Abstract:
A golf club head is machined from an extruded bar having an irregular cross-section that is near-net-shape to the vertical profile of the club. To form the club head, the extruded bar is sliced into a club head blank. The blank is secured to a machining fixture and machined into the final configuration. Because the club head blanks are formed from an extrusion that is already near-net-shape to the profile of the club, less metal is removed during the machining operations, which results in faster process times, less wasted material and therefore substantial cost savings over the prior art methods of manufacturing golf club heads.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to golf club heads and in particular to golf putters and irons.  
         [0002]     Golf club putters and irons are traditionally made by an investment casting procedure sometimes referred to as lost-wax casting. According to this method, a wax replica of the club head is made by pouring wax into a mold. The wax replica is then dipped repeatedly into a ceramic slurry to build-up a ceramic mold of sufficient thickness to withstand the metal molding process. The wax is melted out of the mold and then the ceramic is fired to harden it. After it has been fired, the ceramic mold is filled with molten metal. Once the metal has cooled, the mold is broken off to reveal a club head blank that is ready for finish machining, which may include several steps of grinding, polishing, and/or milling.  
         [0003]     An alternative method of forming a club head blank is by forging. According to this process, a heated slug of metal is hammered or pressed between a male and female die to form the heated metal into the rough shape of the golf club head. The rough forgine is then subjected to additional machining steps to form the finished club head.  
         [0004]     Golf club heads have also traditionally been made by milling the club head out of a solid billet of metal. This, however, is the most expensive way to fabricate a club head because most of the raw material is wasted in the machining process. Typically, the finished club head weighs from 10% to 20% of the original weight of the billet. The remaining 80% to 90% of the billet ends up as chips on the machine room floor.  
         [0005]     All of the foregoing methods have their disadvantages. In the lost-wax casting process the build up of the mold takes several days and is labor intensive. Forging is expensive because of the additional tooling and machine operations necessary to forge the blanks and it can only be carried out on materials that respond well to forging. As noted hereinbefore, milling is the most expensive method of manufacturing because of the time necessary to mill a solid billet of metal and because of the substantial wasted material.  
       SUMMARY OF THE INVENTION  
       [0006]     The present invention comprises a method of manufacturing a golf club head in which the club head is machined from an extrusion that is already near-net-shape to a vertical profile of the finished club head. According to one embodiment of the invention, an extruded bar having an irregular cross-section that is near-net-shape to the front profile of the club is sliced into a club head blank. Datum are formed in the club head blank by drilling positioning holes, which are used to secure the club head blank to a machining fixture. The club head blanks are then machined into the final configuration including the face, the rear body and hose1 shank while secured to the fixture. In an alternative embodiment of the present invention, the club head blanks are sliced from an extrusion having an irregular cross-section that is near-net-shape to the side profile of the finished club head. A datum surface is created by rough machining a tab that extends forward from what will be the face of the club. The club head blank is secured to a machining fixture by clamping the tab to the fixture. The club head body is then machined into its finished form, after which the face is machined, removing the tab in the process.  
         [0007]     Because the club head blanks are formed from an extrusion that is already near-net-shape to the profile of the club, less metal is removed during the machining operations, which results in faster process times, less wasted material and therefore substantial cost savings over the prior art methods of manufacturing golf club heads. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0008]     The present invention will be better understood from a reading of the following detailed description, taken in conjunction with the accompanying drawings figures in which like references designate like elements and, in which:  
         [0009]      FIG. 1  is a front elevational view of a golf club incorporating features of the present invention;  
         [0010]      FIG. 2  is a rear perspective view of the golf club of  FIG. 1 ;  
         [0011]      FIG. 3  is a front perspective view of a club head blank used to manufacture the club head of  FIG. 1 ;  
         [0012]      FIG. 4  is a perspective view of a plurality of club head blanks mounted on a fixture for machining in accordance with the present invention;  
         [0013]      FIG. 5   a  is a vertical cross section of the club head blank of  FIG. 3 ;  
         [0014]      FIG. 5   b  is a representation of the front profile of the golf club of  FIG. 1  projected onto a vertical surface parallel to a horizontal line tangent to the face;  
         [0015]      FIG. 6  is a perspective view of an alternative embodiment of a club head incorporating features of the present invention;  
         [0016]      FIG. 7  is a perspective view of a club head blank used to manufacture the club head of  FIG. 6 ;  
         [0017]      FIG. 8   a  is a vertical cross section of the club head blank of  FIG. 6 ; and  
         [0018]      FIG. 8   b  is a representation of the side profile of the golf club head of  FIG. 6  projected onto a vertical plane normal to the face. 
     
    
     DETAILED DESCRIPTION  
       [0019]     With reference to  FIGS. 1 and 2 , a golf club head  10 , preferably a golf putter head, comprises a body  12  and a hose1 shank  14  with a boss  16  counterbored for receiving one end of a golf club shaft (not shown). The body  12  has a front face  18 , a heel end  20  and a toe end  22 . Front face  18  may optionally include a face insert  24  secured within a recess in face  18 . Golf club head  10  is fully machined from a metal material such as steel, titanium, or preferably an aluminum alloy such as Alcoa C805-T6511 or berrylium-free alloy C37H-T6511.  
