Patent Publication Number: US-6339869-B1

Title: Method of making a golf club head

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional of U.S. patent application Ser. No. 08/963,089, filed Nov. 3, 1997, now U.S. Pat. No. 6,162,133. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates in general to golf clubs, and more particularly to a golf club head. 
     BACKGROUND 
     Golf clubs are typically divided into three main classes—the putters, irons and woods. The woods are generally used to hit the golf ball a long distance and the woods are traditionally constructed from wood, such as persimmon. Today, however, many woods are constructed from metal, which are generally referred to as metal woods. Metal woods allow the weight of the club head to be balanced and weight distributed around the periphery of the club head, which allows the location and size of the sweet spot of the club head to be adjusted. 
     A conventional metal wood is shown in U.S. Pat. No. 4,432,549 issued to Zebelean which discloses a metal driver that is cast in two parts. The first part or body includes a face plate, top crown, and sides which surround a large opening; and the second part includes a sole plate or bottom surface which is configured to fit into the large opening in the first part of the club head. After casting, the sole plate is welded to the body to form the golf club head of the metal driver. This golf club head, however, is unsatisfactory because it includes two components that must be welded together, which involves a significant amount of time and increases cost of the club head. Additionally, the lie, loft and face angle of the club head often undesirably changes because the independently formed components do not always mate in an identical manner, and the sole plate is not always welded to the body at the same angle. Thus, significant resources must be used to test and eliminate defects that occur because the sole plate and the body are not always joined at the same manner, which further increases the complexity of the manufacturing process. 
     Conventional metal woods which require welding the sole plate to the body are unsatisfactory because not all welds are identical. For example, differences in penetration and sealing of a weld affect the strength and structural integrity of the club head, which changes the characteristics of the club head. Welding also undesirably increases the weight and the thickness of the club head, and the differently sized welds cause an unequal weight distribution in a club head. This added weight is disadvantageous because a lightweight club head is important, and the weight is desirably positioned only in specific locations. Additionally, welding not only introduces variables during the manufacture of a single club head, it also causes variation between different club heads. Further, pieces of the weld inside the club head may break off during play. These pieces, which are located inside the sealed club head, rattle every time the club is used. The annoying rattle requires additional time, effort, money and materials to correct. 
     Conventional club heads are finished with a large degree of care to create the desired appearance and esthetics. For example, golf club heads are often subjected to the expensive and time consuming steps of grinding, sanding, sand blasting, polishing, tumbling and painting to finish the club head. Conventional club heads require that these steps be completed after the components are welded together because the high temperature welding will destroy or mar a finished club head. Disadvantageously, it is difficult to modify or customize the club head after it is welded together. For example, the Zebelean patent discloses filling the hollow club head with a hardening material, such as polyurethane. The Zebelean patent explains that, after the sole plate is welded to the body and the club head is finished, an opening is drilled through the center of the sole of the club head to insert the hardening material. Various types of plugging screws are used to close the opening. This golf club head is unsatisfactory because drilling the opening, filling the club head with the hardening material and sealing the opening often damages or mars the polished surface of the club head. Further, the plugging screw alters the weight and balance of the club head. 
     Another conventional golf club head is shown in U.S. Pat. No. 4,021,047 issued to Mader which discloses a two piece metal club head held together by mechanical fasteners. The Mader patent discloses a sole plate, face plate and hosel which are cast out of a unitary piece of metal. A wood or plastic cap fits along the top of the face plate and extends to the rear surface of the club head to form a crown and rear capping piece. The cap is attached by two screws which extend through the sole plate and hollow cavity of the club head. This golf club head, however, is unsatisfactory because the mechanical fasteners tended to loosen during play, add unnecessary weight to the club head and the weight is added to the club head in undesired locations. 
     Another conventional golf club head is shown in U.S. Pat. No. 5,292,129 issued to Long, et al. The Long patent discloses a metal golf club head which is reinforced by three ribs which extend between the internal surface of the striking face and the internal surface of the top side to reinforce both the striking face and the top side. This golf club head is unsatisfactory because the sole plate must be welded to the body of the golf club, and the reinforcement ribs are not interconnected to the sole plate. Disadvantageously, this allows sole plate to deform and buckle when striking a golf ball. 
