Bridgestone Sports Co., Ltd.

Toru Ogawana

Hiroshi Higuchi

Akira Kimura

Atsushi Nanba

Katsunobu Mochizuki

Junji Umezawa

Hiroyuki Nagasawa

Naoki Miyakoshi

Jun Shindo

Junji Hayashi

Tsuyoshi Nakajima

Kae Iizuka

Ryota Nakamura

In order to satisfy at a high level the golf ball flight and control performances relied on by professional golfers and skilled amateurs, this invention provides a multi-piece solid golf ball G having a corea coverand an intermediate layertherebetween wherein the core is formed of a rubber composition that includes an alcohol having a value obtained by dividing the molecular weight of the alcohol by the number of hydroxyl groups thereon which is 70 or less. Also, letting Hc be the JIS-C hardness at the center of the core, H12 be the JIS-C hardness at a position 12 mm from the core center and Ho be the JIS-C hardness at the surface of the core, the core has a hardness profile in which these hardnesses satisfy fixed relationships defined by specific formulas.

Golf ball

In order to satisfy at a high level the golf ball flight and control performances relied on by professional golfers and skilled amateurs, this invention provides a multi-piece solid golf ball G having a core, a coverand an intermediate layertherebetween wherein the core is formed of a rubber composition that includes a lower alcohol having a molecular weight below 200. Also, letting Hc be the JIS-C hardness at the center of the core, H12 be the JIS-C hardness at a position 12 mm from the core center and Ho be the JIS-C hardness at the surface of the core, the core has a hardness profile in which these hardnesses satisfy fixed relationships defined by specific formulas.

In order to satisfy at a high level the golf ball flight and control performances relied on by professional golfers and skilled amateurs, this invention provides a multi-piece solid golf ball G having a core, a coverand an intermediate layertherebetween wherein, letting Hc be the JIS-C hardness at a center of the core, H12 be the JIS-C hardness at a position 12 mm from the core center and Ho be the JIS-C hardness at a surface of the core, the core has a hardness profile which satisfies the condition (Ho&#x2212;H12)&#x2212;(H12&#x2212;Hc)&#x2265;10; letting (Ho&#x2212;H12)&#x2212;(H12&#x2212;Hc) above be A, the spin index of the ball, defined as the dynamic coefficient of friction of the ball multiplied by A, is at least 3.0; and the hardness profile index, defined as the deflection (mm) of the core when compressed under a final load of 1,275 N (130 kgf) from an initial load of 98 N (10 kgf) multiplied by A, is at least 40.

In a multi-piece solid golf ball having a core, a cover and an intermediate layer therebetween, letting Hc be the JIS-C hardness at the core center, H12 be the JIS-C hardness at a position 12 mm from the core center and Ho be the JIS-C hardness at the core surface, the core has a hardness profile which satisfies the conditions 0&#x2266;H12&#x2212;Hc&#x2266;15, 15&#x2266;Ho&#x2212;H12&#x2266;30, (Ho&#x2212;H12)&#x2212;(H12&#x2212;Hc)&#x2267;10 and 20&#x2266;Ho&#x2212;Hc&#x2266;40. Also, letting A be the value represented by (Ho&#x2212;H12)&#x2212;(H12&#x2212;Hc), the spin index of the ball, defined as the dynamic coefficient of friction for the ball multiplied by A, is at least 3.0. This golf ball can satisfy at a high level the flight and control performance relied on by professional golfers and skilled amateurs.

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&#x2212;C&#x2267;7, (2) C&#x2212;B&#x2266;7, (3) (D&#x2212;C)&#x2212;(C&#x2212;B)&#x2267;7, and (4) E&#x2212;A&#x2267;16.

In a multi-piece solid golf ball having a core formed of a center core encased by an envelope layer, a cover having a plurality of dimples on its surface, and one or more intermediate layer disposed between the core and the cover, the center core and the envelope layer are each made of an elastic material, the radius r (mm) of the center core satisfies the condition 5&#x2266;r&#x2266;15, and the core has a cross-sectional hardness profile that satisfies specific conditions. This golf ball has an increased distance and a soft feel at impact, and also is able to prevent a decline in the durability to cracking.

Multi-piece solid golf ball

A multi-piece solid golf ball has a solid core, an envelope layer that encloses the solid core, an intermediate layer that encloses the envelope layer, and a cover that encloses the intermediate layer and has a plurality of dimples on a surface thereof. The diameter of the solid core, the center hardness, surface hardness and hardness difference between the center and surface of the solid core, the thickness and surface hardness of the envelope layer, and the thickness and surface hardness of the intermediate layer are each optimized within specific ranges. Moreover, the intermediate layer is formed so as to be harder than the envelope layer and the cover. In addition, the thickness and surface hardness of the cover, and the combined thickness of the envelope layer, intermediate layer and cover are each optimized within specific ranges.

