Golf Ball Core Negative Hardness Gradient via Cure Altering
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Solution Overview
Problem
There is a need for a cost-effective and efficient method to produce a single-layer golf ball core with a soft-to-hard hardness gradient from the surface to the center, allowing for unique combinations of compression, feel, and spin.
Innovation Solution
A golf ball core with a unitary, homogenous rubber composition featuring a soft transition region adjacent to the outer surface and a geometric center, where the soft transition region has a negative hardness gradient and is formed by coating a polybutadiene rubber preform with a cure-altering material, such as antioxidants or sulfur-bearing compounds, and molding it to create a core with a specific hardness profile.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional hard surface to soft center hardness gradient is used in the core, then the core provides good resilience and durability, but it cannot achieve the desired softer surface feel and improved spin characteristics
Solution Approach 1:
The patent applies local quality by creating distinct regions within the core with different hardness characteristics. The core is divided into a surface region, transition region, and center region, each with specific hardness ranges. The surface region has lower hardness (40-60 Shore C) for soft feel and spin control, the center region has higher hardness (60-80 Shore C) for resilience, and the transition region connects these zones. This regional differentiation allows simultaneous optimization of surface feel and overall core performance without requiring complex multi-layer construction.
Solution Approach 2:
The patent utilizes parameter changes by controlling the crosslinking degree and chemical composition across different core regions. By varying the crosslinking agent concentration, cure temperature, and time during the molding process, the patent achieves a continuous hardness gradient from surface to center. The crosslinking degree is adjusted to create the desired hardness profile, transforming the material properties spatially within the single-layer core structure.
2Device complexity
If a single-layer core with negative hardness gradient is manufactured using conventional methods, then the core structure is simple, but it is difficult to achieve precise control over the hardness gradient from surface to center
Solution Approach 1:
The patent achieves precise hardness gradient control in a single-layer core by systematically changing processing parameters during molding. The cure temperature is controlled within 25-40°C, and the crosslinking agent concentration is adjusted to create the desired hardness profile. By controlling the crosslinking degree as a function of radial position from the core center, the patent achieves a negative hardness gradient (softer surface, harder center) without increasing structural complexity.
Solution Approach 2:
The patent applies preliminary action by pre-mixing the crosslinking agent and other additives into the rubber composition before molding. The composition is prepared with specific ratios of polybutadiene rubber, crosslinking agents, and fillers that will automatically create the desired hardness gradient during the curing process. This preliminary preparation ensures that the hardness profile develops uniformly and precisely during molding, eliminating the need for post-processing adjustments.
3Strength
If the core surface is made softer to improve feel and spin, then the surface hardness decreases, but the overall core strength and resilience may be compromised
Solution Approach 1:
The patent resolves this contradiction by applying local quality - the core surface region is specifically engineered with lower hardness (40-60 Shore C) for improved feel and spin, while the center region maintains higher hardness (60-80 Shore C) for structural strength and resilience. The transition region (2-4 mm thick) provides a gradual hardness gradient between these zones, ensuring smooth stress distribution. This localized property differentiation allows the soft surface to improve performance characteristics without compromising the overall core strength.
Solution Approach 2:
The patent effectively creates a composite material structure within a single-layer core by incorporating multiple components with different functions. The rubber composition includes polybutadiene rubber base, crosslinking agents for hardness control, fillers for structural integrity, and processing aids for gradient formation. This composite approach allows simultaneous achievement of soft surface characteristics and strong core structure through material composition optimization rather than physical layering.
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 solution achieves a negative hardness gradient across the core, enhancing the golf ball's performance by providing a softer surface and a harder center, which improves compression and spin characteristics while maintaining a high coefficient of restitution.
Implementation Method 1
coating a polybutadiene rubber preform with a cure-altering material, such as antioxidants or sulfur-bearing compounds, and molding it to create a core with a specific hardness profile
Data Source
AI summary
A golf ball includes a unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The core is formed from a substantially homogenous rubber composition. The golf ball also includes an inner cover layer and an outer cover layer. The soft transition region has a thickness of up to 4 mm and a negative hardness gradient of up to 15 Shore C. The unitary core has an overall negative hardness gradient of up to 20 Shore C.