GOLF BALLS HAVING VOLUMETRIC EQUIVALENCE ON OPPOSING HEMISPHERES AND SYMMETRIC FLIGHT PERFORMANCE AND METHODS OF MAKING SAME

FIELD OF THE INVENTION

The present invention relates to golf balls with symmetric flight performance due to volumetric equivalence in the dimples on opposing hemispheres on the ball. In particular, golf balls according to the present invention achieve flight symmetry and overall satisfactory flight performance due to a dimple volume ratio that is equivalent between opposing hemispheres despite the use of different dimple geometry on the opposing hemispheres.

BACKGROUND OF THE INVENTION

Golf balls were originally made with smooth outer surfaces. However, in the late nineteenth century, players observed that gutta-percha golf balls traveled further as they aged and their surfaces were roughened. As a result, players began roughening the surfaces of new golf balls to increase flight distance; and manufacturers began molding non-smooth outer surfaces on golf balls.

By the mid 1900's almost every manufactured golf ball had 336 dimples arranged in an octahedral pattern. Generally, these balls had about 60 percent of their outer surface covered by dimples. Over time, improvements in ball performance were developed by utilizing different dimple patterns. In 1983, for instance, Titleist introduced the TITLEIST 384, which, not surprisingly, had 384 dimples that were arranged in an icosahedral pattern. With about 76 percent of its outer surface covered with dimples, the TITLEIST 384 exhibited improved aerodynamic performance. Today, dimpled golf balls travel nearly two times farther than similar balls without dimples.

The dimples on a golf ball play an important role in reducing drag and increasing lift. More specifically, the dimples on a golf ball create a turbulent boundary layer around the ball, i.e., a thin layer of air adjacent to the ball that flows in a turbulent manner. The turbulent nature of the boundary layer of air around the ball energizes the boundary layer, and helps the air flow stay attached farther around the ball. The prolonged attachment of the air flow around the surface of the ball reduces the area of the wake behind the ball, effectively yielding an increase in pressure behind the ball, thereby substantially reducing drag and increasing lift on the ball during flight.

As such, manufacturers continually experiment with different dimple shapes and patterns in an effort to improve the aerodynamic forces exerted on golf balls, with the goal of increasing travel distances of the balls. However, the United States Golf Association (USGA) requires that a ball must not be designed, manufactured, or intentionally modified to have properties that differ from those of a spherically symmetric ball. In other words, manufacturers desire to better aerodynamic performance of a golf ball are also required to conform with the overall distance and symmetry requirements of the USGA. In particular, a golf ball is considered to achieve flight symmetry when it is found, under calibrated testing conditions, to fly at substantially the same height and distance, and remain in flight for substantially the same period of time, regardless of how it is placed on the tee. The testing conditions for assessing flight symmetry of a golf ball are provided in USGA-TPX3006, Revision 2.0.0, “Actual Launch Conditions Overall Distance and Symmetry Test Procedure (Phase II)”. Accordingly, conventional golf balls typically remain hemispherically identical with regard to the dimples thereon in order to maintain the required flight symmetry and performance.

As such, there has been little to no focus on the use of differing dimple geometry on the opposing hemispheres of a golf ball—likely due to the previous inability to achieve volumetric equivalence between the opposing hemispheres and, thus, flight symmetry. Accordingly, there remains a need in the art for a golf ball that has opposing hemispheres that differ from one another in that the dimple shapes and/or dimple profiles are not identical on both hemispheres, while still achieving flight symmetry and overall satisfactory flight performance.

SUMMARY OF THE INVENTION

The present invention relates to a golf ball including: a first hemisphere comprising a plurality of dimples; and a second hemisphere comprising a plurality of dimples, wherein a first dimple in the first hemisphere comprises a first plan shape, a first profile, and a first geometric center, the first geometric center being located at a position defined by a first polar angle θ_Nmeasured from a pole of the first hemisphere; a second dimple in the second hemisphere comprises a second plan shape, a second profile shape, and a second geometric center, the second geometric center being located at a position defined by a second polar angle θ_Smeasured from a pole of the second hemisphere, wherein the first polar angle θ_Ndiffers from the second polar angle θ_Sby no more than 3°, the first dimple differs from the second dimple by at least one of (i) the first plan shape differing from the second plan shape and (ii) the first profile differing from the second profile; and the first dimple and the second dimple have substantially identical surface volumes.

In one embodiment, the first plan shape differs from the second plan shape. In another embodiment, the first profile shape differs from the second profile shape. In still another embodiment, the first plan shape includes a first shape of a first size, the second plan shape includes a second shape of a second size, and the first size is different from the second size.

In this aspect of the invention, the first profile may differ from the second profile. In one embodiment, the geometric center of the first dimple is separated from the geometric center of the second dimple by an offset angle γ. In another embodiment, a third dimple in the first hemisphere includes a third plan shape, a third profile, and a third geometric center, the third geometric center being located at a position defined by a third polar angle θ_N′ measured from the pole of the first hemisphere. In yet another embodiment, a fourth dimple in the second hemisphere includes a fourth plan shape, a fourth profile, and a fourth geometric center, the fourth geometric center being located at a position defined by a fourth polar angle θ_S′ measured from the pole of the second hemisphere. The third polar angle θ_N′ may differ from the fourth polar angle θ_S′ by no more than 3°. In another embodiment, the third dimple differs from the fourth dimple by at least one of: (i) the third plan shape differing from the fourth plan shape; (ii) the third profile differing from the fourth profile shape; and the third dimple and the fourth dimple have substantially identical surface volumes.

