Patent Application
20090118037
1. Field of the Invention
The present invention relates to a golf club, and, more particularly, the present invention relates to a golf club head having a multi-material construction.
2. Description of the Related Art
Golf club heads come in many different forms and makes, such as wood- or metal-type, iron-type (including wedge-type club heads), utility- or specialty-type, and putter-type. Each of these styles has a prescribed function and make-up. The present invention will be discussed as relating to iron-type clubs, but the inventive teachings disclosed herein may be applied to other types of clubs.
Iron-type and utility-type golf club heads generally include a front or striking face, a hosel, and a sole. The front face interfaces with and strikes the golf ball. A plurality of grooves, sometimes referred to as “score lines,” is provided on the face to assist in imparting spin to the ball. The hosel is generally configured to have a particular look to the golfer, to provide a lodging for the golf shaft, and to provide structural rigidity for the club head. The sole of the golf club is particularly important to the golf shot because it contacts and interacts with the playing surface during the swing.
In conventional sets of iron-type golf clubs, each club includes a shaft with a club head attached to one end and a grip attached to the other end. The club head includes a face for striking a golf ball. The angle between the face and a vertical plane is called the loft angle.
The set generally includes irons that are designated number 3 through number 9, and a pitching wedge. One or more additional long irons, such as those designated number 1 or number 2, and wedges, such as a gap wedge, a sand wedge, and a lob wedge, may optionally be included with the set. Alternatively, the set may include irons that are designated number 4 through number 9, a pitching wedge, and a gap wedge. Each iron has a shaft length that usually decreases through the set as the loft for each club head increases from the long irons to the short irons. The overall weight of each club head increases through the set as the shaft length decreases from the long irons to the short irons. To properly ensure that each club has a similar feel or balance during a golf swing, a measurement known as “swingweight” is often used as a criterion to define the club head weight and the shaft length. Because each of the clubs within the set is typically designed to have the same swingweight value for each different lofted club head or given shaft length, the weight of the club head is confined to a particular range.
The length of the shaft, along with the club head loft, moment of inertia, and center of gravity location, impart various performance characteristics to the ball's launch conditions upon impact and dictate the golf ball's launch angle, spin rate, flight trajectory, and the distance the ball will travel. Flight distance generally increases with a decrease in loft angle and an increase in club length. However, difficulty of use also increases with a decrease in loft angle and an increase in club length.
Iron-type golf clubs generally can be divided into three categories: blades and muscle backs, conventional cavity backs, and modern multi-material cavity backs. Blades are traditional clubs with a substantially uniform appearance from the sole to the top line, although there may be some tapering from sole to top line. Similarly, muscle backs are substantially uniform, but have extra material on the back thereof in the form of a rib that can be used to lower the club head center of gravity. A club head with a lower center of gravity than the ball center of gravity facilitates getting the golf ball airborne. Because blade and muscle back designs have a small sweet spot, which is a term that refers to the area of the face that results in a desirable golf shot upon striking a golf ball, these designs are relatively difficult to wield and are typically only used by skilled golfers. However, these designs allow the skilled golfer to work the ball and shape the golf shot as desired.
Cavity backs move some of the club mass to the perimeter of the club by providing a hollow or cavity in the back of the club, opposite the striking face. The perimeter weighting created by the cavity increases the club's moment of inertia, which is a measurement of the club's resistance to torque, for example the torque resulting from an off-center hit. This produces a more forgiving club with a larger sweet spot. Having a larger sweet spot increases the ease of use. The decrease in club head mass resulting from the cavity also allows the size of the club face to be increased, further enlarging the sweet spot. These clubs are easier to hit than blades and muscle backs, and are therefore more readily usable by less-skilled and beginner golfers.
Modern multi-material cavity backs are the latest attempt by golf club designers to make cavity backs more forgiving and easier to hit. Some of these designs replace certain areas of the club head, such as the striking face or sole, with a second material that can be either heavier or lighter than the first material. These designs can also contain undercuts, which stem from the rear cavity, or secondary cavities. By incorporating materials of varying densities or providing cavities and undercuts, mass can be freed up to increase the overall size of the club head, expand the sweet spot, enhance the moment of inertia, and/or optimize the club head center of gravity location.