     Therefore, there is a need for a golf club head without these significant disadvantages. In addition, there is a need for an improved golf club head which does not require welding or mechanical fasteners to attach the top crown or sole plate to the face plate. 
     SUMMARY OF THE INVENTION 
     One aspect of the invention is a golf club head with a unitary, one-piece body including a face plate, top crown and sole plate. Advantageously, the face plate, sole plate and top crown of the golf club are always correctly positioned in the desired configuration, and this eliminates variations in lie, loft and face angle. Significantly, the golf club head of the present invention does not require welding or other types of fasteners to attach the sole plate or top crown to the face plate. Because welding or mechanical fasteners are not required, the manufacturing process is simplified and more of the weight of the golf club can be distributed in the desired locations. 
     Another aspect is a golf club head with a reinforcement structure which strengthens the face plate of the golf club head. Preferably, the reinforcement structure includes one or more ribs which are integrally formed with the top crown, face plate and sole plate of the club head. Advantageously, the reinforcement structure strengthens the top crown, face plate and sole plate of the club head. Thus, the club head does not significantly deform when the face plate strikes the golf ball. In addition, the reinforced club head provides increased elasticity or rebound to the club face, which results in more energy transferred to the golf ball so that the ball can travel a greater distance. 
     In one embodiment of the invention, the golf club head includes a unitary, one-piece body having a top crown, a face plate, a sole plate and a side skirt. The side skirt includes an opening which provides access to an interior portion of said one-piece body, and a cap is configured to cover the opening in the side skirt. 
     In another embodiment of the invention, the golf club head includes a face plate and a sole plate which are integrally connected to form a single unit. The club head also includes a top crown connected to the face plate, and a side skirt is connected to the top crown, face plate and sole plate. The face plate, sole plate, top crown and side skirt form a generally hollow body. 
     In a further embodiment of the invention, a method of making a golf club head includes forming a unitary one-piece body including a face plate, a top crown, a sole plate, a side skirt, and an opening in said side skirt; forming a side skirt cap configured to cover the opening in the side skirt; and attaching the side skirt cap to the body. Preferably, the one-piece body further includes a reinforcement structure which reinforces the face plate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features of the present invention will now be described with reference to the drawings of preferred embodiments, which are intended to illustrate and not to limit the invention, in which: 
     FIG. 1 is a perspective front view of a golf club head in accordance with an embodiment the present invention; 
     FIG. 2 is an exploded perspective back view of the golf club head shown in FIG. 1, illustrating the cap removed from the skirt; 
     FIG. 3 is a cross-sectional side view along lines  3 — 3  of the golf club head shown in FIG. 2; 
     FIG. 4 is a bottom plan view of the golf club head shown in FIG. 1 with a portion of the top crown cut away, illustrating the reinforcement structure; and 
     FIG. 5 is the bottom plan view of the golf club shown in FIG. 4, illustrating reinforcing material on the inner surface of the face plate. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in FIG. 1, the golf club head  10  includes a face plate  12  which is adapted to strike a golf ball. The face plate  12  includes a plurality of grooves  14  which preferably extend the majority of the length of the face plate, and the grooves  14  may be generally U-shaped or V-shaped in configuration. The grooves  14  preferably conform to the United States Golf Association (“USGA”) rules, but any grooves or no grooves may also be used. The club head  10  also includes a top crown  16 , a hosel or neck  18  which is configured to receive a shaft  20  (shown in phantom), and a sole plate  22 . The hosel  18  includes an opening  19  and the upper portion of the hosel preferably extends between about ¼ inch (0.6 cm) and 1 inch (2.5 cm), and more preferably about ½ inch (1.2 cm), above the upper surface of the top crown  16 . Alternatively, the club head  10  may include a longer or shorter hosel  18 , or no hosel. Preferably, the opening  19  in the hosel  18  extends through the club head  10  and sole plate  22 , and the shaft  20  is inserted through the opening and finished flush with the bottom surface of the sole plate  22 . The hosel  18  may also be a blind hosel in which the opening  19  extends through only a portion of the club head  10  and not through the sole plate  22 . 
