Golf ball
AssigneeSRI Sports Limited
InventorsYoshiko Matsuyama, Takahiro Sajima, Keiji Ohama
Life of this patent
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Abstract
A golf ball 2 includes a spherical core 4, a mid layer 6 outside the core 4, and a cover 8 outside the mid layer 6. The core 4 includes a spherical center 10 and an envelope layer 12 outside the center 10. At all points P included in a zone that extends over a distance range from equal to or greater than 1 mm to equal to or less than 15 mm from the central point of the core 4, the following mathematical formula is satisfied. −5<H2−H1<5 In the mathematical formula, H1 indicates the JIS-C hardness at a point P1 located radially inward of each point P at a distance of 1 mm from the point P, and H2 indicates the JIS-C hardness at a point P2 located radially outward of each point P at a distance of 1 mm from the point P.
Claims20
A golf ball comprising a core, a mid layer positioned outside the core, and a cover positioned outside the mid layer, wherein
- the core comprises a center and an envelope layer positioned outside the center,
- the hardness of the center hardness gradually increases from its central point to its surface,
- the hardness of the envelope layer gradually increases from its innermost portion to its surface,
- a ratio of a volume of the core to a volume of a phantom sphere of the golf ball is equal to or greater than 76%,
- a difference (He−Ho) between a JIS-C hardness He at a surface of the core and a JIS-C hardness Ho at a central point of the core is equal to or greater than 15 but equal to or less than 30,
- a JIS-C hardness He of the cover is less than the hardness Ho,
- at all points P included in a zone that extends over a distance range from equal to or greater than 1 mm to equal to or less than 15 mm from the central point of the core, the following mathematical formula is satisfied,
- −5<H2−H1<5
- and in the mathematical formula, H1 indicates a JIS-C hardness at a point P1 that is located radially inward of each point P at a distance of 1 mm from the point P, and H2 indicates a JIS-C hardness at a point P2 that is located radially outward of each point P at a distance of 1 mm from the point P.
Dependencies are inferred from the claim text.