Abstract:
Devices for converting a printing plate cylinder from a first configuration that provides a first printable length to a second configuration that provides a second printable length greater than the first printable length

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the benefit under 35 USC §119(e) of U.S. Provisional Patent Application No. 61/236,325, filed Aug. 24, 2009, which is incorporated herein by reference in its entirety and for all purposes. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to printing presses. More particularly, the present invention relates to conversion of printing plate cylinders from a first configuration that provides a first printable length to a second configuration that provides a second printable length greater than the first printable length. In an exemplary embodiment, the present invention relates to conversion of printing plate cylinders from a two-page-around configuration to a three-page-around configuration. 
       BACKGROUND 
       [0003]    A schematic drawing of an exemplary printing unit  10  for use in web printing is shown in  FIG. 1 . The printing unit  10  includes, among other functional components, plate cylinders  12  and blanket cylinders  14 . In use, the blanket cylinders  14  press web  16  (or substrate), typically paper, against printing plates,  18  and  20 , mounted on the plate cylinders  12  that include the image to be printed. The printing plates,  18  and  20 , as shown, are wrapped around the plate cylinders  12  and secured in place with two lockup mechanisms,  22  and  24 , that are each removably positioned within respective channel,  26  and  28 , of the plate cylinders  12 . 
         [0004]    The printing unit  10  illustrated in  FIG. 1  is conventionally referred to as being configured for two-page-around printing because two printing plates are used to form two printed pages. In one configuration, both printing plates have the same image so that two identical pages are printed with one revolution of the plate cylinders  12 . In another configuration, the printing plates have different images such as consecutive pages so that two pages can be printed with one revolution of the plate cylinders  12 . 
         [0005]    Referring to  FIG. 2 , an exemplary web  16  to be printed is shown. In the illustrated exemplary two-page-around configuration there are two printable image regions,  15  and  17 , of the web  16  having length x (and width that depends on the particular printing unit) and two non-printable regions,  19  and  21 , of the web  16  where no image is printed having length y. Printable image regions,  15  and  17 , correspond with image regions of printing plates,  18  and  20 , respectively. Non-printable regions,  19  and  21 , include a margin adjacent the ends of printing plates,  18  and  20 , and the space (or gap) between the ends of printing plates,  18  and  20 , that exists when printing plates,  18  and  20 , are held in place with lockup mechanisms,  22  and  24 . In this configuration, the maximum length of a printed page is limited to x. 
         [0006]    In some printing applications it is desirable to maximize the length of printable area. One exemplary application is where it is desired to use a single printing plate to form three pages. Other exemplary applications include where it is desired to print a single page of increased length or plural pages of desired length. Printing plate cylinders configured for forming three pages are conventionally referred to as having a three-page-around configuration. The most common way to convert a printing plate cylinder configured for two-page-around printing to a plate cylinder configured for three-page-around printing is to replace the printing cylinders. Replacement of printing cylinders can be costly and time consuming. Moreover, replacement of printing cylinders requires significant time to convert back to the two-page-around configuration if desired. 
       SUMMARY 
       [0007]    The present invention thus provides devices that can be inserted in place of a lockup mechanism (or similar device) in a printing plate cylinder to convert the printing plate cylinder from a first configuration that provides a first printable length to a second configuration that provides a second printable length greater than the first printable length. 
         [0008]    In an exemplary aspect of the present invention a conversion device for use with a printing plate cylinder to replace a lockup mechanism (or similar device) is provided. The conversion device preferably comprises one or more mounting features to attach the device to a printing plate cylinder and a support surface having a radius substantially matching the radius of a supporting surface of the printing plate cylinder. 
         [0009]    In another exemplary aspect of the present invention a method of converting a printing plate cylinder from a first configuration that provides a first printable length to a second configuration that provides a second printable length greater than the first printable length is provided. The method comprises removing a lockup mechanism (or similar device) from a channel of a printing plate cylinder and positioning a conversion device in accordance with the present invention in the channel of the printing plate cylinder, wherein the conversion device comprises a supporting surface having a radius matching the radius of the supporting surface of the printing plate cylinder. 
         [0010]    In another exemplary aspect of the present invention a method of converting a printing plate cylinder from a two-page-around configuration to a three-page-around configuration is provided. The method comprises removing a lockup mechanism (or similar device) from a channel of a printing plate cylinder and positioning a conversion device in accordance with the present invention in the channel of the printing plate cylinder, wherein the conversion device comprises a supporting surface having a radius matching the radius of the supporting surface of the printing plate cylinder. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The accompanying drawings, which are incorporated in and constitute a part of this disclosure, illustrate several aspects of the present invention and together with description of the exemplary embodiments serve to explain the principles of the present invention. A brief description of the drawings is as follows: 
           [0012]      FIG. 1  is a schematic view of an exemplary printing unit showing plate cylinders having printing plates and that can include a conversion device in accordance with the present invention in the place of a lockup mechanism (or similar device). 
