Abstract:
The present invention discloses an iron-type golf club head formed from multiple materials that increase torsional stiffness of the club and aid in sound performance. In particular, the iron-type golf club head includes a rear flange and a composite component bonded to an external surface of the rear flange. The composite component may cover an entire surface of the rear flange, and may also extend upwards to make contact with a top portion of the club head and thus close off a rear cavity of the club head. The iron-type golf club head may further comprise a face support structure extending from the rear flange, to which the face plate may be affixed via welding or brazing.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation application of U.S. patent application Ser. No. 13/767,751, filed on Feb. 14, 2013, which is a continuation-in-part of U.S. patent application Ser. No. 13/761,863, filed on Feb. 7, 2013, now U.S. Pat. No. 8,821,313, which claims priority to U.S. Provisional Patent Application No. 61/701,533, filed on Sep. 14, 2012, the disclosure of each of which is hereby incorporated by reference in its entirety herein. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a multiple-material iron-type golf club head. More specifically, the present invention relates to an iron-type golf club with composite material disposed on or over a rear surface of the golf club head. 
     2. Description of the Related Art 
     The prior art discloses various types of golf club heads having multiple materials, and various types of golf club heads with sound-enhancing features. There is a need for a golf club head having multiple material configurations that both benefit sound and enhance the mass properties of the golf club head. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention provides an iron-type golf club with features that optimize both sound and mass properties, including moment of inertia, center of gravity (CG) location, and the overall weight of the golf club head. 
     One aspect of the present invention is an iron-type golf club head comprising a cavity and a composite back cap. Another aspect of the present invention is an iron-type golf club head comprising a back flange and a thin layer of composite affixed to a surface of the back flange. 
     Yet another aspect of the present invention is an iron-type golf club head comprising a face component, a body having a top portion, a sole portion, a heel portion, a toe portion, a rear cavity, and a rear flange extending upwards from the sole portion, and a composite material affixed to at least part of an external surface of the rear flange. In some embodiments, the composite material may be a 45 degree composite. In other embodiments, the composite material may have a constant thickness of no less than 0.001 inch and no more than 0.500 inch, or it may have a variable thickness ranging from 0.001 inch to 0.500 inch. 
     In still other embodiments, the face component may be a face plate, and the rear flange may comprise a forward extending portion. In a further embodiment, the face plate may be welded to the top portion, sole portion, heel, and toe of the body, and may be brazed to a forwardmost surface of the forward extending portion. In another further embodiment, the iron-type golf club head may comprise a cavity enclosed by the heel, toe, flange, forward extending portion, and face plate, which may be filled with a lightweight material selected from the group consisting of composite, plastic, rubber, and aluminum alloy. In some embodiments, the face plate may compose part of the top portion and part of the sole portion. 
     In other embodiments, the face component may be a face insert. In some embodiments, the composite material may be affixed to the flange with an adhesive material, and may be affixed to an entire rear surface of the flange. The body of the iron-type golf club head may be composed of a metal alloy material, and the flange may extend upwards from the sole portion and makes contact with the top portion. In some embodiments, the composite material may be affixed to an upper end of the flange and extends upward to make contact with the top portion. In a further embodiment, this composite material may enclose the rear cavity. 
     Another aspect of the present invention is a set of iron-type golf clubs comprising a first club head comprising a body with a first rear flange, a first face place, and a first composite component, and a second club head comprising a body with a second rear flange, a second face plate, and a second composite component, wherein the first composite component is affixed with adhesive to an external surface of the first rear flange, wherein the second composite component is affixed with adhesive to an external surface of the second rear flange, wherein the thickness of the first rear flange is greater than the thickness of the second rear flange, and wherein the thickness of the first composite component is smaller than the thickness of the second composite component. 
     Yet another aspect of the present invention is an iron-type golf club head comprising a face plate, a body having a top portion, a sole portion, a heel portion, a toe portion, a rear cavity, and a rear flange extending upwards from the sole portion, and a composite material affixed with adhesive to the entire rear, external surface of the rear flange, wherein the composite material is composed of 45 degree carbon composite with a constant thickness of no less than 0.001 inch and no more than 0.050 inch, wherein the rear flange comprises a forward extending portion, wherein the face plate is welded to the top portion, sole portion, heel portion, and toe portion of the body, and wherein the face plate is brazed to a forwardmost surface of the forward extending portion. In some embodiments, the composite material may be affixed to the top portion of the body and enclose the rear cavity. In other embodiments, the face plate may be composed of a first material having a first density, the body may be composed of a second material having a second density, and the first density may differ from the second density. 
     Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is a front perspective view of a first embodiment of the present invention. 
         FIG. 2  is a cross-sectional view of the first embodiment along lines  2 - 2 . 
         FIG. 3  is a front perspective view of a second embodiment of the present invention. 
         FIG. 4  is a cross-sectional view of the second embodiment along lines  4 - 4 . 
         FIG. 5  is a top, perspective view of a third embodiment of the present invention. 
         FIG. 6  is a cross-sectional view of the third embodiment along lines  6 - 6 . 
         FIG. 7  is a rear perspective view of the third embodiment shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A preferred embodiment of the iron-type golf club head  10  of the present invention is shown in  FIGS. 1-2 . The golf club head  10  has a top portion  12  (also called a top rail), a sole portion  14 , a heel portion  16 , a toe portion  18 , a hosel  20 , a face plate  30 , a rear cavity  40 , and a rear flange  45  that extends from and is approximately perpendicular to the rearmost edge of the sole portion  14 . The face plate  30  extends from a lowermost edge of the sole portion  14  to an uppermost edge of the top portion  12 , is welded to both of these parts, and forms part of the surface of the top portion  12  and the sole portion  14  as shown in  FIG. 4 . In alternative embodiments, however, the face plate  30  may function as a face insert and not extend completely from the lowest edge of the sole portion  14  to the uppermost edge of the top portion  12 . 
