WO2001030461A1

WO2001030461A1 - Golf club

Info

Publication number: WO2001030461A1
Application number: PCT/US2000/029587
Authority: WO
Inventors: David F. Muller; Adrian R. Grundy; Nathan T. Ulrich
Original assignee: Mile Creek Capital, Llc
Priority date: 1999-10-28
Filing date: 2000-10-27
Publication date: 2001-05-03

Abstract

A golf club head comprises a core zone and a plurality of surrounding fiber zones. The core is preferably formed of a syntactic foam which has dispersed therein a plurality of particles. The fiber zones include either uni-directionally oriented or multi-directionally oriented fiber layers, each of which contains a predetermined weight percentage of resin to cause adherence of the layers to the core and to each other through molding of the club head. The golf club head further includes a weighting element which may be formed within the fiber zones during molding of the club head, or may be subsequently introduced into the club head following molding.

Description

GOLF CLUB

FIELD OF THE INVENTION

This invention relates generally to golf clubs, and more particularly to a golf club head made from a foam core and a surrounding fiber matrix.

BACKGROUND OF THE INVENTION

Recently, as participation in the game of golf has sharply increased, and advances in technology have been concurrently realized, designers have been under heightened pressure to create optimal golf clubs, which, generally stated, would more easily enable a golfer to hit a golf ball a desired distance with proper accuracy.

In seeking to do so, designers are somewhat handcuffed by the Rules of Golf adopted by the United States Golf Association and the Royal and Ancient Golf Club of St. Andrews. For example, Appendix II of the Rules of Golf, which pertains to the design of golf clubs, delineates somewhat restrictive limitations regarding the dimensions and adjustability of golf clubs.

The Rules of Golf, however, do not restrict the weight of golf clubs. Despite this fact, very little variation generally exists between the weight of golf clubs today as compared to those of yesteryear. For example, a golf club made today would likely be nearly identical in weight to a counterpart club made 25 years ago (e.g., a five iron made today would likely be nearly identical in weight to a five iron made in 1975, as would a three wood made today versus a three wood made in 1975).

A likely explanation for this fact is that designers realize that each golf club has an ideal weight that allows an average-sized golfer to swing it with proper mechanics. If a golf club was significantly heavier or lighter than its ideal weight, it would compromise a golfer's swing mechanics and, in turn, negatively affect the accuracy and/or distance of the golfer's shots.

This de facto weight limitation has strongly influenced the design of all golf clubs, but in particular, driver-type golf clubs (i.e. , "drivers"). Unlike other golf clubs, which golfers use to hit a golf ball a specific distance, golfers generally use their driver to hit a golf ball as far as possible. To facilitate this, designers have focused upon constructing the heads of drivers primary or entirely of metal.

Metal-based materials provide a driver head with strength and stiffness, which, in turn, cause a struck golf ball to travel a great distance. But metal-based materials also are quite heavy. Thus, in order to prevent the weight of drivers with metal -based heads from weighing above their ideal weight range, their heads are substantially hollow, with their weight primarily dispersed evenly around the periphery of the club head.

Ideally, designers would like to create a driver (and/or other type of) club head that has its weight more concentrated toward the heel and toe of the club, as such a design would increase the "forgiveness" of the club - that is, the ability of the club to produce shots that travel nearly as far and as accurately as shots hit with the "sweet spot" of the club head despite actually being hit elsewhere on the club head (i.e. , near the toe or heel of the club head). Unfortunately, in order to tailor a metal-based driver head in this manner while still ensuring that the driver has an ideal weight, one would be required to further hollow other areas of the driver head. This would result in a driver head that would be more prone to cracking and fracturing at these areas upon impact with a golf ball.

Perhaps realizing the shortcomings of designing a golf club with a metal-based head, several golf club designers turned their attention to developing golf clubs with heads that are not metal-based, such the golf club heads described in U.S. Patent No. 4,667,963 to Yoneyama and U.S. Patent No. 5,672,120 to Ramirez. These clubs, however, suffer from various problems, most notably highly labor-intensive manufacturing processes and, in the case of the Ramirez club head, the lack of a hosel on the club head.

