Abstract:
A driver type golf club head formed of a metal shell and having an overall volume of at least 400 cc having a geometry and weight distribution and a unique multi-level striking face that locates the center of gravity of the club head below a horizontal midline of the striking face and further locates the center of gravity behind said striking face at least 38 percent of the distance between said striking face and said rear surface or 42 mm behind the striking face.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present invention relates to golf clubs and in particular to driver type wood or metal wood heads having an improved configuration and ball striking performance. 
         [0002]    Golf club heads were originally hand made from blocks of wood having uniform density and weight. There was little or no consideration about the location of the center of mass or center of gravity and how this parameter affected the overall performance of the golf club during the execution of a golf shot. Occasionally these wooden drivers were weighted, usually with lead, to alter the feel of the club as it was swung. In addition the bottom sole was normally provided with a metal bottom sole screwed into the wooden club head to protect the club from damage caused by rough turf, hard ground rocks and stones that were common on early golf courses. These wooden golf clubs have evolved over several centuries from solid wood construction to metals and carbon fiber. Contributing to the design changes is the use of materials such as steel and titanium used more commonly with today&#39;s modern golf clubs. The first generation of metal woods was formed using investment cast stainless steel with a pencil neck hosel. They were slightly smaller than the standard wooden driver club heads of the time. Typically the metal wood driver head had a volume of around 150 cc. Because of the relatively small size, the center of gravity, CG, of these club heads was essentially at or near the center of the club head and they were compact and manageable enough to be able to impart maximum energy transfer to the golf ball. 
         [0003]    The new materials and manufacturing techniques allowed for changes in the overall geometry of the club heads including improved strength and weight distribution that, in turn, affected the overall performance and shot making ability of the golf club. These club heads became widely accepted and titanium has now become the material of choice for nearly all manufacturers that were producing premium driver type golf clubs. Thus modern driver type golf club heads are typically made of titanium material and became much larger and have an overall volume of at least 400 cc as compared to many of the earlier metal woods that were approximately half that size and smaller. As head sizes increased so did the moment of inertia of the club head, making the club heads more forgiving on off-center impacts on the clubface. Gradually these larger sized club heads gained acceptance and became the norm for driver type metal woods. 
         [0004]    The combination of a deeper center of gravity and a taller striking face allowed golfers to hit tee shots that were launched at a higher angle and with less spin compared to earlier constructed drivers. In turn, most golfers were able to achieve longer driving distances using the new generation of titanium club heads. However, the increased geometry of the modern driver club heads typically locates the center of gravity of the club head close to the face and toward the upper parts of the club head. This requires that for a golf ball to be struck opposite the CG, the strike must occur above a horizontal midline of the club head to obtain maximum energy transfer from the golf club to the golf ball while minimizing excess golf ball spin. Some conventional clubs in the marketplace indicate they have a low CG but testing has found that none of these have a CG below a 50% horizontal midline of the face. Similarly conventional clubs claiming a deep CG, actually have a CG location less than 38 percent of the distance between the striking face and/or less than 44 mm from the face. 
         [0005]    Golf professionals and some highly skilled amateurs have the ability to adjust the plane of their golf swing to impact the upper portions of the club head on or above the CG of the club head to achieve maximum energy transfer, however most golfers do not have these skills. In fact, approximately 80 to 95 percent of all golfers have limited skills whereby most of their golf shots are struck in an area on the club face that is below the vertical mid-point on the face. This is particularly true when using the longer, more difficult to control, driver type golf clubs. 
         [0006]    It became apparent that adjustment of the location of the CG enables golfers of lesser skill to be able to execute better golf shots. 
         [0007]    Examples of prior art include a patent to Rugge 5851160 directed to a driver type metal wood golf club having the CG below a face centerline and forward near the striking face. The patent also teaches that the face has a variable thickness. 
         [0008]    U.S. Pat. No. 6,800,038 to Willett and U.S. Pat. No. 6,824,475 to Burnett show a metal wood club head with the rear interior of the striking face formed with raised oval shaped thicknesses; see FIGS. 2, 3 and 4. 
         [0009]    Willett U.S. Pat. No. 6,997,820 et al shows another example of a metal wood having a variable face thickness. 
