Abstract:
A golf club head having a high COR at its face center and a center of gravity located at a point close to the face and the sole is disclosed herein. In particular, the golf club head comprises a hollow body including a weight lip and face component, and the weight lip extends from the sole inside the body towards the face component without making contact with the face component. The golf club head preferably is a two-piece iron-type golf club head, and each piece is heat treated differently before being welded together to further optimize center of gravity location, ball speed, and COR distribution across the face.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
     The present application is a continuation-in-part of U.S. patent application Ser. No. 14/285,479, filed on May 22, 2014, which is a continuation-in-part of U.S. patent application Ser. No. 13/797,507, filed on Mar. 12, 2013, and issued on Dec. 2, 2014, as U.S. Pat. No. 8,900,070, which is a continuation-in-part of U.S. patent application Ser. No. 13/788,173, filed on Mar. 7, 2013, and issued on Jan. 6, 2015, as U.S. Pat. No. 8,926,448, which is a continuation-in-part of U.S. patent application Ser. No. 13/751,447, filed on Jan. 28, 2013, and issued on Apr. 23, 2013, as U.S. Pat. No. 8,425,346, which is a continuation of U.S. patent application Ser. No. 13/667,692, filed on Nov. 2, 2012, and issued on Apr. 9, 2013, as U.S. Pat. No. 8,414,420, which is a continuation of U.S. patent application Ser. No. 13/559,279, filed on Jul. 26, 2012, and issued on Dec. 11, 2012, as U.S. Pat. No. 8,328,661, which is a continuation of U.S. patent application Ser. No. 13/475,497, filed on May 18, 2012, and issued on Sep. 4, 2012, as U.S. Pat. No. 8,257,195, which claims priority to U.S. Provisional Patent Application No. 61/635,363, filed on Apr. 19, 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 
     Field of the Invention 
     The present invention relates to a two piece iron club head having a flexible face and internal weighting that lowers the center of gravity of the golf club head, moves the center of gravity close to the face, and stiffens the body to better support the face. 
     Description of the Related Art 
     Golfers often prefer to use irons having centers of gravity that are low and also close to the face, which increases a golfer&#39;s control over golf balls during play. Two piece irons traditionally have faces formed from 455 carpenter steel, which is not ideal because the properties of this alloy prevents manufacturers from making ultra-thin faces. In face, the face must have a thickness of above 0.080 inch for the face to provide sufficient flex, and thinning the face below 0.080 inch negatively impacts the sound made by the club at impact with a golf ball. Therefore, there is a need for two-piece iron heads having improved internal weighting and flexible, forgiving faces 
     BRIEF SUMMARY OF THE INVENTION 
     One aspect of the present invention is an iron-type golf club head comprising a body comprising a top line, a sole, a heel side, a toe side, a frontal opening, and a weight lip, and face cup comprising a striking face, an upper flange with a first length, and a lower flange with a second length, wherein the striking face comprises a face center, wherein each of the upper flange and lower flange extends rearwards away from the striking face, wherein the first length is less than the second length, wherein the weight lip is disposed proximate the frontal opening and extends towards the face component without touching any portion of the striking face, wherein the face center has a COR value that is higher than a COR value of any point directly above the face center. In some embodiments, the weight lip may extend through the frontal opening, and may not comprise any hollow regions. In other embodiments, the second length may be between 5 mm and 10 mm, the face component may be welded to the body to form a weld line, and the weight lip may extend over the weld line. 
     In some embodiments, the frontal opening may extend completely through the body so that the body comprises a rear opening. In other embodiments, the weight lip may comprise an upper surface and a front surface, and the upper surface may be disposed approximately perpendicular to the front surface. The thickness of the lower flange may vary, and in other embodiments, the weight lip may be welded to the body. In one embodiment, the COR at the face center may be at least 0.795, and in another embodiment, the COR at the face center may be at least 0.800. In one embodiment, the upper flange and the top line may form a complete top line when the face cup is welded to the body, and the complete top line may have a width of no less than 0.200 inch and no more than 0.375 inch, and more preferably approximately 0.300 inch. 
     Another aspect of the present invention is an iron-type golf club head comprising a body comprising a top line, a sole, a heel side, a toe side, and a frontal opening that extends completely through the body so that the body comprises a rear opening, a protrusion, a face cup comprising a striking face, an upper flange, and a lower flange, and a weld seam between the face cup and the body, wherein the striking face comprises a face center, wherein the protrusion is welded to the sole proximate the frontal opening and extends towards the face component without touching any portion of the striking face, wherein the face center has a COR value of at least 0.800, and wherein the COR of the face center is higher than a COR value of any point directly above the face center. In some embodiments, the thickness of the striking face may vary, the striking face may comprise an area of greatest thickness, and the area of greatest thickness may be located no more than 0.300 inch away from the lower flange. In another embodiment, the striking face may have a hardness of 28 to 44 HRC and the body may have a hardness of 30 to 36 HRC. 
