Golf ball and method of manufacture

Patent metadata

Field	Value
Publication number	US-9849346-B2
Application number	US-201615163137-A
Country	US
Kind code	B2
Filing date	May 24, 2016
Priority date	Jun 23, 2015
Publication date	Dec 26, 2017
Grant date	Dec 26, 2017

Abstract

In a golf ball having a core and a cover, the core is formed of a rubber composition, has center and surface portions which are unfoamed regions and has an intermediate portion containing a foamed region. The core is produced by charging the rubber composition, which contains a blowing agent, into a first curing mold and curing under given conditions, then removing the molded rubber material in a semi-cured state from the first mold, transferring the semi-cured material to a second curing mold and curing under given conditions. The foamed region of the core deforms by a certain degree at the time of impact, decreasing the radius of gyration of the ball and enabling a lower spin rate to be achieved. The decrease in resilience due to expansion of the molded material can be held to a minimum.

First claim

The invention claimed is:

1. A golf ball comprising a core and a cover of one or more layer encasing the core, wherein the core is formed of a rubber composition comprising a base rubber, a co-crosslinking agent, an organic peroxide and a blowing agent, has a center portion and a surface portion that are unfoamed regions, and has an intermediate portion containing a foamed region.

2. The golf ball of claim 1 , wherein the blowing agent has a decomposition temperature which is lower than a one-minute half-life temperature of the organic peroxide.

3. The golf ball of claim 1 , wherein when the core is cut hemispherically and the core cross-section is viewed from the center to the surface of the core, the foamed region is concentrically formed as a ring centered on a center of the core.

4. The golf ball of claim 1 wherein the foamed region is formed to a position centered at a distance of 30 to 90% of the core radius from a center of the core as the origin.

5. The golf ball of claim 1 , wherein the foamed region and the unfoamed regions have respective specific gravities such that the specific gravity of the foamed region is at least 5% lower than the specific gravity of the unfoamed regions.

6. The golf ball of claim 1 , wherein the material in the foamed region has an average pore size of less than 500 μm.

7. A method of manufacturing a golf ball having a core and a cover of one or more layer encasing the core, which core is a cured and molded material produced using a first curing mold having a cavity with an inside diameter ø 1 and a second curing mold having a cavity with an inside diameter ø2 such that ø1<ø2, the method comprising:
(a) a first curing step of charging a rubber composition containing a blowing agent into the first curing mold and applying heat and pressure under given temperature and time conditions; and
(b) a second curing step of removing the molded rubber material in a semi-cured state from the first curing mold following the first curing step, transferring the semi-cured material to the second curing mold and applying heat and pressure under given temperature and time conditions,
wherein the cured and molded material has a center portion and a surface portion that are unfoamed regions and has an intermediate portion containing a foamed region.

8. The manufacturing method of claim 7 , wherein the curing time in the first curing step is in the range of 33 to 60% of the sum of the curing time in the first curing step and the curing time in the second curing step.

Assignees

• Bridgestone Sports Co Ltd

Inventors

• Nakajima Tsuyoshi

Classifications

• A63B37/0082

  Density; Specific gravity · CPC title

• B29K2509/00

  Use of inorganic materials not provided for in groups {B29K2503/00 - B29K2507/00,} as filler · CPC title

• B29L2031/546

  Golf balls · CPC title

• B29K2105/0044

  Stabilisers, e.g. against oxydation, light or heat · CPC title

• A63B45/00

  Apparatus or methods for manufacturing balls (working of plastics or substances in a plastic state B29) · CPC title