Games using tangible projectile – Golf – Ball
Reexamination Certificate
2000-08-18
2002-12-17
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S351000
Reexamination Certificate
active
06494793
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 good shot feel at the time of hitting, excellent flight performance and excellent durability.
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 longer flight distance and better durability.
In order to improve the performance of the two-piece solid golf ball, there have been many proposals. The two-piece solid golf balls, of which the performances, such as flight distance (rebound characteristics), durability, shot feel, controllability are improved by adjusting a hardness and hardness distribution of the core to a proper range, have been proposed in, for example, Japanese Patent Kokoku Publication Nos. 21426/1986, 44302/1993, 98206/1996, Japanese Patent Kokai Publication Nos. 182278/1990, 98949/1994, 154357/1994, 327792/1994, 194732/1995, 239067/1997, and the like.
Japanese Patent Kokoku Publication No. 21426/1986 suggests a two-piece golf ball in which a hardness distribution of the core is controlled such that a JIS-C hardness of the surface layer is 72 to 78, a hardness at a distance of 5 mm inner from the surface in the direction of the center point is 77 to 83, a hardness at a distance of 10 mm inner from the surface is 72 to 80, a hardness at a distance of 15 mm inner from the surface is 67 to 75, and a hardness at a distance of more than 15 mm inner from the surface is less than 75. However, the golf ball has low surface hardness of the core and has poor rebound characteristics.
Japanese Patent Kokoku Publication No. 44302/1993 suggests a two-piece golf ball in which a hardness distribution of the core is controlled such that a hardness in JIS-C hardness at a distance of less than 10 mm from the center point of the core is 60 to 79 and a hardness at a distance of more than 10 mm from the center point is 80 to 90, and a deformation amount when applying from an initial load of 10 kgf to a final load of 130 kgf is 1.9 to 2.4 mm. However, the resulting golf ball has poor shot feel, because the golf ball has small deformation amount and is hard.
Japanese Patent Kokoku Publication No. 98206/1996 suggests a two-piece golf ball in which a hardness distribution of the core is controlled such that a hardness difference in JIS-A hardness between the center point and the periphery of the core is not more than 10%. However, it is difficult to improve both the shot feel and flight performance of the golf ball, because of only a hardness difference between the center point and the periphery of the core is considered.
Japanese Patent Kokai Publication No. 182278/1990 suggests a two-piece golf ball in which a hardness distribution of the core is controlled such as to substantially decrease the hardness from the surface to the center point of the core, and a relation of the hardness with the distance from the surface is adjusted to a specified range. However, the resulting golf ball has poor shot feel, because the surface of the core has the highest hardness in the core and the center hardness of the core is high.
Japanese Patent Kokai Publication Nos. 98949/1994 and 154357/1994 suggest a two-piece golf ball in which a hardness distribution of the core is controlled so as to increase hardness in order, a center point, 5 to 10 mm from the center point, 15 mm from the center point and a surface.
However, the resulting golf ball has poor shot feel, because the surface of the core has the highest hardness in the core.
Japanese Patent Kokai Publication No. 327792/1994 suggests a two-piece golf ball in which a hardness distribution in JIS-C hardness of the core is controlled such that a center hardness is 65 to 79, a hardness at a distance of 5 mm from the center point in the direction of the surface is 70 to 80, a hardness at a distance of 10 mm from the center point in the direction of the surface is 73 to 80, a hardness at a distance of 15 mm from the center point in the direction of the surface is 75 to 82, the surface hardness is 70 to 85, and a hardness difference between adjacent locations of the measurements is not more than 5. However, since the center hardness of the core is high, the shot feel of the golf ball is poor.
Japanese Patent Kokai Publication No. 194732/1995 suggests a two-piece golf ball, of which a core has a center hardness in JIS-C hardness of 40 to 57, a surface hardness in JIS-C hardness of 70 to 95, and the difference between the surface hardness and center hardness of 20 to 40. However, since the center hardness of the core is low, the durability of the golf ball is poor and the rebound characteristics of the golf ball are sufficiently obtained.
Japanese Patent Kokai Publication No. 239067/1997 suggests a two-piece golf ball, of which a core has a surface hardness in JIS-C hardness of not more than 85, and a hardness distribution that a center hardness is smaller than the surface hardness by 8 to 20 and a hardness at a distance of not more than 5 mm from the surface is smaller than the surface hardness by not more than 8. However, since the surface hardness is the highest in the core, the shot feel of the golf ball is poor.
It is required to solve the above problem and to provide a two-piece golf ball having not only better flight performance and better durability but also having better shot feel. It is further required for the two-piece solid golf ball to improve the above-mentioned physical properties, especially shot feel, because a multi-piece solid golf ball having excellent flight performance and good shot feel has been introduced into market.
OBJECTS OF THE INVENTION
A main object of the present invention is to provide a two-piece solid golf ball having good shot feel at the time of hitting, excellent flight performance and excellent durability.
According to the present invention, the object described above has been accomplished by adjusting a center hardness, surface hardness and a hardness at a distance of 5 mm inward from the surface, and a hardness distribution of the core to a specified range, thereby providing a two-piece solid golf ball having good shot feel at the time of hitting, excellent flight performance and excellent durability.
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
when a center hardness in JIS-C hardness of the core is represented by A, a core inward hardness in JIS-C hardness at a distance of 5 mm inward from the surface of the core is represented by B, a surface hardness in JIS-C hardness of the core is represented by C, a cover hardness in JIS-C hardness is represented by D, a distance in mm between a center point of the core and a point of 5 mm inward from the surface of the core is represented by K and a radius in mm of the golf ball is represented by L,
the golf ball satisfies the following relations;
58 ≦
A <
65,
80 ≦
B ≦
87,
78 <
C,
C is lower than B by 1 to 5, and
0.9≦[(
D−B
)/(
L−K
)]/[(
B−A
)/
K]≦
2.0.
In order to practice the present invention suitably, it is desired that the core have a deformation amount (a) of 2.6 to 3.6 mm when applying from an initial load of 10 kgf to a final load of 130 kgf, the cover hardness (D) be 90 to 97, the cover have a thickness of 1.3 to 2.8 mm, and a ratio (a/b) of the deformation amount of the core (a) to a deformation amount of the golf ball (b) when applying from an initial load of 10 kgf to a final load of 130 kgf be within the range of 1.05 to 1.25.
According to an investigation of flight performance of a two-piece solid golf ball comprising a core and a cover formed on the core, when the hardness difference from the center point to the surface of the core is small, that is, the core has generally even hardness distribution, energy loss with deformation of the core at the time o
Hunter Alvin A.
Sewell Paul T.
Sumitomo Rubber Industries Ltd.
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