Games using tangible projectile – Golf – Ball
Reexamination Certificate
1999-11-05
2001-11-20
Graham, Mark S. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S377000
Reexamination Certificate
active
06319154
ABSTRACT:
This application is based on patent applications Nos. 10-318000 and 11-256158filed in Japan,the contents of which are hereby incorporated by references.
FIELD OF THE INVENTION
The present invention relates to a solid golf ball having a core and a cover, more particularly, to a solid golf ball which has an improved flying distance, controllability and shot feeling.
BACKGROUND OF THE INVENTION
Hitherto, there have been generally used a thread-wound golf ball and a solid golf ball. A thread-wound golf ball is made by winding a rubber thread around a liquid center or solid center, and then covering the wound center with a balata (i.e., trans-polyisoprene) or ionomer-based resin. A solid golf ball, such as a two- and three-piece golf ball, has a rubber core and a resin cover made of a thermoplastic resin such as ionomer resin. Comparing with a thread-wound golf ball, a solid golf ball can attain a longer flying distance due to a higher initial speed of the ball by a shot of a golf club. In addition, the solid golf ball is better in durability. On the contrary, the solid golf ball generally has a higher hardness, thus receiving a large impact at shooting. Furthermore, the solid golf ball makes it difficult for the player to impart intentional spin and therefore it has a poor controllability especially at an approach shot. Because of these reasons, the solid golf ball has not been positively used by skilled golfers such as professional golfers and senior amateur golfers to whom excellent shot feeling and controllability is beneficial.
To improve the shot feeling and controllability of a solid ball, a variety of improvements have been made by adjusting the hardness of a cover, the hardness of a core and/or the hardness distribution thereof. For example, Japanese Unexamined Patent Publication No.9-239067 discloses a two-piece solid golf ball which includes a solid core having a specified hardness distribution for a surface, a center and a point at 5 mm inside from the surface; a cover having a specified hardness and thickness; and a specified number of dimples.
However, the shot feeling and controllability of a solid golf ball have not been improved without decreasing a flying distance and durability of the ball. Therefore, further improvements has been demanded to solve the problem.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a solid golf ball which has an improved shot feeling and controllability without decreasing a flying distance and durability.
According to an aspect of the present invention, a solid golf ball includes a core and a cover. The core has a hardness of 55 to 75 at a center thereof and a hardness on a surface thereof that is greater than the hardness at the center by 10 or more. The cover has a hardness satisfying the following expressions (1) and (2):
(hardness of the cover)−(hardness at the center of the core)≦17 (1),
(hardness of the cover)−(hardness on the surface of the core)≦5 (2).
The hardness is defined in terms of JIS-C scale hardness meter.
According to another aspect of the present invention, a solid golf ball includes a core having a hardness of 55 to 75 at a center thereof and a hardness of 80 to 90 on a surface thereof, and a cover having a hardness of 80 to 90. The hardness of the cover satisfies the following expressions (1) and (2):
0≦(hardness of the cover)−(hardness at the center of the core)≦17 (1),
−10≦(hardness of the cover)−(hardness on the surface of the core)≦5 (2)
The hardness is defined in terms of JIS-C scale hardness meter.
REFERENCES:
patent: 5490673 (1996-02-01), Hiraoka
patent: 5803834 (1998-09-01), Yamagishi et al.
patent: 5994470 (1999-11-01), Tanaka et al.
Moriyama Keiji
Yoshida Kazunari
Gorden Raeann
Graham Mark S.
Sumitomo Rubber Industries Limited
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