     The golf club head  10  shown in the accompanying figures and described below is a driver or one wood, but the club head may also be any other type of wood. In addition, the golf club  10  shown in the accompanying figures and described below is an “over-sized” golf club which is larger in size than a traditional golf club, but the club head may also be, for example, a “mid-sized” or “regular-sized” club head. Furthers the club head  10  may be connected to any type of desired shaft  20 , such as steel, graphite, titanium, or composite materials, and the shaft may be any desired size and length. 
     As best seen in FIGS. 1 and 2, the golf club head  10  includes a heel  24  proximate the hosel  18  and a toe  26  distal the hosel  18 , and side skirt  30  which extends around the golf club head  10 . The skirt  30  is connected to the sole plate  22 , top crown  16  and face plate  12  to form the body  32  of the club head  10 . The side skirt  30  also includes an opening  34 , and a cap  36  is configured to cover the opening  34 . These different parts combine to form the exterior surfaces of the club head  10 , and because the club head  10  is substantially hollow, each of these parts has a corresponding inner surface. 
     The face plate  12  and the top crown  16  or sole plate  22  are preferably formed as a unitary, one-piece component; and more preferably, the face plate  12 , top crown  16 , sole plate  22  and side skirt  30  are formed as a unitary, one-piece component. Because the face plate  12  and the sole plate  22  are formed as part of the one-piece body  32 , the face plate and sole plate are always correctly positioned at the desired configuration and angle. Advantageously, because there is little or no variation between the angle of the face plate  12  and sole plate  22 , each club head  10  will have essentially the same loft, lie and face angle. 
     Additionally, the one-piece body  32  greatly simplifies the manufacturing process because the sole plate  22  does not have to be welded to the face plate  12 —this saves time and resources, and reduces the weight of the golf club. Reducing the weight of the club head  10  typically allows a higher club head speed, which results in more power and energy being transferred to the golf ball. Alternatively, instead of reducing the weight of the club head, the weight saved by the one-piece body can be used, for example, to make a larger sized club head and/or the weight can be redistributed within the club head. For example, the weight may be redistributed to change the center of gravity, additional weight may be positioned directly behind the club face, or additional weight may be distributed around the perimeter of the club head. 
     The club head  10  is preferably fabricated as a unitary, one-piece body  32  by casting, such as investment, die or lost wax casting; but the club head may also be forged, molded, pressed, or constructed by any other known means such as dynamic compaction or isostatic compaction. The one-piece body  32  is preferably constructed from a titanium alloy, such as titanium 6A1-4V, but any metal or metal alloy such as stainless steel or aluminum may also be used. Additionally, any composite or amorphous materials may be used to construct the body  32 . Further, all or a portion of the body  32  may also be constructed from plastic or composite materials; and the face plate  12  may include an insert, such as graphite or other materials, on the front face designed to impact the golf ball. 
     The face plate  12  of the golf club head  10  preferably has a thickness in the range of about 0.06 inches (1.5 mm) to about 0.12 inches (3 mm), and more preferably about 0.08 inches (2 mm). The top crown  16  has a thickness of about 0.04 inches (1 mm), the sole plate  22  has a thickness of about 0.04 inches (1 mm), and the skirt  30  has a thickness of about 0.04 inches (1 mm). Of course, the thickness of either or all of these surfaces may also be larger or smaller depending, for example, upon the desired strength and configuration of the club head  10 , or the materials used to construct the club head. The thickness may also be nonuniform and the thickness may vary to distribute the weight in the desired locations of the club head. 
     The face plate  12  desirably has a width of about 3.5 inches (88 mm) and a height of about 2.4 inches (60 mm), and the sole plate  22  desirably has a length of about 3.6 inches (91 cm). The overall volume of the club head  10  is preferably between about 15 cubic inches (250 cc) and about 18 cubic inches (300 cc). It will be understood the dimensions of the club head  10  may vary, for example, according to the type of club head and whether the club head is over-sized, mid-sized or regular-sized. The face plate  12  and the sole plate  22  are preferably constructed with a lie between about 55□ and about 59□, and more preferably about 58□; and the soled or rest loft of the golf club is preferably between about 5□ and about 13□. The face angle of the club head is preferably between about −1□ and about +3□, wherein the minus sign indicates the “open” position and the plus sign indicates the “closed” position. Of course, these measurements may vary, for example, according to the type of club head and the preferences of the user. As discussed above, because the face plate  12  and sole plate  22  are desirably constructed as part of a one-piece body  32 , these components are always correctly positioned at the desired configuration and angle such that there is little or no variation between club heads. Advantageously, this ensures each club head has the desired shape and characteristics. 
