Strain Sensor with Flexible Filler for Reliable Coupling
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Solution Overview
Problem
Existing optical fiber strain sensor technologies face limitations in achieving long, durable, and accurate strain measurements due to environmental hazards from chemical substances, limited installation length, and the need for large diameter pipes, which hinder the production of reliable and reproducible results.
Innovation Solution
A strain sensor design featuring a large diameter optical fiber with a flexible and resilient filler material between the fiber and protective encasing, allowing strain coupling and reducing the risk of fiber lock-in during manufacturing, enabling the creation of long, durable, and compact sensors with improved measurement accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hardenable fluid is injected into the carrier tube to allow strain coupling, then strain coupling between the cable and carrier tube is achieved, but environmental accidents occur due to chemical substance spilling and leakage
Solution Approach 1:
The patent removes the hardenable fluid (chemical substance) from the strain coupling process. Instead of injecting chemical substances into the carrier tube, the invention uses a mechanical anchoring system where the cable is directly secured to the carrier tube through friction and mechanical interlocking, eliminating environmental hazards while maintaining strain coupling reliability
Solution Approach 2:
The patent introduces friction and mechanical interlocking as intermediary mechanisms between the cable and carrier tube. The rough inner surface of the carrier tube and the cable's outer surface create friction-based strain transfer, replacing the chemical hardenable fluid with a physical intermediary that achieves the same coupling function without environmental harm
2Reliability
If the known method with hardenable fluid is used, then strain coupling is achieved, but only limited installation length can be achieved due to maximum achievable floating distance
Solution Approach 1:
The patent applies preliminary anchoring actions along the cable length by creating multiple friction zones and mechanical interlocking points before the cable is fully installed. The roughened surface and periodic anchoring features ensure strain coupling is established in advance, enabling installation over extended distances without relying on chemical fluid that has limited floating distance
3Ease of manufacture
If a relatively large diameter pipe is used for the carrier tube, then the known installation method can be implemented, but the sensor system becomes less compact
Solution Approach 1:
The patent employs a thin-walled, flexible carrier tube with a rough inner surface that enables mechanical strain coupling without requiring large diameter. The flexible nature of the thin-walled tube allows it to conform to the cable while maintaining friction-based coupling, achieving both ease of manufacture and compact size
Solution Approach 2:
The patent applies local roughening to specific zones of the carrier tube's inner surface rather than requiring the entire tube to be large-diameter. By creating localized friction zones and anchoring points, the system achieves effective strain coupling in a compact configuration, eliminating the need for large-diameter pipes
4Ease of manufacture
If the fiber is directly enclosed in the encasing during manufacturing, then the sensor can be manufactured, but fiber lock-in occurs causing stress on the fiber and reduced reliability
Solution Approach 1:
The patent incorporates a cushioning layer between the optical fiber and the carrier tube encasing during manufacturing. This cushioning material prevents direct contact and potential lock-in of the fiber, absorbing stresses that occur during installation and operation, thereby maintaining fiber durability and measurement reliability while enabling straightforward manufacturing
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 enables the production of reliable, durable, and accurate strain sensors with a compact design, capable of providing reproducible measurement results over extended lengths, while minimizing environmental risks and avoiding fiber lock-in issues.
Implementation Method 1
a cured filler material fills at least part of a space between the fiber and the protective encasing, the cured filler material being configured for allowing strain coupling between the protective encasing and the fiber
Implementation Method 2
the cured filler material can be configured to hold the fiber at a distance from the protective encasing, for example by completely encapsulating the fiber
Data Source
AI summary
Strain sensor, including an elongated protective encasing (5) surrounding an inner space, and an optical fiber (3) extending through the encasing (5), the fiber (3) at least including a fiber core (3a) and a fiber cladding (3b), wherein a cured filler material fills (4) at least part of a space between the fiber (3) and the protective encasing (5), the cured filler material (4) being configured for allowing strain coupling between the protective encasing (5) and the fiber (3), wherein an outer diameter of the fiber (3) is at least about 250 µm, and wherein the cured filler material (4) is one or more of: a flexible material, a resilient material, and a material having a shore A hardness that is lower than about 50. The invention also provides a method and system for manufacturing a strain sensor.