Sheet Conveyance Apparatus Early Jam Detection Mechanism
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Solution Overview
Problem
Conventional image forming apparatuses fail to detect sheet jams at an early stage, leading to potential damage and operational inefficiencies.
Innovation Solution
A sheet conveyance apparatus featuring a first moving member with a projection portion that retracts upon contact with the sheet, and a second moving member that moves relative to the first, allowing for early detection of sheet jams by altering the position of a detection unit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single sheet discharge sensor is used to detect the trailing edge of the sheet, then the device complexity is reduced, but the jam detection timing is delayed
Solution Approach 1:
The detection function is segmented into two independent detection units: a leading edge detection unit that detects when the leading edge of the sheet passes through, and a trailing edge detection unit that detects when the trailing edge passes through. This segmentation allows each unit to perform its specific detection function independently, enabling earlier jam detection without significantly increasing overall device complexity.
Solution Approach 2:
The leading edge detection unit performs preliminary detection to determine when the sheet enters the discharge path. By establishing this timing reference in advance, the system can then accurately measure the time interval until the trailing edge is detected, enabling early jam detection before the sheet fully discharges.
2Reliability
If the sheet discharge sensor detects the trailing edge after the sheet has already passed through, then the detection timing is delayed, but the manufacturing precision and reliability are maintained
Solution Approach 1:
The detection system is segmented into two spatially separated detection units positioned at different locations in the discharge path. The leading edge detection unit is positioned upstream to detect sheet entry, while the trailing edge detection unit is positioned downstream to detect sheet exit. This spatial segmentation enables the system to detect abnormalities during the conveyance process rather than after the sheet has fully discharged, maintaining both reliability and timely detection.
Solution Approach 2:
The leading edge detection unit performs preliminary detection to establish the timing when the sheet enters the discharge path. This preliminary timing information is then used as a reference to calculate the time interval until the trailing edge is detected. By having this reference in advance, the system can identify jams early without compromising detection accuracy.
3Productivity
If the conveyance unit continues operating after jam occurrence, then productivity is maintained, but damage risk increases
Solution Approach 1:
The detection units provide continuous feedback signals to the control unit about the sheet's position and movement status. When the trailing edge detection unit detects the trailing edge at an abnormal time interval, it sends a feedback signal to the control unit, which then stops the conveyance unit. This feedback mechanism allows the system to maintain productivity under normal conditions while automatically preventing damage when jams occur.
Solution Approach 2:
The system performs preliminary detection of the trailing edge position and time interval before any damage can occur. By detecting the trailing edge early and comparing its position against the expected timing window, the system can stop the conveyance unit in advance, preventing the sheet from causing damage while maintaining continuous operation during normal productivity periods.
Data Source
AI summary
A sheet conveyance apparatus includes a conveyance unit and first and second moving members respectively including first and second projection portions. When the first projection portion contacts a sheet, the first moving member is moved from a first projection position, where the first projection portion projects to a conveyance path, to a first retraction position, where the first projection portion is retracted from the first projection position. When the first moving member moves to the first retraction position, the second moving member moves from a second retraction position, where the second projection portion is retracted from the second projection position, to a second projection position, where the second projection portion projects to the conveyance path. When a sheet pushes the second projection portion, the second moving member is moved from the second projection position to the second retraction position with the first moving member located at the first retraction position.