Dynamic Pressing Angle for Staple Deformation in Sheet Folding
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Solution Overview
Problem
Conventional additional-folding techniques for saddle-stitched booklets often result in deformation of staples and drooping of the sheet bundle ends, impairing the stacking property due to fixed angle reinforcement methods.
Innovation Solution
A sheet processing device with a pair of pressing rollers that adjusts the angle between the thickness direction of the folded sheet bundle and the line connecting the centers of the rollers during additional-folding, preventing deformation and drooping by dynamically changing the angle of reinforcement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If additional-folding is performed at a substantially constant angle using conventional techniques, then the fold line part is reinforced, but the staple deforms or the end of the sheet bundle droops, impairing stacking property
Solution Approach 1:
The pressing angle θ is changed dynamically during the additional-folding process. The pressing unit adjusts the angle between the thickness direction of the folded sheet bundle and the line connecting the centers of the pressing rollers in the middle of movement, allowing the folding angle to vary according to the position along the fold line rather than maintaining a constant angle throughout.
Solution Approach 2:
The angle parameter θ is changed during the additional-folding operation. By varying the pressing angle θ between the thickness direction of the folded sheet bundle and the line connecting the centers of the pressing rollers, the invention optimizes fold reinforcement while preventing staple deformation and end drooping that occur with constant angle pressing.
2Strength
If three folding rollers are used with different diameters to create shifted nips, then fold line reinforcement is improved, but the line connecting roller centers shifts from the thickness direction, causing deformation
Solution Approach 1:
Instead of using fixed offset positions with three rollers of different diameters, the invention uses a pair of pressing rollers that dynamically change their pressing angle θ during movement. This allows the line connecting the roller centers to remain aligned with the thickness direction while still achieving variable angle pressing for optimal fold reinforcement without deformation.
Data Source
AI summary
A sheet processing device comprising: a pressing unit that presses a fold line part of a folded sheet bundle; and a moving unit that moves a pressing position of the pressing unit in a fold direction of the folded sheet bundle, wherein the pressing unit includes a pair of pressing rollers that holds the folded sheet bundle therebetween, and the pair of pressing rollers changes an angle θ between a thickness direction of the folded sheet bundle and a line connecting the rotational centers of the pressing rollers in the middle of movement.