Abstract:
A golf club head having a dual wall internally pressurized face plate and an apparatus for varying the pressurization thereof.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     This invention relates generally to a metal “wood” golf club heads and iron golf club heads, and more particularly, to a golf club head having a dual wall internally pressurized face plate and an optional method and apparatus for varying the pressurization thereof.  
         [0003]     2. Description of the Related Art  
         [0004]     Golf club manufacturers have fabricated multiple designs for golf clubs all with the goal of improving a golfer&#39;s performance. Different materials including metals for the “woods” have been used to increase ball flight distance and improve the feel of the club. Various weighting schemes, including perimeter weighting, have been proposed to optimize the center of gravity and moment of inertia of club heads. Oversized club heads have been utilized to attempt to provide a large sweet spot on the ball striking face. However, the weight of golf clubs that can be used in professional or PGA sanctioned events is strictly controlled by golf associations. Accordingly, particularly for the oversized club heads, weight or metal thickness in or around the faceplate may be sacrificed to allow adequate thickness throughout the entirety of the oversized head.  
         [0005]     Perhaps the most important factor in hitting a golf ball well is the location of impact of the ball on the striking surface or the faceplate. A ball which is hit in the center or the sweet spot of the faceplate will generally go farther and straighter than a ball impacting near the heel or toe or above or below the sweet spot of the faceplate. For this reason, the weight or mass distribution in or at the periphery of the faceplate becomes increasingly significant for hitting golf balls at a location moving away from the sweet spot to try to compensate for an off center hit. Thus, club designers seek to maximize efficiency of both on target strikes within the sweet spot and off target strikes outside of the sweet spot in the design of golf club heads.  
         [0006]     Another important factor in hitting a golf ball well is the coefficient of restitution (“COR”) of the striking surface of the faceplate of the golf club. Increasing the COR will increase the force imparted to the golf ball and thus the distance the ball will travel for a given club head speed. However, a high COR may also cause a ball that is hit of center of the sweet spot to travel off line further than it would for a lower COR club head. Accordingly, while expert or professional players may be able to utilize and take advantage of high COR club heads on a more consistent basis, average players may only realize the benefit of a high COR club head infrequently, when they hit the ball in the sweet spot, and the remainder of the time a high COR club head may be detrimental.  
         [0007]     A club head that combines a high COR or a variable COR, with better off-sweet spot control, would be beneficial to both professional and average golfers.  
       BRIEF SUMMARY OF THE INVENTION  
       [0008]     The present invention provides a golf club faceplate having a double wall defining there between a chamber that can be internally pressurized, during manufacture or with the use of a pump, to vary the COR of the golf club. The double wall faceplate, sole plate and hozel, and potentially the toe, heel, top and rear wall, are preferably formed from metal such as an iron alloy or titanium.  
         [0009]     A valve either at the edge of the double wall faceplate or extending through the back wall thereof allows for the introduction of pressurized air or gas into the cavity between the strike wall and back wall of the double wall faceplate. By pressurizing the cavity between the strike wall and back wall of the double wall faceplate, the COR of the club can be adjusted to a players specification.  
         [0010]     The above described and many other features and attendant advantages of the present invention will become apparent from a consideration of the following detailed description in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     A detailed description of the invention will be made with reference to the accompanying drawings wherein:  
         [0012]      FIG. 1  is a side perspective partial cross sectional view of a golf club head having the double wall faceplate of the present invention;  
         [0013]      FIG. 2  is a side perspective cross sectional view through the double wall faceplate of the golf club of the present invention illustrating the deflection occurring for an on-center hit;  
         [0014]      FIG. 3  is a side perspective cross sectional view through the double wall faceplate of the golf club of the present invention illustrating the deflection occurring for an off-center hit;  
         [0015]      FIG. 4  is a top perspective partially-cross section view of an alternative embodiment of the golf club head of  FIG. 1 ; and  
         [0016]      FIG. 5  is partial view of another alternative embodiment of the golf club head according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0017]      FIGS. 1-5  show various views and embodiments of a double wall faceplate for a golf club head  10  in accordance with the present invention. The golf club head  10  is depicted as a metal wood, although the concept is also applicable to the design of irons.  
         [0018]      FIG. 1  depicts a side-cross section from front to back through the golf club head  10 . The golf club head  10  includes a strike wall  12  and a back wall  14 , defining there between a cavity  16 . The golf club head  10  also includes a top  18  and a sole plate  20 . The sole plate  20  may include a rear portion  22 . The strike wall  12 , back wall  14  and sole plate  20  are preferably formed from metal. The top  18  may be formed from metal or it may be formed from a plastic, graphite or composite material, as discussed for example in pending U.S. application Ser. No. 10/766,220, filed Jan. 28, 2004, herein incorporated by reference.  
         [0019]     The strike wall  12  and back wall  14  may be formed to an equal thickness, however, it is preferred that the back wall  14  be thicker and thereby less flexible than the front wall  12 . The thicknesses of the strike wall  12  and back wall  14  are preferably in the range of between 0.1 mm to 6.0 mm. The thicknesses may be either constant from the top to bottom and heel to toe, or the thickness may vary. Similarly, the cross-sectional dimensions of the cavity  16  may be constant or may vary from the top to bottom and/or from the heel to the toe. Generally, the cross-sectional dimensions of the cavity are in the range of 0.1 mm to 6.0 mm.  
