Golf club with flexible grip portion

Abstract

A golf club shaft wherein the flexibility of the club over a short segment at the butt or grip end is increased in a controlled manner. A flexible hollow shaft insert of approximately 6.5 to 10 inches in total length having an insert stub portion of approximately 1.5 to 3 inches in length is fitted within the shaft, and an extension member of approximately 5 to 7 inches in length extends from the insert stub portion, the outer diameter of the extension member being greater than the outer diameter of the insert stub member, such that a shoulder is defined at the juncture. The shoulder is abutted against the butt end of the golf shaft, thereby creating a flex point whereby the extension portion flexes in a hinge-like angular manner relative to the golf club shaft. The extension portion is constructed to be substantially stiff or rigid, such that it remains substantially linear when bent relative to the golf shaft.

Description

This application is a continuation-in-part of U.S. patent application Ser. No. 12/004,239, filed Dec. 20, 2007, claiming the benefit of U.S. Provisional Patent Application Ser. No. 60/876,817, filed Dec. 22, 2006.

BACKGROUND OF THE INVENTION

The different embodiments of the invention relate generally to the field of golf clubs, and more particularly to the field of golf club shafts having variations in flexibility along certain portions of the shaft, and even more particularly relate to golf club shafts wherein the variation in flexibility occurs in the grip portion, and most particularly wherein the flexibility in the grip portion is localized such that the flex performs in a hinge-like manner.

Steel and graphite composite golf club shafts both have a graduated bend when flexed. Shafts can be designed to be stiffer or more flexible depending on the particular club, the ability of the golfer, etc. The amount of bend in a standard golf shaft is gradually progressive, in that the flex is greater near the tip end, i.e., the club head end, than near the butt or grip end. The flex of the golf shaft enables the golfer to generate increased club head speed, as the shaft bends and then recoils when striking the golf shot. Professional golfers use a stiffer, less flexible shaft because they can then attain the optimum distance with more control. Most golfers, however, need a more flexible shaft in order to maximize club head speed as the ball is struck—the key factor in driving distance. There is a trade-off, however, between power and control, because the more flexible shafts, while increasing distance, have more twist or torque. Torque resistance is desirable in a golf shaft because most golfers do not hit the ball in the center of the clubface. When the ball is hit off-center toward the heel or toe of the club head, the shaft twists and the ball is propelled to the left or right in an exaggerated and undesirable manner. Consequently, there is a need to balance increased distance with loss of control.

The USGA in its “Rules of Golf” requires that at any point along the length of the shaft, the shaft shall bend in such a way that the deflection is the same regardless of how the shaft is rotated about the longitudinal axis and shall twist the same amount in both directions. In other words, there cannot be any preferential deflection in the shaft in a chosen direction, such as in the direction parallel to the perfect shot direction.

Standard golf shafts are tubular members of slightly diminishing diameter progressing from the butt or grip end (the proximal end held by the golfer) to the tip end (the end connected to the club head). The flex of the shaft is determined primarily by the diameter of the shaft. If the diameter is wider throughout the shaft, it will be stiffer than a shaft constructed of similar material that is thinner in diameter through the shaft. The flex and torque of the shaft can be controlled more in graphite shafts as opposed to metal shafts thorough selectivity and application of resins and carbon fiber materials. However, in the traditional design, it is difficult for either steel or graphite shaft makers to significantly alter the flex point of the shaft or create other desirable performance characteristics in a shaft.

Attempts to optimize golf club shaft design and structure can be seen in U.S. Pat. No. 5,842,930 to Koterba, U.S. Pat. No. 5,733,204 to Carrara, U.S. Pat. No. 2,250,429 to Vickery, U.S. Pat. No. 5,735,752 to Antonious, U.S. Pat. No. 6,024,651 to Cheng, U.S. Pat. No. 6,042,485 to Cheng, U.S. Pat. No. 6,280,347 to Herber, U.S. Pat. No. 5,439,219 to Vincent, U.S. Pat. No. 1,968,616 to Oldham, U.S. Pat. No. 3,809,403 to Hunter, U.S. Pat. No. 5,322,290 to Minami, U.S. Pat. No. 6,582,320 to Fendel, U.S. Patent Application Publication No. 2001/0012803 to Feeney, and U.S. Patent Application Publication No. 2002/0098907 to Hsu. These devices have failed to provide an optimum solution to the problem of balancing control and distance.

