Racket Grommet Bulge Design for String Resilience
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Solution Overview
Problem
The existing grommets for tennis or badminton rackets, with smooth strip-shaped portions between cylindrical portions, cause the string to expand when compressed, reducing the string's resilience and length of flexure deformation upon hitting a ball, leading to decreased ball resilience and spin performance.
Innovation Solution
A grommet design featuring a strip-shaped portion with bulge portions and protrusions on one surface, where the string is folded back at the bulge, increasing the effective length of string deformation and enhancing friction, thereby improving resilience and spin performance by positioning the fold-back on the outer side of the frame and increasing contact pressure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a smooth strip-shaped portion is used in the grommet, then the string can pass through easily, but the contact area expands to the inner side of the frame when the folded portion is depressed, shortening the flexure deformation length and reducing ball resilience
Solution Approach 1:
The strip-shaped portion is designed with different local properties: a smooth surface in the string passage region for easy string insertion, and a bulge portion at the fold-back position to maintain string length and resilience. This local differentiation resolves the contradiction between ease of operation and ball resilience.
2Ease of manufacture
If the string is folded back at the opening position of the cylindrical portion, then the string can be easily inserted, but the length of flexure deformation is shortened, reducing the resilience of the ball at hitting
Solution Approach 1:
Instead of folding the string back at the opening position (one-dimensional approach), the invention positions the fold-back at a bulge portion that extends in the thickness direction of the strip-shaped portion. This dimensional change maintains the string's flexure deformation length and improves ball resilience while still allowing easy string insertion.
3Reliability
If protrusions are added to increase friction and restrict string movement, then spin performance improves, but the device complexity increases
Solution Approach 1:
Protrusions are added only at specific locations where the string folds back, rather than uniformly across the entire strip-shaped portion. This localized approach increases friction and spin performance while minimizing the increase in device complexity.
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 grommet design effectively lengthens the string's deformation, enhancing its resilience and spin performance by positioning the fold-back on the outer side of the frame, increasing friction and contact pressure, resulting in improved ball carry and spin capabilities.
Implementation Method 1
a length of the string that possibly has the flexure deformation at hitting a ball
Implementation Method 2
the string can contact or bite into the distal end of the protrusion. This causes friction between the string and the protrusion to ensure restricting movement of the string
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
To enhance a resilience performance of a ball at hitting the ball. A grommet (26) is configured to include a strip-shaped portion (31) extending in a predetermined direction and a cylindrical portion (32) projecting from one surface of the strip-shaped portion, the cylindrical portion (32) being a portion through which a string (21) passes. A bulge portion (41) is formed on a part on another surface of the strip-shaped portion, the part being along an inner periphery of the cylindrical portion. The bulge portion has a shape bulged more than the other surface of the strip-shaped portion, and the string is folded back at the bulge portion. A plurality of the protrusions (42) are formed between the cylindrical portions adjacent to one another, the plurality of the protrusions (42) being portions to which the string contacts.