     The rear flange  45  includes a forward projecting portion  47  that extends from and is approximately perpendicular to the rear flange  45 , and extends towards the face plate  30 . The face plate  30  preferably is brazed to a forwardmost surface of the forward projecting portion  47 , though in alternative embodiments the face plate  30  may be welded, glued, or otherwise affixed to the forward projecting portion  47 . The golf club head  10  also includes an internal cavity  42  that is bounded by the rear flange  45 , the forward projecting portion  47 , the heel portion  16 , the toe portion  18 , and the face plate  30 , and a sole cavity  44  that is filled with a high-density weight  50 . The internal cavity  42  may be filled with any material known to a person skilled in the art, but preferably is left empty to reduce the overall weight of the golf club head  10 . 
     The lower portion of the iron club head shown in  FIG. 2  behaves in torsion about an axis  80  extending from the heel to toe as a closed cell beam. The closed cell  70  surrounds the internal cavity  42  and is composed of the rear flange  45 , the forward projecting portion  47 , a lower portion  32  of the face plate  30 , and the sole portion  14 . It is considered closed by the existence of the connection of the forward projecting portion  47  with the face plate  30  by brazing, welding, bonding or other means of affixing the two components. The torsional rigidity, GJ, of a closed cell section can be approximated by: 
             GJ   =       4   ⁢     A   m   2         ∮       ⅆ   s     Gt               
where s is the closed cell contour coordinate which follows a wall midplane  72  around the cross-section, ds is a differential element of that coordinate, G is the shear modulus of elasticity of the wall material, t is the local wall thickness perpendicular to the midplane contour, and A m  is the area enclosed by the midplane of the thickness around the closed cell contour.
 
     Torsional rigidity, GJ, of the lower portion of an iron-type club head  10  can be increased by adding carbon composite sheet  60  to the cross-section as shown in  FIG. 2 . The composite sheet  60  preferably is affixed with an adhesive to a rear surface of the rear flange  45 . This composite sheet  60 , which has a thickness ranging from 0.001 to 0.500 inch, preferably extends from the point  48  at which the sole portion  14  contacts the rear flange  45  to the top most surface of the rear flange  45 , and more preferably covers the entire rear surface of the rear flange  45 , though in some embodiments the composite sheet  60  may extend onto or be solely affixed to the sole portion  14 . The composite sheet  60 , which preferably is composed of a multi-directional composite laminate, and most preferably by composite composed of plies oriented at ±45 degrees with respect the heel to toe axis  80  (which is perpendicular to the plane of the cross-section shown in  FIG. 2 ), increases the torsional stiffness of the golf club head  10  while at the same time improving sound performance. While fiber orientations other than ±45 degrees can be used, the ±45 degree orientation allows for the greatest increase in shear modulus of elasticity, and lower angles will have less effect on torsional rigidity. In another embodiment, the composite sheet  60  is composed of a single ply of composite prepreg with a thickness of approximately 0.005 inch. 
     When a composite sheet  60  is included with the golf club head  10  as shown in  FIG. 2 , the variable G is replaced by the effective shear modulus, G eff , of the combined carbon composite and parent material, which is given by; 
               G   eff     =           G   1     ⁢     t   1       +       G   2     ⁢     t   2             t   1     +     t   2               
where, G 1  is the shear modulus of elasticity of the parent material, t 1  is the thickness of the parent material, G 2  is the shear modulus of elasticity of the carbon composite material, t 2  is the thickness of the carbon composite material, and t=total thickness of the carbon composite plus the parent material=t 1 +t 2 .
 
     An additional benefit of using carbon composite with the golf club head  10  of the present invention is its low density relative to materials typically used in the face, sole and flange of irons. As a result, a significant increase in torsional stiffness can be achieved at a very low mass. This approach allows the vibration and feel properties of the head to be improved without adversely affecting key mass properties such as center of gravity location. The inherent damping properties of composite materials and the adhesive bond joining it to the parent structure also improve the impact feel and sound properties of the club head. 
     Another embodiment of the golf club head  10  is shown in  FIGS. 3-4 . Like the preferred embodiment, this embodiment includes a face plate  30  affixed to a body having a top portion  12 , sole portion  14 , heel portion  16 , toe portion  18 , hosel  20 , rear cavity  40 , and rear flange  45 , though in this embodiment the rear flange  45  extends diagonally upwards from a rearward-most edge of the sole portion  14  and projects towards the face plate  30 . As in the preferred embodiment, this embodiment includes a composite sheet  60  that is adhered to and covers the entire rear surface of the rear flange  45 . 
     As shown in  FIG. 4 , the face plate  30  is affixed to a forwardmost surface of the rear flange  45  via brazing. Together with the sole portion  14 , heel portion  16 , toe portion  18 , and face plate  30 , the rear flange  45  creates an internal cavity  42 , which in this embodiment includes a high-density weight  50 , which preferably is composed of a tungsten alloy. Any additional space within the internal cavity  42  is filled with a low density polymer material  55  to improve the resilience of the face. This polymer material  55 , which preferably is a rubber material, is injected through a hole  15  in the sole portion  14 , which can be closed off with a simple plug (not shown). 
     In another embodiment, shown in  FIGS. 5-7 , the composite sheet  60  is affixed to a first lip  46  extending from the rear flange  45  and a second lip  13  extending from a lower surface of the top portion  12 , and in this way closes the rear cavity  40  of the golf club head  10 . 
     The disclosure of U.S. patent application Ser. No. 13/761,863 is hereby incorporated by reference in its entirety herein. 
     From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.