The present invention relates to a golf club. In particular, the present invention relates to a golf club head having a multi-material construction. Traditionally, all or a large portion of the club head body is made of a metallic material. While it is beneficial to form some parts of the club head, such as the striking face, hosel, and sole, from a metallic material, it is not necessarily beneficial to form other parts of the club head from the same material. Most of the material beyond what is required to maintain structural integrity can be considered parasitic when it comes to designing a more forgiving golf club. The present invention provides an improved golf club by removing this excess or superfluous material and redistributing it elsewhere such that it may do one or more of the following: increase the overall size of the club head, optimize the club head center of gravity, produce a greater club head moment of inertia, and/or expand the size of the club head sweet spot.
A golf club head of the present invention includes a body defining a striking face, a top line, a sole, a back, a heel, a toe, and a hosel. The body is formed of multiple parts. A first body part includes the face, the hosel, and at least a portion of the sole. This first body portion is formed of a metallic material such that it can resist the forces imposed upon it through impact with a golf ball or the golfing surface, and other forces normally incurred through use of a golf club. The striking face of first body part, however, is thinner than conventional golf club heads, while still maintaining sufficient structural integrity, such that mass (and weight) is “freed up” to be redistributed to other, more beneficial locations of the club head.
This golf club head further includes a second body part that is made of a lightweight material, such that it provides for a traditional or otherwise desired appearance without imparting significant weight to the club head. Additionally, the second body part acts as a damping member, which can dissipate unwanted vibrations generated during use of the golf club. The second body part may form part of the club head sole. This second body part also acts as a spacer, allowing the inclusion of one or more dense third body parts. These third body parts can be positioned as desired to obtain beneficial attributes and playing characteristics. Exemplary positions for the third body parts (which may be considered weight members) include low and rear portions of the club head. The club head designer can thus manipulate the center of gravity position, moment of inertia, and other club head attributes.
The face of the club head may be unitary with the first body part, or it may be a separate insert that is joined to the club head body. Providing the face as a separate part allows the designer more freedom in selecting the material of the ball striking face, which may be different than the rest of the club head body. Use of a face insert also allows for the use of a damping member that is retained in a state of compression, which further enhances vibration damping.
Other features, such as an undercut body and a ledge to which the face insert is attached, may also beneficially be included with the inventive club head.
The present invention is described with reference to the accompanying drawings, in which like reference characters reference like elements, and wherein:
Other than in the operating examples, or unless otherwise expressly specified, all of the numerical ranges, amounts, values, and percentages, such as those for amounts of materials, moments of inertias, center of gravity locations, and others in the following portion of the specification, may be read as if prefaced by the word “about” even though the term “about” may not expressly appear with the value, amount, or range. Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following description and claims are approximations that may vary depending upon the desired properties sought to be obtained by the present invention. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.
Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in any specific examples are reported as precisely as possible. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard deviation found in their respective testing measurements. Furthermore, when numerical ranges of varying scope are set forth herein, it is contemplated that any combination of these values inclusive of the recited values may be used.
As shown in
The second body portion 22 is coupled to a rear surface of the first body portion 20, preferably opposite the face 11, and forms a middle portion of the club head 1. This portion of the club head 1 preferably is formed of a lightweight material. Thus, this portion of the club head 1 does not have a significant effect on the physical characteristics of the club head 1. Preferred materials for the second body part 22 include a bulk molding compound, rubber, urethane, polyurethane, a viscoelastic material, a thermoplastic or thermoset polymer, butadiene, polybutadiene, silicone, and combinations thereof. Through the use of these materials, the second body portion 22 may also function as a damper to diminish vibrations in the club head 1, including vibrations generated during an off-center hit.