For example, Koterba provides for a flexible cylindrical member positioned above the end of the golf club shaft, with a flexible grip member coaxially mounted over the flexible member and the end of the golf club shaft. The length of the flexible member is such that a flex point occurs between the hands of the golfer during the backswing. With this design however, all of the stress from the flexing occurs in the grip member. Over time, this repeated flexing will result in failure of the grip member.

It is an object of this invention to provide a golf club wherein the flex is optimized relative to standard golf club shaft construction. It is a further object to provide a golf shaft and club of improved flex and control wherein the improved flexibility occurs at or near the proximal end of the golf club, i.e., within the upper butt section or grip portion of the club. It is a further object to provide a golf shaft and club of improved flex and control wherein the improved flexibility occurs between the upper and lower hands of the golfer gripping the club. It is a further object to provide a golf shaft and club of improved flex and control wherein the flex is localized such that the flex performs in a hinge-like manner.

SUMMARY OF THE INVENTION

The invention is a golf club wherein the flexibility of the golf club shaft at the butt or grip end is increased in a controlled manner by providing a more flexible section along the butt end of the golf club shaft.

In one embodiment, the flexible portion extends approximately 5 to 7 inches in length. A flexible tubular shaft insert member of approximately 7 to 10 inches in length comprising an insert extension portion approximately 5 to 7 inches in length and an insert tapered portion approximately 2 to 3 inches in length and of greater diameter than the extension portion, is mated with the golf shaft. The tapered portion has an outer diameter sized and configured so as to correspond and mate with the inner diameter and internal tapering of the golf club shaft. The tapered portion is inserted into the proximal end of the shaft such that the extension portion extends coaxially from the end of the golf shaft. A flexible sleeve is disposed about the insert extension portion, the outer diameter of the flexible sleeve approximating the outer diameter of the golf club shaft, such that a standard grip may be applied over the butt end of the shaft and the extension portion of the shaft insert. Preferably, the flexible tubular shaft insert is composed of a graphite composite material.

In a second embodiment, a one-piece tubular or hollow shaft insert member of approximately 6.5 to 10 inches in length comprising an extension portion approximately 5 to 7 inches in length and an internal stub portion, preferably slightly tapered, approximately 1.5 to 3 inches in length and of lesser diameter than the extension portion, is mated with the golf shaft. The wall thicknesses and material of composition of the hollow shaft insert member are chosen such that the extension portion flexes angularly relative to the golf shaft, in a hinge-like manner, at the location of the junction between the extension portion and the end of the golf shaft, and further such that the extension portion remains substantially linear when it is in the flexed orientation. The club grip member extends beyond the end of the extension portion and onto the golf shaft, with the grip member being composed of a material more flexible than the extension portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-sectional view of one embodiment of the improved golf club.

FIG. 2 is a view of the flexible insert member of the embodiment of FIG. 1.

FIG. 3 is a partial view of the golf club of the embodiment of FIG. 1, showing in dashed lines the extension portion of the flexible insert member in the flexed state.

FIG. 4 is a partial cross-sectional view of another embodiment of the improved golf club.

FIG. 5 is a view of the flexible insert member of the embodiment of FIG. 4.

FIG. 6 is a partial view of the golf club of the embodiment of FIG. 4, showing in dashed lines the extension portion of the flexible insert member in the flexed state.

