Games using tangible projectile – Golf – Ball
Reexamination Certificate
2002-12-13
2004-04-27
Vidovich, Gregory (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S351000
Reexamination Certificate
active
06726578
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a two-piece solid golf ball excellent in resilience and thereby flight distance characteristic, controllability and feel of hitting.
Golf balls have been requited to be excellent in resilience and thereby flight performance, and feel of hitting upon shots and controllability, and to meet such requirements, various kinds of golf balls have been proposed, for example, in Japanese Patent Laid-open Nos. Hei 6-319830 and Hei 8-294549, and U.S. Pat. Nos. 6,142,886, and 6,218,453B1.
The use of silicone materials for producing golf balls has been proposed, for example, in Japanese Patent Laid-open No. 2001-170213, and U.S. Pat. Nos. 6,159,110, 6,162,134, and 6,204,331. Such golf balls using silicon materials, however, have been recently required by golf players to be further improved in terms of resilience, feel of hitting, and controllability.
SUMMARY OF THE INVENTION
In view of the foregoing, the present invention has been made, and an object of the present invention is to provide a two-piece golf ball excellent in resilience and thereby flight distance characteristic, and further controllability and feel of hitting.
To achieve the above object of the present invention, according to an aspect of the present invention, there is provided a two-piece golf ball including: a core made from a rubber composition mainly containing polybutadiene; and a cover having a thickness of 0.5 to 2.5 mm, the cover being made from a material obtained by dispersedly blending at least one kind of silicone powder selected from a silicone rubber powder, a silicon resin powder, and a composite powder thereof, in a main resin component mainly containing an ionomer resin; wherein the core has a hardness corresponding to a deflection in a range of 3.0 to 5.5 mm under an applied load of 100 kg; the cover has a Durometer D hardness in a range of 45 to 55; and dimples of the number of 300 to 550 pieces are formed in the surface of the golf ball in such a manner that a dimple total volume ratio V
R,
which is a ratio of the total of volumes of dimple spaces under the planes surrounded by edges of the dimples in the surface of the gold ball to the total volume of a virtual ball as a result of assumption that no dimple is formed in the surface of the golf ball, is in a range of 0.85% or less.
An average particle size of the silicon powder is preferably in a range of 0.5 to 700 &mgr;m.
The content of the silicon powder is preferably in a range of 0.5 to 20 parts by weight on the basis of 100 parts by weight of the main resin component.
The rubber composition forming the core preferably contains an organic sulfur compound.
The main resin component forming the cover preferably contains an ethylene-(meth)acrylic acid-acrylate copolymer.
According to the golf ball of the present invention, since the silicone powder is dispersedly blended in the cover, the resilience of the ball is improved, which compensates for a reduction in resilience due to hardening of the ball, to thereby improve the flight performance, and further the temperature dependency of the ball is improved. In addition, since the core is soft, the initial condition upon hitting can be set with a low spin rate and a high launch angle, to increase the flight distance of the ball. Also, since the overall ball is soft, the deformation of the ball becomes, upon full-shot, large, to lower the spin rate, thereby increasing the flight distance of the ball, and since the cover is soft, the spin rate becomes, upon approach, large to improve the controllability of the ball. Further, since the dimple total volume is optimized, it is possible to prevent occurrence of a drop phenomenon of the trajectory of the ball due to a low spin rate, and hence to obtain a good flight distance characteristic due to optimization of the trajectory of the ball. Additionally, since the core contains an organic sulfur compound, it is possible to improve the resilience of the core. The golf ball of the present invention also gives a soft feel of hitting.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention will be more fully described below.
The two-piece golf ball of the present invention includes a core and a cover.
The core is formed from a rubber composition containing a main rubber component. The main rubber component mainly contains polybutadiene which preferably contains 40% or more, especially, 90% or more of cis-1,4-bonds. The main rubber component may contain, in addition to polybutadiene, a diene based rubber such as polyisoprene rubber, styrene-butadiene rubber, or natural rubber. The content of polybutadiene in the main rubber component is preferably in a range of 50% (“% by weight”, the same applying correspondingly to the following) or more, especially, 70% or more.
The rubber composition used herein contains, in addition to the main rubber component, a crosslinking agent, preferably, in an amount of 15 to 40 parts (“parts by weight”, the same applying correspondingly to the following) on the basis of 100 parts of the main rubber component. The crosslinking agent may be selected from zinc salts, magnesium salts, and other metal salts of unsaturated fatty acids such as zinc acrylate and zinc methacrylate, esters such as triethanolpropane methacrylate, and unsaturated fatty acids such as methacrylic acids.
The rubber composition may also contain an organic peroxide such as dicumyl peroxide, preferably, in an amount of 0.1 to 3 parts on the basis of 100 parts of the main rubber component. To improve the resilience of the core, the rubber composition may further contain a vulcanizing agent such as an organic sulfur compound, for example, zinc salt of pentachlorothiophenol or diphenyldisulfide in an amount of 0.01 to 5 parts, especially, 0.2 to 3 parts on the basis of 100 parts of the main rubber component.
The rubber composition may further contain, if needed, an antioxidant such as 2,2-methylene bis(4-methyl-6-tert-buthylphenol), and a filler for adjustment of a specific gravity, such as zinc oxide, barium sulfate, or calcium carbonate. The filler may be generally contained in the main rubber component in an amount of 130 parts or less on the basis of 100 parts of the main rubber component. In particular, to improve the resilience of the core, the filler may be contained in the main rubber component in an amount of, preferably, 50 parts or less, more preferably, 45 parts or less, especially, 40 parts or less on the basis of 100 parts of the main rubber component. The lower limit of the content of the filler may be set to 1 part or more, especially, 3 parts or more, and further, 20 parts or more. In particular, to adjust a specific gravity, the filler composed of a combination of barium sulfate and zinc oxide is often used; however, from the viewpoint of improvement of the resilience of the core, it is preferred for the filler to mainly contain zinc oxide and additionally contain barium sulfate in a range of 10 parts or less, especially, 0 part.
The core can be prepared from the above-described rubber composition, for example, by kneading the components of the rubber composition in an ordinary kneader such as a Banbury mixer or a roll mill, and molding the resultant compound into a desired shape by a compression molding process or an injection molding process. In this molding process, vulcanization can be performed at a temperature of 130 to 180° C. for 10 to 60 min.
The deflection (corresponding to hardness) of the core under an applied load of 100 kg may be in a range of 3.0 mm or more, preferably, 3.2 mm or more, more preferably, 3.5 mm or more, with the upper limit thereof being set to 5.5 mm or less, preferably, 5.0 mm or less, more preferably, 4.8 mm or less. Too small a deflection of the core (too large a hardness of the core) tends to give a hard feel of hitting the ball, and to increase the spin rates and thereby reduce the flight distance of the ball. Too large a deflection of the core (too small a hardness of the core) tends to reduce the resilience of the core and also the durability of the core
Hayashi Junji
Ichikawa Yasushi
Shimizu Yasumasa
Yamagishi Hisashi
Bridgestone Sports CO, LTD
Hunter, Jr. Alvin A.
Vidovich Gregory
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