Golf ball with improved flight performance

[0001] This application is a continuation of U.S. patent application Ser. No. 10/784,744, filed Feb. 24, 2004, now U.S. Pat. No. 6,913,550, which is a continuation of U.S. patent application Ser. No. 10/096,852, filed Mar. 14, 2002, now U.S. Pat. No. 6,729,976, which is a continuation-in-part of U.S. patent application Ser. No. 09/989,191, filed Nov. 21, 2001, now U.S. Pat. No. 6,796,912, and also a continuation-in-part of U.S. patent application Ser. No. 09/404,164, filed Sep. 27, 1999, now U.S. Pat. No. 6,358,161, which is a divisional of U.S. patent application Ser. No. 08/922,633, filed Sep. 3, 1997, now U.S. Pat. No. 5,957,786. The entire disclosures of the related applications are incorporated by reference herein.

[0002] 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.

[0003] 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.

[0004] 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.

[0005] 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.

[0006] 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 S1 and S2, 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, S1, is further back than the position of separation of the boundary layer at the bottom of the ball, S2. 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.

[0007] 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 S1 and S2, 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.

[0008] 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.

[0009] 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.

[0010] 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.

[0011] 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_L²+C_D²) 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.

[0012] 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 magnitude is from about 0.32 to about 0.35 and a sixth aerodynamic force angle is from about 40 degrees to about 44 degrees at a Reynolds Number of about 115000 and a spin ratio of about 0.170. In a further embodiment, the golf ball has a seventh aerodynamic coefficient magnitude from about 0.36 to about 0.40 and a seventh aerodynamic force angle of about 41 degrees to about 45 degrees at a Reynolds Number of about 92000 and a spin ratio of about 0.213 and an eighth aerodynamic coefficient magnitude from about 0.40 to about 0.45 and an eighth aerodynamic force angle of about 40 degrees to about 44 degrees at a Reynolds Number of about 69000 and a spin ratio of about 0.284.

[0013] The aerodynamic coefficient magnitudes may vary from each other by about 6 percent or less, and more preferably, about 3 percent or less, at any two axes of ball rotation. In another embodiment, the plurality of dimples cover about 80 percent or greater of the ball surface. In yet another embodiment, at least 80 percent of the dimples have a diameter greater than about 6.5 percent of the ball diameter. The dimples are preferably arranged in an icosahedron or an octahedron pattern. In one embodiment, the dimples have at least three different dimple diameters. In another embodiment, at least 10 percent of the plurality of dimples have a shape defined by catenary curve. In yet another embodiment, at least a first portion of the dimples have a shape factor of less than 60 and a second portion of the dimples have a shape factor of greater than 60. The golf ball may have at least one core and at least one cover layer, wherein at least one of the layers comprises urethane, ionomer, balata, polyurethane, and mixtures thereof.

[0014] The present invention is also directed to a golf ball with a plurality of dimples having an aerodynamic coefficient magnitude defined by C_mag=√(C_L²+C_D²) 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 comprises a first aerodynamic coefficient magnitude from about 0.40 to about 0.45 and a first aerodynamic force angle of about 40 degrees to about 44 degrees at a Reynolds Number of about 69000 and a spin ratio of about 0.284 and a second aerodynamic coefficient magnitude from about 0.36 to about 0.40 and a second aerodynamic force angle of about 41 degrees to about 45 degrees at a Reynolds Number of about 92000 and a spin ratio of about 0.213.

[0015] The golf ball may also have a third aerodynamic coefficient magnitude from about 0.32 to about 0.35 and a third aerodynamic force angle of about 40 degrees to about 44 degrees at a Reynolds Number of about 115000 and a spin ratio of about 0.170 and a fourth aerodynamic coefficient magnitude from about 0.29 to about 0.32 and a fourth aerodynamic force angle of about 39 degrees to about 43 degrees at a Reynolds Number of about 138000 and a spin ratio of about 0.142. In another embodiment, the golf ball has a fifth aerodynamic coefficient magnitude from about 0.27 to about 0.30 and a fifth 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 and a sixth aerodynamic coefficient magnitude from about 0.26 to about 0.29 and a sixth aerodynamic force angle of about 35 degrees to about 39 degrees at a Reynolds Number of about 184000 and a spin ratio of about 0.106.

[0016] In one embodiment, the aerodynamic coefficient magnitudes vary from each other by about 6 percent, and more preferably, about 3 percent, or less at any two axes of ball rotation. In another embodiment, the plurality of dimples cover about 80 percent or greater of the ball surface. In yet another embodiment, at least 80 percent of the dimples have a diameter greater than about 6.5 percent of the ball diameter and the dimples are preferably arranged in an icosahedron or an octahedron pattern. In one embodiment, the dimples have at least three different dimple diameters. In another embodiment, at least 10 percent of the plurality of dimples have a shape defined by catenary curve. In yet another embodiment, at least a first portion of the dimples have a shape factor of less than 60 and a second portion of the dimples have a shape factor of greater than 60. The golf ball may have at least one core and at least one cover layer, wherein at least one of the layers comprises urethane, ionomer, balata, polyurethane, and mixtures thereof.

[0017] The present invention is also related to a golf ball with a plurality of dimples having an aerodynamic coefficient magnitude defined by C_mag=√(C_L²+C_D²) 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 0.40 to about 0.45 and a first aerodynamic force angle of about 40 degrees to about 44 degrees at a Reynolds Number of about 69000 and a spin ratio of about 0.284 for a ball weight W of 1.62 ounces and a diameter D of 1.68 inches and a second aerodynamic coefficient magnitude from about 0.36 to about 0.40 and a second aerodynamic force angle of about 41 degrees to about 45 degrees at a Reynolds Number of about 92000 and a spin ratio of about 0.213 for a ball weight of 1.62 ounces and a diameter of 1.68 inches, wherein the aerodynamic coefficient magnitudes and force angles are adjusted for ball weight and diameter in the following manner:
Adjusted C_mag=C_mag√((sin(Angle)*(W/1.62)*(1.68/D)²)²+(cos(Angle))²)
Adjusted Angle=tan⁻¹(tan(Angle)*(W/1.62)*(1.68/D)²).

