Solid golf ball

Details Solid golf ball Solid golf ball

1998-11-10

2001-06-19

Graham, Mark S. (Department: 3711)

Games using tangible projectile

Golf

Ball

C473S376000

Reexamination Certificate

active

06248029

ABSTRACT:

This invention relates to a solid golf ball suitable for golfers having a relatively low club head speed of less than 40 m/s.
BACKGROUND OF THE INVENTION
Numerous attempts have been made to achieve golf balls endowed with both increased carry and a good feel when hit. The approach most commonly taken in solid golf balls has been to alter the hardnesses of the cover and the core.
Solid golf balls having a multilayer solid core with a core inner layer and a core outer layer have recently been proposed. For example, JP-A 23069/1994 discloses a solid golf ball having a three-layer construction comprising a core, a core outer layer, and a cover wherein the core has a diameter of 23 to 35 mm and a Shore D hardness of 30 to 62 The core outer layer has a Shore D hardness of 30 to 56 whereby a suitable spin is maintained and the rebound characteristics and carry are improved. However, when this solid golf ball is hit at a relatively low head speed of about 35 m/s, the ball is given a low initial velocity, failing to have sufficient carry.
JP-A 170012/1994 describes a solid golf ball in which the core inner layer is made of Surlyn ionomer resin, commonly used as a cover material, that has been foamed (&rgr;=0.2 to 1.0). Yet, the core inner layer is so soft that the ball provides a poor rebound and an inadequate carry.
Because most conventional golf balls are targeted at professional golfers and skilled amateurs, they have been designed for optimal performance in a relatively club high head speed range of about 40 to 45 m/s. But these golf balls are often less than ideal for use by relatively low club head speed players such as women golfers and seniors who strike the ball at club head speeds of less than 40 m/s. If a low club head speed golfer plays a full shot with a driver, for instance, the speed upon impact (initial velocity) conventional balls acquire will be too low to provide an adequate carry.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a golf ball which is suitable for use by players having a relatively low head speed of under 40 m/s, affording in particular a good carry when hit with a driver, and which also has a good feel.
The present invention provides a solid golf ball comprising a solid core and a cover enclosing the solid core. The solid core has a multilayer construction consisting essentially of a core inner layer and a core outer layer enclosing the core inner layer. The core inner layer has a diameter of 15 to 22 mm and a Shore D hardness of 40 to 70, and the core outer layer has a JIS-C hardness of 40 to 75. Each of the core inner layer and the core outer layer is formed of a polybutadiene base rubber composition. The cover has a gage of 0.5 to 3 mm. Preferably, the core inner layer has a specific gravity of 1.1 to 1.65, and the core outer layer has a specific gravity of 1.05 to 1.25. Also preferably, the solid golf ball undergoes a deformation of 2.4 to 3.8 mm under a load of 100 kg.
The golf ball of this construction is suitable for use by players having a relatively low club head speed of under 40 m/s. More particularly, the relatively hard core inner layer having a relatively small diameter cooperates with the soft core outer layer having high resilience so that the ball may be sufficiently deformed when a player having a relatively low club head speed of under 40 m/s plays a full shot with a driver. As a result, the initial velocity is increased to insure an outstandingly increased carry and the feel is also improved.
It is noted that JP-A 23069/1994 discloses a golf ball wherein the core inner layer and the core outer layer are formed of polybutadiene base rubber compositions as in the present invention. The core inner layer has a diameter as large as 23 to 35 mm. As seen from Example describing that the golf ball exhibits excellent flight performance when hit at a very high head speed of 108 MPH (=48.3 m/s), this golf ball is designed optimum for very high club head speed players, typically professional golfers, but not suitable for players who swing at a relatively low club head speed of under 40 m/s.


REFERENCES:
patent: 4863167 (1989-09-01), Matsuki et al.
patent: 5779562 (1998-07-01), Melvin et al.
patent: 6-23069 (1994-02-01), None
patent: 6-170012 (1994-06-01), None

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