Abstract:
A golf club head having a defined internal cavity, and a golf club head containing a bi-material weight having a nonhomogeneous structure is disclosed herein. A method to add the bi-material weight to the golf club entails heating, vibration and cooling to produce the nonhomogeneous structure is also disclosed herein.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This patent application is a continuation-in-part application of U.S. patent application Ser. No. 09/752,398, filed on Dec. 29, 2000, now U.S. Pat. No. 6,379,263, which is a continuation application of U.S. patent application Ser. No. 09/330,292, filed on Jun. 12, 1999, now U.S. Pat. No. 6,210,290. 
    
    
     FEDERAL RESEARCH STATEMENT 
     [Federal Research Statement Paragraph] 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to golf clubs and, more specifically golf club heads with additional weighting to provide better performance, greater weighting flexibility and lower production costs. 
     2. Description of the Related Art 
     The location and distribution of weight within a golf club is an important factor in the performance of the golf club. In particular, weight placement at the bottom of the golf club head provides a low center of gravity to help propel a golf ball into the air during impact, and weight concentrated at the toe and heel of the golf club head provides a resistance to twisting, or high moment of inertia, during golf ball impact. Both the low center of gravity and high moment of inertia are important performance variables which affect playability and feel of the golf club. Alternative designs have resulted in many innovations for varying the weight location and distribution in a golf club head portion. Among these designs is a combination of high and low density materials within the golf club head, and associated methods for combining these materials. 
     One example of multiple materials used in the construction of the golf club head is a high density material attached to a lower density material golf club head. A high density block or contoured shape is attached, via mechanical means such as friction fit, fasteners or screws, to a reciprocal recess in the golf club head, as shown in U.S. Pat. No. 5,776,010, issued to Helmstetter et al. Although supplying the desired performance enhancements, the high density block and the reciprocal recess must be machined to precise tolerances, involving high production costs. 
     Another example of weighting the golf club is pouring a high density fluid into a reservoir within the golf club. This ensures an exact placement of the weighting material within the golf club, as the fluid will conform to the internal shape of the reservoir without the need for mechanical or an adhesive bonding. One drawback of this type of processing is the requirement that one must operate below the melt or softening temperature of the club head material. In addition, as processing temperatures increase the associated costs will increase to accommodate higher energy use and high temperature equipment. The limitations for a low melt temperature, yet high density, material restricts the available options for this type of process. 
     To overcome the limitations associated with a single material, the advent of multi-component weighting systems makes use of the high density materials in combination with a carrier fluid, such as a polymer. A particulate form of the high density material is mixed with the carrier fluid and poured into the reservoir in the golf club, wherein the carrier fluid is allowed to solidify to form a composite weighting material. Readily available materials include a thermoset polymer carrier fluid, such as epoxy, which allows ambient temperature processing and solidification of the high density material and epoxy mixture. A thermoplastic polymer carrier fluid, such as polypropylene, requires heat to obtain a fluid state and cools to a solid at ambient temperatures, with the capability to be re-heated to the fluid state, in distinction to the epoxy. A disadvantage of the multi-component weighting system is the low density associated with the carrier fluid, typically 1 g/cm 3 , thus requiring a high ratio of the weighting material to the carrier fluid to obtain the desired high density for a bi-material weight. The carrier fluid also acts as a binder for the weighting material to ensure the bi-material weight forms a solid block. 
     A drawback to the multi-component weighting system is the need to use small amounts of carrier fluid relative to the weighting material, leading to entrapped air or voids and incomplete binding in the bi-material weight. Incorporating larger amounts of the carrier fluid promotes better mixing within the bi-material weight in conjunction with an attendant decrease in density. Therefore, it is desirable to provide a bi-material weight containing a higher density carrier fluid to provide greater weighting flexibility for allocating weight within a golf club head in conjunction with lower cost production. It is further desirable to provide a golf club head to accommodate the bi-material weight and enable a variable location of the bi-material weight. 
     SUMMARY OF THE INVENTION 
     The present invention further increases the playability of irons for all types of golfers by lowering the center of gravity of the golf club head while creating a forgiving hitting area. The present invention is able to accomplish this by use of a front wall that has variable thickness and a weighting means that lowers the center of gravity of the golf club head. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     FIG. 1 is a rear view of a golf club head of the present invention. 
