Patent Publication Number: US-2018036606-A1

Title: Method and apparatus for optimizing launch characteristics of a golf club

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of U.S. patent application Ser. No. 15/491,645, filed Apr. 19, 2017, which claims priority to U.S. Provisional Patent Application Ser. No. 62/325,124, filed Apr. 20, 2016. The disclosure of each of the aforementioned patent applicants is fully incorporated herein by reference. 
    
    
     BACKGROUND OF THE DISCLOSURE 
     The present disclosure relates to golf clubs and related sports applications. More particularly, it relates to enhanced surface strike performance of a golf club head, which may be achieved by an insert attached to the golf club head. Although a preferred embodiment of the present disclosure is directed to a golf club head, it is contemplated that other types of sports equipment (e.g., baseball bats, hockey sticks, polo mallets, croquet mallets bocce balls, bowling balls, billiard balls, etc., and the like) may similarly benefit from the enhanced surface strike performance disclosed herein. 
     The design of typical golf clubs includes specific features that affect the flight characteristics of the golf ball after impact. For example, the loft angle of the club, face grooves and surface characteristics of the club impart a combination of angular spin and forward velocity at impact. The forward velocity is further directed along a vector (launch angle) by virtue of the balls interaction with the clubface at impact. 
     The introduction of spin can be a benefit for the highly skilled golfer and allow the golfer to “work the ball” by deliberately curving the flight path in a left-to-right or right-to-left direction. High spin rates may also facilitate the skilled golfer in reducing the amount of travel on the ground of short shots to the green (i.e., getting the ball to “check up”). 
     The vast majority of golfers are insufficiently skilled in the control of spin on the ball. Therefore, the inadvertent and errant introduction of spin commonly results in either hooking or slicing the balls flight path in an unintended direction. 
     At impact the club head transfers its kinetic energy to the ball. Conventional golf clubs impart some energy to spin the ball and the remaining energy to propel the ball. Depending upon the angle of impact of the club face the proportion of energy diverted to either spin or propulsion will vary. 
     It is preferable to configure a golf club head to achieve less spin, greater launch angle and increased carry distance. Historically, one known way modify these golf ball characteristics is to use a “slippery” clubface. For example, Vaseline®, Chopstick®, or other temporary substances applied to the striking face of the golf club is widely known. These practices, however, are not “legally conforming” to the Rules of Golf issued by the United States Golf Association (“USGA”), as these substances are “temporary modifications.” The removal of grooves on the golf clubface is also widely known in the industry to modify the aforementioned characteristics of golf balls, and clubs having groove-less and highly polished clubfaces are currently marketed today. 
     Several patents disclose a number of attempts to achieve these results. For example, U.S. Pat. No. 6,974,392 (“Chang”) describes a golf club for minimizing spin of the golf ball. The method described employs the use of low friction substances that cover the impact surface of the golf club, such as PTFE and variants of PTFE (Teflon). These substances are known for their low coefficient of friction, and are thus an obvious attribute for coating that is expected to reduce the spin of a struck golf ball. 
     Chang further describes how to overcome the limitations of the method that was previously discussed in U.S. Pat. No. 5,423,535 (“Shaw”). Shaw also listed PTFE as a candidate for spin reduction treatment of golf club face. While being somewhat effective, this approach of using PTFE had limited functionality and practicality. As a result, the PTFE coatings on the golf club did not reach the level of performance expectation. Chang describes the problem as ultimately relating to the softness of the PTFE and that at impact the compression of the golf ball into the layer of PTFE produces a mechanical engagement of the ball against the surface and introduces unexpected and unwanted spin of the golf ball. The solution proposed in Chang is to limit the thickness of the PTFE coating and employ a supporting layer under the PTFE. However, this limits the degree of mechanical engagement of the PTFE layer with the golf ball. 
     Thus, there is a need for a new and improved method and apparatus for providing a strike surface of a golf club which will overcome the above mentioned deficiencies while providing a better overall result. Specifically, the present disclosure overcomes the limitations of the existing attempts through the use of non-obvious methods. 
     SUMMARY OF THE DISCLOSURE 
     The present disclosure relates to golf clubs and related sports applications. More particularly, it relates to an enhanced strike surface of a golf club head, which may be achieved by an insert attached to the golf club head. 
     In the present disclosure a much more significant portion of the kinetic energy is transferred to the propulsion of the golf ball forward/upward and a much lower amount of the energy (than conventional golf clubs) is converted to rotational energy that spins the ball. This results in an improved launch angle and greater carry distance than a conventional golf club for any given clubhead speed at impact and less inadvertent loss of accuracy from off axis spin of the ball. 
     In particular, the present disclosure describes a method for producing golf clubs that have design features and characteristics that enhance the directional accuracy, reduce the inadvertent hooking and slicing and improve the distance performance of a golf club of given loft angle. 
     The present disclosure overcomes the cost and complexity of such manufacturing techniques and results in a dramatic improvement in golf club performance. 
     Specifically, in accordance with one embodiment of the disclosure, the ball striking surface of the clubface is provided by an insert attached to the clubface. The insert can be substantially smooth or can have surface features as described below. Moreover, the insert provides the ball striking surface having an advantageous combination of properties, such as smoothness, hardness and durability. 
     Furthermore, in accordance with another embodiment of the disclosure, the insert includes a ball striking surface having surface features configured as one or more ridges or ribs. Alternatively, the one or more surface features can be configured as one or more grooves. The one or more surface features can further be configured as punch marks spaced across the insert. In still a further embodiment, the one or more surface features can be configured as a combination of ridges, grooves, and/or punch marks. The insert and ball striking surface with surface features are made from a material providing an advantageous combination of properties, such as smoothness, hardness and durability, adapted to improve golf club performance. The intrinsic coefficient of friction is not a critical characteristic of the chosen material for the insert and ball striking surface that results in the enhanced performance. 
     In one particular embodiment of the disclosure, the insert and its ball striking surface are made from an injection moldable material which provides enhanced performance. The injection moldable material can be a polymeric material which includes Acetal. 
     Still other aspects of this disclosure will become apparent upon reading and understanding of the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a better understanding of the present invention, reference may be had to the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  is a partial perspective view of a golf club including a clubface with a ball striking surface having enhanced performance in accordance with one embodiment of the present disclosure. 
         FIG. 2  is a partial perspective view of a golf club head which has surface features on the clubface in accordance with another embodiment of the present disclosure. 
         FIG. 3  is a partial perspective view of a golf club head which has a smooth clubface in accordance with another embodiment of the present disclosure. 
         FIG. 4A  illustrates a partial perspective view of a golf club head which has an insert providing a ball striking surface having enhanced performance in accordance with another embodiment of the present disclosure. 
         FIG. 4B  illustrates a partial perspective view of a golf club head which has an insert providing a ball striking surface having enhanced performance in accordance with another embodiment of the present disclosure. 
         FIG. 4C  illustrates a partial perspective view of a golf club head which has an insert providing a ball striking surface having enhanced performance in accordance with another embodiment of the present disclosure. 
         FIG. 5  is a partial perspective view of a golf club head which has an insert providing a ball striking surface which has one or more surface features, including one or more raised ridge or rib portions and/or grooved portions. 
         FIG. 6  is a partial perspective view of a golf club head which has an insert providing a ball striking surface which has one or more surface features, including a first repeating pattern of grooved portions and second repeating pattern of a pair of raised ridge portions. 
         FIG. 7  is a partial perspective view of a golf club head which has an insert providing a ball striking surface which has one or more surface features, including punch marks spaced across the insert. 
         FIG. 8  is a partial cross-sectional view of a layer of coating disposed on a clubface of a golf club head according one aspect of the present embodiments. 
     