[0018] The golf ball may also have a third aerodynamic coefficient magnitude from about 0.32 to about 0.35 and a third aerodynamic force angle of about 40 degrees to about 44 degrees at a Reynolds Number of about 115000 and a spin ratio of about 0.170 and a fourth aerodynamic coefficient magnitude from about 0.29 to about 0.32 and a fourth aerodynamic force angle of about 39 degrees to about 43 degrees at a Reynolds Number of about 138000 and a spin ratio of about 0.142. In another embodiment, the golf ball has a fifth aerodynamic coefficient magnitude from about 0.27 to about 0.30 and a fifth 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 and a sixth aerodynamic coefficient magnitude from about 0.26 to about 0.29 and a sixth aerodynamic force angle of about 35 degrees to about 39 degrees at a Reynolds Number of about 184000 and a spin ratio of about 0.106. In yet another embodiment, a seventh aerodynamic coefficient magnitude is from about 0.25 to about 0.28 and a seventh aerodynamic force angle is from about 34 degrees to about 38 degrees at a Reynolds Number of about 207000 and a spin ratio of about 0.095 and an eighth aerodynamic coefficient magnitude is from about 0.24 to about 0.27 and an eighth aerodynamic force angle is from about 31 degrees to about 35 degrees at a Reynolds Number of about 230000 and a spin ratio of about 0.085.

[0019] In one embodiment, the aerodynamic coefficient magnitudes vary from each other by about 6 percent, and more preferably, about 3 percent, or less at any two axes of ball rotation. In another embodiment, the plurality of dimples cover about 80 percent or greater of the ball surface. In yet another embodiment, at least 80 percent of the dimples have a diameter greater than about 6.5 percent of the ball diameter and the dimples are preferably arranged in an icosahedron or an octahedron pattern. In one embodiment, the dimples have at least three different dimple diameters. In another embodiment, at least 10 percent of the plurality of dimples have a shape defined by catenary curve. In yet another embodiment, at least a first portion of the dimples have a shape factor of less than 60 and a second portion of the dimples have a shape factor of greater than 60. The golf ball may have at least one core and at least one cover layer, wherein at least one of the layers comprises urethane, ionomer, balata, polyurethane, and mixtures thereof.

[0020] The present invention is further directed to a golf ball with a plurality of dimples having an aerodynamic coefficient magnitude defined by C_mag=√(C_L²+C_D²) 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 0.40 to about 0.44 and a first aerodynamic force angle of about 40 degrees to about 42 degrees at a Reynolds Number of about 69000 and a spin ratio of about 0.284 and a second aerodynamic coefficient magnitude from about 0.36 to about 0.39 and a second aerodynamic force angle of about 41 degrees to about 43 degrees at a Reynolds Number of about 92000 and a spin ratio of about 0.213.

[0021] In one embodiment, the golf ball further includes a third aerodynamic coefficient magnitude from about 0.32 to about 0.344 and a third aerodynamic force angle of about 40 degrees to about 42 degrees at a Reynolds Number of about 115000 and a spin ratio of about 0.170 and a fourth aerodynamic coefficient magnitude from about 0.29 to about 0.311 and a fourth aerodynamic force angle of about 39 degrees to about 41 degrees at a Reynolds Number of about 138000 and a spin ratio of about 0.142. The golf ball may also include a fifth aerodynamic coefficient magnitude from about 0.27 to about 0.291 and a fifth aerodynamic force angle of about 37 degrees to about 40 degrees at a Reynolds Number of about 161000 and a spin ratio of about 0.122 and a sixth aerodynamic coefficient magnitude from about 0.26 to about 0.28 and a sixth aerodynamic force angle of about 35 degrees to about 38 degrees at a Reynolds Number of about 184000 and a spin ratio of about 0.106. In another embodiment, a seventh aerodynamic coefficient magnitude from about 0.25 to about 0.271 and a seventh aerodynamic force angle of about 34 degrees to about 36 degrees at a Reynolds Number of about 207000 and a spin ratio of about 0.095 and an eighth aerodynamic coefficient magnitude from about 0.24 to about 0.265 and an eighth aerodynamic force angle of about 31 degrees to about 33 degrees at a Reynolds Number of about 230000 and a spin ratio of about 0.085 may further define the golf ball.

[0022] In one embodiment, the aerodynamic coefficient magnitudes vary from each other by about 6 percent, and more preferably, about 3 percent, or less at any two axes of ball rotation. In another embodiment, the plurality of dimples cover about 80 percent or greater of the ball surface. In yet another embodiment, at least 80 percent of the dimples have a diameter greater than about 6.5 percent of the ball diameter and the dimples are preferably arranged in an icosahedron or an octahedron pattern. In one embodiment, the dimples have at least three different dimple diameters. In another embodiment, at least 10 percent of the plurality of dimples have a shape defined by catenary curve. In yet another embodiment, at least a first portion of the dimples have a shape factor of less than 60 and a second portion of the dimples have a shape factor of greater than 60. The golf ball may have at least one core and at least one cover layer, wherein at least one of the layers comprises urethane, ionomer, balata, polyurethane, and mixtures thereof.

[0023] The present invention is also directed to a golf ball dimple pattern that provides a surprisingly better dimple packing than any previous pattern so that a greater percentage of the surface of the golf ball is covered by dimples. The prior art golf balls have dimple patterns that leave many large spaces between adjacent dimples and/or use small dimples to fill in the spaces. The golf balls according to the present invention have triangular regions with a plurality of dimple sizes arranged to provide a remarkably high percentage of dimple coverage while avoiding groupings of relatively large dimples.

[0024] The triangular regions have a first set of dimples formed in a large triangle and a second set of dimples formed in a small triangle inside of and adjacent to the large triangle. The first set of dimples forming the large triangle comprises dimples that increase in size from the dimples on the points of the triangle toward the midpoint of the triangle side. Thus, the dimples close to or on the midpoint of the sides of the triangle are the largest dimples on the large triangle. Each dimple diameter along the triangle side is equal to or greater than the adjacent dimple toward the vertex or triangle point. Through this layout and with proper sizing, as set forth below, the dimple coverage is greater than 80 percent of the surface of the golf ball.

[0025] Further, the dimples are arranged so that there are three or less great circle paths that do not intersect any dimples to minimize undimpled surface area. Great circles take up a significant amount of the surface area and an intersection of more than two great circles creates very small angles that have to be filled with very small dimples or large gaps are created.

[0026] Still further, the dimples are arranged such that there are no more than two adjacent dimples of the largest diameter. Thus, the largest dimples are more evenly spaced over the ball and are not clumped together.

[0027] In one embodiment of the present invention, dimples cover more than 80 percent of the outer surface. More importantly, the dimple coverage is not accomplished by the mere addition of very small dimples that do not effectively contribute to the creation of turbulence. In a preferred embodiment, the total number of dimples is about 300 to about 500 and at least about 80 percent of the dimples have a diameter of about 0.11 inches or greater, and, more preferably, at least about 90 percent of the dimples have a diameter of about 0.11 inches or greater. More preferably, at least about 95 percent of the dimples have a diameter of about 0.11 inches or greater.

