Patent Publication Number: US-6902496-B2

Title: Methods and apparatus for a putter club head with high-density inserts

Description:
BACKGROUND OF THE INVENTION 
   1. Technical Field 
   This invention relates, generally, to golf clubs and, in particular, to a putter golf club head having high-density heel and toe inserts. 
   2. Background Information 
   A golfer&#39;s putting stroke is highly individualized, depending not only on the mechanical properties of the golf club, but also upon complex subjective and psychological factors. Thus, a putter club head may be designed to prioritize one particular mechanical characteristic of the club head over other competing and equally important characteristics of the club. 
   For example, it is often desirable to incorporate heel and toe weighting into a club head body to increase the moment of inertia of the club. This increased moment of inertia tends to decrease club head twisting in the event the golfer strikes the golf ball off-center. In an effort to increase the moment of inertia, prior art club heads generally utilize a low-density material (such as aluminum) for the club head body in conjunction with a higher density material for the heel and toe weights. 
   For example, U.S. Pat. No. 4,508,350 discloses a golf club putter having a high polar moment of inertia provided by forming the club head body out of aluminum. Similarly, U.S. Pat. No. 4,915,385 discloses metallic (e.g., copper) heel and toe weights used in conjunction with a lower-density (e.g., aluminum) club head. 
   While the use of low-density materials for the club head body may help to increase the club head&#39;s moment of inertia, such materials exhibit undesirable mechanical properties for some golfers. For example, many golfer&#39;s prefer a hard, highly-responsive solid metal surface and the attendant “hard” sound and feel when striking a golf ball. Low-density materials such as aluminum do not typically provide this type of response. 
   BRIEF SUMMARY OF THE INVENTION 
   The present invention provides a putter club head having a body fitted with heel and toe inserts having a density greater than that of the golf club body. The respective materials for the body and inserts are selected to provide a high moment of inertia while at the same time providing a desirable dynamic response at impact. In accordance with one aspect of the present invention, for example, a golf putter club head includes a body formed of a first material (e.g., titanium) having a density of approximately 3.0 g/cm 3  to 7.0 g/cm 3 . Two cavities are formed in the body, one in or adjacent to the heel region of the body, and another in or adjacent to the toe region. Inserts are provided in each of the two cavities and are formed of a second material (e.g, tungsten) having a density ranging from approximately 15.0 g/cm 3  to 20.0 g/cm 3 . 
   In accordance with another aspect of the present invention, the first and second inserts may be configured such that they comprise a portion of the bottom surface and/or the front face of the club head. In accordance with a further aspect of the present invention, the front face of the body may be machined (e.g., milled) such that the inserts are substantially flush with the front face. 
   In accordance with yet another aspect of the present invention, the body of the putter club head has an elastic modulus greater than approximately 90 GPa while the density of the insert material is greater than the density of the body material by a factor of at least 3.0. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The subject invention will hereinafter be described in conjunction with the appended drawing figures, wherein like numerals denote like elements, and: 
       FIG. 1  is an isometric overview of a golf putter club head in accordance with one embodiment of the present invention; 
       FIG. 2  is an isometric overview of a golf putter club head and associated inserts; 
       FIG. 3  is an isometric overview of a golf putter club head in accordance with one embodiment of the present invention; 
       FIG. 4  is an isometric overview of a golf putter club head in accordance with an alternative embodiment of the present invention; 
       FIG. 5  is an isometric overview of a golf putter club head in accordance with a further embodiment of the present invention; 
       FIG. 6  is an isometric overview of a golf putter club head in accordance with yet another embodiment of the present invention; 
       FIG. 7  is a graph showing the quantitative relationship between body and insert density in accordance with various embodiments of the present invention; 
       FIG. 8  is a graph showing the quantitative relationship between elastic modulus and insert density in accordance with various embodiments of the present invention; 
       FIGS. 9 and 10  are rear views of various golf putter club heads in accordance with yet another aspect of the present invention. 
   

   DETAILED DESCRIPTION 
   The present invention provides a golf putter club head having heel and toe inserts formed from a material having a density greater than that of the club head body material and falling within a specified range of values. In accordance with one aspect of the present invention, materials are selected to balance the need for a high density ratio (i.e., the ratio of insert material density and body material density) with the need for a body material that provides a suitable dynamic response, characterized, for example, by modulus of elasticity, hardness, and/or any other such property or properties. 
