Yarn sensor for optical detection of a yarn moving in a longitudinal direction
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Solution Overview
Problem
Existing optical yarn sensors are prone to contamination from dust, dirt particles, and finishing agents, leading to falsified measurements due to the non-contact monitoring of yarns, which affects the reliability and accuracy of yarn quality assessment.
Innovation Solution
A yarn sensor utilizing the principle of frustrated total internal reflection (FTIR) with a light-guiding means that brings the yarn into contact, causing scattered light to be detected, which reduces contamination issues and enhances self-cleaning through the 'brush effect' and boundary layer flow, allowing for reliable yarn detection and quality assessment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If non-contact optical monitoring is used to detect yarn, then the yarn sensor can monitor yarn presence and quality without physical contact, but dust, dirt particles, and finishing agents settle on the sensor surfaces causing contamination that significantly distorts measured values
Solution Approach 1:
A light guide element is introduced as an intermediary component between the light source/detector and the yarn. The light guide element's outer surface serves as the contact point for the yarn, while the optical components remain protected inside the housing. This mediator allows optical interaction with the yarn while physically isolating the sensitive optical components from contamination.
Solution Approach 2:
The patent replaces the conventional direct optical path (where light travels directly from source to detector through air) with a guided optical path using a light guide element. This substitution enables the system to maintain non-contact monitoring of the yarn bulk while allowing controlled contact at the light guide surface, thereby eliminating the contamination problem without sacrificing monitoring capability.
2Reliability
If the yarn is brought into contact with the light guide surface, then the self-cleaning brush effect and boundary layer flow reduce contamination, but the sensor structure becomes more complex
Solution Approach 1:
The light guide element is integrated with the yarn guide means, combining the functions of light guidance and yarn direction into a single component. The light guide element serves both as the optical waveguide and as the yarn guide that brings the yarn into contact with its outer surface, thereby reducing overall structural complexity while maintaining contamination resistance.
Solution Approach 2:
The light guide element performs multiple functions simultaneously: it guides light from the light source to the detector, serves as the contact surface for the yarn, and enables the self-cleaning effect through its outer surface. This multi-functionality reduces the need for separate components, thereby simplifying the overall sensor structure while achieving reliable contamination resistance.
3Device complexity
If total reflection is used to detect yarn presence, then the sensor can operate with a simple optical path, but any contamination on the light guide surface will falsify measurements
Solution Approach 1:
The light guide element acts as an intermediary that separates the measurement function (detecting yarn presence via total reflection) from the contamination exposure function. The outer surface of the light guide element is the only part exposed to potential contamination, while the internal optical path remains clean and simple. This mediator allows the system to maintain a simple optical path design without sacrificing measurement precision.
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 solution significantly reduces contamination effects, enhances the reliability of yarn sensors, and provides accurate monitoring of yarn presence, diameter, and quality, including detection of foreign fibers, with a compact and minimally complex structure.
Implementation Method 1
The light guide means are designed such that, when no yarn is in contact with the outer surface of the light guide, total reflection is achieved
Implementation Method 2
contact with the yarn couples at least part of the light out of the light guide... Based on the effect of frustrated total internal reflection (FTIR)
Data Source
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AI summary
To optically detect a yarn (3) moving in its longitudinal direction, a yarn sensor (6) comprising a light source (19), a detector (26), and a light guide (21) is proposed. The yarn sensor (6) is based on the frustrated total internal reflection (FTIR) effect. Due to the FTIR effect, scattered light (25) emitted from the light guide (21) in the contact area (24) between the yarn (3) and the outer surface (23) of the light guide (21) is detected by the detector (26), thus enabling the detection of the yarn (3) in contact with the outer surface (23). Alternatively, the reduced intensity in the totally reflected beam is detected by the detector (26). The intensity in the totally reflected beam is essentially reduced by the scattered light coupled out from the light guide.