Multi-piece Golf Ball Core Hardness Gradient for Spin Control
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Solution Overview
Problem
Multi-piece solid golf balls fail to achieve a balance between distance and controllability, particularly in lowering spin rates on shots with a driver, leading to inadequate distance and durability issues.
Innovation Solution
A multi-piece solid golf ball design featuring a core with a gradually increasing hardness from center to surface, an envelope layer softer than the intermediate layer, and a cover with specific thickness and hardness relationships, utilizing materials like polybutadiene for the core and thermoplastic polyurethane for the cover, to optimize flight performance and scuff resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the golf ball uses a multi-piece solid construction with optimized layer hardness relationships, then flight performance and controllability are improved, but the spin rate on driver shots remains too high
Solution Approach 1:
The patent applies local quality by creating distinct hardness characteristics in different regions of the core. The core has a softer center region and a harder outer region, allowing the center to deform and reduce spin while the outer region maintains structural integrity and flight performance. This regional differentiation resolves the contradiction between low spin and good flight characteristics.
Solution Approach 2:
The patent uses composite materials with different hardness properties in various layers. The core combines softer and harder rubber materials, the intermediate layer uses a different hardness than both core regions, and the cover has its own optimized hardness. This multi-material composite structure enables simultaneous achievement of low spin rate and excellent flight performance.
2Length of moving object
If the golf ball uses a four-layer construction with varied interior layers, then distance potential is increased, but the balance between distance and controllability deteriorates
Solution Approach 1:
The patent systematically varies key parameters including the hardness of each layer, the thickness ratios, and the material composition. By optimizing these parameters - specifically setting the core center softer than the outer region, the intermediate layer harder than the core, and the cover with specific hardness - the patent achieves both extended distance and maintained controllability.
3Strength
If the golf ball uses repeated impact durability enhancement, then resistance to cracking improves, but scuff resistance on the surface deteriorates
Solution Approach 1:
The patent applies local quality by giving different hardness characteristics to different layers. The intermediate layer is designed with higher hardness to resist cracking from repeated impacts, while the cover maintains optimized hardness and material properties for scuff resistance. This regional hardness differentiation allows each layer to specialize in its primary protective function.
Data Source
AI summary
The invention provides a multi-piece solid golf ball comprising a core, an envelope layer encasing the core, an intermediate layer encasing the envelope layer, and a cover which encases the intermediate layer and has formed on a surface thereof a plurality of dimples. The core is formed primarily of a rubber material, and has a hardness which gradually increases from a center to a surface thereof, the hardness difference in JIS-C hardness units between the core center and the core surface being at least 15 and, letting (I) be the average value for cross-sectional hardnesses at a position 15 mm from the core center and at the core center and letting (II) be the cross-sectional hardness at a position 7.5 mm from the core center, the hardness difference (I)-(II) therebetween in JIS-C units being not more than ±2. The envelope layer and the intermediate layer are each formed primarily of the same or different resin materials. The cover is formed primarily of a thermoplastic resin or a thermoplastic elastomer. The envelope layer, intermediate layer and cover have thicknesses which satisfy the relationship cover thickness<intermediate layer thickness<envelope thickness; and the envelope layer, intermediate layer and cover have surface hardnesses (JIS-C hardness) which satisfy the relationship envelope layer surface hardness<intermediate layer surface hardness>cover surface hardness, −10≦(JIS-C hardness of cover surface−JIS-C hardness of intermediate layer surface)<0, and 1≦(JIS-C hardness of intermediate layer surface−JIS-C hardness of envelope layer surface)≦30. The golf ball has an excellent flight performance and controllability that are acceptable to professionals and other skilled golfers, while also having an excellent durability to cracking on repeated impact and an excellent scuff resistance.