The present invention relates generally to printing presses, and more particularly to a folder for a printing press.
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.
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.
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.
As shown in
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.
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.
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.
A preferred embodiment of the present invention will be elucidated with reference to the drawings, in which:
When chopper blade 24 is above and below center axis CA1, chopper blade 24 extends radially outward from center axis CA1. As shown in
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.
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 CA1 can be used to create an additional fold. In the prior art, this extension of the chopper blade above CA1, called a phantom chop, is not used to create a fold.
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.
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.
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