Multi-piece Golf Ball Core Hardness Profile for Spin Control

Solution Overview

Problem

Existing golf balls with two-layer cores do not fully optimize core hardness profiles, leading to suboptimal spin rates and distances for mid- to high-level golfers, as they fail to balance spin performance on approach shots with distance on full shots.

Innovation Solution

A multi-piece solid golf ball design featuring a two-layer core with a soft inner layer and hard outer layer, an intermediate layer, and a cover with a paint film, where the core hardness profile is optimized with specific JIS-C hardness gradients and the use of synthetic resin materials, ensuring a higher surface hardness of the core-encased sphere compared to the ball surface.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Speed

If the core hardness profile is made softer to reduce spin rate on full shots, then distance on driver shots is improved, but spin performance on approach shots deteriorates

Engineering Contradiction:

Improveinitial velocity on full shotsVSAvoidspin performance on approach shots

Core Design Contradiction:

SpeedVSReliability

Solution Approach 1:

The core is divided into two distinct layers: an inner core layer with softer hardness (JIS-C 40-60) to reduce spin rate and increase distance on full shots, and an outer core layer with harder hardness (JIS-C 70-90) to maintain spin performance on approach shots. This segmentation allows each layer to fulfill different functional requirements simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the core are assigned different hardness properties: the center region (inner core layer) is softer to promote distance, while the outer region (outer core layer) is harder to maintain spin control. This local differentiation of material properties enables the core to exhibit both low spin rate on full shots and high spin performance on approach shots.

Inventive Principle:

Principle #3Local quality

2Reliability

If the core is made harder to maintain spin performance on approach shots, then spin control is improved, but distance on full shots deteriorates

Engineering Contradiction:

Improvespin performance on approach shotsVSAvoidinitial velocity on full shots

Core Design Contradiction:

ReliabilityVSSpeed

Solution Approach 1:

The core is divided into two distinct layers: an inner core layer with softer hardness (JIS-C 40-60) to reduce spin rate and increase distance on full shots, and an outer core layer with harder hardness (JIS-C 70-90) to maintain spin performance on approach shots. This segmentation allows each layer to fulfill different functional requirements simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different regions of the core are assigned different hardness properties: the center region (inner core layer) is softer to promote distance, while the outer region (outer core layer) is harder to maintain spin control. This local differentiation of material properties enables the core to exhibit both low spin rate on full shots and high spin performance on approach shots.

Inventive Principle:

Principle #3Local quality

3Device complexity

If a single-layer core is used to simplify construction, then manufacturing complexity is reduced, but the ability to optimize both spin rate and distance simultaneously deteriorates

Engineering Contradiction:

Improvecore construction complexityVSAvoidspin rate and distance optimization

Core Design Contradiction:

Device complexityVSAdaptability or versatility

Solution Approach 1:

The core is divided into two distinct layers: an inner core layer with softer hardness (JIS-C 40-60) to reduce spin rate and increase distance on full shots, and an outer core layer with harder hardness (JIS-C 70-90) to maintain spin performance on approach shots. This segmentation allows each layer to fulfill different functional requirements simultaneously.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The core utilizes a composite structure combining two rubber materials with different hardness characteristics. The inner core layer uses softer rubber compound while the outer core layer uses harder rubber compound, creating a composite core that optimizes both spin rate control and distance performance that cannot be achieved with a single homogeneous material.

Inventive Principle:

Principle #40Composite materials

Data Source

PatentUS9968829B2Multi-piece solid golf ball

Publication Date: 2018.05.15 BRIDGESTONE SPORTS CO LTD

AI summary

In a multi-piece solid golf ball having a two-layer core consisting of an inner layer and an outer layer, a cover, at least one intermediate layer between the core and the cover, and a paint film layer formed on the cover surface, each layer of the two-layer core is formed primarily of a rubber composition, the intermediate layer and the cover are each formed primarily of a resin material, the core has a hardness profile which satisfies specific conditions, and the sphere consisting of the core encased by the intermediate layer has a higher surface hardness than the ball. When used by mid- to high-level golfers, this ball achieves sufficient reduction in the spin rate on full shots with a driver, enabling the distance to be increased, and the spin performance on approach shots is excellent, enhancing the enjoyability of the game.