Multilayer golf ball

Details Multilayer golf ball Multilayer golf ball

1998-09-28

2001-11-13

Passaniti, Sebastiano (Department: 3711)

Games using tangible projectile

Golf

Ball

C524S432000

Reexamination Certificate

active

06315680

ABSTRACT:

FIELD OF THE INVENTION
This invention relates generally to golf balls, and more specifically, to a multilayer golf ball. In particular, this invention relates to a golf ball having a core, a cover and one or more mantle layers disposed between the core and cover. This invention is also directed to a composition used for the manufacture of golf ball cores, mantle layers and covers for multilayer golf balls. The multilayer golf balls of the present invention have been found to provide improved playing characteristics.
BACKGROUND OF THE INVENTION
Conventional golf balls can be divided into two general types or groups: two-piece balls or wound balls (also known as three-piece balls). The difference in play characteristics resulting from these different types of constructions can be quite significant.
Balls having a two-piece construction are generally most popular with the average recreational golfer because they provide a very durable ball while also providing maximum distance. Two-piece balls are made with a single solid core, usually made of a crosslinked rubber, which is encased by a cover material. Typically the solid core is made of polybutadiene which is chemically crosslinked with zinc diacrylate and/or similar crosslinking agents and is covered by a tough, cut-proof blended cover. The cover is generally a material such as SURLYN®, which is a trademark for an ionomer resin produced by DuPont. The combination of the core and cover materials provide a “hard” ball that is virtually indestructible by golfers. Further, such a combination imparts a high initial velocity to the ball which results in improved distance. Because these materials are very rigid, two-piece balls have a hard “feel” when struck with a club. Likewise, due to their hardness, these balls have a relatively low spin rate which provides greater distance.
A number of polymers, such as polybutadiene, natural rubber, styrene butadiene, and isoprene, are commonly used in fabricating golf ball cores. Today, golf ball cores are predominantly made of polybutadiene. Moreover, in order to obtain the desired physical properties for golf balls, manufacturers have added cross-linking agents, such as metallic salts of an unsaturated carboxylic acid. The amount of cross-linking agent added is typically about 20 to 50 parts per hundred parts of polybutadiene. Most commonly, zinc diacrylate or zinc dimethacrylate are used for this purpose. Of these two cross-linkers, zinc diacrylate has been found to produce golf balls with greater initial velocity than zinc dimethacrylate.
Typically, about 5 to 50 pph (parts per hundred) of zinc oxide (ZnO) is also added to the composition. This material serves as both a filler and an activation agent for the zinc diacrylate/peroxide cure system. The zinc diacrylate/peroxide cure system, which is well known to those of ordinary skill in this art, cross-links the polybutadiene during the core molding process. The high specific gravity of zinc oxide (5.57) can serve the dual purposes of adjusting the weight of the golf ball, in addition to acting as an activation agent.
At the present time, the wound ball remains the preferred ball of the more advanced players due to its spin and feel characteristics. Wound balls typically have either a solid rubber or liquid center core around which many yards of a stretched elastic thread or yarn are wound. The wound core is then covered with a durable cover material such as a SURLYN® or similar material or a softer cover such as Balata or polyurethane. Wound balls are generally softer and provide more spin, which enables a skilled golfer to have more control over the ball's flight and final position. Particularly, with approach shots onto the green, the high spin rate of soft, wound balls enables the golfer to stop the ball very near its landing position.
DESCRIPTION OF THE PRIOR ART
Several patents have been issued which are directed towards modifying the properties of a conventional two-piece ball by altering the typical single layer core and single cover layer construction to provide a multi-layer core. The inventions disclosed in the prior art patents are directed towards improving a variety of golf ball characteristics.
Several patents are directed towards improving the carry distance of the ball. For example, U.S. Pat. No. 4,863,167 relates to a three-piece solid golf ball having improved rebound characteristics in order to increase its flight distance. This golf ball has a center portion and the outer layer formed from a rubber composition, preferably having a base rubber of polybutadiene, wherein the outer layer further contains a gravity filler such as tungsten or tungsten carbide so as to impart a higher specific gravity to the outer layer than that of the inner layer. The difference in specific gravity of the layers should be 0.15-0.8 for small balls and 0.15-0.45 for large balls. Preferably, the outer layer is harder than the center portion.
U.S. Pat. No. 4,431,193 relates to a solid core golf ball with a multilayer cover construction. The first layer includes a hard, high flexural modulus resinous material and the second layer includes a soft low flexural modulus resinous material. The construction and material allows the ball to obtain the maximum initial velocity permitted by the United States Golf Association Rules while having a good playing characteristics or “feel.” Preferably, the first layer is made of SURLYN® resin type 1605 and the second layer is made of SURLYN® resin type 1855.
U.S. Pat. No. 5,184,828 relates to a solid three-piece golf ball having improved rebound characteristics and carry distance while maintaining an adequate spin rate. These characteristics are obtained by controlling the size of the inner core and outer layer as well as the specific gravity and hardness. The core and mantle layers are made from a rubber compound such as polybutadiene, and have a Shore D hardness of 30-62 and 30-56 respectively. The key to obtaining the desired rebound characteristics is that the maximum hardness (42-62) must be located at the interface between the core and the mantle and the hardness must then decrease both inwardly and outwardly.
U.S. Pat. No. 4,714,253 is also directed towards a three-piece golf ball having an excellent rebound coefficient. This golf ball has a core with a Shore C hardness of 57-80 in its center, but not more than 83 at a distance between 5-10mm from its center and an outer layer with a Shore C hardness of 70-83.
Additionally, there are a number of patents also directed towards improving the spin, click and feel of solid balls while maintaining the distance provided by the solid construction. A variety of approaches to manipulating the core construction are described in the art. For example, U.S. Pat. No. 5,072,944 discloses a three-piece solid golf ball having a center and outer layer which are prepared from a rubber composition, preferably having a base rubber of polybutadiene. It is desirable that the center core is softer than the outer layer, each having a hardness (Shore C) of 25-50 and 70-90 respectively.
U.S. Pat. No. 4,625,964 relates to a solid golf ball having a polybutadiene rubber core of a diameter not more than 32mm, and a polybutadiene rubber intermediate layer having a specific gravity of higher than that of the core material, and a cover.
U.S. Pat. No. 4,650,193 is directed towards a solid golf ball having a core comprising of a central portion and an integral outer layer. Preferably the core is a curable elastomer such as polybutadiene which is treated with a cure altering agent to soften an outer layer of the core, thereby producing a central layer with a hardness (Shore C) of greater than 75 and an outer layer with a hardness (Shore A) of less than 80.
U.S. Pat. No. 4,848,770 discloses a non-wound three-piece golf ball which includes a core of a highly filled synthetic rubber or polymeric material, an intermediate mantle of an unfilled synthetic rubber and a cover. The core and intermediate mantle have a hardness of between 50-95.
U.S. Pat. No. 5,002,281 is directed towards a three-

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