Multi-layer Cover Golf Ball with Hardness Gradient Core
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Solution Overview
Problem
There is a need for a cost-effective and efficient method to produce golf balls with a single-layer core that exhibits a shallow hard-to-soft hardness gradient from the surface to the center, which is not efficiently addressed by existing technologies that often result in large hardness gradients and time-consuming manufacturing processes.
Innovation Solution
A golf ball design featuring a single core with a double cover system, where the inner cover layer is made from an ionomeric material with a hardness of 60 Shore D or greater, and the outer cover layer is made from a castable polyurea or polyurethane with a hardness of 60 Shore D or less, creating a shallow positive hardness gradient with specific trans content and hardness values across the core.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional hard-to-soft hardness gradient cores are used, then spin rate and feel are improved, but the hardness gradient becomes excessively large (15-25+ Shore C points)
Solution Approach 1:
The patent applies parameter changes by precisely controlling the hardness gradient magnitude (reducing from 15-25+ Shore C points to a more controlled range) and the trans-content distribution profile across the core. This involves adjusting curing parameters, rubber composition ratios, and processing conditions to achieve the desired shallow gradient while maintaining performance.
Solution Approach 2:
The patent implements local quality by creating specific regional variations in trans-content and hardness within the core structure. The core is designed with differentiated zones having specific trans-content ranges (e.g., 5-15% near surface, 0-5% at center) to achieve the desired hardness gradient profile, where each region has optimized properties for its specific function.
2Manufacturing precision
If multi-layer cores with different elastomers are used, then hardness gradient is achieved, but manufacturing complexity and time increase
Solution Approach 1:
The patent merges multiple functions into a single core layer by achieving the hardness gradient through compositional and structural variations within one layer rather than requiring multiple separate elastomer layers. This consolidation maintains the desired hardness gradient while simplifying the manufacturing process and reducing production time.
Solution Approach 2:
The patent employs composite material principles by creating a core with heterogeneous composition within a single layer, combining different trans-content regions and rubber compound variations to achieve the hardness gradient effect without requiring physically separate elastomer layers, thus reducing manufacturing complexity.
3Productivity
If shallow hardness gradient cores are produced, then manufacturing efficiency improves, but control over spin and feel characteristics becomes more difficult
Solution Approach 1:
The patent maintains reliability of spin and feel characteristics by precisely controlling critical parameters including trans-content distribution (specific ranges at different radial positions), hardness gradient magnitude, and rubber composition ratios. These parameter controls ensure consistent performance despite the simplified single-layer structure and improved manufacturing efficiency.
Data Source
AI summary
A golf ball having an inner core layer having an outer surface and a geometric center and being formed from a rubber composition. An outer core layer surrounds the inner core to form a dual core. An inner cover layer surrounds the dual core, and includes a high-acid ionomer having a hardness of about 66 to 75 Shore D and an acid content of 16 wt. % or greater. An outer cover layer surrounds the inner cover layer, and includes a polyurethane and having a material hardness of about 38 to 56 Shore D. The inner core layer surface hardness is from 0 Shore C to 10 Shore C lower than the geometric center hardness to define a negative hardness gradient and the outer core layer has a surface hardness at least 10 Shore C greater than the geometric center hardness to define a dual core positive hardness gradient.