The geometric center of the first dimple may be separated from the geometric center of the second dimple by an offset angle γ, the geometric center of the third dimple is separated from the geometric center of the fourth dimple by an offset angle γ, and the offset angle γ between the geometric centers of the first and second dimples differs from the offset angle γ between the geometric centers of the third and fourth dimples by no more than 3°.

In one embodiment, the first plan shape includes a first shape at a first size, the second plan shape includes a second shape at a second size, the third plan shape includes a third shape at a third size, the fourth plan shape includes a fourth shape at a fourth size, the first shape is the same as the third shape, and the second shape is the same as the fourth shape. In another embodiment, the first shape is different from the second shape.

The present invention also relates to a golf ball including first and second hemispheres each including a plurality of dimples, wherein each dimple in the first hemisphere has a respective geometric center located at a position defined by a respective polar angle θ_Nmeasured from a pole of the first hemisphere, wherein each dimple in the second hemisphere has a respective geometric center located at a position defined by a respective polar angle θ_Smeasured from a pole of the second hemisphere, wherein each dimple in the first hemisphere corresponds with a dimple in the second hemisphere, with the dimples in each pair of corresponding dimples satisfying a relationship whereby the polar angle θ_Nof the dimple in the first hemisphere is substantially equal to the polar angle θ_Sof the dimple in the second hemisphere, and wherein (i) in each pair of corresponding dimples, the geometric center of the dimple in the first hemisphere is separated from the geometric center of the dimple in the second hemisphere by an offset angle γ, with the offset angle γ being the same in all pairs of corresponding dimples, (ii) in each pair of corresponding dimples, the dimple in the first hemisphere differs from the dimple in the second hemisphere by at least one of (i) a difference in plan shape and (ii) a difference in profile, and (iii) the first hemisphere and the second hemisphere have substantially equivalent surface volumes.

In one embodiment, in each pair of corresponding dimples, the dimple in the first hemisphere differs from the dimple in the second hemisphere in that the two dimples have different plan shapes. In another embodiment, in each pair of corresponding dimples, the dimple in the first hemisphere differs from the dimple in the second hemisphere in that the two dimples have different profiles.

The present invention also relates to a golf ball including a first hemisphere including a first plurality of dimples and a second hemisphere including a second plurality of dimples, wherein each dimple in the first plurality of dimples has a corresponding dimple in the second plurality of dimples, wherein a dimple in the first hemisphere differs from a corresponding dimple in the second hemisphere by at least one of (i) a difference in plan shapes and (ii) a difference in profile shapes.

In one embodiment, the dimple in the first hemisphere differs from the corresponding dimple in the second hemisphere in that the two dimples have different plan shapes. In another embodiment, the dimple in the first hemisphere has a first shape at a first size; the corresponding dimple in the second hemisphere has a second shape at a second size, wherein the first size is different than the second size. In yet another embodiment, the dimple in the first hemisphere has a first shape at a first size, the corresponding dimple in the second hemisphere has a second shape at a second size, the shape of the dimple in the first hemisphere is the same shape as the shape of the dimple in the second hemisphere, and the first size differs from the second size. In this aspect of the invention, the dimple in the first hemisphere may differ from the corresponding dimple in the second hemisphere in that the two dimples have different profiles. In addition, the dimple in the first hemisphere may differ from the corresponding dimple in the second hemisphere in that the two dimples have different profiles and different plan shapes.

Both the foregoing general description and the following detailed description are exemplary and explanatory only and are intended to provide further explanation of the invention as claimed. The accompanying drawings are included to provide a further understanding of the invention; are incorporated in and constitute part of this specification; illustrate embodiments of the invention; and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the invention can be ascertained from the following detailed description that is provided in connection with the drawings described below:

FIG. 1 depicts an equatorial, profile view of a golf ball according to one embodiment of the invention, illustrating the polar angles (θ_Nand θ_S) of two corresponding dimples in two different hemispheres of a golf ball according to the present invention;

FIG. 2 depicts a polar, plan view of the golf ball in FIG. 1, showing the rotation offset angle γ between the two corresponding dimples, as measured around the equator of the ball;

FIG. 3 depicts an overlaying comparison of the plan shapes of the two corresponding dimples in FIG. 1, for calculating an absolute residual via a first intersection line;

FIG. 4 depicts an overlaying comparison of the plan shapes of the two corresponding dimples in FIG. 1, for calculating a mean absolute residual via a plurality of intersection lines;

FIG. 5 depicts an overlaying comparison of the profile shapes of the two corresponding dimples in FIG. 1, for calculating an absolute residual via a first intersection line;

FIG. 6 depicts an overlaying comparison of the profile shapes of the two corresponding dimples in FIG. 1, for calculating a mean absolute residual via a plurality of intersection lines;

FIG. 7 depicts a volumetric plotting based on the surface volumes of the two corresponding dimples in FIG. 1;

FIG. 8 depicts a volumetric plotting and linear regression analysis based on the surface volumes of a plurality of corresponding dimples from the golf ball in FIG. 1;

FIG. 9a depicts an example of a golf ball having hemispheres with dimples having different geometries based on dimples having different plan shapes with like profiles;

FIG. 9b depicts the plan shape of a first dimple in a first hemisphere of the golf ball in FIG. 9a;

