Monofilament String With Variable Tangent Modulus
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Solution Overview
Problem
Monofilament strings for tennis rackets are too stiff, making it difficult for beginners to control the ball, especially when playing soft, and they quickly lose tension, leading to diminished control and a frustrating playing experience.
Innovation Solution
A monofilament string design featuring a thermoplastic elastomer 'sea' region with island regions of thermoplastic plastic doped with doping agents, arranged to increase tangent modulus with strain in the playing stress range, providing enhanced elasticity and comfort.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If monofilament strings are made with standard polymer materials and uniform structure, then durability and tensile strength are improved, but stiffness increases making ball control difficult for beginners
Solution Approach 1:
The patent applies local quality by creating a non-uniform monofilament structure with distinct core and sheath regions having different material properties. The core region contains a first polymer blend providing elasticity and comfort, while the sheath region contains a second polymer blend providing durability and tension stability. This local differentiation allows the string to exhibit both softness for ball control and strength for durability simultaneously.
Solution Approach 2:
The patent employs composite materials by combining different polymer blends in a layered configuration. The core uses a polymer blend with higher elastomeric content (at least 20 wt%) for cushioning and control, while the sheath uses a polymer blend optimized for strength and tension maintenance. This composite structure resolves the contradiction by allowing each region to contribute its specialized properties to the overall string performance.
2Reliability
If monofilament strings use higher polymer content for durability, then resistance to abrasion and creasing is improved, but tension relaxation increases causing string to feel loose
Solution Approach 1:
The patent applies local quality by assigning different polymer compositions to the core and sheath regions. The sheath region, which directly contacts the ball and experiences abrasion, contains a polymer blend optimized for durability (at least 80 wt% of the sheath). The core region contains a polymer blend with higher elastomeric content (at least 20 wt%) that maintains tension stability. This spatial separation of functions resolves the contradiction between abrasion resistance and tension stability.
Solution Approach 2:
The patent uses composite materials with a specific layered architecture where the core and sheath regions have distinct polymer blends. The core's elastomeric-rich composition (at least 20 wt% elastomer) provides tension retention, while the sheath's durable polymer composition (at least 80 wt% of sheath) provides abrasion resistance. This composite structure allows the string to maintain both tension stability and durability simultaneously.
3Ease of operation
If monofilament strings are designed for hard playing characteristics, then control on hard shots is improved, but comfort and feel deteriorate
Solution Approach 1:
The patent applies local quality by creating a core region with high elastomeric content (at least 20 wt%) that provides cushioning and comfort during ball impact. The sheath region provides the structural integrity for control on hard shots. This local differentiation allows the string to be comfortable during soft play while maintaining control on hard shots.
Solution Approach 2:
The patent employs composite materials where the core's elastomeric-rich polymer blend (at least 20 wt% elastomer) absorbs impact energy for comfort, while the sheath's durable polymer blend maintains string structure for control. This composite architecture resolves the contradiction between comfort and control by allowing each region to fulfill its specialized function.
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 string offers improved ball control and comfort for beginners, maintaining high durability and tension, allowing for better feel and faster improvement in playing skills, with increased elasticity in the playing stress range.
Implementation Method 1
a sea region comprising a thermoplastic elastomer; and a plurality of island regions comprising a thermoplastic plastic doped with one or more doping agents, wherein the plurality of island regions is embedded in the sea region; and wherein a geometry and/or a distribution of the island regions in the sea region is such that a tangent modulus of a stress-strain curve of the monofilament string increases with increasing strain in a playing stress range
Data Source
AI summary
A monofilament string for use in string racket sports, wherein the monofilament string comprises: a covering material; a core material embedded in the covering material, wherein the core material comprises: a sea region comprising a thermoplastic elastomer; and a plurality of island regions comprising a thermoplastic plastic doped with one or more doping agents, wherein the plurality of island regions is embedded in the sea region; and wherein a geometry and/or a distribution of the island regions in the sea region is such that a tangent modulus of a stress-strain curve of the monofilament string increases with increasing strain in a playing stress range.