Bridgestone Sports Co., Ltd.

Katsunori Sato

Atsuki Kasashima

Takuma Nakagawa

Hideo Watanabe

Hiroshi Higuchi

Kae Iizuka

Yoichi Omura

Takashi Ohira

Atsushi Komatsu

Daisuke Arai

Hirotaka Shinohara

Yuichiro Ozawa

Masanobu Kuwahara

Masataka Kai

Motoki Furuyama

Tasuku Takita

Junji Umezawa

Atsushi Mitamura

A golf ball for amateur golfers exhibits excellent flight characteristics when hit by the average golfer and also has a good feel at impact that is both soft and solid. The golf ball includes a core, an intermediate layer and a cover, and has coefficient of restitution and compressive deformation relationships that satisfy specific conditions.

Golf ball

A multi-piece solid golf ball having a two-layer core with an inner core layer and an outer core layer and having a cover of at least two layers including an intermediate layer and an outer layer with numerous dimples on the surface is characterized in that the hardest cover layer has a specific material hardness and the ball has a specific value obtained by subtracting the surface hardness of the overall core from the surface hardness of the hardest cover layer, a specific deflection, and a specific value obtained by subtracting the initial velocity of the inner core layer from the initial velocity of the sphere consisting of the inner core layer encased by the outer core layer. This golf ball enables relatively low head speed golfers to achieve a good distance on full shots with drivers and iron clubs and also provides a soft, comfortable feel at impact.

Multi-piece solid golf ball

In a multi-piece solid golf ball having a core, an intermediate layer encasing the core and a cover which encases the intermediate layer and has numerous dimples on an outside surface thereof, the intermediate layer is formed of a resin material, the cover is formed of a urethane resin material, the core has a diameter of at least 38.0 mm, the sphere obtained by encasing the core with the intermediate layer has a surface hardness on the Shore D hardness scale of at least 69, the cover has a material hardness on the Shore D hardness scale of 55 or less, the (intermediate layer thickness)/(core diameter) value is from 0.025 to 0.043, the (cover thickness)/(core diameter) value is from 0.014 to 0.027, and the sphere obtained by encasing the core with the intermediate layer has an initial velocity A and the core has an initial velocity B which together satisfy the condition A&#x2212;B&#x2265;0 m/s.

In a multi-piece solid golf ball made up of, successively, a core, an intermediate layer and a cover having numerous dimples on the surface thereof, the intermediate layer is formed of a resin material and the cover is formed of a urethane resin material, each having a specific respective Shore D hardness. The ball has a specific (intermediate layer thickness)/(core diameter) value and a specific (cover thickness)/(core diameter) value, and the core has a specific deflection. The sphere consisting of the core encased by the intermediate layer has an initial velocity A and the core has an initial velocity B which together satisfy the condition A&#x2212;B&#x2265;0 m/s. This golf ball provides an increased distance and has both a soft feel when played and a high durability to repeated impact.

A multi-piece solid golf ball having a two-layer core with an inner core layer and an outer core layer and having a cover of one or more layer with numerous dimples on the surface is characterized in that the hardest cover layer has a specific material hardness and the ball has a specific value obtained by subtracting the surface hardness of the overall core from the surface hardness of the hardest cover layer, a specific deflection, and a specific value obtained by subtracting the initial velocity of the inner core layer from the initial velocity of the sphere consisting of the inner core layer encased by the outer core layer. This golf ball enables relatively low head speed golfers to achieve a good distance on full shots with drivers and iron clubs and also provides a soft, comfortable feel at impact.

A method for forming a golf ball provides a core member comprising a core of a golf ball into a cavity of a mold so that the core member is supported by a movable holding pin disposed in the mold; forming a layer outside the core member by injecting a material of the layer into the cavity; and retracting the pin from the cavity into the mold during the material injection so that a portion projecting from a surface of the layer is formed by a tip of the pin, the projecting portion having a site area of at least 0.2% in relation to an entire area of the tip of the pin and having a height of at least 0.2 mm. This method can be implemented by controlling the retraction of the pin, or alternatively by using the pin having a predetermined indentation portion on the tip.

Method for forming golf ball and mold therefor

A golf ball includes a plurality of dimples on the surface thereof and satisfies the following expression (1):&#xd7;100&#x2265;6.25 (mm)&#x2003;&#x2003;(1),wherein H is a deformation amount, which is expressed by a compressive deformation amount of the golf ball; S is a virtual plane area, which is a surface area of the golf ball determined supposing that no dimple exists on the surface of the golf ball; and PSis a pressurized area, which is an area of the golf ball contacting a plane when a load of 6864 N is applied to the golf ball. The bottom of the dimple includes a center protruding portion with a curved shape protruding toward an outside of the golf ball.

