Ultrasonic Welding Stitching for Tamper-Evident Security Documents
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Solution Overview
Problem
Current methods for securing passport booklets against fraudulent alteration by preventing access to the stitching thread are inadequate, as they either require additional chemical components, can cause staining, or are not tamper-evident, and do not effectively prevent re-use of the thread after tampering.
Innovation Solution
The method involves ultrasonic welding of the stitching threads after they are interlaced, using an ultrasonic welding apparatus to structurally modify the threads, ensuring they cannot be opened without damage, and optionally joining the threads with a spine tape containing synthetic fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If UV curing adhesive is added on top of the stitching, then the thread becomes more difficult to remove and tamper evidence is created, but additional chemical components are required and staining of security paper may occur
Solution Approach 1:
The patent replaces the chemical bonding mechanism (UV adhesive) with a mechanical interlocking system. The stitching thread is designed with protruding elements that engage with corresponding recesses in the security document pages, creating a mechanical lock that prevents removal without damage. This eliminates the need for additional chemical components and avoids staining issues while maintaining tamper evidence functionality.
Solution Approach 2:
The stitching thread is constructed as a composite material structure combining different fiber types or structural elements within the same thread. This composite design provides both the strength needed for secure binding and the protruding features for mechanical interlocking, achieving tamper evidence through the thread's inherent structure rather than external chemical treatments.
2Stability of the object's composition
If thermoplastic material is used to fuse threads and pages together, then structural modification of threads is achieved, but additional heating equipment and process complexity are required
Solution Approach 1:
The thread is pre-formed with protruding elements and structural features during the threading process, before the stitching operation. This preliminary structuring allows the thread to create mechanical interlocks during normal stitching without requiring subsequent heating or structural modification steps, thereby eliminating the need for additional heating equipment while achieving stable thread composition.
3Ease of manufacture
If conventional stitching with same material threads is used, then manufacturing simplicity is maintained, but the stitching can be opened without tamper evidence
Solution Approach 1:
The stitching thread is designed with asymmetric features including protruding elements at specific intervals and varying thread diameters along its length. This asymmetric structure creates one-way mechanical interlocks that are easy to insert but difficult to remove or undo, providing tamper evidence while maintaining compatibility with conventional stitching machinery and manufacturing processes.
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 method securely binds the stitching threads, making them tamper-evident without visible changes, preventing re-use and maintaining the integrity of the document, while being cost-efficient and environmentally friendly, without requiring additional chemical components or altering the manufacturing process.
Implementation Method 1
a step of treating at least a part of the stitching with welding so as to structurally modify at least one of the threads
Data Source
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AI summary
The invention concerns a method for securing a security document (100) comprising at least personal data pages (120) and a cover sheet (110) placed outside the personal data pages (120), the method comprising, during security document manufacturing, a step of stitching the personal data pages (120) and the cover sheet (110) together by means of an upper thread (131) and a lower thread (132) interlaced together and a step of treating at least a part of the stitching with ultrasonic welding so as to structurally modify the thread. The invention concerns also a security document (100) comprising at least a part of the stitching (130) which is secured by the method.