[0028] In another embodiment of the present invention, the golf ball has an icosahedron dimple pattern. The pattern includes 20 triangles made from about 362 dimples and does not have a great circle that does not intersect any dimples. Each of the large triangles, preferably, has an odd number of dimples (7) along each side and the small triangles have an even number of dimples (4) along each side. To properly pack the dimples, the large triangle has nine more dimples than the small triangle. In another embodiment, the ball has five different sizes of dimples in total. The sides of the large triangle have four different sizes of dimples and the small triangles have two different sizes of dimples.

[0029] In yet another embodiment of the present invention, the golf ball has an icosahedron dimple pattern with a large triangle including three different dimples and the small triangles having only one diameter of dimple. In a preferred embodiment, there are 392 dimples and one great circle that does not intersect any dimples. In another embodiment, more than five alternative dimple diameters are used.

[0030] In one embodiment of the present invention, the golf ball has an octahedron dimple pattern. The pattern includes eight triangles made from about 440 dimples and has three great circles that do not intersect any dimples. In the octahedron pattern, the pattern includes a third set of dimples formed in a smallest triangle inside of and adjacent to the small triangle. To properly pack the dimples, the large triangle has nine more dimples than the small triangle and the small triangle has nine more dimples than the smallest triangle. In this embodiment, the ball has six different dimple diameters distributed over the surface of the ball. The large triangle has five different dimple diameters, the small triangle has three different dimple diameters and the smallest triangle has two different dimple diameters.

[0031] The present invention is also directed to defining the dimple profile on a golf ball by revolving a catenary curve about its symmetrical axis. In one embodiment, the catenary curve used to define a golf ball dimple is a hyperbolic cosine function in the form of:
Y=(d(cos h(ax)−1))/(cos h(ar)−1)
where:

• • [0032] Y is the vertical distance from the dimple apex,
  • [0033] x is the radial distance from the dimple apex,
  • [0034] a is the shape constant;
  • [0035] d is the depth of the dimple, and
  • [0036] r is the radius of the dimple (r=D/2)
  • [0037] D is the dimple diameter.

[0038] In one embodiment, at least 10 percent of the dimples have a shape defined by the revolution of a catenary curve. In another embodiment, at least 10 percent of the dimples have a shape factor, a, of greater than 60. In yet another embodiment, at least two different catenary shape factors are used to define dimple profiles on the golf ball. In one embodiment, at least 20 percent of the dimples have a catenary shape factor of less than 60 and at least 20 percent of the dimples have a shape factor of greater than 70. In another embodiment, at least three dimple profiles on the golf ball are defined by at least three different catenary shape factors.

[0061] The present invention is directed to golf balls having improved aerodynamic efficiency, resulting in uniformly increased flight distance for golfers of all swing speeds. In particular, the present invention is directed to the selection of dimple arrangements and dimple profiles to obtain a unique set of aerodynamic criteria, which results in consistently improved aerodynamic efficiency. The desired aerodynamic criteria are defined by the magnitude and direction of the aerodynamic force, for the range of Spin Ratios and Reynolds Numbers that encompass the flight regime for typical golf ball trajectories.

Aerodynamic Force

[0062] The forces acting on a golf ball in flight are enumerated in Equation 1 and illustrated in FIG. 2:
F=F_L+F_D+F_G  (Eq. 1)
Where

• • [0063] F=total force acting on the ball
  • [0064] F_L=lift force
  • [0065] F_D=drag force
  • [0066] F_G=gravity force

[0067] The lift force (F_L) acts in a direction dictated by the cross product of the spin vector and the velocity vector. The drag force (F_D) acts in a direction that is directly opposite the velocity vector. The lift and drag forces of Equation 1 are calculated in Equations 2 and 3, respectively:
F_L=0.5C_LρAV²  (Eq. 2)
F_D=0.5C_DρAV²  (Eq. 3)
where

• • [0068] ρ=density of air (slugs/ft³)
  • [0069] A=projected area of the ball (ft²) ((π/4)D²)
  • [0070] D=ball diameter (ft)
  • [0071] V=ball velocity (ft/s)
  • [0072] C_L=dimensionless lift coefficient
  • [0073] C_D=dimensionless drag coefficient

[0074] Lift and drag coefficients are used to quantify the force imparted to a ball in flight and are dependent on air density, air viscosity, ball speed, and spin rate; the influence of all these parameters may be captured by two dimensionless parameters Spin Ratio (SR) and Reynolds Number (N_Re). Spin Ratio is the rotational surface speed of the ball divided by ball velocity. Reynolds Number quantifies the ratio of inertial to viscous forces acting on the golf ball moving through air. SR and N_Re are calculated in Equations 4 and 5 below:
SR=ω(D/2)/V  (Eq. 4)
N_Re=DVρ/μ  (Eq. 5)
where

• • [0075] ω=ball rotation rate (radians/s) (2π(RPS))
  • [0076] RPS=ball rotation rate (revolution/s)
  • [0077] V=ball velocity (ft/s)
  • [0078] D=ball diameter (ft)
  • [0079] ρ=air density (slugs/ft³)
  • [0080] μ=absolute viscosity of air (lb/ft-s)

[0081] There are a number of suitable methods for determining the lift and drag coefficients for a given range of SR and N_Re, which include the use of indoor test ranges with ballistic screen technology. U.S. Pat. No. 5,682,230, the entire disclosure of which is incorporated by reference herein, teach the use of a series of ballistic screens to acquire lift and drag coefficients. U.S. Pat. Nos. 6,186,002 and 6,285,445, also incorporated in their entirety by reference herein, disclose methods for determining lift and drag coefficients for a given range of velocities and spin rates using an indoor test range, wherein the values for C_L and C_D are related to SR and N_Re for each shot. One skilled in the art of golf ball aerodynamics testing could readily determine the lift and drag coefficients through the use of an indoor test range.

[0082] The present invention is directed to a golf ball having improved flight distance as defined by two novel parameters that account for both lift and drag simultaneously: 1) the magnitude of aerodynamic force (C_mag); and 2) the direction of the aerodynamic force (Angle). It has now been discovered that flight performance improvements are attained when the dimple pattern and dimple profiles are selected to satisfy specific magnitude and direction criteria. The magnitude and angle of the aerodynamic force are linearly related to the lift and drag coefficients and, therefore, the magnitude and angle of the aerodynamic coefficients are used to establish the preferred criteria. The magnitude and the angle of the aerodynamic coefficients are defined in Equations 6 and 7 below:
C_mag=√(C_L²+C_D²)  (Eq. 6)
Angle=tan⁻¹(C_L/C_D)  (Eq. 7)

[0083] Table 1 illustrates the aerodynamic criteria for a golf ball of the present invention that results in increased flight distances. The criteria are specified as low, median, and high C_mag and Angle for eight specific combinations of SR and N_Re. Golf balls with C_mag and Angle values between the low and the high number are preferred. More preferably, the golf balls of the invention have C_mag and Angle values between the low and the median numbers delineated in Table 1. The C_mag values delineated in Table 1 are intended for golf balls that conform to USGA size and weight regulations. The size and weight of the golf balls used with the aerodynamic criteria of Table 1 are 1.68 inches and 1.62 ounces, respectively.

