Weighting system for a golf club head

[0002] 1 Field of the Invention

[0003] The present invention relates to a golf club head. More specifically, the present invention relates to a weighting system for a large volume golf club head.

[0004] 2 Description of the Related Art

[0005] Golf club designs are constantly evolving with the primary purpose to improve a golfer's performance. While the improvements may address a number of areas, a designer strives to design a more forgiving golf club. Forgiveness in a golf club may be achieved by shifting the center-of-gravity of a golf club to a desirable location, and creating a larger moment of inertia.

[0006] It is difficult to increase forgiveness in a golf club head composed of a homogeneous or monolithic material, such as stainless steel, since there is a limit on the overall weight of a golf club acceptable to the typical golfer. To overcome this difficulty, designers have resorted to combining different materials (high density and low density) to achieve the desired center-of-gravity and large moment of inertia. A very high-greatest freedom in improving the performance of a golf club head since less volume is needed to achieve the proper weighting. The most economical, commercially available material with a very high density is tungsten, which has a density of 19.3 grams per cubic centimeter.

[0007] One challenge in using heterogeneous materials is the ability to join the materials together in a golf club head. Numerous techniques have been created by the golf industry to join heterogeneous materials in a golf club head. One example is the GREAT BIG BERTHA® TUNGSTEN-TITANIUM™ irons, developed by the Callaway Golf Company of Carlsbad, California, which used a screw to attach a tungsten block to the rear and sole of a titanium iron. Another example is the GREAT BIG BERTHA® TUNGSTEN-INJECTED™ HAWK EYE® irons, also developed by the Callaway Golf Company, which feature an internal cavity with tungsten pellets in a solder, as set forth in co-pending U.S. patent application Ser. No. 09/330,292, for an Internal Cavity Tungsten Titanium Iron, filed on Jun. 11, 1999. An example of a wood is the GREAT BIG BERTHA® HAWK EYE® drivers and fairway woods, also developed by the Callaway Golf Company, which use a tungsten screw in the sole of a titanium club head body. Other techniques use adhesives to join the materials, press fit the materials, braze the materials, or structurally hold one material piece within another material piece using undercuts or pockets.

[0008] For the most part, these techniques require a precisely machined weighting piece to fit within a precise location on a golf club head. The most economical method is to cast a golf club head body with a cavity for the weighting piece and attaching the weighting piece with a screw. However, casting tolerance are low, and require either machining of the cavity itself, or machining of the weighting piece to fit each cavity. The use of softer materials is undesirable since this creates difficulty in finishing the final product due to smearing of such soft materials during grinding of the golf club head.

[0009] Further, a co-casting process, where the weighting piece is incorporated in the mold prior to pouring the base metal, is very problematic depending on the materials since the weighting piece is relatively cold when the hot liquid base metal is cast around it causing thermal shock. Also, thermal expansion mismatch of materials is a problem with co-casting of heterogeneous materials. Other problems arise during re-shafting, where the golf club head is heated to remove the shaft. Such heating will result in low melting temperature materials (epoxies and solder) to flow, resulting in the possible movement of weighting pieces. Additionally, the secure and specific weighting mechanism of the prior art prevents the club from being weighted according to a particular swing of a particular golfer.

[0010] The present invention overcomes the weighting problems of the prior art by providing a golf club head with a weighting system that is incorporated after the entirety of the golf club head has been formed thereby allowing for post-formation weighting. This enables the golf club head of the present invention to adjust its weight according to a particular golfer.

[0011] One aspect of the present invention is a golf club head that includes a body, a weight compartment and a weight member. The body has a crown, a sole, a striking plate, a heel end an toe end and a hollow interior. The weight compartment is disposed within the hollow interior and connected to the sole. The weight compartment defines a chamber of a predetermined volume. The weight member is disposed within the weight compartment. The weight member weighs between 3 grams and 70 grams, and is composed of a material having a density between 7 grams/cubic centimeter and 20 grams/cubic centimeter.

[0012] The weight member is preferably composed of bismuth. The body of the golf club head may have a volume of 130 cubic centimeters to 350 cubic centimeters. The body of the golf club head may weigh between 140 grams to 205 grams.

[0013] Another aspect of the present invention is a method for weighting a golf club head. The method includes orienting a body of a golf club head for introduction of a weighting material. Then, a weight member is injected into the weight compartment. In a preferred embodiment, the weight member is bismuth that is injected into the weight compartment through a portal.

[0014] Yet another aspect of the present invention is a driver club head that is composed of a forged titanium alloy material. The driver club head has a volume in excess of 300 cubic centimeters, and a weight less than 215 grams. The hollow interior of the driver golf club head has a weight compartment therein. A weight member composed of bismuth and weighing between 3 to 20 grams is injected into the weight compartment.

