Document Feeder Retard Roller Inversion for Double Feed Prevention
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Solution Overview
Problem
Existing document feeders face challenges in efficiently handling overlapping documents, leading to double feeding and conveyance errors, particularly when multiple sheets are stacked or when documents with attachments like sticky notes are processed.
Innovation Solution
A document feeder system incorporating a lift plate, pickup roller, retard roller, and control unit that adjusts the conveyance direction of the retard roller based on mode selection, allowing for separation of overlapping documents and manual feed modes to prevent double feeding and ensure accurate document alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pickup roller continuously feeds documents in the conveyance direction, then document conveyance efficiency is improved, but double feeding occurs when multiple documents overlap
Solution Approach 1:
The retard roller applies a preliminary opposing force to the document being fed by the pickup roller. By rotating in the direction opposite to document conveyance, it creates friction that prevents the document from being fed twice, thus preventing double feeding before it can occur
Solution Approach 2:
Instead of having all rollers rotate in the conveyance direction to improve feeding efficiency, the retard roller is designed to rotate in the opposite direction. This inversion allows it to apply frictional force against the document, preventing unintended continuous sheet feeding while the pickup roller continues to feed documents efficiently
2Reliability
If the retard roller rotates in the direction opposite to conveyance to prevent double feeding, then double feeding is eliminated, but document conveyance speed decreases
Solution Approach 1:
The retard roller is positioned only at a specific location downstream of the pickup roller, applying frictional force only in that local area. This localized action prevents double feeding without creating resistance along the entire conveyance path, thus minimizing the impact on overall conveyance speed
Solution Approach 2:
The control unit dynamically adjusts the rotation speed and direction of the retard roller based on detection signals. By changing the operational parameters of the retard roller, the system can prevent double feeding while minimizing the reduction in document conveyance speed through optimized friction application
3Reliability
If the lift plate raises documents to contact the pickup roller, then document pickup reliability is improved, but documents with attachments like sticky notes may not be properly fed
Solution Approach 1:
The retard roller acts as an intermediary between the pickup roller and the document. It applies frictional force that complements the lift plate's raising action, ensuring that documents with attachments are properly gripped and fed without damaging the attachments or causing feeding failures
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 system effectively prevents double feeding and ensures accurate conveyance of documents, even when multiple sheets are stacked or when documents with attachments are processed, by dynamically adjusting the conveyance direction and speed to maintain document alignment and prevent unintended continuous sheet feeding.
Implementation Method 1
The pickup roller contacts the uppermost document among the documents set on the lift plate. The pickup roller rotates to feed the document in a document conveyance direction.
Implementation Method 2
The retard roller comes into contact with the document fed by the pickup roller. When a normal mode is selected, the control unit rotates the retard roller to feed the document in a direction opposite to the conveyance direction.
Implementation Method 3
The lift motor raises and lowers the lift plate. When starting to feed a document, the lift motor raises the lift plate until the uppermost document comes into contact with the pickup roller.
Data Source
AI summary
A document feeder includes a lift plate, a pickup roller, a lift motor, a retard roller, and a control unit. In a manual feed mode, the control unit rotates the retard roller to feed a document in a document conveyance direction. Further, the control unit causes the lift motor to start lowering the lift plate while the pickup roller is feeding a document after the rotation of the pickup roller is started.