Abstract:
A substantially hollow body metal wood golf club head has a wrap around insert that comprises a substantial portion of the front face. The insert having a wing-like extension that extends around the heel portion of the club head and a pre-determined distance of about 0.657 inch into the skirt portion of the club head. A gap of about 0.06 inch to about 0.36 inch is created between an internal thru-hosel and the interior wall of the heel. The gap represents material and weight that may be used more effectively in other parts of the club head. The lack of connection between the hosel and the front face creates a greater unsupported front face and therefore a greater “sweet spot” area.

Description:
FIELD OF THE INVENTION 
   The present invention relates generally to a metallic hollow golf club head, and specifically to the placement of a wrapped face insert having a wing element extending into the heel/skirt portion of the club body. 
   BACKGROUND OF THE INVENTION 
   Golf club “metal woods”, were originally manufactured primarily by casting of durable metals such as stainless steel, aluminum, beryllium copper, etc. into a unitary structure comprising of a metal body, face and hosel. As technology progressed it became more desirable to strengthen the face of the club, and usually this was achieved by using titanium material. 
   With a high percentage of amateur golfers constantly searching for more distance on their drives, the golf industry has responded by providing golf clubs specifically designed with distance in mind. The head sizes have increased which allows for the club to possess a higher moment of inertia, which translates to a greater ability to resist twisting on off-center hits. However, as a wood head becomes larger, its center of gravity will be moved back away from the face resulting in hits flying higher than expected. Reducing the lofts of larger head clubs is one way to compensate for this. Also with the larger heads, the center of gravity is moved further away from the axis that is created by the intersection of the hosel with the sole plate. This can cause these large head clubs to remain open on contact, thereby inducing a “slice” effect (in the case of a right-handed golfer, the ball deviates to the right). Offsetting the head and incorporating a hook face angle can help compensate for this by “squaring” the face at impact, but often more is required to eliminate the “slice” tendency. 
   The technological breakthrough in recent years towards providing the average golfer with more distance, by increasing the club head size, has been to keep the weight constant or even lighter, by casting consistently thinner shell thickness and going to lighter materials such as titanium. Also, the club head faces have been steadily becoming extremely thin. These thinner faces will maximize what is known as the Coefficient of Restitution (COR), which means that the more the face rebounds upon impact, the more energy that may be imparted to the ball, thereby increasing distance. In order to make the faces thinner, manufacturers have moved to forged or stamped metal faces which are stronger, in most cases, than those that are cast. Common practice is to integrate the forged or stamped metal face by welding it to the body at the sole and crown transitions. These transitions are the points on the club head that absorb the greatest amount of stresses as the club strikes the ball. 
   A common feature of most metal wood designs that exhibit a thru-hosel construction is that there is an intimate connection between the face, hosel tube and heel portion of the skirt wall. This often results in a reduced unsupported face area due to a narrower supporting perimeter, thereby reducing the overall face flexibility and “sweet spot”. 
   Therefore, it is very desirable to provide a method for attaching the impact face portion to the body of the club head without sacrificing any COR (Coefficient of Restitution) value or “sweet spot” size. 
   SUMMARY OF THE INVENTION 
   In accordance with one aspect of the invention, a metal wood golf club head is provided which includes a hollow body having a wrap around insert welded to the front face. The body is preferably cast as a single member and includes a sole portion, a crown portion, a front face, a toe portion that extends into the impact area of the front face portion, a heel portion, a skirt portion connecting the heel portion to the toe portion, a hosel portion comprising an internal thru-bore hosel tube, and an opening defined in the front face for receiving the wrap-around insert. The wrap around insert forms a substantial portion of the impact face of the club, and has at a distal end a wing section extending around and beyond the hosel tube and into the body at the heel/skirt area of the club. The distance the wing section extends into the skirt portion is at least 0.60 inch, and preferably about 0.657 inch. 