    
    
     DETAILED DESCRIPTION OF THE DISCLOSURE 
     A preferred embodiment of the present disclosure is a golf club of low cost manufacture that includes a ball striking surface able to perform to the above specifications. For a performance enhancing ball-striking surface to be practical and useful it must be durable, smooth, resist impact forces of normal use, and reduce the imparted spin on the golf ball. The USGA requires that the surface have a hardness that passes the ‘fingernail test.” This hardness corresponds to a Mohs hardness of 2.5, compared with a copper penny having a Mohs hardness of 3.0. The intent of this ruling is to render common lubricants, adhesive patches and other waxy or liquid substances that may be applied to the striking surface as non-conforming. 
     In contrast, existing methods use surface coatings (PTFE and its variants) with a specific coefficient of friction. Coefficient of friction is a complex property that is known to be unpredictable and can be highly dependent on normal forces at the contact surfaces as well as being limited by the mechanical properties of the substances being tested (i.e., hardness, compressive strength, yield strength, etc.). While PTFE would seem to be a viable substance to coat a golf club for reduced spin, it has been determined that, from a practical standpoint, PTFE has fails to be useful. In particular, PTFE is not sufficiently durable or impact resistant to satisfy the requirements of a viable surface of a golf club. 
     According to one embodiment of the present disclosure, a ball striking surface of the clubface is the surface of an insert attached to the clubface of the golf club. The ball striking surface may be substantially smooth or comprise one or more surface features. The ball striking surface of the golf club satisfying the physical attributes listed below, while still meeting the physical attributes required by the USGA, will reduce a spin rate, increase a launch angle, and increase a carry distance on the golf ball compared with a similar golf club without the ball striking surface of the present disclosure. 
     Specifically, in accordance with the preferred embodiment of this disclosure, the resulting ball striking surface  18  (see  FIGS. 1-7 ) may include some or all of the following properties: 
     a) A hardness of greater than Shore D 65; 
     b) A surface roughness Ra of 1.0 micron or less (i.e., a substantially smooth surface), where Ra is the roughness average of the ball striking surface&#39;s measured microscopic peaks and valleys; 
     c) A wear resistance minimum of zero loss at 1 kg per 1000 Cycles (ASTM-C-501); 
     d) A flexural strength of greater than 3000 psi (ASTM C-580); 
     e) An indentation resistance (Mil-D-3134F sec 4.7.4) of greater than 1500 psi for a duration of 30 minutes; 
     f) A tensile strength of greater than 3000 psi (ASTM C-307); and 
     g) A compressive strength of greater than 5000 psi. 
     A ball striking surface having a combination of some or all of properties a)-g) above has been found to dramatically improve the performance characteristics of a golf ball struck by the ball striking surface. For example, the hardness and compressive strength properties of the ball striking surface in combination with the smoothness prevents the golf ball from developing significant mechanical engagement with ball striking surface upon impact with the golf club, thereby reducing the amount of imparted spin. 
     Referring now to  FIG. 1 , a golf club  10  is shown having a shaft  12  and a head  14  connected to the shaft in a manner well known in the art. While the golf club head  14  illustrated in  FIG. 1  is shown as being configured for a driver  11  or a “wood” club, it should be understood that the present disclosure is not necessarily limited thereto, and other types of golf club heads are also contemplated (See  FIGS. 3-4 ). Additionally, other types of sports equipment adapted to strike respective balls associated with the sport are contemplated. In this regard, the head  14  can more generally be referred to as a body member adapted to strike an associated ball. The body member or golf club head  14  includes a clubface  16 , which is the surface of the golf club head that faces an associated golf ball (not shown) as a user prepares to swing the golf club. Alternatively, in more general terms, the body member  14  includes a face which is the surface of the body member that faces an associated game ball. At least a portion of the face or clubface  16  comprises a ball striking surface  18 . The ball striking surface  18  is adapted to contact an associated game ball, such as a golf ball, and transfer the kinetic energy of the golf club to the golf ball. In this regard, the ball striking surface  18  may comprise substantially all of the face or clubface  16  of the body member or golf club head  14 , or just a portion thereof (e.g., a centrally located “sweet spot” of the clubface). 
       FIG. 2  illustrates a golf club head  22  which is configured as an “iron” club. The clubface  16  of the golf club head  22  has a ball striking surface  18  which includes surface features  24 . In one embodiment, the surface features  24  can be configured as one or more ridges or ribs. Alternatively, the surface features  24  can be configured as one or more grooves. In still a further embodiment, the surface features  24  can be configured as a combination of ridges and grooves. Other surface features such as punch marks are also contemplated, and the surface features of the present disclosure are not limited to the geometry of those illustrated in  FIG. 2 . The ridged and/or grooved ball striking surface  18  is adapted to contact an associated golf ball and transfer the kinetic energy of the golf club to the golf ball. In this regard, the ridged and/or grooved ball striking surface  18  of golf club head  22  may comprise just a portion of the clubface  16  or substantially all of the clubface (e.g., except for perimeter portions of the clubface), provided the surface features are in accordance with the Rules of Golf issued by the USGA. 
