Sheet Folding Device with Shifting Nip Pressure for Wrinkle-Free Folds
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Solution Overview
Problem
Conventional sheet folding technologies face issues with uneven pressure distribution and deflection, leading to wrinkles, due to dispersed pressurizing force and complex control requirements, especially when forming desired fold lines on sheets ejected from image forming apparatuses.
Innovation Solution
A sheet folding device with a fold-enhancing unit comprising multiple rotator pairs, where sheet holding members shift from both sides towards the central portion along the conveying direction, ensuring intensive pressure application and minimizing deflection by using rotator pairs with nip portions that hold both sides and central portions of the sheet.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the nip portion between fold-enhancing rollers is pressurized to form a desired fold line on the sheet, then the fold line is enhanced, but the mechanism causes a deviation in pressure distribution leading to deflection and wrinkles
Solution Approach 1:
The fold-enhancing unit is divided into multiple rotator pairs (first rotator pair and second rotator pair) that operate at different positions along the sheet conveying direction. Each rotator pair applies pressurizing force to different regions of the folded portion, segmenting the pressure application process to prevent deflection and wrinkles while maintaining fold line quality.
Solution Approach 2:
The first rotator pair applies pressurizing force to a first region of the folded portion while the second rotator pair applies pressurizing force to a second region of the folded portion. This local differentiation of pressure application ensures uniform fold enhancement without causing deflection or wrinkles in any specific area.
2Manufacturing precision
If a fold-enhancing roller with whole width nip portion is used to apply fold, then the fold is enhanced, but the pressurizing force is dispersed and a satisfactory fold line cannot be formed
Solution Approach 1:
Instead of using a single fold-enhancing roller with whole width nip portion that disperses pressure, the invention uses multiple rotator pairs positioned at different locations. Each rotator pair concentrates pressurizing force on its specific region, preventing force dispersion while achieving comprehensive fold enhancement across the entire folded portion.
Solution Approach 2:
The invention transitions from a single-dimension pressure application (one roller across the width) to a two-dimension approach by arranging multiple rotator pairs along the sheet conveying direction. This dimensional change allows concentrated pressure application at multiple points simultaneously, preventing force dispersion while maintaining fold line quality.
3Manufacturing precision
If multiple fold-enhancing roller pairs are arranged to enhance fold over the whole sheet, then the fold is enhanced, but control becomes complicated and high productivity is difficult to achieve
Solution Approach 1:
The invention merges the fold-enhancing function into a single integrated unit that contains multiple rotator pairs. This unified structure simplifies control by managing all rotator pairs through one control system, reducing the complexity that would arise from coordinating multiple independent fold-enhancing roller pairs while still achieving uniform fold enhancement across the entire sheet.
4Manufacturing precision
If the fold at the central portion is enhanced first with high pressurizing force, then the fold is enhanced, but the both sides of the sheet move upward causing phase difference and deflection leading to wrinkles
Solution Approach 1:
The first rotator pair applies pressurizing force to a first region of the folded portion before the second rotator pair applies force to the second region. This preliminary action sequence prevents sudden upward movement of the sheet sides by gradually applying pressure from one region to another, eliminating phase differences that would cause deflection and wrinkles while still achieving high-quality fold lines.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration allows for the formation of strong, uniform fold lines without wrinkles, maintaining high productivity by simplifying control and concentrating pressure, thus effectively addressing the issues of dispersed pressure and deflection.
Implementation Method 1
a fold-enhancing unit that performs fold enhancement on the sheet applied with the fold by the folding unit, the fold-enhancing unit including at least two rotator pairs each provided with a sheet holding member that holds and pressurizes the sheet applied with the fold
Implementation Method 2
sheet holding members of the at least two or more rotator pairs are provided so that an area for holding the sheet shifts from both sides of the sheet toward a central portion of the sheet along a sheet conveying direction
Data Source
AI summary
A sheet folding device includes a folding unit that applies a fold to a sheet, and a fold-enhancing unit that performs fold enhancement on the sheet applied with the fold by the folding unit. The fold-enhancing unit includes at least two or more rotator pairs each provided with a sheet holding member that holds and pressurizes the sheet applied with the fold so as to enhance the hold. In the at least two or more rotator pairs, the sheet holding member is provided so that an area for holding the sheet shifts from both sides of the sheet toward a central portion of the sheet along a sheet conveying direction from an upstream to a downstream in the fold-enhancing unit.