Metal wood club

Abstract

A golf club head having indentions provided in a transition zone of the club head. The transition zone of the club head is provided between a first portion of the club head having a first thickness and a second portion of the club head having a second thickness. The indentations are provided at non-structural areas to reduce the weight of the transition zone. The mass can then be moved to a more desirable location in the club head, thereby improving the playability characteristics of the club head, including center of gravity and moment of inertia. The transition zone may be provided at different areas of the club head including the hosel, between the face and the body of the club head and between the crown and sole of the club head. The indentations are provided with the desired height, length and width to achieve weight reduction without effecting the structural integrity of the club head.

We claim: 
     
         1 . A golf club head comprising:
 a first club portion having a first thickness t 1 ;   a second club portion having a second thickness t 2 ;   a transition zone having a mass and connecting the first club portion to the second club portion; and   at least two indentations provided in the transition zone, at least one of the indentations having a maximum depth d, where d is about 40% to about 60% of the first thickness t 1 ,   wherein the club head is hollow with a volume of at least 250 cubic centimeters and the indentations are provided on an interior nonvisible surface of the hollow portion of the club head, and   wherein the indentations reduce the mass of the transition zone by at least 0.5%.   
     
     
         2 . The golf club head of  claim 1 , wherein the indentations reduce the mass of the transition zone by about 10% to about 40%. 
     
     
         3 . The golf club head of  claim 1 , wherein the indentations reduce the mass of the transition zone without the indentations by about 0.5 g to about 10 g. 
     
     
         4 . The golf club head of  claim 3 , wherein the indentations reduce the mass by about 2 g to about 8 g. 
     
     
         5 . The golf club head of  claim 3 , wherein the maximum depth d is between about 0.5 mm to about 2 mm. 
     
     
         6 . The golf club head of  claim 3 , wherein the indentations have lengths ranging from about 1 mm to about 20 mm and a maximum width w ranging from about 0.5 mm to about 5 mm. 
     
     
         7 . The golf club head of  claim 3 , wherein a minimum spacing distance s between the indentations is about 1 mm to about 10 mm. 
     
     
         8 . The golf club head of  claim 3 , wherein the indentations are formed by machining or chemical etching. 
     
     
         9 . The golf club head of  claim 3 , wherein the indentations are formed by casting. 
     
     
         10 . The golf club head of  claim 1 , wherein the first portion of the club head is a crown portion of the club head, the second portion of the club head is a sole portion of the club head, and the transition zone is provided between the crown portion and the sole portion of the club head. 
     
     
         11 . The golf club head of  claim 10 , wherein the center of gravity is provided below a horizontal center line of the club head by at least 1 mm. 
     
     
         12 . The golf club head of  claim 1 , wherein the transition zone is provided proximate a face insert of the club head. 
     
     
         13 . The golf club head of  claim 12 , wherein the first portion of the club head is a face insert, the second portion of the club head is a body of the club head, and the transition zone is provided between the face insert and the body of the club head. 
     
     
         14 . The golf club head of  claim 13 , wherein the center of gravity is moved toward a rear of the club head by at least 0.5 mm and lowered in the club head by at least about 0.2 mm. 
     
     
         15 . The golf club head of  claim 13 , wherein the face insert is forged and the body of the club head is cast. 
     
     
         16 . The golf club head of  claim 13 , wherein the face insert further comprises:
 a central zone having a first flexural stiffness; and   an intermediate zone concentric with the central zone, the intermediate zone having a second flexural stiffness, and wherein the first flexural stiffness is higher than the second flexural stiffness.   
     
     
         17 . The golf club head of  claim 1 , wherein the moment of inertia about the vertical axis though the center of gravity of the club head, I yy , is about 2500 g·cm 2  to about 6000 g·cm 2 . 
     
     
         18 . The golf club head of  claim 1 , wherein the moment of inertia about the vertical axis though the center of gravity of the club head, I xx , is about 1500 g·cm 2  to about 5000 g·cm 2 . 
     
     
         19 . The golf club head of  claim 1 , wherein the moment of inertia about the vertical axis though the center of gravity of the club head, I zz , is about 1500 g·cm 2  to about 6000 g·cm 2 . 
     
     
         20 . The golf club head of  claim 1 , wherein the mass removed from the transition zone is thereafter provided in the perimeter of the club head.