Patent Publication Number: US-2021178228-A1

Title: Dimple patterns for golf balls

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 16/558,131, filed Sep. 1, 2019, which is a continuation-in-part of U.S. patent application Ser. No. 16/035,816, filed Jul. 16, 2018, now U.S. Pat. No. 10,398,941, which is a continuation of U.S. patent application Ser. No. 15/431,838, filed Feb. 14, 2017, now U.S. Pat. No. 10,022,592, which is a continuation of U.S. patent application Ser. No. 14/144,483, filed Dec. 30, 2013, now U.S. Pat. No. 9,566,473, the entire disclosures of which are hereby incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to golf balls having two hemispheres, each hemisphere having a dimple pattern based on a pyramid having dissimilar sides. 
     BACKGROUND OF THE INVENTION 
     U.S. Patent Application Publication No. 2013/0072325 to Madson et al. discloses a golf ball dimple pattern having an underlying geometry based on a dipyramid. 
     U.S. Pat. No. 7,503,856 to Nardacci et al. discloses a golf ball dimple pattern based on a hexagonal dipyramid, wherein the dimples are arranged in six substantially similar mating dimple sections on each hemisphere. 
     U.S. Patent Application Publication No. 2012/0004053 to Kim discloses a designing method for a dimple pattern of a golf ball including the steps of (1) dividing a surface of a phantom sphere of the golf ball into a plurality of units by division lines obtained by projecting edge lines of a regular polyhedron inscribed in the phantom sphere, on the surface of the phantom sphere; (2) obtaining a base pattern by randomly arranging a plurality of dimples in one unit such that the dimples do not overlap each other; and (3) developing the base pattern over other units such that patterns of two adjacent units are not mirror-symmetrical to each other. 
     SUMMARY OF THE INVENTION 
     In one embodiment, the present invention is directed to a golf ball having a first hemisphere and a second hemisphere separated by an equator, each hemisphere comprising on the outer surface thereof, a plurality of dimples arranged in a pattern defined by an n-sided pyramid projected on a hemisphere as n lines of longitude from pole to equator. The dimple arrangement along each longitudinal line is identical, and the overall dimple pattern on each hemisphere contains no rotational symmetry about the polar axis. In a particular aspect of this embodiment, at least one hemisphere includes at least one side with a dimple free area that has a surface area of ≥0.06 in 2 . 
     In another embodiment, the present invention is directed to a golf ball having a first hemisphere and a second hemisphere separated by an equator, each hemisphere comprising on the outer surface thereof, a plurality of dimples arranged in a pattern defined by an n-sided pyramid projected on a hemisphere, the side edges of the pyramid representing n lines of longitude from pole to equator, wherein n≥3. Within each hemisphere, the dimple arrangement along each of the n longitudinal lines is identical, and every longitudinal line having said identical dimple arrangement thereon corresponds to one of the side edges of the pyramid. Within each hemisphere, at least two of the sides have a different longitudinal angle. The equator intersects a portion of the plurality of dimples, and all of the dimples that are intersected by the equator have the same dimple diameter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings, which form a part of the specification and are to be read in conjunction therewith, and in which like reference numerals are used to indicate like parts in the various views: 
         FIG. 1  is a polar view of a golf ball having a dimple pattern arranged according to a method known in the art; 
         FIG. 2  is a polar view of the golf ball of  FIG. 1  rotated 72° about the polar axis; 
         FIG. 3  is a polar view of a golf ball having a dimple pattern arranged according to a method known in the art; 
         FIG. 4  is a polar view of the golf ball of  FIG. 3  rotated 180° about the polar axis; 
         FIG. 5  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 6  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 7  is a polar view of a golf ball having dimples arranged according to an embodiment of the present invention; 
         FIG. 8  is a polar view of a golf ball having dimples arranged according to an embodiment of the present invention; 
         FIG. 9  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 10  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 11  is a polar view of a golf ball having dimples arranged according to an embodiment of the present invention; 
         FIG. 12  is a polar view of a golf ball having dimples arranged according to an embodiment of the present invention; 
         FIG. 13  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 14  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 15  is a polar view of a golf ball having dimples arranged according to an embodiment of the present invention; 
         FIG. 16  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 17  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 18  illustrates a polar view of a golf ball having dimples arranged according to an embodiment of the present invention; 
         FIG. 19  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 20  illustrates a polar view of a golf ball having dimples arranged according to an embodiment of the present invention; 
         FIG. 21  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 22  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; 
         FIG. 23  illustrates a side of a pyramid projected on a hemisphere and packed with dimples; and 
         FIG. 24  illustrates a polar view of a golf ball having dimples arranged according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Golf balls of the present invention include a first pole, a second pole opposite the first pole, and an equator evenly spaced between the first and second poles so as to divide the golf ball into a first hemisphere including the first pole and a second hemisphere including the second pole. The outer surface of each hemisphere includes a plurality of dimples arranged in a pattern defined by an n-sided pyramid projected on a hemisphere as n lines of longitude from pole to equator, wherein n≥3. In a particular embodiment, n≥4 for one or both of the hemispheres. At least two of the sides of the pyramid are dissimilar. For purposes of the present invention, one side of the pyramid is dissimilar to another side of the pyramid if they have a different longitudinal angle, ϕ i , and a different arrangement of dimples. When combined, the longitudinal angles of each hemisphere sum to 360. For a hemisphere having m dissimilar sides, and r repetitions of each side: 
       Σ i=1   m   r   i ϕ i =360  (Equation 1).
 
