Golf ball dimple plan shape
The present invention is directed to golf balls having improved aerodynamic performance due, at least in part, to the selection of the plan shapes of the dimples thereon. In particular, the present invention is directed to a golf ball that includes at least a portion of its dimples having a plan shape defined by a periodic cosine function mapped along a circular closed path. In addition, the present invention provides methods for designing dimples having a plan shape defined by a periodic cosine function mapped along a circular closed path.
1. A golf ball having a generally spherical surface and comprising from 250 to 400 dimples on the spherical surface, wherein at least 80% of the dimples are non-circular plan shape dimples having a plan shape defined by a periodic function mapped along a circular closed path, wherein the periodic function is a periodic cosine function having a period of 4.
2. The golf ball of claim 1 , wherein the absolute distance, d, of any point on the non-circular plan shape from the circular path is defined by the following equation:
d =√{square root over (( x circle −x plan ) 2 +( y circle −y plan ) 2 )}
where d is a directed distance calculated along a line from the plan shape centroid through corresponding points on the plan shape and circular path, and the maximum value, d max , for all calculated distances, d, is 0.007 inches or less.
3. The golf ball of claim 2 , wherein the maximum value, d max , for all calculated distances, d, is from 0.003 inches to 0.007 inches.
4. The golf ball of claim 1 , wherein each one of the dimples having said non-circular plan shape comprises a first dimple profile and a second dimple profile, the first dimple profile having a first edge angle (Φ EDGE1 ) and a second edge angle (Φ EDGE2 ) and the second dimple profile having a third edge angle (Φ EDGE3 ) and a fourth edge angle (Φ EDGE4 ), and Φ EDGE1 =Φ EDGE2 , Φ EDGE3 =Φ EDGE4 , and Φ EDGE1 Φ EDGE3 ; and wherein, for each one of the dimples having said non-circular plan shape, the difference between the maximum edge angle and the minimum edge angle of all of the dimple profiles of that dimple is from 0.30° to 3.00°.
5. The golf ball of claim 4 , wherein, for each one of the dimples having said non-circular plan shape, the difference between the first edge angle and the second edge angle of each of the dimple profiles of that dimple is less than 0.25°.
6. The golf ball of claim 1 , wherein the surface of each of the non-circular plan shape dimples includes a protruding center portion.
7. The golf ball of claim 6 , wherein the protruding center portion lies below the nominal chord plane of the dimple.
8. The golf ball of claim 1 , wherein, for each one of the non-circular plan shape dimples, the average of the edge angles of all of the dimple profiles of that dimple is from 11° to 18°.