Document Feeder Skew Prevention via Balanced Paper Presence Flags
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Solution Overview
Problem
Automatic document feeders in scanning apparatuses often cause document skewing due to off-centered paper presence flags, leading to faulty scanning, and existing solutions like de-skew rollers or complex algorithms are costly or computationally demanding.
Innovation Solution
The use of two balanced paper presence flags, pivotally mounted on opposite sides of the document path with adjustable torsion springs to ensure equal friction on both sides of the document, preventing skewing without the need for additional rollers or complex algorithms.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single off-center paper presence flag is used to detect paper presence, then the sensor can detect whether paper is loaded in the input tray, but the off-centered friction from the flag causes one side of the sheet to slow down and results in skewing of the sheet
Solution Approach 1:
The patent applies asymmetry by using two flags positioned symmetrically on opposite sides of the paper path, where each flag is intentionally offset from the centerline but balanced against the other. This asymmetric positioning relative to the paper center creates equal and opposite friction forces that cancel out, preventing skew while maintaining detection capability
Solution Approach 2:
The second flag acts as a counterweight to the first flag, with both flags positioned to create balanced friction forces. The symmetric placement on opposite sides of the paper path ensures that the friction generated by each flag counterbalances the other, eliminating net skewing force while maintaining paper presence detection
2Manufacturing precision
If de-skew or registration rollers are added inside the ADF paper path to prevent skewing, then the sheet can be aligned properly before being advanced, but the cost of the apparatus increases significantly due to additional rollers and a motor
Solution Approach 1:
The patent extracts the skew prevention function from the traditional de-skew roller system and integrates it into the paper presence detection flags. By positioning the flags to create balanced friction forces, the skew prevention capability is achieved using existing detection components rather than adding separate mechanical systems
Solution Approach 2:
The paper presence flags serve multiple functions: they detect whether paper is loaded in the input tray and simultaneously prevent skewing during sheet feeding. This multi-functionality eliminates the need for separate de-skew rollers and motors, reducing device complexity while maintaining alignment precision
3Manufacturing precision
If a skew correcting algorithm is provided to adjust for skewing, then digital de-skewing can be achieved, but the algorithm tends to be very complex and many scanning apparatus do not employ enough computing power
Solution Approach 1:
The patent replaces the computational approach with a mechanical solution. Instead of using complex algorithms to correct skew digitally, the physical flags are positioned to prevent skew mechanically during the feeding process, eliminating the need for computationally intensive processing
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 solution effectively prevents document skewing by ensuring balanced friction during feeding, allowing for accurate scanning without the need for costly additional components or excessive computational power.
Implementation Method 1
adjustable torsion springs to ensure equal friction on both sides of the document
Implementation Method 2
The paper present flag drags on each sheet of the document as it is being fed into the ADF and thus produces friction
Data Source
AI summary
A document feeder includes a tray for holding one or more document sheets and a first flag disposed adjacent to the tray so as to engage a document sheet in the tray. A second flag is disposed adjacent to the tray to engage the document sheet so that the first and second flags produce balanced amounts of friction on the document sheet.