   With reference to  FIG. 1 , an exemplary golf putter club head  100  in accordance with one embodiment of the present invention includes a body  102  having a front face  112 , a bottom surface or “sole”  114 , a heel region  106 , and a toe region  104 . Body  102  is typically attached to a shaft  110  via a suitable hosel  108 . Body  102  of club head  100  is formed such that it includes two cavities (not shown) configured to receive respective inserts at heel region  106  and toe region  104 . 
   More particularly, referring to  FIG. 2 , body  102  includes two cavities, “cut-outs”, slots, holes, or other such wholly or partially bounded volumes  206  and  208  located in, near, or adjacent to toe region  104  and heel region  106  respectively. Inserts  202  and  204  are configured to be received within, attached to, or otherwise integrated with body  102  such that they substantially fill respective cavities  206  and  208 . 
   Body  102  comprises any suitable metal, plastic, composite material, or combination thereof selected in accordance with various criteria as described in further detail below. In accordance with one embodiment, for example, body  102  comprises a material having a density of approximately 3.0 g/cm 3  to 7.0 g/cm 3 , such as titanium or a high-purity titanium alloy. More particularly, body  102  suitably comprises a material which includes as its primary constituent a metal having an elemental density greater than a predetermined value, e.g., approximately 4.0 g/cm 3 . 
   The term “primary constituent” as used herein refers to the particular element or material comprising the highest percentage of the total mass of body  102 . For example, body  102  may be formed from commercial pure grade 2 titanium, which includes up to about 0.25% oxygen, 0.03% nitrogen, 0.08% carbon, 0.015% hydrogen, 0.3% iron, and 0.4% residual elements. In another example embodiment, body  102  is formed using titanium alloyed with approximately 3.0% aluminum and 2.5% cadmium In both cases, titanium is the primary constituent. The term “elemental density” refers to the density of the unalloyed or “pure” element. For example, the elemental density of titanium is approximately 4.5 g/cm 3 , while the elemental density of aluminum is approximately 2.7 g/cm 3 . 
   While the embodiments described above include a body  102  fabricated from a metallic material, the present invention is not so limited. For example, the primary constituent of body  102  might include a composite or plastic material having the desired characteristics. 
   Depending upon the selected material or materials, body  102  may be fabricated using any suitable process now known or later developed, including a variety of conventional casting methods such as investment-casting, powdered-metal processing, and/or metal machining. In one embodiment, body  102  is formed via a suitable casting process and thereafter milled to finish the various exposed surfaces. In this regard, conventional investment casting techniques are well known to those skilled in the art and will not be described in detail herein. For more information regarding such processes, see, e.g., S OPCAK , H ANDBOOK OF  L OST  W AX OR  I NVESTMENT  C ASTING (1986), which is hereby incorporated by reference. 
   Body  102  is defined by any suitable club head shape depending upon any number of factors, including, for example, club head type (putter, wood, etc.), desired moment of inertia (e.g., the polar moment of inertia around an axis normal to the club head sole), desired center of gravity, desired aesthetic properties (e.g., visual cues provided by the club head&#39;s contours as viewed from above during play), and/or the desired weight, mass, and density. In this regard, it will be appreciated that the exemplary club head shapes depicted in  FIGS. 1-6  are for illustrative purposes only, and that the present invention is not so limited. 
   Body  102  has a suitable face thickness t which may vary across the length of face  112 . The thickness t, particularly near the center of face  112 , is selected to provide a suitable response to club head  100  striking a golf ball. In one embodiment, thickness t has a value ranging from approximately 200 mils (7.9 microns) to approximately 500 mils (19.7 microns), preferably between 300 mils (11.8 microns) to 400 mils (15.7 microns), most preferably approximately 325 mils (12.8 microns). 