Therefore, a need exists for a easy-to-manufacture golf club head that may be manufactured to allow for increased weighting at certain areas of the club head, while still being structurally sound and having a weight that falls within the club head's ideal weight range. SUMMARY OF THE INVENTION

The present invention provides a golf club head manufactured to have a foam core and at least one single or multi-layered fiber zone. The fibers in the layers that make up the fiber zone(s) may be unidirectional and/or multi-directional in their orientation. In one aspect of the invention, one fiber zone has multiple layers, with the fibers in each layer being uni-directionally oriented, and another fiber zone has multiple layers, with the fibers in each layer being multi-directionally oriented. Such a design offers a construction having a weight less than that of a club head made from metals or metal alloys. At the same time, however, the club head possesses strength and stiffness properties that are comparable to or greater than those of many metal- or metal alloy- based club heads.

Preferably, the core of the club head is or includes a syntactic foam. Syntactic foams comprise a matrix of a polymeric material having dispersed therein a plurality of discrete particles, such as glass microspheres and/or thermoplastic balloons. Additionally, non-foam components such as chopped graphite fibers and/or metal -based beads may be added to the syntactic foam to increase its density and, thus, its weight.

The golf club head of the present invention may also include one or more inserts. The insert(s) may be formed within the fiber zone(s) during molding and/or they may be introduced into one or more cavities defined within the fiber zone(s) after the molding process. The insert(s) add additional weight to the club head, increase its durability (e.g. , by thwarting pitting), and/or change the loft angle of the club head. Also, if placed at or near the striking surface of the club head, an insert will allow the club head to produce a sound, upon impact with a golf ball, that more closely resembles the sound produced when a golf ball is struck by a primarily or entirely metal-based golf club head.

The invention also provides a method of manufacturing a golf club head having the characteristics and properties discussed above. BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a front view of a golf club head in accordance with the present invention;

FIG. 2 is a cross-sectional side view along line 2-2 of the golf club head of FIG. i;

FIG. 3 is an enlarged view of region A of the golf club head of FIG. 2; FIG. 4 is an enlarged view of region B of the golf club head of FIG. 2; FIG. 5 is a cross-sectional side view of an alternate embodiment of the golf club head of FIG..2 having an insert formed within the leading surface of the club head;

FIG. 6 is a cross-sectional side view of an another alternate embodiment of the golf club head of FIG. 2 having an insert formed within the sole surface of the club head; FIG. 7 is a top view of yet another alternate embodiment of the golf club head of FIG. 1 having an insert that is slidably insertable into communication with the leading surface of the club head; and

FIG. 8 is a top view of still yet another alternative embodiment of the golf club head of FIG. 1 having inserts formed within the toe and heel portion of the club head.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 depicts a golf club head 10 in accordance with the present invention. The club head 10 has a hosel 12, which allows for the attachment of a shaft 13 in order to form a golf club. The club head 10 also includes a toe portion 14 and a heel portion 16, and has a sole surface 18 and an opposed top surface 20. The leading surface 22 of the club head 10 includes a striking surface 24, approximately a central portion of which represents the so-called "sweet spot" of the club head.

The striking surface 24 and/ or other portions of the leading surface 22 of the club head 10 may be coated with a material effective to alter its coefficient of friction so as to optimize the amount of time during which a golf ball struck by the club head 10 adheres to surface 24. To reduce the coefficient of friction and, thus, the amount of time of adherence, the surface(s) may be coated with polytetrafluoroethylene and/or other known friction-reducing materials. To increase the coefficient of friction and, thus, the amount of time of adherence, a grit and/or another friction-enhancing material may be applied to the surface(s) . As shown in FIG. 2, the internal construction of the club head 10 includes a core 30 and at least one fiber zone. In the exemplary embodiment of FIG. 2, the club head 10 includes two fiber zones 40, 50. Internal fiber zone 40 immediately surrounds the core 30, while external fiber zone 50 immediately surrounds the internal fiber zone and forms an external surface of the club head. A club head 10 containing such an arrangement of a core 30 and fiber zones 40, 50 is molded as described below to form a strong, stiff golf club head that requires little to no end finishing, and that weighs less than a primarily or entirely metal -based club head.