     FIG. 1A is rear view of a golf club head of the present invention with a medallion. 
     FIG. 1B is a rear view of an alternative embodiment of the golf club head of the present invention. 
     FIG. 2 is a front perspective view of the golf club head of the present invention. 
     FIG. 3 is a rear perspective view of the golf club head of the present invention. 
     FIG. 4 is a front view of the golf club head of the present invention. 
     FIG. 5 is a top view of the golf club head of the present invention. 
     FIG. 6 is a bottom view of the golf club head of the present invention. 
     FIG. 7 is a toe view of the golf club head of the present invention. 
     FIG. 8 is a heel view of the golf club head of the present invention. 
     FIG. 9 is a cut-away view along line  9 — 9  of FIG.  4 . 
     FIG. 10 is a cut-away view along line  10 — 10  of FIG.  4 . 
     FIG. 11 is a front view of the golf club head of the present invention with the front wall partitioned into quadrants to demonstrate the variable face thickness aspect of the present invention. 
     FIG. 12 is a cut-away view of the golf club head and the first weight material of an embodiment of the present invention. 
     FIG. 13 is a top perspective view of the golf club head within a fixture of an embodiment of the present invention. 
     FIG. 14 is a heel view of the golf club head during addition of the second weight material of an embodiment of the present invention. 
     FIG. 15 is a top perspective view for clamping the golf club head of an embodiment of the present invention. 
     FIG. 16 is a cut-away view of the golf club head containing the bi-material weight of an embodiment of the present invention. 
     FIG. 17 is a table of the mass without weighting, the volume of the internal cavity and the mass with weighting for golf club heads of a preferred embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION 
     As shown in FIGS. 1-8 a golf club of the present invention is generally designated  20 . The golf club has a golf club head  22  and a shaft  24 . The shaft  24  is attached to a hosel  26  of the golf club head  22 . The hosel  26  has a bore  28  with an ingress opening  30  and optionally an egress opening  32 . A tip end  34  of the shaft  24  is inserted into the bore  28 . In a preferred embodiment the golf club head  22  is composed of a titanium alloy, however, those skilled in the relevant art will recognize that other materials such as stainless steel, carbon steel, and the like may be utilized without departing from the scope and spirit of the present invention. 
     The golf club head  22  has a front wall  40  with a face surface  42  and a rear surface  44 . The face surface  42  preferably has a plurality of scorelines  43  thereon, and face surface  42  contacts a golf ball during a golfer&#39;s swing. In a preferred embodiment, the top of the hosel  26  is lower than the toe end of the front wall  40  allowing for more weight to be redistributed from the hosel  26  thereby lowering the center of gravity of the golf club head  22 . The golf club head also has a top wall  46 , a bottom wall  48 , a heel wall  50  and a toe wall  52 . The top wall  46  extends rearward from a top end  54  of the front wall  40 , in a direction opposite the face surface  42 . The bottom wall  48  extends rearward from a bottom end  56  of the front wall  40 , in a direction opposite the face surface  42 . The heel wall  50  extends rearward from a heel end  58  of the front wall  40 , in a direction opposite the face surface  42 . The toe wall  52  extends rearward from a toe end  60  of the front wall  40 , in a direction opposite the face surface  42 . The rear surface  44 , the top wall  46 , the bottom wall  48 , the heel wall  50  and the toe wall  52  define an external rear cavity  62  of the golf club head  22 . The top wall  46 , the bottom wall  48 , the heel wall  50  and the toe wall  52  also provide the golf club head  22  with perimeter weighting to make the golf club  20  more forgiving for better performance for the typical golfer. 
     An aft wall  64  extends upward from an aft end  66  of the bottom wall  48  to partially cover the external rear cavity  62 . The aft wall  64  has an apex  67  near its center and gradually declines in height toward the heel wall  50  and the toe wall  52 . In a preferred embodiment, the aft wall  64  has a pseudo-triangular shape. 
     An internal cavity  70  of the golf club head  22  is accessed through an opening  72  in the aft wall  64 . The opening  72  is defined by a recess  76  in the aft wall  64  into which a plate  74  is optionally placed over the opening  72 . A medallion  78  is preferably placed within the recess  76  for swing weighting purposes, as shown in FIG.  1 A. Alternatively, the opening  72  is covered with a plate  74  and polished over as illustrated in FIG.  1 B. The internal cavity  70  is defined by the aft wall  64 , a ceiling wall  68 , a portion of the bottom wall  48 , a portion of the front wall  40 , a portion of the heel wall  50  and a portion of the toe wall  52 . The internal cavity  70  preferably has a main chamber  70   a  that extends from the heel wall  50  to the toe wall  52  and a minor chamber that is within the aft wall  64 . The main chamber  70   a  and the minor chamber  70   b  are in flow communication with each other. 
