Patent Publication Number: US-8122826-B2

Title: Infinitely variable cut off printing press

Description:
BACKGROUND OF INVENTION 
     The present invention relates generally to a printing press and more specifically to a variable cut off apparatus and method. 
     U.S. Pat. No. 5,950,536 discloses a variable cutoff offset press unit wherein a fixed cutoff press is adapted to a variable cutoff press while maintaining the size of the blanket cylinders. A plate cylinder sleeve has a variable outer diameter, whereby a length of an image to be printed is varied proportionally to a variable outer diameter while maintaining an outer diameter of the gapless blanket cylinder sleeve constant. The size of a plate cylinder is changed by using a sleeve mounted over the plate cylinder or adding packing under a plate to increase the diameter of the plate cylinder. 
     U.S. Pat. No. 6,327,975 discloses a method and apparatus for printing elongate images on a web. A first printing unit prints a first image portion on the web at prescribed spacings, by moving the impression cylinder away from the blanket cylinder each time one first image portion is printed. A second printing unit prints a second image portion on the spacings left on the web by the first printing unit, also by moving the impression cylinder away from the blanket cylinder each time one second image portion is printed. A variable velocity motor rotates each blanket cylinder, while each time the associated impression cylinder is held away to create a space on the web for causing printing of the first or the second printing portion at required spacings. 
     U.S. Pat. No. 7,066,088 discloses a variable cut-off offset press system and method of operation which utilizes a continuous image transfer belt. The offset printing system comprises at least two plate cylinders adapted to have thereon respective printing sleeves. Each of the printing sleeves is adapted to receive colored ink from a respective ink source. The system further comprises at least an impression cylinder, wherein the image transfer belt is positioned to contact each of the printing sleeves at respective nips formed between respective ones of the plate cylinders and the at least one impression cylinder. 
     BRIEF SUMMARY OF THE INVENTION 
     A variable cutoff printing press is provided that includes a plate cylinder, a first blanket cylinder including a first circumferential section movable with respect to a second circumferential section, and a second blanket cylinder including a third circumferential section movable with respect to a fourth circumferential section. The first, second, third and fourth circumferential sections contact the plate during a printing mode and print continuous images having a cutoff length on a web. 
     A method of printing an image on a web with a cutoff using a variable cutoff offset printing press is also provided. The steps include transferring an image to a first circumferential section of a first cylinder movable with respect to a second circumferential section of a second cylinder; printing the image on a web with the first circumferential section; transferring a second image to the second circumferential section; and printing the second image on the web with the second circumferential section. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention is described below by reference to the following drawings, in which: 
         FIG. 1  shows a schematic side view of a nonperfecting printing press according to an embodiment of the present invention; 
         FIG. 2  shows a schematic front view of a blanket cylinder shown in  FIG. 1 ; 
         FIG. 3  shows a schematic side view of the nonperfecting printing press shown in  FIG. 1  including inked images on the plates; 
         FIG. 4   a  shows a schematic side view of a perfecting printing press according to an embodiment of the present invention; 
         FIG. 4   b  shows a schematic side view of the perfecting printing press shown in  FIG. 4   a;    
         FIG. 4   c  shows a schematic side view of the perfecting printing press shown in  FIGS. 4   a  and  4   b ; and 
         FIG. 5  shows a schematic side view of the perfecting printing press shown in  FIGS. 4   a  to  4   c  without blanket cylinder bodies. 
     
    
    
     DETAILED DESCRIPTION 
     Variable cut off printing presses have been developed to allow for printing products of different sizes on the same printing press without having to change plate and blanket cylinders. Changing plate and blanket cylinders to correspond to the size of the image that needs to be printed can be a time consuming and difficult process and may also require purchasing and storing cylinders of multiple sizes. 
       FIG. 1  shows a nonperfecting printing press  30  according to an embodiment of the present invention. Printing press  30  includes a plate cylinder  11  transferring inked image portions via plates  12 ,  13 , mounted on plate cylinder  11 , to raised blanket cylinders  214 ,  224 , respectively, which in turn print the image portions on a passing web  17  during a printing mode. Blanket cylinders  214 ,  224  include respective blanket cylinder bodies  14 ,  24  and respective circumferential sections  15 ,  16 ,  25 ,  26  disposed about respective cylinder bodies  14 ,  24 . During the printing mode circumferential blanket sections  15 ,  16 ,  25 ,  26  are rotated clockwise about respective blanket cylinder bodies  14 ,  24  by individuals motors  85 ,  86 ,  95 ,  96 , respectively, and plate cylinder  11 , including plates  12 ,  13 , is rotated counterclockwise by a motor  81 . A controller  100  controls motors  85 ,  86 ,  95 ,  96 . Impression cylinder  18  contacts circumferential sections  15 ,  16  via web  17  at a nip  39  and impression cylinder  28  contacts circumferential sections  25 ,  26  via web  17  at a nip  38 , during the printing mode. 
