Multiple-piece golf ball

Abstract

A multiple-piece golf ball in accordance with the present invention includes a core located in the center of the golf ball, at least two intermediate layers surrounding the core, and a cover further surrounding the intermediate layers. The golf ball has a spherical zone having a bulk specific gravity of about 0.7 or less, the spherical zone having a radius of 18.5 mm with the same center point as the golf ball. The moment of inertia of this golf ball is preferably about 85 g·cm 2 or more.

What is claimed is: 
     
         1 . A multiple-piece golf ball comprising:
 a core located in a center of the golf ball;   at least two intermediate layers surrounding the core; and   a cover further surrounding the intermediate layers,   wherein the golf ball has a spherical zone having a bulk specific gravity of up to about 0.7, the spherical zone having a radius of 18.5 mm with the same center point as the golf ball.   
     
     
         2 . The golf ball according to  claim 1 , wherein the core includes a hollow part in a center thereof and a surrounding layer surrounding the hollow part. 
     
     
         3 . The golf ball according to  claim 2 , wherein at least either one of the innermost intermediate layer of the at least two intermediate layers and the surrounding layer has a bulk specific gravity of up to about 0.8. 
     
     
         4 . The golf ball according to  claim 2 , wherein the hollow part has a spherical shape having a diameter smaller than about 5 mm. 
     
     
         5 . The golf ball according to  claim 2 , wherein the surrounding layer is a foam. 
     
     
         6 . The golf ball according to  claim 2 , wherein an intermediate layer located in the spherical zone of the at least two intermediate layers is a foam. 
     
     
         7 . The golf ball according to  claim 2 , wherein the surrounding layer has a space not filled with a material. 
     
     
         8 . The golf ball according to  claim 2 , wherein an intermediate layer located in the spherical zone of the at least two intermediate layers has a space not filled with a material. 
     
     
         9 . The golf ball according to  claim 1 , wherein the core is a foam. 
     
     
         10 . The golf ball according to  claim 1 , wherein the core has a space not filled with a material.