DETAILED DESCRIPTION OF THE INVENTION

With reference to the drawing, the invention will now be described in detail with, regard for the best mode and preferred embodiments. In general, the invention is an improved construction for a golf club wherein the flexibility of the club at or near the butt end, i.e., at the grip portion, is increased in a controlled manner.

In one embodiment, illustrated in FIGS. 1-3, the invention comprises a flexible tubular insert 30, preferably composed of a graphite composite material formed in a layered manner, the flexible insert 30 comprising a tapered portion 31 and a tubular extension portion 32, preferably cylindrical, with an insert bore 33 extending the length of the flexible insert 30. The degree of flexibility in the flexible insert 30 and therefore the degree of flexibility of the butt end portion of the golf club may be varied by altering the material, pattern of layering, reinforcement material, bore size 33, etc., of the flexible insert 30. Other materials, such as carbon rods, fiberglass or materials with similar characteristics, may also be use to form the flexible insert 30. The flexible insert 30 may be formed as a single member, or the tapered portion 31 may be formed by positioning a tapered sleeve over one end of a tubular rod, as shown in FIG. 1. The degree of taper in the tapered portion 31 is chosen to correspond with the tapering found in the bore 12 of the golf club shaft 10 at its shaft butt end 11.

With the tapered portion 31 inserted into the shaft bore 12 and bonded using suitable adhesives, the tubular insert extension portion 32 extends coaxially beyond the butt end 11 of the golf club shaft 10. The inner and outer diameters of the insert extension portion 32 preferably approximate the inner and outer diameters of the golf club shaft 10 at its tip, such that the insert extension portion 32 is much more flexible than the proximal portion of the golf shaft 10, due to the much greater outer diameter of the golf shaft 10. A flexible cover sleeve 40 is coaxially placed around the insert extension portion 32, the thickness of the cover sleeve 40 being chosen such that its outer diameter generally matches the outer diameter of the golf club shaft 10 at its butt end 11. In this manner, a standard grip member 20 and grip cap member 21 may be disposed on the golf club shaft 10 and flexible insert 30 in known manner without resulting in any undesirable transition shoulders or edges. The flexibility of the cover sleeve 40 may also be varied in order to affect the flexibility of the flexible insert 30. Thus, the flexible cover sleeve 40 may be stiffer in order to reduce the flexibility of the flexible insert member 30, or the cover sleeve 40 may be composed of material similar or even greater in flex characteristics to the material composing the flexible insert 30 such that minimal limiting effect is created.

With this construction, the golf club has a flex range or bend profile beginning at the location 34 where the insert extension portion 32 meets the shaft butt end 11 and extending to the end of the club, with the construction of the flexible insert member 30 allowing the flex to diffuse along the extension portion 32 such that excessive shear forces are not present at the initial flex point 34. This construction allows for flex over the full length of the insert extension portion 32 and between the hands of the golfer. This creates a whip-like response in the club as it is swung. The degree of flex can be controlled and optimized relative to the strength and skill levels of individual golfers. The shaft flex at the top of the golf swing can be increased by 30 degrees over a standard golf shaft. The lightweight composition of the flexible shaft insert 30 does not adversely affect the balance of the club. In fact, the weight of the insert requires that some additional weight be added to the club head in order to maintain the traditional swing weight in the range of D1 to D5. This counterbalancing allows for a club head weight that can be about 15 to 20 grams heavier. The result of this additional club head mass is greater distance, assuming that the club head velocity increases as well. The physics is E=MV², where the increased mass times velocity squared translates into greater distance for a golfer using this club.

While absolute dimensions will vary due to many factors, a representative flexible insert 30 may be between about 7 and 10 inches in length, preferably about 7 to 8 inches. The tapered portion 31 will preferably have a length of about 2 to 3 inches, and the insert extension portion 32 will preferably have a length of about 5 to 7 inches. In a typical golf club shaft 10 having a wall thickness of about 1/32 inches and an inner bore 12 of about 11/32 inches at its butt end 11, the tapered portion 31 will have outer dimensions diminishing from about 16/32 to about 11/32 inches to match the taper of the shaft 10. The insert bore 33 is about 6/32 inches with a thickness of about 3/32 inches on the extension portion 32, the extension portion 32 having an outer diameter of about 12/32 inches.

