Golf ball
AssigneeBridgestone Sports Co., Ltd.
InventorsAkira Kimura, Toru Ogawana, Ryota Nakamura, Tsuyoshi Nakajima
Life of this patent
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Abstract
The invention provides a golf ball having a core and a cover of at least one layer. The core has a cross-sectional hardness which, letting R (mm) be the radius of the core, A be the JIS-C hardness at a center of the core, B be the JIS-C hardness at a position R/3 mm from the core center, C be the JIS-C hardness at a position R/1.8 mm from the core center, D be the JIS-C hardness at a position R/1.3 mm from the core center, and E be the JIS-C hardness at a surface of the core, satisfies the formulas (1) D−C≧7, (2) C−B≦7, (3) (D−C)−(C−B)≧7, and (4) E−A≧16.
Claims15
A golf ball comprising a core and a cover of at least one layer, wherein the core has a cross-sectional hardness which, letting R (mm) be a radius of the core, A be a JIS-C hardness at a center of the core, B be a JIS-C hardness at a position R/3 mm from the core center, C be a JIS-C hardness at a position R/1.8 mm from the core center, D be a JIS-C hardness at a position R/1.3 mm from the core center, and E be a JIS-C hardness at a surface of the core, satisfies formulas (1) to (4) below:
- D−C≧7 (1)
- C−B≦7 (2)
- (D−C)−(C−B)≧7 (3)
- E−A≧16, (4)
- wherein the core is formed from a material molded under heat and is formed from a rubber composition comprising a base rubber, a crosslinking initiator, and water,
- wherein the difference between the crosslink density at the core surface and the crosslink density at the core center, both of which are crosslink densities measured based on a toluene swelling test, is at least 9×102 mol/m3, and
- wherein the base rubber consists of polybutadiene synthesized with a rare-earth catalyst and/or a polybutadiene synthesized with a nickel catalyst.
A golf ball comprising a core, an envelope layer, an intermediate layer and an outermost layer, wherein the core has a cross-sectional hardness which, letting R (mm) be a radius of the core, A be a JIS-C hardness at a center of the core, B be a JIS-C hardness at a position R/3 mm from the core center, C be a JIS-C hardness at a position R/1.8 mm from the core center, D be a JIS-C hardness at a position R/1.3 mm from the core center, and E be a JIS-C hardness at a surface of the core, satisfies formulas (1) to (4) below:
- D−C≧7 (1)
- C−B≦2 (2)
- (D−C)−(C−B)≧7 (3)
- E−A≧16, and (4)
- wherein the material hardness of the intermediate layer, expressed as the Shore D hardness, is from 62 to 70,
- wherein the core is formed from a material molded under heat and is formed from a rubber composition comprising a base rubber, a crosslinking initiator, and water, and
- wherein the difference between the crosslink density at the core surface and the crosslink density at the core center, both of which are crosslink densities measured based on a toluene swelling test, is at least 9×102 mol/m3, and
- wherein the base rubber consists of polybutadiene synthesized with a rare-earth catalyst and/or a polybutadiene synthesized with a nickel catalyst.
Dependencies are inferred from the claim text.