Golf Ball Core Hardness Gradient via Thermoplastic and Thermoset Layers

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Solution Overview

Problem

Conventional golf ball cores, particularly those with thermoset materials, struggle to achieve varying properties across the core, limiting the creation of desired hardness gradients, which affect compression, feel, and spin.

Innovation Solution

A golf ball design featuring a thermoplastic inner core with a negative hardness gradient and a thermoset outer core with a positive hardness gradient, utilizing specific materials and treatments to achieve a controlled hardness distribution, including ionomers, diene rubber, and gradient-promoting additives.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a thermoset material is used for the golf ball core, then the core can achieve certain desirable characteristics through heating and crosslinking, but the ability to achieve varied properties across the core is limited

Engineering Contradiction:

Improvecore characteristicsVSAvoidvaried properties across core

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent applies local quality by creating distinct hardness zones within the core through a dual-layer construction. The inner core layer has a first hardness value while the outer core layer has a second hardness value, allowing different regions of the core to exhibit different mechanical properties. This enables localized optimization of performance characteristics such as compression and spin in specific areas of the core.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent employs composite materials by combining two different thermoset rubber compositions with distinct hardness values into a single core structure. The inner core layer uses one thermoset composition while the outer core layer uses another, creating a composite core that leverages the advantageous properties of both materials to achieve varied performance characteristics across the core.

Inventive Principle:

Principle #40Composite materials

2Ease of manufacture

If a single core layer is used, then the manufacturing process is simpler, but the ability to create controlled hardness gradients is limited

Engineering Contradiction:

Improvecore manufacturingVSAvoidhardness gradient control

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies segmentation by dividing the core into two distinct layers - an inner core layer and an outer core layer - each with controlled hardness values. This segmentation allows for independent formulation and processing of each layer, enabling precise control over the hardness gradient from the center to the periphery of the core while maintaining a relatively simple dual-step manufacturing process.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS8753231B2Golf ball having a thermoplastic positive hardness gradient inner core layer and a thermoset shallow positive hardness gradient outer core layer

Publication Date: 2014.06.17 ACUSHNET CO

AI summary

A golf ball has an inner core layer including a thermoplastic highly-neutralized ionomer and having a geometric center hardness less than a surface hardness to define a first positive hardness gradient. An outer core layer is formed about the inner core and includes a homogenous thermoset composition. The outer core has an interior hardness less than an outer surface hardness to define a second positive hardness gradient. An inner and outer cover layers are disposed about outer core layer. The first and second hardness gradients each have a slope and the slope of the second hardness gradient is less than the slope of the first hardness gradient such that a ratio of the first and second slopes is 0.8 to 0.85.