     The internal cavity  70  preferably has a volume from 5 cm &#39; to 25 cm 3 , and in a most preferred embodiment from 9 cm 3  to 15 cm 3 . The length and volume of the internal cavity allow for flexibility in the placement of a weighting member  80  therein to control the location of the center of gravity in order to improve the feel during impact of the golf club head  22  with a golf ball. 
     In a preferred embodiment, a medallion recess area  82  is disposed on the rear surface  44  of the front wall  40 . A medallion  84  is preferably disposed within the recess area  82 , and more preferably a holographic medallion  84  is disposed within the recess area  82 . 
     In a preferred embodiment, the golf club head  22  has an undercut recess  90  in communication with the external rear cavity  62 . In a preferred embodiment, a bottom wall undercut recess  90   a  is within the bottom wall  48 , a top wall undercut recess  90   b  is within the top wall  46 , a heel wall undercut recess  90   c  is within the heel wall  50  and a toe wall undercut recess  90   d  is within the toe wall  52 . Alternatively, the golf club head  22  has only one of one the undercut recess  90   a ,  90   b ,  90   c  and  90   d . In yet another alternative embodiment, the golf club head  22  has only two of the undercut recesses  90   a ,  90   b ,  90   c  and  90   d . In still yet another alternative embodiment, the golf club head  22  has only three of the undercut recesses  90   a ,  90   b ,  90   c  and  90   d . Such an undercut recess  90  is disclosed in greater detail in U.S. Pat. No. 5,409,229, for a Golf Head With Audible Vibration Attenuation, which is hereby incorporated by reference in its entirety. 
     In a preferred embodiment, the front wall  40  has a variable thickness that ranges from 0.060 inch to 1.90 inch. The variable thickness allows for less weight in the front wall allowing for the center of gravity to be lowered in the golf club head  22  through use of the weighting member  80 . As shown in FIG. 11, the front wall  40  is partitioned into an upper toe quadrant  100 , a lower toe quadrant  102 , a lower heel quadrant  104  and an upper heel quadrant  106 . The upper toe quadrant  100  is the thinnest quadrant of the front wall  40  preferably ranging in thickness from 0.060 inch to 0.105 inch. The upper heel quadrant  106  is the thickest preferably ranging from 0.120 inch to 0.190 inch. In a preferred embodiment, point  111  has a thickness ranging from 0.060 inch to 0.105 inch, more preferably ranging from 0.068 inch to 0.098 inch, even more preferably ranging from 0.070 inch to 0.082 inch, and is most preferably 0.073 inch. In a preferred embodiment, point  113  has a thickness ranging from 0.070 inch to 0.125 inch, more preferably ranging from 0.075 inch to 0.120 inch, even more preferably ranging from 0.083 inch to 0.095 inch, and is most preferably 0.089 inch. In a preferred embodiment, point  115  has a thickness ranging from 0.100 inch to 0.170 inch, more preferably ranging from 0.125 inch to 0.165 inch, and is most preferably 0.138 inch. In a preferred embodiment, point  117  has a thickness ranging from 0.125 inch to 0.200 inch, more preferably ranging from 0.150 inch to 0.190 inch, and is most preferably 0.169 inch. A more detailed description of the variable face thickness is disclosed in U.S. Pat. No. 5,971,868, for a Contoured Back Surface Of Golf Club Face, which is hereby incorporated by reference in its entirety. 
