Golf club head

The present invention, in one embodiment, provides a method for making a wood-type golf club head. The method includes the steps of: forming a face portion of the golf club head from a piece of sheet metal consisting essentially of a titanium alloy; and after forming the face portion, attaching the formed face portion to a crown and a sole of the golf club head. The step of forming the face portion includes pressing the piece of sheet metal into a die at about 70 tons psi.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates, generally, to a golf club head and, more specifically, to a golf club head with a face made from a titanium alloy.

2. Discussion of the Background

When a golf club strikes a golf ball at rest, the ball is propelled at high speed from the tee to the landing area. Thus, the kinetic energy of the moving club head is converted to kinetic energy in the moving golf ball. The golf ball is only in contact with the face of the golf club for a few millionths of a second during impact and the distance achieved by the golf ball is a result of the combination of the initial velocity of the ball after impact, the launch angle, and the spin of the ball. Generally, however, the greater the velocity of the ball after impact, the farther the ball will travel.

The mass of the club head and the velocity at impact combine to determine the initial velocity of the golf ball after impact. However, not all of the energy transferred to the ball is converted to kinetic energy and manifested as velocity. Some of the energy manifests as heat in the ball. Much of the kinetic energy lost as heat is related to the viscoelastic response of the ball during deformation.

The present invention is, in part, a result of the discovery that a golf club face that deforms in preference to the ball will, unless it is a lossy viscoelastomer, generally have a smaller hysteresis loop on deformation and, therefore, result in less energy loss. In addition, it has been found that it is preferable that the face of the club head deform more than the remainder of the club head body. Thus, controlling deformation of the golf club head in preference to deformation of the golf ball will result in the golf ball traveling farther.

Generally, a golf club comprises a shaft portion, a head portion, and a grip portion. The part of the golf club head portion that comprises the hitting surface is referred to as the golf club “face”. Generally, a golf club face abuts or is adjacent to both a top wall (or crown) of the club head and a bottom wall (or sole) of the club head.

Most “woods”, such as the driver and the fairway woods, are in the form of a hollow shell (or perhaps filled with foam), usually of metal. Because only the best and strongest golfers can effectively swing a driver head that weighs more than 220 grams, the maximum weight of the club head is essentially a design constraint of the club head. Further, when the front side of the face of the golf club head strikes a golf ball, extremely large impact forces are produced potentially causing cracking and/or material failure. Thus, the golf club face portion must be structurally adequate to withstand large repeated forces, such as those associated with ball impact. In addition, a large club head face is highly desirable because it strongly reduces the percentage of errant hits.

Thus, there are contrasting design considerations when designing a golf club head—the desirability of a light club head, but with a large club face and a club head that is durable enough to withstand repeated striking of the ball. One method of increasing the durability of the club head is to add additional material (e.g., steel or titanium) to thicken the club face or to add ribs to the club face. However, the designer cannot simply add additional material to strengthen the face indiscriminately because doing so also increases the overall weight of the club head, which is undesirable.

Prior golf club heads typically had relatively thick faces, which would deform only slightly at impact thereby causing the golf ball to deform, which created a significant loss of kinetic energy through conversion of heat in the ball.

Thus, there is a need for a new golf club head with a club face structure providing enhanced deformation for improving club performance, and that has structural integrity, thereby reducing cracking and material failure, without otherwise adversely affecting club performance, look, and feel; and with limited affect on club head weight.

SUMMARY OF THE INVENTION

The primary object of the present invention is to overcome the deficiencies of the prior art described above by providing a golf club head with enhanced deformation for hitting a golf ball farther.

The present invention accomplishes this object by providing, in one embodiment, a golf club head having a face made from titanium alloy BT-22.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following description, for purposes of explanation and not limitation, specific details are set forth, such as particular materials, shapes, methods of manufacture, casting processes, etc. in order to provide a thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced in other embodiments that depart from these specific details. Detailed descriptions of well-known casting processes, materials, golf club shapes, methods of manufacturing, devices, components, shafts, uses, techniques, and associated technologies, are omitted so as not to obscure the description of the present invention.

