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 geometries on the opposing hemispheres.

The present invention is directed to golf balls having improved aesthetics and desirable aerodynamic properties due, at least in part, to the novel shape of the dimples on the surface thereof. In particular, the present invention is directed to a golf ball that includes at least a portion of its dimples having a shape obtained from the intersection of a toroid and a sphere. The resulting curve of intersection represents the dimple perimeter and the intersecting portion of the surface of the toroid represents the dimple surface shape.

The present invention provides a method for arranging dimples on a golf ball surface in which the dimples are arranged in a pattern derived from at least one irregular domain generated from a regular or non-regular polyhedron. The method includes choosing control points of a polyhedron, generating an irregular domain based on those control points, packing the irregular domain with dimples, and tessellating the irregular domain to cover the surface of the golf ball. The control points include the center of a polyhedral face, a vertex of the polyhedron, a midpoint or other point on an edge of the polyhedron and others. The method ensures that the symmetry of the underlying polyhedron is preserved while minimizing or eliminating great circles due to parting lines.

A golf ball has a lower drag than conventional golf balls due to the arrangement of dimples on the outer surface of the golf ball, which arrangement produces a correspondingly lower percentage of outer surface area that is covered by the dimples. In particular, dimple coverage area may be less than 70%, and more specifically between about 18.6% and about 60.8%, of the outer surface area. Various combinations of dimple characteristics can be combined to produce the low dimple coverage, low drag golf ball, such as the number of dimples, pattern and spacing of dimples, dimple diameter, dimple depth, and dimple shape. The dimple characteristics can be selected so that the golf ball meets the requirements of the United States Golf Association and other golf organizations.

The present invention provides a golf ball including a two-layer core having an inner layer core and an outer layer core, an intermediate layer, and a cover, in which a large number of dimples are formed on an outer surface of the cover, and a relationship between a surface hardness of an intermediate layer-encased sphere and a ball surface hardness satisfies the following condition:

(ball surface hardness)< (surface hardness of intermediate layer-encased sphere) (where hardness means Shore D hardness).

Further, a value obtained by subtracting a center hardness of the entire core from a surface hardness of the entire core is at least 25 on the Shore C hardness scale, and a lift coefficient and a drag coefficient at a predetermined Reynolds number and spin rate of the dimples are set within a predetermined range.

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 geometries on the opposing hemispheres.

A golf ball has a large number of dimples 10 on a surface thereof. The dimples 10 include a plurality of small dimples 10S each having an area of less than 8.0 mm.sup.2, and a plurality of large dimples 10L each having an area of equal to or greater than 8.0 mm.sup.2. A ratio PS of a sum of areas of all the small dimples 10S to a surface area of a phantom sphere of the golf ball is less than 2.0%. The number NL of the large dimples 10L is equal to or greater than 250 but less than 450. The number NL of the large dimples 10L and a degree G of uniformity of areas of the large dimples 10L satisfy the following mathematical formula (II):
G<0.0032.Math.NL+0.26(II).

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 geometries on the opposing hemispheres.

The present invention is directed to golf balls having improved aesthetics and desirable aerodynamic properties due, at least in part, to the novel shape of the dimples on the surface thereof. In particular, the present invention is directed to a golf ball that includes at least a portion of its dimples having a shape obtained from the intersection of a toroid and a sphere. The resulting curve of intersection represents the dimple perimeter and the intersecting portion of the surface of the toroid represents the dimple surface shape.

A golf ball 2 has, on a surface thereof, a plurality of types of dimples 8 having different diameters from each other. A standard deviation V of the volumes of all the dimples 8 is equal to or less than 0.095 mm.sup.3. The ratio (V/D) of the standard deviation V to a standard deviation D of the diameters of all the dimples 8 is equal to or less than 0.35. Preferably, the shape of each dimple 8 is a portion of a spherical surface. The standard deviation V is preferably equal to or less than 0.087 mm.sup.3. The ratio (V/D) is preferably equal to or less than 0.29.