Sheet Retraction Curvature Control in Image Forming Apparatus
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Solution Overview
Problem
Existing image forming apparatuses face challenges in handling elongated sheets during double-side printing, as the reverse feeding mechanism can cause increased resistance, leading to sheet damage due to drooping, especially when the sheet length exceeds a certain limit, and existing solutions either increase resistance or fail to prevent drooping effectively.
Innovation Solution
The apparatus incorporates a guiding member with an inner surface curved to guide the sheet in a direction crossing the vertical plane, combined with a preventing member to contact and support the leading end of the sheet, reducing feeding resistance and preventing drooping by ensuring the sheet is retracted in a curved state without increasing resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a retraction feeding passage is curved at a plurality of positions to retract the sheet, then the sheet can be retracted, but the feeding resistance increases particularly at the curved portions
Solution Approach 1:
The retraction feeding passage is divided into multiple sections with different curvature radii. The upstream section has a larger curvature radius while the downstream section has a smaller curvature radius, allowing the sheet to be retracted through curved passages without uniformly high resistance across the entire passage.
Solution Approach 2:
Different sections of the retraction feeding passage have different local properties (curvature radii). The upstream portion uses a larger curvature radius to reduce resistance at the entry point, while the downstream portion uses a smaller curvature radius to achieve effective retraction, optimizing the balance between resistance and retraction capability at different locations.
2Force
If the guiding member is disposed only on one side of the retraction feeding passage to alleviate feeding resistance, then feeding resistance is reduced, but the leading end of the sheet droops due to self-weight
Solution Approach 1:
A supporting member is introduced as an intermediary element in the retraction feeding passage. This supporting member provides lateral support to the sheet at the leading end, preventing drooping due to self-weight, while the guiding member on one side maintains low feeding resistance. The supporting member acts as a mediator between the sheet and the passage structure.
3Reliability
If the sheet is retracted in a curved state to prevent drooping, then sheet damage is prevented, but feeding resistance increases
Solution Approach 1:
The curved retraction feeding passage is segmented into upstream and downstream sections with different curvature radii. The upstream section uses a larger curvature radius to reduce feeding resistance, while the downstream section uses a smaller curvature radius to maintain the sheet in a curved state and prevent damage, achieving both goals through spatial segmentation.
Data Source
AI summary
An image forming apparatus includes an image forming portion, a sheet reversing roller portion, a first sheet feeding passage, a second sheet feeding passage, a sheet a guiding member forming a retraction feeding passage for guiding upward a leading end of the sheet fed from the reversing roller portion rotating in the first direction and then for guiding the sheet, guided upward, in a direction crossing a vertical direction, the guiding member having an inner surface curved to guide one side of the sheet, and a preventing member for preventing a droop of the leading end of the sheet by contact with the sheet guided in the direction crossing the vertical direction by the sheet guiding member.