Games using tangible projectile – Golf – Ball
Reexamination Certificate
2002-03-14
2004-05-04
Gorden, Raeann (Department: 3711)
Games using tangible projectile
Golf
Ball
Reexamination Certificate
active
06729976
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to golf balls having improved aerodynamic characteristics that yield improved flight performance and longer ball flight. The improved aerodynamic characteristics are obtained through the use of specific dimple arrangements and dimple profiles. The aerodynamic improvements are applicable to golf balls of any size and weight. The invention further relates to golf balls with symmetric flight characteristics.
BACKGROUND OF THE INVENTION
The flight of a golf ball is determined by many factors, however, the majority of the properties that determine flight are outside of the control of a golfer. While a golfer can control the speed, the launch angle, and the spin rate of a golf ball by hitting the ball with a particular club, the final resting point of the ball depends upon golf ball construction and materials, as well as environmental conditions, e.g., terrain and weather. Since flight distance and consistency are critical factor in reducing golf scores, manufacturers continually strive to make even the slightest incremental improvements in golf ball flight consistency and flight distance, e.g., one or more yards, through various aerodynamic properties and golf ball constructions. Flight consistency is a significant problem for manufacturers because the many of golf ball dimple patterns and/or dimple shapes that yield increased flight distance also result in asymmetric flight performance. Asymmetric flight performance prescribes that the overall flight distance is a function of ball orientation when struck with a club.
Historically, manufacturers improved flight performance via iterative testing, where golf balls with numerous dimple patterns and dimple profiles are produced and tested using mechanical golfers. Flight performance is characterized in these tests by measuring the landing position of the various ball designs. To determine if a particular ball design has desirable flight characteristics for a broad range of players, i.e., high and low swing speed players, manufacturers perform the mechanical golfer test with different ball launch conditions, which involves immense time and financial commitments. Furthermore, it is difficult to identify incremental performance improvements using these methods due to the statistical noise generated by environmental conditions, which necessitates large sample sizes for sufficient confidence intervals.
Another more precise method of determining specific dimple arrangements and dimple shapes that results in an aerodynamic advantage involves the direct measurement of aerodynamic characteristics as opposed to ball landing positions. These aerodynamic characteristics define the forces acting upon the golf ball throughout flight.
Aerodynamic forces acting on a golf ball are typically resolved into orthogonal components of lift and drag. Lift is defined as the aerodynamic force component acting perpendicular to the flight path. It results from a difference in pressure that is created by a distortion in the air flow that results from the back spin of the ball. A boundary layer forms at the stagnation point of the ball, B, then grows and separates at points S
1
and S
2
, as shown in FIG.
1
. Due to the ball backspin, the top of the ball moves in the direction of the airflow, which retards the separation of the boundary layer. In contrast, the bottom of the ball moves against the direction of airflow, thus advancing the separation of the boundary layer at the bottom of the ball. Therefore, the position of separation of the boundary layer at the top of the ball, S
1
, is further back than the position of separation of the boundary layer at the bottom of the ball, S
2
. This asymmetrical separation creates an arch in the flow pattern, requiring the air over the top of the ball to move faster and, thus, have lower pressure than the air underneath the ball.
Drag is defined as the aerodynamic force component acting parallel to the ball flight direction. As the ball travels through the air, the air surrounding the ball has different velocities and, accordingly, different pressures. The air exerts maximum pressure at the stagnation point, B, on the front of the ball, as shown in FIG.
1
. The air then flows over the sides of the ball and has increased velocity and reduced pressure. The air separates from the surface of the ball at points S
1
and S
2
, leaving a large turbulent flow area with low pressure, i.e., the wake. The difference between the high pressure in front of the ball and the low pressure behind the ball reduces the ball speed and acts as the primary source of drag for a golf ball.
The dimples on a golf ball are used to adjust drag and lift properties of a golf ball and, therefore, the majority of golf ball manufacturers research dimple patterns, shape, volume, and cross-section in order to improve overall flight distance of a golf ball. The dimples create a thin turbulent boundary layer around the ball. The turbulence energizes the boundary layer and aids in maintaining attachment to and around the ball to reduce the area of the wake. The pressure behind the ball is increased and the drag is substantially reduced.
There is minimal prior art disclosing preferred aerodynamic characteristics for golf balls. U.S. Pat. No. 5,935,023 discloses preferred lift and drag coefficients for a single speed with a functional dependence on spin ratio. U.S. Pat. Nos. 6,213,898 and 6,290,615 disclose golf ball dimple patterns that reduce high-speed drag and increase low speed lift. It has now been discovered, contrary to the disclosures of these patents, that reduced high-speed drag and increased low speed lift does not necessarily result in improved flight performance. For example, excessive high-speed lift or excessive low-speed drag may result in undesirable flight performance characteristics. The prior art is silent, however, as to aerodynamic features that influence other portions of golf ball flight, such as flight consistency, as well as enhanced aerodynamic coefficients for balls of varying size and weight.
Thus, there is a need to optimize the aerodynamics of a golf ball to improve flight distance and consistency. There is also a need to develop dimple arrangements and profiles that result in longer distance and more consistent flights regardless of the swing-speed of a player, the orientation of the ball when impacted, or the physical properties of the ball being played.
SUMMARY OF THE INVENTION
The present invention is directed to a golf ball with improved aerodynamic performance. In one embodiment, a golf ball with a plurality of dimples has an aerodynamic coefficient magnitude defined by C
mag
=(C
L
2
+C
D
2
) and an aerodynamic force angle defined by Angle=tan
−1
(C
L
/C
D
), wherein C
L
is a lift coefficient and C
D
is a drag coefficient, wherein the golf ball has a first aerodynamic coefficient magnitude from about 0.24 to about 0.27 and a first aerodynamic force angle of about 31 degrees to about 35 degrees at a Reynolds Number of about 230000 and a spin ratio of about 0.085 and a second aerodynamic coefficient magnitude from about 0.25 to about 0.28 and a second aerodynamic force angle of about 34 degrees to about 38 degrees at a Reynolds Number of about 207000 and a spin ratio of about 0.095.
In another embodiment, the golf ball has a third aerodynamic coefficient magnitude from about 0.26 to about 0.29 and a third aerodynamic force angle from about 35 degrees to about 39 degrees at a Reynolds Number of about 184000 and a spin ratio of about 0.106 and a fourth aerodynamic coefficient magnitude from about 0.27 to about 0.30 and a fourth aerodynamic force angle of about 37 degrees to about 42 degrees at a Reynolds Number of about 161000 and a spin ratio of about 0.122. In yet another embodiment, a fifth aerodynamic coefficient magnitude is from about 0.29 to about 0.32 and a fifth aerodynamic force angle is from about 39 degrees to about 43 degrees at a Reynolds Number of about 138000 and a spin ratio of about 0.142 and a sixth aerodynamic coefficient magnitud
Aoyama Steven
Bissonnette Laurent C.
Dalton Jeffrey L.
Acushnet Company
Gorden Raeann
Swidler Berlin Shereff & Friedman, LLP
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