Golf ball

[0001] The present application is a continuation-in-part of U.S. patent application Ser. No. 15/220,703, filed Jul. 27, 2016, which is a continuation-in-part of U.S. patent application Ser. No. 15/162,717, filed May 24, 2016, which is continuation of U.S. patent application Ser. No. 14/159,495, filed Jan. 21, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 12/895,105, filed Sep. 30, 2010, now U.S. Pat. No. 8,632,425, the entire disclosures of which are hereby incorporated herein by reference.

[0002] The present invention relates to golf balls, and more particularly, to golf balls having modified dimples that improve symmetric performance.

[0003] Golf balls generally include a spherical outer surface with a plurality of dimples formed thereon. The dimples on a golf ball improve the aerodynamic characteristics of a golf ball and, therefore, golf ball manufacturers have researched dimple patterns, shape, volume, and cross-section in order to improve the aerodynamic performance of a golf ball. Determining specific dimple arrangements and dimple shapes that result in an aerodynamic advantage requires an understanding of how a golf ball travels through air.

[0004] When a golf ball travels through the air, the air surrounding the ball has different velocities and, thus, different pressures. The air develops a thin boundary layer adjacent to the ball's outer surface. The air exerts maximum pressure at a stagnation point on the front of the ball. 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 a top and a bottom separation point, leaving a large turbulent flow area called the wake that has low pressure. The difference in the high pressure in front of the ball and the low pressure behind the ball slows the ball down. This is the primary source of drag, which is the air resistance that acts on the golf ball in the direction opposite the ball's flight direction.

[0005] The dimples on a golf ball cause the thin boundary layer to flow in a turbulent manner. Rather than flowing in smooth, continuous layers (i.e., a laminar boundary layer), this turbulent boundary layer has a microscopic pattern of fluctuations and randomized flow. It is the circumference of each dimple, where the dimple wall drops away from the outer surface of the ball, which actually creates the turbulence in the boundary layer. The turbulence energizes the boundary layer and helps move the separation points further backward, so that the layer stays attached further along the ball's outer surface. As a result, there is a reduction in the area of the wake, increasing the average pressure behind the ball, and a substantial reduction in drag.

[0006] The shape of each dimple is also important in optimizing lift, which is an upward force on the ball that is created by a difference in pressure between the top of the ball and the bottom of the ball. This difference in pressure is created by a warp in the air flow that results from the ball's backspin. Due to the backspin, the top of the ball moves in the direction of the airflow, which shifts the top separation point to a location further backward. Conversely, the bottom of the ball moves against the air flow, which moves the bottom separation point forward. This asymmetrical separation creates an arch in the flow pattern that requires the air that flows over the top of the ball to move faster than the air that flows along the bottom of the ball. As a result, the air above the ball is at a lower pressure than the air underneath the ball. This pressure difference results in the overall force, called lift, which is exerted upwardly on the ball.

[0007] By using dimples to decrease drag and increase lift, almost every golf ball manufacturer has increased their golf ball flight distances. However, a golf ball must meet certain standards in order to be included on the official Conforming Golf Balls List (the “List”) produced by the United States Golf Association and The Royal and Ancient Golf Club of St. Andrews, Scotland, the two ruling bodies for the game of golf Inclusion on the List is important for the commercial success of a golf ball, because it is a requirement for use in competitive golf, and because, even for recreational golf, most serious players won't use a ball unless it appears on the List.

[0008] One of the standards, commonly referred to as the “Symmetry Rule,” specifies that a ball must fly essentially the same distance and for essentially the same amount of time regardless of how it is oriented when struck by the golf club. It is important for a ball to have this property not only for inclusion on the List, but also to ensure consistent performance in use. If a ball flies farther when oriented in a certain way, it would cause the golfer to hit the ball farther than intended if the ball happened to be oriented that way before being struck. Commercial golf balls may fly differently in particular orientations, mostly due to asymmetry in the dimple pattern resulting from the inclusion of a straight dimple-free path around the equator of the ball. This path, or “parting line” or “great circle” was necessary to provide a place for the two halves of the mold to separate during the molding process. The effect was worsened by abrasive buffing that was performed on the parting line to remove flash and other molding artifacts. It was discovered that the effect could be minimized or eliminated by altering a group of dimples centered at the pole of each hemisphere, usually by making them shallower.