       FIG. 3  illustrates a golf club head  26  which, similar to golf club head  22  shown in  FIG. 2 , is also configured as an “iron” club. However, the clubface  16  of golf club head  26  has a ball striking surface  18  without any surface features. In other words, the ball striking surface  18  of head  26  is configured to be substantially smooth. The substantially smooth ball striking surface is adapted to contact an associated golf ball and transfer the kinetic energy of the golf club to the golf ball. In this regard, the substantially smooth ball striking surface  18  of golf club head  26  may comprise substantially all of the clubface  16  of the golf club head  14 , or just a portion thereof (e.g., a centrally located “sweet spot” of the clubface). 
     Referring back to  FIG. 1 , the ball striking surface  18  of the golf club head  14  can be configured similarly to that of golf ball heads  22 ,  26  illustrated in  FIGS. 2 and 3 , respectfully. That is, the ball striking surface  18  of the driver golf club head  14  can be configured to have one or more ridges or grooves or be configured to be substantially smooth. 
       FIGS. 4A-4C  and  FIGS. 5-7  show a golf club head  30  which is configured as an “iron” club, such as the 7-iron illustrated in  FIG. 4A . However, it should be understood that golf club head  30  could also be configured as any other iron club or as a “wood” or driver club without departing from the scope of the present disclosure. Additionally, other types of sports equipment adapted to strike respective balls associated with the sport are contemplated. In this regard, the head  30  can more generally be referred to as a body member adapted to strike an associated ball. The body member or golf club head  30  of  FIGS. 4A-4C  and  FIGS. 5-7  differ from those illustrated in  FIGS. 1-3  in that the ball striking surface  18  comprises a separate insert  32  that is completely separate from the rest of the body member or golf club head. The separate insert  32  can be configured as an overlay insert or an inlay insert, both of which can be attached to the clubface  16 . The insert  32  can be attached to the clubface  16  in a manner well known in the art, such as through the use of adhesives or through a mechanical means such as fasteners, etc. The insert  32  comprising the ball striking surface  18  is adapted to contact an associated golf ball and transfer the kinetic energy of the golf club to the golf ball. 
     The embodiments illustrated in  FIGS. 4A-4C  and  FIGS. 5-7  show the insert  32  being configured as an inlay insert. In this regard, the clubface  16  includes a receiving portion  34  ( FIG. 4A ) adapted to receive the inlay insert  32 . The inlay insert  32  is attached to the receiving portion  34  in the same manner as discussed above, i.e., through the use of adhesives or mechanical fasteners known in the art. Generally, when configured as an inlay, the insert  32  is attached to the clubface  16  to provide the ball striking surface  18  comprising just a portion of the clubface of the body member or golf club head  30  such as central portion. In this regard, the receiving portion  34  can be recessed into the clubface  16  such that the inlay insert  32 , and thus the ball striking surface  18 , is substantially flush with the surrounding portions of the clubface in accordance with the Rules of Golf issued by the USGA. 
     In other embodiments, the separate insert  32  is configured as an overlay insert (not shown). When the insert  32  is configured as an overlay, the insert is attached to the clubface  16  to provide the ball striking surface  18  comprising substantially all of the clubface of the golf club head  30 . In other words, when configured as an overlay, the entire clubface  16  acts as the receiving portion for the insert  32  such that the insert completely overlays or covers the clubface. Again, when configured as an overlay insert, the insert  32  is attached to the clubface in the same manner as discussed above, i.e., through the use of adhesives or mechanical fasteners known in the art. 
     The ball striking surface  18  of the separate insert  32  attached to the face or clubface  16  of the body member or golf club head  30  can be configured similarly to that of golf ball heads  22 ,  26  illustrated in  FIGS. 2 and 3 , respectfully. That is, the ball striking surface  18  of the insert  32  can be configured to have one or more surface features or textures, such as ridges or grooves, or be configured to be substantially smooth. In the embodiment illustrated in  FIGS. 4A-4C , the ball striking surface  18  of the insert  32  is configured to be substantially smooth. 
     In contrast to  FIGS. 4A-4C , the embodiments illustrated in  FIGS. 5-7  show an insert  32  with a ball striking surface  18  having a variety of one or more surface features  36 . The different types of surface features  36  illustrated in  FIGS. 5-7  are only exemplary, and it should be understood that the striking surface  18  can comprise any number of desirable patterns or textures not limited to those illustrated in  FIGS. 5-7 . 
     Referring specifically to  FIG. 5 , the ball striking surface  18 ′ of the insert  32 ′ has surface features  36 ′ configured as one or more ridges or ribs  38 . The ridges or ribs  38  are raised, or in other words, protrude outward from the insert  32 ′. As a result of each ridge or rib  38  protruding upward from the clubface  16 , valleys or grooved portions  40  are located in between adjacent ridges or ribs. Alternatively, the raised/grooved arrangement of the surface features  36 ′ in  FIG. 5  can be reversed, such that reference numeral  38  of  FIG. 5  can refer to valleys or grooves and reference numeral  40  can refer to raised rib or ridge portions. As shown in  FIG. 5 , the ridges/ribs  38  and grooves  40  generally extend vertically between the top and bottom of the insert  32 ′ and comprise substantially all of the insert. Moreover, the vertical direction of the ridges/ribs  38  and grooves  40  is generally oriented parallel to a plane having an angle substantially similar to the loft angle of the clubface  16 . Alternatively, the ridges/ribs  38  and grooves  40  can be generally oriented in a horizontal direction perpendicular to the plane having an angle substantially similar to the loft angle of the clubface  16  (not shown). In other words, the ridges/ribs  38  and grooves  40  can extend horizontally between the left and right side of the insert  32 ′. 