FIG. 9c depicts the plan shape of a second dimple in a second hemisphere of the golf ball in FIG. 9a;

FIG. 9d depicts the profile of the first dimple in the first hemisphere of the golf ball in FIG. 9a;

FIG. 9e depicts the profile of the second dimple in the second hemisphere of the golf ball in FIG. 9a;

FIG. 10a depicts an example of a golf ball having hemispheres with dimples having different geometries based on dimples having like plan shapes with different profiles;

FIG. 10b depicts the plan shape of a first dimple in a first hemisphere of the golf ball in FIG. 10a;

FIG. 10c depicts the plan shape of a second dimple in a second hemisphere of the golf ball in FIG. 10a;

FIG. 10d depicts the profile of the first dimple in the first hemisphere of the golf ball in FIG. 10a;

FIG. 10e depicts the profile of the second dimple in the second hemisphere of the golf ball in FIG. 10a;

FIG. 11a depicts an example of a golf ball having hemispheres with dimples having different geometries based on dimples having different plan shapes and different profiles;

FIG. 11b depicts the plan shape of a first dimple in a first hemisphere of the golf ball in FIG. 11a;

FIG. 11c depicts the plan shape of a second dimple in a second hemisphere of the golf ball in FIG. 11a;

FIG. 11d depicts the profile of the first dimple in the first hemisphere of the golf ball in FIG. 11a;

FIG. 11e depicts the profile of the second dimple in the second hemisphere of the golf ball in FIG. 11a;

FIG. 12a depicts an example of a golf ball having hemispheres with dimples having different geometries based on dimples having like plan shapes and like profiles, with different plan shape orientations;

FIG. 12b depicts the plan shape of a first dimple in a first hemisphere of the golf ball in FIG. 12a;

FIG. 12c depicts the plan shape of a second dimple in a second hemisphere of the golf ball in FIG. 12a;

FIG. 12d depicts the profile of the first dimple in the first hemisphere of the golf ball in FIG. 12a; and

FIG. 12e depicts the profile of the second dimple in the second hemisphere of the golf ball in FIG. 12a.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides golf balls with opposing hemispheres that differ from one another, e.g., by having different dimple plan shapes or profiles, while also achieving flight symmetry and overall satisfactory flight performance. In this aspect, the present invention provides golf balls that permit a multitude of unique appearances, while also conforming to the USGA's requirements for overall distance and flight symmetry. The present invention is also directed to methods of developing the dimple geometries applied to the opposing hemispheres, as well as methods of making the finished golf balls with the inventive dimple patterns applied thereto.

In particular, finished golf balls according to the present invention have opposing hemispheres with dimple geometries that differ from one another in that the dimples on one hemisphere have different plan shapes (the shape of the dimple in a plan view), different profile shapes (the shape of the dimple cross-section, as seen in a profile view of a plane extending transverse to the center of the golf ball and through the geometric center of the dimple), or a combination thereof, as compared to dimples on an opposing hemisphere. Despite the difference the dimples on one hemisphere have dimple volumes that are substantially similar to the dimple volumes on an opposing hemisphere.

Though the dimple geometry on the opposing hemispheres are designed to differ in that the plan shape and/or profile shape of the dimples in one hemisphere are different from the plan shape and/or profile shape of the dimples in another hemisphere, the hemispheres nonetheless have the same dimple arrangement or pattern. In other words, the dimples in one hemisphere are positioned such that the locations of their geometric centers are substantially identical to the locations of the geometric centers of the dimples in the other hemisphere in terms of polar angles θ (measuring the rotational offset of an individual dimple from the polar axis of its respective hemisphere) and offset angles γ (measuring the rotational offset between two corresponding dimples, as rotated around the equator of the golf ball).

Dimple Arrangement

A non-limiting example of suitable dimple geometries for use on a golf ball according to the present invention is shown in FIGS. 1-2. In particular, in one embodiment, a first hemisphere may have a first dimple geometry and a second hemisphere may have a second dimple geometry, where the first and second dimple geometries differ from each other. In this aspect, the first and second dimple geometries may each have a plurality of corresponding dimples each offset from the polar axis of the respective hemispheres by a predetermined angle. The geometric centers of the corresponding dimples may be separated by a predetermined angle that is equal to the rotational offset between the two corresponding dimples as measured around the equator of the golf ball.

For example, as shown in FIG. 1, for each dimple 100 in a first hemisphere 10 of the golf ball 1 (e.g., a “northern” hemisphere 10) there is a corresponding dimple 200 in a second hemisphere 20 (e.g., an opposing “southern” hemisphere 20). In each pair of corresponding dimples 100/200, the dimple 100 in the first hemisphere 10 is offset from the polar axis 30_Nof the first hemisphere 10 by a polar angle θ_N, and the dimple 200 in the second hemisphere 20 is offset from the polar axis 30_Sof the second hemisphere 20 by a polar angle θ_S; with the two polar angles being equal to one another (i.e., θ_N=θ_S). Though the polar angles (θ_N, θ_S) of corresponding dimples are preferably equal to one another, the polar angles may differ by about 1° and up to about 3°.

As shown in FIG. 2, in each pair of corresponding dimples 100/200, the geometric centers 101/201 of the dimples are separated from one another by an offset angle γ, which represents a rotational offset between the two corresponding dimples 100/200 as measured around the equator 40 of the golf ball 1. In each pair of corresponding dimples 100/200, the offset angles (γ₁, γ₂, γ3, etc.) are preferably substantially equal (e.g., γ₁=γ₂=γ₃). However, the offset angles may differ by about 1° and up to about 3°.