     Each blanket cylinder  214 ,  224 , for illustrative purposes, can be broken up into four sections A, B, C and D, shown divided by the dashed lines in  FIG. 1 . For this embodiment, sections B and D are of equal size and the dashed lines of each blanket cylinder  214 ,  224  intersect at respective centers of blanket cylinders  214 ,  224 . Each blanket cylinder  214 ,  224  has two raised circumferential sections  15 ,  16 ,  25 ,  26 , respectively, located on surfaces of sections B and D. Each blanket cylinder  214 ,  224  also has two non-raised sections A and C, located in between circumferential sections  15 ,  16 ,  25 ,  26 , respectively. 
     While each circumferential section  15 ,  16  performs a single revolution about blanket cylinder body  14 , each circumferential section  15 ,  16  accepts an image portion from plate  12  and prints the image portion on passing web  17 . While each circumferential section  25 ,  26  performs a single revolution about blanket cylinder body  24 , each circumferential section  25 ,  26  accepts an image portion from plate  13  and prints the image portion on passing web  17 . Circumferential sections  15 ,  16 ,  25 ,  26 , along with plate cylinder  11 , can be phased and positioned so that circumferential sections  15 ,  16 ,  25 ,  26  print image portions on web  17  that are aligned with adjacent image portions. Each circumferential section  15 ,  16 ,  25 ,  26  will print every fourth image portion on web  17 . Circumferential sections  15 ,  16  will print every other image portion on web  17 , with circumferential sections  25 ,  26  printing the intervening image portions. In a preferred embodiment no unprinted space will exist on web  17  between image portions printed on web  17  by circumferential sections  15 ,  16 ,  25 ,  26 . 
     In the embodiment shown in  FIG. 1 , a lead roll  20  guides web  17 . Lead roll  20  is positioned in relation to cylinders  214 ,  224  so that circumferential sections  15 ,  16 ,  25 ,  26  print image portions on web  17  that align with adjacent image portions. The length of web  17  between nips  38 ,  39  is determined by the position of lead roll  20 , which can be adjusted as desired by moving lead roll  20 . In an alternative embodiment, lead roll  20  can be eliminated, resulting in a direct path between nips  38 ,  39 . Circumferential sections  15 ,  16 ,  25 ,  26  may also be accelerated and decelerated when circumferential sections  15 ,  16 ,  25 ,  26  are not in contact with respective plates  12 ,  13  or web  17 , to ensure image portions printed by circumferential sections  15 ,  16 ,  25 ,  26  are properly aligned on web  17 . 
     In an alternative embodiment a continuous plate carrying one continuous image may be disposed about plate cylinder  1  in place of plates  12 ,  13 . In this alternative embodiment circumferential sections  15 ,  16  transfer a portion of the continuous image from the continuous plate to web  17  and circumferential sections  25 ,  26  transfers another portion of the continuous image from the continuous plate to web  17  so that the circumferential sections  15 ,  16 ,  25 ,  26  print the continuous image on web  17 . Also, in another preferred embodiment, plates are not required, as images are imaged directly on plate cylinder  11 . 
     In operation, for the embodiment shown in  FIG. 1 , plate cylinder  11  can rotate counterclockwise and transfer an image portion on plate  12  to circumferential section  15 , which is being rotated clockwise about blanket cylinder body  14 . Circumferential section  15  can continue to rotate clockwise and print the image portion on web  17 , which can be traveling at a constant velocity in the direction of the arrow shown in  FIG. 1 . While circumferential section  15  is printing on web  17 , circumferential section  16  can be rotating clockwise about blanket cylinder body  14  and receiving the same image portion that circumferential section  15  received from plate  12 . Circumferential section  16  can continue to rotate about blanket cylinder body  14  and can print the image portion received from plate  12  on web  17  while circumferential section  15  is receiving the same image portion again from plate  12 . Meanwhile, an image portion on plate  13  can be transferred to circumferential section  25 , which is rotating clockwise about blanket cylinder  24 . Circumferential section  25  can continue to rotate clockwise and print the image portion received from plate  13  on passing web  17 . While circumferential section  25  is printing the image portion on web  17 , circumferential section  26  can be rotating clockwise about blanket cylinder body  14  and receiving the same image portion from plate  13 , which circumferential section  26  can print on web  17  while circumferential section  25  is receiving the same image portion again from plate  13 . 