     In some embodiments, the face cup may comprise a toe side flange extending between the upper flange and the lower flange and a heel side edge. In a further embodiment, the striking face may comprise a plurality of scorelines, and each of the plurality of scorelines may be spaced at least 0.025 inch away from the heel side edge of the face cup. In another embodiment, the weld seam may have a constant thickness. In some embodiments, the face cup may be cast from 17-4 stainless steel, and the body may be cast from 450 stainless steel. 
     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 rear elevational view of the golf club head of the present invention. 
         FIG. 2  is an exploded view of the golf club head shown in  FIG. 1 . 
         FIG. 3  is a cross-sectional view of the golf club head shown in  FIG. 1  along lines  3 - 3 . 
         FIG. 4  is a cross-sectional view of the face cup shown in  FIG. 2  along lines  4 - 4 . 
         FIG. 5  is a heel side perspective view of the face cup shown in  FIG. 2 . 
         FIG. 6  is a rear perspective view of the face cup shown in  FIG. 2 . 
         FIG. 7  is a front elevational view of the golf club head shown in  FIG. 1 . 
         FIG. 8  is a flow chart of a preferred forging method. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is generally directed to an iron-type golf club head having internal weighting that places the golf club center of gravity (CG) at a point near the face and the sole of the golf club head. In the preferred embodiment, the iron-type golf club head  10  comprises a partial face cup  100  and a body  200  that are welded together to form a weld seam  20 , which preferably has a constant thickness, and an undercut area  290 , which creates a lower center of gravity and an improvement in ball speed. 
     As shown in  FIGS. 2-6 , the face cup  100  comprises a striking face  110 , an upper flange  120 , and a lower flange  130 , which has a length L 1  in a front to rear direction that is longer than the length L 2  in a front to rear direction of the upper flange  120 . Length L 1  preferably is between 5 and 10 mm, and more preferably is 6 to 9 mm. The thickness of lower flange  130  preferably varies as it extends away from the striking face  110 , which improves the performance of the golf club head  10  and the ease with which the face cup  100  is welded to the body  200 . In some embodiments, the lower flange  130  increases in thickness as it extends away from the striking face  110 , thus increasing the surface area of the edge  135  where it is welded to the body  200 . The face cup  100  also comprises a thin toe-side flange  140  extending between the upper flange  120  and lower flange  130 , as shown in  FIGS. 2, 5, and 6 , but no flange along its heel side  160 , where the face cup  100  is welded directly to a heel end  250  of the body  200  proximate the hosel  230 . The region of the face cup  100  where the flanges  120 ,  130 ,  140  connect with the striking face  110  is the hinge  150 , shown as the shaded areas of  FIGS. 5 and 6 . 
     The face cup  100  preferably constitutes about 20 to 40 percent of the total volume of the golf club head  10 , and preferably is composed of a high yield, low modulus material such as 17-4 stainless steel. This material allows the striking face  110  to flex without cracking, and also allows some or all of the striking face  110  to be as thin as 0.070 inch, and the hinge  150  thickness to be as thin as 0.050-0.065 inch, while maintaining a desired sound at impact with a golf ball, preferably at 85-95 decibels and a frequency of 4000-8000 Hz, more preferably at 93 decibels and a frequency of 5000 Hz. The face cup  100  preferably is cast, which allows for the creation of different striking face  110  thicknesses, also known as variable face technology, at a much lower cost than forging, stamping or machining, though in other embodiments it may be forged to improve its strength. In the preferred embodiment, the area of the striking face  110  with the greatest thickness is located a distance D 1  of within 0.300 inch of the lower flange  130  as shown in  FIG. 5 . When the face cup  100  is cast, the scorelines  160  should originate a distance D 2  away from the heel side edge of the face cup  100 , which preferably is approximately 0.025-0.250 inch, in order to avoid the weld seam  20  between the face cup  100  and the body  200 . The upper flange  120  also preferably forms at least a part of the overall topline  30  of the golf club head  10  to improve the durability of the golf club head  10 . 