   In the invention a stamped plate is used for the wrap around insert, and since a stamped plate made of beta-titanium generally exhibits better strength and ductility properties than cast titanium, it is preferable to use it as a substantial portion of the impact face of the front section. It is appreciated that in the joining of the insert to the front face of the body, the welding is removed away from the crown/face and sole/face transition seams, which are points of critical stress. The present invention provides for these welds to be done a distance away from the transition seams, thereby keeping the thickness at the transitions much thinner than if welds were present. This increases the structural integrity of the club head and also achieves maximum allowable COR values. 
   In the invention, the wrap around design of the insert provides the ability to increase the club head volume behind the plane of the hosel, without having to add material and overall weight to maintain the connection between the hosel tube and adjacent skirt wall. The result of this is a larger unsupported face area and in addition to increasing the hitting area “sweet spot”, it allows for more discretionary weight to be available to further optimize the mass properties of the club head, which is one of the key elements for achieving ideal launch conditions and overall performance. 
   The wrap around feature of the insert creates a gap of about 0.3 inch to about 0.625 inch between the hosel tube and the wall of the heel portion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a front view of the club head body of the present invention showing the hosel tube and an opening in the body. 
       FIG. 2  is a front view of the thru-hosel design. 
       FIG. 3  is a heel elevation view showing the opening as it extends into the skirt section to accommodate the wrap around insert. 
       FIG. 4  is a front elevation view of the wrapped face insert. 
       FIG. 5  is a top view of the insert of  FIG. 4 . 
       FIG. 6  is a partial cross section bottom view taken along line B—B of  FIG. 4 . 
       FIG. 7  is a partial cross sectional toe view along lines A—A of  FIG. 4 . 
       FIG. 8  is a heel view of  FIG. 4 . 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to the present invention, as shown in  FIGS. 1–8 , there is provided a golf club head  20 , adapted for attachment to a golf club shaft, which for the sake of clarity, is not shown. Club head  20  is integrally formed by coupling the edges of a wrap-around metal insert  40 , to a substantially hollow body  21  so as to form a cavity  22  therein. The preferred means for coupling is welding. 
   Body  21  is preferably cast of a titanium alloy. It may also comprise materials such as stainless steel, aluminum or composites. Body  21  includes a crown portion  23 , a heel portion  24 , a toe portion  25 , a sole portion  26 , a front face  27 , a skirt portion  28  connecting the heel portion  24  to the toe portion  25 , a hosel portion  29  comprising a hosel tube  30 , and an opening  31  defined in the front face  27  of a size and shape for receiving the wrap around insert  40 . The hosel tube  30  has a centerline C/L that intersects the sole portion  26 , and the heel portion  24  has an outer surface line H/L. 
   As shown in  FIGS. 4–8 , the wrap around insert  40  includes an impact face  41 , an upper edge  42 , a lower edge  43 , and a wing section  44  for extending outwardly into the skirt portion  28  and also below and beyond the hosel tube  30 . Wing section  44  has a length y that is preferably greater than about 20 mm, and a width w that is preferably greater than 10 mm. Insert  40  is preferably made of stamped titanium plate, more preferably beta-titanium and may be of variable thickness. 
   The present invention, by incorporating the aforementioned wing section  44  into body  21 , enables weight that is normally used in the hosel area, to be placed elsewhere in the club head  20  for optimum ball flight. The preferred size of the present invention club head is about 420 cc club head, and that size yield a savings of at least about 6 grams of material which can be then positioned at another location in the club head for improved performance. 
   The design of the cast body  21 , in which the toe portion  25 , crown portion  23  and sole portion  26  form part of the front face  27 , is such that welding of these portions to the insert  40  is kept a relative distance away from the transition seams formed by those portions. This increases the stability of the cast body  21  during manufacture and also insures minimum deformation of the aesthetically critical toe portion  25  during welding or polishing. The welding engagement along the perimeter of the insert  40  shifts the weld zone away from the critical crown/face and sole/face transition seams, therein reducing the thickness at the seams; this is a vital parameter in maximizing COR value. Beta-titanium and Alpha-titanium materials are preferred in the impact face  41  of the insert  40  because of superior mechanical properties, such as strength and ductility. 