     Referring now to  FIG. 6 , an additional embodiment of an insert  32 ″ with a ball striking surface  18 ″ having a one or more surface features  36 ″ is illustrated. The surface features  36 ″ of  FIG. 6  are configured in a more complex pattern compared to the ridges and/or grooves illustrated in  FIG. 5 . In particular, the surface features  36 ″ comprising the ball striking surface  18 ″ in  FIG. 6  include two repeating patterns that cover substantially all of the insert  32 ″. The first repeating surface feature pattern is a series of short grooves  42  that are generally oriented in a vertical direction parallel with a plane having an angle substantially similar to the loft angle of the clubface  16 . The grooves  42  protrude inward into the insert  32 ″ and repeat horizontally between the left and right side of the insert. The grooves  42  are generally spaced equidistant to one another. The second repeating surface feature pattern is a pair of raised ribs or ridges  44  that are oriented perpendicular to the grooves  42 . The raised ribs or ridges  44  are also generally oriented in a horizontal direction perpendicular to the plane having an angle substantially similar to the loft angle of the clubface  16 . In other words, the raised ribs or ridges  44  extend horizontally between the left and right side of the insert  32 ″. Alternatively, the raised/grooved arrangement of the surface features  36 ″ in  FIG. 6  can be reversed, such that reference numeral  42  of  FIG. 6  can refer to a repeating pattern of raised rib or ridge portions and reference numeral  44  can refer to a pair of valleys or grooves. Moreover, it is contemplated that the orientation of the surface features  36 ″ in  FIG. 6  can be reversed, such that the grooves  42  extend horizontally and the ridges  44  extend vertically. 
     The first and second patterns  42 ,  44  are shown in  FIG. 6  as alternating in a one-to-one fashion. That is, a first grooved pattern follows a first pair of raised ridges, a second pair of raised ridges follows the first grooved pattern, a second grooved pattern follows the second pair of raised ridges, etc. It should be understood, however, that the repeating surface feature patterns can alternate in any desired arrangement without departing from the scope of the present disclosure. For example, two sets of grooves may be located between a pair of raised ridges, etc. 
     Turning now  FIG. 7 , a further embodiment of an insert  32 ′″ with a ball striking surface  18 ′″ having a one or more surface features  36 ′″ is illustrated. The surface features  36  of  FIG. 7  are configured as a pattern of punch marks  46 . The punch marks  46  cover substantially all of the insert  32 ′″ and are sunken into or depressed therein. Moreover, the punch marks  46  are generally spaced equidistant to one another to form a pattern that can generally be described as cubic. However, it should be understood that the spacing of adjacent punch marks can be varied in any desired arrangement without departing from the scope of the present disclosure. For example, the punch marks  46  can form different patterns across the insert  32 ′″, such as a diamond pattern, a radial pattern, etc. 
     As illustrated in  FIGS. 5-7 , each of the different surface features  36 ′,  36 ″,  36 ′″ making up the ball striking surfaces  18 ′,  18 ″,  18 ′″ of the inserts are adapted to contact an associated golf ball and transfer the kinetic energy of the golf club to the golf ball. Moreover, the inserts and the surface features which make up the ball striking surfaces may cover substantially all of the clubface  16  (except for perimeter portions thereof), as illustrated in  FIGS. 5-7 . Alternatively, the inserts  32 ′,  32 ″,  32 ′″, and thus the surface features  36 ′,  36 ″,  36 ′″, may cover just a smaller portion of the clubface such as a central “sweet spot” (not shown). However, in any event, the surface features illustrated in  FIGS. 5-7  should be in accordance with the Rules of Golf issued by the USGA. Furthermore, while the various surface features illustrated in  FIGS. 5-7  are mostly shown as being included on the insert individually, it should be understood that any combination of the individual surface features illustrated in  FIGS. 5-7  could be included on an insert without departing from the scope of the present disclosure. For example, an insert could include at least two or more of the surface features illustrated in  FIGS. 5-7 , such as two or more surface features selected from a ridge or groove extending vertically between a top and a bottom of the face insert, a ridge or groove extending horizontally between the sides of the insert, and a bottom of the face insert, punch marks spaced across the insert, and repeating patterns thereof. 
