Golf club head

Abstract

A golf club head with an increased moment of inertia (MOI) about the X axis and the Z axis. Generally, the MOI about the Z axis is at least about 4400 g·cm 2 and the MOI about the X axis is at least about 2500 g·cm 2 . The radius of the bulge of the club face is increased while the radius of the roll is reduced to compensate for the gear effect produced by the increased MOIs. The bulge curvature is generally between about 0.016 cm −1 and about 0.028 cm −1 , and the roll curvature is between about 0.033 cm −1 and about 0.066 cm −1 . The roll curvature is greater than the bulge curvature.

We claim: 
     
         1 . A golf club head comprising:
 a club head body having an external surface with a heel portion, a toe portion, a crown, a sole, and a face;   wherein the face includes:
 a front side and a back side that define a variable face thickness; 
 a bulge curvature; 
 a roll curvature; and 
 wherein the bulge curvature is greater than 0 cm −1  and less than about 0.027 cm −1  and the inverse of the bulge curvature is greater than the inverse of the roll curvature by at least 7.62 cm; and 
 wherein the golf club head has a moment of inertia about the CG Z axis, I zz , wherein I xx  is at least about 3000 g·cm 2  and I zz  is greater than I xx , 
   wherein the bulge curvature defines a bulge radius, R Bulge , relates to I zz  such that R Bulge  is about 0.00505*I zz +13.95.   
     
     
         2 . The golf club head of  claim 1 , wherein a ratio of the bulge curvature divided by the roll curvature is between about 0.28 and about 0.75 at a roll curvature between about 0.033 cm −1  and about 0.066 cm −1 . 
     
     
         3 . The golf club head of  claim 2 , wherein the ratio of the bulge curvature divided by the roll curvature is between about 0.33 and about 0.75 when the I zz  is between about 4400 g·cm 2  and about 5000 g·cm 2 . 
     
     
         4 . The golf club head of  claim 2 , wherein the ratio of the bulge curvature divided by the roll curvature is between about 0.31 and about 0.67 when the I zz  is between about 5000 g·cm 2  and about 5500 g·cm 2 . 
     
     
         5 . The golf club head of  claim 2 , wherein the ratio of the bulge curvature divided by the roll curvature is between about 0.28 and about 0.61 when the I zz  is between about 5500 g·cm 2  and about 6000 g·cm 2 . 
     
     
         6 . The golf club head of  claim 2 , wherein the ratio of the bulge curvature divided by the roll curvature is between about 0.28 and about 0.56 when the I zz  is about 6000 g·cm 2 . 
     
     
         7 . The golf club head of  claim 1 , wherein the bulge curvature is between about 0.016 cm −1  and about 0.027 cm −1 . 
     
     
         8 . The golf club head of  claim 1 , wherein the roll curvature is between about 0.033 cm −1  and about 0.066 cm −1 . 
     
     
         9 . The golf club head of  claim 1 , wherein the ratio of the bulge curvature divided by the roll curvature is less than about 0.84 at a roll curvature of about 0.049 cm −1 . 
     
     
         10 . The golf club head of  claim 1 , wherein the bulge curvature and the roll curvature are constant over the face of the golf club head. 
     
     
         11 . A golf club comprising:
 a shaft with a golf club head coupled thereto;   the club head body comprising:   an external surface with a heel portion, a toe portion, a crown, a sole, and a face;   a moment of inertia about the CG Z axis, I zz ; and   a moment of inertia about the CG X axis, I xx , wherein I xx  is at least about 3000 g·cm 2  and wherein I zz  is greater than
 wherein the face includes: 
 a front side and a back side that define a variable face thickness; 
 a bulge curvature and a roll curvature; and 
 wherein the ratio of the bulge curvature divided by the roll curvature, R C , satisfies the following: 
   
       
         
           
             
               
                 1 
                 
                   
                     ( 
                     
                       5.6 
                       × 
                       
                         10 
                         
                           - 
                           4 
                         
                       
                       * 
                       
                         I 
                         ZZ 
                       
                     
                     ) 
                   
                   + 
                   0.222 
                 
               
               ≤ 
               
                 R 
                 C 
               
               ≤ 
               
                 
                   1 
                   
                     
                       ( 
                       
                         2.8 
                         × 
                         
                           10 
                           
                             - 
                             4 
                           
                         
                         * 
                         
                           I 
                           ZZ 
                         
                       
                       ) 
                     
                     + 
                     0.111 
                   
                 
                 . 
               
             
           
         
       
     
     
         12 . The golf club of  claim 11  wherein the ratio of the bulge curvature divided by the roll curvature, R C , is greater than about 0.28 and less than about 0.75. 
     
     
         13 . The golf club of  claim 11  wherein the roll curvature is between about 0.033 cm −1  and about 0.066 cm −1 , and wherein the bulge curvature is greater than 0 cm −1  and less than about 0.027 cm −1  and the inverse of the bulge curvature is greater than the inverse of the roll curvature by at least 7.62 cm.