Multi-feed Detection Using Dual Optical Sensors
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Solution Overview
Problem
Existing multi-feed detection technologies in image forming apparatuses face challenges in accurately detecting multi-feed conditions across various paper types, particularly with coated papers and two-ply papers, due to issues like paper scratching with contact sensors, ultrasonic wave attenuation, and limited applicability of ultrasonic and photo-interrupter technologies.
Innovation Solution
A multi-feed detection apparatus utilizing two movement amount sensors positioned on either side of the paper path to detect the movement difference of sheets, with a determination module that assesses the difference in movement amounts to determine multi-feed, and adjusts thresholds based on paper type, humidity, and cumulative usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a contact sensor such as a displacement meter is used to detect multi-feed, then multi-feed detection can be performed, but the paper face is scratched due to contact by a lever
Solution Approach 1:
The patent replaces the mechanical contact sensor (displacement meter with lever) with a non-contact optical sensor system. The optical sensor detects paper movement by monitoring changes in light reflection or transmission as the paper passes through the sensor beam, thereby detecting multi-feed conditions without physically contacting the paper surface and causing scratches.
Solution Approach 2:
The patent introduces light as an intermediary medium between the sensor and the paper. Instead of direct mechanical contact, the optical sensor uses light beams to detect paper position and movement. When multi-feed occurs, the light reflection or transmission characteristics change, enabling detection without physical contact with the paper surface.
2Object-affected harmful factors
If an ultrasonic sensor is used to detect multi-feed, then non-contact detection is achieved, but the attenuation factor of ultrasonic wave differs depending on the paper type making it difficult to detect multi-feed independently of paper type
Solution Approach 1:
The patent changes the detection parameter from ultrasonic wave attenuation (which varies with paper type) to optical properties such as light reflection or transmission intensity. By using optical sensors, the detection method becomes less sensitive to paper type variations, as the optical characteristics of different paper types are more consistent and can be standardized across various paper materials including coated papers and two-ply papers.
3Reliability
If a photo-interrupter is used to detect multi-feed, then detection can be performed, but it is limited to translucent paper
Solution Approach 1:
The patent inverts the detection approach from transmission-based (photo-interrupter measuring light passing through paper) to reflection-based (optical sensor measuring light reflected from paper surface). This inversion allows detection of both translucent and opaque papers, as the reflection method does not require light to pass through the paper material, thereby expanding applicability to all paper types including coated and thick papers.
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
Enables accurate and non-contact multi-feed detection independent of paper type, preventing paper damage and improving print quality by early detection and appropriate conveyance control.
Implementation Method 1
a first movement amount sensor disposed on the paper path to face a first surface of the sheet to detect a movement amount of the sheet; a second movement amount sensor disposed, on the paper path, in a position at which the first movement amount sensor is disposed to face a second surface of the sheet to detect a movement amount of the sheet
Data Source
AI summary
A multi-feed detection apparatus for detecting multi-feed of a sheet conveyed along a paper path is provided. The apparatus includes a first movement amount sensor disposed on the paper path to face a first surface of the sheet to detect a movement amount of the sheet; a second movement amount sensor disposed, on the paper path, in a position at which the first movement amount sensor is disposed to face a second surface of the sheet to detect a movement amount of the sheet; and a determination portion configured to determine that a conveyance state of the sheet is multi-feed when a difference between the movement amount of the sheet detected by the first movement amount sensor and the movement amount of the sheet detected by the second movement amount sensor is equal to or greater than a threshold.