Games using tangible projectile – Golf – Ball
Reexamination Certificate
2001-07-13
2003-02-18
Sewell, Paul T. (Department: 3711)
Games using tangible projectile
Golf
Ball
C473S373000, C473S374000, C473S376000, C473S377000, C473S351000
Reexamination Certificate
active
06520870
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to golf balls exhibiting high potential spin rate characteristics. More particularly, the invention relates to high spinning golf balls having a relatively soft, high resilience, solid polybutadiene core and a soft outer cover. Preferably, the balls are of two-piece construction comprising a large core and a thin cover.
BACKGROUND OF THE INVENTION
Until relatively recently, many highly skilled, low handicap golfers had utilized wound golf balls for competitive play. These balls have a wound core (i.e., a liquid or solid center and elastic windings) and a balata or balata-like cover.
Balata covered wound golf balls are known for their soft feel and high spin rate potential. However, balata covered balls suffer from the drawback of low durability. Among other things, even in normal use, the balata covering can become cut and scuffed, making the ball unsuitable for further play. Additionally, the internal elastic windings are susceptible to breakage upon ball striking, and/or the center of the ball can be knocked off center or “out of round”. Furthermore, the coefficient of restitution of wound balls is reduced at low temperatures.
The problems associated with balata covered balls have resulted in the widespread use of durable ionomeric resins as golf ball covers. However, balls made with ionomer resin covers typically have higher PGA® compression ratings. Those familiar with golf ball technology and manufacture will recognize that golf balls with higher PGA® compression ratings are considered to be harder than conventional balata covered balls.
Consequently, it would be useful to develop a golf ball having a durable, yet comparatively soft, cover which has the sound and feel of a balata covered wound ball. It would also be useful to develop a solid core golf ball having the overall desired spin and flight characteristics exhibited by balata covered wound balls.
Taken as a whole, the solid core balls of the present invention exhibit the high spin (mid-iron through wedge), flight characteristics (i.e., launch angle, trajectory, etc.) and feel produced by balata covered wound golf balls. The balls of the invention also exhibit enhanced durability with equal or superior distance.
The present invention is accomplished, in part, by combining a soft, durable cover with a relatively soft, solid core. The core is constructed using high molecular weight polybutadiene or other rubbers exhibiting enhanced coefficient of restitution (C.O.R.). The golf balls of the invention have a core compression and an overall ball PGA® compression of 90 or less, preferably less than 80, and most preferably less than 75. The hardness of the cover is soft enough so that the PGA® compression of the overall ball is substantially the same or lower than that of the core.
Moreover, the properties of the core and/or cover of the balls of the invention can be adjusted to obtain the particular spin rates desired. For example, larger or heavier cores can be utilized for even greater spin rates, (although lower C.O.R. may result), softer covers can be utilized for higher spin rates, etc. Preferably, the golf balls of the present invention utilize relatively large, soft cores and thin, soft covers. The cores and/or balls of the invention can be optionally irradiated to additionally improve such properties as C.O.R., scuff, and melt resistance.
In addition, the particular dimple pattern of the balls can be selected to further optimize the desired spin rates. Similarly, the flight/trajectory of the ball can be adjusted depending upon the dimple pattern selected and the core and cover materials utilized in construction.
Prior to the present invention, high spin, two-piece golf balls consisted generally of hard cores having covers varying in hardness/softness. The hard cores were necessary to achieve the desired resiliency, i.e., C.O.R., needed for enhanced distance, etc. Additionally, hard cores were utilized to produce higher spin rates. This is because at impact, the hard core compresses the cover of the ball against the clubface to a much greater degree than a soft core. This compression results in more “grab” of the ball on the clubface and subsequent higher spin rate. In effect the cover is squeezed between the relatively incompressible core and clubhead. When a softer core is used, the cover is under much less compressive stress than when a harder core is used and therefore does not contact the clubface as intimately. This results in lower spin rates.
However, while the hard core, two-piece balls exhibited enhanced spin rates, this was essentially for all clubs. Additionally, the hard core, two-piece balls produced generally a poor, or hard, responsive feel to the golfer.
The resulting balls of the present invention utilize a soft, high resilience core and a relatively thin, soft cover. Preferably, the balls of the invention comprise two-piece golf balls. The balls produce high spin rates, equal to or greater than balata covered wound golf balls with the same or better distance. The balls also produce improved feel over traditional two-piece golf balls.
Additionally, machine and limited player testing also indicates that the flight/trajectory of the balls of the invention approaches the “rising” trajectory exhibited by the balata covered wound golf balls. The “rising”, as opposed to a “boring” or “penetrating” trajectory, is preferred by players who find it difficult to attack tight pin positions or be those who find it difficult to keep the ball in narrow fairways off the tee.
With respect to several of the enhanced properties of the invention, two of the principal properties involved in the performance of golf balls are resilience and hardness. Resilience is determined by the coefficient of restitution (referred to as “C.O.R.”), also expressed as the constant “e”, which is the ratio of the relative velocity of two elastic spheres after direct impact to that before impact, or more generally, the ratio of the outgoing velocity to incoming velocity of a rebounding ball. As a result, the coefficient of restitution (i.e. “e”) can vary from zero to one, with one being equivalent to an elastic collision and zero being equivalent to an inelastic collision.
Hardness/softness of a ball is determined as the deformation (i.e. compression) of the ball under various load conditions applied across the ball's diameter. The lower the deformation, the harder the material.
Resilience (C.O.R.), along with additional factors such as clubhead speed, angle of trajectory, and ball configuration (i.e. dimple pattern), generally determine the distance a ball will travel when hit. Since clubhead speed and the angle of trajectory are not factors easily controllable, particularly by golf ball manufacturers, the factors usually of concern among manufacturers are the coefficient of restitution (C.O.R.) and the surface configuration of the ball.
In this regard, the coefficient of restitution of a golf ball is generally measured by propelling a ball at a given speed against a hard surface and electronically measuring the ball's incoming and outgoing velocity. The coefficient of restitution is believed to be carefully controlled in all commercial golf balls in order for the ball to be within the specifications regulated by the United States Golfers Association (“U.S.G.A.”).
Along this line, the U.S.G.A. standards indicate that a “regulation” ball cannot have an initial velocity (i.e. the speed off the club) exceeding 255 feet per second (250 feet per second with a 2% tolerance). Since the coefficient of restitution of a ball is related to the ball's initial velocity (i.e. as the C.O.R. of a ball is increased, the ball's initial velocity will also increase), it is highly desirable to produce a ball having a sufficiently high coefficient of restitution to closely approach the U.S.G.A. limit on initial velocity, while having an ample degree of hardness (i.e. impact resistance) to produce enhanced durability.
The coefficient of restitution (C.O.R.) in solid core balls
Binette Mark L.
Kennedy, III Thomas J.
Nealon John L.
Tzivanis Michael J.
Duong Tom
Sewell Paul T.
Spalding Sports Worldwide Inc.
LandOfFree
Golf ball does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Golf ball, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Golf ball will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3178725