[0015] Having briefly described the present invention, the above and further objects, features and advantages thereof will be recognized by those skilled in the pertinent art from the following detailed description of the invention when taken in conjunction with the accompanying drawings.

[0016] FIG. 1 is a bottom plan view of the sole of the golf club head of the present invention.

[0017] FIG. 2 is a bottom plan view of the sole of the golf club head of the present invention with a medallion positioned within a rear facet recess.

[0018] FIG. 3 is a front view of the golf club head of the present invention.

[0019] FIG. 4 is a side view of the toe end of the golf club head of the present invention.

[0020] FIG. 5 is a top plan view of the golf club head of the present invention.

[0021] FIG. 6 is side view of the heel end of the golf club head of the present invention.

[0022] FIG. 7 is a rear view of the golf club head of the present invention.

[0023] FIG. 8 is a bottom plan view of the sole of the golf club head of the present invention with indicia on the sole.

[0024] FIG. 9 is an exploded top view of the components of the preferred embodiment of the golf club head of the present invention.

[0025] FIG. 10 is an exploded top view of the components of an alternative embodiment of the golf club head of the present invention.

[0026] FIG. 11 is an exploded bottom view of FIG. 10.

[0027] FIG. 12 is a bottom view of the golf club head of FIG. 10 showing the weight compartment in phantom lines.

[0028] FIG. 13 is a bottom view of the golf club head of FIG. 9 showing the weight compartment in phantom lines.

[0029] FIG. 14 is a cross-sectional view of the golf club head of FIG. 10.

[0030] FIG. 15 is a cross-sectional view of the golf club head of FIG. 9.

[0031] FIG. 16 is an isolated top plan view of a weight compartment of the present invention.

[0032] FIG. 17 is an isolated top plan view of a weight compartment of the present invention.

[0033] FIG. 18 is an isolated top plan view of a weight compartment of the present invention.

[0034] As shown in FIGS. 1-8, the golf club head of the present invention is generally designated 20. The golf club head 20 is a driver, however, the golf club head of the present invention may alternatively be a fairway wood. The golf club head has a body 22 that is preferably composed of a metal material such as titanium, titanium alloy, stainless steel, or the like, and is most preferably composed of a forged titanium material. However, the body 22, or a portion of the body 22, may be composed of a graphite composite material or the like. The body 22, when designed as a driver, preferably has a large volume, typically greater than 300 cubic centimeters, and is most preferably 350 cubic centimeters for a body composed of titanium. However, when designed as a driver, a body 22 composed of stainless steel may have a volume range of 200 cubic centimeters to 275 cubic centimeters, and a body 22 composed of a composite material may have a volume of 325 cubic centimeters to 400 cubic centimeters. The body 22, when designed as a driver, preferably weighs no more than 215 grams, and most preferably weighs between 180 and 205 grams. When the body 22 is designed as a fairway wood, the body weighs from 135 grams to 180 grams, and preferably from 140 grams to 165 grams. The body 22 has a hollow interior 23.

[0035] The body 22 has a crown 24, a heel end 26, a toe end 28, a sole 30, a striking plate 32 and a ribbon 34. A shaft, not shown, is placed within a hosel, not shown, at the heel end 26. In a preferred embodiment, the hosel is internal to the body 22, and the shaft extends to the sole 30 at a bore 36. The body 22 also has a rear section 38 that is opposite the striking plate 32.

[0036] The sole 30 of the present invention is designed to function in a high performance, large volume driver or fairway wood. Such a high performance, large volume driver or fairway wood is designed for compliance during impact with a golf ball in order to reduce the energy loss for greater distance. Such a driver or fairway wood is disclosed in co-pending U.S. patent application Ser. No. 09/431,982 filed on Nov. 1, 1999 for a Golf Club Head With A Forged Titanium Striking Plate, which is hereby incorporated by reference in its entirety. The sole 30 of the present invention is able to function in a high performance, large volume driver due to its unique four facet structure. Such a structure is disclosed in co-pending U.S. patent application Ser. No. 09/606,661 filed on Jun. 28, 2000 for a Four-Faceted Sole Plate For A Golf Club Head, which is hereby incorporated by reference in its entirety.

[0037] The sole 30 of the present invention has a central facet 40, a heel facet 42, a toe facet 44 and a rear facet 46. The rear facet 46 preferably defines a recess 48 that is covered by a medallion 50. Due to the angle to the central facet 40, the heel facet 42 and the toe facet 44 have a transition edge 52 and 54 respectively. The rear facet 46 is also angled to the central facet 40, and is used for access to the hollow interior 23 of the body 22 through a portal 56.

[0038] FIGS. 9-15 illustrate the weight system of the golf club head 20 of the present invention. A body 61 and a weight chamber 66 define the weight compartment 60. A top lid 62 allows for access to the weight chamber 66, however, the top lid 62 is sealed prior to weighting of the golf club head 20. A weight member 64 is injected into the weight chamber 66 via the portal 56, as further described below. The portal 56 allows for access to the weight compartment 60 after the crown 24 has been welded to the entirety of the body 22. After injection of the weight member 64, the portal is sealed by placement of the medallion 50 into the recess 48.

