Racket Grommet Non-Circular Tip Opening Trajectory Control
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Solution Overview
Problem
Tennis rackets struggle to maintain a stable ball trajectory when the ball is hit at points away from the center of the racket face, particularly below the center, leading to low launch angles and potential failure to clear the net.
Innovation Solution
The racket features a grommet system with tubular parts that include non-circular tip openings, allowing strings to pass through and be in contact with the side wall from the base opening to the tip opening, which helps maintain a stable string movement and trajectory.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the ball is hit at a point below the center of the racket face, then the ball flies at a small launch angle, but this leads to a low trajectory and failure to pass over the net
Solution Approach 1:
The patent applies local quality by creating asymmetric grommet structures at specific locations. The first grommet has a non-circular cross-section with different dimensions in different directions, while the second grommet has a circular cross-section. This local differentiation in grommet geometry at different positions on the racket face allows for optimized string movement control specifically针对 off-center hits, thereby improving launch angle and trajectory stability without requiring complete redesign of all grommets
Solution Approach 2:
The patent employs asymmetry principle by designing the first grommet with a non-circular cross-section where the diameter in the direction parallel to the racket face differs from the diameter in the perpendicular direction. This asymmetric geometry creates differential friction constraints on string movement, generating a mechanical effect that increases launch angle when the ball is hit below the center, thus resolving the contradiction between force direction and trajectory stability
2Reliability
If the grommet has a circular opening, then the structure is simple and easy to manufacture, but it cannot provide stable string movement control for off-center hits
Solution Approach 1:
The patent applies segmentation by dividing the grommet system into two distinct types: first grommets with non-circular cross-sections for enhanced string control, and second grommets with circular cross-sections for simpler applications. This segmentation allows the complex non-circular grommets to be strategically placed only where needed for trajectory control, while maintaining simplicity in other areas, thus balancing manufacturing ease with functional performance
Solution Approach 2:
The patent demonstrates multi-functionality by designing the non-circular grommet to serve multiple purposes: it provides friction-based string movement control, generates launch angle correction for off-center hits, and maintains structural integration with the racket frame. The single non-circular grommet design thus performs multiple functions that would otherwise require separate components, reducing overall system complexity while improving reliability
Data Source
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AI summary
A grommet of a racket includes a tubular part. The tubular part includes a through hole through which a string is passed. The through hole includes a base opening, a side wall, and a non-circular tip opening. Assuming an imaginary dividing plane that is perpendicular to a face of the racket and that divides the non-circular tip opening into a first opening portion and a second opening portion shorter than the first opening portion in a direction parallel to the face, an inside dimension of the first opening portion in the direction perpendicular to the face increases gradually from one end of the non-circular tip opening in the direction parallel to the face to the dividing plane. In the tubular part, the string passes through the first opening portion and is in contact with the side wall from the base opening to the tip opening.