Sheet Conveyor Assembly Media-Dependent Transfer Control
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Solution Overview
Problem
In sheet printers, undetected displacement of sheets on endless belt conveyors can lead to misalignment during printing, especially when the sheet slips or has a similar color and material to the belt, requiring additional sensors and increasing costs, and existing solutions for direct sheet sensing are not reliable or cost-effective.
Innovation Solution
A sheet conveyor assembly with a first conveyor having a holding device that exerts a holding force proportional to the sheet's coverage on an air-permeable belt and a second conveyor with a registration device for adjusting the sheet's position and orientation, using a controller to determine a suitable release timing based on media type characteristics to ensure accurate transfer and prevent slippage, allowing the print head assembly to control printing based on transport information without direct sheet sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If direct sensing of the sheet is implemented to eliminate position uncertainty, then measurement precision is improved, but device complexity and cost increase due to additional sensors
Solution Approach 1:
The patent introduces an intermediary registration device with registration marks that mediates between the sheet and the sensing system. Instead of directly sensing the sheet position, the system detects registration marks on the sheet which serve as intermediaries to infer sheet position and orientation, thereby avoiding the need for complex direct sheet sensing while maintaining measurement precision
Solution Approach 2:
The patent uses registration marks as simplified copies or representations of the sheet's position and orientation information. These marks are detected by sensors to determine sheet parameters without requiring direct measurement of the entire sheet, reducing sensor complexity while maintaining detection accuracy
2Productivity
If the sheet is released early from the second conveyor to increase productivity, then productivity is improved, but manufacturing precision deteriorates due to insufficient coverage and potential slippage
Solution Approach 1:
The patent applies preliminary action by pre-positioning registration marks on the sheet and pre-configuring the registration device to detect these marks. This allows the system to determine sheet parameters in advance, enabling early release from the second conveyor without sacrificing position accuracy, as the registration information is already available to guide the transfer process
Solution Approach 2:
The patent implements feedback through the detection of registration marks, which provide real-time information about sheet position and orientation. This feedback allows the control system to adjust the release timing and transfer parameters dynamically, ensuring that sheets are released at the optimal moment for both productivity and precision based on actual sheet conditions
3Reliability
If holding force is increased to prevent slippage, then reliability is improved, but use of energy increases due to stronger holding requirements
Solution Approach 1:
The patent applies partial action by using registration marks that require only partial sheet coverage for accurate detection. The holding device needs to secure only the portions of the sheet with registration marks rather than the entire sheet, reducing the required holding force and energy consumption while maintaining sufficient reliability for accurate position determination and transfer
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution ensures accurate and reliable transfer of sheets between conveyors, reducing the need for additional sensors and minimizing misalignment, thereby enhancing printing precision and reducing costs while maintaining accurate tracking of the sheet's position and orientation.
Implementation Method 1
an endless, air permeable belt of the first conveyor
Data Source
AI summary
A sheet printer includes a sheet conveyor assembly including a first conveyor with a first holding device configured for exerting a holding force on a sheet proportional to a coverage of the sheet on the first conveyor and a second conveyor upstream of the first conveyor including a second holding device configured for holding and releasing the sheet, a print head assembly positioned over the first conveyor, a detector assembly for sensing the transport of the first conveyor, a controller storing on its memory a sheet media catalogue and configured to control a release timing of the second holding device for releasing the sheet partially engaged by the first conveyor based on a media type parameter selected from the media catalogue and to control the print head assembly to commence printing the sheet based on transport information from the detector assembly.