Surfboard Leash Flex Ring Stress Dispersion
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Solution Overview
Problem
Surfboard leashes experience high stress concentration and breakage at the connection point between the cord and the swivel connector, leading to premature wear and failure.
Innovation Solution
Incorporating a flexible ring made of a softer, more resilient material between the cord and the overmolded swivel connector, which disperses tensile loads and reduces wear at the connection point by varying the durometer hardness of the materials used for the cord, swivel connector, and flex ring.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the cord is made of high quality polyurethane to dampen tensile shock, then the shock damping performance is improved, but the cord eventually wears out and breaks at the connection point
Solution Approach 1:
The patent applies different material properties to different parts of the leash system. The cord maintains high polyurethane hardness (90A) for shock damping, while the flex ring uses softer material (40-60A) specifically at the connection point to reduce wear and stress concentration. This local differentiation resolves the contradiction by allowing each component to have optimized properties for its specific function.
Solution Approach 2:
The flex ring acts as an intermediary element between the cord and swivel connector. It mediates the stress transmission by absorbing and dispersing tensile loads through its softer material properties, preventing direct stress concentration at the connection point while maintaining the overall structural integrity of the leash.
2Strength
If the cord is made resiliently extendable to dampen tensile shock, then the shock absorption is improved, but the surfboard flies back towards the surfer
Solution Approach 1:
The patent changes the durometer hardness parameter of the cord to approximately 90A, which provides the optimal balance between resilience for shock dampening and control to prevent excessive spring back. This parameter optimization resolves the contradiction by finding the precise value that achieves both desired effects.
3Strength
If the swivel connector is molded over the cord to provide secure connection, then the connection strength is improved, but stress concentration occurs at the connection point
Solution Approach 1:
The flex ring serves as a stress-dispersing intermediary between the swivel connector and the cord. It distributes the tensile loads across a larger area at the connection point, reducing stress concentration while maintaining the secure molded connection through its flexible yet supportive properties.
Solution Approach 2:
The connection point becomes a composite structure combining the cord material (90A polyurethane), the flex ring material (40-60A softer polymer), and the swivel connector material. This composite construction allows each material to contribute its specific properties, with the softer flex ring material specifically addressing stress concentration issues.
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 flexible ring reduces stress concentrations and extends the lifespan of the surfboard leash by absorbing shock and preventing breakages at the connection point, ensuring a secure and durable attachment between the surfboard and the surfer's leg.
Implementation Method 1
the flexible ring having the effect of dispersing tensile loads experienced by the cord as the cord is bent into tight curves at the connection point during use. The flex ring generally being constructed of a softer, more resilient, less stiff material than the cord and the overmolded swivel connector
Implementation Method 2
the flexible ring reduces stress concentrations and extends the lifespan of the surfboard leash by absorbing shock and preventing breakages at the connection point
Data Source
AI summary
A surfboard leash, including a cord having a first durometer hardness, a connector having a second durometer hardness molded over an end of the cord, and a flex ring having a third durometer hardness positioned a least partially around the cord and at least partially between the cord and the connector, wherein the third shore durometer is less than first shore durometer and the second shore durometer.