[0039] The post-golf club head formation weighting allows for weight to be added to the golf club head 20 for adjustments and/or customization for a particular golfer. Further, this allows for weight to be added to the golf club head 20 after the weight of the body 22 has been determined in order to meet predetermined specifications for the golf club head 20. Preferably, the weight compartment 60 is cast with the body 22 if the club head is composed of cast titanium or cast steel. Alternatively, the weight compartment 60 may be welded to the interior surface of the sole 30 if it is formed separate from the body 22.

[0040] The volume of the weight chamber 66 may vary from 4 cubic centimeters (“cc”) to 14 cc depending on the club. The preferred volumes of the weight chambers 66 for fairway woods is set forth in Table One. The weight chambers 66 for drivers will have volumes that vary from the fairway woods. The weight member 64 preferably occupies between 30% to 95% of the volume of the weight chamber 66, and most preferably from 50% to 80% of the volume of the weight chamber 66.

[0041] The volume of the weight member 64 will also vary depending on the club. The preferred minimum and maximum volumes for the weight member 64 is set forth in Table One. In a preferred embodiment, the weight member 64 is composed of bismuth, which is introduced into the weight chamber 66 via the portal while in a liquid form. The melting temperature of bismuth is 271° C. The density of bismuth is 9.80 g/cc while the density of titanium is 4.5 g/cc. Thus, bismuth has a density much greater than titanium allowing for minimum volume while optimizing mass. Further, bismuth will expand upon solidification, thus providing a mechanical locking within the weight chamber 66. The weight member 64, while in liquid form, will conform to the shape of the weight chamber 66. The weight of the weight member 64 may preferably range from 3 grams to 70 grams, more preferably range from 7 grams to 20 grams, and is most preferably 15 grams (including the weight chamber 66). The density of the weight member 64 varies from 7 g/cc to 20 g/cc. The weight of the weight member 64 will vary according to the particular fairway wood and the loft of the driver, as shown in Table Two.

[0042] The weight compartment 60 is positioned within the hollow interior 23 of the body 22 to adjust the center of gravity of the golf club head 20 off-center toward the heel end 26. The center of gravity will vary for drivers of depending on the loft, and for fairway woods depending on the fairway wood. The center of gravity, CG, for the driver golf club head of FIGS. 1-8, is shown in FIGS. 5 and 6. The ability of the liquid bismuth to flow and conform to a particular weight chamber allows for greater control of the center of gravity of the golf club head, and also allows for better control of the moment of inertia of the golf club head.

[0043] The bismuth weight member 64 is introduced through the portal 56 while the striking plate 32 is oriented downward and lying “flat” on a surface. Thus, the bismuth weight member 64 will first occupy the space of the weight chamber 66 that is towards the striking plate 32 and continue to fill the weight chamber 66 toward the rear of the body 22. In a preferred method, 90% of the predetermined amount of liquid bismuth weight chamber 64 is introduced, and then the golf club head 20 is weighed to determine if any additional bismuth is needed to meet the specifications of the particular golf club. Additional bismuth is added to the weight chamber 66 if necessary to meet the specification requirements. Those skilled in the pertinent art will recognize that other materials may be used as the weight member 64 without departing from the scope and spirit of the present invention.

[0044] Isolated views of various weight compartments 60a-care shown in FIGS. 16-18. The depths of the weight compartments 60a-cpreferably vary from 0.5 inch to 2.0 inches. The area of the particular weight compartment 60 varies depending on the club. In FIG. 16, the length, L₁, of the weight compartment 60ais preferably 1.474 inches and the length, L₂, is 0.754 inch. In FIG. 17, the length, L₁, of the weight compartment 60bis preferably 1.836 inches, the length, L₂, is 1.609 inches, and the length, L₃, is 1.269 inches. In FIG. 18, the length, L₁, of the weight compartment 60cis preferably 1.511 inches, the length, L₂, is 1.395 inches, and the length, L₃, is 0.934 inches. The shape and the location of the weight compartment 60 will affect the center of gravity of the golf club head 20 and the moment of inertia.

[0045] From the foregoing it is believed that those skilled in the pertinent art will recognize the meritorious advancement of this invention and will readily understand that while the present invention has been described in association with a preferred embodiment thereof, and other embodiments illustrated in the accompanying drawings, numerous changes, modifications and substitutions of equivalents may be made therein without departing from the spirit and scope of this invention which is intended to be unlimited by the foregoing except as may appear in the following appended claims. Therefore, the embodiments of the invention in which an exclusive property or privilege is claimed are defined in the following appended claims.