Hollow solid golf ball

Details Hollow solid golf ball Hollow solid golf ball

1998-03-23

2001-03-13

Gerrity, Stephen F. (Department: 3711)

Games using tangible projectile

Golf

Ball

C473S372000

Reexamination Certificate

active

06200231

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a solid golf ball comprising a hollow core and a cover layer. More particularly, it relates to a golf ball having good shot feel at the time of hitting, large inertia moment, large launch angle at the time of hitting and increased flight distance.
TECHNICAL BACKGROUND
In the prior art, there are two kinds of golf balls. The one is a solid golf ball, such as a two-piece solid golf ball, which is composed of a core of an integrally molded rubber member and a thermoplastic resin (e.g. ionomer resin, etc.) covered on the core. The other is a thread wound golf ball and is obtained by winding thread rubber on a solid or liquid center and covering it with a cover of an ionomer resin, balata, etc. having a thickness of 1 to 2 mm. The two-piece solid golf ball is used by many golfers, particularly amateur golfers, because of good durability, longer flight distance attained by high ball velocity at the time of hitting and excellent flight performance in comparison with the thread wound golf ball. On the other hand, the two-piece solid golf ball has a problem wherein the shot feel at the time of hitting is hard.
In order to improve the drawback of the two-piece solid golf ball, softening the cover or the core has been suggested, but the softening adversely lowers the rigidity of the golf ball and reduces the impact force of the golf ball at the time of hitting, which results in a reduction in flight distance.
In addition, in order to improve this drawback, it has been tried to make the core and the cover of multiple layers. However, a two piece solid golf ball having satisfactory performance has not yet been obtained.
In order to improve the shot feel of a solid golf ball, a hollow portion golf ball having a hollow core at its center has been proposed in Japanese Utility Model Publication No. 3(1992)-63354. By forming a hollow portion in the center of the golf ball, the weight is disposed to the outside of the golf ball to increase moment of inertia, thereby making it possible to increase the flight distance. Since the hollow portion is present at its center, the impact force at the time of hitting can also be reduced.
Although it is actually possible to increase the moment of inertia by forming a hollow portion inside of the golf ball, the golf ball weight is undesirably reduced. To compensate for the ball weight, the rubber composition for the golf ball is made heavier or with a higher specific gravity by adding thereto a larger amount of a filler. The formulation of a filler in a larger amount adversely decreases the rubber content in the rubber composition to result in the degradation of the rebound characteristics. With respect to the impact force upon hitting, providing a hollow portion inside of the golf ball increases the deformation of the golf ball upon hitting and reduces the impact force, thus reducing the shot feel upon hitting. However, the larger the deformation of the golf ball, the larger the energy loss which often degrades the rebound characteristics.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the above problems of the conventional two-piece solid golf ball and to provide a solid golf ball having good shot feel at the time of hitting without deteriorating the excellent flight performance inherent in the two-piece solid golf ball.
As a result, the present inventors have found that, by employing a hollow core (
5
) composed of a hollow portion (
1
) having a diameter of 5 to 30 mm and a hollow core outer layer portion (
2
), the shot feel at the time of hitting is improved and the moment of inertia increases, which results in a high launch angle and a small spin amount immediately after hitting. In addition, the specific hollow core reduces the rate of spin dumping between the ascending of the ball and descending, which increases flight distance.
When a golf ball is hit with a golf club, spin is applied on the golf ball and lifting power acts on the golf ball in the normal direction to the flight curve of the golf ball due to the spin. However, when the ball is ascending, the partial force of the lifting power in the horizontal direction acts negative to the ball's flight direction. The lifting power reduces ball speed, althought the ball speed is very high immediately after hitting. However, after the ball passes the highest point of the flight curve of the golf ball and is descending to the ground, the lifting power caused by the spin acts positively to the ball flight direction in a partial force in the horizontal direction of the lifting power. Accordingly, a large lifting power at the time the ball is descending is preferable for increasing the flight distance. In order to increase the flight distance of the golf ball, it is preferred that the spin is small at the time the ball is ascending, immediately after hitting and the spin is large at the time the ball is descending. For perfecting the above function, it is more preferred that the moment of inertia of the golf ball is large.


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patent: 5480155 (1996-01-01), Molitor et al.
patent: 5944621 (1999-08-01), Tsujinaka et al.
patent: 5980395 (1999-11-01), Tsunoda et al.
patent: 5997416 (1998-07-01), Maruko

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