Abstract:
A golf club head is disclosed having a club face comprised of a plurality of plates that act in concert to provide a spring-like response when the club impacts a golf ball. The plates are fluidly coupled by providing appropriate surfaces to the plates at their interface or by locating a viscous fluid between the plates. The plates are held in place by coupling them to the head body. One or more plates may be integrally formed with the body of the golf club head. Various parameters may be selected to optimize response or to customize the response for different golfing styles including the relative thickness of the plates, the presence of a viscous fluid between the plates, the type and viscosity of the viscous fluid, the material of the plates, (and hence, their coefficient of elasticity) and the type of mechanical coupling of the plates to the body of the golf club head.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention pertains to the field of golf clubs. 
     2. Description of the Related Art 
     Golf is a familiar game in which players use long-shafted clubs to strike golf balls to drive them down a fairway, onto a green and into a cup located on the green. The golf &#34;system&#34; comprises three elements: the golfer, the golf club, and the golf ball. As noted, the present invention pertains to the golf club. 
     Golfers seek golf clubs that provide control and power. A superior golf club will allow a skilled golfer to hit a golf ball straight and far. The most important parameter in achieving these goals is the skill of the golfer. However, the performance of the golf club is also a significant factor. In particular, the response of the golf club due to impact with the golf ball affects the direction and range of the golf ball. 
     Traditionally, golf clubs are divided into two types, drivers and irons. Until recently, drivers were long shafted clubs having bulbous heads with a metal or plastic face fastened to the wood. In contrast, irons have somewhat shorter shafts and an all metal head that is often substantially planar along front and back surfaces. Irons are used for fairway shots and where substantial ball control is necessary, such as when chipping onto a green or putting. 
     Drivers have undergone many recent innovations including the advent of metal drivers, sometimes called &#34;metal woods.&#34; The metal drivers have a similar shape as the traditional wood drivers, but the head size has increased. The new metal drivers are typically one-piece, cast bulbous heads having an interior cavity that some manufacturers leave empty and others fill with a foam. The use of metal gives manufacturers precise control over the quality of the product and the location of weight throughout the head, properties that were often lacking in the drivers constructed of wood. 
     Because of the continuing popularity of the sport, there is ongoing effort to develop clubs with superior response. 
     In Anderson et al., U.S. Pat. No. 5,255,918 the inventor discloses an iron that has a cast head with a rimmed recess that can receive a separately formed face plate. This permits the use of forged, hardened, face plates and easily cast bodies. In Anderson, the cast head includes a planar web that closes the back of the recess. Accordingly, when the front plate is attached to the head a substantial space is formed between the web and the face plate. As noted in the patent, the space allows the face plate 21 to deflect rearward during impact with a golf ball. 
     Additionally, golf shots are most effective when the ball and club meet at the club&#39;s center of percussion, defined as a point where an impulsive force can be applied with no reaction force at the point of support. An area around the center of percussion is referred to as a &#34;sweet spot.&#34; Many research and development efforts attempt to enlarge the sweet spot so that a club is more forgiving when a ball is slightly mis-hit. 
     SUMMARY OF THE INVENTION 
     The present invention provides an improved performance golf club wherein the head includes a body that has a ball-contacting area that includes fluidly coupled plates that deform upon impact with a golf ball. The deformation causes the ball-contacting area to act as a leaf spring to effectively store energy from the impact between the golf club and the ball and then return energy to the ball as it leaves the face of the club. This returned energy provides greater distance to the ball. 
     The fluidly coupled plates may also enlarge the sweet spot of the club head. Further testing is required to confirm the affect of the present invention on the sweet spot. 
     Various advantages and features of novelty which characterize the invention are particularized in the claims forming a part hereof. However, for a better understanding of the invention and its advantages, refer to the drawings and the accompanying description in which there is illustrated and described preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is top perspective view of a golf club head of the present invention also showing a portion of a golf club shaft connected to the head. 
     FIG. 2 is a front elevation view of a face of the golf club head of FIG. 1. 
     FIG. 3 is a cross section view taken along line 3--3 of FIG. 2. 
