Golf Ball Core with Negative Hardness Gradient and Trans-Polybutadiene
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Solution Overview
Problem
There is a need for a single layer golf ball core with a soft-to-hard hardness gradient from the surface to the center, which is both inexpensive and efficient to produce, allowing for unique combinations of compression, feel, and spin.
Innovation Solution
A golf ball with a unitary core having a soft transition region adjacent to the outer surface, formed from a substantially homogeneous rubber composition with a negative hardness gradient, where the transition region includes 8-20% trans-polybutadiene isomer and the core outer surface includes 10-30% trans-polybutadiene isomer, achieving a specific gradient quotient defined by the equation G+T10×COR≤7, where G is the overall negative hardness gradient and COR is the coefficient of restitution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a conventional hard surface to soft center hardness gradient is used in the core, then the golf ball achieves traditional compression and spin characteristics, but the manufacturer cannot create unique combinations of compression, feel, and spin with a soft outer portion
Solution Approach 1:
The patent inverts the conventional hardness gradient by creating a soft-to-hard gradient (softer outer portion and harder center) instead of the traditional hard surface to soft center gradient. This inversion allows the golf ball core to achieve unique combinations of compression, feel, and spin characteristics that differ from conventional designs, while maintaining structural integrity through the harder center region.
2Adaptability or versatility
If a soft-to-hard hardness gradient with soft outer portion is created, then unique combinations of compression, feel, and spin are achieved, but the manufacturing process becomes more complex and time-consuming
Solution Approach 1:
The patent segments the core into distinct regions with different hardness characteristics - a softer outer portion and a harder center region - formed through a multi-stage curing process. This segmentation allows each region to contribute differently to the ball's performance characteristics while being manufactured as a single integrated core structure.
Solution Approach 2:
The patent applies preliminary action by using a cure-altering agent on the outer surface of the uncured elastomer before the final curing process. This pre-treatment creates a softer outer layer that will have different mechanical properties after curing, enabling the soft-to-hard gradient without requiring separate manufacturing steps for different core regions.
3Reliability
If trans-polybutadiene isomer content is increased in the outer surface (10-30%), then the coefficient of restitution is improved, but the hardness of the outer surface decreases
Solution Approach 1:
The patent changes the chemical composition parameter by increasing the trans-polybutadiene isomer content in the outer surface region to 10-30%. This compositional change directly affects the material's mechanical properties, resulting in a lower hardness outer surface that provides improved coefficient of restitution for better ball flight performance.
Solution Approach 2:
The patent applies local quality by creating a non-uniform distribution of trans-polybutadiene isomer content throughout the core, with higher concentrations (10-30%) in the outer surface region and lower concentrations in the center. This localized compositional variation allows the outer surface to have optimized rebound properties while the center maintains structural integrity.
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 enables the creation of golf balls with a unique combination of compression, feel, and spin, achieving a high coefficient of restitution and a negative hardness gradient, which is unusual for a core with a soft outer portion, while maintaining comparable compression.
Implementation Method 1
a unitary core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface... The soft transition region has a thickness of up to 4 mm and includes about 8 to 20 percent trans-polybutadiene isomer. The soft transition region also has a negative hardness gradient of up to 15 Shore C.
Implementation Method 2
The unitary core has an overall negative hardness gradient of up to 20 Shore C and has a gradient quotient, GQ... and COR is the coefficient of restitution measured at an incoming velocity of 125 ft/s
Data Source
AI summary
A golf ball includes a core having an outer surface, a geometric center, and a soft transition region adjacent to the outer surface. The soft transition region has a thickness of about 4 mm or less and includes about 2 to 10 percent of a trans-polybutadiene isomer. An outer cover layer has a hardness of about 50 Shore M or greater. The core outer surface hardness is greater than the hardness at the geometric center to define a positive hardness gradient of about 10 to 48 Shore C. The core has a secondary gradient quotient, GQ′, of 1.5 to 7.25, GQ′ being defined by the equation:G′+T10×CORwhere G′ is the positive hardness gradient in Shore C, T is the percent trans-polybutadiene isomer at the core outer surface, and COR is the coefficient of restitution of the core measured at an incoming velocity of 125 ft/s.