Forged iron-type golf clubs

Abstract

Forged cavity back iron-type clubs and oversize clubs are disclosed. These forged clubs have thin, durable hitting face and relatively large cavity volumes. These clubs have high rotational moments of inertia to minimize distance and accuracy penalties associated with off-center hits. Long irons with hitting face of about 0.100 inch thick are achievable by the present invention. Also disclosed are forged irons made from stainless steels and annealed to achieve the desired hardness and ductility.

1 . An iron-type golf club comprising: 
 a club head having a hosel, a front and a back, wherein the back comprises a cavity defined by a perimeter member and the front has a hitting zone located opposite to and coinciding with the cavity, and wherein the club head is forged from stainless steel and then annealed, wherein the cavity volume is greater than or equal to 8.68 cc.    
   
   
       2 . The iron-type golf club of  claim 1 , wherein the cavity is further adjoined by a first portion and a reinforced portion located on the back of the club head and wherein the reinforced portion is thicker than the first portion.  
   
   
       3 . The iron-type golf club of  claim 2 , wherein the first portion is located on top of the reinforced portion.  
   
   
       4 . The iron-type golf club of  claim 2 , wherein the thickness of the reinforced portion is about 1.2 times to about 3 times higher than the thickness of the first portion.  
   
   
       5 . The iron-type golf club of  claim 2 , wherein the first portion occupies from about 50% to about 90% of the total area of the hitting zone.  
   
   
       6 . The iron-type golf club of  claim 5 , wherein the first portion occupies from about 60% to about 80% of the total area of the hitting zone.  
   
   
       7 . The iron-type golf club of  claim 1 , wherein the perimeter member is thicker on the bottom of the club head than on the top.  
   
   
       8 . The iron-type golf club of  claim 1 , wherein the stainless steel has a yield strength less than about 90,000 psi and an elongation of greater than about 13%.  
   
   
       9 . The iron-type golf club of  claim 8 , wherein the yield strength is less than about 85,000 psi and the stainless steel has an ultimate elongation of about 15% to about 21%.  
   
   
       10 . The iron-type golf club of  claim 1 , wherein the stainless steel comprises more than about 10% of chromium.  
   
   
       11 . The iron-type golf club of  claim 1 , wherein the grain size of the forged and annealed stainless steel is greater than about 10 μm.  
   
   
       12 . The iron-type golf club of  claim 11 , wherein the grain size of the forged and annealed stainless steel is between about 10 μm and about 50 μm.  
   
   
       13 . The iron-type golf club of  claim 1 , wherein the club head is a unitary club head.  
   
   
       14 . The iron-type golf club of  claim 1 , wherein the club head further comprises a forged face insert, and wherein the face insert is made from stainless steel.  
   
   
       15 . The iron-type golf club of  claim 1 , wherein the club head further comprises a stamped face insert and wherein the face insert is made from the stainless steel.  
   
   
       16 . The iron-type golf club of  claim 1 , wherein the club head has a hardness of less than about 90 Rockwell Hardness B.  
   
   
       17 . The iron-type golf club of  claim 1 , wherein the stainless steel is selected from a group consisting of 410 stainless steel, 403 stainless steel, 431 stainless steel, 416 stainless steel, 303 stainless steel, 304 stainless steel, 329 stainless steel, 316 stainless steel, 259 stainless steel, Nitronic 40, Nitronic 50 and Nitronic 60.  
   
   
       18 . The iron-type golf club of  claim 1 , wherein the club head is selected from a group consisting of the number 1-9 irons, the pitching wedge, the sand wedge and the gap wedge.  
   
   
       19 . The iron-type golf club of  claim 1 , wherein the rotational moment of inertia about a shaft axis is greater than about 500 kg·mm 2 .  
   
   
       20 . The iron-type golf club of  claim 19 , wherein the rotational moment of inertia about the shaft axis is greater than about 650 kg·mm 2 .  
   
   
       21 . The iron-type golf club of  claim 1 , wherein the hitting zone has a minimum thickness of less than about 0.2 inch.  
   
   
       22 . The iron-type golf club of  claim 21 , wherein the minimum thickness is less than about 0.13 inch when the loft angle is less than about 35°.  
   
   
       23 . The iron-type golf club of  claim 21 , wherein the minimum thickness is about 0.1 inch.  
   
   
       24 . The iron-type golf club of  claim 1 , wherein the hitting zone has an aspect ratio in accordance to the following equation:  
       aspect ratio≧−((1/4.5)×loft angle°)+25,  
     wherein the aspect ratio is the area of the hitting zone (inch 2 ) divided by a minimum thickness (inch) of the hitting zone.  
   
   
       25 . An iron-type golf club comprising: 
 a club head having a hosel, a front and a back, wherein the back comprises a cavity defined by a perimeter member and the front has a hitting zone located opposite to and coinciding with the cavity, and wherein the club head is forged from stainless steel and then annealed, wherein the cavity volume is greater than or equal to 13.05 cc.