[0009] Seamless balls have been developed which use a corrugated or staggered parting line that weaves around the dimples to disguise its presence and minimize the disruption to the dimple pattern. Although it was believed that this type of parting line would improve symmetry of flight, it was found that seamless balls do not always display satisfactory symmetrical flight performance.

[0010] Using modified dimples in polar regions of seamless golf balls has been proposed as a means of improving symmetry, as disclosed, for example, in U.S. Patent Application Publication No. 2010/0240473, the entire disclosure of which is hereby incorporated herein by reference.

[0011] In one embodiment, the present invention is directed to a golf ball comprising dimples on the outermost surface thereof. The dimples have a catenary cross-sectional shape and consist of a majority of unmodified dimples and a plurality of modified dimples. The modified dimples are arranged in two or more groups, each group forming an axially symmetric pattern about a different geometric center. Each modified dimple has a shape factor that is from 10% to 60% different than that of the unmodified dimples and/or a chord depth that is from 0.0002 inches to 0.0010 inches different than that of the unmodified dimples.

[0012] In another embodiment, the present invention is directed to a golf ball comprising a plurality of dimples on the outermost surface thereof. The golf ball consists of two hemispheres. Each hemisphere consists of two first regions and two second regions. The two first regions have an identical first dimple pattern. The two second regions have an identical second dimple pattern. Each of the first dimple pattern and the second dimple pattern comprises a plurality of unmodified dimples having a circular plan shape and at least one modified dimple having a non-circular plan shape.

[0013] In another embodiment, the present invention is directed to a golf ball having dimples on the outermost surface thereof, wherein the dimples consist of a majority of unmodified dimples having the same edge angle, and a plurality of modified dimples having an edge angle that is from 1° to 4° different than the edge angle of the unmodified dimples. The modified dimples are arranged in a plurality of modified dimple groups, each group forming an axially symmetric pattern about a different geometric center located on a non-polar axis of the ball. The axially symmetric patterns formed by the modified dimple groups include at least two different patterns. The golf ball consists of four quarter-spheres, each quarter-sphere comprising at least two modified dimple groups.

[0014] In another embodiment, the present invention is directed to a golf ball having dimples on the outermost surface thereof, wherein the dimples consist of a majority of unmodified dimples having the same edge angle, and a plurality of modified dimples having an edge angle that is from 1° to 4° different than the edge angle of the unmodified dimples. The modified dimples are arranged in two or more groups, each group forming an axially symmetric pattern about a different geometric center located on a non-polar axis of the ball. The difference in diameter between any two modified dimples within a single modified dimple group is 0.020 inches or less.

[0015] In another embodiment, the present invention is directed to a golf ball having dimples on the outermost surface thereof, wherein the dimples consist of a majority of unmodified dimples having the same edge angle, and a plurality of modified dimples having an edge angle that is from 1° to 4° different than the edge angle of the unmodified dimples. The modified dimples are arranged in a plurality of modified dimple groups, each group consisting of modified dimples forming an axially symmetric pattern about a different geometric center located on a non-polar axis of the ball. The golf ball consists of two hemispheres having identical dimple patterns, each hemisphere comprising at least three modified dimple groups. Each of the plurality of modified dimple groups consists of modified dimples having at least two different diameters.

[0016] In another embodiment, the present invention is directed to a golf ball having dimples on the outermost surface thereof, wherein the dimples consist of a majority of unmodified dimples having the same edge angle, and a plurality of modified dimples having an edge angle that is from 1° to 4° different than the edge angle of the unmodified dimples. The modified dimples are arranged in a plurality of modified dimple groups, each group consisting of modified dimples forming an axially symmetric pattern about a different geometric center located on a non-polar axis of the ball. The golf ball consists of two hemispheres having identical dimple patterns, each hemisphere consisting three modified dimple groups. The axially symmetric pattern formed by each of the modified dimple groups includes a modified dimple having a center that is coincident with the geometric center of the pattern.

