| 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 60 Shore C to about 85 Shore C. The geometric center comprises a first hardness and the first outer surface comprises a second hardness wherein the second hardness is greater than the first hardness to define a positive hardness gradient of from about 5 Shore C to about 20 Shore C. 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 60 Shore C to about 95 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 to define a positive hardness gradient of about 20 Shore C or lower. The third hardness may be similar to the second 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 third hardness and the fourth hardness. Alternatively, the region may extend radially from about 13 mm to about 20 mm from the geometric center. Finally, the fourth hardness is greater than the first hardness to define a positive hardness gradient of about 30 Shore C or lower. In a second embodiment, the outer core layer differs from that of the first embodiment at least in that: the fourth hardness is less than the third hardness to define a negative hardness gradient of about 20 Shore C or lower; the fifth hardness is less than the third hardness and the fourth hardness; and the fourth hardness is greater than the first hardness to define a positive hardness gradient of about 18 Shore C or lower. The present invention is also directed to a golf ball having certain Shore D hardnesses as disclosed herein.
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