Racket String Layout with Alternating Materials for Balanced Performance

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Solution Overview

Problem

Existing tennis rackets with mixed material strings fail to fully leverage the advantages of different materials due to uneven tension distribution and material contributions, leading to imbalanced performance in spin, control, rebound, and hitting feeling.

Innovation Solution

A racket design featuring alternating first and second longitudinal threads made of different materials (e.g., polyester and nylon or natural gut) with varying elongation rates and tensions, ensuring balanced performance by maintaining distinct characteristics in each thread type.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a single material string is used, then the racket has consistent performance, but it cannot achieve balanced performance in spin, control, rebound, and hitting feeling simultaneously

Engineering Contradiction:
Improveperformance balanceVSAvoidstring structure
Core Design Contradiction:
Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent applies local quality by using different string materials in different regions of the racket face. Specifically, it uses a combination of polyester strings (for spin and control) and nylon or natural gut strings (for rebound and hitting feeling) in specific patterns. This allows different areas of the racket to have optimized properties for different performance aspects, achieving balanced overall performance while maintaining a structured but not overly complex string configuration.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining different string materials (polyester, nylon, natural gut) within the same racket stringing system. This composite approach allows the racket to leverage the advantages of each material: polyester for spin and control, nylon for rebound and feeling, and natural gut for elasticity and comfort. The composite material strategy enables simultaneous achievement of multiple performance characteristics without requiring excessive structural complexity.

Inventive Principle:
Principle #40Composite materials

2Adaptability or versatility

If different material strings are used for main and cross strings, then the racket can have advantages of both materials, but the contribution of cross string is small so advantages are not fully exerted

Engineering Contradiction:
Improvematerial advantage utilizationVSAvoidperformance contribution
Core Design Contradiction:
Adaptability or versatilityVSProductivity

Solution Approach 1:

The patent addresses the unequal contribution problem by applying local quality through strategic material placement. Instead of simply using different materials for main and cross strings, it creates patterns where high-rebound materials (nylon, natural gut) are positioned in areas that maximize their contribution to ball interaction. The design ensures that materials with superior rebound properties are placed where they can most effectively influence ball response, thereby fully exerting their advantages despite the cross string's traditionally smaller contribution.

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent utilizes dimensional change by considering the three-dimensional spatial distribution of string materials across the racket face. It moves beyond the simple main/cross string binary to create multi-zone patterns where different materials are distributed across different regions (center, perimeter, various quadrants). This spatial dimensionality allows optimal placement of each material type to maximize its performance contribution, ensuring that even cross strings with smaller individual contribution are strategically positioned to fully leverage their material advantages.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

3Adaptability or versatility

If high-tension and low-tension regions are formed on the string, then the racket can have advantages of both regions, but tension changes during repeated use causing performance degradation

Engineering Contradiction:
Improvetension region advantageVSAvoidperformance consistency
Core Design Contradiction:
Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies parameter changes by strategically selecting materials with different elastic properties and tension characteristics for different string positions. It uses materials whose mechanical properties are optimized for their specific tension requirements and positional demands. By matching material parameters (elasticity, tensile strength, damping characteristics) to the specific requirements of high-tension versus low-tension regions, the design achieves initial performance optimization while the materials' inherent properties provide resistance to tension-induced performance degradation during repeated use.

Inventive Principle:
Principle #35Parameter changes

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 design achieves well-balanced performance in spin, control, rebound, and hitting feeling by optimizing material and tension differences between threads, maintaining performance consistency over repeated use.

Implementation Method 1

An elongation rate E1 of the first longitudinal thread may be different from an elongation rate E2 of the second longitudinal thread

Methodology Applied
Scientific EffectElastic deformation: Elasticity

Implementation Method 2

A tension T1 of the first longitudinal thread may be different from a tension T2 of the second longitudinal thread

Methodology Applied
Scientific EffectTension: Tension

Data Source

PatentEP3871742B1racket
Publication Date: 2025.09.17 SUMITOMO RUBBER INDUSTRIES LTD
  • EP3871742B1 patent drawingFigure 1
  • EP3871742B1 patent drawingFigure 2
  • EP3871742B1 patent drawingFigure 3

AI summary

A face of a racket includes a plurality of first longitudinal threads 30a, a plurality of second longitudinal threads 30b, and a plurality of transverse threads. The first longitudinal threads 30a and the second longitudinal threads 30b are arranged alternately from a center of the face toward outside in a width direction of the racket. A material of each first longitudinal thread 30a is different from a material of each second longitudinal thread 30b. A tension of the first longitudinal thread 30a may be different from a tension of the second longitudinal thread 30b. Preferably, a ratio (N1/N2) of a number N1 of the first longitudinal threads to a number N2 of the second longitudinal threads is greater than or equal to 2/8, but less than or equal to 8/2.