     The body  32  of the club head  10  defines a substantially hollow interior portion  40 . As shown in FIGS. 2-4, the opening  34  in the side skirt  30  provides access to the interior portion  40 . The opening  34  is preferably located substantially opposite the face plate  12 , but the opening may be located anywhere in the skirt  30 . In addition, the opening  34  may include a portion of the top crown  16  or sole plate  22 , or the opening may be entirely located in the sole plate or top crown. The opening  34  is preferably generally rectangular in configuration with a height of about 1 inch (2.5 cm) and a length of about 2 inches (5 cm), but the opening may also have other configurations such as circular or square, or be larger or smaller depending upon the desired size and configuration of the golf club  10 . 
     The cap  36  is preferably configured and sized to cover the opening  34  in the skirt  30 . As best seen in FIGS. 2 and 3, the cap  36  has an outer edge  42  with a groove  44  which extends around the outer perimeter of the cap, and the opening  34  in the skirt  30  has an inner edge  46 . The groove  44  in the outer edge  42  of the cap  36  is configured to engage the inner edge  46  of the opening  34 , such that the inner edge  46  fits securely within the groove  44 . Desirably, this creates a “snap” fit between the cap  36  and the opening  34 , which releasably secures the cap  36  to the body  32 . Additionally, the cap  36  is preferably configured to cover the opening  34  in a manner which creates a generally smooth exterior surface of the skirt  30 . 
     The cap  36  is attached to the opening  34  in the skirt  30  to enclose the substantially hollow internal portion  40 . As discussed above, the cap  36  is preferably releasably connected to the skirt  30  by a snap fit; but a press fit, interference fit or fasteners such as bolts, screws and glue may also be used. Desirably, the removable cap  36  provides access to the interior portion  40 , even after the club head is finished. Advantageously, because the cap  36  is not welded to the skirt  30 , the club head can be finished in any desired manner and then the cap  36  closes the interior portion  40  without damaging or marring the finished surface. 
     The removable cap  36  advantageously allows materials and/or components to be simply and easily inserted or removed from the finished club head. For example, weight can be added to the heel  24  or toe  26  of the club head  10  to adjust the torque of the golf club head, or weight can be added to lower the center of gravity of the club head. Additionally, weight can be added or removed to balance the club head  10 , or to adjust the club head to suit a golfer&#39;s particular style or preference. The cap  36  allows additional reinforcement material be added to the club head  10 , or removed; and the cap  36  allows materials such as foam or polyurethane to be inserted into the club head  10  before, during or after the manufacturing process. Thus, the removable cap  36  allows the manufacturer, user or others to simply and easily modify and/or repair the club head  10 , but the cap  36  may also be permanently connected to the skirt  30  by welding, fusing and the like. Desirably, the cap  36  is constructed in accordance with the rules of the USGA such that the club head can be used in competition. 
     The cap  36  may be constructed from the same material as the one-piece body  32  and the cap may be cast at the same time the one-piece body. For example, the cap  36  may be produced as part of the body  32 , and then the cap may be cut out of the body such that the cap  36  and the opening  34  have precisely the same size and configuration, but the cap can also be constructed separately from the body  32 . While the cap  36  may be constructed from the same titanium alloy as the body  32 , the cap is preferably constructed from a plastic material, but a wide variety of materials including any of a number of metals, polymers, composites or amorphous materials may be used to construct the cap  36 . Further, the cap  36  preferably has a thickness of about 0.4 inches (1 mm), but the thickness may also be larger or smaller depending, for example, upon the desired strength and configuration of the cap  36 . 
     A reinforcement structure  50  is located within the interior portion  40  of the club head  10 . The reinforcement structure  50  is desirably positioned behind the face plate  12  and, more desirably, integrally connected to the face plate to form a single unit. The reinforcement structure  50  strengthens the face plate  12  and increases the structural rigidity of the club head  10 , which allows the club head to withstand repeated impacts with a golf ball. The structure  50  also helps prevent the energy of the club head from being absorbed (and therefore lost) by deformation of the face plate  12  when the club head  10  strikes the golf ball. The result of such deformation is a loss of energy transfer from the club head  10  to the golf ball, and thus a loss of initial ball velocity which undesirably results in less distance traveled by the golf ball. It will be understood that the club head  10  does not require the use of the reinforcement structure  50 . 
