Sheet Feeding Device Driven Roller Jam Detection
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Solution Overview
Problem
Conventional sheet feeding devices inaccurately detect feed jams due to reliance on elapsed time and moving distance detection, which can be affected by changes in transport speed and reverse sheet movement, leading to potential machinery damage and waste.
Innovation Solution
Incorporating a driven roller with a detecting unit that measures sheet movement and a dead-zone mechanism to prevent detection during reverse rotation, ensuring accurate jam detection by setting a range where reverse movement is not detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If elapsed time measurement is used to detect feed jam, then the detection mechanism is simple, but detection accuracy deteriorates when transport speed changes
Solution Approach 1:
The patent changes the detection parameter from time-based to distance-based measurement. The driven roller rotates in response to sheet movement, and the detecting unit measures the rotation amount to calculate moving distance. This parameter change makes detection accurate regardless of transport speed variations, as distance measurement is independent of time-based speed fluctuations.
2Measurement precision
If moving distance detection is used to improve feed jam detection accuracy, then detection accuracy improves, but false detection occurs when sheet moves in reverse direction
Solution Approach 1:
The patent applies local quality by creating a dead zone in specific rotational positions of the driven roller. The dead-zone mechanism prevents detection during reverse rotation by blocking the detecting unit when the roller rotates in the reverse direction. This localized non-detection area allows the system to distinguish between normal forward movement and reverse movement, improving reliability while maintaining detection accuracy.
3Reliability
If dead-zone mechanism is added to prevent reverse movement detection, then detection reliability improves, but device complexity increases
Solution Approach 1:
The patent introduces a dead-zone mechanism as an intermediary component between the driven roller and the detecting unit. This mechanism includes a detection prevention portion that physically blocks the detecting unit during reverse rotation. The intermediary structure allows the system to maintain simple roller-based detection while adding reliability through selective blocking, rather than requiring complex software or multiple sensors.
Data Source
AI summary
A sheet feeding device includes a driven roller that rotates in response to movement of a sheet, and a rotary encoder that detects a moving distance of the sheet based on rotation of the driven roller. The driven roller and the rotary encoder are connected by a gear unit having backlash. When the sheet moves in a reverse direction and thereby the driven roller rotates in reverse, the rotary encoder does not detect the moving distance of the sheet.