Games using tangible projectile – Golf – Ball
Reexamination Certificate
1999-08-11
2001-12-04
Graham, Mark S. (Department: 3711)
Games using tangible projectile
Golf
Ball
C524S432000
Reexamination Certificate
active
06325730
ABSTRACT:
FIELD OF THE INVENTION
The present invention is directed to golf balls utilizing improved polybutadiene compositions for use in molded golf ball cores in conjunction with a particular type of cover composition. In one aspect, the improved polybutadiene compositions utilize one or more particular butadiene rubbers synthesized through the use of neodymium and cobalt-containing catalysts. The polybutadiene is preferably an ultra-high Mooney viscosity polybutadiene. In another aspect, the improved polybutadiene compositions utilize a particular solid butadiene rubber that exhibits an ultra-high Mooney viscosity and/or a high molecular weight and a low dispersity. The use of such butadiene rubber and/or blend of butadiene rubbers increases the resiliency of the ball. In addition, significantly improved mixing properties are achieved. In another aspect, the golf balls feature particular cover constructions that result in the balls exhibiting a soft feel and a particular mechanical impedance.
BACKGROUND OF THE INVENTION
Two of the principal properties involved in the performance of golf balls are resilience and hardness. Resilience is determined by the coefficient of restitution (referred to as “C.O.R.”), also expressed as the constant “e”, which is the ratio of the relative velocity of two elastic spheres after direct impact to that before impact, or more generally, the ratio of the outgoing velocity to incoming velocity of a rebounding ball. As a result, the coefficient of restitution (i.e. “e”) can vary from zero to one, with one being equivalent to an elastic collision and zero being equivalent to an inelastic collision. Hardness is determined as the deformation (i.e. compression) of the ball under various load conditions applied across the ball's diameter. The lower the compression value, the harder the material.
Resilience (C.O.R.), along with additional factors such as clubhead speed, angle of trajectory, and ball configuration (i.e. dimple pattern), generally determine the distance a ball will travel when hit. Since clubhead speed and the angle of trajectory are not factors easily controllable, particularly by golf ball manufacturers, the factors of concern among manufacturers are the coefficient of restitution (C.O.R.) and the surface configuration of the ball.
In this regard, the coefficient of restitution of a golf ball is generally measured by propelling a ball at a given speed against a hard surface and electronically measuring the ball's incoming and outgoing velocity. The coefficient of restitution must be carefully controlled in all commercial golf balls in order for the ball to be within the specifications regulated by the United States Golfers Association (“U.S.G.A.”). Along this line, the U.S.G.A. standards indicate that a “regulation” ball cannot have an initial velocity (i.e. the speed off the club) exceeding 255 feet per second (250 feet per second with a 2% tolerance). Since the coefficient of restitution of a ball is related to the ball's initial velocity (i.e. as the C.O.R. of a ball is increased, the ball's initial velocity will also increase), it is highly desirable to produce a ball having a sufficiently high coefficient of restitution to closely approach the U.S.G.A. limit on initial velocity, while having an ample degree of hardness (i.e. impact resistance) to produce enhanced durability.
The coefficient of restitution (C.O.R.) in solid core balls is a function of the composition of the molded core and of the cover. In balls containing a wound core (i.e. balls comprising a liquid or solid center, elastic windings, and a cover), the coefficient of restitution is a function of not only the composition of the center and cover, but also the composition and tension of the elastomeric windings.
Polybutadiene has been utilized in forming golf ball cores. Prior artisans have investigated utilizing various grades of polybutadiene in core compositions. For example, such attempts are described in U.S. Pat. Nos. 5,385,440; 4,931,376; 4,683,257; 4,955,613; and 4,984,803; and in Japanese Patent References JP 58225138 and JP 7268132, all of which are hereby incorporated by reference. Although some of the core compositions described in these disclosures are satisfactory, a need remains for an improved composition for forming golf ball cores.
For example, U.S. Pat. No. 4,929,678 relates to a golf ball formed from a polybutadiene core composition having a broad Mooney viscosity of 45-90, preferably 50-70, and more preferably 55 to 65. However, the dispersity of the core composition is limited to the range of 4.0 to 8.0, and preferably 4.0 to 6.0. According to the '678 patent, a dispersity of less then 4.0 produces deleterious workability.
Similarly, U.S. Pat. No. 5,082,285 generally discloses the preparation of a solid golf ball from an ultra-high molecular weight polybutadiene having a number average molecular weight of 40×10
4
or more, which has dispersity characteristics as noted. See also U.S. Pat. Nos. 4,974,852 and 5,585,440, wherein Mooney viscosity is discussed without reference to dispersity.
Accordingly, it is an object of the present invention to provide an improved polybutadiene composition which, when utilized to formulate golf ball cores, produces golf balls exhibiting enhanced C.O.R. without increasing hardness. An additional object of the invention is to produce a golf ball core from a polybutadiene composition having a high Mooney viscosity and/or a high molecular weight and low dispersity.
Accordingly, it is an object of the present invention to provide an improved core composition which, when utilized to formulate golf ball cores, produces golf balls exhibiting enhanced C.O.R. and improved processing.
The spin rate and “feel” of a golf ball are particularly important aspects to consider when selecting a golf ball for play. A golf ball with the capacity to obtain a high rate of spin allows a skilled golfer the opportunity to maximize control over the ball. This is particularly beneficial when hitting a shot on an approach to the green.
Golfers have traditionally judged the softness of a ball by the sound of the ball as it is hit with a club. Soft golf balls tend to have a low frequency sound when struck with a club. This sound is associated with a soft feel and thus is desirable to a skilled golfer.
Balata covered wound golf balls are known for their soft feel and high spin rate potential. However, balata covered balls suffer from the drawback of low durability. Even in normal use, the balata covering can become cut and scuffed, making the ball unsuitable for further play. Furthermore, the coefficient of restitution of wound balls is reduced by low temperatures.
The problems associated with balata covered balls have resulted in the widespread use of durable ionomeric resins as golf ball covers. However, balls made with ionomer resin covers typically have PGA compression ratings in the range of 90-100. Those familiar with golf ball technology and manufacture will recognize that golf balls with PGA compression ratings in this range are considered to be somewhat harder than conventional balata covered balls. It would be useful to develop a golf ball having a durable cover which has the sound and feel of a balata covered wound ball.
These and other objects and features of the invention will be apparent from the following summary and description of the invention and from the claims.
SUMMARY OF THE INVENTION
The present invention achieves all of the foregoing objectives and provides, in a first aspect, a golf ball comprising a core including a particular combination of polybutadiene rubbers, and a cover disposed about the core wherein the cover has a certain formulation. The core utilizes a first polybutadiene rubber obtained utilizing a cobalt catalyst and having Mooney viscosity in the range of from about 70 to about 83, and a second polybutadiene rubber obtained utilizing a neodymium series catalyst and having a Mooney viscosity of from about 30 to about 70. The cover includes at least one sodium ionomer and at least one zin
Binette Mark L.
Kennedy, III Thomas J.
Nealon John L.
Nesbitt R. Dennis
Shannon Kevin
Gorden Raeann
Graham Mark S.
Spalding Sports Worldwide Inc.
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