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 greater than the geometric center hardness to define a second positive hardness gradient of about 12 to 22 Shore C; and
a cover layer disposed about the outer core layer;
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 the second slope, S 2 , to the first slope, S 1 , is about 1.0 or greater.
2. The golf ball of claim 1 , wherein the ratio of the second slope, S 2 , to the first slope, S 1 , is about 5.0 or greater.
3. The golf ball of claim 1 , wherein the ratio of the second slope, S 2 , to the first slope, S 1 , is about 1.0 to about 10.0.
4. The golf ball of claim 3 , wherein the ratio of the second slope, S 2 , to the first slope, S 1 , is about 5.0 to about 10.0.
5. The golf ball of claim 1 , wherein the first positive hardness gradient is about 3 to 10 Shore C.
6. The golf ball of claim 5 , wherein the first positive hardness gradient is about 4 to 9 Shore C.
7. The golf ball of claim 1 , wherein the first positive hardness gradient of about 1 to 5 Shore D.
8. The golf ball of claim 1 , wherein the cover layer comprises a polyurea, a polyurethane, or a hybrid thereof.
9. The golf ball of claim 1 , wherein the cover layer comprises an inner cover layer and an outer cover layer.
10. The golf ball of claim 9 , 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.
11. The golf ball of claim 1 , wherein the second positive hardness gradient is about 13 to about 21 Shore C.
12. The golf ball of claim 11 , wherein the second positive hardness gradient is about 14 to about 20 Shore C.
13. The golf ball of claim 12 , wherein the second positive hardness gradient is about 8 to about 13 Shore D.
14. The golf ball of claim 1 , wherein the geometric center hardness is from about 65 to about 75 Shore C and the second surface hardness is about 85 Shore C or greater.
15. The golf ball of claim 1 , wherein an angle between an intersection of linear regression fits of the first and second positive 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
)
)
)
.
16. The golf ball of claim 15 , wherein θ is about 100° or greater.
17. The golf ball of claim 16 , wherein θ is about 110° or greater.
18. The golf ball of claim 17 , wherein θ is about 120° or greater.