The third body portion 24 is coupled to at least one of the first and second body portions 20, 22. The third body portion 24 may be a single piece, or it may be provided as a plurality of separate pieces that are attached to the first and/or second body portions 20, 22. The third body portion 24 preferably is positioned in the sole 13 or rear of the club head 1. This portion of the club head 1 preferably is formed of a dense, and more preferably very dense, material. High density materials are more effective for affecting mass and other properties of the club head 1, but stock alloys may alternatively be used. Preferred materials for this portion of the club head 1 include tungsten, and a tungsten alloy, including castable tungsten alloys. The density of the third body portion 24 preferably is greater than 7.5 gm/cc, and more preferably is 10 gm/cc or greater. The density of the third body portion 24 should be greater than the density of the first body portion 20, which in turn should be greater than the density of the second body portion 22. The third body portion 24 can be provided in a variety of forms, such as in the form of a bar or one or more weight inserts. The third body portion 24 can be formed in a variety of manners, including by powdered metallurgy, casting, and forging. An exemplary mass range for the third body portion 24 is 2-30 grams. Alternatively, the third body portion 24 may comprise 10% or more of the overall club head weight.
This multi-part design allows the removal of unneeded mass (and weight), which can be redistributed to other, more beneficial locations of the club head 1. For example, this “freed” mass can be redistributed to do one or more of the following, while maintaining the desired club head weight and swingweight: increase the overall size of the club head 1, expand the size of the club head sweet-spot, reposition the club head center of gravity (COG), and/or produce a greater moment of inertia (MOI) measured about either an axis parallel to the Y-axis or Z-axis passing through the COG. Inertia is a property of matter by which a body remains at rest or in uniform motion unless acted upon by some external force. MOI is a measure of the resistance of a body to angular acceleration about a given axis, and is equal to the sum of the products of each element of mass in the body and the square of the element's distance from the axis. Thus, as the distance from the axis increases, the MOI increases, making the club more forgiving for off-center hits because less energy is lost during impact from club head twisting. Moving or rearranging mass to the club head perimeter enlarges the sweet spot and produces a more forgiving club. Moving as much mass as possible to the extreme outermost areas of the club head 1, such as the heel 15, the toe 16, or the sole 13, maximizes the opportunity to enlarge the sweet spot or produce a greater MOI. The face portion of the first body portion 20 preferably is provided as thin as possible, while still maintaining sufficient structural integrity to withstand the forces incurred during normal use of the golf club and while still providing a good feel to the golf club. The second body part 22 provides for a traditional or otherwise desired appearance without adding appreciable weight. The second body part 22 also acts as a spacer, allowing the third body part 24 to be positioned at a desired distance rearward from the face 11, which in turn repositions the COG rearward and/or lower with respect to traditional club heads. By so positioning the center of gravity, the golf club is more forgiving. The COG position may be lowered further by removing unnecessary mass from the top line 12. Preferred methods of doing so are disclosed in pending U.S. patent application Ser. Nos. 10/843,622, published as Publication No. US2005/0255938, 11/266,172, published as Publication No. US2006/0052183, and 11/266,180, published as Publication No. US2006/0052184, which are incorporated herein in their entireties.
The third body portion 24 may be positioned so that a spring-mass damping system is formed. One such location is shown by the dashed lines of
In the illustrated embodiment of
The club head 1 may be assembled in a variety of manners. One preferred assembly method includes first forming the first and third body portions 20, 24, such as by casting or forging. These portions 20, 24 may then be placed in a mold, and then the material forming the second body part 22 inserted into the mold. Thus, the second body portion 22 is molded onto and/or around the first and third body portions 20, 24, creating the final club head shape. The second body part 22 may thus be bonded to either or both of the first and third body portions 20, 24. This is referred to as a co-molding process.
The face insert 30 to body 10 connection may be facilitated by the use of a groove and lock tab configuration. Such a configuration is shown in
An adhesive or other joining agent may be used to further ensure that the face insert 30 is retained as intended. The face insert 30 and/or upper ledge wall portion may be designed to define a groove 102 around the face insert 30 to provide a run-off or collection volume for any excess adhesive. This not only provides a pleasing aesthetic appearance in the finished golf club, but also beneficially reduces assembly and manufacturing time. Exemplary ways of creating the groove 102 include by angling the upper portion of the ledge side wall and/or by stepping-in the outer portion of the face insert 30.
