Golf ball
Golf ball 2 has a center 5, a mid layer 6, a cover 4 and numerous dimples 8. A product Pm of a volume Vm multiplied by a flexural rigidity Fm in the mid layer 6 and a product Pc of a volume Vc multiplied by a flexural rigidity Fc in the cover meet the following formulae (I) and (II). 1400<( Pm+Pc )<2000 (I) 5.0<( Pc/Pm )<7.6 (II) Provided that mean diameter of all the dimples 8 is Da, a ratio (N1/N) of number N1 of adjacent dimple pairs having a pitch of (Da/4) or less to total number N of the dimples 8 is equal to or greater than 2.70. A ratio (N2/N1) of number N2 of the adjacent dimple pairs having a pitch of (Da/20) or less to the number N1 is equal to or greater than 0.50.
1. A golf ball comprising a center, a mid layer positioned outside of the center, a cover positioned outside of the mid layer and numerous dimples formed on a surface of the cover,
wherein a product Pm of a volume Vm (cm 3 ) multiplied by a flexural rigidity Fm (Mpa) in the mid layer and a product Pc of a volume Vc (cm 3 ) multiplied by a flexural rigidity Fc (MPa) in the cover meet the following formulae (I) and (II),
1400<( Pm+Pc )<2000 (I)
5.0<( Pc/Pm )<7.6 (II),
provided that mean diameter of all the dimples is Da,
a ratio (N1/N) of a number N1 of adjacent dimple pairs having a pitch of (Da/4) or less to a total number N of the dimples is equal to or greater than 2.70,
a ratio (N2/N1) of a number N2 of the adjacent dimple pairs having a pitch of (Da/20) or less to the number N1 is equal to or greater than 0.50, and
a ratio (N3/N1) of a number N3 of crossing adjacent dimple pairs to the number N1 is equal to or lesser than 0.06.
2. The golf ball according to claim 1 wherein a thickness Tm of the mid layer is equal to or less than 1.2 mm, a thickness of the cover Tc is equal to or less than 1.4 mm and a total thickness (Tm+Tc) is equal to or less than 2.4 mm.
3. The golf ball according to claim 1 wherein the mid layer has a hardness (Shore D) of 32 or greater and 39 or less.
4. The golf ball according to claim 1 wherein the ratio (N2/N1) is equal to or greater than 0.60.
5. The golf ball according to claim 1 wherein the mean diameter Da is equal to or greater than 4.00 mm,
the total number N of the dimples is equal to or less than 362, and
a proportion of a total area of all dimples to a surface area of a phantom sphere is equal to or greater than 75%.
6. The golf ball according to claim 1 wherein each of a northern hemisphere and a southern hemisphere of a surface of the golf ball has a pole vicinity region, an equator vicinity region and a coordination region which is located between the pole vicinity region and the equator vicinity region,
a dimple pattern in the pole vicinity region includes multiple units which are rotationally symmetric to each other centered on a pole point,
a dimple pattern in the equator vicinity region includes multiple units which are rotationally symmetric to each other centered on the pole point,
a number of the units in the pole vicinity region is different from a number of the units in the equator vicinity region,
a dimple pattern in the coordination region is either a pattern which cannot be comparted into multiple units that are rotationally symmetric to each other centered on the pole point, or a pattern including multiple units that are rotationally symmetric to each other centered on the pole point with a number of the units being different from numbers of the units in the pole vicinity region and the equator vicinity region.
7. The golf ball according to claim 1 wherein any great circle that does not cross the dimple is not present on the surface of the golf ball.
8. The golf ball according to claim 1 wherein the ratio (N1/N) is equal to or greater than 2.90 and equal to or less than 4.00; and wherein the ratio (N2/N1) is equal to or greater than 0.64 and equal to or less than 1.00.
9. The golf ball according to claim 1 wherein the ratio (N4/N) of a number N4 of dimples having a diameter of equal to or less than 3.50 mm to the total number N is equal to or less than 0.20.