As shown inFIGS. 1–5, the present invention includes a sole200, a crown300, and a face portion100, which together form club head10. Referring specifically toFIG. 3, in the example embodiment of the present invention, the face portion100includes an upper portion110, which is above the dashed line145shown inFIG. 3, and a lower portion120, which is below the dashed line145shown inFIG. 3. The horizontal and vertical lines ofFIG. 3identify portions of the face portion100that have substantially the same thicknesses.

The lower portion120includes a lower toe portion125that is located towards the toe of the club head, a lower heel portion135that is positioned towards the heel of the club head, and a center portion130between the lower toe portion125and lower heel portion135. The lower toe portion125, which is generally oval in shape or more particularly shaped in two inverted ellipses, or approximately like a football, includes an outer edge126that is towards the sole200and the toe205of the club head and an inner edge127that is adjacent the center portion130. Likewise, the lower heel portion135, which is generally oval in shape, or more particularly shaped like a football, includes an outer edge136that is towards the sole200and heel210of the club head and an inner edge137that is adjacent the center portion130.

The outer edge126of the lower toe portion125is slightly curved and is adapted to mate with the front edge of sole200. The inner edge127of the lower toe portion125is curved and in particular is generally parabolic in shape in this example embodiment. In addition, the inner edge127extends from the upper portion110near the toe205to about one third of the distance to the heel210from the toe205. The radius of curvature of the inner edge127of the lower toe portion125is 0.75 inches as the inner edge127approaches the center portion130.

The outer edge136of the lower heel portion135is slightly curved and is adapted to mate with the front edge of sole200. The inner edge137of the lower heel portion135is curved and in particular is generally parabolic in shape in this example embodiment. In addition, the inner edge137extends from the upper portion110near the heel210to about one third of the distance to the toe205from the heel210. The radius of curvature of the inner edge137of the lower heel portion135is 0.75 inches as the inner edge137approaches the center portion130.

The center portion130of lower portion120includes a heel side edge which coincides with inner edge137, a bottom edge133, a toe side edge which coincides with inner edge127, and a top edge indicated by dashed line145. The bottom edge133of the center portion is substantially straight and is 0.079 inches in length. The top edge of the center portion130is integral with the upper portion110and the vertical distance from the bottom edge133of the center portion130to the top center edge146of the upper portion110is 1.75 inches. As discussed above, the parabolic shape of the edges provide increased strength, which greatly enhances the ability of the club face to deform more than the ball while maintaining structural integrity.

As is evident in the figures, the upper portion110extends substantially the entire length of the face100(i.e., substantially the entire distance from the heel to the toe). In addition, the upper portion110in this example embodiment extends from near the top center146edge of the face100about one fourth to one half of the distance from the top center edge146to the bottom center edge147as indicated by the dashed line145inFIG. 3. In this embodiment, the dashed line145indicates the separation of the upper110and lower portions120also coincides with the upper ends129and139of inner edges127and137, respectively. In alternate embodiments of the present invention, the upper portion110could extend a longer or shorter distance down the face100. In this embodiment, the upper portion110extends nearly, but not quite all the way, to the very top edge146. The radius of curvature of the upper end129of the upper portion110near the toe is 1.675 inches.

Substantially all of the upper portion110and the lower center portion130have substantially the same thicknesses. In this example embodiment, the thickness of lower center portion130and upper portion110is in the range of 0.070 inches to 0.095 inches and is preferably from 0.080 inches to 0.085 inches. The lower toe portion125and the lower heel portion135are also substantially the same thickness, which is in the range of 0.055 to 0.065 inches and preferably 0.0575 to 0.0625 inches and most preferably approximately 0.060 inches.

As shown inFIGS. 3 and 5, in this embodiment a channel140is disposed around the peripheral of the face100. The channel140has a curved surface on the inside of the club head10(i.e., the back side of the face100). In addition, the channel140is thinner than the other portions of the face100, thereby aiding in the deformation of the club face100. In this example embodiment, the channel140is approximately 0.005 inches thinner than the thickness of the adjacent face portion100. The channel140is 0.003 inches wide and is preferably in the range of 0.0525 inches to 0.0575 inches and more preferably approximately 0.055 inches thick at its thinnest point. Channels in other embodiments of the present invention may extend only partially around the face, or not at all, and may be other thicknesses.

