Printing Apparatus Roller Pair Configuration for Sheet Corrugation Control
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Solution Overview
Problem
Existing printing apparatuses face challenges in achieving accurate image printing due to sheet corrugation, which causes variations in the distance between the printing head and the sheet surface, leading to potential contact with the printing head and difficulties in maintaining consistent inkjet impingement times.
Innovation Solution
The printing apparatus employs an upstream and downstream roller pair configuration where the second roller's rotation shaft is positioned downstream of the first roller's, with each roller pair holding the sheet between them, to minimize sheet corrugation and maintain consistent sheet tension, reducing the likelihood of contact with the printing head and improving image printing accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a continuous sheet is drawn out of a roll, then the sheet can be supplied to the printing unit, but the sheet becomes corrugated at the end portions due to length variation, making it difficult to perform accurate image printing
Solution Approach 1:
The decurling unit applies a pre-curl in the opposite direction to the natural curl formed during sheet manufacturing. By intentionally curling the sheet in reverse before it reaches the printing unit, the unit counteracts the length variation-induced corrugation, ensuring the sheet remains flat and stable during printing, thus maintaining printing accuracy while enabling continuous sheet supply
2Shape
If a decurling unit is used to remove curl from the sheet, then the sheet curl is reduced, but the unit cannot eliminate corrugation caused by length variation, and the sheet may still contact the printing head
Solution Approach 1:
The sheet tensioning unit is positioned upstream of the printing unit to pre-establish uniform tension across the sheet before it enters the printing zone. This preliminary tensioning action prevents the formation of corrugation waves that could cause the sheet to contact the printing head, ensuring stable and reliable printing operations
3Length of moving object
If the sheet length varies from place to place, then the sheet becomes corrugated, but the distance between the printing head and sheet surface varies, making it difficult to maintain consistent inkjet impingement times
Solution Approach 1:
The sheet tensioning unit applies uniform tension to the sheet upstream of the printing unit, pre-stabilizing the sheet's physical state before it reaches the printing zone. This preliminary action ensures consistent sheet position and distance from the printing head, maintaining reliable inkjet impingement timing
Data Source
AI summary
A printing apparatus includes: a upstream roller pair arranged on the upstream side of a printing head with respect to a direction in which a sheet is conveyed; and a downstream roller pair arranged on the downstream side of the printing head with respect to the direction, wherein each of the upstream roller pair and the downstream roller pair includes a first roller and a second roller configured to hold the sheet therebetween. In both of the upstream roller pair and the downstream roller pair, a rotation shaft of the second roller is provided to be situated on the downstream side of a rotation shaft of the first roller with respect to the direction.