GOLF BALL HAVING A HOLLOW CENTER
A golf ball including a spherical inner core shell layer formed from a thermoset rubber composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center. A thermoplastic outer core layer is formed about the shell layer. An optional inner cover layer is formed about the outer core layer, the inner cover including an ionomeric material. An outer cover layer is formed over the core or option inner cover layer, the outer cover including a polyurea or a polyurethane and having a second hardness less than the optional inner cover layer. The hollow center has a diameter of about 0.15 to 1.1 inches. The shell layer has a surface hardness greater than its inner surface hardness by about 3 to 25 Shore C to define a hardness gradient, and the thermoplastic outer core layer has a second hardness gradient.
1 . A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer formed from a first thermoset rubber composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
a thermoplastic outer core layer disposed about the shell layer;
an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a first hardness; and
an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a second hardness less than the first;
wherein the hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 3 to 25 Shore C to define a first hardness gradient, and the thermoplastic outer core layer has a second hardness gradient.
2 . The golf ball of claim 1 , wherein the shell layer has a surface hardness greater than about 55 Shore C.
3 . The golf ball of claim 1 , wherein the spherical inner core shell layer has a coefficient of restitution less than about 0.700 when measured at an incoming velocity of 125 ft/s.
4 . The golf ball of claim 1 , wherein the outer core layer has a coefficient of restitution, measured at an incoming velocity of 125 ft/s, higher than the coefficient of restitution, measured at an incoming velocity of 125 ft/s, of the inner core shell layer by 10-50%.
5 . The golf ball of claim 1 , wherein the second hardness gradient is about 0 Shore C.
6 . The golf ball of claim 1 , wherein the second hardness gradient is a negative hardness gradient of about 1 to 10 Shore C.
7 . The golf ball of claim 1 , wherein the second hardness gradient is a positive hardness gradient of about 1 to 10 Shore C.
8 . The golf ball of claim 1 , wherein the inner cover has a hardness of greater than about 60 Shore D and the outer cover layer has a hardness of less than about 60 Shore D.
9 . The golf ball of claim 1 , wherein the golf ball has a first volume and the hollow center has a second volume that is about 2% to 30% of the first volume.
10 . A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer formed from a first thermoset rubber composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
a thermoplastic outer core layer;
a thermoplastic intermediate core layer disposed between the shell layer and the outer core layer;
an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a first hardness; and
an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a second hardness less than the first;
wherein the hollow center has a diameter of about 0.15 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 3 to 25 Shore C to define a first hardness gradient, and the thermoplastic outer core layer or the thermoplastic intermediate core layer has a second hardness gradient.
11 . The golf ball of claim 10 , wherein the second hardness gradient is about 0 Shore C.
12 . The golf ball of claim 10 , wherein the second hardness gradient is a negative hardness gradient of about 1 to 10 Shore C.
13 . The golf ball of claim 10 , wherein the second hardness gradient is a positive hardness gradient of about 1 to 10 Shore C.
14 . A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer formed from a first thermoset rubber composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
a thermoplastic outer core layer;
a thermoset intermediate core layer disposed between the shell layer and the outer core layer, the intermediate core layer comprising a second thermoset rubber composition different from the first;
an inner cover layer disposed about the outer core layer, the inner cover comprising an ionomeric material and having a hardness greater than about 60 Shore D; and
an outer cover layer disposed about the inner cover layer, the outer cover comprising a polyurea or a polyurethane and having a hardness less than about 60 Shore D;
wherein the hollow center has a diameter of about 0.51 to 1.1 inches, the shell layer has a surface hardness greater than an inner surface hardness by about 3 to 25 Shore C to define a first hardness gradient, the thermoplastic outer core layer has a second hardness gradient, and the thermoset intermediate core layer has a third hardness gradient different from the first or second hardness gradients.
15 . The golf ball of claim 14 , wherein the shell layer has a surface hardness greater than about 55 Shore C.
16 . The golf ball of claim 14 , wherein the spherical inner core shell layer has a coefficient of restitution less than about 0.700 when measured at an incoming velocity of 125 ft/s.
17 . The golf ball of claim 14 , wherein the outer core layer has a coefficient of restitution, measured at an incoming velocity of 125 ft/s, higher than the coefficient of restitution, measured at an incoming velocity of 125 ft/s, of the inner core shell layer by 10-50%.
18 . The golf ball of claim 14 , wherein the second hardness gradient is about 0 Shore C.
19 . The golf ball of claim 14 , wherein the second hardness gradient is a negative hardness gradient of about 3 to 25 Shore C.
20 . The golf ball of claim 14 , wherein the second hardness gradient is a positive hardness gradient of about 3 to 25 Shore C.
21 . The golf ball of claim 14 , wherein the golf ball has a first volume and the hollow center has a second volume that is about 2% to 30% of the first volume.