FIGS. 3 and 4 depict enlarged views of the core 30 and fiber zones 40, 50 of the club head 10. Generally, the fiber zones 40, 50 are each formed of layers of both fiber- based material and a resin component. Such a mixture is advantageous because the fiber-based material provides the club head with strength and stiffness properties without contributing much weight. The resin component contributes to the formation of the fiber zones 40, 50, and enables them to adhere to one another and/or to the core 30. The mixture of fiber layers and resin may be prepared by prepreg, wet-lay or resin transfer molding processes, each of which is a preparation technique known to one of ordinary skill in the art. Prepreg preparation is currently preferred over the other methods of preparation because, unlike either wet-lay or resin transfer molding processes, it currently enables better control of the weight percentage of resin in the fiber zones 40, 50. The relative amounts of resin and fiber layers included within each of the fiber zones 40, 50 may vary; however, at least about 35 % by weight of resin should be present in each fiber layer in order to provide suitable adhesion of the fiber layers. The amount of resin present should not exceed about 50% by weight of resin in each fiber layer of fiber zones 40, 50, because the presence of excess resin will detract from the amount of fiber material in the fiber zones and, consequently, reduce the strength and stiffness of the club head. One of ordinary skill in the art will appreciate that a variety of different fibers and resins may be employed in accordance with the present invention. Exemplary resin materials include, but are not limited to, epoxy, polyester, vinyl ester and cyanate ester. Epoxy is a currently preferred resin. Suitable materials that may form the fiber component of each fiber zone 40, 50 include, but are not limited to, carbon fiber, polyaramid fiber (available commercially as KEVLAR™), linear polyethylene fiber (available commercially as SPECTRA™), liquid crystal polymer fiber (available commercially as VECTRAN™), fiberglass, boron fiber, and ceramic fiber.

In a currently preferred embodiment, carbon fiber (s) are used as the fiber component in each of the fiber zones 40, 50. Exemplary raw carbon fibers are available from many suppliers, such as BP Amoco Chemicals of New York, NY, Grafil Inc. of Irvine, CA, Hexcel Composites Inc. of Northborough, MA, and the Toray Group of Tokyo, Japan. Exemplary suppliers of "made to order" prepreg carbon fibers impregnated with resin are The Advanced Composites Group of Tulsa, OK and Newport Adhesives & Composites of Irvine, CA.

The fibers included in the fiber component are preferably part of a fiber mat in which individual fibers are continuous. One of ordinary skill in the art will appreciate that the individual fibers present within the mat may have a variety of orientations, properties, diameters, and tow counts (i.e. , numbers of filaments per strand of fiber). Preferred diameters for individual fiber strands are in the range of about 5 micrometers to 10 micrometers, with about 7 micrometers being a more preferred per strand diameter. Preferred tow counts are in the range of about 3,000 filaments per strand of fiber to 12,000 filaments per strand of fiber.

In one embodiment of the present invention, the fibers in each layer of the internal fiber zone 40 are uni-directionally oriented, and the fibers in each layer of the external fiber zone 50 are multi-directionally oriented. Also, although the club head 10 of FIGS. 1-4 is depicted as including two fiber zones 40, 50, the number of zones may be greater or less than two without departing from the scope of the invention. However, in an embodiment in which the club head includes only one fiber zone, the fibers in each layer of that zone are preferably multi-directionally oriented because such layers possess an isotropic toughness that is more suitable for the outermost layer of the club head.

Each fiber zone 40, 50 may be comprised of from 1 to 20 or more layers or plies of fiber. In a preferred embodiment, there are between one and ten plies in the internal fiber zone 40 or any other zone comprised of uni-directionally oriented fibers, and between one and five plies in the external fiber zone 50 or any other zone comprised of multi-directionally oriented fibers.

The material characteristics of two exemplary uni-directionally oriented fibers (T700 carbon/epoxy and M55J carbon/epoxy — the former being supplied by The Toray Group, and the latter by Hexcel Composites) and an exemplary multi-directionally oriented fibers (T300 carbon/epoxy 4X4 twill - supplied by The Toray Group) are listed below in Table I in comparison to three common metal-based golf club head materials (7075-T6 aluminum, 6AL-4V titanium STA (solution-treated and aged), and 15-5 stainless steel). The characteristics of the exemplary uni-directionally oriented and multi-directionally oriented fibers are independent of the number of layers of fibers present.

TABLE I

+ Density for composite materials is approximate; it depends on resin content and cured compaction As can be seen from the data contained in Table I, each of the fiber materials has a tensile strength greater than or comparable to each of the metal -based materials, and at least a three-fold greater specific tensile strength than any of the metal-based materials. Each of the uni-directionally oriented fiber materials also has a three-fold or greater specific stiffness than any of the metal-based materials, while the multi- directionally oriented fiber material has a specific stiffness that is comparable to that of the metal-based materials. Moreover, both the uni-directionally oriented fiber materials and the multi-directionally oriented fiber material have mass densities that are between approximately one-half to one-fourth the mass densities of the metal-based materials. Thus, a golf club head that is made with these uni-directional and/or multi-directionally oriented fiber materials will have as great or greater strength and stiffness as a golf club head made entirely out of one of the metal-based materials, while weighing much less.

