Games using tangible projectile – Golf – Ball
Reexamination Certificate
1999-04-07
2002-05-14
Vo, Peter (Department: 3729)
Games using tangible projectile
Golf
Ball
C473S373000, C473S374000, C473S375000, C473S377000
Reexamination Certificate
active
06386993
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a two-piece solid golf ball. More particularly, it relates to a two-piece solid golf ball having excellent flight performance and good shot feel when hit by a driver, and excellent controllability when hit by an iron club.
BACKGROUND OF THE INVENTION
Many types of golf balls are commercially selling, but two-piece solid golf balls and thread wound golf balls are generally used for round games. The two-piece solid golf ball, when compared with the thread wound golf ball, has better durability and better flight performance because of larger initial velocity when hitting and longer flight distance. The two piece solid golf ball is generally approved of or employed by many golfers, especially amateur golfers. On the other hand, the two-piece solid golf ball has poor shot feel at the time of hitting and poor controllability at approach shot because of spin rate.
In the past, golf balls having good shot feel and controllability have been proposed in, for example, Japanese Patent Kokai Publication No. 98949/1994, Japanese Patent Kokai Publication No. 154357/1994, Japanese Patent Kokai Publication No. 289661/1995, Japanese Patent Kokai Publication No. 194732/1995, Japanese Patent Kokai Publication No. 239607/1997. These golf balls adopt a two-piece structure in which hardness distribution from a center point to a surface of a core is controlled to a proper range, to obtain shot feel and controllability similar to the thread wound golf ball.
For example, Japanese Patent Kokai Publication Nos. 98949/1994 and 154357/1994 suggest a two-piece golf ball in which hardness distribution of the core is controlled so as to increase the hardness in order, a center point, 5 to 10 mm from the center point, 15 mm from the center point and a surface. However, since a cover, which has a flexural modulus of 3,000 to 4,500 kgf/cm
2
, is hard, shot feel and controllability of the golf ball are poor.
Japanese Patent Kokai Publication No. 289661/1995 suggests a two-piece golf ball, of which a core has a JIS-C surface hardness of 55 to 75, a JIS-C hardness of cross section other than the surface of 65 to 85 and a variance of hardness over the cross section of not more than 5. The surface hardness is smaller than the hardness of the cross section by not less than 5. However, since the surface of the core is soft in the golf ball, shot feel is poor.
Japanese Patent Kokai Publication No. 194782/1995 suggests a two-piece golf ball, of which a core has a JIS-C center hardness of 40 to 57, a JIS-C surface hardness of 70 to 95, and difference between the center hardness and the surface hardness of 20 to 40. However, since the cover, which has a thickness of 1.4 to 2.7 mm, is thick and hard in the golf ball, shot feel and controllability are poor.
Japanese Patent Kokai Publication No. 239067/1997 suggests a two-piece golf ball, of which a core has a JIS-C surface hardness of not more than 85, and hardness distribution that a center hardness is smaller w than the surface hardness by 8 to 20 and a hardness at the portion of not more than 5 mm from the surface is smaller than the surface hardness by not more than 8. However, since the difference between the center hardness and the surface hardness is small in the golf ball, shot feel is poor, and fight performance is not sufficient.
It is required to solve the above problem and provide a two-piece golf ball having better flight performance, better shot feel and better controllability. Therefore, it is required to improve such physical properties further.
OBJECTS OF THE INVENTION
A main object of the present invention is to provide a two-piece solid golf ball having excellent flight performance and good shot feel when hit by a driver, and excellent controllability when hit by an iron club.
According to the present invention, the object described above has been accomplished by adjusting a center hardness, surface hardness, a difference between the center hardness and the surface hardness and a deformation amount when applying from an initial load of 10 kgf to a final load of 130 kgf of the core, and a hardness and thickness of the cover to a specified range, thereby providing a two-piece solid golf ball having excellent flight performance and good shot feel when hit by a driver, and excellent controllability when hit by an iron club.
SUMMARY OF THE INVENTION
The present invention provides a two-piece solid golf ball comprising a core, and a cover formed on the core, wherein the core has a JIS-C center hardness of not more than 60, a JIS-C surface hardness of 70 to 95, a difference between the center hardness and surface hardness of 20 to 40 and a deformation amount of 2.6 to 3.5 mm when applying from an initial load of 10 kgf to a final load of 130 kgf, and the cover has a Shore D hardness of not more than 60 and a thickness of 1.2 to 2.0 mm.
DETAILED DESCRIPTION OF THE INVENTION
The two-piece solid golf ball of the present invention comprises a core, and a cover formed on the core. The core is obtained by press molding and vulcanizing a rubber composition using a method and condition which have been conventionally used for preparing the core of solid golf balls. The rubber composition contains a base rubber, a co-crosslinking agent, an organic peroxide, and optionally an organic sulfide compound, a filler, an antioxidant and the like.
The base rubber used for the core of the present invention may be natural rubber and/or synthetic rubber, which has been conventionally used for solid golf balls. Preferred is high-cis polybutadiene rubber containing not less than 40%, preferably not less than 80% of a cis-1, 4 bond. The high-cis polybutadiene rubber may be mixed with natural rubber, polyisoprene rubber, styrene-butadiene rubber, ethylene-propylene-diene rubber. (EPDM) and the like.
The co-crosslinking agent can be a metal salt of &agr;, &bgr;-unsaturated carboxylic acid, including mono or divalent metal salts, such as zinc or magnesium salts of &agr;,&bgr;-unsaturated carboxylic acids having 3 to 8 carbon atoms (e.g. acrylic acid, methacrylic acid, etc.). Preferred co-crosslinking agent is zinc diacrylate because it imparts high rebound characteristics to the resulting golf ball. An amount of the metal salt of the unsaturated carboxylic acid in the rubber composition may be from 20 to 40 parts by weight, preferably from 22 to 38 parts by weight, based on 100 parts by weight of the base rubber. When the amount of the metal salt of the unsaturated carboxylic acid is smaller than 20 parts by weight, the core is too soft, and rebound characteristics are degraded to reduce flight distance. On the other hand, when the amount of the metal salt of the unsaturated carboxylic acid is larger than 40 parts by weight, the core is too hard, and shot feel is poor.
The organic peroxide includes, for example, dicumyl peroxide, 1,1-bis(t-butylperoxy)-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(t-butylperoxy) hexane, di-t-butyl peroxide and the like. Preferred organic peroxide is dicumyl peroxide. An amount of the organic peroxide may be from 0.3 to 5.0 parts by weight, preferably 0.5 to 3.0 parts by weight, based on 100 parts by weight of the base rubber. When the amount of the organic peroxide is smaller than 0.3 parts by weight, the core is too soft and rebound characteristics are degraded to reduce flight distance. On the other hand, when the amount of the organic peroxide is larger than 5.0 parts by weight, the core is too hard, and shot feel is poor.
The rubber composition for the core of the golf ball of the present invention may optionally contain an organic sulfide compound in addition to the above components. The organic sulfide compound includes polysulfides having 2 to 4 sulfur atoms, such as diphenyl polysulfide, dibenzyl polysulfide, dibenzoyl polysulfide, dibenzothiazoyl polysulfide, dithiobenzoyl polysulfide and the like. Preferred organic sulfide compound is diphenyl disulfide, in view of rebound characteristics. An amount of the organic sulfide compound may be from 0.1 to 3.0 parts by weight, preferably from 0.3
Kim Paul D
Sumitomo Rubber Industries Ltd.
Vo Peter
LandOfFree
Two-piece solid golf ball does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Two-piece solid golf ball, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Two-piece solid golf ball will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2871486