Sheet Curl Sensor with Dual Constraint Rollers
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Solution Overview
Problem
Existing sheet curl sensors in the printing industry face challenges in accurately measuring and controlling lead edge sheet curl, particularly due to limitations in resolution and the inability to handle varying paper weights and properties, which can lead to sheet feeding jams and distortion in finished products.
Innovation Solution
A lead edge and trail edge sheet curl sensor system with a dual constraint system using pairs of rollers to maintain consistent sheet height and angle, combined with light emitters and detectors to measure curl by detecting the time delay and order of light beam interruptions, ensuring accurate curl detection and measurement resolution of less than 0.01 mm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single elastomer roller is used to constrain the lead edge of the sheet, then the device complexity is reduced, but the measurement precision deteriorates due to inadequate constraint and variable sheet height/angle
Solution Approach 1:
The constraint system is segmented into multiple functional rollers: a first pair of constraint rollers (611, 612) positioned before the sensor to constrain the lead edge, and a second pair of constraint rollers (613, 614) positioned after the sensor to constrain the trail edge. This segmentation allows each roller pair to independently perform its specific constraint function, improving overall measurement precision while maintaining manageable system complexity through modular design.
Solution Approach 2:
The constraint rollers act as intermediaries between the sheet transport system and the curl sensor. By positioning the rollers at specific locations (before and after the sensor) and adjusting their speeds independently, they mediate the sheet's movement to ensure consistent height and angle at the sensor without directly contacting or interfering with the sheet's natural curl characteristics.
2Measurement precision
If the constraint rollers are positioned close to the sensor, then the measurement precision is improved by reducing buckling and corrugation, but the device complexity increases due to tighter spatial arrangement and speed control requirements
Solution Approach 1:
The constraint rollers are designed with independent speed control, allowing dynamic adjustment of each roller's rotational speed to match the sheet transport speed. This dynamic capability enables the rollers to maintain optimal positioning close to the sensor while adapting to varying operating conditions, reducing buckling and corrugation effects without creating fixed complex mechanical linkages.
Solution Approach 2:
The system changes the operational parameters of the constraint rollers by independently controlling their rotational speeds rather than using a fixed mechanical connection. This parameter-based control allows the rollers to be positioned close to the sensor for high-precision measurement while maintaining flexibility in the system response to different sheet conditions and transport speeds.
3Measurement precision
If light emitters and detectors are positioned to measure both lead and trail edge curl, then the measurement precision is improved, but the device complexity increases due to additional optical components and signal processing requirements
Solution Approach 1:
The optical sensing system is designed with multi-functionality to measure both lead edge and trail edge curl using a coordinated arrangement of light emitters and detectors. The first and second pairs of light emitters and detectors work together to provide comprehensive curl measurement capability, allowing a single integrated system to perform multiple measurement functions that would otherwise require separate apparatus.
Solution Approach 2:
The optical system incorporates feedback mechanisms where the light detectors monitor the interruption patterns caused by the sheet edges at different positions. By analyzing the timing and sequence of light beam interruptions, the system can distinguish between lead edge and trail edge curl characteristics, providing precise dual-edge measurement through signal processing rather than requiring complex separate measurement systems.
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
The system effectively constrains and measures sheet curl, preventing buckling and corrugation, allowing for precise detection of both lead and trail edge curls, ensuring accurate sheet feeding and minimizing distortion in printed products.
Implementation Method 1
A lead edge and trail edge sheet curl sensor system with a dual constraint system using pairs of rollers to maintain consistent sheet height and angle, combined with light emitters and detectors to measure curl by detecting the time delay and order of light beam interruptions
Data Source
AI summary
A lead edge and/or trail edge sheet curl sensing and constraint method and system. First and second light emitters and detector pairs are aligned such that the light beams from the first light emitter and second light emitter cross at the transport media sheet substrate path, which constitutes the path of a media sheet substrate with zero curl. A media sheet substrate with either positive or negative curl on the lead edge of the sheet substrate interrupts light beams from the first and second light emitters, as detected by first and second light detectors. A similar approach can be used to detect the trail edge curl. The time delay between the light beam interruptions is proportional to the sheet substrate curl, and the order of interruptions indicates whether the sheet substrate curl is positive or negative. A first pair and a second pair of substrate constraint rollers can also be provided in the paper path upstream and downstream of the sensing system. The roller pairs closest to the sensor are made of relatively non-deformable materials or of materials of similar elasticity so that different media are constrained in the sensor zone with the same sheet trajectory relative to the nip.