As shown in FIGS. 3 and 4, the interior of the club head 10 also includes a core zone 30. The core 30 is preferably comprised of a material that has a high compressive strength, and that expands when the club head is molded. The compressive strength is advantageous because it causes the core material to compress and rebound while striking a golf ball, thus allowing for a golf ball struck by the club head 10 to properly "bounce" from the club. The ability of the material to expand during manufacturing or molding is also advantageous because expansion of the core material places pressure on the fiber layers in the internal fiber zone 40 of the club head which, in turn, places pressure on the fiber layers in the external fiber zone 50 of the club head. The fiber layers in the external fiber zone 50 are thus forced against the mold during curing and, consequently, emerge from the mold with a surface finish that requires little or no end- finishing. Preferably, the core material should also contain an amount of resin that is effective to ensure that the core 30 adheres to the fiber layers in the internal fiber zone 40 of the club head 10 during molding of the club head. Exemplary resins include, but are not limited to, epoxy, polyester, vinyl ester and cyanate ester, with epoxy being currently preferred. Generally, the weight percentage of resin in the foam should be in the range of about 35 % to 45 % . An exemplary core material that provides the above-noted advantageous characteristics is syntactic foam. Syntactic foams comprise a polymer matrix with a plurality of discrete components 52 dispersed therein. Exemplary such components 52 may include, but are not limited to, hollow or solid microspheres of glass or other material and/or thermoplastic "balloons" of materials such as polyester, nylon and/or polystyrene and other material dispersed therein.

The size of the components 52 may vary within broad limits. For example, each glass microsphere generally has a diameter in the range of about 1 micron to 1000 microns, preferably between 10 microns and 300 microns, and a wall thickness equal to approximately 10% of its diameter.

Suitable syntactic foams may be either of the "high density" or "low density" variety. Generally, a syntactic foam with a mass density of at least 0.5 g/cc is considered "high density" syntactic foam, while one with a mass density below that number is "low density. " Exemplary properties of "low density" and "high density "syntactic foams are shown in Table II.

TABLE II

Density for composite materials is approximate; it depends on resin content and cured compaction

The syntactic foam that comprises the core 30 may also include non-foam components in addition to the components 52 already dispersed therein to vary the density of the foam. Exemplary non-foam components may include, but are not limited to, chopped graphite fibers and/or metal-based beads such as titanium, aluminum, tungsten, spent uranium and/or stainless steel. These non-foam components may be added to the syntactic foam by the manufacturer, a commercial supplier or, generally, by an end user.

An exemplary high density syntactic foam that possesses the material characteristics listed in Table II is LORD 4300, which is commercially available from Lord Corporation of Fountain Valley, CA. The exact composition of the LORD 4300 foam is proprietary, however, the foam does contain less than 45% by weight of epoxy resin, less than 3 % by weight of Oxybis (benzene-sulfonyl) hydrazide, and a variable weight percentage of glass microspheres . Also, the LORD 4300 foam is readily co- curable at 135°C with prepregs or adhesive resin systems. One of ordinary skill in the art will readily appreciate that other syntactic foams possessing the material characteristics of Table II exist, including, but not limited to, expanding foam available from the Durham Boat Company of Durham, N.H. While the composition of this expanding foam is also proprietary, it has a lower density than the LORD 4300 syntactic foam and includes, as components dispersed within the foam, a combination of epoxy resin, glass microspheres, polymer microspheres, and chopped graphite fibers.

A golf club head of the present invention is prepared generally as follows. First, a mold is selected depending on the specific type of golf club head to be prepared. For example, the mold preferably consists of two halves that are secured or otherwise placed together during the molding process to produce one or more club heads. One of ordinary skill in the art will readily appreciate that the mold halves should be polished and/or treated with mold release either periodically or prior to each use.

The fiber layers are then placed into the mold halves in desired orientations. Preferably, the multi-directionally oriented fiber layer(s) is/are added first in order to rest directly against the mold halves, and such that they will form the external fiber zone 50 of the club head. The number of multi-directionally oriented layers added onto each mold half generally will be in the range of one to five, with an equal number of layers generally being added onto each mold half. When making a driver club head, for example, one multi-directionally oriented fiber layer preferably is added on each mold half, and the total weight of multi-directionally oriented fiber material added should be approximately 10 grams, of which in the range of about 3.5 grams to 5.0 grams is resin.

