Medium gradient dual core golf ball
View Patent ↗A golf ball includes an inner core layer having a first surface hardness and a geometric center hardness. The center hardness is less than the first surface hardness to define a first positive hardness gradient of about 1 to 12 Shore C. An outer core layer has a second surface hardness. A cover layer is formed over the outer core layer. The second outer surface hardness is greater than the geometric center hardness to define a second positive hardness gradient of about 12 to 22 Shore C.
1. A golf ball comprising:
an inner core layer having a first surface hardness and a geometric center hardness, the center hardness being less than the first surface hardness to define a first positive hardness gradient of about 1 to 12 Shore C;
an outer core layer having a second surface hardness; and
a cover layer disposed about the outer core layer;
wherein the second outer surface hardness is greater than the geometric center hardness to define a second positive hardness gradient of about 12 to 22 Shore C, and wherein the first hardness gradient has a first slope, S 1 , and the second hardness gradient has a second slope, S 2 , and a ratio of S 2 to S 1 is about 10.0 or greater.
2. The golf ball of claim 1 , wherein the geometric center hardness is about 65 to 75 Shore C and the second surface hardness is greater than about 85 Shore C.
3. The golf ball of claim 1 , wherein the first hardness gradient is about 3 to 10 Shore C.
4. The golf ball of claim 3 , wherein the first hardness gradient is about 4 to 9 Shore C.
5. The golf ball of claim 1 , wherein the first hardness gradient of about 1 to 5 Shore D.
6. The golf ball of claim 1 , wherein the cover layer comprises a polyurea, a polyurethane, or a hybrid thereof.
7. The golf ball of claim 1 , wherein the cover layer comprises an inner cover layer and an outer cover layer.
8. The golf ball of claim 7 , wherein the inner cover layer comprises an ionomer and the outer cover layer comprises a polyurethane, the inner cover layer being harder than the outer cover layer.
9. The golf ball of claim 1 , wherein the second positive hardness gradient is about 13 to 21 Shore C.
10. The golf ball of claim 9 , wherein the second positive hardness gradient is about 14 to 20 Shore C.
11. The golf ball of claim 10 , wherein the second positive hardness gradient is about 8 to 13 Shore D.
12. The golf ball of claim 1 , wherein the ratio of S 2 to S 1 is from about 15.0 to about 20.0.
13. The golf ball of claim 1 , wherein an angle between an intersection of linear regression fits of the first and second hardness gradients, θ, is about 90° or greater, wherein θ is defined by the equation:
θ
=
180
-
(
180
π
(
tan
-
1
(
S
2
)
-
tan
-
1
(
S
1
)
)
)
.
14. The golf ball of claim 13 , wherein θ is about 100° or greater.
15. The golf ball of claim 14 , wherein θ is about 110° or greater.
16. The golf ball of claim 15 , wherein θ is about 120° or greater.
17. A golf ball comprising:
an inner core layer having a first surface hardness of about 75 to 79 Shore C and a geometric center hardness, the center hardness being about 69 to 73 Shore C and less than the first surface hardness to define a first positive hardness gradient of about 5 to 9 Shore C, the first positive hardness gradient having a first slope S 1 ;
an outer core layer having a second surface hardness of about 86 to 91 Shore C; and
a cover layer disposed about the outer core layer;
wherein the second outer surface hardness is greater than the geometric center hardness to define a second positive hardness gradient of about 16 to 19 Shore C, the second positive hardness gradient having a second slope S 2 such that a ratio of S 2 to S 1 is about 10.0 or greater; and wherein the inner core layer comprises an antioxidant and the outer core layer is substantially free from antioxidant.