     FIG. 4 is an enlarged cross section view of a portion of FIG. 3 showing a ball-contacting area of the golf club head. 
     FIG. 5 is a cross section view of a second embodiment of the golf club head of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 1-3 show a first embodiment of a golf club head 10 of the present invention. The golf club head 10 is a portion of a golf club which impacts a golf ball during play. The head 10 connects to a shaft 12 that extends upward to a handle portion (not shown). 
     In a preferred embodiment, the head 10 includes a body 14, a bottom plate 16 and an interior, or back, plate 18. 
     The body 14 includes a hosel 20, a top surface 22, a back surface 24 and a face 26. The hosel 20 may be integral with, or fixedly connected to, the body 14. The hosel 20 connects the body 14, and hence the head 10, to the shaft 12. The body 14 also includes reinforced portions 28 that include threaded bores (not separately shown or numbered) for receiving bolts 30. 
     Preferably, the face 26 is a planar plate integrally formed with the body. The face 26 includes a plurality of flutes 32 to provide a nonslip surface for contact with a golf ball. At the outwardmost end of the head 10 is a toe 34 while the rearwardmost end is a heel 36. Accordingly, the face 26 extends from the heel 36 to the toe 34. 
     The bottom plate 16 is mechanically fastened to the body 14 by the bolts 30 which pass through the bottom plate and connect to the threaded bores in the reinforced portions 28. Preferably, there are at least three bolts 30 and reinforced portions 28. Only two bolts 30 and two reinforced portions 28 are visible in the cross section of FIG. 3. 
     The bottom plate 16 and body 14 cooperate to define a cavity 38. The cavity is completely enclosed by the body and bottom plate. However, alternative embodiments may include minor openings in the body or bottom plate. The cavity may be hollow or foam filled. 
     The bottom plate 16 and body 14 further cooperate to define an annular groove or channel 40 that extends around the interior periphery of the body and bottom plate near an inside surface 44 of the face 26. The back plate 18 is received within the channel 40 and held in place when the bottom plate 16 is fastened to the body 14. 
     The back plate 18 and face 26 cooperate to define a ball-contacting region 42 of the head 10. Preferably, the back plate 18 is substantially planar and the face 26 is a substantially planar portion of the body 14. In addition, in the preferred embodiment the back plate 18 is located substantially parallel to the planar inside surface 44 of the face 26. The back plate 18 is fluidly (or viscously) coupled to the face 26. 
     In its broadest sense, fluidly coupled means that the plates are located near one another, are not adhesively joined along their major, central common surfaces and react mutually to applied loads. In a somewhat more narrow sense, the plates are viscously coupled meaning that the plates are located near one another thereby defining a void between the plates and a viscous liquid is located in the void. In the preferred embodiment shown in FIGS. 1-3 the back plate 18 is held in place by the channel 40 and a liquid 46 (FIG. 4) is located between, and in contact with, the back plate 18 and the rear surface 44 of the face 26 thus viscously coupling the plates. The back plate 18 and plate face 26 are also mechanically coupled by virtue of being coupled to the body 14. Fluidic-coupling and viscous-coupling allow the plates to slide relative to one another when one or both plates are deformed. Thus, the fluidic-coupling/viscous-coupling allows the plates to react similarly to a leaf spring. Note that this reaction is contrary to laminate bodies that are adhesively coupled such as laminar beams which, due to the adhesively coupling, are rigid and decidedly not springlike. 
     Because the back plate 18 is captured within the channel 40 it is not free to substantially move relative to the body 14 or the face 26, except when the face or back plate are deformed. When the face 26 impacts a golf ball the force will deform the face 26 inwardly toward the cavity 38. That force will attempt to compress and move the liquid 46. However, because the time of impact is extremely small (estimated at 1/500th of a second), and because the liquid 46 is trapped between the back plate 18 and the face 26, the force of the impact will be communicated through the liquid to the back plate 18 also causing it to deform inwardly toward the cavity 38. By hitting a ball, the face 26 is deformed spherically, and the back plate 18 will deform around that spherical deformation but will have a larger radius of deformation due to the geometry by which the back plate 18 is forced to &#34;cup&#34; around the face 26. 