Next, the uni-directionally oriented fiber layer(s), if included, is/are added in one or more layers on top of the multi-directionally oriented fiber layers so as to form the internal fiber zone 40 of the club head. The number of uni-directionally oriented layers added on each mold half will be in the range of one to ten. Preferably, the number of uni-directionally oriented layers added to each mold half will differ, with more layers being added to the mold half that will produce the leading surface 22 (see FIG. 1) of the club head. When making a driver club head, for example, preferably, the number of uni-directionally oriented layers added to that mold half is in the range of three to ten, while the number added to the other mold half is in the range of one to five. The total weight of uni-directionally oriented fiber material in the layers should be approximately 20 grams, of which in the range of 7 grams to 10 grams is resin.

The syntactic foam, in the form of a putty, is then placed on the exposed fiber layer(s) in either or both halves of the mold, after which the mold halves are closed. If desired, non-foam components such as chopped graphite fibers and/or metal-based beads or spheres of titanium, aluminum, tungsten, spent uranium and/or stainless steel may be added (i.e. , mixed) into the syntactic foam prior to its placement in the mold. When preparing a driver club head, the weight of syntactic foam, including any non- foam components, should be approximately 120 grams, of which in the range of about 42 grams to 52 grams is resin.

Prior to commencing the curing of the club head, the closed mold halves preferably are securely closed, e.g. , via bolting the mold halves together. This is done because the pressure encountered during the molding process due to the presence of the expanding syntactic foam could otherwise force open the mold halves during the curing process.

The specific club head molding conditions may vary in accordance with the present invention. Generally, however, the composition contained within the mold is cured in a medium temperature curing environment wherein the temperature is in the range of about 220° F to 280° F, with about 250° F being a preferred curing temperature. The club head can also be adapted to be cured at a higher temperature, e.g., up to approximately 600°F. The molding pressure generated by the foam during curing is generally at least 1.0 atmospheres, but can be higher. These conditions generally do not vary depending on the specific club head being molded.

The mold may be cured according to one of several techniques, including in a conventional oven, via heat transfer thereto, via the inclusion of heater or electrical resistance elements in the body thereof, or through the use of one or more presses (e.g., hydraulic press(es)). The curing time can range from a few minutes to a few hours depending on the curing environment and/or the resin system. For example, an exemplary curing time when employing a conventional oven at a temperature in the range of about 220 °F to 280° F is approximately two hours, while an exemplary curing time when employing a hydraulic press at a temperature in the range of about 220 °F to 280°F is in the range of about 15 minutes to 1.5 hours. Curing the mold via a hydraulic press is a currently preferred curing technique.

The above-described process may be adapted to produce in the club head a protruding hosel 12 into which a shaft 13 may be inserted (see FIG. 1). Such a hosel

12 can be formed either from shaped fiber layers similar to those included in the fiber zones 40, 50 of the club head, or, preferably, from a metal-based insert that was placed within the multi-directionally oriented fiber layer(s) prior to curing.

In the' case of the latter, the metal-based insert should be selected, prepared and/or pre-treated as is generally known in the art in order to assure adherence thereof to the club head via the resin present in the multi-directionally oriented fiber layer(s). By way of non-limiting example, one may employ mechanical keying through the use of annular grooves and/or a barbed hose fitting to ensure integral bonding of the insert to the resin present within the multi-directionally oriented fiber layer(s). The club head emerges from the mold with several desirable properties.

Because of the presence of the expanding syntactic foam in the core zone of the club head, the resulting club head has a surface finish that requires little or no end finishing. Moreover, the presence of fiber layers in the internal and external fiber zones of the club head ensures that the club head has a strength and stiffness equal to or greater than a comparable primarily or entirely metal-based golf club head, while having a much lower weight. In fact, in an exemplary embodiment of the present invention, the weight of a driver club head upon emerging from the mold is approximately 150 grams, which is approximately 55 grams less than the typical weight of a driver club head. This allows for the addition of extra weight to the club head to improve the performance of the club. To this end, the process described above may include several embodiments in which weight-adding inserts (depicted in FIGS. 5-8) are added to the club head in strategic locations either during or following the molding process.

FIGS. 5 and 6 depict examples of club heads 10, each of which contains an insert 60. In such embodiments, the insert 60 is generally placed within the layer(s) of multi-directionally oriented fibers prior to the closing of the mold. Preferably, mechanical keying, e.g., the use of annular grooves and/or a barbed hose fitting, is employed in order to promote integral bonding of the insert 60 to the resin present within the multi-directionally oriented fiber layer(s) during the curing process.