     Circumferential section  16  is beginning to print an image portion in a space  34  on web  17  directly following an image portion  33  printed by circumferential section  26 , and directly preceding an image portion  35  printed by circumferential section  25 . Directly preceding image portion  33  on web  17  is an image portion  32  printed by circumferential section  15 , which is directly preceded by an image portion  31  printed by circumferential section  25 . Directly following space  34  is image portion  35  printed by circumferential section  25  and a space  36  for an image portion to be printed by circumferential section  15 . Circumferential section  26  is printing an image portion  37  on web  17 , following a space  36 . Preferably, after image portions are printed in spaces  34 ,  36  there is no space between image portions  31 ,  32 ,  33 , the image portion printed in space  34 , image portion  35 , the image portion printed in space  36 , and image portion  37 . Two adjacent image portion may form one continuous image. In a preferred embodiment, each of these three exemplary continuous images has the same cutoff length. 
     In a preferred embodiment, blanket cylinder bodies  14 ,  24  can be equal size and circumferential sections  15 ,  16 ,  25 ,  26  can be equal size. In this embodiment, if sections A, B, C, D are each equal size, plates  12 ,  13  of plate cylinder  11  can be of equal length and can print images that are equal in length to plates  12 ,  13 , respectively. Therefore, circumferential sections  15 ,  16 ,  25 ,  26  may be moving at the same constant velocity while printing images on web  17 . As a result plate cylinder  11  can be moving at substantially a same velocity as web  17 . 
     Plates  12 ,  13  can be replaced with replacement plates of nominally the same size carrying replacement images that differ in length from the images carried by plates  12 ,  13 . Replacing plates  12 ,  13  with replacement plates having different image lengths allows an operator of printing press  30  to vary the cutoff of images printed on web  17 . 
       FIG. 2  shows a schematic front view of an embodiment of blanket cylinder  214  shown in  FIG. 1 . Blanket cylinder  214  has a support shaft  91 , which can attach to a frame or other supporting device to stabilize blanket cylinder body  14  and circumferential sections  15 ,  16 . In this embodiment, circumferential sections  15 ,  16  independently rotate about blanket cylinder body  14 . Circumferential sections  15 ,  16  are attached to support arms  94 ,  194 , respectively. Support arms  94 ,  194  are attached to respective bearings  92 ,  93  that are rotatably attached to support shaft  91 . Bearings  92 ,  93  are rotated by respective motors  85 ,  86  about support shaft  91 , thereby driving circumferential sections  15 ,  16 , respectively, about blanket cylinder body  14 . 
       FIG. 3  shows a schematic side view of nonperfecting printing press  30  shown in  FIG. 1  including inked image portions  132 ,  133  on plates  12 ,  13 , respectively. Plate  12  of plate cylinder  11  transfers image portion  132  to circumferential section  15  and plate  13  of plate cylinder  11  transfers image portion  133  to circumferential section  25 . The length of image portion  132  is less than the length of plate  12 , therefore, a surface of plate  12  includes a non-print area. Similarly, the length of image portion  133  is less than the length of plate  13 , therefore, a surface of plate  13  includes a non-print area. 
     During each full revolution plate cylinder  11  makes about an axis of plate cylinder  11  plate  12  transfers image portion  132  to one circumferential section  15 ,  16  of blanket cylinder  214  and plate  13  transfers image portion  133  to one circumferential section  25 ,  26  of blanket cylinder  224 . During two full revolutions of plate cylinder  11 , plate  12  transfers image portion  132  to both circumferential sections  15 ,  16  and plate  13  transfers image portion  133  to both circumferential sections  25 ,  26 . In a time it takes plate cylinder  11  to make two full revolutions, circumferential sections  15 ,  16 ,  25 ,  26  travel an entire revolution about respective blanket cylinder bodies  14 ,  24 . Therefore, circumferential sections  15 ,  16 ,  25 ,  26  each print one respective image portion  132 ,  133  on web  17  in the time plate cylinder  11  makes two complete revolutions. 