As discussed below, at least one of the corresponding dimple pairs from the plurality of corresponding dimples on each hemisphere differ in plan shape, profile, or a combination thereof. In other words, as shown in FIG. 1, the plan shapes of a corresponding dimple pair (100/200) may be different whereas other corresponding dimple pairs need not differ (not shown in FIG. 1). In one embodiment, at least about 50 percent of the corresponding dimple pairs from the plurality of corresponding dimples on each hemisphere differ from each other in plan shape, profile, or a combination thereof. In another embodiment, at least 75 percent of the corresponding dimple pairs from the plurality of corresponding dimples on each hemisphere differ from each other in plan shape, profile, or a combination thereof. In still another embodiment, all of the corresponding dimple pairs from the plurality of corresponding dimples on each hemisphere differ from each other in plan shape, profile, or a combination thereof. For example, as shown in FIG. 1, each dimple in the first hemisphere 10 has a plan shape that differs from its mate in the second hemisphere 20.

Accordingly, it should be understood that any discussion relating to a corresponding dimple pair 100/200 is intended to be representative of a portion of or all of the remaining corresponding dimple pairs in the plurality of dimples, when more than at least one corresponding dimple pair differs.

Dimple Plan Shapes

As briefly discussed above, one way to achieve differing dimple geometries with the same dimple arrangement on opposing hemispheres in accordance with the present invention is to include corresponding dimples that differ in plan shape. Thus, in one aspect of the present invention, the dimples in two hemispheres are considered different from one another if, in a given pair of corresponding dimples, a dimple in one hemisphere has a different plan shape than the plan shape of the corresponding dimple in the other hemisphere. In another aspect of the present invention, the dimples in two hemispheres are considered different from one another if, in a given pair of corresponding dimples, a dimple in one hemisphere has a different plan shape orientation than the plan shape orientation of the corresponding dimple in the other hemisphere.

In one embodiment, at least about 25 percent of the corresponding dimples in the opposing hemispheres have different plan shapes. In another embodiment, at least about 50 percent of the corresponding dimples in the opposing hemispheres have different plan shapes. In yet another embodiment, at least about 75 percent of the corresponding dimples in the opposing hemispheres have different plan shapes. In still another embodiment, all of the corresponding dimples in the opposing hemispheres have different plan shapes.

The plan shapes (or plan shape orientations) of two dimples are considered different from one another if a comparison of the overlaid dimples yields a mean absolute residual r, over a number of n equally spaced points around the geometric centers of the overlaid dimples, that is significantly different from zero. In other words, the distribution of the residuals are compared using a t-distribution having an average of zero to test for equivalence and, as such, the range of t-values that is considered significantly different from zero is dependent on the number of intersection lines n used. For example, as shown in the non-limiting T-Table below, if the number of intersection lines is 30, the t-value must be greater than 1.699 for the absolute residual r to be considered significantly different from zero. Similarly, if the number of intersection lines is 200, the t-value must be greater than 1.653 for the absolute residual r to be considered significantly different from zero.