         [0010]    Williams U.S. Pat. No. 7,166,038 shows a generally square club head with a MOI greater than 4000 g/cm squared. 
         [0011]    The Greaney et al application 2012/0172146 shows a metal wood type golf club with a CG location measured from the Z axis and having different material for the crown and sole, a more expensive manufacturing process, and which has the same thickness of the crown, sole and skirt. 
         [0012]    Greaney U.S. Pat. No. 8,012,039 discloses a metal wood golf club and teaches the CG is located midway between the face and the rear without any specific reference to the breadth of the club head. 
         [0013]    Kinoshita U.S. Pat. No. 5,094,457 shows a driver type golf club with a CG below a midline between the crown and sole. The CG depth is less than 12.446 mm behind the face plane for easier manipulation of the club face. 
         [0014]    Application 2014/0302946 to Rae teaches the CG location can be improved by placing mass low and deep in the club head. 
         [0015]    Billing&#39;s U.S. Pat. Nos. 7,004,852, 7,189,169, 7,344,450, 7,828,672, 8,177,662 and 8,491,413 are directed to driver type golf club heads having a weighting port that allows customizing the location of the center of gravity lower but in a fixed CG depth location due to the orientation of the adjustable weight cavity. 
         [0016]    Ballow U.S. Pat. No. 6,716,110 and Billings U.S. Pat. No. 8,382,604 disclose putter type club heads with a rear CG location. 
         [0017]    Another Beach U.S. Pat. No. 8,771,102 to shows a metal wood with a CG location low and toward the rear of the club head. 
         [0018]    Ferguson U.S. Pat. No. 8,617,000 et al discloses a metal wood golf club with externally protruding rear weights. 
         [0019]    Klin U.S. Pat. No. 1,549,993 shows a driver club head with a weight attached into a recess at the rear of the club head. 
         [0020]    U.S. Pat. No. 1,659,273 to Link shows a wood type golf club with a rear weight attached by screws. 
         [0021]    U.S. Pat. No. 5,669,827 to Nagamoto discloses a metal wood with a laminated weight construction at the rear of the club head for locating the CG rearward of the face of the club head. 
         [0022]    U.S. Pat. No. 6,890,267 to Mahaffey et al shows a metal wood with rear peripheral weight and lower surfaces to increase MOI of the club head. 
         [0023]    U.S. Pat. No. 7,377,860 to Breier shows a secondary toe and heel weight that create a rearward and low CG. 
         [0024]    U.S. Pat. Nos. 6,659,884, 6,659,885, 7,131,912, 7,273,421 and 7,481,717 to Knuth disclose metal wood type club heads with various face geometries and parabolic club head body configurations. 
       SUMMARY OF THE INVENTIONS 
       [0025]    The present invention relates to a driver type golf club head formed of a metal shell body having an overall volume of at least 400 cc and having a geometry and weight distribution that locates the center of gravity of the club head below a horizontal midline of the ball striking face and further locates the center of gravity behind the striking face at least 38 percent of the distance between the striking face and the rear surface or at least 44 mm from the striking face. This creates a moment of inertia, MOI, greater than 5,000 grams per centimeters squared. The lower and rearward CG location and high MOI reduces the spin of a golf ball struck with the club head and creates vertical roll to engage vertical gear effect resulting in the golf ball traveling higher and longer and with less dispersion. 
         [0026]    In a preferred embodiment, the location of the CG is accomplished by a unique weight distribution of the sole, side surfaces forming a skirt that joins the crown and the sole and top crown whereby the sole thickness is greater than the thickness of the crown and the skirt and the thickness of the crown is less than the skirt. In this embodiment, the rear wall of the club head shell is approximately twice the thickness of the maximum thickness of the striking face. This thickened structure creates a mass at the rear of the club head that aids in locating the CG rearward of the striking face. In this particular embodiment the CG is at least 44 mm behind the face. In addition, the ball striking face of the driver is formed of multiple sections that are thinner at the upper areas of the face. 
         [0027]    An alternate embodiment of the club head of the present invention is essentially the same as the club head described above, the one major difference being the rear wall is not thick and there is no additional mass at the rear. This embodiment locates the CG slightly closer to the face at 42 mm behind the face. 