         [0020]     With reference to  FIG. 3 , golf club head  10  is machined from a club head blank  26 . Club head blank  26  is formed by sawing-off a portion of an extruded bar  28 , along a plane  27  transverse to the longitudinal axis  29  of extruded bar  28 . As can be seen from  FIG. 3 , the cross-section of extruded bar  28  defines a surface  30  that is near-net-shape to (i.e., having an area no more than 150% greater than) the area of the vertical front profile of club head  10 . After club head blank  26  is severed from extruded bar  28 , positioning holes  32  and  34  are drilled through tabs  36  and  38  of club head blank  26 . Positioning hole  33  is similarly drilled through hose1 shank portion  37  of club head blank  26 . Positioning holes  32 ,  33  and  34  are then used to secure club head blank  26  to a fixture such as a “tombstone” horizontal milling fixture  40  as shown in  FIG. 4 . Once attached to tombstone  40 , club head blank is machined to form the rear surface of the body and hose1 shank of club head  10 . Club head blank  26  is then reversed and attached to tombstone  40  to allow the face and remaining features of golf club head  10  to be machined. Golf club head  10  is then removed from the tombstone  40  to permit tabs  36  and  38  to be removed and the hose1 bore to be drilled into boss  16 .  
         [0021]     With reference to  FIGS. 5   a  and  5   b , if the front profile of golf club head  10  is projected onto a vertical plane parallel to a horizontal line tangent to face  18  it yields a profile  40  encompassing an area of approximately 4.9 inches. The area of surface  30  of club head blank  26  is less than 10 square inches and is preferably approximately 8 square inches. Accordingly, throughout the entire machining operation the surface area  30  of club head blank  26  is reduced by only 40%-50%, that is, the area of profile  40  of the finished club head  10  is from 50%-60% of the area of the cross-section of extruded bar  28 . This compares very favorably to solid billet machining in which 80%-90% of the billet is machined away.  
         [0022]      FIG. 6  is a perspective view of an alternative embodiment of a golf club manufactured according to the present invention. For “mallet” style putters or other clubs that do not have a hose1 shank, such as club head  42 , in accordance with the present invention, the least amount of material is wasted if the club head is machined from a club head blank that is near-net-shape to the vertical side profile of the club. Accordingly, club head  42 , which comprises a face  44  and a body  46  is formed from a club head blank  50  that is near-net-shape to the side profile of club head  42 . With reference to  FIG. 7 , club head blank  50  itself is formed by severing a portion of an extruded bar  52  along a plane  53  transverse to the longitudinal axis  54  of the extruded bar  52 . As can be seen from  FIG. 7 , the cross section of extruded bar  52  is near-net-shape to the vertical side profile of club head  42 .  
         [0023]     To form club head  42 , club head blank  50  is attached to a machining fixture similar to tombstone  40  by clamping tab  56  to the machining fixture. Once club head blank  50  is clamped in place, the lateral surface  58 , lower surface  60  and upper surface  62  of body  46  are machined. Thereafter, club head blank  50  is removed from the machining fixture and placed in a second fixture to allow tab  56  to be machined off and face  44  finished. Thereafter, hose1 bore  48  is drilled into body  46  to complete the club head.  
         [0024]     With reference to FIG.s  8   a  and  8   b , the side profile of club head  42  projected onto a vertical plane normal to face  44  generates a contour  64  encompassing an area of approximately 1.56 square inches. The cross-sectional area  66  of extruded bar  52  (i.e. the area of blank  50 ) is approximately 2.1 square inches. Thus, throughout the entire machining operation the cross-sectional area of club head blank  50  is reduced by only approximately 25%. Club heads of different configurations can similarly be produced using side profile near-net-shape extrusions in which the machining operations remove only 15% to 30% of the profile area of the original extrusion. Indeed, the machining operations are so efficient that the finished parts still weigh between 30% and 45% of the weight of the original blank. This compares extremely favorably to billet machining in which the finished part often weighs only 10% to 20% of the weight of original billet. As used herein, near-net-shape means that the extrusion from which the club head blank is severed is no more than 150% larger in cross-section than the corresponding vertical profile (side or front) of the finished part, as opposed to machining of a billet or other wrought material typically provided in regular cross section shapes (e.g. square, round, rectangle). In many cases, however, as demonstrated above, the cross sectional area of the extrusion is only 100% larger or, in the case of the second embodiment, only 17% to 43% larger than the vertical profile area of the finished part (the finished part having a vertical profile area 70% to 85% of the area of the extrusion).  
         [0025]     As can be seen from the foregoing use of a near-net-shape extrusion to form the blank from which the golf club head is machined allows for a very highly efficient machining operation with less wasted machining time, less wasted material and therefore substantial cost savings over the prior art methods of manufacturing golf club heads.  
         [0026]     Although certain illustrative embodiments and methods have been disclosed herein, it will be apparent from the foregoing disclosure to those skilled in the art that variations and modifications of such embodiments and methods may be made without departing from the spirit and scope of the invention. Accordingly, it is intended that the invention shall be limited only to the extent required by the appended claims and the rules and principals of applicable law.