           [0013]      FIG. 2  is a schematic view of an exemplary web that can be printed on with the printing unit shown in  FIG. 1  and showing exemplary printable and non-printable areas for an exemplary two-page-around configuration. 
           [0014]      FIG. 3A  is a partial perspective view of an exemplary plate cylinder having an exemplary conversion device in accordance with the present invention in the place of a lockup mechanism (or similar device). 
           [0015]      FIG. 3B  is an end view of the plate cylinder of  FIG. 3A . 
           [0016]      FIG. 3C  is a partial cross-sectional of the plate cylinder of  FIG. 3A . 
           [0017]      FIG. 3D  is a partial top view of the plate cylinder of  FIG. 3A . 
           [0018]      FIG. 4  is a schematic view of an exemplary web that can be printed on with the printing unit shown in  FIG. 1  and showing exemplary printable and non-printable areas for an exemplary single plate configuration in accordance with the present invention. 
           [0019]      FIG. 5A  is a partial cross-sectional view of the conversion device of the plate cylinder of  FIGS. 3A-3D . 
           [0020]      FIG. 5B  is a partial cross-sectional view of the conversion device of the plate cylinder of  FIGS. 3A-3D  and showing in particular an exemplary fastener used to fasten the conversion device to the plate cylinder in accordance with the present invention. 
           [0021]      FIG. 5C  is a partial cross-sectional view of a portion of the conversion device of the plate cylinder of  FIGS. 3A-3D . 
           [0022]      FIG. 6A  is a perspective view of another exemplary conversion device in accordance with the present invention. 
           [0023]      FIG. 6B  is a top view of the conversion device shown in  FIG. 6A . 
           [0024]      FIG. 6C  is a side view of the conversion device shown in  FIG. 6A . 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The exemplary embodiments of the present invention described herein are not intended to be exhaustive or to limit the present invention to the precise forms disclosed in the following detailed description. Rather the exemplary embodiments described herein are chosen and described so those skilled in the art can appreciate and understand the principles and practices of the present invention. 
         [0026]    An exemplary plate cylinder  30  modified in accordance with the present invention is illustrated in  FIGS. 3A-3D . Plate cylinder  30  is modified in accordance with the present invention to convert plate cylinder  30  from a first configuration using two printing plates (plates not shown) to a second printing configuration using a single printing plate (plate not shown). As shown, plate cylinder  30  includes lockup mechanism  32  positioned in channel  34  and conversion device  36  positioned in channel  38  (replacing the second lockup mechanism). Conversion device  36  is preferably secured in channel  38  with exemplary fasteners  41 , as shown in described below with respect to  FIG. 5B . 
         [0027]    Referring to  FIG. 4 , exemplary web  16  shows printable area  23  and non-printable area  25  for an exemplary single plate configuration in accordance with the present invention. In this exemplary configuration the length of printable area  23  is equal to 2x+y as compared to the web shown in  FIG. 2 . Advantageously, using conversion devices in accordance with the present invention thus provides an increased printable length by providing the ability to print an image in non-image area  19 . 
         [0028]    Referring to  FIGS. 5A-5C , cross-sectional views of conversion device  36  as positioned within channel  34  of plate cylinder  30  are shown. In  FIGS. 5A-5C , printing plate  40  is shown as operatively positioned on and supported by plate cylinder  30 . Referring to  FIG. 5B , a partial cross-sectional view of conversion device  36  taken through exemplary fastener  41  is shown. Fastener  41 , as shown, comprises a conventional threaded bolt. It is contemplated however, that any desired fastening technique can be used to functionally and operatively secure a conversion device relative to a plate cylinder in accordance with the present invention. Moreover, fasteners that provide additional functionality, such as for adjusting the position of a conversion device relative to a plate cylinder in accordance with the present invention can be used. Devices for providing such adjusting can also comprise a device distinct from a device, such as a fastener or the like, for securing a conversion device relative to a plate cylinder in accordance with the present invention. 
