re-phasing the color cylinders for the new job, and rerouting the web through the machine for the new job. Then the press is run for a minimum of one revolution  1011  so that the new phase offsets of the color cylinders relative to the drive shaft and folder (in the example of the newspaper press above) can be determined. From these measurements the current phase angle differences between adjacent print operations is calculated resulting in current distance offset measurement between adjacent print operations  1013 . This distance is combined with the current compensator position profile curve distance and compared with the stored value. For the press to be in register, the difference should be zero. If not, the compensator is moved (utilizing the profile curve) to make the difference zero. 
         [0044]    Another embodiment of the method of the present invention is a technique whereby one can get finer resolution than possible using only encoder tooth pulses. One can do this by counting a high frequency (fixed frequency) pulse between adjacent teeth and relating that to velocity, giving us intra-tooth measurement accuracy. This turns out to be necessary to get the register as close as possible as tooth accuracy alone may not be sufficient. 
         [0045]    Although the preferred embodiments of the present invention have been described herein, the above description is merely illustrative. Further modification of the invention herein disclosed will occur to those skilled in the respective arts and all such modifications are deemed to be within the scope of the invention as defined by the appended claims.