BACKGROUND OF THE INVENTION
This invention relates generally to golf clubs and, in particular, to so-called metal wood drivers.
Recent developments in golf club design have included improvements in drivers, which are clubs used primarily to strike a golf ball resting on a golf tee. These improvements have resulted in drivers with club heads consisting of a hollow shell usually made of metal, such as steel, aluminum, or titanium. One example of a golf club head consisting of a hollow metal shell is disclosed in U.S. Pat. No. 5,851,160 to Rugge, et al. In an effort to obtain better and better performance from these hollow metal wood drivers, however, golf club manufactures have increased the head volume from a moderate volume of 250 cubic centimeters as disclosed in Rugge, et al. to over 400 cubic centimeters in recent years. The striking face of a metal wood driver must be of a certain minimal thickness in order to withstand the impact forces generated upon impact with a golf ball. Accordingly, as head size increases, less and less material is available for fabricating the crown, sole and skirt of the club head while maintaining the club head of these super-oversized drivers within acceptable weight limitations (i.e., around 200 grams mass).
More recently, in U.S. Pat. No. 6,471,604, one golf club manufacturer has suggested a club head having a metallic face bonded to an aft body composed of a non-metal material such as a composite or thermoplastic material. The lightweight plastic rear body enables more metal to be dedicated to the striking face, however, many golfers dislike the impact sound produced by a club head having a low resonance, highly damped non-metallic rear body. Moreover, because of the discontinuity between the all-composite or thermoplastic rear body and the striking face, the striking face is not significantly supported by the rear body. Consequently, more material must be dedicated to striking face itself, thereby canceling out much of the weight savings attributable to the non-metallic rear body.
- SUMMARY OF THE INVENTION
Accordingly, what is needed is a club head having a metal-organic composite rear body, which is integral to the striking face and therefore maintains some of the stiffness (and frequency) of a fully-metallic rear body, while still providing a lightweight rear body structure.
DESCRIPTION OF THE DRAWINGS
The present invention comprises a golf club head formed of a hollow body having a metallic face and a rear body portion forming a shell at least a portion of which is made of a metal-organic composite material. According to a preferred embodiment, the rear body portion of the club head includes a metallic stringer that extends along a crown-skirt interface and a plurality of ribs intersecting the metallic stringer to form a lattice frame, the openings of which are filled with an organic composite material such as graphite epoxy. In the preferred embodiment, the lattice frame forms at least a portion of the crown of the rear body portion. An additional aperture formed in the skirt is also filled with the same graphite epoxy material. Because the graphite epoxy is lighter than the surrounding metal lattice frame, the rear body portion of the golf club head is lighter than a comparable all metal club head. Yet, the presence of the metallic stringer and lattice frame renders the metal-organic composite rear body portion substantially stiffer than a comparable all-composite rear body portion.
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:
FIG. 1 is a front view of a golf club head incorporating features of the present invention;
FIG. 2 is a rear perspective view of the golf club head of FIG. 1;
FIG. 3 is a top view of the golf club head of FIG. 1;
FIG. 4 is a toe-end side view of the golf club head of FIG. I;
FIG. 5 is a heel-end side view of the golf club head of FIG. I;
FIG. 6 is a bottom view of the golf club head of FIG. I;
FIG. 7 is a cross-sectional view of the golf club head of FIG. 6 taken along line 7-7;
FIG. 8 is a top view of an alternative embodiment of a golf club head incorporating features of the present invention; and
DESCRIPTION OF THE INVENTION
FIG. 9 is a rear perspective view of another alternative embodiment of a golf club head incorporating features of the present invention.
The drawing figures are intended to illustrate the general manner of construction and are not necessarily to scale. In the detailed description and in the drawing figures, specific illustrative examples are shown and herein described in detail. It should be understood, however, that the drawing figures and the detailed description are not intended to limit the invention to the particular form disclosed but are merely illustrative and intended to teach one of ordinary skill how to make and/or use the invention claimed herein and for setting forth the best mode for carrying out the invention.
With reference to FIGS. 1-7, and in particular FIGS. 1 and 2, golf club head 10 comprises a hollow body 12 formed of a metal material having a front wall including a face 14 for impacting a golf ball, and a hose 16 adapted to receive a golf club shaft (not shown). Hollow body 12 further comprises a rear body portion 18, which is made up of a crown 20, a sole 22 and a skirt 24 that form a shell. Crown 20 and skirt 24 meet at apex 26 which comprises an area having a small cross sectional radius of curvature 27 (FIG. 7) and which extends in an arcuate path (as viewed in FIG. 3) from a position proximal the heel end 28 of hollow body 12 to a position proximal the toe end 30 of hollow body 12.
