Games using tangible projectile – Golf – Ball
Reexamination Certificate
2002-09-06
2004-07-27
Graham, Mark S. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S367000, C473S351000
Reexamination Certificate
active
06767294
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to golf balls and specifically to the construction of solid, non-wound, golf balls for regulation play. More particularly, the invention is directed to improved golf balls comprising multi-component core assemblies which have a pressurized foamed center component. The pressurized foam center is encapsulated by one or more core layers which are then surrounded by a cover. The golf balls of this invention are of the same size and weight as conventional balls and have comparable or better performance characteristics.
BACKGROUND OF THE INVENTION
Golf balls traditionally have been categorized into three different groups. These are one piece balls, multi-piece solid balls comprising two or more solid pieces 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. In many instances, the one piece solid ball does not possess any significant difference in composition between the interior and exterior of the ball. One piece balls are described, for example, in U.S. Pat. Nos. 3,313,545; 3,373,123; and, 3,384,612.
A 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 semi-solid center to form a wound core and thereafter enclosed in a single or multi-layer covering of tough protective material. For many years the wound ball was desired by many skilled, low handicap golfers, due to reported enhanced playability characteristics.
More particularly, the three piece wound ball typically has a balata or balata like cover which is relatively soft and flexible. Upon impact, the balata cover 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. This allows a skilled golfer 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 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 highly skilled players.
However, a three piece wound ball also has several disadvantages. For example, a wound ball is relatively 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.
Moreover, wound balls can also be knocked “out of round”. One or more severe hits can damage the windings and knock the center “off center”. Such a ball is then unbalanced, making putting, etc. more difficult.
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. For example, 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, despite all the benefits of balata, balata covered balls are easily cut and/or damaged if mishit. Consequently, golf balls produced with balata or balata containing cover compositions can exhibit relatively short life spans. 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 golf ball manufacturers by materials comprising ionomeric resins and other elastomers such as polyurethanes.
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 ionomeric resins lack the “feel” characteristic associated with the softer balata related covers.
As a result, while there are currently more than fifty (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 golf ball cover compositions 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.
Moreover, a number of multi-piece solid balls have also been produced to address the various needs of the golfing population. The different types of material used to formulate the core(s), cover(s), etc. of these balls dramatically alter the balls' overall characteristics.
In this regard, various structures have been suggested using multi-layer 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 layers. The '167 patent relates to a golf ball having a center portion and an outer layer having a high specific gravity. 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.
Similarly, a number of patents for multi-piece solid balls 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
Callaway Golf Company
Graham Mark S.
Hunter, Jr. Alvin A.
LandOfFree
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