[0035] While the present invention is not meant to be limited by any particular pattern of the overall dimple arrangement, golf balls of the present invention preferably have an overall dimple pattern formed by generating one or more domains from a polyhedron, and tessellating the domain(s) over the ball, as disclosed, for example, in U.S. Patent Application Publication No. 2010/0113187, the entire disclosure of which is hereby incorporated herein by reference. By arranging dimples in this manner, the symmetry of the underlying polyhedron is preserved and great circles due to parting lines are eliminated. The resulting overall dimple pattern has multiple axes of symmetry, typically including a polar symmetry axis and multiple non-polar symmetry axes. For purposes of the present disclosure, the symmetry axes are lines about which the overall dimple pattern can be rotated through some angle smaller than 360° which brings the pattern to a new orientation which appears identical to its starting position. The symmetry axes of an overall dimple pattern on a golf ball necessarily intersect at a common point at the center of the ball.

[0036] Golf balls of the present invention include, on each hemisphere of the ball, at least one modified dimple group having a geometric center, also referred to herein as a Correction Area Centroid (“CAC”), located on one of the multiple axes of symmetry in the overall dimple pattern, preferably a non-polar axis of symmetry. In one embodiment, golf balls of the present invention include at least one modified dimple group on each quarter-sphere of the ball. In another embodiment, golf balls of the present invention include at least two modified dimple groups on each quarter-sphere of the ball. In another embodiment, each hemisphere of the ball comprises at least three modified dimple groups, each of the modified dimple groups having a geometric center located on one of the multiple axes of symmetry in the overall dimple pattern, preferably non-polar axes of symmetry. In another embodiment, each hemisphere of the ball consists of three modified dimple groups, each of the modified dimple groups having a geometric center located on one of the multiple axes of symmetry in the overall dimple pattern.

[0037] The CAC of each group may fall within an unmodified dimple, a modified dimple, or on the land area of the golf ball surface.

[0038] Preferably, the modified dimple groups are located such that the CAC of each group is located at a latitude angle (“φ_CAC”) of greater than 0°, or greater than 5°, or greater than 15°, or greater than 30°, or 45° or greater, or greater than 45°, or 50° or greater, or at a φ_CAC within a range having a lower limit of 5° or 15° or 30° or 35° or 40° or 45° and an upper limit of 55° or 60° or 65° or 75° or 80° or 90°, where 0° represents the hemispherical pole and 90° represents the equator.

[0039] Modified dimple groups of the present invention include groups of one or more modified dimples. For purposes of the present invention, the term “modified” means altered from the typical configuration based on the overall pattern of dimples on the ball, and the term “dimple” includes any texturizing on the surface of a golf ball, e.g., depressions and projections, which may have a variety of planform shapes, including, but not limited to, circular, polygonal, oval, or irregular shapes, and a variety of cross-sectional shapes, including, but not limited to, circular, catenary, elliptical, or conical shapes.

[0040] The approximate total number of dimples to be modified and the location of the modified dimple groups on the outermost surface of the ball are determined based on the flight performance of the ball prior to modifying dimples and the desired flight performance of the final product. Preferably, the same modifications are performed on both hemispheres of the ball, i.e., the ball consists of identical hemispheres. In a particular embodiment, the same modifications are performed on all four quarter-spheres of the ball. In another particular embodiment, each hemisphere can be divided into three identical regions, with the same modifications performed on each region.