     The total number of distinct hemispheres that can be created, τ, is calculated as the number of circular permutations: 
     
       
         
           
             
               
                 
                   
                     τ 
                     = 
                     
                       
                         
                           ( 
                           
                             n 
                             - 
                             1 
                           
                           ) 
                         
                         ! 
                       
                       
                         
                           r 
                           1 
                         
                          
                         
                           ! 
                           
                             × 
                             
                               
                                 r 
                                 2 
                               
                               ! 
                             
                             × 
                             … 
                             × 
                             
                               
                                 r 
                                 m 
                               
                               ! 
                             
                           
                         
                       
                     
                   
                   , 
                 
               
               
                 
                   ( 
                   
                     Equation 
                      
                     
                         
                     
                      
                     2 
                   
                   ) 
                 
               
             
           
         
       
     
     where n, the total number of sides for a hemisphere, is: 
         n=Σ   i=1   m   r   i   (Equation 3).
 
     In a particular embodiment, the first hemisphere and the second hemisphere have the same number of sides. In a particular aspect of this embodiment, the dimple arrangement of the first hemisphere and the dimple arrangement of the second hemisphere are the same. In another particular aspect of this embodiment, the dimple arrangement of the first hemisphere and the dimple arrangement of the second hemisphere are different. 
     In another particular embodiment, the first hemisphere and the second hemisphere have a different number of sides. 
     Each dimple is either located entirely within a single side of the pyramid or is intersected by a side edge of the pyramid such that the center of the dimple lies on the same plane as the side edge, i.e., a longitudinal line. In a particular embodiment, the dimple arrangement along each longitudinal line of a hemisphere is identical, meaning that each dimple that is located along a side edge of the pyramid is replicated on all side edges of the pyramid. For purposes of the present invention, a dimple on one edge is a replicate of a dimple on another edge if the dimples have the same latitudinal angle and diameter. By way of definition, if such a dimple arrangement is repeated on multiple longitudinal lines, then those lines define the edges of the segments. If more than one such a dimple arrangement exists then the segments edges are defined by the arrangement that produces the greatest number of segments on the ball. If more than one such a dimple arrangement exists and they produce the same number of segments, then any one arrangement can be used to define the edges of the segment, but not more than one. 