The present invention also includes the removal of conventional score lines in the center of the face where the face is thickest, in a shape that profiles the parabolic shape. More specifically, the face portion100includes a portion that has no score lines that is shaped substantially as an inverted triangle (i.e., base at the top) with a truncated apex (i.e., connected points129,139with the respective corners of the lower center portion130as shown inFIG. 3). The score lines on the outside of the face portion100end outside the internal parabolic shaped inner edges137,127of the lower heel portion135and lower toe portion125. The effect is to further strengthen the hitting area of the face and to further improve durability. Alternate embodiments of the present invention could include score lines over part or all of the face.

As shown inFIG. 4, the sole200of the club head10includes a ridge across the sole200that produces a center rail203from back to front with a parabolic rise towards the face100of the club. The parabolic rise (indicated by the arrows labeled C inFIG. 4) on the sole200provides additional lateral strength to the club head, without adding thickness to the sole200while still permitting the sole200to bend at impact with a golf ball on the face. The center rail203also aids the golfer when setting up to strike the ball and assists the golfer in getting the ball airborne. Thus, the center rail203reduces friction should the club hit the ground while swinging so that the club may be used as a fairway wood. The wall thickness of the sole200is 0.035 inches and the radius of curvature of the parabolic rise is 0.5 inches. The center rail is approximately 1.09 inches wide at its narrowest point.

As shown inFIG. 2, the crown300includes a center ridge303across the crown300from back to front with a parabolic rise towards the face100of the club. The parabolic rise (indicated by the arrows labeled D inFIG. 2) on the crown300provides additional lateral strength to the club head, without adding thickness to the crown300while still permitting the crown300to bend at impact. The center ridge303also provides a visual aid to the golfer when setting up to strike the ball. The wall thickness of the crown300is 0.035 inches and the radius of curvature of the parabolic rise is 1.150 inches. The center ridge303is approximately 0.7 inches wide at the rear of the club and is 3.4 inches wide towards the front of the club head.

As discussed above, the parabolic rise in the sole200and crown300provides increased strength, which greatly enhances the ability of the club face to deform more than the ball and to maintain structural integrity.

It is also preferable that the wall thickness of the sole200and crown300vary, being slightly thicker toward the heel. The varying thickness moves the center of gravity toward the heel, which improves performance by building in a hook bias thereby assisting the golfer in pronating the club head as the club approaches the ball during the swing. In this example embodiment, the crown and sole vary from about 0.035 inches at the toe to about 0.040 inches at the heel.

In one method of making the golf club head10, the crown is cast with the face and a small lip that extends rearward approximately 0.25 inches from the face. The sole is then welded to the crown and to the lip extending from the face as shown by the jagged line ofFIG. 5. By this manufacturing procedure, the thickness of the connection of the face to the crown can be accurately controlled. In this embodiment, the club head is formed of steel, but other embodiments may use alternative materials such as titanium, Teflon, or like materials, and different portions of the club head may be made of different materials. The face of the steel club head may be polished (shiny) so that the impact of the ball with the club head results in a mark where the ball impacted the club head face. Thus, the club head face provides feedback to the golfer regarding where on the club face the golfer is striking the ball. The polished nature of the club face allows the golfer to repeatedly get the feedback by periodically wiping the club face clean.

In the present example embodiment, the shaft is attached to the club head10in any conventional fashion. The shaft may be any shaft suitable for the golfer such as Penley® or Graphite Design® shafts. The hosel neck protrudes 0.500 inch out of the heel end of the crown. The total hosel depth is 1.500 inch from the top of the hosel to the seat within the club head, so the hosel is one inch into the club head. The total distance from the tip of the hosel to the sole is 3.150 inch.

The club of the above example is USGA compliant with a club head that is 280 cubic centimeters and weighs 200 g 4 g. The weight of the sole plate is 46 g 4 g. Tables 1 and 2 below provide a number of parameters for golf clubs having 9.5 and 11 degree lofts, respectively.

The outside diameter of the hosel is 0.500 inch and the inside diameter is 0.348 inch.