[0041] The pattern of each modified dimple group can vary substantially, and the present invention is not meant to be limited by any particular pattern. Preferably, each modified dimple group has a pattern that is axially symmetric, i.e., symmetric about the axis of symmetry containing the group's CAC. In embodiments of the present invention wherein each hemisphere includes two or more modified dimple groups, the pattern formed by one group can be the same as or different than the pattern formed by another group within the hemisphere, and the dimple count among modified dimple groups having different patterns may be the same or different. Similarly, in embodiments of the present invention wherein each quarter-sphere includes two or more modified dimple groups, the pattern formed by one group can be the same as or different than the pattern formed by another group within the quarter-sphere, and the dimple count among modified dimple groups having different patterns may be the same or different. Thus, in one embodiment, each quarter-sphere of the ball comprises at least two modified dimple groups, including at least two different patterns within each quarter-sphere. In a particular aspect of this embodiment, the modified dimple groups have one or more of the following properties:

[0042] (a) at least one pattern is present in all of the quarter-spheres;

[0043] (b) at least two patterns are present in all of the quarter-spheres; and

[0044] (c) at least two patterns are present in all of the quarter-spheres, including at least two patterns having different dimple counts.

[0045] In a particular aspect of embodiments of the present invention wherein the dimple count among modified dimple groups is different, the difference in dimple count between any two modified dimple groups is four dimples or less, or three dimples or less, or two dimples or less, or the difference is one dimple.

[0046] Each modified dimple group can typically be circumscribed by a circle having a diameter of no greater than 0.875 inches, or no greater than 0.800 inches, or no greater than 0.600 inches. For purposes of the present invention, the “circle circumscribing a modified dimple group” refers to the circle having the smallest diameter that is drawn around all of the modified dimples in the group without cutting any of the modified dimples and has a point of tangency with at least one of the modified dimples. In embodiments of the present invention where a modified dimple group consists of a single dimple, the diameter of the circle circumscribing the modified dimple group is equal to the diameter of the modified dimple. In a particular embodiment, among modified dimple groups having different patterns, the difference between the diameter of the circle circumscribing one modified dimple group and the diameter of the circle circumscribing another modified dimple group having a different pattern, excluding modified dimple groups consisting of one dimple, is 0.200 inches or less. In a particular aspect of this embodiment, the circles circumscribing the modified dimples groups have substantially the same diameter such that the ratio of the diameters is from 0.90 to 1.10. In another particular embodiment, among modified dimple groups having different patterns, the difference between the diameter of the circle circumscribing one modified dimple group and the diameter of the circle circumscribing all other modified dimple groups having a different pattern, excluding modified dimple groups consisting of one dimple, is 0.200 inches or less. In a particular aspect of this embodiment, all of the circles circumscribing the modified dimples groups on the ball, excluding modified dimple groups consisting of one dimple, have substantially the same diameter such that the ratio of the diameters is from 0.90 to 1.10.

[0047] In another particular embodiment, among modified dimple groups having different patterns, the ratio of the surface area of the fret of one modified dimple group to the surface area of the fret of another modified dimple group having a different pattern, excluding modified dimple groups consisting of one dimple, is 0.80 or 0.90 or 1.10 or 1.25 or is within a range having a lower limit and an upper limit selected from these values. In another particular embodiment, among modified dimple groups having different patterns, the ratio of the surface area of the fret of one modified dimple group to the surface area of the fret of all other modified dimple groups having a different pattern, excluding modified dimple groups consisting of one dimple, is 0.80 or 0.90 or 1.10 or 1.25 or is within a range having a lower limit and an upper limit selected from these values. For purposes of the present invention, the “surface area of the fret of a modified dimple group” refers to the surface area of the golf ball not covered by dimples within the circle circumscribing the modified dimple group.

[0048] In another particular embodiment, the ratio of the average surface volume of the dimples in one modified dimple group to the average surface volume of the dimples in another modified dimple group is 0.60 or 0.80 or 1.25 or 1.67 or is within a range having a lower limit and an upper limit selected from these values. In another particular embodiment, the ratio of the average surface volume of the dimples in one modified dimple group to the average surface volume of the dimples in all other modified dimple groups is 0.60 or 0.80 or 1.25 or 1.67 or is within a range having a lower limit and an upper limit selected from these values.