     The body  200  preferably comprises a top line  210 , a sole  220 , a hosel  230 , a toe end  240 , a heel end  250 , a rear wall  260 , and a front opening  270  that extends completely through the body  200  such that the body  200  has an open back  205 . The body  200  also includes a weight lip  280 , which extends from the sole  220  and the rear wall  260  of the body  200  towards the front opening  270 , and also extends from the heel end  250  towards the toe end  240  of the body  200 . At least a portion of the weight lip  280  protrudes through the front opening  270 , such that when the body  200  is assembled with the face cup  100 , the weight lip  280  extends over the weld seam  20  and approaches, but does not make contact with, the rear surface  115  of the striking face  110 . In some embodiments, the weight lip  280  may contact both the toe and heel ends  240 ,  250 , but in the preferred embodiment, as shown in  FIG. 2 , the weight lip  280  only makes contact with the heel end  250  proximate the hosel  230 . The weight lip  280  preferably has an upper surface  282  that is approximately perpendicular to its forward surface  284 , but in alternative embodiments the weight lip  280  may have different dimensions and cross-sectional shapes. 
     The inertia of the weight lip  280  during impact of the golf club head  10  with a ball improves sole  220  compliance by enhancing the bending capabilities of thinner regions of the sole  220 . The weight construction shown in the Figures also allows for the use of a face cup  100  construction without sacrificing an optimized center of gravity location, and also allows the manufacturer of the club head  10  to take weight away from, and thus thin out, the sole  220 , which allows the sole  220  to flex and bend more easily and thus contribute more to performance of the face cup  100 . 
     If the body  200  is cast, it preferably is integrally cast from a stiffer stainless steel than that of the face cup  100 , such as 450 stainless steel. The weight lip  280 , which contributes to stiffening the body  200  and thus supporting flexure of the face cup  100 , may be integrally cast with the body  200 , but doing so makes it difficult for a manufacturer to fine tune the interior dimensions of the body  200  during casting and thus lower the center of gravity as much as possible. In fact, it is difficult during the typical casting process to remove the casting shell from the undercut area  290  under the weight lip  280 , and increasing the size of the undercut area  290  to make it easier to remove the casting shell only increases the height of the golf club&#39;s center of gravity. Therefore, when the body  200  is cast, it is preferable that the weight lip  280  be affixed to the body  200  via welding, soldering, brazing, or another method known to a person skilled in the art after both pieces  200 ,  280  are independently created. 
     In the preferred embodiment, however, the body  200  is forged from the same material as the face cup  100  (e.g., 1020, 1025, 1045 stainless steel), so that it can support the striking face  110  as it flexes and force energy transmitted to the club  10  during impact with a golf ball into flexing the striking face  110 . Forging increases the stiffness of the body  200 , allows the weight lip  280  to be integrally created with the body  200  instead of being added to the body  200  later, and preferably is performed using the following quadruple net forging process, which is illustrated in  FIG. 8 : first, a cylinder of steel material (preferably a carbon steel) is bent at a right angle  300 ; second, the bent steel cylinder is rough hot formed to create a rough body shape  310 ; third, the rough body shape is rough cut to create a first cut of the body  320 ; fourth, the first cut is forged  330 ; fifth, excess material is timed from the first cut to form a second cut  340 ; sixth, the second cut is forged  350 ; seventh, excess material is trimmed from the second cut to form a final cut  360 ; and finally, the final cut is hot formed to create a finished body  370 . After the body  200  is finished, it is welded to the face cup  100 , preferably via laser or plasma welding. In some embodiments, the face cup  100  or the body  200  may include a channel with the weld material built in, such that additional material does not need to be added to weld the parts together. 
     Regardless of how it is created, a stiffer body  200  provides necessary support to the face cup  100  and prevents twisting energy from creating an undesirable sound at impact. The flexibility of the face cup  100 , and the stiffness of the body  200 , of the two piece iron of the present invention are further optimized by heat treating these parts differently so that the face cup  100  has a hardness of 38-44 HRC on the Rockwell Scale and the body has a hardness of 30-36 HRC on the Rockwell Scale when the face cup  100  and body  200  are made from stainless steel. 
     The combination of the structure and heat treatment of the golf club head  10  of the present invention optimizes the coefficient of restitution (“COR”) measurements of the striking face  110 . COR values are measured according to USGA rules. Traditionally, cavity back irons had a highest COR measurement at a point above the center of the face due to the weakness of these irons&#39; toplines. The iron club heads of the present invention have stiffer toplines  30 , with widths W ranging from 0.200-0.375 inch, and more preferably approximately 0.300 inch, which forces the hot spot downwards across the striking face  110 . These clubs  10  thus have COR measurements that are higher at the face center  112  than at any point directly above the face center  112 , with COR measurements at the face center  112  of at least 0.795, and more preferably at least 0.800. As shown in  FIG. 7 , the face center  112  of the golf club head  10  is located a distance D 3  of 0.725 inch above a ground plane, measured in the vertical direction along a plane created by the striking face  110 , and in the horizontal direction at the center of the area framed by the scorelines  160 . 
     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.