Abstract:
A golf club iron having a thin front face which is supported by a biasly bent L-shaped insert that is disposed into a rear cavity of the iron to both support the front face and to create a “spring like” effect. The coefficient of restitution of the club head is greater than 0.8. The insert has a lower specific gravity and a higher Young&#39;s Modulus than the front face.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a divisional of co-pending U.S. application Ser. No. 10/606,318 which was filed Jun. 25, 2003, and is incorporated herein in its entirety by express reference thereto. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to an improved golf club iron head, and more particularly, the invention relates to a golf club head having an insert wedged behind a thin front face.  
       BACKGROUND OF THE INVENTION  
       [0003]     The desire for perimeter weighting in a golf club iron is well known in the art. This desire stems from the fact that as the mass of the iron is distributed towards the perimeter, the trajectory of the hit ball becomes more consistent for off-center hits away from the sweet spot of the golf club face or hitting surface. Consequently, many modern golf club irons have a “cavity back” design. These clubs are made by removing the weight from the center of the club head and redistributing it along the bottom, the top, the heel and toe portions of the club head. Club heads of the latter type have enjoyed considerable success since they effectively enlarge the “sweet spot” of the club head.  
         [0004]     The “sweet spot” of the club head is generally regarded to be that area on the striking face of the club head immediately surrounding the center of gravity of the club head. By enlarging the sweet spot, perimeter weighted club heads allow golfers of all abilities to realize improved results over conventional club heads when the golfer fails to strike the golf ball in line with the center of gravity of the club head. These improved results translate into “mis-hit” shots that travel farther and straighter than they would if struck with a club having another conventional club head design.  
         [0005]     The weight saved by creating a rear cavity in the iron, is re-distributed to the perimeter of the golf club head. The greater the volume of the cavity, the greater the amount of mass of metal that can be redistributed to the perimeter of the golf club head. However, if the thickness of the face hitting surface is reduced to an extent where it becomes too thin, the strength of the face becomes too low to resist the force of the ball hitting the face. Thus, it would be desirable to find a way to further increase the volume of the cavity without causing the face to fail upon impact with the ball. One way of achieving this increase in cavity volume is to increase the cross-section of the cavity as it approaches the rear of the front face or hitting surface of the club head, or in other words, create an undercut rear cavity perimeter. Unfortunately, such an undercut perimeter creates a trap area in which dirt and moisture can accumulate, which can otherwise create a surface integrity problem as a result of rust or otherwise detrimentally affect the aesthetics of the club head that can reduce its commercial success.  
         [0006]     As is well known in the golf club art, a typical set of men&#39;s golf club irons includes 8 or 9 irons having variations in shaft length, weight, lie and loft among other parameters. By way of example, the iron having the lowest weight, longest shaft and the lowest loft is typically the number two iron and the club having the shortest shaft and the highest loft is typically called a wedge.  
         [0007]     It would be desirable to provide a means for creating a thin faced club head having a high COR for increased distance in each iron of a set of golf club irons, or at least the longer irons. However, a limiting parameter is when the face thickness becomes so thin, it adversely effects the strength of the face. One well-known cure is to support the face with a low-density insert, preferably one placed into a rear cavity opening. The present invention utilizes the insert to provide an alternative means for increasing the COR.  
       SUMMARY OF THE INVENTION  
       [0008]     The present invention overcomes the disadvantages of the prior art by providing a club head having a low density rear cavity insert, which is bent and introduced into the cavity under tension, thereby creating a spring-like effect upon the front face of the club head during impact.  
         [0009]     One embodiment of the invention provides for a club head having a front face and a rear cavity with an L-shaped insert bent into the cavity. The combination of this feature, along with the thinning of the front face, provides a club head having an increased coefficient of restitution (COR).  
         [0010]     Another embodiment of the golf club head includes a U-shaped insert inserted into the rear cavity. Preferably, the insert covers at least 50 percent of the height of the front face.  
         [0011]     Another embodiment of the invention includes a set of golf irons wherein the long irons include a rear cavity and a rear recess. An insert is bent into place to juxtapose the front face and the top of the sole recess. In some embodiments a void is created between a back surface of the front face and the insert.  
         [0012]     In one embodiment, the insert has a Young&#39;s Modulus that is greater than that of the front face and a specific gravity less than the club face. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]      FIG. 1  is a cross-sectional view of a golf club iron head of the present invention showing the relationship of the insert to the front face.  
         [0014]      FIG. 2  is a cross-sectional view of a golf club iron head of another embodiment of the invention showing a U-shaped insert.  
         [0015]      FIG. 3  is a cross-sectional view of a golf club iron head of another embodiment of the invention depicting an L-shaped insert.  
         [0016]      FIG. 4  is a cross-sectional view of a golf club iron head of another embodiment of the invention describing an acutely bent insert.  
         [0017]      FIG. 5  is a cross-sectional view of a golf club iron head of another embodiment of the invention wherein the insert creates a void in a sole recess. 