[0049] While the degree of dimple modification depends on the ball's overall dimple pattern and the total number of dimples, the total number of modified dimples is preferably ¼ of the total number of dimples or less.

[0050] The modified dimples can be altered in any suitable manner, including, but not limited to, modifying diameter, depth, volume, edge angle, edge radius, cross-sectional shape, perimeter shape, and any combination of two or more thereof.

[0051] In a particular embodiment, the majority of the unmodified dimples have a catenary cross-sectional shape and each of the modified dimples has a catenary cross-sectional shape, wherein each of the modified dimples has a shape factor and/or a chord depth that is different than the shape factor and/or chord depth of the catenary-shaped unmodified dimples. In a particular aspect of this embodiment, each modified dimple has a shape factor that is at least 10%, or at least 20%, different than that of the unmodified dimples, or a shape factor that is from 10% or 20% or 25% to 45% or 50% or 60% different than that of the unmodified dimples. Each modified dimple can have the same shape factor or a different shape factor than the other modified dimples. The shape factor is an independent variable in the mathematical function that defines a catenary dimple cross-sectional shape, as further disclosed in, for example, U.S. Pat. No. 6,796,912 to Dalton et al., U.S. Pat. No. 7,163,472 to Dalton et al., U.S. Pat. No. 7,491,137 to Bissonnette et al., and U.S. Pat. No. 7,887,439 to Aoyama et al., the entire disclosures of which are hereby incorporated herein by reference. In another particular aspect of this embodiment, each modified dimple has a chord depth that is at least 0.0001 inches, or at least 0.0002 inches, different than that of the unmodified dimples, or a chord depth that is from 0.0001 inches or 0.0002 inches to 0.0005 inches or 0.0010 inches different than that of the unmodified dimples. Each modified dimple can have the same chord depth or a different chord depth than the other modified dimples.

[0052] In another particular embodiment, a majority of the dimples (i.e., the unmodified dimples) have the same edge angle and a plurality of the dimples (i.e., the modified dimples) have an edge angle that is from 1° to 4°, or from 1° to 3°, different than the edge angle of the majority of the dimples. For purposes of the present invention, dimples have the “same edge angle” if their respective edge angles differ by no more than 0.2°. In a particular aspect of this embodiment, the dimples have one or more of the following properties:

• • [0053] (a) the difference in diameter between any two modified dimples within a single modified dimple group is 0.020 inches or less;
  • [0054] (b) the difference in diameter between any two modified dimples on the golf ball is 0.050 inches or less;
  • [0055] (c) at least one of the modified dimple groups consists of modified dimples having substantially the same diameter, i.e., their respective diameters differ by less than 0.005 inches;
  • [0056] (d) all of the dimples in a first modified dimple group have substantially the same diameter, all of the dimples in a second modified dimple group in the same quarter-sphere as the first modified dimple group have substantially the same diameter, but the diameter of the dimples in the first modified dimple group is different from the diameter of the dimples in the second modified dimple group;
  • [0057] (e) all of the modified dimples on the golf ball have substantially the same diameter;
  • [0058] (f) each of the unmodified dimples has a circular plan shape; and
  • [0059] (g) each of the modified dimples has a circular plan shape.
    In another particular aspect of this embodiment, the dimples have one or more of the following properties:
  • [0060] (a) each modified dimple group consists of modified dimples having at least two different diameters;
  • [0061] (b) the axially symmetric pattern formed by each of the modified dimple groups is identical;
  • [0062] (c) each modified dimple group includes at least three modified dimples, or at least four modified dimples, or at least five modified dimples, or at least six modified dimples, or at least seven modified dimples;
  • [0063] (d) the difference in diameter between any two modified dimples on the golf ball is 0.100 inches or less;
  • [0064] (e) the average dimple diameter of all modified dimples on the golf ball is 0.165 inches or greater;
  • [0065] (f) the average dimple diameter of all modified dimples on the golf ball is 0.160 inches or less;
  • [0066] (g) the geometric center of each modified dimple group is located at a latitude angle of greater than 45°, where 0° represents the hemispherical pole and 90° represents the equator;
  • [0067] (h) each of the majority of unmodified dimples has a circular plan shape;
  • [0068] (i) each of the plurality of modified dimples has a circular plan shape;
  • [0069] (j) each modified dimple group can be circumscribed by a circle having a diameter of 0.800 inches or less, or 0.600 inches or less;
  • [0070] (k) the geometric center of each modified dimple group is coincident with the center of a modified dimple;
  • [0071] (l) the geometric center of each modified dimple group is coincident with the center of an unmodified dimple; and
  • [0072] (m) the dimple pattern on each hemisphere on the ball is identical, each hemisphere can be divided into three regions having identical dimple patterns, and each region includes at least one modified dimple group.