     To ensure proper alignment of image portions  132 ,  133  on web  17 , web  17  can travel a distance equal to the total length of these four image portions in the time it takes plate cylinder  11  to make two entire revolutions. If image portions  132 ,  133  are the same image length L 1 , and plates  12 ,  13  are the same plate length L P , a time T in which web  17  travels a distance equal to four image lengths L 1  is equal to a time in which the surface of plate cylinder  11  travels a distance of four plate lengths L P . Therefore, because the plate length L P  of plates  12 ,  13  is greater than the image length L 1  of image portions  132 ,  133 , the surface of plates  12 ,  13  must travel a greater distance than web  17  in the same amount of time T, the velocity V P  of the surface of plates  12 ,  13  must be greater than the velocity of web  17  V W  (T=L/V W =L P /V P ), in order for images  132 ,  133  to be properly aligned on web  17 . For example, if plate cylinder  11 , including plates  12 ,  13 , has a permanent circumference of 50 inches, and is covered by plates  12 ,  13  that are each 25 inches long but each printing an image that is only 21 inches long, then web  17  travels 16% (50−(2)*(21))/50=8/50=0.16) more slowly than the surfaces of plates  12 ,  13 . 
     When web  17  and surfaces of plates  12 ,  13  are traveling at different velocities the velocities of circumferential sections  15 ,  16 ,  25 ,  26  may need to be adjusted throughout each revolution to effectively interact with plates  12 ,  13  and web  17 . When each circumferential section  15 ,  16 ,  25 ,  26  comes into contact with respective plate  12 ,  13  a surface of each circumferential section  15 ,  16 ,  25 ,  26  can be traveling at substantially the same velocity as a surface of respective plate  12 ,  13 . When each circumferential section  15 ,  16 ,  25 ,  26  comes into contact with web  17  a surface of each circumferential section  15 ,  16 ,  25 ,  26  can be traveling at substantially the same velocity as web  17 . Therefore, if surfaces of plates  12 ,  13  are traveling faster than web  17 , each circumferential section  15 ,  16 ,  25 ,  26  can decelerate after receiving respective inked image portion  132 ,  133  from respective plate  12 ,  13  to reach the velocity of web  17  by the time respective circumferential section  15 ,  16 ,  25 ,  26  contacts web  17  to print respective image portions  132 ,  133  on web  17 . Each circumferential section  15 ,  16 ,  25 ,  26  will then have to accelerate back to the surface velocity of respective plates  12 ,  13 , in order to effectively receives images from respective plate  12 ,  13 . In this embodiment spacing on a surface of blanket cylinder body  14  between circumferential sections  15 ,  16  and spacing on the surface of blanket cylinder body  24  between circumferential sections  25 ,  26  may be constantly changing as respective surface velocities of circumferential sections  15 ,  16 ,  25 ,  26  change. 
       FIGS. 4   a  to  4   c  show schematic side views of a perfecting printing press  35  according to an embodiment of the present invention while printing press  35  is in successive stages of printing images on a web  37 .  FIGS. 4   a  to  4   c  show an example of how, according to an embodiment of the present invention, circumferential sections may rotate to receive inked images from respective plates and print images on a web, in a manner similar to the embodiment in  FIG. 1 . Printing unit  40  prints on a first side  137  of a web  37  and printing unit  50  prints on a second side  237  of web  37 . Printing units  40 ,  50  each include a plate cylinder  41 ,  51  and two blanket cylinders  242 ,  243 ,  252 ,  253 , respectively. Plate cylinder  41  transfers inked images via plates  48 ,  49  to circumferential sections  44 ,  45 ,  46 ,  47  of blanket cylinders  242 ,  243 . Circumferential sections  44 ,  45 ,  46 ,  47  then print the inked images on first side  137  of passing web  37 . Plate cylinder  51  transfers inked images via plates  58 ,  59  to respective circumferential sections  54 ,  55 ,  56 ,  57  of blanket cylinders  252 ,  253 . Circumferential sections  54 ,  55 ,  56 ,  57  print inked images on second side  237  of passing web  37 . Plate cylinders  41 ,  51  can be rotated by respective motors  101 ,  111  during printing mode. 