TABLE 1

T-Table

Intersection
Degrees of
Critical

Lines
Freedom
T-value

30
29
1.699

31
30
1.697

32
31
1.696

33
32
1.694

34
33
1.692

35
34
1.691

36
35
1.690

37
36
1.688

38
37
1.687

39
38
1.686

40
39
1.685

41
40
1.684

42
41
1.683

43
42
1.682

44
43
1.681

45
44
1.680

46
45
1.679

47
46
1.679

48
47
1.678

49
48
1.677

50
49
1.677

51
50
1.676

52
51
1.675

53
52
1.675

54
53
1.674

55
54
1.674

56
55
1.673

57
56
1.673

58
57
1.672

59
58
1.672

60
59
1.671

61
60
1.671

62
61
1.670

63
62
1.670

64
63
1.669

65
64
1.669

66
65
1.669

67
66
1.668

68
67
1.668

69
68
1.668

70
69
1.667

71
70
1.667

72
71
1.667

73
72
1.666

74
73
1.666

75
74
1.666

76
75
1.665

77
76
1.665

78
77
1.665

79
78
1.665

80
79
1.664

81
80
1.664

82
81
1.664

83
82
1.664

84
83
1.663

85
84
1.663

86
85
1.663

87
86
1.663

88
87
1.663

89
88
1.662

90
89
1.662

91
90
1.662

92
91
1.662

93
92
1.662

94
93
1.661

95
94
1.661

96
95
1.661

97
96
1.661

98
97
1.661

99
98
1.661

100
99
1.660

101
100
1.660

102
101
1.660

103
102
1.660

104
103
1.660

105
104
1.660

106
105
1.659

107
106
1.659

108
107
1.659

109
108
1.659

110
109
1.659

111
110
1.659

112
111
1.659

113
112
1.659

114
113
1.658

115
114
1.658

116
115
1.658

117
116
1.658

118
117
1.658

119
118
1.658

120
119
1.658

121
120
1.658

122
121
1.658

123
122
1.657

124
123
1.657

125
124
1.657

126
125
1.657

127
126
1.657

128
127
1.657

129
128
1.657

130
129
1.657

131
130
1.657

132
131
1.657

133
132
1.656

134
133
1.656

135
134
1.656

136
135
1.656

137
136
1.656

138
137
1.656

139
138
1.656

140
139
1.656

141
140
1.656

142
141
1.656

143
142
1.656

144
143
1.656

145
144
1.656

146
145
1.655

147
146
1.655

148
147
1.655

149
148
1.655

150
149
1.655

151
150
1.655

152
151
1.655

153
152
1.655

154
153
1.655

155
154
1.655

156
155
1.655

157
156
1.655

158
157
1.655

159
158
1.655

160
159
1.654

161
160
1.654

162
161
1.654

163
162
1.654

164
163
1.654

165
164
1.654

166
165
1.654

167
166
1.654

168
167
1.654

169
168
1.654

170
169
1.654

171
170
1.654

172
171
1.654

173
172
1.654

174
173
1.654

175
174
1.654

176
175
1.654

177
176
1.654

178
177
1.654

179
178
1.653

180
179
1.653

181
180
1.653

182
181
1.653

183
182
1.653

184
183
1.653

185
184
1.653

186
185
1.653

187
186
1.653

188
187
1.653

189
188
1.653

190
189
1.653

191
190
1.653

192
191
1.653

193
192
1.653

194
193
1.653

195
194
1.653

196
195
1.653

197
196
1.653

198
197
1.653

199
198
1.653

200
199
1.653

In order to make the overlaying comparison, dimples in a pair of corresponding dimples must be aligned with one another. For example, the dimple in the southern hemisphere is transformed γ degrees about the polar axis such that the centroid of the southern hemisphere dimple lies in a common plane (P) as the centroid of the northern hemisphere dimple and the golf ball centroid. The southern hemisphere dimple is then transformed by an angle of [2*(90−θ)] degrees about an axis that is normal to plane P and passes though the golf ball centroid. The plan shape is then rotated by 180 degrees about an axis connecting the dimple centroid to the golf ball centroid. These transformations will result in the plan shapes of the southern and northern dimples, in a pair of corresponding dimples, to be properly oriented in the same plane such that differences between their plan shape and plan shape orientation can be determined by calculating the absolute residual. In another example, where the plan shapes of the dimples are not axially symmetric, the dimples may be aligned with one another by positioning the two dimples relative to one another such that a single axis passes through the centroid of each plan shape.

An absolute residual r is determined by overlaying the plan shapes of two dimples 100/200 with the geometric centers 101/201 of the two plan shapes aligned with one another, as shown in FIG. 3. An intersection line 300 is made to extend from the aligned geometric centers 101/201 in any chosen direction, with the intersection line 300 extending a sufficient length to intersect a perimeter point 103 of the first dimple 100, as well as a perimeter point 203 of the second dimple 200. A distance d₁is then measured from the geometric centers 101/201 to the perimeter point 103 of the first dimple 100; and a distance d₂is measured from the geometric centers 101/201 to the perimeter point 203 of the second dimple 200. An absolute residual r is then calculated as the absolute value of the difference between the two measured distances, such that r=|d₁−d₂|.

A mean absolute residual r is calculated by calculating an absolute residual r over a number of n equally spaced intersection lines 300_n, and then averaging the separately calculated absolute residuals r. FIG. 4 shows one simplified example of a number of n equally spaced intersection lines 300_nin an overlaying comparison of plan shapes. As seen in FIG. 4, a number (n) of intersection lines 300_nare equally spaced over a 360° range around the geometric centers 101/201, with each intersection line 300_nmade to extend a sufficient length from the geometric centers 101/201 to intersect both a perimeter point 103 of the first dimple 100 as well as a perimeter point 203 of the second dimple 200. Preferably, the intersection lines 300_nare spaced from one another such that there is an identical angle θ_Lbetween each adjacent pair of intersection lines 300_n, the angle θ_Lmeasuring (1.8°≦θ_L≦12°) and being selected based on the number of intersection lines 300_n. For each intersection line 300_n, distances d₁and d₂are measured and an absolute residual r is calculated as the absolute value of the difference between the two distances, with r=|d₁−d₂|, such that there is acquired a total number (n) of absolute residuals r. The number (n) of absolute residuals r are then averaged to yield a mean absolute residual r. The number (n) of intersection lines 300_n, and hence the number of absolute residuals r, should be greater than or equal to about thirty but less than or equal to about two hundred.

A residual standard deviation S_ris calculated for the group of (n) residuals r, via the following equation:

$S_{r} = \sqrt{\frac{1}{n - 1} \sum_{i = 1}^{n} {(r_{i} - \overline{r})}^{2}}$

A t-statistic (t_j) is then calculated according to the following equation:

$t_{j} = \frac{\overline{r}}{\frac{S_{r}}{\sqrt{n}}}$

The calculated t-statistic (t_j) is compared to a critical t value from a t-distribution with (n−1) degrees of freedom and an alpha value of 0.05, via the following equation:

t
_j
>t
_α,n−1

If the foregoing equation comparing t_jand t is logically true, then the overlaid plan shapes are considered different.

The foregoing procedure may be repeated for any dimple pair on the ball that could be considered different. However, as one of ordinary skill in the art would readily understand, and because not all dimple pairs on the ball will have different shapes, the foregoing procedure would only be applied to dimple pairs with a different plan shape. In one embodiment, the foregoing procedure is performed only until dimples in a single pair of corresponding dimples are determined to be different, with the understanding that identification of different dimples within even a single pair of corresponding dimples is sufficient to conclude that the two hemispheres on which the dimples are located have different dimple geometries.