A golf ball includes plural dimples formed on a surface thereof and plural depressed or protruded portions spaced apart from each other and arranged along an outer periphery of at least one of the plural dimples. The plural depressed or protruded portions each has, as a part of a contour thereof, a shape substantially similar to a part of a contour of the dimple surrounded with the plural depressed or protruded portions. The plural depressed or protruded portions each has a length of more than 1/10 and less than &#xbd; of an outer peripheral length of the dimple surrounded with the plural depressed or protruded portions.

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.

A golf ball includes oval dimples arranged on the surface thereof. Each of the oval dimples has a long diameter DL and a short diameter DS in a planar shape thereof and further having a depth DPL on a first cross section of the oval dimple along the long diameter DL and a depth DPS on a second cross section of the oval dimple along the short diameter DS, the depth DPL being a distance taken on the first cross section along the long diameter DL from a first line connecting both ends of the first cross section of the oval dimple to a deepest point of a dimple bottom surface, the depth DPS being a distance taken on the second cross section along the short diameter DS from a second line connecting both ends of the second cross section of the oval dimple to a deepest point of a dimple bottom surface, a relationship between the depth DPL and the depth DPS being defined as a following formula (1):DPS&#x3e;DPL&#x2003;&#x2003;(1). Each of the oval dimples further having a cross-sectional area DLA on the first cross section of the oval dimple along the long diameter DL and a cross-sectional area DSA on the second cross section of the oval dimple along the short diameter DS, the cross-sectional area DLA being surrounded by the first line connecting both ends of the first cross section of the oval dimple and the bottom surface thereof, the cross-sectional area DSA being surrounded by the second line connecting both ends of the second cross section of the oval dimple and the bottom surface thereof, a relationship between the cross-sectional area DLA and the cross-sectional area DSA being defined as a following formula (2):DLA&#x2267;DSA&#x2003;&#x2003;(2).

Golf ball having oval dimples

In a multi-piece solid golf ball having a rubber two-layer core consisting of an inner layer and an outer layer, a cover, and at least one intermediate layer therebetween, the inner core layer has a diameter of at least 30 mm, the difference in JIS-C hardness between the center of the inner core layer and the surface of the outer core layer is at least 25, the ball satisfies the relationship A/B&#x2266;1.5, where A and B are the deflections of, respectively, the inner core layer and the two-layer core when compressed under specific loading conditions, and the intermediate layer has a higher material hardness than the cover. This ball enables mid- to high-level golfers both to achieve even longer distances and to maintain the spin performance on approach shots at a high level.

A golf ball includes oval dimples arranged on the surface thereof. Each of the oval dimples has a long diameter DL and a short diameter DS in a planar shape thereof, a relationship between the long diameter and the short diameter being defined as a following formula (1).&#xd7;1.2&#x2003;&#x2003;(1) Each of the oval dimples further has a cross-sectional area DLA on the first cross section of the oval dimple along the long diameter DL and a cross-sectional area DSA on the second cross section of the oval dimple along the short diameter DS, the cross-sectional area DLA being surrounded by a line connecting both ends of the first cross section of the oval dimple and the bottom surface thereof, the cross-sectional area DSA being surrounded by a line connecting both ends of the second cross section of the oval dimple and the bottom surface thereof, a relationship between the cross-sectional area DLA and the cross-sectional area DSA being defined as a following formula (2).DLA&#x2267;DSA&#x2003;&#x2003;(2) The surface coverage SR of all dimples on the surface of the golf ball is at least 70%.

A golf ball mold body having a plurality of mold parts with a parting surface defining a parting line along an equator and removably mating to form a cavity having an inner wall with dimple-forming protrusions, and a support pin extendable into and retractable from the cavity, the support pin extending into the cavity to support a center sphere. An end face of the support pin defines a portion of the cavity inner wall when the support pin is retracted. The support pin has a shape satisfying certain conditions, and the support pin and mold body have a gap therebetween set within a specific range. The invention minimizes formation of uneven flash caused by deflection or shifting of support pins, appearance defects caused by damage to the cavity inner wall and contamination by rubbing debris, and the life of the mold is extended.

Golf ball mold and golf ball manufacturing method

A golf ball mold that includes a mold body configured as a plurality of mold parts which have at least a parting surface that defines a parting line at a golf ball equator and removably mate to form a cavity having an inner wall with a plurality of dimple-forming protrusions thereon is provided. The golf ball mold includes a support pin which has an end face with a plurality of dimple-forming protrusions thereon and is extendable into and retractable from the cavity. The support pin extends into the cavity to support a center sphere and, when in a retracted state, the end face thereof defines a portion of the inner wall of the cavity. The end face of the support pin includes a pole of the cavity and has a peripheral edge which intersects a parallel of latitude at 10 degrees from the pole.

Growing community of inventors

Chichibu, Japan

Katsunori Sato