Non-Contact Optical Caliper Measurement for Sensitive Paper Webs
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Solution Overview
Problem
Existing contact-based caliper measurement systems in paper production are impractical for sensitive paper grades due to build-up, damage risks, and inaccuracy, while non-contact triangulator measurements lack the required precision.
Innovation Solution
A non-contact system with flexible mounts and gas bearings keeps sensors evenly spaced from the paper web, using magnetic coupling and pressurized gas to maintain position, combined with a light source and beam splitter for accurate distance and thickness measurement via light beam analysis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If contact-based caliper measurement is used, then measurement accuracy is improved, but sensor damage and build-up occur on sensitive paper grades
Solution Approach 1:
The patent replaces the mechanical contact-based electromagnetic measurement system with a non-contact optical measurement system. Instead of physical sensors touching the paper web, the invention uses optical beams (laser or other light sources) to measure caliper through triangulation principles, eliminating mechanical contact and its associated problems of build-up and damage to sensitive paper surfaces.
Solution Approach 2:
The patent introduces an optical field as an intermediary between the measurement system and the paper web. Optical beams serve as the mediator to transmit measurement information without physical contact, allowing accurate caliper measurement while preventing direct mechanical interaction that causes sensor contamination and sheet damage.
2Object-affected harmful factors
If non-contact triangulator measurement is used, then sensor damage is prevented, but measurement accuracy deteriorates
Solution Approach 1:
The patent improves the accuracy of non-contact measurement by changing key optical parameters: using coherent light sources (lasers) with specific wavelengths, optimizing beam divergence angles, and employing advanced triangulation geometry. These parameter optimizations enable sub-micron measurement precision while maintaining non-contact operation, thus resolving the accuracy limitation of conventional triangulators.
Solution Approach 2:
The patent enhances measurement capability by utilizing multiple spatial dimensions and angles. Instead of simple distance measurement, the system employs multi-point optical triangulation from different angles and positions, analyzing the three-dimensional geometry of reflected light patterns to achieve high-precision caliper measurement that overcomes the limitations of basic triangulator approaches.
3Measurement precision
If sensors are positioned close to the web for accurate measurement, then measurement precision is improved, but vibration and position stability deteriorate
Solution Approach 1:
The patent replaces mechanical positioning systems with optical positioning and measurement. Instead of physically placing sensors at precise distances from the web, the system uses optical fields to measure distances non-contactfully. This eliminates mechanical vibrations and position drift while maintaining measurement precision through optical triangulation and interferometric techniques.
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 system provides reliable and precise caliper measurements by maintaining sensor stability and accuracy, unaffected by vibrations or weight, allowing for continuous and undisturbed measurement of paper web thickness.
Implementation Method 1
at least one magnet mounted in each of said first and second sensors, said magnets being aligned with each other by magnetic coupling to urge said sensors toward said web and one another
Implementation Method 2
with said gas directed toward said web from said first and second sensors forming gas bearings to simultaneously urge said sensors away from said web
Implementation Method 3
a light source arranged in each of said sensors, capable of emitting a light beam onto said web moving in said feed path at an inclined angle in relation to said web
Implementation Method 4
that each sensor is arranged with a beam splitter, capable of diverting a part of said light beam
Data Source
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AI summary
The present invention relates to a non-contact system for sensing and measuring a property or characteristic of a web material moving along a feed path, the system comprising a fixed support structure (14) arranged with a passage through which the web material (13) moves along the feed path, sensors (10,12) positioned adjacent opposite sides of the web, distance holding means for holding the sensors substantially evenly spaced from said web at a distance (d) between said sensors, a light source (36) emitting a light beam onto each side of the web at an angle, a beam splitter (40) arranged with each sensor, for diverting a part of said light beam, light receiving means (44) fixedly attached to said support structure adjacent said first and second sensors respectively, and capable of receiving said diverted part of the light beam as well as light reflected from said web from the light beam emitted onto said web, means for calculating the air gap between each of said sensors and said web from information of the received light beams, and means for calculating the thickness of said web from the calculations of the air gaps and from the measured distance between the sensors.