     As best seen in FIGS. 2 and 3, the reinforcement structure  50  is integrally connected to the face plate  12 , top crown  16  and sole plate  22  of the club head  10  as part of the one-piece body  32 . Thus, the reinforcement structure  50  advantageously strengthens not only the face plate  12 , but also the top crown  16  and sole plate  22 . The reinforcement structure  50  allows a thinner face plate  12 , top crown  16  and/or sole plate  22  to be used, while retaining the structural integrity of the club head  10 . As seen in FIGS. 2-4, the reinforcement structure  50  includes three reinforcing ribs  52 A,  52 B and  52 C which extend vertically along the interior surface  54  of the face plate  12 , with one end attached to the inner surface  56  of the sole plate  22  and the other end attached to the inner surface  58  of the top crown  16 . The center rib  52 B is preferably located proximate the center of the face plate  12  and the other ribs  52 A and  52 C are spaced about ½ inch (1.2 cm) apart. Of course, additional or fewer ribs  52  may be utilized, the ribs may be spaced closer or further apart, and the ribs  52  could be at an angle and even horizontal relative to the face plate  12 . 
     As best seen in FIG. 4, the ribs  52 A-C each have a thickness of about 0.4 inches (1 mm) and a generally rectangular cross-section, but the thickness and configuration of the ribs may vary depending, for example, upon the desired strength of the ribs. The individual ribs may also have different shapes and characteristics. As seen in FIG. 2, the inner portion  60  of the ribs  52  is curved with a first, upper radius of curvature  62  and a second, lower radius of curvature  64 . The upper radius of curvature  62  is preferably between about 2 inches (5 cm) and about 4 inches (10 cm); and the lower radius of curvature  62  is preferably between about 2 inches (5 cm) and about 4 inches (10 cm); but the radius of curvature may be larger or smaller. Desirably, the length of the rib from the inner surface  54  of the face plate to the inner section  60  of the rib  52  is between about ¼ inch (0.6 cm) and about ½ inch (1.2 cm) proximate the center of the rib; while the length of the rib proximate top crown  16  is between about ½ inch (1.2 cm) and about 1 inch (2.54 cm); the length of the rib proximate the sole plate  22  is between about ½ inch (1.2 cm) and about 1 inch (2.54 cm). Desirably, the curved inner section  60  of the rib  52  decreases the weight of the club head  10 , but the ribs may also be straight or have another configuration. 
     As shown in FIG. 5, the club head  10  may also include reinforcing material  66  which is installed in the inner portion  40  of the club head, preferably behind the face plate  12 . The reinforcing material  66  further increases the rigidity of the face plate  12 , and may be used with or without the ribs  52 . The reinforcing material  66  is preferably constructed from a carbon material, such as graphite, but any material which increases the rigidity of the face plate may be utilized. Advantageously, the reinforcing material  66  can be added after the club head  10  is constructed and finished, without damaging the finished surfaces, because the reinforcing material may be inserted through the opening  34  in the one-piece body  32  of the club head  10 . 
     The present invention also includes a method of making substantially identically-shaped golf club heads  10 . The method includes forming the face plate  12 , top crown  16 , sole plate  22  and skirt  30  as a unitary, one-piece body  32 . The one-piece body is desirably formed by investment lost was casting, but the body may also be formed by die casting, injection molding, dynamic compaction, isostatic compaction, forging, lamination and the like. Desirably, the reinforcing ribs  52  are constructed as part of the unitary one-piece body  32 . The cap  36  covers the opening  34  in the body  32  to seal the inner portion  40  of the club head. Advantageously, the cap  36  provides access to the inner portion  40  of the club head  10 , for example, to change the weight of the club head or increase the strength of the club head. 
     Although this invention has been described in terms of certain preferred embodiments, other embodiments apparent to those of ordinary skill in the art are also within the scope of this invention. Accordingly, the scope of the invention is intended to be defined only by the claims which follow.