Sheet Folding Device with Angled Nip for Crease Quality
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Solution Overview
Problem
Existing folding techniques for glossy printed sheets result in reduced crease quality due to low friction between sheets, leading to potential sheet rupture and crease shallowness, which is exacerbated by incorrect grain orientation.
Innovation Solution
A method involving pre-folding along a crease line into a main plane, followed by imparting a meandering pattern perpendicular to the main plane to deepen the crease, and optionally repeating this process with mirrored patterns to break fibers in multiple directions, independent of grain orientation, using a device with angled nip rollers and a tiltable arm to enhance crease formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If glossy printing material is used to achieve glossy appearance, then surface quality is improved, but friction between sheets is reduced leading to poor crease quality
Solution Approach 1:
The patent applies preliminary action by pre-folding the stack of sheets along a crease line before the final folding operation. This preliminary fold creates initial fiber breakage and establishes the crease path, ensuring that when the glossy sheets are subsequently folded, the crease forms properly despite the reduced friction between sheets. The pre-fold action prepares the material structure in advance to compensate for the slippery surface properties of glossy printing material.
2Productivity
If knife folding technique is used to fold sheets, then folding speed is improved, but outer sheets slide over each other resulting in reduced crease quality
Solution Approach 1:
The patent applies preliminary action by pre-folding the stack of sheets along a crease line before the final folding operation. This preliminary fold creates initial fiber breakage and establishes the crease path, ensuring that when the glossy sheets are subsequently folded, the crease forms properly despite the reduced friction between sheets. The pre-fold action prepares the material structure in advance to compensate for the slippery surface properties of glossy printing material.
Solution Approach 2:
The patent introduces an intermediary element - a folding plate or anvil - that acts as a mediator between the knife blade and the sheets. This intermediary surface provides the necessary friction and support during the folding process, preventing the outer sheets from sliding over each other while still allowing the knife to create the crease efficiently. The intermediary surface compensates for the low friction between glossy sheets.
3Manufacturing precision
If grain orientation is perpendicular to crease for sharp crease, then crease sharpness is improved, but sheet orientation flexibility is reduced
Solution Approach 1:
The patent applies preliminary action by pre-folding the stack of sheets along a crease line before the final folding operation. This preliminary fold creates initial fiber breakage and establishes the crease path, ensuring that when the glossy sheets are subsequently folded, the crease forms properly despite the reduced friction between sheets. The pre-fold action prepares the material structure in advance to compensate for the slippery surface properties of glossy printing material.
Solution Approach 2:
The patent applies dimensionality change by introducing a meandering pattern in a secondary plane perpendicular to the main folding plane. This additional dimensional deformation causes fibers to break in multiple directions, creating a deep crease that is independent of the original grain orientation. The meandering pattern adds a third dimension to the folding process, transforming a two-dimensional grain orientation problem into a three-dimensional solution.
4Manufacturing precision
If secondary rollers press with higher force to sharpen crease, then crease sharpness is improved, but sheet damage risk increases
Solution Approach 1:
The patent applies preliminary action by pre-folding the stack of sheets along a crease line before the final folding operation. This preliminary fold creates initial fiber breakage and establishes the crease path, ensuring that when the glossy sheets are subsequently folded, the crease forms properly despite the reduced friction between sheets. The pre-fold action prepares the material structure in advance to compensate for the slippery surface properties of glossy printing material.
Solution Approach 2:
The patent applies dimensionality change by introducing a meandering pattern in a secondary plane perpendicular to the main folding plane. This additional dimensional deformation causes fibers to break in multiple directions, creating a deep crease that is independent of the original grain orientation. The meandering pattern adds a third dimension to the folding process, transforming a two-dimensional grain orientation problem into a three-dimensional solution.
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
The method and device create a deeper, higher-quality crease that is less dependent on grain orientation, preventing sheet rupture and improving crease sharpness across the entire booklet length.
Implementation Method 1
urging a part of the back into a meandering pattern, wherein the meandering pattern is caused in a secondary plane perpendicular to the main plane
Implementation Method 2
The meandering pattern is urged along the full length of the back of the booklet, such that additional fibers over the full length are broken
Implementation Method 3
a tilted arm (10) attached to the carriage (11) and forming an angle greater than zero with respect to an axis that passes through the nip (7) and is perpendicular to the direction of movement (C) of the carriage (11)
Data Source
AI summary
Provided herein is a device for folding a stack of sheets. The device includes a frame, means for pre-folding a stack of sheets along a crease line into a main plane such that a booklet with a straight back is obtained, means for keeping the pre-folded booklet relative to the frame, a carriage movably arranged to the frame and moveable parallel to the back of the booklet, and a nip arranged to the carriage for receiving the back of the pre-folded booklet. The nip direction forms an angle greater than zero with respect to a direction of movement of the carriage.