Games using tangible projectile – Golf – Ball
Reexamination Certificate
2000-01-25
2004-04-13
Graham, Mark S. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S383000, C473S357000
Reexamination Certificate
active
06719646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The instant invention is directed to golf balls, and more particularly to a ball having the optimal cover composition, cover hardness, center weight, the size of the thread windings, and dimple configuration to provide superior playability capabilities with respect to softness and spin without sacrificing superior distance capabilities.
2. Description of the Related Art
There are a number of physical properties that affect the performance of a golf ball. The core of the golf ball is the source of the ball's major elastic properties. Among other things, the core affects the ball's “feel” and its initial velocity. The initial velocity is the velocity at which the golf ball travels immediately following impact. The initial velocity can be grouped with launch angle and spin to describe the ball's initial conditions, or the conditions exhibited by the ball immediately after impact. The initial conditions along with dimple pattern determine the ball's trajectory and ultimately its distance. The “feel” is the overall sensation transmitted to the golfer through the golf ball at impact. The overall construction of the ball influences the “feel” of a golf ball. Properties such as cover hardness, compression, and rebound can be used to gauge the response of a golfer to a ball's construction. But ultimately, the ball's “feel” can only be determined by the avid golfer. One property commonly tested by golfers to judge the “feel” of a ball is the sound made at impact between the ball and the club. This sound or “click” provides the golfer with a lasting impression of the ball's feel. Generally, lower cover hardness, compression, and rebound give the golfer an impression of a softer “feel” and a corresponding lower, softer click.
Until the late 1960's, most golf balls were constructed with a thread wound core and a cover of compounds based on natural balata and gutta percha or synthetic transpolyisoprene. These golf balls have been and are still known to provide good flight distance. Additionally, due to the relative softness of the balata cover, skilled golfers can impart various spins on the ball in order to control the ball's flight path (e.g., “fade” or “draw”) and “bite” characteristics upon landing on a green.
“Fade” is a term used in golf to describe a particular golf ball flight path that is characterized by a curved or arched flight exhibited towards the latter portion of the flight path that veers off from the center line of the initial flight path to the opposite side from which the golfer stands. Upon contact with the ground, a ball hit with a “fade” will stop in a relatively short distance. This is a result of an open club face at impact imparting more spin and a higher trajectory than normal.
“Draw” is the term used in golf to describe a particular golf ball flight path that is characterized by a curved or arched flight exhibited towards the latter portion of the flight path that veers off from the center line of the initial flight path to the same side on which the golfer stands. Upon contact with the ground, a ball hit with a “draw”, unlike that of a ball hit with a “fade”, will roll for a considerable distance. This is a result of a closed club face at impact imparting less spin and a lower trajectory than normal.
“Check” or “bite” is the term used in golf to describe the effect of imparting a substantial amount of backspin to an approach shot to a green that causes the golf ball to stop abruptly upon contact with the green.
Another desirable feature of balata-based compounds is that they are readily adaptable to molding. These compounds therefore can be easily compression molded about a spherical core to produce golf balls.
Though possessing many desirable properties, there are substantial drawbacks to use of balata or transpolyisoprene-based compounds for golf ball covers. From a manufacturing standpoint, balata-type materials are expensive and the manufacturing procedures used are time consuming and labor-intensive, thereby adding to the material expense. From a player's perspective, golf balls constructed with balata-based covers are very susceptible to being cut from mishits and being sheared from sharp grooves on a club face. As a result, they have a relatively short life span.
In response to these drawbacks to balata-based golf ball covers, the golf ball manufacturing industry has shifted to the use of synthetic thermoplastic materials, most notably ionomers sold by E. I. DuPont De Nemours & Company under the name SURLYN®. Surlyn is an ionomeric resin that is an ionic copolymer of an olefin having from about 2 to about 8 carbon atoms, such as ethylene, and a metal salt of an alpha, beta-ethylenically unsaturated mono- or dicarboxylic acid such as acrylic acid, methacrylic acid, or maleic acid. The pendent ionic groups in the ionomeric resins interact to form ion-rich aggregates contained in a non-polar polymer matrix. Metal ions, such as sodium, zinc, or lithium are used to neutralize some portions of the acid groups in the copolymer resulting in a thermoplastic elastomer exhibiting enhanced properties such as improved durability.
Thread wound balls with ionomer covers are less costly to manufacture than balls with balata covers. They are more durable and produce satisfactory flight distance. However, these materials are relatively hard compared to balata and thus lack the “feel” of a balata covered golf ball.
In an attempt to overcome the negative factors of the hard ionomer covers, DuPont introduced low modulus SURLYN® ionomers in the early 1980's. These SURLYN® ionomers have a flexural modulus of from about 3000 to about 7000 PSI and hardness of from 25 to about 40 as measured on the Shore D scale—ASTM 2240. The low modulus ionomers are terpolymers, typically of ethylene, methacrylic acid and n or iso-butylacrylate, neutralized with sodium, zinc, magnesium or lithium cations. E.I. DuPont De Nemours & Company has disclosed that the low modulus ionomers can be blended with other grades of previously commercialized ionomers of high flexural modulus from about 30,000 to 55,000 PSI to produce balata-like properties. However, “soft” blends, typically 52 Shore D and lower (balata-like hardness), do not exhibit good physical properties and are prone to cut and shear damage.
The low modulus ionomers when used without blends produce covers with very similar physical properties to those of balata, including poor cut and shear resistance. Worse, wound balls with these covers tend to go “out-of-round” quicker than wound balls with balata covers. Blending with hard SURLYN® ionomers was found to improve these properties.
Another approach taken to provide a golf ball cover that has the playing characteristics of balata is described in U.S. Pat. No. 5,334,673 (the '673 patent) assigned to the Acushnet Company. The '673 patent discloses a cover composition comprising a diisocyanate, a polyol and a slow-reacting polyamine curing agent. The diisocyanates claimed in the '673 patent are relatively fast reacting. Due to this fact, catalysts are not needed to lower the activation energy threshold. However, since relatively fast-reacting prepolymer systems are used, the reaction rate cannot be easily controlled thereby requiring the implementation of substantial processing controls and precise reactant concentrations in order to obtain a desired product.
To avoid the problems associated with fast-reacting prepolymer systems, slow-reacting systems such as Toluene diisocyanate (TDI) prepolymer systems can be employed. However, these systems, while avoiding the problems associated with fast-reacting systems, present similar problems, albeit for different reasons. The most noteworthy problem with slow-reacting pre-polymer systems is the requirement for a catalyst.
By introducing a catalyst into the system, processing problems similar to those associated with fast-reacting pre-polymer systems are virtually inevitable. As is well known in the art, the use of a catalyst can
Calabria John A.
John Jens A.
Kuttappa Sanjay M.
Lemons Lane D.
Stanczak Matthew B.
Dunlop Slazenger Sports
Gordon Raeann
Graham Mark S.
Lorusso Loud & Kelly LLP
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