   Although the size of conventional face inserts varies from one design to another, one common feature that these constructions have is an intimate connection between the face, hosel tube, and heel portion of the skirt wall. This results in a reduced unsupported face area if a narrower supporting perimeter was utilized. This can also potentially reduce the overall face flexibility and sweet spot. The wrapped face insert  40  of the present design eliminates all interior connections with the front face portion  27 , thereby maximizing the unsupported face area and allowing greater opportunity to increase the hitting area sweet spot. One notable improvement in the design of the wrap around insert  40  is the ability to increase the volume of the club head  20  behind the hosel plane, by eliminating material, and therefore overall weight, that has been necessary to maintain the connection between the hosel tube  30  and adjacent skirt wall  28 . This results in a larger face area and more discretionary weight available to further optimize the mass properties of the club head  20 , which is a key aspects towards achieving ideal launch conditional and overall performance. 
   As previously stated, the design of the wrap around insert  40  facilitates the removal of undesirable weight that is positioned between the internal hosel tube  30  and the skirt wall directly adjacent the hosel tube  30 . Prior art cast body construction of any metal wood club head, when coupled with the thru-bore hosel design, usually requires a connection between the hosel tube and the adjacent skirt wall due to the complexity and manufacturability of a collapsible core that creates the hollow cavity. The present design utilizes the wrap around insert  41 , which extends into and wraps around the heel portion of the face/skirt junction, thereby allowing access behind the hosel tube  30 . This additional access behind the internal portion of the hosel tube  30  provides the clearance needed to increase the core volume to a point where is fully extends behind the hosel tube  30 , yielding a hollow area where there once was unwanted material and added weight. 
   The wing section  44  extends into and engages the skirt portion  28  at a pre-determined distance. In a preferred embodiment, the predetermined distance x is at least 0.6 inch and preferably about 0.657 inch, as measured from the front center portion of the insert  40  to the edge  46  of the wing section  44 . The insert  40  is attached to the body  21  generally by welding along an engagement line  45 . 
   As described above, the wrapped face insert  40  may be preferably formed from a single stamped metal sheet plate, as shown in  FIGS. 4–8 , and may be of uniform thickness, but preferably is of a varied thickness with a wing section  44  formed by bending of the sheet metal. The thickness T 1  at the central portion of the insert  40  is about 0.13 inch; and at the bending area the thickness T 2  is about 0.08 inch, wherein it then tapers to a thickness T 3  of about 0.06 inch, preferably about 0.057 inch, at the distal end of the wing section  44 . 
   As stated above, the insert  40  attaches into the skirt junction of the body to create a gap  46  between the hosel tube  30  and the internal wall at the heel. The gap  46  is accessible only because the insert  40  wraps around the heel section of face and skirt junction. The distance CD between the hosel bore centerline C/L and the adjacent outer surface of the heel is in a range between about 0.3″ to 0.625″, and preferably about 0.388 inch for the present invention. The width GD of the gap  46  which is created between the hosel and the internal wall, is in a range between about 0.06″ to about 0.36″, and preferably about 0.125″ for the present invention. Presently, the USGA rules App. 11 1d.ii indicates that the maximum distance allowable between the hosel bore centerline C/L and the adjacent outer surface of the heel is 0.625 inch. 
   While various descriptions of the present invention are described above, it should be understood that the various features of each embodiment can be used singly or in any combination thereof. Therefore, this invention is not to be limited to only the specifically preferred embodiments depicted herein. Further, it should be understood that variations and modifications within the spirit and scope of the invention may occur to those skilled in the art to which the invention pertains. Accordingly, all expedient modifications readily attainable by one versed in the art from the disclosure set forth herein that are within the scope and spirit of the present invention are to be included as further embodiments of the present invention. The scope of the present invention is accordingly defined as set forth in the appended claims.