         [0020]     The club head  10  as shown in the cross-sectional view of  FIG. 1  has a strike wall  12  and a back wall  14  with uniform thicknesses in the range of 1.5 mm to 3 mm. Further, the cavity  16  has an approximately uniform cross-sectional dimension in the range of 1.5 mm to 3 mm. With this construction, the front face  12  may be deflected toward the back wall  14  up to the full dimension of the cavity  16  before the back wall  14  provides direct physical reinforcement to the strike wall  12 . The dimensions of the strike wall  12  and cavity  16  may be selected so that the strike wall  12  will not deflect all of the way back toward the back wall  14  for a normal range of use irrespective of the pressurization of the cavity  16 .  
         [0021]      FIGS. 2 and 3  are partial cross-sectional views similar to  FIG. 1  showing the deflection of the strike wall  12  during impact with a golf ball  30 .  FIG. 2  illustrates the deflection when the golf ball  30  is struck in the sweet spot near the center of the strike wall  12 . For this circumstance, the deflection of the strike wall is rearward at the location of contact with the golf ball  30 . However, when the cavity  16  is pressurized and the back wall  14  has a sufficient structural rigidity to resist deflection, the internal pressurization of the cavity  16  may cause the periphery of the strike wall to deflect outward on impact with the golf ball  30 . As the golf club  10  and golf ball  30  advance following the initial impact, the strike wall  12  will spring back from the initial deflection and impart the energy absorbed by the deflection to the golf ball  30 . The golf ball  30  is depicted as oblong during the impact as it will also go through a deformation and restoration cycle upon being stuck by the golf club  10 .  
         [0022]      FIG. 3  depicts the deflection of the strike wall  12  during impact with a golf ball  30  for an off-sweet spot hit. In  FIG. 3 , the point of impact is above the sweet spot of the strike wall  12 . Due to the increased structural resistance to deflection close to the periphery of the strike wall  12 , and because of the contoured surface curving back close to the periphery, there is less deflection inward or near the top of the strike walls  12  close to the periphery then there is on the lower side of the strike wall  12  below the golf ball  30 . This differential has a tendency to compensate for the off-center strike of the golf ball  30 , imparting a corrected trajectory as if the ball had been struck in the sweet spot. This compensation extends the dimension of the sweet spot towards the periphery of the strike wall  12 . A similar effect occurs for hits moving toward the toe or heel of the strike wall  12 .  
         [0023]     While the cavity  16  is formed during the process of securing, for example by welding, the strike wall  12  and the back wall  14 . During the process, the cavity  16  may be sealed at atmospheric pressure, under a partial vacuum or under pressure. Sealing cavity  16  under a partial vacuum will tend to make the deflection of the strike wall  12  more pronounced and reduce the coefficient of restitution of the golf club. By comparison, sealing the cavity under pressure will reduce the deflection of the strike wall  12  and increase the coefficient of restitution for the golf club.  
         [0024]     Moreover, the present invention contemplates the incorporation of a valve into the golf club head  10  that allows the user to selectively pressurize the space within cavity  16 . As shown in  FIG. 4 , a value  40  is incorporated into the toe  22  of the golf club head  10  traversing through the strike wall  12 . The valve is configured to allow attachment to a pump  42 , or pressurized cartridge  44 , that can be used to pressurize the cavity  16 . Preferably, the cavity  16  is pressurized with a compressible gas or air. However, cavity  16  could be filed with an incompressible fluid.  
         [0025]      FIG. 5  depicts an alternative configuration for the invention wherein a valve  50  is incorporated into heel  22  side of the club head  10  (for a right handed club), and is joined to the back wall  14  at the intersection with the bottom of the hozel  46 . This configuration allows for the pressure to be introduced through the shaft of the golf club, or for a pump to be built into the shaft of the golf club.  
         [0026]     The valve  40  of  FIGS. 4 and 5  is preferably a one-way valve allowing air or other fluid media to be pumped into cavity  16 . However, the valve  40  may also be configured to allow for a release of pressure from cavity  16  if desired.  
         [0027]     The club head  10  may incorporate a composite cover, designed so as to fit snugly over and conform to the top plate  18 , and the toe  22  and heel  24  portion of the sole plate  20 . The composite cover is bonded to the metallic portion  12  using an appropriate bonding material, such as a glue, epoxy or solvent based adherent.  
         [0028]     The hozel  46  is positioned in the hollow interior of the golf club head at the joint between the heel  24  of the sole plate  20  and the back wall  14  and is formed and placed in the club head  10  to receive a golf club shaft. The hozel  16  is preferably aligned with or offset from the center of gravity of the club head  10 . The club head  10  depicted is for a right handed user, while a club head for a left handed user would have a mirror image construction.  
         [0029]     The materials used to form the metal portion  12  of the club head  10  include steel, stainless steel, titanium, and other metallic materials having similar or enhanced strength and resilience properties, however titanium is preferred.  
         [0030]     Having thus described different embodiments of the invention, other variations and embodiments that do not depart from the spirit of the invention will become readily apparent to those skilled in the art. The scope of the present invention is thus not limited to any one particular embodiment, but is instead set forth in the appended claims and the legal equivalents thereof.