The plan shape of each dimple in a corresponding dimple pair may be any shape within the context of the above disclosure. In one embodiment, the plan shape may be any one of a circle, square, triangle, rectangle, oval, or other geometric or non-geometric shape providing that the corresponding dimple in another hemisphere differs. By way of example, in a pair of corresponding dimples, the dimple in the first hemisphere may be a circle and the corresponding dimple in the second hemisphere may be a square (as generally shown in FIG. 1). In another embodiment, the plan shape of two dimples in a pair of corresponding dimples may be generally the same (i.e., each dimple in a corresponding dimple pair is the same general shape of a circle, square, oval, etc.), though the two dimples may nonetheless have different plan shapes due to a difference in size.

Dimple Profile

Another way to achieve differing dimple geometries with the same dimple arrangement on opposing hemispheres in accordance with the present invention is to include corresponding dimples that differ in profile shape. Thus, in another embodiment, the dimples on opposing hemispheres are considered different from one another if, in a pair of corresponding dimples, the profile shapes of the corresponding dimples differ from one another. The profile shapes of two dimples are considered different from one another if an overlaying comparison of the profile shapes of the two dimples yields a mean absolute residual r, over a number of (n+1) equally spaced points along the overlaid profile shapes, that is significantly different from zero.

In one embodiment, at least about 25 percent of the corresponding dimples in the opposing hemispheres have different profile shapes. In another embodiment, at least about 50 percent of the corresponding dimples in the opposing hemispheres have different profile shapes. In yet another embodiment, at least about 75 percent of the corresponding dimples in the opposing hemispheres have different profile shapes. In still another embodiment, all of the corresponding dimples in the opposing hemispheres have different profile shapes.

An absolute residual r is determined by overlaying the profile shapes of two dimples 100/200, as shown in FIG. 5. The dimple cross-sections used in this analysis must be cross-sections taken along planes that pass through the geometric centers 101/201 of the respective dimples 100/200. If the dimple is axially symmetric, then the dimple cross-section may be taken along any plane that runs through the geometric center. However, if the dimple is not axially symmetric, then the dimple cross-section is taken along a plane passing through the geometric center of that dimple which produces the widest dimple profile shape in a cross-section view. In one embodiment, in the case where a dimple is not axially symmetric, multiple mean residual calculations are conducted and at least one is significantly different than zero. In another embodiment at least five mean residuals are calculated and at least one is significantly different than zero.

The dimple profile shapes are overlaid with one another such that the geometric centers 101/201 of the two dimples 100/200 are aligned on a common vertical axis Y-Y, and such that the peripheral edges 105/205 of the two profile shapes (i.e., the edges of the dimple perimeter that intersect the outer surface of the golf ball 1) are aligned on a common horizontal axis X-X, as shown in FIG. 5. An initial intersection line 400 is made to extend from the center of the golf ball 1 through both geometric centers 101/201 (i.e., the initial intersection line 400 is drawn to extend along the common vertical axis Y-Y). The initial intersection line 400 is made to extend a sufficient length to also pass through a phantom point 3 where the initial intersection line 400 would intersect a phantom surface 5 of the golf ball 1. A distance d₁is then measured from the point where the initial intersection line 400 intersects the profile shape of the first dimple 100 (i.e., the geometric center 101) to the point where the initial intersection line 400 intersects the phantom surface 5 (i.e., the phantom point 3). Similarly, a distance d₂is measured from the point where the initial intersection line 400 intersects the profile shape of the second dimple 200 (i.e., the geometric center 201) to the point where the initial intersection line 400 intersects the phantom surface 5 (i.e., the phantom point 3). An absolute residual r is then calculated as the absolute value of the difference between the two measured distances, such that r=|d₁−d₂|.

A mean absolute residual r is calculated by calculating an absolute residual r over a number (n+1) of equally spaced intersection lines 400/400′, and averaging the separately calculated absolute residuals r. FIG. 6 shows one simplified example of a number (n+1) of equally spaced intersection lines 400/400′ in an overlaying comparison of profile shapes. As seen in FIG. 6, a number of (n) additional intersection lines 400′ are equally spaced along the length of the overlaid profile shapes of the corresponding dimples 100/200, with the (n) additional intersection lines 400′ arranged symmetrically about the initial intersection line 400, such that there are (n/2) additional intersection lines 400′ on each side of the initial intersection line 400, and such that none of the additional intersection lines 400′ intersect a point on the peripheral edges 105/205, where there profile shapes contact the surface of the golf ball 1. Each intersection line 400′ is made to extend a sufficient length to pass through a point 107 on the profile shape of the first dimple 100, a point 207 on the profile shape of the second dimple 200, and a phantom point 4 on the phantom surface 5 of the golf ball 1. For each intersection line 400′, distances d₁and d₂are measured and an absolute residual r is calculated as the absolute value of the difference between the two distances, with r=|d₁−d₂|, such that there is acquired a total number (n+1) of absolute residuals r. The number (n+1) of absolute residuals r are then averaged to yield a mean absolute residual r. The total number (n+1) of intersection lines 400/400′, and hence the number of absolute residuals r, should be greater than or equal to about thirty-one but less than or equal to about two hundred one.