     A preferred method for adding weight material to the golf club head  22  involves a bi-material weighting operation. FIG. 12 is a cut-away view of the golf club head  22  of a method embodiment of the present invention. The golf club head  22  is weighed and a predetermined, or specific, weight of a first weight material  86  is added to the internal cavity  70 . In a preferred embodiment the first weight material  86  occupies 10% to 40% of the internal cavity  70 . In a more preferred embodiment the first weight material  86  is a metal material that exhibits a high density, good compatibility with structural metals such as titanium and steel, high environmental stability and good commercial availability. Available choices for the first weight material  86  are copper metals, brass metals, steel and tungsten metals. In a preferred embodiment the density of the first weight material  86  is greater than 12 g/cm 3 , more preferred is between 12 g/cm 3  and 20 g/cm 3 . In a most preferred embodiment, the first weight material  86  comprises tungsten alloy spheres, with approximately 18 g/cm 3  density and having a diameter greater than 3 mm, dispensed into the internal cavity  70  of the golf club head  22 . The requirement for a diameter in excess of 3 mm is to provide an effective fluid path between the spheres and ensure a fully dense weight block. 
     In manufacturing the golf club head  22 , the golf club head  22  and the first weight material  86  are raised to a temperature sufficient to maintain a second weight material  88  (as shown in FIG. 14) in a fluid or liquid phase. In a preferred embodiment, a continuous oven is used to raise the temperature of the golf club head  22  and the first weight material  86  to at least 350° F. Although several heating methods are available, in a preferred operation, the golf club head  22 , containing tungsten alloy spheres as the first weight material  86 , is placed upon a heated conveyor moving at 5.5 inches/minute through a 24 inch heat zone. 
     After exiting the heating operation the golf club head  22  containing the tungsten alloy spheres is secured in a fixture  156 , as shown in FIG.  13 . The second weight material  88  is dispensed into the internal cavity  70  of the golf club head  22 , as shown in FIG.  14 . In a preferred embodiment the density of the second weight material  88  is less than 14 g/cm 3 , more preferred is between 6 g/cm 3  and 10 g/cm 3 . In a most preferred embodiment, the second weight material  88  is a bismuth-tin solder, with approximately 8.6 g/cm 3  density, heated to a liquid phase of at least 350° F. The weighting method may include any number of combinations associated with heating the golf club head  22  and the first and second weight materials  86  and  88  to form a finished product. Attached to the fixture  156  is a scale  158  to measure the total weight of the golf club head  22  during addition of the second weight material  88 . In a preferred embodiment, the scale  158  is used throughout the weighting method to ensure that the proper amount of the first and the second weight material  86  and  88  have been added to the golf club head  22 . 
     The golf club head  22  is forced against the fixture  156  and a mounting pad  164  via a clamp  162 , as shown in FIG.  15 . The mounting pad  164  is used to tilt the golf club head  22  to any desired orientation allowing the first weight material  86  to migrate to the lowest point in the internal cavity  70  under the influence of vibrational energy. Vibrational energy treatment of the golf club  22  and a bi-material weight  80  (as shown in FIG. 16) may be accomplished by a mechanical device, ultrasound, radiation, or any other means of imparting vibrational energy. In a preferred embodiment, a mechanical vibration device supplies a small amplitude vibration to the golf club head  22 . The timing for starting and stopping the vibration is an important factor in obtaining the benefits of the present invention. The second weight material  88  should be in a liquid phase while exposed to vibration energy to prevent the first weight material  86  from creating voids or migrating out of the second weight material  88 . In a preferred embodiment, the vibrational energy is sustained for approximately twenty seconds. Following termination of the vibrational treatment, the golf club head  22  is cooled to allow the second weight material  88  to solidify. Cooling of the bi-material weight  80  may be accomplished by refrigeration, immersion in a cold fluid such as water, or simply allowing the golf club head  22  to cool naturally to ambient temperature. In a preferred embodiment, an air nozzle  168  supplies cooling air to the golf club head  22 . 
     FIG. 16 shows the golf club head  22  containing the bi-material weight  80  comprising the first weight material  86  and the second weight material  88 . The golf club head  22  may have a range of initial weights reflecting variability in manufacturing the golf club head  22 . In FIG. 17, preferred specifications for irons  1 - 9  along with pitching wedge, approach wedge, sand wedge and lob wedge for the golf club head  22  of the present invention are listed with the mass of the golf club head  22  (in grams) without weighting in column  2 , the volume of the internal cavity  70  (in cubic centimeters) in column  3 , and the golf club head  22  with the weighting (in grams) in column  4 . 
     It is understood that various modifications can be made to the golf club head  22  and method of weighting, both outlined above, and remain within the scope of the present invention. For example, the golf club head  22  can be a wood-type golf club, a putter or an iron-type golf club, and can be made from various materials including metals and non-metals.