   Cavities  206  and  208  include suitable “cut-outs”, slots, holes, or any other such defined volumes. Cavities  206  and  208  may be fashioned within body  102  such that, when inserts  202  and  204  are inserted in their respective cavities, the finished club head has a distinct visual appearance. This distinct visual appearance may be provided through the use of any combination of shapes, colors, textures, and/or the like.  FIGS. 2-6  depict exemplary configurations for inserts  202  and  204  with respect to body  102 . It will be appreciated, however, that the exemplary insert shapes  202  and  204  shown in  FIGS. 2-6  are not intended as a limitation of possible insert geometries. 
   Cavities  206  and  208  may be configured with respect to body  102  such that inserts  202  and  204  comprise a portion of one or more exposed surfaces of club head  100 , e.g., the top, back, bottom, front, and/or sides of the club head. In various embodiments of the present invention, shown in  FIGS. 2-6 , inserts  202  and  204  comprise a portion of front face  112  and bottom surface  114 . This placement assists in positioning the relatively high-density inserts toward the antipodal extremes of toe region  104  and heel region  106  (thus increasing the moment of inertia of club head  100 ) while at the same time keeping the weight low and close to bottom surface  114  (thus lowering the center of mass and facilitating desirable spin characteristics upon impact). In this regard, while the various embodiments shown in  FIGS. 2-6  depict inserts that intersect the bottom surface  114  and front face  112  of body  102 , the present invention comprehends that one or more of the inserts may be wholly or partially encapsulated by body  102  or may extend to the outer surfaces of body  102  at any number of locations. 
   Inserts  202  and  204  are fabricated from a material or materials having a density that is greater than that of body  102 . The incorporation of relatively high-density inserts  202  and  204  in this way results in a higher moment of inertia for club head  100 . The higher the moment of inertia, the less likely club head  100  will twist when it impacts a golf ball at an off-center location. In this regard, inserts  202  and  204  may be fabricated using any suitable material, including various metals, plastics, composite materials, or any combination thereof. In one embodiment, inserts  202  and  204  comprise a material such as tungsten having a density ranging from approximately 15.0 g/cm 3  to 20.0 g/cm 3 . In a preferred embodiment, the density of inserts  202  and  204  is in the range of 17.0 g/cm 3  to 19.0 g/cm 3 . 
   Inserts  202  and  204  may be configured to provide an appropriate amount of weighting to heel region  106  and toe region  104 . In one embodiment, the total weight of inserts  202  and  204  is within the range of 50 grams to 100 grams. In a particular embodiment, wherein the total weight of club head  100  is approximately 315 to 380 grams (preferably about 345 grams), the total weight of inserts  202  and  204  is in the range of 75 to 105 grams, preferably about 85 to 95 grams, and most preferably approximately 90 grams. In the interest of symmetry, it is advantageous to fit club head  100  with inserts  202  and  204  having substantially the same weight. The present invention, however, also contemplates the use of inserts having different weights and/or manufactured from different materials. Such an embodiment might be advantageous, for example, to compensate for other non-symmetrical features of club head  100  and to better align the center of mass of club head  100  with the center of front face  112 . 
   Inserts  202  and  204  may be fixed within respective cavities  206  and  208  using any suitable method now known or later developed, including the use of adhesives and/or conventional metal-joining operations such as soldering, brazing, and the like. In one embodiment, inserts  202  and  204  are attached to one or more inner surfaces of respective cavities  206  and  208  using a conventional copper brazing process. The brazing process may be accompanied by a suitable plating process as is well known in the art. In the event inserts  202  and  204  extend to one or more of the outer surfaces of body  102  (e.g., front face  112  or bottom surface  114  as shown in FIGS.  2 - 6 ), it is advantageous to mill the resulting surfaces such that inserts  202  and  204  are substantially flush with body  102 . 
   In accordance with another aspect of the present invention, one or more inserts may be integrated toward the back of the club head, i.e., along the edges and/or back surfaces of the club head. Such an embodiment may be particularly advantageous in “mallet-shaped” club heads. The use of additional inserts in this way assists in increasing the polar moment of inertia of the club head. At the same time, the center of gravity for the club head may be lowered by using lower profile inserts. That is, for a given total insert weight, the use of more, lower-profile inserts results in a lower center of gravity.  FIG. 9 , for example, shows a single weight  902  (for example, a tungsten weight as described above) centered opposite front face  112 .  FIG. 10  shows the use of a pair of weights  904  and  906  secured within the back of the club head at generally heel and toe locations. As with inserts  206  and  208 , inserts  902 ,  904 , and/or  906  may be shaped and positioned within body  102  such that they form a portion of any of the various exposed surfaces of the club head. Alternatively, inserts  902 ,  904 , and/or  906  may be entirely or substantially encapsulated by body  102 . 