     
    
     DETAILED DESCRIPTION  
       [0018]     Referring to  FIGS. 1-5 , an iron type golf club head  20  includes a perimeter weight  21  and a front face  22 . The perimeter weight  21  includes a top portion  24  and a sole portion  26  that are spaced apart. The club head  20  is preferably cast or forged from suitable material such as stainless steel. The front face  22  is arranged for impact with a golf ball (not shown) and extends between the top and sole portions  24 ,  26  along a front side of the perimeter weight  21 .  
         [0019]     Preferably, the golf club iron has a high moment of inertia (MOI). The present invention accomplishes this by positioning the center of gravity low and towards the back of the club head  20 . Perimeter weight  21  protrudes rearward from the front face  22  to define a rear cavity  28  and a sole recess  29  in the lower back of the head  20 . The sole recess  29  is the area defined by the sole height ht, and the sole width SW of the sole portion  26 . The wider sole portion  26  of the invention is also positioned further rearward, thereby creating a lower center of gravity in the club head  20 . The repositioned center of gravity helps the flight of the ball obtain a higher trajectory because of the increased dynamic loft that yields a higher launch angle and greater sweet spot when compared to a conventional golf club.  
         [0020]     In an embodiment of the invention is shown in  FIG. 1 , a thin front face  22  is supported by an L-shaped rear cavity insert  30   a . The insert can be bent when inserted to create potential energy by the insert  30   a  being biasly placed into the rear cavity  28  and sole recess  29 . Preferably, the insert  30   a  is bent or flexed at a bend angle Ø that is less than about 95°, and more preferably less than about 80°, and then juxtaposed against a back surface  32  of the front face  22  and an inner surface  33  of the sole portion  26 . Prior to being inserted, the insert  30   a  preferably has an angle that is at least 2% larger than angle Ø. This tension creates a leaf spring effect, which helps the club face to achieve a high COR. In a preferred embodiment the COR is greater than 0.79. This is especially desirable in at least the long irons, (2 to 4), and possibly middle irons (5-7). The bent insert  30   a  exerts a pre-load against the front face  22  of between 0 to 3000 lbs, and more preferably about 50 to 1000 lbs.  
         [0021]     Embodiments of the invention are illustrated in  FIGS. 2-5 . In  FIG. 2 , a U-shaped insert  30   b , is placed into the rear cavity  28  and sole recess  29  to achieve the spring-like effect. In this U-shaped embodiment, the bend in the insert  30   b  defines an opening width OW, which is less than the sole width SW of the sole recess  29 . However, the opening width OW can be larger than the sole width SW of the sole recess  29 , prior to the insert  30   b  being located in the rear cavity  28 .  
         [0022]     In  FIG. 3 , an insert  30   c , only supports a partial section of the back surface  32 . However, the insert  30   c  preferably supports at least 50 percent of the height of the front face  22 . In  FIG. 4 , an embodiment is shown wherein the insert  30   d  is bent at an extremely acute angle and is of a more V-shaped design.  
         [0023]     In the previous embodiments shown in  FIGS. 1-4 , each of the inserts  30   a, b, c , and d, is at least partially located in both the rear cavity  28  and the sole recess  29 , and preferably, the inserts abut the back surface  32  of the front face  22  and the inner surface  33  of the sole portion  26 . In  FIG. 5  an embodiment is shown wherein the insert  30   e  is bent into place to juxtapose the front face  22  and a top surface A-A of the sole recess  29 . A void  34  is thereby created in the sole recess  29  between the insert  30   e  and the back surface  33  of the front face  22  and inner surface  33  of the sole portion  26 .  
         [0024]     The uniqueness of the present invention may be shown in the manufacturing process of the club head  20 , which is forged or cast. The body is generally cast out of a stainless steel. In a forged embodiment, the periphery can be cast or forged and the front face  22  can be made of rolled, stamped or forged high strength steel, such as stainless steel  455  and more preferably stainless steel  465 . Using high strength steel permits the front face  22  to be thinned-down. This provides a higher COR face thickness (at least 0.06 to 0.1 inch for long irons).  
         [0025]     Composites comprising graphite or Kevlar fibers, as well as low specific gravity metals such as magnesium, titanium and aluminum are desirable materials for the inserts  30   a, b, c, d , and e. The specific gravity of the inserts  30   a - e  are lower than the specific gravity of the front face  22 , and preferably are less than 85 percent of the front face&#39;s specific gravity. In a preferred embodiment, the specific gravity of the front face  22  is greater than about 7.0 and inserts  30   a - e , less than about 2.0.  
         [0026]     While it is apparent that the illustrative embodiments of the invention herein disclosed fulfills the objectives stated above, it will be appreciated that numerous modifications and other embodiments may be devised by those skilled in the art. Therefore, it will be appreciated that the appended claims are intended to cover all such modifications and embodiments which come within the spirit and scope of the present.