     In addition, the different surface features  36 ′,  36 ″,  36 ′″ illustrated in  FIGS. 5-7  may vary throughout a set of golf clubs, from wedges to longer irons, depending upon the desired launch characteristics needed for optimal flight of each club. For example, it may be desirable to provide one type of surface feature on a longer iron, which may not be desirable on a wedge. To further exemplify this aspect of the present disclosure, the surface features  36 ′ illustrated in  FIG. 5  (i.e., vertically oriented ridges and/or grooves  38 ,  40 ) may be desired to optimize launch characteristics of shorter clubs in wet conditions, where the ridges and/or grooves help to disperse water yet not induce spin. As another example, a combination of horizontal/vertical ridges or grooves  42 ,  44  comprising the surface features illustrated in  FIGS. 5-7  can be combined and varied in any number of arrangements on the clubface of each individual golf club, in order to optimize various performance characteristics. These performance characteristics include, but are not limited to, launch angle, spin rate, and carry distance (e.g., yardage) of the golf ball. 
     In some embodiments, the insert  32 ,  32 ′,  32 ″,  32 ″ is removably attached to the clubface  16 . Such a configuration allows the insert to be removed from the clubface  16  whenever desired by the user of the golf club. After a significant period of use, the ball striking surface  18 ,  18 ′,  18 ″,  18 ′″, which may include one or more surface features  36 ,  36 ′,  36 ″,  36 ″ as described above, may exhibit a degradation in performance characteristics due to, for example, the forceful nature of the impact between golf clubs and golf balls, the presence of debris (e.g., sand, dirt, grass, etc.), and/or exposure to natural elements (e.g., sunlight, water, cold air, etc.). As such, a user may want to remove the insert for reconditioning or replacement of the ball striking surface, thereby saving on costs which might otherwise be spent on replacing the entire golf club. Moreover, manufacturers may release upgraded or improved inserts and ball striking surfaces for various golf club models, if warranted by performance tuning and optimization demands that commonly change over time. These upgrades or improvements may include making the insert from a different material which provides the desired performance tuning and optimization. In this regard, a removable insert permits a golf club user to upgrade just the striking surface of the golf club head, as opposed to the entire golf club. 
     In accordance with a preferred embodiment of the disclosure, the ball striking surface  18 ,  18 ′,  18 ″,  18 ′″ of each of the golf club heads described above and shown in  FIGS. 1-7  has a combination of properties and/or surface features configured to improve various performance characteristics associated with the game of golf. These performance characteristics include but are not limited to an increased launch angle of the golf ball, a decreased spin rate of the golf ball, and an increased carry distance (e.g., yardage) of the golf ball. As mentioned above, the ball striking surface&#39;s combination of properties advantageously improves these performance characteristics at any given club speed by permitting a much more significant portion of the kinetic energy to be transferred to the propulsion of the golf ball forward/upward at impact and a much lower amount of the energy (than conventional golf clubs) to be converted to rotational energy that spins the ball. Moreover, less inadvertent loss of accuracy from off axis spin of the ball is achieved. Specifically, this combination of properties is achieved by a ball striking surface having some or all of the properties a) through g) described previously in this disclosure. Importantly, it has been found that the intrinsic lubricity of the ball striking surface is not a required characteristic. In other words, a particular coefficient of friction of the ball striking surface is not a critical property that results in the enhanced performance. 
     In particular, the properties of hardness, indentation resistance or compressive strength, and smoothness are preferred. A ball striking surface with some or all of the properties a) through g) described above also imparts improved durability, such that the ball striking surface can withstand repeated forceful golf ball impacts without a significant degradation in performance (a common problem with PTFE coatings). The ball striking surface thus forms a support structure for carrying the force of a golf ball impact from the clubface  16  to the heads  14 ,  22 ,  26 , and  30  with minimal, if any, indentation. 
     In accordance with a preferred embodiment of the present disclosure, the clubface  16  comprises a ball striking surface  18 ,  18 ′,  18 ″, 18 ′″ which is provided by a face insert, such as insert  32 ,  32 ′,  32 ″,  32 ″ described above. In other words, the ball striking surface and the insert are integral. That is, the ball striking surface and the insert are included as part of a whole rather than supplied as separate components. In such an embodiment, the advantageous combination of properties disclosed herein is intrinsic to the insert  32 ,  32 ′,  32 ″,  32 ″. This may be achieved, for example, by using an injection molding manufacturing process to form the insert and ball striking surface as a single body and from the same material which has the advantageous combination of properties. The material used to form the insert and striking surface can be the same or different from the material used to make the body member or golf club head  30 . 
     The unitary or single bodied insert  32 ,  32 ′,  32 ″,  32 ″ and ball striking surface  18 ,  18 ′,  18 ″,  18 ″ is made from a material chosen for having the advantageous combination or properties discussed herein, including smoothness, hardness and durability. However, the intrinsic coefficient of friction is not the critical characteristic of the chosen coating that results in the enhanced performance. In particular embodiments, the insert is made from a polymeric material such as Acetal. Acetal is commercially available under the tradename Delrin. In other embodiments, the insert can be made from other polymeric materials, reinforced polymers, or ceramic or porcelain-based substances. Polymeric materials such as Acetal are preferable due to their ability to be injection molded and to provide high levels of hardness, compared with other plastic materials. Injection molding permits the manufacturing of inserts  32 ,  32 ′,  32 ″,  32 ″ having a wide variety of ball striking surfaces, which are easily imparted to the insert by designing a mold having the desired striking surface. For example, an injection mold can provide an insert with a smooth ball striking surface, such as the surface  36  illustrated in  FIGS. 4A-4C , and/or the various surface features  36 ′,  36 ″,  36 ′″ illustrated in  FIGS. 5-7 . 