In a preferred embodiment of making the golf club head10, the crown300and sole200are cast as one seamless and joined piece to form a cast body with a face opening that is only two millimeters larger than a precision formed face portion100. The face portion100is then attached onto the cast body by, for example, welding or the like. The face portion100may be polished after welding and then the body may be painted. Next, a shaft may be fitted and gripped.

According to one embodiment, a method of making the face portion100includes forming the face portion from sheet metal (e.g., steel, titanium, titanium alloy, etc. sheet metal) formulated to provide very high strength and durability. In one embodiment the thickness of the sheet metal is about 0.075 inches and 275 steel, which is stronger than 17-5 stainless steel, may be used. A face portion formed from 275 steel can be manufactured with extreme accuracy and repeatability and will not lose durability over time.

In one embodiment, the face portion may be made from or include a material having the following properties: ultimate strength (Mpa) of about 1100–1250; yield strength (Mpa) of about 1000; elongation (%) of about 10; stress, time and temperature to produce 0.2% elongation (creep) of about 320 Mpa/100 hours/400 degrees centigrade; hardness (brinell) of about 285; beta transus (C) of about 840–880; density (g/cc) of about 4.6; modulus of elasticity (tension Gpa) of about 110; and specific heat (W/m*K) at room temperature of about 8.32. One material that has these or many of these properties is a Russian titanium alloy referred to herein as “BT-22.” In one embodiment, BT-22 preferably includes or consists essentially of about 4.4 to 5.7 percent weight aluminum, 4.0 to 5.5 percent weight molybdenum, 4.0 to 5.5 percent weight vanadium, 0.5 to 1.5 percent weight chromium and 0.5 to 1.5 percent weight iron and the remainder being substantially titanium. Other formulations of BT-22 are contemplated. BT-22 preferably has a maximum of 0.1 percent weight carbon, 0.15 percent weight silicon, 0.18 percent weight oxygen, 0.05 percent weight nitrogen and 0.015 percent weight hydrogen. A face plate made from sheet metal consisting of or essentially of BT-22 produces excellent results. BT-22 can be obtained from Cronos Ltd., Moscow, Russia.

Based on the specified size and curvature of the desired face portion100, the sheet metal is laser cut, thereby forming a laser cut blank. The laser cut blank is then precision machined to provide the variable thickness in the face design as described herein. The scorelines (e.g., grooves), if any, may be engraved onto the outside of the laser cut blank using, for example, 70,000 RPM high speed spindles. The machined blank is then pressed into a die at, for example, 70 tons psi, to form the desired face portion100. The pressure applied to the machined blank forms the blank into a precise face portion with exact bulge and roll characteristics according to specifications described herein. The face portion100is then heat treated at high temperature to raise the Rockwell Hardness of the face portion to 45 or higher. Once completed the process yields a very high strength precision formed face portion.

FIG. 7depicts the vibrational response of a golf club embodying an embodiment of the present invention striking a golf ball, which relates to the club's fundamental frequency. The resultant golf club provides a higher fundamental frequency than existing club heads. The combination of high fundamental frequency and greater deformation of the club head reduces the energy lost as heat in the golf ball (and club) at impact.

The club heads described herein are suitable for use as a driver or wood. The size, weight, and angle on the face of the club head of the present invention may vary depending on the use of the club head in, for example, a driver, 3-wood, 5-wood, etc. For example, the club head of the present invention used in a 3-wood is about ⅔ the size of the club head used in a driver, and the angle on the face is about 13 degrees. The angle on the face of the club head of the present invention used in, for example, a 5-wood is about 17 degrees. The volume of a club head of the present invention used in a driver may be, for example, about 280 cc, or may be about 400 cc or 460 cc in an oversized or jumbo type driver made of titanium, for example.

While the above example embodiment includes a center portion130that has two curved sides that abut lower heel portion135and lower toe portion125, in an alternative embodiment the sides could be straight so that inner edges137and127are straight. In addition, while the transition from the thickness of the center portion to the thickness of the lower toe portion125and lower heel portion135(which define edges127and137, respectively) is abrupt in the above example embodiments, in an alternate embodiment the transition could be more gradual (for example, transitioning over a half inch, three eighths of an inch, quarter inch, eighth inch, or sixteenth of an inch).

