Games using tangible projectile – Golf – Ball
Reexamination Certificate
2001-02-06
2003-05-13
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S351000
Reexamination Certificate
active
06561925
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a multi-piece solid golf ball having at least three layers, more specifically, a solid core, at least one intermediate layer, and a cover having at least one cover layer, and particularly to a multi-piece solid golf ball which is capable of giving a player a desirable soft feeling of hitting the golf ball upon putter shot or approach shot and also a desirable feeling of hitting the golf ball upon driver shot, and which is capable of improving the flying performance of the golf ball.
Solid golf balls have been variously improved. For example, an attempt has been made to soften the hardness of a cover of a two-piece golf ball for giving a player a desirable feeling of hitting the golf ball.
In the case of the above two-piece golf ball, however, if the hardness of the cover is softened, there arises a new problem that the flying distance of the golf ball is shortened.
On the other hand, it has been known that the flying performance of a golf ball can be improved by increasing the hardness of a cover of the golf ball; however, in this case, there arises another problem that the player's feeling of hitting the golf ball upon putter shot or approach shot is degraded.
In this way, it has been difficult to obtain a solid golf ball capable of giving a player a desirable feeling of hitting the golf ball as well as improving the flying performance of the golf ball.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a multi-piece solid golf ball which is capable of giving a player a desirable feeling of hitting the golf ball upon putter shot or approach shot and also a desirable feeling of hitting the golf ball upon driver shot, and which is capable of improving the flying performance of the golf ball.
To achieve the above object, the present inventor has made studies on a multi-piece solid golf ball including at least one intermediate layer between a solid core and a cover.
Eventually, the present inventor has found that a multi-piece solid golf ball characterized in that the solid core has a compression deflection of 3.0 mm or more when a load range of initial 10 kgf to final 130 kgf is applied, the intermediate layer is mainly made from a thermoplastic resin and has a Shore D hardness (ASTM D-2240-75) of 45 to 55 and a specific gravity of 1.2 or less, and the cover has a Shore D hardness of 60 or more and a thickness of 1.6 to 2.3 mm; a ratio of the compression deflection of a sphere composed of the intermediate layer and the solid core covered therewith to the compression deflection of the solid core is more than 0.900 and less than 0.970 [0.900<(compression deflection of sphere/compression deflection of solid core)<0.970]; and a difference in JIS-C hardness (specified under JIS K6301-1996) between the surface and the center of the solid core is equal to or less than 5 [5≦(surface hardness-center hardness)], is advantageous in that the hardness distribution of the solid core, the intermediate layer, and the cover are optimized by specifying the difference in hardness between the surface and the center of the solid core and by increasing the repulsion characteristic of the intermediate layer and increasing the hardness of the cover, with a result that such a golf ball is capable of giving a player a desirable soft feeling of hitting the golf ball upon putter shot or approach shot and also a desirable feeling of hitting the golf ball upon driver shot, and is capable of improving the flying performance of the golf ball to such an extent as to satisfy a player of an average class with a head speed of 40 m/s or less.
Accordingly, the present invention provides a multi-piece solid golf ball comprising: a solid core; at least one intermediate layer for covering the solid core; and a cover having at least one cover layer for covering the intermediate layer; wherein the solid core has a compression deflection of 3.0 mm or more when a load range of initial 10 kgf to final 130 kgf is applied, the intermediate layer is mainly made from a thermoplastic resin and has a Shore D hardness of 45 to 55 and a specific gravity of 1.2 or less, and the cover has a Shore D hardness of 60 or more and a thickness of 1.6 to 2.3 mm; a ratio of the compression deflection of a sphere composed of the intermediate layer and the solid core covered therewith to the compression deflection of the solid core is more than 0.900 and less than 0.970 [0.900<(compression deflection of sphere/compression deflection of solid core)<0.970]; and a difference in JIS-C hardness (specified under JIS K6301-1996) between the surface and the center of the solid core is equal to or less than 5 [5≦(surface hardness-center hardness)].
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M.R. Farrally et al., Science and Golf III: Proceedings of the World Scientific Congress of Golf, Illinois: Human Kinetics, copy right 1999, p. 411.
Kawata Akira
Shimizu Yasumasa
Watanabe Hideo
Bridgestone Sports Co. Ltd.
Hunter, Jr. Alvin A.
Sewell Paul T.
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