GOLF BALL HAVING A HOLLOW CENTER
A golf ball includes a thermoset spherical inner core shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center; a thermoset outer core layer formed about the shell layer; and an inner and outer cover layer formed about the outer core layer. The inner cover includes an ionomeric material and the outer cover layer includes a polyurea or a polyurethane having a hardness less than the inner cover layer. 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, and the outer core layer has a second hardness gradient different from the first.
1 . A golf ball comprising a hollow core, the golf ball comprising:
a spherical inner core shell layer comprising a first thermoset rubber composition, the shell layer having an outer surface, an inner surface, and an inner diameter to define a hollow center;
an outer core layer disposed about the shell layer, the outer core layer comprising a second thermoset material;
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 0.51 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, and the outer core layer has a second hardness gradient different from the first.
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 2 to 25 Shore C.
7 . The golf ball of claim 1 , wherein the second hardness gradient is a positive hardness gradient of about 3 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;
an outer core layer comprising a second thermoset material;
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 material 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 material hardness of less than about 60 Shore D;
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 10 to 25 Shore C to define a first hardness gradient, and the thermoset outer core layer has a second hardness gradient different from the first.
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 2 to 25 Shore C.
13 . The golf ball of claim 10 , wherein the second hardness gradient is a positive hardness gradient of about 3 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;
an outer core layer comprising a second thermoset material;
a thermoset intermediate core layer disposed between the shell layer and the outer core layer, the intermediate core layer comprising a third thermoset rubber composition different from the first and the second;
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 10 to 25 Shore C to define a first hardness gradient, and at least one of the thermoset outer core layer or thermoset intermediate core layer has a hardness gradient different from the first.
15 . The golf ball of claim 14 , wherein the second hardness gradient is about 0 Shore C.
16 . The golf ball of claim 14 , wherein the second hardness gradient is a negative hardness gradient of about 2 to 25 Shore C.
17 . The golf ball of claim 14 , wherein the second hardness gradient is a positive hardness gradient of about 3 to 10 Shore C.