In another embodiment, illustrated in FIGS. 4-6, the invention comprises a flexible hollow insert 70, preferably tubular and preferably composed as a one-piece bladder-molded member of a graphite composite material, the flexible insert 70 comprising an internal stub portion 71, preferably slightly tapered to match the taper of the golf club internal shaft bore 52, and an extension portion 32. The flexible hollow insert 70 further comprises an internal hollow area 73. The hollow insert 70 may be open on one end, open on both ends, or closed on both ends. The degree of flexibility in the flexible insert 30 and therefore the degree of flexibility of the butt end portion of the golf club is controlled through choice of the material of composition, reinforcement material, wall thickness, etc., of the flexible insert 70. Other materials, such as carbon rods, fiberglass or materials with similar characteristics, may also be use to form the flexible insert 70. Retention members 75, shown as annular ridges in FIG. 5, may be disposed on outer surface of the internal stub portion 71 to better fit and secure the internal stub portion 71 to the golf shaft 50. The internal stub portion 71 may be bonded, glued, heat welded or the like to permanently connect the internal stub portion 71 to the golf shaft 50.

The outer diameter of the internal stub portion 71 is smaller than the outer diameter of the extension portion 72, such that a shoulder 76 is defined. The internal stub portion 71 is fully inserted into the shaft bore 52 such that the shoulder 76 abuts the shaft butt end 51. The outer diameter of the extension portion 72 adjacent the shoulder 76 is chosen so that it is substantially equal to the outer diameter of the shaft butt end 51. The outer surface of the extension portion 72 is preferably tapered to correspond to the taper of the golf shaft 50, such that the outer diameter increases as the distance from the shoulder 76 increases. The extension portion 72 of the flexible insert member and a short segment of the golf shaft 50 are covered in known manner by a grip member 60. The grip member 60 is more flexible than the extension portion 72.

The flexible insert member 70 is designed and constructed such that a flex point 74 exists at the junction of the internal stub portion 71 and extension portion 72, such that the extension portion 72 is able to bend or flex in a hinge-like manner relative to the internal stub portion 71 and golf shaft 50. The external portion 72 of the insert member 70 is designed and constructed to be substantially stiff or rigid, such that it remains substantially linear when the extension portion 72 is angularly bent relative to the internal stub portion 71 and golf shaft 50, as shown in FIG. 6.

With this construction, the stresses created by the bending movement are shared by the insert member 70 and the grip member 60, thereby greatly increasing the life of the club. The embodiment shown in FIGS. 4-6 presents a relatively lightweight insert member 70, easily being constructed to have a total weight of 15 to 20 grams. This is useful in maintaining a lower overall shaft weight, which is a desirable quality.

The flex point 74 occurs at a location between the hands of the golfer when the club is being swung. During the upper backswing, the portion of the club containing the extension portion 72, i.e., the portion of the club held by the upper hand of golfer, angularly bends at the flex point 74 relative to the golf shaft 50 in a lever-like fashion. This results in increased club head speed in the down stroke because the lag and whip action into the critical ball impact area is increased. An average golfer can now use a stiffer shaft 50 having greater torque resistance, resulting in better ball control, because of the higher club head speed.

It is contemplated that equivalents and substitutions for certain elements and structure set forth above may be obvious to those skilled in the art, and therefore the true scope and definition of the invention is to be as set forth in the following claims.

