Patent Publication Number: US-2010122637-A1

Title: Reverse Air Flow Web Stabilizer

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This is a continuation of U.S. patent application Ser. No. 11/345,801, filed on Feb. 2, 2006, which is hereby incorporated by reference herein. 
    
    
     BACKGROUND 
     The present invention relates to printing presses and more particularly to a web stabilization apparatus. 
     In a web fed rotary printing press having multiple printing units, it may be desired to stop printing one or more printing units by throwing the blanket cylinders away from the web. This can permit, for example, a plate or blanket change. Automatic plate changes can occur using an automatic transfer printing unit. Such a printing press is, for example, manufactured by Goss International as the Sunday 2000 Autotransfer Press. 
     When the blanket cylinders are separated from the web, the web can pass freely between the two blanket cylinders. As the web passes between the separated blanket cylinders the web may demonstrate out-of-plane vibrations. More specifically, these out-of-plane vibrations can occur when the auto transfer unit blanket cylinders are rotating while off impression and when the web is passing through at normal printing speeds. 
     When the web experiences out-of-plane vibrations, unintentional web contact can occur with the blanket cylinders. Unintentional web contact with the blanket cylinders could result in print defects on the web or web breakage. It is known in the printing industry to use rollers located upstream and downstream from a printing unit in an attempt to stabilize a moving web. However, rollers can produce marking or damage to the web. 
     U.S. Pat. No. 5,924,619, hereby incorporated by reference herein, describes an apparatus for passing a printed web between separated cylinders of a deactivated printing unit, and uses blast air devices. 
     Referring to  FIG. 1 , a prior art printing press  100  is shown with a web  110  and without a web stabilization device. Printing press  100  has printing units  105 - 1  through  105 - a , where a is a predetermined value, preferably 5 or 8 for an automatic transfer press with 5 units having two black printing units and 8 having two printing units each for magenta, cyan, yellow and black. The printing units  105 - 1  through  105 - a  each have 4 cylinders, 2 blanket cylinders, 2 plate cylinders and 2 automatic plate changers. Printing unit  105 - 1  has blanket cylinders  115 - 1   a,b  plate cylinders  120 - 1   a,b , and automatic plate changers  160 - 1   a,b . Print unit  105 - 2  has blanket cylinders  115 - 2   a,b  and plate cylinders  120 - 2   a,b , where all 4 cylinders are rolling without contact, which can permit, for example, automatic plate transfer by automatic plate changers  160 - 2   a,b . As shown in  FIG. 1 , as web  110  moves in the direction denoted by arrow  125 , web  110  experiences out-of-plane vibrations (denoted by arrow  130 ) where unintentional web contact can occur with blanket cylinders  115 - 2   a,b.    
     SUMMARY OF THE INVENTION 
     The present invention provides a web print unit including a first plate cylinder, a first blanket cylinder for contacting the first plate cylinder, a second blanket cylinder, and a second plate cylinder for contacting the second blanket cylinder. A web to be printed passes between the first blanket cylinder and the second blanket cylinder at a blanket to blanket location, the first and second blanket cylinders are capable of being thrown apart and rotating while apart. An air source is located on a side of the web and oriented to blow air upstream toward the blanket to blanket location when the cylinders are apart and rotating. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further objects, features and advantages of the invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  illustrates a prior art automatic transfer printing press having multiple printing units without stabilizing a web; 
         FIG. 2  illustrates a printing press with noncontact stabilizers in accordance with an embodiment of the present invention; 
         FIG. 3  illustrates an embodiment of a blower in accordance with an embodiment of the present invention; and 
         FIG. 4  illustrates an embodiment of a blower in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with the embodiments of the present invention, one or more blowers blow air in an upstream direction at the blanket to blanket nip exit in the vicinity of a web, which can reduce flutter and stabilize the web while the blanket cylinders are rotating. 
       FIG. 2  illustrates a printing press of the present invention with blowers  230  and  235  for improving out-of-plane web stability of moving web  210 . As shown in  FIG. 2 , a printing press  200  has print units  205 - 1  through  205 - n , where n is a predetermined value. Each print unit  205 - 1  through  205 - n  is shown with 4 cylinders: blanket cylinders  215 - 1   a,b  through  215 - na,b , plate cylinders  220 - 1   a,b  through  220 - na,b , and automatic plate change units  221 - 1   a,b  through  221 - na,b.    
     As shown in  FIG. 2 , print units  205 - 1  and  205 - n  have all four cylinders rolling and blanket cylinders  215 - 1 a,b and  215 -na,b in contact with web  210 . In contrast, print unit  205 - 2  has blanket cylinders  215 - 2   a,b  and plate cylinders  220 - 2   a,b  rolling without contact with web  210 . Web  210  moves from print unit  205 - 1  to print unit  205 - n  in the direction denoted by arrow  225 . Web  210  passes between print unit  205 - 1  and between print unit  205 - 2  before passing between blowers  230  and  235 . 
     In accordance with an embodiment of the present invention, blowers  230  and  235  are positioned on the exit side of the blanket to blanket nip. Blowers  230  and  235  are oriented to blow air upstream toward the blanket to blanket location, thus decreasing out-of-plane vibrations of web  210 . The destabilizing forces causing web  210  to vibrate out-of-plane are disrupted by the air flow from blowers  230  and  235 , which cause web  210  to return to its nominal running position. Further, in accordance with an embodiment of the present invention, a single blower, for example blower  235 , can be used to stabilize web  210 . 
     Blowers  230  and  235  are moveable by actuators  232  so that the distance and angle between web  210  and blowers  230  and  235  can be adjusted. As mentioned above, the air flows created by blowers  230  and  235  prevent out-of-plane vibrations of web  210  and stabilize web  210  as it exits print unit  205 - 2 . 
     Various embodiments of blowers  230  and  235  in accordance with the present invention are shown in  FIGS. 3 and 4 .  FIG. 3  shows an embodiment where blower  230  has a manifold  325  with 4 air outputs  305  through  320 .  FIG. 4  shows another embodiment where blower  230  includes a single nozzle  405  with an opening elongated in the web width direction for directing the air output towards the blanket to blanket exit nip. The blowers  230  and  235  can be incorporated into existing structures within the printing press. 
     The desired volume flow of air can be determined for example by experiment at certain speeds, and can be varied as a function of web speed. During stabilization the plates can be automatically changed. The number of print units preferably is 5 or more, but can be any number. 
     As opposed to separate blowers, air from any source, such as compressed air available from a compressor in the printing press plant, may be used. For example, compressed air at 90 psi could be connected to a regulator to set nozzle pressure at 10 to 15 psi. Each side of the web may have a regulator, and the pressure or nozzle locations and orientations varied to center or bias the web to a specific location within the blanket-to-blanket gap. For example, the pressure on one side can be lowered or set to zero to move the web in that direction. The pressure or nozzle locations and orientations also could be varied as a function of blanket cylinder speed. 
     Preferably no air is blown from the upstream side into the blanket-to-blanket gap.