[0084]

TABLE 1
AERODYNAMIC CHARACTERISTICS
BALL DIAMETER = 1.68 INCHES, BALL WEIGHT = 1.62 OUNCES
	Magnitude1	Angle2 (0)
NRe	SR	Low	Median	High	Low	Median	High
230000	0.085	0.24	0.265	0.27	31	33	35
207000	0.095	0.25	0.271	0.28	34	36	38
184000	0.106	0.26	0.280	0.29	35	38	39
161000	0.122	0.27	0.291	0.30	37	40	42
138000	0.142	0.29	0.311	0.32	38	41	43
115000	0.170	0.32	0.344	0.35	40	42	44
92000	0.213	0.36	0.390	0.40	41	43	45
69000	0.284	0.40	0.440	0.45	40	42	44
1As defined by Eq. 6
2As defined by Eq. 7

[0085] To ensure consistent flight performance regardless of ball orientation, the percent deviation of C_mag for each of the SR and N_Re combinations listed in Table 1 plays an important role. The percent deviation of C_mag may be calculated in accordance with Equation 8, wherein the ratio of the absolute value of the difference between the C_mag for two orientations to the average of the C_mag for the two orientations is multiplied by 100.
Percent deviation C_mag=|(C_mag1−C_mag2)|/((C_mag1+C_mag2)/2)*100  (Eq. 8)
where

• • [0086] C_mag1=C_mag for orientation 1
  • [0087] C_mag2=C_mag for orientation 2

[0088] In one embodiment, the percent deviation is about 6 percent or less. In another embodiment, the deviation of C_mag is about 3 percent or less. To achieve the consistent flight performance, the percent deviation criteria of Equation 8 is preferably satisfied for each of the eight C_mag values associated with the eight SR and N_Re values contained in Table 1.

[0089] Aerodynamic asymmetry typically arises from parting lines inherent in the dimple arrangement or from parting lines associated with the manufacturing process. The percent C_mag deviation should be obtained using C_mag values measured with the axis of rotation normal to the parting line, commonly referred to as a poles horizontal, PH, orientation and C_mag values measured in an orientation orthogonal to PH, commonly referred to as a pole over pole, PP orientation. The maximum aerodynamic asymmetry is generally measured between the PP and PH orientation.

[0090] One of ordinary skill in the art would be aware, however, that the percent deviation of C_mag as outlined above applies to PH and PP, as well as any other two orientations. For example, if a particular dimple pattern is used having a great circle of shallow dimples, which will be described in greater detail below, different orientations should be measured. The axis of rotation to be used for measurement of symmetry in the above example scenario would be normal to the plane described by the great circle and coincident to the plane of the great circle.

[0091] It has also been discovered that the C_mag and Angle criteria delineated in Table 1 for golf balls with a nominal diameter of 1.68 and a nominal weight of 1.62 ounces may be advantageously scaled to obtain the similar optimized criteria for golf balls of any size and weight. The aerodynamic criteria of Table 1 may be adjusted to obtain the C_mag and angle for golf balls of any size and weight in accordance with Equations 9 and 10.
C_mag(ball)=C_{mag(Table 1)}√((sin(Angle_{(Table 1)})*(W_ball/1.62)*(1.68/D_ball)²)²+(cos(Angle_(Table1))²)  (Eq. 9)
Angle_(ball)=tan⁻¹(tan(Angle_{(Table 1)})*(W_ball/1.62)*(1.68/D_ball)²)  (Eq. 10)
For example, Table 2 illustrates aerodynamic criteria for balls with a diameter of 1.60 inches and a weight of 1.7 ounces as calculated using Table 1, ball diameter, ball weight, and Equations 9 and 10.

[0092]

TABLE 2
AERODYNAMIC CHARACTERISTICS
BALL DIAMETER = 1.60 INCHES, BALL WEIGHT = 1.70 OUNCES
	Magnitude1	Angle2 (0)
NRe	SR	Low	Median	High	Low	Median	High
230000	0.085	0.24	0.265	0.27	31	33	35
207000	0.095	0.262	0.287	0.297	38	40	42
184000	0.106	0.271	0.297	0.308	39	42	44
161000	0.122	0.83	0.311	0.322	42	44	46
138000	0.142	0.304	0.333	0.346	43	45	47
115000	0.170	0.337	0.370	0.383	44	46	49
92000	0.213	0.382	0.420	0.435	45	47	50
69000	0.284	0.430	0.473	0.489	44	47	49
1As defined by Eq. 9
2As defined by Eq. 10

[0093] Table 3 shows lift and drag coefficients (C_L, C_D), as well as C_mag and Angle, for a golf ball having a nominal diameter of 1.68 inches and a nominal weight of 1.61 ounces, with an icosahedron pattern with 392 dimples and two dimple diameters, of which the dimple pattern will be described in more detail below. The percent deviation in C_mag for PP and PH ball orientations are also shown over the range of N_Re and SR. The deviation in C_mag for the two orientations over the entire range is less than about 3 percent.

[0094]

TABLE 3
AERODYNAMIC CHARACTERISTICS
BALL DIAMETER = 1.68 INCHES, BALL WEIGHT = 1.61 OUNCES
	PP Orientation	PH Orientation	% Dev
NRe	SR	CL	CD	Cmag1	Angle2	CL	CD	Cmag1	Angle2	Cmag
230000	0.085	0.144	0.219	0.262	33.4	0.138	0.217	0.257	32.6	1.9
207000	0.095	0.159	0.216	0.268	36.3	0.154	0.214	0.264	35.7	1.8
184000	0.106	0.169	0.220	0.277	37.5	0.166	0.216	0.272	37.5	1.8
161000	0.122	0.185	0.221	0.288	39.8	0.181	0.221	0.286	39.4	0.9
138000	0.142	0.202	0.232	0.308	41.1	0.199	0.233	0.306	40.5	0.5
115000	0.170	0.229	0.252	0.341	42.2	0.228	0.252	0.340	42.2	0.2
92000	0.213	0.264	0.281	0.386	43.2	0.270	0.285	0.393	43.5	1.8
69000	0.284	0.278	0.305	0.413	42.3	0.290	0.309	0.423	43.2	2.5
			SUM	2.543			SUM	2.541
1As defined by Eq. 9
2As defined by Eq. 10

[0095] Table 4 shows lift and drag coefficients (C_L, C_D), as well as C_mag and Angle for a prior golf ball having a nominal diameter of 1.68 inches and a nominal weight of 1.61 ounces. The percent deviation in C_mag for PP and PH ball orientations are also shown over the range of N_Re and SR. The deviation in C_mag for the two orientations is greater than about 3 percent over the entire range, greater than about 6 percent for N_Re of 161000, 138000, 115000, and 92000, and exceeds 10 percent at a N_Re of 69000.