A damping member 40 is positioned intermediate the body 10 and the face insert 30. As the face 30 deflects during use, the deflection forces are imparted to the damping member 40, which dissipates such forces and reduces the resulting vibration. This lessens and may eliminate vibrations—such as those incurred during an off-center hit—being transmitted through the club head and shaft to the golfer, resulting in a club with better feel and a more enjoyable experience to the golfer. Preferably, the damping member 40 is held in compression between the body 10 and the face 30, which enhances the effectiveness of the vibration damping aspects of the damping insert 40. Preferably, the damping member 40 is positioned such that it is in contact with a rear surface of the face insert 30 opposite the club head sweet spot. The damping member 40 may contact the rear surface of the face insert 30 at other locations, such as the heel 15 or toe 16 or top line 12, in addition to or instead of at the sweet spot.
As shown for example in
In one preferred embodiment, the COG is located 17.5 mm or less above the sole 13. Such a COG location is beneficial because a lower COG facilitates getting the golf ball airborne upon being struck during a golf swing. Also, the MOI measured about a vertical axis passing through the club head COG when grounded at the address position is preferably 2750 g·cm2 or greater. This measurement reflects a stable, forgiving club head.
These attributes may be related conveniently through the expression of a ratio. Thus, using these measurements, the golf club head has a MOI-to-COG ratio of approximately 1600 g·cm or greater. As used herein, “MOI-to-COG ratio” refers to the MOI about a vertical axis passing the club head COG when grounded at the address position divided by the COG distance above the sole 13.
Preferred materials for the body 10 and the face insert 30 are discussed above with respect to the first body portion 20, and preferred materials for the damping member 40 are discussed above with respect to second body part 22. Additionally, when a face insert is used, it preferably may comprise a high strength steel or a metal matrix composite material, a high strength aluminum, or titanium. A high-strength steel typically means steels other than mild low-carbon steels. A metal matrix composite (MMC) material is a type of composite material with at least two constituent parts, one being a metal. The other material may be a different metal or another material, such as a ceramic or organic compound. These materials have high strength-to-weight ratios that allow the face insert 30 to be lighter than a standard face, further freeing mass to be beneficially repositioned on the club head 1 and further enhancing the playability of the resulting golf club. It should be noted that when a face insert is used, material selection is not limited by such constraints as a requirement for malleability (such as is often the case when choosing materials for the body and hosel). If a dissimilar material with respect to the body 10 is chosen for the face insert 30 such that welding is not a readily available coupling method, brazing, explosion welding, and/or crimping may be used to couple the face insert 30 to the body 10.
The face insert 30 may be formed of titanium or a titanium alloy. This face insert 30 may be used in conjunction with a stainless steel body 10, an exemplary stainless steel being 17-4. As these two materials are not readily joined by welding, crimping is a preferred joining method. This typically includes formation of a raised edge along all or portions of the face opening perimeter, which is mechanically deformed after the placement of face insert, locking the two together. The face insert may be beveled or otherwise formed to facilitate crimping. One or more machining/polishing steps may be performed to ensure that the strike face is smooth.
Alternatively, the face insert 30 may be formed of a stainless steel, which allows the face insert 30 and the body 10 to be readily joined via welding. One preferred material is 1770 stainless steel alloy. As this face insert material is more dense than titanium or titanium alloy, the resulting face insert 30-body 10 combination has an increased weight. This may be addressed by increasing the size (i.e., the volume) of the undercut 38, such that the overall size and weight of the club heads are the same.
This embodiment of the club head 1 may be assembled in a variety of manners. One preferred method of assembly includes casting, forging, or otherwise forming the body 10 and the face insert 30 (in separate processes). The face insert 30 may be formed such that it has one or more raised areas 32 on a rear surface thereof. (See
The damping member 40 may comprises a plurality of materials. For example, the damping member 40 may include a first material in contact with the face insert 30 and a second material in contact with the body 10. The materials of the damping member may have varying physical characteristics, such as the first material (adjacent the face insert 30) being harder than the second material (adjacent the body 10). The differing materials may be provided in layer form, with the layers joined together in known fashion, such as through use of an adhesive or bonding.