     In a particular embodiment, at least one side of a hemisphere, i.e., at least one dimple segment on the ball, has a dimple free area having a surface area of ≥0.06 in 2 . For purposes of the present disclosure, the term “dimple free area” refers to a dimple free area that has a surface area of ≥0.06 in 2 . All dimple patterns inherently have a certain amount of dimple free “fret area” between dimples. The portion of the golf ball surface that one of ordinary skill in the art would generally consider “fret area” is not meant to be included in calculating the surface area of the “dimple free area” of the present invention. Rather, for purposes of the present invention, a dimple free area having a surface area of ≥0.06 in 2 , is an area on the surface of the ball onto which a rectangle having that area can be projected without intersecting any dimples or including any dimples within its boundaries. 
     In a particular aspect of this embodiment, one hemisphere has at least one dimple segment with a dimple free area and the other hemisphere has no dimple segments with a dimple free area. In another particular aspect of this embodiment, one hemisphere has at least two dimple segments with a dimple free area and the other hemisphere has no dimple segments with a dimple free area. In another particular aspect of this embodiment, both hemispheres have at least one dimple segment with a dimple free area. In another particular aspect of this embodiment, one hemisphere has at least two dimple segments with a dimple free area and the other hemisphere has at least one dimple segment with a dimple free area. In another particular aspect of this embodiment, both hemispheres have two dimple segments with a dimple free area. In embodiments of the present invention wherein at least two dimple segments have a dimple free area, the dimple free area of one segment may be the same size or a different size than the dimple free area of another segment. 
     Preferably, the dimple free area(s) on the ball include a marking. Suitable markings include logos, and letters, numbers, and shapes that are part of a nameplate, side stamp, or logo. “Nameplate” typically, but not necessarily, refers to a marking corresponding to the golf ball brand. “Side stamp” typically, but not necessarily, refers to a marking corresponding to the model of the golf ball. In embodiments of the present invention wherein at least two dimple segments include a dimple free space with a marking, the marking of one dimple segment may be the same as or different from the marking of another dimple segment. 
     Each marking may be printed on the golf ball surface either underneath or on top of a coating layer, or engraved into the surface of the ball. For purposes of the present disclosure, “engraved” refers to the final appearance of the marking as being cut into, rather than printed on the surface of, the golf ball. Thus, engraved markings, for purposes of the present disclosure, includes markings that are cut directly into the golf ball using, for example, a machining or laser etching process, and markings that are formed by machining the marking into the master tool used to make dimpled cavities whereby the marking is transferred to the golf ball during the molding process. 
     In a particular embodiment, the overall dimple pattern on each hemisphere does not have rotational symmetry about the polar axis. The polar axis is defined herein as the axis connecting the pole of the first hemisphere to the pole of the second hemisphere. Rotational symmetry is said to exist if a hemisphere can be rotated by any angle and result in an identical pattern, as with conventional golf ball dimple patterns.  FIG. 1  is a polar view of a golf ball having a dimple pattern with rotational symmetry. When rotated 72° about the polar axis, the resulting pattern, shown in  FIG. 2 , is identical to the original pattern. A pattern is said to have x-fold rotational symmetry on a given hemisphere if any rotational angle γ about the polar axis exists such that 
     
       
         
           
             
               
                 360 
                 γ 
               
               = 
               x 
             
             , 
           
         
       