   As mentioned above, the materials for body  102  and inserts  202  and  204  are preferably selected such that the density of the material used for inserts  202  and  204  is substantially greater than that used for body  102 . In this regard,  FIG. 7  shows a graphical representation of exemplary density ranges for insert and body materials. One rectangular design region  704  is defined by a body material density ranging from approximately 3.0 g/cm 3  to 7.0 g/cm 3  and an insert material density ranging from 15.0 g/cm 3  to 20.0 g/cm 3 . A second design region  702  is defined by a body material density ranging from approximately 40 g/cm 3  to 60 g/cm 3 , and an insert material density ranging from approximately 17.0 g/cm 3  to 19.0 g/cm 3 . 
   In a particular embodiment lying close to the center of design region  702 , a high-purity titanium is used for the body material (e.g., a grade 2 commercial purity titanium having a density of approximately 4.5 g/cm 3 ), and a high-purity tungsten is used for the insert material (e.g., a powdered-metal pressed tungsten having a density of approximately 18.0 g/cm 3 ). 
   In accordance with another embodiment of the present invention, the various materials for the body and inserts are selected to maximize the club head&#39;s moment of inertia and, at the same time, to provide a desirable response at impact. While the moment of inertia of club head  100  may be increased to a very high value by utilizing a body material having a very low density (e.g., aluminum, or any number of polymeric compounds), such a low density material may exhibit other mechanical properties that result in undesirable dynamics when front face  112  of club head  100  strikes a golf ball. 
   Various mechanical properties control the nature of ball impact and resultant dynamics. The modulus of elasticity of the body material, for example, affects to a large extent the efficiency of energy transfer (or “coefficient of restitution”) at the moment of impact. For example, high-purity aluminum has a density of approximately 2.7 g/cm 3 , which is lower than high-purity titanium (and significantly less expensive); however, the modulus of elasticity of high-purity aluminum is approximately 70 GPa, while the modulus of elasticity of high-purity titanium is greater than 90 GPa, and generally ranges from 110 GPa to 115 GPa. Thus, it is desirable in many instances to utilize body and insert materials which balance the need for a high density ratio (i.e., the ratio of insert material density and body material density) with the need for a body material which provides a suitable dynamic response (characterized, for example, by modulus of elasticity, hardness, and/or any other such property). 
   Toward this end,  FIG. 8  depicts various design regions in accordance with a further aspect of the present invention wherein the material densities are selected to achieve a particular insert material density while at the same time utilizing a body material having an advantageously high modulus of elasticity. Design region  802  is defined by an elastic modulus greater than or equal to 90 GPa and an insert material density ranging from approximately 15.0 g/cm 3  to 20.0 g/cm 3 . Design region  804  is defined by an elastic modulus greater than or equal to 110.0 GPa and an insert material density ranging from approximately 17.0 g/cm 3  to 19.0 g/cm 3 . 
   Again, while the embodiments described above include a body  102  fabricated from a metallic material, the primary constituent of body  102  might include a composite or plastic material having a density and/or modulus of elasticity within the desired range. 
   In conclusion, what has been provided is a putter golf club head having a relatively low-density body (e.g., a titanium body) fitted with relatively high-density heel and toe inserts (e.g., tungsten inserts). Although the invention has been described herein in conjunction with the appended drawings, those skilled in the art will appreciate that the scope of the invention is not so limited. For example, while the present invention has been described in terms of golf putters, many other types of golf clubs would profit from the present invention, including irons, metal woods, etc. Moreover, while titanium and tungsten have been cited as preferred materials for the body and inserts respectively, it will be appreciated that any suitable material now known or later developed may be used in connection with the present invention, including various metals, alloys, composites, ceramics, and the like. These and other modifications in the selection, design, and arrangement of the various components and steps discussed herein may be made without departing from the scope of the invention as set forth in the appended claims.