         [0028]    Another feature is a multi-level ball striking face that is applicable for use with the club heads described herein or with more conventional club heads. The striking face is formed with up to seven sections having different thickness levels with a thickest section at a central location on the striking face and with the upper toe and heel sections that are the thinnest sections. The remaining sections are thicker toward the bottom of the face and thinner toward the top of the face in order to locate weight toward the bottom of the club head for the purpose of lowering the CG on whatever type club head the striking face is used with. 
         [0029]    Among the objects of the present invention is the provision of a driver type golf club head having improved CG location and increased MOI. 
         [0030]    Another object is the provision of a driver having a unique striking face geometry that increases distance and reduces dispersion of a golf ball struck with the driver. 
         [0031]    Yet another object is the provision of a driver that provides improved stability, increased ball speed and distance, limited dispersion on off center strikes against the golf ball. 
         [0032]    Still another object is the provision of a driver that reduces the spin of a golf ball at impact allowing the ball to travel straighter and longer. 
         [0033]    Still a further object is to provide a driver design having low and rearward CG that is more efficient and less costly to produce compared to using different materials for the body and using weight ports. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0034]      FIG. 1  is a front perspective view of a golf club head in accordance with the present invention. 
           [0035]      FIG. 2  is a front elevational view of the club head of  FIG. 1 . 
           [0036]      FIG. 3  is a toe side elevational view of the club head. 
           [0037]      FIG. 4  is a sectional view taken along line  4 - 4  of  FIG. 1 . 
           [0038]      FIG. 5  is a bottom view of the club head. 
           [0039]      FIG. 6  is a top elevational view of the club head. 
           [0040]      FIG. 7  is a frontal view of a ball striking face used with the club head of the present invention. 
           [0041]      FIG. 7 a    is a sectional view taken along the line  7   a - 7   a  of  FIG. 7 . 
           [0042]      FIG. 7 b    is a sectional view taken along the line  7   b - 7   b  of  FIG. 7 . 
           [0043]      FIG. 8  is a sectional view of an alternative embodiment of a club head in accordance with the present invention. 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0044]    Referring to the drawings, a golf club head  100  in accordance with the present invention is formed of a hollow metallic shell  101  that is generally conventional in shape and includes a top crown  102 , bottom sole  104 , heel  106 , toe  108 , rear surface  110 , toe side surface  112 , heel side surface  113 , ball striking face  114  and hosel  116  for connection to a golf shaft. The crown  102  includes a parabolic shaped, aerodynamic raised surface  118 . The bottom sole  104  also includes a parabolic shaped, aerodynamic raised surface  120  that is complimentary to the aerodynamic surface  118  on the crown  102 . The ball striking face  114  is a driver type having a loft angle less than 13 degrees and is formed of multiple levels as described in detail below. 
         [0045]    As seen in the sectional view of  FIG. 4 , the metallic shell  101  has a top crown  102  with a thickness of no greater than 0.75 mm, but preferably 0.45 to 0.5 mm, that is less than the thickness of 0.85 mm of the bottom sole. In addition, the toe side and heel side surfaces  112  and  113  have a thickness no greater than 0.75 mm and preferably 0.65 mm or less than the thickness of the bottom sole. There is a transition area  115  between the striking face  114  and the remaining areas of the metallic shell  101  ranging from 2.6 mm wide at the bottom to 1.2 mm wide near the upper parts of the shell  101 . It will be appreciated the thickness of the transition area decreases away from the striking face  114  until it becomes the thickness of the remainder of the shell  101 , namely the crown  102 , the bottom sole  104 , toe side surface  112  and heel side surface  113 . The variation in the thickness of the structure of the club head  100  concentrates more weight at the bottom of the club head  100  that, in turn, lowers the center of gravity, CG. 
         [0046]    An additional rear mass  122  of the same material as the rest of the club head shell  101  is integrally formed with the rear surface  110  having a thickness of at least 6 mm at the widest location. The thickness of the rear mass  122  is approximately twice the thickness of the thickest portion of the striking face  114 . The rear mass  122  is located directly centered behind and in-line with the thickest part of the striking face  114  and extends into the interior  124  of the club head  100 . This additional, rear mass  122  insures a lower, more rearward CG location. 