     The unitary or single bodied insert  32 ,  32 ′,  32 ″,  32 ″ and ball striking surface  18 ,  18 ′,  18 ″,  18 ″ can have any desired thickness which protects against abrasion without exposing the underlying material of the golf club head, and which provides the advantageous combination of properties disclosed herein. Abrasion can result from the forceful nature of the impact between golf clubs and golf balls, the presence of debris (e.g., mineral particles, sand, dirt, grass, etc.), and/or exposure to natural elements (e.g., sunlight, water, cold air, etc.). In some particular embodiments, the insert has a thickness of about 500 μm to about 2,500 μm, and preferably about 750 μm to about 2,250 μm, and more preferably about 1,000 μm to about 2,000 μm. 
     In accordance with another embodiment of the present disclosure, the ball striking surface  18  and the clubface  16  of the golf club heads  14 ,  22 ,  26 , and  30  are integral. That is, the ball striking surface  18  and clubface  16  are included as part of a whole rather than supplied separately. In such an embodiment, the advantageous combination of properties disclosed herein is intrinsic to the clubface and the ball striking surface. This may be achieved, for example, by manufacturing the golf club head, clubface, and ball striking surface from the same material having the advantageous combination of properties. As another example, a surface treatment could be performed on the clubface to form the ball striking surface with the combination of properties, such as through a surface hardening or work hardening process known in the art. 
       FIG. 8  illustrates another embodiment according to aspects of the present disclosure, wherein the clubface  16  of the golf club head  14  is supplied with a separate component which provides the ball striking surface  18  having the advantageous combination of properties presently disclosed. In particular, the separate component is one or more layers of a coating  20  disposed on at least a portion of the clubface  16  of golf club head  14  to form a ball striking surface  18 . The coating  20  can comprise multiple layers at any desired thickness t to form the ball striking surface  18  with the advantageous combination or properties. The coating  20  is a substance chosen for having the advantageous combination or properties discussed herein, including smoothness, hardness and durability. However, the intrinsic coefficient of friction is not the critical characteristic of the chosen coating that results in the enhanced performance. 
     The coating  20  forming the ball contacting surface  18  is adapted to impact an associated golf ball and transfer the kinetic energy of the golf club to the golf ball. In this regard, the ball striking surface  18  comprising the coating  20  may comprise substantially all of the clubface  16  of the golf club head  14 , or just a portion thereof. For example, the coating  20  can be applied at a centrally located “sweet spot” of the clubface, or could be applied to cover the entire clubface. Moreover, while golf club head  14  is illustrated in  FIG. 8  as receiving the coating  20 , it should be understood that any of the golf club heads discussed herein could similarly receive the coating without departing from the scope of the present disclosure, including heads  22 ,  26 , and  30  illustrated in  FIGS. 2, 3, 4A-4C , and  5 - 7 , respectively. 
     If the coating  20  is applied to head  22  of  FIG. 2 , the surface features  24  can already be formed on the clubface  16  such that the coating is disposed over the surface features to form the ridged and/or grooved ball striking surface  18  of the golf club head. Alternatively, the coating  20  can be applied to the clubface  16  such that the coating itself forms the surface features  24  of golf club head  22 . 
     Referring now to golf club head  30  of  FIGS. 4A-4C , the coating  20  can be applied to the insert  32  to form the ball striking surface  18 . In this regard, the insert  32  may further comprise a substrate (not shown) and the coating  20  is applied to at least a portion of the substrate. The substrate of the insert  32  and the clubface  16  of the golf club head  30  can be made from the same or different materials. However, when the insert  32  is configured as an inlay insert as described above, the coating  20  is applied to the substrate of the insert such that when the insert is attached to the clubface  16 , the ball striking surface  18  formed by the coating is still substantially flush with the surrounding portions of the clubface in accordance with the Rules of Golf issued by the USGA. When the insert  32  is configured as an overlay insert as described above, the coating  20  is applied to the entire substrate of the insert to provide a ball striking surface  18  which entirely covers the clubface  16 . 
     With reference back to  FIG. 8 , in some particular embodiments the coating  20  material is a polymeric isocyanate derivative such as polyurethane, including modified polyurethanes like oil modified polyurethane. A polyurethane coating  20  is applied at a suitable thickness t to provide the advantageous combination of properties disclosed herein, including a range of about 100 μm to about 200 μm, and preferably about 115 μm to about 185 μm, and more preferably about 125 μm to about 185 μm. When the coating  20  is applied as one or more layers, the thickness of the one or more layers comprising the coating is preferably maintained within the aforementioned range. A coating material which is commercially available under the trade POR-15® is presently preferred for use. The application of ball striking surfaces comprising the POR-15® coating, a coating not known for its low coefficient of friction nor commonly used in connection with golf clubs, unexpectedly enhanced the performance characteristics of golf clubs, as shown in the Example below. 