FIG. 5 depicts the insert 60 as a face plate formed within the leading surface 22 of the club head 10, while FIG. 6 depicts the insert 60 as a sole plate formed within the sole surface 18 of the club head. Placement of the insert 60 at the leading surface of the club head 10 is preferable as it will cause a sound, when the club head impacts a golf ball, that more closely resembles that of metal-based club head impacting a golf ball. The areas of the club head 10 where the insert 60 is located may vary beyond those that are shown in FIGS. 5 and 6 without departing from the scope of the invention. For example, the insert may be located at or proximate to the toe portion 14 (see FIG. 1) or heel portion 16 (see FIG. 1) of the club head. Such a placement is desired in order to provide the club head with more "forgiveness" - that is, increased ability to allow slightly mishit shots to travel nearly as far and as accurately as shots made when the ball is hit with the "sweet spot" of the club head.

Moreover, the exact mater ial(s) from which the insert 60 is made will depend on the weight the insert is to have; however, the insert generally will be made entirely or partially from a metal or metal alloy material such as aluminum, titanium, tungsten, spent uranium or stainless steel. The material chosen should be capable of being prepared and/or pre-treated in order to promote adherence thereof to the resin in the fiber zones of the club head via mechanical keying.

Additionally or alternatively, an insert 60 may be added to the club head 10 after it has been molded. For example, FIG. 7 illustrates a club head that has been molded to have a cavity 70 defined therein. To define the cavity, a mandrel made out of a metal-based material, such as aluminum, is placed into the mold. Generally, the mandrel is placed within the layers of multi-directionally oriented fibers, but may be placed elsewhere without departing from the scope of the present invention. Following curing of the club head, the mandrel is removed to leave a cavity 70 into which a golf club shaft or insert may be introduced. To assure that the mandrel may be removed without harming the structure of the molded club head, the mandrel should be highly polished and/or treated with a mold release agent prior to its placement within the mold. In either case, the mold preferably has a precise surface topography and finish in the region corresponding to the leading surface 22 (see FIG. 1) of the club head. In the exemplary embodiment shown in FIG. 7, the cavity 70 is defined to allow for the slidable insertion of an insert 60. The insert 60 contains a protruding area 62 that may be slidably inserted into the cavity 70 of the club head 10 from above or below such that the protruding area enters the cavity and depresses and/or engages detents 80 to lock the insert in place as is generally known in the art. Although not shown, one may use a plurality of slidably insertable inserts 60 in conjunction with the club head of FIG. 7 in order to replicate the weight and loft angle of different golf clubs. This will enable a golfer to buy only two golf clubs (one with a "wood-type" club head and one with an "iron-type" club head) and a "set" of slidably- insertable and removable inserts 60 the type shown in FIG. 7, wherein insertion of each insert 60 allows the club head to simulate the weight and loft angle of a comparable customary club head.

One of ordinary skill in the art will appreciate that the detents 80 may be greater or fewer in number than the two detents depicted in FIG. 7, and may be located in a different area of the cavity 70 than depicted in FIG. 7. Furthermore, the club head 10 can be adapted to contain cavities 70 at any portion thereof and the club head may contain more than one cavity. Also, one of ordinary skill in the art will ascertain that the cavity or cavities 70 may alternatively be threaded to allow for the threaded connection of an insert 60 to the club head 10.

FIG. 8 depicts a club head 10 that includes more than one weight-adding insert 60. Generally, these inserts may be made of the same materials from which the inserts of FIGS. 5-7 are made. Also, one, some or all of these inserts 60 may be formed within the club head 10 during manufacture or molding as discussed above with reference to FIGS. 5 and 6, and/or added to the club head following molding as discussed with reference to FIG. 7.

