Solid golf ball

Details Solid golf ball Solid golf ball

1999-12-16

2001-07-03

Graham, Mark S. (Department: 3711)

Games using tangible projectile

Golf

Ball

C473S376000

Reexamination Certificate

active

06254495

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a golf ball of a four layer or multilayer structure offering pleasant feel and click when hit, improved durability, and increased distance.
2. Related Art
A variety of multi-piece golf balls including three-piece and four-piece ball constructions have been developed over the past few years in order to improve ball performance. The practice is known of balancing a soft feel with good resilience in multi-piece golf balls by giving the ball a hardness distribution across its core in such a way as to retain both properties. The predominant concept for achieving a soft feel is to soften the core. It is generally believed that hardening the core compromises the feel.
By contrast, golf balls using hard cores are also known (see JP-A 10-127818 and 11-57070). The hard core is reduced in diameter so as to avoid any adverse effect on the soft feel. The use of a hard core allegedly contributes to pleasant click and improved distance performance when hit at low head speeds.
The golf balls disclosed in the above-referred patents has an intermediate layer of a rubber composition formed on the surface of the core. Regrettably, this gives rise to a new problem that stresses tend to concentrate at the interface between the core and the intermediate layer due to the hardness difference therebetween so that the soft rubber layer is sensitive to crack.
SUMMARY OF THE INVENTION
An object of the invention is to provide a solid golf ball of four or multilayer structure offering pleasant feel and click when hit, improved durability, and increased distance.
According to the invention, there is provided a solid golf ball of four or multilayer structure comprising a core, an enclosing layer around the core, an intermediate layer around the enclosing layer, and a cover around the intermediate layer. The core is comprised of a thermoplastic resin or thermoplastic elastomer as a base and has a diameter of 3 to 18 mm and a Shore D hardness of 50 to 95. The enclosing layer is comprised of a thermoplastic resin or thermoplastic elastomer as a base.
Preferably the intermediate layer is formed of a composition comprising polybutadiene as a base. Also preferably, each of the core, the enclosing layer and the intermediate layer has a high specific gravity filler blended therein. The enclosing layer typically has a thickness of 1.0 to 5.0 mm and a Shore D hardness which is at least 10 units lower than that of the core. The difference in Shore D hardness between the enclosing layer and the intermediate layer is preferably less than 40 units.
The invention is directed to a solid golf ball of multilayer structure comprising at least four layers: a core, an enclosing layer, an intermediate layer, and a cover. It has been found that when the core is formed primarily of a thermoplastic resin or thermoplastic elastomer to a diameter of 3 to 18 mm and a Shore D hardness of 50 to 95, and the enclosing layer is formed primarily of a thermoplastic resin or thermoplastic elastomer, the golf ball becomes durable against strikes and offers pleasant feel and click and travels good distance when hit. The use of a thermoplastic resin or elastomer as the small-diameter core makes the manufacture smooth and efficient as compared with the use of rubber compositions. Since the characteristic of the properties of the resin as the core base have a relatively little influence on the overall ball, the ball maintains excellent performance and has improved durability, good resilience and stable distance performance.


REFERENCES:
patent: 5772531 (1998-06-01), Ohsumi et al.
patent: 6045460 (2000-04-01), Hayashi et al.

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