         [0047]    As further seen in  FIG. 4 , the CG is at least 44 mm behind the striking face  114 , or at least 38 percent of the distance between the striking face  114  and the rear surface  110 , but not greater than 50 percent of the distance between the striking face  114  and the rear surface. The CG is also below a horizontal midline HM between a top edge  134  and bottom edge  136  of the striking face  114  and extending rearward between the striking face  114  and the rear surface  110 . 
         [0048]    Referring to  FIGS. 7, 7   a  and  7   b,  the striking face  114  is shown in more detail, formed with multiple thickness levels. The multi-level ball striking face  114  is applicable for use with the club heads described herein or with more conventional club heads. The striking face  114  has seven separate sections, integrally formed by conventional machining or molding techniques, each having variable thicknesses as described below. The impact area at the center of the striking face  114  is formed as a centrally located, oval shaped section  114   a  having a thickness of 3.1 to 3.4 mm that is similar to the thickness of conventional, single thickness driver striking faces. A second section  114   b  is also oval shaped and is adjacent to and surrounds the first section  114   a  and has a lesser thickness of 2.5 to 3.1 mm. An uppermost section  114   c,  adjacent the top crown  102 , has a still lesser thickness of 2.2 to 2.6 mm to minimize mass at the upper portion of the striking face  114 . This thickness variation further reduces weight at the upper portions of the club head  100  to insure a lower location of the CG no matter what the geometry or weight configuration of the rest of the club head. This upper section  114   c  may be tunable to insure an appropriate coefficient of restitution range. 
         [0049]    A central section  114   d  is located above and partially around outer oval section  114   b  and below upper section  114   c  and has a thickness of 2.5 to 3.1 mm. A lower section  114   e  fills in the bottom of the striking face  114  and has a thickness of 2.4 to 2.6 mm that is thicker than upper section  114   c  locating more mass toward the bottom of the club head  100 . Sections  114   d  and  114   e  depict similar wall thicknesses, however slight variations of the thickness of these sections independently of each other allows adjustment of the desired weight requirements and fine tuning of the coefficient of restitution. 
         [0050]    A toe section  114   f  and heel section  114   g  form the outermost areas of the striking face  114  away from the center and are formed with parabolic edges at an interior location on the face  114  that interface with adjoining upper section  114   c,  intermediate section  114   d  and an upper edge of lower section  114   e.  The toe section  114   f  and heel section  114   g  are thinner in the upper areas of the club head  100  where corner welding support stiffens this area of the club head  100 . Toe section  114   f  has a thickness of 1.7 to 1.9 mm and heel section  114   g  has a thickness of 2.2 to 2.5 mm. Since the toe section  114   f  and heel section  114   g  are the thinnest and consequently have less mass, placing these sections in an upper portion of the striking face  114  contributes to the lower location of the CG. 
         [0051]    The parabolic edges of the toe section  114   f  and heel section  114   g  are complimentary to the parabolic shaped, aerodynamic raised surface  120  on the bottom sole  104  and to the parabolic shaped, aerodynamic raised surface  118  on the crown  102 . The parabolic shape that interfaces with the other striking face  114  sections add additional strength in the heel and toe area and overcomes potential weakness due to the thinner dimensions of the toe section  114   f  and heel section  114   g.  This structure provides more efficient energy transfer to the golf ball during the execution of a golf shot, particularly when a golf ball is struck away from the center of the club face  114 . 
         [0052]      FIG. 8  shows a sectional view of an alternative embodiment of a golf club head  200  of the type illustrated and described in  FIGS. 1 to 7 . In this embodiment the thickness and weight of the striking face  214 , top crown  202  and bottom sole  204  are essentially the same as the above described embodiments. This embodiment does not use a rear weight at the rear surface  210  and directly behind the striking face  214 . This, in turn, locates the CG slightly closer to the face  214  at 42 mm behind the striking face  214 , approximately 2 mm closer to the face  214  than the first embodiment described hereinabove. In this embodiment the top crown is 0.45 mm to 0.5 mm but may be up to 0.75 mm. The skirt, not shown, is approximately 0.75 or greater and is thicker than the crown. The bottom sole is 0.85 mm or thicker and is thicker than the crown and skirt.