Security Thread Embedding Elongation Control
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Solution Overview
Problem
Existing methods for producing banknote paper with security threads are sensitive to distance and prone to errors in detecting overstretching, leading to inefficiencies in reject detection and cancellation.
Innovation Solution
A method and device that embed a security thread with features spaced along its length, allowing for imaging and determination of elongation after embedding, with a control unit invalidating areas where the elongation exceeds a maximum, using image sensors and pattern comparison to ensure accurate detection and prevention of overstretching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If magnetic features are used to detect security thread expansion, then detection sensitivity is improved, but distance dependence increases making detection difficult
Solution Approach 1:
The patent replaces magnetic detection with optical imaging. Instead of using magnetic sensors that are highly sensitive to distance, the invention uses optical cameras to capture images of transparent features embedded in the security thread. This substitution of detection methodology eliminates the strong distance dependence characteristic of magnetic measurements while maintaining high detection sensitivity for thread expansion.
Solution Approach 2:
The patent creates optical copies (images) of the security thread features using transparent elements that can be captured by cameras. These transparent features act as visual replicas or markers within the thread structure, allowing optical systems to detect thread expansion through image analysis rather than direct magnetic field measurement, thereby resolving the distance dependence issue.
2Difficulty of detecting and measuring
If image-based detection is used to determine thread elongation, then distance dependence is reduced, but manufacturing complexity increases
Solution Approach 1:
The patent divides the security thread into multiple segments with individually spaced transparent features. By segmenting the thread and placing discrete optical markers at known intervals, the system can determine overall thread elongation by measuring the relative position changes of these segmented features in captured images, simplifying the imaging and analysis process.
Solution Approach 2:
The transparent features are embedded in the security thread during the thread manufacturing process itself, before the thread is incorporated into the banknote. This preliminary action of pre-positioning the optical markers ensures their correct spacing and orientation, reducing the complexity of subsequent detection and eliminating the need for complex alignment procedures during banknote production.
3Strength
If security thread is embedded under tension to prevent overstretching, then thread integrity is improved, but detection reliability decreases due to difficulty in monitoring
Solution Approach 1:
The patent implements a feedback system where images of the transparent features are captured and analyzed to determine the actual tension applied to the security thread during embedding. This visual feedback allows real-time monitoring of thread elongation, enabling operators to adjust embedding parameters to maintain thread integrity while preventing overstretching, thereby improving both strength and detection reliability.
Solution Approach 2:
The patent replaces mechanical tension monitoring systems with optical measurement. By using transparent features whose positions can be precisely measured in images, the system substitutes complex mechanical sensors and force measurements with simpler optical positioning detection, improving reliability while maintaining thread integrity during the embedding process.
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 approach significantly reduces errors in thread overstretching, providing reliable and precise reject detection and cancellation, ensuring high-quality banknote paper production with minimal overstretched threads.
Implementation Method 1
In step b) the recording can be carried out in transmitted light or reflected light.
Implementation Method 2
expansion-sensitive magnetic features that are integrated in the security thread are detected with a sensor
Data Source
AI summary
The invention relates to a method for producing a sheet-type substrate comprising a security thread, in particular a banknote paper comprising a security thread. In said method, a) a security thread having features that are spaced apart from one another in the longitudinal direction of the security thread is introduced into the substrate in such a way as to be at least partially embedded in the substrate, b) at least one of the features is copied as an image after embedding the security thread, c) based on the image of the at least one feature, the extension of the embedded security thread in the longitudinal direction is determined, and d) the substrate region in which the determined extension of the security thread exceeds a predefined maximum extension is invalidated in accordance with the determined extension.