Abstract:
A multiple-image-carrying cylinder has a cylinder section having at least part of a first image to be printed, a shell axially movable with respect to the cylinder section, the shell having at least part of a second image to be printed, and a ring located between the shell and the cylinder section and axially movable with respect to the shell and the cylinder section, the ring capable of having another part of the first image when connected to the cylinder section and capable of having another part of the second image when connected to the shell.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates generally to printing presses and other imaging devices and more particularly to an image-carrying cylinder. 
     2. Background Information 
     In a web offset lithographic printing press, a printing plate for an image to be printed is inked, and the image is then transferred to a blanket, which transfers the image to a continuous web of material. The printing press typically has four printing units, each for printing one of four colors on the web. As the web passes by the blanket cylinders of the printing units, it becomes moist, which can lead to an expansion of the web. The expansion of the web in the axial direction of the printing cylinders is known as web fanout. If fanout occurs, the print or images on the web thus expand slightly as the web passes each printing unit. The second and further printing units need to be properly registered with respect to the web images or print in an axial direction of the cylinders, so that, for example, a second color is applied by the second print unit directly over an image already printed by the first printing unit. 
     For some printing applications, multi-plate plate cylinders carrying a plurality of images across the width of the cylinder are used. These plate cylinders have a plurality of axially-spaced printing plates. For proper register of each printing plate and to correct web fanout, the plates may be movable independently of one another in an axial direction. 
     U.S. Pat. No. 4,207,815 purports to disclose a two-plate plate cylinder. One plate fits on a large diameter portion and another plate fits on a tube rotatable and axially movable with respect to the large diameter portion. The tube is fastened to a stepped shaft. Helical gearing is provided to set the axial and circumferential register of the plates. 
     U.S. Pat. No. 5,383,393 purports to disclose a multicolor lithographic rotary press comprising a plurality of printing sections arranged along a traveling line of a paper web, a plurality of register adjusting means, a paper stretching means, and a plurality of width adjusting means. Each of the printing sections further includes at least one divided plate cylinder, each divided section of which is independently moved in the axial direction and/or circumferential direction. The device of the &#39;393 patent further discloses a register adjusting means mechanically connected to each of the divided plate cylinders in the printing sections, and includes an adjusting mechanism for actuating the divided sections in response to the control unit connected to a sensor for detecting the lines and images printed on the paper web by each of the printing sections. 
     BRIEF SUMMARY OF THE INVENTION 
     Commonly-owned U.S. Ser. No. 09/627,639 entitled “Multi-Plate Plate Cylinder for a Printing Press”, which is hereby incorporated by reference herein, discloses a multi-plate plate cylinder having independently registerable shells. Commonly-owned U.S. Ser. No. 09/675,494 entitled “Web Fanout Control System”, which is hereby incorporated by reference herein, discloses a web fanout control system for a printing press having multiple images carrying by the plate cylinder. 
     An object of the present invention is to provide a multiple-image-carrying cylinder and printing press that can accommodate variable image and web format sizes, i.e., different image and web widths. An alternate or additional object of the present invention is to permit web fanout control and proper register for such a printing press. 
     The present invention provides a multiple-image-carrying cylinder having a cylinder section having at least part of a first image to be printed. A shell is axially movable with respect to the cylinder section, the shell having at least part of a second image to be printed. A ring located between the shell and the cylinder section and is axially movable with respect to the shell and the cylinder section, the ring capable of having another part of the first image when connected to the cylinder section and capable of having another part of the second image when connected to the shell. 
     “Ring” and “shell” as defined herein are simply any type of structure having at least a partially curved outer surface. 
     By having the ring move between the cylinder section and the shell, various width images can be accommodated by the cylinder, while still permitting web fanout control and proper register. 
     A controller can set the shell as a function of a web width. 
     If the first image, for example, is narrow enough to fit entirely on the cylinder section, the ring is moved against the shell. The second image next to the first image thus is located on the outer surface of both the ring and the shell. The ring and shell can then move together axially to provide proper web fanout control. 
     If a new wider image is desired to replace the narrow first image, the ring is moved against the cylinder section and the wider image is located on both the cylinder section and the ring. A new image alongside the wider image is located entirely on the shell. The cylinder section and the ring then remain together and the shell can move to provide web fanout control and spacing between the two images. 
     Additional rings, axially movable with respect to the ring, shell and cylinder section, can be provided between the shell and the cylinder section to provide for even more formats. 
     Preferably, the cylinder section is axially stationary. 
     An additional shell maybe provided opposite the shell on another side of the cylinder section, as is an additional ring. 
