| 摘要 |
The present invention is directed to an improved multi-layered core golf ball wherein each core layer comprises its own specific hardness gradient (positive, negative or a combination) in addition to an overall specific hardness gradient from one core layer to the next. In a first embodiment, the golf ball comprises a two layer core and a cover disposed about the two layer core. The two layer core comprises an inner core layer and an outer core layer disposed about the inner core layer. The inner core layer comprises a geometric center and a first outer surface. The inner core layer is formed from a substantially homogenous formulation, comprises a diameter of about 30 mm or lower, and has a plurality of hardnesses of from about 50 Shore C to about 80 Shore C. The geometric center comprises a first hardness and the first outer surface comprises a second hardness, wherein the first hardness is greater than the second hardness to define a negative hardness gradient about 20 Shore C or less. The outer core layer comprises an inner surface and a second outer surface. The outer core layer is formed from a substantially homogenous formulation, comprises a thickness of about 10 mm or lower, and has a plurality of hardnesses of from about 50 Shore C to about 90 Shore C. The inner surface comprises a third hardness and the second outer surface comprises a fourth hardness, wherein the fourth hardness is greater than the third hardness. The outer core layer further comprises a fifth hardness disposed between the inner surface and the second outer surface in a region extending between about 10% and about 90% of the distance from the inner surface to the second outer surface, wherein the fifth hardness is greater than the first hardness, the third hardness and the fourth hardness. Finally, the fourth hardness is greater than the first hardness to define a two layer core having a positive hardness gradient of less than about 20 Shore C. In a second embodiment, the dual layer core differs from that of the first embodiment at least in that: The outer core has a plurality of hardnesses of from about 50 Shore C to about 80 Shore C, the fifth hardness is greater than the third hardness and the fourth hardness and similar to the first hardness; and the fourth hardness is less than the first hardness to define a two layer core having a negative hardness gradient of less than about 10 Shore C or the fourth hardness is less than the first hardness to define a two layer core having a negative hardness gradient of less than about 7 Shore C. The present invention is also directed to a golf ball having certain Shore D hardnesses as disclosed herein.
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