Multi-gripper impression cylinder for variable sheet length printing
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Solution Overview
Problem
Traditional gripper-based architectures in lithographic systems are ill-suited for digital printing due to fixed sheet size limitations, leading to mis-registration and print quality defects when handling sheets of varying sizes, as they cannot maintain registration precision and efficient print rates simultaneously.
Innovation Solution
A modified lithographic press architecture with multiple grippers angularly spaced around the circumference of an impression cylinder, where a cover provides a smooth curved surface over unused grippers, allowing for dynamic sheet gripping and printing of sheets of different lengths without inducing print quality defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple grippers are positioned for multiple sheet lengths, then registration precision is improved, but print quality defects occur due to unsupported portions bridging gaps
Solution Approach 1:
The patent removes or deactivates certain grippers from the system based on the detected sheet length. When a long sheet is detected, the system selectively disables grippers that would create unsupported portions, extracting only the necessary gripping points that maintain registration precision without causing print defects.
Solution Approach 2:
The system dynamically adjusts the number and positioning of active grippers based on the detected sheet length. The gripper configuration changes from static to dynamic, allowing the system to optimize between registration precision and print quality for different sheet sizes by activating or deactivating specific grippers in real-time.
2Device complexity
If a single gripper cadence is used, then device complexity is reduced, but productivity is limited for smaller sheet sizes
Solution Approach 1:
The gripper system is segmented into multiple independently controllable units around the impression cylinder. Each gripper can be activated or deactivated based on sheet length, allowing the system to maintain a simple base architecture while enabling dynamic adaptation for high-speed printing of smaller sheets through selective engagement of gripper segments.
3Manufacturing precision
If grippers are positioned for long sheets, then registration precision is maintained, but efficient print rates for smaller sheets cannot be achieved
Solution Approach 1:
The system performs preliminary detection of sheet length before the sheet enters the printing zone. Based on this advance information, the controller pre-configures which grippers should be active, ensuring that the optimal gripper pattern is already in place before printing begins, thereby maintaining precision for long sheets while enabling high-speed operation for short sheets.
Data Source
AI summary
Devices and methods to enable a sheet conveyance system within a printing device. According to an apparatus herein, a sheet supply device feeds substrates to a printing system. The apparatus includes an impression cylinder. A first gripper is positioned in a first location on a circumferential wall of the impression cylinder. A second gripper is positioned in a second location on the circumferential wall of the impression cylinder. The second location is angularly spaced apart from the first location around the circumferential wall. A cover selectively covers the second gripper. Responsive to the first gripper gripping an edge of a substrate of a first length supplied from the sheet supply device, the first length being greater than the length of the circumferential arc between the first gripper and the second gripper, the cover provides a smooth curved surface over the second gripper.