[0096]

TABLE 4
AERODYNAMIC CHARACTERISTICS FOR PRIOR ART GOLF BALL
BALL DIAMETER = 1.68 INCHES, BALL WEIGHT = 1.61 OUNCES
	PP Orientation	PH Orientation	% Dev
NRe	SR	CL	CD	Cmag1	Angle2	CL	CD	Cmag1	Angle2	Cmag
230000	0.085	0.151	0.222	0.269	34.3	0.138	0.219	0.259	32.3	3.6
207000	0.095	0.160	0.223	0.274	35.6	0.145	0.219	0.263	33.4	4.1
184000	0.106	0.172	0.227	0.285	37.2	0.154	0.221	0.269	34.8	5.6
161000	0.122	0.188	0.233	0.299	38.9	0.166	0.225	0.279	36.5	6.9
138000	0.142	0.209	0.245	0.322	40.5	0.184	0.231	0.295	38.5	8.7
115000	0.170	0.242	0.269	0.361	42.0	0.213	0.249	0.328	40.5	9.7
92000	0.213	0.280	0.309	0.417	42.2	0.253	0.283	0.380	41.8	9.5
69000	0.284	0.270	0.308	0.409	41.2	0.308	0.337	0.457	42.5	10.9
			SUM	2.637			SUM	2.531
1As defined by Eq. 9
2As defined by Eq. 10

[0097] Table 5 illustrates the flight performance of a golf ball of the present invention having a nominal diameter of 1.68 inches and weight of 1.61 ounces, compared to a prior art golf ball having similar diameter and weight. Each prior art ball is compared to a golf ball of the present invention at the same speed, angle, and back spin.

[0098]

TABLE 5
BALL FLIGHT PERFORMANCE, INVENTION VS. PRIOR ART GOLF BALL
BALL DIAMETER = 1.68 INCHES, BALL WEIGHT = 1.61 OUNCES
	Launch Conditions
Ball		Rotation	Ball Flight
	Ball	Speed		Rate	Distance		Impact
	Orientation	(mph)	Angle	(rpm)	(yds)	Time (s)	Angle
Prior Art	PP	168.4	8.0	3500	267.2	7.06	41.4
	PH	168.4	8.0	3500	271.0	6.77	36.2
Invention	PP	168.4	8.0	3500	276.7	7.14	39.9
	PH	168.4	8.0	3500	277.6	7.14	39.2
Prior Art	PP	145.4	8.0	3000	220.8	5.59	31.3
	PH	145.4	8.0	3000	216.9	5.18	25.4
Invention	PP	145.4	8.0	3000	226.5	5.61	29.3
	PH	145.4	8.0	3000	226.5	5.60	28.7

[0099] Table 5 shows an improvement in flight distance for a golf ball of the present invention of between about 6 to about 10 yards over a similar size and weight prior art golf ball. Table 5 also shows that the flight distance of prior art golf balls is dependent on the orientation when struck, i.e., a deviation between a PP and PH orientation results in about 4 yards distance between the two orientations. In contrast, golf balls of the present invention exhibit less than about 1 yard variation in flight distance due to orientation. Additionally, prior art golf balls exhibit large variations in the angle of ball impact with the ground at the end of flight, i.e., about 5°, for the two orientations, while golf balls of the present invention have a variation in impact angles for the two orientations of less than about 1°. A large variation in impact angle typically leads to significantly different amounts of roll when the ball strikes the ground.

[0100] The advantageously consistent flight performance of a golf ball of the present invention, i.e., the less variation in flight distance and impact angle, results in more accurate play and potentially yields lower golf scores. FIGS. 3 and 4 illustrate the magnitude of the aerodynamic coefficients and the angle of aerodynamic force plotted versus N_Re for a golf ball of the present invention and a prior art golf ball, each having a diameter of about 1.68 inches and a weight of about 1.61 ounces with a fixed spin rate of 3000 rpm. As shown in FIG. 3, the magnitude of the aerodynamic coefficient is substantially lower and more consistent between orientations for a golf ball of the present invention as compared to a prior art golf ball throughout the range of N_Re tested. FIG. 4 illustrates that the angle of the aerodynamic force is more consistent for a golf ball of the present invention as compared to a prior art golf ball.

[0101] A variety of golf ball sizes and weights, constructions, including dimple patterns and profiles, and materials are contemplated to fit the aerodynamic characteristics as outlined in Table 1, and as modified for different sizes and weights in accordance with Equations 9 and 10. Several non-limiting examples follow.

Dimple Patterns

[0102] One way of adjusting the magnitude of aerodynamic coefficients and angle of aerodynamic force for a ball to satisfy the aerodynamic criteria of Table 1 is through different dimple patterns and profiles. As used herein, the term “dimple”, may include any texturizing on the surface of a golf ball, e.g., depressions and extrusions. Some non-limiting examples of depressions and extrusions include, but are not limited to, spherical depressions, meshes, raised ridges, and brambles. The depressions and extrusions may take a variety of planform shapes, such as circular, polygonal, oval, or irregular. Dimples that have multi-level configurations, i.e., dimple within a dimple, are also contemplated by the invention to obtain desirable aerodynamic charateristics.

[0103] Dimple patterns that provide a high percentage of surface coverage are preferred, and are well known in the art. For example, U.S. Pat. Nos. 5,562,552, 5,575,477, 5,957,787, 5,249,804, and 4,925,193 disclose geometric patterns for positioning dimples on a golf ball. In one embodiment of the present invention, the dimple pattern is at least partially defined by phyllotaxis-based patterns, such as those described U.S. Pat. No. 6,338,684, which is incorporated by reference in its entirety. In one embodiment, a dimple pattern that provides greater than about 50 percent surface coverage is selected. In another embodiment, the dimple pattern provides greater than about 70 percent surface coverage, and more preferably, the dimple surface coverage is greater than 80 percent.

[0104] Several additional non-limiting examples follow of different dimple pattern geometries that may be used to obtain the aerodynamic criteria of Table 1.