     It is believed to be desirable to equalize the amount of rearward deflection of the face 26 and the back plate 18. Accordingly, the geometry or physical properties, or both, will be selected to achieve substantially similar rearward deflection. 
     The face 26 has a thickness 48 and the back plate 18 has a thickness 50. To achieve the substantially similar rearward deflection, the thickness 48 of the face may be made more narrow than the thickness 50 of the back plate. 
     Alternatively, the materials of the face and back plate may be selected so that the face has a higher coefficient of elasticity than the material of the back plate 18. Empirical data may be easily collected to optimize the relationship of the thicknesses 48 and 50 and the relative coefficients of elasticity of the face 26 and the back plate 18. The current best mode comprises using the same material (and hence, the same coefficient of elasticity) for the back plate 18 and the face 26 and making the face thickness 48 somewhat more narrow than the back plate thickness 50. 
     In the present embodiment, as particularly shown in FIG. 4, the liquid 46 is located in a void 52 between the back plate 18 and the face 26. In preferred embodiments, the void has a width, defined as the shortest distance between the rear surface 44 and the back plate 18, of approximately 0.254 mm (0.01 inches). Satisfactory results may also be obtained with void widths as small as 0.127 mm (0.005 inches) or as large as 2.54 mm (0.10 inches). 
     The liquid 46 is preferably a viscous fluid such as grease, TEFLON, silicon, or other suitable fluids that will assist the back plate 18 and the face to move relative to one another without creating substantial shear stresses between the plates when the plates are deflected rearward. In a preferred embodiment the void width is 0.254 mm and the liquid 46 is a grease. Further testing may indicate other combinations of void width and fluid viscosity having optimum performance factors. In addition, manufacturability considerations may dictate different combinations. 
     It is noted that silicon will adhesively couple the plates. However, because silicon elastically deforms easily compared to an adhesive such as resorcinol (a common adhesive for laminer wood beams) the coupling created by silicon is a viscous coupling within the meaning of this specification. 
     In a form of fluidic coupling, the materials of the back plate 18 and the face 26 may have sufficiently slippery or smooth surfaces so that they are able to slide relative to one another when the face and plate are deformed rearwardly. In this alternative embodiment the fluid in the void is atmospheric air. 
     A further embodiment of the present invention is shown in FIG. 5 which includes a body 14&#39; and a bottom plate 16&#39; connected to the body 14&#39; by bolts 30&#39; that thread into reinforced portions 28&#39;. The body 14&#39; further includes a hosel 20&#39; that fixedly connects to a club shaft 12&#39;. In this embodiment, the ball-contacting region 42 includes two substantially planar plates, a face plate 54 and an interior plate 56. Both plates are mounted in a channel 58 defined in the body 14&#39; and the bottom plate 16&#39;. As before, the plates 54 and 56 are viscously coupled and in the preferred embodiment, there is a void 52&#39; between the plates having a fluid, such as liquid 46. 
     This second embodiment permits a greater range of selection of materials and relative thicknesses of the plates 54 and 56. In addition, the plates 54 and 56 may be custom installed at the point of sale of the golf club to accommodate different golfers. 
     As with the previous embodiments, the bottom plate 16&#39; may be decoupled from the body 14&#39; by removing the bolts 30&#39;. Decoupling the bottom plate 16&#39; permits the plates 54 and 56 to be removed from the head 14&#39;. The player may then select plates 54 or 56 having different materials, different relative thicknesses, or may select a different fluid for the void 52&#39;. The plates can then be reinserted in the channel 58 and the bottom plate 16&#39; recoupled to the body 14&#39;. 
     Numerous characteristics and advantages of the invention have been set forth in the foregoing description, together with details of the structure and function of the invention. The novel features hereof are pointed out in the appended claims. The disclosure is illustrative only, and changes may be made in detail, especially in matters of shape, size, and arrangement of parts within the principle of the invention to the full extent indicated by the broad general meaning of the terms in the claims.