Games using tangible projectile – Golf – Ball
Reexamination Certificate
2000-04-19
2002-04-30
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S351000, C473S373000, C473S374000
Reexamination Certificate
active
06379269
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to golf balls and is more particularly concerned with a new and improved solid golf ball comprising both a multilayer core and a multilayer cover. In particular, one preferred embodiment of the present invention relates to golf balls utilizing double cover layer assemblies in combination with dual and triple layer cores. The cover and core assemblies are selected to provide a particular combination of properties for the resulting golf balls. The invention also provides an embodiment utilizing a metal or metal filled center. The present invention golf balls are generally free from density reducing filler materials and exhibit relatively low moments of rotational inertia.
BACKGROUND OF THE INVENTION
Golf balls traditionally have been categorized in three different groups, namely, as one piece balls, multi-piece (two or more pieces) solid balls, and wound (three piece) balls. The one piece ball typically is formed from a solid mass of moldable material which has been cured to develop the necessary degree of hardness. It possesses no significant difference in composition between the interior and exterior of the ball. These balls do not have an enclosing cover. One piece balls are described, for example, in U.S. Pat. No. 5 3,313,545; U.S. Pat. No. 3,373,123 and U.S. Pat. No. 3,384,612.
The wound ball is frequently referred to as a three piece ball since it is made with a vulcanized rubber thread wound under tension around a solid or semisolid core and thereafter enclosed in a single or multilayer covering of tough protective material. For many years the wound ball satisfied the standards of the U.S.G.A. and was desired by many skilled, low handicap
One type of three piece wound ball typically has a balata cover which is relatively soft and flexible. Upon impact, it compresses against the surface of the club producing high spin. Consequently, the soft and flexible balata covers along with the wound cores provide an experienced golfer with the ability to apply a spin to control the ball in flight in order to produce a draw or a fade or a backspin which causes the ball to “bite” or stop abruptly on contact with the green. Moreover, the soft balata cover produces a soft “feel” to the low handicap player. Such playability properties of workability, feel, etc. are particularly important in short iron play with low swing speeds and are exploited significantly by relatively skilled players.
However, a three piece wound ball also has several disadvantages. For example, a wound ball is difficult to manufacture due to the number of production steps required and the careful control which must be exercised in each stage of manufacture to achieve suitable roundness, velocity, rebound, “click”, “feel”, and the like.
Additionally, a soft wound (three piece) ball is not well suited for use by the less skilled and/or high handicap golfer who cannot intentionally control the spin of the ball. The unintentional application of side spin by a less skilled golfer produces hooking or slicing. The side spin reduces the golfer's control over the ball as well as reducing travel distance.
Similarly, all the benefits of balata, balata covered balls are easily cut and/or damaged if mishit. Golf balls produced with balata or balata containing cover compositions, therefore, have a relatively short life span. As a result of this negative property, balata and its synthetic substitute, trans polyisoprene, and resin blends, have been essentially replaced as the cover materials of choice by new cover materials comprising ionomeric resins.
Conventional multi-piece solid golf balls, on the other hand, include a solid resilient core having single or multiple cover layers employing different types of material molded on the core. The one piece golf ball and the solid core for a multi-piece solid (nonwound) ball frequently are formed from a combination of materials such as polybutadiene and other rubbers cross linked with zinc diacrylate or zinc dimethacrylate, and containing fillers and curing agents which are molded under high pressure and temperature to provide a ball of suitable hardness and resilience. For multi-piece nonwound golf balls, the cover typically contains a substantial quantity of ionomeric resins that impart toughness and cut resistance to the covers.
Ionomeric resins are generally ionic copolymers of an olefin, such as ethylene, and a metal salt of a unsaturated carboxylic acid, such as acrylic acid, methacrylic acid or maleic acid. Metal ions, such as sodium or zinc, are used to neutralize some portion of the acidic group in the copolymer, resulting in a thermoplastic elastomer exhibiting enhanced properties, such as durability, for golf ball cover construction. However, some of the advantages gained in increased durability have been offset to some degree by decreases in playability. This is because, although the ionomeric resins are very durable, they also tend to be quite hard when utilized for golf ball cover construction and thus lack the degree of softness required to impart the spin necessary to control the ball in flight. Since most ionomeric resins are harder than balata, the ionomeric resin covers do not compress as much against the face of the club upon impact, thereby producing less spin. In addition, the harder and more durable ionic resins lack the “feel” characteristic associated with the softer balata related covers.
As a result, while there are currently more than 50 commercial grades of ionomers available, both from DuPont and Exxon, with a wide range of properties which vary according to the type and amount of metal ions, molecular weight, composition of the base resin (i.e. relative content of ethylene and methacrylic and/or acrylic acid groups) and additive ingredients, such as reinforcement agents, etc., a great deal of research continues in order to develop a golf ball cover composition exhibiting not only the improved impact resistance and carrying distance properties produced by the “hard” ionomeric resins, but also the playability (i.e. “spin”, “feel”, etc.) characteristics previously associated with the “soft” balata covers, properties which are still desired by the more skilled golfer.
Consequently, a number of multi-piece solid balls have been produced to address these needs. The different types of material used to formulate the cores, covers, etc. of these balls dramatically alter the balls overall characteristics. Various structures have been suggested using multilayer cores and single layer covers wherein the core layers have different physical characteristics. For example, U.S. Pat. Nos. 4,714,253; 4,863,167 and 5,184,828 relate to three piece solid golf balls having improved rebound characteristics in order to increase flight distance. The '253 patent is directed towards differences in the hardness of the different layers. The '167 patent relates to a golf ball having a center portion and an outer layer containing 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. Preferably, the outer layer is harder than the center portion. The '828 patent suggests that the maximum hardness must be located at the interface between the core and the mantle, and the hardness must then decrease both inwardly and outwardly.
A number of patents suggest improving the spin and feel by manipulating the core construction. For example, U.S. Pat. No. 4,625,964 relates to a solid golf ball having a core diameter not more than 32 mm, and an outer layer having a specific gravity lower than that of the core. In U.S. Pat. No. 4,650,193, it is suggested that a curable core elastomer be treated with a cure altering agent to soften an outer layer of the core. U.S. Pat. No. 5,002,281 is directed towards a three piece solid golf ball which has an inner core having a gravity greater than 1.0, but less than or equal to that of the outer shell which must be less than 1.3. U.S. Pat. Nos. 4,848,707 and 5,072,944 disclose three-piece solid golf ball
Melvin Terence
Nesbitt R. Dennis
Sullivan Michael J.
Hunter, Jr. Alvin A.
Sewell Paul T.
Spalding Sports Worldwide Inc.
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