     In a preferred embodiment, at least six images are carried by the cylinder section, the shell and the ring. Thus a six-image-wide press with the capability to support variable formats and to provide web fanout control is provided. 
     Preferably, the cylinder is a plate cylinder for carrying at least two flat printing plates. The cylinder section, shell and ring then all provided with axially-extending gaps having lock-up mechanisms. The lock-up mechanisms can be controlled for example by hydraulic pressure, and may be similar for example to those disclosed in U.S. Pat. No. 5,284,093 to Guaraldi et al., which is hereby incorporated by reference herein. 
     The axial movement of the shell and ring may be controlled by a mechanical actuator or a hydraulic actuator. The mechanical actuator for example may include a motor and lateral drive gear for the shell and a lateral drive gear for the ring. A throwoff gear connects the shell drive gear and the ring drive gear. If the throwoff gear is engaged, the ring moves with the shell and if the throwoff gear is disengaged, the ring remains with the cylinder section. 
     With the gear thrown off, manual adjustment of the ring is also possible. 
     Preferably, the shell and the ring have outer surfaces that define approximate half circles, with matching other half circles completing the full outer surface, for a two-around press. However, fully circular shells and rings for one-around presses are possible. 
     The shell and ring may be attached by dovetail joints to a cylinder body to permit axial movement, but to limit other movements. The cylinder body for example may have a dovetail slot and dovetails of the shells and rings fit into the slot. The dovetails can be smaller than the slot so that a clearance in the slot results, permitting easy axial movement. A sliding wedge can be used to occupy the clearance to fix the dovetails in place during operation. When axial movement is desired, the sliding wedge can be moved so that the clearance again results. 
     The present invention also provides a method for permitting variable width images on a cylinder comprising the steps of:
         providing a first image to be printed to a first cylinder section;   providing a second image to be printed on a same material as the first image to both a second cylinder section and a third cylinder section connected to the second cylinder section, the second and third cylinder sections being axially movable with respect to the first cylinder section;   removing the first and second images; and   providing a third image wider than the first image to both the first cylinder section and the second cylinder section and a fourth image to the third cylinder section, the first and second cylinder sections being connected and axially movable with respect to the third cylinder section.       

     Preferably, the images are located on flat printing plates, and the cylinder sections all have lock-up mechanisms. However, sleeve-shaped printing plates or direct imaging of the cylinder are also possible. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments of the present invention are described below by reference to the following drawings, in which: 
         FIG. 1  shows schematically and in partial detail a preferred offset lithographic web printing press printing press according to the present invention; 
         FIG. 2  shows a six-image-wide cylinder of the present invention configured for a full width web; 
         FIG. 3  shows the cylinder of  FIG. 2  configured for a narrower web; 
         FIG. 4  shows a cross-section of a cylinder with a two-around shell construction and plate lock-ups; and 
         FIG. 5  shows a preferred axial drive mechanism for moving the shell and two intermediate rings with respect to a cylinder section. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows an exemplary offset lithographic web printing press with a first printing unit  5  and a second printing unit  6 , although typically four such units are provided for a four-color press. Printing unit  6  has a first plate cylinder  10 , a first blanket cylinder  12 , a second plate cylinder  20  and a second blanket cylinder  22 . 
     A web  2  is printed with side-by-side images, for example six wide, in a first color in first printing unit  5 . Second printing unit  6  then prints a second color over the first images. Due to fanout of web  2 , the images printed by the second printing unit  6  may be laterally adjusted to compensate for the fanout. 
     A control unit  200 , for example one including a microprocessor, can read inputs from sensors  201 ,  202  for determining a width of web  2 . The sensors  201 ,  202  can be located after or before the blanket cylinders  12 ,  22 . Control unit  200  can then set the proper web width, as will described below. 
       FIG. 2  shows the cylinder  10  in more detail printing a full width web. Cylinder  10  includes a first shell  31 , a first ring  32 , a stationary center cylinder section  33 , a second ring  34 , and a second shell  35 . Shells  31  and  35 , as well as rings  32  and  34  are axially movable with respect to center cylinder section  33 . 
     Shell  31  has a width WS, rings  32  and  34  have a width WR, and section  33  has a width WC. A distance FD for fanout control is adjustable depending on the desired fanout compensation. 
     In  FIG. 2 , a full-width web is printed with six images I 1 , I 2 , I 3 , I 4 , I 5 , I 6 . Shell  31  accommodates images I 1  and I 2 , ring  32  and part of section  33  accommodate image I 3 , the other part of section  33  and ring  34  accommodate image I 4 , and shell  35  accommodates images I 5 , I 6 . The images preferably are located on flat printing plates which are attached to their respective cylinder parts  31 ,  32 ,  33 ,  34 ,  35  by lock-up mechanisms. 