A residual standard deviation S_ris calculated for the group of (n+1) residuals r, via the following equation:

$S_{r} = \sqrt{\frac{1}{n} \sum_{i = 1}^{n} {(r_{i} - \overline{r})}^{2}}$

A t-statistic (t_j) is calculated according to the following equation:

$t_{j} = \overline{r} \frac{S_{r}}{\sqrt{n + 1}}$

The calculated t-statistic (t_j) is compared to a critical t value from a t-distribution with ((n+1)−1) degrees of freedom and an alpha value of 0.05, via the following equation:

t
_j
>t
_α,n

If the foregoing equation comparing t_jand t is logically true, then the overlaid profile shapes are considered different.

The foregoing procedure may be repeated for any dimple pair on the ball that could be considered to have different profile shapes. However, as one of ordinary skill in the art would appreciate, and because not all dimple pairs on the ball will have different profile shapes, the foregoing procedure would only be applied to dimple pairs with a different profile shape. In one embodiment, the foregoing procedure is performed only until dimples in a single pair of corresponding dimples are determined to be different (in plan and/or profile shape), with the understanding that identification of different dimples within even a single pair of corresponding dimples is sufficient to conclude that the two hemispheres on which the dimples are located have different dimple geometries.

The cross-sectional profile of the dimples according to the present invention may be based on any known dimple profile shape that works within the context of the above disclosure. In one embodiment, the profile of the dimples corresponds to a curve. For example, the dimples of the present invention may be defined by the revolution of a catenary curve about an axis, such as that disclosed in U.S. Pat. Nos. 6,796,912 and 6,729,976, the entire disclosures of which are incorporated by reference herein. In another embodiment, the dimple profiles correspond to parabolic curves, ellipses, spherical curves, saucer-shapes, truncated cones, and flattened trapezoids.

The profile of the dimple may also aid in the design of the aerodynamics of the golf ball. For example, shallow dimple depths, such as those in U.S. Pat. No. 5,566,943, the entire disclosure of which is incorporated by reference herein, may be used to obtain a golf ball with high lift and low drag coefficients. Conversely, a relatively deep dimple depth may aid in obtaining a golf ball with low lift and low drag coefficients.

The dimple profile may also be defined by combining a spherical curve and a different curve, such as a cosine curve, a frequency curve or a catenary curve, as disclosed in U.S. Patent Publication No. 2012/0165130, which is incorporated in its entirety by reference herein. Similarly, the dimple profile may be defined by the superposition of two or more curves defined by continuous and differentiable functions that have valid solutions. For example, in one embodiment, the dimple profile is defined by combining a spherical curve and a different curve. In another embodiment, the dimple profile is defined by combining a cosine curve and a different curve. In still another embodiment, the dimple profile is defined by the superposition of a frequency curve and a different curve. In yet another embodiment, the dimple profile is defined by the superposition of a catenary curve and different curve.

In one embodiment, at least about 25 percent of the corresponding dimples in the opposing hemispheres have different profile shapes and different plan shapes. In another embodiment, at least about 50 percent of the corresponding dimples in the opposing hemispheres have different profile shapes and different plan shapes. In yet another embodiment, at least about 75 percent of the corresponding dimples in the opposing hemispheres have different profile shapes and different plan shapes. In still another embodiment, all of the corresponding dimples in the opposing hemispheres have different profile shapes and different plan shapes.

Volumetric Equivalence

As discussed above, even though the dimple geometries on opposing hemispheres differ in that dimples in at least one pair of corresponding dimples have different plan shapes, profile shapes, or a combination thereof; the hemispheres have the same dimple arrangement. Similarly, even though the dimple geometries in the opposing hemispheres differ, an appropriate degree of volumetric equivalence is maintained between the two hemispheres. In this aspect of the invention, the dimples in one hemisphere have dimple volumes similar to the dimple volumes of the dimples in the other hemisphere.

Volumetric equivalence of two hemispheres of a golf ball may be assessed via a regression analysis of dimple surface volumes. This may be done by calculating the surface volumes of the two dimples in a pair of corresponding dimples 100/200, and plotting the calculated surface volumes of the two dimples against one another. An example of a surface volume plotting is shown in FIG. 7, where a first axis (e.g., the horizontal axis) represents the surface volume of the dimple 100 in the first hemisphere 10 and a second axis (e.g., the vertical axis) represents the surface volume of the dimple 200 in the second hemisphere 20. This calculation and plotting of surface volumes is repeated for each pair of corresponding dimples 100/200 sampled, such that there is obtained a multi-point plot with a plotted point for all pairs of corresponding dimples sampled. An example of a simplified multi-point plot is shown in FIG. 8. In one embodiment, at least 25 percent of the corresponding dimples are included in the multi-point plot. In another embodiment, at least 50 percent of the corresponding dimples are included in the multi-point plot. In yet another embodiment, at least 75 percent of the corresponding dimples are included in the multi-point plot. In still another embodiment, all of the corresponding dimples on the ball are included in the multi-point plot.

After the surface volumes for all pairs of corresponding dimples 100/200 have been calculated and plotted, linear regression analysis is performed on the data to yield coefficients in the form y=α+βx. It should be understood by one of ordinary skill in the art the linear function y uses least squares regression to determine the slope β and the y-intercept α, where x represents the surface volume from the dimple on the first hemisphere and y represents the surface volume of the dimple on the second hemisphere. Two hemispheres are considered to have volumetric equivalence when two conditions are met. First, the coefficient β must be about one—which is to say that the coefficient β must be within a range from about 0.90 to about 1.10; preferably from about 0.95 to about 1.05. Second, a coefficient of determination R²must be about one—which is to say that the coefficient of determination R²must be greater than about 0.90; preferably greater than about 0.95. In order to satisfy the requirement of volumetric equivalence both of these conditions must be met.