     A process for applying the polyurethane coating  20  to the clubface  16  or insert  32 ,  32 ′,  32 ″,  32 ′″ of a golf club will now be described. If a substantially smooth ball striking surface is desired, an optional first step is to smooth out the clubface or insert by removing any unwanted surface features and roughness on the clubface by techniques know in the art, including grinding, sanding, etc., and the like. If the clubface or insert is to include surface features, or is already prepared to an adequate smoothness, a surface preparation step is first performed. The surface preparation step involves removing all visible oil, grease, soil, dirt, and other contaminants from the golf club head. Surface preparation can also include an acid etching step known in the art to clean the clubface or insert. The coating can then be disposed on the clubface or insert using known application techniques, such as spraying, airless spraying, brushing, or rolling. Additional layers of coating are then applied as desired, allowing each preceding coat to dry for approximately 1 to 2 hours before application of subsequent coat layers. In some particular embodiments, 3 to 4 layers of coating has been found to impart the advantageous combination of properties to the ball striking surface of the golf club heads disclosed herein. Once the desired number of coating layers is applied, the coating should be allowed to cure for approximately one day. 
     A coating comprising modified polyurethane provides a ball striking surface  18 ,  18 ′,  18 ″,  18 ′″ superior to PTFE in durability, performance and cost of manufacture. Modified polyurethane coatings are typically used for the purpose of corrosion protection of metal surfaces. The application of these compounds to enhance the performance characteristics of golf clubs is both non-obvious and effective. 
     It is contemplated that other coatings and materials can be used and applied to the clubface to provide a ball striking surface having the advantageous combination of properties disclosed herein. For example, the golf clubface may be coated with a baked on porcelain material as used in non-stick cookware or appliance surfaces. Additionally, a ceramic coating may also be used to achieve the required surface properties. A powder coating of polyurethane or other acceptably hard and durable material may also be used. 
     Moreover, even though  FIGS. 1-8  illustrate and the above disclosure describes a preferred embodiment of a golf club providing a clubface  16  and a ball striking surface  18 ,  18 ′,  18 ″,  18 ′″, it is contemplated that, without deviating from the scope of the present disclosure, other items of sports equipment can provide a face having a striking surface with the advantageous combination of properties disclosed herein. For example, other types of sports equipment that may similarly benefit from enhanced surface strike performance due to the advantageous combination of properties disclosed herein include, but are not limited to, baseball bats, hockey sticks, polo mallets, croquet mallets bocce balls, bowling balls, billiard balls, etc., and the like. These additional types of sports equipment can include the combination of properties intrinsically or through the use of coatings and/or inserts as discussed above. 
     The following example is provided to illustrate the processes of the present disclosure. The example is merely illustrative and is not intended to limit the disclosure to the materials, conditions, or process parameters set forth therein. 
     Example 
     Tests were performed to show the advantage of utilizing a ball striking surface having the advantageous combination of properties disclosed herein, including hardness, smoothness, and durability. Various performance characteristics associated with the game of golf can be improved through the use of the ball striking surface having this advantageous combination of properties. Such performance characteristics include an increased launch angle of the golf ball, a decreased spin rate of the golf ball, and an increased carry distance (e.g., yardage) of the golf ball. 
     Two golf clubs of the same type and brand were acquired. In particular, two Callaway® 9-irons were used, each having a 39° loft. One of the golf clubs was modified to have the ball striking surface disclosed herein for comparison with the other golf club, which was left unmodified. To provide the modified golf club with the ball striking surface, a coating of polyurethane material commercially available under the trade name POR-15®, and having the advantageous combination of properties disclosed herein, was used. POR-15® was coated on the clubface of the modified golf club in accordance with the method discussed above. 
     Numerous golf balls of the same brand were struck with the modified and unmodified golf clubs and various measurements were recorded. Using a FlightScope® ball tracking monitor, radar, and launch monitor, the golf ball carry distance, golf ball speed, club speed, golf ball spin rate, and golf ball launch angle were recorded for each golf shot with the modified and unmodified golf club. The shots were taken outside to simulate real-world conditions, and the data was collected for the full flight of the ball. In other words, the carry distances of the golf balls was actually measured and not extrapolated from initial launch conditions. The results are presented in Table 1 below: 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Performance Measurements of Modified and Unmodified Golf Club 
               
