Sheet Conveying Device Guide Rib Height for Reverse Path Stability
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Solution Overview
Problem
Existing sheet conveying devices in image forming apparatuses face challenges in smoothly reversing and guiding sheets during double-sided printing, leading to issues like sheet bending and jamming due to hanging-down of sheet end portions, especially with larger and less stiff print sheets.
Innovation Solution
The implementation of a sheet conveying device with a third conveyance path that reverses the sheet to the image forming portion, utilizing guide ribs of varying heights on the conveyance guide to lift and stabilize the sheet end portions, preventing them from hanging down and ensuring smooth transition through the branch point.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional reverse conveyance path is used without additional guide structures, then the device complexity is reduced, but sheet bending and jamming occur due to hanging-down of sheet end portions
Solution Approach 1:
The conveyance guide is equipped with guide ribs having different heights at different locations. Specifically, the outer guide rib (outward side of discharge roller pair) is formed higher than the inner guide rib (inward side). This local differentiation in rib height provides targeted support to prevent sheet end portions from hanging down at critical locations while maintaining simplicity elsewhere in the structure.
Solution Approach 2:
The guide ribs are positioned in advance along the conveyance path to proactively support the sheet end portions before they can hang down and cause bending or jamming. The higher outer guide rib is strategically placed to preemptively prevent the sheet from sagging outward during reverse conveyance through the branch point.
2Reliability
If guide ribs of uniform height are used, then the manufacturing precision is improved, but sheet stability is reduced due to insufficient support of sheet end portions
Solution Approach 1:
Instead of uniform guide ribs, the invention employs guide ribs with locally differentiated heights. The outer guide rib is formed higher than the inner guide rib to provide enhanced support at the critical outer edge where sheet end portions tend to hang down during reverse conveyance, while the inner guide rib maintains a lower height for adequate support without excessive complexity.
3Reliability
If the outer guide rib is formed higher than the inner guide rib, then sheet hanging-down is prevented, but the manufacturing complexity increases
Solution Approach 1:
The conveyance guide is manufactured with guide ribs of differentiated heights using standard molding or machining processes. The outer guide rib is formed higher than the inner guide rib through localized material removal or additive processes that are compatible with conventional manufacturing methods, thereby preventing sheet bending without significantly increasing fabrication complexity.
Data Source
AI summary
A sheet conveying device is provided in a sheet discharge portion of an image forming apparatus. A curved path and a reverse conveyance path are formed within the sheet conveying device. An outer guide rib and an inner guide rib are provided to a conveyance guide forming a lower-side guide surface of the curved path. The inner guide rib is lower than a reference straight line connecting a pressure contact point of a discharge roller pair to a rotary roller, and the outer guide rib is higher than the reference straight line.