Printing Apparatus Overlap Control for Sheet Stability
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Solution Overview
Problem
Printing apparatuses face challenges in increasing printing speed while preventing sheet jams, image quality deterioration, and stains caused by cockling when sheets overlap during high-density printing, as the moisture from ink can lead to wavy wrinkles and unstable ink landing positions.
Innovation Solution
A control system is implemented in the printing apparatus to manage the overlap between sheets based on the ink amount applied, ensuring the trailing edge of one sheet overlaps the leading edge of another, with a control unit determining the overlap area based on the ink distribution to maintain stability and prevent cockling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sheets are conveyed by making the succeeding sheet overlap the preceding sheet to shorten the interval between printing sheets, then printing speed is improved, but cockling occurs on the printing sheet due to moisture from high-density ink application
Solution Approach 1:
The patent applies different ink amounts to different regions of the sheet. Specifically, the ink amount in the overlap area (where the succeeding sheet overlaps the preceding sheet) is controlled to be smaller than in non-overlap areas. This local differentiation prevents excessive moisture accumulation in the overlap region, thereby preventing cockling while maintaining high-density printing in non-overlap regions for optimal image quality.
Solution Approach 2:
The patent dynamically adjusts the ink amount parameter based on the sheet's position and overlap status. By changing the ink application parameter (ink amount) according to whether the sheet is in an overlap region or not, the system prevents cockling in overlap areas while maintaining high-density printing elsewhere, thus resolving the contradiction between printing speed and sheet flatness.
2Manufacturing precision
If high-density printing is performed on overlapping areas using a large amount of ink, then image quality is improved, but the reverse surface of the sheet is constrained by a flat plate causing cockling
Solution Approach 1:
The patent applies different ink amounts to different regions. In overlap areas, the ink amount is reduced to prevent cockling that would compromise conveyance stability. In non-overlap areas, high-density printing with larger ink amounts is applied to maintain image quality. This spatial differentiation resolves the contradiction between image quality and conveyance stability.
3Productivity
If the interval between printing sheets is shortened to increase productivity, then printing speed is improved, but the distance between the printhead and the obverse surface of the printing sheet becomes unstable causing ink landing position shift
Solution Approach 1:
The patent performs preliminary control of the ink amount before the sheet reaches the printhead in the overlap area. By pre-determining that less ink should be applied in overlap regions, the system compensates for the instability caused by shortened intervals. This preliminary action ensures that even with reduced sheet-to-printhead distance, the ink landing position remains controlled and accurate.
Data Source
AI summary
A printing apparatus includes a feeding roller configured to feed sheets, including at least a preceding sheet and a succeeding sheet, a conveyance roller configured to convey the sheets fed by the feeding roller, and a printing unit configured to print on at least one sheet, of the sheets conveyed by the conveyance roller. A conveyance control unit controls the conveying of the sheets by the conveyance roller to form an overlap state, in which a leading edge of the succeeding sheet overlaps with the preceding sheet. In a case in which the conveyance roller conveys the succeeding sheet to a printing start position at which a printing operation is started by the printing unit, and the conveyance control unit forms the overlap state, the printing unit is configured to print on an overlapping area in which the preceding sheet and the succeeding sheet overlap.