     
     and x is a whole number ≥2. Thus, the pattern shown in  FIGS. 1 and 2  has 5-fold rotational symmetry (360/42=5).  FIG. 3  is a polar view of another golf ball having a dimple pattern with rotational symmetry. When rotated 180° about the polar axis, the resulting pattern, shown in  FIG. 4 , is identical to the original pattern. Thus, the pattern shown in  FIGS. 3 and 4  has 2-fold rotational symmetry (360/180=2). 
     The two hemispheres can be positioned in any manner such that the dimples from one hemisphere do not intersect with dimples from the other hemisphere. In one embodiment, the two hemispheres are mirror images of each other and the ball has a flat, i.e., planar, parting line. In another embodiment, the two hemispheres have an angular rotation relative to one another and create a flat parting line. In another embodiment, the two hemispheres have an angular rotation relative to one another and create a staggered, i.e., non-planar, parting line, such that the dimples near the equator are allowed to cross over the ball equator but do not intersect dimples from the opposing hemisphere. 
     While preferably having a substantially circular plan shape, dimples of the present invention are not limited to a particular plan or cross-sectional shape. 
     Dimples of the present invention may have different properties including, but not limited to, cross-sectional shape, plan shape, dimple diameter, and dimple depth. In a particular embodiment, replicated dimples have the same cross-sectional shape and plan shape. 
     In another particular embodiment, a portion of the dimples are intersected by the equator, and all of the dimples that are intersected by the equator have the same dimple diameter. In a further aspect of this particular embodiment, the overall dimple pattern comprises three or more different dimple diameters, including a minimum dimple diameter, a maximum dimple diameter, and at least one additional dimple diameter, and the dimple diameter of the dimples that are intersected by the equator is not the minimum or maximum dimple diameter. In another further aspect of this particular embodiment, at least one of the dimples located along a side edge of the pyramid has the same dimple diameter as the dimples that are intersected by the equator; alternatively, none of the dimples located along the side edges of the pyramid has the same dimple diameter as the dimples that are intersected by the equator. In another further aspect of this particular embodiment, none of the dimples that are intersected by the equator is also located along a side edge of the pyramid. 
     For purposes of the present disclosure, dimples have the same dimple diameter if their respective diameters, as measure on a final golf ball, differ by less than 0.005 inches due to manufacturing variances. 
     For purposes of the present disclosure, the centroid of a dimple determines which hemisphere the dimple is located in. Preferably, the centroid of each dimple intersected by the equator does not lie on the equator. 
     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 336 or 338 or 342 or 344 or 349 or 350 or 310 or 316 or 318 or 346 or 354 or 358 or 366 or 396. 
     EXAMPLES 
     The examples below are for illustrative purposes only. In no manner is the present invention limited to the specific disclosures therein. 
     Example 1 
     As shown in  FIG. 5 , a first side, S 1 , of a pyramid is projected on a hemisphere and packed with dimples. The first side has a longitudinal angle of 60°. As shown in  FIG. 6 , a second side, S 2 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1 . The second side has a longitudinal angle of 90°. Dimples that intersect the side edges are shaded in  FIGS. 5 and 6 . Dissimilar sides S 1  and S 2  can be combined and repeated to form an overall dimple pattern of a golf ball hemisphere having the characteristics given in Table 1 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 1 
               
               
                   
                   
               
               
                   
                 Dissimilar Segments, 
                 Repetitions, 
                 Longitudinal Angle, 
               
               
                   
                 m 
                 r i   
                 ϕ i   
               
               
                   
                   
               
             
            
               
                   
                 S1 
                 3 
                 60° 
               
               
                   
                 S2 
                 2 
                 90° 
               
               
                   
                   
               
            
           
         
       
     
     Using Equation 3, the total number of sides for the hemisphere, n, is 5. The total number of distinct hemispheres, τ, that can be created is 2, as calculated using Equation 2, 
     
       
         
           
             τ 
             = 
             
               
                 
                   
                     ( 
                     
                       5 
                       - 
                       1 
                     
                     ) 
                   
                   ! 
                 
                 
                   2 
                    
                   
                     ! 
                     
                       × 
                       
                         3 
                         ! 
                       
                     
                   
                 
               
               = 
               
                 2 
                 . 
               
