Golf club head having a high coefficient of restitution and method of making it

Abstract

A golf club head is formed of an alpha-beta titanium alloy body and a beta-type titanium alloy striking plate. The sole and crown of the club head are thin-walled and the striking plate transitions from a 1.7 mm central region to a 1.2 mm periphery adjacent the sole and crown junctions. The measured coefficient of restitution for this club bead is a least 0.90.

We claim:  
     
         1 . A golf club head having a loft angle, comprising: 
 a hollow body having a crown, a sole, and a front striking plate located at the front of said hollow body;    said crown having a thickness of less than about 0.8 mm for at least a crown transition distance of about 20 mm measured rearwardly from a junction of said crown and striking plate;    said sole having a thickness of less than about 1.0 mm for at least a sole transition distance of about 20 mm measured rearwardly from a junction of said sole and striking plate; and    said striking plate having a thickness of less than about 2.2 mm, said striking plate formed of a material having a hardness of at least 30 HRC and a percent elongation of at least 7%, said material having a density less than about 5 g/cc;    wherein said golf club head has a coefficient of restitution of at least about 0.85 if said loft angle exceeds 12 degrees and at least about 0.87 if said loft angle is 12 degrees or less.    
     
     
         2 . The golf club head of  claim 1 , wherein: 
 said thickness of said crown is uniform and about 0.7 mm;    said thickness of said sole is about 0.9 mm; and    said thickness of said striking plate is centrally located on said striking plate and has a maximum value of about 1.7 mm.    
     
     
         3 . The golf club head of  claim 1 , wherein said striking plate comprises beta-type titanium alloy.  
     
     
         4 . The golf club head of  claim 3 , wherein said striking plate is formed of a titanium alloy comprising by weight about 4% aluminum, 20% vanadium, and 1% tin.  
     
     
         5 . The golf club head of  claim 3 , wherein said striking plate is formed of a titanium alloy comprising by weight about 4% aluminum, 16% vanadium, and 6% chromium.  
     
     
         6 . The golf club head of  claim 3 , wherein said striking plate is formed of a titanium alloy comprising by weight about 3% aluminum, 8% vanadium, 6% chromium, 4% molybdenum, and 4% zirconium.  
     
     
         7 . The golf club head of  claim 1 , wherein said striking plate is formed of a titanium alloy comprising by weight about 4.5% aluminum, 2% molybdenum, and 3% vanadium.  
     
     
         8 . The golf club head of  claim 1 , wherein said striking plate has a height of at least about 40 mm.  
     
     
         9 . The golf club head of  claim 1 , wherein the striking plate's periphery has a thickness that is about 0.5 mm less than thickness at the striking plate's geometric center.  
     
     
         10 . The golf club head of  claim 1 , and further comprising a weight member having a mass between 15 and 25 grams, such that the club head has a total mass between about 180 and 200 grams.  
     
     
         11 . A metal golf club head, comprising: 
 a body having a crown and a sole;    a striking plate, said crown and said sole integrally cast to define a front opening and said striking plate being welded thereto;    said crown having a substantially constant first thickness of about 0.7 mm, said sole having a substantially constant second thickness of about 0.9 mm, and said striking plate having a third thickness of about 1.7 mm, said third thickness of said striking plate being centrally located and about 0.5 mm thicker than a peripheral thickness of said striking plate that is located radially outward adjacent the weld joint at said front opening; and    said striking plate formed of a titanium alloy substantially comprising by weight about 4% aluminum, 20% vanadium, and 1% tin;    wherein said golf club head has a coefficient of restitution of at least about 0.89.    
     
     
         12 . The metal golf club head of  claim 11 , wherein said sole has a weight member adding about 20 grams, such that the club head has a total mass of about 190 grams.  
     
     
         13 . A method of manufacturing a golf club head having a loft angle comprising: 
 forming a body having a crown, a skirt, and a sole defining a front opening;    forming a striking plate of a material having a hardness of at least 30 HRC, a percent elongation of at least 7%, a density of less than about 5 g/cc, and a maximum thickness of less than about 2.2 mm, said crown having a thickness of less than about 0.8 mm over at least a crown transition distance of about 20 mm measured rearwardly from the front opening, said sole having a thickness of less than about 1.0 mm over at least a sole transition distance of about 20 mm measured rearwardly from the front opening; and    attaching said striking plate to said front opening of said body;    wherein said golf club head has a coefficient of restitution of at least about 0.85 if said loft angle exceeds 12 degrees and at least about 0.87 if said loft angle is 12 degrees or less.    
     