This alternative embodiment is illustrated inFIGS. 8A–8C.FIG. 8Aillustrates a golf club face800. As shown inFIG. 8A, golf club face800includes three non-overlapping regions: (1) region A; (2) region B1; and (3) region B2. Additionally, face800may include a region C1, which is positioned between regions A and B1, and a region C2, which is located between regions A and B2.

In the embodiment where face800includes region C1, region B1is bounded by a portion of the edge of face800and a line802, otherwise it is bounded by a line832and the portion of the edge of face800. Line802extends from a first point803located at the edge of face800and below an upper left-hand corner810of face800to a second point804located at the edge of face800to the left of a bottom-center-edge point850. In one embodiment, second point804is about 10 mm to the left of bottom-center-edge point850, but other distances are contemplated. Preferably, line802is a curved line in the shape of a parabola, but the line may also be straight.

Similarly, in the embodiment where face800includes region C2, region B2is bounded by a portion of the edge of face800and a line806, otherwise it is bounded by a line836and the portion of the edge of face800. Line806extends from a first point807located at the edge of face800below an upper right-hand corner811of face800to a second point808located at the edge of face800to the right of bottom-center-edge point850. In one embodiment, second point808is about 10 mm to the right of bottom-center-edge point850, but other distances are contemplated. Preferably, line806is a curved line in the shape of a parabola, but the line may also be straight.

Region A encompasses all or substantially all of the remaining portion of face800. Conceptually, region A can be divided along a line890that extends from a point833to a point837. Line890bisects region A into a top region D1and a bottom-center region D2. As shown inFIG. 8A, top region D1can have a width of about 16.5 mm and can extend lengthwise from the upper-right-hand corner811to the upper-left-hand corner810. In other embodiments, the width of top region D1can range between about one quarter and one half of the width of the face (e.g., between about 10 mm and 25 mm, in the embodiment shown inFIG. 8A).

A region C1and a region C2may be positioned between regions A and B1and A and B2, respectively. In the embodiment shown inFIG. 8A, region C1is bounded by line802and line832, and region C2is bounded by line806and line836. Line832extends from a first point833located at the edge of face800and located between point803the upper left-hand corner810of face800to a second point834located at the edge of face800and located between point804and bottom-center-edge point850. Line836extends from a first point837located at the edge of face800and located between point807the upper right-hand corner811of face800to a second point838located at the edge of face800and located between point808and bottom-center-edge point850. Preferably, lines832and836are curved lines, each in the shape of a parabola, but the lines may also be straight.

As shown inFIG. 8A, both point833and point837have the same vertical distance from a top-center-edge point851. In the embodiment shown, this vertical distance is about 16.5 mm. In alternative embodiments, it is contemplated that this vertical distance can be anywhere between about one quarter and one half of the width of the face, which, in the embodiment shown, is about 47 mm.

As discussed above with respect to other embodiments, regions D1, D2, B1, and B2each may have a substantially uniform thickness. Preferably, regions D1and D2have the same thickness and regions B1and B2have the same thickness which is thinner than the thickness of regions D1and D2. This feature is illustrated inFIG. 8B.

FIGS. 8B and 8Cshow that, unlike regions A and B, regions C1and C2do not have a substantially uniform thickness. That is, region C1provides a gradual transition region between regions A and B1so that face800does not have an abrupt change in thickness between regions A and B1. Likewise, region C2provides a gradual transition region between regions A and B2.FIG. 8Calso shows that region C1has a preferred width of about 2.5 mm and a preferred radius of curvature of about 8.4 mm, but other widths and curvatures are contemplated.

While the above example embodiment includes a center portion130that has a substantially flat lower edge, alternate embodiments could include a rounded bottom edge or a pointed lower end. In addition, while the thickness of the lower toe portion125and lower heel portion135are the same in the above example embodiment, in an alternate embodiment they could be different with the lower heel portion135being thicker than the lower toe portion125or vice versa.

The foregoing has described the principles, embodiments, and modes of operation of the present invention. However, the invention should not be construed as being limited to the particular embodiments described above, as they should be regarded as being illustrative and not as restrictive. It should be appreciated that variations may be made in those embodiments by those skilled in the art without departing from the scope of the present invention.

While a preferred embodiment of the present invention has been described above, it should be understood that it has been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by the above described exemplary embodiment.