Games using tangible projectile – Golf – Ball
Reexamination Certificate
2000-06-22
2003-11-18
Wong, Steven (Department: 3711)
Games using tangible projectile
Golf
Ball
C264S250000
Reexamination Certificate
active
06648776
ABSTRACT:
FIELD OF INVENTION
This invention relates generally to golf balls, and more specifically, to a multilayer golf ball having improved adhesion between adjacent component layers as well as method for forming such golf balls. In particular, this invention relates to a golf ball having a core, an inner cover layer and a very thin outer cover layer, wherein the outer cover layer comprises a thermoset material formed from a castable, reactive liquid and the inner cover layer comprises a high flexural modulus material with a textured pattern to improve adhesion between the layers.
BACKGROUND OF THE INVENTION
Conventional golf balls can be divided into three general types or groups: (1) two piece balls, (2) wound balls (also know as three piece balls), and (3) multilayer 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 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 formed 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. The cover comprises tough, cut-proof blends of one or more materials known as ionomers such as SURLYNs®, which are resins sold commercially by DuPont or lotek® which is sold commercially by Exxon.
The combination of the above-described core and cover materials provides a “hard” covered ball that is resistant to cutting and other damage caused by striking the ball with a golf club. Further, such a combination imparts a high initial velocity to the ball which results in increased distance. Due to their hardness however, these balls have a relatively low spin rate which makes them difficult to control, particularly on shorter approach shots. As such, these types of balls are generally considered to be “distance” balls. Because these materials are very rigid, many two piece balls have a hard “feel” when struck with a club. Softer cover materials such as balata and softer ionomers in some instances, have been employed in two piece construction balls in order to provide improved “feel” and increased spin rates.
Wound balls typically have either a solid rubber or liquid filled center around which many yards of a stretched elastic thread or yarn are wound to form a core. 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 than two piece balls and provide more spin, which enables a skilled golfer to have more control over the ball's flight and final position. In particular, it is desirable that a golfer be able to impart back spin to a golf ball for purposes of controlling its flight and controlling the action of the ball upon landing on the ground. For example, substantial back spin will make the ball stop once it strikes the landing surface instead of bounding forward. The ability to impart back spin onto a golf ball is related to the extent to which the golf ball cover deforms when it is struck with a golf club. Because wound balls are traditionally more deformable than conventional two piece balls, it is easier to impart spin to wound balls. However, wound higher spinning balls typically travel a shorter distance when struck as compared to a two piece ball. Moreover, as a result of their more complex structure, wound balls generally require a longer time to manufacture and are more expensive to produce than a two piece ball.
The United States Golf Association (USGA) has instituted a rule that prohibits the competitive use in any USGA sanctioned event of a golf ball that can achieve an initial velocity of greater than 76.2 meters per second (m/s), or 250 ft/s, when struck by a driver with a velocity of 39.6 m/s, i.e., 130 ft/s (referred to hereinafter as “the USGA test”). However, an allowed tolerance of two percent permits manufacturers to produce golf balls that achieve an initial velocity of 77.7 m/s (255 ft/s).
Regardless of the form of the ball, players generally seek a golf ball that delivers maximum distance, which requires a high initial velocity upon impact. Therefore, in an effort to meet the demands of the marketplace, manufacturers strive to produce golf balls with initial velocities in the USGA test that approximate the USGA maximum of 77.7 m/s or 255 ft/s as closely as possible.
Therefore, golf ball manufacturers are continually searching for new ways in which to provide golf balls that deliver the maximum performance in terms of both distance and spin rate for golfers of all skill levels.
Relatively recently, a number of golf ball manufacturers have introduced multilayer golf balls, i.e., having multiple core intermediate mantle and/or cover layers, in an effort to overcome some of the undesirable aspects of conventional two piece balls, such as their hard feel, while maintaining the positive attributes of these golf balls (including their increased initial velocity and distance). Further, it is desirable that such multilayer balls have a “click and feel” as well as spin characteristics approaching that of wound balls.
Multilayer golf balls can be formed using a variety of constructions. For example, multilayer balls may have two or more cover layers molded around a conventional core with one or more intermediate layers interposed between the cover and the core. Likewise, multilayer balls may be formed from cores having more than one core layer and may optionally contain one or more intermediate and/or cover layers. Multilayer balls may even comprise a conventional wound core around which at least one intermediate layer and/or at least one cover layer is formed. Examples of multilayer balls include the Altus Newing (Bridgestone), Reygrande 2×2 (Bridgestone), Giga (Spalding) Metal Mix (Dunlop), Ultra Tour Balata (Wilson).
Typically, the layers of multilayer golf balls are formed by molding them around the core or a preceding intermediate layer or cover layer. Conventional techniques for applying such layers include injection molding, compression molding and casting the layer material around the preceding core or layer. Accordingly, a crucial aspect of the manufacture of multilayer balls is obtaining good adhesion between the various layers. If the adhesion between the layers does not meet desired standards, the performance or durability of the golf ball will be adversely affected. For example, poor adhesion can cause air pockets between the layers which can result in separation of the layers when the ball is struck with a club.
It is well known that the adhesion between the wound core and the cover of a wound ball is enhanced due to the small imperfections created in the uneven outer surface of the winding formed by overlapping the thread. Cover material flows into these imperfections when the cover is molded about the wound core, resulting in improved adhesion. In contrast, however, in two piece and multilayer balls, adhesion between the core, cover and/or intermediate layers is greatly reduced due to the relatively smooth outer surface of the layers.
Accordingly, there are a number of methods known in the art directed towards promoting adhesion between the various solid layers of a golf ball. For example, U.S. Pat. Nos. 4,229,401 and 4,173,345 are directed towards alleviating problems associated with compression molding covers about a core by providing a series of surface channels {fraction (1/16)} of an inch deep which encircle the outer surface of the core and pass through both polar areas thereof. Providing such channels was found to prevent separation of the cover from the core when the ball is struck with a golf club by eliminating the entrapment of air between the cover and the core during the compression molding process.
Additionally, there are a number of patents directed towards promoting adhesion betwee
Boehm Herbert C.
Cavallaro Christopher
Dalton Jeffrey L.
Morgan William E.
Acushnet Company
Gorden Raeann
Swidler Berlin Shereff & Friedman, LLP
Wong Steven
LandOfFree
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