Sheet Transport Nip Sequencing for Stable Skew Correction
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Solution Overview
Problem
Existing printing apparatuses face issues with skew correction of sheets due to deflection formation when the leading end of the sheet is aligned with a correction roller pair, as the nip force of image capturing devices hinders sheet sliding, leading to re-skewing during transport.
Innovation Solution
A printing apparatus with a first and second transport roller pair and a device between them, where the third nip portion has a weaker nip force than the first and second, allowing the leading end to be aligned with the second nip portion before releasing the first nip, facilitating deflection release and maintaining skew correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the leading end of the sheet is aligned with the nip portion of the correction roller pair, then skewing is corrected, but the nip force of the image capturing device hinders sheet sliding, causing deflection formation and re-skewing
Solution Approach 1:
The patent applies preliminary action by aligning the leading end of the sheet with the second nip portion (correction roller pair) before releasing the first nip. This sequencing ensures the sheet is properly positioned for skew correction before the correction mechanism is activated, preventing deflection formation that would occur if alignment attempted to happen during active nipping.
Solution Approach 2:
The patent employs dynamics by temporarily releasing the first nip portion after alignment is achieved. This dynamic adjustment allows the sheet to transition from a constrained state (both nips active) to a more flexible state (first nip released), enabling smooth sheet transport and maintaining the corrected alignment without generating harmful deflections.
2Adaptability or versatility
If the sheet is nipped by the image capturing device on the transport path, then the sheet can be processed, but the nip force hinders sheet sliding in the transport path, preventing leading end alignment with the correction roller pair
Solution Approach 1:
The patent performs preliminary alignment by positioning the leading end of the sheet at the second nip portion before the sheet passes through the image capturing device. This preliminary action ensures alignment is established while the sheet is still accessible to the correction mechanism, allowing subsequent processing by the image capturing device without compromising the alignment achieved earlier.
Solution Approach 2:
The patent segments the sheet handling process into distinct phases: first nipping for initial transport, then alignment at the second nip portion, followed by processing through the image capturing device, and finally release of the first nip. This segmentation allows each function to be performed optimally without interference between the image capturing device's nip force and the alignment requirement.
3Manufacturing precision
If the leading end of the sheet is aligned with the nip portion of the correction roller pair, then skewing is corrected, but the deflection formed is gradually released and the sheet is skewed again during transport
Solution Approach 1:
The patent applies preliminary action by aligning the leading end with the second nip portion before releasing the first nip. This creates a stable reference point for the sheet's leading end, ensuring that when the first nip is released and transport continues, the sheet maintains its corrected alignment rather than reverting to a skewed state.
Solution Approach 2:
The second nip portion (correction roller pair) acts as an intermediary that maintains the sheet's alignment during transport. By having the leading end aligned with this second nip portion before releasing the first nip, the correction roller pair serves as a stabilizing reference that prevents the sheet from skewing again during subsequent transport, effectively mediating between the sheet and the transport path.
Data Source
AI summary
A printing apparatus includes a first transport roller pair configured to transport a medium while nipping the medium at a first nip portion, a second transport roller pair disposed downstream of the first transport roller pair and configured to transport the medium while nipping the medium at a second nip portion, and a device disposed between the first transport roller pair and the second transport roller pair in a transport path for the medium, and configured to nip the medium at a third nip portion, wherein a nip force in the third nip portion is weaker than a nip force in the first nip portion, and in a state where the medium is nipped at the first nip portion, a leading end of the medium is aligned with the second nip portion, and then the nipping at the first nip portion is released.