Movable Guide for Curved Sheet Conveyance
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Solution Overview
Problem
Image forming apparatuses face issues with sheet contact against the outer circumferential wall during curved conveyance, leading to abnormal images and damage due to high toner fusion temperatures and rib formations, especially during double-sided printing and when the discharge rollers' speed is lower than the fixing rollers', causing sheet bending and toner accumulation.
Innovation Solution
A sheet conveying device with a movable guide that changes positions to minimize contact, forming the outer circumferential wall at one position and retracting it radially outward at another, allowing the sheet to travel towards downstream rollers while reducing contact with the wall, thereby minimizing sheet damage and image defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the sheet is conveyed through a curved conveyance path with a fixed outer circumferential wall, then the sheet can be guided to travel toward the discharge rollers, but the sheet contacts the outer circumferential wall causing abnormal images and damage due to high toner fusion temperatures
Solution Approach 1:
The patent applies the dynamics principle by making the outer circumferential wall movable rather than fixed. The movable guide can shift its position radially outward during sheet conveyance, allowing the wall to move away from the sheet to minimize contact. This dynamic adjustment resolves the contradiction by maintaining guiding function while reducing harmful contact between the sheet and the outer wall during curved path traversal.
2Loss of energy
If the discharge rollers operate at lower speed than the fixing rollers, then power consumption is reduced, but the sheet easily bends in a loop shape and contacts the outer circumferential wall more readily
Solution Approach 1:
The patent applies preliminary anti-action by having the movable guide proactively move radially outward before the sheet can contact the outer circumferential wall. This preemptive movement counteracts the tendency of the sheet to bend into loop shapes and contact the wall, especially when discharge rollers operate at lower speeds. The guide anticipates the potential harmful contact and prevents it by creating clearance in advance.
3Ease of operation
If sheet feed ribs are formed on the outer circumferential wall to guide the sheet, then sheet guiding is improved, but the ribs produce abnormal images with stripe marks and cause accumulation and congealment of fused toner
Solution Approach 1:
The patent applies the extraction principle by removing the sheet feed ribs from the outer circumferential wall. Instead of having ribs protrude from the wall surface, the guide uses a smooth movable surface that can shift radially outward. This eliminates the harmful ribs while maintaining the sheet guiding function, preventing both stripe marks in abnormal images and toner accumulation that would occur with rib structures.
4Ease of operation
If the movable guide is positioned at the first position to form the outer circumferential wall, then the sheet is guided toward downstream rollers, but contact between the sheet and the wall increases during curved path traversal
Solution Approach 1:
The patent applies dynamics by enabling the movable guide to shift its position from the first position (forming the outer circumferential wall) to the second position (radially outward retraction). During curved path traversal, the guide dynamically moves to the second position to reduce sheet contact, then returns to the first position for normal guiding operations. This dynamic positioning resolves the contradiction between maintaining guiding function and minimizing harmful contact.
Data Source
AI summary
A sheet conveying device includes: a curved conveyance path; and a pair of downstream side rollers that lies on the downstream side with respect to the curved conveyance path, and catches the sheet conveyed from the upstream side with respect to the curved conveyance path and reaching the curved conveyance path, wherein the curved conveyance path includes a movable guide movable between a first position and a second position, at the first position, the movable guide forms an outer circumferential wall of the curved conveyance path, and guides a tip of the sheet in such a direction that the sheet conveyed to the curved conveyance path travels toward the pair of downstream side rollers, and at the second position, a summit portion of a curve of the outer circumferential wall is retracted toward the outside in a radial direction of the curve with respect to the first position.