The invention provides a multi-piece solid golf ball composed of a solid core, a cover, at least one intermediate layer situated therebetween, and a plurality of dimples on a surface of the ball. The diameter of the solid core, the deflection of the core when compressed under a final load of 130 kgf from an initial load of 10 kgf, the hardness at the center of the core, the hardness in a region 5 mm to 10 mm from the center of the core, the hardness 15 mm from the center of the core, and the surface hardness are set within specific ranges. The intermediate layer is composed primarily of a material obtained by mixing under applied heat a specific resin composition and the cover is formed primarily of polyurethane. And, the number of dimples and the trajectory volume TVT are set within specific ranges. The golf ball of the invention has an excellent flight performance, feel, controllability and scuff resistance.

The invention provides a multi-piece solid golf ball composed of a solid core, a cover, at least one intermediate layer situated therebetween, and a plurality of dimples on a surface of the ball. The diameter of the solid core, the deflection of the core when compressed under a final load of 130 kgf from an initial load of 10 kgf, the hardness at the center of the core, the hardness in a region 5 mm to 10 mm from the center of the core, the hardness 15 mm from the center of the core, and the surface hardness are set within specific ranges. The intermediate layer is composed primarily of a material obtained by mixing under applied heat a specific resin composition. The golf ball of the invention has an excellent flight performance, feel, controllability and scuff resistance.

The present invention provides a three-piece solid golf ball having a core obtained by molding under heat a specific rubber composition and having a two-layer cover and an inner cover layer and an outer cover layer which encase the core and are made of a thermoplastic resin material. By optimizing the deflection of the core under a specific load, optimizing the combined thickness of the cover layers, forming the inner cover layer of a highly neutralized ionomer resin composition, and forming the outer cover layer of a special urethane material, a sufficient reduction in the spin rate of the ball on shots taken with a driver can be achieved, enabling the distance traveled by the ball to be increased. Moreover, the golf ball of the invention has a good feel on shots taken with a driver, and has an excellent spin rate on approach shots.

Three-piece solid golf ball

The present invention provides a three-piece solid golf ball having a core molded under heat from a specific rubber composition and inner and outer cover layers encasing the core. By optimizing the core deflection under a specific load and the overall thickness of the cover layers, by forming the inner cover layer of a highly neutralized ionomer resin composition, and by optimizing within specific ranges the Shore D hardnesses of the inner cover layer and the outer cover layer, the spin rate of the ball on shots with a driver can be sufficiently reduced, enabling an increased distance to be achieved.

The invention provides a multi-piece solid golf ball composed of a solid core, a cover, at least one intermediate layer situated therebetween, and a plurality of dimples on a surface of the ball. The diameter of the solid core, the deflection of the core when compressed under a final load of 130 kgf from an initial load of 10 kgf, the hardness at the center of the core, the hardness in a region 5 mm to 10 mm from the center of the core, the hardness 15 mm from the center of the core, and the surface hardness are set within specific ranges. The intermediate layer is composed primarily of a material obtained by mixing under applied heat a specific resin composition, and the thickness and material hardness of the intermediate layer, as well as the hardness difference between the surface of the solid core and the intermediate layer are set within specific ranges. The cover is formed primarily of polyurethane, and has a thickness and a material hardness set within specific ranges. The golf ball of the invention has an excellent flight performance, feel, controllability and scuff resistance.

The invention provides a method of manufacturing golf balls composed of a core and one or more cover layer which encloses the core, at least one cover layer being a thin layer having a thickness of 1.0 mm or less. The thin layer is formed to a desired thickness on a surface of a core or spherical body by holding within a mold cavity the core or a spherical body composed of the core enclosed by a cover layer and injecting a synthetic resin material into a space defined by a surface of the core or spherical body and an inner face of the mold cavity so as to form a cover layer on the surface of the core or spherical body, then grinding the resulting cover layer to a thickness of at least 0.1 mm with a specific type of grinder. Golf balls obtained in this way can be provided with a good sphericity even when the cover is formed to a very small thickness.

Golf ball manufacturing method

The present invention provides a multi-piece solid golf ball having a core obtained by molding under heat a specific rubber composition and having a cover of at least three layers which encases the core. By optimizing the deflection of the core under a specific load, optimizing the hardness at the center of the core and the hardnesses of the innermost cover layer, outermost cover layer and intermediate cover layer, setting the combined thickness of the cover layers to at least a specific value, and forming the innermost cover layer of a highly neutralized ionomer resin composition, a sufficient reduction in the spin rate of the ball on shots taken with a driver can be achieved, enabling the distance traveled by the ball to be increased.

Growing community of inventors

Chichibu, Japan

Toru Ogawana