[0073] In another particular embodiment, one or more dimple groups are modified in such a way as to make them less aggressive aerodynamically, such as by reducing dimple diameter, depth, volume, and/or edge angle. In another particular embodiment, one or more dimple groups are modified in such a way as to make them more aerodynamically aggressive, such as by increasing edge angle, volume, and/or by adding sub-dimples, i.e., dimples within a dimple. Sub-dimples are further disclosed, for example, in U.S. Pat. No. 6,569,038, the entire disclosure of which is hereby incorporated herein by reference.

[0074] The modified dimples can retain essentially the same appearance as or can be visually different from the unmodified dimples. Alterations that typically, but do not necessarily, result in modified dimples that retain essentially the same appearance as the unmodified dimples include, but are not limited to, changes to the dimple edge angle, depth, and volume, moderate changes to the cross-sectional profile, and moderate changes to the shape factor of catenary dimples. Alterations that typically, but do not necessarily, result in modified dimples that are visually different from the unmodified dimples include, but are not limited to, changes to the dimple diameter, plan shape and size, substantial changes to the cross-sectional profile, and substantial changes to the shape factor of catenary dimples. Dimples of the present invention having a modified depth preferably have a depth that is not greater than 90%, more preferably not greater than 80%, of the thickness of the outermost layer of the golf ball. Some dimples may be removed from the pattern by reducing their volume by about 100% to about zero. In this embodiment, by virtue of the types or magnitudes of the changes, the modified dimples are visually different from the unmodified dimples.

[0075] In embodiments of the present invention wherein each hemisphere includes two or more modified dimple groups, the dimples of one group may be altered in the same manner as or a different manner than another. Similarly, one dimple may be altered in the same or a different way than another dimple in the same dimple group.

[0076] Referring now to the figures, FIGS. 1-5 illustrate the polar view of a seamless golf ball having 352 dimples arranged in a tetrahedron-based pattern, with modified dimples designated by the letter A. Each hemisphere of the ball can be divided by imaginary grid lines into two pairs of identical regions, each region having one modified dimple group arranged about a CAC 10 located on a non-polar axis of symmetry at a latitude angle of 54.7°. In FIG. 1, each region of one pair has a modified dimple group consisting of a set of three pairs of modified dimples, and each region of the other pair has a modified dimple group consisting of six modified dimples forming a hexagon. In FIG. 2, each region of one pair has a modified dimple group consisting of seven modified dimples forming a hexagon, and each region of the other pair has a modified dimple group consisting of three modified dimples forming a triangle. In FIG. 3, each region of one pair has a modified dimple group consisting of six modified dimples forming a triangle, and each region of the other pair has a modified dimple group consisting of three modified dimples forming a triangle and a modified dimple at or near the center of the triangle. FIGS. 4 and 5 illustrate two additional non-limiting examples of suitable patterns for modified dimples of the present invention.