The damping member 40 may comprise a material that changes appearance when subjected to a predetermined load. This would provide the golfer with visual confirmation of the damping at work.
As shown in
As discussed above, incorporating a face plate 30 formed of a relatively lightweight material provides certain benefits to the resulting golf club. Aluminum (including aluminum alloys) is one such lightweight material. M-9, a scandium 7000-series alloy, is one preferred aluminum alloy. Using a face insert 30 that comprises aluminum with a steel body 10, however, can lead to galvanic corrosion and, ultimately, catastrophic failure of the golf club. To realize the benefits both of using a face insert 30 comprising aluminum and a body 10 comprising steel (such as a stainless steel), without being susceptible to galvanic corrosion, a layered face insert 30 may be used.
A second layer 64 is provided to the rear of and abutting the first layer 62. This layer 64 is formed of a lightweight material, such as those discussed above with respect to the second body part 22. This layer 64 provides the desired sizing and damping characteristics as discussed above. The first and second layers 62, 64 may be joined together, such as via bonding. This second layer 64 may contain a lip extending outward around its perimeter, thus forming a cavity, into which the first layer 62 may be retained. In this manner, the metallic material of the first layer 62 may be isolated from the material of the club head body 10, and galvanic electrical flow between the club head body 10 and the metallic portion(s) of the face insert 30 is prevented.
The third main component of the layered face insert 30 is a foil 66. The foil 66 is very thin and may be formed of a variety or materials, including materials that act to prevent galvanic corrosion. The foil 66 includes a pocket or cavity 67 sized to envelop the first and second layers 62, 64. The foil 66 may be joined to the first and second layer 62, 64 combination via an adhesive or other means, or simply by being pressed or otherwise compressed against the rear and perimeter surfaces of the second layer 64. The layered face insert is then joined to the club head body 10 in known manner, such as by bonding and/or crimping.
Other means for preventing galvanic corrosion may also be used. These may include coating the face insert 30 or the corresponding structure of the body 10, such as ledge 37. Preferred coating methods include anodizing, hard anodizing, ion plating, and nickel plating. These alternate corrosion prevention means may be used in conjunction with or alternatively to the three-part face insert construction described herein.
The rear surface of the second layer 64 may be provided with a contoured surface. One such surface being, for example, a logo or other manufacturer indicium. In certain embodiments, the rear surface of the face insert 30 is visible. As the foil layer 66 is very thin and mated to the rear surface of the second layer 64, the textured rear surface of the second layer 64 is visible in these embodiments. The foil 66 may be colored or otherwise decorated to enhance the visibility of the logo, indicium, or other texture of the second layer 64. If the foil 66 is colored or otherwise decorated prior to be joined to the layers 62, 64, the textured surface can be colored and otherwise enhanced without costly and time consuming processes, such as paint filling, that are typically required. A plurality of indicia, examples including manufacturer and product line identifiers, preferably may be included in this manner.
Alternatively or in addition to using a contoured rear second layer surface and the foil 66 to provide indicia, a medallion may be used. An exploded side view of a preferred medallion 70 is shown in
The base member 71 defines a chamber 72 into which the indicia member 75 is positioned and retained. Adhesive, epoxy, and the like may be used to join the base member 71 and the indicia member 75. Corresponding walls of the chamber 72 and the indicia member 75 may be sloped to lock the indicia member 75 in place within the chamber 72. As indicated by the dashed lines in
As used herein, directional references such as rear, front, lower, etc. are made with respect to the club head when grounded at the address position. See, for example,
While the preferred embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. For example, while the inventive concepts have been discussed predominantly with respect to iron-type golf club heads, such concepts may also be applied to other club heads, such as wood-types, hybrid-types, and putter-types. Thus the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Furthermore, while certain advantages of the invention have been described herein, it is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
This application claims the benefit of U.S. Provisional Patent Application No. 60/832,228 filed on Jul. 21, 2006, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 60832228 | Jul 2006 | US |