The club head 10 of FIG. 8 is depicted with two inserts 60, one located proximate to the toe portion 14 of the club head, and another located proximate to the heel portion 16 of the club head. Such an arrangement of inserts 60 is preferred in order to provide "forgiveness" to the club head 10 for shots hit at areas "T' or "H" of the leading surface 22 of the club head (i.e., for shots not hit at the "sweet spot" of the leading surface). Although the inserts 60 of FIG. 8 are depicted as elliptical in shape, they may have virtually any shape without departing from the scope of the present invention. Further, the club head 10 may include more than two inserts 60, e.g. , wherein each additional insert is formed within, or insertable within, the leading surface or sole surface of the club head. However, while the number of inserts 60 that may be included is not limited, the combined weight of the inserts should be such that their weight plus that of the club head 10 allows the overall weight of the club head to fall within that club head's ideal weight. Generally, the overall combined weight of the insert(s) will comprise approximately one-third or less of the overall weight of the club head. Although the club head 10 of the present invention has been described as having a core, one internal fiber zone 40, with one or more layers of uni-directional fibers, and one external fiber zone 50 with one or more layers of multi-directional fibers, the number of fiber zones and the orientation of the fibers in those zones may be varied. In an embodiment in which there is more than two fiber zones 40, 50, additional fiber zones may contain either fiber layers with multi-directionally oriented fibers or fiber layers with uni-directionally oriented fibers. But as long as there is more than one fiber zone present, the fiber zone that immediately surrounds the core should contain only fiber layers with uni-directionally oriented fibers. And regardless of the number of fiber zones present, the outermost layer should contain multi-directionally oriented fibers. For purposes of the present invention, the club head 10 can be used for any type of golf club, including a wood-type club, an iron-type club, or a putter club. Wood- type clubs include, but are not limited to, drivers of any size and fairway woods made of any material. Iron-type golf club heads include, but are not limited to, long irons, short irons, and wedges made of any material. Putter clubs include putters of any size, shape and material.

Furthermore, for purposes of the present invention, the striking surface 24 of the club head 10 may comprise a greater or smaller surface area of the leading surface 22 than depicted in FIG. 1. The striking surface 24 may be indicated with surface features other than the horizontal lines shown in FIG. 1 or, alternatively, may have no differentiating surface features or indications.

One skilled in the art will appreciate further features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated herein by reference in their entirety.

What is claimed is:

Claims

1. A golf club head, comprising: a toe portion, a heel portion, a sole surface, an opposed top surface, and a striking surface disposed on a leading surface of the club head between the sole surface and the top surface, the club head further comprising: a core comprised of a syntactic foam; and a first fiber zone comprising at least one layer of multi-directionally oriented fiber forming an external portion of the club head, and each layer of multi-directionally oriented fibers having from about 35 to 50 weight percent of a first resin component.

2. The golf club head of claim 1, further comprising a second fiber zone disposed between the core and the first fiber zone, the second fiber zone including at least one layer of fibers and an amount of a second resin component in the range of about 35 to 50 weight percent, wherein all fibers in each layer of the at least one layer of fibers are uni-directionally oriented.

3. The golf club head of claim 1 , wherein the syntactic foam has a tensile strength in the range of about 18 MPa to 32 MPa.

4. The golf club head of claim 1, wherein the syntactic foam has a compressive strength in the range of about 60 MPa to 110 MPa.

5. The golf club head of claim 1, wherein the syntactic foam has a mass density in the range of about 0.30 g/cc to 0.55 g/cc.

6. The golf club head of claim 1, wherein the syntactic foam has a foam component with a plurality of discrete components dispersed therein.

7. The golf club head of claim 6, wherein the discrete components are selected from the group consisting of glass microspheres, thermoplastic balloons, and mixtures thereof.

8. The golf club head of claim 7, wherein the thermoplastic balloons are made from a material selected from the group consisting of polyester, nylon, polystyrene and mixtures thereof.

9. The golf club head of claim 7, wherein the syntactic foam further includes a plurality of non-foam components selected from the group consisting of chopped graphite fibers, metal beads, and mixtures thereof.

10. The golf club head of claim 9, wherein the metal beads are made from a material selected from the group consisting of titanium, aluminum, tungsten, spent uranium, stainless steel, and mixtures thereof.

11. The golf club head of claim 2, wherein the fibers present in the first fiber zone and the second fiber zone are formed of materials selected from the group consisting of a carbon fiber, polyaramid fiber, linear polyethylene fiber, liquid crystal polymer fiber, glass fiber, ceramic fiber, and boron fiber.

12. The golf club head of claim 2, wherein the first and second resin components are selected from the group consisting of epoxy, polyester, vinyl ester and cyanate ester.

13. The golf club head of claim 1, further comprising at least one insert disposed at least partially within the club head.

14. The golf club head of claim 13, wherein each of the at least one inserts is made of a metal-based material selected from the group consisting of aluminum, titanium, tungsten, spent uranium, and stainless steel.

15. The golf club head of claim 13, wherein the at least one insert is a hosel having a first end disposed within the club head and a second end disposed outside of the club head.

16. The golf club head of claim 13, wherein each of the at least one insert is located proximate to a portion of the club head selected from the group consisting of the toe portion, the heel portion, the sole surface and the leading surface.