[0077] FIG. 6A illustrates the polar view of a seamless golf ball having 360 dimples arranged in a cuboctahedron-based pattern, with modified dimples designated by the letter A. Each hemisphere of the ball can be divided by imaginary grid lines into three identical regions, each region having one modified dimple group arranged about a CAC 10 located on a non-polar axis of symmetry at a latitude angle of 54.7°. The modified dimple group of each region consists of four modified dimples forming a square and a set of four pairs of modified dimples forming a square. FIG. 6B is an equatorial view of the golf ball illustrated in FIG. 6A.

[0078] FIGS. 7A-7C illustrate a seamless golf ball having 352 dimples arranged in a tetrahedron-based pattern, with modified dimples designated by shading. FIG. 7A is a polar view of the golf ball. The modified dimples within the area designated 101 form a first modified dimple group having an axially symmetric pattern about a CAC 104. The modified dimples within the area designated 201 form a second modified dimple group having an axially symmetric pattern about a CAC 204. The ball can be divided by imaginary grid lines into four quarter-spheres, each quarter-sphere including a modified dimple group having a pattern identical to that of the first modified dimple group and a modified dimple group having a pattern identical to that of the second modified dimple group.

[0079] FIG. 7B is a planar view of the golf ball normal to the axis containing the CAC 104. FIG. 7B shows an imaginary circle 102 circumscribing the first modified dimple group, and the fret 103 of the first modified dimple group, i.e., the surface of the golf ball within circle 102 not covered by dimples.

[0080] FIG. 7C is a planar view of the golf ball normal to the axis containing the CAC 204. FIG. 7C shows an imaginary circle 202 circumscribing the second modified dimple group, and the fret 203 of the second modified dimple group, i.e., the surface of the golf ball within circle 202 not covered by dimples.

[0081] In a particular aspect of the embodiment shown in FIGS. 7A-7C, the modified dimples of the first modified dimple group have the same diameter, the modified dimples of the second modified dimple group have the same diameter, but the difference between the diameter of the modified dimples of the first modified dimple group and the diameter of the modified dimples of the second modified dimple group is 0.015 inches. The ratio of the diameter of circumscribing circle 102 to the diameter of circumscribing circle 202 is 0.997. The ratio of the surface area of the fret 103 to the surface area of the fret 203 is 0.920.

[0082] FIGS. 8A-8C illustrate a seamless golf ball having 328 dimples arranged in a tetrahedron-based pattern, with modified dimples designated by shading. FIG. 8A is a polar view of the golf ball. The modified dimples within the area designated 301 form a first modified dimple group having an axially symmetric pattern about a CAC 304. The modified dimples within the area designated 401 form a second modified dimple group having an axially symmetric pattern about a CAC 404. The ball can be divided by imaginary grid lines into four quarter-spheres, each quarter-sphere including a modified dimple group having a pattern identical to that of the first modified dimple group and a modified dimple group having a pattern identical to that of the second modified dimple group.

[0083] FIG. 8B is a planar view of the golf ball normal to the axis containing the CAC 304. FIG. 8B shows an imaginary circle 302 circumscribing the first modified dimple group, and the fret 303 of the first modified dimple group, i.e., the surface of the golf ball within circle 302 not covered by dimples.

[0084] FIG. 8C is a planar view of the golf ball normal to the axis containing the CAC 404. FIG. 8C shows an imaginary circle 402 circumscribing the second modified dimple group, and the fret 403 of the second modified dimple group, i.e., the surface of the golf ball within circle 402 not covered by dimples.

[0085] In a particular aspect of the embodiment shown in FIGS. 8A-8C, the modified dimples of the first modified dimple group and the modified dimples of the second modified dimple group have the same diameter. The ratio of the diameter of circumscribing circle 302 to the diameter of circumscribing circle 402 is 0.890. The ratio of the surface area of the fret 303 to the surface area of the fret 403 is 0.834.