            
           
           
               
               
               
               
               
               
            
               
                 Shot 
                 Carry (yds) 
                 Ball (mph) 
                 Club (mph) 
                 Spin (rpm) 
                 Launch V (°) 
               
               
                   
               
            
           
           
               
            
               
                 Modified Golf Club 
               
            
           
           
               
               
               
               
               
               
            
               
                 3 
                 165.6 
                 102.6 
                 89.1 
                 2965 
                 29.9 
               
               
                 4 
                 171.6 
                 106.1 
                 86.9 
                 2797 
                 30.5 
               
               
                 5 
                 163.8 
                 105.7 
                 94.5 
                 2553 
                 27.5 
               
               
                 6 
                 150 
                 95.8 
                 87.8 
                 2398 
                 32.6 
               
               
                 Average 
                 162.75 
                 102.55 
                 89.575 
                 2678.25 
                 30.125 
               
            
           
           
               
            
               
                 Unmodified Golf Club 
               
            
           
           
               
               
               
               
               
               
            
               
                 14 
                 134.1 
                 104.3 
                 85.5 
                 7924 
                 25.3 
               
               
                 15 
                 133.5 
                 106.8 
                 85.8 
                 8168 
                 28.6 
               
               
                 16 
                 127.1 
                 98.3 
                 90.2 
                 6368 
                 28.7 
               
               
                 17 
                 132 
                 102.5 
                 86.7 
                 6082 
                 29.1 
               
               
                 Average 
                 131.675 
                 102.975 
                 87.05 
                 7135.5 
                 27.925 
               
               
                   
               
            
           
         
       
     
     As shown in Table 1 above, the modified club produced between about 16 yards to about 45 yards increased carry distance and an average increased carry distance of over 30 yards compared with the unmodified golf club, with no significant increase in ball velocity. In addition, the launch angle achieved by the modified golf club increased by as much as about 7 degrees, with an average launch angle increase of about 2 degrees compared with the unmodified golf club. Moreover, the modified golf club decreased spin rate by as much as about 70%, with an average decrease in spin rate of about 60% compared with the unmodified golf club. In summary, the results in Table 1 show that a ball striking surface having a combination of properties a)-g) disclosed above will increase the launch angle of the struck ball and reduce the spin rate. As a result, longer and higher ball flight, less lateral dispersion of an incorrectly struck ball, and a more beneficial descent angle are achieved. 
     The improved performance characteristics achieved by the modified golf club is attributed to the ball striking surface having the advantageous combination of properties disclosed herein. For example, properties such as hardness and resistance to indentation of the ball striking surface, in combination with the smoothness, prevents the golf ball from developing significant mechanical engagement with ball striking surface upon impact with the golf club, thereby reducing the amount of imparted spin. Because less kinetic energy is converted to rotational energy that spins that ball, a much more significant portion of the kinetic energy is transferred to the forward/upward propulsion of the golf ball, thereby improving the launch angle and increasing the carry distance. The application of ball striking surfaces having this combination of properties to enhance the performance characteristics of golf clubs is un-expected, effective, and non-obvious. 
     The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the above disclosures or the equivalents thereof.