             
           
         
       
     
     The two distinct hemispheres that can be created are shown in  FIGS. 7 and 8 .  FIG. 7  illustrates a hemisphere with a rotational pattern of {S 1 , S 2 , S 1 , S 2 , S 1 }.  FIG. 8  illustrates a hemisphere with a rotational pattern of {S 2 , S 2 , S 1 , S 1 , S 1 }. 
     Example 2 
     As shown in  FIG. 9 , a first side, S 1 , of a pyramid is projected on a hemisphere and packed with dimples. The first side has a longitudinal angle of 45°. As shown in  FIG. 10 , a second side, S 2 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1 . The second side has a longitudinal angle of 60°. Dimples that intersect the side edges are shaded in  FIGS. 9 and 10 . Dissimilar sides S 1  and S 2  can be combined and repeated to form an overall dimple pattern of a golf ball hemisphere having the characteristics given in Table 2 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 2 
               
               
                   
                   
               
               
                   
                 Dissimilar Segments, 
                 Repetitions, 
                 Longitudinal Angle, 
               
               
                   
                 m 
                 r i   
                 ϕ i   
               
               
                   
                   
               
             
            
               
                   
                 S1 
                 4 
                 45° 
               
               
                   
                 S2 
                 3 
                 60° 
               
               
                   
                   
               
            
           
         
       
     
     Using Equation 3, the total number of sides for the hemisphere, n, is 7. The total number of distinct hemispheres, τ, that can be created is 5, as calculated using Equation 2, 
     
       
         
           
             τ 
             = 
             
               
                 
                   
                     ( 
                     
                       7 
                       - 
                       1 
                     
                     ) 
                   
                   ! 
                 
                 
                   4 
                    
                   
                     ! 
                     
                       × 
                       
                         3 
                         ! 
                       
                     
                   
                 
               
               = 
               
                 5 
                 . 
               
             
           
         
       
     
     Two of the five distinct hemispheres that can be created are shown in  FIGS. 11 and 12 .  FIG. 11  illustrates a hemisphere with a rotational pattern of {S 1 , S 1 , S 1 , S 2 , S 2 , S 2 , S 2 }.  FIG. 12  illustrates a hemisphere with a rotational pattern of {S 1 , S 1 , S 2 , S 1 , S 2 , S 1 , S 2 }. 
     Example 3 
     As shown in  FIG. 9 , a first side, S 1 , of a pyramid is projected on a hemisphere and packed with dimples. The first side has a longitudinal angle of 45°. As shown in  FIG. 13 , a second side, S 2 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1 . The second side has a longitudinal angle of 38°. As shown in  FIG. 14 , a third side, S 3 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1  or S 2 . The third side has a longitudinal angle of 111°. Dimples that intersect the side edges are shaded in  FIGS. 9, 13 and 14 . Dissimilar sides S 1 , S 2  and S 3  can be combined and repeated to form an overall dimple pattern of a golf ball hemisphere having the characteristics given in Table 3 below. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 3 
               
               
                   
                   
               
               
                   
                 Dissimilar Segments, 
                 Repetitions, 
                 Longitudinal Angle, 
               
               
                   
                 m 
                 r i   
                 ϕ i   
               
               
                   
                   
               
             
            
               
                   
                 S1 
                 3 
                 45° 
               
               
                   
                 S2 
                 3 
                 38° 
               
               
                   
                 S3 
                 1 
                 111°  
               
               
                   
                   
               
            
           
         
       
     
     Using Equation 3, the total number of sides for the hemisphere, n, is 7. The total number of distinct hemispheres, τ, that can be created is 20, as calculated using Equation 2, 
     
       
         
           
             τ 
             = 
             
               
                 
                   
                     ( 
                     
                       7 
                       - 
                       1 
                     
                     ) 
                   
                   ! 
                 
                 
                   3 
                    
                   
                     ! 
                     
                       × 
                       3 
                        
                       
                         ! 
                         
                           × 
                           
                             1 
                             ! 
                           
                         
                       
                     
                   
                 
               
               = 
               
                 2 
                  
                 
                   0 
                   . 
                 