     Blanket cylinders  242 ,  252 , via respective circumferential sections  44 ,  45 ,  54 ,  55 , can print every other image on respective sides  137 ,  237  of web  37 , for example, in spaces  69 ,  67 ,  65 ,  63 ,  61 . Blanket cylinders  242 ,  252  can print images on respective sides  137 ,  237  of web  37  at the same time, in the same horizontal position on web  37 . Blanket cylinders  243 ,  253 , via respective circumferential sections  46 ,  47 ,  56 ,  57 , can print images in between the images printed by blanket cylinders  242 ,  252  on respective sides  137 ,  237  of web  37 , for example, in spaces  68 ,  66 ,  64 ,  62 ,  60 . Blanket cylinders  242 ,  252  can print images on respective sides  137 ,  237  of web  37  at the same time, in the same horizontal position on web  37 . Respective images printed in spaces  69 ,  68 ,  67 ,  66 ,  65 ,  64 ,  63 ,  62 ,  61 ,  60  can be aligned with adjacent images, with no unprinted area between the respective images and without the respective images overlapping. 
     Circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  can be accelerated and decelerated about blanket cylinder bodies  42 ,  43 ,  52 ,  53  of respective blanket cylinders  242 ,  243 ,  252 ,  253 , by respective motors  104 ,  105 ,  106 ,  107 ,  114 ,  115 ,  116 ,  117  so that circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  print respective images in the proper positions on web  37 . A surface of circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  can be traveling at the same velocity as web  37  when circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  are printing images on web  37  and can be traveling at the same velocity as a surface of respective plate cylinders  41 ,  51  when circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  are receiving images from respective plates  48 ,  49 ,  58 ,  59 . A controller  200  can control motors  101 ,  104 ,  105 ,  106 ,  107 ,  111 ,  114 ,  115 ,  116 ,  117  so that printing units  40 ,  50  effectively print images on web  37  as desired by a user of printing press  35 . 
     In the embodiments discussed above, circumferential sections  15 ,  16 ,  25 ,  26 ,  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  are disposed about respective blanket cylinder bodies  14 ,  24 ,  42 ,  43 ,  52 ,  53 ; however, alternatively circumferential sections  15 ,  16 ,  25 ,  26 ,  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  may, respectively, be circumferential sections on common axes with no respective blanket cylinder bodies  14 ,  24 ,  42 ,  43 ,  52 ,  53 . For example, blanket cylinder body  42  would be absent, with circumferential sections  44  and  45  independently rotating about a common axis to receive images from plate  48  and print those images on web  37 . 
       FIG. 5  shows a schematic side view of perfecting printing press  35  from  FIGS. 4   a  to  4   c  without blanket cylinder bodies  42 ,  43 ,  52 ,  53 . Circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  rotate about shared respective axes X. Each circumferential section  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  may rotate independent of all other circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57 . Circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  print in substantially the same manner as in perfecting printing press  35  in  FIGS. 4   a  to  4   c . Circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  receive images from plates  48 ,  49 ,  58 ,  59 , respectively, and print these images on web  37 . Although the circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  appear to be wedge-shaped in  FIG. 5 , circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  may be in any form known to one of skill in the art that allows operation in the manner described herein, and may be driven by motors. 
     Cylinder as defined herein includes any rotating device. 
     In addition to the those embodiments described herein, where each plate cylinder  41  and  51  has only two plates  48 ,  49 ,  58 ,  59 , respectively, more than two plates can be disposed around each plate cylinder  41  and  52 . Each blanket cylinder  42 ,  43 ,  52 ,  53 , can also have more than two circumferential sections  44 ,  45 ,  46 ,  47 ,  54 ,  55 ,  56 ,  57  disposed about each blanket cylinder  42 ,  43 ,  52 ,  53 . 
     The present invention will be seen to have the advantage of printing various cutoff copies without changing blankets, blanket sleeves or plate sleeves. 
     The present invention will further be seen to have the advantage of a single plate size used for multiple print lengths. 
     The present invention will further be seen to have the advantage of infinite variability of print cutoff with a design range. 
     The present invention will further be seen to have the advantage of mixing cutoffs in line during the print process. 
     The present invention will be further seen to have the advantage of changing from one cutoff to another with no physical changes required to the press. 
     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.