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US 11,938,379 B2Granted
Golf balls having cores with increased hardness gradient
AssigneeAcushnet Company
InventorsErin McDermott, Manjari Kuntimaddi, Dennis Britton
Life of this patent
Estimating the term…
Abstract
Golf balls having cores with increased hardness gradients are provided. The cores have an increased “positive” hardness gradient (or a “hard-to-soft” hardness) where the outer surface of the core is harder than the center. The increased positive hardness gradient can be achieved by introducing a water-releasing agent into the core rubber formulation during the curing process. The resulting golf balls have reduced spin and sufficient impact durability.
Claims17
A golf ball, comprising:
- a solid core having an outer surface and a geometric center, wherein the solid core is formed from a rubber composition cured under heat, the rubber composition comprising:
- a base rubber comprising a mixture of polybutadiene and ethylene-propylene-diene rubber,
- an organic peroxide comprising dimethyl tertbutyl peroxide, dicumyl peroxide, or combinations thereof,
- a cross-linking co-agent comprising a zinc salt of an acrylate, diacrylate, methacrylate, or dimethacrylate,
- calcium sulfate dihydrate present in the rubber composition in an amount of about 1 phr to about 3.9 phr,
- wherein the geometric center and the outer surface each has a hardness and the hardness of the geometric center ranges from about 45 Shore C to about 65 Shore C and the hardness of the outer surface ranges from about 80 Shore C to about 100 Shore C, and
- wherein the hardness of the outer surface is greater than the hardness of the geometric center to define a positive hardness gradient of at least 30 Shore C units;
- and
- a cover layer surrounding the core.
6 more elements
A golf ball, comprising:
- a solid core having an outer surface and a geometric center, wherein the solid core is formed from a rubber composition cured under heat, the rubber composition comprising:
- a base rubber comprising a mixture of two or more polybutadiene rubbers and ethylene-propylene-diene rubber,
- an organic peroxide,
- a cross-linking co-agent comprising zinc diacrylate,
- calcium sulfate dihydrate present in the rubber composition in an amount of about 1 phr to about 3.9 phr,
- wherein the geometric center and the outer surface each has a hardness and the hardness of the geometric center ranges from about 40 Shore C to about 70 Shore C and the hardness of the outer surface ranges from about 75 Shore C to about 105 Shore C,
- wherein the hardness of the outer surface is greater than the hardness of the geometric center to define a positive hardness gradient of 30 Shore C units to 50 Shore C units,
- wherein the amount of calcium sulfate dihydrate and the number of waters of hydration are related to the positive hardness gradient, according to equation (I):
- 2
- ≤
- W
-
- R
-
- A
- C
- *
- W
-
- R
-
- A
- W
-
- O
-
- H
- 1
- -
- 1
- H
- Gr
- ≤
- 1
-
- 5
- (
- I
- )
- where WRAC represents the amount of calcium sulfate dihydrate in parts per hundred;
- HGr represents the positive hardness gradient (Shore C);
- and WRAWOH represents the number of waters of hydration in the calcium sulfate dihydrate;
- an inner cover layer surrounding the core;
- and
- an outer cover layer disposed about the inner cover layer.
42 more elements
A golf ball, comprising:
- a solid core having an outer surface and a geometric center, wherein the solid core is formed from a rubber composition cured under heat, the rubber composition comprising:
- a base rubber comprising a mixture of two or more polybutadiene rubbers and ethyl ene-propyl ene-di ene rubber,
- dicumyl peroxide,
- zinc diacrylate,
- calcium sulfate dihydrate in an amount of about 1 phr to about 3.75 phr,
- an additive selected from zinc pentachlorothiophenol, zinc oxide, barium sulfate, or combinations thereof,
- wherein the geometric center and the outer surface each has a hardness and the hardness of the geometric center ranges from about 40 Shore C to about 70 Shore C and the hardness of the outer surface ranges from about 75 Shore C to about 105 Shore C,
- wherein the hardness of the outer surface is greater than the hardness of the geometric center to define a positive hardness gradient of at least 34 Shore C units;
- an inner cover layer surrounding the core;
- and
- an outer cover layer disposed about the inner cover layer.
8 more elements
Dependencies are inferred from the claim text.