               
             
           
         
       
     
     One of the twenty distinct hemispheres that can be created is shown in  FIG. 15 , which illustrates a hemisphere with a rotational pattern of {S 2 , S 1 , S 1 , S 2 , S 1 , S 2 , S 3 }. 
     Example 4 
     As shown in  FIG. 16 , a first side, S 1 , of a pyramid is projected on a hemisphere and packed with dimples. The first side has a longitudinal angle of 60°. As shown in  FIG. 17 , a second side, S 2 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1 , and includes a dimple free area with a marking. The second side has a longitudinal angle of 120°. First side S 1  can be repeated and combined with second side S 2  to form the overall dimple pattern of a golf ball hemisphere shown in  FIG. 18 , which illustrates a hemisphere with a rotational pattern of {S 1 , S 1 , S 1 , S 1 , S 2 }. In a particular example of the embodiment shown in  FIGS. 16-18 , a golf ball is provided wherein both hemispheres of the ball have the dimple pattern shown in  FIG. 18 . 
     As shown in  FIG. 19 , a third side, S 3 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1  or S 2 , and includes a dimple free area with a marking. The third side has a longitudinal angle of 120°. First side S 1  of  FIG. 16  can be repeated and combined with second side S 2  of  FIG. 17  and third side S 3  of  FIG. 19  to form the overall dimple pattern of a golf ball hemisphere shown in  FIG. 20 , which illustrates a hemisphere with a rotational pattern of {S 1 , S 2 , S 1 , S 3 }. In a particular example of the embodiment shown in  FIGS. 16, 17, 19 and 20 , a golf ball is provided wherein both hemispheres of the ball have the dimple pattern shown in  FIG. 20 . 
     In  FIGS. 16, 17 and 19 , the alphabetical labels within the dimples designate same diameter dimples. For example, all dimples labelled A have the same diameter; all dimples labelled B have the same diameter; and so on. Table 4 below gives illustrative values for dimple diameter and edge angle for a non-limiting particular example of the embodiments shown in  FIGS. 16-20 , wherein the dimples are spherical dimples having a circular plan shape and a cross-sectional profile defined by a spherical function. 
     
       
         
           
               
               
               
               
             
               
                   
                 TABLE 4 
               
               
                   
                   
               
               
                   
                   
                 Dimple Diameter 
                 Edge Angle 
               
               
                   
                 Dimple Label 
                 (in) 
                 (°) 
               
               
                   
                   
               
             
            
               
                   
                 A 
                 0.130 
                 14.8 
               
               
                   
                 B 
                 0.150 
                 14.8 
               
               
                   
                 C 
                 0.155 
                 14.8 
               
               
                   
                 D 
                 0.160 
                 14.8 
               
               
                   
                 E 
                 0.165 
                 14.8 
               
               
                   
                 F 
                 0.170 
                 14.8 
               
               
                   
                 G 
                 0.175 
                 14.8 
               
               
                   
                 H 
                 0.180 
                 14.8 
               
               
                   
                 I 
                 0.200 
                 14.8 
               
               
                   
                 J 
                 0.205 
                 14.8 
               
               
                   
                   
               
            
           
         
       
     
     Example 5 
     As shown in  FIG. 21 , a first side, S 1 , of a pyramid is projected on a hemisphere and packed with dimples. The first side has a longitudinal angle of 60°. As shown in  FIG. 22 , a second side, S 2 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1 . The second side has a longitudinal angle of 72°. As shown in  FIG. 23 , a third side, S 3 , of a pyramid is projected on a hemisphere and packed with dimples in a different arrangement than S 1  or S 2 . The third side has a longitudinal angle of 96°. In  FIGS. 21-23 , dimples that intersect the side edges are shaded black, and dimples that intersect the equator are indicated by hatch mark shading. 
     First side S 1  and second side S 2  can be repeated and combined with third side S 3  to form the overall dimple pattern of a golf ball hemisphere shown in  FIG. 24 , which illustrates a hemisphere with a rotational pattern of {S 1 , S 2 , S 1 , S 2 , S 3 }. 
     In a particular embodiment of the dimple pattern shown in  FIGS. 21-24 , all of the dimples that intersect the equator, i.e., all of the dimples indicated by hatch mark shading, have the same diameter. 
     When numerical lower limits and numerical upper limits are set forth herein, it is contemplated that any combination of these values may be used. 
     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. 
     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.