Sheet Registration Using Edge Sensors for Skew Correction
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Solution Overview
Problem
Current media handling systems in printing face challenges in accurately registering substrate media due to lateral misalignment, skew, and velocity errors, which can lead to image and color registration errors, and require multiple sensors increasing costs and maintenance.
Innovation Solution
A method and apparatus using a first sensor to measure the arrival and position of a sheet's leading or trailing edge, followed by adjustments to correct lateral position, skew, and velocity before reaching a downstream sensor, reducing the number of sensors needed by positioning them further apart and maintaining constant velocity during initial adjustments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple sensors are used to measure sheet position and orientation continuously, then sheet registration precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent extracts the continuous measurement function from multiple sensors and consolidates it into a single lateral edge sensor that measures position at two different locations. This reduces sensor quantity while maintaining registration precision through strategic measurement point selection and processing
Solution Approach 2:
The single lateral edge sensor performs multiple measurement functions by detecting sheet position at two different locations along the process direction. This multi-functional approach replaces what would traditionally require multiple dedicated sensors, reducing system complexity while maintaining precision
2Measurement precision
If sensors are positioned closer together for continuous monitoring, then measurement accuracy is improved, but the adjustment time available before sheet reaches datum is reduced
Solution Approach 1:
The patent performs preliminary lateral position adjustments based on measurements from the first sensor location before the sheet reaches the second sensor location. This staged approach allows sufficient adjustment time while maintaining measurement accuracy through sequential correction
Solution Approach 2:
The measurement and correction process is segmented into two stages: first measurement and initial correction at the first sensor location, then verification and final adjustment at the second sensor location. This segmentation provides adequate time for adjustments while maintaining precision through multiple measurement points
3Manufacturing precision
If sheet velocity is adjusted to correct arrival time errors, then delivery timing precision is improved, but sheet velocity control complexity increases
Solution Approach 1:
The patent uses feedback from the leading edge sensor that detects sheet arrival time at the datum location to automatically adjust sheet velocity. This closed-loop control system measures actual arrival time and makes real-time velocity corrections, improving timing precision while using standard feedback control mechanisms
Solution Approach 2:
The system changes the sheet velocity parameter dynamically based on measured arrival time errors. By adjusting velocity as a controllable parameter in response to timing measurements, the system achieves precise delivery timing through parameter optimization rather than mechanical complexity
Data Source
AI summary
Accurate sheet registration is achieved by measuring the arrival of a leading edge and/or a trailing edge of the sheet using a first sensor. Also, measuring a first position of the sheet using a second sensor on a lateral edge of the sheet. Then performing a first adjustment moving the sheet laterally using the first position measurement. The first adjustment actuated prior to the sheet reaching a third sensor for measuring a second position of the sheet. The third sensor disposed downstream in the process direction of the second sensor and a sheet feeding nip. Then measuring a second position of the sheet using the third sensor on the lateral edge and performing a second adjustment of the sheet with regard to at least one of sheet skew, sheet velocity and sheet lateral position using at least one of the arrival, first position and second position measurements.