Claims

1. A golf club comprising:

a club shaft having a shaft bore and a butt end;

a flexible hollow insert member mated with said club shaft, said insert member comprising an internal stub portion and an extension portion, the junction of said internal stub portion and said extension portion defining a shoulder, wherein said internal stub portion is inserted into said shaft bore such that said shoulder abuts said butt end and said extension portion extends coaxially from said butt end of said club shaft, and wherein the outer diameter of said extension portion is greater than the outer diameter of said internal stub portion, the outer diameter of said extension member adjacent said shoulder corresponding to the outer diameter of said butt end;

a grip member coaxially mounted onto said extension portion and a portion of said club shaft, said grip member being more flexible than said extension portion;

whereby said extension portion bends angularly relative to said club shaft and said internal stub portion, said extension portion remaining substantially linear during such bending.

2. The club of claim 1, wherein said flexible tubular insert member is composed of a graphite composite material.

3. The club of claim 1, wherein said insert member is approximately from 6.5 to 10 inches in length, and wherein said insert stub portion is approximately about 1.5 to 3 inches in length and said extension portion is approximately 5 to 7 inches in length.

4. The club of claim 1, further comprising retention members disposed on said internal stub portion.

5. The club of claim 4, wherein said retention members comprise annular ridges.

6. The club of claim 1, wherein said internal stub portion and said extension portion are tapered.

7. A golf club comprising:

a club shaft having a shaft bore and a butt end;

a flexible hollow insert member mated with said club shaft, said insert member comprising an internal stub portion and an extension portion, the junction of said internal stub portion and said extension portion defining a shoulder, wherein said internal stub portion is inserted into said shaft bore such that said shoulder abuts said butt end and said extension portion extends coaxially from said butt end of said club shaft, and wherein the outer diameter of said extension portion is greater than the outer diameter of said internal stub portion, the outer diameter of said extension member adjacent said shoulder corresponding to the outer diameter of said butt end;

a grip member coaxially mounted onto said extension portion and a portion of said club shaft, said grip member being more flexible than said extension portion;

said golf club having a flex point at the junction of said internal stub portion and said extension portion, whereby said extension portion bends angularly at said flex point relative to said club shaft and said internal stub portion, said extension portion remaining substantially linear during such bending.

8. The club of claim 7, wherein said flexible tubular insert member is composed of a graphite composite material.

9. The club of claim 7, wherein said insert member is approximately from 6.5 to 10 inches in length, and wherein said insert stub portion is approximately about 1.5 to 3 inches in length and said extension portion is approximately 5 to 7 inches in length.

10. The club of claim 7, further comprising retention members disposed on said internal stub portion.

11. The club of claim 10, wherein said retention members comprise annular ridges.

12. The club of claim 7, wherein said internal stub portion and said extension portion are tapered.

13. A golf club comprising:

a club shaft having a shaft bore and a butt end;

a flexible hollow insert member mated with said club shaft, said insert member comprising an internal stub portion and an extension portion, the junction of said internal stub portion and said extension portion defining a shoulder, wherein said internal stub portion is inserted into said shaft bore such that said shoulder abuts said butt end and said extension portion extends coaxially from said butt end of said club shaft, and wherein the outer diameter of said extension portion is greater than the outer diameter of said internal stub portion, the outer diameter of said extension member adjacent said shoulder corresponding to the outer diameter of said butt end;

a grip member coaxially mounted onto said extension portion and a portion of said club shaft, said grip member being more flexible than said extension portion;

said golf club having a flex point at the junction of said internal stub portion and said extension portion, whereby said flex point is positioned between the hands of a golfer when said golf club is in use;

whereby said extension portion bends angularly at said flex point relative to said club shaft and said internal stub portion, said extension portion remaining substantially linear during such bending.

14. The club of claim 13, wherein said flexible tubular insert member is composed of a graphite composite material.

15. The club of claim 13, wherein said insert member is approximately from 6.5 to 10 inches in length, and wherein said insert stub portion is approximately about 1.5 to 3 inches in length and said extension portion is approximately 5 to 7 inches in length.

16. The club of claim 13, further comprising retention members disposed on said internal stub portion.

17. The club of claim 16, wherein said retention members comprise annular ridges.

18. The club of claim 13, wherein said internal stub portion and said extension portion are tapered.