Dual-core comprising negative gradient center and positive gradient outer core layer

• US 8,137,214 B2
• Filed: 12/22/2010
• Issued: 03/20/2012
• Est. Priority Date: 07/03/2007
• Status: Active Grant

• Current Assignee: Acushnet Company (FILA Holdings Corp.)
• Original Assignee: Acushnet Company (FILA Holdings Corp.)
• Inventors: Sullivan, Michael J., Comeau, Brian, Ladd, Derek A., Cooper, Scott
• Primary Examiner(s): Gorden, Raeann
• Application Number:
  US12/976,197
• Publication Number:
  US 20110092313A1
• Time in Patent Office: 454 Days
• Field of Search: 473/376, 473/373, 473/374
• US Class Current: 473/376
• CPC Class Codes: A63B 37/0003 Golf balls
• CPC Class Codes: A63B 37/0051 Materials other than polybutadienes; Constructional details
• CPC Class Codes: A63B 37/00621 Centre hardness
• CPC Class Codes: A63B 37/00622 Surface hardness
• CPC Class Codes: A63B 37/0063 Hardness gradient
• CPC Class Codes: A63B 37/0064 Diameter
• CPC Class Codes: A63B 37/06 Elastic cores

Abstract

A golf ball including an inner core having a geometric center and a first outer surface, the inner core being formed from a first substantially homogenous rubber composition, and an outer core layer formed from a second substantially homogenous rubber composition, the outer core layer having a second outer surface. An inner cover layer is formed over the core and includes an ionomeric material. An outer cover layer is formed over the inner cover layer and includes a castable polyurea or a castable polyurethane. The first outer surface has a hardness of up to about 20 Shore C less than a hardness at the geometric center to define a negative hardness gradient inner core and the second outer surface has a hardness of up to 18 Shore C greater than the geometric center hardness to define a positive gradient outer core layer and a shallow positive hardness gradient core.

Claims

1. A golf ball comprising:

an inner core having a geometric center and a first outer surface, the inner core being formed from a first substantially homogenous rubber composition;

an outer core layer formed from a second substantially homogenous rubber composition, the outer core layer having a second outer surface;

an inner cover layer disposed about the core, the inner cover comprising an ionomeric material and having a material hardness of about 60 Shore D or greater; and

an outer cover layer disposed about the inner cover layer, the outer cover comprising a castable polyurea or a castable polyurethane and having a material hardness of about 60 Shore D or less;

wherein the first outer surface has a hardness of up to about 20 Shore C less than a hardness at the geometric center to define a negative hardness gradient inner core and the second outer surface has a hardness of up to 18 Shore C greater than the geometric center hardness to define a positive hardness gradient core.

2. The golf ball of claim 1, wherein the hardness of the first outer surface is about 1 to about 15 Shore C less than the geometric center hardness to define a negative hardness gradient of about −

1 to about −

15 Shore C.

3. The golf ball of claim 2, wherein the hardness of the first outer surface is about 2 to about 12 Shore C less than the geometric center hardness to define a negative hardness gradient of about −

2 to about −

12 Shore C.

4. The golf ball of claim 1, wherein the inner core has an outer diameter of about 0.5 to about 1.40 inches.

5. The golf ball of claim 4, wherein the inner core has an outer diameter of about 0.8 to about 1.30 inches.

6. The golf ball of claim 1, wherein the hardness of the core geometric center is about 55 to 82 Shore C.

7. The golf ball of claim 6, wherein the hardness of the geometric center is about 60 to 80 Shore C.

8. The golf ball of claim 7, wherein the hardness of the geometric center is about 65 to 78 Shore C.

9. The golf ball of claim 1, wherein the hardness of the surface of the inner core is about 50 to 82 Shore C.

10. The golf ball of claim 9, wherein the hardness of the surface of the inner core is about 55 to 78 Shore C.

11. The golf ball of claim 10, wherein the hardness of the surface of the inner core is about 60 to 75 Shore C.

12. The golf ball of claim 1, wherein the core surface hardness is about 82 to 98 Shore C.

13. The golf ball of claim 1, wherein the first substantially homogenous rubber composition comprises an antioxidant-to-initiator ratio of about 0.4 or greater.

14. The golf ball of claim 1, wherein the ionomeric material comprises a Na-, Li-, or Zn-ionomer having an acid content of about 11 wt % to about 20 wt %.

15. The golf ball of claim 1, wherein the ionomeric material comprises an ionomer having an acid content of about 16 wt % or greater and a maleic-anhydride grafted metallocene-catalyzed polyolefin.

16. A golf ball comprising:

an inner core having a geometric center and a first outer surface positioned about 0.8 to about 1.3 inches from the geometric center, the inner core being formed from a first substantially homogenous rubber composition comprising an antioxidant-to-initiator ratio of about 0.5 or greater;

an outer core layer formed from a second substantially homogenous rubber composition different from the first, the outer core layer having a second outer surface positioned about 1.53 to about 1.58 inches from the geometric center;

an inner cover layer disposed about the core, the inner cover comprising an ionomer having an acid content of about 16 wt % or greater and a maleic-anhydride grafted metallocene-catalyzed polyolefin; and

an outer cover layer disposed about the inner cover layer, the outer cover comprising a castable polyurea or a castable polyurethane;

wherein the first outer surface has a hardness less than a hardness at the geometric center to define a negative hardness gradient of about −

1 to about −

15 and the second outer surface has a hardness of up to 12 Shore C greater than a hardness at an inner surface of the outer core layer to define a positive hardness gradient outer core layer.