Tennis Racket Frame Stiffness Optimization for Repulsion and Control
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Solution Overview
Problem
Tennis players require rackets that balance high repulsion performance with high controllability, a demand not fully met by existing rackets.
Innovation Solution
A racket design featuring a frame with a maximum thickness less than 26.0 mm, an in-plane stiffness index (Gi) between 5000 and 8000, and an out-of-plane stiffness index (Go) between 45000 and 60000, achieved through the use of fiber reinforced layers with bias-type and straight-type reinforcement fibers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the frame thickness is increased to improve repulsion performance, then the ball can fly at higher velocity, but the controllability deteriorates
Solution Approach 1:
The patent applies parameter changes by precisely controlling the frame thickness within the range of 18.0 mm to 25.0 mm and optimizing the stiffness indices (Gi: 5000-8000, Go: 45000-60000). This parameter optimization allows the frame to be thick enough for repulsion performance while thin enough to maintain controllability, resolving the contradiction between ball velocity and controllability.
Solution Approach 2:
The patent employs composite materials by combining fiber reinforced layers with bias-type and straight-type reinforcement fibers in specific configurations. This composite structure enables the frame to achieve both sufficient stiffness for repulsion and appropriate flexibility for controllability, allowing simultaneous optimization of ball velocity and player control.
2Speed
If the in-plane stiffness is increased to improve repulsion performance, then the ball can fly at higher velocity, but the contact time with the ball decreases
Solution Approach 1:
The patent optimizes the in-plane stiffness index Gi to fall within the specific range of 5000 to 8000. This controlled parameter range ensures the frame provides sufficient repulsion force for high ball velocity while maintaining adequate contact time with the ball, preventing the stiffness from being so high that contact time is excessively reduced.
Solution Approach 2:
The patent applies local quality by using bias-type reinforcement fibers in specific regions of the frame where repulsion performance is most critical, while using straight-type reinforcement fibers in other regions. This localized fiber placement optimizes the stiffness distribution across the frame, ensuring high repulsion performance where needed while maintaining appropriate contact time characteristics.
3Strength
If the frame thickness is increased to improve structural strength, then the repulsion performance improves, but the manufacturing complexity increases
Solution Approach 1:
The patent uses composite materials with fiber reinforced layers to achieve high frame strength without excessive thickness. The fiber reinforcement provides structural strength while maintaining a manageable thickness range (18.0-25.0 mm), simplifying the manufacturing process compared to using thicker frames made from homogeneous materials.
Solution Approach 2:
The patent specifies precise parameter ranges for frame thickness (18.0-25.0 mm) and stiffness indices (Gi: 5000-8000, Go: 45000-60000). These controlled parameters ensure the frame achieves necessary strength while remaining within manufacturable thickness limits, avoiding the need for overly complex manufacturing processes that would be required for much thicker frames.
Data Source
AI summary
A racket 2 includes a frame 4, a grip 6, a grommet 10, and a string 12. The frame 4 includes a head 14, a first throat 16a, a second throat 16b, and a shaft 18. A maximum value of a thickness of the frame 4 is less than 26.0 mm. The racket 2 has an in-plane stiffness index Gi of greater than or equal to 5000 and less than or equal to 8000. The in-plane stiffness index Gi is a product of a top pressure stiffness value Git (kgf/cm) and a side pressure stiffness value Gis (kgf/cm). The racket 2 has an out-of-plane stiffness index Go of greater than or equal to 45000 and less than or equal to 60000. The out-of-plane stiffness index Go is a product of a throat stiffness value Gos (kgf/cm) and a ball-hitting face stiffness value Goh (kgf/cm).