Thus, a suitable dimple pattern has a coefficient β that ranges from about 0.90 to about 1.10 and a coefficient of determination R²greater than about 0.90.

Dimple Dimensions

The dimples on golf balls according to the present invention may comprise any width, depth, and edge angle; and the dimple patterns may comprise multitudes of dimples having different widths, depths, and edge angles. In one embodiment, the surface volume of dimples in a golf ball according to the present invention is within a range of about 0.000001 in³to about 0.0005 in³. In one embodiment, the surface volume is about 0.00003 in³to about 0.0005 in³. In another embodiment, the surface volume is about 0.00003 in³to about 0.00035 in³.

Golf Ball Construction

Dimple patterns according to the present invention may be used with practically any type of ball construction. For instance, the golf ball may have a two-piece design, a double cover, or veneer cover construction depending on the type of performance desired of the ball. Other suitable golf ball constructions include solid, wound, liquid-filled, and/or dual cores, and multiple intermediate layers.

Different materials may be used in the construction of golf balls according to 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. Conventional and non-conventional materials may be used for forming core and intermediate layers of the ball including polybutadiene and other rubber-based core formulations, ionomer resins, highly neutralized polymers, and the like.

EXAMPLES

The following non-limiting examples demonstrate dimple patterns that may be made in accordance with the present invention. The examples are merely illustrative of the preferred embodiments of the present invention, and are not to be construed as limiting the invention, the scope of which is defined by the appended claims. In fact, it will be appreciated by those skilled in the art that golf balls according to the present invention may take on a number of permutations, provided volumetric equivalence between the two hemispheres is achieved. Again, volumetric equivalence between two hemispheres may be achieved by adapting the surface volumes of the dimples in the two separate hemispheres to yield substantially identical hemispherical volumes, in accord with the discussion above.

Golf Ball with Dimple Patterns Having Differing Plan Shapes

FIGS. 9a-9e present one example of a golf ball 1 according to the present invention wherein dimples 100 in a first hemisphere 10 differ from dimples 200 in a second hemisphere 20 based, at least, on a difference in plan shapes. As shown in FIGS. 9a-9e, the difference in plan shapes may be one wherein the plan shapes of the dimples 100 in the first-hemisphere 10 are of a shape (e.g., circular, square, triangle, rectangle, oval, or any other geometric or non-geometric shape) that is different from the shape of the plan shapes of the dimples 200 in the second-hemisphere 20. In a variation of this example, the plan shapes of the first-hemisphere dimples may be of a shape (e.g., circular, square, triangle, rectangle, oval, or any other geometric or non-geometric shape) that is the same as the shape of the plan shapes of the second-hemisphere dimples; though the two plan shapes may be of different sizes (e.g., both dimple plan shapes may have a circular plan shape, though one circular plan shape may have a smaller diameter than the other) or of different orientations (such as the example illustrated in FIGS. 12a-12e).

Golf Ball with Dimple Patterns Having Differing Profiles

FIGS. 10a-10e present one example of a golf ball 1 according to the present invention wherein dimples 100 in a first hemisphere 10 differ from dimples 200 in a second hemisphere 20 based, at least, on a difference in profile. For example, as shown in FIGS. 10a-10e, the first and second hemisphere dimples 100/200 may both have circular plan shapes, though the first hemisphere dimples 100 may have arcuate profiles while the second hemisphere dimples 200 have substantially planar profiles. In a variation of this example, the difference in profile may be one wherein the profile of the first-hemisphere dimples correspond to a curve and the profile of the second-hemisphere dimples correspond to a truncated cone.

Golf Ball with Dimple Patterns Having Differing Plan and Profile Shapes

FIGS. 11a-11e presents one example of a golf ball 1 according to the present invention wherein dimples 100 in a first hemisphere 10 differ from dimples 200 in a second hemisphere 20 based, both, on a difference in plan shapes (e.g., circular versus square) and a difference in profiles (e.g., arcuate versus conical).

Although the present invention is described with reference to particular embodiments, it will be understood to those skilled in the art that the foregoing disclosure addresses exemplary embodiments only; that the scope of the invention is not limited to the disclosed embodiments; and that the scope of the invention may encompass additional embodiments embracing various changes and modifications relative to the examples disclosed herein without departing from the scope of the invention as defined in the appended claims and equivalents thereto.

Though the foregoing disclosure describes the invention relative to examples of golf balls having two different hemispheres with dimple patterns having different dimples, those skilled in the art will appreciate the invention may also be practiced with golf balls that are divided into another number of different regions (e.g., patterns based on tetrahedrons, octahedrons, cuboctahedrons, icosahedrons, icosadodecahedrons, and dipyramids).

To the extent necessary to understand or complete the disclosure of the present invention, all publications, patents, and patent applications mentioned herein are expressly incorporated by reference herein to the same extent as though each were individually so incorporated. No license, express or implied, is granted to any patent incorporated herein. Ranges expressed in the disclosure include the endpoints of each range, all values in between the endpoints, and all intermediate ranges subsumed by the endpoints.

The present invention is not limited to the exemplary embodiments illustrated herein, but is instead characterized by the appended claims.

GOLF BALLS HAVING VOLUMETRIC EQUIVALENCE ON OPPOSING HEMISPHERES AND SYMMETRIC FLIGHT PERFORMANCE AND METHODS OF MAKING SAME

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