The region surrounding apex 26 forms an arcuate perimeter region 32 that smoothly blends the high crown curve of apex 26 into the low crown curve of crown 20 and skirt 24. Arcuate perimeter region 32 preferably extends 0.700 inches above and 0.700 inches below the peak of apex 26, preferably 0.350 inches above and 0.350 inches below the peak of apex 26 and most preferably about 0.250 inches above and 0.250 inches below the peak of apex 26. Arcuate perimeter region 32 is unsupported above and below by any of the metal forming hollow body 12 for at least a portion of its span.
Hollow body 12 may be assembled from a series of forged metal pieces that are welded or brazed together, but in the illustrative embodiment of FIGS. 1-7, comprises a titanium investment casting. Crown 20 is formed with a solid return portion 33 that extends rearward from face 14 and a series of apertures 34 proximal the rear end of hollow body 12. Skirt 24 is formed with solid return portions 35 and 37 that extend rearward from face 14 and an aperture 36 proximal the rear end of hollow body 12. Apertures 34 and 36 cooperate to form a metallic stringer 38 that extends along a portion of the arcuate perimeter region 32 as well as a plurality of ribs 40 that support stringer 38 along a portion of its span. In the illustrative embodiment, a second stringer 42 disposed radially inward from stringer 38 is tied to ribs 40 to form an open lattice frame.
Apertures 34 and 36 are filled with a material that is of lower density than the relatively denser metallic hollow body 12. The material may be a lightweight non-metallic material 44 such as thermoplastic, or thermoset plastic, or preferably a fiber reinforced organic resin such as fiberglass-epoxy, fiberglass-polyester, ceramic-fiber epoxy, aramid-epoxy or other fiber-organic resin composites. Preferably, the non-metallic material comprises graphite-epoxy, which is laid up on the interior surface 46 (FIG. 7) of hollow body 12 extending across all of the stringers 38, 42 and ribs 40 to form a part titanium part carbon graphite composite rear body portion 18.
In the illustrative embodiment of FIGS. 1-7, non-metallic material 44 comprises prepreg layers of graphite epoxy which are laid up on the interior surface 46 of hollow body 12 covering apertures 34, 36 and an inflatable bladder (not shown) is then inserted into the cavity 48 of hollow body 12 through one of the apertures 50 and 52 disposed in the bottom of weight pockets 54 and 56. Hollow body 12 is placed in a mold cavity (not shown) that conforms to the outer surface of the hollow body 12. The bladder is then inflated and the mold heated to cure the prepreg epoxy.
By eliminating metal from portions of the crown 20 and the skirt 24, as represented by apertures 34 and 36, the illustrative embodiment of FIGS. 1-7 accomplishes a club head 10 in excess of 400 cubic centimeters in volume with the hollow body 12 weighing from 150 to 170 grams and the composite filler weighing from 10 to 40 grams. In doing so, the face 14 can be increased to at least 5.00 square inches (preferably approximately 5.30 square inches) with a maximum thickness of between 0.110 and 0.160 inches proximal the geometric center 58 (FIG. 7) of the face 14 tapering downward to a lesser thickness of 0.070 to 0.090 inches towards the perimeter 60 of the face 14. This is accomplished without sacrificing structural integrity and without exceeding the desired total weight of about 200 grams mass. Moreover, the presence of the metallic stringers 38, 42 and ribs 40, which are integrally attached to the face 14 (i.e., formed as a single casting, welded or brazed together as opposed to adhesively bonded or attached with fasteners) provide support for the face 14 not present in pure composite back body designs while also maintaining the desirable dominant natural frequency of at least 3,500 hertz.
With reference to FIG. 8, an alternative embodiment of a metal-organic composite golf club head in accordance with the present invention comprises a hollow body 62 having a crown 64. A series of apertures 66 are formed in crown 64 in three rows, which form a plurality of ribs 68, an outer metallic stringer 70 as well as inner metallic stringers 72 and 74, each of the inner metallic stringers 72 and 74 being displaced radially inward from stringer 70. As with the embodiment of FIGS. 1-7, apertures 66 are filled with a lightweight non-metallic material, preferably a graphite epoxy to seal the interior cavity of hollow body 62 and to provide a smooth exterior surface.
With reference to FIG. 9, another alternative embodiment of a metal-organic composite golf club head in accordance with the present invention comprises a hollow body 82 having a crown 84 and a skirt 86. As with the embodiment of FIGS. 1-7, crown 84 and skirt 86 each have a metallic return portion 88 and 90, respectively, that extends rearward from the face of the club head. Single large apertures 92 and 94 are formed in crown 84 and skirt 86 which results in a metallic stringer 96 that extends almost the full length of arcuate perimeter region 98 of hollow body 82. As with the embodiment of FIGS. 1-7, apertures 92 and 94 are filled with a lightweight non-metallic material, preferably a graphite epoxy.
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 should be limited only to extent required by the appended claims and the rules and principals of applicable law.