[0105] FIGS. 5 and 6 show the TITLEIST PROFESSIONAL golf ball 10 with a plurality of dimples 11 on the outer surface that are formed into a dimple pattern having two sizes of dimples. The first set of dimples A have diameters of about 0.14 inches and form the outer triangle 12 of the icosahedron dimple pattern. The second set of dimples B have diameters of about 0.16 inches and form the inner triangle 13 and the center dimple 14. The dimples 11 cover less than 80 percent of the outer surface of the golf ball and there are a significant number of large spaces 15 between adjacent dimples, i.e., spaces that could hold a dimple of 0.03 inches diameter or greater.

[0106] FIGS. 7 and 8 show a golf ball 20 according to the first dimple pattern embodiment of the present invention with a plurality of dimples 21 in an icosahedron pattern. In an icosahedron pattern, there are twenty triangular regions that are generally formed from the dimples. The icosahedron pattern has five triangles formed at both the top and bottom of the ball, each of which shares the pole dimple as a point. There are also ten triangles that extend around the middle of the ball.

[0107] In this first dimple pattern embodiment, there are five different sized dimples A–E, wherein dimples E (D_E) are greater than dimples D (D_D), which are greater than dimples C (D_C), which are greater than dimples B(D_B), which are greater than dimples A (D_A); D_E>D_D>D_C>D_B>D_A. Dimple minimum sizes according to this embodiment are set forth in Table 6 below:

[0108]

TABLE 6
DIMPLE SIZES FOR FIRST DIMPLE PATTERN EMBODIMENT
		Percent of Ball
	Dimple	Diameter
	A	6.55
	B	8.33
	C	9.52
	D	10.12
	E	10.71

[0109] The dimples of this embodiment are formed in large triangles 22 and small triangles 23. The dimples along the sides of the large triangle 22 increase in diameter toward the midpoint 24 of the sides. The largest dimple along the sides, D_E, is located at the midpoint 24 of each side of the large triangle 22, and the smallest dimples, D_A, are located at the triangle points 25. In this embodiment, each dimple along the sides is larger than the adjacent dimple toward the triangle point.

[0110] FIGS. 9–12 illustrate a second dimple pattern embodiment contemplated for the golf ball of the present invention. In this embodiment, there are again five different sized dimples A–E, wherein dimples E (D_E) are greater than dimples D (D_D), which are greater than dimples C (D_C), which are greater than dimples B(D_B), which are greater than dimples A (D_A); D_E>D_D>D_C>D_B>D_A. Dimple minimum sizes according to this embodiment are set forth in Table 7 below:

[0111]

TABLE 7
DIMPLE SIZES FOR SECOND DIMPLE PATTERN EMBODIMENT
		Percent of Ball
	Dimple	Diameter
	A	6.55
	B	8.93
	C	9.23
	D	9.52
	E	10.12

[0112] In the second dimple pattern embodiment, the dimples are again formed in large triangles 22 and small triangles 23 as shown in FIG. 11. The dimples along the sides of the large triangle 22 increase in diameter toward the midpoint 24 of the sides. The largest dimple along the sides, D_D, is located at the midpoint 24 of each side of the large triangle 22, and the smallest dimples, D_A, are located at the triangle points 25. In this embodiment, each dimple along the sides is larger than the adjacent dimple toward the triangle point, i.e., D_B>D_A and D_D>D_B

[0113] A third dimple pattern embodiment is illustrated in FIGS. 13–14, wherein the golf ball has an octahedral dimple pattern. In an octahedral dimple pattern, there are eight spherical triangular regions 30 that form the ball. In this third dimple pattern embodiment, there are six different sized dimples A–F, wherein dimples F (D_F) are greater than dimples E (D_E), which are greater than dimples D (D_D), which are greater than dimples C (D_C), which are greater than dimples B(D_B), which are greater than dimples A (D_A); D_F>D_E>D_D>D_C>D_B>D_A. Dimple minimum sizes according to this embodiment are set forth in Table 8 below:

[0114]

TABLE 8
DIMPLE SIZES FOR THIRD DIMPLE PATTERN EMBODIMENT
		Percentage of Ball
	Dimple	Diameter
	A	5.36
	B	6.55
	C	8.33
	D	9.83
	E	9.52
	F	10.12

[0115] In this third dimple pattern embodiment, the dimples are formed in large triangles 31, small triangles 32 and smallest triangles 33. Each dimple along the sides of the large triangle 31 is equal to or larger than the adjacent dimple from the point 34 to the midpoint 35 of the triangle 31. The dimples at the midpoint 35 of the side, D_E, are the largest dimples along the side and the dimples at the points 34 of the triangle, D_A, are the smallest. In addition, each dimple along the sides of the small triangle 32 is also equal to or larger than the adjacent dimple from the point 36 to the midpoint 37 of the triangle 32. The dimple at the midpoint 37 of the side, D_F, is the largest dimple along the side and the dimples at the points 36 of the triangle, D_C, are the smallest.

Dimple Packing

[0116] In one embodiment, the golf balls of the invention include an icosahedron dimple pattern, wherein each of the sides of the large triangles are formed from an odd number of dimples and each of the side of the small triangles are formed with an even number of dimples.

[0117] For example, in the icosahedron pattern shown in FIGS. 7–8 and 9–12, there are seven dimples along each of the sides of the large triangle 22 and four dimples along each of the sides of the small triangle 23. Thus, the large triangle 22 has nine more dimples than the small triangle 23, which creates hexagonal packing 26, i.e., each dimple is surrounded by six other dimples for most of the dimples on the ball. For example, the center dimple, D_E, is surrounded by six dimples slightly smaller, D_D. In one embodiment, at least 75 percent of the dimples have 6 adjacent dimples. In another embodiment, only the dimples forming the points of the large triangle 25, D_A, do not have hexagonal packing. Since D_A are smaller than the adjacent dimples, the gaps between adjacent dimples is surprisingly small when compared to the prior art golf ball shown in FIG. 7.

[0118] The golf ball 20 has a greater dispersion of the largest dimples. For example, in FIG. 7, there are four of the largest diameter dimples, D_E, located in the center of the triangles and at the mid-points of the triangle sides. Thus, there are no two adjacent dimples of the largest diameter. This improves dimple packing and aerodynamic uniformity. Similarily, in FIG. 9, there is only one largest diameter dimple, D_E, which is located in the center of the triangles. Even the next to the largest dimples, D_D are dispersed at the mid-points of the large triangles such that there are no two adjacent dimples of the two largest diameters, except where extra dimples have been added along the equator.

[0119] In the third dimple pattern embodiment, each of the sides of the large triangle 31 has an even number of dimples, each of the sides of the small triangle 32 has an odd number of dimples and each of the sides of the smallest triangle 33 has an even number of dimples. There are ten dimples along the sides of the large triangles 31, seven dimples along the sides of the small triangles 32, and four dimples along the sides of the smallest triangles 33. Thus, the large triangle 31 has nine more dimples than the small triangle 32 and the small triangle 32 has nine more dimples than the smallest triangle 33. This creates the hexagonal packing for all of the dimples inside of the large triangles 31.