         [0029]    In typical use, pressure is applied to printing plate  40  to transfer an image from printing plate  40  to a substrate or web such as paper, for example. To provide image transfer, printing plate  40  needs to be properly and sufficiently supported to receive such pressure. ASuch support is provided by the outside surface of plate cylinder  30  and is important for achieving the desired image quality. However, when a plate cylinder having plural lockup mechanisms (or similar devices), such as exemplary plate cylinder  30 , is used with a single printing plate (such as printing plate  40 ), only one of the lockup mechanisms is needed. Omission of the additional lockup mechanism(s) creates an undesired gap in the supporting surface of the plate cylinder corresponding with the channel of the additional lockup mechanism(s). See for example, channel  38  of plate cylinder  30 . This gap causes the region of printing plate corresponding with the gap to be unsupported, which can cause poor or no image transfer at that region. 
         [0030]    Exemplary conversion device  36  in accordance with the present invention can be used to replace a lockup mechanism (or similar device) and provide adequate support of printing plate  40  to prevent undesired loss of image transfer. Using a conversion device in accordane with the present invention, a plate cylinder configured for use with two (or more) printing plates can easily be converted to a plate cylinder configured for use with a single printing plate. Advantageously, the entire plate cylinder does not need to be replaced. 
         [0031]    A conversion device in accordance with the present invention is preferably designed to mount in place of a lockup mechanism (or similar device) of a printing cylinder. Preferably, mounting features of the plate cylinder such as threaded holes and the like are used to mount the conversion device to the printing cylinder to avoid the need to modify the printing cylinder. Any mounting for securing techniques for positioning a conversion device in accordance with the present invention relative to a plate cylinder can be used. 
         [0032]    A conversion device in accordance with the present invention preferably provides a supporting surface for a printing plate in place of a gap created by omission of a lockup mechanism (or similar device). Preferably, the supporting surface of the conversion device has the same radius as that of the outside supporting surface of the printing cylinder. 
         [0033]    Omission of a lockup mechanism of a plate cylinder can potentially create an imbalance when the printing cylinders rotated at printing speeds. A conversion device in accordance with the present invention is preferably designed to provide proper balance of the plate cylinder with which the conversion device is used. In particular, the conversion device can be designed to incorporate geometry that provides proper balancing at desired rotational speeds. Such balancing can also be provided by addition of one or more balancing weights or by removal of material such as by drilling or cutting and opening. 
         [0034]    A conversion device in accordance with the present invention can be made as a single part or can be made of a plurality of assembled parts. 
         [0035]    A conversion device in accordance with the present invention preferably includes one or more features that allow the position of the conversion device to be adjusted relative to a plate cylinder in which the conversion device is installed. In one exemplary embodiment, conventional shims are used. In another exemplary embodiment, mechanical devices integrated with a conversion device are used. For example, one or more set screws can be used to adjust the position of the conversion device relative to a plate cylinder. Preferably, the supporting surface of the conversion device is sufficiently aligned with the supporting surface of a plate cylinder so a sufficiently smooth transition between the supporting surface of the plate cylinder and the supporting surface of the conversion device is provided. See  FIG. 5C , for example, which shows the portion of  FIG. 5A  identified with reference numeral  43 . Preferably, as shown, conversion device  36  includes bench  45  that minimizes any potential gap (or un-supporting region) between conversion device  36  and plate cylinder  30 . Conversion device  36 , in the region where conversion device  36  meets plate cylinder  30 , may comprise any features or geometry such as extension portions or the like that function to minimize any potential gap formed between conversion device  36  and plate cylinder  30 . 
         [0036]    Any desired material can be used for a conversion device in accordance with the present invention. Preferably, the material used for a conversion device matches the material used for a plate cylinder of which the conversion device is used. The materials of the conversion devices and plate cylinders do not, however, need to match. Dissimilar materials can be used, if desired. 
         [0037]    An exemplary conversion device  42  in accordance with the present invention is shown in  FIG. 6  and can be used in the same manner as described with respect to conversion device  36  herein. Conversion device  42  comprises mounting features  44  for attaching conversion device  44  to a plate cylinder and includes openings  46  for mass management of conversion device  42 . Conversion device  42  also includes support surface  48  and which is formed to have the radius of the plate with which conversion device  42  will be used. Other geometrical aspects of conversion device  42  are determined based on the particular plate cylinder with which conversion device  42  will be used. 
         [0038]    The present invention has now been described with reference to several exemplary embodiments thereof. The entire disclosure of any patent or patent application identified herein is hereby incorporated by reference for all purposes. The foregoing disclosure has been provided for clarity of understanding by those skilled in the art of printing technology. No unnecessary limitations should be taken from the foregoing disclosure. It will be apparent to those skilled in the art that changes can be made in the exemplary embodiments described herein without departing from the scope of the present invention. Thus, the scope of the present invention should not be limited to the exemplary structures and methods described herein, but only by the structures and methods described by the language of the claims and the equivalents of those claimed structures and methods.