     
         14 . The method of  claim 13 , wherein said attaching of said striking plate comprises welding.  
     
     
         15 . The method of  claim 13 , wherein said forming comprises cold forming constituting at least about 30% cold working of said striking plate.  
     
     
         16 . The method of  claim 13 , and further comprising integrally forming a thickened plate on an interior surface of said sole, to add between 15 and 25 grams to the mass of said golf club head.  
     
     
         17 . The method of  claim 13 , and further comprising attaching a weight member to an interior surface of said sole, to add between 15 and 25 grams to the mass of said golf club head.  
     
     
         18 . A method of manufacturing a golf club head, comprising the steps of: 
 casting a body of a titanium alloy, said body having a crown, a skirt, and a sole defining a front opening, said crown having a thickness of about 0.7 mm, said sole having a thickness of about 0.9 mm;    providing a weight member of between 18 to 22 grams to said sole of said body;    cold forming a striking plate of a beta-type titanium alloy to have a hardness of at least 30 HRC and a percent elongation of at least 7%, said string plate having a thickness of between 1.1 and 1.8 mm; and    welding said striking plate to said front opening of said body;    wherein said golf club head has a coefficient of restitution of at least 0.88.    
     
     
         19 . The method of  claim 18 , wherein said striking plate is formed of a titanium alloy substantially comprising by weight about 4% aluminum, 20% vanadium, and 1% tin.  
     
     
         20 . The method of  claim 18 , wherein said cold forming comprises at least 30% cold working of said striking plate.  
     
     
         21 . The method of  claim 20 , wherein said cold forming is performed to create a peripheral thickness of said striking plate that is about 0.5 mm less than a thickness at a center of said striking plate  
     
     
         22 . A metal golf club head, comprising: 
 an integrally cast body having a crown and a sole that define a front opening;    a striking plate welded to the front opening of the cast body;    said crown having a substantially constant first thickness of about 0.7 mm, said sole having a substantially constant second thickness of about 0.9 mm, and said striking plate having a third thickness of about 1.7 mm; and    said striking plate formed of a titanium alloy substantially comprising by weight about 4.5% aluminum, 2% molybdenum, and 3% vanadium; wherein said golf club head has a coefficient of restitution of at least 0.88.    
     
     
         23 . A method of manufacturing a golf club head, comprising: 
 casting a body of a titanium alloy, said body having a crown, a skirt, and a sole defining a front opening, said crown having a thickness of about 0.7 mm and said sole having a thickness of about 0.9 mm;    providing a weight member of between 18 to 22 grams to said sole of said body;    cold forming a striking plate of an alpha-beta-type titanium alloy to have a hardness of at least 30 HRC, a percent elongation of at least 7%, and a thickness of about 1.7 mm; and    welding said string plate to said front opening of said body;    wherein said golf club head has a coefficient of restitution of at least 0.88.    
     
     
         24 . A golf club head having a loft angle, comprising: 
 a hollow body having a crown and a sole, said crown having a substantially uniform thickness of less than about 0.8 mm, and said sole having a thickness of less than about 1.0 mm; and    a striking plate provided at a front of said body and having a thickness of less than about 2.2 mm at a central portion, said striking plate formed of a material having a hardness of at least 30 HRC, a percent elongation of at least 7%, and a density less than about 5 g/cc, said striking plate having an upper portion forming an obtuse angle with said central portion of said striking plate and a lower portion forming an acute angle with said central portion;    wherein said golf club head has a coefficient of restitution of at least about 0.85 if said loft angle exceeds 12 degrees and at least about 0.87 if said loft angle is 12 degrees or less.    
     
     
         25 . The golf club head of  claim 24 , wherein said body comprises a toe and said striking plate has a toe portion wrapping rearward for mating with said toe.  
     
     
         26 . The golf club head of  claim 15 , wherein said body further comprises a heel and said striking plate has a heel portion wrapping rearward for mating with said heel.  
     
     
         27 . The golf club head of  claim 24 , wherein said upper portion and said lower portion each include a thickness of less than about 2.2 mm.  
     
     
         28 . The golf club head of  claim 24 , wherein said striking plate is cold formed.  
     
     
         29 . The golf club head of  claim 24 , wherein said striking plate is hot forged.