[0120] As used herein, adjacent dimples can be considered as any two dimples where the two tangent lines from the first dimple that intersect the center of the second dimple do not intersect any other dimple. In one embodiment, less than 30 percent of the gaps between adjacent dimples is greater than 0.01 inches. In another embodiment, less than 15 percent of the gaps between adjacent dimples is greater than 0.01 inches.

[0121] One embodiment of the present invention contemplates dimple coverage of greater than about 80 percent. For example, the percentages of surface area covered by dimples in the embodiments shown in FIGS. 7–8 and 9–12 are about 85.7 percent and 82 percent, respectively whereas the ball shown in FIG. 5 has less than 80 percent of its surface covered by dimples. The percentage of surface area covered by dimples in the third embodiment shown in FIGS. 13–14 is also about 82 percent, whereas prior art octahedral balls have less than 77 percent of their surface covered by dimples, and most have less than 60 percent. Thus, there is a significant increase in surface area contemplated for the golf balls of the present invention as compared to prior art golf balls.

Parting Line

[0122] A parting line, or annular region, about the equator of a golf ball has been found to separate the flow profile of the air into two distinct halves while the golf ball is in flight and reduce the aerodynamic force associated with pressure recovery, thus improving flight distance and roll. The parting line must coincide with the axis of ball rotation. It is possible to manufacture a golf ball without parting line, however, most balls have one for ease of manufacturing, e.g., buffing of the golf balls after molding, and many players prefer to have a parting line to use as an alignment aid for putting.

[0123] In one embodiment of the present invention, the golf balls include a dimple pattern containing at least one parting line, or annular region. In another embodiment, there is no parting line that does not intersect any dimples, as illustrated in the golf ball shown in FIG. 7. While this increases the percentage of the outer surface that is covered by dimples, the lack of the parting line may make manufacturing more difficult.

[0124] In yet another embodiment, the parting line(s) may include regions of no dimples or regions of shallow dimples. For example, most icosahedron patterns generally have modified triangles around the mid-section to create a parting line that does not intersect any dimples. Referring specifically to FIG. 12, the golf ball in this embodiment has a modified icosahedron pattern to create the parting line 27, which is accomplished by inserting an extra row of dimples. In the triangular section identified with lettered dimples, there is an extra row 28 of D-C-C-D dimples added below the parting line 27. Thus, the modified icosahedron pattern in this embodiment has thirty more dimples than the unmodified icosahedron pattern in the embodiment shown in FIGS. 7–8.

[0125] In another embodiment, there are more than two parting lines that do not intersect any dimples. For example, the octahedral golf ball shown in FIGS. 13–14 contains three parting lines 38 that do not intersect any dimples. This decreases the percentage of the outer surface as compared to the first embodiment, but increases the symmetry of the dimple pattern.

[0126] In another embodiment, the golf balls according to the present invention may have the dimples arranged so that there are less than four parting lines that do not intersect any dimples.

Dimple Count

[0127] In one embodiment, the golf balls according to the present invention have about 300 to about 500 total dimples. In another embodiment, the dimple patterns are icosahedron patterns with about 350 to about 450 total dimples. For example, the golf ball of FIGS. 7–8 have 362 dimples. In the golf ball shown in FIGS. 9–12, there are 392 dimples and in the golf ball shown in FIGS. 13–14, there are 440 dimples.

Dimple Diameter

[0128] In one embodiment, at least about 80 percent of the dimples have a diameter of about 6.5 percent of the ball diameter or greater so that the majority of the dimples are sufficiently large to assist in creating the turbulent boundary layer. In another embodiment, at least about 90 percent of the dimples have a diameter of about 6.5 percent of the ball diameter or greater. In yet another embodiment, at least about 95 percent of the dimples have a diameter of about 6.5 percent of the ball diameter or greater. For example, all of the dimples have a diameter of about 6.5 percent of the ball diameter or greater in the ball illustrated by FIGS. 9–12.

Dimple Profile

[0129] Golf balls may also be designed to fit the aerodynamic criteria of Table 1 by creating dimple patterns wherein all dimples have fixed radii and depth, but vary as to shape. For example, dimple shape variations may be defined as edge radius and edge angle or by catenary shape factor and edge radius.

[0130] In one embodiment, a golf ball of the present invention meets the criteria of Table 1 by including dimples defined by the revolution of a catenary curve about an axis. A catenary curve represents the curve formed by a perfectly flexible, uniformly dense, and inextensible cable suspended from its endpoints. In general, the mathematical formula representing such a curve is expressed as Equation 11:
y=a cos h(bx)  (Eq. 11)
where

• • [0131] a=constant
  • [0132] b=constant
  • [0133] y=vertical axis (on a two dimensional graph)
  • [0134] x=horizontal axis (on a two dimensional graph)

[0135] The dimple shape on the golf ball is generated by revolving the catenary curve about its y axis.

[0136] This embodiment uses variations of Equation 11 to define the cross-section of golf ball dimples. For example, the catenary curve is defined by hyperbolic sine or cosine functions. A hyperbolic sine function is expressed as Equation 12 below:
sin h(x)=(e^x−e^−x)/2  (Eq. 12)
while a hyperbolic cosine function is expressed by Equation 13:
cos h(x)=(e^x+e^−x)/2  (Eq. 13)

[0137] In one embodiment, the mathematical equation for describing the cross-sectional profile of a dimple is expressed by Equation 14:
Y=(d(cos h(ax)−1))/(cos h(ar)−1)  (Eq. 14)
where

• • [0138] Y=vertical distance from the dimple apex
  • [0139] x=radial distance from the dimple apex to the dimple surface
  • [0140] a=shape constant (shape factor)
  • [0141] d=depth of dimple
  • [0142] r=radius of dimple

[0143] The “shape constant” or “shape factor”, a, is an independent variable in the mathematical expression for a catenary curve. The shape factor may be used to independently alter the volume ratio of the dimple while holding the dimple depth and radius fixed. The volume ratio is the fractional ratio of the dimple volume divided by the volume of a cylinder defined by a similar radius and depth as the dimple.

[0144] Use of the shape factor provides an expedient method of generating alternative dimple profiles, for dimples with fixed radii and depth. For example, to design a golf ball with lift and drag characteristics to fit the aerodynamic criteria of Table 1, alternative shape factors may be employed to obtain alternative lift and drag performance without having to change dimple pattern, depth or size. No modification to the dimple layout on the surface of the ball is required.