[0086] FIGS. 9A-9B illustrate a seamless golf ball having 342 dimples, with modified dimples designated by shading. In a particular aspect of the embodiment illustrated in FIGS. 9A-9B, the unmodified (i.e., unshaded) dimples have the same edge angle and the modified (i.e., shaded) dimples have an edge angle that is from 1° to 4° different than the edge angle of the unmodified dimples. The numerical labels within the shaded dimples designate same diameter dimples. For example, all dimples labelled 1 have the same diameter, and all dimples labelled 2 have the same diameter. In a particular aspect of the embodiment illustrated in FIGS. 9A-9B, the dimples labelled 1 have a diameter of about 0.150 inches, and the dimples labelled 2 have a diameter of about 0.185 inches.

[0087] In FIGS. 9A-9B, the modified dimples within the area designated 501 form a modified dimple group having an axially symmetric pattern about a CAC 504. The ball can be divided into two hemispheres having identical dimple patterns; each hemisphere can be divided into three regions having identical dimple patterns; and each region has a modified dimple group identical to the group of modified dimples within the area designated 501. Each modified dimple group includes a modified dimple having a center that is coincident with the CAC 504.

[0088] FIG. 9A is a polar view of the golf ball. FIG. 9B is an alternate view of the golf ball illustrated in FIG. 9A. More specifically, FIG. 9B is a planar view of the golf ball normal to the axis containing the CAC 504. FIG. 9B shows an imaginary circle 502 circumscribing the modified dimple group and having a diameter of about 0.518 inches.

[0089] FIGS. 10A-10B illustrate a seamless golf ball having 350 dimples, with modified dimples designated by shading. In a particular aspect of the embodiment illustrated in FIGS. 10A-10B, the unmodified (i.e., unshaded) dimples have the same edge angle and the modified (i.e., shaded) dimples have an edge angle that is from 1° to 4° different than the edge angle of the unmodified dimples. The numerical labels within the shaded dimples designate same diameter dimples. For example, all dimples labelled 1 have the same diameter, and all dimples labelled 2 have the same diameter. In a particular aspect of the embodiment illustrated in FIGS. 10A-10B, the dimples labelled 1 have a diameter of about 0.185 inches, and the dimples labelled 2 have a diameter of about 0.205 inches.

[0090] In FIGS. 10A-10B, the modified dimples within the area designated 601 form a modified dimple group having an axially symmetric pattern about a CAC 604. The ball can be divided into two hemispheres having identical dimple patterns; each hemisphere can be divided into three regions having identical dimple patterns; and each region has a modified dimple group identical to the group of modified dimples within the area designated 601. Each modified dimple group includes an unmodified dimple having a center that is coincident with the CAC 604.

[0091] FIG. 10A is a polar view of the golf ball. FIG. 10B is an alternate view of the golf ball illustrated in FIG. 10A. More specifically, FIG. 10B is a planar view of the golf ball normal to the axis containing the CAC 604. FIG. 10B shows an imaginary circle 602 circumscribing the modified dimple group and having a diameter of about 0.715 inches.

[0092] Modifying dimples according to the present invention preferably produces a golf ball with improved flight symmetry compared to a corresponding golf ball without the modified dimples.

[0093] In a particular embodiment, the present invention is directed to a seamless golf ball, wherein the dimples have been modified using the dimple modification method disclosed herein. Seamless golf balls and methods of producing such are further disclosed, for example, in U.S. Pat. Nos. 6,849,007 and 7,422,529, the entire disclosures of which are hereby incorporated herein by reference.

[0094] While golf balls of the present invention are not limited to a particular dimple count, in a particular embodiment, the golf ball has a dimple count of 302 or 312 or 328 or 342 or 348 or 352 or 364 or 376 or 388.

[0095] When numerical lower limits and numerical upper limits are set forth herein, it is contemplated that any combination of these values may be used.

[0096] All patents, publications, test procedures, and other references cited herein, including priority documents, are fully incorporated by reference to the extent such disclosure is not inconsistent with this invention and for all jurisdictions in which such incorporation is permitted.

[0097] While the illustrative embodiments of the invention have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those of ordinary skill in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein, but rather that the claims be construed as encompassing all of the features of patentable novelty which reside in the present invention, including all features which would be treated as equivalents thereof by those of ordinary skill in the art to which the invention pertains.