       FIG. 4  shows for example a cross section through X—X of FIG.  2 . Image  11  is carried on printing plate  40  secured by a lock-up mechanism  50  actuated by a hydraulically-actuated piston  53 . Shell  31  can be moved axially via a drive  56 , shown schematically in  FIG. 4. A  dovetail  54  of shell  31  fits in a dovetail slot of a cylinder body  60  of cylinder  10 . Cylinder body  60  may be integral with cylindrical section  33  (FIG.  2 ). A clearance  57  in the dovetail slot may be filled with a lock mechanism  55 , which preferably is an axially-extending movable wedge that can fix the shell  31  to cylinder body  60  via friction. 
     The cylinder  10  maybe two-around, in which case a paired shell  131 , second printing plate  42 , and second lock-up mechanism  52  are also provided, as shown in FIG.  4 . In a one-around press, shell  31  is substantially circular. Presses with more than two images located circumferentially around the cylinder are also possible. 
     Rings  32 ,  34  and shell  35  may have a similar construction to shell  31 , and may also have corresponding paired rings or shells located circumferentially around the cylinder  10  for a two-around press. 
     All of the lock-up mechanisms for rings  32 ,  34 , shells  31  and  35  and cylindrical section  33  may be hydraulically actuated. Drive  56  can move both shell  31  and ring  32  axially and independently, and a similar drive may be provided on the opposing side for ring  34  and shell  35 . 
     For a different extra ring embodiment of the present invention,  FIG. 5  shows a drive  156  for shell  31 , ring  32  and a second ring  132  in more detail. A motor shaft  70  can rotate a shell drive gear  71 , which rotates a shell shaft  72  supported rotatingly in a fixed support  79 . The other end of shaft  72  has threading which interacts with threading  73  of shell  31  to cause axial movement of shell  31  upon rotation of shaft  72 . Also supported in support  79  are shafts  86  and  87  which interact with threading  88  of ring  32  and threading  89  of ring  132 , respectively. Throw-off gear  75  selectively connects gears  71  and  76  to permit shell  31  and ring  32  to move together. Throw-off gear  78  selectively connects gears  76  and  77  to permit rings  32  and  132  to move together. When throw-off gears  75  and  78  are disengaged, gears  76  and  77  are manually adjustable. 
     Drives  56  and  156  can be controlled by controller  200  (FIG.  1 ), which can thus set the position of rings  132 ,  32 ,  31  as a function of the web width, and also provide for fanout compensation. 
     For the cylinder  10  shown in  FIG. 2 , the gears  77 ,  78  and shaft  87  are unnecessary, since a second ring  132  is not present. Drive  56  thus has may have only two shafts similar to shafts  72  and  86 . 
     For web fanout control of cylinder  10  in  FIG. 2 , the throw-off gear for drive  56  remains disengaged, as only the shell  31  need to be moved to adjust fanout compensation distance FD. 
     If it is desired that a narrower width web be printed with narrower images, the plates or images I 1 , I 2 , I 3 , I 4 , I 5 , I 6  can be removed. Shell  31  can be moved against ring  32 , and the throw-off gear engaged so that ring  32  and shell  31  move together. As shown in  FIG. 3 , narrower images I 1 ′, I 2 ′, I 3 ′, I 4 ′, I 5 ′ and I 6 ′ can then be placed on the cylinder  10 , with image I 2 ′ spanning both ring  32  and part of shell  31  and image I 4 ′ spanning both ring  34  and part of shell  35 . Section B 1  of shell  31  and section B 2  of shell  35  can remain blank. Since shell  31  and ring  32  move together, drive  56  can compensate for fanout by creating a compensation distance FD′. 
     Thus a variable width image-carrying cylinder can be provided which also permits proper fanout control. 
     Instead of the fully mechanical drive  56 , it is also possible to move shell  31  mechanically and move the ring  32  axially via an hydraulic mechanism. The shells and rings may be fixed in place axially by a movable wedge in a dovetail joint clearance. 
     Preferably, the shell width WS is greater than the cylinder section width WC and greater than or equal to section width WC and ring width WR combined. In  FIG. 2 , WS=WC+2*WR, so that the web width is 3*WS (without fanout). In  FIG. 3 , the web width is 3*WC (without fanout). 
     In the embodiment of  FIG. 2 , it should be noted that a single ring could be provided, while still proving variable width capability. The web  2  however would not necessarily be centered on the section  33  at all widths. Moreover, if the web  2  need not be centered on section  33 , the 2-ring embodiment of  FIG. 2  can provide another web width equal to 3*(WC+WR).