[0145] The depth (d) and radius (r) (r=½D) of the dimple may be measured as described in U.S. Pat. No. 4,729,861 (shown in FIG. 15), the disclosure of which is incorporated by reference in its entirety. The dimple diameter is measured from the edges of the dimples, points E and F, along straight line 162. Point J is the deepest part of the dimple 12. The depth is measured from point K on the continuation of the periphery 41 to point J and is indicated by line 164. Line 164 is perpendicular to line 162.

[0146] For Equation 14, shape constant values that are larger than 1 result in dimple volume ratios greater than 0.5. In one embodiment, shape factors are between about 20 to about 100. FIGS. 16–20 illustrate dimple profiles for shape factors of 20, 40, 60, 80, and 100, respectively. Table 9 illustrates how the volume ratio changes for a dimple with a radius of 0.05 inches and a depth of 0.025 inches. Increases in shape factor result in higher volume ratios for a given dimple radius and depth. It has been discovered that the use of dimples with multiple catenary shape factors may be used to obtain the aerodynamic criteria of Table 1 and the symmetry requirements of less than 6 percent variation C_mag.

[0147]

TABLE 9
VOLUME RATIO AS A FUNCTION OF RADIUS AND DEPTH
	SHAPE FACTOR	VOLUME RATIO
	20	0.51
	40	0.55
	60	0.60
	80	0.64
	100	0.69

[0148] A dimple whose profile is defined by the cos h catenary curve with a shape constant of less than about 40 will have a smaller dimple volume than a dimple with a spherical profile. This will result in a larger aerodynamic force angle and higher trajectory. On the other hand, a dimple whose profile is defined by the cos h catenary curve with a shape constant of greater than about 40 will have a larger dimple volume than a dimple with a spherical profile. This will result in a smaller angle of the aerodynamic force and a lower trajectory. Therefore, a golf ball having dimples defined by a catenary curve with a shape constant is advantageous because the shape constant may be selected to obtain the aerodynamic criteria delineated in Table 1.

[0149] While this embodiment is directed toward using a catenary curve for at least one dimple on a golf ball, it is not necessary that catenary curves be used on every dimple on a golf ball. In some cases, the use of a catenary curve may only be used for a small number of dimples. It is preferred, however, that a sufficient number of dimples on the ball have catenary curves so that variation of shape factors will allow a designer to alter the aerodynamic characteristics of the ball to satisfy the aerodynamic criteria of Table 1. In one embodiment, the golf ball has at least about 10 percent, and more preferably at least about 60 percent, of its dimples defined by a catenary curves.

[0150] Moreover, it is not necessary that every dimple have the same shape factor. Instead, differing combinations of shape factors for different dimples on the ball may be used to achieve desired ball flight performance. For example, some of the dimples defined by catenary curves on a golf ball may have one shape factor while others have a different shape factor. In addition, the use of differing shape factors may be used for different diameter dimples, as described above in FIGS. 6–14.

[0151] Therefore, once a dimple pattern is selected for the golf ball, alternative shape factors for the catenary profile can be tested in light gate test range, as described in U.S. Pat. No. 6,186,002, to empirically determine the catenary shape factor that provides the desired aerodynamic characteristics of Table 1.

Aerodynamic Symmetry

[0152] To create a ball that adheres to the Rules of Golf, as approved by the United States Golf Association, the ball must not be designed, manufactured or intentionally modified to have properties that differ from those of a spherically symmetrical ball. Aerodynamic symmetry allows the ball to fly with little variation no matter how the golf ball is placed on the tee or ground.

[0153] Dimple patterns are preferably designed to cover the maximum surface area of the golf ball without detrimentally affecting the aerodynamic symmetry of the golf ball. A representative coordinate system used to model some of the dimple patterns discussed above is shown in FIG. 21. The XY plane is the equator of the ball while the Z direction goes through the pole of the ball. Preferably, the dimple pattern is generated from the equator of the golf ball, the XY plane, to the pole of the golf ball, the Z direction.

[0154] As discussed above, golf balls containing dimple patterns having a parting line about the equator may result in orientation specific flight characteristics. As mentioned above, the parting lines are desired by manufacturers for ease of production, as well as by many golfers for lining up a shot for putting or off the tee. It has now been discovered that selective design of golf balls with dimple patterns including a parting line meeting the aerodynamic criteria set forth in Table 1 result in flight distances far improved over prior art. Geometrically, these parting lines must be orthogonal with the axis of rotation. However, in one embodiment of the present invention, there may be a plurality of parting lines with multiple orientations.

[0155] In one embodiment, the aerodynamic coefficient magnitude for a golf ball varies less than about 6 percent whether a golf ball has a PH or PP orientation. In another embodiment, the variation of the aerodynamic coefficient magnitude between the two orientations is less than about 3 percent.

Ball Construction

[0156] The present invention may be used with any type of ball construction. For example, the ball may have a 1-piece design, a 2-piece design, a three-piece design, a double core, a double cover, or multi-core and multi-cover construction depending on the type of performance desired of the ball. Non-limiting examples of these and other types of ball constructions that may be used with the present invention include those described in U.S. Pat. Nos. 5,688,191, 5,713,801, 5,803,831, 5,885,172, 5,919,100, 5,965,669, 5,981,654, 5,981,658, and 6,149,535, as well as in Publication No. US2001/0009310 A1. The entire disclosures of these applications are incorporated by reference herein.

[0157] Different materials also may be used in the construction of the golf balls made with the present invention. For example, the cover of the ball may be made of a thermoset or thermoplastic, a castable or non-castable polyurethane and polyurea, an ionomer resin, balata, or any other suitable cover material known to those skilled in the art. Different materials also may be used for forming core and intermediate layers of the ball. For example, golf balls having solid, wound, liquid filled, dual cores, and multi-layer intermediate components are contemplated by the invention. For example, the most common core material is polybutadiene, although one of ordinary skill in the art is aware of the various materials that may be used with the present invention. After selecting the desired ball construction, the aerodynamic performance of the golf ball designed to satisfy the aerodynamic criteria outlined in Table 1 according to the design, placement, and number of dimples on the ball.

[0158] As explained above, the use of various dimple patterns and profiles provides a relatively effective way to modify the aerodynamic characteristics. The use of the catenary curve profile allows a golf ball design to meet the aerodynamic criteria of Table 1 without significantly altering the dimple pattern. Different materials and ball constructions can also be selected to achieve a desired performance.

[0159] While it is apparent that the illustrative embodiments of the invention herein disclosed fulfill the objectives stated above, it will be appreciated that numerous modifications and other embodiments such as tetrahedrons having four triangles may be devised by those skilled in the art. Therefore, it will be understood that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present invention.