Abstract:
A folder includes a first signature conveyor conveying first signatures along a first signature path; a second signature conveyor conveying second signatures along a second signature path; and a chopper located between the first and second signature paths imparting a fold on both the first and second signatures. A chopper and method are also provided.

Description:
[0001]    The present invention relates generally to printing presses, and more particularly to a folder for a printing press. 
       BACKGROUND OF THE INVENTION 
       [0002]    In the web offset printing process, a continuous web of paper is transported through a printing press. Near the beginning of the press, one or more printing units apply ink to the web to repeatedly create a pattern, or impression, of text and images. At the end of the press, a web conversion machine, such as a folder, is typically used to cut and fold the web into signatures. 
         [0003]    There are many known ways to convert a web into signatures. The web is commonly slit into ribbons, which can be stacked on top of each other and then former folded. Some folders, such as pinless former folders, cut the ribbons or web and deliver one or more streams of signatures. Other folders, such as combination folders, commonly introduce additional folds, such as half-folds and quarter-folds. 
         [0004]    A common method of creating a quarter fold uses a chopper module. A chopper module has a blade that forces signatures through a nip formed by two rotating rollers. The signature is folded as it passes through the nip. 
         [0005]    As shown in  FIG. 1 , due to limitations on space between consecutive signatures, paper dynamics, and mechanical component strength, a high speed folder  10  typically has two chopper modules  12 ,  14 , each folding every other signature. Using two chopper modules  12 ,  14  allows both chopper modules  12 ,  14  to run at roughly half the speed of the printing press, making it possible to produce high quality quarter folded products. Chopper modules  12 ,  14  are expensive from both a cost and space standpoint. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a folder including a first signature conveyor conveying first signatures along a first signature path; a second signature conveyor conveying second signatures along a second signature path; and a chopper located between the first and second signature paths imparting a fold on both the first and second signatures. 
         [0007]    The present invention also provides a chopper including a chopper drum having a first axis of rotation; a chopper blade attached to the chopper drum and having a second axis of rotation different from the first axis of rotation; and two chopper tables having gaps, the chopper blades extending through the gaps as the chopper drum rotates about the first axis of rotation and the chopper blade rotates about the second axis of rotation. 
         [0008]    The present invention also provides a method for folding signatures using a chopper including the steps of transporting first signatures along a first signature path; transporting second signatures along a second signature path; and folding the first and second signatures using a common chopper located between the first and second signature paths. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1  shows a prior art folder having two chopper modules. 
           [0010]    A preferred embodiment of the present invention will be elucidated with reference to the drawings, in which: 
           [0011]      FIGS. 2A and 2B  show two-dimensional views of a chopper module according to the present invention; and 
           [0012]      FIGS. 3A and 3B  show three-dimensional views of a chopper module according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIGS. 2A and 2B  describe a chopper module  20  according to the present invention, having a chopper drum  22 , a chopper blade  24 , an upper chopper table  26 , a lower chopper table  28 , upper rollers  30 ,  32  and lower rollers  34 ,  36 . During folder operation, chopper drum  22  rotates about center axis CA 1 . As chopper drum  22  rotates, chopper blade  24  rotates with respect to chopper drum  22  about center axis CA 2 . 
         [0014]    When chopper blade  24  is above and below center axis CA 1 , chopper blade  24  extends radially outward from center axis CA 1 . As shown in  FIG. 2A , when chopper blade  24  is above center axis CA 1 , chopper blade  24  passes through a gap  38  in upper chopper table  26  and approaches a nip  40  formed by upper rollers  30 ,  32 . As shown in  FIG. 2B , when chopper blade  24  is below center axis CA 1 , chopper blade  24  passes through a gap  42  in lower chopper table  28  and approaches a nip  44  formed by lower rollers  34 ,  36 . 
         [0015]    During folder operation, signatures are transported along a first signature path  45  and a second signature path  47 . First signature conveyors  62 ,  162  transport every other signature along first signature path  45  adjacent to inner surface  46  of chopper table  26 . Second signature conveyors  64 ,  164  transport intermediate signatures along second signature path  47  adjacent to inner surface  48  of chopper table  28 . When the signatures are properly positioned next to chopper drum  22 , chopper blade  24  pushes the signatures through gaps  38 ,  42  and into nips  40 ,  44  to create folds. Transport tapes  50 ,  56  or other guides carry the folded signatures to fans  52 ,  58 . Fans  52 ,  58  place the signatures on deliveries  54 ,  60 . 
         [0016]      FIGS. 3A and 3B  show three-dimensional views of chopper module  20  in the same configurations as  FIGS. 2A and 2B , respectively. Rollers  30 ,  32 ,  34 ,  36  are omitted from  FIGS. 3A and 3B  so that chopper blade  24  can be seen passing through gaps  38 ,  42 . 
         [0017]    Chopper module  20  is similar to prior art chopper modules  12 ,  14  except that chopper module  20  includes upper chopper table  26  and upper rollers  30 ,  32 . By adding upper chopper table  26  and upper rollers  30 ,  32 , the radial extension of chopper blade  24  above center axis CA 1  can be used to create an additional fold. In the prior art, this extension of the chopper blade above CA 1 , called a phantom chop, is not used to create a fold. 
         [0018]    By using the phantom chop to create a fold, chopper module  20  can produce the same number of folds as prior art chopper modules  12 ,  14  combined. The present invention thus allows two chopper modules  12 ,  14  to be replaced by one chopper module  20 . Chopper module  20  can operate at the same RPM as existing choppers  12 ,  14  and thus can create two folded books of the same quality of the existing choppers  12 ,  14 . Folder design is advantageously simplified and cost-reduced. 
         [0019]    In a further embodiment, a folder can include two chopper modules  20 , each imparting a fold on opposing signatures instead of one chopper module  20 . Using two chopper modules  20  allows the rotational speed of chopper modules  20  to be cut in half for the same output produced by prior art chopper modules  12 ,  14 . The lower rotational speed advantageously produces higher quality folds and reduces the speed requirements of post-press equipment while maintaining the throughput of the folder.