In a golf ball having a two-layer core consisting of an inner core layer and an outer core layer and a cover of one or more layer, the inner core layer and outer core layer are each formed of a rubber composition made up primarily of a base rubber, the inner core layer has a diameter of not more than 30 mm; and the core has specific hardness ratios (JIS-C hardness/Shore D hardness) at specific points on the cross-section thereof. This golf ball has a reduced spin rate on full shots with a driver and middle irons, thus imparting to an excellent flight performance, and moreover has a good controllability in the short game on approach shots, making it ideal as a golf ball for professional golfers and mid- and high-level amateur golfers.

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.

Golf balls including at least one modified dimple group are disclosed. The modified dimple group comprises one or more modified dimples forming an axially symmetric pattern about a Correction Area Centroid located on an axis of symmetry at a latitude greater than 0, where 0 represents the hemispherical pole and 90 represents the equator. The modified dimples can be altered, for example, by changing dimple coverage, dimple diameter, dimple depth, dimple edge angle, dimple volume, dimple cross-sectional shape, and/or dimple plan shape. Optionally, the dimples have a catenary cross-sectional shape and the modified dimples are altered by changing the shape factor and/or chord depth. Such modifications preferably produce a golf ball that flies more consistently regardless of orientation when struck than a corresponding golf ball without such modifications.

A golf ball includes a center, a mid layer, a cover and dimples. The cover has a Shore D hardness of 30-50. The golf ball has an amount of compressive deformation of 3.0-5.0 mm. The ball meets a mathematical formula (I):

0.80((L1+L2)/2)0.95(I).

L1 represents a ratio of a lift coefficient relative to a drag coefficient, the lift coefficient and the drag coefficient being measured under conditions of a Reynolds number of 1.29010.sup.5 and a spin rate of 2820 rpm. L2 represents a ratio of a lift coefficient relative to a drag coefficient, the lift coefficient and the drag coefficient being measured under conditions of a Reynolds number of 1.77110.sup.5 and a spin rate of 2940 rpm.

In a golf ball having a core, an intermediate layer and a cover, the intermediate layer-encased sphere has a higher surface hardness than the ball. The core hardness profile in the ball is designed such that the core surface has a Shore C hardness value which is at least 27 higher than the Shore C hardness value at the core center, and the surface areas A to F calculated from hardness differences between positions located at specific distances in the core and differences between the specific distances satisfy a specific formula. This golf ball has an excellent flight performance when struck by skilled amateur golfers and professionals, and also has a good controllability on shots with an iron.

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 low frequency periodic functions along a closed simple path. In addition, the present invention provides methods for designing dimples having a plan shape defined by a low frequency periodic function along a closed simple path.

Golf balls according to the present invention achieve flight symmetry and overall satisfactory flight performance due to a dimple surface volume ratio that is equivalent between opposing hemispheres despite the use of different dimple geometries, different dimple arrangements, and/or different dimple counts on the opposing hemispheres.

A golf ball having a core and a cover that is formed of a resin composition which includes (A) a polyurethane or a polyurea and (B) a styrenic resin material, when dropped from a height of 3 m and made to collide with a metal plate, has velocities 200 ms before and 200 ms after contact that satisfy the condition: (incident velocity)(rebound velocity)0.80 m/s. The ball has a good controllability on approach shots without a loss in the distance achieved on shots with a driver, and thus is particularly useful to professional golfers and skilled amateurs.

The present invention is directed to golf balls having improved aerodynamic performance due, at least in part, to the alteration of the dimple surfaces. In particular, the present invention relates to a golf ball that includes at least a portion of its dimples having circular perimeters and dimple profiles having a concentric groove or a non-concentric groove on the surface of the dimple. The golf ball dimples of the present invention provide golf ball surfaces having unique appearances, while maintaining ideal aerodynamic characteristics.

In a golf ball having a two-layer core consisting of an inner core layer and an outer core layer, an intermediate layer and a cover, the core is formed primarily of a base rubber, the diameter of the inner core layer is at least 21 mm, the intermediate layer and cover are each formed primarily of a resin material, the overall core has a specific hardness profile, the inner core layer has a higher specific gravity than the outer core layer, and the sphere consisting of the core encased by the intermediate layer has a higher surface hardness than the ball. This golf ball has a high initial velocity at impact while holding down the spin rate on full shots with a driver or long iron, enabling a good distance to be achieved. The ball also has a good controllability in the short game.