17. The golf club head of claim 16, wherein a first insert is located proximate to the toe portion of the club head and a second insert is proximate to the toe portion of the club head.

18. The golf club head of claim 17, further comprising a third insert located proximate to the leading surface of the club head.

19. The golf club head of claim 13, wherein the golf club head has a first overall weight and the at least one insert has a second overall weight, the second overall weight representing approximately one-third of the first overall weight.

20. The golf club head of claim 13, wherein the at least one insert is slidably insertable into a position at least partially within the golf club head.

21. A method of manufacturing a golf club head, comprising the steps of: placing a first fiber component into a mold in a predetermined orientation, the first fiber component including at least one layer of a first fiber and an amount of a first resin component in the range of about 35 to 50 weight percent; placing a core material atop the at least one layer of the first fiber of the first fiber component; closing the mold; and heating the mold at a temperature and for an amount of time sufficient to cure the first fiber component and the core.

22. The method of claim 21, wherein the first fiber zone is formed of multiple layers of the first fiber, each layer being multi-directionally oriented.

23. The method of claim 21, further comprising: prior to the step of placing the core material, placing a second fiber component within the mold and on top of the first fiber component in a predetermined orientation, the second fiber component including at least one layer of a second fiber and an amount of a second resin component in the range of about 35 to 50 weight percent.

24. The method of claim 23, wherein the first and second resin components are each selected from the group consisting of epoxy, polyester, vinyl ester and cyanate ester.

25. The method of claim 21, wherein the core material is formed of a syntactic foam.

26. The method of claim 25, wherein the syntactic foam has a tensile strength in the range of about 18 MPa to 32 MPa.

27. The method of claim 25, wherein the syntactic foam has a compressive strength in the range of about 60 MPa to 110 MPa.

28. The method of claim 25, wherein the syntactic foam has a mass density in the range of about 0.30 g/cc to 0.55 g/cc.

29. The method of claim 25, wherein the syntactic foam has a foam component with a plurality of discrete components dispersed therein.

30. The method of claim 29, wherein the components are selected from the group consisting of glass microspheres, thermoplastic balloons, and mixtures thereof.

31. The method of claim 30, wherein the thermoplastic spheres are made from a material selected from the group consisting of polyester, nylon, polystyrene and mixtures thereof.

32. The method of claim 30, wherein the syntactic foam further includes a plurality of non-foam components selected from the group consisting of chopped graphite fibers, metal beads, and mixtures thereof.

33. The method of claim 32, wherein the metal beads are made from a material selected from the group consisting of titanium, aluminum, tungsten, spent uranium, stainless steel, and mixtures thereof.

34. The method of claim 23, wherein the first fiber and the second fiber are each selected from the group consisting of a carbon fiber, polyaramid fiber, linear polyethylene fiber, liquid crystal polymer fiber, glass fiber, ceramic fiber, boron fiber, and mixtures thereof.

35. The method of claim 21, wherein the mold is heated at a temperature in the range of about 220 °F to 280 °F for a time in the range of about 15 minutes to two hours.

36. The method of claim 21, further comprising the step of: prior to the step of heating the mold, placing at least one insert at least partially within the first fiber component.

37. The method of claim 36, wherein each of the at least one inserts is made of a metal-based material selected from the group consisting of aluminum, titanium, tungsten, spent uranium, and stainless steel.

38. The method of claim 36, wherein the at least one insert is a hosel having a first end disposed within the first fiber component and a second end disposed outside of the first fiber component.

39. The method of claim 36, wherein each of the at least one inserts is placed at a location proximate to a portion of the club head selected from the group consisting of the toe portion, the heel portion, the sole surface and the leading surface.

40. The method of claim 39, wherein a first insert is placed at a location proximate to the toe portion of the club head and a second insert is placed proximate to the toe portion of the club head.

41. The method of claim 40, wherein a third insert is placed at a location proximate to the leading surface of the club head.

42. The method of claim 36, wherein the golf club head has a first overall weight and the at least one insert has a second overall weight, the second overall weight representing approximately one-third of the first overall weight.

43. The method of claim 36, wherein the at least one insert is slidably insertable into a position at least partially within the golf club head.

44. The method of claim 36, wherein the insert is a mandrel, and wherein the mandrel is removed from within the first fiber component to define a cavity therewithin following the step of heating the mold.

45. The method of claim 44, further comprising the step of: introducing at least one weight-adding insert into the cavity following the step of removing the mandrel.

46. The method of claim 45, wherein the at least one weight-adding insert is slidably introduced into the cavity.